xref: /rk3399_rockchip-uboot/README (revision 7a28441f4d89cac6885a7e817e41379c83cb35aa)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG and CREDITS files to find out
38who contributed the specific port. The boards.cfg file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136    /cpu		CPU specific files
137      /arc700		Files specific to ARC 700 CPUs
138    /lib		Architecture specific library files
139  /arm			Files generic to ARM architecture
140    /cpu		CPU specific files
141      /arm720t		Files specific to ARM 720 CPUs
142      /arm920t		Files specific to ARM 920 CPUs
143	/at91		Files specific to Atmel AT91RM9200 CPU
144	/imx		Files specific to Freescale MC9328 i.MX CPUs
145	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
146      /arm926ejs	Files specific to ARM 926 CPUs
147      /arm1136		Files specific to ARM 1136 CPUs
148      /pxa		Files specific to Intel XScale PXA CPUs
149      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
150    /lib		Architecture specific library files
151  /avr32		Files generic to AVR32 architecture
152    /cpu		CPU specific files
153    /lib		Architecture specific library files
154  /blackfin		Files generic to Analog Devices Blackfin architecture
155    /cpu		CPU specific files
156    /lib		Architecture specific library files
157  /m68k			Files generic to m68k architecture
158    /cpu		CPU specific files
159      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
160      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
161      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
162      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
163      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
164    /lib		Architecture specific library files
165  /microblaze		Files generic to microblaze architecture
166    /cpu		CPU specific files
167    /lib		Architecture specific library files
168  /mips			Files generic to MIPS architecture
169    /cpu		CPU specific files
170      /mips32		Files specific to MIPS32 CPUs
171      /mips64		Files specific to MIPS64 CPUs
172    /lib		Architecture specific library files
173  /nds32		Files generic to NDS32 architecture
174    /cpu		CPU specific files
175      /n1213		Files specific to Andes Technology N1213 CPUs
176    /lib		Architecture specific library files
177  /nios2		Files generic to Altera NIOS2 architecture
178    /cpu		CPU specific files
179    /lib		Architecture specific library files
180  /openrisc		Files generic to OpenRISC architecture
181    /cpu		CPU specific files
182    /lib		Architecture specific library files
183  /powerpc		Files generic to PowerPC architecture
184    /cpu		CPU specific files
185      /mpc5xx		Files specific to Freescale MPC5xx CPUs
186      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
187      /mpc8xx		Files specific to Freescale MPC8xx CPUs
188      /mpc8260		Files specific to Freescale MPC8260 CPUs
189      /mpc85xx		Files specific to Freescale MPC85xx CPUs
190      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
191    /lib		Architecture specific library files
192  /sh			Files generic to SH architecture
193    /cpu		CPU specific files
194      /sh2		Files specific to sh2 CPUs
195      /sh3		Files specific to sh3 CPUs
196      /sh4		Files specific to sh4 CPUs
197    /lib		Architecture specific library files
198  /sparc		Files generic to SPARC architecture
199    /cpu		CPU specific files
200      /leon2		Files specific to Gaisler LEON2 SPARC CPU
201      /leon3		Files specific to Gaisler LEON3 SPARC CPU
202    /lib		Architecture specific library files
203  /x86			Files generic to x86 architecture
204    /cpu		CPU specific files
205    /lib		Architecture specific library files
206/api			Machine/arch independent API for external apps
207/board			Board dependent files
208/common			Misc architecture independent functions
209/disk			Code for disk drive partition handling
210/doc			Documentation (don't expect too much)
211/drivers		Commonly used device drivers
212/dts			Contains Makefile for building internal U-Boot fdt.
213/examples		Example code for standalone applications, etc.
214/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
215/include		Header Files
216/lib			Files generic to all architectures
217  /libfdt		Library files to support flattened device trees
218  /lzma			Library files to support LZMA decompression
219  /lzo			Library files to support LZO decompression
220/net			Networking code
221/post			Power On Self Test
222/spl			Secondary Program Loader framework
223/tools			Tools to build S-Record or U-Boot images, etc.
224
225Software Configuration:
226=======================
227
228Configuration is usually done using C preprocessor defines; the
229rationale behind that is to avoid dead code whenever possible.
230
231There are two classes of configuration variables:
232
233* Configuration _OPTIONS_:
234  These are selectable by the user and have names beginning with
235  "CONFIG_".
236
237* Configuration _SETTINGS_:
238  These depend on the hardware etc. and should not be meddled with if
239  you don't know what you're doing; they have names beginning with
240  "CONFIG_SYS_".
241
242Later we will add a configuration tool - probably similar to or even
243identical to what's used for the Linux kernel. Right now, we have to
244do the configuration by hand, which means creating some symbolic
245links and editing some configuration files. We use the TQM8xxL boards
246as an example here.
247
248
249Selection of Processor Architecture and Board Type:
250---------------------------------------------------
251
252For all supported boards there are ready-to-use default
253configurations available; just type "make <board_name>_defconfig".
254
255Example: For a TQM823L module type:
256
257	cd u-boot
258	make TQM823L_defconfig
259
260For the Cogent platform, you need to specify the CPU type as well;
261e.g. "make cogent_mpc8xx_defconfig". And also configure the cogent
262directory according to the instructions in cogent/README.
263
264
265Sandbox Environment:
266--------------------
267
268U-Boot can be built natively to run on a Linux host using the 'sandbox'
269board. This allows feature development which is not board- or architecture-
270specific to be undertaken on a native platform. The sandbox is also used to
271run some of U-Boot's tests.
272
273See board/sandbox/README.sandbox for more details.
274
275
276Configuration Options:
277----------------------
278
279Configuration depends on the combination of board and CPU type; all
280such information is kept in a configuration file
281"include/configs/<board_name>.h".
282
283Example: For a TQM823L module, all configuration settings are in
284"include/configs/TQM823L.h".
285
286
287Many of the options are named exactly as the corresponding Linux
288kernel configuration options. The intention is to make it easier to
289build a config tool - later.
290
291
292The following options need to be configured:
293
294- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
295
296- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
297
298- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
299		Define exactly one, e.g. CONFIG_ATSTK1002
300
301- CPU Module Type: (if CONFIG_COGENT is defined)
302		Define exactly one of
303		CONFIG_CMA286_60_OLD
304--- FIXME --- not tested yet:
305		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
306		CONFIG_CMA287_23, CONFIG_CMA287_50
307
308- Motherboard Type: (if CONFIG_COGENT is defined)
309		Define exactly one of
310		CONFIG_CMA101, CONFIG_CMA102
311
312- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
313		Define one or more of
314		CONFIG_CMA302
315
316- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
317		Define one or more of
318		CONFIG_LCD_HEARTBEAT	- update a character position on
319					  the LCD display every second with
320					  a "rotator" |\-/|\-/
321
322- Marvell Family Member
323		CONFIG_SYS_MVFS		- define it if you want to enable
324					  multiple fs option at one time
325					  for marvell soc family
326
327- 8xx CPU Options: (if using an MPC8xx CPU)
328		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
329					  get_gclk_freq() cannot work
330					  e.g. if there is no 32KHz
331					  reference PIT/RTC clock
332		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
333					  or XTAL/EXTAL)
334
335- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
336		CONFIG_SYS_8xx_CPUCLK_MIN
337		CONFIG_SYS_8xx_CPUCLK_MAX
338		CONFIG_8xx_CPUCLK_DEFAULT
339			See doc/README.MPC866
340
341		CONFIG_SYS_MEASURE_CPUCLK
342
343		Define this to measure the actual CPU clock instead
344		of relying on the correctness of the configured
345		values. Mostly useful for board bringup to make sure
346		the PLL is locked at the intended frequency. Note
347		that this requires a (stable) reference clock (32 kHz
348		RTC clock or CONFIG_SYS_8XX_XIN)
349
350		CONFIG_SYS_DELAYED_ICACHE
351
352		Define this option if you want to enable the
353		ICache only when Code runs from RAM.
354
355- 85xx CPU Options:
356		CONFIG_SYS_PPC64
357
358		Specifies that the core is a 64-bit PowerPC implementation (implements
359		the "64" category of the Power ISA). This is necessary for ePAPR
360		compliance, among other possible reasons.
361
362		CONFIG_SYS_FSL_TBCLK_DIV
363
364		Defines the core time base clock divider ratio compared to the
365		system clock.  On most PQ3 devices this is 8, on newer QorIQ
366		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
367
368		CONFIG_SYS_FSL_PCIE_COMPAT
369
370		Defines the string to utilize when trying to match PCIe device
371		tree nodes for the given platform.
372
373		CONFIG_SYS_PPC_E500_DEBUG_TLB
374
375		Enables a temporary TLB entry to be used during boot to work
376		around limitations in e500v1 and e500v2 external debugger
377		support. This reduces the portions of the boot code where
378		breakpoints and single stepping do not work.  The value of this
379		symbol should be set to the TLB1 entry to be used for this
380		purpose.
381
382		CONFIG_SYS_FSL_ERRATUM_A004510
383
384		Enables a workaround for erratum A004510.  If set,
385		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
386		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
387
388		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
389		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
390
391		Defines one or two SoC revisions (low 8 bits of SVR)
392		for which the A004510 workaround should be applied.
393
394		The rest of SVR is either not relevant to the decision
395		of whether the erratum is present (e.g. p2040 versus
396		p2041) or is implied by the build target, which controls
397		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
398
399		See Freescale App Note 4493 for more information about
400		this erratum.
401
402		CONFIG_A003399_NOR_WORKAROUND
403		Enables a workaround for IFC erratum A003399. It is only
404		required during NOR boot.
405
406		CONFIG_A008044_WORKAROUND
407		Enables a workaround for T1040/T1042 erratum A008044. It is only
408		required during NAND boot and valid for Rev 1.0 SoC revision
409
410		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
411
412		This is the value to write into CCSR offset 0x18600
413		according to the A004510 workaround.
414
415		CONFIG_SYS_FSL_DSP_DDR_ADDR
416		This value denotes start offset of DDR memory which is
417		connected exclusively to the DSP cores.
418
419		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
420		This value denotes start offset of M2 memory
421		which is directly connected to the DSP core.
422
423		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
424		This value denotes start offset of M3 memory which is directly
425		connected to the DSP core.
426
427		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
428		This value denotes start offset of DSP CCSR space.
429
430		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
431		Single Source Clock is clocking mode present in some of FSL SoC's.
432		In this mode, a single differential clock is used to supply
433		clocks to the sysclock, ddrclock and usbclock.
434
435		CONFIG_SYS_CPC_REINIT_F
436		This CONFIG is defined when the CPC is configured as SRAM at the
437		time of U-boot entry and is required to be re-initialized.
438
439		CONFIG_DEEP_SLEEP
440		Indicates this SoC supports deep sleep feature. If deep sleep is
441		supported, core will start to execute uboot when wakes up.
442
443- Generic CPU options:
444		CONFIG_SYS_GENERIC_GLOBAL_DATA
445		Defines global data is initialized in generic board board_init_f().
446		If this macro is defined, global data is created and cleared in
447		generic board board_init_f(). Without this macro, architecture/board
448		should initialize global data before calling board_init_f().
449
450		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
451
452		Defines the endianess of the CPU. Implementation of those
453		values is arch specific.
454
455		CONFIG_SYS_FSL_DDR
456		Freescale DDR driver in use. This type of DDR controller is
457		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
458		SoCs.
459
460		CONFIG_SYS_FSL_DDR_ADDR
461		Freescale DDR memory-mapped register base.
462
463		CONFIG_SYS_FSL_DDR_EMU
464		Specify emulator support for DDR. Some DDR features such as
465		deskew training are not available.
466
467		CONFIG_SYS_FSL_DDRC_GEN1
468		Freescale DDR1 controller.
469
470		CONFIG_SYS_FSL_DDRC_GEN2
471		Freescale DDR2 controller.
472
473		CONFIG_SYS_FSL_DDRC_GEN3
474		Freescale DDR3 controller.
475
476		CONFIG_SYS_FSL_DDRC_GEN4
477		Freescale DDR4 controller.
478
479		CONFIG_SYS_FSL_DDRC_ARM_GEN3
480		Freescale DDR3 controller for ARM-based SoCs.
481
482		CONFIG_SYS_FSL_DDR1
483		Board config to use DDR1. It can be enabled for SoCs with
484		Freescale DDR1 or DDR2 controllers, depending on the board
485		implemetation.
486
487		CONFIG_SYS_FSL_DDR2
488		Board config to use DDR2. It can be eanbeld for SoCs with
489		Freescale DDR2 or DDR3 controllers, depending on the board
490		implementation.
491
492		CONFIG_SYS_FSL_DDR3
493		Board config to use DDR3. It can be enabled for SoCs with
494		Freescale DDR3 or DDR3L controllers.
495
496		CONFIG_SYS_FSL_DDR3L
497		Board config to use DDR3L. It can be enabled for SoCs with
498		DDR3L controllers.
499
500		CONFIG_SYS_FSL_DDR4
501		Board config to use DDR4. It can be enabled for SoCs with
502		DDR4 controllers.
503
504		CONFIG_SYS_FSL_IFC_BE
505		Defines the IFC controller register space as Big Endian
506
507		CONFIG_SYS_FSL_IFC_LE
508		Defines the IFC controller register space as Little Endian
509
510		CONFIG_SYS_FSL_PBL_PBI
511		It enables addition of RCW (Power on reset configuration) in built image.
512		Please refer doc/README.pblimage for more details
513
514		CONFIG_SYS_FSL_PBL_RCW
515		It adds PBI(pre-boot instructions) commands in u-boot build image.
516		PBI commands can be used to configure SoC before it starts the execution.
517		Please refer doc/README.pblimage for more details
518
519		CONFIG_SPL_FSL_PBL
520		It adds a target to create boot binary having SPL binary in PBI format
521		concatenated with u-boot binary.
522
523		CONFIG_SYS_FSL_DDR_BE
524		Defines the DDR controller register space as Big Endian
525
526		CONFIG_SYS_FSL_DDR_LE
527		Defines the DDR controller register space as Little Endian
528
529		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
530		Physical address from the view of DDR controllers. It is the
531		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
532		it could be different for ARM SoCs.
533
534		CONFIG_SYS_FSL_DDR_INTLV_256B
535		DDR controller interleaving on 256-byte. This is a special
536		interleaving mode, handled by Dickens for Freescale layerscape
537		SoCs with ARM core.
538
539		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
540		Number of controllers used as main memory.
541
542		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
543		Number of controllers used for other than main memory.
544
545		CONFIG_SYS_FSL_SEC_BE
546		Defines the SEC controller register space as Big Endian
547
548		CONFIG_SYS_FSL_SEC_LE
549		Defines the SEC controller register space as Little Endian
550
551- Intel Monahans options:
552		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
553
554		Defines the Monahans run mode to oscillator
555		ratio. Valid values are 8, 16, 24, 31. The core
556		frequency is this value multiplied by 13 MHz.
557
558		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
559
560		Defines the Monahans turbo mode to oscillator
561		ratio. Valid values are 1 (default if undefined) and
562		2. The core frequency as calculated above is multiplied
563		by this value.
564
565- MIPS CPU options:
566		CONFIG_SYS_INIT_SP_OFFSET
567
568		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
569		pointer. This is needed for the temporary stack before
570		relocation.
571
572		CONFIG_SYS_MIPS_CACHE_MODE
573
574		Cache operation mode for the MIPS CPU.
575		See also arch/mips/include/asm/mipsregs.h.
576		Possible values are:
577			CONF_CM_CACHABLE_NO_WA
578			CONF_CM_CACHABLE_WA
579			CONF_CM_UNCACHED
580			CONF_CM_CACHABLE_NONCOHERENT
581			CONF_CM_CACHABLE_CE
582			CONF_CM_CACHABLE_COW
583			CONF_CM_CACHABLE_CUW
584			CONF_CM_CACHABLE_ACCELERATED
585
586		CONFIG_SYS_XWAY_EBU_BOOTCFG
587
588		Special option for Lantiq XWAY SoCs for booting from NOR flash.
589		See also arch/mips/cpu/mips32/start.S.
590
591		CONFIG_XWAY_SWAP_BYTES
592
593		Enable compilation of tools/xway-swap-bytes needed for Lantiq
594		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
595		be swapped if a flash programmer is used.
596
597- ARM options:
598		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
599
600		Select high exception vectors of the ARM core, e.g., do not
601		clear the V bit of the c1 register of CP15.
602
603		CONFIG_SYS_THUMB_BUILD
604
605		Use this flag to build U-Boot using the Thumb instruction
606		set for ARM architectures. Thumb instruction set provides
607		better code density. For ARM architectures that support
608		Thumb2 this flag will result in Thumb2 code generated by
609		GCC.
610
611		CONFIG_ARM_ERRATA_716044
612		CONFIG_ARM_ERRATA_742230
613		CONFIG_ARM_ERRATA_743622
614		CONFIG_ARM_ERRATA_751472
615		CONFIG_ARM_ERRATA_794072
616		CONFIG_ARM_ERRATA_761320
617
618		If set, the workarounds for these ARM errata are applied early
619		during U-Boot startup. Note that these options force the
620		workarounds to be applied; no CPU-type/version detection
621		exists, unlike the similar options in the Linux kernel. Do not
622		set these options unless they apply!
623
624- Tegra SoC options:
625		CONFIG_TEGRA_SUPPORT_NON_SECURE
626
627		Support executing U-Boot in non-secure (NS) mode. Certain
628		impossible actions will be skipped if the CPU is in NS mode,
629		such as ARM architectural timer initialization.
630
631- Driver Model
632		Driver model is a new framework for devices in U-Boot
633		introduced in early 2014. U-Boot is being progressively
634		moved over to this. It offers a consistent device structure,
635		supports grouping devices into classes and has built-in
636		handling of platform data and device tree.
637
638		To enable transition to driver model in a relatively
639		painful fashion, each subsystem can be independently
640		switched between the legacy/ad-hoc approach and the new
641		driver model using the options below. Also, many uclass
642		interfaces include compatibility features which may be
643		removed once the conversion of that subsystem is complete.
644		As a result, the API provided by the subsystem may in fact
645		not change with driver model.
646
647		See doc/driver-model/README.txt for more information.
648
649		CONFIG_DM
650
651		Enable driver model. This brings in the core support,
652		including scanning of platform data on start-up. If
653		CONFIG_OF_CONTROL is enabled, the device tree will be
654		scanned also when available.
655
656		CONFIG_CMD_DM
657
658		Enable driver model test commands. These allow you to print
659		out the driver model tree and the uclasses.
660
661		CONFIG_DM_DEMO
662
663		Enable some demo devices and the 'demo' command. These are
664		really only useful for playing around while trying to
665		understand driver model in sandbox.
666
667		CONFIG_SPL_DM
668
669		Enable driver model in SPL. You will need to provide a
670		suitable malloc() implementation. If you are not using the
671		full malloc() enabled by CONFIG_SYS_SPL_MALLOC_START,
672		consider using CONFIG_SYS_MALLOC_SIMPLE. In that case you
673		must provide CONFIG_SYS_MALLOC_F_LEN to set the size.
674		In most cases driver model will only allocate a few uclasses
675		and devices in SPL, so 1KB should be enable. See
676		CONFIG_SYS_MALLOC_F_LEN for more details on how to enable
677		it.
678
679		CONFIG_DM_SERIAL
680
681		Enable driver model for serial. This replaces
682		drivers/serial/serial.c with the serial uclass, which
683		implements serial_putc() etc. The uclass interface is
684		defined in include/serial.h.
685
686		CONFIG_DM_GPIO
687
688		Enable driver model for GPIO access. The standard GPIO
689		interface (gpio_get_value(), etc.) is then implemented by
690		the GPIO uclass. Drivers provide methods to query the
691		particular GPIOs that they provide. The uclass interface
692		is defined in include/asm-generic/gpio.h.
693
694		CONFIG_DM_SPI
695
696		Enable driver model for SPI. The SPI slave interface
697		(spi_setup_slave(), spi_xfer(), etc.) is then implemented by
698		the SPI uclass. Drivers provide methods to access the SPI
699		buses that they control. The uclass interface is defined in
700		include/spi.h. The existing spi_slave structure is attached
701		as 'parent data' to every slave on each bus. Slaves
702		typically use driver-private data instead of extending the
703		spi_slave structure.
704
705		CONFIG_DM_SPI_FLASH
706
707		Enable driver model for SPI flash. This SPI flash interface
708		(spi_flash_probe(), spi_flash_write(), etc.) is then
709		implemented by the SPI flash uclass. There is one standard
710		SPI flash driver which knows how to probe most chips
711		supported by U-Boot. The uclass interface is defined in
712		include/spi_flash.h, but is currently fully compatible
713		with the old interface to avoid confusion and duplication
714		during the transition parent. SPI and SPI flash must be
715		enabled together (it is not possible to use driver model
716		for one and not the other).
717
718		CONFIG_DM_CROS_EC
719
720		Enable driver model for the Chrome OS EC interface. This
721		allows the cros_ec SPI driver to operate with CONFIG_DM_SPI
722		but otherwise makes few changes. Since cros_ec also supports
723		I2C and LPC (which don't support driver model yet), a full
724		conversion is not yet possible.
725
726
727		** Code size options: The following options are enabled by
728		default except in SPL. Enable them explicitly to get these
729		features in SPL.
730
731		CONFIG_DM_WARN
732
733		Enable the dm_warn() function. This can use up quite a bit
734		of space for its strings.
735
736		CONFIG_DM_STDIO
737
738		Enable registering a serial device with the stdio library.
739
740		CONFIG_DM_DEVICE_REMOVE
741
742		Enable removing of devices.
743
744
745- Linux Kernel Interface:
746		CONFIG_CLOCKS_IN_MHZ
747
748		U-Boot stores all clock information in Hz
749		internally. For binary compatibility with older Linux
750		kernels (which expect the clocks passed in the
751		bd_info data to be in MHz) the environment variable
752		"clocks_in_mhz" can be defined so that U-Boot
753		converts clock data to MHZ before passing it to the
754		Linux kernel.
755		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
756		"clocks_in_mhz=1" is automatically included in the
757		default environment.
758
759		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
760
761		When transferring memsize parameter to Linux, some versions
762		expect it to be in bytes, others in MB.
763		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
764
765		CONFIG_OF_LIBFDT
766
767		New kernel versions are expecting firmware settings to be
768		passed using flattened device trees (based on open firmware
769		concepts).
770
771		CONFIG_OF_LIBFDT
772		 * New libfdt-based support
773		 * Adds the "fdt" command
774		 * The bootm command automatically updates the fdt
775
776		OF_CPU - The proper name of the cpus node (only required for
777			MPC512X and MPC5xxx based boards).
778		OF_SOC - The proper name of the soc node (only required for
779			MPC512X and MPC5xxx based boards).
780		OF_TBCLK - The timebase frequency.
781		OF_STDOUT_PATH - The path to the console device
782
783		boards with QUICC Engines require OF_QE to set UCC MAC
784		addresses
785
786		CONFIG_OF_BOARD_SETUP
787
788		Board code has addition modification that it wants to make
789		to the flat device tree before handing it off to the kernel
790
791		CONFIG_OF_SYSTEM_SETUP
792
793		Other code has addition modification that it wants to make
794		to the flat device tree before handing it off to the kernel.
795		This causes ft_system_setup() to be called before booting
796		the kernel.
797
798		CONFIG_OF_BOOT_CPU
799
800		This define fills in the correct boot CPU in the boot
801		param header, the default value is zero if undefined.
802
803		CONFIG_OF_IDE_FIXUP
804
805		U-Boot can detect if an IDE device is present or not.
806		If not, and this new config option is activated, U-Boot
807		removes the ATA node from the DTS before booting Linux,
808		so the Linux IDE driver does not probe the device and
809		crash. This is needed for buggy hardware (uc101) where
810		no pull down resistor is connected to the signal IDE5V_DD7.
811
812		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
813
814		This setting is mandatory for all boards that have only one
815		machine type and must be used to specify the machine type
816		number as it appears in the ARM machine registry
817		(see http://www.arm.linux.org.uk/developer/machines/).
818		Only boards that have multiple machine types supported
819		in a single configuration file and the machine type is
820		runtime discoverable, do not have to use this setting.
821
822- vxWorks boot parameters:
823
824		bootvx constructs a valid bootline using the following
825		environments variables: bootfile, ipaddr, serverip, hostname.
826		It loads the vxWorks image pointed bootfile.
827
828		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
829		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
830		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
831		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
832
833		CONFIG_SYS_VXWORKS_ADD_PARAMS
834
835		Add it at the end of the bootline. E.g "u=username pw=secret"
836
837		Note: If a "bootargs" environment is defined, it will overwride
838		the defaults discussed just above.
839
840- Cache Configuration:
841		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
842		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
843		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
844
845- Cache Configuration for ARM:
846		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
847				      controller
848		CONFIG_SYS_PL310_BASE - Physical base address of PL310
849					controller register space
850
851- Serial Ports:
852		CONFIG_PL010_SERIAL
853
854		Define this if you want support for Amba PrimeCell PL010 UARTs.
855
856		CONFIG_PL011_SERIAL
857
858		Define this if you want support for Amba PrimeCell PL011 UARTs.
859
860		CONFIG_PL011_CLOCK
861
862		If you have Amba PrimeCell PL011 UARTs, set this variable to
863		the clock speed of the UARTs.
864
865		CONFIG_PL01x_PORTS
866
867		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
868		define this to a list of base addresses for each (supported)
869		port. See e.g. include/configs/versatile.h
870
871		CONFIG_PL011_SERIAL_RLCR
872
873		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
874		have separate receive and transmit line control registers.  Set
875		this variable to initialize the extra register.
876
877		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
878
879		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
880		boot loader that has already initialized the UART.  Define this
881		variable to flush the UART at init time.
882
883		CONFIG_SERIAL_HW_FLOW_CONTROL
884
885		Define this variable to enable hw flow control in serial driver.
886		Current user of this option is drivers/serial/nsl16550.c driver
887
888- Console Interface:
889		Depending on board, define exactly one serial port
890		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
891		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
892		console by defining CONFIG_8xx_CONS_NONE
893
894		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
895		port routines must be defined elsewhere
896		(i.e. serial_init(), serial_getc(), ...)
897
898		CONFIG_CFB_CONSOLE
899		Enables console device for a color framebuffer. Needs following
900		defines (cf. smiLynxEM, i8042)
901			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
902						(default big endian)
903			VIDEO_HW_RECTFILL	graphic chip supports
904						rectangle fill
905						(cf. smiLynxEM)
906			VIDEO_HW_BITBLT		graphic chip supports
907						bit-blit (cf. smiLynxEM)
908			VIDEO_VISIBLE_COLS	visible pixel columns
909						(cols=pitch)
910			VIDEO_VISIBLE_ROWS	visible pixel rows
911			VIDEO_PIXEL_SIZE	bytes per pixel
912			VIDEO_DATA_FORMAT	graphic data format
913						(0-5, cf. cfb_console.c)
914			VIDEO_FB_ADRS		framebuffer address
915			VIDEO_KBD_INIT_FCT	keyboard int fct
916						(i.e. i8042_kbd_init())
917			VIDEO_TSTC_FCT		test char fct
918						(i.e. i8042_tstc)
919			VIDEO_GETC_FCT		get char fct
920						(i.e. i8042_getc)
921			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
922						(requires blink timer
923						cf. i8042.c)
924			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
925			CONFIG_CONSOLE_TIME	display time/date info in
926						upper right corner
927						(requires CONFIG_CMD_DATE)
928			CONFIG_VIDEO_LOGO	display Linux logo in
929						upper left corner
930			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
931						linux_logo.h for logo.
932						Requires CONFIG_VIDEO_LOGO
933			CONFIG_CONSOLE_EXTRA_INFO
934						additional board info beside
935						the logo
936
937		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
938		a limited number of ANSI escape sequences (cursor control,
939		erase functions and limited graphics rendition control).
940
941		When CONFIG_CFB_CONSOLE is defined, video console is
942		default i/o. Serial console can be forced with
943		environment 'console=serial'.
944
945		When CONFIG_SILENT_CONSOLE is defined, all console
946		messages (by U-Boot and Linux!) can be silenced with
947		the "silent" environment variable. See
948		doc/README.silent for more information.
949
950		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
951			is 0x00.
952		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
953			is 0xa0.
954
955- Console Baudrate:
956		CONFIG_BAUDRATE - in bps
957		Select one of the baudrates listed in
958		CONFIG_SYS_BAUDRATE_TABLE, see below.
959		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
960
961- Console Rx buffer length
962		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
963		the maximum receive buffer length for the SMC.
964		This option is actual only for 82xx and 8xx possible.
965		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
966		must be defined, to setup the maximum idle timeout for
967		the SMC.
968
969- Pre-Console Buffer:
970		Prior to the console being initialised (i.e. serial UART
971		initialised etc) all console output is silently discarded.
972		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
973		buffer any console messages prior to the console being
974		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
975		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
976		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
977		bytes are output before the console is initialised, the
978		earlier bytes are discarded.
979
980		'Sane' compilers will generate smaller code if
981		CONFIG_PRE_CON_BUF_SZ is a power of 2
982
983- Safe printf() functions
984		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
985		the printf() functions. These are defined in
986		include/vsprintf.h and include snprintf(), vsnprintf() and
987		so on. Code size increase is approximately 300-500 bytes.
988		If this option is not given then these functions will
989		silently discard their buffer size argument - this means
990		you are not getting any overflow checking in this case.
991
992- Boot Delay:	CONFIG_BOOTDELAY - in seconds
993		Delay before automatically booting the default image;
994		set to -1 to disable autoboot.
995		set to -2 to autoboot with no delay and not check for abort
996		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
997
998		See doc/README.autoboot for these options that
999		work with CONFIG_BOOTDELAY. None are required.
1000		CONFIG_BOOT_RETRY_TIME
1001		CONFIG_BOOT_RETRY_MIN
1002		CONFIG_AUTOBOOT_KEYED
1003		CONFIG_AUTOBOOT_PROMPT
1004		CONFIG_AUTOBOOT_DELAY_STR
1005		CONFIG_AUTOBOOT_STOP_STR
1006		CONFIG_AUTOBOOT_DELAY_STR2
1007		CONFIG_AUTOBOOT_STOP_STR2
1008		CONFIG_ZERO_BOOTDELAY_CHECK
1009		CONFIG_RESET_TO_RETRY
1010
1011- Autoboot Command:
1012		CONFIG_BOOTCOMMAND
1013		Only needed when CONFIG_BOOTDELAY is enabled;
1014		define a command string that is automatically executed
1015		when no character is read on the console interface
1016		within "Boot Delay" after reset.
1017
1018		CONFIG_BOOTARGS
1019		This can be used to pass arguments to the bootm
1020		command. The value of CONFIG_BOOTARGS goes into the
1021		environment value "bootargs".
1022
1023		CONFIG_RAMBOOT and CONFIG_NFSBOOT
1024		The value of these goes into the environment as
1025		"ramboot" and "nfsboot" respectively, and can be used
1026		as a convenience, when switching between booting from
1027		RAM and NFS.
1028
1029- Bootcount:
1030		CONFIG_BOOTCOUNT_LIMIT
1031		Implements a mechanism for detecting a repeating reboot
1032		cycle, see:
1033		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
1034
1035		CONFIG_BOOTCOUNT_ENV
1036		If no softreset save registers are found on the hardware
1037		"bootcount" is stored in the environment. To prevent a
1038		saveenv on all reboots, the environment variable
1039		"upgrade_available" is used. If "upgrade_available" is
1040		0, "bootcount" is always 0, if "upgrade_available" is
1041		1 "bootcount" is incremented in the environment.
1042		So the Userspace Applikation must set the "upgrade_available"
1043		and "bootcount" variable to 0, if a boot was successfully.
1044
1045- Pre-Boot Commands:
1046		CONFIG_PREBOOT
1047
1048		When this option is #defined, the existence of the
1049		environment variable "preboot" will be checked
1050		immediately before starting the CONFIG_BOOTDELAY
1051		countdown and/or running the auto-boot command resp.
1052		entering interactive mode.
1053
1054		This feature is especially useful when "preboot" is
1055		automatically generated or modified. For an example
1056		see the LWMON board specific code: here "preboot" is
1057		modified when the user holds down a certain
1058		combination of keys on the (special) keyboard when
1059		booting the systems
1060
1061- Serial Download Echo Mode:
1062		CONFIG_LOADS_ECHO
1063		If defined to 1, all characters received during a
1064		serial download (using the "loads" command) are
1065		echoed back. This might be needed by some terminal
1066		emulations (like "cu"), but may as well just take
1067		time on others. This setting #define's the initial
1068		value of the "loads_echo" environment variable.
1069
1070- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
1071		CONFIG_KGDB_BAUDRATE
1072		Select one of the baudrates listed in
1073		CONFIG_SYS_BAUDRATE_TABLE, see below.
1074
1075- Monitor Functions:
1076		Monitor commands can be included or excluded
1077		from the build by using the #include files
1078		<config_cmd_all.h> and #undef'ing unwanted
1079		commands, or using <config_cmd_default.h>
1080		and augmenting with additional #define's
1081		for wanted commands.
1082
1083		The default command configuration includes all commands
1084		except those marked below with a "*".
1085
1086		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
1087		CONFIG_CMD_ASKENV	* ask for env variable
1088		CONFIG_CMD_BDI		  bdinfo
1089		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
1090		CONFIG_CMD_BMP		* BMP support
1091		CONFIG_CMD_BSP		* Board specific commands
1092		CONFIG_CMD_BOOTD	  bootd
1093		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
1094		CONFIG_CMD_CACHE	* icache, dcache
1095		CONFIG_CMD_CLK   	* clock command support
1096		CONFIG_CMD_CONSOLE	  coninfo
1097		CONFIG_CMD_CRC32	* crc32
1098		CONFIG_CMD_DATE		* support for RTC, date/time...
1099		CONFIG_CMD_DHCP		* DHCP support
1100		CONFIG_CMD_DIAG		* Diagnostics
1101		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
1102		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1103		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1104		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1105		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1106		CONFIG_CMD_ECHO		  echo arguments
1107		CONFIG_CMD_EDITENV	  edit env variable
1108		CONFIG_CMD_EEPROM	* EEPROM read/write support
1109		CONFIG_CMD_ELF		* bootelf, bootvx
1110		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1111		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1112		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1113		CONFIG_CMD_EXPORTENV	* export the environment
1114		CONFIG_CMD_EXT2		* ext2 command support
1115		CONFIG_CMD_EXT4		* ext4 command support
1116		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1117					  that work for multiple fs types
1118		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1119		CONFIG_CMD_SAVEENV	  saveenv
1120		CONFIG_CMD_FDC		* Floppy Disk Support
1121		CONFIG_CMD_FAT		* FAT command support
1122		CONFIG_CMD_FLASH	  flinfo, erase, protect
1123		CONFIG_CMD_FPGA		  FPGA device initialization support
1124		CONFIG_CMD_FUSE		* Device fuse support
1125		CONFIG_CMD_GETTIME	* Get time since boot
1126		CONFIG_CMD_GO		* the 'go' command (exec code)
1127		CONFIG_CMD_GREPENV	* search environment
1128		CONFIG_CMD_HASH		* calculate hash / digest
1129		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1130		CONFIG_CMD_I2C		* I2C serial bus support
1131		CONFIG_CMD_IDE		* IDE harddisk support
1132		CONFIG_CMD_IMI		  iminfo
1133		CONFIG_CMD_IMLS		  List all images found in NOR flash
1134		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1135		CONFIG_CMD_IMMAP	* IMMR dump support
1136		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1137		CONFIG_CMD_IMPORTENV	* import an environment
1138		CONFIG_CMD_INI		* import data from an ini file into the env
1139		CONFIG_CMD_IRQ		* irqinfo
1140		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1141		CONFIG_CMD_JFFS2	* JFFS2 Support
1142		CONFIG_CMD_KGDB		* kgdb
1143		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1144		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1145					  (169.254.*.*)
1146		CONFIG_CMD_LOADB	  loadb
1147		CONFIG_CMD_LOADS	  loads
1148		CONFIG_CMD_MD5SUM	* print md5 message digest
1149					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1150		CONFIG_CMD_MEMINFO	* Display detailed memory information
1151		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1152					  loop, loopw
1153		CONFIG_CMD_MEMTEST	* mtest
1154		CONFIG_CMD_MISC		  Misc functions like sleep etc
1155		CONFIG_CMD_MMC		* MMC memory mapped support
1156		CONFIG_CMD_MII		* MII utility commands
1157		CONFIG_CMD_MTDPARTS	* MTD partition support
1158		CONFIG_CMD_NAND		* NAND support
1159		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1160		CONFIG_CMD_NFS		  NFS support
1161		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1162		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1163		CONFIG_CMD_PCI		* pciinfo
1164		CONFIG_CMD_PCMCIA		* PCMCIA support
1165		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1166					  host
1167		CONFIG_CMD_PORTIO	* Port I/O
1168		CONFIG_CMD_READ		* Read raw data from partition
1169		CONFIG_CMD_REGINFO	* Register dump
1170		CONFIG_CMD_RUN		  run command in env variable
1171		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1172		CONFIG_CMD_SAVES	* save S record dump
1173		CONFIG_CMD_SCSI		* SCSI Support
1174		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1175					  (requires CONFIG_CMD_I2C)
1176		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1177					  (4xx only)
1178		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1179		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1180					  (requires CONFIG_CMD_MEMORY)
1181		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1182		CONFIG_CMD_SOURCE	  "source" command Support
1183		CONFIG_CMD_SPI		* SPI serial bus support
1184		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1185		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1186		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1187		CONFIG_CMD_TIMER	* access to the system tick timer
1188		CONFIG_CMD_USB		* USB support
1189		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1190		CONFIG_CMD_MFSL		* Microblaze FSL support
1191		CONFIG_CMD_XIMG		  Load part of Multi Image
1192		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1193
1194		EXAMPLE: If you want all functions except of network
1195		support you can write:
1196
1197		#include "config_cmd_all.h"
1198		#undef CONFIG_CMD_NET
1199
1200	Other Commands:
1201		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1202
1203	Note:	Don't enable the "icache" and "dcache" commands
1204		(configuration option CONFIG_CMD_CACHE) unless you know
1205		what you (and your U-Boot users) are doing. Data
1206		cache cannot be enabled on systems like the 8xx or
1207		8260 (where accesses to the IMMR region must be
1208		uncached), and it cannot be disabled on all other
1209		systems where we (mis-) use the data cache to hold an
1210		initial stack and some data.
1211
1212
1213		XXX - this list needs to get updated!
1214
1215- Regular expression support:
1216		CONFIG_REGEX
1217		If this variable is defined, U-Boot is linked against
1218		the SLRE (Super Light Regular Expression) library,
1219		which adds regex support to some commands, as for
1220		example "env grep" and "setexpr".
1221
1222- Device tree:
1223		CONFIG_OF_CONTROL
1224		If this variable is defined, U-Boot will use a device tree
1225		to configure its devices, instead of relying on statically
1226		compiled #defines in the board file. This option is
1227		experimental and only available on a few boards. The device
1228		tree is available in the global data as gd->fdt_blob.
1229
1230		U-Boot needs to get its device tree from somewhere. This can
1231		be done using one of the two options below:
1232
1233		CONFIG_OF_EMBED
1234		If this variable is defined, U-Boot will embed a device tree
1235		binary in its image. This device tree file should be in the
1236		board directory and called <soc>-<board>.dts. The binary file
1237		is then picked up in board_init_f() and made available through
1238		the global data structure as gd->blob.
1239
1240		CONFIG_OF_SEPARATE
1241		If this variable is defined, U-Boot will build a device tree
1242		binary. It will be called u-boot.dtb. Architecture-specific
1243		code will locate it at run-time. Generally this works by:
1244
1245			cat u-boot.bin u-boot.dtb >image.bin
1246
1247		and in fact, U-Boot does this for you, creating a file called
1248		u-boot-dtb.bin which is useful in the common case. You can
1249		still use the individual files if you need something more
1250		exotic.
1251
1252- Watchdog:
1253		CONFIG_WATCHDOG
1254		If this variable is defined, it enables watchdog
1255		support for the SoC. There must be support in the SoC
1256		specific code for a watchdog. For the 8xx and 8260
1257		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1258		register.  When supported for a specific SoC is
1259		available, then no further board specific code should
1260		be needed to use it.
1261
1262		CONFIG_HW_WATCHDOG
1263		When using a watchdog circuitry external to the used
1264		SoC, then define this variable and provide board
1265		specific code for the "hw_watchdog_reset" function.
1266
1267		CONFIG_AT91_HW_WDT_TIMEOUT
1268		specify the timeout in seconds. default 2 seconds.
1269
1270- U-Boot Version:
1271		CONFIG_VERSION_VARIABLE
1272		If this variable is defined, an environment variable
1273		named "ver" is created by U-Boot showing the U-Boot
1274		version as printed by the "version" command.
1275		Any change to this variable will be reverted at the
1276		next reset.
1277
1278- Real-Time Clock:
1279
1280		When CONFIG_CMD_DATE is selected, the type of the RTC
1281		has to be selected, too. Define exactly one of the
1282		following options:
1283
1284		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1285		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1286		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1287		CONFIG_RTC_MC146818	- use MC146818 RTC
1288		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1289		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1290		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1291		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1292		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1293		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1294		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1295		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1296		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1297					  RV3029 RTC.
1298
1299		Note that if the RTC uses I2C, then the I2C interface
1300		must also be configured. See I2C Support, below.
1301
1302- GPIO Support:
1303		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1304
1305		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1306		chip-ngpio pairs that tell the PCA953X driver the number of
1307		pins supported by a particular chip.
1308
1309		Note that if the GPIO device uses I2C, then the I2C interface
1310		must also be configured. See I2C Support, below.
1311
1312- I/O tracing:
1313		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1314		accesses and can checksum them or write a list of them out
1315		to memory. See the 'iotrace' command for details. This is
1316		useful for testing device drivers since it can confirm that
1317		the driver behaves the same way before and after a code
1318		change. Currently this is supported on sandbox and arm. To
1319		add support for your architecture, add '#include <iotrace.h>'
1320		to the bottom of arch/<arch>/include/asm/io.h and test.
1321
1322		Example output from the 'iotrace stats' command is below.
1323		Note that if the trace buffer is exhausted, the checksum will
1324		still continue to operate.
1325
1326			iotrace is enabled
1327			Start:  10000000	(buffer start address)
1328			Size:   00010000	(buffer size)
1329			Offset: 00000120	(current buffer offset)
1330			Output: 10000120	(start + offset)
1331			Count:  00000018	(number of trace records)
1332			CRC32:  9526fb66	(CRC32 of all trace records)
1333
1334- Timestamp Support:
1335
1336		When CONFIG_TIMESTAMP is selected, the timestamp
1337		(date and time) of an image is printed by image
1338		commands like bootm or iminfo. This option is
1339		automatically enabled when you select CONFIG_CMD_DATE .
1340
1341- Partition Labels (disklabels) Supported:
1342		Zero or more of the following:
1343		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1344		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1345				       Intel architecture, USB sticks, etc.
1346		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1347		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1348				       bootloader.  Note 2TB partition limit; see
1349				       disk/part_efi.c
1350		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1351
1352		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1353		CONFIG_CMD_SCSI) you must configure support for at
1354		least one non-MTD partition type as well.
1355
1356- IDE Reset method:
1357		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1358		board configurations files but used nowhere!
1359
1360		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1361		be performed by calling the function
1362			ide_set_reset(int reset)
1363		which has to be defined in a board specific file
1364
1365- ATAPI Support:
1366		CONFIG_ATAPI
1367
1368		Set this to enable ATAPI support.
1369
1370- LBA48 Support
1371		CONFIG_LBA48
1372
1373		Set this to enable support for disks larger than 137GB
1374		Also look at CONFIG_SYS_64BIT_LBA.
1375		Whithout these , LBA48 support uses 32bit variables and will 'only'
1376		support disks up to 2.1TB.
1377
1378		CONFIG_SYS_64BIT_LBA:
1379			When enabled, makes the IDE subsystem use 64bit sector addresses.
1380			Default is 32bit.
1381
1382- SCSI Support:
1383		At the moment only there is only support for the
1384		SYM53C8XX SCSI controller; define
1385		CONFIG_SCSI_SYM53C8XX to enable it.
1386
1387		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1388		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1389		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1390		maximum numbers of LUNs, SCSI ID's and target
1391		devices.
1392		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1393
1394		The environment variable 'scsidevs' is set to the number of
1395		SCSI devices found during the last scan.
1396
1397- NETWORK Support (PCI):
1398		CONFIG_E1000
1399		Support for Intel 8254x/8257x gigabit chips.
1400
1401		CONFIG_E1000_SPI
1402		Utility code for direct access to the SPI bus on Intel 8257x.
1403		This does not do anything useful unless you set at least one
1404		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1405
1406		CONFIG_E1000_SPI_GENERIC
1407		Allow generic access to the SPI bus on the Intel 8257x, for
1408		example with the "sspi" command.
1409
1410		CONFIG_CMD_E1000
1411		Management command for E1000 devices.  When used on devices
1412		with SPI support you can reprogram the EEPROM from U-Boot.
1413
1414		CONFIG_E1000_FALLBACK_MAC
1415		default MAC for empty EEPROM after production.
1416
1417		CONFIG_EEPRO100
1418		Support for Intel 82557/82559/82559ER chips.
1419		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1420		write routine for first time initialisation.
1421
1422		CONFIG_TULIP
1423		Support for Digital 2114x chips.
1424		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1425		modem chip initialisation (KS8761/QS6611).
1426
1427		CONFIG_NATSEMI
1428		Support for National dp83815 chips.
1429
1430		CONFIG_NS8382X
1431		Support for National dp8382[01] gigabit chips.
1432
1433- NETWORK Support (other):
1434
1435		CONFIG_DRIVER_AT91EMAC
1436		Support for AT91RM9200 EMAC.
1437
1438			CONFIG_RMII
1439			Define this to use reduced MII inteface
1440
1441			CONFIG_DRIVER_AT91EMAC_QUIET
1442			If this defined, the driver is quiet.
1443			The driver doen't show link status messages.
1444
1445		CONFIG_CALXEDA_XGMAC
1446		Support for the Calxeda XGMAC device
1447
1448		CONFIG_LAN91C96
1449		Support for SMSC's LAN91C96 chips.
1450
1451			CONFIG_LAN91C96_BASE
1452			Define this to hold the physical address
1453			of the LAN91C96's I/O space
1454
1455			CONFIG_LAN91C96_USE_32_BIT
1456			Define this to enable 32 bit addressing
1457
1458		CONFIG_SMC91111
1459		Support for SMSC's LAN91C111 chip
1460
1461			CONFIG_SMC91111_BASE
1462			Define this to hold the physical address
1463			of the device (I/O space)
1464
1465			CONFIG_SMC_USE_32_BIT
1466			Define this if data bus is 32 bits
1467
1468			CONFIG_SMC_USE_IOFUNCS
1469			Define this to use i/o functions instead of macros
1470			(some hardware wont work with macros)
1471
1472		CONFIG_DRIVER_TI_EMAC
1473		Support for davinci emac
1474
1475			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1476			Define this if you have more then 3 PHYs.
1477
1478		CONFIG_FTGMAC100
1479		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1480
1481			CONFIG_FTGMAC100_EGIGA
1482			Define this to use GE link update with gigabit PHY.
1483			Define this if FTGMAC100 is connected to gigabit PHY.
1484			If your system has 10/100 PHY only, it might not occur
1485			wrong behavior. Because PHY usually return timeout or
1486			useless data when polling gigabit status and gigabit
1487			control registers. This behavior won't affect the
1488			correctnessof 10/100 link speed update.
1489
1490		CONFIG_SMC911X
1491		Support for SMSC's LAN911x and LAN921x chips
1492
1493			CONFIG_SMC911X_BASE
1494			Define this to hold the physical address
1495			of the device (I/O space)
1496
1497			CONFIG_SMC911X_32_BIT
1498			Define this if data bus is 32 bits
1499
1500			CONFIG_SMC911X_16_BIT
1501			Define this if data bus is 16 bits. If your processor
1502			automatically converts one 32 bit word to two 16 bit
1503			words you may also try CONFIG_SMC911X_32_BIT.
1504
1505		CONFIG_SH_ETHER
1506		Support for Renesas on-chip Ethernet controller
1507
1508			CONFIG_SH_ETHER_USE_PORT
1509			Define the number of ports to be used
1510
1511			CONFIG_SH_ETHER_PHY_ADDR
1512			Define the ETH PHY's address
1513
1514			CONFIG_SH_ETHER_CACHE_WRITEBACK
1515			If this option is set, the driver enables cache flush.
1516
1517- PWM Support:
1518		CONFIG_PWM_IMX
1519		Support for PWM modul on the imx6.
1520
1521- TPM Support:
1522		CONFIG_TPM
1523		Support TPM devices.
1524
1525		CONFIG_TPM_TIS_I2C
1526		Support for i2c bus TPM devices. Only one device
1527		per system is supported at this time.
1528
1529			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1530			Define the the i2c bus number for the TPM device
1531
1532			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1533			Define the TPM's address on the i2c bus
1534
1535			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1536			Define the burst count bytes upper limit
1537
1538		CONFIG_TPM_ATMEL_TWI
1539		Support for Atmel TWI TPM device. Requires I2C support.
1540
1541		CONFIG_TPM_TIS_LPC
1542		Support for generic parallel port TPM devices. Only one device
1543		per system is supported at this time.
1544
1545			CONFIG_TPM_TIS_BASE_ADDRESS
1546			Base address where the generic TPM device is mapped
1547			to. Contemporary x86 systems usually map it at
1548			0xfed40000.
1549
1550		CONFIG_CMD_TPM
1551		Add tpm monitor functions.
1552		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1553		provides monitor access to authorized functions.
1554
1555		CONFIG_TPM
1556		Define this to enable the TPM support library which provides
1557		functional interfaces to some TPM commands.
1558		Requires support for a TPM device.
1559
1560		CONFIG_TPM_AUTH_SESSIONS
1561		Define this to enable authorized functions in the TPM library.
1562		Requires CONFIG_TPM and CONFIG_SHA1.
1563
1564- USB Support:
1565		At the moment only the UHCI host controller is
1566		supported (PIP405, MIP405, MPC5200); define
1567		CONFIG_USB_UHCI to enable it.
1568		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1569		and define CONFIG_USB_STORAGE to enable the USB
1570		storage devices.
1571		Note:
1572		Supported are USB Keyboards and USB Floppy drives
1573		(TEAC FD-05PUB).
1574		MPC5200 USB requires additional defines:
1575			CONFIG_USB_CLOCK
1576				for 528 MHz Clock: 0x0001bbbb
1577			CONFIG_PSC3_USB
1578				for USB on PSC3
1579			CONFIG_USB_CONFIG
1580				for differential drivers: 0x00001000
1581				for single ended drivers: 0x00005000
1582				for differential drivers on PSC3: 0x00000100
1583				for single ended drivers on PSC3: 0x00004100
1584			CONFIG_SYS_USB_EVENT_POLL
1585				May be defined to allow interrupt polling
1586				instead of using asynchronous interrupts
1587
1588		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1589		txfilltuning field in the EHCI controller on reset.
1590
1591		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1592		HW module registers.
1593
1594- USB Device:
1595		Define the below if you wish to use the USB console.
1596		Once firmware is rebuilt from a serial console issue the
1597		command "setenv stdin usbtty; setenv stdout usbtty" and
1598		attach your USB cable. The Unix command "dmesg" should print
1599		it has found a new device. The environment variable usbtty
1600		can be set to gserial or cdc_acm to enable your device to
1601		appear to a USB host as a Linux gserial device or a
1602		Common Device Class Abstract Control Model serial device.
1603		If you select usbtty = gserial you should be able to enumerate
1604		a Linux host by
1605		# modprobe usbserial vendor=0xVendorID product=0xProductID
1606		else if using cdc_acm, simply setting the environment
1607		variable usbtty to be cdc_acm should suffice. The following
1608		might be defined in YourBoardName.h
1609
1610			CONFIG_USB_DEVICE
1611			Define this to build a UDC device
1612
1613			CONFIG_USB_TTY
1614			Define this to have a tty type of device available to
1615			talk to the UDC device
1616
1617			CONFIG_USBD_HS
1618			Define this to enable the high speed support for usb
1619			device and usbtty. If this feature is enabled, a routine
1620			int is_usbd_high_speed(void)
1621			also needs to be defined by the driver to dynamically poll
1622			whether the enumeration has succeded at high speed or full
1623			speed.
1624
1625			CONFIG_SYS_CONSOLE_IS_IN_ENV
1626			Define this if you want stdin, stdout &/or stderr to
1627			be set to usbtty.
1628
1629			mpc8xx:
1630				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1631				Derive USB clock from external clock "blah"
1632				- CONFIG_SYS_USB_EXTC_CLK 0x02
1633
1634				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1635				Derive USB clock from brgclk
1636				- CONFIG_SYS_USB_BRG_CLK 0x04
1637
1638		If you have a USB-IF assigned VendorID then you may wish to
1639		define your own vendor specific values either in BoardName.h
1640		or directly in usbd_vendor_info.h. If you don't define
1641		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1642		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1643		should pretend to be a Linux device to it's target host.
1644
1645			CONFIG_USBD_MANUFACTURER
1646			Define this string as the name of your company for
1647			- CONFIG_USBD_MANUFACTURER "my company"
1648
1649			CONFIG_USBD_PRODUCT_NAME
1650			Define this string as the name of your product
1651			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1652
1653			CONFIG_USBD_VENDORID
1654			Define this as your assigned Vendor ID from the USB
1655			Implementors Forum. This *must* be a genuine Vendor ID
1656			to avoid polluting the USB namespace.
1657			- CONFIG_USBD_VENDORID 0xFFFF
1658
1659			CONFIG_USBD_PRODUCTID
1660			Define this as the unique Product ID
1661			for your device
1662			- CONFIG_USBD_PRODUCTID 0xFFFF
1663
1664- ULPI Layer Support:
1665		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1666		the generic ULPI layer. The generic layer accesses the ULPI PHY
1667		via the platform viewport, so you need both the genric layer and
1668		the viewport enabled. Currently only Chipidea/ARC based
1669		viewport is supported.
1670		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1671		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1672		If your ULPI phy needs a different reference clock than the
1673		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1674		the appropriate value in Hz.
1675
1676- MMC Support:
1677		The MMC controller on the Intel PXA is supported. To
1678		enable this define CONFIG_MMC. The MMC can be
1679		accessed from the boot prompt by mapping the device
1680		to physical memory similar to flash. Command line is
1681		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1682		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1683
1684		CONFIG_SH_MMCIF
1685		Support for Renesas on-chip MMCIF controller
1686
1687			CONFIG_SH_MMCIF_ADDR
1688			Define the base address of MMCIF registers
1689
1690			CONFIG_SH_MMCIF_CLK
1691			Define the clock frequency for MMCIF
1692
1693		CONFIG_GENERIC_MMC
1694		Enable the generic MMC driver
1695
1696		CONFIG_SUPPORT_EMMC_BOOT
1697		Enable some additional features of the eMMC boot partitions.
1698
1699		CONFIG_SUPPORT_EMMC_RPMB
1700		Enable the commands for reading, writing and programming the
1701		key for the Replay Protection Memory Block partition in eMMC.
1702
1703- USB Device Firmware Update (DFU) class support:
1704		CONFIG_DFU_FUNCTION
1705		This enables the USB portion of the DFU USB class
1706
1707		CONFIG_CMD_DFU
1708		This enables the command "dfu" which is used to have
1709		U-Boot create a DFU class device via USB.  This command
1710		requires that the "dfu_alt_info" environment variable be
1711		set and define the alt settings to expose to the host.
1712
1713		CONFIG_DFU_MMC
1714		This enables support for exposing (e)MMC devices via DFU.
1715
1716		CONFIG_DFU_NAND
1717		This enables support for exposing NAND devices via DFU.
1718
1719		CONFIG_DFU_RAM
1720		This enables support for exposing RAM via DFU.
1721		Note: DFU spec refer to non-volatile memory usage, but
1722		allow usages beyond the scope of spec - here RAM usage,
1723		one that would help mostly the developer.
1724
1725		CONFIG_SYS_DFU_DATA_BUF_SIZE
1726		Dfu transfer uses a buffer before writing data to the
1727		raw storage device. Make the size (in bytes) of this buffer
1728		configurable. The size of this buffer is also configurable
1729		through the "dfu_bufsiz" environment variable.
1730
1731		CONFIG_SYS_DFU_MAX_FILE_SIZE
1732		When updating files rather than the raw storage device,
1733		we use a static buffer to copy the file into and then write
1734		the buffer once we've been given the whole file.  Define
1735		this to the maximum filesize (in bytes) for the buffer.
1736		Default is 4 MiB if undefined.
1737
1738		DFU_DEFAULT_POLL_TIMEOUT
1739		Poll timeout [ms], is the timeout a device can send to the
1740		host. The host must wait for this timeout before sending
1741		a subsequent DFU_GET_STATUS request to the device.
1742
1743		DFU_MANIFEST_POLL_TIMEOUT
1744		Poll timeout [ms], which the device sends to the host when
1745		entering dfuMANIFEST state. Host waits this timeout, before
1746		sending again an USB request to the device.
1747
1748- USB Device Android Fastboot support:
1749		CONFIG_CMD_FASTBOOT
1750		This enables the command "fastboot" which enables the Android
1751		fastboot mode for the platform's USB device. Fastboot is a USB
1752		protocol for downloading images, flashing and device control
1753		used on Android devices.
1754		See doc/README.android-fastboot for more information.
1755
1756		CONFIG_ANDROID_BOOT_IMAGE
1757		This enables support for booting images which use the Android
1758		image format header.
1759
1760		CONFIG_USB_FASTBOOT_BUF_ADDR
1761		The fastboot protocol requires a large memory buffer for
1762		downloads. Define this to the starting RAM address to use for
1763		downloaded images.
1764
1765		CONFIG_USB_FASTBOOT_BUF_SIZE
1766		The fastboot protocol requires a large memory buffer for
1767		downloads. This buffer should be as large as possible for a
1768		platform. Define this to the size available RAM for fastboot.
1769
1770		CONFIG_FASTBOOT_FLASH
1771		The fastboot protocol includes a "flash" command for writing
1772		the downloaded image to a non-volatile storage device. Define
1773		this to enable the "fastboot flash" command.
1774
1775		CONFIG_FASTBOOT_FLASH_MMC_DEV
1776		The fastboot "flash" command requires additional information
1777		regarding the non-volatile storage device. Define this to
1778		the eMMC device that fastboot should use to store the image.
1779
1780		CONFIG_FASTBOOT_GPT_NAME
1781		The fastboot "flash" command supports writing the downloaded
1782		image to the Protective MBR and the Primary GUID Partition
1783		Table. (Additionally, this downloaded image is post-processed
1784		to generate and write the Backup GUID Partition Table.)
1785		This occurs when the specified "partition name" on the
1786		"fastboot flash" command line matches this value.
1787		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1788
1789- Journaling Flash filesystem support:
1790		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1791		CONFIG_JFFS2_NAND_DEV
1792		Define these for a default partition on a NAND device
1793
1794		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1795		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1796		Define these for a default partition on a NOR device
1797
1798		CONFIG_SYS_JFFS_CUSTOM_PART
1799		Define this to create an own partition. You have to provide a
1800		function struct part_info* jffs2_part_info(int part_num)
1801
1802		If you define only one JFFS2 partition you may also want to
1803		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1804		to disable the command chpart. This is the default when you
1805		have not defined a custom partition
1806
1807- FAT(File Allocation Table) filesystem write function support:
1808		CONFIG_FAT_WRITE
1809
1810		Define this to enable support for saving memory data as a
1811		file in FAT formatted partition.
1812
1813		This will also enable the command "fatwrite" enabling the
1814		user to write files to FAT.
1815
1816CBFS (Coreboot Filesystem) support
1817		CONFIG_CMD_CBFS
1818
1819		Define this to enable support for reading from a Coreboot
1820		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1821		and cbfsload.
1822
1823- FAT(File Allocation Table) filesystem cluster size:
1824		CONFIG_FS_FAT_MAX_CLUSTSIZE
1825
1826		Define the max cluster size for fat operations else
1827		a default value of 65536 will be defined.
1828
1829- Keyboard Support:
1830		CONFIG_ISA_KEYBOARD
1831
1832		Define this to enable standard (PC-Style) keyboard
1833		support
1834
1835		CONFIG_I8042_KBD
1836		Standard PC keyboard driver with US (is default) and
1837		GERMAN key layout (switch via environment 'keymap=de') support.
1838		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1839		for cfb_console. Supports cursor blinking.
1840
1841		CONFIG_CROS_EC_KEYB
1842		Enables a Chrome OS keyboard using the CROS_EC interface.
1843		This uses CROS_EC to communicate with a second microcontroller
1844		which provides key scans on request.
1845
1846- Video support:
1847		CONFIG_VIDEO
1848
1849		Define this to enable video support (for output to
1850		video).
1851
1852		CONFIG_VIDEO_CT69000
1853
1854		Enable Chips & Technologies 69000 Video chip
1855
1856		CONFIG_VIDEO_SMI_LYNXEM
1857		Enable Silicon Motion SMI 712/710/810 Video chip. The
1858		video output is selected via environment 'videoout'
1859		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1860		assumed.
1861
1862		For the CT69000 and SMI_LYNXEM drivers, videomode is
1863		selected via environment 'videomode'. Two different ways
1864		are possible:
1865		- "videomode=num"   'num' is a standard LiLo mode numbers.
1866		Following standard modes are supported	(* is default):
1867
1868		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1869		-------------+---------------------------------------------
1870		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1871		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1872		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1873		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1874		-------------+---------------------------------------------
1875		(i.e. setenv videomode 317; saveenv; reset;)
1876
1877		- "videomode=bootargs" all the video parameters are parsed
1878		from the bootargs. (See drivers/video/videomodes.c)
1879
1880
1881		CONFIG_VIDEO_SED13806
1882		Enable Epson SED13806 driver. This driver supports 8bpp
1883		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1884		or CONFIG_VIDEO_SED13806_16BPP
1885
1886		CONFIG_FSL_DIU_FB
1887		Enable the Freescale DIU video driver.	Reference boards for
1888		SOCs that have a DIU should define this macro to enable DIU
1889		support, and should also define these other macros:
1890
1891			CONFIG_SYS_DIU_ADDR
1892			CONFIG_VIDEO
1893			CONFIG_CMD_BMP
1894			CONFIG_CFB_CONSOLE
1895			CONFIG_VIDEO_SW_CURSOR
1896			CONFIG_VGA_AS_SINGLE_DEVICE
1897			CONFIG_VIDEO_LOGO
1898			CONFIG_VIDEO_BMP_LOGO
1899
1900		The DIU driver will look for the 'video-mode' environment
1901		variable, and if defined, enable the DIU as a console during
1902		boot.  See the documentation file README.video for a
1903		description of this variable.
1904
1905		CONFIG_VIDEO_VGA
1906
1907		Enable the VGA video / BIOS for x86. The alternative if you
1908		are using coreboot is to use the coreboot frame buffer
1909		driver.
1910
1911
1912- Keyboard Support:
1913		CONFIG_KEYBOARD
1914
1915		Define this to enable a custom keyboard support.
1916		This simply calls drv_keyboard_init() which must be
1917		defined in your board-specific files.
1918		The only board using this so far is RBC823.
1919
1920- LCD Support:	CONFIG_LCD
1921
1922		Define this to enable LCD support (for output to LCD
1923		display); also select one of the supported displays
1924		by defining one of these:
1925
1926		CONFIG_ATMEL_LCD:
1927
1928			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1929
1930		CONFIG_NEC_NL6448AC33:
1931
1932			NEC NL6448AC33-18. Active, color, single scan.
1933
1934		CONFIG_NEC_NL6448BC20
1935
1936			NEC NL6448BC20-08. 6.5", 640x480.
1937			Active, color, single scan.
1938
1939		CONFIG_NEC_NL6448BC33_54
1940
1941			NEC NL6448BC33-54. 10.4", 640x480.
1942			Active, color, single scan.
1943
1944		CONFIG_SHARP_16x9
1945
1946			Sharp 320x240. Active, color, single scan.
1947			It isn't 16x9, and I am not sure what it is.
1948
1949		CONFIG_SHARP_LQ64D341
1950
1951			Sharp LQ64D341 display, 640x480.
1952			Active, color, single scan.
1953
1954		CONFIG_HLD1045
1955
1956			HLD1045 display, 640x480.
1957			Active, color, single scan.
1958
1959		CONFIG_OPTREX_BW
1960
1961			Optrex	 CBL50840-2 NF-FW 99 22 M5
1962			or
1963			Hitachi	 LMG6912RPFC-00T
1964			or
1965			Hitachi	 SP14Q002
1966
1967			320x240. Black & white.
1968
1969		Normally display is black on white background; define
1970		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1971
1972		CONFIG_LCD_ALIGNMENT
1973
1974		Normally the LCD is page-aligned (typically 4KB). If this is
1975		defined then the LCD will be aligned to this value instead.
1976		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1977		here, since it is cheaper to change data cache settings on
1978		a per-section basis.
1979
1980		CONFIG_CONSOLE_SCROLL_LINES
1981
1982		When the console need to be scrolled, this is the number of
1983		lines to scroll by. It defaults to 1. Increasing this makes
1984		the console jump but can help speed up operation when scrolling
1985		is slow.
1986
1987		CONFIG_LCD_BMP_RLE8
1988
1989		Support drawing of RLE8-compressed bitmaps on the LCD.
1990
1991		CONFIG_I2C_EDID
1992
1993		Enables an 'i2c edid' command which can read EDID
1994		information over I2C from an attached LCD display.
1995
1996- Splash Screen Support: CONFIG_SPLASH_SCREEN
1997
1998		If this option is set, the environment is checked for
1999		a variable "splashimage". If found, the usual display
2000		of logo, copyright and system information on the LCD
2001		is suppressed and the BMP image at the address
2002		specified in "splashimage" is loaded instead. The
2003		console is redirected to the "nulldev", too. This
2004		allows for a "silent" boot where a splash screen is
2005		loaded very quickly after power-on.
2006
2007		CONFIG_SPLASHIMAGE_GUARD
2008
2009		If this option is set, then U-Boot will prevent the environment
2010		variable "splashimage" from being set to a problematic address
2011		(see README.displaying-bmps).
2012		This option is useful for targets where, due to alignment
2013		restrictions, an improperly aligned BMP image will cause a data
2014		abort. If you think you will not have problems with unaligned
2015		accesses (for example because your toolchain prevents them)
2016		there is no need to set this option.
2017
2018		CONFIG_SPLASH_SCREEN_ALIGN
2019
2020		If this option is set the splash image can be freely positioned
2021		on the screen. Environment variable "splashpos" specifies the
2022		position as "x,y". If a positive number is given it is used as
2023		number of pixel from left/top. If a negative number is given it
2024		is used as number of pixel from right/bottom. You can also
2025		specify 'm' for centering the image.
2026
2027		Example:
2028		setenv splashpos m,m
2029			=> image at center of screen
2030
2031		setenv splashpos 30,20
2032			=> image at x = 30 and y = 20
2033
2034		setenv splashpos -10,m
2035			=> vertically centered image
2036			   at x = dspWidth - bmpWidth - 9
2037
2038- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
2039
2040		If this option is set, additionally to standard BMP
2041		images, gzipped BMP images can be displayed via the
2042		splashscreen support or the bmp command.
2043
2044- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
2045
2046		If this option is set, 8-bit RLE compressed BMP images
2047		can be displayed via the splashscreen support or the
2048		bmp command.
2049
2050- Do compressing for memory range:
2051		CONFIG_CMD_ZIP
2052
2053		If this option is set, it would use zlib deflate method
2054		to compress the specified memory at its best effort.
2055
2056- Compression support:
2057		CONFIG_GZIP
2058
2059		Enabled by default to support gzip compressed images.
2060
2061		CONFIG_BZIP2
2062
2063		If this option is set, support for bzip2 compressed
2064		images is included. If not, only uncompressed and gzip
2065		compressed images are supported.
2066
2067		NOTE: the bzip2 algorithm requires a lot of RAM, so
2068		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
2069		be at least 4MB.
2070
2071		CONFIG_LZMA
2072
2073		If this option is set, support for lzma compressed
2074		images is included.
2075
2076		Note: The LZMA algorithm adds between 2 and 4KB of code and it
2077		requires an amount of dynamic memory that is given by the
2078		formula:
2079
2080			(1846 + 768 << (lc + lp)) * sizeof(uint16)
2081
2082		Where lc and lp stand for, respectively, Literal context bits
2083		and Literal pos bits.
2084
2085		This value is upper-bounded by 14MB in the worst case. Anyway,
2086		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
2087		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
2088		a very small buffer.
2089
2090		Use the lzmainfo tool to determinate the lc and lp values and
2091		then calculate the amount of needed dynamic memory (ensuring
2092		the appropriate CONFIG_SYS_MALLOC_LEN value).
2093
2094		CONFIG_LZO
2095
2096		If this option is set, support for LZO compressed images
2097		is included.
2098
2099- MII/PHY support:
2100		CONFIG_PHY_ADDR
2101
2102		The address of PHY on MII bus.
2103
2104		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2105
2106		The clock frequency of the MII bus
2107
2108		CONFIG_PHY_GIGE
2109
2110		If this option is set, support for speed/duplex
2111		detection of gigabit PHY is included.
2112
2113		CONFIG_PHY_RESET_DELAY
2114
2115		Some PHY like Intel LXT971A need extra delay after
2116		reset before any MII register access is possible.
2117		For such PHY, set this option to the usec delay
2118		required. (minimum 300usec for LXT971A)
2119
2120		CONFIG_PHY_CMD_DELAY (ppc4xx)
2121
2122		Some PHY like Intel LXT971A need extra delay after
2123		command issued before MII status register can be read
2124
2125- Ethernet address:
2126		CONFIG_ETHADDR
2127		CONFIG_ETH1ADDR
2128		CONFIG_ETH2ADDR
2129		CONFIG_ETH3ADDR
2130		CONFIG_ETH4ADDR
2131		CONFIG_ETH5ADDR
2132
2133		Define a default value for Ethernet address to use
2134		for the respective Ethernet interface, in case this
2135		is not determined automatically.
2136
2137- IP address:
2138		CONFIG_IPADDR
2139
2140		Define a default value for the IP address to use for
2141		the default Ethernet interface, in case this is not
2142		determined through e.g. bootp.
2143		(Environment variable "ipaddr")
2144
2145- Server IP address:
2146		CONFIG_SERVERIP
2147
2148		Defines a default value for the IP address of a TFTP
2149		server to contact when using the "tftboot" command.
2150		(Environment variable "serverip")
2151
2152		CONFIG_KEEP_SERVERADDR
2153
2154		Keeps the server's MAC address, in the env 'serveraddr'
2155		for passing to bootargs (like Linux's netconsole option)
2156
2157- Gateway IP address:
2158		CONFIG_GATEWAYIP
2159
2160		Defines a default value for the IP address of the
2161		default router where packets to other networks are
2162		sent to.
2163		(Environment variable "gatewayip")
2164
2165- Subnet mask:
2166		CONFIG_NETMASK
2167
2168		Defines a default value for the subnet mask (or
2169		routing prefix) which is used to determine if an IP
2170		address belongs to the local subnet or needs to be
2171		forwarded through a router.
2172		(Environment variable "netmask")
2173
2174- Multicast TFTP Mode:
2175		CONFIG_MCAST_TFTP
2176
2177		Defines whether you want to support multicast TFTP as per
2178		rfc-2090; for example to work with atftp.  Lets lots of targets
2179		tftp down the same boot image concurrently.  Note: the Ethernet
2180		driver in use must provide a function: mcast() to join/leave a
2181		multicast group.
2182
2183- BOOTP Recovery Mode:
2184		CONFIG_BOOTP_RANDOM_DELAY
2185
2186		If you have many targets in a network that try to
2187		boot using BOOTP, you may want to avoid that all
2188		systems send out BOOTP requests at precisely the same
2189		moment (which would happen for instance at recovery
2190		from a power failure, when all systems will try to
2191		boot, thus flooding the BOOTP server. Defining
2192		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2193		inserted before sending out BOOTP requests. The
2194		following delays are inserted then:
2195
2196		1st BOOTP request:	delay 0 ... 1 sec
2197		2nd BOOTP request:	delay 0 ... 2 sec
2198		3rd BOOTP request:	delay 0 ... 4 sec
2199		4th and following
2200		BOOTP requests:		delay 0 ... 8 sec
2201
2202		CONFIG_BOOTP_ID_CACHE_SIZE
2203
2204		BOOTP packets are uniquely identified using a 32-bit ID. The
2205		server will copy the ID from client requests to responses and
2206		U-Boot will use this to determine if it is the destination of
2207		an incoming response. Some servers will check that addresses
2208		aren't in use before handing them out (usually using an ARP
2209		ping) and therefore take up to a few hundred milliseconds to
2210		respond. Network congestion may also influence the time it
2211		takes for a response to make it back to the client. If that
2212		time is too long, U-Boot will retransmit requests. In order
2213		to allow earlier responses to still be accepted after these
2214		retransmissions, U-Boot's BOOTP client keeps a small cache of
2215		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2216		cache. The default is to keep IDs for up to four outstanding
2217		requests. Increasing this will allow U-Boot to accept offers
2218		from a BOOTP client in networks with unusually high latency.
2219
2220- DHCP Advanced Options:
2221		You can fine tune the DHCP functionality by defining
2222		CONFIG_BOOTP_* symbols:
2223
2224		CONFIG_BOOTP_SUBNETMASK
2225		CONFIG_BOOTP_GATEWAY
2226		CONFIG_BOOTP_HOSTNAME
2227		CONFIG_BOOTP_NISDOMAIN
2228		CONFIG_BOOTP_BOOTPATH
2229		CONFIG_BOOTP_BOOTFILESIZE
2230		CONFIG_BOOTP_DNS
2231		CONFIG_BOOTP_DNS2
2232		CONFIG_BOOTP_SEND_HOSTNAME
2233		CONFIG_BOOTP_NTPSERVER
2234		CONFIG_BOOTP_TIMEOFFSET
2235		CONFIG_BOOTP_VENDOREX
2236		CONFIG_BOOTP_MAY_FAIL
2237
2238		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2239		environment variable, not the BOOTP server.
2240
2241		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2242		after the configured retry count, the call will fail
2243		instead of starting over.  This can be used to fail over
2244		to Link-local IP address configuration if the DHCP server
2245		is not available.
2246
2247		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2248		serverip from a DHCP server, it is possible that more
2249		than one DNS serverip is offered to the client.
2250		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2251		serverip will be stored in the additional environment
2252		variable "dnsip2". The first DNS serverip is always
2253		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2254		is defined.
2255
2256		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2257		to do a dynamic update of a DNS server. To do this, they
2258		need the hostname of the DHCP requester.
2259		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2260		of the "hostname" environment variable is passed as
2261		option 12 to the DHCP server.
2262
2263		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2264
2265		A 32bit value in microseconds for a delay between
2266		receiving a "DHCP Offer" and sending the "DHCP Request".
2267		This fixes a problem with certain DHCP servers that don't
2268		respond 100% of the time to a "DHCP request". E.g. On an
2269		AT91RM9200 processor running at 180MHz, this delay needed
2270		to be *at least* 15,000 usec before a Windows Server 2003
2271		DHCP server would reply 100% of the time. I recommend at
2272		least 50,000 usec to be safe. The alternative is to hope
2273		that one of the retries will be successful but note that
2274		the DHCP timeout and retry process takes a longer than
2275		this delay.
2276
2277 - Link-local IP address negotiation:
2278		Negotiate with other link-local clients on the local network
2279		for an address that doesn't require explicit configuration.
2280		This is especially useful if a DHCP server cannot be guaranteed
2281		to exist in all environments that the device must operate.
2282
2283		See doc/README.link-local for more information.
2284
2285 - CDP Options:
2286		CONFIG_CDP_DEVICE_ID
2287
2288		The device id used in CDP trigger frames.
2289
2290		CONFIG_CDP_DEVICE_ID_PREFIX
2291
2292		A two character string which is prefixed to the MAC address
2293		of the device.
2294
2295		CONFIG_CDP_PORT_ID
2296
2297		A printf format string which contains the ascii name of
2298		the port. Normally is set to "eth%d" which sets
2299		eth0 for the first Ethernet, eth1 for the second etc.
2300
2301		CONFIG_CDP_CAPABILITIES
2302
2303		A 32bit integer which indicates the device capabilities;
2304		0x00000010 for a normal host which does not forwards.
2305
2306		CONFIG_CDP_VERSION
2307
2308		An ascii string containing the version of the software.
2309
2310		CONFIG_CDP_PLATFORM
2311
2312		An ascii string containing the name of the platform.
2313
2314		CONFIG_CDP_TRIGGER
2315
2316		A 32bit integer sent on the trigger.
2317
2318		CONFIG_CDP_POWER_CONSUMPTION
2319
2320		A 16bit integer containing the power consumption of the
2321		device in .1 of milliwatts.
2322
2323		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2324
2325		A byte containing the id of the VLAN.
2326
2327- Status LED:	CONFIG_STATUS_LED
2328
2329		Several configurations allow to display the current
2330		status using a LED. For instance, the LED will blink
2331		fast while running U-Boot code, stop blinking as
2332		soon as a reply to a BOOTP request was received, and
2333		start blinking slow once the Linux kernel is running
2334		(supported by a status LED driver in the Linux
2335		kernel). Defining CONFIG_STATUS_LED enables this
2336		feature in U-Boot.
2337
2338		Additional options:
2339
2340		CONFIG_GPIO_LED
2341		The status LED can be connected to a GPIO pin.
2342		In such cases, the gpio_led driver can be used as a
2343		status LED backend implementation. Define CONFIG_GPIO_LED
2344		to include the gpio_led driver in the U-Boot binary.
2345
2346		CONFIG_GPIO_LED_INVERTED_TABLE
2347		Some GPIO connected LEDs may have inverted polarity in which
2348		case the GPIO high value corresponds to LED off state and
2349		GPIO low value corresponds to LED on state.
2350		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2351		with a list of GPIO LEDs that have inverted polarity.
2352
2353- CAN Support:	CONFIG_CAN_DRIVER
2354
2355		Defining CONFIG_CAN_DRIVER enables CAN driver support
2356		on those systems that support this (optional)
2357		feature, like the TQM8xxL modules.
2358
2359- I2C Support:	CONFIG_SYS_I2C
2360
2361		This enable the NEW i2c subsystem, and will allow you to use
2362		i2c commands at the u-boot command line (as long as you set
2363		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2364		based realtime clock chips or other i2c devices. See
2365		common/cmd_i2c.c for a description of the command line
2366		interface.
2367
2368		ported i2c driver to the new framework:
2369		- drivers/i2c/soft_i2c.c:
2370		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2371		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2372		    for defining speed and slave address
2373		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2374		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2375		    for defining speed and slave address
2376		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2377		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2378		    for defining speed and slave address
2379		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2380		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2381		    for defining speed and slave address
2382
2383		- drivers/i2c/fsl_i2c.c:
2384		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2385		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2386		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2387		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2388		    bus.
2389		  - If your board supports a second fsl i2c bus, define
2390		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2391		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2392		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2393		    second bus.
2394
2395		- drivers/i2c/tegra_i2c.c:
2396		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2397		  - This driver adds 4 i2c buses with a fix speed from
2398		    100000 and the slave addr 0!
2399
2400		- drivers/i2c/ppc4xx_i2c.c
2401		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2402		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2403		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2404
2405		- drivers/i2c/i2c_mxc.c
2406		  - activate this driver with CONFIG_SYS_I2C_MXC
2407		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2408		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2409		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2410		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2411		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2412		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2413		If those defines are not set, default value is 100000
2414		for speed, and 0 for slave.
2415
2416		- drivers/i2c/rcar_i2c.c:
2417		  - activate this driver with CONFIG_SYS_I2C_RCAR
2418		  - This driver adds 4 i2c buses
2419
2420		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2421		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2422		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2423		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2424		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2425		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2426		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2427		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2428		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2429
2430		- drivers/i2c/sh_i2c.c:
2431		  - activate this driver with CONFIG_SYS_I2C_SH
2432		  - This driver adds from 2 to 5 i2c buses
2433
2434		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2435		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2436		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2437		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2438		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2439		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2440		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2441		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2442		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2443		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2444		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2445		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2446		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2447
2448		- drivers/i2c/omap24xx_i2c.c
2449		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2450		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2451		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2452		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2453		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2454		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2455		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2456		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2457		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2458		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2459		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2460
2461		- drivers/i2c/zynq_i2c.c
2462		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2463		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2464		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2465
2466		- drivers/i2c/s3c24x0_i2c.c:
2467		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2468		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2469		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2470		    with a fix speed from 100000 and the slave addr 0!
2471
2472		- drivers/i2c/ihs_i2c.c
2473		  - activate this driver with CONFIG_SYS_I2C_IHS
2474		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2475		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2476		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2477		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2478		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2479		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2480		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2481		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2482		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2483		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2484		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2485		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2486
2487		additional defines:
2488
2489		CONFIG_SYS_NUM_I2C_BUSES
2490		Hold the number of i2c buses you want to use. If you
2491		don't use/have i2c muxes on your i2c bus, this
2492		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2493		omit this define.
2494
2495		CONFIG_SYS_I2C_DIRECT_BUS
2496		define this, if you don't use i2c muxes on your hardware.
2497		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2498		omit this define.
2499
2500		CONFIG_SYS_I2C_MAX_HOPS
2501		define how many muxes are maximal consecutively connected
2502		on one i2c bus. If you not use i2c muxes, omit this
2503		define.
2504
2505		CONFIG_SYS_I2C_BUSES
2506		hold a list of buses you want to use, only used if
2507		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2508		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2509		CONFIG_SYS_NUM_I2C_BUSES = 9:
2510
2511		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2512					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2513					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2514					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2515					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2516					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2517					{1, {I2C_NULL_HOP}}, \
2518					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2519					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2520					}
2521
2522		which defines
2523			bus 0 on adapter 0 without a mux
2524			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2525			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2526			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2527			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2528			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2529			bus 6 on adapter 1 without a mux
2530			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2531			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2532
2533		If you do not have i2c muxes on your board, omit this define.
2534
2535- Legacy I2C Support:	CONFIG_HARD_I2C
2536
2537		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2538		provides the following compelling advantages:
2539
2540		- more than one i2c adapter is usable
2541		- approved multibus support
2542		- better i2c mux support
2543
2544		** Please consider updating your I2C driver now. **
2545
2546		These enable legacy I2C serial bus commands. Defining
2547		CONFIG_HARD_I2C will include the appropriate I2C driver
2548		for the selected CPU.
2549
2550		This will allow you to use i2c commands at the u-boot
2551		command line (as long as you set CONFIG_CMD_I2C in
2552		CONFIG_COMMANDS) and communicate with i2c based realtime
2553		clock chips. See common/cmd_i2c.c for a description of the
2554		command line interface.
2555
2556		CONFIG_HARD_I2C selects a hardware I2C controller.
2557
2558		There are several other quantities that must also be
2559		defined when you define CONFIG_HARD_I2C.
2560
2561		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2562		to be the frequency (in Hz) at which you wish your i2c bus
2563		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2564		the CPU's i2c node address).
2565
2566		Now, the u-boot i2c code for the mpc8xx
2567		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2568		and so its address should therefore be cleared to 0 (See,
2569		eg, MPC823e User's Manual p.16-473). So, set
2570		CONFIG_SYS_I2C_SLAVE to 0.
2571
2572		CONFIG_SYS_I2C_INIT_MPC5XXX
2573
2574		When a board is reset during an i2c bus transfer
2575		chips might think that the current transfer is still
2576		in progress.  Reset the slave devices by sending start
2577		commands until the slave device responds.
2578
2579		That's all that's required for CONFIG_HARD_I2C.
2580
2581		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2582		then the following macros need to be defined (examples are
2583		from include/configs/lwmon.h):
2584
2585		I2C_INIT
2586
2587		(Optional). Any commands necessary to enable the I2C
2588		controller or configure ports.
2589
2590		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2591
2592		I2C_PORT
2593
2594		(Only for MPC8260 CPU). The I/O port to use (the code
2595		assumes both bits are on the same port). Valid values
2596		are 0..3 for ports A..D.
2597
2598		I2C_ACTIVE
2599
2600		The code necessary to make the I2C data line active
2601		(driven).  If the data line is open collector, this
2602		define can be null.
2603
2604		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2605
2606		I2C_TRISTATE
2607
2608		The code necessary to make the I2C data line tri-stated
2609		(inactive).  If the data line is open collector, this
2610		define can be null.
2611
2612		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2613
2614		I2C_READ
2615
2616		Code that returns true if the I2C data line is high,
2617		false if it is low.
2618
2619		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2620
2621		I2C_SDA(bit)
2622
2623		If <bit> is true, sets the I2C data line high. If it
2624		is false, it clears it (low).
2625
2626		eg: #define I2C_SDA(bit) \
2627			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2628			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2629
2630		I2C_SCL(bit)
2631
2632		If <bit> is true, sets the I2C clock line high. If it
2633		is false, it clears it (low).
2634
2635		eg: #define I2C_SCL(bit) \
2636			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2637			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2638
2639		I2C_DELAY
2640
2641		This delay is invoked four times per clock cycle so this
2642		controls the rate of data transfer.  The data rate thus
2643		is 1 / (I2C_DELAY * 4). Often defined to be something
2644		like:
2645
2646		#define I2C_DELAY  udelay(2)
2647
2648		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2649
2650		If your arch supports the generic GPIO framework (asm/gpio.h),
2651		then you may alternatively define the two GPIOs that are to be
2652		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2653		have GPIO-based defaults assigned to them as appropriate.
2654
2655		You should define these to the GPIO value as given directly to
2656		the generic GPIO functions.
2657
2658		CONFIG_SYS_I2C_INIT_BOARD
2659
2660		When a board is reset during an i2c bus transfer
2661		chips might think that the current transfer is still
2662		in progress. On some boards it is possible to access
2663		the i2c SCLK line directly, either by using the
2664		processor pin as a GPIO or by having a second pin
2665		connected to the bus. If this option is defined a
2666		custom i2c_init_board() routine in boards/xxx/board.c
2667		is run early in the boot sequence.
2668
2669		CONFIG_SYS_I2C_BOARD_LATE_INIT
2670
2671		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2672		defined a custom i2c_board_late_init() routine in
2673		boards/xxx/board.c is run AFTER the operations in i2c_init()
2674		is completed. This callpoint can be used to unreset i2c bus
2675		using CPU i2c controller register accesses for CPUs whose i2c
2676		controller provide such a method. It is called at the end of
2677		i2c_init() to allow i2c_init operations to setup the i2c bus
2678		controller on the CPU (e.g. setting bus speed & slave address).
2679
2680		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2681
2682		This option enables configuration of bi_iic_fast[] flags
2683		in u-boot bd_info structure based on u-boot environment
2684		variable "i2cfast". (see also i2cfast)
2685
2686		CONFIG_I2C_MULTI_BUS
2687
2688		This option allows the use of multiple I2C buses, each of which
2689		must have a controller.	 At any point in time, only one bus is
2690		active.	 To switch to a different bus, use the 'i2c dev' command.
2691		Note that bus numbering is zero-based.
2692
2693		CONFIG_SYS_I2C_NOPROBES
2694
2695		This option specifies a list of I2C devices that will be skipped
2696		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2697		is set, specify a list of bus-device pairs.  Otherwise, specify
2698		a 1D array of device addresses
2699
2700		e.g.
2701			#undef	CONFIG_I2C_MULTI_BUS
2702			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2703
2704		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2705
2706			#define CONFIG_I2C_MULTI_BUS
2707			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2708
2709		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2710
2711		CONFIG_SYS_SPD_BUS_NUM
2712
2713		If defined, then this indicates the I2C bus number for DDR SPD.
2714		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2715
2716		CONFIG_SYS_RTC_BUS_NUM
2717
2718		If defined, then this indicates the I2C bus number for the RTC.
2719		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2720
2721		CONFIG_SYS_DTT_BUS_NUM
2722
2723		If defined, then this indicates the I2C bus number for the DTT.
2724		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2725
2726		CONFIG_SYS_I2C_DTT_ADDR:
2727
2728		If defined, specifies the I2C address of the DTT device.
2729		If not defined, then U-Boot uses predefined value for
2730		specified DTT device.
2731
2732		CONFIG_SOFT_I2C_READ_REPEATED_START
2733
2734		defining this will force the i2c_read() function in
2735		the soft_i2c driver to perform an I2C repeated start
2736		between writing the address pointer and reading the
2737		data.  If this define is omitted the default behaviour
2738		of doing a stop-start sequence will be used.  Most I2C
2739		devices can use either method, but some require one or
2740		the other.
2741
2742- SPI Support:	CONFIG_SPI
2743
2744		Enables SPI driver (so far only tested with
2745		SPI EEPROM, also an instance works with Crystal A/D and
2746		D/As on the SACSng board)
2747
2748		CONFIG_SH_SPI
2749
2750		Enables the driver for SPI controller on SuperH. Currently
2751		only SH7757 is supported.
2752
2753		CONFIG_SPI_X
2754
2755		Enables extended (16-bit) SPI EEPROM addressing.
2756		(symmetrical to CONFIG_I2C_X)
2757
2758		CONFIG_SOFT_SPI
2759
2760		Enables a software (bit-bang) SPI driver rather than
2761		using hardware support. This is a general purpose
2762		driver that only requires three general I/O port pins
2763		(two outputs, one input) to function. If this is
2764		defined, the board configuration must define several
2765		SPI configuration items (port pins to use, etc). For
2766		an example, see include/configs/sacsng.h.
2767
2768		CONFIG_HARD_SPI
2769
2770		Enables a hardware SPI driver for general-purpose reads
2771		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2772		must define a list of chip-select function pointers.
2773		Currently supported on some MPC8xxx processors.	 For an
2774		example, see include/configs/mpc8349emds.h.
2775
2776		CONFIG_MXC_SPI
2777
2778		Enables the driver for the SPI controllers on i.MX and MXC
2779		SoCs. Currently i.MX31/35/51 are supported.
2780
2781		CONFIG_SYS_SPI_MXC_WAIT
2782		Timeout for waiting until spi transfer completed.
2783		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2784
2785- FPGA Support: CONFIG_FPGA
2786
2787		Enables FPGA subsystem.
2788
2789		CONFIG_FPGA_<vendor>
2790
2791		Enables support for specific chip vendors.
2792		(ALTERA, XILINX)
2793
2794		CONFIG_FPGA_<family>
2795
2796		Enables support for FPGA family.
2797		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2798
2799		CONFIG_FPGA_COUNT
2800
2801		Specify the number of FPGA devices to support.
2802
2803		CONFIG_CMD_FPGA_LOADMK
2804
2805		Enable support for fpga loadmk command
2806
2807		CONFIG_CMD_FPGA_LOADP
2808
2809		Enable support for fpga loadp command - load partial bitstream
2810
2811		CONFIG_CMD_FPGA_LOADBP
2812
2813		Enable support for fpga loadbp command - load partial bitstream
2814		(Xilinx only)
2815
2816		CONFIG_SYS_FPGA_PROG_FEEDBACK
2817
2818		Enable printing of hash marks during FPGA configuration.
2819
2820		CONFIG_SYS_FPGA_CHECK_BUSY
2821
2822		Enable checks on FPGA configuration interface busy
2823		status by the configuration function. This option
2824		will require a board or device specific function to
2825		be written.
2826
2827		CONFIG_FPGA_DELAY
2828
2829		If defined, a function that provides delays in the FPGA
2830		configuration driver.
2831
2832		CONFIG_SYS_FPGA_CHECK_CTRLC
2833		Allow Control-C to interrupt FPGA configuration
2834
2835		CONFIG_SYS_FPGA_CHECK_ERROR
2836
2837		Check for configuration errors during FPGA bitfile
2838		loading. For example, abort during Virtex II
2839		configuration if the INIT_B line goes low (which
2840		indicated a CRC error).
2841
2842		CONFIG_SYS_FPGA_WAIT_INIT
2843
2844		Maximum time to wait for the INIT_B line to de-assert
2845		after PROB_B has been de-asserted during a Virtex II
2846		FPGA configuration sequence. The default time is 500
2847		ms.
2848
2849		CONFIG_SYS_FPGA_WAIT_BUSY
2850
2851		Maximum time to wait for BUSY to de-assert during
2852		Virtex II FPGA configuration. The default is 5 ms.
2853
2854		CONFIG_SYS_FPGA_WAIT_CONFIG
2855
2856		Time to wait after FPGA configuration. The default is
2857		200 ms.
2858
2859- Configuration Management:
2860		CONFIG_BUILD_TARGET
2861
2862		Some SoCs need special image types (e.g. U-Boot binary
2863		with a special header) as build targets. By defining
2864		CONFIG_BUILD_TARGET in the SoC / board header, this
2865		special image will be automatically built upon calling
2866		make / MAKEALL.
2867
2868		CONFIG_IDENT_STRING
2869
2870		If defined, this string will be added to the U-Boot
2871		version information (U_BOOT_VERSION)
2872
2873- Vendor Parameter Protection:
2874
2875		U-Boot considers the values of the environment
2876		variables "serial#" (Board Serial Number) and
2877		"ethaddr" (Ethernet Address) to be parameters that
2878		are set once by the board vendor / manufacturer, and
2879		protects these variables from casual modification by
2880		the user. Once set, these variables are read-only,
2881		and write or delete attempts are rejected. You can
2882		change this behaviour:
2883
2884		If CONFIG_ENV_OVERWRITE is #defined in your config
2885		file, the write protection for vendor parameters is
2886		completely disabled. Anybody can change or delete
2887		these parameters.
2888
2889		Alternatively, if you #define _both_ CONFIG_ETHADDR
2890		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2891		Ethernet address is installed in the environment,
2892		which can be changed exactly ONCE by the user. [The
2893		serial# is unaffected by this, i. e. it remains
2894		read-only.]
2895
2896		The same can be accomplished in a more flexible way
2897		for any variable by configuring the type of access
2898		to allow for those variables in the ".flags" variable
2899		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2900
2901- Protected RAM:
2902		CONFIG_PRAM
2903
2904		Define this variable to enable the reservation of
2905		"protected RAM", i. e. RAM which is not overwritten
2906		by U-Boot. Define CONFIG_PRAM to hold the number of
2907		kB you want to reserve for pRAM. You can overwrite
2908		this default value by defining an environment
2909		variable "pram" to the number of kB you want to
2910		reserve. Note that the board info structure will
2911		still show the full amount of RAM. If pRAM is
2912		reserved, a new environment variable "mem" will
2913		automatically be defined to hold the amount of
2914		remaining RAM in a form that can be passed as boot
2915		argument to Linux, for instance like that:
2916
2917			setenv bootargs ... mem=\${mem}
2918			saveenv
2919
2920		This way you can tell Linux not to use this memory,
2921		either, which results in a memory region that will
2922		not be affected by reboots.
2923
2924		*WARNING* If your board configuration uses automatic
2925		detection of the RAM size, you must make sure that
2926		this memory test is non-destructive. So far, the
2927		following board configurations are known to be
2928		"pRAM-clean":
2929
2930			IVMS8, IVML24, SPD8xx, TQM8xxL,
2931			HERMES, IP860, RPXlite, LWMON,
2932			FLAGADM, TQM8260
2933
2934- Access to physical memory region (> 4GB)
2935		Some basic support is provided for operations on memory not
2936		normally accessible to U-Boot - e.g. some architectures
2937		support access to more than 4GB of memory on 32-bit
2938		machines using physical address extension or similar.
2939		Define CONFIG_PHYSMEM to access this basic support, which
2940		currently only supports clearing the memory.
2941
2942- Error Recovery:
2943		CONFIG_PANIC_HANG
2944
2945		Define this variable to stop the system in case of a
2946		fatal error, so that you have to reset it manually.
2947		This is probably NOT a good idea for an embedded
2948		system where you want the system to reboot
2949		automatically as fast as possible, but it may be
2950		useful during development since you can try to debug
2951		the conditions that lead to the situation.
2952
2953		CONFIG_NET_RETRY_COUNT
2954
2955		This variable defines the number of retries for
2956		network operations like ARP, RARP, TFTP, or BOOTP
2957		before giving up the operation. If not defined, a
2958		default value of 5 is used.
2959
2960		CONFIG_ARP_TIMEOUT
2961
2962		Timeout waiting for an ARP reply in milliseconds.
2963
2964		CONFIG_NFS_TIMEOUT
2965
2966		Timeout in milliseconds used in NFS protocol.
2967		If you encounter "ERROR: Cannot umount" in nfs command,
2968		try longer timeout such as
2969		#define CONFIG_NFS_TIMEOUT 10000UL
2970
2971- Command Interpreter:
2972		CONFIG_AUTO_COMPLETE
2973
2974		Enable auto completion of commands using TAB.
2975
2976		CONFIG_SYS_PROMPT_HUSH_PS2
2977
2978		This defines the secondary prompt string, which is
2979		printed when the command interpreter needs more input
2980		to complete a command. Usually "> ".
2981
2982	Note:
2983
2984		In the current implementation, the local variables
2985		space and global environment variables space are
2986		separated. Local variables are those you define by
2987		simply typing `name=value'. To access a local
2988		variable later on, you have write `$name' or
2989		`${name}'; to execute the contents of a variable
2990		directly type `$name' at the command prompt.
2991
2992		Global environment variables are those you use
2993		setenv/printenv to work with. To run a command stored
2994		in such a variable, you need to use the run command,
2995		and you must not use the '$' sign to access them.
2996
2997		To store commands and special characters in a
2998		variable, please use double quotation marks
2999		surrounding the whole text of the variable, instead
3000		of the backslashes before semicolons and special
3001		symbols.
3002
3003- Command Line Editing and History:
3004		CONFIG_CMDLINE_EDITING
3005
3006		Enable editing and History functions for interactive
3007		command line input operations
3008
3009- Default Environment:
3010		CONFIG_EXTRA_ENV_SETTINGS
3011
3012		Define this to contain any number of null terminated
3013		strings (variable = value pairs) that will be part of
3014		the default environment compiled into the boot image.
3015
3016		For example, place something like this in your
3017		board's config file:
3018
3019		#define CONFIG_EXTRA_ENV_SETTINGS \
3020			"myvar1=value1\0" \
3021			"myvar2=value2\0"
3022
3023		Warning: This method is based on knowledge about the
3024		internal format how the environment is stored by the
3025		U-Boot code. This is NOT an official, exported
3026		interface! Although it is unlikely that this format
3027		will change soon, there is no guarantee either.
3028		You better know what you are doing here.
3029
3030		Note: overly (ab)use of the default environment is
3031		discouraged. Make sure to check other ways to preset
3032		the environment like the "source" command or the
3033		boot command first.
3034
3035		CONFIG_ENV_VARS_UBOOT_CONFIG
3036
3037		Define this in order to add variables describing the
3038		U-Boot build configuration to the default environment.
3039		These will be named arch, cpu, board, vendor, and soc.
3040
3041		Enabling this option will cause the following to be defined:
3042
3043		- CONFIG_SYS_ARCH
3044		- CONFIG_SYS_CPU
3045		- CONFIG_SYS_BOARD
3046		- CONFIG_SYS_VENDOR
3047		- CONFIG_SYS_SOC
3048
3049		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
3050
3051		Define this in order to add variables describing certain
3052		run-time determined information about the hardware to the
3053		environment.  These will be named board_name, board_rev.
3054
3055		CONFIG_DELAY_ENVIRONMENT
3056
3057		Normally the environment is loaded when the board is
3058		initialised so that it is available to U-Boot. This inhibits
3059		that so that the environment is not available until
3060		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
3061		this is instead controlled by the value of
3062		/config/load-environment.
3063
3064- DataFlash Support:
3065		CONFIG_HAS_DATAFLASH
3066
3067		Defining this option enables DataFlash features and
3068		allows to read/write in Dataflash via the standard
3069		commands cp, md...
3070
3071- Serial Flash support
3072		CONFIG_CMD_SF
3073
3074		Defining this option enables SPI flash commands
3075		'sf probe/read/write/erase/update'.
3076
3077		Usage requires an initial 'probe' to define the serial
3078		flash parameters, followed by read/write/erase/update
3079		commands.
3080
3081		The following defaults may be provided by the platform
3082		to handle the common case when only a single serial
3083		flash is present on the system.
3084
3085		CONFIG_SF_DEFAULT_BUS		Bus identifier
3086		CONFIG_SF_DEFAULT_CS		Chip-select
3087		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3088		CONFIG_SF_DEFAULT_SPEED		in Hz
3089
3090		CONFIG_CMD_SF_TEST
3091
3092		Define this option to include a destructive SPI flash
3093		test ('sf test').
3094
3095		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
3096
3097		Define this option to use the Bank addr/Extended addr
3098		support on SPI flashes which has size > 16Mbytes.
3099
3100		CONFIG_SF_DUAL_FLASH		Dual flash memories
3101
3102		Define this option to use dual flash support where two flash
3103		memories can be connected with a given cs line.
3104		Currently Xilinx Zynq qspi supports these type of connections.
3105
3106		CONFIG_SYS_SPI_ST_ENABLE_WP_PIN
3107		enable the W#/Vpp signal to disable writing to the status
3108		register on ST MICRON flashes like the N25Q128.
3109		The status register write enable/disable bit, combined with
3110		the W#/VPP signal provides hardware data protection for the
3111		device as follows: When the enable/disable bit is set to 1,
3112		and the W#/VPP signal is driven LOW, the status register
3113		nonvolatile bits become read-only and the WRITE STATUS REGISTER
3114		operation will not execute. The only way to exit this
3115		hardware-protected mode is to drive W#/VPP HIGH.
3116
3117- SystemACE Support:
3118		CONFIG_SYSTEMACE
3119
3120		Adding this option adds support for Xilinx SystemACE
3121		chips attached via some sort of local bus. The address
3122		of the chip must also be defined in the
3123		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3124
3125		#define CONFIG_SYSTEMACE
3126		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3127
3128		When SystemACE support is added, the "ace" device type
3129		becomes available to the fat commands, i.e. fatls.
3130
3131- TFTP Fixed UDP Port:
3132		CONFIG_TFTP_PORT
3133
3134		If this is defined, the environment variable tftpsrcp
3135		is used to supply the TFTP UDP source port value.
3136		If tftpsrcp isn't defined, the normal pseudo-random port
3137		number generator is used.
3138
3139		Also, the environment variable tftpdstp is used to supply
3140		the TFTP UDP destination port value.  If tftpdstp isn't
3141		defined, the normal port 69 is used.
3142
3143		The purpose for tftpsrcp is to allow a TFTP server to
3144		blindly start the TFTP transfer using the pre-configured
3145		target IP address and UDP port. This has the effect of
3146		"punching through" the (Windows XP) firewall, allowing
3147		the remainder of the TFTP transfer to proceed normally.
3148		A better solution is to properly configure the firewall,
3149		but sometimes that is not allowed.
3150
3151- Hashing support:
3152		CONFIG_CMD_HASH
3153
3154		This enables a generic 'hash' command which can produce
3155		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3156
3157		CONFIG_HASH_VERIFY
3158
3159		Enable the hash verify command (hash -v). This adds to code
3160		size a little.
3161
3162		CONFIG_SHA1 - support SHA1 hashing
3163		CONFIG_SHA256 - support SHA256 hashing
3164
3165		Note: There is also a sha1sum command, which should perhaps
3166		be deprecated in favour of 'hash sha1'.
3167
3168- Freescale i.MX specific commands:
3169		CONFIG_CMD_HDMIDETECT
3170		This enables 'hdmidet' command which returns true if an
3171		HDMI monitor is detected.  This command is i.MX 6 specific.
3172
3173		CONFIG_CMD_BMODE
3174		This enables the 'bmode' (bootmode) command for forcing
3175		a boot from specific media.
3176
3177		This is useful for forcing the ROM's usb downloader to
3178		activate upon a watchdog reset which is nice when iterating
3179		on U-Boot.  Using the reset button or running bmode normal
3180		will set it back to normal.  This command currently
3181		supports i.MX53 and i.MX6.
3182
3183- Signing support:
3184		CONFIG_RSA
3185
3186		This enables the RSA algorithm used for FIT image verification
3187		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3188
3189		The Modular Exponentiation algorithm in RSA is implemented using
3190		driver model. So CONFIG_DM needs to be enabled by default for this
3191		library to function.
3192
3193		The signing part is build into mkimage regardless of this
3194		option. The software based modular exponentiation is built into
3195		mkimage irrespective of this option.
3196
3197- bootcount support:
3198		CONFIG_BOOTCOUNT_LIMIT
3199
3200		This enables the bootcounter support, see:
3201		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3202
3203		CONFIG_AT91SAM9XE
3204		enable special bootcounter support on at91sam9xe based boards.
3205		CONFIG_BLACKFIN
3206		enable special bootcounter support on blackfin based boards.
3207		CONFIG_SOC_DA8XX
3208		enable special bootcounter support on da850 based boards.
3209		CONFIG_BOOTCOUNT_RAM
3210		enable support for the bootcounter in RAM
3211		CONFIG_BOOTCOUNT_I2C
3212		enable support for the bootcounter on an i2c (like RTC) device.
3213			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3214			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3215						    the bootcounter.
3216			CONFIG_BOOTCOUNT_ALEN = address len
3217
3218- Show boot progress:
3219		CONFIG_SHOW_BOOT_PROGRESS
3220
3221		Defining this option allows to add some board-
3222		specific code (calling a user-provided function
3223		"show_boot_progress(int)") that enables you to show
3224		the system's boot progress on some display (for
3225		example, some LED's) on your board. At the moment,
3226		the following checkpoints are implemented:
3227
3228- Detailed boot stage timing
3229		CONFIG_BOOTSTAGE
3230		Define this option to get detailed timing of each stage
3231		of the boot process.
3232
3233		CONFIG_BOOTSTAGE_USER_COUNT
3234		This is the number of available user bootstage records.
3235		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
3236		a new ID will be allocated from this stash. If you exceed
3237		the limit, recording will stop.
3238
3239		CONFIG_BOOTSTAGE_REPORT
3240		Define this to print a report before boot, similar to this:
3241
3242		Timer summary in microseconds:
3243		       Mark    Elapsed  Stage
3244			  0          0  reset
3245		  3,575,678  3,575,678  board_init_f start
3246		  3,575,695         17  arch_cpu_init A9
3247		  3,575,777         82  arch_cpu_init done
3248		  3,659,598     83,821  board_init_r start
3249		  3,910,375    250,777  main_loop
3250		 29,916,167 26,005,792  bootm_start
3251		 30,361,327    445,160  start_kernel
3252
3253		CONFIG_CMD_BOOTSTAGE
3254		Add a 'bootstage' command which supports printing a report
3255		and un/stashing of bootstage data.
3256
3257		CONFIG_BOOTSTAGE_FDT
3258		Stash the bootstage information in the FDT. A root 'bootstage'
3259		node is created with each bootstage id as a child. Each child
3260		has a 'name' property and either 'mark' containing the
3261		mark time in microsecond, or 'accum' containing the
3262		accumulated time for that bootstage id in microseconds.
3263		For example:
3264
3265		bootstage {
3266			154 {
3267				name = "board_init_f";
3268				mark = <3575678>;
3269			};
3270			170 {
3271				name = "lcd";
3272				accum = <33482>;
3273			};
3274		};
3275
3276		Code in the Linux kernel can find this in /proc/devicetree.
3277
3278Legacy uImage format:
3279
3280  Arg	Where			When
3281    1	common/cmd_bootm.c	before attempting to boot an image
3282   -1	common/cmd_bootm.c	Image header has bad	 magic number
3283    2	common/cmd_bootm.c	Image header has correct magic number
3284   -2	common/cmd_bootm.c	Image header has bad	 checksum
3285    3	common/cmd_bootm.c	Image header has correct checksum
3286   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3287    4	common/cmd_bootm.c	Image data   has correct checksum
3288   -4	common/cmd_bootm.c	Image is for unsupported architecture
3289    5	common/cmd_bootm.c	Architecture check OK
3290   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3291    6	common/cmd_bootm.c	Image Type check OK
3292   -6	common/cmd_bootm.c	gunzip uncompression error
3293   -7	common/cmd_bootm.c	Unimplemented compression type
3294    7	common/cmd_bootm.c	Uncompression OK
3295    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3296   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3297
3298    9	common/image.c		Start initial ramdisk verification
3299  -10	common/image.c		Ramdisk header has bad	   magic number
3300  -11	common/image.c		Ramdisk header has bad	   checksum
3301   10	common/image.c		Ramdisk header is OK
3302  -12	common/image.c		Ramdisk data   has bad	   checksum
3303   11	common/image.c		Ramdisk data   has correct checksum
3304   12	common/image.c		Ramdisk verification complete, start loading
3305  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3306   13	common/image.c		Start multifile image verification
3307   14	common/image.c		No initial ramdisk, no multifile, continue.
3308
3309   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3310
3311  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3312  -31	post/post.c		POST test failed, detected by post_output_backlog()
3313  -32	post/post.c		POST test failed, detected by post_run_single()
3314
3315   34	common/cmd_doc.c	before loading a Image from a DOC device
3316  -35	common/cmd_doc.c	Bad usage of "doc" command
3317   35	common/cmd_doc.c	correct usage of "doc" command
3318  -36	common/cmd_doc.c	No boot device
3319   36	common/cmd_doc.c	correct boot device
3320  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3321   37	common/cmd_doc.c	correct chip ID found, device available
3322  -38	common/cmd_doc.c	Read Error on boot device
3323   38	common/cmd_doc.c	reading Image header from DOC device OK
3324  -39	common/cmd_doc.c	Image header has bad magic number
3325   39	common/cmd_doc.c	Image header has correct magic number
3326  -40	common/cmd_doc.c	Error reading Image from DOC device
3327   40	common/cmd_doc.c	Image header has correct magic number
3328   41	common/cmd_ide.c	before loading a Image from a IDE device
3329  -42	common/cmd_ide.c	Bad usage of "ide" command
3330   42	common/cmd_ide.c	correct usage of "ide" command
3331  -43	common/cmd_ide.c	No boot device
3332   43	common/cmd_ide.c	boot device found
3333  -44	common/cmd_ide.c	Device not available
3334   44	common/cmd_ide.c	Device available
3335  -45	common/cmd_ide.c	wrong partition selected
3336   45	common/cmd_ide.c	partition selected
3337  -46	common/cmd_ide.c	Unknown partition table
3338   46	common/cmd_ide.c	valid partition table found
3339  -47	common/cmd_ide.c	Invalid partition type
3340   47	common/cmd_ide.c	correct partition type
3341  -48	common/cmd_ide.c	Error reading Image Header on boot device
3342   48	common/cmd_ide.c	reading Image Header from IDE device OK
3343  -49	common/cmd_ide.c	Image header has bad magic number
3344   49	common/cmd_ide.c	Image header has correct magic number
3345  -50	common/cmd_ide.c	Image header has bad	 checksum
3346   50	common/cmd_ide.c	Image header has correct checksum
3347  -51	common/cmd_ide.c	Error reading Image from IDE device
3348   51	common/cmd_ide.c	reading Image from IDE device OK
3349   52	common/cmd_nand.c	before loading a Image from a NAND device
3350  -53	common/cmd_nand.c	Bad usage of "nand" command
3351   53	common/cmd_nand.c	correct usage of "nand" command
3352  -54	common/cmd_nand.c	No boot device
3353   54	common/cmd_nand.c	boot device found
3354  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3355   55	common/cmd_nand.c	correct chip ID found, device available
3356  -56	common/cmd_nand.c	Error reading Image Header on boot device
3357   56	common/cmd_nand.c	reading Image Header from NAND device OK
3358  -57	common/cmd_nand.c	Image header has bad magic number
3359   57	common/cmd_nand.c	Image header has correct magic number
3360  -58	common/cmd_nand.c	Error reading Image from NAND device
3361   58	common/cmd_nand.c	reading Image from NAND device OK
3362
3363  -60	common/env_common.c	Environment has a bad CRC, using default
3364
3365   64	net/eth.c		starting with Ethernet configuration.
3366  -64	net/eth.c		no Ethernet found.
3367   65	net/eth.c		Ethernet found.
3368
3369  -80	common/cmd_net.c	usage wrong
3370   80	common/cmd_net.c	before calling NetLoop()
3371  -81	common/cmd_net.c	some error in NetLoop() occurred
3372   81	common/cmd_net.c	NetLoop() back without error
3373  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3374   82	common/cmd_net.c	trying automatic boot
3375   83	common/cmd_net.c	running "source" command
3376  -83	common/cmd_net.c	some error in automatic boot or "source" command
3377   84	common/cmd_net.c	end without errors
3378
3379FIT uImage format:
3380
3381  Arg	Where			When
3382  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3383 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3384  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3385 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3386  102	common/cmd_bootm.c	Kernel unit name specified
3387 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3388  103	common/cmd_bootm.c	Found configuration node
3389  104	common/cmd_bootm.c	Got kernel subimage node offset
3390 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3391  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3392 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3393  106	common/cmd_bootm.c	Architecture check OK
3394 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3395  107	common/cmd_bootm.c	Kernel subimage type OK
3396 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3397  108	common/cmd_bootm.c	Got kernel subimage data/size
3398 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3399 -109	common/cmd_bootm.c	Can't get kernel subimage type
3400 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3401 -111	common/cmd_bootm.c	Can't get kernel subimage os
3402 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3403 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3404
3405  120	common/image.c		Start initial ramdisk verification
3406 -120	common/image.c		Ramdisk FIT image has incorrect format
3407  121	common/image.c		Ramdisk FIT image has correct format
3408  122	common/image.c		No ramdisk subimage unit name, using configuration
3409 -122	common/image.c		Can't get configuration for ramdisk subimage
3410  123	common/image.c		Ramdisk unit name specified
3411 -124	common/image.c		Can't get ramdisk subimage node offset
3412  125	common/image.c		Got ramdisk subimage node offset
3413 -125	common/image.c		Ramdisk subimage hash verification failed
3414  126	common/image.c		Ramdisk subimage hash verification OK
3415 -126	common/image.c		Ramdisk subimage for unsupported architecture
3416  127	common/image.c		Architecture check OK
3417 -127	common/image.c		Can't get ramdisk subimage data/size
3418  128	common/image.c		Got ramdisk subimage data/size
3419  129	common/image.c		Can't get ramdisk load address
3420 -129	common/image.c		Got ramdisk load address
3421
3422 -130	common/cmd_doc.c	Incorrect FIT image format
3423  131	common/cmd_doc.c	FIT image format OK
3424
3425 -140	common/cmd_ide.c	Incorrect FIT image format
3426  141	common/cmd_ide.c	FIT image format OK
3427
3428 -150	common/cmd_nand.c	Incorrect FIT image format
3429  151	common/cmd_nand.c	FIT image format OK
3430
3431- legacy image format:
3432		CONFIG_IMAGE_FORMAT_LEGACY
3433		enables the legacy image format support in U-Boot.
3434
3435		Default:
3436		enabled if CONFIG_FIT_SIGNATURE is not defined.
3437
3438		CONFIG_DISABLE_IMAGE_LEGACY
3439		disable the legacy image format
3440
3441		This define is introduced, as the legacy image format is
3442		enabled per default for backward compatibility.
3443
3444- FIT image support:
3445		CONFIG_FIT
3446		Enable support for the FIT uImage format.
3447
3448		CONFIG_FIT_BEST_MATCH
3449		When no configuration is explicitly selected, default to the
3450		one whose fdt's compatibility field best matches that of
3451		U-Boot itself. A match is considered "best" if it matches the
3452		most specific compatibility entry of U-Boot's fdt's root node.
3453		The order of entries in the configuration's fdt is ignored.
3454
3455		CONFIG_FIT_SIGNATURE
3456		This option enables signature verification of FIT uImages,
3457		using a hash signed and verified using RSA. See
3458		doc/uImage.FIT/signature.txt for more details.
3459
3460		WARNING: When relying on signed FIT images with required
3461		signature check the legacy image format is default
3462		disabled. If a board need legacy image format support
3463		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3464
3465		CONFIG_FIT_DISABLE_SHA256
3466		Supporting SHA256 hashes has quite an impact on binary size.
3467		For constrained systems sha256 hash support can be disabled
3468		with this option.
3469
3470- Standalone program support:
3471		CONFIG_STANDALONE_LOAD_ADDR
3472
3473		This option defines a board specific value for the
3474		address where standalone program gets loaded, thus
3475		overwriting the architecture dependent default
3476		settings.
3477
3478- Frame Buffer Address:
3479		CONFIG_FB_ADDR
3480
3481		Define CONFIG_FB_ADDR if you want to use specific
3482		address for frame buffer.  This is typically the case
3483		when using a graphics controller has separate video
3484		memory.  U-Boot will then place the frame buffer at
3485		the given address instead of dynamically reserving it
3486		in system RAM by calling lcd_setmem(), which grabs
3487		the memory for the frame buffer depending on the
3488		configured panel size.
3489
3490		Please see board_init_f function.
3491
3492- Automatic software updates via TFTP server
3493		CONFIG_UPDATE_TFTP
3494		CONFIG_UPDATE_TFTP_CNT_MAX
3495		CONFIG_UPDATE_TFTP_MSEC_MAX
3496
3497		These options enable and control the auto-update feature;
3498		for a more detailed description refer to doc/README.update.
3499
3500- MTD Support (mtdparts command, UBI support)
3501		CONFIG_MTD_DEVICE
3502
3503		Adds the MTD device infrastructure from the Linux kernel.
3504		Needed for mtdparts command support.
3505
3506		CONFIG_MTD_PARTITIONS
3507
3508		Adds the MTD partitioning infrastructure from the Linux
3509		kernel. Needed for UBI support.
3510
3511		CONFIG_MTD_NAND_VERIFY_WRITE
3512		verify if the written data is correct reread.
3513
3514- UBI support
3515		CONFIG_CMD_UBI
3516
3517		Adds commands for interacting with MTD partitions formatted
3518		with the UBI flash translation layer
3519
3520		Requires also defining CONFIG_RBTREE
3521
3522		CONFIG_UBI_SILENCE_MSG
3523
3524		Make the verbose messages from UBI stop printing.  This leaves
3525		warnings and errors enabled.
3526
3527
3528		CONFIG_MTD_UBI_WL_THRESHOLD
3529		This parameter defines the maximum difference between the highest
3530		erase counter value and the lowest erase counter value of eraseblocks
3531		of UBI devices. When this threshold is exceeded, UBI starts performing
3532		wear leveling by means of moving data from eraseblock with low erase
3533		counter to eraseblocks with high erase counter.
3534
3535		The default value should be OK for SLC NAND flashes, NOR flashes and
3536		other flashes which have eraseblock life-cycle 100000 or more.
3537		However, in case of MLC NAND flashes which typically have eraseblock
3538		life-cycle less than 10000, the threshold should be lessened (e.g.,
3539		to 128 or 256, although it does not have to be power of 2).
3540
3541		default: 4096
3542
3543		CONFIG_MTD_UBI_BEB_LIMIT
3544		This option specifies the maximum bad physical eraseblocks UBI
3545		expects on the MTD device (per 1024 eraseblocks). If the
3546		underlying flash does not admit of bad eraseblocks (e.g. NOR
3547		flash), this value is ignored.
3548
3549		NAND datasheets often specify the minimum and maximum NVM
3550		(Number of Valid Blocks) for the flashes' endurance lifetime.
3551		The maximum expected bad eraseblocks per 1024 eraseblocks
3552		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3553		which gives 20 for most NANDs (MaxNVB is basically the total
3554		count of eraseblocks on the chip).
3555
3556		To put it differently, if this value is 20, UBI will try to
3557		reserve about 1.9% of physical eraseblocks for bad blocks
3558		handling. And that will be 1.9% of eraseblocks on the entire
3559		NAND chip, not just the MTD partition UBI attaches. This means
3560		that if you have, say, a NAND flash chip admits maximum 40 bad
3561		eraseblocks, and it is split on two MTD partitions of the same
3562		size, UBI will reserve 40 eraseblocks when attaching a
3563		partition.
3564
3565		default: 20
3566
3567		CONFIG_MTD_UBI_FASTMAP
3568		Fastmap is a mechanism which allows attaching an UBI device
3569		in nearly constant time. Instead of scanning the whole MTD device it
3570		only has to locate a checkpoint (called fastmap) on the device.
3571		The on-flash fastmap contains all information needed to attach
3572		the device. Using fastmap makes only sense on large devices where
3573		attaching by scanning takes long. UBI will not automatically install
3574		a fastmap on old images, but you can set the UBI parameter
3575		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3576		that fastmap-enabled images are still usable with UBI implementations
3577		without	fastmap support. On typical flash devices the whole fastmap
3578		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3579
3580		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3581		Set this parameter to enable fastmap automatically on images
3582		without a fastmap.
3583		default: 0
3584
3585- UBIFS support
3586		CONFIG_CMD_UBIFS
3587
3588		Adds commands for interacting with UBI volumes formatted as
3589		UBIFS.  UBIFS is read-only in u-boot.
3590
3591		Requires UBI support as well as CONFIG_LZO
3592
3593		CONFIG_UBIFS_SILENCE_MSG
3594
3595		Make the verbose messages from UBIFS stop printing.  This leaves
3596		warnings and errors enabled.
3597
3598- SPL framework
3599		CONFIG_SPL
3600		Enable building of SPL globally.
3601
3602		CONFIG_SPL_LDSCRIPT
3603		LDSCRIPT for linking the SPL binary.
3604
3605		CONFIG_SPL_MAX_FOOTPRINT
3606		Maximum size in memory allocated to the SPL, BSS included.
3607		When defined, the linker checks that the actual memory
3608		used by SPL from _start to __bss_end does not exceed it.
3609		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3610		must not be both defined at the same time.
3611
3612		CONFIG_SPL_MAX_SIZE
3613		Maximum size of the SPL image (text, data, rodata, and
3614		linker lists sections), BSS excluded.
3615		When defined, the linker checks that the actual size does
3616		not exceed it.
3617
3618		CONFIG_SPL_TEXT_BASE
3619		TEXT_BASE for linking the SPL binary.
3620
3621		CONFIG_SPL_RELOC_TEXT_BASE
3622		Address to relocate to.  If unspecified, this is equal to
3623		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3624
3625		CONFIG_SPL_BSS_START_ADDR
3626		Link address for the BSS within the SPL binary.
3627
3628		CONFIG_SPL_BSS_MAX_SIZE
3629		Maximum size in memory allocated to the SPL BSS.
3630		When defined, the linker checks that the actual memory used
3631		by SPL from __bss_start to __bss_end does not exceed it.
3632		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3633		must not be both defined at the same time.
3634
3635		CONFIG_SPL_STACK
3636		Adress of the start of the stack SPL will use
3637
3638		CONFIG_SPL_RELOC_STACK
3639		Adress of the start of the stack SPL will use after
3640		relocation.  If unspecified, this is equal to
3641		CONFIG_SPL_STACK.
3642
3643		CONFIG_SYS_SPL_MALLOC_START
3644		Starting address of the malloc pool used in SPL.
3645
3646		CONFIG_SYS_SPL_MALLOC_SIZE
3647		The size of the malloc pool used in SPL.
3648
3649		CONFIG_SPL_FRAMEWORK
3650		Enable the SPL framework under common/.  This framework
3651		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3652		NAND loading of the Linux Kernel.
3653
3654		CONFIG_SPL_OS_BOOT
3655		Enable booting directly to an OS from SPL.
3656		See also: doc/README.falcon
3657
3658		CONFIG_SPL_DISPLAY_PRINT
3659		For ARM, enable an optional function to print more information
3660		about the running system.
3661
3662		CONFIG_SPL_INIT_MINIMAL
3663		Arch init code should be built for a very small image
3664
3665		CONFIG_SPL_LIBCOMMON_SUPPORT
3666		Support for common/libcommon.o in SPL binary
3667
3668		CONFIG_SPL_LIBDISK_SUPPORT
3669		Support for disk/libdisk.o in SPL binary
3670
3671		CONFIG_SPL_I2C_SUPPORT
3672		Support for drivers/i2c/libi2c.o in SPL binary
3673
3674		CONFIG_SPL_GPIO_SUPPORT
3675		Support for drivers/gpio/libgpio.o in SPL binary
3676
3677		CONFIG_SPL_MMC_SUPPORT
3678		Support for drivers/mmc/libmmc.o in SPL binary
3679
3680		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3681		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3682		Address and partition on the MMC to load U-Boot from
3683		when the MMC is being used in raw mode.
3684
3685		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3686		Partition on the MMC to load U-Boot from when the MMC is being
3687		used in raw mode
3688
3689		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3690		Sector to load kernel uImage from when MMC is being
3691		used in raw mode (for Falcon mode)
3692
3693		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3694		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3695		Sector and number of sectors to load kernel argument
3696		parameters from when MMC is being used in raw mode
3697		(for falcon mode)
3698
3699		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3700		Partition on the MMC to load U-Boot from when the MMC is being
3701		used in fs mode
3702
3703		CONFIG_SPL_FAT_SUPPORT
3704		Support for fs/fat/libfat.o in SPL binary
3705
3706		CONFIG_SPL_EXT_SUPPORT
3707		Support for EXT filesystem in SPL binary
3708
3709		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3710		Filename to read to load U-Boot when reading from filesystem
3711
3712		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3713		Filename to read to load kernel uImage when reading
3714		from filesystem (for Falcon mode)
3715
3716		CONFIG_SPL_FS_LOAD_ARGS_NAME
3717		Filename to read to load kernel argument parameters
3718		when reading from filesystem (for Falcon mode)
3719
3720		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3721		Set this for NAND SPL on PPC mpc83xx targets, so that
3722		start.S waits for the rest of the SPL to load before
3723		continuing (the hardware starts execution after just
3724		loading the first page rather than the full 4K).
3725
3726		CONFIG_SPL_SKIP_RELOCATE
3727		Avoid SPL relocation
3728
3729		CONFIG_SPL_NAND_BASE
3730		Include nand_base.c in the SPL.  Requires
3731		CONFIG_SPL_NAND_DRIVERS.
3732
3733		CONFIG_SPL_NAND_DRIVERS
3734		SPL uses normal NAND drivers, not minimal drivers.
3735
3736		CONFIG_SPL_NAND_ECC
3737		Include standard software ECC in the SPL
3738
3739		CONFIG_SPL_NAND_SIMPLE
3740		Support for NAND boot using simple NAND drivers that
3741		expose the cmd_ctrl() interface.
3742
3743		CONFIG_SPL_MTD_SUPPORT
3744		Support for the MTD subsystem within SPL.  Useful for
3745		environment on NAND support within SPL.
3746
3747		CONFIG_SPL_NAND_RAW_ONLY
3748		Support to boot only raw u-boot.bin images. Use this only
3749		if you need to save space.
3750
3751		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3752		Set for the SPL on PPC mpc8xxx targets, support for
3753		drivers/ddr/fsl/libddr.o in SPL binary.
3754
3755		CONFIG_SPL_COMMON_INIT_DDR
3756		Set for common ddr init with serial presence detect in
3757		SPL binary.
3758
3759		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3760		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3761		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3762		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3763		CONFIG_SYS_NAND_ECCBYTES
3764		Defines the size and behavior of the NAND that SPL uses
3765		to read U-Boot
3766
3767		CONFIG_SPL_NAND_BOOT
3768		Add support NAND boot
3769
3770		CONFIG_SYS_NAND_U_BOOT_OFFS
3771		Location in NAND to read U-Boot from
3772
3773		CONFIG_SYS_NAND_U_BOOT_DST
3774		Location in memory to load U-Boot to
3775
3776		CONFIG_SYS_NAND_U_BOOT_SIZE
3777		Size of image to load
3778
3779		CONFIG_SYS_NAND_U_BOOT_START
3780		Entry point in loaded image to jump to
3781
3782		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3783		Define this if you need to first read the OOB and then the
3784		data. This is used, for example, on davinci platforms.
3785
3786		CONFIG_SPL_OMAP3_ID_NAND
3787		Support for an OMAP3-specific set of functions to return the
3788		ID and MFR of the first attached NAND chip, if present.
3789
3790		CONFIG_SPL_SERIAL_SUPPORT
3791		Support for drivers/serial/libserial.o in SPL binary
3792
3793		CONFIG_SPL_SPI_FLASH_SUPPORT
3794		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3795
3796		CONFIG_SPL_SPI_SUPPORT
3797		Support for drivers/spi/libspi.o in SPL binary
3798
3799		CONFIG_SPL_RAM_DEVICE
3800		Support for running image already present in ram, in SPL binary
3801
3802		CONFIG_SPL_LIBGENERIC_SUPPORT
3803		Support for lib/libgeneric.o in SPL binary
3804
3805		CONFIG_SPL_ENV_SUPPORT
3806		Support for the environment operating in SPL binary
3807
3808		CONFIG_SPL_NET_SUPPORT
3809		Support for the net/libnet.o in SPL binary.
3810		It conflicts with SPL env from storage medium specified by
3811		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3812
3813		CONFIG_SPL_PAD_TO
3814		Image offset to which the SPL should be padded before appending
3815		the SPL payload. By default, this is defined as
3816		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3817		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3818		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3819
3820		CONFIG_SPL_TARGET
3821		Final target image containing SPL and payload.  Some SPLs
3822		use an arch-specific makefile fragment instead, for
3823		example if more than one image needs to be produced.
3824
3825		CONFIG_FIT_SPL_PRINT
3826		Printing information about a FIT image adds quite a bit of
3827		code to SPL. So this is normally disabled in SPL. Use this
3828		option to re-enable it. This will affect the output of the
3829		bootm command when booting a FIT image.
3830
3831- TPL framework
3832		CONFIG_TPL
3833		Enable building of TPL globally.
3834
3835		CONFIG_TPL_PAD_TO
3836		Image offset to which the TPL should be padded before appending
3837		the TPL payload. By default, this is defined as
3838		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3839		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3840		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3841
3842Modem Support:
3843--------------
3844
3845[so far only for SMDK2400 boards]
3846
3847- Modem support enable:
3848		CONFIG_MODEM_SUPPORT
3849
3850- RTS/CTS Flow control enable:
3851		CONFIG_HWFLOW
3852
3853- Modem debug support:
3854		CONFIG_MODEM_SUPPORT_DEBUG
3855
3856		Enables debugging stuff (char screen[1024], dbg())
3857		for modem support. Useful only with BDI2000.
3858
3859- Interrupt support (PPC):
3860
3861		There are common interrupt_init() and timer_interrupt()
3862		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3863		for CPU specific initialization. interrupt_init_cpu()
3864		should set decrementer_count to appropriate value. If
3865		CPU resets decrementer automatically after interrupt
3866		(ppc4xx) it should set decrementer_count to zero.
3867		timer_interrupt() calls timer_interrupt_cpu() for CPU
3868		specific handling. If board has watchdog / status_led
3869		/ other_activity_monitor it works automatically from
3870		general timer_interrupt().
3871
3872- General:
3873
3874		In the target system modem support is enabled when a
3875		specific key (key combination) is pressed during
3876		power-on. Otherwise U-Boot will boot normally
3877		(autoboot). The key_pressed() function is called from
3878		board_init(). Currently key_pressed() is a dummy
3879		function, returning 1 and thus enabling modem
3880		initialization.
3881
3882		If there are no modem init strings in the
3883		environment, U-Boot proceed to autoboot; the
3884		previous output (banner, info printfs) will be
3885		suppressed, though.
3886
3887		See also: doc/README.Modem
3888
3889Board initialization settings:
3890------------------------------
3891
3892During Initialization u-boot calls a number of board specific functions
3893to allow the preparation of board specific prerequisites, e.g. pin setup
3894before drivers are initialized. To enable these callbacks the
3895following configuration macros have to be defined. Currently this is
3896architecture specific, so please check arch/your_architecture/lib/board.c
3897typically in board_init_f() and board_init_r().
3898
3899- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3900- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3901- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3902- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3903
3904Configuration Settings:
3905-----------------------
3906
3907- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3908		Optionally it can be defined to support 64-bit memory commands.
3909
3910- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3911		undefine this when you're short of memory.
3912
3913- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3914		width of the commands listed in the 'help' command output.
3915
3916- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3917		prompt for user input.
3918
3919- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3920
3921- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3922
3923- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3924
3925- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3926		the application (usually a Linux kernel) when it is
3927		booted
3928
3929- CONFIG_SYS_BAUDRATE_TABLE:
3930		List of legal baudrate settings for this board.
3931
3932- CONFIG_SYS_CONSOLE_INFO_QUIET
3933		Suppress display of console information at boot.
3934
3935- CONFIG_SYS_CONSOLE_IS_IN_ENV
3936		If the board specific function
3937			extern int overwrite_console (void);
3938		returns 1, the stdin, stderr and stdout are switched to the
3939		serial port, else the settings in the environment are used.
3940
3941- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3942		Enable the call to overwrite_console().
3943
3944- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3945		Enable overwrite of previous console environment settings.
3946
3947- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3948		Begin and End addresses of the area used by the
3949		simple memory test.
3950
3951- CONFIG_SYS_ALT_MEMTEST:
3952		Enable an alternate, more extensive memory test.
3953
3954- CONFIG_SYS_MEMTEST_SCRATCH:
3955		Scratch address used by the alternate memory test
3956		You only need to set this if address zero isn't writeable
3957
3958- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3959		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3960		this specified memory area will get subtracted from the top
3961		(end) of RAM and won't get "touched" at all by U-Boot. By
3962		fixing up gd->ram_size the Linux kernel should gets passed
3963		the now "corrected" memory size and won't touch it either.
3964		This should work for arch/ppc and arch/powerpc. Only Linux
3965		board ports in arch/powerpc with bootwrapper support that
3966		recalculate the memory size from the SDRAM controller setup
3967		will have to get fixed in Linux additionally.
3968
3969		This option can be used as a workaround for the 440EPx/GRx
3970		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3971		be touched.
3972
3973		WARNING: Please make sure that this value is a multiple of
3974		the Linux page size (normally 4k). If this is not the case,
3975		then the end address of the Linux memory will be located at a
3976		non page size aligned address and this could cause major
3977		problems.
3978
3979- CONFIG_SYS_LOADS_BAUD_CHANGE:
3980		Enable temporary baudrate change while serial download
3981
3982- CONFIG_SYS_SDRAM_BASE:
3983		Physical start address of SDRAM. _Must_ be 0 here.
3984
3985- CONFIG_SYS_MBIO_BASE:
3986		Physical start address of Motherboard I/O (if using a
3987		Cogent motherboard)
3988
3989- CONFIG_SYS_FLASH_BASE:
3990		Physical start address of Flash memory.
3991
3992- CONFIG_SYS_MONITOR_BASE:
3993		Physical start address of boot monitor code (set by
3994		make config files to be same as the text base address
3995		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3996		CONFIG_SYS_FLASH_BASE when booting from flash.
3997
3998- CONFIG_SYS_MONITOR_LEN:
3999		Size of memory reserved for monitor code, used to
4000		determine _at_compile_time_ (!) if the environment is
4001		embedded within the U-Boot image, or in a separate
4002		flash sector.
4003
4004- CONFIG_SYS_MALLOC_LEN:
4005		Size of DRAM reserved for malloc() use.
4006
4007- CONFIG_SYS_MALLOC_F_LEN
4008		Size of the malloc() pool for use before relocation. If
4009		this is defined, then a very simple malloc() implementation
4010		will become available before relocation. The address is just
4011		below the global data, and the stack is moved down to make
4012		space.
4013
4014		This feature allocates regions with increasing addresses
4015		within the region. calloc() is supported, but realloc()
4016		is not available. free() is supported but does nothing.
4017		The memory will be freed (or in fact just forgotten) when
4018		U-Boot relocates itself.
4019
4020		Pre-relocation malloc() is only supported on ARM and sandbox
4021		at present but is fairly easy to enable for other archs.
4022
4023- CONFIG_SYS_MALLOC_SIMPLE
4024		Provides a simple and small malloc() and calloc() for those
4025		boards which do not use the full malloc in SPL (which is
4026		enabled with CONFIG_SYS_SPL_MALLOC_START).
4027
4028- CONFIG_SYS_NONCACHED_MEMORY:
4029		Size of non-cached memory area. This area of memory will be
4030		typically located right below the malloc() area and mapped
4031		uncached in the MMU. This is useful for drivers that would
4032		otherwise require a lot of explicit cache maintenance. For
4033		some drivers it's also impossible to properly maintain the
4034		cache. For example if the regions that need to be flushed
4035		are not a multiple of the cache-line size, *and* padding
4036		cannot be allocated between the regions to align them (i.e.
4037		if the HW requires a contiguous array of regions, and the
4038		size of each region is not cache-aligned), then a flush of
4039		one region may result in overwriting data that hardware has
4040		written to another region in the same cache-line. This can
4041		happen for example in network drivers where descriptors for
4042		buffers are typically smaller than the CPU cache-line (e.g.
4043		16 bytes vs. 32 or 64 bytes).
4044
4045		Non-cached memory is only supported on 32-bit ARM at present.
4046
4047- CONFIG_SYS_BOOTM_LEN:
4048		Normally compressed uImages are limited to an
4049		uncompressed size of 8 MBytes. If this is not enough,
4050		you can define CONFIG_SYS_BOOTM_LEN in your board config file
4051		to adjust this setting to your needs.
4052
4053- CONFIG_SYS_BOOTMAPSZ:
4054		Maximum size of memory mapped by the startup code of
4055		the Linux kernel; all data that must be processed by
4056		the Linux kernel (bd_info, boot arguments, FDT blob if
4057		used) must be put below this limit, unless "bootm_low"
4058		environment variable is defined and non-zero. In such case
4059		all data for the Linux kernel must be between "bootm_low"
4060		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
4061		variable "bootm_mapsize" will override the value of
4062		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
4063		then the value in "bootm_size" will be used instead.
4064
4065- CONFIG_SYS_BOOT_RAMDISK_HIGH:
4066		Enable initrd_high functionality.  If defined then the
4067		initrd_high feature is enabled and the bootm ramdisk subcommand
4068		is enabled.
4069
4070- CONFIG_SYS_BOOT_GET_CMDLINE:
4071		Enables allocating and saving kernel cmdline in space between
4072		"bootm_low" and "bootm_low" + BOOTMAPSZ.
4073
4074- CONFIG_SYS_BOOT_GET_KBD:
4075		Enables allocating and saving a kernel copy of the bd_info in
4076		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
4077
4078- CONFIG_SYS_MAX_FLASH_BANKS:
4079		Max number of Flash memory banks
4080
4081- CONFIG_SYS_MAX_FLASH_SECT:
4082		Max number of sectors on a Flash chip
4083
4084- CONFIG_SYS_FLASH_ERASE_TOUT:
4085		Timeout for Flash erase operations (in ms)
4086
4087- CONFIG_SYS_FLASH_WRITE_TOUT:
4088		Timeout for Flash write operations (in ms)
4089
4090- CONFIG_SYS_FLASH_LOCK_TOUT
4091		Timeout for Flash set sector lock bit operation (in ms)
4092
4093- CONFIG_SYS_FLASH_UNLOCK_TOUT
4094		Timeout for Flash clear lock bits operation (in ms)
4095
4096- CONFIG_SYS_FLASH_PROTECTION
4097		If defined, hardware flash sectors protection is used
4098		instead of U-Boot software protection.
4099
4100- CONFIG_SYS_DIRECT_FLASH_TFTP:
4101
4102		Enable TFTP transfers directly to flash memory;
4103		without this option such a download has to be
4104		performed in two steps: (1) download to RAM, and (2)
4105		copy from RAM to flash.
4106
4107		The two-step approach is usually more reliable, since
4108		you can check if the download worked before you erase
4109		the flash, but in some situations (when system RAM is
4110		too limited to allow for a temporary copy of the
4111		downloaded image) this option may be very useful.
4112
4113- CONFIG_SYS_FLASH_CFI:
4114		Define if the flash driver uses extra elements in the
4115		common flash structure for storing flash geometry.
4116
4117- CONFIG_FLASH_CFI_DRIVER
4118		This option also enables the building of the cfi_flash driver
4119		in the drivers directory
4120
4121- CONFIG_FLASH_CFI_MTD
4122		This option enables the building of the cfi_mtd driver
4123		in the drivers directory. The driver exports CFI flash
4124		to the MTD layer.
4125
4126- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
4127		Use buffered writes to flash.
4128
4129- CONFIG_FLASH_SPANSION_S29WS_N
4130		s29ws-n MirrorBit flash has non-standard addresses for buffered
4131		write commands.
4132
4133- CONFIG_SYS_FLASH_QUIET_TEST
4134		If this option is defined, the common CFI flash doesn't
4135		print it's warning upon not recognized FLASH banks. This
4136		is useful, if some of the configured banks are only
4137		optionally available.
4138
4139- CONFIG_FLASH_SHOW_PROGRESS
4140		If defined (must be an integer), print out countdown
4141		digits and dots.  Recommended value: 45 (9..1) for 80
4142		column displays, 15 (3..1) for 40 column displays.
4143
4144- CONFIG_FLASH_VERIFY
4145		If defined, the content of the flash (destination) is compared
4146		against the source after the write operation. An error message
4147		will be printed when the contents are not identical.
4148		Please note that this option is useless in nearly all cases,
4149		since such flash programming errors usually are detected earlier
4150		while unprotecting/erasing/programming. Please only enable
4151		this option if you really know what you are doing.
4152
4153- CONFIG_SYS_RX_ETH_BUFFER:
4154		Defines the number of Ethernet receive buffers. On some
4155		Ethernet controllers it is recommended to set this value
4156		to 8 or even higher (EEPRO100 or 405 EMAC), since all
4157		buffers can be full shortly after enabling the interface
4158		on high Ethernet traffic.
4159		Defaults to 4 if not defined.
4160
4161- CONFIG_ENV_MAX_ENTRIES
4162
4163	Maximum number of entries in the hash table that is used
4164	internally to store the environment settings. The default
4165	setting is supposed to be generous and should work in most
4166	cases. This setting can be used to tune behaviour; see
4167	lib/hashtable.c for details.
4168
4169- CONFIG_ENV_FLAGS_LIST_DEFAULT
4170- CONFIG_ENV_FLAGS_LIST_STATIC
4171	Enable validation of the values given to environment variables when
4172	calling env set.  Variables can be restricted to only decimal,
4173	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4174	the variables can also be restricted to IP address or MAC address.
4175
4176	The format of the list is:
4177		type_attribute = [s|d|x|b|i|m]
4178		access_attribute = [a|r|o|c]
4179		attributes = type_attribute[access_attribute]
4180		entry = variable_name[:attributes]
4181		list = entry[,list]
4182
4183	The type attributes are:
4184		s - String (default)
4185		d - Decimal
4186		x - Hexadecimal
4187		b - Boolean ([1yYtT|0nNfF])
4188		i - IP address
4189		m - MAC address
4190
4191	The access attributes are:
4192		a - Any (default)
4193		r - Read-only
4194		o - Write-once
4195		c - Change-default
4196
4197	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4198		Define this to a list (string) to define the ".flags"
4199		environment variable in the default or embedded environment.
4200
4201	- CONFIG_ENV_FLAGS_LIST_STATIC
4202		Define this to a list (string) to define validation that
4203		should be done if an entry is not found in the ".flags"
4204		environment variable.  To override a setting in the static
4205		list, simply add an entry for the same variable name to the
4206		".flags" variable.
4207
4208- CONFIG_ENV_ACCESS_IGNORE_FORCE
4209	If defined, don't allow the -f switch to env set override variable
4210	access flags.
4211
4212- CONFIG_SYS_GENERIC_BOARD
4213	This selects the architecture-generic board system instead of the
4214	architecture-specific board files. It is intended to move boards
4215	to this new framework over time. Defining this will disable the
4216	arch/foo/lib/board.c file and use common/board_f.c and
4217	common/board_r.c instead. To use this option your architecture
4218	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
4219	its config.mk file). If you find problems enabling this option on
4220	your board please report the problem and send patches!
4221
4222- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4223	This is set by OMAP boards for the max time that reset should
4224	be asserted. See doc/README.omap-reset-time for details on how
4225	the value can be calculated on a given board.
4226
4227- CONFIG_USE_STDINT
4228	If stdint.h is available with your toolchain you can define this
4229	option to enable it. You can provide option 'USE_STDINT=1' when
4230	building U-Boot to enable this.
4231
4232The following definitions that deal with the placement and management
4233of environment data (variable area); in general, we support the
4234following configurations:
4235
4236- CONFIG_BUILD_ENVCRC:
4237
4238	Builds up envcrc with the target environment so that external utils
4239	may easily extract it and embed it in final U-Boot images.
4240
4241- CONFIG_ENV_IS_IN_FLASH:
4242
4243	Define this if the environment is in flash memory.
4244
4245	a) The environment occupies one whole flash sector, which is
4246	   "embedded" in the text segment with the U-Boot code. This
4247	   happens usually with "bottom boot sector" or "top boot
4248	   sector" type flash chips, which have several smaller
4249	   sectors at the start or the end. For instance, such a
4250	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4251	   such a case you would place the environment in one of the
4252	   4 kB sectors - with U-Boot code before and after it. With
4253	   "top boot sector" type flash chips, you would put the
4254	   environment in one of the last sectors, leaving a gap
4255	   between U-Boot and the environment.
4256
4257	- CONFIG_ENV_OFFSET:
4258
4259	   Offset of environment data (variable area) to the
4260	   beginning of flash memory; for instance, with bottom boot
4261	   type flash chips the second sector can be used: the offset
4262	   for this sector is given here.
4263
4264	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4265
4266	- CONFIG_ENV_ADDR:
4267
4268	   This is just another way to specify the start address of
4269	   the flash sector containing the environment (instead of
4270	   CONFIG_ENV_OFFSET).
4271
4272	- CONFIG_ENV_SECT_SIZE:
4273
4274	   Size of the sector containing the environment.
4275
4276
4277	b) Sometimes flash chips have few, equal sized, BIG sectors.
4278	   In such a case you don't want to spend a whole sector for
4279	   the environment.
4280
4281	- CONFIG_ENV_SIZE:
4282
4283	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4284	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4285	   of this flash sector for the environment. This saves
4286	   memory for the RAM copy of the environment.
4287
4288	   It may also save flash memory if you decide to use this
4289	   when your environment is "embedded" within U-Boot code,
4290	   since then the remainder of the flash sector could be used
4291	   for U-Boot code. It should be pointed out that this is
4292	   STRONGLY DISCOURAGED from a robustness point of view:
4293	   updating the environment in flash makes it always
4294	   necessary to erase the WHOLE sector. If something goes
4295	   wrong before the contents has been restored from a copy in
4296	   RAM, your target system will be dead.
4297
4298	- CONFIG_ENV_ADDR_REDUND
4299	  CONFIG_ENV_SIZE_REDUND
4300
4301	   These settings describe a second storage area used to hold
4302	   a redundant copy of the environment data, so that there is
4303	   a valid backup copy in case there is a power failure during
4304	   a "saveenv" operation.
4305
4306BE CAREFUL! Any changes to the flash layout, and some changes to the
4307source code will make it necessary to adapt <board>/u-boot.lds*
4308accordingly!
4309
4310
4311- CONFIG_ENV_IS_IN_NVRAM:
4312
4313	Define this if you have some non-volatile memory device
4314	(NVRAM, battery buffered SRAM) which you want to use for the
4315	environment.
4316
4317	- CONFIG_ENV_ADDR:
4318	- CONFIG_ENV_SIZE:
4319
4320	  These two #defines are used to determine the memory area you
4321	  want to use for environment. It is assumed that this memory
4322	  can just be read and written to, without any special
4323	  provision.
4324
4325BE CAREFUL! The first access to the environment happens quite early
4326in U-Boot initialization (when we try to get the setting of for the
4327console baudrate). You *MUST* have mapped your NVRAM area then, or
4328U-Boot will hang.
4329
4330Please note that even with NVRAM we still use a copy of the
4331environment in RAM: we could work on NVRAM directly, but we want to
4332keep settings there always unmodified except somebody uses "saveenv"
4333to save the current settings.
4334
4335
4336- CONFIG_ENV_IS_IN_EEPROM:
4337
4338	Use this if you have an EEPROM or similar serial access
4339	device and a driver for it.
4340
4341	- CONFIG_ENV_OFFSET:
4342	- CONFIG_ENV_SIZE:
4343
4344	  These two #defines specify the offset and size of the
4345	  environment area within the total memory of your EEPROM.
4346
4347	- CONFIG_SYS_I2C_EEPROM_ADDR:
4348	  If defined, specified the chip address of the EEPROM device.
4349	  The default address is zero.
4350
4351	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4352	  If defined, the number of bits used to address bytes in a
4353	  single page in the EEPROM device.  A 64 byte page, for example
4354	  would require six bits.
4355
4356	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4357	  If defined, the number of milliseconds to delay between
4358	  page writes.	The default is zero milliseconds.
4359
4360	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4361	  The length in bytes of the EEPROM memory array address.  Note
4362	  that this is NOT the chip address length!
4363
4364	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4365	  EEPROM chips that implement "address overflow" are ones
4366	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4367	  address and the extra bits end up in the "chip address" bit
4368	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4369	  byte chips.
4370
4371	  Note that we consider the length of the address field to
4372	  still be one byte because the extra address bits are hidden
4373	  in the chip address.
4374
4375	- CONFIG_SYS_EEPROM_SIZE:
4376	  The size in bytes of the EEPROM device.
4377
4378	- CONFIG_ENV_EEPROM_IS_ON_I2C
4379	  define this, if you have I2C and SPI activated, and your
4380	  EEPROM, which holds the environment, is on the I2C bus.
4381
4382	- CONFIG_I2C_ENV_EEPROM_BUS
4383	  if you have an Environment on an EEPROM reached over
4384	  I2C muxes, you can define here, how to reach this
4385	  EEPROM. For example:
4386
4387	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4388
4389	  EEPROM which holds the environment, is reached over
4390	  a pca9547 i2c mux with address 0x70, channel 3.
4391
4392- CONFIG_ENV_IS_IN_DATAFLASH:
4393
4394	Define this if you have a DataFlash memory device which you
4395	want to use for the environment.
4396
4397	- CONFIG_ENV_OFFSET:
4398	- CONFIG_ENV_ADDR:
4399	- CONFIG_ENV_SIZE:
4400
4401	  These three #defines specify the offset and size of the
4402	  environment area within the total memory of your DataFlash placed
4403	  at the specified address.
4404
4405- CONFIG_ENV_IS_IN_SPI_FLASH:
4406
4407	Define this if you have a SPI Flash memory device which you
4408	want to use for the environment.
4409
4410	- CONFIG_ENV_OFFSET:
4411	- CONFIG_ENV_SIZE:
4412
4413	  These two #defines specify the offset and size of the
4414	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4415	  aligned to an erase sector boundary.
4416
4417	- CONFIG_ENV_SECT_SIZE:
4418
4419	  Define the SPI flash's sector size.
4420
4421	- CONFIG_ENV_OFFSET_REDUND (optional):
4422
4423	  This setting describes a second storage area of CONFIG_ENV_SIZE
4424	  size used to hold a redundant copy of the environment data, so
4425	  that there is a valid backup copy in case there is a power failure
4426	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4427	  aligned to an erase sector boundary.
4428
4429	- CONFIG_ENV_SPI_BUS (optional):
4430	- CONFIG_ENV_SPI_CS (optional):
4431
4432	  Define the SPI bus and chip select. If not defined they will be 0.
4433
4434	- CONFIG_ENV_SPI_MAX_HZ (optional):
4435
4436	  Define the SPI max work clock. If not defined then use 1MHz.
4437
4438	- CONFIG_ENV_SPI_MODE (optional):
4439
4440	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4441
4442- CONFIG_ENV_IS_IN_REMOTE:
4443
4444	Define this if you have a remote memory space which you
4445	want to use for the local device's environment.
4446
4447	- CONFIG_ENV_ADDR:
4448	- CONFIG_ENV_SIZE:
4449
4450	  These two #defines specify the address and size of the
4451	  environment area within the remote memory space. The
4452	  local device can get the environment from remote memory
4453	  space by SRIO or PCIE links.
4454
4455BE CAREFUL! For some special cases, the local device can not use
4456"saveenv" command. For example, the local device will get the
4457environment stored in a remote NOR flash by SRIO or PCIE link,
4458but it can not erase, write this NOR flash by SRIO or PCIE interface.
4459
4460- CONFIG_ENV_IS_IN_NAND:
4461
4462	Define this if you have a NAND device which you want to use
4463	for the environment.
4464
4465	- CONFIG_ENV_OFFSET:
4466	- CONFIG_ENV_SIZE:
4467
4468	  These two #defines specify the offset and size of the environment
4469	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4470	  aligned to an erase block boundary.
4471
4472	- CONFIG_ENV_OFFSET_REDUND (optional):
4473
4474	  This setting describes a second storage area of CONFIG_ENV_SIZE
4475	  size used to hold a redundant copy of the environment data, so
4476	  that there is a valid backup copy in case there is a power failure
4477	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4478	  aligned to an erase block boundary.
4479
4480	- CONFIG_ENV_RANGE (optional):
4481
4482	  Specifies the length of the region in which the environment
4483	  can be written.  This should be a multiple of the NAND device's
4484	  block size.  Specifying a range with more erase blocks than
4485	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4486	  the range to be avoided.
4487
4488	- CONFIG_ENV_OFFSET_OOB (optional):
4489
4490	  Enables support for dynamically retrieving the offset of the
4491	  environment from block zero's out-of-band data.  The
4492	  "nand env.oob" command can be used to record this offset.
4493	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4494	  using CONFIG_ENV_OFFSET_OOB.
4495
4496- CONFIG_NAND_ENV_DST
4497
4498	Defines address in RAM to which the nand_spl code should copy the
4499	environment. If redundant environment is used, it will be copied to
4500	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4501
4502- CONFIG_ENV_IS_IN_UBI:
4503
4504	Define this if you have an UBI volume that you want to use for the
4505	environment.  This has the benefit of wear-leveling the environment
4506	accesses, which is important on NAND.
4507
4508	- CONFIG_ENV_UBI_PART:
4509
4510	  Define this to a string that is the mtd partition containing the UBI.
4511
4512	- CONFIG_ENV_UBI_VOLUME:
4513
4514	  Define this to the name of the volume that you want to store the
4515	  environment in.
4516
4517	- CONFIG_ENV_UBI_VOLUME_REDUND:
4518
4519	  Define this to the name of another volume to store a second copy of
4520	  the environment in.  This will enable redundant environments in UBI.
4521	  It is assumed that both volumes are in the same MTD partition.
4522
4523	- CONFIG_UBI_SILENCE_MSG
4524	- CONFIG_UBIFS_SILENCE_MSG
4525
4526	  You will probably want to define these to avoid a really noisy system
4527	  when storing the env in UBI.
4528
4529- CONFIG_ENV_IS_IN_FAT:
4530       Define this if you want to use the FAT file system for the environment.
4531
4532       - FAT_ENV_INTERFACE:
4533
4534         Define this to a string that is the name of the block device.
4535
4536       - FAT_ENV_DEV_AND_PART:
4537
4538         Define this to a string to specify the partition of the device. It can
4539         be as following:
4540
4541           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4542               - "D:P": device D partition P. Error occurs if device D has no
4543                        partition table.
4544               - "D:0": device D.
4545               - "D" or "D:": device D partition 1 if device D has partition
4546                              table, or the whole device D if has no partition
4547                              table.
4548               - "D:auto": first partition in device D with bootable flag set.
4549                           If none, first valid partition in device D. If no
4550                           partition table then means device D.
4551
4552       - FAT_ENV_FILE:
4553
4554         It's a string of the FAT file name. This file use to store the
4555         environment.
4556
4557       - CONFIG_FAT_WRITE:
4558         This should be defined. Otherwise it cannot save the environment file.
4559
4560- CONFIG_ENV_IS_IN_MMC:
4561
4562	Define this if you have an MMC device which you want to use for the
4563	environment.
4564
4565	- CONFIG_SYS_MMC_ENV_DEV:
4566
4567	  Specifies which MMC device the environment is stored in.
4568
4569	- CONFIG_SYS_MMC_ENV_PART (optional):
4570
4571	  Specifies which MMC partition the environment is stored in. If not
4572	  set, defaults to partition 0, the user area. Common values might be
4573	  1 (first MMC boot partition), 2 (second MMC boot partition).
4574
4575	- CONFIG_ENV_OFFSET:
4576	- CONFIG_ENV_SIZE:
4577
4578	  These two #defines specify the offset and size of the environment
4579	  area within the specified MMC device.
4580
4581	  If offset is positive (the usual case), it is treated as relative to
4582	  the start of the MMC partition. If offset is negative, it is treated
4583	  as relative to the end of the MMC partition. This can be useful if
4584	  your board may be fitted with different MMC devices, which have
4585	  different sizes for the MMC partitions, and you always want the
4586	  environment placed at the very end of the partition, to leave the
4587	  maximum possible space before it, to store other data.
4588
4589	  These two values are in units of bytes, but must be aligned to an
4590	  MMC sector boundary.
4591
4592	- CONFIG_ENV_OFFSET_REDUND (optional):
4593
4594	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4595	  hold a redundant copy of the environment data. This provides a
4596	  valid backup copy in case the other copy is corrupted, e.g. due
4597	  to a power failure during a "saveenv" operation.
4598
4599	  This value may also be positive or negative; this is handled in the
4600	  same way as CONFIG_ENV_OFFSET.
4601
4602	  This value is also in units of bytes, but must also be aligned to
4603	  an MMC sector boundary.
4604
4605	- CONFIG_ENV_SIZE_REDUND (optional):
4606
4607	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4608	  set. If this value is set, it must be set to the same value as
4609	  CONFIG_ENV_SIZE.
4610
4611- CONFIG_SYS_SPI_INIT_OFFSET
4612
4613	Defines offset to the initial SPI buffer area in DPRAM. The
4614	area is used at an early stage (ROM part) if the environment
4615	is configured to reside in the SPI EEPROM: We need a 520 byte
4616	scratch DPRAM area. It is used between the two initialization
4617	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4618	to be a good choice since it makes it far enough from the
4619	start of the data area as well as from the stack pointer.
4620
4621Please note that the environment is read-only until the monitor
4622has been relocated to RAM and a RAM copy of the environment has been
4623created; also, when using EEPROM you will have to use getenv_f()
4624until then to read environment variables.
4625
4626The environment is protected by a CRC32 checksum. Before the monitor
4627is relocated into RAM, as a result of a bad CRC you will be working
4628with the compiled-in default environment - *silently*!!! [This is
4629necessary, because the first environment variable we need is the
4630"baudrate" setting for the console - if we have a bad CRC, we don't
4631have any device yet where we could complain.]
4632
4633Note: once the monitor has been relocated, then it will complain if
4634the default environment is used; a new CRC is computed as soon as you
4635use the "saveenv" command to store a valid environment.
4636
4637- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4638		Echo the inverted Ethernet link state to the fault LED.
4639
4640		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4641		      also needs to be defined.
4642
4643- CONFIG_SYS_FAULT_MII_ADDR:
4644		MII address of the PHY to check for the Ethernet link state.
4645
4646- CONFIG_NS16550_MIN_FUNCTIONS:
4647		Define this if you desire to only have use of the NS16550_init
4648		and NS16550_putc functions for the serial driver located at
4649		drivers/serial/ns16550.c.  This option is useful for saving
4650		space for already greatly restricted images, including but not
4651		limited to NAND_SPL configurations.
4652
4653- CONFIG_DISPLAY_BOARDINFO
4654		Display information about the board that U-Boot is running on
4655		when U-Boot starts up. The board function checkboard() is called
4656		to do this.
4657
4658- CONFIG_DISPLAY_BOARDINFO_LATE
4659		Similar to the previous option, but display this information
4660		later, once stdio is running and output goes to the LCD, if
4661		present.
4662
4663- CONFIG_BOARD_SIZE_LIMIT:
4664		Maximum size of the U-Boot image. When defined, the
4665		build system checks that the actual size does not
4666		exceed it.
4667
4668Low Level (hardware related) configuration options:
4669---------------------------------------------------
4670
4671- CONFIG_SYS_CACHELINE_SIZE:
4672		Cache Line Size of the CPU.
4673
4674- CONFIG_SYS_DEFAULT_IMMR:
4675		Default address of the IMMR after system reset.
4676
4677		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4678		and RPXsuper) to be able to adjust the position of
4679		the IMMR register after a reset.
4680
4681- CONFIG_SYS_CCSRBAR_DEFAULT:
4682		Default (power-on reset) physical address of CCSR on Freescale
4683		PowerPC SOCs.
4684
4685- CONFIG_SYS_CCSRBAR:
4686		Virtual address of CCSR.  On a 32-bit build, this is typically
4687		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4688
4689		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4690		for cross-platform code that uses that macro instead.
4691
4692- CONFIG_SYS_CCSRBAR_PHYS:
4693		Physical address of CCSR.  CCSR can be relocated to a new
4694		physical address, if desired.  In this case, this macro should
4695		be set to that address.	 Otherwise, it should be set to the
4696		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4697		is typically relocated on 36-bit builds.  It is recommended
4698		that this macro be defined via the _HIGH and _LOW macros:
4699
4700		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4701			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4702
4703- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4704		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4705		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4706		used in assembly code, so it must not contain typecasts or
4707		integer size suffixes (e.g. "ULL").
4708
4709- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4710		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4711		used in assembly code, so it must not contain typecasts or
4712		integer size suffixes (e.g. "ULL").
4713
4714- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4715		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4716		forced to a value that ensures that CCSR is not relocated.
4717
4718- Floppy Disk Support:
4719		CONFIG_SYS_FDC_DRIVE_NUMBER
4720
4721		the default drive number (default value 0)
4722
4723		CONFIG_SYS_ISA_IO_STRIDE
4724
4725		defines the spacing between FDC chipset registers
4726		(default value 1)
4727
4728		CONFIG_SYS_ISA_IO_OFFSET
4729
4730		defines the offset of register from address. It
4731		depends on which part of the data bus is connected to
4732		the FDC chipset. (default value 0)
4733
4734		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4735		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4736		default value.
4737
4738		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4739		fdc_hw_init() is called at the beginning of the FDC
4740		setup. fdc_hw_init() must be provided by the board
4741		source code. It is used to make hardware-dependent
4742		initializations.
4743
4744- CONFIG_IDE_AHB:
4745		Most IDE controllers were designed to be connected with PCI
4746		interface. Only few of them were designed for AHB interface.
4747		When software is doing ATA command and data transfer to
4748		IDE devices through IDE-AHB controller, some additional
4749		registers accessing to these kind of IDE-AHB controller
4750		is required.
4751
4752- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4753		DO NOT CHANGE unless you know exactly what you're
4754		doing! (11-4) [MPC8xx/82xx systems only]
4755
4756- CONFIG_SYS_INIT_RAM_ADDR:
4757
4758		Start address of memory area that can be used for
4759		initial data and stack; please note that this must be
4760		writable memory that is working WITHOUT special
4761		initialization, i. e. you CANNOT use normal RAM which
4762		will become available only after programming the
4763		memory controller and running certain initialization
4764		sequences.
4765
4766		U-Boot uses the following memory types:
4767		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4768		- MPC824X: data cache
4769		- PPC4xx:  data cache
4770
4771- CONFIG_SYS_GBL_DATA_OFFSET:
4772
4773		Offset of the initial data structure in the memory
4774		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4775		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4776		data is located at the end of the available space
4777		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4778		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4779		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4780		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4781
4782	Note:
4783		On the MPC824X (or other systems that use the data
4784		cache for initial memory) the address chosen for
4785		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4786		point to an otherwise UNUSED address space between
4787		the top of RAM and the start of the PCI space.
4788
4789- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4790
4791- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4792
4793- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4794
4795- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4796
4797- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4798
4799- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4800
4801- CONFIG_SYS_OR_TIMING_SDRAM:
4802		SDRAM timing
4803
4804- CONFIG_SYS_MAMR_PTA:
4805		periodic timer for refresh
4806
4807- CONFIG_SYS_DER:	Debug Event Register (37-47)
4808
4809- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4810  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4811  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4812  CONFIG_SYS_BR1_PRELIM:
4813		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4814
4815- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4816  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4817  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4818		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4819
4820- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4821  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4822		Machine Mode Register and Memory Periodic Timer
4823		Prescaler definitions (SDRAM timing)
4824
4825- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4826		enable I2C microcode relocation patch (MPC8xx);
4827		define relocation offset in DPRAM [DSP2]
4828
4829- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4830		enable SMC microcode relocation patch (MPC8xx);
4831		define relocation offset in DPRAM [SMC1]
4832
4833- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4834		enable SPI microcode relocation patch (MPC8xx);
4835		define relocation offset in DPRAM [SCC4]
4836
4837- CONFIG_SYS_USE_OSCCLK:
4838		Use OSCM clock mode on MBX8xx board. Be careful,
4839		wrong setting might damage your board. Read
4840		doc/README.MBX before setting this variable!
4841
4842- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4843		Offset of the bootmode word in DPRAM used by post
4844		(Power On Self Tests). This definition overrides
4845		#define'd default value in commproc.h resp.
4846		cpm_8260.h.
4847
4848- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4849  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4850  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4851  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4852  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4853  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4854  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4855  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4856		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4857
4858- CONFIG_PCI_DISABLE_PCIE:
4859		Disable PCI-Express on systems where it is supported but not
4860		required.
4861
4862- CONFIG_PCI_ENUM_ONLY
4863		Only scan through and get the devices on the buses.
4864		Don't do any setup work, presumably because someone or
4865		something has already done it, and we don't need to do it
4866		a second time.	Useful for platforms that are pre-booted
4867		by coreboot or similar.
4868
4869- CONFIG_PCI_INDIRECT_BRIDGE:
4870		Enable support for indirect PCI bridges.
4871
4872- CONFIG_SYS_SRIO:
4873		Chip has SRIO or not
4874
4875- CONFIG_SRIO1:
4876		Board has SRIO 1 port available
4877
4878- CONFIG_SRIO2:
4879		Board has SRIO 2 port available
4880
4881- CONFIG_SRIO_PCIE_BOOT_MASTER
4882		Board can support master function for Boot from SRIO and PCIE
4883
4884- CONFIG_SYS_SRIOn_MEM_VIRT:
4885		Virtual Address of SRIO port 'n' memory region
4886
4887- CONFIG_SYS_SRIOn_MEM_PHYS:
4888		Physical Address of SRIO port 'n' memory region
4889
4890- CONFIG_SYS_SRIOn_MEM_SIZE:
4891		Size of SRIO port 'n' memory region
4892
4893- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4894		Defined to tell the NAND controller that the NAND chip is using
4895		a 16 bit bus.
4896		Not all NAND drivers use this symbol.
4897		Example of drivers that use it:
4898		- drivers/mtd/nand/ndfc.c
4899		- drivers/mtd/nand/mxc_nand.c
4900
4901- CONFIG_SYS_NDFC_EBC0_CFG
4902		Sets the EBC0_CFG register for the NDFC. If not defined
4903		a default value will be used.
4904
4905- CONFIG_SPD_EEPROM
4906		Get DDR timing information from an I2C EEPROM. Common
4907		with pluggable memory modules such as SODIMMs
4908
4909  SPD_EEPROM_ADDRESS
4910		I2C address of the SPD EEPROM
4911
4912- CONFIG_SYS_SPD_BUS_NUM
4913		If SPD EEPROM is on an I2C bus other than the first
4914		one, specify here. Note that the value must resolve
4915		to something your driver can deal with.
4916
4917- CONFIG_SYS_DDR_RAW_TIMING
4918		Get DDR timing information from other than SPD. Common with
4919		soldered DDR chips onboard without SPD. DDR raw timing
4920		parameters are extracted from datasheet and hard-coded into
4921		header files or board specific files.
4922
4923- CONFIG_FSL_DDR_INTERACTIVE
4924		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4925
4926- CONFIG_SYS_83XX_DDR_USES_CS0
4927		Only for 83xx systems. If specified, then DDR should
4928		be configured using CS0 and CS1 instead of CS2 and CS3.
4929
4930- CONFIG_ETHER_ON_FEC[12]
4931		Define to enable FEC[12] on a 8xx series processor.
4932
4933- CONFIG_FEC[12]_PHY
4934		Define to the hardcoded PHY address which corresponds
4935		to the given FEC; i. e.
4936			#define CONFIG_FEC1_PHY 4
4937		means that the PHY with address 4 is connected to FEC1
4938
4939		When set to -1, means to probe for first available.
4940
4941- CONFIG_FEC[12]_PHY_NORXERR
4942		The PHY does not have a RXERR line (RMII only).
4943		(so program the FEC to ignore it).
4944
4945- CONFIG_RMII
4946		Enable RMII mode for all FECs.
4947		Note that this is a global option, we can't
4948		have one FEC in standard MII mode and another in RMII mode.
4949
4950- CONFIG_CRC32_VERIFY
4951		Add a verify option to the crc32 command.
4952		The syntax is:
4953
4954		=> crc32 -v <address> <count> <crc32>
4955
4956		Where address/count indicate a memory area
4957		and crc32 is the correct crc32 which the
4958		area should have.
4959
4960- CONFIG_LOOPW
4961		Add the "loopw" memory command. This only takes effect if
4962		the memory commands are activated globally (CONFIG_CMD_MEM).
4963
4964- CONFIG_MX_CYCLIC
4965		Add the "mdc" and "mwc" memory commands. These are cyclic
4966		"md/mw" commands.
4967		Examples:
4968
4969		=> mdc.b 10 4 500
4970		This command will print 4 bytes (10,11,12,13) each 500 ms.
4971
4972		=> mwc.l 100 12345678 10
4973		This command will write 12345678 to address 100 all 10 ms.
4974
4975		This only takes effect if the memory commands are activated
4976		globally (CONFIG_CMD_MEM).
4977
4978- CONFIG_SKIP_LOWLEVEL_INIT
4979		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4980		low level initializations (like setting up the memory
4981		controller) are omitted and/or U-Boot does not
4982		relocate itself into RAM.
4983
4984		Normally this variable MUST NOT be defined. The only
4985		exception is when U-Boot is loaded (to RAM) by some
4986		other boot loader or by a debugger which performs
4987		these initializations itself.
4988
4989- CONFIG_SPL_BUILD
4990		Modifies the behaviour of start.S when compiling a loader
4991		that is executed before the actual U-Boot. E.g. when
4992		compiling a NAND SPL.
4993
4994- CONFIG_TPL_BUILD
4995		Modifies the behaviour of start.S  when compiling a loader
4996		that is executed after the SPL and before the actual U-Boot.
4997		It is loaded by the SPL.
4998
4999- CONFIG_SYS_MPC85XX_NO_RESETVEC
5000		Only for 85xx systems. If this variable is specified, the section
5001		.resetvec is not kept and the section .bootpg is placed in the
5002		previous 4k of the .text section.
5003
5004- CONFIG_ARCH_MAP_SYSMEM
5005		Generally U-Boot (and in particular the md command) uses
5006		effective address. It is therefore not necessary to regard
5007		U-Boot address as virtual addresses that need to be translated
5008		to physical addresses. However, sandbox requires this, since
5009		it maintains its own little RAM buffer which contains all
5010		addressable memory. This option causes some memory accesses
5011		to be mapped through map_sysmem() / unmap_sysmem().
5012
5013- CONFIG_USE_ARCH_MEMCPY
5014  CONFIG_USE_ARCH_MEMSET
5015		If these options are used a optimized version of memcpy/memset will
5016		be used if available. These functions may be faster under some
5017		conditions but may increase the binary size.
5018
5019- CONFIG_X86_RESET_VECTOR
5020		If defined, the x86 reset vector code is included. This is not
5021		needed when U-Boot is running from Coreboot.
5022
5023- CONFIG_SYS_MPUCLK
5024		Defines the MPU clock speed (in MHz).
5025
5026		NOTE : currently only supported on AM335x platforms.
5027
5028- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
5029		Enables the RTC32K OSC on AM33xx based plattforms
5030
5031- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
5032		Option to disable subpage write in NAND driver
5033		driver that uses this:
5034		drivers/mtd/nand/davinci_nand.c
5035
5036Freescale QE/FMAN Firmware Support:
5037-----------------------------------
5038
5039The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
5040loading of "firmware", which is encoded in the QE firmware binary format.
5041This firmware often needs to be loaded during U-Boot booting, so macros
5042are used to identify the storage device (NOR flash, SPI, etc) and the address
5043within that device.
5044
5045- CONFIG_SYS_FMAN_FW_ADDR
5046	The address in the storage device where the FMAN microcode is located.  The
5047	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5048	is also specified.
5049
5050- CONFIG_SYS_QE_FW_ADDR
5051	The address in the storage device where the QE microcode is located.  The
5052	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
5053	is also specified.
5054
5055- CONFIG_SYS_QE_FMAN_FW_LENGTH
5056	The maximum possible size of the firmware.  The firmware binary format
5057	has a field that specifies the actual size of the firmware, but it
5058	might not be possible to read any part of the firmware unless some
5059	local storage is allocated to hold the entire firmware first.
5060
5061- CONFIG_SYS_QE_FMAN_FW_IN_NOR
5062	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
5063	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
5064	virtual address in NOR flash.
5065
5066- CONFIG_SYS_QE_FMAN_FW_IN_NAND
5067	Specifies that QE/FMAN firmware is located in NAND flash.
5068	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
5069
5070- CONFIG_SYS_QE_FMAN_FW_IN_MMC
5071	Specifies that QE/FMAN firmware is located on the primary SD/MMC
5072	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5073
5074- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
5075	Specifies that QE/FMAN firmware is located on the primary SPI
5076	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5077
5078- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
5079	Specifies that QE/FMAN firmware is located in the remote (master)
5080	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
5081	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
5082	window->master inbound window->master LAW->the ucode address in
5083	master's memory space.
5084
5085Freescale Layerscape Management Complex Firmware Support:
5086---------------------------------------------------------
5087The Freescale Layerscape Management Complex (MC) supports the loading of
5088"firmware".
5089This firmware often needs to be loaded during U-Boot booting, so macros
5090are used to identify the storage device (NOR flash, SPI, etc) and the address
5091within that device.
5092
5093- CONFIG_FSL_MC_ENET
5094	Enable the MC driver for Layerscape SoCs.
5095
5096- CONFIG_SYS_LS_MC_FW_ADDR
5097	The address in the storage device where the firmware is located.  The
5098	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
5099	is also specified.
5100
5101- CONFIG_SYS_LS_MC_FW_LENGTH
5102	The maximum possible size of the firmware.  The firmware binary format
5103	has a field that specifies the actual size of the firmware, but it
5104	might not be possible to read any part of the firmware unless some
5105	local storage is allocated to hold the entire firmware first.
5106
5107- CONFIG_SYS_LS_MC_FW_IN_NOR
5108	Specifies that MC firmware is located in NOR flash, mapped as
5109	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
5110	virtual address in NOR flash.
5111
5112Building the Software:
5113======================
5114
5115Building U-Boot has been tested in several native build environments
5116and in many different cross environments. Of course we cannot support
5117all possibly existing versions of cross development tools in all
5118(potentially obsolete) versions. In case of tool chain problems we
5119recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
5120which is extensively used to build and test U-Boot.
5121
5122If you are not using a native environment, it is assumed that you
5123have GNU cross compiling tools available in your path. In this case,
5124you must set the environment variable CROSS_COMPILE in your shell.
5125Note that no changes to the Makefile or any other source files are
5126necessary. For example using the ELDK on a 4xx CPU, please enter:
5127
5128	$ CROSS_COMPILE=ppc_4xx-
5129	$ export CROSS_COMPILE
5130
5131Note: If you wish to generate Windows versions of the utilities in
5132      the tools directory you can use the MinGW toolchain
5133      (http://www.mingw.org).  Set your HOST tools to the MinGW
5134      toolchain and execute 'make tools'.  For example:
5135
5136       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5137
5138      Binaries such as tools/mkimage.exe will be created which can
5139      be executed on computers running Windows.
5140
5141U-Boot is intended to be simple to build. After installing the
5142sources you must configure U-Boot for one specific board type. This
5143is done by typing:
5144
5145	make NAME_defconfig
5146
5147where "NAME_defconfig" is the name of one of the existing configu-
5148rations; see boards.cfg for supported names.
5149
5150Note: for some board special configuration names may exist; check if
5151      additional information is available from the board vendor; for
5152      instance, the TQM823L systems are available without (standard)
5153      or with LCD support. You can select such additional "features"
5154      when choosing the configuration, i. e.
5155
5156      make TQM823L_defconfig
5157	- will configure for a plain TQM823L, i. e. no LCD support
5158
5159      make TQM823L_LCD_defconfig
5160	- will configure for a TQM823L with U-Boot console on LCD
5161
5162      etc.
5163
5164
5165Finally, type "make all", and you should get some working U-Boot
5166images ready for download to / installation on your system:
5167
5168- "u-boot.bin" is a raw binary image
5169- "u-boot" is an image in ELF binary format
5170- "u-boot.srec" is in Motorola S-Record format
5171
5172By default the build is performed locally and the objects are saved
5173in the source directory. One of the two methods can be used to change
5174this behavior and build U-Boot to some external directory:
5175
51761. Add O= to the make command line invocations:
5177
5178	make O=/tmp/build distclean
5179	make O=/tmp/build NAME_defconfig
5180	make O=/tmp/build all
5181
51822. Set environment variable KBUILD_OUTPUT to point to the desired location:
5183
5184	export KBUILD_OUTPUT=/tmp/build
5185	make distclean
5186	make NAME_defconfig
5187	make all
5188
5189Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5190variable.
5191
5192
5193Please be aware that the Makefiles assume you are using GNU make, so
5194for instance on NetBSD you might need to use "gmake" instead of
5195native "make".
5196
5197
5198If the system board that you have is not listed, then you will need
5199to port U-Boot to your hardware platform. To do this, follow these
5200steps:
5201
52021.  Add a new configuration option for your board to the toplevel
5203    "boards.cfg" file, using the existing entries as examples.
5204    Follow the instructions there to keep the boards in order.
52052.  Create a new directory to hold your board specific code. Add any
5206    files you need. In your board directory, you will need at least
5207    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
52083.  Create a new configuration file "include/configs/<board>.h" for
5209    your board
52103.  If you're porting U-Boot to a new CPU, then also create a new
5211    directory to hold your CPU specific code. Add any files you need.
52124.  Run "make <board>_defconfig" with your new name.
52135.  Type "make", and you should get a working "u-boot.srec" file
5214    to be installed on your target system.
52156.  Debug and solve any problems that might arise.
5216    [Of course, this last step is much harder than it sounds.]
5217
5218
5219Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5220==============================================================
5221
5222If you have modified U-Boot sources (for instance added a new board
5223or support for new devices, a new CPU, etc.) you are expected to
5224provide feedback to the other developers. The feedback normally takes
5225the form of a "patch", i. e. a context diff against a certain (latest
5226official or latest in the git repository) version of U-Boot sources.
5227
5228But before you submit such a patch, please verify that your modifi-
5229cation did not break existing code. At least make sure that *ALL* of
5230the supported boards compile WITHOUT ANY compiler warnings. To do so,
5231just run the "MAKEALL" script, which will configure and build U-Boot
5232for ALL supported system. Be warned, this will take a while. You can
5233select which (cross) compiler to use by passing a `CROSS_COMPILE'
5234environment variable to the script, i. e. to use the ELDK cross tools
5235you can type
5236
5237	CROSS_COMPILE=ppc_8xx- MAKEALL
5238
5239or to build on a native PowerPC system you can type
5240
5241	CROSS_COMPILE=' ' MAKEALL
5242
5243When using the MAKEALL script, the default behaviour is to build
5244U-Boot in the source directory. This location can be changed by
5245setting the BUILD_DIR environment variable. Also, for each target
5246built, the MAKEALL script saves two log files (<target>.ERR and
5247<target>.MAKEALL) in the <source dir>/LOG directory. This default
5248location can be changed by setting the MAKEALL_LOGDIR environment
5249variable. For example:
5250
5251	export BUILD_DIR=/tmp/build
5252	export MAKEALL_LOGDIR=/tmp/log
5253	CROSS_COMPILE=ppc_8xx- MAKEALL
5254
5255With the above settings build objects are saved in the /tmp/build,
5256log files are saved in the /tmp/log and the source tree remains clean
5257during the whole build process.
5258
5259
5260See also "U-Boot Porting Guide" below.
5261
5262
5263Monitor Commands - Overview:
5264============================
5265
5266go	- start application at address 'addr'
5267run	- run commands in an environment variable
5268bootm	- boot application image from memory
5269bootp	- boot image via network using BootP/TFTP protocol
5270bootz   - boot zImage from memory
5271tftpboot- boot image via network using TFTP protocol
5272	       and env variables "ipaddr" and "serverip"
5273	       (and eventually "gatewayip")
5274tftpput - upload a file via network using TFTP protocol
5275rarpboot- boot image via network using RARP/TFTP protocol
5276diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5277loads	- load S-Record file over serial line
5278loadb	- load binary file over serial line (kermit mode)
5279md	- memory display
5280mm	- memory modify (auto-incrementing)
5281nm	- memory modify (constant address)
5282mw	- memory write (fill)
5283cp	- memory copy
5284cmp	- memory compare
5285crc32	- checksum calculation
5286i2c	- I2C sub-system
5287sspi	- SPI utility commands
5288base	- print or set address offset
5289printenv- print environment variables
5290setenv	- set environment variables
5291saveenv - save environment variables to persistent storage
5292protect - enable or disable FLASH write protection
5293erase	- erase FLASH memory
5294flinfo	- print FLASH memory information
5295nand	- NAND memory operations (see doc/README.nand)
5296bdinfo	- print Board Info structure
5297iminfo	- print header information for application image
5298coninfo - print console devices and informations
5299ide	- IDE sub-system
5300loop	- infinite loop on address range
5301loopw	- infinite write loop on address range
5302mtest	- simple RAM test
5303icache	- enable or disable instruction cache
5304dcache	- enable or disable data cache
5305reset	- Perform RESET of the CPU
5306echo	- echo args to console
5307version - print monitor version
5308help	- print online help
5309?	- alias for 'help'
5310
5311
5312Monitor Commands - Detailed Description:
5313========================================
5314
5315TODO.
5316
5317For now: just type "help <command>".
5318
5319
5320Environment Variables:
5321======================
5322
5323U-Boot supports user configuration using Environment Variables which
5324can be made persistent by saving to Flash memory.
5325
5326Environment Variables are set using "setenv", printed using
5327"printenv", and saved to Flash using "saveenv". Using "setenv"
5328without a value can be used to delete a variable from the
5329environment. As long as you don't save the environment you are
5330working with an in-memory copy. In case the Flash area containing the
5331environment is erased by accident, a default environment is provided.
5332
5333Some configuration options can be set using Environment Variables.
5334
5335List of environment variables (most likely not complete):
5336
5337  baudrate	- see CONFIG_BAUDRATE
5338
5339  bootdelay	- see CONFIG_BOOTDELAY
5340
5341  bootcmd	- see CONFIG_BOOTCOMMAND
5342
5343  bootargs	- Boot arguments when booting an RTOS image
5344
5345  bootfile	- Name of the image to load with TFTP
5346
5347  bootm_low	- Memory range available for image processing in the bootm
5348		  command can be restricted. This variable is given as
5349		  a hexadecimal number and defines lowest address allowed
5350		  for use by the bootm command. See also "bootm_size"
5351		  environment variable. Address defined by "bootm_low" is
5352		  also the base of the initial memory mapping for the Linux
5353		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5354		  bootm_mapsize.
5355
5356  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5357		  This variable is given as a hexadecimal number and it
5358		  defines the size of the memory region starting at base
5359		  address bootm_low that is accessible by the Linux kernel
5360		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5361		  as the default value if it is defined, and bootm_size is
5362		  used otherwise.
5363
5364  bootm_size	- Memory range available for image processing in the bootm
5365		  command can be restricted. This variable is given as
5366		  a hexadecimal number and defines the size of the region
5367		  allowed for use by the bootm command. See also "bootm_low"
5368		  environment variable.
5369
5370  updatefile	- Location of the software update file on a TFTP server, used
5371		  by the automatic software update feature. Please refer to
5372		  documentation in doc/README.update for more details.
5373
5374  autoload	- if set to "no" (any string beginning with 'n'),
5375		  "bootp" will just load perform a lookup of the
5376		  configuration from the BOOTP server, but not try to
5377		  load any image using TFTP
5378
5379  autostart	- if set to "yes", an image loaded using the "bootp",
5380		  "rarpboot", "tftpboot" or "diskboot" commands will
5381		  be automatically started (by internally calling
5382		  "bootm")
5383
5384		  If set to "no", a standalone image passed to the
5385		  "bootm" command will be copied to the load address
5386		  (and eventually uncompressed), but NOT be started.
5387		  This can be used to load and uncompress arbitrary
5388		  data.
5389
5390  fdt_high	- if set this restricts the maximum address that the
5391		  flattened device tree will be copied into upon boot.
5392		  For example, if you have a system with 1 GB memory
5393		  at physical address 0x10000000, while Linux kernel
5394		  only recognizes the first 704 MB as low memory, you
5395		  may need to set fdt_high as 0x3C000000 to have the
5396		  device tree blob be copied to the maximum address
5397		  of the 704 MB low memory, so that Linux kernel can
5398		  access it during the boot procedure.
5399
5400		  If this is set to the special value 0xFFFFFFFF then
5401		  the fdt will not be copied at all on boot.  For this
5402		  to work it must reside in writable memory, have
5403		  sufficient padding on the end of it for u-boot to
5404		  add the information it needs into it, and the memory
5405		  must be accessible by the kernel.
5406
5407  fdtcontroladdr- if set this is the address of the control flattened
5408		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5409		  defined.
5410
5411  i2cfast	- (PPC405GP|PPC405EP only)
5412		  if set to 'y' configures Linux I2C driver for fast
5413		  mode (400kHZ). This environment variable is used in
5414		  initialization code. So, for changes to be effective
5415		  it must be saved and board must be reset.
5416
5417  initrd_high	- restrict positioning of initrd images:
5418		  If this variable is not set, initrd images will be
5419		  copied to the highest possible address in RAM; this
5420		  is usually what you want since it allows for
5421		  maximum initrd size. If for some reason you want to
5422		  make sure that the initrd image is loaded below the
5423		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5424		  variable to a value of "no" or "off" or "0".
5425		  Alternatively, you can set it to a maximum upper
5426		  address to use (U-Boot will still check that it
5427		  does not overwrite the U-Boot stack and data).
5428
5429		  For instance, when you have a system with 16 MB
5430		  RAM, and want to reserve 4 MB from use by Linux,
5431		  you can do this by adding "mem=12M" to the value of
5432		  the "bootargs" variable. However, now you must make
5433		  sure that the initrd image is placed in the first
5434		  12 MB as well - this can be done with
5435
5436		  setenv initrd_high 00c00000
5437
5438		  If you set initrd_high to 0xFFFFFFFF, this is an
5439		  indication to U-Boot that all addresses are legal
5440		  for the Linux kernel, including addresses in flash
5441		  memory. In this case U-Boot will NOT COPY the
5442		  ramdisk at all. This may be useful to reduce the
5443		  boot time on your system, but requires that this
5444		  feature is supported by your Linux kernel.
5445
5446  ipaddr	- IP address; needed for tftpboot command
5447
5448  loadaddr	- Default load address for commands like "bootp",
5449		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5450
5451  loads_echo	- see CONFIG_LOADS_ECHO
5452
5453  serverip	- TFTP server IP address; needed for tftpboot command
5454
5455  bootretry	- see CONFIG_BOOT_RETRY_TIME
5456
5457  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5458
5459  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5460
5461  ethprime	- controls which interface is used first.
5462
5463  ethact	- controls which interface is currently active.
5464		  For example you can do the following
5465
5466		  => setenv ethact FEC
5467		  => ping 192.168.0.1 # traffic sent on FEC
5468		  => setenv ethact SCC
5469		  => ping 10.0.0.1 # traffic sent on SCC
5470
5471  ethrotate	- When set to "no" U-Boot does not go through all
5472		  available network interfaces.
5473		  It just stays at the currently selected interface.
5474
5475  netretry	- When set to "no" each network operation will
5476		  either succeed or fail without retrying.
5477		  When set to "once" the network operation will
5478		  fail when all the available network interfaces
5479		  are tried once without success.
5480		  Useful on scripts which control the retry operation
5481		  themselves.
5482
5483  npe_ucode	- set load address for the NPE microcode
5484
5485  silent_linux  - If set then Linux will be told to boot silently, by
5486		  changing the console to be empty. If "yes" it will be
5487		  made silent. If "no" it will not be made silent. If
5488		  unset, then it will be made silent if the U-Boot console
5489		  is silent.
5490
5491  tftpsrcport	- If this is set, the value is used for TFTP's
5492		  UDP source port.
5493
5494  tftpdstport	- If this is set, the value is used for TFTP's UDP
5495		  destination port instead of the Well Know Port 69.
5496
5497  tftpblocksize - Block size to use for TFTP transfers; if not set,
5498		  we use the TFTP server's default block size
5499
5500  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5501		  seconds, minimum value is 1000 = 1 second). Defines
5502		  when a packet is considered to be lost so it has to
5503		  be retransmitted. The default is 5000 = 5 seconds.
5504		  Lowering this value may make downloads succeed
5505		  faster in networks with high packet loss rates or
5506		  with unreliable TFTP servers.
5507
5508  vlan		- When set to a value < 4095 the traffic over
5509		  Ethernet is encapsulated/received over 802.1q
5510		  VLAN tagged frames.
5511
5512The following image location variables contain the location of images
5513used in booting. The "Image" column gives the role of the image and is
5514not an environment variable name. The other columns are environment
5515variable names. "File Name" gives the name of the file on a TFTP
5516server, "RAM Address" gives the location in RAM the image will be
5517loaded to, and "Flash Location" gives the image's address in NOR
5518flash or offset in NAND flash.
5519
5520*Note* - these variables don't have to be defined for all boards, some
5521boards currenlty use other variables for these purposes, and some
5522boards use these variables for other purposes.
5523
5524Image		    File Name	     RAM Address       Flash Location
5525-----		    ---------	     -----------       --------------
5526u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5527Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5528device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5529ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5530
5531The following environment variables may be used and automatically
5532updated by the network boot commands ("bootp" and "rarpboot"),
5533depending the information provided by your boot server:
5534
5535  bootfile	- see above
5536  dnsip		- IP address of your Domain Name Server
5537  dnsip2	- IP address of your secondary Domain Name Server
5538  gatewayip	- IP address of the Gateway (Router) to use
5539  hostname	- Target hostname
5540  ipaddr	- see above
5541  netmask	- Subnet Mask
5542  rootpath	- Pathname of the root filesystem on the NFS server
5543  serverip	- see above
5544
5545
5546There are two special Environment Variables:
5547
5548  serial#	- contains hardware identification information such
5549		  as type string and/or serial number
5550  ethaddr	- Ethernet address
5551
5552These variables can be set only once (usually during manufacturing of
5553the board). U-Boot refuses to delete or overwrite these variables
5554once they have been set once.
5555
5556
5557Further special Environment Variables:
5558
5559  ver		- Contains the U-Boot version string as printed
5560		  with the "version" command. This variable is
5561		  readonly (see CONFIG_VERSION_VARIABLE).
5562
5563
5564Please note that changes to some configuration parameters may take
5565only effect after the next boot (yes, that's just like Windoze :-).
5566
5567
5568Callback functions for environment variables:
5569---------------------------------------------
5570
5571For some environment variables, the behavior of u-boot needs to change
5572when their values are changed.  This functionality allows functions to
5573be associated with arbitrary variables.  On creation, overwrite, or
5574deletion, the callback will provide the opportunity for some side
5575effect to happen or for the change to be rejected.
5576
5577The callbacks are named and associated with a function using the
5578U_BOOT_ENV_CALLBACK macro in your board or driver code.
5579
5580These callbacks are associated with variables in one of two ways.  The
5581static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5582in the board configuration to a string that defines a list of
5583associations.  The list must be in the following format:
5584
5585	entry = variable_name[:callback_name]
5586	list = entry[,list]
5587
5588If the callback name is not specified, then the callback is deleted.
5589Spaces are also allowed anywhere in the list.
5590
5591Callbacks can also be associated by defining the ".callbacks" variable
5592with the same list format above.  Any association in ".callbacks" will
5593override any association in the static list. You can define
5594CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5595".callbacks" environment variable in the default or embedded environment.
5596
5597
5598Command Line Parsing:
5599=====================
5600
5601There are two different command line parsers available with U-Boot:
5602the old "simple" one, and the much more powerful "hush" shell:
5603
5604Old, simple command line parser:
5605--------------------------------
5606
5607- supports environment variables (through setenv / saveenv commands)
5608- several commands on one line, separated by ';'
5609- variable substitution using "... ${name} ..." syntax
5610- special characters ('$', ';') can be escaped by prefixing with '\',
5611  for example:
5612	setenv bootcmd bootm \${address}
5613- You can also escape text by enclosing in single apostrophes, for example:
5614	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5615
5616Hush shell:
5617-----------
5618
5619- similar to Bourne shell, with control structures like
5620  if...then...else...fi, for...do...done; while...do...done,
5621  until...do...done, ...
5622- supports environment ("global") variables (through setenv / saveenv
5623  commands) and local shell variables (through standard shell syntax
5624  "name=value"); only environment variables can be used with "run"
5625  command
5626
5627General rules:
5628--------------
5629
5630(1) If a command line (or an environment variable executed by a "run"
5631    command) contains several commands separated by semicolon, and
5632    one of these commands fails, then the remaining commands will be
5633    executed anyway.
5634
5635(2) If you execute several variables with one call to run (i. e.
5636    calling run with a list of variables as arguments), any failing
5637    command will cause "run" to terminate, i. e. the remaining
5638    variables are not executed.
5639
5640Note for Redundant Ethernet Interfaces:
5641=======================================
5642
5643Some boards come with redundant Ethernet interfaces; U-Boot supports
5644such configurations and is capable of automatic selection of a
5645"working" interface when needed. MAC assignment works as follows:
5646
5647Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5648MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5649"eth1addr" (=>eth1), "eth2addr", ...
5650
5651If the network interface stores some valid MAC address (for instance
5652in SROM), this is used as default address if there is NO correspon-
5653ding setting in the environment; if the corresponding environment
5654variable is set, this overrides the settings in the card; that means:
5655
5656o If the SROM has a valid MAC address, and there is no address in the
5657  environment, the SROM's address is used.
5658
5659o If there is no valid address in the SROM, and a definition in the
5660  environment exists, then the value from the environment variable is
5661  used.
5662
5663o If both the SROM and the environment contain a MAC address, and
5664  both addresses are the same, this MAC address is used.
5665
5666o If both the SROM and the environment contain a MAC address, and the
5667  addresses differ, the value from the environment is used and a
5668  warning is printed.
5669
5670o If neither SROM nor the environment contain a MAC address, an error
5671  is raised.
5672
5673If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5674will be programmed into hardware as part of the initialization process.	 This
5675may be skipped by setting the appropriate 'ethmacskip' environment variable.
5676The naming convention is as follows:
5677"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5678
5679Image Formats:
5680==============
5681
5682U-Boot is capable of booting (and performing other auxiliary operations on)
5683images in two formats:
5684
5685New uImage format (FIT)
5686-----------------------
5687
5688Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5689to Flattened Device Tree). It allows the use of images with multiple
5690components (several kernels, ramdisks, etc.), with contents protected by
5691SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5692
5693
5694Old uImage format
5695-----------------
5696
5697Old image format is based on binary files which can be basically anything,
5698preceded by a special header; see the definitions in include/image.h for
5699details; basically, the header defines the following image properties:
5700
5701* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5702  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5703  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5704  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5705  INTEGRITY).
5706* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5707  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5708  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5709* Compression Type (uncompressed, gzip, bzip2)
5710* Load Address
5711* Entry Point
5712* Image Name
5713* Image Timestamp
5714
5715The header is marked by a special Magic Number, and both the header
5716and the data portions of the image are secured against corruption by
5717CRC32 checksums.
5718
5719
5720Linux Support:
5721==============
5722
5723Although U-Boot should support any OS or standalone application
5724easily, the main focus has always been on Linux during the design of
5725U-Boot.
5726
5727U-Boot includes many features that so far have been part of some
5728special "boot loader" code within the Linux kernel. Also, any
5729"initrd" images to be used are no longer part of one big Linux image;
5730instead, kernel and "initrd" are separate images. This implementation
5731serves several purposes:
5732
5733- the same features can be used for other OS or standalone
5734  applications (for instance: using compressed images to reduce the
5735  Flash memory footprint)
5736
5737- it becomes much easier to port new Linux kernel versions because
5738  lots of low-level, hardware dependent stuff are done by U-Boot
5739
5740- the same Linux kernel image can now be used with different "initrd"
5741  images; of course this also means that different kernel images can
5742  be run with the same "initrd". This makes testing easier (you don't
5743  have to build a new "zImage.initrd" Linux image when you just
5744  change a file in your "initrd"). Also, a field-upgrade of the
5745  software is easier now.
5746
5747
5748Linux HOWTO:
5749============
5750
5751Porting Linux to U-Boot based systems:
5752---------------------------------------
5753
5754U-Boot cannot save you from doing all the necessary modifications to
5755configure the Linux device drivers for use with your target hardware
5756(no, we don't intend to provide a full virtual machine interface to
5757Linux :-).
5758
5759But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5760
5761Just make sure your machine specific header file (for instance
5762include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5763Information structure as we define in include/asm-<arch>/u-boot.h,
5764and make sure that your definition of IMAP_ADDR uses the same value
5765as your U-Boot configuration in CONFIG_SYS_IMMR.
5766
5767Note that U-Boot now has a driver model, a unified model for drivers.
5768If you are adding a new driver, plumb it into driver model. If there
5769is no uclass available, you are encouraged to create one. See
5770doc/driver-model.
5771
5772
5773Configuring the Linux kernel:
5774-----------------------------
5775
5776No specific requirements for U-Boot. Make sure you have some root
5777device (initial ramdisk, NFS) for your target system.
5778
5779
5780Building a Linux Image:
5781-----------------------
5782
5783With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5784not used. If you use recent kernel source, a new build target
5785"uImage" will exist which automatically builds an image usable by
5786U-Boot. Most older kernels also have support for a "pImage" target,
5787which was introduced for our predecessor project PPCBoot and uses a
5788100% compatible format.
5789
5790Example:
5791
5792	make TQM850L_defconfig
5793	make oldconfig
5794	make dep
5795	make uImage
5796
5797The "uImage" build target uses a special tool (in 'tools/mkimage') to
5798encapsulate a compressed Linux kernel image with header	 information,
5799CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5800
5801* build a standard "vmlinux" kernel image (in ELF binary format):
5802
5803* convert the kernel into a raw binary image:
5804
5805	${CROSS_COMPILE}-objcopy -O binary \
5806				 -R .note -R .comment \
5807				 -S vmlinux linux.bin
5808
5809* compress the binary image:
5810
5811	gzip -9 linux.bin
5812
5813* package compressed binary image for U-Boot:
5814
5815	mkimage -A ppc -O linux -T kernel -C gzip \
5816		-a 0 -e 0 -n "Linux Kernel Image" \
5817		-d linux.bin.gz uImage
5818
5819
5820The "mkimage" tool can also be used to create ramdisk images for use
5821with U-Boot, either separated from the Linux kernel image, or
5822combined into one file. "mkimage" encapsulates the images with a 64
5823byte header containing information about target architecture,
5824operating system, image type, compression method, entry points, time
5825stamp, CRC32 checksums, etc.
5826
5827"mkimage" can be called in two ways: to verify existing images and
5828print the header information, or to build new images.
5829
5830In the first form (with "-l" option) mkimage lists the information
5831contained in the header of an existing U-Boot image; this includes
5832checksum verification:
5833
5834	tools/mkimage -l image
5835	  -l ==> list image header information
5836
5837The second form (with "-d" option) is used to build a U-Boot image
5838from a "data file" which is used as image payload:
5839
5840	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5841		      -n name -d data_file image
5842	  -A ==> set architecture to 'arch'
5843	  -O ==> set operating system to 'os'
5844	  -T ==> set image type to 'type'
5845	  -C ==> set compression type 'comp'
5846	  -a ==> set load address to 'addr' (hex)
5847	  -e ==> set entry point to 'ep' (hex)
5848	  -n ==> set image name to 'name'
5849	  -d ==> use image data from 'datafile'
5850
5851Right now, all Linux kernels for PowerPC systems use the same load
5852address (0x00000000), but the entry point address depends on the
5853kernel version:
5854
5855- 2.2.x kernels have the entry point at 0x0000000C,
5856- 2.3.x and later kernels have the entry point at 0x00000000.
5857
5858So a typical call to build a U-Boot image would read:
5859
5860	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5861	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5862	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5863	> examples/uImage.TQM850L
5864	Image Name:   2.4.4 kernel for TQM850L
5865	Created:      Wed Jul 19 02:34:59 2000
5866	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5867	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5868	Load Address: 0x00000000
5869	Entry Point:  0x00000000
5870
5871To verify the contents of the image (or check for corruption):
5872
5873	-> tools/mkimage -l examples/uImage.TQM850L
5874	Image Name:   2.4.4 kernel for TQM850L
5875	Created:      Wed Jul 19 02:34:59 2000
5876	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5877	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5878	Load Address: 0x00000000
5879	Entry Point:  0x00000000
5880
5881NOTE: for embedded systems where boot time is critical you can trade
5882speed for memory and install an UNCOMPRESSED image instead: this
5883needs more space in Flash, but boots much faster since it does not
5884need to be uncompressed:
5885
5886	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5887	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5888	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5889	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5890	> examples/uImage.TQM850L-uncompressed
5891	Image Name:   2.4.4 kernel for TQM850L
5892	Created:      Wed Jul 19 02:34:59 2000
5893	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5894	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5895	Load Address: 0x00000000
5896	Entry Point:  0x00000000
5897
5898
5899Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5900when your kernel is intended to use an initial ramdisk:
5901
5902	-> tools/mkimage -n 'Simple Ramdisk Image' \
5903	> -A ppc -O linux -T ramdisk -C gzip \
5904	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5905	Image Name:   Simple Ramdisk Image
5906	Created:      Wed Jan 12 14:01:50 2000
5907	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5908	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5909	Load Address: 0x00000000
5910	Entry Point:  0x00000000
5911
5912The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5913option performs the converse operation of the mkimage's second form (the "-d"
5914option). Given an image built by mkimage, the dumpimage extracts a "data file"
5915from the image:
5916
5917	tools/dumpimage -i image -T type -p position data_file
5918	  -i ==> extract from the 'image' a specific 'data_file'
5919	  -T ==> set image type to 'type'
5920	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5921
5922
5923Installing a Linux Image:
5924-------------------------
5925
5926To downloading a U-Boot image over the serial (console) interface,
5927you must convert the image to S-Record format:
5928
5929	objcopy -I binary -O srec examples/image examples/image.srec
5930
5931The 'objcopy' does not understand the information in the U-Boot
5932image header, so the resulting S-Record file will be relative to
5933address 0x00000000. To load it to a given address, you need to
5934specify the target address as 'offset' parameter with the 'loads'
5935command.
5936
5937Example: install the image to address 0x40100000 (which on the
5938TQM8xxL is in the first Flash bank):
5939
5940	=> erase 40100000 401FFFFF
5941
5942	.......... done
5943	Erased 8 sectors
5944
5945	=> loads 40100000
5946	## Ready for S-Record download ...
5947	~>examples/image.srec
5948	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5949	...
5950	15989 15990 15991 15992
5951	[file transfer complete]
5952	[connected]
5953	## Start Addr = 0x00000000
5954
5955
5956You can check the success of the download using the 'iminfo' command;
5957this includes a checksum verification so you can be sure no data
5958corruption happened:
5959
5960	=> imi 40100000
5961
5962	## Checking Image at 40100000 ...
5963	   Image Name:	 2.2.13 for initrd on TQM850L
5964	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5965	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5966	   Load Address: 00000000
5967	   Entry Point:	 0000000c
5968	   Verifying Checksum ... OK
5969
5970
5971Boot Linux:
5972-----------
5973
5974The "bootm" command is used to boot an application that is stored in
5975memory (RAM or Flash). In case of a Linux kernel image, the contents
5976of the "bootargs" environment variable is passed to the kernel as
5977parameters. You can check and modify this variable using the
5978"printenv" and "setenv" commands:
5979
5980
5981	=> printenv bootargs
5982	bootargs=root=/dev/ram
5983
5984	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5985
5986	=> printenv bootargs
5987	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5988
5989	=> bootm 40020000
5990	## Booting Linux kernel at 40020000 ...
5991	   Image Name:	 2.2.13 for NFS on TQM850L
5992	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5993	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5994	   Load Address: 00000000
5995	   Entry Point:	 0000000c
5996	   Verifying Checksum ... OK
5997	   Uncompressing Kernel Image ... OK
5998	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
5999	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
6000	time_init: decrementer frequency = 187500000/60
6001	Calibrating delay loop... 49.77 BogoMIPS
6002	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
6003	...
6004
6005If you want to boot a Linux kernel with initial RAM disk, you pass
6006the memory addresses of both the kernel and the initrd image (PPBCOOT
6007format!) to the "bootm" command:
6008
6009	=> imi 40100000 40200000
6010
6011	## Checking Image at 40100000 ...
6012	   Image Name:	 2.2.13 for initrd on TQM850L
6013	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6014	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6015	   Load Address: 00000000
6016	   Entry Point:	 0000000c
6017	   Verifying Checksum ... OK
6018
6019	## Checking Image at 40200000 ...
6020	   Image Name:	 Simple Ramdisk Image
6021	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6022	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6023	   Load Address: 00000000
6024	   Entry Point:	 00000000
6025	   Verifying Checksum ... OK
6026
6027	=> bootm 40100000 40200000
6028	## Booting Linux kernel at 40100000 ...
6029	   Image Name:	 2.2.13 for initrd on TQM850L
6030	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6031	   Data Size:	 335725 Bytes = 327 kB = 0 MB
6032	   Load Address: 00000000
6033	   Entry Point:	 0000000c
6034	   Verifying Checksum ... OK
6035	   Uncompressing Kernel Image ... OK
6036	## Loading RAMDisk Image at 40200000 ...
6037	   Image Name:	 Simple Ramdisk Image
6038	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
6039	   Data Size:	 566530 Bytes = 553 kB = 0 MB
6040	   Load Address: 00000000
6041	   Entry Point:	 00000000
6042	   Verifying Checksum ... OK
6043	   Loading Ramdisk ... OK
6044	Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
6045	Boot arguments: root=/dev/ram
6046	time_init: decrementer frequency = 187500000/60
6047	Calibrating delay loop... 49.77 BogoMIPS
6048	...
6049	RAMDISK: Compressed image found at block 0
6050	VFS: Mounted root (ext2 filesystem).
6051
6052	bash#
6053
6054Boot Linux and pass a flat device tree:
6055-----------
6056
6057First, U-Boot must be compiled with the appropriate defines. See the section
6058titled "Linux Kernel Interface" above for a more in depth explanation. The
6059following is an example of how to start a kernel and pass an updated
6060flat device tree:
6061
6062=> print oftaddr
6063oftaddr=0x300000
6064=> print oft
6065oft=oftrees/mpc8540ads.dtb
6066=> tftp $oftaddr $oft
6067Speed: 1000, full duplex
6068Using TSEC0 device
6069TFTP from server 192.168.1.1; our IP address is 192.168.1.101
6070Filename 'oftrees/mpc8540ads.dtb'.
6071Load address: 0x300000
6072Loading: #
6073done
6074Bytes transferred = 4106 (100a hex)
6075=> tftp $loadaddr $bootfile
6076Speed: 1000, full duplex
6077Using TSEC0 device
6078TFTP from server 192.168.1.1; our IP address is 192.168.1.2
6079Filename 'uImage'.
6080Load address: 0x200000
6081Loading:############
6082done
6083Bytes transferred = 1029407 (fb51f hex)
6084=> print loadaddr
6085loadaddr=200000
6086=> print oftaddr
6087oftaddr=0x300000
6088=> bootm $loadaddr - $oftaddr
6089## Booting image at 00200000 ...
6090   Image Name:	 Linux-2.6.17-dirty
6091   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6092   Data Size:	 1029343 Bytes = 1005.2 kB
6093   Load Address: 00000000
6094   Entry Point:	 00000000
6095   Verifying Checksum ... OK
6096   Uncompressing Kernel Image ... OK
6097Booting using flat device tree at 0x300000
6098Using MPC85xx ADS machine description
6099Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
6100[snip]
6101
6102
6103More About U-Boot Image Types:
6104------------------------------
6105
6106U-Boot supports the following image types:
6107
6108   "Standalone Programs" are directly runnable in the environment
6109	provided by U-Boot; it is expected that (if they behave
6110	well) you can continue to work in U-Boot after return from
6111	the Standalone Program.
6112   "OS Kernel Images" are usually images of some Embedded OS which
6113	will take over control completely. Usually these programs
6114	will install their own set of exception handlers, device
6115	drivers, set up the MMU, etc. - this means, that you cannot
6116	expect to re-enter U-Boot except by resetting the CPU.
6117   "RAMDisk Images" are more or less just data blocks, and their
6118	parameters (address, size) are passed to an OS kernel that is
6119	being started.
6120   "Multi-File Images" contain several images, typically an OS
6121	(Linux) kernel image and one or more data images like
6122	RAMDisks. This construct is useful for instance when you want
6123	to boot over the network using BOOTP etc., where the boot
6124	server provides just a single image file, but you want to get
6125	for instance an OS kernel and a RAMDisk image.
6126
6127	"Multi-File Images" start with a list of image sizes, each
6128	image size (in bytes) specified by an "uint32_t" in network
6129	byte order. This list is terminated by an "(uint32_t)0".
6130	Immediately after the terminating 0 follow the images, one by
6131	one, all aligned on "uint32_t" boundaries (size rounded up to
6132	a multiple of 4 bytes).
6133
6134   "Firmware Images" are binary images containing firmware (like
6135	U-Boot or FPGA images) which usually will be programmed to
6136	flash memory.
6137
6138   "Script files" are command sequences that will be executed by
6139	U-Boot's command interpreter; this feature is especially
6140	useful when you configure U-Boot to use a real shell (hush)
6141	as command interpreter.
6142
6143Booting the Linux zImage:
6144-------------------------
6145
6146On some platforms, it's possible to boot Linux zImage. This is done
6147using the "bootz" command. The syntax of "bootz" command is the same
6148as the syntax of "bootm" command.
6149
6150Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6151kernel with raw initrd images. The syntax is slightly different, the
6152address of the initrd must be augmented by it's size, in the following
6153format: "<initrd addres>:<initrd size>".
6154
6155
6156Standalone HOWTO:
6157=================
6158
6159One of the features of U-Boot is that you can dynamically load and
6160run "standalone" applications, which can use some resources of
6161U-Boot like console I/O functions or interrupt services.
6162
6163Two simple examples are included with the sources:
6164
6165"Hello World" Demo:
6166-------------------
6167
6168'examples/hello_world.c' contains a small "Hello World" Demo
6169application; it is automatically compiled when you build U-Boot.
6170It's configured to run at address 0x00040004, so you can play with it
6171like that:
6172
6173	=> loads
6174	## Ready for S-Record download ...
6175	~>examples/hello_world.srec
6176	1 2 3 4 5 6 7 8 9 10 11 ...
6177	[file transfer complete]
6178	[connected]
6179	## Start Addr = 0x00040004
6180
6181	=> go 40004 Hello World! This is a test.
6182	## Starting application at 0x00040004 ...
6183	Hello World
6184	argc = 7
6185	argv[0] = "40004"
6186	argv[1] = "Hello"
6187	argv[2] = "World!"
6188	argv[3] = "This"
6189	argv[4] = "is"
6190	argv[5] = "a"
6191	argv[6] = "test."
6192	argv[7] = "<NULL>"
6193	Hit any key to exit ...
6194
6195	## Application terminated, rc = 0x0
6196
6197Another example, which demonstrates how to register a CPM interrupt
6198handler with the U-Boot code, can be found in 'examples/timer.c'.
6199Here, a CPM timer is set up to generate an interrupt every second.
6200The interrupt service routine is trivial, just printing a '.'
6201character, but this is just a demo program. The application can be
6202controlled by the following keys:
6203
6204	? - print current values og the CPM Timer registers
6205	b - enable interrupts and start timer
6206	e - stop timer and disable interrupts
6207	q - quit application
6208
6209	=> loads
6210	## Ready for S-Record download ...
6211	~>examples/timer.srec
6212	1 2 3 4 5 6 7 8 9 10 11 ...
6213	[file transfer complete]
6214	[connected]
6215	## Start Addr = 0x00040004
6216
6217	=> go 40004
6218	## Starting application at 0x00040004 ...
6219	TIMERS=0xfff00980
6220	Using timer 1
6221	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6222
6223Hit 'b':
6224	[q, b, e, ?] Set interval 1000000 us
6225	Enabling timer
6226Hit '?':
6227	[q, b, e, ?] ........
6228	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6229Hit '?':
6230	[q, b, e, ?] .
6231	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6232Hit '?':
6233	[q, b, e, ?] .
6234	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6235Hit '?':
6236	[q, b, e, ?] .
6237	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6238Hit 'e':
6239	[q, b, e, ?] ...Stopping timer
6240Hit 'q':
6241	[q, b, e, ?] ## Application terminated, rc = 0x0
6242
6243
6244Minicom warning:
6245================
6246
6247Over time, many people have reported problems when trying to use the
6248"minicom" terminal emulation program for serial download. I (wd)
6249consider minicom to be broken, and recommend not to use it. Under
6250Unix, I recommend to use C-Kermit for general purpose use (and
6251especially for kermit binary protocol download ("loadb" command), and
6252use "cu" for S-Record download ("loads" command).  See
6253http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6254for help with kermit.
6255
6256
6257Nevertheless, if you absolutely want to use it try adding this
6258configuration to your "File transfer protocols" section:
6259
6260	   Name	   Program			Name U/D FullScr IO-Red. Multi
6261	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6262	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6263
6264
6265NetBSD Notes:
6266=============
6267
6268Starting at version 0.9.2, U-Boot supports NetBSD both as host
6269(build U-Boot) and target system (boots NetBSD/mpc8xx).
6270
6271Building requires a cross environment; it is known to work on
6272NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6273need gmake since the Makefiles are not compatible with BSD make).
6274Note that the cross-powerpc package does not install include files;
6275attempting to build U-Boot will fail because <machine/ansi.h> is
6276missing.  This file has to be installed and patched manually:
6277
6278	# cd /usr/pkg/cross/powerpc-netbsd/include
6279	# mkdir powerpc
6280	# ln -s powerpc machine
6281	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6282	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6283
6284Native builds *don't* work due to incompatibilities between native
6285and U-Boot include files.
6286
6287Booting assumes that (the first part of) the image booted is a
6288stage-2 loader which in turn loads and then invokes the kernel
6289proper. Loader sources will eventually appear in the NetBSD source
6290tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6291meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6292
6293
6294Implementation Internals:
6295=========================
6296
6297The following is not intended to be a complete description of every
6298implementation detail. However, it should help to understand the
6299inner workings of U-Boot and make it easier to port it to custom
6300hardware.
6301
6302
6303Initial Stack, Global Data:
6304---------------------------
6305
6306The implementation of U-Boot is complicated by the fact that U-Boot
6307starts running out of ROM (flash memory), usually without access to
6308system RAM (because the memory controller is not initialized yet).
6309This means that we don't have writable Data or BSS segments, and BSS
6310is not initialized as zero. To be able to get a C environment working
6311at all, we have to allocate at least a minimal stack. Implementation
6312options for this are defined and restricted by the CPU used: Some CPU
6313models provide on-chip memory (like the IMMR area on MPC8xx and
6314MPC826x processors), on others (parts of) the data cache can be
6315locked as (mis-) used as memory, etc.
6316
6317	Chris Hallinan posted a good summary of these issues to the
6318	U-Boot mailing list:
6319
6320	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6321	From: "Chris Hallinan" <clh@net1plus.com>
6322	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6323	...
6324
6325	Correct me if I'm wrong, folks, but the way I understand it
6326	is this: Using DCACHE as initial RAM for Stack, etc, does not
6327	require any physical RAM backing up the cache. The cleverness
6328	is that the cache is being used as a temporary supply of
6329	necessary storage before the SDRAM controller is setup. It's
6330	beyond the scope of this list to explain the details, but you
6331	can see how this works by studying the cache architecture and
6332	operation in the architecture and processor-specific manuals.
6333
6334	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6335	is another option for the system designer to use as an
6336	initial stack/RAM area prior to SDRAM being available. Either
6337	option should work for you. Using CS 4 should be fine if your
6338	board designers haven't used it for something that would
6339	cause you grief during the initial boot! It is frequently not
6340	used.
6341
6342	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6343	with your processor/board/system design. The default value
6344	you will find in any recent u-boot distribution in
6345	walnut.h should work for you. I'd set it to a value larger
6346	than your SDRAM module. If you have a 64MB SDRAM module, set
6347	it above 400_0000. Just make sure your board has no resources
6348	that are supposed to respond to that address! That code in
6349	start.S has been around a while and should work as is when
6350	you get the config right.
6351
6352	-Chris Hallinan
6353	DS4.COM, Inc.
6354
6355It is essential to remember this, since it has some impact on the C
6356code for the initialization procedures:
6357
6358* Initialized global data (data segment) is read-only. Do not attempt
6359  to write it.
6360
6361* Do not use any uninitialized global data (or implicitly initialized
6362  as zero data - BSS segment) at all - this is undefined, initiali-
6363  zation is performed later (when relocating to RAM).
6364
6365* Stack space is very limited. Avoid big data buffers or things like
6366  that.
6367
6368Having only the stack as writable memory limits means we cannot use
6369normal global data to share information between the code. But it
6370turned out that the implementation of U-Boot can be greatly
6371simplified by making a global data structure (gd_t) available to all
6372functions. We could pass a pointer to this data as argument to _all_
6373functions, but this would bloat the code. Instead we use a feature of
6374the GCC compiler (Global Register Variables) to share the data: we
6375place a pointer (gd) to the global data into a register which we
6376reserve for this purpose.
6377
6378When choosing a register for such a purpose we are restricted by the
6379relevant  (E)ABI  specifications for the current architecture, and by
6380GCC's implementation.
6381
6382For PowerPC, the following registers have specific use:
6383	R1:	stack pointer
6384	R2:	reserved for system use
6385	R3-R4:	parameter passing and return values
6386	R5-R10: parameter passing
6387	R13:	small data area pointer
6388	R30:	GOT pointer
6389	R31:	frame pointer
6390
6391	(U-Boot also uses R12 as internal GOT pointer. r12
6392	is a volatile register so r12 needs to be reset when
6393	going back and forth between asm and C)
6394
6395    ==> U-Boot will use R2 to hold a pointer to the global data
6396
6397    Note: on PPC, we could use a static initializer (since the
6398    address of the global data structure is known at compile time),
6399    but it turned out that reserving a register results in somewhat
6400    smaller code - although the code savings are not that big (on
6401    average for all boards 752 bytes for the whole U-Boot image,
6402    624 text + 127 data).
6403
6404On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6405	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6406
6407    ==> U-Boot will use P3 to hold a pointer to the global data
6408
6409On ARM, the following registers are used:
6410
6411	R0:	function argument word/integer result
6412	R1-R3:	function argument word
6413	R9:	platform specific
6414	R10:	stack limit (used only if stack checking is enabled)
6415	R11:	argument (frame) pointer
6416	R12:	temporary workspace
6417	R13:	stack pointer
6418	R14:	link register
6419	R15:	program counter
6420
6421    ==> U-Boot will use R9 to hold a pointer to the global data
6422
6423    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6424
6425On Nios II, the ABI is documented here:
6426	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6427
6428    ==> U-Boot will use gp to hold a pointer to the global data
6429
6430    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6431    to access small data sections, so gp is free.
6432
6433On NDS32, the following registers are used:
6434
6435	R0-R1:	argument/return
6436	R2-R5:	argument
6437	R15:	temporary register for assembler
6438	R16:	trampoline register
6439	R28:	frame pointer (FP)
6440	R29:	global pointer (GP)
6441	R30:	link register (LP)
6442	R31:	stack pointer (SP)
6443	PC:	program counter (PC)
6444
6445    ==> U-Boot will use R10 to hold a pointer to the global data
6446
6447NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6448or current versions of GCC may "optimize" the code too much.
6449
6450Memory Management:
6451------------------
6452
6453U-Boot runs in system state and uses physical addresses, i.e. the
6454MMU is not used either for address mapping nor for memory protection.
6455
6456The available memory is mapped to fixed addresses using the memory
6457controller. In this process, a contiguous block is formed for each
6458memory type (Flash, SDRAM, SRAM), even when it consists of several
6459physical memory banks.
6460
6461U-Boot is installed in the first 128 kB of the first Flash bank (on
6462TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6463booting and sizing and initializing DRAM, the code relocates itself
6464to the upper end of DRAM. Immediately below the U-Boot code some
6465memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6466configuration setting]. Below that, a structure with global Board
6467Info data is placed, followed by the stack (growing downward).
6468
6469Additionally, some exception handler code is copied to the low 8 kB
6470of DRAM (0x00000000 ... 0x00001FFF).
6471
6472So a typical memory configuration with 16 MB of DRAM could look like
6473this:
6474
6475	0x0000 0000	Exception Vector code
6476	      :
6477	0x0000 1FFF
6478	0x0000 2000	Free for Application Use
6479	      :
6480	      :
6481
6482	      :
6483	      :
6484	0x00FB FF20	Monitor Stack (Growing downward)
6485	0x00FB FFAC	Board Info Data and permanent copy of global data
6486	0x00FC 0000	Malloc Arena
6487	      :
6488	0x00FD FFFF
6489	0x00FE 0000	RAM Copy of Monitor Code
6490	...		eventually: LCD or video framebuffer
6491	...		eventually: pRAM (Protected RAM - unchanged by reset)
6492	0x00FF FFFF	[End of RAM]
6493
6494
6495System Initialization:
6496----------------------
6497
6498In the reset configuration, U-Boot starts at the reset entry point
6499(on most PowerPC systems at address 0x00000100). Because of the reset
6500configuration for CS0# this is a mirror of the on board Flash memory.
6501To be able to re-map memory U-Boot then jumps to its link address.
6502To be able to implement the initialization code in C, a (small!)
6503initial stack is set up in the internal Dual Ported RAM (in case CPUs
6504which provide such a feature like MPC8xx or MPC8260), or in a locked
6505part of the data cache. After that, U-Boot initializes the CPU core,
6506the caches and the SIU.
6507
6508Next, all (potentially) available memory banks are mapped using a
6509preliminary mapping. For example, we put them on 512 MB boundaries
6510(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6511on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6512programmed for SDRAM access. Using the temporary configuration, a
6513simple memory test is run that determines the size of the SDRAM
6514banks.
6515
6516When there is more than one SDRAM bank, and the banks are of
6517different size, the largest is mapped first. For equal size, the first
6518bank (CS2#) is mapped first. The first mapping is always for address
65190x00000000, with any additional banks following immediately to create
6520contiguous memory starting from 0.
6521
6522Then, the monitor installs itself at the upper end of the SDRAM area
6523and allocates memory for use by malloc() and for the global Board
6524Info data; also, the exception vector code is copied to the low RAM
6525pages, and the final stack is set up.
6526
6527Only after this relocation will you have a "normal" C environment;
6528until that you are restricted in several ways, mostly because you are
6529running from ROM, and because the code will have to be relocated to a
6530new address in RAM.
6531
6532
6533U-Boot Porting Guide:
6534----------------------
6535
6536[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6537list, October 2002]
6538
6539
6540int main(int argc, char *argv[])
6541{
6542	sighandler_t no_more_time;
6543
6544	signal(SIGALRM, no_more_time);
6545	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6546
6547	if (available_money > available_manpower) {
6548		Pay consultant to port U-Boot;
6549		return 0;
6550	}
6551
6552	Download latest U-Boot source;
6553
6554	Subscribe to u-boot mailing list;
6555
6556	if (clueless)
6557		email("Hi, I am new to U-Boot, how do I get started?");
6558
6559	while (learning) {
6560		Read the README file in the top level directory;
6561		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6562		Read applicable doc/*.README;
6563		Read the source, Luke;
6564		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6565	}
6566
6567	if (available_money > toLocalCurrency ($2500))
6568		Buy a BDI3000;
6569	else
6570		Add a lot of aggravation and time;
6571
6572	if (a similar board exists) {	/* hopefully... */
6573		cp -a board/<similar> board/<myboard>
6574		cp include/configs/<similar>.h include/configs/<myboard>.h
6575	} else {
6576		Create your own board support subdirectory;
6577		Create your own board include/configs/<myboard>.h file;
6578	}
6579	Edit new board/<myboard> files
6580	Edit new include/configs/<myboard>.h
6581
6582	while (!accepted) {
6583		while (!running) {
6584			do {
6585				Add / modify source code;
6586			} until (compiles);
6587			Debug;
6588			if (clueless)
6589				email("Hi, I am having problems...");
6590		}
6591		Send patch file to the U-Boot email list;
6592		if (reasonable critiques)
6593			Incorporate improvements from email list code review;
6594		else
6595			Defend code as written;
6596	}
6597
6598	return 0;
6599}
6600
6601void no_more_time (int sig)
6602{
6603      hire_a_guru();
6604}
6605
6606
6607Coding Standards:
6608-----------------
6609
6610All contributions to U-Boot should conform to the Linux kernel
6611coding style; see the file "Documentation/CodingStyle" and the script
6612"scripts/Lindent" in your Linux kernel source directory.
6613
6614Source files originating from a different project (for example the
6615MTD subsystem) are generally exempt from these guidelines and are not
6616reformatted to ease subsequent migration to newer versions of those
6617sources.
6618
6619Please note that U-Boot is implemented in C (and to some small parts in
6620Assembler); no C++ is used, so please do not use C++ style comments (//)
6621in your code.
6622
6623Please also stick to the following formatting rules:
6624- remove any trailing white space
6625- use TAB characters for indentation and vertical alignment, not spaces
6626- make sure NOT to use DOS '\r\n' line feeds
6627- do not add more than 2 consecutive empty lines to source files
6628- do not add trailing empty lines to source files
6629
6630Submissions which do not conform to the standards may be returned
6631with a request to reformat the changes.
6632
6633
6634Submitting Patches:
6635-------------------
6636
6637Since the number of patches for U-Boot is growing, we need to
6638establish some rules. Submissions which do not conform to these rules
6639may be rejected, even when they contain important and valuable stuff.
6640
6641Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6642
6643Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6644see http://lists.denx.de/mailman/listinfo/u-boot
6645
6646When you send a patch, please include the following information with
6647it:
6648
6649* For bug fixes: a description of the bug and how your patch fixes
6650  this bug. Please try to include a way of demonstrating that the
6651  patch actually fixes something.
6652
6653* For new features: a description of the feature and your
6654  implementation.
6655
6656* A CHANGELOG entry as plaintext (separate from the patch)
6657
6658* For major contributions, your entry to the CREDITS file
6659
6660* When you add support for a new board, don't forget to add a
6661  maintainer e-mail address to the boards.cfg file, too.
6662
6663* If your patch adds new configuration options, don't forget to
6664  document these in the README file.
6665
6666* The patch itself. If you are using git (which is *strongly*
6667  recommended) you can easily generate the patch using the
6668  "git format-patch". If you then use "git send-email" to send it to
6669  the U-Boot mailing list, you will avoid most of the common problems
6670  with some other mail clients.
6671
6672  If you cannot use git, use "diff -purN OLD NEW". If your version of
6673  diff does not support these options, then get the latest version of
6674  GNU diff.
6675
6676  The current directory when running this command shall be the parent
6677  directory of the U-Boot source tree (i. e. please make sure that
6678  your patch includes sufficient directory information for the
6679  affected files).
6680
6681  We prefer patches as plain text. MIME attachments are discouraged,
6682  and compressed attachments must not be used.
6683
6684* If one logical set of modifications affects or creates several
6685  files, all these changes shall be submitted in a SINGLE patch file.
6686
6687* Changesets that contain different, unrelated modifications shall be
6688  submitted as SEPARATE patches, one patch per changeset.
6689
6690
6691Notes:
6692
6693* Before sending the patch, run the MAKEALL script on your patched
6694  source tree and make sure that no errors or warnings are reported
6695  for any of the boards.
6696
6697* Keep your modifications to the necessary minimum: A patch
6698  containing several unrelated changes or arbitrary reformats will be
6699  returned with a request to re-formatting / split it.
6700
6701* If you modify existing code, make sure that your new code does not
6702  add to the memory footprint of the code ;-) Small is beautiful!
6703  When adding new features, these should compile conditionally only
6704  (using #ifdef), and the resulting code with the new feature
6705  disabled must not need more memory than the old code without your
6706  modification.
6707
6708* Remember that there is a size limit of 100 kB per message on the
6709  u-boot mailing list. Bigger patches will be moderated. If they are
6710  reasonable and not too big, they will be acknowledged. But patches
6711  bigger than the size limit should be avoided.
6712