xref: /rk3399_rockchip-uboot/README (revision da384a9d7628c77140023e7c095f79ecfe5a4e2d)
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      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
186      /mpc5xx		Files specific to Freescale MPC5xx CPUs
187      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
188      /mpc8xx		Files specific to Freescale MPC8xx CPUs
189      /mpc824x		Files specific to Freescale MPC824x CPUs
190      /mpc8260		Files specific to Freescale MPC8260 CPUs
191      /mpc85xx		Files specific to Freescale MPC85xx CPUs
192      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
193    /lib		Architecture specific library files
194  /sh			Files generic to SH architecture
195    /cpu		CPU specific files
196      /sh2		Files specific to sh2 CPUs
197      /sh3		Files specific to sh3 CPUs
198      /sh4		Files specific to sh4 CPUs
199    /lib		Architecture specific library files
200  /sparc		Files generic to SPARC architecture
201    /cpu		CPU specific files
202      /leon2		Files specific to Gaisler LEON2 SPARC CPU
203      /leon3		Files specific to Gaisler LEON3 SPARC CPU
204    /lib		Architecture specific library files
205  /x86			Files generic to x86 architecture
206    /cpu		CPU specific files
207    /lib		Architecture specific library files
208/api			Machine/arch independent API for external apps
209/board			Board dependent files
210/common			Misc architecture independent functions
211/disk			Code for disk drive partition handling
212/doc			Documentation (don't expect too much)
213/drivers		Commonly used device drivers
214/dts			Contains Makefile for building internal U-Boot fdt.
215/examples		Example code for standalone applications, etc.
216/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
217/include		Header Files
218/lib			Files generic to all architectures
219  /libfdt		Library files to support flattened device trees
220  /lzma			Library files to support LZMA decompression
221  /lzo			Library files to support LZO decompression
222/net			Networking code
223/post			Power On Self Test
224/spl			Secondary Program Loader framework
225/tools			Tools to build S-Record or U-Boot images, etc.
226
227Software Configuration:
228=======================
229
230Configuration is usually done using C preprocessor defines; the
231rationale behind that is to avoid dead code whenever possible.
232
233There are two classes of configuration variables:
234
235* Configuration _OPTIONS_:
236  These are selectable by the user and have names beginning with
237  "CONFIG_".
238
239* Configuration _SETTINGS_:
240  These depend on the hardware etc. and should not be meddled with if
241  you don't know what you're doing; they have names beginning with
242  "CONFIG_SYS_".
243
244Later we will add a configuration tool - probably similar to or even
245identical to what's used for the Linux kernel. Right now, we have to
246do the configuration by hand, which means creating some symbolic
247links and editing some configuration files. We use the TQM8xxL boards
248as an example here.
249
250
251Selection of Processor Architecture and Board Type:
252---------------------------------------------------
253
254For all supported boards there are ready-to-use default
255configurations available; just type "make <board_name>_config".
256
257Example: For a TQM823L module type:
258
259	cd u-boot
260	make TQM823L_config
261
262For the Cogent platform, you need to specify the CPU type as well;
263e.g. "make cogent_mpc8xx_config". And also configure the cogent
264directory according to the instructions in cogent/README.
265
266
267Sandbox Environment:
268--------------------
269
270U-Boot can be built natively to run on a Linux host using the 'sandbox'
271board. This allows feature development which is not board- or architecture-
272specific to be undertaken on a native platform. The sandbox is also used to
273run some of U-Boot's tests.
274
275See board/sandbox/sandbox/README.sandbox for more details.
276
277
278Configuration Options:
279----------------------
280
281Configuration depends on the combination of board and CPU type; all
282such information is kept in a configuration file
283"include/configs/<board_name>.h".
284
285Example: For a TQM823L module, all configuration settings are in
286"include/configs/TQM823L.h".
287
288
289Many of the options are named exactly as the corresponding Linux
290kernel configuration options. The intention is to make it easier to
291build a config tool - later.
292
293
294The following options need to be configured:
295
296- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
297
298- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
299
300- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
301		Define exactly one, e.g. CONFIG_ATSTK1002
302
303- CPU Module Type: (if CONFIG_COGENT is defined)
304		Define exactly one of
305		CONFIG_CMA286_60_OLD
306--- FIXME --- not tested yet:
307		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
308		CONFIG_CMA287_23, CONFIG_CMA287_50
309
310- Motherboard Type: (if CONFIG_COGENT is defined)
311		Define exactly one of
312		CONFIG_CMA101, CONFIG_CMA102
313
314- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
315		Define one or more of
316		CONFIG_CMA302
317
318- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
319		Define one or more of
320		CONFIG_LCD_HEARTBEAT	- update a character position on
321					  the LCD display every second with
322					  a "rotator" |\-/|\-/
323
324- Board flavour: (if CONFIG_MPC8260ADS is defined)
325		CONFIG_ADSTYPE
326		Possible values are:
327			CONFIG_SYS_8260ADS	- original MPC8260ADS
328			CONFIG_SYS_8266ADS	- MPC8266ADS
329			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
330			CONFIG_SYS_8272ADS	- MPC8272ADS
331
332- Marvell Family Member
333		CONFIG_SYS_MVFS		- define it if you want to enable
334					  multiple fs option at one time
335					  for marvell soc family
336
337- MPC824X Family Member (if CONFIG_MPC824X is defined)
338		Define exactly one of
339		CONFIG_MPC8240, CONFIG_MPC8245
340
341- 8xx CPU Options: (if using an MPC8xx CPU)
342		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
343					  get_gclk_freq() cannot work
344					  e.g. if there is no 32KHz
345					  reference PIT/RTC clock
346		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
347					  or XTAL/EXTAL)
348
349- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
350		CONFIG_SYS_8xx_CPUCLK_MIN
351		CONFIG_SYS_8xx_CPUCLK_MAX
352		CONFIG_8xx_CPUCLK_DEFAULT
353			See doc/README.MPC866
354
355		CONFIG_SYS_MEASURE_CPUCLK
356
357		Define this to measure the actual CPU clock instead
358		of relying on the correctness of the configured
359		values. Mostly useful for board bringup to make sure
360		the PLL is locked at the intended frequency. Note
361		that this requires a (stable) reference clock (32 kHz
362		RTC clock or CONFIG_SYS_8XX_XIN)
363
364		CONFIG_SYS_DELAYED_ICACHE
365
366		Define this option if you want to enable the
367		ICache only when Code runs from RAM.
368
369- 85xx CPU Options:
370		CONFIG_SYS_PPC64
371
372		Specifies that the core is a 64-bit PowerPC implementation (implements
373		the "64" category of the Power ISA). This is necessary for ePAPR
374		compliance, among other possible reasons.
375
376		CONFIG_SYS_FSL_TBCLK_DIV
377
378		Defines the core time base clock divider ratio compared to the
379		system clock.  On most PQ3 devices this is 8, on newer QorIQ
380		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
381
382		CONFIG_SYS_FSL_PCIE_COMPAT
383
384		Defines the string to utilize when trying to match PCIe device
385		tree nodes for the given platform.
386
387		CONFIG_SYS_PPC_E500_DEBUG_TLB
388
389		Enables a temporary TLB entry to be used during boot to work
390		around limitations in e500v1 and e500v2 external debugger
391		support. This reduces the portions of the boot code where
392		breakpoints and single stepping do not work.  The value of this
393		symbol should be set to the TLB1 entry to be used for this
394		purpose.
395
396		CONFIG_SYS_FSL_ERRATUM_A004510
397
398		Enables a workaround for erratum A004510.  If set,
399		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
400		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
401
402		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
403		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
404
405		Defines one or two SoC revisions (low 8 bits of SVR)
406		for which the A004510 workaround should be applied.
407
408		The rest of SVR is either not relevant to the decision
409		of whether the erratum is present (e.g. p2040 versus
410		p2041) or is implied by the build target, which controls
411		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
412
413		See Freescale App Note 4493 for more information about
414		this erratum.
415
416		CONFIG_A003399_NOR_WORKAROUND
417		Enables a workaround for IFC erratum A003399. It is only
418		requred during NOR boot.
419
420		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
421
422		This is the value to write into CCSR offset 0x18600
423		according to the A004510 workaround.
424
425		CONFIG_SYS_FSL_DSP_DDR_ADDR
426		This value denotes start offset of DDR memory which is
427		connected exclusively to the DSP cores.
428
429		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
430		This value denotes start offset of M2 memory
431		which is directly connected to the DSP core.
432
433		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
434		This value denotes start offset of M3 memory which is directly
435		connected to the DSP core.
436
437		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
438		This value denotes start offset of DSP CCSR space.
439
440		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
441		Single Source Clock is clocking mode present in some of FSL SoC's.
442		In this mode, a single differential clock is used to supply
443		clocks to the sysclock, ddrclock and usbclock.
444
445		CONFIG_SYS_CPC_REINIT_F
446		This CONFIG is defined when the CPC is configured as SRAM at the
447		time of U-boot entry and is required to be re-initialized.
448
449		CONFIG_DEEP_SLEEP
450		Inidcates this SoC supports deep sleep feature. If deep sleep is
451		supported, core will start to execute uboot when wakes up.
452
453- Generic CPU options:
454		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
455
456		Defines the endianess of the CPU. Implementation of those
457		values is arch specific.
458
459		CONFIG_SYS_FSL_DDR
460		Freescale DDR driver in use. This type of DDR controller is
461		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
462		SoCs.
463
464		CONFIG_SYS_FSL_DDR_ADDR
465		Freescale DDR memory-mapped register base.
466
467		CONFIG_SYS_FSL_DDR_EMU
468		Specify emulator support for DDR. Some DDR features such as
469		deskew training are not available.
470
471		CONFIG_SYS_FSL_DDRC_GEN1
472		Freescale DDR1 controller.
473
474		CONFIG_SYS_FSL_DDRC_GEN2
475		Freescale DDR2 controller.
476
477		CONFIG_SYS_FSL_DDRC_GEN3
478		Freescale DDR3 controller.
479
480		CONFIG_SYS_FSL_DDRC_GEN4
481		Freescale DDR4 controller.
482
483		CONFIG_SYS_FSL_DDRC_ARM_GEN3
484		Freescale DDR3 controller for ARM-based SoCs.
485
486		CONFIG_SYS_FSL_DDR1
487		Board config to use DDR1. It can be enabled for SoCs with
488		Freescale DDR1 or DDR2 controllers, depending on the board
489		implemetation.
490
491		CONFIG_SYS_FSL_DDR2
492		Board config to use DDR2. It can be eanbeld for SoCs with
493		Freescale DDR2 or DDR3 controllers, depending on the board
494		implementation.
495
496		CONFIG_SYS_FSL_DDR3
497		Board config to use DDR3. It can be enabled for SoCs with
498		Freescale DDR3 or DDR3L controllers.
499
500		CONFIG_SYS_FSL_DDR3L
501		Board config to use DDR3L. It can be enabled for SoCs with
502		DDR3L controllers.
503
504		CONFIG_SYS_FSL_DDR4
505		Board config to use DDR4. It can be enabled for SoCs with
506		DDR4 controllers.
507
508		CONFIG_SYS_FSL_IFC_BE
509		Defines the IFC controller register space as Big Endian
510
511		CONFIG_SYS_FSL_IFC_LE
512		Defines the IFC controller register space as Little Endian
513
514		CONFIG_SYS_FSL_PBL_PBI
515		It enables addition of RCW (Power on reset configuration) in built image.
516		Please refer doc/README.pblimage for more details
517
518		CONFIG_SYS_FSL_PBL_RCW
519		It adds PBI(pre-boot instructions) commands in u-boot build image.
520		PBI commands can be used to configure SoC before it starts the execution.
521		Please refer doc/README.pblimage for more details
522
523		CONFIG_SPL_FSL_PBL
524		It adds a target to create boot binary having SPL binary in PBI format
525		concatenated with u-boot binary.
526
527		CONFIG_SYS_FSL_DDR_BE
528		Defines the DDR controller register space as Big Endian
529
530		CONFIG_SYS_FSL_DDR_LE
531		Defines the DDR controller register space as Little Endian
532
533		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
534		Physical address from the view of DDR controllers. It is the
535		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
536		it could be different for ARM SoCs.
537
538		CONFIG_SYS_FSL_DDR_INTLV_256B
539		DDR controller interleaving on 256-byte. This is a special
540		interleaving mode, handled by Dickens for Freescale layerscape
541		SoCs with ARM core.
542
543- Intel Monahans options:
544		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
545
546		Defines the Monahans run mode to oscillator
547		ratio. Valid values are 8, 16, 24, 31. The core
548		frequency is this value multiplied by 13 MHz.
549
550		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
551
552		Defines the Monahans turbo mode to oscillator
553		ratio. Valid values are 1 (default if undefined) and
554		2. The core frequency as calculated above is multiplied
555		by this value.
556
557- MIPS CPU options:
558		CONFIG_SYS_INIT_SP_OFFSET
559
560		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
561		pointer. This is needed for the temporary stack before
562		relocation.
563
564		CONFIG_SYS_MIPS_CACHE_MODE
565
566		Cache operation mode for the MIPS CPU.
567		See also arch/mips/include/asm/mipsregs.h.
568		Possible values are:
569			CONF_CM_CACHABLE_NO_WA
570			CONF_CM_CACHABLE_WA
571			CONF_CM_UNCACHED
572			CONF_CM_CACHABLE_NONCOHERENT
573			CONF_CM_CACHABLE_CE
574			CONF_CM_CACHABLE_COW
575			CONF_CM_CACHABLE_CUW
576			CONF_CM_CACHABLE_ACCELERATED
577
578		CONFIG_SYS_XWAY_EBU_BOOTCFG
579
580		Special option for Lantiq XWAY SoCs for booting from NOR flash.
581		See also arch/mips/cpu/mips32/start.S.
582
583		CONFIG_XWAY_SWAP_BYTES
584
585		Enable compilation of tools/xway-swap-bytes needed for Lantiq
586		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
587		be swapped if a flash programmer is used.
588
589- ARM options:
590		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
591
592		Select high exception vectors of the ARM core, e.g., do not
593		clear the V bit of the c1 register of CP15.
594
595		CONFIG_SYS_THUMB_BUILD
596
597		Use this flag to build U-Boot using the Thumb instruction
598		set for ARM architectures. Thumb instruction set provides
599		better code density. For ARM architectures that support
600		Thumb2 this flag will result in Thumb2 code generated by
601		GCC.
602
603		CONFIG_ARM_ERRATA_716044
604		CONFIG_ARM_ERRATA_742230
605		CONFIG_ARM_ERRATA_743622
606		CONFIG_ARM_ERRATA_751472
607		CONFIG_ARM_ERRATA_794072
608		CONFIG_ARM_ERRATA_761320
609
610		If set, the workarounds for these ARM errata are applied early
611		during U-Boot startup. Note that these options force the
612		workarounds to be applied; no CPU-type/version detection
613		exists, unlike the similar options in the Linux kernel. Do not
614		set these options unless they apply!
615
616- CPU timer options:
617		CONFIG_SYS_HZ
618
619		The frequency of the timer returned by get_timer().
620		get_timer() must operate in milliseconds and this CONFIG
621		option must be set to 1000.
622
623- Linux Kernel Interface:
624		CONFIG_CLOCKS_IN_MHZ
625
626		U-Boot stores all clock information in Hz
627		internally. For binary compatibility with older Linux
628		kernels (which expect the clocks passed in the
629		bd_info data to be in MHz) the environment variable
630		"clocks_in_mhz" can be defined so that U-Boot
631		converts clock data to MHZ before passing it to the
632		Linux kernel.
633		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
634		"clocks_in_mhz=1" is automatically included in the
635		default environment.
636
637		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
638
639		When transferring memsize parameter to linux, some versions
640		expect it to be in bytes, others in MB.
641		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
642
643		CONFIG_OF_LIBFDT
644
645		New kernel versions are expecting firmware settings to be
646		passed using flattened device trees (based on open firmware
647		concepts).
648
649		CONFIG_OF_LIBFDT
650		 * New libfdt-based support
651		 * Adds the "fdt" command
652		 * The bootm command automatically updates the fdt
653
654		OF_CPU - The proper name of the cpus node (only required for
655			MPC512X and MPC5xxx based boards).
656		OF_SOC - The proper name of the soc node (only required for
657			MPC512X and MPC5xxx based boards).
658		OF_TBCLK - The timebase frequency.
659		OF_STDOUT_PATH - The path to the console device
660
661		boards with QUICC Engines require OF_QE to set UCC MAC
662		addresses
663
664		CONFIG_OF_BOARD_SETUP
665
666		Board code has addition modification that it wants to make
667		to the flat device tree before handing it off to the kernel
668
669		CONFIG_OF_BOOT_CPU
670
671		This define fills in the correct boot CPU in the boot
672		param header, the default value is zero if undefined.
673
674		CONFIG_OF_IDE_FIXUP
675
676		U-Boot can detect if an IDE device is present or not.
677		If not, and this new config option is activated, U-Boot
678		removes the ATA node from the DTS before booting Linux,
679		so the Linux IDE driver does not probe the device and
680		crash. This is needed for buggy hardware (uc101) where
681		no pull down resistor is connected to the signal IDE5V_DD7.
682
683		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
684
685		This setting is mandatory for all boards that have only one
686		machine type and must be used to specify the machine type
687		number as it appears in the ARM machine registry
688		(see http://www.arm.linux.org.uk/developer/machines/).
689		Only boards that have multiple machine types supported
690		in a single configuration file and the machine type is
691		runtime discoverable, do not have to use this setting.
692
693- vxWorks boot parameters:
694
695		bootvx constructs a valid bootline using the following
696		environments variables: bootfile, ipaddr, serverip, hostname.
697		It loads the vxWorks image pointed bootfile.
698
699		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
700		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
701		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
702		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
703
704		CONFIG_SYS_VXWORKS_ADD_PARAMS
705
706		Add it at the end of the bootline. E.g "u=username pw=secret"
707
708		Note: If a "bootargs" environment is defined, it will overwride
709		the defaults discussed just above.
710
711- Cache Configuration:
712		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
713		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
714		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
715
716- Cache Configuration for ARM:
717		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
718				      controller
719		CONFIG_SYS_PL310_BASE - Physical base address of PL310
720					controller register space
721
722- Serial Ports:
723		CONFIG_PL010_SERIAL
724
725		Define this if you want support for Amba PrimeCell PL010 UARTs.
726
727		CONFIG_PL011_SERIAL
728
729		Define this if you want support for Amba PrimeCell PL011 UARTs.
730
731		CONFIG_PL011_CLOCK
732
733		If you have Amba PrimeCell PL011 UARTs, set this variable to
734		the clock speed of the UARTs.
735
736		CONFIG_PL01x_PORTS
737
738		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
739		define this to a list of base addresses for each (supported)
740		port. See e.g. include/configs/versatile.h
741
742		CONFIG_PL011_SERIAL_RLCR
743
744		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
745		have separate receive and transmit line control registers.  Set
746		this variable to initialize the extra register.
747
748		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
749
750		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
751		boot loader that has already initialized the UART.  Define this
752		variable to flush the UART at init time.
753
754		CONFIG_SERIAL_HW_FLOW_CONTROL
755
756		Define this variable to enable hw flow control in serial driver.
757		Current user of this option is drivers/serial/nsl16550.c driver
758
759- Console Interface:
760		Depending on board, define exactly one serial port
761		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
762		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
763		console by defining CONFIG_8xx_CONS_NONE
764
765		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
766		port routines must be defined elsewhere
767		(i.e. serial_init(), serial_getc(), ...)
768
769		CONFIG_CFB_CONSOLE
770		Enables console device for a color framebuffer. Needs following
771		defines (cf. smiLynxEM, i8042)
772			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
773						(default big endian)
774			VIDEO_HW_RECTFILL	graphic chip supports
775						rectangle fill
776						(cf. smiLynxEM)
777			VIDEO_HW_BITBLT		graphic chip supports
778						bit-blit (cf. smiLynxEM)
779			VIDEO_VISIBLE_COLS	visible pixel columns
780						(cols=pitch)
781			VIDEO_VISIBLE_ROWS	visible pixel rows
782			VIDEO_PIXEL_SIZE	bytes per pixel
783			VIDEO_DATA_FORMAT	graphic data format
784						(0-5, cf. cfb_console.c)
785			VIDEO_FB_ADRS		framebuffer address
786			VIDEO_KBD_INIT_FCT	keyboard int fct
787						(i.e. i8042_kbd_init())
788			VIDEO_TSTC_FCT		test char fct
789						(i.e. i8042_tstc)
790			VIDEO_GETC_FCT		get char fct
791						(i.e. i8042_getc)
792			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
793						(requires blink timer
794						cf. i8042.c)
795			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
796			CONFIG_CONSOLE_TIME	display time/date info in
797						upper right corner
798						(requires CONFIG_CMD_DATE)
799			CONFIG_VIDEO_LOGO	display Linux logo in
800						upper left corner
801			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
802						linux_logo.h for logo.
803						Requires CONFIG_VIDEO_LOGO
804			CONFIG_CONSOLE_EXTRA_INFO
805						additional board info beside
806						the logo
807
808		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
809		a limited number of ANSI escape sequences (cursor control,
810		erase functions and limited graphics rendition control).
811
812		When CONFIG_CFB_CONSOLE is defined, video console is
813		default i/o. Serial console can be forced with
814		environment 'console=serial'.
815
816		When CONFIG_SILENT_CONSOLE is defined, all console
817		messages (by U-Boot and Linux!) can be silenced with
818		the "silent" environment variable. See
819		doc/README.silent for more information.
820
821		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
822			is 0x00.
823		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
824			is 0xa0.
825
826- Console Baudrate:
827		CONFIG_BAUDRATE - in bps
828		Select one of the baudrates listed in
829		CONFIG_SYS_BAUDRATE_TABLE, see below.
830		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
831
832- Console Rx buffer length
833		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
834		the maximum receive buffer length for the SMC.
835		This option is actual only for 82xx and 8xx possible.
836		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
837		must be defined, to setup the maximum idle timeout for
838		the SMC.
839
840- Pre-Console Buffer:
841		Prior to the console being initialised (i.e. serial UART
842		initialised etc) all console output is silently discarded.
843		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
844		buffer any console messages prior to the console being
845		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
846		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
847		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
848		bytes are output before the console is initialised, the
849		earlier bytes are discarded.
850
851		'Sane' compilers will generate smaller code if
852		CONFIG_PRE_CON_BUF_SZ is a power of 2
853
854- Safe printf() functions
855		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
856		the printf() functions. These are defined in
857		include/vsprintf.h and include snprintf(), vsnprintf() and
858		so on. Code size increase is approximately 300-500 bytes.
859		If this option is not given then these functions will
860		silently discard their buffer size argument - this means
861		you are not getting any overflow checking in this case.
862
863- Boot Delay:	CONFIG_BOOTDELAY - in seconds
864		Delay before automatically booting the default image;
865		set to -1 to disable autoboot.
866		set to -2 to autoboot with no delay and not check for abort
867		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
868
869		See doc/README.autoboot for these options that
870		work with CONFIG_BOOTDELAY. None are required.
871		CONFIG_BOOT_RETRY_TIME
872		CONFIG_BOOT_RETRY_MIN
873		CONFIG_AUTOBOOT_KEYED
874		CONFIG_AUTOBOOT_PROMPT
875		CONFIG_AUTOBOOT_DELAY_STR
876		CONFIG_AUTOBOOT_STOP_STR
877		CONFIG_AUTOBOOT_DELAY_STR2
878		CONFIG_AUTOBOOT_STOP_STR2
879		CONFIG_ZERO_BOOTDELAY_CHECK
880		CONFIG_RESET_TO_RETRY
881
882- Autoboot Command:
883		CONFIG_BOOTCOMMAND
884		Only needed when CONFIG_BOOTDELAY is enabled;
885		define a command string that is automatically executed
886		when no character is read on the console interface
887		within "Boot Delay" after reset.
888
889		CONFIG_BOOTARGS
890		This can be used to pass arguments to the bootm
891		command. The value of CONFIG_BOOTARGS goes into the
892		environment value "bootargs".
893
894		CONFIG_RAMBOOT and CONFIG_NFSBOOT
895		The value of these goes into the environment as
896		"ramboot" and "nfsboot" respectively, and can be used
897		as a convenience, when switching between booting from
898		RAM and NFS.
899
900- Bootcount:
901		CONFIG_BOOTCOUNT_LIMIT
902		Implements a mechanism for detecting a repeating reboot
903		cycle, see:
904		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
905
906		CONFIG_BOOTCOUNT_ENV
907		If no softreset save registers are found on the hardware
908		"bootcount" is stored in the environment. To prevent a
909		saveenv on all reboots, the environment variable
910		"upgrade_available" is used. If "upgrade_available" is
911		0, "bootcount" is always 0, if "upgrade_available" is
912		1 "bootcount" is incremented in the environment.
913		So the Userspace Applikation must set the "upgrade_available"
914		and "bootcount" variable to 0, if a boot was successfully.
915
916- Pre-Boot Commands:
917		CONFIG_PREBOOT
918
919		When this option is #defined, the existence of the
920		environment variable "preboot" will be checked
921		immediately before starting the CONFIG_BOOTDELAY
922		countdown and/or running the auto-boot command resp.
923		entering interactive mode.
924
925		This feature is especially useful when "preboot" is
926		automatically generated or modified. For an example
927		see the LWMON board specific code: here "preboot" is
928		modified when the user holds down a certain
929		combination of keys on the (special) keyboard when
930		booting the systems
931
932- Serial Download Echo Mode:
933		CONFIG_LOADS_ECHO
934		If defined to 1, all characters received during a
935		serial download (using the "loads" command) are
936		echoed back. This might be needed by some terminal
937		emulations (like "cu"), but may as well just take
938		time on others. This setting #define's the initial
939		value of the "loads_echo" environment variable.
940
941- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
942		CONFIG_KGDB_BAUDRATE
943		Select one of the baudrates listed in
944		CONFIG_SYS_BAUDRATE_TABLE, see below.
945
946- Monitor Functions:
947		Monitor commands can be included or excluded
948		from the build by using the #include files
949		<config_cmd_all.h> and #undef'ing unwanted
950		commands, or using <config_cmd_default.h>
951		and augmenting with additional #define's
952		for wanted commands.
953
954		The default command configuration includes all commands
955		except those marked below with a "*".
956
957		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
958		CONFIG_CMD_ASKENV	* ask for env variable
959		CONFIG_CMD_BDI		  bdinfo
960		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
961		CONFIG_CMD_BMP		* BMP support
962		CONFIG_CMD_BSP		* Board specific commands
963		CONFIG_CMD_BOOTD	  bootd
964		CONFIG_CMD_CACHE	* icache, dcache
965		CONFIG_CMD_CLK   	* clock command support
966		CONFIG_CMD_CONSOLE	  coninfo
967		CONFIG_CMD_CRC32	* crc32
968		CONFIG_CMD_DATE		* support for RTC, date/time...
969		CONFIG_CMD_DHCP		* DHCP support
970		CONFIG_CMD_DIAG		* Diagnostics
971		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
972		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
973		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
974		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
975		CONFIG_CMD_DTT		* Digital Therm and Thermostat
976		CONFIG_CMD_ECHO		  echo arguments
977		CONFIG_CMD_EDITENV	  edit env variable
978		CONFIG_CMD_EEPROM	* EEPROM read/write support
979		CONFIG_CMD_ELF		* bootelf, bootvx
980		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
981		CONFIG_CMD_ENV_FLAGS	* display details about env flags
982		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
983		CONFIG_CMD_EXPORTENV	* export the environment
984		CONFIG_CMD_EXT2		* ext2 command support
985		CONFIG_CMD_EXT4		* ext4 command support
986		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
987					  that work for multiple fs types
988		CONFIG_CMD_SAVEENV	  saveenv
989		CONFIG_CMD_FDC		* Floppy Disk Support
990		CONFIG_CMD_FAT		* FAT command support
991		CONFIG_CMD_FLASH	  flinfo, erase, protect
992		CONFIG_CMD_FPGA		  FPGA device initialization support
993		CONFIG_CMD_FUSE		* Device fuse support
994		CONFIG_CMD_GETTIME	* Get time since boot
995		CONFIG_CMD_GO		* the 'go' command (exec code)
996		CONFIG_CMD_GREPENV	* search environment
997		CONFIG_CMD_HASH		* calculate hash / digest
998		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
999		CONFIG_CMD_I2C		* I2C serial bus support
1000		CONFIG_CMD_IDE		* IDE harddisk support
1001		CONFIG_CMD_IMI		  iminfo
1002		CONFIG_CMD_IMLS		  List all images found in NOR flash
1003		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1004		CONFIG_CMD_IMMAP	* IMMR dump support
1005		CONFIG_CMD_IMPORTENV	* import an environment
1006		CONFIG_CMD_INI		* import data from an ini file into the env
1007		CONFIG_CMD_IRQ		* irqinfo
1008		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1009		CONFIG_CMD_JFFS2	* JFFS2 Support
1010		CONFIG_CMD_KGDB		* kgdb
1011		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1012		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1013					  (169.254.*.*)
1014		CONFIG_CMD_LOADB	  loadb
1015		CONFIG_CMD_LOADS	  loads
1016		CONFIG_CMD_MD5SUM	* print md5 message digest
1017					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1018		CONFIG_CMD_MEMINFO	* Display detailed memory information
1019		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1020					  loop, loopw
1021		CONFIG_CMD_MEMTEST	* mtest
1022		CONFIG_CMD_MISC		  Misc functions like sleep etc
1023		CONFIG_CMD_MMC		* MMC memory mapped support
1024		CONFIG_CMD_MII		* MII utility commands
1025		CONFIG_CMD_MTDPARTS	* MTD partition support
1026		CONFIG_CMD_NAND		* NAND support
1027		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1028		CONFIG_CMD_NFS		  NFS support
1029		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1030		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1031		CONFIG_CMD_PCI		* pciinfo
1032		CONFIG_CMD_PCMCIA		* PCMCIA support
1033		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1034					  host
1035		CONFIG_CMD_PORTIO	* Port I/O
1036		CONFIG_CMD_READ		* Read raw data from partition
1037		CONFIG_CMD_REGINFO	* Register dump
1038		CONFIG_CMD_RUN		  run command in env variable
1039		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1040		CONFIG_CMD_SAVES	* save S record dump
1041		CONFIG_CMD_SCSI		* SCSI Support
1042		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1043					  (requires CONFIG_CMD_I2C)
1044		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1045					  (4xx only)
1046		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1047		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1048					  (requires CONFIG_CMD_MEMORY)
1049		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1050		CONFIG_CMD_SOURCE	  "source" command Support
1051		CONFIG_CMD_SPI		* SPI serial bus support
1052		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1053		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1054		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1055		CONFIG_CMD_TIMER	* access to the system tick timer
1056		CONFIG_CMD_USB		* USB support
1057		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1058		CONFIG_CMD_MFSL		* Microblaze FSL support
1059		CONFIG_CMD_XIMG		  Load part of Multi Image
1060		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1061
1062		EXAMPLE: If you want all functions except of network
1063		support you can write:
1064
1065		#include "config_cmd_all.h"
1066		#undef CONFIG_CMD_NET
1067
1068	Other Commands:
1069		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1070
1071	Note:	Don't enable the "icache" and "dcache" commands
1072		(configuration option CONFIG_CMD_CACHE) unless you know
1073		what you (and your U-Boot users) are doing. Data
1074		cache cannot be enabled on systems like the 8xx or
1075		8260 (where accesses to the IMMR region must be
1076		uncached), and it cannot be disabled on all other
1077		systems where we (mis-) use the data cache to hold an
1078		initial stack and some data.
1079
1080
1081		XXX - this list needs to get updated!
1082
1083- Regular expression support:
1084		CONFIG_REGEX
1085		If this variable is defined, U-Boot is linked against
1086		the SLRE (Super Light Regular Expression) library,
1087		which adds regex support to some commands, as for
1088		example "env grep" and "setexpr".
1089
1090- Device tree:
1091		CONFIG_OF_CONTROL
1092		If this variable is defined, U-Boot will use a device tree
1093		to configure its devices, instead of relying on statically
1094		compiled #defines in the board file. This option is
1095		experimental and only available on a few boards. The device
1096		tree is available in the global data as gd->fdt_blob.
1097
1098		U-Boot needs to get its device tree from somewhere. This can
1099		be done using one of the two options below:
1100
1101		CONFIG_OF_EMBED
1102		If this variable is defined, U-Boot will embed a device tree
1103		binary in its image. This device tree file should be in the
1104		board directory and called <soc>-<board>.dts. The binary file
1105		is then picked up in board_init_f() and made available through
1106		the global data structure as gd->blob.
1107
1108		CONFIG_OF_SEPARATE
1109		If this variable is defined, U-Boot will build a device tree
1110		binary. It will be called u-boot.dtb. Architecture-specific
1111		code will locate it at run-time. Generally this works by:
1112
1113			cat u-boot.bin u-boot.dtb >image.bin
1114
1115		and in fact, U-Boot does this for you, creating a file called
1116		u-boot-dtb.bin which is useful in the common case. You can
1117		still use the individual files if you need something more
1118		exotic.
1119
1120- Watchdog:
1121		CONFIG_WATCHDOG
1122		If this variable is defined, it enables watchdog
1123		support for the SoC. There must be support in the SoC
1124		specific code for a watchdog. For the 8xx and 8260
1125		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1126		register.  When supported for a specific SoC is
1127		available, then no further board specific code should
1128		be needed to use it.
1129
1130		CONFIG_HW_WATCHDOG
1131		When using a watchdog circuitry external to the used
1132		SoC, then define this variable and provide board
1133		specific code for the "hw_watchdog_reset" function.
1134
1135- U-Boot Version:
1136		CONFIG_VERSION_VARIABLE
1137		If this variable is defined, an environment variable
1138		named "ver" is created by U-Boot showing the U-Boot
1139		version as printed by the "version" command.
1140		Any change to this variable will be reverted at the
1141		next reset.
1142
1143- Real-Time Clock:
1144
1145		When CONFIG_CMD_DATE is selected, the type of the RTC
1146		has to be selected, too. Define exactly one of the
1147		following options:
1148
1149		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1150		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1151		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1152		CONFIG_RTC_MC146818	- use MC146818 RTC
1153		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1154		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1155		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1156		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1157		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1158		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1159		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1160		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1161					  RV3029 RTC.
1162
1163		Note that if the RTC uses I2C, then the I2C interface
1164		must also be configured. See I2C Support, below.
1165
1166- GPIO Support:
1167		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1168
1169		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1170		chip-ngpio pairs that tell the PCA953X driver the number of
1171		pins supported by a particular chip.
1172
1173		Note that if the GPIO device uses I2C, then the I2C interface
1174		must also be configured. See I2C Support, below.
1175
1176- Timestamp Support:
1177
1178		When CONFIG_TIMESTAMP is selected, the timestamp
1179		(date and time) of an image is printed by image
1180		commands like bootm or iminfo. This option is
1181		automatically enabled when you select CONFIG_CMD_DATE .
1182
1183- Partition Labels (disklabels) Supported:
1184		Zero or more of the following:
1185		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1186		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1187				       Intel architecture, USB sticks, etc.
1188		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1189		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1190				       bootloader.  Note 2TB partition limit; see
1191				       disk/part_efi.c
1192		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1193
1194		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1195		CONFIG_CMD_SCSI) you must configure support for at
1196		least one non-MTD partition type as well.
1197
1198- IDE Reset method:
1199		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1200		board configurations files but used nowhere!
1201
1202		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1203		be performed by calling the function
1204			ide_set_reset(int reset)
1205		which has to be defined in a board specific file
1206
1207- ATAPI Support:
1208		CONFIG_ATAPI
1209
1210		Set this to enable ATAPI support.
1211
1212- LBA48 Support
1213		CONFIG_LBA48
1214
1215		Set this to enable support for disks larger than 137GB
1216		Also look at CONFIG_SYS_64BIT_LBA.
1217		Whithout these , LBA48 support uses 32bit variables and will 'only'
1218		support disks up to 2.1TB.
1219
1220		CONFIG_SYS_64BIT_LBA:
1221			When enabled, makes the IDE subsystem use 64bit sector addresses.
1222			Default is 32bit.
1223
1224- SCSI Support:
1225		At the moment only there is only support for the
1226		SYM53C8XX SCSI controller; define
1227		CONFIG_SCSI_SYM53C8XX to enable it.
1228
1229		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1230		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1231		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1232		maximum numbers of LUNs, SCSI ID's and target
1233		devices.
1234		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1235
1236		The environment variable 'scsidevs' is set to the number of
1237		SCSI devices found during the last scan.
1238
1239- NETWORK Support (PCI):
1240		CONFIG_E1000
1241		Support for Intel 8254x/8257x gigabit chips.
1242
1243		CONFIG_E1000_SPI
1244		Utility code for direct access to the SPI bus on Intel 8257x.
1245		This does not do anything useful unless you set at least one
1246		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1247
1248		CONFIG_E1000_SPI_GENERIC
1249		Allow generic access to the SPI bus on the Intel 8257x, for
1250		example with the "sspi" command.
1251
1252		CONFIG_CMD_E1000
1253		Management command for E1000 devices.  When used on devices
1254		with SPI support you can reprogram the EEPROM from U-Boot.
1255
1256		CONFIG_E1000_FALLBACK_MAC
1257		default MAC for empty EEPROM after production.
1258
1259		CONFIG_EEPRO100
1260		Support for Intel 82557/82559/82559ER chips.
1261		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1262		write routine for first time initialisation.
1263
1264		CONFIG_TULIP
1265		Support for Digital 2114x chips.
1266		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1267		modem chip initialisation (KS8761/QS6611).
1268
1269		CONFIG_NATSEMI
1270		Support for National dp83815 chips.
1271
1272		CONFIG_NS8382X
1273		Support for National dp8382[01] gigabit chips.
1274
1275- NETWORK Support (other):
1276
1277		CONFIG_DRIVER_AT91EMAC
1278		Support for AT91RM9200 EMAC.
1279
1280			CONFIG_RMII
1281			Define this to use reduced MII inteface
1282
1283			CONFIG_DRIVER_AT91EMAC_QUIET
1284			If this defined, the driver is quiet.
1285			The driver doen't show link status messages.
1286
1287		CONFIG_CALXEDA_XGMAC
1288		Support for the Calxeda XGMAC device
1289
1290		CONFIG_LAN91C96
1291		Support for SMSC's LAN91C96 chips.
1292
1293			CONFIG_LAN91C96_BASE
1294			Define this to hold the physical address
1295			of the LAN91C96's I/O space
1296
1297			CONFIG_LAN91C96_USE_32_BIT
1298			Define this to enable 32 bit addressing
1299
1300		CONFIG_SMC91111
1301		Support for SMSC's LAN91C111 chip
1302
1303			CONFIG_SMC91111_BASE
1304			Define this to hold the physical address
1305			of the device (I/O space)
1306
1307			CONFIG_SMC_USE_32_BIT
1308			Define this if data bus is 32 bits
1309
1310			CONFIG_SMC_USE_IOFUNCS
1311			Define this to use i/o functions instead of macros
1312			(some hardware wont work with macros)
1313
1314		CONFIG_DRIVER_TI_EMAC
1315		Support for davinci emac
1316
1317			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1318			Define this if you have more then 3 PHYs.
1319
1320		CONFIG_FTGMAC100
1321		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1322
1323			CONFIG_FTGMAC100_EGIGA
1324			Define this to use GE link update with gigabit PHY.
1325			Define this if FTGMAC100 is connected to gigabit PHY.
1326			If your system has 10/100 PHY only, it might not occur
1327			wrong behavior. Because PHY usually return timeout or
1328			useless data when polling gigabit status and gigabit
1329			control registers. This behavior won't affect the
1330			correctnessof 10/100 link speed update.
1331
1332		CONFIG_SMC911X
1333		Support for SMSC's LAN911x and LAN921x chips
1334
1335			CONFIG_SMC911X_BASE
1336			Define this to hold the physical address
1337			of the device (I/O space)
1338
1339			CONFIG_SMC911X_32_BIT
1340			Define this if data bus is 32 bits
1341
1342			CONFIG_SMC911X_16_BIT
1343			Define this if data bus is 16 bits. If your processor
1344			automatically converts one 32 bit word to two 16 bit
1345			words you may also try CONFIG_SMC911X_32_BIT.
1346
1347		CONFIG_SH_ETHER
1348		Support for Renesas on-chip Ethernet controller
1349
1350			CONFIG_SH_ETHER_USE_PORT
1351			Define the number of ports to be used
1352
1353			CONFIG_SH_ETHER_PHY_ADDR
1354			Define the ETH PHY's address
1355
1356			CONFIG_SH_ETHER_CACHE_WRITEBACK
1357			If this option is set, the driver enables cache flush.
1358
1359- TPM Support:
1360		CONFIG_TPM
1361		Support TPM devices.
1362
1363		CONFIG_TPM_TIS_I2C
1364		Support for i2c bus TPM devices. Only one device
1365		per system is supported at this time.
1366
1367			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1368			Define the the i2c bus number for the TPM device
1369
1370			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1371			Define the TPM's address on the i2c bus
1372
1373			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1374			Define the burst count bytes upper limit
1375
1376		CONFIG_TPM_ATMEL_TWI
1377		Support for Atmel TWI TPM device. Requires I2C support.
1378
1379		CONFIG_TPM_TIS_LPC
1380		Support for generic parallel port TPM devices. Only one device
1381		per system is supported at this time.
1382
1383			CONFIG_TPM_TIS_BASE_ADDRESS
1384			Base address where the generic TPM device is mapped
1385			to. Contemporary x86 systems usually map it at
1386			0xfed40000.
1387
1388		CONFIG_CMD_TPM
1389		Add tpm monitor functions.
1390		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1391		provides monitor access to authorized functions.
1392
1393		CONFIG_TPM
1394		Define this to enable the TPM support library which provides
1395		functional interfaces to some TPM commands.
1396		Requires support for a TPM device.
1397
1398		CONFIG_TPM_AUTH_SESSIONS
1399		Define this to enable authorized functions in the TPM library.
1400		Requires CONFIG_TPM and CONFIG_SHA1.
1401
1402- USB Support:
1403		At the moment only the UHCI host controller is
1404		supported (PIP405, MIP405, MPC5200); define
1405		CONFIG_USB_UHCI to enable it.
1406		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1407		and define CONFIG_USB_STORAGE to enable the USB
1408		storage devices.
1409		Note:
1410		Supported are USB Keyboards and USB Floppy drives
1411		(TEAC FD-05PUB).
1412		MPC5200 USB requires additional defines:
1413			CONFIG_USB_CLOCK
1414				for 528 MHz Clock: 0x0001bbbb
1415			CONFIG_PSC3_USB
1416				for USB on PSC3
1417			CONFIG_USB_CONFIG
1418				for differential drivers: 0x00001000
1419				for single ended drivers: 0x00005000
1420				for differential drivers on PSC3: 0x00000100
1421				for single ended drivers on PSC3: 0x00004100
1422			CONFIG_SYS_USB_EVENT_POLL
1423				May be defined to allow interrupt polling
1424				instead of using asynchronous interrupts
1425
1426		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1427		txfilltuning field in the EHCI controller on reset.
1428
1429		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1430		interval for usb hub power-on delay.(minimum 100msec)
1431
1432- USB Device:
1433		Define the below if you wish to use the USB console.
1434		Once firmware is rebuilt from a serial console issue the
1435		command "setenv stdin usbtty; setenv stdout usbtty" and
1436		attach your USB cable. The Unix command "dmesg" should print
1437		it has found a new device. The environment variable usbtty
1438		can be set to gserial or cdc_acm to enable your device to
1439		appear to a USB host as a Linux gserial device or a
1440		Common Device Class Abstract Control Model serial device.
1441		If you select usbtty = gserial you should be able to enumerate
1442		a Linux host by
1443		# modprobe usbserial vendor=0xVendorID product=0xProductID
1444		else if using cdc_acm, simply setting the environment
1445		variable usbtty to be cdc_acm should suffice. The following
1446		might be defined in YourBoardName.h
1447
1448			CONFIG_USB_DEVICE
1449			Define this to build a UDC device
1450
1451			CONFIG_USB_TTY
1452			Define this to have a tty type of device available to
1453			talk to the UDC device
1454
1455			CONFIG_USBD_HS
1456			Define this to enable the high speed support for usb
1457			device and usbtty. If this feature is enabled, a routine
1458			int is_usbd_high_speed(void)
1459			also needs to be defined by the driver to dynamically poll
1460			whether the enumeration has succeded at high speed or full
1461			speed.
1462
1463			CONFIG_SYS_CONSOLE_IS_IN_ENV
1464			Define this if you want stdin, stdout &/or stderr to
1465			be set to usbtty.
1466
1467			mpc8xx:
1468				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1469				Derive USB clock from external clock "blah"
1470				- CONFIG_SYS_USB_EXTC_CLK 0x02
1471
1472				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1473				Derive USB clock from brgclk
1474				- CONFIG_SYS_USB_BRG_CLK 0x04
1475
1476		If you have a USB-IF assigned VendorID then you may wish to
1477		define your own vendor specific values either in BoardName.h
1478		or directly in usbd_vendor_info.h. If you don't define
1479		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1480		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1481		should pretend to be a Linux device to it's target host.
1482
1483			CONFIG_USBD_MANUFACTURER
1484			Define this string as the name of your company for
1485			- CONFIG_USBD_MANUFACTURER "my company"
1486
1487			CONFIG_USBD_PRODUCT_NAME
1488			Define this string as the name of your product
1489			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1490
1491			CONFIG_USBD_VENDORID
1492			Define this as your assigned Vendor ID from the USB
1493			Implementors Forum. This *must* be a genuine Vendor ID
1494			to avoid polluting the USB namespace.
1495			- CONFIG_USBD_VENDORID 0xFFFF
1496
1497			CONFIG_USBD_PRODUCTID
1498			Define this as the unique Product ID
1499			for your device
1500			- CONFIG_USBD_PRODUCTID 0xFFFF
1501
1502- ULPI Layer Support:
1503		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1504		the generic ULPI layer. The generic layer accesses the ULPI PHY
1505		via the platform viewport, so you need both the genric layer and
1506		the viewport enabled. Currently only Chipidea/ARC based
1507		viewport is supported.
1508		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1509		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1510		If your ULPI phy needs a different reference clock than the
1511		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1512		the appropriate value in Hz.
1513
1514- MMC Support:
1515		The MMC controller on the Intel PXA is supported. To
1516		enable this define CONFIG_MMC. The MMC can be
1517		accessed from the boot prompt by mapping the device
1518		to physical memory similar to flash. Command line is
1519		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1520		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1521
1522		CONFIG_SH_MMCIF
1523		Support for Renesas on-chip MMCIF controller
1524
1525			CONFIG_SH_MMCIF_ADDR
1526			Define the base address of MMCIF registers
1527
1528			CONFIG_SH_MMCIF_CLK
1529			Define the clock frequency for MMCIF
1530
1531- USB Device Firmware Update (DFU) class support:
1532		CONFIG_DFU_FUNCTION
1533		This enables the USB portion of the DFU USB class
1534
1535		CONFIG_CMD_DFU
1536		This enables the command "dfu" which is used to have
1537		U-Boot create a DFU class device via USB.  This command
1538		requires that the "dfu_alt_info" environment variable be
1539		set and define the alt settings to expose to the host.
1540
1541		CONFIG_DFU_MMC
1542		This enables support for exposing (e)MMC devices via DFU.
1543
1544		CONFIG_DFU_NAND
1545		This enables support for exposing NAND devices via DFU.
1546
1547		CONFIG_DFU_RAM
1548		This enables support for exposing RAM via DFU.
1549		Note: DFU spec refer to non-volatile memory usage, but
1550		allow usages beyond the scope of spec - here RAM usage,
1551		one that would help mostly the developer.
1552
1553		CONFIG_SYS_DFU_DATA_BUF_SIZE
1554		Dfu transfer uses a buffer before writing data to the
1555		raw storage device. Make the size (in bytes) of this buffer
1556		configurable. The size of this buffer is also configurable
1557		through the "dfu_bufsiz" environment variable.
1558
1559		CONFIG_SYS_DFU_MAX_FILE_SIZE
1560		When updating files rather than the raw storage device,
1561		we use a static buffer to copy the file into and then write
1562		the buffer once we've been given the whole file.  Define
1563		this to the maximum filesize (in bytes) for the buffer.
1564		Default is 4 MiB if undefined.
1565
1566		DFU_DEFAULT_POLL_TIMEOUT
1567		Poll timeout [ms], is the timeout a device can send to the
1568		host. The host must wait for this timeout before sending
1569		a subsequent DFU_GET_STATUS request to the device.
1570
1571		DFU_MANIFEST_POLL_TIMEOUT
1572		Poll timeout [ms], which the device sends to the host when
1573		entering dfuMANIFEST state. Host waits this timeout, before
1574		sending again an USB request to the device.
1575
1576- Journaling Flash filesystem support:
1577		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1578		CONFIG_JFFS2_NAND_DEV
1579		Define these for a default partition on a NAND device
1580
1581		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1582		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1583		Define these for a default partition on a NOR device
1584
1585		CONFIG_SYS_JFFS_CUSTOM_PART
1586		Define this to create an own partition. You have to provide a
1587		function struct part_info* jffs2_part_info(int part_num)
1588
1589		If you define only one JFFS2 partition you may also want to
1590		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1591		to disable the command chpart. This is the default when you
1592		have not defined a custom partition
1593
1594- FAT(File Allocation Table) filesystem write function support:
1595		CONFIG_FAT_WRITE
1596
1597		Define this to enable support for saving memory data as a
1598		file in FAT formatted partition.
1599
1600		This will also enable the command "fatwrite" enabling the
1601		user to write files to FAT.
1602
1603CBFS (Coreboot Filesystem) support
1604		CONFIG_CMD_CBFS
1605
1606		Define this to enable support for reading from a Coreboot
1607		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1608		and cbfsload.
1609
1610- Keyboard Support:
1611		CONFIG_ISA_KEYBOARD
1612
1613		Define this to enable standard (PC-Style) keyboard
1614		support
1615
1616		CONFIG_I8042_KBD
1617		Standard PC keyboard driver with US (is default) and
1618		GERMAN key layout (switch via environment 'keymap=de') support.
1619		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1620		for cfb_console. Supports cursor blinking.
1621
1622		CONFIG_CROS_EC_KEYB
1623		Enables a Chrome OS keyboard using the CROS_EC interface.
1624		This uses CROS_EC to communicate with a second microcontroller
1625		which provides key scans on request.
1626
1627- Video support:
1628		CONFIG_VIDEO
1629
1630		Define this to enable video support (for output to
1631		video).
1632
1633		CONFIG_VIDEO_CT69000
1634
1635		Enable Chips & Technologies 69000 Video chip
1636
1637		CONFIG_VIDEO_SMI_LYNXEM
1638		Enable Silicon Motion SMI 712/710/810 Video chip. The
1639		video output is selected via environment 'videoout'
1640		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1641		assumed.
1642
1643		For the CT69000 and SMI_LYNXEM drivers, videomode is
1644		selected via environment 'videomode'. Two different ways
1645		are possible:
1646		- "videomode=num"   'num' is a standard LiLo mode numbers.
1647		Following standard modes are supported	(* is default):
1648
1649		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1650		-------------+---------------------------------------------
1651		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1652		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1653		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1654		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1655		-------------+---------------------------------------------
1656		(i.e. setenv videomode 317; saveenv; reset;)
1657
1658		- "videomode=bootargs" all the video parameters are parsed
1659		from the bootargs. (See drivers/video/videomodes.c)
1660
1661
1662		CONFIG_VIDEO_SED13806
1663		Enable Epson SED13806 driver. This driver supports 8bpp
1664		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1665		or CONFIG_VIDEO_SED13806_16BPP
1666
1667		CONFIG_FSL_DIU_FB
1668		Enable the Freescale DIU video driver.	Reference boards for
1669		SOCs that have a DIU should define this macro to enable DIU
1670		support, and should also define these other macros:
1671
1672			CONFIG_SYS_DIU_ADDR
1673			CONFIG_VIDEO
1674			CONFIG_CMD_BMP
1675			CONFIG_CFB_CONSOLE
1676			CONFIG_VIDEO_SW_CURSOR
1677			CONFIG_VGA_AS_SINGLE_DEVICE
1678			CONFIG_VIDEO_LOGO
1679			CONFIG_VIDEO_BMP_LOGO
1680
1681		The DIU driver will look for the 'video-mode' environment
1682		variable, and if defined, enable the DIU as a console during
1683		boot.  See the documentation file README.video for a
1684		description of this variable.
1685
1686		CONFIG_VIDEO_VGA
1687
1688		Enable the VGA video / BIOS for x86. The alternative if you
1689		are using coreboot is to use the coreboot frame buffer
1690		driver.
1691
1692
1693- Keyboard Support:
1694		CONFIG_KEYBOARD
1695
1696		Define this to enable a custom keyboard support.
1697		This simply calls drv_keyboard_init() which must be
1698		defined in your board-specific files.
1699		The only board using this so far is RBC823.
1700
1701- LCD Support:	CONFIG_LCD
1702
1703		Define this to enable LCD support (for output to LCD
1704		display); also select one of the supported displays
1705		by defining one of these:
1706
1707		CONFIG_ATMEL_LCD:
1708
1709			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1710
1711		CONFIG_NEC_NL6448AC33:
1712
1713			NEC NL6448AC33-18. Active, color, single scan.
1714
1715		CONFIG_NEC_NL6448BC20
1716
1717			NEC NL6448BC20-08. 6.5", 640x480.
1718			Active, color, single scan.
1719
1720		CONFIG_NEC_NL6448BC33_54
1721
1722			NEC NL6448BC33-54. 10.4", 640x480.
1723			Active, color, single scan.
1724
1725		CONFIG_SHARP_16x9
1726
1727			Sharp 320x240. Active, color, single scan.
1728			It isn't 16x9, and I am not sure what it is.
1729
1730		CONFIG_SHARP_LQ64D341
1731
1732			Sharp LQ64D341 display, 640x480.
1733			Active, color, single scan.
1734
1735		CONFIG_HLD1045
1736
1737			HLD1045 display, 640x480.
1738			Active, color, single scan.
1739
1740		CONFIG_OPTREX_BW
1741
1742			Optrex	 CBL50840-2 NF-FW 99 22 M5
1743			or
1744			Hitachi	 LMG6912RPFC-00T
1745			or
1746			Hitachi	 SP14Q002
1747
1748			320x240. Black & white.
1749
1750		Normally display is black on white background; define
1751		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1752
1753		CONFIG_LCD_ALIGNMENT
1754
1755		Normally the LCD is page-aligned (tyically 4KB). If this is
1756		defined then the LCD will be aligned to this value instead.
1757		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1758		here, since it is cheaper to change data cache settings on
1759		a per-section basis.
1760
1761		CONFIG_CONSOLE_SCROLL_LINES
1762
1763		When the console need to be scrolled, this is the number of
1764		lines to scroll by. It defaults to 1. Increasing this makes
1765		the console jump but can help speed up operation when scrolling
1766		is slow.
1767
1768		CONFIG_LCD_BMP_RLE8
1769
1770		Support drawing of RLE8-compressed bitmaps on the LCD.
1771
1772		CONFIG_I2C_EDID
1773
1774		Enables an 'i2c edid' command which can read EDID
1775		information over I2C from an attached LCD display.
1776
1777- Splash Screen Support: CONFIG_SPLASH_SCREEN
1778
1779		If this option is set, the environment is checked for
1780		a variable "splashimage". If found, the usual display
1781		of logo, copyright and system information on the LCD
1782		is suppressed and the BMP image at the address
1783		specified in "splashimage" is loaded instead. The
1784		console is redirected to the "nulldev", too. This
1785		allows for a "silent" boot where a splash screen is
1786		loaded very quickly after power-on.
1787
1788		CONFIG_SPLASHIMAGE_GUARD
1789
1790		If this option is set, then U-Boot will prevent the environment
1791		variable "splashimage" from being set to a problematic address
1792		(see README.displaying-bmps).
1793		This option is useful for targets where, due to alignment
1794		restrictions, an improperly aligned BMP image will cause a data
1795		abort. If you think you will not have problems with unaligned
1796		accesses (for example because your toolchain prevents them)
1797		there is no need to set this option.
1798
1799		CONFIG_SPLASH_SCREEN_ALIGN
1800
1801		If this option is set the splash image can be freely positioned
1802		on the screen. Environment variable "splashpos" specifies the
1803		position as "x,y". If a positive number is given it is used as
1804		number of pixel from left/top. If a negative number is given it
1805		is used as number of pixel from right/bottom. You can also
1806		specify 'm' for centering the image.
1807
1808		Example:
1809		setenv splashpos m,m
1810			=> image at center of screen
1811
1812		setenv splashpos 30,20
1813			=> image at x = 30 and y = 20
1814
1815		setenv splashpos -10,m
1816			=> vertically centered image
1817			   at x = dspWidth - bmpWidth - 9
1818
1819- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1820
1821		If this option is set, additionally to standard BMP
1822		images, gzipped BMP images can be displayed via the
1823		splashscreen support or the bmp command.
1824
1825- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1826
1827		If this option is set, 8-bit RLE compressed BMP images
1828		can be displayed via the splashscreen support or the
1829		bmp command.
1830
1831- Do compresssing for memory range:
1832		CONFIG_CMD_ZIP
1833
1834		If this option is set, it would use zlib deflate method
1835		to compress the specified memory at its best effort.
1836
1837- Compression support:
1838		CONFIG_GZIP
1839
1840		Enabled by default to support gzip compressed images.
1841
1842		CONFIG_BZIP2
1843
1844		If this option is set, support for bzip2 compressed
1845		images is included. If not, only uncompressed and gzip
1846		compressed images are supported.
1847
1848		NOTE: the bzip2 algorithm requires a lot of RAM, so
1849		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1850		be at least 4MB.
1851
1852		CONFIG_LZMA
1853
1854		If this option is set, support for lzma compressed
1855		images is included.
1856
1857		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1858		requires an amount of dynamic memory that is given by the
1859		formula:
1860
1861			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1862
1863		Where lc and lp stand for, respectively, Literal context bits
1864		and Literal pos bits.
1865
1866		This value is upper-bounded by 14MB in the worst case. Anyway,
1867		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1868		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1869		a very small buffer.
1870
1871		Use the lzmainfo tool to determinate the lc and lp values and
1872		then calculate the amount of needed dynamic memory (ensuring
1873		the appropriate CONFIG_SYS_MALLOC_LEN value).
1874
1875		CONFIG_LZO
1876
1877		If this option is set, support for LZO compressed images
1878		is included.
1879
1880- MII/PHY support:
1881		CONFIG_PHY_ADDR
1882
1883		The address of PHY on MII bus.
1884
1885		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1886
1887		The clock frequency of the MII bus
1888
1889		CONFIG_PHY_GIGE
1890
1891		If this option is set, support for speed/duplex
1892		detection of gigabit PHY is included.
1893
1894		CONFIG_PHY_RESET_DELAY
1895
1896		Some PHY like Intel LXT971A need extra delay after
1897		reset before any MII register access is possible.
1898		For such PHY, set this option to the usec delay
1899		required. (minimum 300usec for LXT971A)
1900
1901		CONFIG_PHY_CMD_DELAY (ppc4xx)
1902
1903		Some PHY like Intel LXT971A need extra delay after
1904		command issued before MII status register can be read
1905
1906- Ethernet address:
1907		CONFIG_ETHADDR
1908		CONFIG_ETH1ADDR
1909		CONFIG_ETH2ADDR
1910		CONFIG_ETH3ADDR
1911		CONFIG_ETH4ADDR
1912		CONFIG_ETH5ADDR
1913
1914		Define a default value for Ethernet address to use
1915		for the respective Ethernet interface, in case this
1916		is not determined automatically.
1917
1918- IP address:
1919		CONFIG_IPADDR
1920
1921		Define a default value for the IP address to use for
1922		the default Ethernet interface, in case this is not
1923		determined through e.g. bootp.
1924		(Environment variable "ipaddr")
1925
1926- Server IP address:
1927		CONFIG_SERVERIP
1928
1929		Defines a default value for the IP address of a TFTP
1930		server to contact when using the "tftboot" command.
1931		(Environment variable "serverip")
1932
1933		CONFIG_KEEP_SERVERADDR
1934
1935		Keeps the server's MAC address, in the env 'serveraddr'
1936		for passing to bootargs (like Linux's netconsole option)
1937
1938- Gateway IP address:
1939		CONFIG_GATEWAYIP
1940
1941		Defines a default value for the IP address of the
1942		default router where packets to other networks are
1943		sent to.
1944		(Environment variable "gatewayip")
1945
1946- Subnet mask:
1947		CONFIG_NETMASK
1948
1949		Defines a default value for the subnet mask (or
1950		routing prefix) which is used to determine if an IP
1951		address belongs to the local subnet or needs to be
1952		forwarded through a router.
1953		(Environment variable "netmask")
1954
1955- Multicast TFTP Mode:
1956		CONFIG_MCAST_TFTP
1957
1958		Defines whether you want to support multicast TFTP as per
1959		rfc-2090; for example to work with atftp.  Lets lots of targets
1960		tftp down the same boot image concurrently.  Note: the Ethernet
1961		driver in use must provide a function: mcast() to join/leave a
1962		multicast group.
1963
1964- BOOTP Recovery Mode:
1965		CONFIG_BOOTP_RANDOM_DELAY
1966
1967		If you have many targets in a network that try to
1968		boot using BOOTP, you may want to avoid that all
1969		systems send out BOOTP requests at precisely the same
1970		moment (which would happen for instance at recovery
1971		from a power failure, when all systems will try to
1972		boot, thus flooding the BOOTP server. Defining
1973		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1974		inserted before sending out BOOTP requests. The
1975		following delays are inserted then:
1976
1977		1st BOOTP request:	delay 0 ... 1 sec
1978		2nd BOOTP request:	delay 0 ... 2 sec
1979		3rd BOOTP request:	delay 0 ... 4 sec
1980		4th and following
1981		BOOTP requests:		delay 0 ... 8 sec
1982
1983- DHCP Advanced Options:
1984		You can fine tune the DHCP functionality by defining
1985		CONFIG_BOOTP_* symbols:
1986
1987		CONFIG_BOOTP_SUBNETMASK
1988		CONFIG_BOOTP_GATEWAY
1989		CONFIG_BOOTP_HOSTNAME
1990		CONFIG_BOOTP_NISDOMAIN
1991		CONFIG_BOOTP_BOOTPATH
1992		CONFIG_BOOTP_BOOTFILESIZE
1993		CONFIG_BOOTP_DNS
1994		CONFIG_BOOTP_DNS2
1995		CONFIG_BOOTP_SEND_HOSTNAME
1996		CONFIG_BOOTP_NTPSERVER
1997		CONFIG_BOOTP_TIMEOFFSET
1998		CONFIG_BOOTP_VENDOREX
1999		CONFIG_BOOTP_MAY_FAIL
2000
2001		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2002		environment variable, not the BOOTP server.
2003
2004		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2005		after the configured retry count, the call will fail
2006		instead of starting over.  This can be used to fail over
2007		to Link-local IP address configuration if the DHCP server
2008		is not available.
2009
2010		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2011		serverip from a DHCP server, it is possible that more
2012		than one DNS serverip is offered to the client.
2013		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2014		serverip will be stored in the additional environment
2015		variable "dnsip2". The first DNS serverip is always
2016		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2017		is defined.
2018
2019		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2020		to do a dynamic update of a DNS server. To do this, they
2021		need the hostname of the DHCP requester.
2022		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2023		of the "hostname" environment variable is passed as
2024		option 12 to the DHCP server.
2025
2026		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2027
2028		A 32bit value in microseconds for a delay between
2029		receiving a "DHCP Offer" and sending the "DHCP Request".
2030		This fixes a problem with certain DHCP servers that don't
2031		respond 100% of the time to a "DHCP request". E.g. On an
2032		AT91RM9200 processor running at 180MHz, this delay needed
2033		to be *at least* 15,000 usec before a Windows Server 2003
2034		DHCP server would reply 100% of the time. I recommend at
2035		least 50,000 usec to be safe. The alternative is to hope
2036		that one of the retries will be successful but note that
2037		the DHCP timeout and retry process takes a longer than
2038		this delay.
2039
2040 - Link-local IP address negotiation:
2041		Negotiate with other link-local clients on the local network
2042		for an address that doesn't require explicit configuration.
2043		This is especially useful if a DHCP server cannot be guaranteed
2044		to exist in all environments that the device must operate.
2045
2046		See doc/README.link-local for more information.
2047
2048 - CDP Options:
2049		CONFIG_CDP_DEVICE_ID
2050
2051		The device id used in CDP trigger frames.
2052
2053		CONFIG_CDP_DEVICE_ID_PREFIX
2054
2055		A two character string which is prefixed to the MAC address
2056		of the device.
2057
2058		CONFIG_CDP_PORT_ID
2059
2060		A printf format string which contains the ascii name of
2061		the port. Normally is set to "eth%d" which sets
2062		eth0 for the first Ethernet, eth1 for the second etc.
2063
2064		CONFIG_CDP_CAPABILITIES
2065
2066		A 32bit integer which indicates the device capabilities;
2067		0x00000010 for a normal host which does not forwards.
2068
2069		CONFIG_CDP_VERSION
2070
2071		An ascii string containing the version of the software.
2072
2073		CONFIG_CDP_PLATFORM
2074
2075		An ascii string containing the name of the platform.
2076
2077		CONFIG_CDP_TRIGGER
2078
2079		A 32bit integer sent on the trigger.
2080
2081		CONFIG_CDP_POWER_CONSUMPTION
2082
2083		A 16bit integer containing the power consumption of the
2084		device in .1 of milliwatts.
2085
2086		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2087
2088		A byte containing the id of the VLAN.
2089
2090- Status LED:	CONFIG_STATUS_LED
2091
2092		Several configurations allow to display the current
2093		status using a LED. For instance, the LED will blink
2094		fast while running U-Boot code, stop blinking as
2095		soon as a reply to a BOOTP request was received, and
2096		start blinking slow once the Linux kernel is running
2097		(supported by a status LED driver in the Linux
2098		kernel). Defining CONFIG_STATUS_LED enables this
2099		feature in U-Boot.
2100
2101		Additional options:
2102
2103		CONFIG_GPIO_LED
2104		The status LED can be connected to a GPIO pin.
2105		In such cases, the gpio_led driver can be used as a
2106		status LED backend implementation. Define CONFIG_GPIO_LED
2107		to include the gpio_led driver in the U-Boot binary.
2108
2109		CONFIG_GPIO_LED_INVERTED_TABLE
2110		Some GPIO connected LEDs may have inverted polarity in which
2111		case the GPIO high value corresponds to LED off state and
2112		GPIO low value corresponds to LED on state.
2113		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2114		with a list of GPIO LEDs that have inverted polarity.
2115
2116- CAN Support:	CONFIG_CAN_DRIVER
2117
2118		Defining CONFIG_CAN_DRIVER enables CAN driver support
2119		on those systems that support this (optional)
2120		feature, like the TQM8xxL modules.
2121
2122- I2C Support:	CONFIG_SYS_I2C
2123
2124		This enable the NEW i2c subsystem, and will allow you to use
2125		i2c commands at the u-boot command line (as long as you set
2126		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2127		based realtime clock chips or other i2c devices. See
2128		common/cmd_i2c.c for a description of the command line
2129		interface.
2130
2131		ported i2c driver to the new framework:
2132		- drivers/i2c/soft_i2c.c:
2133		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2134		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2135		    for defining speed and slave address
2136		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2137		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2138		    for defining speed and slave address
2139		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2140		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2141		    for defining speed and slave address
2142		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2143		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2144		    for defining speed and slave address
2145
2146		- drivers/i2c/fsl_i2c.c:
2147		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2148		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2149		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2150		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2151		    bus.
2152		  - If your board supports a second fsl i2c bus, define
2153		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2154		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2155		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2156		    second bus.
2157
2158		- drivers/i2c/tegra_i2c.c:
2159		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2160		  - This driver adds 4 i2c buses with a fix speed from
2161		    100000 and the slave addr 0!
2162
2163		- drivers/i2c/ppc4xx_i2c.c
2164		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2165		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2166		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2167
2168		- drivers/i2c/i2c_mxc.c
2169		  - activate this driver with CONFIG_SYS_I2C_MXC
2170		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2171		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2172		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2173		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2174		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2175		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2176		If thoses defines are not set, default value is 100000
2177		for speed, and 0 for slave.
2178
2179		- drivers/i2c/rcar_i2c.c:
2180		  - activate this driver with CONFIG_SYS_I2C_RCAR
2181		  - This driver adds 4 i2c buses
2182
2183		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2184		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2185		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2186		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2187		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2188		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2189		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2190		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2191		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2192
2193		- drivers/i2c/sh_i2c.c:
2194		  - activate this driver with CONFIG_SYS_I2C_SH
2195		  - This driver adds from 2 to 5 i2c buses
2196
2197		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2198		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2199		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2200		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2201		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2202		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2203		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2204		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2205		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2206		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2207		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2208		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2209		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2210
2211		- drivers/i2c/omap24xx_i2c.c
2212		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2213		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2214		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2215		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2216		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2217		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2218		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2219		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2220		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2221		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2222		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2223
2224		- drivers/i2c/zynq_i2c.c
2225		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2226		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2227		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2228
2229		- drivers/i2c/s3c24x0_i2c.c:
2230		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2231		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2232		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2233		    with a fix speed from 100000 and the slave addr 0!
2234
2235		additional defines:
2236
2237		CONFIG_SYS_NUM_I2C_BUSES
2238		Hold the number of i2c busses you want to use. If you
2239		don't use/have i2c muxes on your i2c bus, this
2240		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2241		omit this define.
2242
2243		CONFIG_SYS_I2C_DIRECT_BUS
2244		define this, if you don't use i2c muxes on your hardware.
2245		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2246		omit this define.
2247
2248		CONFIG_SYS_I2C_MAX_HOPS
2249		define how many muxes are maximal consecutively connected
2250		on one i2c bus. If you not use i2c muxes, omit this
2251		define.
2252
2253		CONFIG_SYS_I2C_BUSES
2254		hold a list of busses you want to use, only used if
2255		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2256		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2257		CONFIG_SYS_NUM_I2C_BUSES = 9:
2258
2259		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2260					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2261					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2262					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2263					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2264					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2265					{1, {I2C_NULL_HOP}}, \
2266					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2267					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2268					}
2269
2270		which defines
2271			bus 0 on adapter 0 without a mux
2272			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2273			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2274			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2275			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2276			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2277			bus 6 on adapter 1 without a mux
2278			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2279			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2280
2281		If you do not have i2c muxes on your board, omit this define.
2282
2283- Legacy I2C Support:	CONFIG_HARD_I2C
2284
2285		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2286		provides the following compelling advantages:
2287
2288		- more than one i2c adapter is usable
2289		- approved multibus support
2290		- better i2c mux support
2291
2292		** Please consider updating your I2C driver now. **
2293
2294		These enable legacy I2C serial bus commands. Defining
2295		CONFIG_HARD_I2C will include the appropriate I2C driver
2296		for the selected CPU.
2297
2298		This will allow you to use i2c commands at the u-boot
2299		command line (as long as you set CONFIG_CMD_I2C in
2300		CONFIG_COMMANDS) and communicate with i2c based realtime
2301		clock chips. See common/cmd_i2c.c for a description of the
2302		command line interface.
2303
2304		CONFIG_HARD_I2C selects a hardware I2C controller.
2305
2306		There are several other quantities that must also be
2307		defined when you define CONFIG_HARD_I2C.
2308
2309		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2310		to be the frequency (in Hz) at which you wish your i2c bus
2311		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2312		the CPU's i2c node address).
2313
2314		Now, the u-boot i2c code for the mpc8xx
2315		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2316		and so its address should therefore be cleared to 0 (See,
2317		eg, MPC823e User's Manual p.16-473). So, set
2318		CONFIG_SYS_I2C_SLAVE to 0.
2319
2320		CONFIG_SYS_I2C_INIT_MPC5XXX
2321
2322		When a board is reset during an i2c bus transfer
2323		chips might think that the current transfer is still
2324		in progress.  Reset the slave devices by sending start
2325		commands until the slave device responds.
2326
2327		That's all that's required for CONFIG_HARD_I2C.
2328
2329		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2330		then the following macros need to be defined (examples are
2331		from include/configs/lwmon.h):
2332
2333		I2C_INIT
2334
2335		(Optional). Any commands necessary to enable the I2C
2336		controller or configure ports.
2337
2338		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2339
2340		I2C_PORT
2341
2342		(Only for MPC8260 CPU). The I/O port to use (the code
2343		assumes both bits are on the same port). Valid values
2344		are 0..3 for ports A..D.
2345
2346		I2C_ACTIVE
2347
2348		The code necessary to make the I2C data line active
2349		(driven).  If the data line is open collector, this
2350		define can be null.
2351
2352		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2353
2354		I2C_TRISTATE
2355
2356		The code necessary to make the I2C data line tri-stated
2357		(inactive).  If the data line is open collector, this
2358		define can be null.
2359
2360		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2361
2362		I2C_READ
2363
2364		Code that returns true if the I2C data line is high,
2365		false if it is low.
2366
2367		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2368
2369		I2C_SDA(bit)
2370
2371		If <bit> is true, sets the I2C data line high. If it
2372		is false, it clears it (low).
2373
2374		eg: #define I2C_SDA(bit) \
2375			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2376			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2377
2378		I2C_SCL(bit)
2379
2380		If <bit> is true, sets the I2C clock line high. If it
2381		is false, it clears it (low).
2382
2383		eg: #define I2C_SCL(bit) \
2384			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2385			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2386
2387		I2C_DELAY
2388
2389		This delay is invoked four times per clock cycle so this
2390		controls the rate of data transfer.  The data rate thus
2391		is 1 / (I2C_DELAY * 4). Often defined to be something
2392		like:
2393
2394		#define I2C_DELAY  udelay(2)
2395
2396		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2397
2398		If your arch supports the generic GPIO framework (asm/gpio.h),
2399		then you may alternatively define the two GPIOs that are to be
2400		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2401		have GPIO-based defaults assigned to them as appropriate.
2402
2403		You should define these to the GPIO value as given directly to
2404		the generic GPIO functions.
2405
2406		CONFIG_SYS_I2C_INIT_BOARD
2407
2408		When a board is reset during an i2c bus transfer
2409		chips might think that the current transfer is still
2410		in progress. On some boards it is possible to access
2411		the i2c SCLK line directly, either by using the
2412		processor pin as a GPIO or by having a second pin
2413		connected to the bus. If this option is defined a
2414		custom i2c_init_board() routine in boards/xxx/board.c
2415		is run early in the boot sequence.
2416
2417		CONFIG_SYS_I2C_BOARD_LATE_INIT
2418
2419		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2420		defined a custom i2c_board_late_init() routine in
2421		boards/xxx/board.c is run AFTER the operations in i2c_init()
2422		is completed. This callpoint can be used to unreset i2c bus
2423		using CPU i2c controller register accesses for CPUs whose i2c
2424		controller provide such a method. It is called at the end of
2425		i2c_init() to allow i2c_init operations to setup the i2c bus
2426		controller on the CPU (e.g. setting bus speed & slave address).
2427
2428		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2429
2430		This option enables configuration of bi_iic_fast[] flags
2431		in u-boot bd_info structure based on u-boot environment
2432		variable "i2cfast". (see also i2cfast)
2433
2434		CONFIG_I2C_MULTI_BUS
2435
2436		This option allows the use of multiple I2C buses, each of which
2437		must have a controller.	 At any point in time, only one bus is
2438		active.	 To switch to a different bus, use the 'i2c dev' command.
2439		Note that bus numbering is zero-based.
2440
2441		CONFIG_SYS_I2C_NOPROBES
2442
2443		This option specifies a list of I2C devices that will be skipped
2444		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2445		is set, specify a list of bus-device pairs.  Otherwise, specify
2446		a 1D array of device addresses
2447
2448		e.g.
2449			#undef	CONFIG_I2C_MULTI_BUS
2450			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2451
2452		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2453
2454			#define CONFIG_I2C_MULTI_BUS
2455			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2456
2457		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2458
2459		CONFIG_SYS_SPD_BUS_NUM
2460
2461		If defined, then this indicates the I2C bus number for DDR SPD.
2462		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2463
2464		CONFIG_SYS_RTC_BUS_NUM
2465
2466		If defined, then this indicates the I2C bus number for the RTC.
2467		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2468
2469		CONFIG_SYS_DTT_BUS_NUM
2470
2471		If defined, then this indicates the I2C bus number for the DTT.
2472		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2473
2474		CONFIG_SYS_I2C_DTT_ADDR:
2475
2476		If defined, specifies the I2C address of the DTT device.
2477		If not defined, then U-Boot uses predefined value for
2478		specified DTT device.
2479
2480		CONFIG_SOFT_I2C_READ_REPEATED_START
2481
2482		defining this will force the i2c_read() function in
2483		the soft_i2c driver to perform an I2C repeated start
2484		between writing the address pointer and reading the
2485		data.  If this define is omitted the default behaviour
2486		of doing a stop-start sequence will be used.  Most I2C
2487		devices can use either method, but some require one or
2488		the other.
2489
2490- SPI Support:	CONFIG_SPI
2491
2492		Enables SPI driver (so far only tested with
2493		SPI EEPROM, also an instance works with Crystal A/D and
2494		D/As on the SACSng board)
2495
2496		CONFIG_SH_SPI
2497
2498		Enables the driver for SPI controller on SuperH. Currently
2499		only SH7757 is supported.
2500
2501		CONFIG_SPI_X
2502
2503		Enables extended (16-bit) SPI EEPROM addressing.
2504		(symmetrical to CONFIG_I2C_X)
2505
2506		CONFIG_SOFT_SPI
2507
2508		Enables a software (bit-bang) SPI driver rather than
2509		using hardware support. This is a general purpose
2510		driver that only requires three general I/O port pins
2511		(two outputs, one input) to function. If this is
2512		defined, the board configuration must define several
2513		SPI configuration items (port pins to use, etc). For
2514		an example, see include/configs/sacsng.h.
2515
2516		CONFIG_HARD_SPI
2517
2518		Enables a hardware SPI driver for general-purpose reads
2519		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2520		must define a list of chip-select function pointers.
2521		Currently supported on some MPC8xxx processors.	 For an
2522		example, see include/configs/mpc8349emds.h.
2523
2524		CONFIG_MXC_SPI
2525
2526		Enables the driver for the SPI controllers on i.MX and MXC
2527		SoCs. Currently i.MX31/35/51 are supported.
2528
2529- FPGA Support: CONFIG_FPGA
2530
2531		Enables FPGA subsystem.
2532
2533		CONFIG_FPGA_<vendor>
2534
2535		Enables support for specific chip vendors.
2536		(ALTERA, XILINX)
2537
2538		CONFIG_FPGA_<family>
2539
2540		Enables support for FPGA family.
2541		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2542
2543		CONFIG_FPGA_COUNT
2544
2545		Specify the number of FPGA devices to support.
2546
2547		CONFIG_SYS_FPGA_PROG_FEEDBACK
2548
2549		Enable printing of hash marks during FPGA configuration.
2550
2551		CONFIG_SYS_FPGA_CHECK_BUSY
2552
2553		Enable checks on FPGA configuration interface busy
2554		status by the configuration function. This option
2555		will require a board or device specific function to
2556		be written.
2557
2558		CONFIG_FPGA_DELAY
2559
2560		If defined, a function that provides delays in the FPGA
2561		configuration driver.
2562
2563		CONFIG_SYS_FPGA_CHECK_CTRLC
2564		Allow Control-C to interrupt FPGA configuration
2565
2566		CONFIG_SYS_FPGA_CHECK_ERROR
2567
2568		Check for configuration errors during FPGA bitfile
2569		loading. For example, abort during Virtex II
2570		configuration if the INIT_B line goes low (which
2571		indicated a CRC error).
2572
2573		CONFIG_SYS_FPGA_WAIT_INIT
2574
2575		Maximum time to wait for the INIT_B line to deassert
2576		after PROB_B has been deasserted during a Virtex II
2577		FPGA configuration sequence. The default time is 500
2578		ms.
2579
2580		CONFIG_SYS_FPGA_WAIT_BUSY
2581
2582		Maximum time to wait for BUSY to deassert during
2583		Virtex II FPGA configuration. The default is 5 ms.
2584
2585		CONFIG_SYS_FPGA_WAIT_CONFIG
2586
2587		Time to wait after FPGA configuration. The default is
2588		200 ms.
2589
2590- Configuration Management:
2591		CONFIG_IDENT_STRING
2592
2593		If defined, this string will be added to the U-Boot
2594		version information (U_BOOT_VERSION)
2595
2596- Vendor Parameter Protection:
2597
2598		U-Boot considers the values of the environment
2599		variables "serial#" (Board Serial Number) and
2600		"ethaddr" (Ethernet Address) to be parameters that
2601		are set once by the board vendor / manufacturer, and
2602		protects these variables from casual modification by
2603		the user. Once set, these variables are read-only,
2604		and write or delete attempts are rejected. You can
2605		change this behaviour:
2606
2607		If CONFIG_ENV_OVERWRITE is #defined in your config
2608		file, the write protection for vendor parameters is
2609		completely disabled. Anybody can change or delete
2610		these parameters.
2611
2612		Alternatively, if you #define _both_ CONFIG_ETHADDR
2613		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2614		Ethernet address is installed in the environment,
2615		which can be changed exactly ONCE by the user. [The
2616		serial# is unaffected by this, i. e. it remains
2617		read-only.]
2618
2619		The same can be accomplished in a more flexible way
2620		for any variable by configuring the type of access
2621		to allow for those variables in the ".flags" variable
2622		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2623
2624- Protected RAM:
2625		CONFIG_PRAM
2626
2627		Define this variable to enable the reservation of
2628		"protected RAM", i. e. RAM which is not overwritten
2629		by U-Boot. Define CONFIG_PRAM to hold the number of
2630		kB you want to reserve for pRAM. You can overwrite
2631		this default value by defining an environment
2632		variable "pram" to the number of kB you want to
2633		reserve. Note that the board info structure will
2634		still show the full amount of RAM. If pRAM is
2635		reserved, a new environment variable "mem" will
2636		automatically be defined to hold the amount of
2637		remaining RAM in a form that can be passed as boot
2638		argument to Linux, for instance like that:
2639
2640			setenv bootargs ... mem=\${mem}
2641			saveenv
2642
2643		This way you can tell Linux not to use this memory,
2644		either, which results in a memory region that will
2645		not be affected by reboots.
2646
2647		*WARNING* If your board configuration uses automatic
2648		detection of the RAM size, you must make sure that
2649		this memory test is non-destructive. So far, the
2650		following board configurations are known to be
2651		"pRAM-clean":
2652
2653			IVMS8, IVML24, SPD8xx, TQM8xxL,
2654			HERMES, IP860, RPXlite, LWMON,
2655			FLAGADM, TQM8260
2656
2657- Access to physical memory region (> 4GB)
2658		Some basic support is provided for operations on memory not
2659		normally accessible to U-Boot - e.g. some architectures
2660		support access to more than 4GB of memory on 32-bit
2661		machines using physical address extension or similar.
2662		Define CONFIG_PHYSMEM to access this basic support, which
2663		currently only supports clearing the memory.
2664
2665- Error Recovery:
2666		CONFIG_PANIC_HANG
2667
2668		Define this variable to stop the system in case of a
2669		fatal error, so that you have to reset it manually.
2670		This is probably NOT a good idea for an embedded
2671		system where you want the system to reboot
2672		automatically as fast as possible, but it may be
2673		useful during development since you can try to debug
2674		the conditions that lead to the situation.
2675
2676		CONFIG_NET_RETRY_COUNT
2677
2678		This variable defines the number of retries for
2679		network operations like ARP, RARP, TFTP, or BOOTP
2680		before giving up the operation. If not defined, a
2681		default value of 5 is used.
2682
2683		CONFIG_ARP_TIMEOUT
2684
2685		Timeout waiting for an ARP reply in milliseconds.
2686
2687		CONFIG_NFS_TIMEOUT
2688
2689		Timeout in milliseconds used in NFS protocol.
2690		If you encounter "ERROR: Cannot umount" in nfs command,
2691		try longer timeout such as
2692		#define CONFIG_NFS_TIMEOUT 10000UL
2693
2694- Command Interpreter:
2695		CONFIG_AUTO_COMPLETE
2696
2697		Enable auto completion of commands using TAB.
2698
2699		Note that this feature has NOT been implemented yet
2700		for the "hush" shell.
2701
2702
2703		CONFIG_SYS_HUSH_PARSER
2704
2705		Define this variable to enable the "hush" shell (from
2706		Busybox) as command line interpreter, thus enabling
2707		powerful command line syntax like
2708		if...then...else...fi conditionals or `&&' and '||'
2709		constructs ("shell scripts").
2710
2711		If undefined, you get the old, much simpler behaviour
2712		with a somewhat smaller memory footprint.
2713
2714
2715		CONFIG_SYS_PROMPT_HUSH_PS2
2716
2717		This defines the secondary prompt string, which is
2718		printed when the command interpreter needs more input
2719		to complete a command. Usually "> ".
2720
2721	Note:
2722
2723		In the current implementation, the local variables
2724		space and global environment variables space are
2725		separated. Local variables are those you define by
2726		simply typing `name=value'. To access a local
2727		variable later on, you have write `$name' or
2728		`${name}'; to execute the contents of a variable
2729		directly type `$name' at the command prompt.
2730
2731		Global environment variables are those you use
2732		setenv/printenv to work with. To run a command stored
2733		in such a variable, you need to use the run command,
2734		and you must not use the '$' sign to access them.
2735
2736		To store commands and special characters in a
2737		variable, please use double quotation marks
2738		surrounding the whole text of the variable, instead
2739		of the backslashes before semicolons and special
2740		symbols.
2741
2742- Commandline Editing and History:
2743		CONFIG_CMDLINE_EDITING
2744
2745		Enable editing and History functions for interactive
2746		commandline input operations
2747
2748- Default Environment:
2749		CONFIG_EXTRA_ENV_SETTINGS
2750
2751		Define this to contain any number of null terminated
2752		strings (variable = value pairs) that will be part of
2753		the default environment compiled into the boot image.
2754
2755		For example, place something like this in your
2756		board's config file:
2757
2758		#define CONFIG_EXTRA_ENV_SETTINGS \
2759			"myvar1=value1\0" \
2760			"myvar2=value2\0"
2761
2762		Warning: This method is based on knowledge about the
2763		internal format how the environment is stored by the
2764		U-Boot code. This is NOT an official, exported
2765		interface! Although it is unlikely that this format
2766		will change soon, there is no guarantee either.
2767		You better know what you are doing here.
2768
2769		Note: overly (ab)use of the default environment is
2770		discouraged. Make sure to check other ways to preset
2771		the environment like the "source" command or the
2772		boot command first.
2773
2774		CONFIG_ENV_VARS_UBOOT_CONFIG
2775
2776		Define this in order to add variables describing the
2777		U-Boot build configuration to the default environment.
2778		These will be named arch, cpu, board, vendor, and soc.
2779
2780		Enabling this option will cause the following to be defined:
2781
2782		- CONFIG_SYS_ARCH
2783		- CONFIG_SYS_CPU
2784		- CONFIG_SYS_BOARD
2785		- CONFIG_SYS_VENDOR
2786		- CONFIG_SYS_SOC
2787
2788		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2789
2790		Define this in order to add variables describing certain
2791		run-time determined information about the hardware to the
2792		environment.  These will be named board_name, board_rev.
2793
2794		CONFIG_DELAY_ENVIRONMENT
2795
2796		Normally the environment is loaded when the board is
2797		intialised so that it is available to U-Boot. This inhibits
2798		that so that the environment is not available until
2799		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2800		this is instead controlled by the value of
2801		/config/load-environment.
2802
2803- DataFlash Support:
2804		CONFIG_HAS_DATAFLASH
2805
2806		Defining this option enables DataFlash features and
2807		allows to read/write in Dataflash via the standard
2808		commands cp, md...
2809
2810- Serial Flash support
2811		CONFIG_CMD_SF
2812
2813		Defining this option enables SPI flash commands
2814		'sf probe/read/write/erase/update'.
2815
2816		Usage requires an initial 'probe' to define the serial
2817		flash parameters, followed by read/write/erase/update
2818		commands.
2819
2820		The following defaults may be provided by the platform
2821		to handle the common case when only a single serial
2822		flash is present on the system.
2823
2824		CONFIG_SF_DEFAULT_BUS		Bus identifier
2825		CONFIG_SF_DEFAULT_CS		Chip-select
2826		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2827		CONFIG_SF_DEFAULT_SPEED		in Hz
2828
2829		CONFIG_CMD_SF_TEST
2830
2831		Define this option to include a destructive SPI flash
2832		test ('sf test').
2833
2834		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2835
2836		Define this option to use the Bank addr/Extended addr
2837		support on SPI flashes which has size > 16Mbytes.
2838
2839		CONFIG_SF_DUAL_FLASH		Dual flash memories
2840
2841		Define this option to use dual flash support where two flash
2842		memories can be connected with a given cs line.
2843		currently Xilinx Zynq qspi support these type of connections.
2844
2845- SystemACE Support:
2846		CONFIG_SYSTEMACE
2847
2848		Adding this option adds support for Xilinx SystemACE
2849		chips attached via some sort of local bus. The address
2850		of the chip must also be defined in the
2851		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2852
2853		#define CONFIG_SYSTEMACE
2854		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2855
2856		When SystemACE support is added, the "ace" device type
2857		becomes available to the fat commands, i.e. fatls.
2858
2859- TFTP Fixed UDP Port:
2860		CONFIG_TFTP_PORT
2861
2862		If this is defined, the environment variable tftpsrcp
2863		is used to supply the TFTP UDP source port value.
2864		If tftpsrcp isn't defined, the normal pseudo-random port
2865		number generator is used.
2866
2867		Also, the environment variable tftpdstp is used to supply
2868		the TFTP UDP destination port value.  If tftpdstp isn't
2869		defined, the normal port 69 is used.
2870
2871		The purpose for tftpsrcp is to allow a TFTP server to
2872		blindly start the TFTP transfer using the pre-configured
2873		target IP address and UDP port. This has the effect of
2874		"punching through" the (Windows XP) firewall, allowing
2875		the remainder of the TFTP transfer to proceed normally.
2876		A better solution is to properly configure the firewall,
2877		but sometimes that is not allowed.
2878
2879- Hashing support:
2880		CONFIG_CMD_HASH
2881
2882		This enables a generic 'hash' command which can produce
2883		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2884
2885		CONFIG_HASH_VERIFY
2886
2887		Enable the hash verify command (hash -v). This adds to code
2888		size a little.
2889
2890		CONFIG_SHA1 - support SHA1 hashing
2891		CONFIG_SHA256 - support SHA256 hashing
2892
2893		Note: There is also a sha1sum command, which should perhaps
2894		be deprecated in favour of 'hash sha1'.
2895
2896- Freescale i.MX specific commands:
2897		CONFIG_CMD_HDMIDETECT
2898		This enables 'hdmidet' command which returns true if an
2899		HDMI monitor is detected.  This command is i.MX 6 specific.
2900
2901		CONFIG_CMD_BMODE
2902		This enables the 'bmode' (bootmode) command for forcing
2903		a boot from specific media.
2904
2905		This is useful for forcing the ROM's usb downloader to
2906		activate upon a watchdog reset which is nice when iterating
2907		on U-Boot.  Using the reset button or running bmode normal
2908		will set it back to normal.  This command currently
2909		supports i.MX53 and i.MX6.
2910
2911- Signing support:
2912		CONFIG_RSA
2913
2914		This enables the RSA algorithm used for FIT image verification
2915		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2916
2917		The signing part is build into mkimage regardless of this
2918		option.
2919
2920- bootcount support:
2921		CONFIG_BOOTCOUNT_LIMIT
2922
2923		This enables the bootcounter support, see:
2924		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2925
2926		CONFIG_AT91SAM9XE
2927		enable special bootcounter support on at91sam9xe based boards.
2928		CONFIG_BLACKFIN
2929		enable special bootcounter support on blackfin based boards.
2930		CONFIG_SOC_DA8XX
2931		enable special bootcounter support on da850 based boards.
2932		CONFIG_BOOTCOUNT_RAM
2933		enable support for the bootcounter in RAM
2934		CONFIG_BOOTCOUNT_I2C
2935		enable support for the bootcounter on an i2c (like RTC) device.
2936			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2937			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2938						    the bootcounter.
2939			CONFIG_BOOTCOUNT_ALEN = address len
2940
2941- Show boot progress:
2942		CONFIG_SHOW_BOOT_PROGRESS
2943
2944		Defining this option allows to add some board-
2945		specific code (calling a user-provided function
2946		"show_boot_progress(int)") that enables you to show
2947		the system's boot progress on some display (for
2948		example, some LED's) on your board. At the moment,
2949		the following checkpoints are implemented:
2950
2951- Detailed boot stage timing
2952		CONFIG_BOOTSTAGE
2953		Define this option to get detailed timing of each stage
2954		of the boot process.
2955
2956		CONFIG_BOOTSTAGE_USER_COUNT
2957		This is the number of available user bootstage records.
2958		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2959		a new ID will be allocated from this stash. If you exceed
2960		the limit, recording will stop.
2961
2962		CONFIG_BOOTSTAGE_REPORT
2963		Define this to print a report before boot, similar to this:
2964
2965		Timer summary in microseconds:
2966		       Mark    Elapsed  Stage
2967			  0          0  reset
2968		  3,575,678  3,575,678  board_init_f start
2969		  3,575,695         17  arch_cpu_init A9
2970		  3,575,777         82  arch_cpu_init done
2971		  3,659,598     83,821  board_init_r start
2972		  3,910,375    250,777  main_loop
2973		 29,916,167 26,005,792  bootm_start
2974		 30,361,327    445,160  start_kernel
2975
2976		CONFIG_CMD_BOOTSTAGE
2977		Add a 'bootstage' command which supports printing a report
2978		and un/stashing of bootstage data.
2979
2980		CONFIG_BOOTSTAGE_FDT
2981		Stash the bootstage information in the FDT. A root 'bootstage'
2982		node is created with each bootstage id as a child. Each child
2983		has a 'name' property and either 'mark' containing the
2984		mark time in microsecond, or 'accum' containing the
2985		accumulated time for that bootstage id in microseconds.
2986		For example:
2987
2988		bootstage {
2989			154 {
2990				name = "board_init_f";
2991				mark = <3575678>;
2992			};
2993			170 {
2994				name = "lcd";
2995				accum = <33482>;
2996			};
2997		};
2998
2999		Code in the Linux kernel can find this in /proc/devicetree.
3000
3001Legacy uImage format:
3002
3003  Arg	Where			When
3004    1	common/cmd_bootm.c	before attempting to boot an image
3005   -1	common/cmd_bootm.c	Image header has bad	 magic number
3006    2	common/cmd_bootm.c	Image header has correct magic number
3007   -2	common/cmd_bootm.c	Image header has bad	 checksum
3008    3	common/cmd_bootm.c	Image header has correct checksum
3009   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3010    4	common/cmd_bootm.c	Image data   has correct checksum
3011   -4	common/cmd_bootm.c	Image is for unsupported architecture
3012    5	common/cmd_bootm.c	Architecture check OK
3013   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3014    6	common/cmd_bootm.c	Image Type check OK
3015   -6	common/cmd_bootm.c	gunzip uncompression error
3016   -7	common/cmd_bootm.c	Unimplemented compression type
3017    7	common/cmd_bootm.c	Uncompression OK
3018    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3019   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3020
3021    9	common/image.c		Start initial ramdisk verification
3022  -10	common/image.c		Ramdisk header has bad	   magic number
3023  -11	common/image.c		Ramdisk header has bad	   checksum
3024   10	common/image.c		Ramdisk header is OK
3025  -12	common/image.c		Ramdisk data   has bad	   checksum
3026   11	common/image.c		Ramdisk data   has correct checksum
3027   12	common/image.c		Ramdisk verification complete, start loading
3028  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3029   13	common/image.c		Start multifile image verification
3030   14	common/image.c		No initial ramdisk, no multifile, continue.
3031
3032   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3033
3034  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3035  -31	post/post.c		POST test failed, detected by post_output_backlog()
3036  -32	post/post.c		POST test failed, detected by post_run_single()
3037
3038   34	common/cmd_doc.c	before loading a Image from a DOC device
3039  -35	common/cmd_doc.c	Bad usage of "doc" command
3040   35	common/cmd_doc.c	correct usage of "doc" command
3041  -36	common/cmd_doc.c	No boot device
3042   36	common/cmd_doc.c	correct boot device
3043  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3044   37	common/cmd_doc.c	correct chip ID found, device available
3045  -38	common/cmd_doc.c	Read Error on boot device
3046   38	common/cmd_doc.c	reading Image header from DOC device OK
3047  -39	common/cmd_doc.c	Image header has bad magic number
3048   39	common/cmd_doc.c	Image header has correct magic number
3049  -40	common/cmd_doc.c	Error reading Image from DOC device
3050   40	common/cmd_doc.c	Image header has correct magic number
3051   41	common/cmd_ide.c	before loading a Image from a IDE device
3052  -42	common/cmd_ide.c	Bad usage of "ide" command
3053   42	common/cmd_ide.c	correct usage of "ide" command
3054  -43	common/cmd_ide.c	No boot device
3055   43	common/cmd_ide.c	boot device found
3056  -44	common/cmd_ide.c	Device not available
3057   44	common/cmd_ide.c	Device available
3058  -45	common/cmd_ide.c	wrong partition selected
3059   45	common/cmd_ide.c	partition selected
3060  -46	common/cmd_ide.c	Unknown partition table
3061   46	common/cmd_ide.c	valid partition table found
3062  -47	common/cmd_ide.c	Invalid partition type
3063   47	common/cmd_ide.c	correct partition type
3064  -48	common/cmd_ide.c	Error reading Image Header on boot device
3065   48	common/cmd_ide.c	reading Image Header from IDE device OK
3066  -49	common/cmd_ide.c	Image header has bad magic number
3067   49	common/cmd_ide.c	Image header has correct magic number
3068  -50	common/cmd_ide.c	Image header has bad	 checksum
3069   50	common/cmd_ide.c	Image header has correct checksum
3070  -51	common/cmd_ide.c	Error reading Image from IDE device
3071   51	common/cmd_ide.c	reading Image from IDE device OK
3072   52	common/cmd_nand.c	before loading a Image from a NAND device
3073  -53	common/cmd_nand.c	Bad usage of "nand" command
3074   53	common/cmd_nand.c	correct usage of "nand" command
3075  -54	common/cmd_nand.c	No boot device
3076   54	common/cmd_nand.c	boot device found
3077  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3078   55	common/cmd_nand.c	correct chip ID found, device available
3079  -56	common/cmd_nand.c	Error reading Image Header on boot device
3080   56	common/cmd_nand.c	reading Image Header from NAND device OK
3081  -57	common/cmd_nand.c	Image header has bad magic number
3082   57	common/cmd_nand.c	Image header has correct magic number
3083  -58	common/cmd_nand.c	Error reading Image from NAND device
3084   58	common/cmd_nand.c	reading Image from NAND device OK
3085
3086  -60	common/env_common.c	Environment has a bad CRC, using default
3087
3088   64	net/eth.c		starting with Ethernet configuration.
3089  -64	net/eth.c		no Ethernet found.
3090   65	net/eth.c		Ethernet found.
3091
3092  -80	common/cmd_net.c	usage wrong
3093   80	common/cmd_net.c	before calling NetLoop()
3094  -81	common/cmd_net.c	some error in NetLoop() occurred
3095   81	common/cmd_net.c	NetLoop() back without error
3096  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3097   82	common/cmd_net.c	trying automatic boot
3098   83	common/cmd_net.c	running "source" command
3099  -83	common/cmd_net.c	some error in automatic boot or "source" command
3100   84	common/cmd_net.c	end without errors
3101
3102FIT uImage format:
3103
3104  Arg	Where			When
3105  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3106 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3107  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3108 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3109  102	common/cmd_bootm.c	Kernel unit name specified
3110 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3111  103	common/cmd_bootm.c	Found configuration node
3112  104	common/cmd_bootm.c	Got kernel subimage node offset
3113 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3114  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3115 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3116  106	common/cmd_bootm.c	Architecture check OK
3117 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3118  107	common/cmd_bootm.c	Kernel subimage type OK
3119 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3120  108	common/cmd_bootm.c	Got kernel subimage data/size
3121 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3122 -109	common/cmd_bootm.c	Can't get kernel subimage type
3123 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3124 -111	common/cmd_bootm.c	Can't get kernel subimage os
3125 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3126 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3127
3128  120	common/image.c		Start initial ramdisk verification
3129 -120	common/image.c		Ramdisk FIT image has incorrect format
3130  121	common/image.c		Ramdisk FIT image has correct format
3131  122	common/image.c		No ramdisk subimage unit name, using configuration
3132 -122	common/image.c		Can't get configuration for ramdisk subimage
3133  123	common/image.c		Ramdisk unit name specified
3134 -124	common/image.c		Can't get ramdisk subimage node offset
3135  125	common/image.c		Got ramdisk subimage node offset
3136 -125	common/image.c		Ramdisk subimage hash verification failed
3137  126	common/image.c		Ramdisk subimage hash verification OK
3138 -126	common/image.c		Ramdisk subimage for unsupported architecture
3139  127	common/image.c		Architecture check OK
3140 -127	common/image.c		Can't get ramdisk subimage data/size
3141  128	common/image.c		Got ramdisk subimage data/size
3142  129	common/image.c		Can't get ramdisk load address
3143 -129	common/image.c		Got ramdisk load address
3144
3145 -130	common/cmd_doc.c	Incorrect FIT image format
3146  131	common/cmd_doc.c	FIT image format OK
3147
3148 -140	common/cmd_ide.c	Incorrect FIT image format
3149  141	common/cmd_ide.c	FIT image format OK
3150
3151 -150	common/cmd_nand.c	Incorrect FIT image format
3152  151	common/cmd_nand.c	FIT image format OK
3153
3154- FIT image support:
3155		CONFIG_FIT
3156		Enable support for the FIT uImage format.
3157
3158		CONFIG_FIT_BEST_MATCH
3159		When no configuration is explicitly selected, default to the
3160		one whose fdt's compatibility field best matches that of
3161		U-Boot itself. A match is considered "best" if it matches the
3162		most specific compatibility entry of U-Boot's fdt's root node.
3163		The order of entries in the configuration's fdt is ignored.
3164
3165		CONFIG_FIT_SIGNATURE
3166		This option enables signature verification of FIT uImages,
3167		using a hash signed and verified using RSA. See
3168		doc/uImage.FIT/signature.txt for more details.
3169
3170- Standalone program support:
3171		CONFIG_STANDALONE_LOAD_ADDR
3172
3173		This option defines a board specific value for the
3174		address where standalone program gets loaded, thus
3175		overwriting the architecture dependent default
3176		settings.
3177
3178- Frame Buffer Address:
3179		CONFIG_FB_ADDR
3180
3181		Define CONFIG_FB_ADDR if you want to use specific
3182		address for frame buffer.  This is typically the case
3183		when using a graphics controller has separate video
3184		memory.  U-Boot will then place the frame buffer at
3185		the given address instead of dynamically reserving it
3186		in system RAM by calling lcd_setmem(), which grabs
3187		the memory for the frame buffer depending on the
3188		configured panel size.
3189
3190		Please see board_init_f function.
3191
3192- Automatic software updates via TFTP server
3193		CONFIG_UPDATE_TFTP
3194		CONFIG_UPDATE_TFTP_CNT_MAX
3195		CONFIG_UPDATE_TFTP_MSEC_MAX
3196
3197		These options enable and control the auto-update feature;
3198		for a more detailed description refer to doc/README.update.
3199
3200- MTD Support (mtdparts command, UBI support)
3201		CONFIG_MTD_DEVICE
3202
3203		Adds the MTD device infrastructure from the Linux kernel.
3204		Needed for mtdparts command support.
3205
3206		CONFIG_MTD_PARTITIONS
3207
3208		Adds the MTD partitioning infrastructure from the Linux
3209		kernel. Needed for UBI support.
3210
3211- UBI support
3212		CONFIG_CMD_UBI
3213
3214		Adds commands for interacting with MTD partitions formatted
3215		with the UBI flash translation layer
3216
3217		Requires also defining CONFIG_RBTREE
3218
3219		CONFIG_UBI_SILENCE_MSG
3220
3221		Make the verbose messages from UBI stop printing.  This leaves
3222		warnings and errors enabled.
3223
3224- UBIFS support
3225		CONFIG_CMD_UBIFS
3226
3227		Adds commands for interacting with UBI volumes formatted as
3228		UBIFS.  UBIFS is read-only in u-boot.
3229
3230		Requires UBI support as well as CONFIG_LZO
3231
3232		CONFIG_UBIFS_SILENCE_MSG
3233
3234		Make the verbose messages from UBIFS stop printing.  This leaves
3235		warnings and errors enabled.
3236
3237- SPL framework
3238		CONFIG_SPL
3239		Enable building of SPL globally.
3240
3241		CONFIG_SPL_LDSCRIPT
3242		LDSCRIPT for linking the SPL binary.
3243
3244		CONFIG_SPL_MAX_FOOTPRINT
3245		Maximum size in memory allocated to the SPL, BSS included.
3246		When defined, the linker checks that the actual memory
3247		used by SPL from _start to __bss_end does not exceed it.
3248		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3249		must not be both defined at the same time.
3250
3251		CONFIG_SPL_MAX_SIZE
3252		Maximum size of the SPL image (text, data, rodata, and
3253		linker lists sections), BSS excluded.
3254		When defined, the linker checks that the actual size does
3255		not exceed it.
3256
3257		CONFIG_SPL_TEXT_BASE
3258		TEXT_BASE for linking the SPL binary.
3259
3260		CONFIG_SPL_RELOC_TEXT_BASE
3261		Address to relocate to.  If unspecified, this is equal to
3262		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3263
3264		CONFIG_SPL_BSS_START_ADDR
3265		Link address for the BSS within the SPL binary.
3266
3267		CONFIG_SPL_BSS_MAX_SIZE
3268		Maximum size in memory allocated to the SPL BSS.
3269		When defined, the linker checks that the actual memory used
3270		by SPL from __bss_start to __bss_end does not exceed it.
3271		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3272		must not be both defined at the same time.
3273
3274		CONFIG_SPL_STACK
3275		Adress of the start of the stack SPL will use
3276
3277		CONFIG_SPL_RELOC_STACK
3278		Adress of the start of the stack SPL will use after
3279		relocation.  If unspecified, this is equal to
3280		CONFIG_SPL_STACK.
3281
3282		CONFIG_SYS_SPL_MALLOC_START
3283		Starting address of the malloc pool used in SPL.
3284
3285		CONFIG_SYS_SPL_MALLOC_SIZE
3286		The size of the malloc pool used in SPL.
3287
3288		CONFIG_SPL_FRAMEWORK
3289		Enable the SPL framework under common/.  This framework
3290		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3291		NAND loading of the Linux Kernel.
3292
3293		CONFIG_SPL_OS_BOOT
3294		Enable booting directly to an OS from SPL.
3295		See also: doc/README.falcon
3296
3297		CONFIG_SPL_DISPLAY_PRINT
3298		For ARM, enable an optional function to print more information
3299		about the running system.
3300
3301		CONFIG_SPL_INIT_MINIMAL
3302		Arch init code should be built for a very small image
3303
3304		CONFIG_SPL_LIBCOMMON_SUPPORT
3305		Support for common/libcommon.o in SPL binary
3306
3307		CONFIG_SPL_LIBDISK_SUPPORT
3308		Support for disk/libdisk.o in SPL binary
3309
3310		CONFIG_SPL_I2C_SUPPORT
3311		Support for drivers/i2c/libi2c.o in SPL binary
3312
3313		CONFIG_SPL_GPIO_SUPPORT
3314		Support for drivers/gpio/libgpio.o in SPL binary
3315
3316		CONFIG_SPL_MMC_SUPPORT
3317		Support for drivers/mmc/libmmc.o in SPL binary
3318
3319		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3320		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3321		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3322		Address, size and partition on the MMC to load U-Boot from
3323		when the MMC is being used in raw mode.
3324
3325		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3326		Sector to load kernel uImage from when MMC is being
3327		used in raw mode (for Falcon mode)
3328
3329		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3330		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3331		Sector and number of sectors to load kernel argument
3332		parameters from when MMC is being used in raw mode
3333		(for falcon mode)
3334
3335		CONFIG_SPL_FAT_SUPPORT
3336		Support for fs/fat/libfat.o in SPL binary
3337
3338		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3339		Filename to read to load U-Boot when reading from FAT
3340
3341		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3342		Filename to read to load kernel uImage when reading
3343		from FAT (for Falcon mode)
3344
3345		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3346		Filename to read to load kernel argument parameters
3347		when reading from FAT (for Falcon mode)
3348
3349		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3350		Set this for NAND SPL on PPC mpc83xx targets, so that
3351		start.S waits for the rest of the SPL to load before
3352		continuing (the hardware starts execution after just
3353		loading the first page rather than the full 4K).
3354
3355		CONFIG_SPL_SKIP_RELOCATE
3356		Avoid SPL relocation
3357
3358		CONFIG_SPL_NAND_BASE
3359		Include nand_base.c in the SPL.  Requires
3360		CONFIG_SPL_NAND_DRIVERS.
3361
3362		CONFIG_SPL_NAND_DRIVERS
3363		SPL uses normal NAND drivers, not minimal drivers.
3364
3365		CONFIG_SPL_NAND_ECC
3366		Include standard software ECC in the SPL
3367
3368		CONFIG_SPL_NAND_SIMPLE
3369		Support for NAND boot using simple NAND drivers that
3370		expose the cmd_ctrl() interface.
3371
3372		CONFIG_SPL_MTD_SUPPORT
3373		Support for the MTD subsystem within SPL.  Useful for
3374		environment on NAND support within SPL.
3375
3376		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3377		Set for the SPL on PPC mpc8xxx targets, support for
3378		drivers/ddr/fsl/libddr.o in SPL binary.
3379
3380		CONFIG_SPL_COMMON_INIT_DDR
3381		Set for common ddr init with serial presence detect in
3382		SPL binary.
3383
3384		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3385		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3386		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3387		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3388		CONFIG_SYS_NAND_ECCBYTES
3389		Defines the size and behavior of the NAND that SPL uses
3390		to read U-Boot
3391
3392		CONFIG_SPL_NAND_BOOT
3393		Add support NAND boot
3394
3395		CONFIG_SYS_NAND_U_BOOT_OFFS
3396		Location in NAND to read U-Boot from
3397
3398		CONFIG_SYS_NAND_U_BOOT_DST
3399		Location in memory to load U-Boot to
3400
3401		CONFIG_SYS_NAND_U_BOOT_SIZE
3402		Size of image to load
3403
3404		CONFIG_SYS_NAND_U_BOOT_START
3405		Entry point in loaded image to jump to
3406
3407		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3408		Define this if you need to first read the OOB and then the
3409		data. This is used for example on davinci plattforms.
3410
3411		CONFIG_SPL_OMAP3_ID_NAND
3412		Support for an OMAP3-specific set of functions to return the
3413		ID and MFR of the first attached NAND chip, if present.
3414
3415		CONFIG_SPL_SERIAL_SUPPORT
3416		Support for drivers/serial/libserial.o in SPL binary
3417
3418		CONFIG_SPL_SPI_FLASH_SUPPORT
3419		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3420
3421		CONFIG_SPL_SPI_SUPPORT
3422		Support for drivers/spi/libspi.o in SPL binary
3423
3424		CONFIG_SPL_RAM_DEVICE
3425		Support for running image already present in ram, in SPL binary
3426
3427		CONFIG_SPL_LIBGENERIC_SUPPORT
3428		Support for lib/libgeneric.o in SPL binary
3429
3430		CONFIG_SPL_ENV_SUPPORT
3431		Support for the environment operating in SPL binary
3432
3433		CONFIG_SPL_NET_SUPPORT
3434		Support for the net/libnet.o in SPL binary.
3435		It conflicts with SPL env from storage medium specified by
3436		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3437
3438		CONFIG_SPL_PAD_TO
3439		Image offset to which the SPL should be padded before appending
3440		the SPL payload. By default, this is defined as
3441		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3442		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3443		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3444
3445		CONFIG_SPL_TARGET
3446		Final target image containing SPL and payload.  Some SPLs
3447		use an arch-specific makefile fragment instead, for
3448		example if more than one image needs to be produced.
3449
3450		CONFIG_FIT_SPL_PRINT
3451		Printing information about a FIT image adds quite a bit of
3452		code to SPL. So this is normally disabled in SPL. Use this
3453		option to re-enable it. This will affect the output of the
3454		bootm command when booting a FIT image.
3455
3456- TPL framework
3457		CONFIG_TPL
3458		Enable building of TPL globally.
3459
3460		CONFIG_TPL_PAD_TO
3461		Image offset to which the TPL should be padded before appending
3462		the TPL payload. By default, this is defined as
3463		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3464		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3465		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3466
3467Modem Support:
3468--------------
3469
3470[so far only for SMDK2400 boards]
3471
3472- Modem support enable:
3473		CONFIG_MODEM_SUPPORT
3474
3475- RTS/CTS Flow control enable:
3476		CONFIG_HWFLOW
3477
3478- Modem debug support:
3479		CONFIG_MODEM_SUPPORT_DEBUG
3480
3481		Enables debugging stuff (char screen[1024], dbg())
3482		for modem support. Useful only with BDI2000.
3483
3484- Interrupt support (PPC):
3485
3486		There are common interrupt_init() and timer_interrupt()
3487		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3488		for CPU specific initialization. interrupt_init_cpu()
3489		should set decrementer_count to appropriate value. If
3490		CPU resets decrementer automatically after interrupt
3491		(ppc4xx) it should set decrementer_count to zero.
3492		timer_interrupt() calls timer_interrupt_cpu() for CPU
3493		specific handling. If board has watchdog / status_led
3494		/ other_activity_monitor it works automatically from
3495		general timer_interrupt().
3496
3497- General:
3498
3499		In the target system modem support is enabled when a
3500		specific key (key combination) is pressed during
3501		power-on. Otherwise U-Boot will boot normally
3502		(autoboot). The key_pressed() function is called from
3503		board_init(). Currently key_pressed() is a dummy
3504		function, returning 1 and thus enabling modem
3505		initialization.
3506
3507		If there are no modem init strings in the
3508		environment, U-Boot proceed to autoboot; the
3509		previous output (banner, info printfs) will be
3510		suppressed, though.
3511
3512		See also: doc/README.Modem
3513
3514Board initialization settings:
3515------------------------------
3516
3517During Initialization u-boot calls a number of board specific functions
3518to allow the preparation of board specific prerequisites, e.g. pin setup
3519before drivers are initialized. To enable these callbacks the
3520following configuration macros have to be defined. Currently this is
3521architecture specific, so please check arch/your_architecture/lib/board.c
3522typically in board_init_f() and board_init_r().
3523
3524- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3525- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3526- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3527- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3528
3529Configuration Settings:
3530-----------------------
3531
3532- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3533		Optionally it can be defined to support 64-bit memory commands.
3534
3535- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3536		undefine this when you're short of memory.
3537
3538- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3539		width of the commands listed in the 'help' command output.
3540
3541- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3542		prompt for user input.
3543
3544- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3545
3546- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3547
3548- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3549
3550- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3551		the application (usually a Linux kernel) when it is
3552		booted
3553
3554- CONFIG_SYS_BAUDRATE_TABLE:
3555		List of legal baudrate settings for this board.
3556
3557- CONFIG_SYS_CONSOLE_INFO_QUIET
3558		Suppress display of console information at boot.
3559
3560- CONFIG_SYS_CONSOLE_IS_IN_ENV
3561		If the board specific function
3562			extern int overwrite_console (void);
3563		returns 1, the stdin, stderr and stdout are switched to the
3564		serial port, else the settings in the environment are used.
3565
3566- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3567		Enable the call to overwrite_console().
3568
3569- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3570		Enable overwrite of previous console environment settings.
3571
3572- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3573		Begin and End addresses of the area used by the
3574		simple memory test.
3575
3576- CONFIG_SYS_ALT_MEMTEST:
3577		Enable an alternate, more extensive memory test.
3578
3579- CONFIG_SYS_MEMTEST_SCRATCH:
3580		Scratch address used by the alternate memory test
3581		You only need to set this if address zero isn't writeable
3582
3583- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3584		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3585		this specified memory area will get subtracted from the top
3586		(end) of RAM and won't get "touched" at all by U-Boot. By
3587		fixing up gd->ram_size the Linux kernel should gets passed
3588		the now "corrected" memory size and won't touch it either.
3589		This should work for arch/ppc and arch/powerpc. Only Linux
3590		board ports in arch/powerpc with bootwrapper support that
3591		recalculate the memory size from the SDRAM controller setup
3592		will have to get fixed in Linux additionally.
3593
3594		This option can be used as a workaround for the 440EPx/GRx
3595		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3596		be touched.
3597
3598		WARNING: Please make sure that this value is a multiple of
3599		the Linux page size (normally 4k). If this is not the case,
3600		then the end address of the Linux memory will be located at a
3601		non page size aligned address and this could cause major
3602		problems.
3603
3604- CONFIG_SYS_LOADS_BAUD_CHANGE:
3605		Enable temporary baudrate change while serial download
3606
3607- CONFIG_SYS_SDRAM_BASE:
3608		Physical start address of SDRAM. _Must_ be 0 here.
3609
3610- CONFIG_SYS_MBIO_BASE:
3611		Physical start address of Motherboard I/O (if using a
3612		Cogent motherboard)
3613
3614- CONFIG_SYS_FLASH_BASE:
3615		Physical start address of Flash memory.
3616
3617- CONFIG_SYS_MONITOR_BASE:
3618		Physical start address of boot monitor code (set by
3619		make config files to be same as the text base address
3620		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3621		CONFIG_SYS_FLASH_BASE when booting from flash.
3622
3623- CONFIG_SYS_MONITOR_LEN:
3624		Size of memory reserved for monitor code, used to
3625		determine _at_compile_time_ (!) if the environment is
3626		embedded within the U-Boot image, or in a separate
3627		flash sector.
3628
3629- CONFIG_SYS_MALLOC_LEN:
3630		Size of DRAM reserved for malloc() use.
3631
3632- CONFIG_SYS_BOOTM_LEN:
3633		Normally compressed uImages are limited to an
3634		uncompressed size of 8 MBytes. If this is not enough,
3635		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3636		to adjust this setting to your needs.
3637
3638- CONFIG_SYS_BOOTMAPSZ:
3639		Maximum size of memory mapped by the startup code of
3640		the Linux kernel; all data that must be processed by
3641		the Linux kernel (bd_info, boot arguments, FDT blob if
3642		used) must be put below this limit, unless "bootm_low"
3643		environment variable is defined and non-zero. In such case
3644		all data for the Linux kernel must be between "bootm_low"
3645		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3646		variable "bootm_mapsize" will override the value of
3647		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3648		then the value in "bootm_size" will be used instead.
3649
3650- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3651		Enable initrd_high functionality.  If defined then the
3652		initrd_high feature is enabled and the bootm ramdisk subcommand
3653		is enabled.
3654
3655- CONFIG_SYS_BOOT_GET_CMDLINE:
3656		Enables allocating and saving kernel cmdline in space between
3657		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3658
3659- CONFIG_SYS_BOOT_GET_KBD:
3660		Enables allocating and saving a kernel copy of the bd_info in
3661		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3662
3663- CONFIG_SYS_MAX_FLASH_BANKS:
3664		Max number of Flash memory banks
3665
3666- CONFIG_SYS_MAX_FLASH_SECT:
3667		Max number of sectors on a Flash chip
3668
3669- CONFIG_SYS_FLASH_ERASE_TOUT:
3670		Timeout for Flash erase operations (in ms)
3671
3672- CONFIG_SYS_FLASH_WRITE_TOUT:
3673		Timeout for Flash write operations (in ms)
3674
3675- CONFIG_SYS_FLASH_LOCK_TOUT
3676		Timeout for Flash set sector lock bit operation (in ms)
3677
3678- CONFIG_SYS_FLASH_UNLOCK_TOUT
3679		Timeout for Flash clear lock bits operation (in ms)
3680
3681- CONFIG_SYS_FLASH_PROTECTION
3682		If defined, hardware flash sectors protection is used
3683		instead of U-Boot software protection.
3684
3685- CONFIG_SYS_DIRECT_FLASH_TFTP:
3686
3687		Enable TFTP transfers directly to flash memory;
3688		without this option such a download has to be
3689		performed in two steps: (1) download to RAM, and (2)
3690		copy from RAM to flash.
3691
3692		The two-step approach is usually more reliable, since
3693		you can check if the download worked before you erase
3694		the flash, but in some situations (when system RAM is
3695		too limited to allow for a temporary copy of the
3696		downloaded image) this option may be very useful.
3697
3698- CONFIG_SYS_FLASH_CFI:
3699		Define if the flash driver uses extra elements in the
3700		common flash structure for storing flash geometry.
3701
3702- CONFIG_FLASH_CFI_DRIVER
3703		This option also enables the building of the cfi_flash driver
3704		in the drivers directory
3705
3706- CONFIG_FLASH_CFI_MTD
3707		This option enables the building of the cfi_mtd driver
3708		in the drivers directory. The driver exports CFI flash
3709		to the MTD layer.
3710
3711- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3712		Use buffered writes to flash.
3713
3714- CONFIG_FLASH_SPANSION_S29WS_N
3715		s29ws-n MirrorBit flash has non-standard addresses for buffered
3716		write commands.
3717
3718- CONFIG_SYS_FLASH_QUIET_TEST
3719		If this option is defined, the common CFI flash doesn't
3720		print it's warning upon not recognized FLASH banks. This
3721		is useful, if some of the configured banks are only
3722		optionally available.
3723
3724- CONFIG_FLASH_SHOW_PROGRESS
3725		If defined (must be an integer), print out countdown
3726		digits and dots.  Recommended value: 45 (9..1) for 80
3727		column displays, 15 (3..1) for 40 column displays.
3728
3729- CONFIG_FLASH_VERIFY
3730		If defined, the content of the flash (destination) is compared
3731		against the source after the write operation. An error message
3732		will be printed when the contents are not identical.
3733		Please note that this option is useless in nearly all cases,
3734		since such flash programming errors usually are detected earlier
3735		while unprotecting/erasing/programming. Please only enable
3736		this option if you really know what you are doing.
3737
3738- CONFIG_SYS_RX_ETH_BUFFER:
3739		Defines the number of Ethernet receive buffers. On some
3740		Ethernet controllers it is recommended to set this value
3741		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3742		buffers can be full shortly after enabling the interface
3743		on high Ethernet traffic.
3744		Defaults to 4 if not defined.
3745
3746- CONFIG_ENV_MAX_ENTRIES
3747
3748	Maximum number of entries in the hash table that is used
3749	internally to store the environment settings. The default
3750	setting is supposed to be generous and should work in most
3751	cases. This setting can be used to tune behaviour; see
3752	lib/hashtable.c for details.
3753
3754- CONFIG_ENV_FLAGS_LIST_DEFAULT
3755- CONFIG_ENV_FLAGS_LIST_STATIC
3756	Enable validation of the values given to environment variables when
3757	calling env set.  Variables can be restricted to only decimal,
3758	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3759	the variables can also be restricted to IP address or MAC address.
3760
3761	The format of the list is:
3762		type_attribute = [s|d|x|b|i|m]
3763		access_atribute = [a|r|o|c]
3764		attributes = type_attribute[access_atribute]
3765		entry = variable_name[:attributes]
3766		list = entry[,list]
3767
3768	The type attributes are:
3769		s - String (default)
3770		d - Decimal
3771		x - Hexadecimal
3772		b - Boolean ([1yYtT|0nNfF])
3773		i - IP address
3774		m - MAC address
3775
3776	The access attributes are:
3777		a - Any (default)
3778		r - Read-only
3779		o - Write-once
3780		c - Change-default
3781
3782	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3783		Define this to a list (string) to define the ".flags"
3784		envirnoment variable in the default or embedded environment.
3785
3786	- CONFIG_ENV_FLAGS_LIST_STATIC
3787		Define this to a list (string) to define validation that
3788		should be done if an entry is not found in the ".flags"
3789		environment variable.  To override a setting in the static
3790		list, simply add an entry for the same variable name to the
3791		".flags" variable.
3792
3793- CONFIG_ENV_ACCESS_IGNORE_FORCE
3794	If defined, don't allow the -f switch to env set override variable
3795	access flags.
3796
3797- CONFIG_SYS_GENERIC_BOARD
3798	This selects the architecture-generic board system instead of the
3799	architecture-specific board files. It is intended to move boards
3800	to this new framework over time. Defining this will disable the
3801	arch/foo/lib/board.c file and use common/board_f.c and
3802	common/board_r.c instead. To use this option your architecture
3803	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3804	its config.mk file). If you find problems enabling this option on
3805	your board please report the problem and send patches!
3806
3807- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3808	This is set by OMAP boards for the max time that reset should
3809	be asserted. See doc/README.omap-reset-time for details on how
3810	the value can be calulated on a given board.
3811
3812The following definitions that deal with the placement and management
3813of environment data (variable area); in general, we support the
3814following configurations:
3815
3816- CONFIG_BUILD_ENVCRC:
3817
3818	Builds up envcrc with the target environment so that external utils
3819	may easily extract it and embed it in final U-Boot images.
3820
3821- CONFIG_ENV_IS_IN_FLASH:
3822
3823	Define this if the environment is in flash memory.
3824
3825	a) The environment occupies one whole flash sector, which is
3826	   "embedded" in the text segment with the U-Boot code. This
3827	   happens usually with "bottom boot sector" or "top boot
3828	   sector" type flash chips, which have several smaller
3829	   sectors at the start or the end. For instance, such a
3830	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3831	   such a case you would place the environment in one of the
3832	   4 kB sectors - with U-Boot code before and after it. With
3833	   "top boot sector" type flash chips, you would put the
3834	   environment in one of the last sectors, leaving a gap
3835	   between U-Boot and the environment.
3836
3837	- CONFIG_ENV_OFFSET:
3838
3839	   Offset of environment data (variable area) to the
3840	   beginning of flash memory; for instance, with bottom boot
3841	   type flash chips the second sector can be used: the offset
3842	   for this sector is given here.
3843
3844	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3845
3846	- CONFIG_ENV_ADDR:
3847
3848	   This is just another way to specify the start address of
3849	   the flash sector containing the environment (instead of
3850	   CONFIG_ENV_OFFSET).
3851
3852	- CONFIG_ENV_SECT_SIZE:
3853
3854	   Size of the sector containing the environment.
3855
3856
3857	b) Sometimes flash chips have few, equal sized, BIG sectors.
3858	   In such a case you don't want to spend a whole sector for
3859	   the environment.
3860
3861	- CONFIG_ENV_SIZE:
3862
3863	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3864	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3865	   of this flash sector for the environment. This saves
3866	   memory for the RAM copy of the environment.
3867
3868	   It may also save flash memory if you decide to use this
3869	   when your environment is "embedded" within U-Boot code,
3870	   since then the remainder of the flash sector could be used
3871	   for U-Boot code. It should be pointed out that this is
3872	   STRONGLY DISCOURAGED from a robustness point of view:
3873	   updating the environment in flash makes it always
3874	   necessary to erase the WHOLE sector. If something goes
3875	   wrong before the contents has been restored from a copy in
3876	   RAM, your target system will be dead.
3877
3878	- CONFIG_ENV_ADDR_REDUND
3879	  CONFIG_ENV_SIZE_REDUND
3880
3881	   These settings describe a second storage area used to hold
3882	   a redundant copy of the environment data, so that there is
3883	   a valid backup copy in case there is a power failure during
3884	   a "saveenv" operation.
3885
3886BE CAREFUL! Any changes to the flash layout, and some changes to the
3887source code will make it necessary to adapt <board>/u-boot.lds*
3888accordingly!
3889
3890
3891- CONFIG_ENV_IS_IN_NVRAM:
3892
3893	Define this if you have some non-volatile memory device
3894	(NVRAM, battery buffered SRAM) which you want to use for the
3895	environment.
3896
3897	- CONFIG_ENV_ADDR:
3898	- CONFIG_ENV_SIZE:
3899
3900	  These two #defines are used to determine the memory area you
3901	  want to use for environment. It is assumed that this memory
3902	  can just be read and written to, without any special
3903	  provision.
3904
3905BE CAREFUL! The first access to the environment happens quite early
3906in U-Boot initalization (when we try to get the setting of for the
3907console baudrate). You *MUST* have mapped your NVRAM area then, or
3908U-Boot will hang.
3909
3910Please note that even with NVRAM we still use a copy of the
3911environment in RAM: we could work on NVRAM directly, but we want to
3912keep settings there always unmodified except somebody uses "saveenv"
3913to save the current settings.
3914
3915
3916- CONFIG_ENV_IS_IN_EEPROM:
3917
3918	Use this if you have an EEPROM or similar serial access
3919	device and a driver for it.
3920
3921	- CONFIG_ENV_OFFSET:
3922	- CONFIG_ENV_SIZE:
3923
3924	  These two #defines specify the offset and size of the
3925	  environment area within the total memory of your EEPROM.
3926
3927	- CONFIG_SYS_I2C_EEPROM_ADDR:
3928	  If defined, specified the chip address of the EEPROM device.
3929	  The default address is zero.
3930
3931	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3932	  If defined, the number of bits used to address bytes in a
3933	  single page in the EEPROM device.  A 64 byte page, for example
3934	  would require six bits.
3935
3936	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3937	  If defined, the number of milliseconds to delay between
3938	  page writes.	The default is zero milliseconds.
3939
3940	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3941	  The length in bytes of the EEPROM memory array address.  Note
3942	  that this is NOT the chip address length!
3943
3944	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3945	  EEPROM chips that implement "address overflow" are ones
3946	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3947	  address and the extra bits end up in the "chip address" bit
3948	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3949	  byte chips.
3950
3951	  Note that we consider the length of the address field to
3952	  still be one byte because the extra address bits are hidden
3953	  in the chip address.
3954
3955	- CONFIG_SYS_EEPROM_SIZE:
3956	  The size in bytes of the EEPROM device.
3957
3958	- CONFIG_ENV_EEPROM_IS_ON_I2C
3959	  define this, if you have I2C and SPI activated, and your
3960	  EEPROM, which holds the environment, is on the I2C bus.
3961
3962	- CONFIG_I2C_ENV_EEPROM_BUS
3963	  if you have an Environment on an EEPROM reached over
3964	  I2C muxes, you can define here, how to reach this
3965	  EEPROM. For example:
3966
3967	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3968
3969	  EEPROM which holds the environment, is reached over
3970	  a pca9547 i2c mux with address 0x70, channel 3.
3971
3972- CONFIG_ENV_IS_IN_DATAFLASH:
3973
3974	Define this if you have a DataFlash memory device which you
3975	want to use for the environment.
3976
3977	- CONFIG_ENV_OFFSET:
3978	- CONFIG_ENV_ADDR:
3979	- CONFIG_ENV_SIZE:
3980
3981	  These three #defines specify the offset and size of the
3982	  environment area within the total memory of your DataFlash placed
3983	  at the specified address.
3984
3985- CONFIG_ENV_IS_IN_REMOTE:
3986
3987	Define this if you have a remote memory space which you
3988	want to use for the local device's environment.
3989
3990	- CONFIG_ENV_ADDR:
3991	- CONFIG_ENV_SIZE:
3992
3993	  These two #defines specify the address and size of the
3994	  environment area within the remote memory space. The
3995	  local device can get the environment from remote memory
3996	  space by SRIO or PCIE links.
3997
3998BE CAREFUL! For some special cases, the local device can not use
3999"saveenv" command. For example, the local device will get the
4000environment stored in a remote NOR flash by SRIO or PCIE link,
4001but it can not erase, write this NOR flash by SRIO or PCIE interface.
4002
4003- CONFIG_ENV_IS_IN_NAND:
4004
4005	Define this if you have a NAND device which you want to use
4006	for the environment.
4007
4008	- CONFIG_ENV_OFFSET:
4009	- CONFIG_ENV_SIZE:
4010
4011	  These two #defines specify the offset and size of the environment
4012	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4013	  aligned to an erase block boundary.
4014
4015	- CONFIG_ENV_OFFSET_REDUND (optional):
4016
4017	  This setting describes a second storage area of CONFIG_ENV_SIZE
4018	  size used to hold a redundant copy of the environment data, so
4019	  that there is a valid backup copy in case there is a power failure
4020	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4021	  aligned to an erase block boundary.
4022
4023	- CONFIG_ENV_RANGE (optional):
4024
4025	  Specifies the length of the region in which the environment
4026	  can be written.  This should be a multiple of the NAND device's
4027	  block size.  Specifying a range with more erase blocks than
4028	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4029	  the range to be avoided.
4030
4031	- CONFIG_ENV_OFFSET_OOB (optional):
4032
4033	  Enables support for dynamically retrieving the offset of the
4034	  environment from block zero's out-of-band data.  The
4035	  "nand env.oob" command can be used to record this offset.
4036	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4037	  using CONFIG_ENV_OFFSET_OOB.
4038
4039- CONFIG_NAND_ENV_DST
4040
4041	Defines address in RAM to which the nand_spl code should copy the
4042	environment. If redundant environment is used, it will be copied to
4043	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4044
4045- CONFIG_ENV_IS_IN_UBI:
4046
4047	Define this if you have an UBI volume that you want to use for the
4048	environment.  This has the benefit of wear-leveling the environment
4049	accesses, which is important on NAND.
4050
4051	- CONFIG_ENV_UBI_PART:
4052
4053	  Define this to a string that is the mtd partition containing the UBI.
4054
4055	- CONFIG_ENV_UBI_VOLUME:
4056
4057	  Define this to the name of the volume that you want to store the
4058	  environment in.
4059
4060	- CONFIG_ENV_UBI_VOLUME_REDUND:
4061
4062	  Define this to the name of another volume to store a second copy of
4063	  the environment in.  This will enable redundant environments in UBI.
4064	  It is assumed that both volumes are in the same MTD partition.
4065
4066	- CONFIG_UBI_SILENCE_MSG
4067	- CONFIG_UBIFS_SILENCE_MSG
4068
4069	  You will probably want to define these to avoid a really noisy system
4070	  when storing the env in UBI.
4071
4072- CONFIG_ENV_IS_IN_MMC:
4073
4074	Define this if you have an MMC device which you want to use for the
4075	environment.
4076
4077	- CONFIG_SYS_MMC_ENV_DEV:
4078
4079	  Specifies which MMC device the environment is stored in.
4080
4081	- CONFIG_SYS_MMC_ENV_PART (optional):
4082
4083	  Specifies which MMC partition the environment is stored in. If not
4084	  set, defaults to partition 0, the user area. Common values might be
4085	  1 (first MMC boot partition), 2 (second MMC boot partition).
4086
4087	- CONFIG_ENV_OFFSET:
4088	- CONFIG_ENV_SIZE:
4089
4090	  These two #defines specify the offset and size of the environment
4091	  area within the specified MMC device.
4092
4093	  If offset is positive (the usual case), it is treated as relative to
4094	  the start of the MMC partition. If offset is negative, it is treated
4095	  as relative to the end of the MMC partition. This can be useful if
4096	  your board may be fitted with different MMC devices, which have
4097	  different sizes for the MMC partitions, and you always want the
4098	  environment placed at the very end of the partition, to leave the
4099	  maximum possible space before it, to store other data.
4100
4101	  These two values are in units of bytes, but must be aligned to an
4102	  MMC sector boundary.
4103
4104	- CONFIG_ENV_OFFSET_REDUND (optional):
4105
4106	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4107	  hold a redundant copy of the environment data. This provides a
4108	  valid backup copy in case the other copy is corrupted, e.g. due
4109	  to a power failure during a "saveenv" operation.
4110
4111	  This value may also be positive or negative; this is handled in the
4112	  same way as CONFIG_ENV_OFFSET.
4113
4114	  This value is also in units of bytes, but must also be aligned to
4115	  an MMC sector boundary.
4116
4117	- CONFIG_ENV_SIZE_REDUND (optional):
4118
4119	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4120	  set. If this value is set, it must be set to the same value as
4121	  CONFIG_ENV_SIZE.
4122
4123- CONFIG_SYS_SPI_INIT_OFFSET
4124
4125	Defines offset to the initial SPI buffer area in DPRAM. The
4126	area is used at an early stage (ROM part) if the environment
4127	is configured to reside in the SPI EEPROM: We need a 520 byte
4128	scratch DPRAM area. It is used between the two initialization
4129	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4130	to be a good choice since it makes it far enough from the
4131	start of the data area as well as from the stack pointer.
4132
4133Please note that the environment is read-only until the monitor
4134has been relocated to RAM and a RAM copy of the environment has been
4135created; also, when using EEPROM you will have to use getenv_f()
4136until then to read environment variables.
4137
4138The environment is protected by a CRC32 checksum. Before the monitor
4139is relocated into RAM, as a result of a bad CRC you will be working
4140with the compiled-in default environment - *silently*!!! [This is
4141necessary, because the first environment variable we need is the
4142"baudrate" setting for the console - if we have a bad CRC, we don't
4143have any device yet where we could complain.]
4144
4145Note: once the monitor has been relocated, then it will complain if
4146the default environment is used; a new CRC is computed as soon as you
4147use the "saveenv" command to store a valid environment.
4148
4149- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4150		Echo the inverted Ethernet link state to the fault LED.
4151
4152		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4153		      also needs to be defined.
4154
4155- CONFIG_SYS_FAULT_MII_ADDR:
4156		MII address of the PHY to check for the Ethernet link state.
4157
4158- CONFIG_NS16550_MIN_FUNCTIONS:
4159		Define this if you desire to only have use of the NS16550_init
4160		and NS16550_putc functions for the serial driver located at
4161		drivers/serial/ns16550.c.  This option is useful for saving
4162		space for already greatly restricted images, including but not
4163		limited to NAND_SPL configurations.
4164
4165- CONFIG_DISPLAY_BOARDINFO
4166		Display information about the board that U-Boot is running on
4167		when U-Boot starts up. The board function checkboard() is called
4168		to do this.
4169
4170- CONFIG_DISPLAY_BOARDINFO_LATE
4171		Similar to the previous option, but display this information
4172		later, once stdio is running and output goes to the LCD, if
4173		present.
4174
4175Low Level (hardware related) configuration options:
4176---------------------------------------------------
4177
4178- CONFIG_SYS_CACHELINE_SIZE:
4179		Cache Line Size of the CPU.
4180
4181- CONFIG_SYS_DEFAULT_IMMR:
4182		Default address of the IMMR after system reset.
4183
4184		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4185		and RPXsuper) to be able to adjust the position of
4186		the IMMR register after a reset.
4187
4188- CONFIG_SYS_CCSRBAR_DEFAULT:
4189		Default (power-on reset) physical address of CCSR on Freescale
4190		PowerPC SOCs.
4191
4192- CONFIG_SYS_CCSRBAR:
4193		Virtual address of CCSR.  On a 32-bit build, this is typically
4194		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4195
4196		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4197		for cross-platform code that uses that macro instead.
4198
4199- CONFIG_SYS_CCSRBAR_PHYS:
4200		Physical address of CCSR.  CCSR can be relocated to a new
4201		physical address, if desired.  In this case, this macro should
4202		be set to that address.	 Otherwise, it should be set to the
4203		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4204		is typically relocated on 36-bit builds.  It is recommended
4205		that this macro be defined via the _HIGH and _LOW macros:
4206
4207		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4208			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4209
4210- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4211		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4212		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4213		used in assembly code, so it must not contain typecasts or
4214		integer size suffixes (e.g. "ULL").
4215
4216- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4217		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4218		used in assembly code, so it must not contain typecasts or
4219		integer size suffixes (e.g. "ULL").
4220
4221- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4222		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4223		forced to a value that ensures that CCSR is not relocated.
4224
4225- Floppy Disk Support:
4226		CONFIG_SYS_FDC_DRIVE_NUMBER
4227
4228		the default drive number (default value 0)
4229
4230		CONFIG_SYS_ISA_IO_STRIDE
4231
4232		defines the spacing between FDC chipset registers
4233		(default value 1)
4234
4235		CONFIG_SYS_ISA_IO_OFFSET
4236
4237		defines the offset of register from address. It
4238		depends on which part of the data bus is connected to
4239		the FDC chipset. (default value 0)
4240
4241		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4242		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4243		default value.
4244
4245		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4246		fdc_hw_init() is called at the beginning of the FDC
4247		setup. fdc_hw_init() must be provided by the board
4248		source code. It is used to make hardware dependant
4249		initializations.
4250
4251- CONFIG_IDE_AHB:
4252		Most IDE controllers were designed to be connected with PCI
4253		interface. Only few of them were designed for AHB interface.
4254		When software is doing ATA command and data transfer to
4255		IDE devices through IDE-AHB controller, some additional
4256		registers accessing to these kind of IDE-AHB controller
4257		is requierd.
4258
4259- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4260		DO NOT CHANGE unless you know exactly what you're
4261		doing! (11-4) [MPC8xx/82xx systems only]
4262
4263- CONFIG_SYS_INIT_RAM_ADDR:
4264
4265		Start address of memory area that can be used for
4266		initial data and stack; please note that this must be
4267		writable memory that is working WITHOUT special
4268		initialization, i. e. you CANNOT use normal RAM which
4269		will become available only after programming the
4270		memory controller and running certain initialization
4271		sequences.
4272
4273		U-Boot uses the following memory types:
4274		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4275		- MPC824X: data cache
4276		- PPC4xx:  data cache
4277
4278- CONFIG_SYS_GBL_DATA_OFFSET:
4279
4280		Offset of the initial data structure in the memory
4281		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4282		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4283		data is located at the end of the available space
4284		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4285		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4286		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4287		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4288
4289	Note:
4290		On the MPC824X (or other systems that use the data
4291		cache for initial memory) the address chosen for
4292		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4293		point to an otherwise UNUSED address space between
4294		the top of RAM and the start of the PCI space.
4295
4296- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4297
4298- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4299
4300- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4301
4302- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4303
4304- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4305
4306- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4307
4308- CONFIG_SYS_OR_TIMING_SDRAM:
4309		SDRAM timing
4310
4311- CONFIG_SYS_MAMR_PTA:
4312		periodic timer for refresh
4313
4314- CONFIG_SYS_DER:	Debug Event Register (37-47)
4315
4316- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4317  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4318  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4319  CONFIG_SYS_BR1_PRELIM:
4320		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4321
4322- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4323  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4324  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4325		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4326
4327- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4328  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4329		Machine Mode Register and Memory Periodic Timer
4330		Prescaler definitions (SDRAM timing)
4331
4332- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4333		enable I2C microcode relocation patch (MPC8xx);
4334		define relocation offset in DPRAM [DSP2]
4335
4336- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4337		enable SMC microcode relocation patch (MPC8xx);
4338		define relocation offset in DPRAM [SMC1]
4339
4340- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4341		enable SPI microcode relocation patch (MPC8xx);
4342		define relocation offset in DPRAM [SCC4]
4343
4344- CONFIG_SYS_USE_OSCCLK:
4345		Use OSCM clock mode on MBX8xx board. Be careful,
4346		wrong setting might damage your board. Read
4347		doc/README.MBX before setting this variable!
4348
4349- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4350		Offset of the bootmode word in DPRAM used by post
4351		(Power On Self Tests). This definition overrides
4352		#define'd default value in commproc.h resp.
4353		cpm_8260.h.
4354
4355- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4356  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4357  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4358  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4359  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4360  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4361  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4362  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4363		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4364
4365- CONFIG_PCI_DISABLE_PCIE:
4366		Disable PCI-Express on systems where it is supported but not
4367		required.
4368
4369- CONFIG_PCI_ENUM_ONLY
4370		Only scan through and get the devices on the busses.
4371		Don't do any setup work, presumably because someone or
4372		something has already done it, and we don't need to do it
4373		a second time.	Useful for platforms that are pre-booted
4374		by coreboot or similar.
4375
4376- CONFIG_PCI_INDIRECT_BRIDGE:
4377		Enable support for indirect PCI bridges.
4378
4379- CONFIG_SYS_SRIO:
4380		Chip has SRIO or not
4381
4382- CONFIG_SRIO1:
4383		Board has SRIO 1 port available
4384
4385- CONFIG_SRIO2:
4386		Board has SRIO 2 port available
4387
4388- CONFIG_SRIO_PCIE_BOOT_MASTER
4389		Board can support master function for Boot from SRIO and PCIE
4390
4391- CONFIG_SYS_SRIOn_MEM_VIRT:
4392		Virtual Address of SRIO port 'n' memory region
4393
4394- CONFIG_SYS_SRIOn_MEM_PHYS:
4395		Physical Address of SRIO port 'n' memory region
4396
4397- CONFIG_SYS_SRIOn_MEM_SIZE:
4398		Size of SRIO port 'n' memory region
4399
4400- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4401		Defined to tell the NAND controller that the NAND chip is using
4402		a 16 bit bus.
4403		Not all NAND drivers use this symbol.
4404		Example of drivers that use it:
4405		- drivers/mtd/nand/ndfc.c
4406		- drivers/mtd/nand/mxc_nand.c
4407
4408- CONFIG_SYS_NDFC_EBC0_CFG
4409		Sets the EBC0_CFG register for the NDFC. If not defined
4410		a default value will be used.
4411
4412- CONFIG_SPD_EEPROM
4413		Get DDR timing information from an I2C EEPROM. Common
4414		with pluggable memory modules such as SODIMMs
4415
4416  SPD_EEPROM_ADDRESS
4417		I2C address of the SPD EEPROM
4418
4419- CONFIG_SYS_SPD_BUS_NUM
4420		If SPD EEPROM is on an I2C bus other than the first
4421		one, specify here. Note that the value must resolve
4422		to something your driver can deal with.
4423
4424- CONFIG_SYS_DDR_RAW_TIMING
4425		Get DDR timing information from other than SPD. Common with
4426		soldered DDR chips onboard without SPD. DDR raw timing
4427		parameters are extracted from datasheet and hard-coded into
4428		header files or board specific files.
4429
4430- CONFIG_FSL_DDR_INTERACTIVE
4431		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4432
4433- CONFIG_SYS_83XX_DDR_USES_CS0
4434		Only for 83xx systems. If specified, then DDR should
4435		be configured using CS0 and CS1 instead of CS2 and CS3.
4436
4437- CONFIG_ETHER_ON_FEC[12]
4438		Define to enable FEC[12] on a 8xx series processor.
4439
4440- CONFIG_FEC[12]_PHY
4441		Define to the hardcoded PHY address which corresponds
4442		to the given FEC; i. e.
4443			#define CONFIG_FEC1_PHY 4
4444		means that the PHY with address 4 is connected to FEC1
4445
4446		When set to -1, means to probe for first available.
4447
4448- CONFIG_FEC[12]_PHY_NORXERR
4449		The PHY does not have a RXERR line (RMII only).
4450		(so program the FEC to ignore it).
4451
4452- CONFIG_RMII
4453		Enable RMII mode for all FECs.
4454		Note that this is a global option, we can't
4455		have one FEC in standard MII mode and another in RMII mode.
4456
4457- CONFIG_CRC32_VERIFY
4458		Add a verify option to the crc32 command.
4459		The syntax is:
4460
4461		=> crc32 -v <address> <count> <crc32>
4462
4463		Where address/count indicate a memory area
4464		and crc32 is the correct crc32 which the
4465		area should have.
4466
4467- CONFIG_LOOPW
4468		Add the "loopw" memory command. This only takes effect if
4469		the memory commands are activated globally (CONFIG_CMD_MEM).
4470
4471- CONFIG_MX_CYCLIC
4472		Add the "mdc" and "mwc" memory commands. These are cyclic
4473		"md/mw" commands.
4474		Examples:
4475
4476		=> mdc.b 10 4 500
4477		This command will print 4 bytes (10,11,12,13) each 500 ms.
4478
4479		=> mwc.l 100 12345678 10
4480		This command will write 12345678 to address 100 all 10 ms.
4481
4482		This only takes effect if the memory commands are activated
4483		globally (CONFIG_CMD_MEM).
4484
4485- CONFIG_SKIP_LOWLEVEL_INIT
4486		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4487		low level initializations (like setting up the memory
4488		controller) are omitted and/or U-Boot does not
4489		relocate itself into RAM.
4490
4491		Normally this variable MUST NOT be defined. The only
4492		exception is when U-Boot is loaded (to RAM) by some
4493		other boot loader or by a debugger which performs
4494		these initializations itself.
4495
4496- CONFIG_SPL_BUILD
4497		Modifies the behaviour of start.S when compiling a loader
4498		that is executed before the actual U-Boot. E.g. when
4499		compiling a NAND SPL.
4500
4501- CONFIG_TPL_BUILD
4502		Modifies the behaviour of start.S  when compiling a loader
4503		that is executed after the SPL and before the actual U-Boot.
4504		It is loaded by the SPL.
4505
4506- CONFIG_SYS_MPC85XX_NO_RESETVEC
4507		Only for 85xx systems. If this variable is specified, the section
4508		.resetvec is not kept and the section .bootpg is placed in the
4509		previous 4k of the .text section.
4510
4511- CONFIG_ARCH_MAP_SYSMEM
4512		Generally U-Boot (and in particular the md command) uses
4513		effective address. It is therefore not necessary to regard
4514		U-Boot address as virtual addresses that need to be translated
4515		to physical addresses. However, sandbox requires this, since
4516		it maintains its own little RAM buffer which contains all
4517		addressable memory. This option causes some memory accesses
4518		to be mapped through map_sysmem() / unmap_sysmem().
4519
4520- CONFIG_USE_ARCH_MEMCPY
4521  CONFIG_USE_ARCH_MEMSET
4522		If these options are used a optimized version of memcpy/memset will
4523		be used if available. These functions may be faster under some
4524		conditions but may increase the binary size.
4525
4526- CONFIG_X86_RESET_VECTOR
4527		If defined, the x86 reset vector code is included. This is not
4528		needed when U-Boot is running from Coreboot.
4529
4530- CONFIG_SYS_MPUCLK
4531		Defines the MPU clock speed (in MHz).
4532
4533		NOTE : currently only supported on AM335x platforms.
4534
4535- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4536		Enables the RTC32K OSC on AM33xx based plattforms
4537
4538- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4539		Option to disable subpage write in NAND driver
4540		driver that uses this:
4541		drivers/mtd/nand/davinci_nand.c
4542
4543Freescale QE/FMAN Firmware Support:
4544-----------------------------------
4545
4546The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4547loading of "firmware", which is encoded in the QE firmware binary format.
4548This firmware often needs to be loaded during U-Boot booting, so macros
4549are used to identify the storage device (NOR flash, SPI, etc) and the address
4550within that device.
4551
4552- CONFIG_SYS_FMAN_FW_ADDR
4553	The address in the storage device where the FMAN microcode is located.  The
4554	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4555	is also specified.
4556
4557- CONFIG_SYS_QE_FW_ADDR
4558	The address in the storage device where the QE microcode is located.  The
4559	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4560	is also specified.
4561
4562- CONFIG_SYS_QE_FMAN_FW_LENGTH
4563	The maximum possible size of the firmware.  The firmware binary format
4564	has a field that specifies the actual size of the firmware, but it
4565	might not be possible to read any part of the firmware unless some
4566	local storage is allocated to hold the entire firmware first.
4567
4568- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4569	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4570	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4571	virtual address in NOR flash.
4572
4573- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4574	Specifies that QE/FMAN firmware is located in NAND flash.
4575	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4576
4577- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4578	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4579	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4580
4581- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4582	Specifies that QE/FMAN firmware is located on the primary SPI
4583	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4584
4585- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4586	Specifies that QE/FMAN firmware is located in the remote (master)
4587	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4588	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4589	window->master inbound window->master LAW->the ucode address in
4590	master's memory space.
4591
4592Building the Software:
4593======================
4594
4595Building U-Boot has been tested in several native build environments
4596and in many different cross environments. Of course we cannot support
4597all possibly existing versions of cross development tools in all
4598(potentially obsolete) versions. In case of tool chain problems we
4599recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4600which is extensively used to build and test U-Boot.
4601
4602If you are not using a native environment, it is assumed that you
4603have GNU cross compiling tools available in your path. In this case,
4604you must set the environment variable CROSS_COMPILE in your shell.
4605Note that no changes to the Makefile or any other source files are
4606necessary. For example using the ELDK on a 4xx CPU, please enter:
4607
4608	$ CROSS_COMPILE=ppc_4xx-
4609	$ export CROSS_COMPILE
4610
4611Note: If you wish to generate Windows versions of the utilities in
4612      the tools directory you can use the MinGW toolchain
4613      (http://www.mingw.org).  Set your HOST tools to the MinGW
4614      toolchain and execute 'make tools'.  For example:
4615
4616       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4617
4618      Binaries such as tools/mkimage.exe will be created which can
4619      be executed on computers running Windows.
4620
4621U-Boot is intended to be simple to build. After installing the
4622sources you must configure U-Boot for one specific board type. This
4623is done by typing:
4624
4625	make NAME_config
4626
4627where "NAME_config" is the name of one of the existing configu-
4628rations; see boards.cfg for supported names.
4629
4630Note: for some board special configuration names may exist; check if
4631      additional information is available from the board vendor; for
4632      instance, the TQM823L systems are available without (standard)
4633      or with LCD support. You can select such additional "features"
4634      when choosing the configuration, i. e.
4635
4636      make TQM823L_config
4637	- will configure for a plain TQM823L, i. e. no LCD support
4638
4639      make TQM823L_LCD_config
4640	- will configure for a TQM823L with U-Boot console on LCD
4641
4642      etc.
4643
4644
4645Finally, type "make all", and you should get some working U-Boot
4646images ready for download to / installation on your system:
4647
4648- "u-boot.bin" is a raw binary image
4649- "u-boot" is an image in ELF binary format
4650- "u-boot.srec" is in Motorola S-Record format
4651
4652By default the build is performed locally and the objects are saved
4653in the source directory. One of the two methods can be used to change
4654this behavior and build U-Boot to some external directory:
4655
46561. Add O= to the make command line invocations:
4657
4658	make O=/tmp/build distclean
4659	make O=/tmp/build NAME_config
4660	make O=/tmp/build all
4661
46622. Set environment variable BUILD_DIR to point to the desired location:
4663
4664	export BUILD_DIR=/tmp/build
4665	make distclean
4666	make NAME_config
4667	make all
4668
4669Note that the command line "O=" setting overrides the BUILD_DIR environment
4670variable.
4671
4672
4673Please be aware that the Makefiles assume you are using GNU make, so
4674for instance on NetBSD you might need to use "gmake" instead of
4675native "make".
4676
4677
4678If the system board that you have is not listed, then you will need
4679to port U-Boot to your hardware platform. To do this, follow these
4680steps:
4681
46821.  Add a new configuration option for your board to the toplevel
4683    "boards.cfg" file, using the existing entries as examples.
4684    Follow the instructions there to keep the boards in order.
46852.  Create a new directory to hold your board specific code. Add any
4686    files you need. In your board directory, you will need at least
4687    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46883.  Create a new configuration file "include/configs/<board>.h" for
4689    your board
46903.  If you're porting U-Boot to a new CPU, then also create a new
4691    directory to hold your CPU specific code. Add any files you need.
46924.  Run "make <board>_config" with your new name.
46935.  Type "make", and you should get a working "u-boot.srec" file
4694    to be installed on your target system.
46956.  Debug and solve any problems that might arise.
4696    [Of course, this last step is much harder than it sounds.]
4697
4698
4699Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4700==============================================================
4701
4702If you have modified U-Boot sources (for instance added a new board
4703or support for new devices, a new CPU, etc.) you are expected to
4704provide feedback to the other developers. The feedback normally takes
4705the form of a "patch", i. e. a context diff against a certain (latest
4706official or latest in the git repository) version of U-Boot sources.
4707
4708But before you submit such a patch, please verify that your modifi-
4709cation did not break existing code. At least make sure that *ALL* of
4710the supported boards compile WITHOUT ANY compiler warnings. To do so,
4711just run the "MAKEALL" script, which will configure and build U-Boot
4712for ALL supported system. Be warned, this will take a while. You can
4713select which (cross) compiler to use by passing a `CROSS_COMPILE'
4714environment variable to the script, i. e. to use the ELDK cross tools
4715you can type
4716
4717	CROSS_COMPILE=ppc_8xx- MAKEALL
4718
4719or to build on a native PowerPC system you can type
4720
4721	CROSS_COMPILE=' ' MAKEALL
4722
4723When using the MAKEALL script, the default behaviour is to build
4724U-Boot in the source directory. This location can be changed by
4725setting the BUILD_DIR environment variable. Also, for each target
4726built, the MAKEALL script saves two log files (<target>.ERR and
4727<target>.MAKEALL) in the <source dir>/LOG directory. This default
4728location can be changed by setting the MAKEALL_LOGDIR environment
4729variable. For example:
4730
4731	export BUILD_DIR=/tmp/build
4732	export MAKEALL_LOGDIR=/tmp/log
4733	CROSS_COMPILE=ppc_8xx- MAKEALL
4734
4735With the above settings build objects are saved in the /tmp/build,
4736log files are saved in the /tmp/log and the source tree remains clean
4737during the whole build process.
4738
4739
4740See also "U-Boot Porting Guide" below.
4741
4742
4743Monitor Commands - Overview:
4744============================
4745
4746go	- start application at address 'addr'
4747run	- run commands in an environment variable
4748bootm	- boot application image from memory
4749bootp	- boot image via network using BootP/TFTP protocol
4750bootz   - boot zImage from memory
4751tftpboot- boot image via network using TFTP protocol
4752	       and env variables "ipaddr" and "serverip"
4753	       (and eventually "gatewayip")
4754tftpput - upload a file via network using TFTP protocol
4755rarpboot- boot image via network using RARP/TFTP protocol
4756diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4757loads	- load S-Record file over serial line
4758loadb	- load binary file over serial line (kermit mode)
4759md	- memory display
4760mm	- memory modify (auto-incrementing)
4761nm	- memory modify (constant address)
4762mw	- memory write (fill)
4763cp	- memory copy
4764cmp	- memory compare
4765crc32	- checksum calculation
4766i2c	- I2C sub-system
4767sspi	- SPI utility commands
4768base	- print or set address offset
4769printenv- print environment variables
4770setenv	- set environment variables
4771saveenv - save environment variables to persistent storage
4772protect - enable or disable FLASH write protection
4773erase	- erase FLASH memory
4774flinfo	- print FLASH memory information
4775nand	- NAND memory operations (see doc/README.nand)
4776bdinfo	- print Board Info structure
4777iminfo	- print header information for application image
4778coninfo - print console devices and informations
4779ide	- IDE sub-system
4780loop	- infinite loop on address range
4781loopw	- infinite write loop on address range
4782mtest	- simple RAM test
4783icache	- enable or disable instruction cache
4784dcache	- enable or disable data cache
4785reset	- Perform RESET of the CPU
4786echo	- echo args to console
4787version - print monitor version
4788help	- print online help
4789?	- alias for 'help'
4790
4791
4792Monitor Commands - Detailed Description:
4793========================================
4794
4795TODO.
4796
4797For now: just type "help <command>".
4798
4799
4800Environment Variables:
4801======================
4802
4803U-Boot supports user configuration using Environment Variables which
4804can be made persistent by saving to Flash memory.
4805
4806Environment Variables are set using "setenv", printed using
4807"printenv", and saved to Flash using "saveenv". Using "setenv"
4808without a value can be used to delete a variable from the
4809environment. As long as you don't save the environment you are
4810working with an in-memory copy. In case the Flash area containing the
4811environment is erased by accident, a default environment is provided.
4812
4813Some configuration options can be set using Environment Variables.
4814
4815List of environment variables (most likely not complete):
4816
4817  baudrate	- see CONFIG_BAUDRATE
4818
4819  bootdelay	- see CONFIG_BOOTDELAY
4820
4821  bootcmd	- see CONFIG_BOOTCOMMAND
4822
4823  bootargs	- Boot arguments when booting an RTOS image
4824
4825  bootfile	- Name of the image to load with TFTP
4826
4827  bootm_low	- Memory range available for image processing in the bootm
4828		  command can be restricted. This variable is given as
4829		  a hexadecimal number and defines lowest address allowed
4830		  for use by the bootm command. See also "bootm_size"
4831		  environment variable. Address defined by "bootm_low" is
4832		  also the base of the initial memory mapping for the Linux
4833		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4834		  bootm_mapsize.
4835
4836  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4837		  This variable is given as a hexadecimal number and it
4838		  defines the size of the memory region starting at base
4839		  address bootm_low that is accessible by the Linux kernel
4840		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4841		  as the default value if it is defined, and bootm_size is
4842		  used otherwise.
4843
4844  bootm_size	- Memory range available for image processing in the bootm
4845		  command can be restricted. This variable is given as
4846		  a hexadecimal number and defines the size of the region
4847		  allowed for use by the bootm command. See also "bootm_low"
4848		  environment variable.
4849
4850  updatefile	- Location of the software update file on a TFTP server, used
4851		  by the automatic software update feature. Please refer to
4852		  documentation in doc/README.update for more details.
4853
4854  autoload	- if set to "no" (any string beginning with 'n'),
4855		  "bootp" will just load perform a lookup of the
4856		  configuration from the BOOTP server, but not try to
4857		  load any image using TFTP
4858
4859  autostart	- if set to "yes", an image loaded using the "bootp",
4860		  "rarpboot", "tftpboot" or "diskboot" commands will
4861		  be automatically started (by internally calling
4862		  "bootm")
4863
4864		  If set to "no", a standalone image passed to the
4865		  "bootm" command will be copied to the load address
4866		  (and eventually uncompressed), but NOT be started.
4867		  This can be used to load and uncompress arbitrary
4868		  data.
4869
4870  fdt_high	- if set this restricts the maximum address that the
4871		  flattened device tree will be copied into upon boot.
4872		  For example, if you have a system with 1 GB memory
4873		  at physical address 0x10000000, while Linux kernel
4874		  only recognizes the first 704 MB as low memory, you
4875		  may need to set fdt_high as 0x3C000000 to have the
4876		  device tree blob be copied to the maximum address
4877		  of the 704 MB low memory, so that Linux kernel can
4878		  access it during the boot procedure.
4879
4880		  If this is set to the special value 0xFFFFFFFF then
4881		  the fdt will not be copied at all on boot.  For this
4882		  to work it must reside in writable memory, have
4883		  sufficient padding on the end of it for u-boot to
4884		  add the information it needs into it, and the memory
4885		  must be accessible by the kernel.
4886
4887  fdtcontroladdr- if set this is the address of the control flattened
4888		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4889		  defined.
4890
4891  i2cfast	- (PPC405GP|PPC405EP only)
4892		  if set to 'y' configures Linux I2C driver for fast
4893		  mode (400kHZ). This environment variable is used in
4894		  initialization code. So, for changes to be effective
4895		  it must be saved and board must be reset.
4896
4897  initrd_high	- restrict positioning of initrd images:
4898		  If this variable is not set, initrd images will be
4899		  copied to the highest possible address in RAM; this
4900		  is usually what you want since it allows for
4901		  maximum initrd size. If for some reason you want to
4902		  make sure that the initrd image is loaded below the
4903		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4904		  variable to a value of "no" or "off" or "0".
4905		  Alternatively, you can set it to a maximum upper
4906		  address to use (U-Boot will still check that it
4907		  does not overwrite the U-Boot stack and data).
4908
4909		  For instance, when you have a system with 16 MB
4910		  RAM, and want to reserve 4 MB from use by Linux,
4911		  you can do this by adding "mem=12M" to the value of
4912		  the "bootargs" variable. However, now you must make
4913		  sure that the initrd image is placed in the first
4914		  12 MB as well - this can be done with
4915
4916		  setenv initrd_high 00c00000
4917
4918		  If you set initrd_high to 0xFFFFFFFF, this is an
4919		  indication to U-Boot that all addresses are legal
4920		  for the Linux kernel, including addresses in flash
4921		  memory. In this case U-Boot will NOT COPY the
4922		  ramdisk at all. This may be useful to reduce the
4923		  boot time on your system, but requires that this
4924		  feature is supported by your Linux kernel.
4925
4926  ipaddr	- IP address; needed for tftpboot command
4927
4928  loadaddr	- Default load address for commands like "bootp",
4929		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4930
4931  loads_echo	- see CONFIG_LOADS_ECHO
4932
4933  serverip	- TFTP server IP address; needed for tftpboot command
4934
4935  bootretry	- see CONFIG_BOOT_RETRY_TIME
4936
4937  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4938
4939  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4940
4941  ethprime	- controls which interface is used first.
4942
4943  ethact	- controls which interface is currently active.
4944		  For example you can do the following
4945
4946		  => setenv ethact FEC
4947		  => ping 192.168.0.1 # traffic sent on FEC
4948		  => setenv ethact SCC
4949		  => ping 10.0.0.1 # traffic sent on SCC
4950
4951  ethrotate	- When set to "no" U-Boot does not go through all
4952		  available network interfaces.
4953		  It just stays at the currently selected interface.
4954
4955  netretry	- When set to "no" each network operation will
4956		  either succeed or fail without retrying.
4957		  When set to "once" the network operation will
4958		  fail when all the available network interfaces
4959		  are tried once without success.
4960		  Useful on scripts which control the retry operation
4961		  themselves.
4962
4963  npe_ucode	- set load address for the NPE microcode
4964
4965  silent_linux  - If set then linux will be told to boot silently, by
4966		  changing the console to be empty. If "yes" it will be
4967		  made silent. If "no" it will not be made silent. If
4968		  unset, then it will be made silent if the U-Boot console
4969		  is silent.
4970
4971  tftpsrcport	- If this is set, the value is used for TFTP's
4972		  UDP source port.
4973
4974  tftpdstport	- If this is set, the value is used for TFTP's UDP
4975		  destination port instead of the Well Know Port 69.
4976
4977  tftpblocksize - Block size to use for TFTP transfers; if not set,
4978		  we use the TFTP server's default block size
4979
4980  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4981		  seconds, minimum value is 1000 = 1 second). Defines
4982		  when a packet is considered to be lost so it has to
4983		  be retransmitted. The default is 5000 = 5 seconds.
4984		  Lowering this value may make downloads succeed
4985		  faster in networks with high packet loss rates or
4986		  with unreliable TFTP servers.
4987
4988  vlan		- When set to a value < 4095 the traffic over
4989		  Ethernet is encapsulated/received over 802.1q
4990		  VLAN tagged frames.
4991
4992The following image location variables contain the location of images
4993used in booting. The "Image" column gives the role of the image and is
4994not an environment variable name. The other columns are environment
4995variable names. "File Name" gives the name of the file on a TFTP
4996server, "RAM Address" gives the location in RAM the image will be
4997loaded to, and "Flash Location" gives the image's address in NOR
4998flash or offset in NAND flash.
4999
5000*Note* - these variables don't have to be defined for all boards, some
5001boards currenlty use other variables for these purposes, and some
5002boards use these variables for other purposes.
5003
5004Image		    File Name	     RAM Address       Flash Location
5005-----		    ---------	     -----------       --------------
5006u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5007Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5008device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5009ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5010
5011The following environment variables may be used and automatically
5012updated by the network boot commands ("bootp" and "rarpboot"),
5013depending the information provided by your boot server:
5014
5015  bootfile	- see above
5016  dnsip		- IP address of your Domain Name Server
5017  dnsip2	- IP address of your secondary Domain Name Server
5018  gatewayip	- IP address of the Gateway (Router) to use
5019  hostname	- Target hostname
5020  ipaddr	- see above
5021  netmask	- Subnet Mask
5022  rootpath	- Pathname of the root filesystem on the NFS server
5023  serverip	- see above
5024
5025
5026There are two special Environment Variables:
5027
5028  serial#	- contains hardware identification information such
5029		  as type string and/or serial number
5030  ethaddr	- Ethernet address
5031
5032These variables can be set only once (usually during manufacturing of
5033the board). U-Boot refuses to delete or overwrite these variables
5034once they have been set once.
5035
5036
5037Further special Environment Variables:
5038
5039  ver		- Contains the U-Boot version string as printed
5040		  with the "version" command. This variable is
5041		  readonly (see CONFIG_VERSION_VARIABLE).
5042
5043
5044Please note that changes to some configuration parameters may take
5045only effect after the next boot (yes, that's just like Windoze :-).
5046
5047
5048Callback functions for environment variables:
5049---------------------------------------------
5050
5051For some environment variables, the behavior of u-boot needs to change
5052when their values are changed.  This functionailty allows functions to
5053be associated with arbitrary variables.  On creation, overwrite, or
5054deletion, the callback will provide the opportunity for some side
5055effect to happen or for the change to be rejected.
5056
5057The callbacks are named and associated with a function using the
5058U_BOOT_ENV_CALLBACK macro in your board or driver code.
5059
5060These callbacks are associated with variables in one of two ways.  The
5061static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5062in the board configuration to a string that defines a list of
5063associations.  The list must be in the following format:
5064
5065	entry = variable_name[:callback_name]
5066	list = entry[,list]
5067
5068If the callback name is not specified, then the callback is deleted.
5069Spaces are also allowed anywhere in the list.
5070
5071Callbacks can also be associated by defining the ".callbacks" variable
5072with the same list format above.  Any association in ".callbacks" will
5073override any association in the static list. You can define
5074CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5075".callbacks" envirnoment variable in the default or embedded environment.
5076
5077
5078Command Line Parsing:
5079=====================
5080
5081There are two different command line parsers available with U-Boot:
5082the old "simple" one, and the much more powerful "hush" shell:
5083
5084Old, simple command line parser:
5085--------------------------------
5086
5087- supports environment variables (through setenv / saveenv commands)
5088- several commands on one line, separated by ';'
5089- variable substitution using "... ${name} ..." syntax
5090- special characters ('$', ';') can be escaped by prefixing with '\',
5091  for example:
5092	setenv bootcmd bootm \${address}
5093- You can also escape text by enclosing in single apostrophes, for example:
5094	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5095
5096Hush shell:
5097-----------
5098
5099- similar to Bourne shell, with control structures like
5100  if...then...else...fi, for...do...done; while...do...done,
5101  until...do...done, ...
5102- supports environment ("global") variables (through setenv / saveenv
5103  commands) and local shell variables (through standard shell syntax
5104  "name=value"); only environment variables can be used with "run"
5105  command
5106
5107General rules:
5108--------------
5109
5110(1) If a command line (or an environment variable executed by a "run"
5111    command) contains several commands separated by semicolon, and
5112    one of these commands fails, then the remaining commands will be
5113    executed anyway.
5114
5115(2) If you execute several variables with one call to run (i. e.
5116    calling run with a list of variables as arguments), any failing
5117    command will cause "run" to terminate, i. e. the remaining
5118    variables are not executed.
5119
5120Note for Redundant Ethernet Interfaces:
5121=======================================
5122
5123Some boards come with redundant Ethernet interfaces; U-Boot supports
5124such configurations and is capable of automatic selection of a
5125"working" interface when needed. MAC assignment works as follows:
5126
5127Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5128MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5129"eth1addr" (=>eth1), "eth2addr", ...
5130
5131If the network interface stores some valid MAC address (for instance
5132in SROM), this is used as default address if there is NO correspon-
5133ding setting in the environment; if the corresponding environment
5134variable is set, this overrides the settings in the card; that means:
5135
5136o If the SROM has a valid MAC address, and there is no address in the
5137  environment, the SROM's address is used.
5138
5139o If there is no valid address in the SROM, and a definition in the
5140  environment exists, then the value from the environment variable is
5141  used.
5142
5143o If both the SROM and the environment contain a MAC address, and
5144  both addresses are the same, this MAC address is used.
5145
5146o If both the SROM and the environment contain a MAC address, and the
5147  addresses differ, the value from the environment is used and a
5148  warning is printed.
5149
5150o If neither SROM nor the environment contain a MAC address, an error
5151  is raised.
5152
5153If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5154will be programmed into hardware as part of the initialization process.	 This
5155may be skipped by setting the appropriate 'ethmacskip' environment variable.
5156The naming convention is as follows:
5157"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5158
5159Image Formats:
5160==============
5161
5162U-Boot is capable of booting (and performing other auxiliary operations on)
5163images in two formats:
5164
5165New uImage format (FIT)
5166-----------------------
5167
5168Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5169to Flattened Device Tree). It allows the use of images with multiple
5170components (several kernels, ramdisks, etc.), with contents protected by
5171SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5172
5173
5174Old uImage format
5175-----------------
5176
5177Old image format is based on binary files which can be basically anything,
5178preceded by a special header; see the definitions in include/image.h for
5179details; basically, the header defines the following image properties:
5180
5181* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5182  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5183  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5184  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5185  INTEGRITY).
5186* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5187  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5188  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5189* Compression Type (uncompressed, gzip, bzip2)
5190* Load Address
5191* Entry Point
5192* Image Name
5193* Image Timestamp
5194
5195The header is marked by a special Magic Number, and both the header
5196and the data portions of the image are secured against corruption by
5197CRC32 checksums.
5198
5199
5200Linux Support:
5201==============
5202
5203Although U-Boot should support any OS or standalone application
5204easily, the main focus has always been on Linux during the design of
5205U-Boot.
5206
5207U-Boot includes many features that so far have been part of some
5208special "boot loader" code within the Linux kernel. Also, any
5209"initrd" images to be used are no longer part of one big Linux image;
5210instead, kernel and "initrd" are separate images. This implementation
5211serves several purposes:
5212
5213- the same features can be used for other OS or standalone
5214  applications (for instance: using compressed images to reduce the
5215  Flash memory footprint)
5216
5217- it becomes much easier to port new Linux kernel versions because
5218  lots of low-level, hardware dependent stuff are done by U-Boot
5219
5220- the same Linux kernel image can now be used with different "initrd"
5221  images; of course this also means that different kernel images can
5222  be run with the same "initrd". This makes testing easier (you don't
5223  have to build a new "zImage.initrd" Linux image when you just
5224  change a file in your "initrd"). Also, a field-upgrade of the
5225  software is easier now.
5226
5227
5228Linux HOWTO:
5229============
5230
5231Porting Linux to U-Boot based systems:
5232---------------------------------------
5233
5234U-Boot cannot save you from doing all the necessary modifications to
5235configure the Linux device drivers for use with your target hardware
5236(no, we don't intend to provide a full virtual machine interface to
5237Linux :-).
5238
5239But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5240
5241Just make sure your machine specific header file (for instance
5242include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5243Information structure as we define in include/asm-<arch>/u-boot.h,
5244and make sure that your definition of IMAP_ADDR uses the same value
5245as your U-Boot configuration in CONFIG_SYS_IMMR.
5246
5247
5248Configuring the Linux kernel:
5249-----------------------------
5250
5251No specific requirements for U-Boot. Make sure you have some root
5252device (initial ramdisk, NFS) for your target system.
5253
5254
5255Building a Linux Image:
5256-----------------------
5257
5258With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5259not used. If you use recent kernel source, a new build target
5260"uImage" will exist which automatically builds an image usable by
5261U-Boot. Most older kernels also have support for a "pImage" target,
5262which was introduced for our predecessor project PPCBoot and uses a
5263100% compatible format.
5264
5265Example:
5266
5267	make TQM850L_config
5268	make oldconfig
5269	make dep
5270	make uImage
5271
5272The "uImage" build target uses a special tool (in 'tools/mkimage') to
5273encapsulate a compressed Linux kernel image with header	 information,
5274CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5275
5276* build a standard "vmlinux" kernel image (in ELF binary format):
5277
5278* convert the kernel into a raw binary image:
5279
5280	${CROSS_COMPILE}-objcopy -O binary \
5281				 -R .note -R .comment \
5282				 -S vmlinux linux.bin
5283
5284* compress the binary image:
5285
5286	gzip -9 linux.bin
5287
5288* package compressed binary image for U-Boot:
5289
5290	mkimage -A ppc -O linux -T kernel -C gzip \
5291		-a 0 -e 0 -n "Linux Kernel Image" \
5292		-d linux.bin.gz uImage
5293
5294
5295The "mkimage" tool can also be used to create ramdisk images for use
5296with U-Boot, either separated from the Linux kernel image, or
5297combined into one file. "mkimage" encapsulates the images with a 64
5298byte header containing information about target architecture,
5299operating system, image type, compression method, entry points, time
5300stamp, CRC32 checksums, etc.
5301
5302"mkimage" can be called in two ways: to verify existing images and
5303print the header information, or to build new images.
5304
5305In the first form (with "-l" option) mkimage lists the information
5306contained in the header of an existing U-Boot image; this includes
5307checksum verification:
5308
5309	tools/mkimage -l image
5310	  -l ==> list image header information
5311
5312The second form (with "-d" option) is used to build a U-Boot image
5313from a "data file" which is used as image payload:
5314
5315	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5316		      -n name -d data_file image
5317	  -A ==> set architecture to 'arch'
5318	  -O ==> set operating system to 'os'
5319	  -T ==> set image type to 'type'
5320	  -C ==> set compression type 'comp'
5321	  -a ==> set load address to 'addr' (hex)
5322	  -e ==> set entry point to 'ep' (hex)
5323	  -n ==> set image name to 'name'
5324	  -d ==> use image data from 'datafile'
5325
5326Right now, all Linux kernels for PowerPC systems use the same load
5327address (0x00000000), but the entry point address depends on the
5328kernel version:
5329
5330- 2.2.x kernels have the entry point at 0x0000000C,
5331- 2.3.x and later kernels have the entry point at 0x00000000.
5332
5333So a typical call to build a U-Boot image would read:
5334
5335	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5336	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5337	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5338	> examples/uImage.TQM850L
5339	Image Name:   2.4.4 kernel for TQM850L
5340	Created:      Wed Jul 19 02:34:59 2000
5341	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5342	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5343	Load Address: 0x00000000
5344	Entry Point:  0x00000000
5345
5346To verify the contents of the image (or check for corruption):
5347
5348	-> tools/mkimage -l examples/uImage.TQM850L
5349	Image Name:   2.4.4 kernel for TQM850L
5350	Created:      Wed Jul 19 02:34:59 2000
5351	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5352	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5353	Load Address: 0x00000000
5354	Entry Point:  0x00000000
5355
5356NOTE: for embedded systems where boot time is critical you can trade
5357speed for memory and install an UNCOMPRESSED image instead: this
5358needs more space in Flash, but boots much faster since it does not
5359need to be uncompressed:
5360
5361	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5362	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5363	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5364	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5365	> examples/uImage.TQM850L-uncompressed
5366	Image Name:   2.4.4 kernel for TQM850L
5367	Created:      Wed Jul 19 02:34:59 2000
5368	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5369	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5370	Load Address: 0x00000000
5371	Entry Point:  0x00000000
5372
5373
5374Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5375when your kernel is intended to use an initial ramdisk:
5376
5377	-> tools/mkimage -n 'Simple Ramdisk Image' \
5378	> -A ppc -O linux -T ramdisk -C gzip \
5379	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5380	Image Name:   Simple Ramdisk Image
5381	Created:      Wed Jan 12 14:01:50 2000
5382	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5383	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5384	Load Address: 0x00000000
5385	Entry Point:  0x00000000
5386
5387The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5388option performs the converse operation of the mkimage's second form (the "-d"
5389option). Given an image built by mkimage, the dumpimage extracts a "data file"
5390from the image:
5391
5392	tools/dumpimage -i image -p position data_file
5393	  -i ==> extract from the 'image' a specific 'data_file', \
5394	   indexed by 'position'
5395
5396
5397Installing a Linux Image:
5398-------------------------
5399
5400To downloading a U-Boot image over the serial (console) interface,
5401you must convert the image to S-Record format:
5402
5403	objcopy -I binary -O srec examples/image examples/image.srec
5404
5405The 'objcopy' does not understand the information in the U-Boot
5406image header, so the resulting S-Record file will be relative to
5407address 0x00000000. To load it to a given address, you need to
5408specify the target address as 'offset' parameter with the 'loads'
5409command.
5410
5411Example: install the image to address 0x40100000 (which on the
5412TQM8xxL is in the first Flash bank):
5413
5414	=> erase 40100000 401FFFFF
5415
5416	.......... done
5417	Erased 8 sectors
5418
5419	=> loads 40100000
5420	## Ready for S-Record download ...
5421	~>examples/image.srec
5422	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5423	...
5424	15989 15990 15991 15992
5425	[file transfer complete]
5426	[connected]
5427	## Start Addr = 0x00000000
5428
5429
5430You can check the success of the download using the 'iminfo' command;
5431this includes a checksum verification so you can be sure no data
5432corruption happened:
5433
5434	=> imi 40100000
5435
5436	## Checking Image at 40100000 ...
5437	   Image Name:	 2.2.13 for initrd on TQM850L
5438	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5439	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5440	   Load Address: 00000000
5441	   Entry Point:	 0000000c
5442	   Verifying Checksum ... OK
5443
5444
5445Boot Linux:
5446-----------
5447
5448The "bootm" command is used to boot an application that is stored in
5449memory (RAM or Flash). In case of a Linux kernel image, the contents
5450of the "bootargs" environment variable is passed to the kernel as
5451parameters. You can check and modify this variable using the
5452"printenv" and "setenv" commands:
5453
5454
5455	=> printenv bootargs
5456	bootargs=root=/dev/ram
5457
5458	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5459
5460	=> printenv bootargs
5461	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5462
5463	=> bootm 40020000
5464	## Booting Linux kernel at 40020000 ...
5465	   Image Name:	 2.2.13 for NFS on TQM850L
5466	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5467	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5468	   Load Address: 00000000
5469	   Entry Point:	 0000000c
5470	   Verifying Checksum ... OK
5471	   Uncompressing Kernel Image ... OK
5472	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
5473	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5474	time_init: decrementer frequency = 187500000/60
5475	Calibrating delay loop... 49.77 BogoMIPS
5476	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5477	...
5478
5479If you want to boot a Linux kernel with initial RAM disk, you pass
5480the memory addresses of both the kernel and the initrd image (PPBCOOT
5481format!) to the "bootm" command:
5482
5483	=> imi 40100000 40200000
5484
5485	## Checking Image at 40100000 ...
5486	   Image Name:	 2.2.13 for initrd on TQM850L
5487	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5488	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5489	   Load Address: 00000000
5490	   Entry Point:	 0000000c
5491	   Verifying Checksum ... OK
5492
5493	## Checking Image at 40200000 ...
5494	   Image Name:	 Simple Ramdisk Image
5495	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5496	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5497	   Load Address: 00000000
5498	   Entry Point:	 00000000
5499	   Verifying Checksum ... OK
5500
5501	=> bootm 40100000 40200000
5502	## Booting Linux kernel at 40100000 ...
5503	   Image Name:	 2.2.13 for initrd on TQM850L
5504	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5505	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5506	   Load Address: 00000000
5507	   Entry Point:	 0000000c
5508	   Verifying Checksum ... OK
5509	   Uncompressing Kernel Image ... OK
5510	## Loading RAMDisk Image at 40200000 ...
5511	   Image Name:	 Simple Ramdisk Image
5512	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5513	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5514	   Load Address: 00000000
5515	   Entry Point:	 00000000
5516	   Verifying Checksum ... OK
5517	   Loading Ramdisk ... OK
5518	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
5519	Boot arguments: root=/dev/ram
5520	time_init: decrementer frequency = 187500000/60
5521	Calibrating delay loop... 49.77 BogoMIPS
5522	...
5523	RAMDISK: Compressed image found at block 0
5524	VFS: Mounted root (ext2 filesystem).
5525
5526	bash#
5527
5528Boot Linux and pass a flat device tree:
5529-----------
5530
5531First, U-Boot must be compiled with the appropriate defines. See the section
5532titled "Linux Kernel Interface" above for a more in depth explanation. The
5533following is an example of how to start a kernel and pass an updated
5534flat device tree:
5535
5536=> print oftaddr
5537oftaddr=0x300000
5538=> print oft
5539oft=oftrees/mpc8540ads.dtb
5540=> tftp $oftaddr $oft
5541Speed: 1000, full duplex
5542Using TSEC0 device
5543TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5544Filename 'oftrees/mpc8540ads.dtb'.
5545Load address: 0x300000
5546Loading: #
5547done
5548Bytes transferred = 4106 (100a hex)
5549=> tftp $loadaddr $bootfile
5550Speed: 1000, full duplex
5551Using TSEC0 device
5552TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5553Filename 'uImage'.
5554Load address: 0x200000
5555Loading:############
5556done
5557Bytes transferred = 1029407 (fb51f hex)
5558=> print loadaddr
5559loadaddr=200000
5560=> print oftaddr
5561oftaddr=0x300000
5562=> bootm $loadaddr - $oftaddr
5563## Booting image at 00200000 ...
5564   Image Name:	 Linux-2.6.17-dirty
5565   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5566   Data Size:	 1029343 Bytes = 1005.2 kB
5567   Load Address: 00000000
5568   Entry Point:	 00000000
5569   Verifying Checksum ... OK
5570   Uncompressing Kernel Image ... OK
5571Booting using flat device tree at 0x300000
5572Using MPC85xx ADS machine description
5573Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5574[snip]
5575
5576
5577More About U-Boot Image Types:
5578------------------------------
5579
5580U-Boot supports the following image types:
5581
5582   "Standalone Programs" are directly runnable in the environment
5583	provided by U-Boot; it is expected that (if they behave
5584	well) you can continue to work in U-Boot after return from
5585	the Standalone Program.
5586   "OS Kernel Images" are usually images of some Embedded OS which
5587	will take over control completely. Usually these programs
5588	will install their own set of exception handlers, device
5589	drivers, set up the MMU, etc. - this means, that you cannot
5590	expect to re-enter U-Boot except by resetting the CPU.
5591   "RAMDisk Images" are more or less just data blocks, and their
5592	parameters (address, size) are passed to an OS kernel that is
5593	being started.
5594   "Multi-File Images" contain several images, typically an OS
5595	(Linux) kernel image and one or more data images like
5596	RAMDisks. This construct is useful for instance when you want
5597	to boot over the network using BOOTP etc., where the boot
5598	server provides just a single image file, but you want to get
5599	for instance an OS kernel and a RAMDisk image.
5600
5601	"Multi-File Images" start with a list of image sizes, each
5602	image size (in bytes) specified by an "uint32_t" in network
5603	byte order. This list is terminated by an "(uint32_t)0".
5604	Immediately after the terminating 0 follow the images, one by
5605	one, all aligned on "uint32_t" boundaries (size rounded up to
5606	a multiple of 4 bytes).
5607
5608   "Firmware Images" are binary images containing firmware (like
5609	U-Boot or FPGA images) which usually will be programmed to
5610	flash memory.
5611
5612   "Script files" are command sequences that will be executed by
5613	U-Boot's command interpreter; this feature is especially
5614	useful when you configure U-Boot to use a real shell (hush)
5615	as command interpreter.
5616
5617Booting the Linux zImage:
5618-------------------------
5619
5620On some platforms, it's possible to boot Linux zImage. This is done
5621using the "bootz" command. The syntax of "bootz" command is the same
5622as the syntax of "bootm" command.
5623
5624Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5625kernel with raw initrd images. The syntax is slightly different, the
5626address of the initrd must be augmented by it's size, in the following
5627format: "<initrd addres>:<initrd size>".
5628
5629
5630Standalone HOWTO:
5631=================
5632
5633One of the features of U-Boot is that you can dynamically load and
5634run "standalone" applications, which can use some resources of
5635U-Boot like console I/O functions or interrupt services.
5636
5637Two simple examples are included with the sources:
5638
5639"Hello World" Demo:
5640-------------------
5641
5642'examples/hello_world.c' contains a small "Hello World" Demo
5643application; it is automatically compiled when you build U-Boot.
5644It's configured to run at address 0x00040004, so you can play with it
5645like that:
5646
5647	=> loads
5648	## Ready for S-Record download ...
5649	~>examples/hello_world.srec
5650	1 2 3 4 5 6 7 8 9 10 11 ...
5651	[file transfer complete]
5652	[connected]
5653	## Start Addr = 0x00040004
5654
5655	=> go 40004 Hello World! This is a test.
5656	## Starting application at 0x00040004 ...
5657	Hello World
5658	argc = 7
5659	argv[0] = "40004"
5660	argv[1] = "Hello"
5661	argv[2] = "World!"
5662	argv[3] = "This"
5663	argv[4] = "is"
5664	argv[5] = "a"
5665	argv[6] = "test."
5666	argv[7] = "<NULL>"
5667	Hit any key to exit ...
5668
5669	## Application terminated, rc = 0x0
5670
5671Another example, which demonstrates how to register a CPM interrupt
5672handler with the U-Boot code, can be found in 'examples/timer.c'.
5673Here, a CPM timer is set up to generate an interrupt every second.
5674The interrupt service routine is trivial, just printing a '.'
5675character, but this is just a demo program. The application can be
5676controlled by the following keys:
5677
5678	? - print current values og the CPM Timer registers
5679	b - enable interrupts and start timer
5680	e - stop timer and disable interrupts
5681	q - quit application
5682
5683	=> loads
5684	## Ready for S-Record download ...
5685	~>examples/timer.srec
5686	1 2 3 4 5 6 7 8 9 10 11 ...
5687	[file transfer complete]
5688	[connected]
5689	## Start Addr = 0x00040004
5690
5691	=> go 40004
5692	## Starting application at 0x00040004 ...
5693	TIMERS=0xfff00980
5694	Using timer 1
5695	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5696
5697Hit 'b':
5698	[q, b, e, ?] Set interval 1000000 us
5699	Enabling timer
5700Hit '?':
5701	[q, b, e, ?] ........
5702	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5703Hit '?':
5704	[q, b, e, ?] .
5705	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5706Hit '?':
5707	[q, b, e, ?] .
5708	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5709Hit '?':
5710	[q, b, e, ?] .
5711	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5712Hit 'e':
5713	[q, b, e, ?] ...Stopping timer
5714Hit 'q':
5715	[q, b, e, ?] ## Application terminated, rc = 0x0
5716
5717
5718Minicom warning:
5719================
5720
5721Over time, many people have reported problems when trying to use the
5722"minicom" terminal emulation program for serial download. I (wd)
5723consider minicom to be broken, and recommend not to use it. Under
5724Unix, I recommend to use C-Kermit for general purpose use (and
5725especially for kermit binary protocol download ("loadb" command), and
5726use "cu" for S-Record download ("loads" command).  See
5727http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5728for help with kermit.
5729
5730
5731Nevertheless, if you absolutely want to use it try adding this
5732configuration to your "File transfer protocols" section:
5733
5734	   Name	   Program			Name U/D FullScr IO-Red. Multi
5735	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5736	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5737
5738
5739NetBSD Notes:
5740=============
5741
5742Starting at version 0.9.2, U-Boot supports NetBSD both as host
5743(build U-Boot) and target system (boots NetBSD/mpc8xx).
5744
5745Building requires a cross environment; it is known to work on
5746NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5747need gmake since the Makefiles are not compatible with BSD make).
5748Note that the cross-powerpc package does not install include files;
5749attempting to build U-Boot will fail because <machine/ansi.h> is
5750missing.  This file has to be installed and patched manually:
5751
5752	# cd /usr/pkg/cross/powerpc-netbsd/include
5753	# mkdir powerpc
5754	# ln -s powerpc machine
5755	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5756	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5757
5758Native builds *don't* work due to incompatibilities between native
5759and U-Boot include files.
5760
5761Booting assumes that (the first part of) the image booted is a
5762stage-2 loader which in turn loads and then invokes the kernel
5763proper. Loader sources will eventually appear in the NetBSD source
5764tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5765meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5766
5767
5768Implementation Internals:
5769=========================
5770
5771The following is not intended to be a complete description of every
5772implementation detail. However, it should help to understand the
5773inner workings of U-Boot and make it easier to port it to custom
5774hardware.
5775
5776
5777Initial Stack, Global Data:
5778---------------------------
5779
5780The implementation of U-Boot is complicated by the fact that U-Boot
5781starts running out of ROM (flash memory), usually without access to
5782system RAM (because the memory controller is not initialized yet).
5783This means that we don't have writable Data or BSS segments, and BSS
5784is not initialized as zero. To be able to get a C environment working
5785at all, we have to allocate at least a minimal stack. Implementation
5786options for this are defined and restricted by the CPU used: Some CPU
5787models provide on-chip memory (like the IMMR area on MPC8xx and
5788MPC826x processors), on others (parts of) the data cache can be
5789locked as (mis-) used as memory, etc.
5790
5791	Chris Hallinan posted a good summary of these issues to the
5792	U-Boot mailing list:
5793
5794	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5795	From: "Chris Hallinan" <clh@net1plus.com>
5796	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5797	...
5798
5799	Correct me if I'm wrong, folks, but the way I understand it
5800	is this: Using DCACHE as initial RAM for Stack, etc, does not
5801	require any physical RAM backing up the cache. The cleverness
5802	is that the cache is being used as a temporary supply of
5803	necessary storage before the SDRAM controller is setup. It's
5804	beyond the scope of this list to explain the details, but you
5805	can see how this works by studying the cache architecture and
5806	operation in the architecture and processor-specific manuals.
5807
5808	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5809	is another option for the system designer to use as an
5810	initial stack/RAM area prior to SDRAM being available. Either
5811	option should work for you. Using CS 4 should be fine if your
5812	board designers haven't used it for something that would
5813	cause you grief during the initial boot! It is frequently not
5814	used.
5815
5816	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5817	with your processor/board/system design. The default value
5818	you will find in any recent u-boot distribution in
5819	walnut.h should work for you. I'd set it to a value larger
5820	than your SDRAM module. If you have a 64MB SDRAM module, set
5821	it above 400_0000. Just make sure your board has no resources
5822	that are supposed to respond to that address! That code in
5823	start.S has been around a while and should work as is when
5824	you get the config right.
5825
5826	-Chris Hallinan
5827	DS4.COM, Inc.
5828
5829It is essential to remember this, since it has some impact on the C
5830code for the initialization procedures:
5831
5832* Initialized global data (data segment) is read-only. Do not attempt
5833  to write it.
5834
5835* Do not use any uninitialized global data (or implicitely initialized
5836  as zero data - BSS segment) at all - this is undefined, initiali-
5837  zation is performed later (when relocating to RAM).
5838
5839* Stack space is very limited. Avoid big data buffers or things like
5840  that.
5841
5842Having only the stack as writable memory limits means we cannot use
5843normal global data to share information beween the code. But it
5844turned out that the implementation of U-Boot can be greatly
5845simplified by making a global data structure (gd_t) available to all
5846functions. We could pass a pointer to this data as argument to _all_
5847functions, but this would bloat the code. Instead we use a feature of
5848the GCC compiler (Global Register Variables) to share the data: we
5849place a pointer (gd) to the global data into a register which we
5850reserve for this purpose.
5851
5852When choosing a register for such a purpose we are restricted by the
5853relevant  (E)ABI  specifications for the current architecture, and by
5854GCC's implementation.
5855
5856For PowerPC, the following registers have specific use:
5857	R1:	stack pointer
5858	R2:	reserved for system use
5859	R3-R4:	parameter passing and return values
5860	R5-R10: parameter passing
5861	R13:	small data area pointer
5862	R30:	GOT pointer
5863	R31:	frame pointer
5864
5865	(U-Boot also uses R12 as internal GOT pointer. r12
5866	is a volatile register so r12 needs to be reset when
5867	going back and forth between asm and C)
5868
5869    ==> U-Boot will use R2 to hold a pointer to the global data
5870
5871    Note: on PPC, we could use a static initializer (since the
5872    address of the global data structure is known at compile time),
5873    but it turned out that reserving a register results in somewhat
5874    smaller code - although the code savings are not that big (on
5875    average for all boards 752 bytes for the whole U-Boot image,
5876    624 text + 127 data).
5877
5878On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5879	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5880
5881    ==> U-Boot will use P3 to hold a pointer to the global data
5882
5883On ARM, the following registers are used:
5884
5885	R0:	function argument word/integer result
5886	R1-R3:	function argument word
5887	R9:	platform specific
5888	R10:	stack limit (used only if stack checking is enabled)
5889	R11:	argument (frame) pointer
5890	R12:	temporary workspace
5891	R13:	stack pointer
5892	R14:	link register
5893	R15:	program counter
5894
5895    ==> U-Boot will use R9 to hold a pointer to the global data
5896
5897    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5898
5899On Nios II, the ABI is documented here:
5900	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5901
5902    ==> U-Boot will use gp to hold a pointer to the global data
5903
5904    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5905    to access small data sections, so gp is free.
5906
5907On NDS32, the following registers are used:
5908
5909	R0-R1:	argument/return
5910	R2-R5:	argument
5911	R15:	temporary register for assembler
5912	R16:	trampoline register
5913	R28:	frame pointer (FP)
5914	R29:	global pointer (GP)
5915	R30:	link register (LP)
5916	R31:	stack pointer (SP)
5917	PC:	program counter (PC)
5918
5919    ==> U-Boot will use R10 to hold a pointer to the global data
5920
5921NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5922or current versions of GCC may "optimize" the code too much.
5923
5924Memory Management:
5925------------------
5926
5927U-Boot runs in system state and uses physical addresses, i.e. the
5928MMU is not used either for address mapping nor for memory protection.
5929
5930The available memory is mapped to fixed addresses using the memory
5931controller. In this process, a contiguous block is formed for each
5932memory type (Flash, SDRAM, SRAM), even when it consists of several
5933physical memory banks.
5934
5935U-Boot is installed in the first 128 kB of the first Flash bank (on
5936TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5937booting and sizing and initializing DRAM, the code relocates itself
5938to the upper end of DRAM. Immediately below the U-Boot code some
5939memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5940configuration setting]. Below that, a structure with global Board
5941Info data is placed, followed by the stack (growing downward).
5942
5943Additionally, some exception handler code is copied to the low 8 kB
5944of DRAM (0x00000000 ... 0x00001FFF).
5945
5946So a typical memory configuration with 16 MB of DRAM could look like
5947this:
5948
5949	0x0000 0000	Exception Vector code
5950	      :
5951	0x0000 1FFF
5952	0x0000 2000	Free for Application Use
5953	      :
5954	      :
5955
5956	      :
5957	      :
5958	0x00FB FF20	Monitor Stack (Growing downward)
5959	0x00FB FFAC	Board Info Data and permanent copy of global data
5960	0x00FC 0000	Malloc Arena
5961	      :
5962	0x00FD FFFF
5963	0x00FE 0000	RAM Copy of Monitor Code
5964	...		eventually: LCD or video framebuffer
5965	...		eventually: pRAM (Protected RAM - unchanged by reset)
5966	0x00FF FFFF	[End of RAM]
5967
5968
5969System Initialization:
5970----------------------
5971
5972In the reset configuration, U-Boot starts at the reset entry point
5973(on most PowerPC systems at address 0x00000100). Because of the reset
5974configuration for CS0# this is a mirror of the onboard Flash memory.
5975To be able to re-map memory U-Boot then jumps to its link address.
5976To be able to implement the initialization code in C, a (small!)
5977initial stack is set up in the internal Dual Ported RAM (in case CPUs
5978which provide such a feature like MPC8xx or MPC8260), or in a locked
5979part of the data cache. After that, U-Boot initializes the CPU core,
5980the caches and the SIU.
5981
5982Next, all (potentially) available memory banks are mapped using a
5983preliminary mapping. For example, we put them on 512 MB boundaries
5984(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5985on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5986programmed for SDRAM access. Using the temporary configuration, a
5987simple memory test is run that determines the size of the SDRAM
5988banks.
5989
5990When there is more than one SDRAM bank, and the banks are of
5991different size, the largest is mapped first. For equal size, the first
5992bank (CS2#) is mapped first. The first mapping is always for address
59930x00000000, with any additional banks following immediately to create
5994contiguous memory starting from 0.
5995
5996Then, the monitor installs itself at the upper end of the SDRAM area
5997and allocates memory for use by malloc() and for the global Board
5998Info data; also, the exception vector code is copied to the low RAM
5999pages, and the final stack is set up.
6000
6001Only after this relocation will you have a "normal" C environment;
6002until that you are restricted in several ways, mostly because you are
6003running from ROM, and because the code will have to be relocated to a
6004new address in RAM.
6005
6006
6007U-Boot Porting Guide:
6008----------------------
6009
6010[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6011list, October 2002]
6012
6013
6014int main(int argc, char *argv[])
6015{
6016	sighandler_t no_more_time;
6017
6018	signal(SIGALRM, no_more_time);
6019	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6020
6021	if (available_money > available_manpower) {
6022		Pay consultant to port U-Boot;
6023		return 0;
6024	}
6025
6026	Download latest U-Boot source;
6027
6028	Subscribe to u-boot mailing list;
6029
6030	if (clueless)
6031		email("Hi, I am new to U-Boot, how do I get started?");
6032
6033	while (learning) {
6034		Read the README file in the top level directory;
6035		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6036		Read applicable doc/*.README;
6037		Read the source, Luke;
6038		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6039	}
6040
6041	if (available_money > toLocalCurrency ($2500))
6042		Buy a BDI3000;
6043	else
6044		Add a lot of aggravation and time;
6045
6046	if (a similar board exists) {	/* hopefully... */
6047		cp -a board/<similar> board/<myboard>
6048		cp include/configs/<similar>.h include/configs/<myboard>.h
6049	} else {
6050		Create your own board support subdirectory;
6051		Create your own board include/configs/<myboard>.h file;
6052	}
6053	Edit new board/<myboard> files
6054	Edit new include/configs/<myboard>.h
6055
6056	while (!accepted) {
6057		while (!running) {
6058			do {
6059				Add / modify source code;
6060			} until (compiles);
6061			Debug;
6062			if (clueless)
6063				email("Hi, I am having problems...");
6064		}
6065		Send patch file to the U-Boot email list;
6066		if (reasonable critiques)
6067			Incorporate improvements from email list code review;
6068		else
6069			Defend code as written;
6070	}
6071
6072	return 0;
6073}
6074
6075void no_more_time (int sig)
6076{
6077      hire_a_guru();
6078}
6079
6080
6081Coding Standards:
6082-----------------
6083
6084All contributions to U-Boot should conform to the Linux kernel
6085coding style; see the file "Documentation/CodingStyle" and the script
6086"scripts/Lindent" in your Linux kernel source directory.
6087
6088Source files originating from a different project (for example the
6089MTD subsystem) are generally exempt from these guidelines and are not
6090reformated to ease subsequent migration to newer versions of those
6091sources.
6092
6093Please note that U-Boot is implemented in C (and to some small parts in
6094Assembler); no C++ is used, so please do not use C++ style comments (//)
6095in your code.
6096
6097Please also stick to the following formatting rules:
6098- remove any trailing white space
6099- use TAB characters for indentation and vertical alignment, not spaces
6100- make sure NOT to use DOS '\r\n' line feeds
6101- do not add more than 2 consecutive empty lines to source files
6102- do not add trailing empty lines to source files
6103
6104Submissions which do not conform to the standards may be returned
6105with a request to reformat the changes.
6106
6107
6108Submitting Patches:
6109-------------------
6110
6111Since the number of patches for U-Boot is growing, we need to
6112establish some rules. Submissions which do not conform to these rules
6113may be rejected, even when they contain important and valuable stuff.
6114
6115Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6116
6117Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6118see http://lists.denx.de/mailman/listinfo/u-boot
6119
6120When you send a patch, please include the following information with
6121it:
6122
6123* For bug fixes: a description of the bug and how your patch fixes
6124  this bug. Please try to include a way of demonstrating that the
6125  patch actually fixes something.
6126
6127* For new features: a description of the feature and your
6128  implementation.
6129
6130* A CHANGELOG entry as plaintext (separate from the patch)
6131
6132* For major contributions, your entry to the CREDITS file
6133
6134* When you add support for a new board, don't forget to add a
6135  maintainer e-mail address to the boards.cfg file, too.
6136
6137* If your patch adds new configuration options, don't forget to
6138  document these in the README file.
6139
6140* The patch itself. If you are using git (which is *strongly*
6141  recommended) you can easily generate the patch using the
6142  "git format-patch". If you then use "git send-email" to send it to
6143  the U-Boot mailing list, you will avoid most of the common problems
6144  with some other mail clients.
6145
6146  If you cannot use git, use "diff -purN OLD NEW". If your version of
6147  diff does not support these options, then get the latest version of
6148  GNU diff.
6149
6150  The current directory when running this command shall be the parent
6151  directory of the U-Boot source tree (i. e. please make sure that
6152  your patch includes sufficient directory information for the
6153  affected files).
6154
6155  We prefer patches as plain text. MIME attachments are discouraged,
6156  and compressed attachments must not be used.
6157
6158* If one logical set of modifications affects or creates several
6159  files, all these changes shall be submitted in a SINGLE patch file.
6160
6161* Changesets that contain different, unrelated modifications shall be
6162  submitted as SEPARATE patches, one patch per changeset.
6163
6164
6165Notes:
6166
6167* Before sending the patch, run the MAKEALL script on your patched
6168  source tree and make sure that no errors or warnings are reported
6169  for any of the boards.
6170
6171* Keep your modifications to the necessary minimum: A patch
6172  containing several unrelated changes or arbitrary reformats will be
6173  returned with a request to re-formatting / split it.
6174
6175* If you modify existing code, make sure that your new code does not
6176  add to the memory footprint of the code ;-) Small is beautiful!
6177  When adding new features, these should compile conditionally only
6178  (using #ifdef), and the resulting code with the new feature
6179  disabled must not need more memory than the old code without your
6180  modification.
6181
6182* Remember that there is a size limit of 100 kB per message on the
6183  u-boot mailing list. Bigger patches will be moderated. If they are
6184  reasonable and not too big, they will be acknowledged. But patches
6185  bigger than the size limit should be avoided.
6186