xref: /rk3399_rockchip-uboot/README (revision 258060905e04fe2eb509756ef3b37e23e220a2d6)
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
755- Console Interface:
756		Depending on board, define exactly one serial port
757		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
758		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
759		console by defining CONFIG_8xx_CONS_NONE
760
761		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
762		port routines must be defined elsewhere
763		(i.e. serial_init(), serial_getc(), ...)
764
765		CONFIG_CFB_CONSOLE
766		Enables console device for a color framebuffer. Needs following
767		defines (cf. smiLynxEM, i8042)
768			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
769						(default big endian)
770			VIDEO_HW_RECTFILL	graphic chip supports
771						rectangle fill
772						(cf. smiLynxEM)
773			VIDEO_HW_BITBLT		graphic chip supports
774						bit-blit (cf. smiLynxEM)
775			VIDEO_VISIBLE_COLS	visible pixel columns
776						(cols=pitch)
777			VIDEO_VISIBLE_ROWS	visible pixel rows
778			VIDEO_PIXEL_SIZE	bytes per pixel
779			VIDEO_DATA_FORMAT	graphic data format
780						(0-5, cf. cfb_console.c)
781			VIDEO_FB_ADRS		framebuffer address
782			VIDEO_KBD_INIT_FCT	keyboard int fct
783						(i.e. i8042_kbd_init())
784			VIDEO_TSTC_FCT		test char fct
785						(i.e. i8042_tstc)
786			VIDEO_GETC_FCT		get char fct
787						(i.e. i8042_getc)
788			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
789						(requires blink timer
790						cf. i8042.c)
791			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
792			CONFIG_CONSOLE_TIME	display time/date info in
793						upper right corner
794						(requires CONFIG_CMD_DATE)
795			CONFIG_VIDEO_LOGO	display Linux logo in
796						upper left corner
797			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
798						linux_logo.h for logo.
799						Requires CONFIG_VIDEO_LOGO
800			CONFIG_CONSOLE_EXTRA_INFO
801						additional board info beside
802						the logo
803
804		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
805		a limited number of ANSI escape sequences (cursor control,
806		erase functions and limited graphics rendition control).
807
808		When CONFIG_CFB_CONSOLE is defined, video console is
809		default i/o. Serial console can be forced with
810		environment 'console=serial'.
811
812		When CONFIG_SILENT_CONSOLE is defined, all console
813		messages (by U-Boot and Linux!) can be silenced with
814		the "silent" environment variable. See
815		doc/README.silent for more information.
816
817		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
818			is 0x00.
819		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
820			is 0xa0.
821
822- Console Baudrate:
823		CONFIG_BAUDRATE - in bps
824		Select one of the baudrates listed in
825		CONFIG_SYS_BAUDRATE_TABLE, see below.
826		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
827
828- Console Rx buffer length
829		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
830		the maximum receive buffer length for the SMC.
831		This option is actual only for 82xx and 8xx possible.
832		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
833		must be defined, to setup the maximum idle timeout for
834		the SMC.
835
836- Pre-Console Buffer:
837		Prior to the console being initialised (i.e. serial UART
838		initialised etc) all console output is silently discarded.
839		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
840		buffer any console messages prior to the console being
841		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
842		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
843		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
844		bytes are output before the console is initialised, the
845		earlier bytes are discarded.
846
847		'Sane' compilers will generate smaller code if
848		CONFIG_PRE_CON_BUF_SZ is a power of 2
849
850- Safe printf() functions
851		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
852		the printf() functions. These are defined in
853		include/vsprintf.h and include snprintf(), vsnprintf() and
854		so on. Code size increase is approximately 300-500 bytes.
855		If this option is not given then these functions will
856		silently discard their buffer size argument - this means
857		you are not getting any overflow checking in this case.
858
859- Boot Delay:	CONFIG_BOOTDELAY - in seconds
860		Delay before automatically booting the default image;
861		set to -1 to disable autoboot.
862		set to -2 to autoboot with no delay and not check for abort
863		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
864
865		See doc/README.autoboot for these options that
866		work with CONFIG_BOOTDELAY. None are required.
867		CONFIG_BOOT_RETRY_TIME
868		CONFIG_BOOT_RETRY_MIN
869		CONFIG_AUTOBOOT_KEYED
870		CONFIG_AUTOBOOT_PROMPT
871		CONFIG_AUTOBOOT_DELAY_STR
872		CONFIG_AUTOBOOT_STOP_STR
873		CONFIG_AUTOBOOT_DELAY_STR2
874		CONFIG_AUTOBOOT_STOP_STR2
875		CONFIG_ZERO_BOOTDELAY_CHECK
876		CONFIG_RESET_TO_RETRY
877
878- Autoboot Command:
879		CONFIG_BOOTCOMMAND
880		Only needed when CONFIG_BOOTDELAY is enabled;
881		define a command string that is automatically executed
882		when no character is read on the console interface
883		within "Boot Delay" after reset.
884
885		CONFIG_BOOTARGS
886		This can be used to pass arguments to the bootm
887		command. The value of CONFIG_BOOTARGS goes into the
888		environment value "bootargs".
889
890		CONFIG_RAMBOOT and CONFIG_NFSBOOT
891		The value of these goes into the environment as
892		"ramboot" and "nfsboot" respectively, and can be used
893		as a convenience, when switching between booting from
894		RAM and NFS.
895
896- Bootcount:
897		CONFIG_BOOTCOUNT_LIMIT
898		Implements a mechanism for detecting a repeating reboot
899		cycle, see:
900		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
901
902		CONFIG_BOOTCOUNT_ENV
903		If no softreset save registers are found on the hardware
904		"bootcount" is stored in the environment. To prevent a
905		saveenv on all reboots, the environment variable
906		"upgrade_available" is used. If "upgrade_available" is
907		0, "bootcount" is always 0, if "upgrade_available" is
908		1 "bootcount" is incremented in the environment.
909		So the Userspace Applikation must set the "upgrade_available"
910		and "bootcount" variable to 0, if a boot was successfully.
911
912- Pre-Boot Commands:
913		CONFIG_PREBOOT
914
915		When this option is #defined, the existence of the
916		environment variable "preboot" will be checked
917		immediately before starting the CONFIG_BOOTDELAY
918		countdown and/or running the auto-boot command resp.
919		entering interactive mode.
920
921		This feature is especially useful when "preboot" is
922		automatically generated or modified. For an example
923		see the LWMON board specific code: here "preboot" is
924		modified when the user holds down a certain
925		combination of keys on the (special) keyboard when
926		booting the systems
927
928- Serial Download Echo Mode:
929		CONFIG_LOADS_ECHO
930		If defined to 1, all characters received during a
931		serial download (using the "loads" command) are
932		echoed back. This might be needed by some terminal
933		emulations (like "cu"), but may as well just take
934		time on others. This setting #define's the initial
935		value of the "loads_echo" environment variable.
936
937- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
938		CONFIG_KGDB_BAUDRATE
939		Select one of the baudrates listed in
940		CONFIG_SYS_BAUDRATE_TABLE, see below.
941
942- Monitor Functions:
943		Monitor commands can be included or excluded
944		from the build by using the #include files
945		<config_cmd_all.h> and #undef'ing unwanted
946		commands, or using <config_cmd_default.h>
947		and augmenting with additional #define's
948		for wanted commands.
949
950		The default command configuration includes all commands
951		except those marked below with a "*".
952
953		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
954		CONFIG_CMD_ASKENV	* ask for env variable
955		CONFIG_CMD_BDI		  bdinfo
956		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
957		CONFIG_CMD_BMP		* BMP support
958		CONFIG_CMD_BSP		* Board specific commands
959		CONFIG_CMD_BOOTD	  bootd
960		CONFIG_CMD_CACHE	* icache, dcache
961		CONFIG_CMD_CLK   	* clock command support
962		CONFIG_CMD_CONSOLE	  coninfo
963		CONFIG_CMD_CRC32	* crc32
964		CONFIG_CMD_DATE		* support for RTC, date/time...
965		CONFIG_CMD_DHCP		* DHCP support
966		CONFIG_CMD_DIAG		* Diagnostics
967		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
968		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
969		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
970		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
971		CONFIG_CMD_DTT		* Digital Therm and Thermostat
972		CONFIG_CMD_ECHO		  echo arguments
973		CONFIG_CMD_EDITENV	  edit env variable
974		CONFIG_CMD_EEPROM	* EEPROM read/write support
975		CONFIG_CMD_ELF		* bootelf, bootvx
976		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
977		CONFIG_CMD_ENV_FLAGS	* display details about env flags
978		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
979		CONFIG_CMD_EXPORTENV	* export the environment
980		CONFIG_CMD_EXT2		* ext2 command support
981		CONFIG_CMD_EXT4		* ext4 command support
982		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
983					  that work for multiple fs types
984		CONFIG_CMD_SAVEENV	  saveenv
985		CONFIG_CMD_FDC		* Floppy Disk Support
986		CONFIG_CMD_FAT		* FAT command support
987		CONFIG_CMD_FLASH	  flinfo, erase, protect
988		CONFIG_CMD_FPGA		  FPGA device initialization support
989		CONFIG_CMD_FUSE		* Device fuse support
990		CONFIG_CMD_GETTIME	* Get time since boot
991		CONFIG_CMD_GO		* the 'go' command (exec code)
992		CONFIG_CMD_GREPENV	* search environment
993		CONFIG_CMD_HASH		* calculate hash / digest
994		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
995		CONFIG_CMD_I2C		* I2C serial bus support
996		CONFIG_CMD_IDE		* IDE harddisk support
997		CONFIG_CMD_IMI		  iminfo
998		CONFIG_CMD_IMLS		  List all images found in NOR flash
999		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1000		CONFIG_CMD_IMMAP	* IMMR dump support
1001		CONFIG_CMD_IMPORTENV	* import an environment
1002		CONFIG_CMD_INI		* import data from an ini file into the env
1003		CONFIG_CMD_IRQ		* irqinfo
1004		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1005		CONFIG_CMD_JFFS2	* JFFS2 Support
1006		CONFIG_CMD_KGDB		* kgdb
1007		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1008		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1009					  (169.254.*.*)
1010		CONFIG_CMD_LOADB	  loadb
1011		CONFIG_CMD_LOADS	  loads
1012		CONFIG_CMD_MD5SUM	* print md5 message digest
1013					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1014		CONFIG_CMD_MEMINFO	* Display detailed memory information
1015		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1016					  loop, loopw
1017		CONFIG_CMD_MEMTEST	* mtest
1018		CONFIG_CMD_MISC		  Misc functions like sleep etc
1019		CONFIG_CMD_MMC		* MMC memory mapped support
1020		CONFIG_CMD_MII		* MII utility commands
1021		CONFIG_CMD_MTDPARTS	* MTD partition support
1022		CONFIG_CMD_NAND		* NAND support
1023		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1024		CONFIG_CMD_NFS		  NFS support
1025		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1026		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1027		CONFIG_CMD_PCI		* pciinfo
1028		CONFIG_CMD_PCMCIA		* PCMCIA support
1029		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1030					  host
1031		CONFIG_CMD_PORTIO	* Port I/O
1032		CONFIG_CMD_READ		* Read raw data from partition
1033		CONFIG_CMD_REGINFO	* Register dump
1034		CONFIG_CMD_RUN		  run command in env variable
1035		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1036		CONFIG_CMD_SAVES	* save S record dump
1037		CONFIG_CMD_SCSI		* SCSI Support
1038		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1039					  (requires CONFIG_CMD_I2C)
1040		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1041					  (4xx only)
1042		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1043		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1044					  (requires CONFIG_CMD_MEMORY)
1045		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1046		CONFIG_CMD_SOURCE	  "source" command Support
1047		CONFIG_CMD_SPI		* SPI serial bus support
1048		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1049		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1050		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1051		CONFIG_CMD_TIMER	* access to the system tick timer
1052		CONFIG_CMD_USB		* USB support
1053		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1054		CONFIG_CMD_MFSL		* Microblaze FSL support
1055		CONFIG_CMD_XIMG		  Load part of Multi Image
1056		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1057
1058		EXAMPLE: If you want all functions except of network
1059		support you can write:
1060
1061		#include "config_cmd_all.h"
1062		#undef CONFIG_CMD_NET
1063
1064	Other Commands:
1065		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1066
1067	Note:	Don't enable the "icache" and "dcache" commands
1068		(configuration option CONFIG_CMD_CACHE) unless you know
1069		what you (and your U-Boot users) are doing. Data
1070		cache cannot be enabled on systems like the 8xx or
1071		8260 (where accesses to the IMMR region must be
1072		uncached), and it cannot be disabled on all other
1073		systems where we (mis-) use the data cache to hold an
1074		initial stack and some data.
1075
1076
1077		XXX - this list needs to get updated!
1078
1079- Regular expression support:
1080		CONFIG_REGEX
1081		If this variable is defined, U-Boot is linked against
1082		the SLRE (Super Light Regular Expression) library,
1083		which adds regex support to some commands, as for
1084		example "env grep" and "setexpr".
1085
1086- Device tree:
1087		CONFIG_OF_CONTROL
1088		If this variable is defined, U-Boot will use a device tree
1089		to configure its devices, instead of relying on statically
1090		compiled #defines in the board file. This option is
1091		experimental and only available on a few boards. The device
1092		tree is available in the global data as gd->fdt_blob.
1093
1094		U-Boot needs to get its device tree from somewhere. This can
1095		be done using one of the two options below:
1096
1097		CONFIG_OF_EMBED
1098		If this variable is defined, U-Boot will embed a device tree
1099		binary in its image. This device tree file should be in the
1100		board directory and called <soc>-<board>.dts. The binary file
1101		is then picked up in board_init_f() and made available through
1102		the global data structure as gd->blob.
1103
1104		CONFIG_OF_SEPARATE
1105		If this variable is defined, U-Boot will build a device tree
1106		binary. It will be called u-boot.dtb. Architecture-specific
1107		code will locate it at run-time. Generally this works by:
1108
1109			cat u-boot.bin u-boot.dtb >image.bin
1110
1111		and in fact, U-Boot does this for you, creating a file called
1112		u-boot-dtb.bin which is useful in the common case. You can
1113		still use the individual files if you need something more
1114		exotic.
1115
1116- Watchdog:
1117		CONFIG_WATCHDOG
1118		If this variable is defined, it enables watchdog
1119		support for the SoC. There must be support in the SoC
1120		specific code for a watchdog. For the 8xx and 8260
1121		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1122		register.  When supported for a specific SoC is
1123		available, then no further board specific code should
1124		be needed to use it.
1125
1126		CONFIG_HW_WATCHDOG
1127		When using a watchdog circuitry external to the used
1128		SoC, then define this variable and provide board
1129		specific code for the "hw_watchdog_reset" function.
1130
1131- U-Boot Version:
1132		CONFIG_VERSION_VARIABLE
1133		If this variable is defined, an environment variable
1134		named "ver" is created by U-Boot showing the U-Boot
1135		version as printed by the "version" command.
1136		Any change to this variable will be reverted at the
1137		next reset.
1138
1139- Real-Time Clock:
1140
1141		When CONFIG_CMD_DATE is selected, the type of the RTC
1142		has to be selected, too. Define exactly one of the
1143		following options:
1144
1145		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1146		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1147		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1148		CONFIG_RTC_MC146818	- use MC146818 RTC
1149		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1150		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1151		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1152		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1153		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1154		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1155		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1156		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1157					  RV3029 RTC.
1158
1159		Note that if the RTC uses I2C, then the I2C interface
1160		must also be configured. See I2C Support, below.
1161
1162- GPIO Support:
1163		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1164
1165		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1166		chip-ngpio pairs that tell the PCA953X driver the number of
1167		pins supported by a particular chip.
1168
1169		Note that if the GPIO device uses I2C, then the I2C interface
1170		must also be configured. See I2C Support, below.
1171
1172- Timestamp Support:
1173
1174		When CONFIG_TIMESTAMP is selected, the timestamp
1175		(date and time) of an image is printed by image
1176		commands like bootm or iminfo. This option is
1177		automatically enabled when you select CONFIG_CMD_DATE .
1178
1179- Partition Labels (disklabels) Supported:
1180		Zero or more of the following:
1181		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1182		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1183				       Intel architecture, USB sticks, etc.
1184		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1185		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1186				       bootloader.  Note 2TB partition limit; see
1187				       disk/part_efi.c
1188		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1189
1190		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1191		CONFIG_CMD_SCSI) you must configure support for at
1192		least one non-MTD partition type as well.
1193
1194- IDE Reset method:
1195		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1196		board configurations files but used nowhere!
1197
1198		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1199		be performed by calling the function
1200			ide_set_reset(int reset)
1201		which has to be defined in a board specific file
1202
1203- ATAPI Support:
1204		CONFIG_ATAPI
1205
1206		Set this to enable ATAPI support.
1207
1208- LBA48 Support
1209		CONFIG_LBA48
1210
1211		Set this to enable support for disks larger than 137GB
1212		Also look at CONFIG_SYS_64BIT_LBA.
1213		Whithout these , LBA48 support uses 32bit variables and will 'only'
1214		support disks up to 2.1TB.
1215
1216		CONFIG_SYS_64BIT_LBA:
1217			When enabled, makes the IDE subsystem use 64bit sector addresses.
1218			Default is 32bit.
1219
1220- SCSI Support:
1221		At the moment only there is only support for the
1222		SYM53C8XX SCSI controller; define
1223		CONFIG_SCSI_SYM53C8XX to enable it.
1224
1225		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1226		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1227		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1228		maximum numbers of LUNs, SCSI ID's and target
1229		devices.
1230		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1231
1232		The environment variable 'scsidevs' is set to the number of
1233		SCSI devices found during the last scan.
1234
1235- NETWORK Support (PCI):
1236		CONFIG_E1000
1237		Support for Intel 8254x/8257x gigabit chips.
1238
1239		CONFIG_E1000_SPI
1240		Utility code for direct access to the SPI bus on Intel 8257x.
1241		This does not do anything useful unless you set at least one
1242		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1243
1244		CONFIG_E1000_SPI_GENERIC
1245		Allow generic access to the SPI bus on the Intel 8257x, for
1246		example with the "sspi" command.
1247
1248		CONFIG_CMD_E1000
1249		Management command for E1000 devices.  When used on devices
1250		with SPI support you can reprogram the EEPROM from U-Boot.
1251
1252		CONFIG_E1000_FALLBACK_MAC
1253		default MAC for empty EEPROM after production.
1254
1255		CONFIG_EEPRO100
1256		Support for Intel 82557/82559/82559ER chips.
1257		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1258		write routine for first time initialisation.
1259
1260		CONFIG_TULIP
1261		Support for Digital 2114x chips.
1262		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1263		modem chip initialisation (KS8761/QS6611).
1264
1265		CONFIG_NATSEMI
1266		Support for National dp83815 chips.
1267
1268		CONFIG_NS8382X
1269		Support for National dp8382[01] gigabit chips.
1270
1271- NETWORK Support (other):
1272
1273		CONFIG_DRIVER_AT91EMAC
1274		Support for AT91RM9200 EMAC.
1275
1276			CONFIG_RMII
1277			Define this to use reduced MII inteface
1278
1279			CONFIG_DRIVER_AT91EMAC_QUIET
1280			If this defined, the driver is quiet.
1281			The driver doen't show link status messages.
1282
1283		CONFIG_CALXEDA_XGMAC
1284		Support for the Calxeda XGMAC device
1285
1286		CONFIG_LAN91C96
1287		Support for SMSC's LAN91C96 chips.
1288
1289			CONFIG_LAN91C96_BASE
1290			Define this to hold the physical address
1291			of the LAN91C96's I/O space
1292
1293			CONFIG_LAN91C96_USE_32_BIT
1294			Define this to enable 32 bit addressing
1295
1296		CONFIG_SMC91111
1297		Support for SMSC's LAN91C111 chip
1298
1299			CONFIG_SMC91111_BASE
1300			Define this to hold the physical address
1301			of the device (I/O space)
1302
1303			CONFIG_SMC_USE_32_BIT
1304			Define this if data bus is 32 bits
1305
1306			CONFIG_SMC_USE_IOFUNCS
1307			Define this to use i/o functions instead of macros
1308			(some hardware wont work with macros)
1309
1310		CONFIG_DRIVER_TI_EMAC
1311		Support for davinci emac
1312
1313			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1314			Define this if you have more then 3 PHYs.
1315
1316		CONFIG_FTGMAC100
1317		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1318
1319			CONFIG_FTGMAC100_EGIGA
1320			Define this to use GE link update with gigabit PHY.
1321			Define this if FTGMAC100 is connected to gigabit PHY.
1322			If your system has 10/100 PHY only, it might not occur
1323			wrong behavior. Because PHY usually return timeout or
1324			useless data when polling gigabit status and gigabit
1325			control registers. This behavior won't affect the
1326			correctnessof 10/100 link speed update.
1327
1328		CONFIG_SMC911X
1329		Support for SMSC's LAN911x and LAN921x chips
1330
1331			CONFIG_SMC911X_BASE
1332			Define this to hold the physical address
1333			of the device (I/O space)
1334
1335			CONFIG_SMC911X_32_BIT
1336			Define this if data bus is 32 bits
1337
1338			CONFIG_SMC911X_16_BIT
1339			Define this if data bus is 16 bits. If your processor
1340			automatically converts one 32 bit word to two 16 bit
1341			words you may also try CONFIG_SMC911X_32_BIT.
1342
1343		CONFIG_SH_ETHER
1344		Support for Renesas on-chip Ethernet controller
1345
1346			CONFIG_SH_ETHER_USE_PORT
1347			Define the number of ports to be used
1348
1349			CONFIG_SH_ETHER_PHY_ADDR
1350			Define the ETH PHY's address
1351
1352			CONFIG_SH_ETHER_CACHE_WRITEBACK
1353			If this option is set, the driver enables cache flush.
1354
1355- TPM Support:
1356		CONFIG_TPM
1357		Support TPM devices.
1358
1359		CONFIG_TPM_TIS_I2C
1360		Support for i2c bus TPM devices. Only one device
1361		per system is supported at this time.
1362
1363			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1364			Define the the i2c bus number for the TPM device
1365
1366			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1367			Define the TPM's address on the i2c bus
1368
1369			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1370			Define the burst count bytes upper limit
1371
1372		CONFIG_TPM_ATMEL_TWI
1373		Support for Atmel TWI TPM device. Requires I2C support.
1374
1375		CONFIG_TPM_TIS_LPC
1376		Support for generic parallel port TPM devices. Only one device
1377		per system is supported at this time.
1378
1379			CONFIG_TPM_TIS_BASE_ADDRESS
1380			Base address where the generic TPM device is mapped
1381			to. Contemporary x86 systems usually map it at
1382			0xfed40000.
1383
1384		CONFIG_CMD_TPM
1385		Add tpm monitor functions.
1386		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1387		provides monitor access to authorized functions.
1388
1389		CONFIG_TPM
1390		Define this to enable the TPM support library which provides
1391		functional interfaces to some TPM commands.
1392		Requires support for a TPM device.
1393
1394		CONFIG_TPM_AUTH_SESSIONS
1395		Define this to enable authorized functions in the TPM library.
1396		Requires CONFIG_TPM and CONFIG_SHA1.
1397
1398- USB Support:
1399		At the moment only the UHCI host controller is
1400		supported (PIP405, MIP405, MPC5200); define
1401		CONFIG_USB_UHCI to enable it.
1402		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1403		and define CONFIG_USB_STORAGE to enable the USB
1404		storage devices.
1405		Note:
1406		Supported are USB Keyboards and USB Floppy drives
1407		(TEAC FD-05PUB).
1408		MPC5200 USB requires additional defines:
1409			CONFIG_USB_CLOCK
1410				for 528 MHz Clock: 0x0001bbbb
1411			CONFIG_PSC3_USB
1412				for USB on PSC3
1413			CONFIG_USB_CONFIG
1414				for differential drivers: 0x00001000
1415				for single ended drivers: 0x00005000
1416				for differential drivers on PSC3: 0x00000100
1417				for single ended drivers on PSC3: 0x00004100
1418			CONFIG_SYS_USB_EVENT_POLL
1419				May be defined to allow interrupt polling
1420				instead of using asynchronous interrupts
1421
1422		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1423		txfilltuning field in the EHCI controller on reset.
1424
1425		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1426		interval for usb hub power-on delay.(minimum 100msec)
1427
1428- USB Device:
1429		Define the below if you wish to use the USB console.
1430		Once firmware is rebuilt from a serial console issue the
1431		command "setenv stdin usbtty; setenv stdout usbtty" and
1432		attach your USB cable. The Unix command "dmesg" should print
1433		it has found a new device. The environment variable usbtty
1434		can be set to gserial or cdc_acm to enable your device to
1435		appear to a USB host as a Linux gserial device or a
1436		Common Device Class Abstract Control Model serial device.
1437		If you select usbtty = gserial you should be able to enumerate
1438		a Linux host by
1439		# modprobe usbserial vendor=0xVendorID product=0xProductID
1440		else if using cdc_acm, simply setting the environment
1441		variable usbtty to be cdc_acm should suffice. The following
1442		might be defined in YourBoardName.h
1443
1444			CONFIG_USB_DEVICE
1445			Define this to build a UDC device
1446
1447			CONFIG_USB_TTY
1448			Define this to have a tty type of device available to
1449			talk to the UDC device
1450
1451			CONFIG_USBD_HS
1452			Define this to enable the high speed support for usb
1453			device and usbtty. If this feature is enabled, a routine
1454			int is_usbd_high_speed(void)
1455			also needs to be defined by the driver to dynamically poll
1456			whether the enumeration has succeded at high speed or full
1457			speed.
1458
1459			CONFIG_SYS_CONSOLE_IS_IN_ENV
1460			Define this if you want stdin, stdout &/or stderr to
1461			be set to usbtty.
1462
1463			mpc8xx:
1464				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1465				Derive USB clock from external clock "blah"
1466				- CONFIG_SYS_USB_EXTC_CLK 0x02
1467
1468				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1469				Derive USB clock from brgclk
1470				- CONFIG_SYS_USB_BRG_CLK 0x04
1471
1472		If you have a USB-IF assigned VendorID then you may wish to
1473		define your own vendor specific values either in BoardName.h
1474		or directly in usbd_vendor_info.h. If you don't define
1475		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1476		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1477		should pretend to be a Linux device to it's target host.
1478
1479			CONFIG_USBD_MANUFACTURER
1480			Define this string as the name of your company for
1481			- CONFIG_USBD_MANUFACTURER "my company"
1482
1483			CONFIG_USBD_PRODUCT_NAME
1484			Define this string as the name of your product
1485			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1486
1487			CONFIG_USBD_VENDORID
1488			Define this as your assigned Vendor ID from the USB
1489			Implementors Forum. This *must* be a genuine Vendor ID
1490			to avoid polluting the USB namespace.
1491			- CONFIG_USBD_VENDORID 0xFFFF
1492
1493			CONFIG_USBD_PRODUCTID
1494			Define this as the unique Product ID
1495			for your device
1496			- CONFIG_USBD_PRODUCTID 0xFFFF
1497
1498- ULPI Layer Support:
1499		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1500		the generic ULPI layer. The generic layer accesses the ULPI PHY
1501		via the platform viewport, so you need both the genric layer and
1502		the viewport enabled. Currently only Chipidea/ARC based
1503		viewport is supported.
1504		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1505		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1506		If your ULPI phy needs a different reference clock than the
1507		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1508		the appropriate value in Hz.
1509
1510- MMC Support:
1511		The MMC controller on the Intel PXA is supported. To
1512		enable this define CONFIG_MMC. The MMC can be
1513		accessed from the boot prompt by mapping the device
1514		to physical memory similar to flash. Command line is
1515		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1516		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1517
1518		CONFIG_SH_MMCIF
1519		Support for Renesas on-chip MMCIF controller
1520
1521			CONFIG_SH_MMCIF_ADDR
1522			Define the base address of MMCIF registers
1523
1524			CONFIG_SH_MMCIF_CLK
1525			Define the clock frequency for MMCIF
1526
1527- USB Device Firmware Update (DFU) class support:
1528		CONFIG_DFU_FUNCTION
1529		This enables the USB portion of the DFU USB class
1530
1531		CONFIG_CMD_DFU
1532		This enables the command "dfu" which is used to have
1533		U-Boot create a DFU class device via USB.  This command
1534		requires that the "dfu_alt_info" environment variable be
1535		set and define the alt settings to expose to the host.
1536
1537		CONFIG_DFU_MMC
1538		This enables support for exposing (e)MMC devices via DFU.
1539
1540		CONFIG_DFU_NAND
1541		This enables support for exposing NAND devices via DFU.
1542
1543		CONFIG_DFU_RAM
1544		This enables support for exposing RAM via DFU.
1545		Note: DFU spec refer to non-volatile memory usage, but
1546		allow usages beyond the scope of spec - here RAM usage,
1547		one that would help mostly the developer.
1548
1549		CONFIG_SYS_DFU_DATA_BUF_SIZE
1550		Dfu transfer uses a buffer before writing data to the
1551		raw storage device. Make the size (in bytes) of this buffer
1552		configurable. The size of this buffer is also configurable
1553		through the "dfu_bufsiz" environment variable.
1554
1555		CONFIG_SYS_DFU_MAX_FILE_SIZE
1556		When updating files rather than the raw storage device,
1557		we use a static buffer to copy the file into and then write
1558		the buffer once we've been given the whole file.  Define
1559		this to the maximum filesize (in bytes) for the buffer.
1560		Default is 4 MiB if undefined.
1561
1562		DFU_DEFAULT_POLL_TIMEOUT
1563		Poll timeout [ms], is the timeout a device can send to the
1564		host. The host must wait for this timeout before sending
1565		a subsequent DFU_GET_STATUS request to the device.
1566
1567		DFU_MANIFEST_POLL_TIMEOUT
1568		Poll timeout [ms], which the device sends to the host when
1569		entering dfuMANIFEST state. Host waits this timeout, before
1570		sending again an USB request to the device.
1571
1572- Journaling Flash filesystem support:
1573		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1574		CONFIG_JFFS2_NAND_DEV
1575		Define these for a default partition on a NAND device
1576
1577		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1578		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1579		Define these for a default partition on a NOR device
1580
1581		CONFIG_SYS_JFFS_CUSTOM_PART
1582		Define this to create an own partition. You have to provide a
1583		function struct part_info* jffs2_part_info(int part_num)
1584
1585		If you define only one JFFS2 partition you may also want to
1586		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1587		to disable the command chpart. This is the default when you
1588		have not defined a custom partition
1589
1590- FAT(File Allocation Table) filesystem write function support:
1591		CONFIG_FAT_WRITE
1592
1593		Define this to enable support for saving memory data as a
1594		file in FAT formatted partition.
1595
1596		This will also enable the command "fatwrite" enabling the
1597		user to write files to FAT.
1598
1599CBFS (Coreboot Filesystem) support
1600		CONFIG_CMD_CBFS
1601
1602		Define this to enable support for reading from a Coreboot
1603		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1604		and cbfsload.
1605
1606- Keyboard Support:
1607		CONFIG_ISA_KEYBOARD
1608
1609		Define this to enable standard (PC-Style) keyboard
1610		support
1611
1612		CONFIG_I8042_KBD
1613		Standard PC keyboard driver with US (is default) and
1614		GERMAN key layout (switch via environment 'keymap=de') support.
1615		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1616		for cfb_console. Supports cursor blinking.
1617
1618		CONFIG_CROS_EC_KEYB
1619		Enables a Chrome OS keyboard using the CROS_EC interface.
1620		This uses CROS_EC to communicate with a second microcontroller
1621		which provides key scans on request.
1622
1623- Video support:
1624		CONFIG_VIDEO
1625
1626		Define this to enable video support (for output to
1627		video).
1628
1629		CONFIG_VIDEO_CT69000
1630
1631		Enable Chips & Technologies 69000 Video chip
1632
1633		CONFIG_VIDEO_SMI_LYNXEM
1634		Enable Silicon Motion SMI 712/710/810 Video chip. The
1635		video output is selected via environment 'videoout'
1636		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1637		assumed.
1638
1639		For the CT69000 and SMI_LYNXEM drivers, videomode is
1640		selected via environment 'videomode'. Two different ways
1641		are possible:
1642		- "videomode=num"   'num' is a standard LiLo mode numbers.
1643		Following standard modes are supported	(* is default):
1644
1645		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1646		-------------+---------------------------------------------
1647		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1648		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1649		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1650		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1651		-------------+---------------------------------------------
1652		(i.e. setenv videomode 317; saveenv; reset;)
1653
1654		- "videomode=bootargs" all the video parameters are parsed
1655		from the bootargs. (See drivers/video/videomodes.c)
1656
1657
1658		CONFIG_VIDEO_SED13806
1659		Enable Epson SED13806 driver. This driver supports 8bpp
1660		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1661		or CONFIG_VIDEO_SED13806_16BPP
1662
1663		CONFIG_FSL_DIU_FB
1664		Enable the Freescale DIU video driver.	Reference boards for
1665		SOCs that have a DIU should define this macro to enable DIU
1666		support, and should also define these other macros:
1667
1668			CONFIG_SYS_DIU_ADDR
1669			CONFIG_VIDEO
1670			CONFIG_CMD_BMP
1671			CONFIG_CFB_CONSOLE
1672			CONFIG_VIDEO_SW_CURSOR
1673			CONFIG_VGA_AS_SINGLE_DEVICE
1674			CONFIG_VIDEO_LOGO
1675			CONFIG_VIDEO_BMP_LOGO
1676
1677		The DIU driver will look for the 'video-mode' environment
1678		variable, and if defined, enable the DIU as a console during
1679		boot.  See the documentation file README.video for a
1680		description of this variable.
1681
1682		CONFIG_VIDEO_VGA
1683
1684		Enable the VGA video / BIOS for x86. The alternative if you
1685		are using coreboot is to use the coreboot frame buffer
1686		driver.
1687
1688
1689- Keyboard Support:
1690		CONFIG_KEYBOARD
1691
1692		Define this to enable a custom keyboard support.
1693		This simply calls drv_keyboard_init() which must be
1694		defined in your board-specific files.
1695		The only board using this so far is RBC823.
1696
1697- LCD Support:	CONFIG_LCD
1698
1699		Define this to enable LCD support (for output to LCD
1700		display); also select one of the supported displays
1701		by defining one of these:
1702
1703		CONFIG_ATMEL_LCD:
1704
1705			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1706
1707		CONFIG_NEC_NL6448AC33:
1708
1709			NEC NL6448AC33-18. Active, color, single scan.
1710
1711		CONFIG_NEC_NL6448BC20
1712
1713			NEC NL6448BC20-08. 6.5", 640x480.
1714			Active, color, single scan.
1715
1716		CONFIG_NEC_NL6448BC33_54
1717
1718			NEC NL6448BC33-54. 10.4", 640x480.
1719			Active, color, single scan.
1720
1721		CONFIG_SHARP_16x9
1722
1723			Sharp 320x240. Active, color, single scan.
1724			It isn't 16x9, and I am not sure what it is.
1725
1726		CONFIG_SHARP_LQ64D341
1727
1728			Sharp LQ64D341 display, 640x480.
1729			Active, color, single scan.
1730
1731		CONFIG_HLD1045
1732
1733			HLD1045 display, 640x480.
1734			Active, color, single scan.
1735
1736		CONFIG_OPTREX_BW
1737
1738			Optrex	 CBL50840-2 NF-FW 99 22 M5
1739			or
1740			Hitachi	 LMG6912RPFC-00T
1741			or
1742			Hitachi	 SP14Q002
1743
1744			320x240. Black & white.
1745
1746		Normally display is black on white background; define
1747		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1748
1749		CONFIG_LCD_ALIGNMENT
1750
1751		Normally the LCD is page-aligned (tyically 4KB). If this is
1752		defined then the LCD will be aligned to this value instead.
1753		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1754		here, since it is cheaper to change data cache settings on
1755		a per-section basis.
1756
1757		CONFIG_CONSOLE_SCROLL_LINES
1758
1759		When the console need to be scrolled, this is the number of
1760		lines to scroll by. It defaults to 1. Increasing this makes
1761		the console jump but can help speed up operation when scrolling
1762		is slow.
1763
1764		CONFIG_LCD_BMP_RLE8
1765
1766		Support drawing of RLE8-compressed bitmaps on the LCD.
1767
1768		CONFIG_I2C_EDID
1769
1770		Enables an 'i2c edid' command which can read EDID
1771		information over I2C from an attached LCD display.
1772
1773- Splash Screen Support: CONFIG_SPLASH_SCREEN
1774
1775		If this option is set, the environment is checked for
1776		a variable "splashimage". If found, the usual display
1777		of logo, copyright and system information on the LCD
1778		is suppressed and the BMP image at the address
1779		specified in "splashimage" is loaded instead. The
1780		console is redirected to the "nulldev", too. This
1781		allows for a "silent" boot where a splash screen is
1782		loaded very quickly after power-on.
1783
1784		CONFIG_SPLASHIMAGE_GUARD
1785
1786		If this option is set, then U-Boot will prevent the environment
1787		variable "splashimage" from being set to a problematic address
1788		(see README.displaying-bmps).
1789		This option is useful for targets where, due to alignment
1790		restrictions, an improperly aligned BMP image will cause a data
1791		abort. If you think you will not have problems with unaligned
1792		accesses (for example because your toolchain prevents them)
1793		there is no need to set this option.
1794
1795		CONFIG_SPLASH_SCREEN_ALIGN
1796
1797		If this option is set the splash image can be freely positioned
1798		on the screen. Environment variable "splashpos" specifies the
1799		position as "x,y". If a positive number is given it is used as
1800		number of pixel from left/top. If a negative number is given it
1801		is used as number of pixel from right/bottom. You can also
1802		specify 'm' for centering the image.
1803
1804		Example:
1805		setenv splashpos m,m
1806			=> image at center of screen
1807
1808		setenv splashpos 30,20
1809			=> image at x = 30 and y = 20
1810
1811		setenv splashpos -10,m
1812			=> vertically centered image
1813			   at x = dspWidth - bmpWidth - 9
1814
1815- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1816
1817		If this option is set, additionally to standard BMP
1818		images, gzipped BMP images can be displayed via the
1819		splashscreen support or the bmp command.
1820
1821- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1822
1823		If this option is set, 8-bit RLE compressed BMP images
1824		can be displayed via the splashscreen support or the
1825		bmp command.
1826
1827- Do compresssing for memory range:
1828		CONFIG_CMD_ZIP
1829
1830		If this option is set, it would use zlib deflate method
1831		to compress the specified memory at its best effort.
1832
1833- Compression support:
1834		CONFIG_GZIP
1835
1836		Enabled by default to support gzip compressed images.
1837
1838		CONFIG_BZIP2
1839
1840		If this option is set, support for bzip2 compressed
1841		images is included. If not, only uncompressed and gzip
1842		compressed images are supported.
1843
1844		NOTE: the bzip2 algorithm requires a lot of RAM, so
1845		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1846		be at least 4MB.
1847
1848		CONFIG_LZMA
1849
1850		If this option is set, support for lzma compressed
1851		images is included.
1852
1853		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1854		requires an amount of dynamic memory that is given by the
1855		formula:
1856
1857			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1858
1859		Where lc and lp stand for, respectively, Literal context bits
1860		and Literal pos bits.
1861
1862		This value is upper-bounded by 14MB in the worst case. Anyway,
1863		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1864		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1865		a very small buffer.
1866
1867		Use the lzmainfo tool to determinate the lc and lp values and
1868		then calculate the amount of needed dynamic memory (ensuring
1869		the appropriate CONFIG_SYS_MALLOC_LEN value).
1870
1871		CONFIG_LZO
1872
1873		If this option is set, support for LZO compressed images
1874		is included.
1875
1876- MII/PHY support:
1877		CONFIG_PHY_ADDR
1878
1879		The address of PHY on MII bus.
1880
1881		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1882
1883		The clock frequency of the MII bus
1884
1885		CONFIG_PHY_GIGE
1886
1887		If this option is set, support for speed/duplex
1888		detection of gigabit PHY is included.
1889
1890		CONFIG_PHY_RESET_DELAY
1891
1892		Some PHY like Intel LXT971A need extra delay after
1893		reset before any MII register access is possible.
1894		For such PHY, set this option to the usec delay
1895		required. (minimum 300usec for LXT971A)
1896
1897		CONFIG_PHY_CMD_DELAY (ppc4xx)
1898
1899		Some PHY like Intel LXT971A need extra delay after
1900		command issued before MII status register can be read
1901
1902- Ethernet address:
1903		CONFIG_ETHADDR
1904		CONFIG_ETH1ADDR
1905		CONFIG_ETH2ADDR
1906		CONFIG_ETH3ADDR
1907		CONFIG_ETH4ADDR
1908		CONFIG_ETH5ADDR
1909
1910		Define a default value for Ethernet address to use
1911		for the respective Ethernet interface, in case this
1912		is not determined automatically.
1913
1914- IP address:
1915		CONFIG_IPADDR
1916
1917		Define a default value for the IP address to use for
1918		the default Ethernet interface, in case this is not
1919		determined through e.g. bootp.
1920		(Environment variable "ipaddr")
1921
1922- Server IP address:
1923		CONFIG_SERVERIP
1924
1925		Defines a default value for the IP address of a TFTP
1926		server to contact when using the "tftboot" command.
1927		(Environment variable "serverip")
1928
1929		CONFIG_KEEP_SERVERADDR
1930
1931		Keeps the server's MAC address, in the env 'serveraddr'
1932		for passing to bootargs (like Linux's netconsole option)
1933
1934- Gateway IP address:
1935		CONFIG_GATEWAYIP
1936
1937		Defines a default value for the IP address of the
1938		default router where packets to other networks are
1939		sent to.
1940		(Environment variable "gatewayip")
1941
1942- Subnet mask:
1943		CONFIG_NETMASK
1944
1945		Defines a default value for the subnet mask (or
1946		routing prefix) which is used to determine if an IP
1947		address belongs to the local subnet or needs to be
1948		forwarded through a router.
1949		(Environment variable "netmask")
1950
1951- Multicast TFTP Mode:
1952		CONFIG_MCAST_TFTP
1953
1954		Defines whether you want to support multicast TFTP as per
1955		rfc-2090; for example to work with atftp.  Lets lots of targets
1956		tftp down the same boot image concurrently.  Note: the Ethernet
1957		driver in use must provide a function: mcast() to join/leave a
1958		multicast group.
1959
1960- BOOTP Recovery Mode:
1961		CONFIG_BOOTP_RANDOM_DELAY
1962
1963		If you have many targets in a network that try to
1964		boot using BOOTP, you may want to avoid that all
1965		systems send out BOOTP requests at precisely the same
1966		moment (which would happen for instance at recovery
1967		from a power failure, when all systems will try to
1968		boot, thus flooding the BOOTP server. Defining
1969		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1970		inserted before sending out BOOTP requests. The
1971		following delays are inserted then:
1972
1973		1st BOOTP request:	delay 0 ... 1 sec
1974		2nd BOOTP request:	delay 0 ... 2 sec
1975		3rd BOOTP request:	delay 0 ... 4 sec
1976		4th and following
1977		BOOTP requests:		delay 0 ... 8 sec
1978
1979- DHCP Advanced Options:
1980		You can fine tune the DHCP functionality by defining
1981		CONFIG_BOOTP_* symbols:
1982
1983		CONFIG_BOOTP_SUBNETMASK
1984		CONFIG_BOOTP_GATEWAY
1985		CONFIG_BOOTP_HOSTNAME
1986		CONFIG_BOOTP_NISDOMAIN
1987		CONFIG_BOOTP_BOOTPATH
1988		CONFIG_BOOTP_BOOTFILESIZE
1989		CONFIG_BOOTP_DNS
1990		CONFIG_BOOTP_DNS2
1991		CONFIG_BOOTP_SEND_HOSTNAME
1992		CONFIG_BOOTP_NTPSERVER
1993		CONFIG_BOOTP_TIMEOFFSET
1994		CONFIG_BOOTP_VENDOREX
1995		CONFIG_BOOTP_MAY_FAIL
1996
1997		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1998		environment variable, not the BOOTP server.
1999
2000		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2001		after the configured retry count, the call will fail
2002		instead of starting over.  This can be used to fail over
2003		to Link-local IP address configuration if the DHCP server
2004		is not available.
2005
2006		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2007		serverip from a DHCP server, it is possible that more
2008		than one DNS serverip is offered to the client.
2009		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2010		serverip will be stored in the additional environment
2011		variable "dnsip2". The first DNS serverip is always
2012		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2013		is defined.
2014
2015		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2016		to do a dynamic update of a DNS server. To do this, they
2017		need the hostname of the DHCP requester.
2018		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2019		of the "hostname" environment variable is passed as
2020		option 12 to the DHCP server.
2021
2022		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2023
2024		A 32bit value in microseconds for a delay between
2025		receiving a "DHCP Offer" and sending the "DHCP Request".
2026		This fixes a problem with certain DHCP servers that don't
2027		respond 100% of the time to a "DHCP request". E.g. On an
2028		AT91RM9200 processor running at 180MHz, this delay needed
2029		to be *at least* 15,000 usec before a Windows Server 2003
2030		DHCP server would reply 100% of the time. I recommend at
2031		least 50,000 usec to be safe. The alternative is to hope
2032		that one of the retries will be successful but note that
2033		the DHCP timeout and retry process takes a longer than
2034		this delay.
2035
2036 - Link-local IP address negotiation:
2037		Negotiate with other link-local clients on the local network
2038		for an address that doesn't require explicit configuration.
2039		This is especially useful if a DHCP server cannot be guaranteed
2040		to exist in all environments that the device must operate.
2041
2042		See doc/README.link-local for more information.
2043
2044 - CDP Options:
2045		CONFIG_CDP_DEVICE_ID
2046
2047		The device id used in CDP trigger frames.
2048
2049		CONFIG_CDP_DEVICE_ID_PREFIX
2050
2051		A two character string which is prefixed to the MAC address
2052		of the device.
2053
2054		CONFIG_CDP_PORT_ID
2055
2056		A printf format string which contains the ascii name of
2057		the port. Normally is set to "eth%d" which sets
2058		eth0 for the first Ethernet, eth1 for the second etc.
2059
2060		CONFIG_CDP_CAPABILITIES
2061
2062		A 32bit integer which indicates the device capabilities;
2063		0x00000010 for a normal host which does not forwards.
2064
2065		CONFIG_CDP_VERSION
2066
2067		An ascii string containing the version of the software.
2068
2069		CONFIG_CDP_PLATFORM
2070
2071		An ascii string containing the name of the platform.
2072
2073		CONFIG_CDP_TRIGGER
2074
2075		A 32bit integer sent on the trigger.
2076
2077		CONFIG_CDP_POWER_CONSUMPTION
2078
2079		A 16bit integer containing the power consumption of the
2080		device in .1 of milliwatts.
2081
2082		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2083
2084		A byte containing the id of the VLAN.
2085
2086- Status LED:	CONFIG_STATUS_LED
2087
2088		Several configurations allow to display the current
2089		status using a LED. For instance, the LED will blink
2090		fast while running U-Boot code, stop blinking as
2091		soon as a reply to a BOOTP request was received, and
2092		start blinking slow once the Linux kernel is running
2093		(supported by a status LED driver in the Linux
2094		kernel). Defining CONFIG_STATUS_LED enables this
2095		feature in U-Boot.
2096
2097		Additional options:
2098
2099		CONFIG_GPIO_LED
2100		The status LED can be connected to a GPIO pin.
2101		In such cases, the gpio_led driver can be used as a
2102		status LED backend implementation. Define CONFIG_GPIO_LED
2103		to include the gpio_led driver in the U-Boot binary.
2104
2105		CONFIG_GPIO_LED_INVERTED_TABLE
2106		Some GPIO connected LEDs may have inverted polarity in which
2107		case the GPIO high value corresponds to LED off state and
2108		GPIO low value corresponds to LED on state.
2109		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2110		with a list of GPIO LEDs that have inverted polarity.
2111
2112- CAN Support:	CONFIG_CAN_DRIVER
2113
2114		Defining CONFIG_CAN_DRIVER enables CAN driver support
2115		on those systems that support this (optional)
2116		feature, like the TQM8xxL modules.
2117
2118- I2C Support:	CONFIG_SYS_I2C
2119
2120		This enable the NEW i2c subsystem, and will allow you to use
2121		i2c commands at the u-boot command line (as long as you set
2122		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2123		based realtime clock chips or other i2c devices. See
2124		common/cmd_i2c.c for a description of the command line
2125		interface.
2126
2127		ported i2c driver to the new framework:
2128		- drivers/i2c/soft_i2c.c:
2129		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2130		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2131		    for defining speed and slave address
2132		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2133		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2134		    for defining speed and slave address
2135		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2136		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2137		    for defining speed and slave address
2138		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2139		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2140		    for defining speed and slave address
2141
2142		- drivers/i2c/fsl_i2c.c:
2143		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2144		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2145		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2146		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2147		    bus.
2148		  - If your board supports a second fsl i2c bus, define
2149		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2150		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2151		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2152		    second bus.
2153
2154		- drivers/i2c/tegra_i2c.c:
2155		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2156		  - This driver adds 4 i2c buses with a fix speed from
2157		    100000 and the slave addr 0!
2158
2159		- drivers/i2c/ppc4xx_i2c.c
2160		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2161		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2162		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2163
2164		- drivers/i2c/i2c_mxc.c
2165		  - activate this driver with CONFIG_SYS_I2C_MXC
2166		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2167		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2168		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2169		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2170		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2171		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2172		If thoses defines are not set, default value is 100000
2173		for speed, and 0 for slave.
2174
2175		- drivers/i2c/rcar_i2c.c:
2176		  - activate this driver with CONFIG_SYS_I2C_RCAR
2177		  - This driver adds 4 i2c buses
2178
2179		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2180		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2181		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2182		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2183		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2184		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2185		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2186		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2187		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2188
2189		- drivers/i2c/sh_i2c.c:
2190		  - activate this driver with CONFIG_SYS_I2C_SH
2191		  - This driver adds from 2 to 5 i2c buses
2192
2193		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2194		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2195		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2196		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2197		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2198		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2199		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2200		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2201		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2202		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2203		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2204		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2205		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2206
2207		- drivers/i2c/omap24xx_i2c.c
2208		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2209		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2210		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2211		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2212		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2213		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2214		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2215		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2216		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2217		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2218		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2219
2220		- drivers/i2c/zynq_i2c.c
2221		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2222		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2223		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2224
2225		- drivers/i2c/s3c24x0_i2c.c:
2226		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2227		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2228		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2229		    with a fix speed from 100000 and the slave addr 0!
2230
2231		additional defines:
2232
2233		CONFIG_SYS_NUM_I2C_BUSES
2234		Hold the number of i2c busses you want to use. If you
2235		don't use/have i2c muxes on your i2c bus, this
2236		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2237		omit this define.
2238
2239		CONFIG_SYS_I2C_DIRECT_BUS
2240		define this, if you don't use i2c muxes on your hardware.
2241		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2242		omit this define.
2243
2244		CONFIG_SYS_I2C_MAX_HOPS
2245		define how many muxes are maximal consecutively connected
2246		on one i2c bus. If you not use i2c muxes, omit this
2247		define.
2248
2249		CONFIG_SYS_I2C_BUSES
2250		hold a list of busses you want to use, only used if
2251		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2252		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2253		CONFIG_SYS_NUM_I2C_BUSES = 9:
2254
2255		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2256					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2257					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2258					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2259					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2260					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2261					{1, {I2C_NULL_HOP}}, \
2262					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2263					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2264					}
2265
2266		which defines
2267			bus 0 on adapter 0 without a mux
2268			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2269			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2270			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2271			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2272			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2273			bus 6 on adapter 1 without a mux
2274			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2275			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2276
2277		If you do not have i2c muxes on your board, omit this define.
2278
2279- Legacy I2C Support:	CONFIG_HARD_I2C
2280
2281		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2282		provides the following compelling advantages:
2283
2284		- more than one i2c adapter is usable
2285		- approved multibus support
2286		- better i2c mux support
2287
2288		** Please consider updating your I2C driver now. **
2289
2290		These enable legacy I2C serial bus commands. Defining
2291		CONFIG_HARD_I2C will include the appropriate I2C driver
2292		for the selected CPU.
2293
2294		This will allow you to use i2c commands at the u-boot
2295		command line (as long as you set CONFIG_CMD_I2C in
2296		CONFIG_COMMANDS) and communicate with i2c based realtime
2297		clock chips. See common/cmd_i2c.c for a description of the
2298		command line interface.
2299
2300		CONFIG_HARD_I2C selects a hardware I2C controller.
2301
2302		There are several other quantities that must also be
2303		defined when you define CONFIG_HARD_I2C.
2304
2305		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2306		to be the frequency (in Hz) at which you wish your i2c bus
2307		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2308		the CPU's i2c node address).
2309
2310		Now, the u-boot i2c code for the mpc8xx
2311		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2312		and so its address should therefore be cleared to 0 (See,
2313		eg, MPC823e User's Manual p.16-473). So, set
2314		CONFIG_SYS_I2C_SLAVE to 0.
2315
2316		CONFIG_SYS_I2C_INIT_MPC5XXX
2317
2318		When a board is reset during an i2c bus transfer
2319		chips might think that the current transfer is still
2320		in progress.  Reset the slave devices by sending start
2321		commands until the slave device responds.
2322
2323		That's all that's required for CONFIG_HARD_I2C.
2324
2325		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2326		then the following macros need to be defined (examples are
2327		from include/configs/lwmon.h):
2328
2329		I2C_INIT
2330
2331		(Optional). Any commands necessary to enable the I2C
2332		controller or configure ports.
2333
2334		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2335
2336		I2C_PORT
2337
2338		(Only for MPC8260 CPU). The I/O port to use (the code
2339		assumes both bits are on the same port). Valid values
2340		are 0..3 for ports A..D.
2341
2342		I2C_ACTIVE
2343
2344		The code necessary to make the I2C data line active
2345		(driven).  If the data line is open collector, this
2346		define can be null.
2347
2348		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2349
2350		I2C_TRISTATE
2351
2352		The code necessary to make the I2C data line tri-stated
2353		(inactive).  If the data line is open collector, this
2354		define can be null.
2355
2356		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2357
2358		I2C_READ
2359
2360		Code that returns true if the I2C data line is high,
2361		false if it is low.
2362
2363		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2364
2365		I2C_SDA(bit)
2366
2367		If <bit> is true, sets the I2C data line high. If it
2368		is false, it clears it (low).
2369
2370		eg: #define I2C_SDA(bit) \
2371			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2372			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2373
2374		I2C_SCL(bit)
2375
2376		If <bit> is true, sets the I2C clock line high. If it
2377		is false, it clears it (low).
2378
2379		eg: #define I2C_SCL(bit) \
2380			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2381			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2382
2383		I2C_DELAY
2384
2385		This delay is invoked four times per clock cycle so this
2386		controls the rate of data transfer.  The data rate thus
2387		is 1 / (I2C_DELAY * 4). Often defined to be something
2388		like:
2389
2390		#define I2C_DELAY  udelay(2)
2391
2392		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2393
2394		If your arch supports the generic GPIO framework (asm/gpio.h),
2395		then you may alternatively define the two GPIOs that are to be
2396		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2397		have GPIO-based defaults assigned to them as appropriate.
2398
2399		You should define these to the GPIO value as given directly to
2400		the generic GPIO functions.
2401
2402		CONFIG_SYS_I2C_INIT_BOARD
2403
2404		When a board is reset during an i2c bus transfer
2405		chips might think that the current transfer is still
2406		in progress. On some boards it is possible to access
2407		the i2c SCLK line directly, either by using the
2408		processor pin as a GPIO or by having a second pin
2409		connected to the bus. If this option is defined a
2410		custom i2c_init_board() routine in boards/xxx/board.c
2411		is run early in the boot sequence.
2412
2413		CONFIG_SYS_I2C_BOARD_LATE_INIT
2414
2415		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2416		defined a custom i2c_board_late_init() routine in
2417		boards/xxx/board.c is run AFTER the operations in i2c_init()
2418		is completed. This callpoint can be used to unreset i2c bus
2419		using CPU i2c controller register accesses for CPUs whose i2c
2420		controller provide such a method. It is called at the end of
2421		i2c_init() to allow i2c_init operations to setup the i2c bus
2422		controller on the CPU (e.g. setting bus speed & slave address).
2423
2424		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2425
2426		This option enables configuration of bi_iic_fast[] flags
2427		in u-boot bd_info structure based on u-boot environment
2428		variable "i2cfast". (see also i2cfast)
2429
2430		CONFIG_I2C_MULTI_BUS
2431
2432		This option allows the use of multiple I2C buses, each of which
2433		must have a controller.	 At any point in time, only one bus is
2434		active.	 To switch to a different bus, use the 'i2c dev' command.
2435		Note that bus numbering is zero-based.
2436
2437		CONFIG_SYS_I2C_NOPROBES
2438
2439		This option specifies a list of I2C devices that will be skipped
2440		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2441		is set, specify a list of bus-device pairs.  Otherwise, specify
2442		a 1D array of device addresses
2443
2444		e.g.
2445			#undef	CONFIG_I2C_MULTI_BUS
2446			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2447
2448		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2449
2450			#define CONFIG_I2C_MULTI_BUS
2451			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2452
2453		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2454
2455		CONFIG_SYS_SPD_BUS_NUM
2456
2457		If defined, then this indicates the I2C bus number for DDR SPD.
2458		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2459
2460		CONFIG_SYS_RTC_BUS_NUM
2461
2462		If defined, then this indicates the I2C bus number for the RTC.
2463		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2464
2465		CONFIG_SYS_DTT_BUS_NUM
2466
2467		If defined, then this indicates the I2C bus number for the DTT.
2468		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2469
2470		CONFIG_SYS_I2C_DTT_ADDR:
2471
2472		If defined, specifies the I2C address of the DTT device.
2473		If not defined, then U-Boot uses predefined value for
2474		specified DTT device.
2475
2476		CONFIG_SOFT_I2C_READ_REPEATED_START
2477
2478		defining this will force the i2c_read() function in
2479		the soft_i2c driver to perform an I2C repeated start
2480		between writing the address pointer and reading the
2481		data.  If this define is omitted the default behaviour
2482		of doing a stop-start sequence will be used.  Most I2C
2483		devices can use either method, but some require one or
2484		the other.
2485
2486- SPI Support:	CONFIG_SPI
2487
2488		Enables SPI driver (so far only tested with
2489		SPI EEPROM, also an instance works with Crystal A/D and
2490		D/As on the SACSng board)
2491
2492		CONFIG_SH_SPI
2493
2494		Enables the driver for SPI controller on SuperH. Currently
2495		only SH7757 is supported.
2496
2497		CONFIG_SPI_X
2498
2499		Enables extended (16-bit) SPI EEPROM addressing.
2500		(symmetrical to CONFIG_I2C_X)
2501
2502		CONFIG_SOFT_SPI
2503
2504		Enables a software (bit-bang) SPI driver rather than
2505		using hardware support. This is a general purpose
2506		driver that only requires three general I/O port pins
2507		(two outputs, one input) to function. If this is
2508		defined, the board configuration must define several
2509		SPI configuration items (port pins to use, etc). For
2510		an example, see include/configs/sacsng.h.
2511
2512		CONFIG_HARD_SPI
2513
2514		Enables a hardware SPI driver for general-purpose reads
2515		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2516		must define a list of chip-select function pointers.
2517		Currently supported on some MPC8xxx processors.	 For an
2518		example, see include/configs/mpc8349emds.h.
2519
2520		CONFIG_MXC_SPI
2521
2522		Enables the driver for the SPI controllers on i.MX and MXC
2523		SoCs. Currently i.MX31/35/51 are supported.
2524
2525- FPGA Support: CONFIG_FPGA
2526
2527		Enables FPGA subsystem.
2528
2529		CONFIG_FPGA_<vendor>
2530
2531		Enables support for specific chip vendors.
2532		(ALTERA, XILINX)
2533
2534		CONFIG_FPGA_<family>
2535
2536		Enables support for FPGA family.
2537		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2538
2539		CONFIG_FPGA_COUNT
2540
2541		Specify the number of FPGA devices to support.
2542
2543		CONFIG_SYS_FPGA_PROG_FEEDBACK
2544
2545		Enable printing of hash marks during FPGA configuration.
2546
2547		CONFIG_SYS_FPGA_CHECK_BUSY
2548
2549		Enable checks on FPGA configuration interface busy
2550		status by the configuration function. This option
2551		will require a board or device specific function to
2552		be written.
2553
2554		CONFIG_FPGA_DELAY
2555
2556		If defined, a function that provides delays in the FPGA
2557		configuration driver.
2558
2559		CONFIG_SYS_FPGA_CHECK_CTRLC
2560		Allow Control-C to interrupt FPGA configuration
2561
2562		CONFIG_SYS_FPGA_CHECK_ERROR
2563
2564		Check for configuration errors during FPGA bitfile
2565		loading. For example, abort during Virtex II
2566		configuration if the INIT_B line goes low (which
2567		indicated a CRC error).
2568
2569		CONFIG_SYS_FPGA_WAIT_INIT
2570
2571		Maximum time to wait for the INIT_B line to deassert
2572		after PROB_B has been deasserted during a Virtex II
2573		FPGA configuration sequence. The default time is 500
2574		ms.
2575
2576		CONFIG_SYS_FPGA_WAIT_BUSY
2577
2578		Maximum time to wait for BUSY to deassert during
2579		Virtex II FPGA configuration. The default is 5 ms.
2580
2581		CONFIG_SYS_FPGA_WAIT_CONFIG
2582
2583		Time to wait after FPGA configuration. The default is
2584		200 ms.
2585
2586- Configuration Management:
2587		CONFIG_IDENT_STRING
2588
2589		If defined, this string will be added to the U-Boot
2590		version information (U_BOOT_VERSION)
2591
2592- Vendor Parameter Protection:
2593
2594		U-Boot considers the values of the environment
2595		variables "serial#" (Board Serial Number) and
2596		"ethaddr" (Ethernet Address) to be parameters that
2597		are set once by the board vendor / manufacturer, and
2598		protects these variables from casual modification by
2599		the user. Once set, these variables are read-only,
2600		and write or delete attempts are rejected. You can
2601		change this behaviour:
2602
2603		If CONFIG_ENV_OVERWRITE is #defined in your config
2604		file, the write protection for vendor parameters is
2605		completely disabled. Anybody can change or delete
2606		these parameters.
2607
2608		Alternatively, if you #define _both_ CONFIG_ETHADDR
2609		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2610		Ethernet address is installed in the environment,
2611		which can be changed exactly ONCE by the user. [The
2612		serial# is unaffected by this, i. e. it remains
2613		read-only.]
2614
2615		The same can be accomplished in a more flexible way
2616		for any variable by configuring the type of access
2617		to allow for those variables in the ".flags" variable
2618		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2619
2620- Protected RAM:
2621		CONFIG_PRAM
2622
2623		Define this variable to enable the reservation of
2624		"protected RAM", i. e. RAM which is not overwritten
2625		by U-Boot. Define CONFIG_PRAM to hold the number of
2626		kB you want to reserve for pRAM. You can overwrite
2627		this default value by defining an environment
2628		variable "pram" to the number of kB you want to
2629		reserve. Note that the board info structure will
2630		still show the full amount of RAM. If pRAM is
2631		reserved, a new environment variable "mem" will
2632		automatically be defined to hold the amount of
2633		remaining RAM in a form that can be passed as boot
2634		argument to Linux, for instance like that:
2635
2636			setenv bootargs ... mem=\${mem}
2637			saveenv
2638
2639		This way you can tell Linux not to use this memory,
2640		either, which results in a memory region that will
2641		not be affected by reboots.
2642
2643		*WARNING* If your board configuration uses automatic
2644		detection of the RAM size, you must make sure that
2645		this memory test is non-destructive. So far, the
2646		following board configurations are known to be
2647		"pRAM-clean":
2648
2649			IVMS8, IVML24, SPD8xx, TQM8xxL,
2650			HERMES, IP860, RPXlite, LWMON,
2651			FLAGADM, TQM8260
2652
2653- Access to physical memory region (> 4GB)
2654		Some basic support is provided for operations on memory not
2655		normally accessible to U-Boot - e.g. some architectures
2656		support access to more than 4GB of memory on 32-bit
2657		machines using physical address extension or similar.
2658		Define CONFIG_PHYSMEM to access this basic support, which
2659		currently only supports clearing the memory.
2660
2661- Error Recovery:
2662		CONFIG_PANIC_HANG
2663
2664		Define this variable to stop the system in case of a
2665		fatal error, so that you have to reset it manually.
2666		This is probably NOT a good idea for an embedded
2667		system where you want the system to reboot
2668		automatically as fast as possible, but it may be
2669		useful during development since you can try to debug
2670		the conditions that lead to the situation.
2671
2672		CONFIG_NET_RETRY_COUNT
2673
2674		This variable defines the number of retries for
2675		network operations like ARP, RARP, TFTP, or BOOTP
2676		before giving up the operation. If not defined, a
2677		default value of 5 is used.
2678
2679		CONFIG_ARP_TIMEOUT
2680
2681		Timeout waiting for an ARP reply in milliseconds.
2682
2683		CONFIG_NFS_TIMEOUT
2684
2685		Timeout in milliseconds used in NFS protocol.
2686		If you encounter "ERROR: Cannot umount" in nfs command,
2687		try longer timeout such as
2688		#define CONFIG_NFS_TIMEOUT 10000UL
2689
2690- Command Interpreter:
2691		CONFIG_AUTO_COMPLETE
2692
2693		Enable auto completion of commands using TAB.
2694
2695		Note that this feature has NOT been implemented yet
2696		for the "hush" shell.
2697
2698
2699		CONFIG_SYS_HUSH_PARSER
2700
2701		Define this variable to enable the "hush" shell (from
2702		Busybox) as command line interpreter, thus enabling
2703		powerful command line syntax like
2704		if...then...else...fi conditionals or `&&' and '||'
2705		constructs ("shell scripts").
2706
2707		If undefined, you get the old, much simpler behaviour
2708		with a somewhat smaller memory footprint.
2709
2710
2711		CONFIG_SYS_PROMPT_HUSH_PS2
2712
2713		This defines the secondary prompt string, which is
2714		printed when the command interpreter needs more input
2715		to complete a command. Usually "> ".
2716
2717	Note:
2718
2719		In the current implementation, the local variables
2720		space and global environment variables space are
2721		separated. Local variables are those you define by
2722		simply typing `name=value'. To access a local
2723		variable later on, you have write `$name' or
2724		`${name}'; to execute the contents of a variable
2725		directly type `$name' at the command prompt.
2726
2727		Global environment variables are those you use
2728		setenv/printenv to work with. To run a command stored
2729		in such a variable, you need to use the run command,
2730		and you must not use the '$' sign to access them.
2731
2732		To store commands and special characters in a
2733		variable, please use double quotation marks
2734		surrounding the whole text of the variable, instead
2735		of the backslashes before semicolons and special
2736		symbols.
2737
2738- Commandline Editing and History:
2739		CONFIG_CMDLINE_EDITING
2740
2741		Enable editing and History functions for interactive
2742		commandline input operations
2743
2744- Default Environment:
2745		CONFIG_EXTRA_ENV_SETTINGS
2746
2747		Define this to contain any number of null terminated
2748		strings (variable = value pairs) that will be part of
2749		the default environment compiled into the boot image.
2750
2751		For example, place something like this in your
2752		board's config file:
2753
2754		#define CONFIG_EXTRA_ENV_SETTINGS \
2755			"myvar1=value1\0" \
2756			"myvar2=value2\0"
2757
2758		Warning: This method is based on knowledge about the
2759		internal format how the environment is stored by the
2760		U-Boot code. This is NOT an official, exported
2761		interface! Although it is unlikely that this format
2762		will change soon, there is no guarantee either.
2763		You better know what you are doing here.
2764
2765		Note: overly (ab)use of the default environment is
2766		discouraged. Make sure to check other ways to preset
2767		the environment like the "source" command or the
2768		boot command first.
2769
2770		CONFIG_ENV_VARS_UBOOT_CONFIG
2771
2772		Define this in order to add variables describing the
2773		U-Boot build configuration to the default environment.
2774		These will be named arch, cpu, board, vendor, and soc.
2775
2776		Enabling this option will cause the following to be defined:
2777
2778		- CONFIG_SYS_ARCH
2779		- CONFIG_SYS_CPU
2780		- CONFIG_SYS_BOARD
2781		- CONFIG_SYS_VENDOR
2782		- CONFIG_SYS_SOC
2783
2784		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2785
2786		Define this in order to add variables describing certain
2787		run-time determined information about the hardware to the
2788		environment.  These will be named board_name, board_rev.
2789
2790		CONFIG_DELAY_ENVIRONMENT
2791
2792		Normally the environment is loaded when the board is
2793		intialised so that it is available to U-Boot. This inhibits
2794		that so that the environment is not available until
2795		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2796		this is instead controlled by the value of
2797		/config/load-environment.
2798
2799- DataFlash Support:
2800		CONFIG_HAS_DATAFLASH
2801
2802		Defining this option enables DataFlash features and
2803		allows to read/write in Dataflash via the standard
2804		commands cp, md...
2805
2806- Serial Flash support
2807		CONFIG_CMD_SF
2808
2809		Defining this option enables SPI flash commands
2810		'sf probe/read/write/erase/update'.
2811
2812		Usage requires an initial 'probe' to define the serial
2813		flash parameters, followed by read/write/erase/update
2814		commands.
2815
2816		The following defaults may be provided by the platform
2817		to handle the common case when only a single serial
2818		flash is present on the system.
2819
2820		CONFIG_SF_DEFAULT_BUS		Bus identifier
2821		CONFIG_SF_DEFAULT_CS		Chip-select
2822		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2823		CONFIG_SF_DEFAULT_SPEED		in Hz
2824
2825		CONFIG_CMD_SF_TEST
2826
2827		Define this option to include a destructive SPI flash
2828		test ('sf test').
2829
2830		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2831
2832		Define this option to use the Bank addr/Extended addr
2833		support on SPI flashes which has size > 16Mbytes.
2834
2835		CONFIG_SF_DUAL_FLASH		Dual flash memories
2836
2837		Define this option to use dual flash support where two flash
2838		memories can be connected with a given cs line.
2839		currently Xilinx Zynq qspi support these type of connections.
2840
2841- SystemACE Support:
2842		CONFIG_SYSTEMACE
2843
2844		Adding this option adds support for Xilinx SystemACE
2845		chips attached via some sort of local bus. The address
2846		of the chip must also be defined in the
2847		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2848
2849		#define CONFIG_SYSTEMACE
2850		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2851
2852		When SystemACE support is added, the "ace" device type
2853		becomes available to the fat commands, i.e. fatls.
2854
2855- TFTP Fixed UDP Port:
2856		CONFIG_TFTP_PORT
2857
2858		If this is defined, the environment variable tftpsrcp
2859		is used to supply the TFTP UDP source port value.
2860		If tftpsrcp isn't defined, the normal pseudo-random port
2861		number generator is used.
2862
2863		Also, the environment variable tftpdstp is used to supply
2864		the TFTP UDP destination port value.  If tftpdstp isn't
2865		defined, the normal port 69 is used.
2866
2867		The purpose for tftpsrcp is to allow a TFTP server to
2868		blindly start the TFTP transfer using the pre-configured
2869		target IP address and UDP port. This has the effect of
2870		"punching through" the (Windows XP) firewall, allowing
2871		the remainder of the TFTP transfer to proceed normally.
2872		A better solution is to properly configure the firewall,
2873		but sometimes that is not allowed.
2874
2875- Hashing support:
2876		CONFIG_CMD_HASH
2877
2878		This enables a generic 'hash' command which can produce
2879		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2880
2881		CONFIG_HASH_VERIFY
2882
2883		Enable the hash verify command (hash -v). This adds to code
2884		size a little.
2885
2886		CONFIG_SHA1 - support SHA1 hashing
2887		CONFIG_SHA256 - support SHA256 hashing
2888
2889		Note: There is also a sha1sum command, which should perhaps
2890		be deprecated in favour of 'hash sha1'.
2891
2892- Freescale i.MX specific commands:
2893		CONFIG_CMD_HDMIDETECT
2894		This enables 'hdmidet' command which returns true if an
2895		HDMI monitor is detected.  This command is i.MX 6 specific.
2896
2897		CONFIG_CMD_BMODE
2898		This enables the 'bmode' (bootmode) command for forcing
2899		a boot from specific media.
2900
2901		This is useful for forcing the ROM's usb downloader to
2902		activate upon a watchdog reset which is nice when iterating
2903		on U-Boot.  Using the reset button or running bmode normal
2904		will set it back to normal.  This command currently
2905		supports i.MX53 and i.MX6.
2906
2907- Signing support:
2908		CONFIG_RSA
2909
2910		This enables the RSA algorithm used for FIT image verification
2911		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2912
2913		The signing part is build into mkimage regardless of this
2914		option.
2915
2916- bootcount support:
2917		CONFIG_BOOTCOUNT_LIMIT
2918
2919		This enables the bootcounter support, see:
2920		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2921
2922		CONFIG_AT91SAM9XE
2923		enable special bootcounter support on at91sam9xe based boards.
2924		CONFIG_BLACKFIN
2925		enable special bootcounter support on blackfin based boards.
2926		CONFIG_SOC_DA8XX
2927		enable special bootcounter support on da850 based boards.
2928		CONFIG_BOOTCOUNT_RAM
2929		enable support for the bootcounter in RAM
2930		CONFIG_BOOTCOUNT_I2C
2931		enable support for the bootcounter on an i2c (like RTC) device.
2932			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2933			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2934						    the bootcounter.
2935			CONFIG_BOOTCOUNT_ALEN = address len
2936
2937- Show boot progress:
2938		CONFIG_SHOW_BOOT_PROGRESS
2939
2940		Defining this option allows to add some board-
2941		specific code (calling a user-provided function
2942		"show_boot_progress(int)") that enables you to show
2943		the system's boot progress on some display (for
2944		example, some LED's) on your board. At the moment,
2945		the following checkpoints are implemented:
2946
2947- Detailed boot stage timing
2948		CONFIG_BOOTSTAGE
2949		Define this option to get detailed timing of each stage
2950		of the boot process.
2951
2952		CONFIG_BOOTSTAGE_USER_COUNT
2953		This is the number of available user bootstage records.
2954		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2955		a new ID will be allocated from this stash. If you exceed
2956		the limit, recording will stop.
2957
2958		CONFIG_BOOTSTAGE_REPORT
2959		Define this to print a report before boot, similar to this:
2960
2961		Timer summary in microseconds:
2962		       Mark    Elapsed  Stage
2963			  0          0  reset
2964		  3,575,678  3,575,678  board_init_f start
2965		  3,575,695         17  arch_cpu_init A9
2966		  3,575,777         82  arch_cpu_init done
2967		  3,659,598     83,821  board_init_r start
2968		  3,910,375    250,777  main_loop
2969		 29,916,167 26,005,792  bootm_start
2970		 30,361,327    445,160  start_kernel
2971
2972		CONFIG_CMD_BOOTSTAGE
2973		Add a 'bootstage' command which supports printing a report
2974		and un/stashing of bootstage data.
2975
2976		CONFIG_BOOTSTAGE_FDT
2977		Stash the bootstage information in the FDT. A root 'bootstage'
2978		node is created with each bootstage id as a child. Each child
2979		has a 'name' property and either 'mark' containing the
2980		mark time in microsecond, or 'accum' containing the
2981		accumulated time for that bootstage id in microseconds.
2982		For example:
2983
2984		bootstage {
2985			154 {
2986				name = "board_init_f";
2987				mark = <3575678>;
2988			};
2989			170 {
2990				name = "lcd";
2991				accum = <33482>;
2992			};
2993		};
2994
2995		Code in the Linux kernel can find this in /proc/devicetree.
2996
2997Legacy uImage format:
2998
2999  Arg	Where			When
3000    1	common/cmd_bootm.c	before attempting to boot an image
3001   -1	common/cmd_bootm.c	Image header has bad	 magic number
3002    2	common/cmd_bootm.c	Image header has correct magic number
3003   -2	common/cmd_bootm.c	Image header has bad	 checksum
3004    3	common/cmd_bootm.c	Image header has correct checksum
3005   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3006    4	common/cmd_bootm.c	Image data   has correct checksum
3007   -4	common/cmd_bootm.c	Image is for unsupported architecture
3008    5	common/cmd_bootm.c	Architecture check OK
3009   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3010    6	common/cmd_bootm.c	Image Type check OK
3011   -6	common/cmd_bootm.c	gunzip uncompression error
3012   -7	common/cmd_bootm.c	Unimplemented compression type
3013    7	common/cmd_bootm.c	Uncompression OK
3014    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3015   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3016
3017    9	common/image.c		Start initial ramdisk verification
3018  -10	common/image.c		Ramdisk header has bad	   magic number
3019  -11	common/image.c		Ramdisk header has bad	   checksum
3020   10	common/image.c		Ramdisk header is OK
3021  -12	common/image.c		Ramdisk data   has bad	   checksum
3022   11	common/image.c		Ramdisk data   has correct checksum
3023   12	common/image.c		Ramdisk verification complete, start loading
3024  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3025   13	common/image.c		Start multifile image verification
3026   14	common/image.c		No initial ramdisk, no multifile, continue.
3027
3028   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3029
3030  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3031  -31	post/post.c		POST test failed, detected by post_output_backlog()
3032  -32	post/post.c		POST test failed, detected by post_run_single()
3033
3034   34	common/cmd_doc.c	before loading a Image from a DOC device
3035  -35	common/cmd_doc.c	Bad usage of "doc" command
3036   35	common/cmd_doc.c	correct usage of "doc" command
3037  -36	common/cmd_doc.c	No boot device
3038   36	common/cmd_doc.c	correct boot device
3039  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3040   37	common/cmd_doc.c	correct chip ID found, device available
3041  -38	common/cmd_doc.c	Read Error on boot device
3042   38	common/cmd_doc.c	reading Image header from DOC device OK
3043  -39	common/cmd_doc.c	Image header has bad magic number
3044   39	common/cmd_doc.c	Image header has correct magic number
3045  -40	common/cmd_doc.c	Error reading Image from DOC device
3046   40	common/cmd_doc.c	Image header has correct magic number
3047   41	common/cmd_ide.c	before loading a Image from a IDE device
3048  -42	common/cmd_ide.c	Bad usage of "ide" command
3049   42	common/cmd_ide.c	correct usage of "ide" command
3050  -43	common/cmd_ide.c	No boot device
3051   43	common/cmd_ide.c	boot device found
3052  -44	common/cmd_ide.c	Device not available
3053   44	common/cmd_ide.c	Device available
3054  -45	common/cmd_ide.c	wrong partition selected
3055   45	common/cmd_ide.c	partition selected
3056  -46	common/cmd_ide.c	Unknown partition table
3057   46	common/cmd_ide.c	valid partition table found
3058  -47	common/cmd_ide.c	Invalid partition type
3059   47	common/cmd_ide.c	correct partition type
3060  -48	common/cmd_ide.c	Error reading Image Header on boot device
3061   48	common/cmd_ide.c	reading Image Header from IDE device OK
3062  -49	common/cmd_ide.c	Image header has bad magic number
3063   49	common/cmd_ide.c	Image header has correct magic number
3064  -50	common/cmd_ide.c	Image header has bad	 checksum
3065   50	common/cmd_ide.c	Image header has correct checksum
3066  -51	common/cmd_ide.c	Error reading Image from IDE device
3067   51	common/cmd_ide.c	reading Image from IDE device OK
3068   52	common/cmd_nand.c	before loading a Image from a NAND device
3069  -53	common/cmd_nand.c	Bad usage of "nand" command
3070   53	common/cmd_nand.c	correct usage of "nand" command
3071  -54	common/cmd_nand.c	No boot device
3072   54	common/cmd_nand.c	boot device found
3073  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3074   55	common/cmd_nand.c	correct chip ID found, device available
3075  -56	common/cmd_nand.c	Error reading Image Header on boot device
3076   56	common/cmd_nand.c	reading Image Header from NAND device OK
3077  -57	common/cmd_nand.c	Image header has bad magic number
3078   57	common/cmd_nand.c	Image header has correct magic number
3079  -58	common/cmd_nand.c	Error reading Image from NAND device
3080   58	common/cmd_nand.c	reading Image from NAND device OK
3081
3082  -60	common/env_common.c	Environment has a bad CRC, using default
3083
3084   64	net/eth.c		starting with Ethernet configuration.
3085  -64	net/eth.c		no Ethernet found.
3086   65	net/eth.c		Ethernet found.
3087
3088  -80	common/cmd_net.c	usage wrong
3089   80	common/cmd_net.c	before calling NetLoop()
3090  -81	common/cmd_net.c	some error in NetLoop() occurred
3091   81	common/cmd_net.c	NetLoop() back without error
3092  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3093   82	common/cmd_net.c	trying automatic boot
3094   83	common/cmd_net.c	running "source" command
3095  -83	common/cmd_net.c	some error in automatic boot or "source" command
3096   84	common/cmd_net.c	end without errors
3097
3098FIT uImage format:
3099
3100  Arg	Where			When
3101  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3102 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3103  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3104 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3105  102	common/cmd_bootm.c	Kernel unit name specified
3106 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3107  103	common/cmd_bootm.c	Found configuration node
3108  104	common/cmd_bootm.c	Got kernel subimage node offset
3109 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3110  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3111 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3112  106	common/cmd_bootm.c	Architecture check OK
3113 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3114  107	common/cmd_bootm.c	Kernel subimage type OK
3115 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3116  108	common/cmd_bootm.c	Got kernel subimage data/size
3117 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3118 -109	common/cmd_bootm.c	Can't get kernel subimage type
3119 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3120 -111	common/cmd_bootm.c	Can't get kernel subimage os
3121 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3122 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3123
3124  120	common/image.c		Start initial ramdisk verification
3125 -120	common/image.c		Ramdisk FIT image has incorrect format
3126  121	common/image.c		Ramdisk FIT image has correct format
3127  122	common/image.c		No ramdisk subimage unit name, using configuration
3128 -122	common/image.c		Can't get configuration for ramdisk subimage
3129  123	common/image.c		Ramdisk unit name specified
3130 -124	common/image.c		Can't get ramdisk subimage node offset
3131  125	common/image.c		Got ramdisk subimage node offset
3132 -125	common/image.c		Ramdisk subimage hash verification failed
3133  126	common/image.c		Ramdisk subimage hash verification OK
3134 -126	common/image.c		Ramdisk subimage for unsupported architecture
3135  127	common/image.c		Architecture check OK
3136 -127	common/image.c		Can't get ramdisk subimage data/size
3137  128	common/image.c		Got ramdisk subimage data/size
3138  129	common/image.c		Can't get ramdisk load address
3139 -129	common/image.c		Got ramdisk load address
3140
3141 -130	common/cmd_doc.c	Incorrect FIT image format
3142  131	common/cmd_doc.c	FIT image format OK
3143
3144 -140	common/cmd_ide.c	Incorrect FIT image format
3145  141	common/cmd_ide.c	FIT image format OK
3146
3147 -150	common/cmd_nand.c	Incorrect FIT image format
3148  151	common/cmd_nand.c	FIT image format OK
3149
3150- FIT image support:
3151		CONFIG_FIT
3152		Enable support for the FIT uImage format.
3153
3154		CONFIG_FIT_BEST_MATCH
3155		When no configuration is explicitly selected, default to the
3156		one whose fdt's compatibility field best matches that of
3157		U-Boot itself. A match is considered "best" if it matches the
3158		most specific compatibility entry of U-Boot's fdt's root node.
3159		The order of entries in the configuration's fdt is ignored.
3160
3161		CONFIG_FIT_SIGNATURE
3162		This option enables signature verification of FIT uImages,
3163		using a hash signed and verified using RSA. See
3164		doc/uImage.FIT/signature.txt for more details.
3165
3166- Standalone program support:
3167		CONFIG_STANDALONE_LOAD_ADDR
3168
3169		This option defines a board specific value for the
3170		address where standalone program gets loaded, thus
3171		overwriting the architecture dependent default
3172		settings.
3173
3174- Frame Buffer Address:
3175		CONFIG_FB_ADDR
3176
3177		Define CONFIG_FB_ADDR if you want to use specific
3178		address for frame buffer.  This is typically the case
3179		when using a graphics controller has separate video
3180		memory.  U-Boot will then place the frame buffer at
3181		the given address instead of dynamically reserving it
3182		in system RAM by calling lcd_setmem(), which grabs
3183		the memory for the frame buffer depending on the
3184		configured panel size.
3185
3186		Please see board_init_f function.
3187
3188- Automatic software updates via TFTP server
3189		CONFIG_UPDATE_TFTP
3190		CONFIG_UPDATE_TFTP_CNT_MAX
3191		CONFIG_UPDATE_TFTP_MSEC_MAX
3192
3193		These options enable and control the auto-update feature;
3194		for a more detailed description refer to doc/README.update.
3195
3196- MTD Support (mtdparts command, UBI support)
3197		CONFIG_MTD_DEVICE
3198
3199		Adds the MTD device infrastructure from the Linux kernel.
3200		Needed for mtdparts command support.
3201
3202		CONFIG_MTD_PARTITIONS
3203
3204		Adds the MTD partitioning infrastructure from the Linux
3205		kernel. Needed for UBI support.
3206
3207- UBI support
3208		CONFIG_CMD_UBI
3209
3210		Adds commands for interacting with MTD partitions formatted
3211		with the UBI flash translation layer
3212
3213		Requires also defining CONFIG_RBTREE
3214
3215		CONFIG_UBI_SILENCE_MSG
3216
3217		Make the verbose messages from UBI stop printing.  This leaves
3218		warnings and errors enabled.
3219
3220- UBIFS support
3221		CONFIG_CMD_UBIFS
3222
3223		Adds commands for interacting with UBI volumes formatted as
3224		UBIFS.  UBIFS is read-only in u-boot.
3225
3226		Requires UBI support as well as CONFIG_LZO
3227
3228		CONFIG_UBIFS_SILENCE_MSG
3229
3230		Make the verbose messages from UBIFS stop printing.  This leaves
3231		warnings and errors enabled.
3232
3233- SPL framework
3234		CONFIG_SPL
3235		Enable building of SPL globally.
3236
3237		CONFIG_SPL_LDSCRIPT
3238		LDSCRIPT for linking the SPL binary.
3239
3240		CONFIG_SPL_MAX_FOOTPRINT
3241		Maximum size in memory allocated to the SPL, BSS included.
3242		When defined, the linker checks that the actual memory
3243		used by SPL from _start to __bss_end does not exceed it.
3244		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3245		must not be both defined at the same time.
3246
3247		CONFIG_SPL_MAX_SIZE
3248		Maximum size of the SPL image (text, data, rodata, and
3249		linker lists sections), BSS excluded.
3250		When defined, the linker checks that the actual size does
3251		not exceed it.
3252
3253		CONFIG_SPL_TEXT_BASE
3254		TEXT_BASE for linking the SPL binary.
3255
3256		CONFIG_SPL_RELOC_TEXT_BASE
3257		Address to relocate to.  If unspecified, this is equal to
3258		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3259
3260		CONFIG_SPL_BSS_START_ADDR
3261		Link address for the BSS within the SPL binary.
3262
3263		CONFIG_SPL_BSS_MAX_SIZE
3264		Maximum size in memory allocated to the SPL BSS.
3265		When defined, the linker checks that the actual memory used
3266		by SPL from __bss_start to __bss_end does not exceed it.
3267		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3268		must not be both defined at the same time.
3269
3270		CONFIG_SPL_STACK
3271		Adress of the start of the stack SPL will use
3272
3273		CONFIG_SPL_RELOC_STACK
3274		Adress of the start of the stack SPL will use after
3275		relocation.  If unspecified, this is equal to
3276		CONFIG_SPL_STACK.
3277
3278		CONFIG_SYS_SPL_MALLOC_START
3279		Starting address of the malloc pool used in SPL.
3280
3281		CONFIG_SYS_SPL_MALLOC_SIZE
3282		The size of the malloc pool used in SPL.
3283
3284		CONFIG_SPL_FRAMEWORK
3285		Enable the SPL framework under common/.  This framework
3286		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3287		NAND loading of the Linux Kernel.
3288
3289		CONFIG_SPL_DISPLAY_PRINT
3290		For ARM, enable an optional function to print more information
3291		about the running system.
3292
3293		CONFIG_SPL_INIT_MINIMAL
3294		Arch init code should be built for a very small image
3295
3296		CONFIG_SPL_LIBCOMMON_SUPPORT
3297		Support for common/libcommon.o in SPL binary
3298
3299		CONFIG_SPL_LIBDISK_SUPPORT
3300		Support for disk/libdisk.o in SPL binary
3301
3302		CONFIG_SPL_I2C_SUPPORT
3303		Support for drivers/i2c/libi2c.o in SPL binary
3304
3305		CONFIG_SPL_GPIO_SUPPORT
3306		Support for drivers/gpio/libgpio.o in SPL binary
3307
3308		CONFIG_SPL_MMC_SUPPORT
3309		Support for drivers/mmc/libmmc.o in SPL binary
3310
3311		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3312		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3313		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3314		Address, size and partition on the MMC to load U-Boot from
3315		when the MMC is being used in raw mode.
3316
3317		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3318		Sector to load kernel uImage from when MMC is being
3319		used in raw mode (for Falcon mode)
3320
3321		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3322		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3323		Sector and number of sectors to load kernel argument
3324		parameters from when MMC is being used in raw mode
3325		(for falcon mode)
3326
3327		CONFIG_SPL_FAT_SUPPORT
3328		Support for fs/fat/libfat.o in SPL binary
3329
3330		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3331		Filename to read to load U-Boot when reading from FAT
3332
3333		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3334		Filename to read to load kernel uImage when reading
3335		from FAT (for Falcon mode)
3336
3337		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3338		Filename to read to load kernel argument parameters
3339		when reading from FAT (for Falcon mode)
3340
3341		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3342		Set this for NAND SPL on PPC mpc83xx targets, so that
3343		start.S waits for the rest of the SPL to load before
3344		continuing (the hardware starts execution after just
3345		loading the first page rather than the full 4K).
3346
3347		CONFIG_SPL_SKIP_RELOCATE
3348		Avoid SPL relocation
3349
3350		CONFIG_SPL_NAND_BASE
3351		Include nand_base.c in the SPL.  Requires
3352		CONFIG_SPL_NAND_DRIVERS.
3353
3354		CONFIG_SPL_NAND_DRIVERS
3355		SPL uses normal NAND drivers, not minimal drivers.
3356
3357		CONFIG_SPL_NAND_ECC
3358		Include standard software ECC in the SPL
3359
3360		CONFIG_SPL_NAND_SIMPLE
3361		Support for NAND boot using simple NAND drivers that
3362		expose the cmd_ctrl() interface.
3363
3364		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3365		Set for the SPL on PPC mpc8xxx targets, support for
3366		drivers/ddr/fsl/libddr.o in SPL binary.
3367
3368		CONFIG_SPL_COMMON_INIT_DDR
3369		Set for common ddr init with serial presence detect in
3370		SPL binary.
3371
3372		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3373		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3374		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3375		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3376		CONFIG_SYS_NAND_ECCBYTES
3377		Defines the size and behavior of the NAND that SPL uses
3378		to read U-Boot
3379
3380		CONFIG_SPL_NAND_BOOT
3381		Add support NAND boot
3382
3383		CONFIG_SYS_NAND_U_BOOT_OFFS
3384		Location in NAND to read U-Boot from
3385
3386		CONFIG_SYS_NAND_U_BOOT_DST
3387		Location in memory to load U-Boot to
3388
3389		CONFIG_SYS_NAND_U_BOOT_SIZE
3390		Size of image to load
3391
3392		CONFIG_SYS_NAND_U_BOOT_START
3393		Entry point in loaded image to jump to
3394
3395		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3396		Define this if you need to first read the OOB and then the
3397		data. This is used for example on davinci plattforms.
3398
3399		CONFIG_SPL_OMAP3_ID_NAND
3400		Support for an OMAP3-specific set of functions to return the
3401		ID and MFR of the first attached NAND chip, if present.
3402
3403		CONFIG_SPL_SERIAL_SUPPORT
3404		Support for drivers/serial/libserial.o in SPL binary
3405
3406		CONFIG_SPL_SPI_FLASH_SUPPORT
3407		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3408
3409		CONFIG_SPL_SPI_SUPPORT
3410		Support for drivers/spi/libspi.o in SPL binary
3411
3412		CONFIG_SPL_RAM_DEVICE
3413		Support for running image already present in ram, in SPL binary
3414
3415		CONFIG_SPL_LIBGENERIC_SUPPORT
3416		Support for lib/libgeneric.o in SPL binary
3417
3418		CONFIG_SPL_ENV_SUPPORT
3419		Support for the environment operating in SPL binary
3420
3421		CONFIG_SPL_NET_SUPPORT
3422		Support for the net/libnet.o in SPL binary.
3423		It conflicts with SPL env from storage medium specified by
3424		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3425
3426		CONFIG_SPL_PAD_TO
3427		Image offset to which the SPL should be padded before appending
3428		the SPL payload. By default, this is defined as
3429		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3430		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3431		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3432
3433		CONFIG_SPL_TARGET
3434		Final target image containing SPL and payload.  Some SPLs
3435		use an arch-specific makefile fragment instead, for
3436		example if more than one image needs to be produced.
3437
3438		CONFIG_FIT_SPL_PRINT
3439		Printing information about a FIT image adds quite a bit of
3440		code to SPL. So this is normally disabled in SPL. Use this
3441		option to re-enable it. This will affect the output of the
3442		bootm command when booting a FIT image.
3443
3444- TPL framework
3445		CONFIG_TPL
3446		Enable building of TPL globally.
3447
3448		CONFIG_TPL_PAD_TO
3449		Image offset to which the TPL should be padded before appending
3450		the TPL payload. By default, this is defined as
3451		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3452		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3453		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3454
3455Modem Support:
3456--------------
3457
3458[so far only for SMDK2400 boards]
3459
3460- Modem support enable:
3461		CONFIG_MODEM_SUPPORT
3462
3463- RTS/CTS Flow control enable:
3464		CONFIG_HWFLOW
3465
3466- Modem debug support:
3467		CONFIG_MODEM_SUPPORT_DEBUG
3468
3469		Enables debugging stuff (char screen[1024], dbg())
3470		for modem support. Useful only with BDI2000.
3471
3472- Interrupt support (PPC):
3473
3474		There are common interrupt_init() and timer_interrupt()
3475		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3476		for CPU specific initialization. interrupt_init_cpu()
3477		should set decrementer_count to appropriate value. If
3478		CPU resets decrementer automatically after interrupt
3479		(ppc4xx) it should set decrementer_count to zero.
3480		timer_interrupt() calls timer_interrupt_cpu() for CPU
3481		specific handling. If board has watchdog / status_led
3482		/ other_activity_monitor it works automatically from
3483		general timer_interrupt().
3484
3485- General:
3486
3487		In the target system modem support is enabled when a
3488		specific key (key combination) is pressed during
3489		power-on. Otherwise U-Boot will boot normally
3490		(autoboot). The key_pressed() function is called from
3491		board_init(). Currently key_pressed() is a dummy
3492		function, returning 1 and thus enabling modem
3493		initialization.
3494
3495		If there are no modem init strings in the
3496		environment, U-Boot proceed to autoboot; the
3497		previous output (banner, info printfs) will be
3498		suppressed, though.
3499
3500		See also: doc/README.Modem
3501
3502Board initialization settings:
3503------------------------------
3504
3505During Initialization u-boot calls a number of board specific functions
3506to allow the preparation of board specific prerequisites, e.g. pin setup
3507before drivers are initialized. To enable these callbacks the
3508following configuration macros have to be defined. Currently this is
3509architecture specific, so please check arch/your_architecture/lib/board.c
3510typically in board_init_f() and board_init_r().
3511
3512- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3513- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3514- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3515- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3516
3517Configuration Settings:
3518-----------------------
3519
3520- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3521		Optionally it can be defined to support 64-bit memory commands.
3522
3523- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3524		undefine this when you're short of memory.
3525
3526- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3527		width of the commands listed in the 'help' command output.
3528
3529- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3530		prompt for user input.
3531
3532- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3533
3534- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3535
3536- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3537
3538- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3539		the application (usually a Linux kernel) when it is
3540		booted
3541
3542- CONFIG_SYS_BAUDRATE_TABLE:
3543		List of legal baudrate settings for this board.
3544
3545- CONFIG_SYS_CONSOLE_INFO_QUIET
3546		Suppress display of console information at boot.
3547
3548- CONFIG_SYS_CONSOLE_IS_IN_ENV
3549		If the board specific function
3550			extern int overwrite_console (void);
3551		returns 1, the stdin, stderr and stdout are switched to the
3552		serial port, else the settings in the environment are used.
3553
3554- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3555		Enable the call to overwrite_console().
3556
3557- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3558		Enable overwrite of previous console environment settings.
3559
3560- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3561		Begin and End addresses of the area used by the
3562		simple memory test.
3563
3564- CONFIG_SYS_ALT_MEMTEST:
3565		Enable an alternate, more extensive memory test.
3566
3567- CONFIG_SYS_MEMTEST_SCRATCH:
3568		Scratch address used by the alternate memory test
3569		You only need to set this if address zero isn't writeable
3570
3571- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3572		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3573		this specified memory area will get subtracted from the top
3574		(end) of RAM and won't get "touched" at all by U-Boot. By
3575		fixing up gd->ram_size the Linux kernel should gets passed
3576		the now "corrected" memory size and won't touch it either.
3577		This should work for arch/ppc and arch/powerpc. Only Linux
3578		board ports in arch/powerpc with bootwrapper support that
3579		recalculate the memory size from the SDRAM controller setup
3580		will have to get fixed in Linux additionally.
3581
3582		This option can be used as a workaround for the 440EPx/GRx
3583		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3584		be touched.
3585
3586		WARNING: Please make sure that this value is a multiple of
3587		the Linux page size (normally 4k). If this is not the case,
3588		then the end address of the Linux memory will be located at a
3589		non page size aligned address and this could cause major
3590		problems.
3591
3592- CONFIG_SYS_LOADS_BAUD_CHANGE:
3593		Enable temporary baudrate change while serial download
3594
3595- CONFIG_SYS_SDRAM_BASE:
3596		Physical start address of SDRAM. _Must_ be 0 here.
3597
3598- CONFIG_SYS_MBIO_BASE:
3599		Physical start address of Motherboard I/O (if using a
3600		Cogent motherboard)
3601
3602- CONFIG_SYS_FLASH_BASE:
3603		Physical start address of Flash memory.
3604
3605- CONFIG_SYS_MONITOR_BASE:
3606		Physical start address of boot monitor code (set by
3607		make config files to be same as the text base address
3608		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3609		CONFIG_SYS_FLASH_BASE when booting from flash.
3610
3611- CONFIG_SYS_MONITOR_LEN:
3612		Size of memory reserved for monitor code, used to
3613		determine _at_compile_time_ (!) if the environment is
3614		embedded within the U-Boot image, or in a separate
3615		flash sector.
3616
3617- CONFIG_SYS_MALLOC_LEN:
3618		Size of DRAM reserved for malloc() use.
3619
3620- CONFIG_SYS_BOOTM_LEN:
3621		Normally compressed uImages are limited to an
3622		uncompressed size of 8 MBytes. If this is not enough,
3623		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3624		to adjust this setting to your needs.
3625
3626- CONFIG_SYS_BOOTMAPSZ:
3627		Maximum size of memory mapped by the startup code of
3628		the Linux kernel; all data that must be processed by
3629		the Linux kernel (bd_info, boot arguments, FDT blob if
3630		used) must be put below this limit, unless "bootm_low"
3631		environment variable is defined and non-zero. In such case
3632		all data for the Linux kernel must be between "bootm_low"
3633		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3634		variable "bootm_mapsize" will override the value of
3635		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3636		then the value in "bootm_size" will be used instead.
3637
3638- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3639		Enable initrd_high functionality.  If defined then the
3640		initrd_high feature is enabled and the bootm ramdisk subcommand
3641		is enabled.
3642
3643- CONFIG_SYS_BOOT_GET_CMDLINE:
3644		Enables allocating and saving kernel cmdline in space between
3645		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3646
3647- CONFIG_SYS_BOOT_GET_KBD:
3648		Enables allocating and saving a kernel copy of the bd_info in
3649		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3650
3651- CONFIG_SYS_MAX_FLASH_BANKS:
3652		Max number of Flash memory banks
3653
3654- CONFIG_SYS_MAX_FLASH_SECT:
3655		Max number of sectors on a Flash chip
3656
3657- CONFIG_SYS_FLASH_ERASE_TOUT:
3658		Timeout for Flash erase operations (in ms)
3659
3660- CONFIG_SYS_FLASH_WRITE_TOUT:
3661		Timeout for Flash write operations (in ms)
3662
3663- CONFIG_SYS_FLASH_LOCK_TOUT
3664		Timeout for Flash set sector lock bit operation (in ms)
3665
3666- CONFIG_SYS_FLASH_UNLOCK_TOUT
3667		Timeout for Flash clear lock bits operation (in ms)
3668
3669- CONFIG_SYS_FLASH_PROTECTION
3670		If defined, hardware flash sectors protection is used
3671		instead of U-Boot software protection.
3672
3673- CONFIG_SYS_DIRECT_FLASH_TFTP:
3674
3675		Enable TFTP transfers directly to flash memory;
3676		without this option such a download has to be
3677		performed in two steps: (1) download to RAM, and (2)
3678		copy from RAM to flash.
3679
3680		The two-step approach is usually more reliable, since
3681		you can check if the download worked before you erase
3682		the flash, but in some situations (when system RAM is
3683		too limited to allow for a temporary copy of the
3684		downloaded image) this option may be very useful.
3685
3686- CONFIG_SYS_FLASH_CFI:
3687		Define if the flash driver uses extra elements in the
3688		common flash structure for storing flash geometry.
3689
3690- CONFIG_FLASH_CFI_DRIVER
3691		This option also enables the building of the cfi_flash driver
3692		in the drivers directory
3693
3694- CONFIG_FLASH_CFI_MTD
3695		This option enables the building of the cfi_mtd driver
3696		in the drivers directory. The driver exports CFI flash
3697		to the MTD layer.
3698
3699- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3700		Use buffered writes to flash.
3701
3702- CONFIG_FLASH_SPANSION_S29WS_N
3703		s29ws-n MirrorBit flash has non-standard addresses for buffered
3704		write commands.
3705
3706- CONFIG_SYS_FLASH_QUIET_TEST
3707		If this option is defined, the common CFI flash doesn't
3708		print it's warning upon not recognized FLASH banks. This
3709		is useful, if some of the configured banks are only
3710		optionally available.
3711
3712- CONFIG_FLASH_SHOW_PROGRESS
3713		If defined (must be an integer), print out countdown
3714		digits and dots.  Recommended value: 45 (9..1) for 80
3715		column displays, 15 (3..1) for 40 column displays.
3716
3717- CONFIG_FLASH_VERIFY
3718		If defined, the content of the flash (destination) is compared
3719		against the source after the write operation. An error message
3720		will be printed when the contents are not identical.
3721		Please note that this option is useless in nearly all cases,
3722		since such flash programming errors usually are detected earlier
3723		while unprotecting/erasing/programming. Please only enable
3724		this option if you really know what you are doing.
3725
3726- CONFIG_SYS_RX_ETH_BUFFER:
3727		Defines the number of Ethernet receive buffers. On some
3728		Ethernet controllers it is recommended to set this value
3729		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3730		buffers can be full shortly after enabling the interface
3731		on high Ethernet traffic.
3732		Defaults to 4 if not defined.
3733
3734- CONFIG_ENV_MAX_ENTRIES
3735
3736	Maximum number of entries in the hash table that is used
3737	internally to store the environment settings. The default
3738	setting is supposed to be generous and should work in most
3739	cases. This setting can be used to tune behaviour; see
3740	lib/hashtable.c for details.
3741
3742- CONFIG_ENV_FLAGS_LIST_DEFAULT
3743- CONFIG_ENV_FLAGS_LIST_STATIC
3744	Enable validation of the values given to environment variables when
3745	calling env set.  Variables can be restricted to only decimal,
3746	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3747	the variables can also be restricted to IP address or MAC address.
3748
3749	The format of the list is:
3750		type_attribute = [s|d|x|b|i|m]
3751		access_atribute = [a|r|o|c]
3752		attributes = type_attribute[access_atribute]
3753		entry = variable_name[:attributes]
3754		list = entry[,list]
3755
3756	The type attributes are:
3757		s - String (default)
3758		d - Decimal
3759		x - Hexadecimal
3760		b - Boolean ([1yYtT|0nNfF])
3761		i - IP address
3762		m - MAC address
3763
3764	The access attributes are:
3765		a - Any (default)
3766		r - Read-only
3767		o - Write-once
3768		c - Change-default
3769
3770	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3771		Define this to a list (string) to define the ".flags"
3772		envirnoment variable in the default or embedded environment.
3773
3774	- CONFIG_ENV_FLAGS_LIST_STATIC
3775		Define this to a list (string) to define validation that
3776		should be done if an entry is not found in the ".flags"
3777		environment variable.  To override a setting in the static
3778		list, simply add an entry for the same variable name to the
3779		".flags" variable.
3780
3781- CONFIG_ENV_ACCESS_IGNORE_FORCE
3782	If defined, don't allow the -f switch to env set override variable
3783	access flags.
3784
3785- CONFIG_SYS_GENERIC_BOARD
3786	This selects the architecture-generic board system instead of the
3787	architecture-specific board files. It is intended to move boards
3788	to this new framework over time. Defining this will disable the
3789	arch/foo/lib/board.c file and use common/board_f.c and
3790	common/board_r.c instead. To use this option your architecture
3791	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3792	its config.mk file). If you find problems enabling this option on
3793	your board please report the problem and send patches!
3794
3795- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3796	This is set by OMAP boards for the max time that reset should
3797	be asserted. See doc/README.omap-reset-time for details on how
3798	the value can be calulated on a given board.
3799
3800The following definitions that deal with the placement and management
3801of environment data (variable area); in general, we support the
3802following configurations:
3803
3804- CONFIG_BUILD_ENVCRC:
3805
3806	Builds up envcrc with the target environment so that external utils
3807	may easily extract it and embed it in final U-Boot images.
3808
3809- CONFIG_ENV_IS_IN_FLASH:
3810
3811	Define this if the environment is in flash memory.
3812
3813	a) The environment occupies one whole flash sector, which is
3814	   "embedded" in the text segment with the U-Boot code. This
3815	   happens usually with "bottom boot sector" or "top boot
3816	   sector" type flash chips, which have several smaller
3817	   sectors at the start or the end. For instance, such a
3818	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3819	   such a case you would place the environment in one of the
3820	   4 kB sectors - with U-Boot code before and after it. With
3821	   "top boot sector" type flash chips, you would put the
3822	   environment in one of the last sectors, leaving a gap
3823	   between U-Boot and the environment.
3824
3825	- CONFIG_ENV_OFFSET:
3826
3827	   Offset of environment data (variable area) to the
3828	   beginning of flash memory; for instance, with bottom boot
3829	   type flash chips the second sector can be used: the offset
3830	   for this sector is given here.
3831
3832	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3833
3834	- CONFIG_ENV_ADDR:
3835
3836	   This is just another way to specify the start address of
3837	   the flash sector containing the environment (instead of
3838	   CONFIG_ENV_OFFSET).
3839
3840	- CONFIG_ENV_SECT_SIZE:
3841
3842	   Size of the sector containing the environment.
3843
3844
3845	b) Sometimes flash chips have few, equal sized, BIG sectors.
3846	   In such a case you don't want to spend a whole sector for
3847	   the environment.
3848
3849	- CONFIG_ENV_SIZE:
3850
3851	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3852	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3853	   of this flash sector for the environment. This saves
3854	   memory for the RAM copy of the environment.
3855
3856	   It may also save flash memory if you decide to use this
3857	   when your environment is "embedded" within U-Boot code,
3858	   since then the remainder of the flash sector could be used
3859	   for U-Boot code. It should be pointed out that this is
3860	   STRONGLY DISCOURAGED from a robustness point of view:
3861	   updating the environment in flash makes it always
3862	   necessary to erase the WHOLE sector. If something goes
3863	   wrong before the contents has been restored from a copy in
3864	   RAM, your target system will be dead.
3865
3866	- CONFIG_ENV_ADDR_REDUND
3867	  CONFIG_ENV_SIZE_REDUND
3868
3869	   These settings describe a second storage area used to hold
3870	   a redundant copy of the environment data, so that there is
3871	   a valid backup copy in case there is a power failure during
3872	   a "saveenv" operation.
3873
3874BE CAREFUL! Any changes to the flash layout, and some changes to the
3875source code will make it necessary to adapt <board>/u-boot.lds*
3876accordingly!
3877
3878
3879- CONFIG_ENV_IS_IN_NVRAM:
3880
3881	Define this if you have some non-volatile memory device
3882	(NVRAM, battery buffered SRAM) which you want to use for the
3883	environment.
3884
3885	- CONFIG_ENV_ADDR:
3886	- CONFIG_ENV_SIZE:
3887
3888	  These two #defines are used to determine the memory area you
3889	  want to use for environment. It is assumed that this memory
3890	  can just be read and written to, without any special
3891	  provision.
3892
3893BE CAREFUL! The first access to the environment happens quite early
3894in U-Boot initalization (when we try to get the setting of for the
3895console baudrate). You *MUST* have mapped your NVRAM area then, or
3896U-Boot will hang.
3897
3898Please note that even with NVRAM we still use a copy of the
3899environment in RAM: we could work on NVRAM directly, but we want to
3900keep settings there always unmodified except somebody uses "saveenv"
3901to save the current settings.
3902
3903
3904- CONFIG_ENV_IS_IN_EEPROM:
3905
3906	Use this if you have an EEPROM or similar serial access
3907	device and a driver for it.
3908
3909	- CONFIG_ENV_OFFSET:
3910	- CONFIG_ENV_SIZE:
3911
3912	  These two #defines specify the offset and size of the
3913	  environment area within the total memory of your EEPROM.
3914
3915	- CONFIG_SYS_I2C_EEPROM_ADDR:
3916	  If defined, specified the chip address of the EEPROM device.
3917	  The default address is zero.
3918
3919	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3920	  If defined, the number of bits used to address bytes in a
3921	  single page in the EEPROM device.  A 64 byte page, for example
3922	  would require six bits.
3923
3924	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3925	  If defined, the number of milliseconds to delay between
3926	  page writes.	The default is zero milliseconds.
3927
3928	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3929	  The length in bytes of the EEPROM memory array address.  Note
3930	  that this is NOT the chip address length!
3931
3932	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3933	  EEPROM chips that implement "address overflow" are ones
3934	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3935	  address and the extra bits end up in the "chip address" bit
3936	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3937	  byte chips.
3938
3939	  Note that we consider the length of the address field to
3940	  still be one byte because the extra address bits are hidden
3941	  in the chip address.
3942
3943	- CONFIG_SYS_EEPROM_SIZE:
3944	  The size in bytes of the EEPROM device.
3945
3946	- CONFIG_ENV_EEPROM_IS_ON_I2C
3947	  define this, if you have I2C and SPI activated, and your
3948	  EEPROM, which holds the environment, is on the I2C bus.
3949
3950	- CONFIG_I2C_ENV_EEPROM_BUS
3951	  if you have an Environment on an EEPROM reached over
3952	  I2C muxes, you can define here, how to reach this
3953	  EEPROM. For example:
3954
3955	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3956
3957	  EEPROM which holds the environment, is reached over
3958	  a pca9547 i2c mux with address 0x70, channel 3.
3959
3960- CONFIG_ENV_IS_IN_DATAFLASH:
3961
3962	Define this if you have a DataFlash memory device which you
3963	want to use for the environment.
3964
3965	- CONFIG_ENV_OFFSET:
3966	- CONFIG_ENV_ADDR:
3967	- CONFIG_ENV_SIZE:
3968
3969	  These three #defines specify the offset and size of the
3970	  environment area within the total memory of your DataFlash placed
3971	  at the specified address.
3972
3973- CONFIG_ENV_IS_IN_REMOTE:
3974
3975	Define this if you have a remote memory space which you
3976	want to use for the local device's environment.
3977
3978	- CONFIG_ENV_ADDR:
3979	- CONFIG_ENV_SIZE:
3980
3981	  These two #defines specify the address and size of the
3982	  environment area within the remote memory space. The
3983	  local device can get the environment from remote memory
3984	  space by SRIO or PCIE links.
3985
3986BE CAREFUL! For some special cases, the local device can not use
3987"saveenv" command. For example, the local device will get the
3988environment stored in a remote NOR flash by SRIO or PCIE link,
3989but it can not erase, write this NOR flash by SRIO or PCIE interface.
3990
3991- CONFIG_ENV_IS_IN_NAND:
3992
3993	Define this if you have a NAND device which you want to use
3994	for the environment.
3995
3996	- CONFIG_ENV_OFFSET:
3997	- CONFIG_ENV_SIZE:
3998
3999	  These two #defines specify the offset and size of the environment
4000	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4001	  aligned to an erase block boundary.
4002
4003	- CONFIG_ENV_OFFSET_REDUND (optional):
4004
4005	  This setting describes a second storage area of CONFIG_ENV_SIZE
4006	  size used to hold a redundant copy of the environment data, so
4007	  that there is a valid backup copy in case there is a power failure
4008	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4009	  aligned to an erase block boundary.
4010
4011	- CONFIG_ENV_RANGE (optional):
4012
4013	  Specifies the length of the region in which the environment
4014	  can be written.  This should be a multiple of the NAND device's
4015	  block size.  Specifying a range with more erase blocks than
4016	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4017	  the range to be avoided.
4018
4019	- CONFIG_ENV_OFFSET_OOB (optional):
4020
4021	  Enables support for dynamically retrieving the offset of the
4022	  environment from block zero's out-of-band data.  The
4023	  "nand env.oob" command can be used to record this offset.
4024	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4025	  using CONFIG_ENV_OFFSET_OOB.
4026
4027- CONFIG_NAND_ENV_DST
4028
4029	Defines address in RAM to which the nand_spl code should copy the
4030	environment. If redundant environment is used, it will be copied to
4031	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4032
4033- CONFIG_ENV_IS_IN_UBI:
4034
4035	Define this if you have an UBI volume that you want to use for the
4036	environment.  This has the benefit of wear-leveling the environment
4037	accesses, which is important on NAND.
4038
4039	- CONFIG_ENV_UBI_PART:
4040
4041	  Define this to a string that is the mtd partition containing the UBI.
4042
4043	- CONFIG_ENV_UBI_VOLUME:
4044
4045	  Define this to the name of the volume that you want to store the
4046	  environment in.
4047
4048	- CONFIG_ENV_UBI_VOLUME_REDUND:
4049
4050	  Define this to the name of another volume to store a second copy of
4051	  the environment in.  This will enable redundant environments in UBI.
4052	  It is assumed that both volumes are in the same MTD partition.
4053
4054	- CONFIG_UBI_SILENCE_MSG
4055	- CONFIG_UBIFS_SILENCE_MSG
4056
4057	  You will probably want to define these to avoid a really noisy system
4058	  when storing the env in UBI.
4059
4060- CONFIG_ENV_IS_IN_MMC:
4061
4062	Define this if you have an MMC device which you want to use for the
4063	environment.
4064
4065	- CONFIG_SYS_MMC_ENV_DEV:
4066
4067	  Specifies which MMC device the environment is stored in.
4068
4069	- CONFIG_SYS_MMC_ENV_PART (optional):
4070
4071	  Specifies which MMC partition the environment is stored in. If not
4072	  set, defaults to partition 0, the user area. Common values might be
4073	  1 (first MMC boot partition), 2 (second MMC boot partition).
4074
4075	- CONFIG_ENV_OFFSET:
4076	- CONFIG_ENV_SIZE:
4077
4078	  These two #defines specify the offset and size of the environment
4079	  area within the specified MMC device.
4080
4081	  If offset is positive (the usual case), it is treated as relative to
4082	  the start of the MMC partition. If offset is negative, it is treated
4083	  as relative to the end of the MMC partition. This can be useful if
4084	  your board may be fitted with different MMC devices, which have
4085	  different sizes for the MMC partitions, and you always want the
4086	  environment placed at the very end of the partition, to leave the
4087	  maximum possible space before it, to store other data.
4088
4089	  These two values are in units of bytes, but must be aligned to an
4090	  MMC sector boundary.
4091
4092	- CONFIG_ENV_OFFSET_REDUND (optional):
4093
4094	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4095	  hold a redundant copy of the environment data. This provides a
4096	  valid backup copy in case the other copy is corrupted, e.g. due
4097	  to a power failure during a "saveenv" operation.
4098
4099	  This value may also be positive or negative; this is handled in the
4100	  same way as CONFIG_ENV_OFFSET.
4101
4102	  This value is also in units of bytes, but must also be aligned to
4103	  an MMC sector boundary.
4104
4105	- CONFIG_ENV_SIZE_REDUND (optional):
4106
4107	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4108	  set. If this value is set, it must be set to the same value as
4109	  CONFIG_ENV_SIZE.
4110
4111- CONFIG_SYS_SPI_INIT_OFFSET
4112
4113	Defines offset to the initial SPI buffer area in DPRAM. The
4114	area is used at an early stage (ROM part) if the environment
4115	is configured to reside in the SPI EEPROM: We need a 520 byte
4116	scratch DPRAM area. It is used between the two initialization
4117	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4118	to be a good choice since it makes it far enough from the
4119	start of the data area as well as from the stack pointer.
4120
4121Please note that the environment is read-only until the monitor
4122has been relocated to RAM and a RAM copy of the environment has been
4123created; also, when using EEPROM you will have to use getenv_f()
4124until then to read environment variables.
4125
4126The environment is protected by a CRC32 checksum. Before the monitor
4127is relocated into RAM, as a result of a bad CRC you will be working
4128with the compiled-in default environment - *silently*!!! [This is
4129necessary, because the first environment variable we need is the
4130"baudrate" setting for the console - if we have a bad CRC, we don't
4131have any device yet where we could complain.]
4132
4133Note: once the monitor has been relocated, then it will complain if
4134the default environment is used; a new CRC is computed as soon as you
4135use the "saveenv" command to store a valid environment.
4136
4137- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4138		Echo the inverted Ethernet link state to the fault LED.
4139
4140		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4141		      also needs to be defined.
4142
4143- CONFIG_SYS_FAULT_MII_ADDR:
4144		MII address of the PHY to check for the Ethernet link state.
4145
4146- CONFIG_NS16550_MIN_FUNCTIONS:
4147		Define this if you desire to only have use of the NS16550_init
4148		and NS16550_putc functions for the serial driver located at
4149		drivers/serial/ns16550.c.  This option is useful for saving
4150		space for already greatly restricted images, including but not
4151		limited to NAND_SPL configurations.
4152
4153- CONFIG_DISPLAY_BOARDINFO
4154		Display information about the board that U-Boot is running on
4155		when U-Boot starts up. The board function checkboard() is called
4156		to do this.
4157
4158- CONFIG_DISPLAY_BOARDINFO_LATE
4159		Similar to the previous option, but display this information
4160		later, once stdio is running and output goes to the LCD, if
4161		present.
4162
4163Low Level (hardware related) configuration options:
4164---------------------------------------------------
4165
4166- CONFIG_SYS_CACHELINE_SIZE:
4167		Cache Line Size of the CPU.
4168
4169- CONFIG_SYS_DEFAULT_IMMR:
4170		Default address of the IMMR after system reset.
4171
4172		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4173		and RPXsuper) to be able to adjust the position of
4174		the IMMR register after a reset.
4175
4176- CONFIG_SYS_CCSRBAR_DEFAULT:
4177		Default (power-on reset) physical address of CCSR on Freescale
4178		PowerPC SOCs.
4179
4180- CONFIG_SYS_CCSRBAR:
4181		Virtual address of CCSR.  On a 32-bit build, this is typically
4182		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4183
4184		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4185		for cross-platform code that uses that macro instead.
4186
4187- CONFIG_SYS_CCSRBAR_PHYS:
4188		Physical address of CCSR.  CCSR can be relocated to a new
4189		physical address, if desired.  In this case, this macro should
4190		be set to that address.	 Otherwise, it should be set to the
4191		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4192		is typically relocated on 36-bit builds.  It is recommended
4193		that this macro be defined via the _HIGH and _LOW macros:
4194
4195		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4196			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4197
4198- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4199		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4200		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4201		used in assembly code, so it must not contain typecasts or
4202		integer size suffixes (e.g. "ULL").
4203
4204- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4205		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4206		used in assembly code, so it must not contain typecasts or
4207		integer size suffixes (e.g. "ULL").
4208
4209- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4210		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4211		forced to a value that ensures that CCSR is not relocated.
4212
4213- Floppy Disk Support:
4214		CONFIG_SYS_FDC_DRIVE_NUMBER
4215
4216		the default drive number (default value 0)
4217
4218		CONFIG_SYS_ISA_IO_STRIDE
4219
4220		defines the spacing between FDC chipset registers
4221		(default value 1)
4222
4223		CONFIG_SYS_ISA_IO_OFFSET
4224
4225		defines the offset of register from address. It
4226		depends on which part of the data bus is connected to
4227		the FDC chipset. (default value 0)
4228
4229		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4230		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4231		default value.
4232
4233		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4234		fdc_hw_init() is called at the beginning of the FDC
4235		setup. fdc_hw_init() must be provided by the board
4236		source code. It is used to make hardware dependant
4237		initializations.
4238
4239- CONFIG_IDE_AHB:
4240		Most IDE controllers were designed to be connected with PCI
4241		interface. Only few of them were designed for AHB interface.
4242		When software is doing ATA command and data transfer to
4243		IDE devices through IDE-AHB controller, some additional
4244		registers accessing to these kind of IDE-AHB controller
4245		is requierd.
4246
4247- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4248		DO NOT CHANGE unless you know exactly what you're
4249		doing! (11-4) [MPC8xx/82xx systems only]
4250
4251- CONFIG_SYS_INIT_RAM_ADDR:
4252
4253		Start address of memory area that can be used for
4254		initial data and stack; please note that this must be
4255		writable memory that is working WITHOUT special
4256		initialization, i. e. you CANNOT use normal RAM which
4257		will become available only after programming the
4258		memory controller and running certain initialization
4259		sequences.
4260
4261		U-Boot uses the following memory types:
4262		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4263		- MPC824X: data cache
4264		- PPC4xx:  data cache
4265
4266- CONFIG_SYS_GBL_DATA_OFFSET:
4267
4268		Offset of the initial data structure in the memory
4269		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4270		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4271		data is located at the end of the available space
4272		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4273		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4274		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4275		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4276
4277	Note:
4278		On the MPC824X (or other systems that use the data
4279		cache for initial memory) the address chosen for
4280		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4281		point to an otherwise UNUSED address space between
4282		the top of RAM and the start of the PCI space.
4283
4284- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4285
4286- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4287
4288- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4289
4290- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4291
4292- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4293
4294- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4295
4296- CONFIG_SYS_OR_TIMING_SDRAM:
4297		SDRAM timing
4298
4299- CONFIG_SYS_MAMR_PTA:
4300		periodic timer for refresh
4301
4302- CONFIG_SYS_DER:	Debug Event Register (37-47)
4303
4304- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4305  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4306  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4307  CONFIG_SYS_BR1_PRELIM:
4308		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4309
4310- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4311  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4312  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4313		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4314
4315- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4316  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4317		Machine Mode Register and Memory Periodic Timer
4318		Prescaler definitions (SDRAM timing)
4319
4320- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4321		enable I2C microcode relocation patch (MPC8xx);
4322		define relocation offset in DPRAM [DSP2]
4323
4324- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4325		enable SMC microcode relocation patch (MPC8xx);
4326		define relocation offset in DPRAM [SMC1]
4327
4328- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4329		enable SPI microcode relocation patch (MPC8xx);
4330		define relocation offset in DPRAM [SCC4]
4331
4332- CONFIG_SYS_USE_OSCCLK:
4333		Use OSCM clock mode on MBX8xx board. Be careful,
4334		wrong setting might damage your board. Read
4335		doc/README.MBX before setting this variable!
4336
4337- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4338		Offset of the bootmode word in DPRAM used by post
4339		(Power On Self Tests). This definition overrides
4340		#define'd default value in commproc.h resp.
4341		cpm_8260.h.
4342
4343- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4344  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4345  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4346  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4347  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4348  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4349  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4350  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4351		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4352
4353- CONFIG_PCI_DISABLE_PCIE:
4354		Disable PCI-Express on systems where it is supported but not
4355		required.
4356
4357- CONFIG_PCI_ENUM_ONLY
4358		Only scan through and get the devices on the busses.
4359		Don't do any setup work, presumably because someone or
4360		something has already done it, and we don't need to do it
4361		a second time.	Useful for platforms that are pre-booted
4362		by coreboot or similar.
4363
4364- CONFIG_PCI_INDIRECT_BRIDGE:
4365		Enable support for indirect PCI bridges.
4366
4367- CONFIG_SYS_SRIO:
4368		Chip has SRIO or not
4369
4370- CONFIG_SRIO1:
4371		Board has SRIO 1 port available
4372
4373- CONFIG_SRIO2:
4374		Board has SRIO 2 port available
4375
4376- CONFIG_SRIO_PCIE_BOOT_MASTER
4377		Board can support master function for Boot from SRIO and PCIE
4378
4379- CONFIG_SYS_SRIOn_MEM_VIRT:
4380		Virtual Address of SRIO port 'n' memory region
4381
4382- CONFIG_SYS_SRIOn_MEM_PHYS:
4383		Physical Address of SRIO port 'n' memory region
4384
4385- CONFIG_SYS_SRIOn_MEM_SIZE:
4386		Size of SRIO port 'n' memory region
4387
4388- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4389		Defined to tell the NAND controller that the NAND chip is using
4390		a 16 bit bus.
4391		Not all NAND drivers use this symbol.
4392		Example of drivers that use it:
4393		- drivers/mtd/nand/ndfc.c
4394		- drivers/mtd/nand/mxc_nand.c
4395
4396- CONFIG_SYS_NDFC_EBC0_CFG
4397		Sets the EBC0_CFG register for the NDFC. If not defined
4398		a default value will be used.
4399
4400- CONFIG_SPD_EEPROM
4401		Get DDR timing information from an I2C EEPROM. Common
4402		with pluggable memory modules such as SODIMMs
4403
4404  SPD_EEPROM_ADDRESS
4405		I2C address of the SPD EEPROM
4406
4407- CONFIG_SYS_SPD_BUS_NUM
4408		If SPD EEPROM is on an I2C bus other than the first
4409		one, specify here. Note that the value must resolve
4410		to something your driver can deal with.
4411
4412- CONFIG_SYS_DDR_RAW_TIMING
4413		Get DDR timing information from other than SPD. Common with
4414		soldered DDR chips onboard without SPD. DDR raw timing
4415		parameters are extracted from datasheet and hard-coded into
4416		header files or board specific files.
4417
4418- CONFIG_FSL_DDR_INTERACTIVE
4419		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4420
4421- CONFIG_SYS_83XX_DDR_USES_CS0
4422		Only for 83xx systems. If specified, then DDR should
4423		be configured using CS0 and CS1 instead of CS2 and CS3.
4424
4425- CONFIG_ETHER_ON_FEC[12]
4426		Define to enable FEC[12] on a 8xx series processor.
4427
4428- CONFIG_FEC[12]_PHY
4429		Define to the hardcoded PHY address which corresponds
4430		to the given FEC; i. e.
4431			#define CONFIG_FEC1_PHY 4
4432		means that the PHY with address 4 is connected to FEC1
4433
4434		When set to -1, means to probe for first available.
4435
4436- CONFIG_FEC[12]_PHY_NORXERR
4437		The PHY does not have a RXERR line (RMII only).
4438		(so program the FEC to ignore it).
4439
4440- CONFIG_RMII
4441		Enable RMII mode for all FECs.
4442		Note that this is a global option, we can't
4443		have one FEC in standard MII mode and another in RMII mode.
4444
4445- CONFIG_CRC32_VERIFY
4446		Add a verify option to the crc32 command.
4447		The syntax is:
4448
4449		=> crc32 -v <address> <count> <crc32>
4450
4451		Where address/count indicate a memory area
4452		and crc32 is the correct crc32 which the
4453		area should have.
4454
4455- CONFIG_LOOPW
4456		Add the "loopw" memory command. This only takes effect if
4457		the memory commands are activated globally (CONFIG_CMD_MEM).
4458
4459- CONFIG_MX_CYCLIC
4460		Add the "mdc" and "mwc" memory commands. These are cyclic
4461		"md/mw" commands.
4462		Examples:
4463
4464		=> mdc.b 10 4 500
4465		This command will print 4 bytes (10,11,12,13) each 500 ms.
4466
4467		=> mwc.l 100 12345678 10
4468		This command will write 12345678 to address 100 all 10 ms.
4469
4470		This only takes effect if the memory commands are activated
4471		globally (CONFIG_CMD_MEM).
4472
4473- CONFIG_SKIP_LOWLEVEL_INIT
4474		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4475		low level initializations (like setting up the memory
4476		controller) are omitted and/or U-Boot does not
4477		relocate itself into RAM.
4478
4479		Normally this variable MUST NOT be defined. The only
4480		exception is when U-Boot is loaded (to RAM) by some
4481		other boot loader or by a debugger which performs
4482		these initializations itself.
4483
4484- CONFIG_SPL_BUILD
4485		Modifies the behaviour of start.S when compiling a loader
4486		that is executed before the actual U-Boot. E.g. when
4487		compiling a NAND SPL.
4488
4489- CONFIG_TPL_BUILD
4490		Modifies the behaviour of start.S  when compiling a loader
4491		that is executed after the SPL and before the actual U-Boot.
4492		It is loaded by the SPL.
4493
4494- CONFIG_SYS_MPC85XX_NO_RESETVEC
4495		Only for 85xx systems. If this variable is specified, the section
4496		.resetvec is not kept and the section .bootpg is placed in the
4497		previous 4k of the .text section.
4498
4499- CONFIG_ARCH_MAP_SYSMEM
4500		Generally U-Boot (and in particular the md command) uses
4501		effective address. It is therefore not necessary to regard
4502		U-Boot address as virtual addresses that need to be translated
4503		to physical addresses. However, sandbox requires this, since
4504		it maintains its own little RAM buffer which contains all
4505		addressable memory. This option causes some memory accesses
4506		to be mapped through map_sysmem() / unmap_sysmem().
4507
4508- CONFIG_USE_ARCH_MEMCPY
4509  CONFIG_USE_ARCH_MEMSET
4510		If these options are used a optimized version of memcpy/memset will
4511		be used if available. These functions may be faster under some
4512		conditions but may increase the binary size.
4513
4514- CONFIG_X86_RESET_VECTOR
4515		If defined, the x86 reset vector code is included. This is not
4516		needed when U-Boot is running from Coreboot.
4517
4518- CONFIG_SYS_MPUCLK
4519		Defines the MPU clock speed (in MHz).
4520
4521		NOTE : currently only supported on AM335x platforms.
4522
4523- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4524		Enables the RTC32K OSC on AM33xx based plattforms
4525
4526Freescale QE/FMAN Firmware Support:
4527-----------------------------------
4528
4529The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4530loading of "firmware", which is encoded in the QE firmware binary format.
4531This firmware often needs to be loaded during U-Boot booting, so macros
4532are used to identify the storage device (NOR flash, SPI, etc) and the address
4533within that device.
4534
4535- CONFIG_SYS_FMAN_FW_ADDR
4536	The address in the storage device where the FMAN microcode is located.  The
4537	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4538	is also specified.
4539
4540- CONFIG_SYS_QE_FW_ADDR
4541	The address in the storage device where the QE microcode is located.  The
4542	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4543	is also specified.
4544
4545- CONFIG_SYS_QE_FMAN_FW_LENGTH
4546	The maximum possible size of the firmware.  The firmware binary format
4547	has a field that specifies the actual size of the firmware, but it
4548	might not be possible to read any part of the firmware unless some
4549	local storage is allocated to hold the entire firmware first.
4550
4551- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4552	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4553	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4554	virtual address in NOR flash.
4555
4556- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4557	Specifies that QE/FMAN firmware is located in NAND flash.
4558	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4559
4560- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4561	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4562	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4563
4564- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4565	Specifies that QE/FMAN firmware is located on the primary SPI
4566	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4567
4568- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4569	Specifies that QE/FMAN firmware is located in the remote (master)
4570	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4571	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4572	window->master inbound window->master LAW->the ucode address in
4573	master's memory space.
4574
4575Building the Software:
4576======================
4577
4578Building U-Boot has been tested in several native build environments
4579and in many different cross environments. Of course we cannot support
4580all possibly existing versions of cross development tools in all
4581(potentially obsolete) versions. In case of tool chain problems we
4582recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4583which is extensively used to build and test U-Boot.
4584
4585If you are not using a native environment, it is assumed that you
4586have GNU cross compiling tools available in your path. In this case,
4587you must set the environment variable CROSS_COMPILE in your shell.
4588Note that no changes to the Makefile or any other source files are
4589necessary. For example using the ELDK on a 4xx CPU, please enter:
4590
4591	$ CROSS_COMPILE=ppc_4xx-
4592	$ export CROSS_COMPILE
4593
4594Note: If you wish to generate Windows versions of the utilities in
4595      the tools directory you can use the MinGW toolchain
4596      (http://www.mingw.org).  Set your HOST tools to the MinGW
4597      toolchain and execute 'make tools'.  For example:
4598
4599       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4600
4601      Binaries such as tools/mkimage.exe will be created which can
4602      be executed on computers running Windows.
4603
4604U-Boot is intended to be simple to build. After installing the
4605sources you must configure U-Boot for one specific board type. This
4606is done by typing:
4607
4608	make NAME_config
4609
4610where "NAME_config" is the name of one of the existing configu-
4611rations; see boards.cfg for supported names.
4612
4613Note: for some board special configuration names may exist; check if
4614      additional information is available from the board vendor; for
4615      instance, the TQM823L systems are available without (standard)
4616      or with LCD support. You can select such additional "features"
4617      when choosing the configuration, i. e.
4618
4619      make TQM823L_config
4620	- will configure for a plain TQM823L, i. e. no LCD support
4621
4622      make TQM823L_LCD_config
4623	- will configure for a TQM823L with U-Boot console on LCD
4624
4625      etc.
4626
4627
4628Finally, type "make all", and you should get some working U-Boot
4629images ready for download to / installation on your system:
4630
4631- "u-boot.bin" is a raw binary image
4632- "u-boot" is an image in ELF binary format
4633- "u-boot.srec" is in Motorola S-Record format
4634
4635By default the build is performed locally and the objects are saved
4636in the source directory. One of the two methods can be used to change
4637this behavior and build U-Boot to some external directory:
4638
46391. Add O= to the make command line invocations:
4640
4641	make O=/tmp/build distclean
4642	make O=/tmp/build NAME_config
4643	make O=/tmp/build all
4644
46452. Set environment variable BUILD_DIR to point to the desired location:
4646
4647	export BUILD_DIR=/tmp/build
4648	make distclean
4649	make NAME_config
4650	make all
4651
4652Note that the command line "O=" setting overrides the BUILD_DIR environment
4653variable.
4654
4655
4656Please be aware that the Makefiles assume you are using GNU make, so
4657for instance on NetBSD you might need to use "gmake" instead of
4658native "make".
4659
4660
4661If the system board that you have is not listed, then you will need
4662to port U-Boot to your hardware platform. To do this, follow these
4663steps:
4664
46651.  Add a new configuration option for your board to the toplevel
4666    "boards.cfg" file, using the existing entries as examples.
4667    Follow the instructions there to keep the boards in order.
46682.  Create a new directory to hold your board specific code. Add any
4669    files you need. In your board directory, you will need at least
4670    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46713.  Create a new configuration file "include/configs/<board>.h" for
4672    your board
46733.  If you're porting U-Boot to a new CPU, then also create a new
4674    directory to hold your CPU specific code. Add any files you need.
46754.  Run "make <board>_config" with your new name.
46765.  Type "make", and you should get a working "u-boot.srec" file
4677    to be installed on your target system.
46786.  Debug and solve any problems that might arise.
4679    [Of course, this last step is much harder than it sounds.]
4680
4681
4682Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4683==============================================================
4684
4685If you have modified U-Boot sources (for instance added a new board
4686or support for new devices, a new CPU, etc.) you are expected to
4687provide feedback to the other developers. The feedback normally takes
4688the form of a "patch", i. e. a context diff against a certain (latest
4689official or latest in the git repository) version of U-Boot sources.
4690
4691But before you submit such a patch, please verify that your modifi-
4692cation did not break existing code. At least make sure that *ALL* of
4693the supported boards compile WITHOUT ANY compiler warnings. To do so,
4694just run the "MAKEALL" script, which will configure and build U-Boot
4695for ALL supported system. Be warned, this will take a while. You can
4696select which (cross) compiler to use by passing a `CROSS_COMPILE'
4697environment variable to the script, i. e. to use the ELDK cross tools
4698you can type
4699
4700	CROSS_COMPILE=ppc_8xx- MAKEALL
4701
4702or to build on a native PowerPC system you can type
4703
4704	CROSS_COMPILE=' ' MAKEALL
4705
4706When using the MAKEALL script, the default behaviour is to build
4707U-Boot in the source directory. This location can be changed by
4708setting the BUILD_DIR environment variable. Also, for each target
4709built, the MAKEALL script saves two log files (<target>.ERR and
4710<target>.MAKEALL) in the <source dir>/LOG directory. This default
4711location can be changed by setting the MAKEALL_LOGDIR environment
4712variable. For example:
4713
4714	export BUILD_DIR=/tmp/build
4715	export MAKEALL_LOGDIR=/tmp/log
4716	CROSS_COMPILE=ppc_8xx- MAKEALL
4717
4718With the above settings build objects are saved in the /tmp/build,
4719log files are saved in the /tmp/log and the source tree remains clean
4720during the whole build process.
4721
4722
4723See also "U-Boot Porting Guide" below.
4724
4725
4726Monitor Commands - Overview:
4727============================
4728
4729go	- start application at address 'addr'
4730run	- run commands in an environment variable
4731bootm	- boot application image from memory
4732bootp	- boot image via network using BootP/TFTP protocol
4733bootz   - boot zImage from memory
4734tftpboot- boot image via network using TFTP protocol
4735	       and env variables "ipaddr" and "serverip"
4736	       (and eventually "gatewayip")
4737tftpput - upload a file via network using TFTP protocol
4738rarpboot- boot image via network using RARP/TFTP protocol
4739diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4740loads	- load S-Record file over serial line
4741loadb	- load binary file over serial line (kermit mode)
4742md	- memory display
4743mm	- memory modify (auto-incrementing)
4744nm	- memory modify (constant address)
4745mw	- memory write (fill)
4746cp	- memory copy
4747cmp	- memory compare
4748crc32	- checksum calculation
4749i2c	- I2C sub-system
4750sspi	- SPI utility commands
4751base	- print or set address offset
4752printenv- print environment variables
4753setenv	- set environment variables
4754saveenv - save environment variables to persistent storage
4755protect - enable or disable FLASH write protection
4756erase	- erase FLASH memory
4757flinfo	- print FLASH memory information
4758nand	- NAND memory operations (see doc/README.nand)
4759bdinfo	- print Board Info structure
4760iminfo	- print header information for application image
4761coninfo - print console devices and informations
4762ide	- IDE sub-system
4763loop	- infinite loop on address range
4764loopw	- infinite write loop on address range
4765mtest	- simple RAM test
4766icache	- enable or disable instruction cache
4767dcache	- enable or disable data cache
4768reset	- Perform RESET of the CPU
4769echo	- echo args to console
4770version - print monitor version
4771help	- print online help
4772?	- alias for 'help'
4773
4774
4775Monitor Commands - Detailed Description:
4776========================================
4777
4778TODO.
4779
4780For now: just type "help <command>".
4781
4782
4783Environment Variables:
4784======================
4785
4786U-Boot supports user configuration using Environment Variables which
4787can be made persistent by saving to Flash memory.
4788
4789Environment Variables are set using "setenv", printed using
4790"printenv", and saved to Flash using "saveenv". Using "setenv"
4791without a value can be used to delete a variable from the
4792environment. As long as you don't save the environment you are
4793working with an in-memory copy. In case the Flash area containing the
4794environment is erased by accident, a default environment is provided.
4795
4796Some configuration options can be set using Environment Variables.
4797
4798List of environment variables (most likely not complete):
4799
4800  baudrate	- see CONFIG_BAUDRATE
4801
4802  bootdelay	- see CONFIG_BOOTDELAY
4803
4804  bootcmd	- see CONFIG_BOOTCOMMAND
4805
4806  bootargs	- Boot arguments when booting an RTOS image
4807
4808  bootfile	- Name of the image to load with TFTP
4809
4810  bootm_low	- Memory range available for image processing in the bootm
4811		  command can be restricted. This variable is given as
4812		  a hexadecimal number and defines lowest address allowed
4813		  for use by the bootm command. See also "bootm_size"
4814		  environment variable. Address defined by "bootm_low" is
4815		  also the base of the initial memory mapping for the Linux
4816		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4817		  bootm_mapsize.
4818
4819  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4820		  This variable is given as a hexadecimal number and it
4821		  defines the size of the memory region starting at base
4822		  address bootm_low that is accessible by the Linux kernel
4823		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4824		  as the default value if it is defined, and bootm_size is
4825		  used otherwise.
4826
4827  bootm_size	- 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 the size of the region
4830		  allowed for use by the bootm command. See also "bootm_low"
4831		  environment variable.
4832
4833  updatefile	- Location of the software update file on a TFTP server, used
4834		  by the automatic software update feature. Please refer to
4835		  documentation in doc/README.update for more details.
4836
4837  autoload	- if set to "no" (any string beginning with 'n'),
4838		  "bootp" will just load perform a lookup of the
4839		  configuration from the BOOTP server, but not try to
4840		  load any image using TFTP
4841
4842  autostart	- if set to "yes", an image loaded using the "bootp",
4843		  "rarpboot", "tftpboot" or "diskboot" commands will
4844		  be automatically started (by internally calling
4845		  "bootm")
4846
4847		  If set to "no", a standalone image passed to the
4848		  "bootm" command will be copied to the load address
4849		  (and eventually uncompressed), but NOT be started.
4850		  This can be used to load and uncompress arbitrary
4851		  data.
4852
4853  fdt_high	- if set this restricts the maximum address that the
4854		  flattened device tree will be copied into upon boot.
4855		  For example, if you have a system with 1 GB memory
4856		  at physical address 0x10000000, while Linux kernel
4857		  only recognizes the first 704 MB as low memory, you
4858		  may need to set fdt_high as 0x3C000000 to have the
4859		  device tree blob be copied to the maximum address
4860		  of the 704 MB low memory, so that Linux kernel can
4861		  access it during the boot procedure.
4862
4863		  If this is set to the special value 0xFFFFFFFF then
4864		  the fdt will not be copied at all on boot.  For this
4865		  to work it must reside in writable memory, have
4866		  sufficient padding on the end of it for u-boot to
4867		  add the information it needs into it, and the memory
4868		  must be accessible by the kernel.
4869
4870  fdtcontroladdr- if set this is the address of the control flattened
4871		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4872		  defined.
4873
4874  i2cfast	- (PPC405GP|PPC405EP only)
4875		  if set to 'y' configures Linux I2C driver for fast
4876		  mode (400kHZ). This environment variable is used in
4877		  initialization code. So, for changes to be effective
4878		  it must be saved and board must be reset.
4879
4880  initrd_high	- restrict positioning of initrd images:
4881		  If this variable is not set, initrd images will be
4882		  copied to the highest possible address in RAM; this
4883		  is usually what you want since it allows for
4884		  maximum initrd size. If for some reason you want to
4885		  make sure that the initrd image is loaded below the
4886		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4887		  variable to a value of "no" or "off" or "0".
4888		  Alternatively, you can set it to a maximum upper
4889		  address to use (U-Boot will still check that it
4890		  does not overwrite the U-Boot stack and data).
4891
4892		  For instance, when you have a system with 16 MB
4893		  RAM, and want to reserve 4 MB from use by Linux,
4894		  you can do this by adding "mem=12M" to the value of
4895		  the "bootargs" variable. However, now you must make
4896		  sure that the initrd image is placed in the first
4897		  12 MB as well - this can be done with
4898
4899		  setenv initrd_high 00c00000
4900
4901		  If you set initrd_high to 0xFFFFFFFF, this is an
4902		  indication to U-Boot that all addresses are legal
4903		  for the Linux kernel, including addresses in flash
4904		  memory. In this case U-Boot will NOT COPY the
4905		  ramdisk at all. This may be useful to reduce the
4906		  boot time on your system, but requires that this
4907		  feature is supported by your Linux kernel.
4908
4909  ipaddr	- IP address; needed for tftpboot command
4910
4911  loadaddr	- Default load address for commands like "bootp",
4912		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4913
4914  loads_echo	- see CONFIG_LOADS_ECHO
4915
4916  serverip	- TFTP server IP address; needed for tftpboot command
4917
4918  bootretry	- see CONFIG_BOOT_RETRY_TIME
4919
4920  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4921
4922  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4923
4924  ethprime	- controls which interface is used first.
4925
4926  ethact	- controls which interface is currently active.
4927		  For example you can do the following
4928
4929		  => setenv ethact FEC
4930		  => ping 192.168.0.1 # traffic sent on FEC
4931		  => setenv ethact SCC
4932		  => ping 10.0.0.1 # traffic sent on SCC
4933
4934  ethrotate	- When set to "no" U-Boot does not go through all
4935		  available network interfaces.
4936		  It just stays at the currently selected interface.
4937
4938  netretry	- When set to "no" each network operation will
4939		  either succeed or fail without retrying.
4940		  When set to "once" the network operation will
4941		  fail when all the available network interfaces
4942		  are tried once without success.
4943		  Useful on scripts which control the retry operation
4944		  themselves.
4945
4946  npe_ucode	- set load address for the NPE microcode
4947
4948  silent_linux  - If set then linux will be told to boot silently, by
4949		  changing the console to be empty. If "yes" it will be
4950		  made silent. If "no" it will not be made silent. If
4951		  unset, then it will be made silent if the U-Boot console
4952		  is silent.
4953
4954  tftpsrcport	- If this is set, the value is used for TFTP's
4955		  UDP source port.
4956
4957  tftpdstport	- If this is set, the value is used for TFTP's UDP
4958		  destination port instead of the Well Know Port 69.
4959
4960  tftpblocksize - Block size to use for TFTP transfers; if not set,
4961		  we use the TFTP server's default block size
4962
4963  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4964		  seconds, minimum value is 1000 = 1 second). Defines
4965		  when a packet is considered to be lost so it has to
4966		  be retransmitted. The default is 5000 = 5 seconds.
4967		  Lowering this value may make downloads succeed
4968		  faster in networks with high packet loss rates or
4969		  with unreliable TFTP servers.
4970
4971  vlan		- When set to a value < 4095 the traffic over
4972		  Ethernet is encapsulated/received over 802.1q
4973		  VLAN tagged frames.
4974
4975The following image location variables contain the location of images
4976used in booting. The "Image" column gives the role of the image and is
4977not an environment variable name. The other columns are environment
4978variable names. "File Name" gives the name of the file on a TFTP
4979server, "RAM Address" gives the location in RAM the image will be
4980loaded to, and "Flash Location" gives the image's address in NOR
4981flash or offset in NAND flash.
4982
4983*Note* - these variables don't have to be defined for all boards, some
4984boards currenlty use other variables for these purposes, and some
4985boards use these variables for other purposes.
4986
4987Image		    File Name	     RAM Address       Flash Location
4988-----		    ---------	     -----------       --------------
4989u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4990Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4991device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4992ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4993
4994The following environment variables may be used and automatically
4995updated by the network boot commands ("bootp" and "rarpboot"),
4996depending the information provided by your boot server:
4997
4998  bootfile	- see above
4999  dnsip		- IP address of your Domain Name Server
5000  dnsip2	- IP address of your secondary Domain Name Server
5001  gatewayip	- IP address of the Gateway (Router) to use
5002  hostname	- Target hostname
5003  ipaddr	- see above
5004  netmask	- Subnet Mask
5005  rootpath	- Pathname of the root filesystem on the NFS server
5006  serverip	- see above
5007
5008
5009There are two special Environment Variables:
5010
5011  serial#	- contains hardware identification information such
5012		  as type string and/or serial number
5013  ethaddr	- Ethernet address
5014
5015These variables can be set only once (usually during manufacturing of
5016the board). U-Boot refuses to delete or overwrite these variables
5017once they have been set once.
5018
5019
5020Further special Environment Variables:
5021
5022  ver		- Contains the U-Boot version string as printed
5023		  with the "version" command. This variable is
5024		  readonly (see CONFIG_VERSION_VARIABLE).
5025
5026
5027Please note that changes to some configuration parameters may take
5028only effect after the next boot (yes, that's just like Windoze :-).
5029
5030
5031Callback functions for environment variables:
5032---------------------------------------------
5033
5034For some environment variables, the behavior of u-boot needs to change
5035when their values are changed.  This functionailty allows functions to
5036be associated with arbitrary variables.  On creation, overwrite, or
5037deletion, the callback will provide the opportunity for some side
5038effect to happen or for the change to be rejected.
5039
5040The callbacks are named and associated with a function using the
5041U_BOOT_ENV_CALLBACK macro in your board or driver code.
5042
5043These callbacks are associated with variables in one of two ways.  The
5044static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5045in the board configuration to a string that defines a list of
5046associations.  The list must be in the following format:
5047
5048	entry = variable_name[:callback_name]
5049	list = entry[,list]
5050
5051If the callback name is not specified, then the callback is deleted.
5052Spaces are also allowed anywhere in the list.
5053
5054Callbacks can also be associated by defining the ".callbacks" variable
5055with the same list format above.  Any association in ".callbacks" will
5056override any association in the static list. You can define
5057CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5058".callbacks" envirnoment variable in the default or embedded environment.
5059
5060
5061Command Line Parsing:
5062=====================
5063
5064There are two different command line parsers available with U-Boot:
5065the old "simple" one, and the much more powerful "hush" shell:
5066
5067Old, simple command line parser:
5068--------------------------------
5069
5070- supports environment variables (through setenv / saveenv commands)
5071- several commands on one line, separated by ';'
5072- variable substitution using "... ${name} ..." syntax
5073- special characters ('$', ';') can be escaped by prefixing with '\',
5074  for example:
5075	setenv bootcmd bootm \${address}
5076- You can also escape text by enclosing in single apostrophes, for example:
5077	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5078
5079Hush shell:
5080-----------
5081
5082- similar to Bourne shell, with control structures like
5083  if...then...else...fi, for...do...done; while...do...done,
5084  until...do...done, ...
5085- supports environment ("global") variables (through setenv / saveenv
5086  commands) and local shell variables (through standard shell syntax
5087  "name=value"); only environment variables can be used with "run"
5088  command
5089
5090General rules:
5091--------------
5092
5093(1) If a command line (or an environment variable executed by a "run"
5094    command) contains several commands separated by semicolon, and
5095    one of these commands fails, then the remaining commands will be
5096    executed anyway.
5097
5098(2) If you execute several variables with one call to run (i. e.
5099    calling run with a list of variables as arguments), any failing
5100    command will cause "run" to terminate, i. e. the remaining
5101    variables are not executed.
5102
5103Note for Redundant Ethernet Interfaces:
5104=======================================
5105
5106Some boards come with redundant Ethernet interfaces; U-Boot supports
5107such configurations and is capable of automatic selection of a
5108"working" interface when needed. MAC assignment works as follows:
5109
5110Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5111MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5112"eth1addr" (=>eth1), "eth2addr", ...
5113
5114If the network interface stores some valid MAC address (for instance
5115in SROM), this is used as default address if there is NO correspon-
5116ding setting in the environment; if the corresponding environment
5117variable is set, this overrides the settings in the card; that means:
5118
5119o If the SROM has a valid MAC address, and there is no address in the
5120  environment, the SROM's address is used.
5121
5122o If there is no valid address in the SROM, and a definition in the
5123  environment exists, then the value from the environment variable is
5124  used.
5125
5126o If both the SROM and the environment contain a MAC address, and
5127  both addresses are the same, this MAC address is used.
5128
5129o If both the SROM and the environment contain a MAC address, and the
5130  addresses differ, the value from the environment is used and a
5131  warning is printed.
5132
5133o If neither SROM nor the environment contain a MAC address, an error
5134  is raised.
5135
5136If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5137will be programmed into hardware as part of the initialization process.	 This
5138may be skipped by setting the appropriate 'ethmacskip' environment variable.
5139The naming convention is as follows:
5140"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5141
5142Image Formats:
5143==============
5144
5145U-Boot is capable of booting (and performing other auxiliary operations on)
5146images in two formats:
5147
5148New uImage format (FIT)
5149-----------------------
5150
5151Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5152to Flattened Device Tree). It allows the use of images with multiple
5153components (several kernels, ramdisks, etc.), with contents protected by
5154SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5155
5156
5157Old uImage format
5158-----------------
5159
5160Old image format is based on binary files which can be basically anything,
5161preceded by a special header; see the definitions in include/image.h for
5162details; basically, the header defines the following image properties:
5163
5164* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5165  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5166  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5167  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5168  INTEGRITY).
5169* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5170  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5171  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5172* Compression Type (uncompressed, gzip, bzip2)
5173* Load Address
5174* Entry Point
5175* Image Name
5176* Image Timestamp
5177
5178The header is marked by a special Magic Number, and both the header
5179and the data portions of the image are secured against corruption by
5180CRC32 checksums.
5181
5182
5183Linux Support:
5184==============
5185
5186Although U-Boot should support any OS or standalone application
5187easily, the main focus has always been on Linux during the design of
5188U-Boot.
5189
5190U-Boot includes many features that so far have been part of some
5191special "boot loader" code within the Linux kernel. Also, any
5192"initrd" images to be used are no longer part of one big Linux image;
5193instead, kernel and "initrd" are separate images. This implementation
5194serves several purposes:
5195
5196- the same features can be used for other OS or standalone
5197  applications (for instance: using compressed images to reduce the
5198  Flash memory footprint)
5199
5200- it becomes much easier to port new Linux kernel versions because
5201  lots of low-level, hardware dependent stuff are done by U-Boot
5202
5203- the same Linux kernel image can now be used with different "initrd"
5204  images; of course this also means that different kernel images can
5205  be run with the same "initrd". This makes testing easier (you don't
5206  have to build a new "zImage.initrd" Linux image when you just
5207  change a file in your "initrd"). Also, a field-upgrade of the
5208  software is easier now.
5209
5210
5211Linux HOWTO:
5212============
5213
5214Porting Linux to U-Boot based systems:
5215---------------------------------------
5216
5217U-Boot cannot save you from doing all the necessary modifications to
5218configure the Linux device drivers for use with your target hardware
5219(no, we don't intend to provide a full virtual machine interface to
5220Linux :-).
5221
5222But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5223
5224Just make sure your machine specific header file (for instance
5225include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5226Information structure as we define in include/asm-<arch>/u-boot.h,
5227and make sure that your definition of IMAP_ADDR uses the same value
5228as your U-Boot configuration in CONFIG_SYS_IMMR.
5229
5230
5231Configuring the Linux kernel:
5232-----------------------------
5233
5234No specific requirements for U-Boot. Make sure you have some root
5235device (initial ramdisk, NFS) for your target system.
5236
5237
5238Building a Linux Image:
5239-----------------------
5240
5241With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5242not used. If you use recent kernel source, a new build target
5243"uImage" will exist which automatically builds an image usable by
5244U-Boot. Most older kernels also have support for a "pImage" target,
5245which was introduced for our predecessor project PPCBoot and uses a
5246100% compatible format.
5247
5248Example:
5249
5250	make TQM850L_config
5251	make oldconfig
5252	make dep
5253	make uImage
5254
5255The "uImage" build target uses a special tool (in 'tools/mkimage') to
5256encapsulate a compressed Linux kernel image with header	 information,
5257CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5258
5259* build a standard "vmlinux" kernel image (in ELF binary format):
5260
5261* convert the kernel into a raw binary image:
5262
5263	${CROSS_COMPILE}-objcopy -O binary \
5264				 -R .note -R .comment \
5265				 -S vmlinux linux.bin
5266
5267* compress the binary image:
5268
5269	gzip -9 linux.bin
5270
5271* package compressed binary image for U-Boot:
5272
5273	mkimage -A ppc -O linux -T kernel -C gzip \
5274		-a 0 -e 0 -n "Linux Kernel Image" \
5275		-d linux.bin.gz uImage
5276
5277
5278The "mkimage" tool can also be used to create ramdisk images for use
5279with U-Boot, either separated from the Linux kernel image, or
5280combined into one file. "mkimage" encapsulates the images with a 64
5281byte header containing information about target architecture,
5282operating system, image type, compression method, entry points, time
5283stamp, CRC32 checksums, etc.
5284
5285"mkimage" can be called in two ways: to verify existing images and
5286print the header information, or to build new images.
5287
5288In the first form (with "-l" option) mkimage lists the information
5289contained in the header of an existing U-Boot image; this includes
5290checksum verification:
5291
5292	tools/mkimage -l image
5293	  -l ==> list image header information
5294
5295The second form (with "-d" option) is used to build a U-Boot image
5296from a "data file" which is used as image payload:
5297
5298	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5299		      -n name -d data_file image
5300	  -A ==> set architecture to 'arch'
5301	  -O ==> set operating system to 'os'
5302	  -T ==> set image type to 'type'
5303	  -C ==> set compression type 'comp'
5304	  -a ==> set load address to 'addr' (hex)
5305	  -e ==> set entry point to 'ep' (hex)
5306	  -n ==> set image name to 'name'
5307	  -d ==> use image data from 'datafile'
5308
5309Right now, all Linux kernels for PowerPC systems use the same load
5310address (0x00000000), but the entry point address depends on the
5311kernel version:
5312
5313- 2.2.x kernels have the entry point at 0x0000000C,
5314- 2.3.x and later kernels have the entry point at 0x00000000.
5315
5316So a typical call to build a U-Boot image would read:
5317
5318	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5319	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5320	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5321	> examples/uImage.TQM850L
5322	Image Name:   2.4.4 kernel for TQM850L
5323	Created:      Wed Jul 19 02:34:59 2000
5324	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5325	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5326	Load Address: 0x00000000
5327	Entry Point:  0x00000000
5328
5329To verify the contents of the image (or check for corruption):
5330
5331	-> tools/mkimage -l examples/uImage.TQM850L
5332	Image Name:   2.4.4 kernel for TQM850L
5333	Created:      Wed Jul 19 02:34:59 2000
5334	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5335	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5336	Load Address: 0x00000000
5337	Entry Point:  0x00000000
5338
5339NOTE: for embedded systems where boot time is critical you can trade
5340speed for memory and install an UNCOMPRESSED image instead: this
5341needs more space in Flash, but boots much faster since it does not
5342need to be uncompressed:
5343
5344	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5345	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5346	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5347	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5348	> examples/uImage.TQM850L-uncompressed
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 (uncompressed)
5352	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5353	Load Address: 0x00000000
5354	Entry Point:  0x00000000
5355
5356
5357Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5358when your kernel is intended to use an initial ramdisk:
5359
5360	-> tools/mkimage -n 'Simple Ramdisk Image' \
5361	> -A ppc -O linux -T ramdisk -C gzip \
5362	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5363	Image Name:   Simple Ramdisk Image
5364	Created:      Wed Jan 12 14:01:50 2000
5365	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5366	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5367	Load Address: 0x00000000
5368	Entry Point:  0x00000000
5369
5370The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5371option performs the converse operation of the mkimage's second form (the "-d"
5372option). Given an image built by mkimage, the dumpimage extracts a "data file"
5373from the image:
5374
5375	tools/dumpimage -i image -p position data_file
5376	  -i ==> extract from the 'image' a specific 'data_file', \
5377	   indexed by 'position'
5378
5379
5380Installing a Linux Image:
5381-------------------------
5382
5383To downloading a U-Boot image over the serial (console) interface,
5384you must convert the image to S-Record format:
5385
5386	objcopy -I binary -O srec examples/image examples/image.srec
5387
5388The 'objcopy' does not understand the information in the U-Boot
5389image header, so the resulting S-Record file will be relative to
5390address 0x00000000. To load it to a given address, you need to
5391specify the target address as 'offset' parameter with the 'loads'
5392command.
5393
5394Example: install the image to address 0x40100000 (which on the
5395TQM8xxL is in the first Flash bank):
5396
5397	=> erase 40100000 401FFFFF
5398
5399	.......... done
5400	Erased 8 sectors
5401
5402	=> loads 40100000
5403	## Ready for S-Record download ...
5404	~>examples/image.srec
5405	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5406	...
5407	15989 15990 15991 15992
5408	[file transfer complete]
5409	[connected]
5410	## Start Addr = 0x00000000
5411
5412
5413You can check the success of the download using the 'iminfo' command;
5414this includes a checksum verification so you can be sure no data
5415corruption happened:
5416
5417	=> imi 40100000
5418
5419	## Checking Image at 40100000 ...
5420	   Image Name:	 2.2.13 for initrd on TQM850L
5421	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5422	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5423	   Load Address: 00000000
5424	   Entry Point:	 0000000c
5425	   Verifying Checksum ... OK
5426
5427
5428Boot Linux:
5429-----------
5430
5431The "bootm" command is used to boot an application that is stored in
5432memory (RAM or Flash). In case of a Linux kernel image, the contents
5433of the "bootargs" environment variable is passed to the kernel as
5434parameters. You can check and modify this variable using the
5435"printenv" and "setenv" commands:
5436
5437
5438	=> printenv bootargs
5439	bootargs=root=/dev/ram
5440
5441	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5442
5443	=> printenv bootargs
5444	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5445
5446	=> bootm 40020000
5447	## Booting Linux kernel at 40020000 ...
5448	   Image Name:	 2.2.13 for NFS on TQM850L
5449	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5450	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5451	   Load Address: 00000000
5452	   Entry Point:	 0000000c
5453	   Verifying Checksum ... OK
5454	   Uncompressing Kernel Image ... OK
5455	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
5456	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5457	time_init: decrementer frequency = 187500000/60
5458	Calibrating delay loop... 49.77 BogoMIPS
5459	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5460	...
5461
5462If you want to boot a Linux kernel with initial RAM disk, you pass
5463the memory addresses of both the kernel and the initrd image (PPBCOOT
5464format!) to the "bootm" command:
5465
5466	=> imi 40100000 40200000
5467
5468	## Checking Image at 40100000 ...
5469	   Image Name:	 2.2.13 for initrd on TQM850L
5470	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5471	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5472	   Load Address: 00000000
5473	   Entry Point:	 0000000c
5474	   Verifying Checksum ... OK
5475
5476	## Checking Image at 40200000 ...
5477	   Image Name:	 Simple Ramdisk Image
5478	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5479	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5480	   Load Address: 00000000
5481	   Entry Point:	 00000000
5482	   Verifying Checksum ... OK
5483
5484	=> bootm 40100000 40200000
5485	## Booting Linux kernel 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	   Uncompressing Kernel Image ... OK
5493	## Loading RAMDisk 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	   Loading Ramdisk ... OK
5501	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
5502	Boot arguments: root=/dev/ram
5503	time_init: decrementer frequency = 187500000/60
5504	Calibrating delay loop... 49.77 BogoMIPS
5505	...
5506	RAMDISK: Compressed image found at block 0
5507	VFS: Mounted root (ext2 filesystem).
5508
5509	bash#
5510
5511Boot Linux and pass a flat device tree:
5512-----------
5513
5514First, U-Boot must be compiled with the appropriate defines. See the section
5515titled "Linux Kernel Interface" above for a more in depth explanation. The
5516following is an example of how to start a kernel and pass an updated
5517flat device tree:
5518
5519=> print oftaddr
5520oftaddr=0x300000
5521=> print oft
5522oft=oftrees/mpc8540ads.dtb
5523=> tftp $oftaddr $oft
5524Speed: 1000, full duplex
5525Using TSEC0 device
5526TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5527Filename 'oftrees/mpc8540ads.dtb'.
5528Load address: 0x300000
5529Loading: #
5530done
5531Bytes transferred = 4106 (100a hex)
5532=> tftp $loadaddr $bootfile
5533Speed: 1000, full duplex
5534Using TSEC0 device
5535TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5536Filename 'uImage'.
5537Load address: 0x200000
5538Loading:############
5539done
5540Bytes transferred = 1029407 (fb51f hex)
5541=> print loadaddr
5542loadaddr=200000
5543=> print oftaddr
5544oftaddr=0x300000
5545=> bootm $loadaddr - $oftaddr
5546## Booting image at 00200000 ...
5547   Image Name:	 Linux-2.6.17-dirty
5548   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5549   Data Size:	 1029343 Bytes = 1005.2 kB
5550   Load Address: 00000000
5551   Entry Point:	 00000000
5552   Verifying Checksum ... OK
5553   Uncompressing Kernel Image ... OK
5554Booting using flat device tree at 0x300000
5555Using MPC85xx ADS machine description
5556Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5557[snip]
5558
5559
5560More About U-Boot Image Types:
5561------------------------------
5562
5563U-Boot supports the following image types:
5564
5565   "Standalone Programs" are directly runnable in the environment
5566	provided by U-Boot; it is expected that (if they behave
5567	well) you can continue to work in U-Boot after return from
5568	the Standalone Program.
5569   "OS Kernel Images" are usually images of some Embedded OS which
5570	will take over control completely. Usually these programs
5571	will install their own set of exception handlers, device
5572	drivers, set up the MMU, etc. - this means, that you cannot
5573	expect to re-enter U-Boot except by resetting the CPU.
5574   "RAMDisk Images" are more or less just data blocks, and their
5575	parameters (address, size) are passed to an OS kernel that is
5576	being started.
5577   "Multi-File Images" contain several images, typically an OS
5578	(Linux) kernel image and one or more data images like
5579	RAMDisks. This construct is useful for instance when you want
5580	to boot over the network using BOOTP etc., where the boot
5581	server provides just a single image file, but you want to get
5582	for instance an OS kernel and a RAMDisk image.
5583
5584	"Multi-File Images" start with a list of image sizes, each
5585	image size (in bytes) specified by an "uint32_t" in network
5586	byte order. This list is terminated by an "(uint32_t)0".
5587	Immediately after the terminating 0 follow the images, one by
5588	one, all aligned on "uint32_t" boundaries (size rounded up to
5589	a multiple of 4 bytes).
5590
5591   "Firmware Images" are binary images containing firmware (like
5592	U-Boot or FPGA images) which usually will be programmed to
5593	flash memory.
5594
5595   "Script files" are command sequences that will be executed by
5596	U-Boot's command interpreter; this feature is especially
5597	useful when you configure U-Boot to use a real shell (hush)
5598	as command interpreter.
5599
5600Booting the Linux zImage:
5601-------------------------
5602
5603On some platforms, it's possible to boot Linux zImage. This is done
5604using the "bootz" command. The syntax of "bootz" command is the same
5605as the syntax of "bootm" command.
5606
5607Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5608kernel with raw initrd images. The syntax is slightly different, the
5609address of the initrd must be augmented by it's size, in the following
5610format: "<initrd addres>:<initrd size>".
5611
5612
5613Standalone HOWTO:
5614=================
5615
5616One of the features of U-Boot is that you can dynamically load and
5617run "standalone" applications, which can use some resources of
5618U-Boot like console I/O functions or interrupt services.
5619
5620Two simple examples are included with the sources:
5621
5622"Hello World" Demo:
5623-------------------
5624
5625'examples/hello_world.c' contains a small "Hello World" Demo
5626application; it is automatically compiled when you build U-Boot.
5627It's configured to run at address 0x00040004, so you can play with it
5628like that:
5629
5630	=> loads
5631	## Ready for S-Record download ...
5632	~>examples/hello_world.srec
5633	1 2 3 4 5 6 7 8 9 10 11 ...
5634	[file transfer complete]
5635	[connected]
5636	## Start Addr = 0x00040004
5637
5638	=> go 40004 Hello World! This is a test.
5639	## Starting application at 0x00040004 ...
5640	Hello World
5641	argc = 7
5642	argv[0] = "40004"
5643	argv[1] = "Hello"
5644	argv[2] = "World!"
5645	argv[3] = "This"
5646	argv[4] = "is"
5647	argv[5] = "a"
5648	argv[6] = "test."
5649	argv[7] = "<NULL>"
5650	Hit any key to exit ...
5651
5652	## Application terminated, rc = 0x0
5653
5654Another example, which demonstrates how to register a CPM interrupt
5655handler with the U-Boot code, can be found in 'examples/timer.c'.
5656Here, a CPM timer is set up to generate an interrupt every second.
5657The interrupt service routine is trivial, just printing a '.'
5658character, but this is just a demo program. The application can be
5659controlled by the following keys:
5660
5661	? - print current values og the CPM Timer registers
5662	b - enable interrupts and start timer
5663	e - stop timer and disable interrupts
5664	q - quit application
5665
5666	=> loads
5667	## Ready for S-Record download ...
5668	~>examples/timer.srec
5669	1 2 3 4 5 6 7 8 9 10 11 ...
5670	[file transfer complete]
5671	[connected]
5672	## Start Addr = 0x00040004
5673
5674	=> go 40004
5675	## Starting application at 0x00040004 ...
5676	TIMERS=0xfff00980
5677	Using timer 1
5678	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5679
5680Hit 'b':
5681	[q, b, e, ?] Set interval 1000000 us
5682	Enabling timer
5683Hit '?':
5684	[q, b, e, ?] ........
5685	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5686Hit '?':
5687	[q, b, e, ?] .
5688	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5689Hit '?':
5690	[q, b, e, ?] .
5691	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5692Hit '?':
5693	[q, b, e, ?] .
5694	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5695Hit 'e':
5696	[q, b, e, ?] ...Stopping timer
5697Hit 'q':
5698	[q, b, e, ?] ## Application terminated, rc = 0x0
5699
5700
5701Minicom warning:
5702================
5703
5704Over time, many people have reported problems when trying to use the
5705"minicom" terminal emulation program for serial download. I (wd)
5706consider minicom to be broken, and recommend not to use it. Under
5707Unix, I recommend to use C-Kermit for general purpose use (and
5708especially for kermit binary protocol download ("loadb" command), and
5709use "cu" for S-Record download ("loads" command).  See
5710http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5711for help with kermit.
5712
5713
5714Nevertheless, if you absolutely want to use it try adding this
5715configuration to your "File transfer protocols" section:
5716
5717	   Name	   Program			Name U/D FullScr IO-Red. Multi
5718	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5719	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5720
5721
5722NetBSD Notes:
5723=============
5724
5725Starting at version 0.9.2, U-Boot supports NetBSD both as host
5726(build U-Boot) and target system (boots NetBSD/mpc8xx).
5727
5728Building requires a cross environment; it is known to work on
5729NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5730need gmake since the Makefiles are not compatible with BSD make).
5731Note that the cross-powerpc package does not install include files;
5732attempting to build U-Boot will fail because <machine/ansi.h> is
5733missing.  This file has to be installed and patched manually:
5734
5735	# cd /usr/pkg/cross/powerpc-netbsd/include
5736	# mkdir powerpc
5737	# ln -s powerpc machine
5738	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5739	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5740
5741Native builds *don't* work due to incompatibilities between native
5742and U-Boot include files.
5743
5744Booting assumes that (the first part of) the image booted is a
5745stage-2 loader which in turn loads and then invokes the kernel
5746proper. Loader sources will eventually appear in the NetBSD source
5747tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5748meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5749
5750
5751Implementation Internals:
5752=========================
5753
5754The following is not intended to be a complete description of every
5755implementation detail. However, it should help to understand the
5756inner workings of U-Boot and make it easier to port it to custom
5757hardware.
5758
5759
5760Initial Stack, Global Data:
5761---------------------------
5762
5763The implementation of U-Boot is complicated by the fact that U-Boot
5764starts running out of ROM (flash memory), usually without access to
5765system RAM (because the memory controller is not initialized yet).
5766This means that we don't have writable Data or BSS segments, and BSS
5767is not initialized as zero. To be able to get a C environment working
5768at all, we have to allocate at least a minimal stack. Implementation
5769options for this are defined and restricted by the CPU used: Some CPU
5770models provide on-chip memory (like the IMMR area on MPC8xx and
5771MPC826x processors), on others (parts of) the data cache can be
5772locked as (mis-) used as memory, etc.
5773
5774	Chris Hallinan posted a good summary of these issues to the
5775	U-Boot mailing list:
5776
5777	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5778	From: "Chris Hallinan" <clh@net1plus.com>
5779	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5780	...
5781
5782	Correct me if I'm wrong, folks, but the way I understand it
5783	is this: Using DCACHE as initial RAM for Stack, etc, does not
5784	require any physical RAM backing up the cache. The cleverness
5785	is that the cache is being used as a temporary supply of
5786	necessary storage before the SDRAM controller is setup. It's
5787	beyond the scope of this list to explain the details, but you
5788	can see how this works by studying the cache architecture and
5789	operation in the architecture and processor-specific manuals.
5790
5791	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5792	is another option for the system designer to use as an
5793	initial stack/RAM area prior to SDRAM being available. Either
5794	option should work for you. Using CS 4 should be fine if your
5795	board designers haven't used it for something that would
5796	cause you grief during the initial boot! It is frequently not
5797	used.
5798
5799	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5800	with your processor/board/system design. The default value
5801	you will find in any recent u-boot distribution in
5802	walnut.h should work for you. I'd set it to a value larger
5803	than your SDRAM module. If you have a 64MB SDRAM module, set
5804	it above 400_0000. Just make sure your board has no resources
5805	that are supposed to respond to that address! That code in
5806	start.S has been around a while and should work as is when
5807	you get the config right.
5808
5809	-Chris Hallinan
5810	DS4.COM, Inc.
5811
5812It is essential to remember this, since it has some impact on the C
5813code for the initialization procedures:
5814
5815* Initialized global data (data segment) is read-only. Do not attempt
5816  to write it.
5817
5818* Do not use any uninitialized global data (or implicitely initialized
5819  as zero data - BSS segment) at all - this is undefined, initiali-
5820  zation is performed later (when relocating to RAM).
5821
5822* Stack space is very limited. Avoid big data buffers or things like
5823  that.
5824
5825Having only the stack as writable memory limits means we cannot use
5826normal global data to share information beween the code. But it
5827turned out that the implementation of U-Boot can be greatly
5828simplified by making a global data structure (gd_t) available to all
5829functions. We could pass a pointer to this data as argument to _all_
5830functions, but this would bloat the code. Instead we use a feature of
5831the GCC compiler (Global Register Variables) to share the data: we
5832place a pointer (gd) to the global data into a register which we
5833reserve for this purpose.
5834
5835When choosing a register for such a purpose we are restricted by the
5836relevant  (E)ABI  specifications for the current architecture, and by
5837GCC's implementation.
5838
5839For PowerPC, the following registers have specific use:
5840	R1:	stack pointer
5841	R2:	reserved for system use
5842	R3-R4:	parameter passing and return values
5843	R5-R10: parameter passing
5844	R13:	small data area pointer
5845	R30:	GOT pointer
5846	R31:	frame pointer
5847
5848	(U-Boot also uses R12 as internal GOT pointer. r12
5849	is a volatile register so r12 needs to be reset when
5850	going back and forth between asm and C)
5851
5852    ==> U-Boot will use R2 to hold a pointer to the global data
5853
5854    Note: on PPC, we could use a static initializer (since the
5855    address of the global data structure is known at compile time),
5856    but it turned out that reserving a register results in somewhat
5857    smaller code - although the code savings are not that big (on
5858    average for all boards 752 bytes for the whole U-Boot image,
5859    624 text + 127 data).
5860
5861On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5862	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5863
5864    ==> U-Boot will use P3 to hold a pointer to the global data
5865
5866On ARM, the following registers are used:
5867
5868	R0:	function argument word/integer result
5869	R1-R3:	function argument word
5870	R9:	platform specific
5871	R10:	stack limit (used only if stack checking is enabled)
5872	R11:	argument (frame) pointer
5873	R12:	temporary workspace
5874	R13:	stack pointer
5875	R14:	link register
5876	R15:	program counter
5877
5878    ==> U-Boot will use R9 to hold a pointer to the global data
5879
5880    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5881
5882On Nios II, the ABI is documented here:
5883	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5884
5885    ==> U-Boot will use gp to hold a pointer to the global data
5886
5887    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5888    to access small data sections, so gp is free.
5889
5890On NDS32, the following registers are used:
5891
5892	R0-R1:	argument/return
5893	R2-R5:	argument
5894	R15:	temporary register for assembler
5895	R16:	trampoline register
5896	R28:	frame pointer (FP)
5897	R29:	global pointer (GP)
5898	R30:	link register (LP)
5899	R31:	stack pointer (SP)
5900	PC:	program counter (PC)
5901
5902    ==> U-Boot will use R10 to hold a pointer to the global data
5903
5904NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5905or current versions of GCC may "optimize" the code too much.
5906
5907Memory Management:
5908------------------
5909
5910U-Boot runs in system state and uses physical addresses, i.e. the
5911MMU is not used either for address mapping nor for memory protection.
5912
5913The available memory is mapped to fixed addresses using the memory
5914controller. In this process, a contiguous block is formed for each
5915memory type (Flash, SDRAM, SRAM), even when it consists of several
5916physical memory banks.
5917
5918U-Boot is installed in the first 128 kB of the first Flash bank (on
5919TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5920booting and sizing and initializing DRAM, the code relocates itself
5921to the upper end of DRAM. Immediately below the U-Boot code some
5922memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5923configuration setting]. Below that, a structure with global Board
5924Info data is placed, followed by the stack (growing downward).
5925
5926Additionally, some exception handler code is copied to the low 8 kB
5927of DRAM (0x00000000 ... 0x00001FFF).
5928
5929So a typical memory configuration with 16 MB of DRAM could look like
5930this:
5931
5932	0x0000 0000	Exception Vector code
5933	      :
5934	0x0000 1FFF
5935	0x0000 2000	Free for Application Use
5936	      :
5937	      :
5938
5939	      :
5940	      :
5941	0x00FB FF20	Monitor Stack (Growing downward)
5942	0x00FB FFAC	Board Info Data and permanent copy of global data
5943	0x00FC 0000	Malloc Arena
5944	      :
5945	0x00FD FFFF
5946	0x00FE 0000	RAM Copy of Monitor Code
5947	...		eventually: LCD or video framebuffer
5948	...		eventually: pRAM (Protected RAM - unchanged by reset)
5949	0x00FF FFFF	[End of RAM]
5950
5951
5952System Initialization:
5953----------------------
5954
5955In the reset configuration, U-Boot starts at the reset entry point
5956(on most PowerPC systems at address 0x00000100). Because of the reset
5957configuration for CS0# this is a mirror of the onboard Flash memory.
5958To be able to re-map memory U-Boot then jumps to its link address.
5959To be able to implement the initialization code in C, a (small!)
5960initial stack is set up in the internal Dual Ported RAM (in case CPUs
5961which provide such a feature like MPC8xx or MPC8260), or in a locked
5962part of the data cache. After that, U-Boot initializes the CPU core,
5963the caches and the SIU.
5964
5965Next, all (potentially) available memory banks are mapped using a
5966preliminary mapping. For example, we put them on 512 MB boundaries
5967(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5968on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5969programmed for SDRAM access. Using the temporary configuration, a
5970simple memory test is run that determines the size of the SDRAM
5971banks.
5972
5973When there is more than one SDRAM bank, and the banks are of
5974different size, the largest is mapped first. For equal size, the first
5975bank (CS2#) is mapped first. The first mapping is always for address
59760x00000000, with any additional banks following immediately to create
5977contiguous memory starting from 0.
5978
5979Then, the monitor installs itself at the upper end of the SDRAM area
5980and allocates memory for use by malloc() and for the global Board
5981Info data; also, the exception vector code is copied to the low RAM
5982pages, and the final stack is set up.
5983
5984Only after this relocation will you have a "normal" C environment;
5985until that you are restricted in several ways, mostly because you are
5986running from ROM, and because the code will have to be relocated to a
5987new address in RAM.
5988
5989
5990U-Boot Porting Guide:
5991----------------------
5992
5993[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5994list, October 2002]
5995
5996
5997int main(int argc, char *argv[])
5998{
5999	sighandler_t no_more_time;
6000
6001	signal(SIGALRM, no_more_time);
6002	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6003
6004	if (available_money > available_manpower) {
6005		Pay consultant to port U-Boot;
6006		return 0;
6007	}
6008
6009	Download latest U-Boot source;
6010
6011	Subscribe to u-boot mailing list;
6012
6013	if (clueless)
6014		email("Hi, I am new to U-Boot, how do I get started?");
6015
6016	while (learning) {
6017		Read the README file in the top level directory;
6018		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6019		Read applicable doc/*.README;
6020		Read the source, Luke;
6021		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6022	}
6023
6024	if (available_money > toLocalCurrency ($2500))
6025		Buy a BDI3000;
6026	else
6027		Add a lot of aggravation and time;
6028
6029	if (a similar board exists) {	/* hopefully... */
6030		cp -a board/<similar> board/<myboard>
6031		cp include/configs/<similar>.h include/configs/<myboard>.h
6032	} else {
6033		Create your own board support subdirectory;
6034		Create your own board include/configs/<myboard>.h file;
6035	}
6036	Edit new board/<myboard> files
6037	Edit new include/configs/<myboard>.h
6038
6039	while (!accepted) {
6040		while (!running) {
6041			do {
6042				Add / modify source code;
6043			} until (compiles);
6044			Debug;
6045			if (clueless)
6046				email("Hi, I am having problems...");
6047		}
6048		Send patch file to the U-Boot email list;
6049		if (reasonable critiques)
6050			Incorporate improvements from email list code review;
6051		else
6052			Defend code as written;
6053	}
6054
6055	return 0;
6056}
6057
6058void no_more_time (int sig)
6059{
6060      hire_a_guru();
6061}
6062
6063
6064Coding Standards:
6065-----------------
6066
6067All contributions to U-Boot should conform to the Linux kernel
6068coding style; see the file "Documentation/CodingStyle" and the script
6069"scripts/Lindent" in your Linux kernel source directory.
6070
6071Source files originating from a different project (for example the
6072MTD subsystem) are generally exempt from these guidelines and are not
6073reformated to ease subsequent migration to newer versions of those
6074sources.
6075
6076Please note that U-Boot is implemented in C (and to some small parts in
6077Assembler); no C++ is used, so please do not use C++ style comments (//)
6078in your code.
6079
6080Please also stick to the following formatting rules:
6081- remove any trailing white space
6082- use TAB characters for indentation and vertical alignment, not spaces
6083- make sure NOT to use DOS '\r\n' line feeds
6084- do not add more than 2 consecutive empty lines to source files
6085- do not add trailing empty lines to source files
6086
6087Submissions which do not conform to the standards may be returned
6088with a request to reformat the changes.
6089
6090
6091Submitting Patches:
6092-------------------
6093
6094Since the number of patches for U-Boot is growing, we need to
6095establish some rules. Submissions which do not conform to these rules
6096may be rejected, even when they contain important and valuable stuff.
6097
6098Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6099
6100Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6101see http://lists.denx.de/mailman/listinfo/u-boot
6102
6103When you send a patch, please include the following information with
6104it:
6105
6106* For bug fixes: a description of the bug and how your patch fixes
6107  this bug. Please try to include a way of demonstrating that the
6108  patch actually fixes something.
6109
6110* For new features: a description of the feature and your
6111  implementation.
6112
6113* A CHANGELOG entry as plaintext (separate from the patch)
6114
6115* For major contributions, your entry to the CREDITS file
6116
6117* When you add support for a new board, don't forget to add a
6118  maintainer e-mail address to the boards.cfg file, too.
6119
6120* If your patch adds new configuration options, don't forget to
6121  document these in the README file.
6122
6123* The patch itself. If you are using git (which is *strongly*
6124  recommended) you can easily generate the patch using the
6125  "git format-patch". If you then use "git send-email" to send it to
6126  the U-Boot mailing list, you will avoid most of the common problems
6127  with some other mail clients.
6128
6129  If you cannot use git, use "diff -purN OLD NEW". If your version of
6130  diff does not support these options, then get the latest version of
6131  GNU diff.
6132
6133  The current directory when running this command shall be the parent
6134  directory of the U-Boot source tree (i. e. please make sure that
6135  your patch includes sufficient directory information for the
6136  affected files).
6137
6138  We prefer patches as plain text. MIME attachments are discouraged,
6139  and compressed attachments must not be used.
6140
6141* If one logical set of modifications affects or creates several
6142  files, all these changes shall be submitted in a SINGLE patch file.
6143
6144* Changesets that contain different, unrelated modifications shall be
6145  submitted as SEPARATE patches, one patch per changeset.
6146
6147
6148Notes:
6149
6150* Before sending the patch, run the MAKEALL script on your patched
6151  source tree and make sure that no errors or warnings are reported
6152  for any of the boards.
6153
6154* Keep your modifications to the necessary minimum: A patch
6155  containing several unrelated changes or arbitrary reformats will be
6156  returned with a request to re-formatting / split it.
6157
6158* If you modify existing code, make sure that your new code does not
6159  add to the memory footprint of the code ;-) Small is beautiful!
6160  When adding new features, these should compile conditionally only
6161  (using #ifdef), and the resulting code with the new feature
6162  disabled must not need more memory than the old code without your
6163  modification.
6164
6165* Remember that there is a size limit of 100 kB per message on the
6166  u-boot mailing list. Bigger patches will be moderated. If they are
6167  reasonable and not too big, they will be acknowledged. But patches
6168  bigger than the size limit should be avoided.
6169