xref: /openbmc/u-boot/README (revision aade20046b7ab5bd9b2afe84ccb31f0adf0c5e1e)
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  /arm			Files generic to ARM architecture
136    /cpu		CPU specific files
137      /arm720t		Files specific to ARM 720 CPUs
138      /arm920t		Files specific to ARM 920 CPUs
139	/at91		Files specific to Atmel AT91RM9200 CPU
140	/imx		Files specific to Freescale MC9328 i.MX CPUs
141	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
142      /arm926ejs	Files specific to ARM 926 CPUs
143      /arm1136		Files specific to ARM 1136 CPUs
144      /pxa		Files specific to Intel XScale PXA CPUs
145      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
146    /lib		Architecture specific library files
147  /avr32		Files generic to AVR32 architecture
148    /cpu		CPU specific files
149    /lib		Architecture specific library files
150  /blackfin		Files generic to Analog Devices Blackfin architecture
151    /cpu		CPU specific files
152    /lib		Architecture specific library files
153  /m68k			Files generic to m68k architecture
154    /cpu		CPU specific files
155      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
156      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
157      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
158      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
159      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
160    /lib		Architecture specific library files
161  /microblaze		Files generic to microblaze architecture
162    /cpu		CPU specific files
163    /lib		Architecture specific library files
164  /mips			Files generic to MIPS architecture
165    /cpu		CPU specific files
166      /mips32		Files specific to MIPS32 CPUs
167      /xburst		Files specific to Ingenic XBurst CPUs
168    /lib		Architecture specific library files
169  /nds32		Files generic to NDS32 architecture
170    /cpu		CPU specific files
171      /n1213		Files specific to Andes Technology N1213 CPUs
172    /lib		Architecture specific library files
173  /nios2		Files generic to Altera NIOS2 architecture
174    /cpu		CPU specific files
175    /lib		Architecture specific library files
176  /openrisc		Files generic to OpenRISC architecture
177    /cpu		CPU specific files
178    /lib		Architecture specific library files
179  /powerpc		Files generic to PowerPC architecture
180    /cpu		CPU specific files
181      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
182      /mpc5xx		Files specific to Freescale MPC5xx CPUs
183      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
184      /mpc8xx		Files specific to Freescale MPC8xx CPUs
185      /mpc824x		Files specific to Freescale MPC824x CPUs
186      /mpc8260		Files specific to Freescale MPC8260 CPUs
187      /mpc85xx		Files specific to Freescale MPC85xx CPUs
188      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
189    /lib		Architecture specific library files
190  /sh			Files generic to SH architecture
191    /cpu		CPU specific files
192      /sh2		Files specific to sh2 CPUs
193      /sh3		Files specific to sh3 CPUs
194      /sh4		Files specific to sh4 CPUs
195    /lib		Architecture specific library files
196  /sparc		Files generic to SPARC architecture
197    /cpu		CPU specific files
198      /leon2		Files specific to Gaisler LEON2 SPARC CPU
199      /leon3		Files specific to Gaisler LEON3 SPARC CPU
200    /lib		Architecture specific library files
201  /x86			Files generic to x86 architecture
202    /cpu		CPU specific files
203    /lib		Architecture specific library files
204/api			Machine/arch independent API for external apps
205/board			Board dependent files
206/common			Misc architecture independent functions
207/disk			Code for disk drive partition handling
208/doc			Documentation (don't expect too much)
209/drivers		Commonly used device drivers
210/dts			Contains Makefile for building internal U-Boot fdt.
211/examples		Example code for standalone applications, etc.
212/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
213/include		Header Files
214/lib			Files generic to all architectures
215  /libfdt		Library files to support flattened device trees
216  /lzma			Library files to support LZMA decompression
217  /lzo			Library files to support LZO decompression
218/net			Networking code
219/post			Power On Self Test
220/spl			Secondary Program Loader framework
221/tools			Tools to build S-Record or U-Boot images, etc.
222
223Software Configuration:
224=======================
225
226Configuration is usually done using C preprocessor defines; the
227rationale behind that is to avoid dead code whenever possible.
228
229There are two classes of configuration variables:
230
231* Configuration _OPTIONS_:
232  These are selectable by the user and have names beginning with
233  "CONFIG_".
234
235* Configuration _SETTINGS_:
236  These depend on the hardware etc. and should not be meddled with if
237  you don't know what you're doing; they have names beginning with
238  "CONFIG_SYS_".
239
240Later we will add a configuration tool - probably similar to or even
241identical to what's used for the Linux kernel. Right now, we have to
242do the configuration by hand, which means creating some symbolic
243links and editing some configuration files. We use the TQM8xxL boards
244as an example here.
245
246
247Selection of Processor Architecture and Board Type:
248---------------------------------------------------
249
250For all supported boards there are ready-to-use default
251configurations available; just type "make <board_name>_config".
252
253Example: For a TQM823L module type:
254
255	cd u-boot
256	make TQM823L_config
257
258For the Cogent platform, you need to specify the CPU type as well;
259e.g. "make cogent_mpc8xx_config". And also configure the cogent
260directory according to the instructions in cogent/README.
261
262
263Configuration Options:
264----------------------
265
266Configuration depends on the combination of board and CPU type; all
267such information is kept in a configuration file
268"include/configs/<board_name>.h".
269
270Example: For a TQM823L module, all configuration settings are in
271"include/configs/TQM823L.h".
272
273
274Many of the options are named exactly as the corresponding Linux
275kernel configuration options. The intention is to make it easier to
276build a config tool - later.
277
278
279The following options need to be configured:
280
281- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
282
283- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
284
285- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
286		Define exactly one, e.g. CONFIG_ATSTK1002
287
288- CPU Module Type: (if CONFIG_COGENT is defined)
289		Define exactly one of
290		CONFIG_CMA286_60_OLD
291--- FIXME --- not tested yet:
292		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
293		CONFIG_CMA287_23, CONFIG_CMA287_50
294
295- Motherboard Type: (if CONFIG_COGENT is defined)
296		Define exactly one of
297		CONFIG_CMA101, CONFIG_CMA102
298
299- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
300		Define one or more of
301		CONFIG_CMA302
302
303- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
304		Define one or more of
305		CONFIG_LCD_HEARTBEAT	- update a character position on
306					  the LCD display every second with
307					  a "rotator" |\-/|\-/
308
309- Board flavour: (if CONFIG_MPC8260ADS is defined)
310		CONFIG_ADSTYPE
311		Possible values are:
312			CONFIG_SYS_8260ADS	- original MPC8260ADS
313			CONFIG_SYS_8266ADS	- MPC8266ADS
314			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
315			CONFIG_SYS_8272ADS	- MPC8272ADS
316
317- Marvell Family Member
318		CONFIG_SYS_MVFS		- define it if you want to enable
319					  multiple fs option at one time
320					  for marvell soc family
321
322- MPC824X Family Member (if CONFIG_MPC824X is defined)
323		Define exactly one of
324		CONFIG_MPC8240, CONFIG_MPC8245
325
326- 8xx CPU Options: (if using an MPC8xx CPU)
327		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
328					  get_gclk_freq() cannot work
329					  e.g. if there is no 32KHz
330					  reference PIT/RTC clock
331		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
332					  or XTAL/EXTAL)
333
334- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
335		CONFIG_SYS_8xx_CPUCLK_MIN
336		CONFIG_SYS_8xx_CPUCLK_MAX
337		CONFIG_8xx_CPUCLK_DEFAULT
338			See doc/README.MPC866
339
340		CONFIG_SYS_MEASURE_CPUCLK
341
342		Define this to measure the actual CPU clock instead
343		of relying on the correctness of the configured
344		values. Mostly useful for board bringup to make sure
345		the PLL is locked at the intended frequency. Note
346		that this requires a (stable) reference clock (32 kHz
347		RTC clock or CONFIG_SYS_8XX_XIN)
348
349		CONFIG_SYS_DELAYED_ICACHE
350
351		Define this option if you want to enable the
352		ICache only when Code runs from RAM.
353
354- 85xx CPU Options:
355		CONFIG_SYS_PPC64
356
357		Specifies that the core is a 64-bit PowerPC implementation (implements
358		the "64" category of the Power ISA). This is necessary for ePAPR
359		compliance, among other possible reasons.
360
361		CONFIG_SYS_FSL_TBCLK_DIV
362
363		Defines the core time base clock divider ratio compared to the
364		system clock.  On most PQ3 devices this is 8, on newer QorIQ
365		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
366
367		CONFIG_SYS_FSL_PCIE_COMPAT
368
369		Defines the string to utilize when trying to match PCIe device
370		tree nodes for the given platform.
371
372		CONFIG_SYS_PPC_E500_DEBUG_TLB
373
374		Enables a temporary TLB entry to be used during boot to work
375		around limitations in e500v1 and e500v2 external debugger
376		support. This reduces the portions of the boot code where
377		breakpoints and single stepping do not work.  The value of this
378		symbol should be set to the TLB1 entry to be used for this
379		purpose.
380
381		CONFIG_SYS_FSL_ERRATUM_A004510
382
383		Enables a workaround for erratum A004510.  If set,
384		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
385		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
386
387		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
388		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
389
390		Defines one or two SoC revisions (low 8 bits of SVR)
391		for which the A004510 workaround should be applied.
392
393		The rest of SVR is either not relevant to the decision
394		of whether the erratum is present (e.g. p2040 versus
395		p2041) or is implied by the build target, which controls
396		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
397
398		See Freescale App Note 4493 for more information about
399		this erratum.
400
401		CONFIG_A003399_NOR_WORKAROUND
402		Enables a workaround for IFC erratum A003399. It is only
403		requred during NOR boot.
404
405		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
406
407		This is the value to write into CCSR offset 0x18600
408		according to the A004510 workaround.
409
410		CONFIG_SYS_FSL_DSP_DDR_ADDR
411		This value denotes start offset of DDR memory which is
412		connected exclusively to the DSP cores.
413
414		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
415		This value denotes start offset of M2 memory
416		which is directly connected to the DSP core.
417
418		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
419		This value denotes start offset of M3 memory which is directly
420		connected to the DSP core.
421
422		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
423		This value denotes start offset of DSP CCSR space.
424
425		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
426		Single Source Clock is clocking mode present in some of FSL SoC's.
427		In this mode, a single differential clock is used to supply
428		clocks to the sysclock, ddrclock and usbclock.
429
430		CONFIG_SYS_CPC_REINIT_F
431		This CONFIG is defined when the CPC is configured as SRAM at the
432		time of U-boot entry and is required to be re-initialized.
433
434		CONFIG_DEEP_SLEEP
435		Inidcates this SoC supports deep sleep feature. If deep sleep is
436		supported, core will start to execute uboot when wakes up.
437
438- Generic CPU options:
439		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
440
441		Defines the endianess of the CPU. Implementation of those
442		values is arch specific.
443
444		CONFIG_SYS_FSL_DDR
445		Freescale DDR driver in use. This type of DDR controller is
446		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
447		SoCs.
448
449		CONFIG_SYS_FSL_DDR_ADDR
450		Freescale DDR memory-mapped register base.
451
452		CONFIG_SYS_FSL_DDR_EMU
453		Specify emulator support for DDR. Some DDR features such as
454		deskew training are not available.
455
456		CONFIG_SYS_FSL_DDRC_GEN1
457		Freescale DDR1 controller.
458
459		CONFIG_SYS_FSL_DDRC_GEN2
460		Freescale DDR2 controller.
461
462		CONFIG_SYS_FSL_DDRC_GEN3
463		Freescale DDR3 controller.
464
465		CONFIG_SYS_FSL_DDRC_GEN4
466		Freescale DDR4 controller.
467
468		CONFIG_SYS_FSL_DDRC_ARM_GEN3
469		Freescale DDR3 controller for ARM-based SoCs.
470
471		CONFIG_SYS_FSL_DDR1
472		Board config to use DDR1. It can be enabled for SoCs with
473		Freescale DDR1 or DDR2 controllers, depending on the board
474		implemetation.
475
476		CONFIG_SYS_FSL_DDR2
477		Board config to use DDR2. It can be eanbeld for SoCs with
478		Freescale DDR2 or DDR3 controllers, depending on the board
479		implementation.
480
481		CONFIG_SYS_FSL_DDR3
482		Board config to use DDR3. It can be enabled for SoCs with
483		Freescale DDR3 or DDR3L controllers.
484
485		CONFIG_SYS_FSL_DDR3L
486		Board config to use DDR3L. It can be enabled for SoCs with
487		DDR3L controllers.
488
489		CONFIG_SYS_FSL_DDR4
490		Board config to use DDR4. It can be enabled for SoCs with
491		DDR4 controllers.
492
493		CONFIG_SYS_FSL_IFC_BE
494		Defines the IFC controller register space as Big Endian
495
496		CONFIG_SYS_FSL_IFC_LE
497		Defines the IFC controller register space as Little Endian
498
499		CONFIG_SYS_FSL_PBL_PBI
500		It enables addition of RCW (Power on reset configuration) in built image.
501		Please refer doc/README.pblimage for more details
502
503		CONFIG_SYS_FSL_PBL_RCW
504		It adds PBI(pre-boot instructions) commands in u-boot build image.
505		PBI commands can be used to configure SoC before it starts the execution.
506		Please refer doc/README.pblimage for more details
507
508		CONFIG_SYS_FSL_DDR_BE
509		Defines the DDR controller register space as Big Endian
510
511		CONFIG_SYS_FSL_DDR_LE
512		Defines the DDR controller register space as Little Endian
513
514		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
515		Physical address from the view of DDR controllers. It is the
516		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
517		it could be different for ARM SoCs.
518
519		CONFIG_SYS_FSL_DDR_INTLV_256B
520		DDR controller interleaving on 256-byte. This is a special
521		interleaving mode, handled by Dickens for Freescale layerscape
522		SoCs with ARM core.
523
524- Intel Monahans options:
525		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
526
527		Defines the Monahans run mode to oscillator
528		ratio. Valid values are 8, 16, 24, 31. The core
529		frequency is this value multiplied by 13 MHz.
530
531		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
532
533		Defines the Monahans turbo mode to oscillator
534		ratio. Valid values are 1 (default if undefined) and
535		2. The core frequency as calculated above is multiplied
536		by this value.
537
538- MIPS CPU options:
539		CONFIG_SYS_INIT_SP_OFFSET
540
541		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
542		pointer. This is needed for the temporary stack before
543		relocation.
544
545		CONFIG_SYS_MIPS_CACHE_MODE
546
547		Cache operation mode for the MIPS CPU.
548		See also arch/mips/include/asm/mipsregs.h.
549		Possible values are:
550			CONF_CM_CACHABLE_NO_WA
551			CONF_CM_CACHABLE_WA
552			CONF_CM_UNCACHED
553			CONF_CM_CACHABLE_NONCOHERENT
554			CONF_CM_CACHABLE_CE
555			CONF_CM_CACHABLE_COW
556			CONF_CM_CACHABLE_CUW
557			CONF_CM_CACHABLE_ACCELERATED
558
559		CONFIG_SYS_XWAY_EBU_BOOTCFG
560
561		Special option for Lantiq XWAY SoCs for booting from NOR flash.
562		See also arch/mips/cpu/mips32/start.S.
563
564		CONFIG_XWAY_SWAP_BYTES
565
566		Enable compilation of tools/xway-swap-bytes needed for Lantiq
567		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
568		be swapped if a flash programmer is used.
569
570- ARM options:
571		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
572
573		Select high exception vectors of the ARM core, e.g., do not
574		clear the V bit of the c1 register of CP15.
575
576		CONFIG_SYS_THUMB_BUILD
577
578		Use this flag to build U-Boot using the Thumb instruction
579		set for ARM architectures. Thumb instruction set provides
580		better code density. For ARM architectures that support
581		Thumb2 this flag will result in Thumb2 code generated by
582		GCC.
583
584		CONFIG_ARM_ERRATA_716044
585		CONFIG_ARM_ERRATA_742230
586		CONFIG_ARM_ERRATA_743622
587		CONFIG_ARM_ERRATA_751472
588		CONFIG_ARM_ERRATA_794072
589		CONFIG_ARM_ERRATA_761320
590
591		If set, the workarounds for these ARM errata are applied early
592		during U-Boot startup. Note that these options force the
593		workarounds to be applied; no CPU-type/version detection
594		exists, unlike the similar options in the Linux kernel. Do not
595		set these options unless they apply!
596
597- CPU timer options:
598		CONFIG_SYS_HZ
599
600		The frequency of the timer returned by get_timer().
601		get_timer() must operate in milliseconds and this CONFIG
602		option must be set to 1000.
603
604- Linux Kernel Interface:
605		CONFIG_CLOCKS_IN_MHZ
606
607		U-Boot stores all clock information in Hz
608		internally. For binary compatibility with older Linux
609		kernels (which expect the clocks passed in the
610		bd_info data to be in MHz) the environment variable
611		"clocks_in_mhz" can be defined so that U-Boot
612		converts clock data to MHZ before passing it to the
613		Linux kernel.
614		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
615		"clocks_in_mhz=1" is automatically included in the
616		default environment.
617
618		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
619
620		When transferring memsize parameter to linux, some versions
621		expect it to be in bytes, others in MB.
622		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
623
624		CONFIG_OF_LIBFDT
625
626		New kernel versions are expecting firmware settings to be
627		passed using flattened device trees (based on open firmware
628		concepts).
629
630		CONFIG_OF_LIBFDT
631		 * New libfdt-based support
632		 * Adds the "fdt" command
633		 * The bootm command automatically updates the fdt
634
635		OF_CPU - The proper name of the cpus node (only required for
636			MPC512X and MPC5xxx based boards).
637		OF_SOC - The proper name of the soc node (only required for
638			MPC512X and MPC5xxx based boards).
639		OF_TBCLK - The timebase frequency.
640		OF_STDOUT_PATH - The path to the console device
641
642		boards with QUICC Engines require OF_QE to set UCC MAC
643		addresses
644
645		CONFIG_OF_BOARD_SETUP
646
647		Board code has addition modification that it wants to make
648		to the flat device tree before handing it off to the kernel
649
650		CONFIG_OF_BOOT_CPU
651
652		This define fills in the correct boot CPU in the boot
653		param header, the default value is zero if undefined.
654
655		CONFIG_OF_IDE_FIXUP
656
657		U-Boot can detect if an IDE device is present or not.
658		If not, and this new config option is activated, U-Boot
659		removes the ATA node from the DTS before booting Linux,
660		so the Linux IDE driver does not probe the device and
661		crash. This is needed for buggy hardware (uc101) where
662		no pull down resistor is connected to the signal IDE5V_DD7.
663
664		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
665
666		This setting is mandatory for all boards that have only one
667		machine type and must be used to specify the machine type
668		number as it appears in the ARM machine registry
669		(see http://www.arm.linux.org.uk/developer/machines/).
670		Only boards that have multiple machine types supported
671		in a single configuration file and the machine type is
672		runtime discoverable, do not have to use this setting.
673
674- vxWorks boot parameters:
675
676		bootvx constructs a valid bootline using the following
677		environments variables: bootfile, ipaddr, serverip, hostname.
678		It loads the vxWorks image pointed bootfile.
679
680		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
681		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
682		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
683		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
684
685		CONFIG_SYS_VXWORKS_ADD_PARAMS
686
687		Add it at the end of the bootline. E.g "u=username pw=secret"
688
689		Note: If a "bootargs" environment is defined, it will overwride
690		the defaults discussed just above.
691
692- Cache Configuration:
693		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
694		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
695		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
696
697- Cache Configuration for ARM:
698		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
699				      controller
700		CONFIG_SYS_PL310_BASE - Physical base address of PL310
701					controller register space
702
703- Serial Ports:
704		CONFIG_PL010_SERIAL
705
706		Define this if you want support for Amba PrimeCell PL010 UARTs.
707
708		CONFIG_PL011_SERIAL
709
710		Define this if you want support for Amba PrimeCell PL011 UARTs.
711
712		CONFIG_PL011_CLOCK
713
714		If you have Amba PrimeCell PL011 UARTs, set this variable to
715		the clock speed of the UARTs.
716
717		CONFIG_PL01x_PORTS
718
719		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
720		define this to a list of base addresses for each (supported)
721		port. See e.g. include/configs/versatile.h
722
723		CONFIG_PL011_SERIAL_RLCR
724
725		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
726		have separate receive and transmit line control registers.  Set
727		this variable to initialize the extra register.
728
729		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
730
731		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
732		boot loader that has already initialized the UART.  Define this
733		variable to flush the UART at init time.
734
735
736- Console Interface:
737		Depending on board, define exactly one serial port
738		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
739		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
740		console by defining CONFIG_8xx_CONS_NONE
741
742		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
743		port routines must be defined elsewhere
744		(i.e. serial_init(), serial_getc(), ...)
745
746		CONFIG_CFB_CONSOLE
747		Enables console device for a color framebuffer. Needs following
748		defines (cf. smiLynxEM, i8042)
749			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
750						(default big endian)
751			VIDEO_HW_RECTFILL	graphic chip supports
752						rectangle fill
753						(cf. smiLynxEM)
754			VIDEO_HW_BITBLT		graphic chip supports
755						bit-blit (cf. smiLynxEM)
756			VIDEO_VISIBLE_COLS	visible pixel columns
757						(cols=pitch)
758			VIDEO_VISIBLE_ROWS	visible pixel rows
759			VIDEO_PIXEL_SIZE	bytes per pixel
760			VIDEO_DATA_FORMAT	graphic data format
761						(0-5, cf. cfb_console.c)
762			VIDEO_FB_ADRS		framebuffer address
763			VIDEO_KBD_INIT_FCT	keyboard int fct
764						(i.e. i8042_kbd_init())
765			VIDEO_TSTC_FCT		test char fct
766						(i.e. i8042_tstc)
767			VIDEO_GETC_FCT		get char fct
768						(i.e. i8042_getc)
769			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
770						(requires blink timer
771						cf. i8042.c)
772			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
773			CONFIG_CONSOLE_TIME	display time/date info in
774						upper right corner
775						(requires CONFIG_CMD_DATE)
776			CONFIG_VIDEO_LOGO	display Linux logo in
777						upper left corner
778			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
779						linux_logo.h for logo.
780						Requires CONFIG_VIDEO_LOGO
781			CONFIG_CONSOLE_EXTRA_INFO
782						additional board info beside
783						the logo
784
785		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
786		a limited number of ANSI escape sequences (cursor control,
787		erase functions and limited graphics rendition control).
788
789		When CONFIG_CFB_CONSOLE is defined, video console is
790		default i/o. Serial console can be forced with
791		environment 'console=serial'.
792
793		When CONFIG_SILENT_CONSOLE is defined, all console
794		messages (by U-Boot and Linux!) can be silenced with
795		the "silent" environment variable. See
796		doc/README.silent for more information.
797
798		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
799			is 0x00.
800		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
801			is 0xa0.
802
803- Console Baudrate:
804		CONFIG_BAUDRATE - in bps
805		Select one of the baudrates listed in
806		CONFIG_SYS_BAUDRATE_TABLE, see below.
807		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
808
809- Console Rx buffer length
810		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
811		the maximum receive buffer length for the SMC.
812		This option is actual only for 82xx and 8xx possible.
813		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
814		must be defined, to setup the maximum idle timeout for
815		the SMC.
816
817- Pre-Console Buffer:
818		Prior to the console being initialised (i.e. serial UART
819		initialised etc) all console output is silently discarded.
820		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
821		buffer any console messages prior to the console being
822		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
823		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
824		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
825		bytes are output before the console is initialised, the
826		earlier bytes are discarded.
827
828		'Sane' compilers will generate smaller code if
829		CONFIG_PRE_CON_BUF_SZ is a power of 2
830
831- Safe printf() functions
832		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
833		the printf() functions. These are defined in
834		include/vsprintf.h and include snprintf(), vsnprintf() and
835		so on. Code size increase is approximately 300-500 bytes.
836		If this option is not given then these functions will
837		silently discard their buffer size argument - this means
838		you are not getting any overflow checking in this case.
839
840- Boot Delay:	CONFIG_BOOTDELAY - in seconds
841		Delay before automatically booting the default image;
842		set to -1 to disable autoboot.
843		set to -2 to autoboot with no delay and not check for abort
844		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
845
846		See doc/README.autoboot for these options that
847		work with CONFIG_BOOTDELAY. None are required.
848		CONFIG_BOOT_RETRY_TIME
849		CONFIG_BOOT_RETRY_MIN
850		CONFIG_AUTOBOOT_KEYED
851		CONFIG_AUTOBOOT_PROMPT
852		CONFIG_AUTOBOOT_DELAY_STR
853		CONFIG_AUTOBOOT_STOP_STR
854		CONFIG_AUTOBOOT_DELAY_STR2
855		CONFIG_AUTOBOOT_STOP_STR2
856		CONFIG_ZERO_BOOTDELAY_CHECK
857		CONFIG_RESET_TO_RETRY
858
859- Autoboot Command:
860		CONFIG_BOOTCOMMAND
861		Only needed when CONFIG_BOOTDELAY is enabled;
862		define a command string that is automatically executed
863		when no character is read on the console interface
864		within "Boot Delay" after reset.
865
866		CONFIG_BOOTARGS
867		This can be used to pass arguments to the bootm
868		command. The value of CONFIG_BOOTARGS goes into the
869		environment value "bootargs".
870
871		CONFIG_RAMBOOT and CONFIG_NFSBOOT
872		The value of these goes into the environment as
873		"ramboot" and "nfsboot" respectively, and can be used
874		as a convenience, when switching between booting from
875		RAM and NFS.
876
877- Bootcount:
878		CONFIG_BOOTCOUNT_LIMIT
879		Implements a mechanism for detecting a repeating reboot
880		cycle, see:
881		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
882
883		CONFIG_BOOTCOUNT_ENV
884		If no softreset save registers are found on the hardware
885		"bootcount" is stored in the environment. To prevent a
886		saveenv on all reboots, the environment variable
887		"upgrade_available" is used. If "upgrade_available" is
888		0, "bootcount" is always 0, if "upgrade_available" is
889		1 "bootcount" is incremented in the environment.
890		So the Userspace Applikation must set the "upgrade_available"
891		and "bootcount" variable to 0, if a boot was successfully.
892
893- Pre-Boot Commands:
894		CONFIG_PREBOOT
895
896		When this option is #defined, the existence of the
897		environment variable "preboot" will be checked
898		immediately before starting the CONFIG_BOOTDELAY
899		countdown and/or running the auto-boot command resp.
900		entering interactive mode.
901
902		This feature is especially useful when "preboot" is
903		automatically generated or modified. For an example
904		see the LWMON board specific code: here "preboot" is
905		modified when the user holds down a certain
906		combination of keys on the (special) keyboard when
907		booting the systems
908
909- Serial Download Echo Mode:
910		CONFIG_LOADS_ECHO
911		If defined to 1, all characters received during a
912		serial download (using the "loads" command) are
913		echoed back. This might be needed by some terminal
914		emulations (like "cu"), but may as well just take
915		time on others. This setting #define's the initial
916		value of the "loads_echo" environment variable.
917
918- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
919		CONFIG_KGDB_BAUDRATE
920		Select one of the baudrates listed in
921		CONFIG_SYS_BAUDRATE_TABLE, see below.
922
923- Monitor Functions:
924		Monitor commands can be included or excluded
925		from the build by using the #include files
926		<config_cmd_all.h> and #undef'ing unwanted
927		commands, or using <config_cmd_default.h>
928		and augmenting with additional #define's
929		for wanted commands.
930
931		The default command configuration includes all commands
932		except those marked below with a "*".
933
934		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
935		CONFIG_CMD_ASKENV	* ask for env variable
936		CONFIG_CMD_BDI		  bdinfo
937		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
938		CONFIG_CMD_BMP		* BMP support
939		CONFIG_CMD_BSP		* Board specific commands
940		CONFIG_CMD_BOOTD	  bootd
941		CONFIG_CMD_CACHE	* icache, dcache
942		CONFIG_CMD_CLK   	* clock command support
943		CONFIG_CMD_CONSOLE	  coninfo
944		CONFIG_CMD_CRC32	* crc32
945		CONFIG_CMD_DATE		* support for RTC, date/time...
946		CONFIG_CMD_DHCP		* DHCP support
947		CONFIG_CMD_DIAG		* Diagnostics
948		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
949		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
950		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
951		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
952		CONFIG_CMD_DTT		* Digital Therm and Thermostat
953		CONFIG_CMD_ECHO		  echo arguments
954		CONFIG_CMD_EDITENV	  edit env variable
955		CONFIG_CMD_EEPROM	* EEPROM read/write support
956		CONFIG_CMD_ELF		* bootelf, bootvx
957		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
958		CONFIG_CMD_ENV_FLAGS	* display details about env flags
959		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
960		CONFIG_CMD_EXPORTENV	* export the environment
961		CONFIG_CMD_EXT2		* ext2 command support
962		CONFIG_CMD_EXT4		* ext4 command support
963		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
964					  that work for multiple fs types
965		CONFIG_CMD_SAVEENV	  saveenv
966		CONFIG_CMD_FDC		* Floppy Disk Support
967		CONFIG_CMD_FAT		* FAT command support
968		CONFIG_CMD_FLASH	  flinfo, erase, protect
969		CONFIG_CMD_FPGA		  FPGA device initialization support
970		CONFIG_CMD_FUSE		* Device fuse support
971		CONFIG_CMD_GETTIME	* Get time since boot
972		CONFIG_CMD_GO		* the 'go' command (exec code)
973		CONFIG_CMD_GREPENV	* search environment
974		CONFIG_CMD_HASH		* calculate hash / digest
975		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
976		CONFIG_CMD_I2C		* I2C serial bus support
977		CONFIG_CMD_IDE		* IDE harddisk support
978		CONFIG_CMD_IMI		  iminfo
979		CONFIG_CMD_IMLS		  List all images found in NOR flash
980		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
981		CONFIG_CMD_IMMAP	* IMMR dump support
982		CONFIG_CMD_IMPORTENV	* import an environment
983		CONFIG_CMD_INI		* import data from an ini file into the env
984		CONFIG_CMD_IRQ		* irqinfo
985		CONFIG_CMD_ITEST	  Integer/string test of 2 values
986		CONFIG_CMD_JFFS2	* JFFS2 Support
987		CONFIG_CMD_KGDB		* kgdb
988		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
989		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
990					  (169.254.*.*)
991		CONFIG_CMD_LOADB	  loadb
992		CONFIG_CMD_LOADS	  loads
993		CONFIG_CMD_MD5SUM	* print md5 message digest
994					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
995		CONFIG_CMD_MEMINFO	* Display detailed memory information
996		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
997					  loop, loopw
998		CONFIG_CMD_MEMTEST	* mtest
999		CONFIG_CMD_MISC		  Misc functions like sleep etc
1000		CONFIG_CMD_MMC		* MMC memory mapped support
1001		CONFIG_CMD_MII		* MII utility commands
1002		CONFIG_CMD_MTDPARTS	* MTD partition support
1003		CONFIG_CMD_NAND		* NAND support
1004		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1005		CONFIG_CMD_NFS		  NFS support
1006		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1007		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1008		CONFIG_CMD_PCI		* pciinfo
1009		CONFIG_CMD_PCMCIA		* PCMCIA support
1010		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1011					  host
1012		CONFIG_CMD_PORTIO	* Port I/O
1013		CONFIG_CMD_READ		* Read raw data from partition
1014		CONFIG_CMD_REGINFO	* Register dump
1015		CONFIG_CMD_RUN		  run command in env variable
1016		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1017		CONFIG_CMD_SAVES	* save S record dump
1018		CONFIG_CMD_SCSI		* SCSI Support
1019		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1020					  (requires CONFIG_CMD_I2C)
1021		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1022					  (4xx only)
1023		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1024		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1025					  (requires CONFIG_CMD_MEMORY)
1026		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1027		CONFIG_CMD_SOURCE	  "source" command Support
1028		CONFIG_CMD_SPI		* SPI serial bus support
1029		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1030		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1031		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1032		CONFIG_CMD_TIMER	* access to the system tick timer
1033		CONFIG_CMD_USB		* USB support
1034		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1035		CONFIG_CMD_MFSL		* Microblaze FSL support
1036		CONFIG_CMD_XIMG		  Load part of Multi Image
1037		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1038
1039		EXAMPLE: If you want all functions except of network
1040		support you can write:
1041
1042		#include "config_cmd_all.h"
1043		#undef CONFIG_CMD_NET
1044
1045	Other Commands:
1046		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1047
1048	Note:	Don't enable the "icache" and "dcache" commands
1049		(configuration option CONFIG_CMD_CACHE) unless you know
1050		what you (and your U-Boot users) are doing. Data
1051		cache cannot be enabled on systems like the 8xx or
1052		8260 (where accesses to the IMMR region must be
1053		uncached), and it cannot be disabled on all other
1054		systems where we (mis-) use the data cache to hold an
1055		initial stack and some data.
1056
1057
1058		XXX - this list needs to get updated!
1059
1060- Regular expression support:
1061		CONFIG_REGEX
1062		If this variable is defined, U-Boot is linked against
1063		the SLRE (Super Light Regular Expression) library,
1064		which adds regex support to some commands, as for
1065		example "env grep" and "setexpr".
1066
1067- Device tree:
1068		CONFIG_OF_CONTROL
1069		If this variable is defined, U-Boot will use a device tree
1070		to configure its devices, instead of relying on statically
1071		compiled #defines in the board file. This option is
1072		experimental and only available on a few boards. The device
1073		tree is available in the global data as gd->fdt_blob.
1074
1075		U-Boot needs to get its device tree from somewhere. This can
1076		be done using one of the two options below:
1077
1078		CONFIG_OF_EMBED
1079		If this variable is defined, U-Boot will embed a device tree
1080		binary in its image. This device tree file should be in the
1081		board directory and called <soc>-<board>.dts. The binary file
1082		is then picked up in board_init_f() and made available through
1083		the global data structure as gd->blob.
1084
1085		CONFIG_OF_SEPARATE
1086		If this variable is defined, U-Boot will build a device tree
1087		binary. It will be called u-boot.dtb. Architecture-specific
1088		code will locate it at run-time. Generally this works by:
1089
1090			cat u-boot.bin u-boot.dtb >image.bin
1091
1092		and in fact, U-Boot does this for you, creating a file called
1093		u-boot-dtb.bin which is useful in the common case. You can
1094		still use the individual files if you need something more
1095		exotic.
1096
1097- Watchdog:
1098		CONFIG_WATCHDOG
1099		If this variable is defined, it enables watchdog
1100		support for the SoC. There must be support in the SoC
1101		specific code for a watchdog. For the 8xx and 8260
1102		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1103		register.  When supported for a specific SoC is
1104		available, then no further board specific code should
1105		be needed to use it.
1106
1107		CONFIG_HW_WATCHDOG
1108		When using a watchdog circuitry external to the used
1109		SoC, then define this variable and provide board
1110		specific code for the "hw_watchdog_reset" function.
1111
1112- U-Boot Version:
1113		CONFIG_VERSION_VARIABLE
1114		If this variable is defined, an environment variable
1115		named "ver" is created by U-Boot showing the U-Boot
1116		version as printed by the "version" command.
1117		Any change to this variable will be reverted at the
1118		next reset.
1119
1120- Real-Time Clock:
1121
1122		When CONFIG_CMD_DATE is selected, the type of the RTC
1123		has to be selected, too. Define exactly one of the
1124		following options:
1125
1126		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1127		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1128		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1129		CONFIG_RTC_MC146818	- use MC146818 RTC
1130		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1131		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1132		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1133		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1134		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1135		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1136		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1137		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1138					  RV3029 RTC.
1139
1140		Note that if the RTC uses I2C, then the I2C interface
1141		must also be configured. See I2C Support, below.
1142
1143- GPIO Support:
1144		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1145
1146		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1147		chip-ngpio pairs that tell the PCA953X driver the number of
1148		pins supported by a particular chip.
1149
1150		Note that if the GPIO device uses I2C, then the I2C interface
1151		must also be configured. See I2C Support, below.
1152
1153- Timestamp Support:
1154
1155		When CONFIG_TIMESTAMP is selected, the timestamp
1156		(date and time) of an image is printed by image
1157		commands like bootm or iminfo. This option is
1158		automatically enabled when you select CONFIG_CMD_DATE .
1159
1160- Partition Labels (disklabels) Supported:
1161		Zero or more of the following:
1162		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1163		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1164				       Intel architecture, USB sticks, etc.
1165		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1166		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1167				       bootloader.  Note 2TB partition limit; see
1168				       disk/part_efi.c
1169		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1170
1171		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1172		CONFIG_CMD_SCSI) you must configure support for at
1173		least one non-MTD partition type as well.
1174
1175- IDE Reset method:
1176		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1177		board configurations files but used nowhere!
1178
1179		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1180		be performed by calling the function
1181			ide_set_reset(int reset)
1182		which has to be defined in a board specific file
1183
1184- ATAPI Support:
1185		CONFIG_ATAPI
1186
1187		Set this to enable ATAPI support.
1188
1189- LBA48 Support
1190		CONFIG_LBA48
1191
1192		Set this to enable support for disks larger than 137GB
1193		Also look at CONFIG_SYS_64BIT_LBA.
1194		Whithout these , LBA48 support uses 32bit variables and will 'only'
1195		support disks up to 2.1TB.
1196
1197		CONFIG_SYS_64BIT_LBA:
1198			When enabled, makes the IDE subsystem use 64bit sector addresses.
1199			Default is 32bit.
1200
1201- SCSI Support:
1202		At the moment only there is only support for the
1203		SYM53C8XX SCSI controller; define
1204		CONFIG_SCSI_SYM53C8XX to enable it.
1205
1206		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1207		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1208		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1209		maximum numbers of LUNs, SCSI ID's and target
1210		devices.
1211		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1212
1213		The environment variable 'scsidevs' is set to the number of
1214		SCSI devices found during the last scan.
1215
1216- NETWORK Support (PCI):
1217		CONFIG_E1000
1218		Support for Intel 8254x/8257x gigabit chips.
1219
1220		CONFIG_E1000_SPI
1221		Utility code for direct access to the SPI bus on Intel 8257x.
1222		This does not do anything useful unless you set at least one
1223		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1224
1225		CONFIG_E1000_SPI_GENERIC
1226		Allow generic access to the SPI bus on the Intel 8257x, for
1227		example with the "sspi" command.
1228
1229		CONFIG_CMD_E1000
1230		Management command for E1000 devices.  When used on devices
1231		with SPI support you can reprogram the EEPROM from U-Boot.
1232
1233		CONFIG_E1000_FALLBACK_MAC
1234		default MAC for empty EEPROM after production.
1235
1236		CONFIG_EEPRO100
1237		Support for Intel 82557/82559/82559ER chips.
1238		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1239		write routine for first time initialisation.
1240
1241		CONFIG_TULIP
1242		Support for Digital 2114x chips.
1243		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1244		modem chip initialisation (KS8761/QS6611).
1245
1246		CONFIG_NATSEMI
1247		Support for National dp83815 chips.
1248
1249		CONFIG_NS8382X
1250		Support for National dp8382[01] gigabit chips.
1251
1252- NETWORK Support (other):
1253
1254		CONFIG_DRIVER_AT91EMAC
1255		Support for AT91RM9200 EMAC.
1256
1257			CONFIG_RMII
1258			Define this to use reduced MII inteface
1259
1260			CONFIG_DRIVER_AT91EMAC_QUIET
1261			If this defined, the driver is quiet.
1262			The driver doen't show link status messages.
1263
1264		CONFIG_CALXEDA_XGMAC
1265		Support for the Calxeda XGMAC device
1266
1267		CONFIG_LAN91C96
1268		Support for SMSC's LAN91C96 chips.
1269
1270			CONFIG_LAN91C96_BASE
1271			Define this to hold the physical address
1272			of the LAN91C96's I/O space
1273
1274			CONFIG_LAN91C96_USE_32_BIT
1275			Define this to enable 32 bit addressing
1276
1277		CONFIG_SMC91111
1278		Support for SMSC's LAN91C111 chip
1279
1280			CONFIG_SMC91111_BASE
1281			Define this to hold the physical address
1282			of the device (I/O space)
1283
1284			CONFIG_SMC_USE_32_BIT
1285			Define this if data bus is 32 bits
1286
1287			CONFIG_SMC_USE_IOFUNCS
1288			Define this to use i/o functions instead of macros
1289			(some hardware wont work with macros)
1290
1291		CONFIG_DRIVER_TI_EMAC
1292		Support for davinci emac
1293
1294			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1295			Define this if you have more then 3 PHYs.
1296
1297		CONFIG_FTGMAC100
1298		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1299
1300			CONFIG_FTGMAC100_EGIGA
1301			Define this to use GE link update with gigabit PHY.
1302			Define this if FTGMAC100 is connected to gigabit PHY.
1303			If your system has 10/100 PHY only, it might not occur
1304			wrong behavior. Because PHY usually return timeout or
1305			useless data when polling gigabit status and gigabit
1306			control registers. This behavior won't affect the
1307			correctnessof 10/100 link speed update.
1308
1309		CONFIG_SMC911X
1310		Support for SMSC's LAN911x and LAN921x chips
1311
1312			CONFIG_SMC911X_BASE
1313			Define this to hold the physical address
1314			of the device (I/O space)
1315
1316			CONFIG_SMC911X_32_BIT
1317			Define this if data bus is 32 bits
1318
1319			CONFIG_SMC911X_16_BIT
1320			Define this if data bus is 16 bits. If your processor
1321			automatically converts one 32 bit word to two 16 bit
1322			words you may also try CONFIG_SMC911X_32_BIT.
1323
1324		CONFIG_SH_ETHER
1325		Support for Renesas on-chip Ethernet controller
1326
1327			CONFIG_SH_ETHER_USE_PORT
1328			Define the number of ports to be used
1329
1330			CONFIG_SH_ETHER_PHY_ADDR
1331			Define the ETH PHY's address
1332
1333			CONFIG_SH_ETHER_CACHE_WRITEBACK
1334			If this option is set, the driver enables cache flush.
1335
1336- TPM Support:
1337		CONFIG_TPM
1338		Support TPM devices.
1339
1340		CONFIG_TPM_TIS_I2C
1341		Support for i2c bus TPM devices. Only one device
1342		per system is supported at this time.
1343
1344			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1345			Define the the i2c bus number for the TPM device
1346
1347			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1348			Define the TPM's address on the i2c bus
1349
1350			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1351			Define the burst count bytes upper limit
1352
1353		CONFIG_TPM_ATMEL_TWI
1354		Support for Atmel TWI TPM device. Requires I2C support.
1355
1356		CONFIG_TPM_TIS_LPC
1357		Support for generic parallel port TPM devices. Only one device
1358		per system is supported at this time.
1359
1360			CONFIG_TPM_TIS_BASE_ADDRESS
1361			Base address where the generic TPM device is mapped
1362			to. Contemporary x86 systems usually map it at
1363			0xfed40000.
1364
1365		CONFIG_CMD_TPM
1366		Add tpm monitor functions.
1367		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1368		provides monitor access to authorized functions.
1369
1370		CONFIG_TPM
1371		Define this to enable the TPM support library which provides
1372		functional interfaces to some TPM commands.
1373		Requires support for a TPM device.
1374
1375		CONFIG_TPM_AUTH_SESSIONS
1376		Define this to enable authorized functions in the TPM library.
1377		Requires CONFIG_TPM and CONFIG_SHA1.
1378
1379- USB Support:
1380		At the moment only the UHCI host controller is
1381		supported (PIP405, MIP405, MPC5200); define
1382		CONFIG_USB_UHCI to enable it.
1383		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1384		and define CONFIG_USB_STORAGE to enable the USB
1385		storage devices.
1386		Note:
1387		Supported are USB Keyboards and USB Floppy drives
1388		(TEAC FD-05PUB).
1389		MPC5200 USB requires additional defines:
1390			CONFIG_USB_CLOCK
1391				for 528 MHz Clock: 0x0001bbbb
1392			CONFIG_PSC3_USB
1393				for USB on PSC3
1394			CONFIG_USB_CONFIG
1395				for differential drivers: 0x00001000
1396				for single ended drivers: 0x00005000
1397				for differential drivers on PSC3: 0x00000100
1398				for single ended drivers on PSC3: 0x00004100
1399			CONFIG_SYS_USB_EVENT_POLL
1400				May be defined to allow interrupt polling
1401				instead of using asynchronous interrupts
1402
1403		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1404		txfilltuning field in the EHCI controller on reset.
1405
1406		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1407		interval for usb hub power-on delay.(minimum 100msec)
1408
1409- USB Device:
1410		Define the below if you wish to use the USB console.
1411		Once firmware is rebuilt from a serial console issue the
1412		command "setenv stdin usbtty; setenv stdout usbtty" and
1413		attach your USB cable. The Unix command "dmesg" should print
1414		it has found a new device. The environment variable usbtty
1415		can be set to gserial or cdc_acm to enable your device to
1416		appear to a USB host as a Linux gserial device or a
1417		Common Device Class Abstract Control Model serial device.
1418		If you select usbtty = gserial you should be able to enumerate
1419		a Linux host by
1420		# modprobe usbserial vendor=0xVendorID product=0xProductID
1421		else if using cdc_acm, simply setting the environment
1422		variable usbtty to be cdc_acm should suffice. The following
1423		might be defined in YourBoardName.h
1424
1425			CONFIG_USB_DEVICE
1426			Define this to build a UDC device
1427
1428			CONFIG_USB_TTY
1429			Define this to have a tty type of device available to
1430			talk to the UDC device
1431
1432			CONFIG_USBD_HS
1433			Define this to enable the high speed support for usb
1434			device and usbtty. If this feature is enabled, a routine
1435			int is_usbd_high_speed(void)
1436			also needs to be defined by the driver to dynamically poll
1437			whether the enumeration has succeded at high speed or full
1438			speed.
1439
1440			CONFIG_SYS_CONSOLE_IS_IN_ENV
1441			Define this if you want stdin, stdout &/or stderr to
1442			be set to usbtty.
1443
1444			mpc8xx:
1445				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1446				Derive USB clock from external clock "blah"
1447				- CONFIG_SYS_USB_EXTC_CLK 0x02
1448
1449				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1450				Derive USB clock from brgclk
1451				- CONFIG_SYS_USB_BRG_CLK 0x04
1452
1453		If you have a USB-IF assigned VendorID then you may wish to
1454		define your own vendor specific values either in BoardName.h
1455		or directly in usbd_vendor_info.h. If you don't define
1456		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1457		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1458		should pretend to be a Linux device to it's target host.
1459
1460			CONFIG_USBD_MANUFACTURER
1461			Define this string as the name of your company for
1462			- CONFIG_USBD_MANUFACTURER "my company"
1463
1464			CONFIG_USBD_PRODUCT_NAME
1465			Define this string as the name of your product
1466			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1467
1468			CONFIG_USBD_VENDORID
1469			Define this as your assigned Vendor ID from the USB
1470			Implementors Forum. This *must* be a genuine Vendor ID
1471			to avoid polluting the USB namespace.
1472			- CONFIG_USBD_VENDORID 0xFFFF
1473
1474			CONFIG_USBD_PRODUCTID
1475			Define this as the unique Product ID
1476			for your device
1477			- CONFIG_USBD_PRODUCTID 0xFFFF
1478
1479		Some USB device drivers may need to check USB cable attachment.
1480		In this case you can enable following config in BoardName.h:
1481			CONFIG_USB_CABLE_CHECK
1482			This enables function definition:
1483			- usb_cable_connected() in include/usb.h
1484			Implementation of this function is board-specific.
1485
1486- ULPI Layer Support:
1487		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1488		the generic ULPI layer. The generic layer accesses the ULPI PHY
1489		via the platform viewport, so you need both the genric layer and
1490		the viewport enabled. Currently only Chipidea/ARC based
1491		viewport is supported.
1492		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1493		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1494		If your ULPI phy needs a different reference clock than the
1495		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1496		the appropriate value in Hz.
1497
1498- MMC Support:
1499		The MMC controller on the Intel PXA is supported. To
1500		enable this define CONFIG_MMC. The MMC can be
1501		accessed from the boot prompt by mapping the device
1502		to physical memory similar to flash. Command line is
1503		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1504		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1505
1506		CONFIG_SH_MMCIF
1507		Support for Renesas on-chip MMCIF controller
1508
1509			CONFIG_SH_MMCIF_ADDR
1510			Define the base address of MMCIF registers
1511
1512			CONFIG_SH_MMCIF_CLK
1513			Define the clock frequency for MMCIF
1514
1515- USB Device Firmware Update (DFU) class support:
1516		CONFIG_DFU_FUNCTION
1517		This enables the USB portion of the DFU USB class
1518
1519		CONFIG_CMD_DFU
1520		This enables the command "dfu" which is used to have
1521		U-Boot create a DFU class device via USB.  This command
1522		requires that the "dfu_alt_info" environment variable be
1523		set and define the alt settings to expose to the host.
1524
1525		CONFIG_DFU_MMC
1526		This enables support for exposing (e)MMC devices via DFU.
1527
1528		CONFIG_DFU_NAND
1529		This enables support for exposing NAND devices via DFU.
1530
1531		CONFIG_DFU_RAM
1532		This enables support for exposing RAM via DFU.
1533		Note: DFU spec refer to non-volatile memory usage, but
1534		allow usages beyond the scope of spec - here RAM usage,
1535		one that would help mostly the developer.
1536
1537		CONFIG_SYS_DFU_DATA_BUF_SIZE
1538		Dfu transfer uses a buffer before writing data to the
1539		raw storage device. Make the size (in bytes) of this buffer
1540		configurable. The size of this buffer is also configurable
1541		through the "dfu_bufsiz" environment variable.
1542
1543		CONFIG_SYS_DFU_MAX_FILE_SIZE
1544		When updating files rather than the raw storage device,
1545		we use a static buffer to copy the file into and then write
1546		the buffer once we've been given the whole file.  Define
1547		this to the maximum filesize (in bytes) for the buffer.
1548		Default is 4 MiB if undefined.
1549
1550		DFU_DEFAULT_POLL_TIMEOUT
1551		Poll timeout [ms], is the timeout a device can send to the
1552		host. The host must wait for this timeout before sending
1553		a subsequent DFU_GET_STATUS request to the device.
1554
1555		DFU_MANIFEST_POLL_TIMEOUT
1556		Poll timeout [ms], which the device sends to the host when
1557		entering dfuMANIFEST state. Host waits this timeout, before
1558		sending again an USB request to the device.
1559
1560- Journaling Flash filesystem support:
1561		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1562		CONFIG_JFFS2_NAND_DEV
1563		Define these for a default partition on a NAND device
1564
1565		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1566		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1567		Define these for a default partition on a NOR device
1568
1569		CONFIG_SYS_JFFS_CUSTOM_PART
1570		Define this to create an own partition. You have to provide a
1571		function struct part_info* jffs2_part_info(int part_num)
1572
1573		If you define only one JFFS2 partition you may also want to
1574		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1575		to disable the command chpart. This is the default when you
1576		have not defined a custom partition
1577
1578- FAT(File Allocation Table) filesystem write function support:
1579		CONFIG_FAT_WRITE
1580
1581		Define this to enable support for saving memory data as a
1582		file in FAT formatted partition.
1583
1584		This will also enable the command "fatwrite" enabling the
1585		user to write files to FAT.
1586
1587CBFS (Coreboot Filesystem) support
1588		CONFIG_CMD_CBFS
1589
1590		Define this to enable support for reading from a Coreboot
1591		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1592		and cbfsload.
1593
1594- Keyboard Support:
1595		CONFIG_ISA_KEYBOARD
1596
1597		Define this to enable standard (PC-Style) keyboard
1598		support
1599
1600		CONFIG_I8042_KBD
1601		Standard PC keyboard driver with US (is default) and
1602		GERMAN key layout (switch via environment 'keymap=de') support.
1603		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1604		for cfb_console. Supports cursor blinking.
1605
1606		CONFIG_CROS_EC_KEYB
1607		Enables a Chrome OS keyboard using the CROS_EC interface.
1608		This uses CROS_EC to communicate with a second microcontroller
1609		which provides key scans on request.
1610
1611- Video support:
1612		CONFIG_VIDEO
1613
1614		Define this to enable video support (for output to
1615		video).
1616
1617		CONFIG_VIDEO_CT69000
1618
1619		Enable Chips & Technologies 69000 Video chip
1620
1621		CONFIG_VIDEO_SMI_LYNXEM
1622		Enable Silicon Motion SMI 712/710/810 Video chip. The
1623		video output is selected via environment 'videoout'
1624		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1625		assumed.
1626
1627		For the CT69000 and SMI_LYNXEM drivers, videomode is
1628		selected via environment 'videomode'. Two different ways
1629		are possible:
1630		- "videomode=num"   'num' is a standard LiLo mode numbers.
1631		Following standard modes are supported	(* is default):
1632
1633		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1634		-------------+---------------------------------------------
1635		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1636		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1637		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1638		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1639		-------------+---------------------------------------------
1640		(i.e. setenv videomode 317; saveenv; reset;)
1641
1642		- "videomode=bootargs" all the video parameters are parsed
1643		from the bootargs. (See drivers/video/videomodes.c)
1644
1645
1646		CONFIG_VIDEO_SED13806
1647		Enable Epson SED13806 driver. This driver supports 8bpp
1648		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1649		or CONFIG_VIDEO_SED13806_16BPP
1650
1651		CONFIG_FSL_DIU_FB
1652		Enable the Freescale DIU video driver.	Reference boards for
1653		SOCs that have a DIU should define this macro to enable DIU
1654		support, and should also define these other macros:
1655
1656			CONFIG_SYS_DIU_ADDR
1657			CONFIG_VIDEO
1658			CONFIG_CMD_BMP
1659			CONFIG_CFB_CONSOLE
1660			CONFIG_VIDEO_SW_CURSOR
1661			CONFIG_VGA_AS_SINGLE_DEVICE
1662			CONFIG_VIDEO_LOGO
1663			CONFIG_VIDEO_BMP_LOGO
1664
1665		The DIU driver will look for the 'video-mode' environment
1666		variable, and if defined, enable the DIU as a console during
1667		boot.  See the documentation file README.video for a
1668		description of this variable.
1669
1670		CONFIG_VIDEO_VGA
1671
1672		Enable the VGA video / BIOS for x86. The alternative if you
1673		are using coreboot is to use the coreboot frame buffer
1674		driver.
1675
1676
1677- Keyboard Support:
1678		CONFIG_KEYBOARD
1679
1680		Define this to enable a custom keyboard support.
1681		This simply calls drv_keyboard_init() which must be
1682		defined in your board-specific files.
1683		The only board using this so far is RBC823.
1684
1685- LCD Support:	CONFIG_LCD
1686
1687		Define this to enable LCD support (for output to LCD
1688		display); also select one of the supported displays
1689		by defining one of these:
1690
1691		CONFIG_ATMEL_LCD:
1692
1693			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1694
1695		CONFIG_NEC_NL6448AC33:
1696
1697			NEC NL6448AC33-18. Active, color, single scan.
1698
1699		CONFIG_NEC_NL6448BC20
1700
1701			NEC NL6448BC20-08. 6.5", 640x480.
1702			Active, color, single scan.
1703
1704		CONFIG_NEC_NL6448BC33_54
1705
1706			NEC NL6448BC33-54. 10.4", 640x480.
1707			Active, color, single scan.
1708
1709		CONFIG_SHARP_16x9
1710
1711			Sharp 320x240. Active, color, single scan.
1712			It isn't 16x9, and I am not sure what it is.
1713
1714		CONFIG_SHARP_LQ64D341
1715
1716			Sharp LQ64D341 display, 640x480.
1717			Active, color, single scan.
1718
1719		CONFIG_HLD1045
1720
1721			HLD1045 display, 640x480.
1722			Active, color, single scan.
1723
1724		CONFIG_OPTREX_BW
1725
1726			Optrex	 CBL50840-2 NF-FW 99 22 M5
1727			or
1728			Hitachi	 LMG6912RPFC-00T
1729			or
1730			Hitachi	 SP14Q002
1731
1732			320x240. Black & white.
1733
1734		Normally display is black on white background; define
1735		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1736
1737		CONFIG_LCD_ALIGNMENT
1738
1739		Normally the LCD is page-aligned (tyically 4KB). If this is
1740		defined then the LCD will be aligned to this value instead.
1741		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1742		here, since it is cheaper to change data cache settings on
1743		a per-section basis.
1744
1745		CONFIG_CONSOLE_SCROLL_LINES
1746
1747		When the console need to be scrolled, this is the number of
1748		lines to scroll by. It defaults to 1. Increasing this makes
1749		the console jump but can help speed up operation when scrolling
1750		is slow.
1751
1752		CONFIG_LCD_BMP_RLE8
1753
1754		Support drawing of RLE8-compressed bitmaps on the LCD.
1755
1756		CONFIG_I2C_EDID
1757
1758		Enables an 'i2c edid' command which can read EDID
1759		information over I2C from an attached LCD display.
1760
1761- Splash Screen Support: CONFIG_SPLASH_SCREEN
1762
1763		If this option is set, the environment is checked for
1764		a variable "splashimage". If found, the usual display
1765		of logo, copyright and system information on the LCD
1766		is suppressed and the BMP image at the address
1767		specified in "splashimage" is loaded instead. The
1768		console is redirected to the "nulldev", too. This
1769		allows for a "silent" boot where a splash screen is
1770		loaded very quickly after power-on.
1771
1772		CONFIG_SPLASHIMAGE_GUARD
1773
1774		If this option is set, then U-Boot will prevent the environment
1775		variable "splashimage" from being set to a problematic address
1776		(see README.displaying-bmps).
1777		This option is useful for targets where, due to alignment
1778		restrictions, an improperly aligned BMP image will cause a data
1779		abort. If you think you will not have problems with unaligned
1780		accesses (for example because your toolchain prevents them)
1781		there is no need to set this option.
1782
1783		CONFIG_SPLASH_SCREEN_ALIGN
1784
1785		If this option is set the splash image can be freely positioned
1786		on the screen. Environment variable "splashpos" specifies the
1787		position as "x,y". If a positive number is given it is used as
1788		number of pixel from left/top. If a negative number is given it
1789		is used as number of pixel from right/bottom. You can also
1790		specify 'm' for centering the image.
1791
1792		Example:
1793		setenv splashpos m,m
1794			=> image at center of screen
1795
1796		setenv splashpos 30,20
1797			=> image at x = 30 and y = 20
1798
1799		setenv splashpos -10,m
1800			=> vertically centered image
1801			   at x = dspWidth - bmpWidth - 9
1802
1803- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1804
1805		If this option is set, additionally to standard BMP
1806		images, gzipped BMP images can be displayed via the
1807		splashscreen support or the bmp command.
1808
1809- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1810
1811		If this option is set, 8-bit RLE compressed BMP images
1812		can be displayed via the splashscreen support or the
1813		bmp command.
1814
1815- Do compresssing for memory range:
1816		CONFIG_CMD_ZIP
1817
1818		If this option is set, it would use zlib deflate method
1819		to compress the specified memory at its best effort.
1820
1821- Compression support:
1822		CONFIG_GZIP
1823
1824		Enabled by default to support gzip compressed images.
1825
1826		CONFIG_BZIP2
1827
1828		If this option is set, support for bzip2 compressed
1829		images is included. If not, only uncompressed and gzip
1830		compressed images are supported.
1831
1832		NOTE: the bzip2 algorithm requires a lot of RAM, so
1833		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1834		be at least 4MB.
1835
1836		CONFIG_LZMA
1837
1838		If this option is set, support for lzma compressed
1839		images is included.
1840
1841		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1842		requires an amount of dynamic memory that is given by the
1843		formula:
1844
1845			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1846
1847		Where lc and lp stand for, respectively, Literal context bits
1848		and Literal pos bits.
1849
1850		This value is upper-bounded by 14MB in the worst case. Anyway,
1851		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1852		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1853		a very small buffer.
1854
1855		Use the lzmainfo tool to determinate the lc and lp values and
1856		then calculate the amount of needed dynamic memory (ensuring
1857		the appropriate CONFIG_SYS_MALLOC_LEN value).
1858
1859		CONFIG_LZO
1860
1861		If this option is set, support for LZO compressed images
1862		is included.
1863
1864- MII/PHY support:
1865		CONFIG_PHY_ADDR
1866
1867		The address of PHY on MII bus.
1868
1869		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1870
1871		The clock frequency of the MII bus
1872
1873		CONFIG_PHY_GIGE
1874
1875		If this option is set, support for speed/duplex
1876		detection of gigabit PHY is included.
1877
1878		CONFIG_PHY_RESET_DELAY
1879
1880		Some PHY like Intel LXT971A need extra delay after
1881		reset before any MII register access is possible.
1882		For such PHY, set this option to the usec delay
1883		required. (minimum 300usec for LXT971A)
1884
1885		CONFIG_PHY_CMD_DELAY (ppc4xx)
1886
1887		Some PHY like Intel LXT971A need extra delay after
1888		command issued before MII status register can be read
1889
1890- Ethernet address:
1891		CONFIG_ETHADDR
1892		CONFIG_ETH1ADDR
1893		CONFIG_ETH2ADDR
1894		CONFIG_ETH3ADDR
1895		CONFIG_ETH4ADDR
1896		CONFIG_ETH5ADDR
1897
1898		Define a default value for Ethernet address to use
1899		for the respective Ethernet interface, in case this
1900		is not determined automatically.
1901
1902- IP address:
1903		CONFIG_IPADDR
1904
1905		Define a default value for the IP address to use for
1906		the default Ethernet interface, in case this is not
1907		determined through e.g. bootp.
1908		(Environment variable "ipaddr")
1909
1910- Server IP address:
1911		CONFIG_SERVERIP
1912
1913		Defines a default value for the IP address of a TFTP
1914		server to contact when using the "tftboot" command.
1915		(Environment variable "serverip")
1916
1917		CONFIG_KEEP_SERVERADDR
1918
1919		Keeps the server's MAC address, in the env 'serveraddr'
1920		for passing to bootargs (like Linux's netconsole option)
1921
1922- Gateway IP address:
1923		CONFIG_GATEWAYIP
1924
1925		Defines a default value for the IP address of the
1926		default router where packets to other networks are
1927		sent to.
1928		(Environment variable "gatewayip")
1929
1930- Subnet mask:
1931		CONFIG_NETMASK
1932
1933		Defines a default value for the subnet mask (or
1934		routing prefix) which is used to determine if an IP
1935		address belongs to the local subnet or needs to be
1936		forwarded through a router.
1937		(Environment variable "netmask")
1938
1939- Multicast TFTP Mode:
1940		CONFIG_MCAST_TFTP
1941
1942		Defines whether you want to support multicast TFTP as per
1943		rfc-2090; for example to work with atftp.  Lets lots of targets
1944		tftp down the same boot image concurrently.  Note: the Ethernet
1945		driver in use must provide a function: mcast() to join/leave a
1946		multicast group.
1947
1948- BOOTP Recovery Mode:
1949		CONFIG_BOOTP_RANDOM_DELAY
1950
1951		If you have many targets in a network that try to
1952		boot using BOOTP, you may want to avoid that all
1953		systems send out BOOTP requests at precisely the same
1954		moment (which would happen for instance at recovery
1955		from a power failure, when all systems will try to
1956		boot, thus flooding the BOOTP server. Defining
1957		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1958		inserted before sending out BOOTP requests. The
1959		following delays are inserted then:
1960
1961		1st BOOTP request:	delay 0 ... 1 sec
1962		2nd BOOTP request:	delay 0 ... 2 sec
1963		3rd BOOTP request:	delay 0 ... 4 sec
1964		4th and following
1965		BOOTP requests:		delay 0 ... 8 sec
1966
1967- DHCP Advanced Options:
1968		You can fine tune the DHCP functionality by defining
1969		CONFIG_BOOTP_* symbols:
1970
1971		CONFIG_BOOTP_SUBNETMASK
1972		CONFIG_BOOTP_GATEWAY
1973		CONFIG_BOOTP_HOSTNAME
1974		CONFIG_BOOTP_NISDOMAIN
1975		CONFIG_BOOTP_BOOTPATH
1976		CONFIG_BOOTP_BOOTFILESIZE
1977		CONFIG_BOOTP_DNS
1978		CONFIG_BOOTP_DNS2
1979		CONFIG_BOOTP_SEND_HOSTNAME
1980		CONFIG_BOOTP_NTPSERVER
1981		CONFIG_BOOTP_TIMEOFFSET
1982		CONFIG_BOOTP_VENDOREX
1983		CONFIG_BOOTP_MAY_FAIL
1984
1985		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1986		environment variable, not the BOOTP server.
1987
1988		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1989		after the configured retry count, the call will fail
1990		instead of starting over.  This can be used to fail over
1991		to Link-local IP address configuration if the DHCP server
1992		is not available.
1993
1994		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1995		serverip from a DHCP server, it is possible that more
1996		than one DNS serverip is offered to the client.
1997		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1998		serverip will be stored in the additional environment
1999		variable "dnsip2". The first DNS serverip is always
2000		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2001		is defined.
2002
2003		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2004		to do a dynamic update of a DNS server. To do this, they
2005		need the hostname of the DHCP requester.
2006		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2007		of the "hostname" environment variable is passed as
2008		option 12 to the DHCP server.
2009
2010		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2011
2012		A 32bit value in microseconds for a delay between
2013		receiving a "DHCP Offer" and sending the "DHCP Request".
2014		This fixes a problem with certain DHCP servers that don't
2015		respond 100% of the time to a "DHCP request". E.g. On an
2016		AT91RM9200 processor running at 180MHz, this delay needed
2017		to be *at least* 15,000 usec before a Windows Server 2003
2018		DHCP server would reply 100% of the time. I recommend at
2019		least 50,000 usec to be safe. The alternative is to hope
2020		that one of the retries will be successful but note that
2021		the DHCP timeout and retry process takes a longer than
2022		this delay.
2023
2024 - Link-local IP address negotiation:
2025		Negotiate with other link-local clients on the local network
2026		for an address that doesn't require explicit configuration.
2027		This is especially useful if a DHCP server cannot be guaranteed
2028		to exist in all environments that the device must operate.
2029
2030		See doc/README.link-local for more information.
2031
2032 - CDP Options:
2033		CONFIG_CDP_DEVICE_ID
2034
2035		The device id used in CDP trigger frames.
2036
2037		CONFIG_CDP_DEVICE_ID_PREFIX
2038
2039		A two character string which is prefixed to the MAC address
2040		of the device.
2041
2042		CONFIG_CDP_PORT_ID
2043
2044		A printf format string which contains the ascii name of
2045		the port. Normally is set to "eth%d" which sets
2046		eth0 for the first Ethernet, eth1 for the second etc.
2047
2048		CONFIG_CDP_CAPABILITIES
2049
2050		A 32bit integer which indicates the device capabilities;
2051		0x00000010 for a normal host which does not forwards.
2052
2053		CONFIG_CDP_VERSION
2054
2055		An ascii string containing the version of the software.
2056
2057		CONFIG_CDP_PLATFORM
2058
2059		An ascii string containing the name of the platform.
2060
2061		CONFIG_CDP_TRIGGER
2062
2063		A 32bit integer sent on the trigger.
2064
2065		CONFIG_CDP_POWER_CONSUMPTION
2066
2067		A 16bit integer containing the power consumption of the
2068		device in .1 of milliwatts.
2069
2070		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2071
2072		A byte containing the id of the VLAN.
2073
2074- Status LED:	CONFIG_STATUS_LED
2075
2076		Several configurations allow to display the current
2077		status using a LED. For instance, the LED will blink
2078		fast while running U-Boot code, stop blinking as
2079		soon as a reply to a BOOTP request was received, and
2080		start blinking slow once the Linux kernel is running
2081		(supported by a status LED driver in the Linux
2082		kernel). Defining CONFIG_STATUS_LED enables this
2083		feature in U-Boot.
2084
2085		Additional options:
2086
2087		CONFIG_GPIO_LED
2088		The status LED can be connected to a GPIO pin.
2089		In such cases, the gpio_led driver can be used as a
2090		status LED backend implementation. Define CONFIG_GPIO_LED
2091		to include the gpio_led driver in the U-Boot binary.
2092
2093		CONFIG_GPIO_LED_INVERTED_TABLE
2094		Some GPIO connected LEDs may have inverted polarity in which
2095		case the GPIO high value corresponds to LED off state and
2096		GPIO low value corresponds to LED on state.
2097		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2098		with a list of GPIO LEDs that have inverted polarity.
2099
2100- CAN Support:	CONFIG_CAN_DRIVER
2101
2102		Defining CONFIG_CAN_DRIVER enables CAN driver support
2103		on those systems that support this (optional)
2104		feature, like the TQM8xxL modules.
2105
2106- I2C Support:	CONFIG_SYS_I2C
2107
2108		This enable the NEW i2c subsystem, and will allow you to use
2109		i2c commands at the u-boot command line (as long as you set
2110		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2111		based realtime clock chips or other i2c devices. See
2112		common/cmd_i2c.c for a description of the command line
2113		interface.
2114
2115		ported i2c driver to the new framework:
2116		- drivers/i2c/soft_i2c.c:
2117		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2118		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2119		    for defining speed and slave address
2120		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2121		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2122		    for defining speed and slave address
2123		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2124		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2125		    for defining speed and slave address
2126		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2127		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2128		    for defining speed and slave address
2129
2130		- drivers/i2c/fsl_i2c.c:
2131		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2132		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2133		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2134		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2135		    bus.
2136		  - If your board supports a second fsl i2c bus, define
2137		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2138		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2139		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2140		    second bus.
2141
2142		- drivers/i2c/tegra_i2c.c:
2143		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2144		  - This driver adds 4 i2c buses with a fix speed from
2145		    100000 and the slave addr 0!
2146
2147		- drivers/i2c/ppc4xx_i2c.c
2148		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2149		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2150		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2151
2152		- drivers/i2c/i2c_mxc.c
2153		  - activate this driver with CONFIG_SYS_I2C_MXC
2154		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2155		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2156		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2157		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2158		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2159		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2160		If thoses defines are not set, default value is 100000
2161		for speed, and 0 for slave.
2162
2163		- drivers/i2c/rcar_i2c.c:
2164		  - activate this driver with CONFIG_SYS_I2C_RCAR
2165		  - This driver adds 4 i2c buses
2166
2167		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2168		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2169		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2170		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2171		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2172		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2173		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2174		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2175		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2176
2177		- drivers/i2c/sh_i2c.c:
2178		  - activate this driver with CONFIG_SYS_I2C_SH
2179		  - This driver adds from 2 to 5 i2c buses
2180
2181		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2182		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2183		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2184		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2185		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2186		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2187		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2188		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2189		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2190		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2191		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2192		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2193		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2194
2195		- drivers/i2c/omap24xx_i2c.c
2196		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2197		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2198		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2199		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2200		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2201		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2202		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2203		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2204		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2205		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2206		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2207
2208		- drivers/i2c/zynq_i2c.c
2209		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2210		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2211		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2212
2213		- drivers/i2c/s3c24x0_i2c.c:
2214		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2215		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2216		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2217		    with a fix speed from 100000 and the slave addr 0!
2218
2219		additional defines:
2220
2221		CONFIG_SYS_NUM_I2C_BUSES
2222		Hold the number of i2c busses you want to use. If you
2223		don't use/have i2c muxes on your i2c bus, this
2224		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2225		omit this define.
2226
2227		CONFIG_SYS_I2C_DIRECT_BUS
2228		define this, if you don't use i2c muxes on your hardware.
2229		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2230		omit this define.
2231
2232		CONFIG_SYS_I2C_MAX_HOPS
2233		define how many muxes are maximal consecutively connected
2234		on one i2c bus. If you not use i2c muxes, omit this
2235		define.
2236
2237		CONFIG_SYS_I2C_BUSES
2238		hold a list of busses you want to use, only used if
2239		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2240		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2241		CONFIG_SYS_NUM_I2C_BUSES = 9:
2242
2243		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2244					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2245					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2246					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2247					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2248					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2249					{1, {I2C_NULL_HOP}}, \
2250					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2251					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2252					}
2253
2254		which defines
2255			bus 0 on adapter 0 without a mux
2256			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2257			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2258			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2259			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2260			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2261			bus 6 on adapter 1 without a mux
2262			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2263			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2264
2265		If you do not have i2c muxes on your board, omit this define.
2266
2267- Legacy I2C Support:	CONFIG_HARD_I2C
2268
2269		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2270		provides the following compelling advantages:
2271
2272		- more than one i2c adapter is usable
2273		- approved multibus support
2274		- better i2c mux support
2275
2276		** Please consider updating your I2C driver now. **
2277
2278		These enable legacy I2C serial bus commands. Defining
2279		CONFIG_HARD_I2C will include the appropriate I2C driver
2280		for the selected CPU.
2281
2282		This will allow you to use i2c commands at the u-boot
2283		command line (as long as you set CONFIG_CMD_I2C in
2284		CONFIG_COMMANDS) and communicate with i2c based realtime
2285		clock chips. See common/cmd_i2c.c for a description of the
2286		command line interface.
2287
2288		CONFIG_HARD_I2C selects a hardware I2C controller.
2289
2290		There are several other quantities that must also be
2291		defined when you define CONFIG_HARD_I2C.
2292
2293		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2294		to be the frequency (in Hz) at which you wish your i2c bus
2295		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2296		the CPU's i2c node address).
2297
2298		Now, the u-boot i2c code for the mpc8xx
2299		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2300		and so its address should therefore be cleared to 0 (See,
2301		eg, MPC823e User's Manual p.16-473). So, set
2302		CONFIG_SYS_I2C_SLAVE to 0.
2303
2304		CONFIG_SYS_I2C_INIT_MPC5XXX
2305
2306		When a board is reset during an i2c bus transfer
2307		chips might think that the current transfer is still
2308		in progress.  Reset the slave devices by sending start
2309		commands until the slave device responds.
2310
2311		That's all that's required for CONFIG_HARD_I2C.
2312
2313		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2314		then the following macros need to be defined (examples are
2315		from include/configs/lwmon.h):
2316
2317		I2C_INIT
2318
2319		(Optional). Any commands necessary to enable the I2C
2320		controller or configure ports.
2321
2322		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2323
2324		I2C_PORT
2325
2326		(Only for MPC8260 CPU). The I/O port to use (the code
2327		assumes both bits are on the same port). Valid values
2328		are 0..3 for ports A..D.
2329
2330		I2C_ACTIVE
2331
2332		The code necessary to make the I2C data line active
2333		(driven).  If the data line is open collector, this
2334		define can be null.
2335
2336		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2337
2338		I2C_TRISTATE
2339
2340		The code necessary to make the I2C data line tri-stated
2341		(inactive).  If the data line is open collector, this
2342		define can be null.
2343
2344		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2345
2346		I2C_READ
2347
2348		Code that returns true if the I2C data line is high,
2349		false if it is low.
2350
2351		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2352
2353		I2C_SDA(bit)
2354
2355		If <bit> is true, sets the I2C data line high. If it
2356		is false, it clears it (low).
2357
2358		eg: #define I2C_SDA(bit) \
2359			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2360			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2361
2362		I2C_SCL(bit)
2363
2364		If <bit> is true, sets the I2C clock line high. If it
2365		is false, it clears it (low).
2366
2367		eg: #define I2C_SCL(bit) \
2368			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2369			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2370
2371		I2C_DELAY
2372
2373		This delay is invoked four times per clock cycle so this
2374		controls the rate of data transfer.  The data rate thus
2375		is 1 / (I2C_DELAY * 4). Often defined to be something
2376		like:
2377
2378		#define I2C_DELAY  udelay(2)
2379
2380		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2381
2382		If your arch supports the generic GPIO framework (asm/gpio.h),
2383		then you may alternatively define the two GPIOs that are to be
2384		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2385		have GPIO-based defaults assigned to them as appropriate.
2386
2387		You should define these to the GPIO value as given directly to
2388		the generic GPIO functions.
2389
2390		CONFIG_SYS_I2C_INIT_BOARD
2391
2392		When a board is reset during an i2c bus transfer
2393		chips might think that the current transfer is still
2394		in progress. On some boards it is possible to access
2395		the i2c SCLK line directly, either by using the
2396		processor pin as a GPIO or by having a second pin
2397		connected to the bus. If this option is defined a
2398		custom i2c_init_board() routine in boards/xxx/board.c
2399		is run early in the boot sequence.
2400
2401		CONFIG_SYS_I2C_BOARD_LATE_INIT
2402
2403		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2404		defined a custom i2c_board_late_init() routine in
2405		boards/xxx/board.c is run AFTER the operations in i2c_init()
2406		is completed. This callpoint can be used to unreset i2c bus
2407		using CPU i2c controller register accesses for CPUs whose i2c
2408		controller provide such a method. It is called at the end of
2409		i2c_init() to allow i2c_init operations to setup the i2c bus
2410		controller on the CPU (e.g. setting bus speed & slave address).
2411
2412		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2413
2414		This option enables configuration of bi_iic_fast[] flags
2415		in u-boot bd_info structure based on u-boot environment
2416		variable "i2cfast". (see also i2cfast)
2417
2418		CONFIG_I2C_MULTI_BUS
2419
2420		This option allows the use of multiple I2C buses, each of which
2421		must have a controller.	 At any point in time, only one bus is
2422		active.	 To switch to a different bus, use the 'i2c dev' command.
2423		Note that bus numbering is zero-based.
2424
2425		CONFIG_SYS_I2C_NOPROBES
2426
2427		This option specifies a list of I2C devices that will be skipped
2428		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2429		is set, specify a list of bus-device pairs.  Otherwise, specify
2430		a 1D array of device addresses
2431
2432		e.g.
2433			#undef	CONFIG_I2C_MULTI_BUS
2434			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2435
2436		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2437
2438			#define CONFIG_I2C_MULTI_BUS
2439			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2440
2441		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2442
2443		CONFIG_SYS_SPD_BUS_NUM
2444
2445		If defined, then this indicates the I2C bus number for DDR SPD.
2446		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2447
2448		CONFIG_SYS_RTC_BUS_NUM
2449
2450		If defined, then this indicates the I2C bus number for the RTC.
2451		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2452
2453		CONFIG_SYS_DTT_BUS_NUM
2454
2455		If defined, then this indicates the I2C bus number for the DTT.
2456		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2457
2458		CONFIG_SYS_I2C_DTT_ADDR:
2459
2460		If defined, specifies the I2C address of the DTT device.
2461		If not defined, then U-Boot uses predefined value for
2462		specified DTT device.
2463
2464		CONFIG_SOFT_I2C_READ_REPEATED_START
2465
2466		defining this will force the i2c_read() function in
2467		the soft_i2c driver to perform an I2C repeated start
2468		between writing the address pointer and reading the
2469		data.  If this define is omitted the default behaviour
2470		of doing a stop-start sequence will be used.  Most I2C
2471		devices can use either method, but some require one or
2472		the other.
2473
2474- SPI Support:	CONFIG_SPI
2475
2476		Enables SPI driver (so far only tested with
2477		SPI EEPROM, also an instance works with Crystal A/D and
2478		D/As on the SACSng board)
2479
2480		CONFIG_SH_SPI
2481
2482		Enables the driver for SPI controller on SuperH. Currently
2483		only SH7757 is supported.
2484
2485		CONFIG_SPI_X
2486
2487		Enables extended (16-bit) SPI EEPROM addressing.
2488		(symmetrical to CONFIG_I2C_X)
2489
2490		CONFIG_SOFT_SPI
2491
2492		Enables a software (bit-bang) SPI driver rather than
2493		using hardware support. This is a general purpose
2494		driver that only requires three general I/O port pins
2495		(two outputs, one input) to function. If this is
2496		defined, the board configuration must define several
2497		SPI configuration items (port pins to use, etc). For
2498		an example, see include/configs/sacsng.h.
2499
2500		CONFIG_HARD_SPI
2501
2502		Enables a hardware SPI driver for general-purpose reads
2503		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2504		must define a list of chip-select function pointers.
2505		Currently supported on some MPC8xxx processors.	 For an
2506		example, see include/configs/mpc8349emds.h.
2507
2508		CONFIG_MXC_SPI
2509
2510		Enables the driver for the SPI controllers on i.MX and MXC
2511		SoCs. Currently i.MX31/35/51 are supported.
2512
2513- FPGA Support: CONFIG_FPGA
2514
2515		Enables FPGA subsystem.
2516
2517		CONFIG_FPGA_<vendor>
2518
2519		Enables support for specific chip vendors.
2520		(ALTERA, XILINX)
2521
2522		CONFIG_FPGA_<family>
2523
2524		Enables support for FPGA family.
2525		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2526
2527		CONFIG_FPGA_COUNT
2528
2529		Specify the number of FPGA devices to support.
2530
2531		CONFIG_SYS_FPGA_PROG_FEEDBACK
2532
2533		Enable printing of hash marks during FPGA configuration.
2534
2535		CONFIG_SYS_FPGA_CHECK_BUSY
2536
2537		Enable checks on FPGA configuration interface busy
2538		status by the configuration function. This option
2539		will require a board or device specific function to
2540		be written.
2541
2542		CONFIG_FPGA_DELAY
2543
2544		If defined, a function that provides delays in the FPGA
2545		configuration driver.
2546
2547		CONFIG_SYS_FPGA_CHECK_CTRLC
2548		Allow Control-C to interrupt FPGA configuration
2549
2550		CONFIG_SYS_FPGA_CHECK_ERROR
2551
2552		Check for configuration errors during FPGA bitfile
2553		loading. For example, abort during Virtex II
2554		configuration if the INIT_B line goes low (which
2555		indicated a CRC error).
2556
2557		CONFIG_SYS_FPGA_WAIT_INIT
2558
2559		Maximum time to wait for the INIT_B line to deassert
2560		after PROB_B has been deasserted during a Virtex II
2561		FPGA configuration sequence. The default time is 500
2562		ms.
2563
2564		CONFIG_SYS_FPGA_WAIT_BUSY
2565
2566		Maximum time to wait for BUSY to deassert during
2567		Virtex II FPGA configuration. The default is 5 ms.
2568
2569		CONFIG_SYS_FPGA_WAIT_CONFIG
2570
2571		Time to wait after FPGA configuration. The default is
2572		200 ms.
2573
2574- Configuration Management:
2575		CONFIG_IDENT_STRING
2576
2577		If defined, this string will be added to the U-Boot
2578		version information (U_BOOT_VERSION)
2579
2580- Vendor Parameter Protection:
2581
2582		U-Boot considers the values of the environment
2583		variables "serial#" (Board Serial Number) and
2584		"ethaddr" (Ethernet Address) to be parameters that
2585		are set once by the board vendor / manufacturer, and
2586		protects these variables from casual modification by
2587		the user. Once set, these variables are read-only,
2588		and write or delete attempts are rejected. You can
2589		change this behaviour:
2590
2591		If CONFIG_ENV_OVERWRITE is #defined in your config
2592		file, the write protection for vendor parameters is
2593		completely disabled. Anybody can change or delete
2594		these parameters.
2595
2596		Alternatively, if you #define _both_ CONFIG_ETHADDR
2597		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2598		Ethernet address is installed in the environment,
2599		which can be changed exactly ONCE by the user. [The
2600		serial# is unaffected by this, i. e. it remains
2601		read-only.]
2602
2603		The same can be accomplished in a more flexible way
2604		for any variable by configuring the type of access
2605		to allow for those variables in the ".flags" variable
2606		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2607
2608- Protected RAM:
2609		CONFIG_PRAM
2610
2611		Define this variable to enable the reservation of
2612		"protected RAM", i. e. RAM which is not overwritten
2613		by U-Boot. Define CONFIG_PRAM to hold the number of
2614		kB you want to reserve for pRAM. You can overwrite
2615		this default value by defining an environment
2616		variable "pram" to the number of kB you want to
2617		reserve. Note that the board info structure will
2618		still show the full amount of RAM. If pRAM is
2619		reserved, a new environment variable "mem" will
2620		automatically be defined to hold the amount of
2621		remaining RAM in a form that can be passed as boot
2622		argument to Linux, for instance like that:
2623
2624			setenv bootargs ... mem=\${mem}
2625			saveenv
2626
2627		This way you can tell Linux not to use this memory,
2628		either, which results in a memory region that will
2629		not be affected by reboots.
2630
2631		*WARNING* If your board configuration uses automatic
2632		detection of the RAM size, you must make sure that
2633		this memory test is non-destructive. So far, the
2634		following board configurations are known to be
2635		"pRAM-clean":
2636
2637			IVMS8, IVML24, SPD8xx, TQM8xxL,
2638			HERMES, IP860, RPXlite, LWMON,
2639			FLAGADM, TQM8260
2640
2641- Access to physical memory region (> 4GB)
2642		Some basic support is provided for operations on memory not
2643		normally accessible to U-Boot - e.g. some architectures
2644		support access to more than 4GB of memory on 32-bit
2645		machines using physical address extension or similar.
2646		Define CONFIG_PHYSMEM to access this basic support, which
2647		currently only supports clearing the memory.
2648
2649- Error Recovery:
2650		CONFIG_PANIC_HANG
2651
2652		Define this variable to stop the system in case of a
2653		fatal error, so that you have to reset it manually.
2654		This is probably NOT a good idea for an embedded
2655		system where you want the system to reboot
2656		automatically as fast as possible, but it may be
2657		useful during development since you can try to debug
2658		the conditions that lead to the situation.
2659
2660		CONFIG_NET_RETRY_COUNT
2661
2662		This variable defines the number of retries for
2663		network operations like ARP, RARP, TFTP, or BOOTP
2664		before giving up the operation. If not defined, a
2665		default value of 5 is used.
2666
2667		CONFIG_ARP_TIMEOUT
2668
2669		Timeout waiting for an ARP reply in milliseconds.
2670
2671		CONFIG_NFS_TIMEOUT
2672
2673		Timeout in milliseconds used in NFS protocol.
2674		If you encounter "ERROR: Cannot umount" in nfs command,
2675		try longer timeout such as
2676		#define CONFIG_NFS_TIMEOUT 10000UL
2677
2678- Command Interpreter:
2679		CONFIG_AUTO_COMPLETE
2680
2681		Enable auto completion of commands using TAB.
2682
2683		Note that this feature has NOT been implemented yet
2684		for the "hush" shell.
2685
2686
2687		CONFIG_SYS_HUSH_PARSER
2688
2689		Define this variable to enable the "hush" shell (from
2690		Busybox) as command line interpreter, thus enabling
2691		powerful command line syntax like
2692		if...then...else...fi conditionals or `&&' and '||'
2693		constructs ("shell scripts").
2694
2695		If undefined, you get the old, much simpler behaviour
2696		with a somewhat smaller memory footprint.
2697
2698
2699		CONFIG_SYS_PROMPT_HUSH_PS2
2700
2701		This defines the secondary prompt string, which is
2702		printed when the command interpreter needs more input
2703		to complete a command. Usually "> ".
2704
2705	Note:
2706
2707		In the current implementation, the local variables
2708		space and global environment variables space are
2709		separated. Local variables are those you define by
2710		simply typing `name=value'. To access a local
2711		variable later on, you have write `$name' or
2712		`${name}'; to execute the contents of a variable
2713		directly type `$name' at the command prompt.
2714
2715		Global environment variables are those you use
2716		setenv/printenv to work with. To run a command stored
2717		in such a variable, you need to use the run command,
2718		and you must not use the '$' sign to access them.
2719
2720		To store commands and special characters in a
2721		variable, please use double quotation marks
2722		surrounding the whole text of the variable, instead
2723		of the backslashes before semicolons and special
2724		symbols.
2725
2726- Commandline Editing and History:
2727		CONFIG_CMDLINE_EDITING
2728
2729		Enable editing and History functions for interactive
2730		commandline input operations
2731
2732- Default Environment:
2733		CONFIG_EXTRA_ENV_SETTINGS
2734
2735		Define this to contain any number of null terminated
2736		strings (variable = value pairs) that will be part of
2737		the default environment compiled into the boot image.
2738
2739		For example, place something like this in your
2740		board's config file:
2741
2742		#define CONFIG_EXTRA_ENV_SETTINGS \
2743			"myvar1=value1\0" \
2744			"myvar2=value2\0"
2745
2746		Warning: This method is based on knowledge about the
2747		internal format how the environment is stored by the
2748		U-Boot code. This is NOT an official, exported
2749		interface! Although it is unlikely that this format
2750		will change soon, there is no guarantee either.
2751		You better know what you are doing here.
2752
2753		Note: overly (ab)use of the default environment is
2754		discouraged. Make sure to check other ways to preset
2755		the environment like the "source" command or the
2756		boot command first.
2757
2758		CONFIG_ENV_VARS_UBOOT_CONFIG
2759
2760		Define this in order to add variables describing the
2761		U-Boot build configuration to the default environment.
2762		These will be named arch, cpu, board, vendor, and soc.
2763
2764		Enabling this option will cause the following to be defined:
2765
2766		- CONFIG_SYS_ARCH
2767		- CONFIG_SYS_CPU
2768		- CONFIG_SYS_BOARD
2769		- CONFIG_SYS_VENDOR
2770		- CONFIG_SYS_SOC
2771
2772		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2773
2774		Define this in order to add variables describing certain
2775		run-time determined information about the hardware to the
2776		environment.  These will be named board_name, board_rev.
2777
2778		CONFIG_DELAY_ENVIRONMENT
2779
2780		Normally the environment is loaded when the board is
2781		intialised so that it is available to U-Boot. This inhibits
2782		that so that the environment is not available until
2783		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2784		this is instead controlled by the value of
2785		/config/load-environment.
2786
2787- DataFlash Support:
2788		CONFIG_HAS_DATAFLASH
2789
2790		Defining this option enables DataFlash features and
2791		allows to read/write in Dataflash via the standard
2792		commands cp, md...
2793
2794- Serial Flash support
2795		CONFIG_CMD_SF
2796
2797		Defining this option enables SPI flash commands
2798		'sf probe/read/write/erase/update'.
2799
2800		Usage requires an initial 'probe' to define the serial
2801		flash parameters, followed by read/write/erase/update
2802		commands.
2803
2804		The following defaults may be provided by the platform
2805		to handle the common case when only a single serial
2806		flash is present on the system.
2807
2808		CONFIG_SF_DEFAULT_BUS		Bus identifier
2809		CONFIG_SF_DEFAULT_CS		Chip-select
2810		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2811		CONFIG_SF_DEFAULT_SPEED		in Hz
2812
2813		CONFIG_CMD_SF_TEST
2814
2815		Define this option to include a destructive SPI flash
2816		test ('sf test').
2817
2818		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2819
2820		Define this option to use the Bank addr/Extended addr
2821		support on SPI flashes which has size > 16Mbytes.
2822
2823		CONFIG_SF_DUAL_FLASH		Dual flash memories
2824
2825		Define this option to use dual flash support where two flash
2826		memories can be connected with a given cs line.
2827		currently Xilinx Zynq qspi support these type of connections.
2828
2829- SystemACE Support:
2830		CONFIG_SYSTEMACE
2831
2832		Adding this option adds support for Xilinx SystemACE
2833		chips attached via some sort of local bus. The address
2834		of the chip must also be defined in the
2835		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2836
2837		#define CONFIG_SYSTEMACE
2838		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2839
2840		When SystemACE support is added, the "ace" device type
2841		becomes available to the fat commands, i.e. fatls.
2842
2843- TFTP Fixed UDP Port:
2844		CONFIG_TFTP_PORT
2845
2846		If this is defined, the environment variable tftpsrcp
2847		is used to supply the TFTP UDP source port value.
2848		If tftpsrcp isn't defined, the normal pseudo-random port
2849		number generator is used.
2850
2851		Also, the environment variable tftpdstp is used to supply
2852		the TFTP UDP destination port value.  If tftpdstp isn't
2853		defined, the normal port 69 is used.
2854
2855		The purpose for tftpsrcp is to allow a TFTP server to
2856		blindly start the TFTP transfer using the pre-configured
2857		target IP address and UDP port. This has the effect of
2858		"punching through" the (Windows XP) firewall, allowing
2859		the remainder of the TFTP transfer to proceed normally.
2860		A better solution is to properly configure the firewall,
2861		but sometimes that is not allowed.
2862
2863- Hashing support:
2864		CONFIG_CMD_HASH
2865
2866		This enables a generic 'hash' command which can produce
2867		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2868
2869		CONFIG_HASH_VERIFY
2870
2871		Enable the hash verify command (hash -v). This adds to code
2872		size a little.
2873
2874		CONFIG_SHA1 - support SHA1 hashing
2875		CONFIG_SHA256 - support SHA256 hashing
2876
2877		Note: There is also a sha1sum command, which should perhaps
2878		be deprecated in favour of 'hash sha1'.
2879
2880- Freescale i.MX specific commands:
2881		CONFIG_CMD_HDMIDETECT
2882		This enables 'hdmidet' command which returns true if an
2883		HDMI monitor is detected.  This command is i.MX 6 specific.
2884
2885		CONFIG_CMD_BMODE
2886		This enables the 'bmode' (bootmode) command for forcing
2887		a boot from specific media.
2888
2889		This is useful for forcing the ROM's usb downloader to
2890		activate upon a watchdog reset which is nice when iterating
2891		on U-Boot.  Using the reset button or running bmode normal
2892		will set it back to normal.  This command currently
2893		supports i.MX53 and i.MX6.
2894
2895- Signing support:
2896		CONFIG_RSA
2897
2898		This enables the RSA algorithm used for FIT image verification
2899		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2900
2901		The signing part is build into mkimage regardless of this
2902		option.
2903
2904- bootcount support:
2905		CONFIG_BOOTCOUNT_LIMIT
2906
2907		This enables the bootcounter support, see:
2908		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2909
2910		CONFIG_AT91SAM9XE
2911		enable special bootcounter support on at91sam9xe based boards.
2912		CONFIG_BLACKFIN
2913		enable special bootcounter support on blackfin based boards.
2914		CONFIG_SOC_DA8XX
2915		enable special bootcounter support on da850 based boards.
2916		CONFIG_BOOTCOUNT_RAM
2917		enable support for the bootcounter in RAM
2918		CONFIG_BOOTCOUNT_I2C
2919		enable support for the bootcounter on an i2c (like RTC) device.
2920			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2921			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2922						    the bootcounter.
2923			CONFIG_BOOTCOUNT_ALEN = address len
2924
2925- Show boot progress:
2926		CONFIG_SHOW_BOOT_PROGRESS
2927
2928		Defining this option allows to add some board-
2929		specific code (calling a user-provided function
2930		"show_boot_progress(int)") that enables you to show
2931		the system's boot progress on some display (for
2932		example, some LED's) on your board. At the moment,
2933		the following checkpoints are implemented:
2934
2935- Detailed boot stage timing
2936		CONFIG_BOOTSTAGE
2937		Define this option to get detailed timing of each stage
2938		of the boot process.
2939
2940		CONFIG_BOOTSTAGE_USER_COUNT
2941		This is the number of available user bootstage records.
2942		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2943		a new ID will be allocated from this stash. If you exceed
2944		the limit, recording will stop.
2945
2946		CONFIG_BOOTSTAGE_REPORT
2947		Define this to print a report before boot, similar to this:
2948
2949		Timer summary in microseconds:
2950		       Mark    Elapsed  Stage
2951			  0          0  reset
2952		  3,575,678  3,575,678  board_init_f start
2953		  3,575,695         17  arch_cpu_init A9
2954		  3,575,777         82  arch_cpu_init done
2955		  3,659,598     83,821  board_init_r start
2956		  3,910,375    250,777  main_loop
2957		 29,916,167 26,005,792  bootm_start
2958		 30,361,327    445,160  start_kernel
2959
2960		CONFIG_CMD_BOOTSTAGE
2961		Add a 'bootstage' command which supports printing a report
2962		and un/stashing of bootstage data.
2963
2964		CONFIG_BOOTSTAGE_FDT
2965		Stash the bootstage information in the FDT. A root 'bootstage'
2966		node is created with each bootstage id as a child. Each child
2967		has a 'name' property and either 'mark' containing the
2968		mark time in microsecond, or 'accum' containing the
2969		accumulated time for that bootstage id in microseconds.
2970		For example:
2971
2972		bootstage {
2973			154 {
2974				name = "board_init_f";
2975				mark = <3575678>;
2976			};
2977			170 {
2978				name = "lcd";
2979				accum = <33482>;
2980			};
2981		};
2982
2983		Code in the Linux kernel can find this in /proc/devicetree.
2984
2985Legacy uImage format:
2986
2987  Arg	Where			When
2988    1	common/cmd_bootm.c	before attempting to boot an image
2989   -1	common/cmd_bootm.c	Image header has bad	 magic number
2990    2	common/cmd_bootm.c	Image header has correct magic number
2991   -2	common/cmd_bootm.c	Image header has bad	 checksum
2992    3	common/cmd_bootm.c	Image header has correct checksum
2993   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2994    4	common/cmd_bootm.c	Image data   has correct checksum
2995   -4	common/cmd_bootm.c	Image is for unsupported architecture
2996    5	common/cmd_bootm.c	Architecture check OK
2997   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2998    6	common/cmd_bootm.c	Image Type check OK
2999   -6	common/cmd_bootm.c	gunzip uncompression error
3000   -7	common/cmd_bootm.c	Unimplemented compression type
3001    7	common/cmd_bootm.c	Uncompression OK
3002    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3003   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3004
3005    9	common/image.c		Start initial ramdisk verification
3006  -10	common/image.c		Ramdisk header has bad	   magic number
3007  -11	common/image.c		Ramdisk header has bad	   checksum
3008   10	common/image.c		Ramdisk header is OK
3009  -12	common/image.c		Ramdisk data   has bad	   checksum
3010   11	common/image.c		Ramdisk data   has correct checksum
3011   12	common/image.c		Ramdisk verification complete, start loading
3012  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3013   13	common/image.c		Start multifile image verification
3014   14	common/image.c		No initial ramdisk, no multifile, continue.
3015
3016   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3017
3018  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3019  -31	post/post.c		POST test failed, detected by post_output_backlog()
3020  -32	post/post.c		POST test failed, detected by post_run_single()
3021
3022   34	common/cmd_doc.c	before loading a Image from a DOC device
3023  -35	common/cmd_doc.c	Bad usage of "doc" command
3024   35	common/cmd_doc.c	correct usage of "doc" command
3025  -36	common/cmd_doc.c	No boot device
3026   36	common/cmd_doc.c	correct boot device
3027  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3028   37	common/cmd_doc.c	correct chip ID found, device available
3029  -38	common/cmd_doc.c	Read Error on boot device
3030   38	common/cmd_doc.c	reading Image header from DOC device OK
3031  -39	common/cmd_doc.c	Image header has bad magic number
3032   39	common/cmd_doc.c	Image header has correct magic number
3033  -40	common/cmd_doc.c	Error reading Image from DOC device
3034   40	common/cmd_doc.c	Image header has correct magic number
3035   41	common/cmd_ide.c	before loading a Image from a IDE device
3036  -42	common/cmd_ide.c	Bad usage of "ide" command
3037   42	common/cmd_ide.c	correct usage of "ide" command
3038  -43	common/cmd_ide.c	No boot device
3039   43	common/cmd_ide.c	boot device found
3040  -44	common/cmd_ide.c	Device not available
3041   44	common/cmd_ide.c	Device available
3042  -45	common/cmd_ide.c	wrong partition selected
3043   45	common/cmd_ide.c	partition selected
3044  -46	common/cmd_ide.c	Unknown partition table
3045   46	common/cmd_ide.c	valid partition table found
3046  -47	common/cmd_ide.c	Invalid partition type
3047   47	common/cmd_ide.c	correct partition type
3048  -48	common/cmd_ide.c	Error reading Image Header on boot device
3049   48	common/cmd_ide.c	reading Image Header from IDE device OK
3050  -49	common/cmd_ide.c	Image header has bad magic number
3051   49	common/cmd_ide.c	Image header has correct magic number
3052  -50	common/cmd_ide.c	Image header has bad	 checksum
3053   50	common/cmd_ide.c	Image header has correct checksum
3054  -51	common/cmd_ide.c	Error reading Image from IDE device
3055   51	common/cmd_ide.c	reading Image from IDE device OK
3056   52	common/cmd_nand.c	before loading a Image from a NAND device
3057  -53	common/cmd_nand.c	Bad usage of "nand" command
3058   53	common/cmd_nand.c	correct usage of "nand" command
3059  -54	common/cmd_nand.c	No boot device
3060   54	common/cmd_nand.c	boot device found
3061  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3062   55	common/cmd_nand.c	correct chip ID found, device available
3063  -56	common/cmd_nand.c	Error reading Image Header on boot device
3064   56	common/cmd_nand.c	reading Image Header from NAND device OK
3065  -57	common/cmd_nand.c	Image header has bad magic number
3066   57	common/cmd_nand.c	Image header has correct magic number
3067  -58	common/cmd_nand.c	Error reading Image from NAND device
3068   58	common/cmd_nand.c	reading Image from NAND device OK
3069
3070  -60	common/env_common.c	Environment has a bad CRC, using default
3071
3072   64	net/eth.c		starting with Ethernet configuration.
3073  -64	net/eth.c		no Ethernet found.
3074   65	net/eth.c		Ethernet found.
3075
3076  -80	common/cmd_net.c	usage wrong
3077   80	common/cmd_net.c	before calling NetLoop()
3078  -81	common/cmd_net.c	some error in NetLoop() occurred
3079   81	common/cmd_net.c	NetLoop() back without error
3080  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3081   82	common/cmd_net.c	trying automatic boot
3082   83	common/cmd_net.c	running "source" command
3083  -83	common/cmd_net.c	some error in automatic boot or "source" command
3084   84	common/cmd_net.c	end without errors
3085
3086FIT uImage format:
3087
3088  Arg	Where			When
3089  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3090 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3091  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3092 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3093  102	common/cmd_bootm.c	Kernel unit name specified
3094 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3095  103	common/cmd_bootm.c	Found configuration node
3096  104	common/cmd_bootm.c	Got kernel subimage node offset
3097 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3098  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3099 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3100  106	common/cmd_bootm.c	Architecture check OK
3101 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3102  107	common/cmd_bootm.c	Kernel subimage type OK
3103 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3104  108	common/cmd_bootm.c	Got kernel subimage data/size
3105 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3106 -109	common/cmd_bootm.c	Can't get kernel subimage type
3107 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3108 -111	common/cmd_bootm.c	Can't get kernel subimage os
3109 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3110 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3111
3112  120	common/image.c		Start initial ramdisk verification
3113 -120	common/image.c		Ramdisk FIT image has incorrect format
3114  121	common/image.c		Ramdisk FIT image has correct format
3115  122	common/image.c		No ramdisk subimage unit name, using configuration
3116 -122	common/image.c		Can't get configuration for ramdisk subimage
3117  123	common/image.c		Ramdisk unit name specified
3118 -124	common/image.c		Can't get ramdisk subimage node offset
3119  125	common/image.c		Got ramdisk subimage node offset
3120 -125	common/image.c		Ramdisk subimage hash verification failed
3121  126	common/image.c		Ramdisk subimage hash verification OK
3122 -126	common/image.c		Ramdisk subimage for unsupported architecture
3123  127	common/image.c		Architecture check OK
3124 -127	common/image.c		Can't get ramdisk subimage data/size
3125  128	common/image.c		Got ramdisk subimage data/size
3126  129	common/image.c		Can't get ramdisk load address
3127 -129	common/image.c		Got ramdisk load address
3128
3129 -130	common/cmd_doc.c	Incorrect FIT image format
3130  131	common/cmd_doc.c	FIT image format OK
3131
3132 -140	common/cmd_ide.c	Incorrect FIT image format
3133  141	common/cmd_ide.c	FIT image format OK
3134
3135 -150	common/cmd_nand.c	Incorrect FIT image format
3136  151	common/cmd_nand.c	FIT image format OK
3137
3138- FIT image support:
3139		CONFIG_FIT
3140		Enable support for the FIT uImage format.
3141
3142		CONFIG_FIT_BEST_MATCH
3143		When no configuration is explicitly selected, default to the
3144		one whose fdt's compatibility field best matches that of
3145		U-Boot itself. A match is considered "best" if it matches the
3146		most specific compatibility entry of U-Boot's fdt's root node.
3147		The order of entries in the configuration's fdt is ignored.
3148
3149		CONFIG_FIT_SIGNATURE
3150		This option enables signature verification of FIT uImages,
3151		using a hash signed and verified using RSA. See
3152		doc/uImage.FIT/signature.txt for more details.
3153
3154- Standalone program support:
3155		CONFIG_STANDALONE_LOAD_ADDR
3156
3157		This option defines a board specific value for the
3158		address where standalone program gets loaded, thus
3159		overwriting the architecture dependent default
3160		settings.
3161
3162- Frame Buffer Address:
3163		CONFIG_FB_ADDR
3164
3165		Define CONFIG_FB_ADDR if you want to use specific
3166		address for frame buffer.  This is typically the case
3167		when using a graphics controller has separate video
3168		memory.  U-Boot will then place the frame buffer at
3169		the given address instead of dynamically reserving it
3170		in system RAM by calling lcd_setmem(), which grabs
3171		the memory for the frame buffer depending on the
3172		configured panel size.
3173
3174		Please see board_init_f function.
3175
3176- Automatic software updates via TFTP server
3177		CONFIG_UPDATE_TFTP
3178		CONFIG_UPDATE_TFTP_CNT_MAX
3179		CONFIG_UPDATE_TFTP_MSEC_MAX
3180
3181		These options enable and control the auto-update feature;
3182		for a more detailed description refer to doc/README.update.
3183
3184- MTD Support (mtdparts command, UBI support)
3185		CONFIG_MTD_DEVICE
3186
3187		Adds the MTD device infrastructure from the Linux kernel.
3188		Needed for mtdparts command support.
3189
3190		CONFIG_MTD_PARTITIONS
3191
3192		Adds the MTD partitioning infrastructure from the Linux
3193		kernel. Needed for UBI support.
3194
3195- UBI support
3196		CONFIG_CMD_UBI
3197
3198		Adds commands for interacting with MTD partitions formatted
3199		with the UBI flash translation layer
3200
3201		Requires also defining CONFIG_RBTREE
3202
3203		CONFIG_UBI_SILENCE_MSG
3204
3205		Make the verbose messages from UBI stop printing.  This leaves
3206		warnings and errors enabled.
3207
3208- UBIFS support
3209		CONFIG_CMD_UBIFS
3210
3211		Adds commands for interacting with UBI volumes formatted as
3212		UBIFS.  UBIFS is read-only in u-boot.
3213
3214		Requires UBI support as well as CONFIG_LZO
3215
3216		CONFIG_UBIFS_SILENCE_MSG
3217
3218		Make the verbose messages from UBIFS stop printing.  This leaves
3219		warnings and errors enabled.
3220
3221- SPL framework
3222		CONFIG_SPL
3223		Enable building of SPL globally.
3224
3225		CONFIG_SPL_LDSCRIPT
3226		LDSCRIPT for linking the SPL binary.
3227
3228		CONFIG_SPL_MAX_FOOTPRINT
3229		Maximum size in memory allocated to the SPL, BSS included.
3230		When defined, the linker checks that the actual memory
3231		used by SPL from _start to __bss_end does not exceed it.
3232		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3233		must not be both defined at the same time.
3234
3235		CONFIG_SPL_MAX_SIZE
3236		Maximum size of the SPL image (text, data, rodata, and
3237		linker lists sections), BSS excluded.
3238		When defined, the linker checks that the actual size does
3239		not exceed it.
3240
3241		CONFIG_SPL_TEXT_BASE
3242		TEXT_BASE for linking the SPL binary.
3243
3244		CONFIG_SPL_RELOC_TEXT_BASE
3245		Address to relocate to.  If unspecified, this is equal to
3246		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3247
3248		CONFIG_SPL_BSS_START_ADDR
3249		Link address for the BSS within the SPL binary.
3250
3251		CONFIG_SPL_BSS_MAX_SIZE
3252		Maximum size in memory allocated to the SPL BSS.
3253		When defined, the linker checks that the actual memory used
3254		by SPL from __bss_start to __bss_end does not exceed it.
3255		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3256		must not be both defined at the same time.
3257
3258		CONFIG_SPL_STACK
3259		Adress of the start of the stack SPL will use
3260
3261		CONFIG_SPL_RELOC_STACK
3262		Adress of the start of the stack SPL will use after
3263		relocation.  If unspecified, this is equal to
3264		CONFIG_SPL_STACK.
3265
3266		CONFIG_SYS_SPL_MALLOC_START
3267		Starting address of the malloc pool used in SPL.
3268
3269		CONFIG_SYS_SPL_MALLOC_SIZE
3270		The size of the malloc pool used in SPL.
3271
3272		CONFIG_SPL_FRAMEWORK
3273		Enable the SPL framework under common/.  This framework
3274		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3275		NAND loading of the Linux Kernel.
3276
3277		CONFIG_SPL_DISPLAY_PRINT
3278		For ARM, enable an optional function to print more information
3279		about the running system.
3280
3281		CONFIG_SPL_INIT_MINIMAL
3282		Arch init code should be built for a very small image
3283
3284		CONFIG_SPL_LIBCOMMON_SUPPORT
3285		Support for common/libcommon.o in SPL binary
3286
3287		CONFIG_SPL_LIBDISK_SUPPORT
3288		Support for disk/libdisk.o in SPL binary
3289
3290		CONFIG_SPL_I2C_SUPPORT
3291		Support for drivers/i2c/libi2c.o in SPL binary
3292
3293		CONFIG_SPL_GPIO_SUPPORT
3294		Support for drivers/gpio/libgpio.o in SPL binary
3295
3296		CONFIG_SPL_MMC_SUPPORT
3297		Support for drivers/mmc/libmmc.o in SPL binary
3298
3299		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3300		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3301		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3302		Address, size and partition on the MMC to load U-Boot from
3303		when the MMC is being used in raw mode.
3304
3305		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3306		Sector to load kernel uImage from when MMC is being
3307		used in raw mode (for Falcon mode)
3308
3309		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3310		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3311		Sector and number of sectors to load kernel argument
3312		parameters from when MMC is being used in raw mode
3313		(for falcon mode)
3314
3315		CONFIG_SPL_FAT_SUPPORT
3316		Support for fs/fat/libfat.o in SPL binary
3317
3318		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3319		Filename to read to load U-Boot when reading from FAT
3320
3321		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3322		Filename to read to load kernel uImage when reading
3323		from FAT (for Falcon mode)
3324
3325		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3326		Filename to read to load kernel argument parameters
3327		when reading from FAT (for Falcon mode)
3328
3329		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3330		Set this for NAND SPL on PPC mpc83xx targets, so that
3331		start.S waits for the rest of the SPL to load before
3332		continuing (the hardware starts execution after just
3333		loading the first page rather than the full 4K).
3334
3335		CONFIG_SPL_NAND_BASE
3336		Include nand_base.c in the SPL.  Requires
3337		CONFIG_SPL_NAND_DRIVERS.
3338
3339		CONFIG_SPL_NAND_DRIVERS
3340		SPL uses normal NAND drivers, not minimal drivers.
3341
3342		CONFIG_SPL_NAND_ECC
3343		Include standard software ECC in the SPL
3344
3345		CONFIG_SPL_NAND_SIMPLE
3346		Support for NAND boot using simple NAND drivers that
3347		expose the cmd_ctrl() interface.
3348
3349		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3350		Set for the SPL on PPC mpc8xxx targets, support for
3351		drivers/ddr/fsl/libddr.o in SPL binary.
3352
3353		CONFIG_SPL_COMMON_INIT_DDR
3354		Set for common ddr init with serial presence detect in
3355		SPL binary.
3356
3357		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3358		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3359		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3360		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3361		CONFIG_SYS_NAND_ECCBYTES
3362		Defines the size and behavior of the NAND that SPL uses
3363		to read U-Boot
3364
3365		CONFIG_SPL_NAND_BOOT
3366		Add support NAND boot
3367
3368		CONFIG_SYS_NAND_U_BOOT_OFFS
3369		Location in NAND to read U-Boot from
3370
3371		CONFIG_SYS_NAND_U_BOOT_DST
3372		Location in memory to load U-Boot to
3373
3374		CONFIG_SYS_NAND_U_BOOT_SIZE
3375		Size of image to load
3376
3377		CONFIG_SYS_NAND_U_BOOT_START
3378		Entry point in loaded image to jump to
3379
3380		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3381		Define this if you need to first read the OOB and then the
3382		data. This is used for example on davinci plattforms.
3383
3384		CONFIG_SPL_OMAP3_ID_NAND
3385		Support for an OMAP3-specific set of functions to return the
3386		ID and MFR of the first attached NAND chip, if present.
3387
3388		CONFIG_SPL_SERIAL_SUPPORT
3389		Support for drivers/serial/libserial.o in SPL binary
3390
3391		CONFIG_SPL_SPI_FLASH_SUPPORT
3392		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3393
3394		CONFIG_SPL_SPI_SUPPORT
3395		Support for drivers/spi/libspi.o in SPL binary
3396
3397		CONFIG_SPL_RAM_DEVICE
3398		Support for running image already present in ram, in SPL binary
3399
3400		CONFIG_SPL_LIBGENERIC_SUPPORT
3401		Support for lib/libgeneric.o in SPL binary
3402
3403		CONFIG_SPL_ENV_SUPPORT
3404		Support for the environment operating in SPL binary
3405
3406		CONFIG_SPL_NET_SUPPORT
3407		Support for the net/libnet.o in SPL binary.
3408		It conflicts with SPL env from storage medium specified by
3409		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3410
3411		CONFIG_SPL_PAD_TO
3412		Image offset to which the SPL should be padded before appending
3413		the SPL payload. By default, this is defined as
3414		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3415		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3416		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3417
3418		CONFIG_SPL_TARGET
3419		Final target image containing SPL and payload.  Some SPLs
3420		use an arch-specific makefile fragment instead, for
3421		example if more than one image needs to be produced.
3422
3423		CONFIG_FIT_SPL_PRINT
3424		Printing information about a FIT image adds quite a bit of
3425		code to SPL. So this is normally disabled in SPL. Use this
3426		option to re-enable it. This will affect the output of the
3427		bootm command when booting a FIT image.
3428
3429- TPL framework
3430		CONFIG_TPL
3431		Enable building of TPL globally.
3432
3433		CONFIG_TPL_PAD_TO
3434		Image offset to which the TPL should be padded before appending
3435		the TPL payload. By default, this is defined as
3436		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3437		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3438		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3439
3440Modem Support:
3441--------------
3442
3443[so far only for SMDK2400 boards]
3444
3445- Modem support enable:
3446		CONFIG_MODEM_SUPPORT
3447
3448- RTS/CTS Flow control enable:
3449		CONFIG_HWFLOW
3450
3451- Modem debug support:
3452		CONFIG_MODEM_SUPPORT_DEBUG
3453
3454		Enables debugging stuff (char screen[1024], dbg())
3455		for modem support. Useful only with BDI2000.
3456
3457- Interrupt support (PPC):
3458
3459		There are common interrupt_init() and timer_interrupt()
3460		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3461		for CPU specific initialization. interrupt_init_cpu()
3462		should set decrementer_count to appropriate value. If
3463		CPU resets decrementer automatically after interrupt
3464		(ppc4xx) it should set decrementer_count to zero.
3465		timer_interrupt() calls timer_interrupt_cpu() for CPU
3466		specific handling. If board has watchdog / status_led
3467		/ other_activity_monitor it works automatically from
3468		general timer_interrupt().
3469
3470- General:
3471
3472		In the target system modem support is enabled when a
3473		specific key (key combination) is pressed during
3474		power-on. Otherwise U-Boot will boot normally
3475		(autoboot). The key_pressed() function is called from
3476		board_init(). Currently key_pressed() is a dummy
3477		function, returning 1 and thus enabling modem
3478		initialization.
3479
3480		If there are no modem init strings in the
3481		environment, U-Boot proceed to autoboot; the
3482		previous output (banner, info printfs) will be
3483		suppressed, though.
3484
3485		See also: doc/README.Modem
3486
3487Board initialization settings:
3488------------------------------
3489
3490During Initialization u-boot calls a number of board specific functions
3491to allow the preparation of board specific prerequisites, e.g. pin setup
3492before drivers are initialized. To enable these callbacks the
3493following configuration macros have to be defined. Currently this is
3494architecture specific, so please check arch/your_architecture/lib/board.c
3495typically in board_init_f() and board_init_r().
3496
3497- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3498- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3499- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3500- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3501
3502Configuration Settings:
3503-----------------------
3504
3505- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3506		Optionally it can be defined to support 64-bit memory commands.
3507
3508- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3509		undefine this when you're short of memory.
3510
3511- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3512		width of the commands listed in the 'help' command output.
3513
3514- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3515		prompt for user input.
3516
3517- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3518
3519- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3520
3521- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3522
3523- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3524		the application (usually a Linux kernel) when it is
3525		booted
3526
3527- CONFIG_SYS_BAUDRATE_TABLE:
3528		List of legal baudrate settings for this board.
3529
3530- CONFIG_SYS_CONSOLE_INFO_QUIET
3531		Suppress display of console information at boot.
3532
3533- CONFIG_SYS_CONSOLE_IS_IN_ENV
3534		If the board specific function
3535			extern int overwrite_console (void);
3536		returns 1, the stdin, stderr and stdout are switched to the
3537		serial port, else the settings in the environment are used.
3538
3539- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3540		Enable the call to overwrite_console().
3541
3542- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3543		Enable overwrite of previous console environment settings.
3544
3545- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3546		Begin and End addresses of the area used by the
3547		simple memory test.
3548
3549- CONFIG_SYS_ALT_MEMTEST:
3550		Enable an alternate, more extensive memory test.
3551
3552- CONFIG_SYS_MEMTEST_SCRATCH:
3553		Scratch address used by the alternate memory test
3554		You only need to set this if address zero isn't writeable
3555
3556- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3557		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3558		this specified memory area will get subtracted from the top
3559		(end) of RAM and won't get "touched" at all by U-Boot. By
3560		fixing up gd->ram_size the Linux kernel should gets passed
3561		the now "corrected" memory size and won't touch it either.
3562		This should work for arch/ppc and arch/powerpc. Only Linux
3563		board ports in arch/powerpc with bootwrapper support that
3564		recalculate the memory size from the SDRAM controller setup
3565		will have to get fixed in Linux additionally.
3566
3567		This option can be used as a workaround for the 440EPx/GRx
3568		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3569		be touched.
3570
3571		WARNING: Please make sure that this value is a multiple of
3572		the Linux page size (normally 4k). If this is not the case,
3573		then the end address of the Linux memory will be located at a
3574		non page size aligned address and this could cause major
3575		problems.
3576
3577- CONFIG_SYS_LOADS_BAUD_CHANGE:
3578		Enable temporary baudrate change while serial download
3579
3580- CONFIG_SYS_SDRAM_BASE:
3581		Physical start address of SDRAM. _Must_ be 0 here.
3582
3583- CONFIG_SYS_MBIO_BASE:
3584		Physical start address of Motherboard I/O (if using a
3585		Cogent motherboard)
3586
3587- CONFIG_SYS_FLASH_BASE:
3588		Physical start address of Flash memory.
3589
3590- CONFIG_SYS_MONITOR_BASE:
3591		Physical start address of boot monitor code (set by
3592		make config files to be same as the text base address
3593		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3594		CONFIG_SYS_FLASH_BASE when booting from flash.
3595
3596- CONFIG_SYS_MONITOR_LEN:
3597		Size of memory reserved for monitor code, used to
3598		determine _at_compile_time_ (!) if the environment is
3599		embedded within the U-Boot image, or in a separate
3600		flash sector.
3601
3602- CONFIG_SYS_MALLOC_LEN:
3603		Size of DRAM reserved for malloc() use.
3604
3605- CONFIG_SYS_BOOTM_LEN:
3606		Normally compressed uImages are limited to an
3607		uncompressed size of 8 MBytes. If this is not enough,
3608		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3609		to adjust this setting to your needs.
3610
3611- CONFIG_SYS_BOOTMAPSZ:
3612		Maximum size of memory mapped by the startup code of
3613		the Linux kernel; all data that must be processed by
3614		the Linux kernel (bd_info, boot arguments, FDT blob if
3615		used) must be put below this limit, unless "bootm_low"
3616		environment variable is defined and non-zero. In such case
3617		all data for the Linux kernel must be between "bootm_low"
3618		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3619		variable "bootm_mapsize" will override the value of
3620		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3621		then the value in "bootm_size" will be used instead.
3622
3623- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3624		Enable initrd_high functionality.  If defined then the
3625		initrd_high feature is enabled and the bootm ramdisk subcommand
3626		is enabled.
3627
3628- CONFIG_SYS_BOOT_GET_CMDLINE:
3629		Enables allocating and saving kernel cmdline in space between
3630		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3631
3632- CONFIG_SYS_BOOT_GET_KBD:
3633		Enables allocating and saving a kernel copy of the bd_info in
3634		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3635
3636- CONFIG_SYS_MAX_FLASH_BANKS:
3637		Max number of Flash memory banks
3638
3639- CONFIG_SYS_MAX_FLASH_SECT:
3640		Max number of sectors on a Flash chip
3641
3642- CONFIG_SYS_FLASH_ERASE_TOUT:
3643		Timeout for Flash erase operations (in ms)
3644
3645- CONFIG_SYS_FLASH_WRITE_TOUT:
3646		Timeout for Flash write operations (in ms)
3647
3648- CONFIG_SYS_FLASH_LOCK_TOUT
3649		Timeout for Flash set sector lock bit operation (in ms)
3650
3651- CONFIG_SYS_FLASH_UNLOCK_TOUT
3652		Timeout for Flash clear lock bits operation (in ms)
3653
3654- CONFIG_SYS_FLASH_PROTECTION
3655		If defined, hardware flash sectors protection is used
3656		instead of U-Boot software protection.
3657
3658- CONFIG_SYS_DIRECT_FLASH_TFTP:
3659
3660		Enable TFTP transfers directly to flash memory;
3661		without this option such a download has to be
3662		performed in two steps: (1) download to RAM, and (2)
3663		copy from RAM to flash.
3664
3665		The two-step approach is usually more reliable, since
3666		you can check if the download worked before you erase
3667		the flash, but in some situations (when system RAM is
3668		too limited to allow for a temporary copy of the
3669		downloaded image) this option may be very useful.
3670
3671- CONFIG_SYS_FLASH_CFI:
3672		Define if the flash driver uses extra elements in the
3673		common flash structure for storing flash geometry.
3674
3675- CONFIG_FLASH_CFI_DRIVER
3676		This option also enables the building of the cfi_flash driver
3677		in the drivers directory
3678
3679- CONFIG_FLASH_CFI_MTD
3680		This option enables the building of the cfi_mtd driver
3681		in the drivers directory. The driver exports CFI flash
3682		to the MTD layer.
3683
3684- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3685		Use buffered writes to flash.
3686
3687- CONFIG_FLASH_SPANSION_S29WS_N
3688		s29ws-n MirrorBit flash has non-standard addresses for buffered
3689		write commands.
3690
3691- CONFIG_SYS_FLASH_QUIET_TEST
3692		If this option is defined, the common CFI flash doesn't
3693		print it's warning upon not recognized FLASH banks. This
3694		is useful, if some of the configured banks are only
3695		optionally available.
3696
3697- CONFIG_FLASH_SHOW_PROGRESS
3698		If defined (must be an integer), print out countdown
3699		digits and dots.  Recommended value: 45 (9..1) for 80
3700		column displays, 15 (3..1) for 40 column displays.
3701
3702- CONFIG_FLASH_VERIFY
3703		If defined, the content of the flash (destination) is compared
3704		against the source after the write operation. An error message
3705		will be printed when the contents are not identical.
3706		Please note that this option is useless in nearly all cases,
3707		since such flash programming errors usually are detected earlier
3708		while unprotecting/erasing/programming. Please only enable
3709		this option if you really know what you are doing.
3710
3711- CONFIG_SYS_RX_ETH_BUFFER:
3712		Defines the number of Ethernet receive buffers. On some
3713		Ethernet controllers it is recommended to set this value
3714		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3715		buffers can be full shortly after enabling the interface
3716		on high Ethernet traffic.
3717		Defaults to 4 if not defined.
3718
3719- CONFIG_ENV_MAX_ENTRIES
3720
3721	Maximum number of entries in the hash table that is used
3722	internally to store the environment settings. The default
3723	setting is supposed to be generous and should work in most
3724	cases. This setting can be used to tune behaviour; see
3725	lib/hashtable.c for details.
3726
3727- CONFIG_ENV_FLAGS_LIST_DEFAULT
3728- CONFIG_ENV_FLAGS_LIST_STATIC
3729	Enable validation of the values given to environment variables when
3730	calling env set.  Variables can be restricted to only decimal,
3731	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3732	the variables can also be restricted to IP address or MAC address.
3733
3734	The format of the list is:
3735		type_attribute = [s|d|x|b|i|m]
3736		access_atribute = [a|r|o|c]
3737		attributes = type_attribute[access_atribute]
3738		entry = variable_name[:attributes]
3739		list = entry[,list]
3740
3741	The type attributes are:
3742		s - String (default)
3743		d - Decimal
3744		x - Hexadecimal
3745		b - Boolean ([1yYtT|0nNfF])
3746		i - IP address
3747		m - MAC address
3748
3749	The access attributes are:
3750		a - Any (default)
3751		r - Read-only
3752		o - Write-once
3753		c - Change-default
3754
3755	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3756		Define this to a list (string) to define the ".flags"
3757		envirnoment variable in the default or embedded environment.
3758
3759	- CONFIG_ENV_FLAGS_LIST_STATIC
3760		Define this to a list (string) to define validation that
3761		should be done if an entry is not found in the ".flags"
3762		environment variable.  To override a setting in the static
3763		list, simply add an entry for the same variable name to the
3764		".flags" variable.
3765
3766- CONFIG_ENV_ACCESS_IGNORE_FORCE
3767	If defined, don't allow the -f switch to env set override variable
3768	access flags.
3769
3770- CONFIG_SYS_GENERIC_BOARD
3771	This selects the architecture-generic board system instead of the
3772	architecture-specific board files. It is intended to move boards
3773	to this new framework over time. Defining this will disable the
3774	arch/foo/lib/board.c file and use common/board_f.c and
3775	common/board_r.c instead. To use this option your architecture
3776	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3777	its config.mk file). If you find problems enabling this option on
3778	your board please report the problem and send patches!
3779
3780- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3781	This is set by OMAP boards for the max time that reset should
3782	be asserted. See doc/README.omap-reset-time for details on how
3783	the value can be calulated on a given board.
3784
3785The following definitions that deal with the placement and management
3786of environment data (variable area); in general, we support the
3787following configurations:
3788
3789- CONFIG_BUILD_ENVCRC:
3790
3791	Builds up envcrc with the target environment so that external utils
3792	may easily extract it and embed it in final U-Boot images.
3793
3794- CONFIG_ENV_IS_IN_FLASH:
3795
3796	Define this if the environment is in flash memory.
3797
3798	a) The environment occupies one whole flash sector, which is
3799	   "embedded" in the text segment with the U-Boot code. This
3800	   happens usually with "bottom boot sector" or "top boot
3801	   sector" type flash chips, which have several smaller
3802	   sectors at the start or the end. For instance, such a
3803	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3804	   such a case you would place the environment in one of the
3805	   4 kB sectors - with U-Boot code before and after it. With
3806	   "top boot sector" type flash chips, you would put the
3807	   environment in one of the last sectors, leaving a gap
3808	   between U-Boot and the environment.
3809
3810	- CONFIG_ENV_OFFSET:
3811
3812	   Offset of environment data (variable area) to the
3813	   beginning of flash memory; for instance, with bottom boot
3814	   type flash chips the second sector can be used: the offset
3815	   for this sector is given here.
3816
3817	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3818
3819	- CONFIG_ENV_ADDR:
3820
3821	   This is just another way to specify the start address of
3822	   the flash sector containing the environment (instead of
3823	   CONFIG_ENV_OFFSET).
3824
3825	- CONFIG_ENV_SECT_SIZE:
3826
3827	   Size of the sector containing the environment.
3828
3829
3830	b) Sometimes flash chips have few, equal sized, BIG sectors.
3831	   In such a case you don't want to spend a whole sector for
3832	   the environment.
3833
3834	- CONFIG_ENV_SIZE:
3835
3836	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3837	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3838	   of this flash sector for the environment. This saves
3839	   memory for the RAM copy of the environment.
3840
3841	   It may also save flash memory if you decide to use this
3842	   when your environment is "embedded" within U-Boot code,
3843	   since then the remainder of the flash sector could be used
3844	   for U-Boot code. It should be pointed out that this is
3845	   STRONGLY DISCOURAGED from a robustness point of view:
3846	   updating the environment in flash makes it always
3847	   necessary to erase the WHOLE sector. If something goes
3848	   wrong before the contents has been restored from a copy in
3849	   RAM, your target system will be dead.
3850
3851	- CONFIG_ENV_ADDR_REDUND
3852	  CONFIG_ENV_SIZE_REDUND
3853
3854	   These settings describe a second storage area used to hold
3855	   a redundant copy of the environment data, so that there is
3856	   a valid backup copy in case there is a power failure during
3857	   a "saveenv" operation.
3858
3859BE CAREFUL! Any changes to the flash layout, and some changes to the
3860source code will make it necessary to adapt <board>/u-boot.lds*
3861accordingly!
3862
3863
3864- CONFIG_ENV_IS_IN_NVRAM:
3865
3866	Define this if you have some non-volatile memory device
3867	(NVRAM, battery buffered SRAM) which you want to use for the
3868	environment.
3869
3870	- CONFIG_ENV_ADDR:
3871	- CONFIG_ENV_SIZE:
3872
3873	  These two #defines are used to determine the memory area you
3874	  want to use for environment. It is assumed that this memory
3875	  can just be read and written to, without any special
3876	  provision.
3877
3878BE CAREFUL! The first access to the environment happens quite early
3879in U-Boot initalization (when we try to get the setting of for the
3880console baudrate). You *MUST* have mapped your NVRAM area then, or
3881U-Boot will hang.
3882
3883Please note that even with NVRAM we still use a copy of the
3884environment in RAM: we could work on NVRAM directly, but we want to
3885keep settings there always unmodified except somebody uses "saveenv"
3886to save the current settings.
3887
3888
3889- CONFIG_ENV_IS_IN_EEPROM:
3890
3891	Use this if you have an EEPROM or similar serial access
3892	device and a driver for it.
3893
3894	- CONFIG_ENV_OFFSET:
3895	- CONFIG_ENV_SIZE:
3896
3897	  These two #defines specify the offset and size of the
3898	  environment area within the total memory of your EEPROM.
3899
3900	- CONFIG_SYS_I2C_EEPROM_ADDR:
3901	  If defined, specified the chip address of the EEPROM device.
3902	  The default address is zero.
3903
3904	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3905	  If defined, the number of bits used to address bytes in a
3906	  single page in the EEPROM device.  A 64 byte page, for example
3907	  would require six bits.
3908
3909	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3910	  If defined, the number of milliseconds to delay between
3911	  page writes.	The default is zero milliseconds.
3912
3913	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3914	  The length in bytes of the EEPROM memory array address.  Note
3915	  that this is NOT the chip address length!
3916
3917	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3918	  EEPROM chips that implement "address overflow" are ones
3919	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3920	  address and the extra bits end up in the "chip address" bit
3921	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3922	  byte chips.
3923
3924	  Note that we consider the length of the address field to
3925	  still be one byte because the extra address bits are hidden
3926	  in the chip address.
3927
3928	- CONFIG_SYS_EEPROM_SIZE:
3929	  The size in bytes of the EEPROM device.
3930
3931	- CONFIG_ENV_EEPROM_IS_ON_I2C
3932	  define this, if you have I2C and SPI activated, and your
3933	  EEPROM, which holds the environment, is on the I2C bus.
3934
3935	- CONFIG_I2C_ENV_EEPROM_BUS
3936	  if you have an Environment on an EEPROM reached over
3937	  I2C muxes, you can define here, how to reach this
3938	  EEPROM. For example:
3939
3940	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3941
3942	  EEPROM which holds the environment, is reached over
3943	  a pca9547 i2c mux with address 0x70, channel 3.
3944
3945- CONFIG_ENV_IS_IN_DATAFLASH:
3946
3947	Define this if you have a DataFlash memory device which you
3948	want to use for the environment.
3949
3950	- CONFIG_ENV_OFFSET:
3951	- CONFIG_ENV_ADDR:
3952	- CONFIG_ENV_SIZE:
3953
3954	  These three #defines specify the offset and size of the
3955	  environment area within the total memory of your DataFlash placed
3956	  at the specified address.
3957
3958- CONFIG_ENV_IS_IN_REMOTE:
3959
3960	Define this if you have a remote memory space which you
3961	want to use for the local device's environment.
3962
3963	- CONFIG_ENV_ADDR:
3964	- CONFIG_ENV_SIZE:
3965
3966	  These two #defines specify the address and size of the
3967	  environment area within the remote memory space. The
3968	  local device can get the environment from remote memory
3969	  space by SRIO or PCIE links.
3970
3971BE CAREFUL! For some special cases, the local device can not use
3972"saveenv" command. For example, the local device will get the
3973environment stored in a remote NOR flash by SRIO or PCIE link,
3974but it can not erase, write this NOR flash by SRIO or PCIE interface.
3975
3976- CONFIG_ENV_IS_IN_NAND:
3977
3978	Define this if you have a NAND device which you want to use
3979	for the environment.
3980
3981	- CONFIG_ENV_OFFSET:
3982	- CONFIG_ENV_SIZE:
3983
3984	  These two #defines specify the offset and size of the environment
3985	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3986	  aligned to an erase block boundary.
3987
3988	- CONFIG_ENV_OFFSET_REDUND (optional):
3989
3990	  This setting describes a second storage area of CONFIG_ENV_SIZE
3991	  size used to hold a redundant copy of the environment data, so
3992	  that there is a valid backup copy in case there is a power failure
3993	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3994	  aligned to an erase block boundary.
3995
3996	- CONFIG_ENV_RANGE (optional):
3997
3998	  Specifies the length of the region in which the environment
3999	  can be written.  This should be a multiple of the NAND device's
4000	  block size.  Specifying a range with more erase blocks than
4001	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4002	  the range to be avoided.
4003
4004	- CONFIG_ENV_OFFSET_OOB (optional):
4005
4006	  Enables support for dynamically retrieving the offset of the
4007	  environment from block zero's out-of-band data.  The
4008	  "nand env.oob" command can be used to record this offset.
4009	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4010	  using CONFIG_ENV_OFFSET_OOB.
4011
4012- CONFIG_NAND_ENV_DST
4013
4014	Defines address in RAM to which the nand_spl code should copy the
4015	environment. If redundant environment is used, it will be copied to
4016	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4017
4018- CONFIG_ENV_IS_IN_UBI:
4019
4020	Define this if you have an UBI volume that you want to use for the
4021	environment.  This has the benefit of wear-leveling the environment
4022	accesses, which is important on NAND.
4023
4024	- CONFIG_ENV_UBI_PART:
4025
4026	  Define this to a string that is the mtd partition containing the UBI.
4027
4028	- CONFIG_ENV_UBI_VOLUME:
4029
4030	  Define this to the name of the volume that you want to store the
4031	  environment in.
4032
4033	- CONFIG_ENV_UBI_VOLUME_REDUND:
4034
4035	  Define this to the name of another volume to store a second copy of
4036	  the environment in.  This will enable redundant environments in UBI.
4037	  It is assumed that both volumes are in the same MTD partition.
4038
4039	- CONFIG_UBI_SILENCE_MSG
4040	- CONFIG_UBIFS_SILENCE_MSG
4041
4042	  You will probably want to define these to avoid a really noisy system
4043	  when storing the env in UBI.
4044
4045- CONFIG_ENV_IS_IN_MMC:
4046
4047	Define this if you have an MMC device which you want to use for the
4048	environment.
4049
4050	- CONFIG_SYS_MMC_ENV_DEV:
4051
4052	  Specifies which MMC device the environment is stored in.
4053
4054	- CONFIG_SYS_MMC_ENV_PART (optional):
4055
4056	  Specifies which MMC partition the environment is stored in. If not
4057	  set, defaults to partition 0, the user area. Common values might be
4058	  1 (first MMC boot partition), 2 (second MMC boot partition).
4059
4060	- CONFIG_ENV_OFFSET:
4061	- CONFIG_ENV_SIZE:
4062
4063	  These two #defines specify the offset and size of the environment
4064	  area within the specified MMC device.
4065
4066	  If offset is positive (the usual case), it is treated as relative to
4067	  the start of the MMC partition. If offset is negative, it is treated
4068	  as relative to the end of the MMC partition. This can be useful if
4069	  your board may be fitted with different MMC devices, which have
4070	  different sizes for the MMC partitions, and you always want the
4071	  environment placed at the very end of the partition, to leave the
4072	  maximum possible space before it, to store other data.
4073
4074	  These two values are in units of bytes, but must be aligned to an
4075	  MMC sector boundary.
4076
4077	- CONFIG_ENV_OFFSET_REDUND (optional):
4078
4079	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4080	  hold a redundant copy of the environment data. This provides a
4081	  valid backup copy in case the other copy is corrupted, e.g. due
4082	  to a power failure during a "saveenv" operation.
4083
4084	  This value may also be positive or negative; this is handled in the
4085	  same way as CONFIG_ENV_OFFSET.
4086
4087	  This value is also in units of bytes, but must also be aligned to
4088	  an MMC sector boundary.
4089
4090	- CONFIG_ENV_SIZE_REDUND (optional):
4091
4092	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4093	  set. If this value is set, it must be set to the same value as
4094	  CONFIG_ENV_SIZE.
4095
4096- CONFIG_SYS_SPI_INIT_OFFSET
4097
4098	Defines offset to the initial SPI buffer area in DPRAM. The
4099	area is used at an early stage (ROM part) if the environment
4100	is configured to reside in the SPI EEPROM: We need a 520 byte
4101	scratch DPRAM area. It is used between the two initialization
4102	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4103	to be a good choice since it makes it far enough from the
4104	start of the data area as well as from the stack pointer.
4105
4106Please note that the environment is read-only until the monitor
4107has been relocated to RAM and a RAM copy of the environment has been
4108created; also, when using EEPROM you will have to use getenv_f()
4109until then to read environment variables.
4110
4111The environment is protected by a CRC32 checksum. Before the monitor
4112is relocated into RAM, as a result of a bad CRC you will be working
4113with the compiled-in default environment - *silently*!!! [This is
4114necessary, because the first environment variable we need is the
4115"baudrate" setting for the console - if we have a bad CRC, we don't
4116have any device yet where we could complain.]
4117
4118Note: once the monitor has been relocated, then it will complain if
4119the default environment is used; a new CRC is computed as soon as you
4120use the "saveenv" command to store a valid environment.
4121
4122- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4123		Echo the inverted Ethernet link state to the fault LED.
4124
4125		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4126		      also needs to be defined.
4127
4128- CONFIG_SYS_FAULT_MII_ADDR:
4129		MII address of the PHY to check for the Ethernet link state.
4130
4131- CONFIG_NS16550_MIN_FUNCTIONS:
4132		Define this if you desire to only have use of the NS16550_init
4133		and NS16550_putc functions for the serial driver located at
4134		drivers/serial/ns16550.c.  This option is useful for saving
4135		space for already greatly restricted images, including but not
4136		limited to NAND_SPL configurations.
4137
4138- CONFIG_DISPLAY_BOARDINFO
4139		Display information about the board that U-Boot is running on
4140		when U-Boot starts up. The board function checkboard() is called
4141		to do this.
4142
4143- CONFIG_DISPLAY_BOARDINFO_LATE
4144		Similar to the previous option, but display this information
4145		later, once stdio is running and output goes to the LCD, if
4146		present.
4147
4148Low Level (hardware related) configuration options:
4149---------------------------------------------------
4150
4151- CONFIG_SYS_CACHELINE_SIZE:
4152		Cache Line Size of the CPU.
4153
4154- CONFIG_SYS_DEFAULT_IMMR:
4155		Default address of the IMMR after system reset.
4156
4157		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4158		and RPXsuper) to be able to adjust the position of
4159		the IMMR register after a reset.
4160
4161- CONFIG_SYS_CCSRBAR_DEFAULT:
4162		Default (power-on reset) physical address of CCSR on Freescale
4163		PowerPC SOCs.
4164
4165- CONFIG_SYS_CCSRBAR:
4166		Virtual address of CCSR.  On a 32-bit build, this is typically
4167		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4168
4169		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4170		for cross-platform code that uses that macro instead.
4171
4172- CONFIG_SYS_CCSRBAR_PHYS:
4173		Physical address of CCSR.  CCSR can be relocated to a new
4174		physical address, if desired.  In this case, this macro should
4175		be set to that address.	 Otherwise, it should be set to the
4176		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4177		is typically relocated on 36-bit builds.  It is recommended
4178		that this macro be defined via the _HIGH and _LOW macros:
4179
4180		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4181			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4182
4183- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4184		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4185		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4186		used in assembly code, so it must not contain typecasts or
4187		integer size suffixes (e.g. "ULL").
4188
4189- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4190		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4191		used in assembly code, so it must not contain typecasts or
4192		integer size suffixes (e.g. "ULL").
4193
4194- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4195		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4196		forced to a value that ensures that CCSR is not relocated.
4197
4198- Floppy Disk Support:
4199		CONFIG_SYS_FDC_DRIVE_NUMBER
4200
4201		the default drive number (default value 0)
4202
4203		CONFIG_SYS_ISA_IO_STRIDE
4204
4205		defines the spacing between FDC chipset registers
4206		(default value 1)
4207
4208		CONFIG_SYS_ISA_IO_OFFSET
4209
4210		defines the offset of register from address. It
4211		depends on which part of the data bus is connected to
4212		the FDC chipset. (default value 0)
4213
4214		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4215		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4216		default value.
4217
4218		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4219		fdc_hw_init() is called at the beginning of the FDC
4220		setup. fdc_hw_init() must be provided by the board
4221		source code. It is used to make hardware dependant
4222		initializations.
4223
4224- CONFIG_IDE_AHB:
4225		Most IDE controllers were designed to be connected with PCI
4226		interface. Only few of them were designed for AHB interface.
4227		When software is doing ATA command and data transfer to
4228		IDE devices through IDE-AHB controller, some additional
4229		registers accessing to these kind of IDE-AHB controller
4230		is requierd.
4231
4232- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4233		DO NOT CHANGE unless you know exactly what you're
4234		doing! (11-4) [MPC8xx/82xx systems only]
4235
4236- CONFIG_SYS_INIT_RAM_ADDR:
4237
4238		Start address of memory area that can be used for
4239		initial data and stack; please note that this must be
4240		writable memory that is working WITHOUT special
4241		initialization, i. e. you CANNOT use normal RAM which
4242		will become available only after programming the
4243		memory controller and running certain initialization
4244		sequences.
4245
4246		U-Boot uses the following memory types:
4247		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4248		- MPC824X: data cache
4249		- PPC4xx:  data cache
4250
4251- CONFIG_SYS_GBL_DATA_OFFSET:
4252
4253		Offset of the initial data structure in the memory
4254		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4255		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4256		data is located at the end of the available space
4257		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4258		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4259		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4260		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4261
4262	Note:
4263		On the MPC824X (or other systems that use the data
4264		cache for initial memory) the address chosen for
4265		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4266		point to an otherwise UNUSED address space between
4267		the top of RAM and the start of the PCI space.
4268
4269- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4270
4271- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4272
4273- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4274
4275- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4276
4277- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4278
4279- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4280
4281- CONFIG_SYS_OR_TIMING_SDRAM:
4282		SDRAM timing
4283
4284- CONFIG_SYS_MAMR_PTA:
4285		periodic timer for refresh
4286
4287- CONFIG_SYS_DER:	Debug Event Register (37-47)
4288
4289- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4290  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4291  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4292  CONFIG_SYS_BR1_PRELIM:
4293		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4294
4295- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4296  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4297  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4298		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4299
4300- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4301  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4302		Machine Mode Register and Memory Periodic Timer
4303		Prescaler definitions (SDRAM timing)
4304
4305- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4306		enable I2C microcode relocation patch (MPC8xx);
4307		define relocation offset in DPRAM [DSP2]
4308
4309- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4310		enable SMC microcode relocation patch (MPC8xx);
4311		define relocation offset in DPRAM [SMC1]
4312
4313- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4314		enable SPI microcode relocation patch (MPC8xx);
4315		define relocation offset in DPRAM [SCC4]
4316
4317- CONFIG_SYS_USE_OSCCLK:
4318		Use OSCM clock mode on MBX8xx board. Be careful,
4319		wrong setting might damage your board. Read
4320		doc/README.MBX before setting this variable!
4321
4322- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4323		Offset of the bootmode word in DPRAM used by post
4324		(Power On Self Tests). This definition overrides
4325		#define'd default value in commproc.h resp.
4326		cpm_8260.h.
4327
4328- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4329  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4330  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4331  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4332  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4333  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4334  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4335  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4336		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4337
4338- CONFIG_PCI_DISABLE_PCIE:
4339		Disable PCI-Express on systems where it is supported but not
4340		required.
4341
4342- CONFIG_PCI_ENUM_ONLY
4343		Only scan through and get the devices on the busses.
4344		Don't do any setup work, presumably because someone or
4345		something has already done it, and we don't need to do it
4346		a second time.	Useful for platforms that are pre-booted
4347		by coreboot or similar.
4348
4349- CONFIG_PCI_INDIRECT_BRIDGE:
4350		Enable support for indirect PCI bridges.
4351
4352- CONFIG_SYS_SRIO:
4353		Chip has SRIO or not
4354
4355- CONFIG_SRIO1:
4356		Board has SRIO 1 port available
4357
4358- CONFIG_SRIO2:
4359		Board has SRIO 2 port available
4360
4361- CONFIG_SRIO_PCIE_BOOT_MASTER
4362		Board can support master function for Boot from SRIO and PCIE
4363
4364- CONFIG_SYS_SRIOn_MEM_VIRT:
4365		Virtual Address of SRIO port 'n' memory region
4366
4367- CONFIG_SYS_SRIOn_MEM_PHYS:
4368		Physical Address of SRIO port 'n' memory region
4369
4370- CONFIG_SYS_SRIOn_MEM_SIZE:
4371		Size of SRIO port 'n' memory region
4372
4373- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4374		Defined to tell the NAND controller that the NAND chip is using
4375		a 16 bit bus.
4376		Not all NAND drivers use this symbol.
4377		Example of drivers that use it:
4378		- drivers/mtd/nand/ndfc.c
4379		- drivers/mtd/nand/mxc_nand.c
4380
4381- CONFIG_SYS_NDFC_EBC0_CFG
4382		Sets the EBC0_CFG register for the NDFC. If not defined
4383		a default value will be used.
4384
4385- CONFIG_SPD_EEPROM
4386		Get DDR timing information from an I2C EEPROM. Common
4387		with pluggable memory modules such as SODIMMs
4388
4389  SPD_EEPROM_ADDRESS
4390		I2C address of the SPD EEPROM
4391
4392- CONFIG_SYS_SPD_BUS_NUM
4393		If SPD EEPROM is on an I2C bus other than the first
4394		one, specify here. Note that the value must resolve
4395		to something your driver can deal with.
4396
4397- CONFIG_SYS_DDR_RAW_TIMING
4398		Get DDR timing information from other than SPD. Common with
4399		soldered DDR chips onboard without SPD. DDR raw timing
4400		parameters are extracted from datasheet and hard-coded into
4401		header files or board specific files.
4402
4403- CONFIG_FSL_DDR_INTERACTIVE
4404		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4405
4406- CONFIG_SYS_83XX_DDR_USES_CS0
4407		Only for 83xx systems. If specified, then DDR should
4408		be configured using CS0 and CS1 instead of CS2 and CS3.
4409
4410- CONFIG_ETHER_ON_FEC[12]
4411		Define to enable FEC[12] on a 8xx series processor.
4412
4413- CONFIG_FEC[12]_PHY
4414		Define to the hardcoded PHY address which corresponds
4415		to the given FEC; i. e.
4416			#define CONFIG_FEC1_PHY 4
4417		means that the PHY with address 4 is connected to FEC1
4418
4419		When set to -1, means to probe for first available.
4420
4421- CONFIG_FEC[12]_PHY_NORXERR
4422		The PHY does not have a RXERR line (RMII only).
4423		(so program the FEC to ignore it).
4424
4425- CONFIG_RMII
4426		Enable RMII mode for all FECs.
4427		Note that this is a global option, we can't
4428		have one FEC in standard MII mode and another in RMII mode.
4429
4430- CONFIG_CRC32_VERIFY
4431		Add a verify option to the crc32 command.
4432		The syntax is:
4433
4434		=> crc32 -v <address> <count> <crc32>
4435
4436		Where address/count indicate a memory area
4437		and crc32 is the correct crc32 which the
4438		area should have.
4439
4440- CONFIG_LOOPW
4441		Add the "loopw" memory command. This only takes effect if
4442		the memory commands are activated globally (CONFIG_CMD_MEM).
4443
4444- CONFIG_MX_CYCLIC
4445		Add the "mdc" and "mwc" memory commands. These are cyclic
4446		"md/mw" commands.
4447		Examples:
4448
4449		=> mdc.b 10 4 500
4450		This command will print 4 bytes (10,11,12,13) each 500 ms.
4451
4452		=> mwc.l 100 12345678 10
4453		This command will write 12345678 to address 100 all 10 ms.
4454
4455		This only takes effect if the memory commands are activated
4456		globally (CONFIG_CMD_MEM).
4457
4458- CONFIG_SKIP_LOWLEVEL_INIT
4459		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4460		low level initializations (like setting up the memory
4461		controller) are omitted and/or U-Boot does not
4462		relocate itself into RAM.
4463
4464		Normally this variable MUST NOT be defined. The only
4465		exception is when U-Boot is loaded (to RAM) by some
4466		other boot loader or by a debugger which performs
4467		these initializations itself.
4468
4469- CONFIG_SPL_BUILD
4470		Modifies the behaviour of start.S when compiling a loader
4471		that is executed before the actual U-Boot. E.g. when
4472		compiling a NAND SPL.
4473
4474- CONFIG_TPL_BUILD
4475		Modifies the behaviour of start.S  when compiling a loader
4476		that is executed after the SPL and before the actual U-Boot.
4477		It is loaded by the SPL.
4478
4479- CONFIG_SYS_MPC85XX_NO_RESETVEC
4480		Only for 85xx systems. If this variable is specified, the section
4481		.resetvec is not kept and the section .bootpg is placed in the
4482		previous 4k of the .text section.
4483
4484- CONFIG_ARCH_MAP_SYSMEM
4485		Generally U-Boot (and in particular the md command) uses
4486		effective address. It is therefore not necessary to regard
4487		U-Boot address as virtual addresses that need to be translated
4488		to physical addresses. However, sandbox requires this, since
4489		it maintains its own little RAM buffer which contains all
4490		addressable memory. This option causes some memory accesses
4491		to be mapped through map_sysmem() / unmap_sysmem().
4492
4493- CONFIG_USE_ARCH_MEMCPY
4494  CONFIG_USE_ARCH_MEMSET
4495		If these options are used a optimized version of memcpy/memset will
4496		be used if available. These functions may be faster under some
4497		conditions but may increase the binary size.
4498
4499- CONFIG_X86_RESET_VECTOR
4500		If defined, the x86 reset vector code is included. This is not
4501		needed when U-Boot is running from Coreboot.
4502
4503- CONFIG_SYS_MPUCLK
4504		Defines the MPU clock speed (in MHz).
4505
4506		NOTE : currently only supported on AM335x platforms.
4507
4508- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4509		Enables the RTC32K OSC on AM33xx based plattforms
4510
4511Freescale QE/FMAN Firmware Support:
4512-----------------------------------
4513
4514The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4515loading of "firmware", which is encoded in the QE firmware binary format.
4516This firmware often needs to be loaded during U-Boot booting, so macros
4517are used to identify the storage device (NOR flash, SPI, etc) and the address
4518within that device.
4519
4520- CONFIG_SYS_FMAN_FW_ADDR
4521	The address in the storage device where the FMAN microcode is located.  The
4522	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4523	is also specified.
4524
4525- CONFIG_SYS_QE_FW_ADDR
4526	The address in the storage device where the QE microcode is located.  The
4527	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4528	is also specified.
4529
4530- CONFIG_SYS_QE_FMAN_FW_LENGTH
4531	The maximum possible size of the firmware.  The firmware binary format
4532	has a field that specifies the actual size of the firmware, but it
4533	might not be possible to read any part of the firmware unless some
4534	local storage is allocated to hold the entire firmware first.
4535
4536- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4537	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4538	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4539	virtual address in NOR flash.
4540
4541- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4542	Specifies that QE/FMAN firmware is located in NAND flash.
4543	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4544
4545- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4546	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4547	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4548
4549- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4550	Specifies that QE/FMAN firmware is located on the primary SPI
4551	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4552
4553- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4554	Specifies that QE/FMAN firmware is located in the remote (master)
4555	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4556	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4557	window->master inbound window->master LAW->the ucode address in
4558	master's memory space.
4559
4560Building the Software:
4561======================
4562
4563Building U-Boot has been tested in several native build environments
4564and in many different cross environments. Of course we cannot support
4565all possibly existing versions of cross development tools in all
4566(potentially obsolete) versions. In case of tool chain problems we
4567recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4568which is extensively used to build and test U-Boot.
4569
4570If you are not using a native environment, it is assumed that you
4571have GNU cross compiling tools available in your path. In this case,
4572you must set the environment variable CROSS_COMPILE in your shell.
4573Note that no changes to the Makefile or any other source files are
4574necessary. For example using the ELDK on a 4xx CPU, please enter:
4575
4576	$ CROSS_COMPILE=ppc_4xx-
4577	$ export CROSS_COMPILE
4578
4579Note: If you wish to generate Windows versions of the utilities in
4580      the tools directory you can use the MinGW toolchain
4581      (http://www.mingw.org).  Set your HOST tools to the MinGW
4582      toolchain and execute 'make tools'.  For example:
4583
4584       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4585
4586      Binaries such as tools/mkimage.exe will be created which can
4587      be executed on computers running Windows.
4588
4589U-Boot is intended to be simple to build. After installing the
4590sources you must configure U-Boot for one specific board type. This
4591is done by typing:
4592
4593	make NAME_config
4594
4595where "NAME_config" is the name of one of the existing configu-
4596rations; see boards.cfg for supported names.
4597
4598Note: for some board special configuration names may exist; check if
4599      additional information is available from the board vendor; for
4600      instance, the TQM823L systems are available without (standard)
4601      or with LCD support. You can select such additional "features"
4602      when choosing the configuration, i. e.
4603
4604      make TQM823L_config
4605	- will configure for a plain TQM823L, i. e. no LCD support
4606
4607      make TQM823L_LCD_config
4608	- will configure for a TQM823L with U-Boot console on LCD
4609
4610      etc.
4611
4612
4613Finally, type "make all", and you should get some working U-Boot
4614images ready for download to / installation on your system:
4615
4616- "u-boot.bin" is a raw binary image
4617- "u-boot" is an image in ELF binary format
4618- "u-boot.srec" is in Motorola S-Record format
4619
4620By default the build is performed locally and the objects are saved
4621in the source directory. One of the two methods can be used to change
4622this behavior and build U-Boot to some external directory:
4623
46241. Add O= to the make command line invocations:
4625
4626	make O=/tmp/build distclean
4627	make O=/tmp/build NAME_config
4628	make O=/tmp/build all
4629
46302. Set environment variable BUILD_DIR to point to the desired location:
4631
4632	export BUILD_DIR=/tmp/build
4633	make distclean
4634	make NAME_config
4635	make all
4636
4637Note that the command line "O=" setting overrides the BUILD_DIR environment
4638variable.
4639
4640
4641Please be aware that the Makefiles assume you are using GNU make, so
4642for instance on NetBSD you might need to use "gmake" instead of
4643native "make".
4644
4645
4646If the system board that you have is not listed, then you will need
4647to port U-Boot to your hardware platform. To do this, follow these
4648steps:
4649
46501.  Add a new configuration option for your board to the toplevel
4651    "boards.cfg" file, using the existing entries as examples.
4652    Follow the instructions there to keep the boards in order.
46532.  Create a new directory to hold your board specific code. Add any
4654    files you need. In your board directory, you will need at least
4655    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46563.  Create a new configuration file "include/configs/<board>.h" for
4657    your board
46583.  If you're porting U-Boot to a new CPU, then also create a new
4659    directory to hold your CPU specific code. Add any files you need.
46604.  Run "make <board>_config" with your new name.
46615.  Type "make", and you should get a working "u-boot.srec" file
4662    to be installed on your target system.
46636.  Debug and solve any problems that might arise.
4664    [Of course, this last step is much harder than it sounds.]
4665
4666
4667Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4668==============================================================
4669
4670If you have modified U-Boot sources (for instance added a new board
4671or support for new devices, a new CPU, etc.) you are expected to
4672provide feedback to the other developers. The feedback normally takes
4673the form of a "patch", i. e. a context diff against a certain (latest
4674official or latest in the git repository) version of U-Boot sources.
4675
4676But before you submit such a patch, please verify that your modifi-
4677cation did not break existing code. At least make sure that *ALL* of
4678the supported boards compile WITHOUT ANY compiler warnings. To do so,
4679just run the "MAKEALL" script, which will configure and build U-Boot
4680for ALL supported system. Be warned, this will take a while. You can
4681select which (cross) compiler to use by passing a `CROSS_COMPILE'
4682environment variable to the script, i. e. to use the ELDK cross tools
4683you can type
4684
4685	CROSS_COMPILE=ppc_8xx- MAKEALL
4686
4687or to build on a native PowerPC system you can type
4688
4689	CROSS_COMPILE=' ' MAKEALL
4690
4691When using the MAKEALL script, the default behaviour is to build
4692U-Boot in the source directory. This location can be changed by
4693setting the BUILD_DIR environment variable. Also, for each target
4694built, the MAKEALL script saves two log files (<target>.ERR and
4695<target>.MAKEALL) in the <source dir>/LOG directory. This default
4696location can be changed by setting the MAKEALL_LOGDIR environment
4697variable. For example:
4698
4699	export BUILD_DIR=/tmp/build
4700	export MAKEALL_LOGDIR=/tmp/log
4701	CROSS_COMPILE=ppc_8xx- MAKEALL
4702
4703With the above settings build objects are saved in the /tmp/build,
4704log files are saved in the /tmp/log and the source tree remains clean
4705during the whole build process.
4706
4707
4708See also "U-Boot Porting Guide" below.
4709
4710
4711Monitor Commands - Overview:
4712============================
4713
4714go	- start application at address 'addr'
4715run	- run commands in an environment variable
4716bootm	- boot application image from memory
4717bootp	- boot image via network using BootP/TFTP protocol
4718bootz   - boot zImage from memory
4719tftpboot- boot image via network using TFTP protocol
4720	       and env variables "ipaddr" and "serverip"
4721	       (and eventually "gatewayip")
4722tftpput - upload a file via network using TFTP protocol
4723rarpboot- boot image via network using RARP/TFTP protocol
4724diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4725loads	- load S-Record file over serial line
4726loadb	- load binary file over serial line (kermit mode)
4727md	- memory display
4728mm	- memory modify (auto-incrementing)
4729nm	- memory modify (constant address)
4730mw	- memory write (fill)
4731cp	- memory copy
4732cmp	- memory compare
4733crc32	- checksum calculation
4734i2c	- I2C sub-system
4735sspi	- SPI utility commands
4736base	- print or set address offset
4737printenv- print environment variables
4738setenv	- set environment variables
4739saveenv - save environment variables to persistent storage
4740protect - enable or disable FLASH write protection
4741erase	- erase FLASH memory
4742flinfo	- print FLASH memory information
4743nand	- NAND memory operations (see doc/README.nand)
4744bdinfo	- print Board Info structure
4745iminfo	- print header information for application image
4746coninfo - print console devices and informations
4747ide	- IDE sub-system
4748loop	- infinite loop on address range
4749loopw	- infinite write loop on address range
4750mtest	- simple RAM test
4751icache	- enable or disable instruction cache
4752dcache	- enable or disable data cache
4753reset	- Perform RESET of the CPU
4754echo	- echo args to console
4755version - print monitor version
4756help	- print online help
4757?	- alias for 'help'
4758
4759
4760Monitor Commands - Detailed Description:
4761========================================
4762
4763TODO.
4764
4765For now: just type "help <command>".
4766
4767
4768Environment Variables:
4769======================
4770
4771U-Boot supports user configuration using Environment Variables which
4772can be made persistent by saving to Flash memory.
4773
4774Environment Variables are set using "setenv", printed using
4775"printenv", and saved to Flash using "saveenv". Using "setenv"
4776without a value can be used to delete a variable from the
4777environment. As long as you don't save the environment you are
4778working with an in-memory copy. In case the Flash area containing the
4779environment is erased by accident, a default environment is provided.
4780
4781Some configuration options can be set using Environment Variables.
4782
4783List of environment variables (most likely not complete):
4784
4785  baudrate	- see CONFIG_BAUDRATE
4786
4787  bootdelay	- see CONFIG_BOOTDELAY
4788
4789  bootcmd	- see CONFIG_BOOTCOMMAND
4790
4791  bootargs	- Boot arguments when booting an RTOS image
4792
4793  bootfile	- Name of the image to load with TFTP
4794
4795  bootm_low	- Memory range available for image processing in the bootm
4796		  command can be restricted. This variable is given as
4797		  a hexadecimal number and defines lowest address allowed
4798		  for use by the bootm command. See also "bootm_size"
4799		  environment variable. Address defined by "bootm_low" is
4800		  also the base of the initial memory mapping for the Linux
4801		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4802		  bootm_mapsize.
4803
4804  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4805		  This variable is given as a hexadecimal number and it
4806		  defines the size of the memory region starting at base
4807		  address bootm_low that is accessible by the Linux kernel
4808		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4809		  as the default value if it is defined, and bootm_size is
4810		  used otherwise.
4811
4812  bootm_size	- Memory range available for image processing in the bootm
4813		  command can be restricted. This variable is given as
4814		  a hexadecimal number and defines the size of the region
4815		  allowed for use by the bootm command. See also "bootm_low"
4816		  environment variable.
4817
4818  updatefile	- Location of the software update file on a TFTP server, used
4819		  by the automatic software update feature. Please refer to
4820		  documentation in doc/README.update for more details.
4821
4822  autoload	- if set to "no" (any string beginning with 'n'),
4823		  "bootp" will just load perform a lookup of the
4824		  configuration from the BOOTP server, but not try to
4825		  load any image using TFTP
4826
4827  autostart	- if set to "yes", an image loaded using the "bootp",
4828		  "rarpboot", "tftpboot" or "diskboot" commands will
4829		  be automatically started (by internally calling
4830		  "bootm")
4831
4832		  If set to "no", a standalone image passed to the
4833		  "bootm" command will be copied to the load address
4834		  (and eventually uncompressed), but NOT be started.
4835		  This can be used to load and uncompress arbitrary
4836		  data.
4837
4838  fdt_high	- if set this restricts the maximum address that the
4839		  flattened device tree will be copied into upon boot.
4840		  For example, if you have a system with 1 GB memory
4841		  at physical address 0x10000000, while Linux kernel
4842		  only recognizes the first 704 MB as low memory, you
4843		  may need to set fdt_high as 0x3C000000 to have the
4844		  device tree blob be copied to the maximum address
4845		  of the 704 MB low memory, so that Linux kernel can
4846		  access it during the boot procedure.
4847
4848		  If this is set to the special value 0xFFFFFFFF then
4849		  the fdt will not be copied at all on boot.  For this
4850		  to work it must reside in writable memory, have
4851		  sufficient padding on the end of it for u-boot to
4852		  add the information it needs into it, and the memory
4853		  must be accessible by the kernel.
4854
4855  fdtcontroladdr- if set this is the address of the control flattened
4856		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4857		  defined.
4858
4859  i2cfast	- (PPC405GP|PPC405EP only)
4860		  if set to 'y' configures Linux I2C driver for fast
4861		  mode (400kHZ). This environment variable is used in
4862		  initialization code. So, for changes to be effective
4863		  it must be saved and board must be reset.
4864
4865  initrd_high	- restrict positioning of initrd images:
4866		  If this variable is not set, initrd images will be
4867		  copied to the highest possible address in RAM; this
4868		  is usually what you want since it allows for
4869		  maximum initrd size. If for some reason you want to
4870		  make sure that the initrd image is loaded below the
4871		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4872		  variable to a value of "no" or "off" or "0".
4873		  Alternatively, you can set it to a maximum upper
4874		  address to use (U-Boot will still check that it
4875		  does not overwrite the U-Boot stack and data).
4876
4877		  For instance, when you have a system with 16 MB
4878		  RAM, and want to reserve 4 MB from use by Linux,
4879		  you can do this by adding "mem=12M" to the value of
4880		  the "bootargs" variable. However, now you must make
4881		  sure that the initrd image is placed in the first
4882		  12 MB as well - this can be done with
4883
4884		  setenv initrd_high 00c00000
4885
4886		  If you set initrd_high to 0xFFFFFFFF, this is an
4887		  indication to U-Boot that all addresses are legal
4888		  for the Linux kernel, including addresses in flash
4889		  memory. In this case U-Boot will NOT COPY the
4890		  ramdisk at all. This may be useful to reduce the
4891		  boot time on your system, but requires that this
4892		  feature is supported by your Linux kernel.
4893
4894  ipaddr	- IP address; needed for tftpboot command
4895
4896  loadaddr	- Default load address for commands like "bootp",
4897		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4898
4899  loads_echo	- see CONFIG_LOADS_ECHO
4900
4901  serverip	- TFTP server IP address; needed for tftpboot command
4902
4903  bootretry	- see CONFIG_BOOT_RETRY_TIME
4904
4905  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4906
4907  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4908
4909  ethprime	- controls which interface is used first.
4910
4911  ethact	- controls which interface is currently active.
4912		  For example you can do the following
4913
4914		  => setenv ethact FEC
4915		  => ping 192.168.0.1 # traffic sent on FEC
4916		  => setenv ethact SCC
4917		  => ping 10.0.0.1 # traffic sent on SCC
4918
4919  ethrotate	- When set to "no" U-Boot does not go through all
4920		  available network interfaces.
4921		  It just stays at the currently selected interface.
4922
4923  netretry	- When set to "no" each network operation will
4924		  either succeed or fail without retrying.
4925		  When set to "once" the network operation will
4926		  fail when all the available network interfaces
4927		  are tried once without success.
4928		  Useful on scripts which control the retry operation
4929		  themselves.
4930
4931  npe_ucode	- set load address for the NPE microcode
4932
4933  silent_linux  - If set then linux will be told to boot silently, by
4934		  changing the console to be empty. If "yes" it will be
4935		  made silent. If "no" it will not be made silent. If
4936		  unset, then it will be made silent if the U-Boot console
4937		  is silent.
4938
4939  tftpsrcport	- If this is set, the value is used for TFTP's
4940		  UDP source port.
4941
4942  tftpdstport	- If this is set, the value is used for TFTP's UDP
4943		  destination port instead of the Well Know Port 69.
4944
4945  tftpblocksize - Block size to use for TFTP transfers; if not set,
4946		  we use the TFTP server's default block size
4947
4948  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4949		  seconds, minimum value is 1000 = 1 second). Defines
4950		  when a packet is considered to be lost so it has to
4951		  be retransmitted. The default is 5000 = 5 seconds.
4952		  Lowering this value may make downloads succeed
4953		  faster in networks with high packet loss rates or
4954		  with unreliable TFTP servers.
4955
4956  vlan		- When set to a value < 4095 the traffic over
4957		  Ethernet is encapsulated/received over 802.1q
4958		  VLAN tagged frames.
4959
4960The following image location variables contain the location of images
4961used in booting. The "Image" column gives the role of the image and is
4962not an environment variable name. The other columns are environment
4963variable names. "File Name" gives the name of the file on a TFTP
4964server, "RAM Address" gives the location in RAM the image will be
4965loaded to, and "Flash Location" gives the image's address in NOR
4966flash or offset in NAND flash.
4967
4968*Note* - these variables don't have to be defined for all boards, some
4969boards currenlty use other variables for these purposes, and some
4970boards use these variables for other purposes.
4971
4972Image		    File Name	     RAM Address       Flash Location
4973-----		    ---------	     -----------       --------------
4974u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4975Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4976device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4977ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4978
4979The following environment variables may be used and automatically
4980updated by the network boot commands ("bootp" and "rarpboot"),
4981depending the information provided by your boot server:
4982
4983  bootfile	- see above
4984  dnsip		- IP address of your Domain Name Server
4985  dnsip2	- IP address of your secondary Domain Name Server
4986  gatewayip	- IP address of the Gateway (Router) to use
4987  hostname	- Target hostname
4988  ipaddr	- see above
4989  netmask	- Subnet Mask
4990  rootpath	- Pathname of the root filesystem on the NFS server
4991  serverip	- see above
4992
4993
4994There are two special Environment Variables:
4995
4996  serial#	- contains hardware identification information such
4997		  as type string and/or serial number
4998  ethaddr	- Ethernet address
4999
5000These variables can be set only once (usually during manufacturing of
5001the board). U-Boot refuses to delete or overwrite these variables
5002once they have been set once.
5003
5004
5005Further special Environment Variables:
5006
5007  ver		- Contains the U-Boot version string as printed
5008		  with the "version" command. This variable is
5009		  readonly (see CONFIG_VERSION_VARIABLE).
5010
5011
5012Please note that changes to some configuration parameters may take
5013only effect after the next boot (yes, that's just like Windoze :-).
5014
5015
5016Callback functions for environment variables:
5017---------------------------------------------
5018
5019For some environment variables, the behavior of u-boot needs to change
5020when their values are changed.  This functionailty allows functions to
5021be associated with arbitrary variables.  On creation, overwrite, or
5022deletion, the callback will provide the opportunity for some side
5023effect to happen or for the change to be rejected.
5024
5025The callbacks are named and associated with a function using the
5026U_BOOT_ENV_CALLBACK macro in your board or driver code.
5027
5028These callbacks are associated with variables in one of two ways.  The
5029static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5030in the board configuration to a string that defines a list of
5031associations.  The list must be in the following format:
5032
5033	entry = variable_name[:callback_name]
5034	list = entry[,list]
5035
5036If the callback name is not specified, then the callback is deleted.
5037Spaces are also allowed anywhere in the list.
5038
5039Callbacks can also be associated by defining the ".callbacks" variable
5040with the same list format above.  Any association in ".callbacks" will
5041override any association in the static list. You can define
5042CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5043".callbacks" envirnoment variable in the default or embedded environment.
5044
5045
5046Command Line Parsing:
5047=====================
5048
5049There are two different command line parsers available with U-Boot:
5050the old "simple" one, and the much more powerful "hush" shell:
5051
5052Old, simple command line parser:
5053--------------------------------
5054
5055- supports environment variables (through setenv / saveenv commands)
5056- several commands on one line, separated by ';'
5057- variable substitution using "... ${name} ..." syntax
5058- special characters ('$', ';') can be escaped by prefixing with '\',
5059  for example:
5060	setenv bootcmd bootm \${address}
5061- You can also escape text by enclosing in single apostrophes, for example:
5062	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5063
5064Hush shell:
5065-----------
5066
5067- similar to Bourne shell, with control structures like
5068  if...then...else...fi, for...do...done; while...do...done,
5069  until...do...done, ...
5070- supports environment ("global") variables (through setenv / saveenv
5071  commands) and local shell variables (through standard shell syntax
5072  "name=value"); only environment variables can be used with "run"
5073  command
5074
5075General rules:
5076--------------
5077
5078(1) If a command line (or an environment variable executed by a "run"
5079    command) contains several commands separated by semicolon, and
5080    one of these commands fails, then the remaining commands will be
5081    executed anyway.
5082
5083(2) If you execute several variables with one call to run (i. e.
5084    calling run with a list of variables as arguments), any failing
5085    command will cause "run" to terminate, i. e. the remaining
5086    variables are not executed.
5087
5088Note for Redundant Ethernet Interfaces:
5089=======================================
5090
5091Some boards come with redundant Ethernet interfaces; U-Boot supports
5092such configurations and is capable of automatic selection of a
5093"working" interface when needed. MAC assignment works as follows:
5094
5095Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5096MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5097"eth1addr" (=>eth1), "eth2addr", ...
5098
5099If the network interface stores some valid MAC address (for instance
5100in SROM), this is used as default address if there is NO correspon-
5101ding setting in the environment; if the corresponding environment
5102variable is set, this overrides the settings in the card; that means:
5103
5104o If the SROM has a valid MAC address, and there is no address in the
5105  environment, the SROM's address is used.
5106
5107o If there is no valid address in the SROM, and a definition in the
5108  environment exists, then the value from the environment variable is
5109  used.
5110
5111o If both the SROM and the environment contain a MAC address, and
5112  both addresses are the same, this MAC address is used.
5113
5114o If both the SROM and the environment contain a MAC address, and the
5115  addresses differ, the value from the environment is used and a
5116  warning is printed.
5117
5118o If neither SROM nor the environment contain a MAC address, an error
5119  is raised.
5120
5121If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5122will be programmed into hardware as part of the initialization process.	 This
5123may be skipped by setting the appropriate 'ethmacskip' environment variable.
5124The naming convention is as follows:
5125"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5126
5127Image Formats:
5128==============
5129
5130U-Boot is capable of booting (and performing other auxiliary operations on)
5131images in two formats:
5132
5133New uImage format (FIT)
5134-----------------------
5135
5136Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5137to Flattened Device Tree). It allows the use of images with multiple
5138components (several kernels, ramdisks, etc.), with contents protected by
5139SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5140
5141
5142Old uImage format
5143-----------------
5144
5145Old image format is based on binary files which can be basically anything,
5146preceded by a special header; see the definitions in include/image.h for
5147details; basically, the header defines the following image properties:
5148
5149* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5150  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5151  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5152  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5153  INTEGRITY).
5154* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5155  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5156  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5157* Compression Type (uncompressed, gzip, bzip2)
5158* Load Address
5159* Entry Point
5160* Image Name
5161* Image Timestamp
5162
5163The header is marked by a special Magic Number, and both the header
5164and the data portions of the image are secured against corruption by
5165CRC32 checksums.
5166
5167
5168Linux Support:
5169==============
5170
5171Although U-Boot should support any OS or standalone application
5172easily, the main focus has always been on Linux during the design of
5173U-Boot.
5174
5175U-Boot includes many features that so far have been part of some
5176special "boot loader" code within the Linux kernel. Also, any
5177"initrd" images to be used are no longer part of one big Linux image;
5178instead, kernel and "initrd" are separate images. This implementation
5179serves several purposes:
5180
5181- the same features can be used for other OS or standalone
5182  applications (for instance: using compressed images to reduce the
5183  Flash memory footprint)
5184
5185- it becomes much easier to port new Linux kernel versions because
5186  lots of low-level, hardware dependent stuff are done by U-Boot
5187
5188- the same Linux kernel image can now be used with different "initrd"
5189  images; of course this also means that different kernel images can
5190  be run with the same "initrd". This makes testing easier (you don't
5191  have to build a new "zImage.initrd" Linux image when you just
5192  change a file in your "initrd"). Also, a field-upgrade of the
5193  software is easier now.
5194
5195
5196Linux HOWTO:
5197============
5198
5199Porting Linux to U-Boot based systems:
5200---------------------------------------
5201
5202U-Boot cannot save you from doing all the necessary modifications to
5203configure the Linux device drivers for use with your target hardware
5204(no, we don't intend to provide a full virtual machine interface to
5205Linux :-).
5206
5207But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5208
5209Just make sure your machine specific header file (for instance
5210include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5211Information structure as we define in include/asm-<arch>/u-boot.h,
5212and make sure that your definition of IMAP_ADDR uses the same value
5213as your U-Boot configuration in CONFIG_SYS_IMMR.
5214
5215
5216Configuring the Linux kernel:
5217-----------------------------
5218
5219No specific requirements for U-Boot. Make sure you have some root
5220device (initial ramdisk, NFS) for your target system.
5221
5222
5223Building a Linux Image:
5224-----------------------
5225
5226With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5227not used. If you use recent kernel source, a new build target
5228"uImage" will exist which automatically builds an image usable by
5229U-Boot. Most older kernels also have support for a "pImage" target,
5230which was introduced for our predecessor project PPCBoot and uses a
5231100% compatible format.
5232
5233Example:
5234
5235	make TQM850L_config
5236	make oldconfig
5237	make dep
5238	make uImage
5239
5240The "uImage" build target uses a special tool (in 'tools/mkimage') to
5241encapsulate a compressed Linux kernel image with header	 information,
5242CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5243
5244* build a standard "vmlinux" kernel image (in ELF binary format):
5245
5246* convert the kernel into a raw binary image:
5247
5248	${CROSS_COMPILE}-objcopy -O binary \
5249				 -R .note -R .comment \
5250				 -S vmlinux linux.bin
5251
5252* compress the binary image:
5253
5254	gzip -9 linux.bin
5255
5256* package compressed binary image for U-Boot:
5257
5258	mkimage -A ppc -O linux -T kernel -C gzip \
5259		-a 0 -e 0 -n "Linux Kernel Image" \
5260		-d linux.bin.gz uImage
5261
5262
5263The "mkimage" tool can also be used to create ramdisk images for use
5264with U-Boot, either separated from the Linux kernel image, or
5265combined into one file. "mkimage" encapsulates the images with a 64
5266byte header containing information about target architecture,
5267operating system, image type, compression method, entry points, time
5268stamp, CRC32 checksums, etc.
5269
5270"mkimage" can be called in two ways: to verify existing images and
5271print the header information, or to build new images.
5272
5273In the first form (with "-l" option) mkimage lists the information
5274contained in the header of an existing U-Boot image; this includes
5275checksum verification:
5276
5277	tools/mkimage -l image
5278	  -l ==> list image header information
5279
5280The second form (with "-d" option) is used to build a U-Boot image
5281from a "data file" which is used as image payload:
5282
5283	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5284		      -n name -d data_file image
5285	  -A ==> set architecture to 'arch'
5286	  -O ==> set operating system to 'os'
5287	  -T ==> set image type to 'type'
5288	  -C ==> set compression type 'comp'
5289	  -a ==> set load address to 'addr' (hex)
5290	  -e ==> set entry point to 'ep' (hex)
5291	  -n ==> set image name to 'name'
5292	  -d ==> use image data from 'datafile'
5293
5294Right now, all Linux kernels for PowerPC systems use the same load
5295address (0x00000000), but the entry point address depends on the
5296kernel version:
5297
5298- 2.2.x kernels have the entry point at 0x0000000C,
5299- 2.3.x and later kernels have the entry point at 0x00000000.
5300
5301So a typical call to build a U-Boot image would read:
5302
5303	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5304	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5305	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5306	> examples/uImage.TQM850L
5307	Image Name:   2.4.4 kernel for TQM850L
5308	Created:      Wed Jul 19 02:34:59 2000
5309	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5310	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5311	Load Address: 0x00000000
5312	Entry Point:  0x00000000
5313
5314To verify the contents of the image (or check for corruption):
5315
5316	-> tools/mkimage -l examples/uImage.TQM850L
5317	Image Name:   2.4.4 kernel for TQM850L
5318	Created:      Wed Jul 19 02:34:59 2000
5319	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5320	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5321	Load Address: 0x00000000
5322	Entry Point:  0x00000000
5323
5324NOTE: for embedded systems where boot time is critical you can trade
5325speed for memory and install an UNCOMPRESSED image instead: this
5326needs more space in Flash, but boots much faster since it does not
5327need to be uncompressed:
5328
5329	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5330	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5331	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5332	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5333	> examples/uImage.TQM850L-uncompressed
5334	Image Name:   2.4.4 kernel for TQM850L
5335	Created:      Wed Jul 19 02:34:59 2000
5336	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5337	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5338	Load Address: 0x00000000
5339	Entry Point:  0x00000000
5340
5341
5342Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5343when your kernel is intended to use an initial ramdisk:
5344
5345	-> tools/mkimage -n 'Simple Ramdisk Image' \
5346	> -A ppc -O linux -T ramdisk -C gzip \
5347	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5348	Image Name:   Simple Ramdisk Image
5349	Created:      Wed Jan 12 14:01:50 2000
5350	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5351	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5352	Load Address: 0x00000000
5353	Entry Point:  0x00000000
5354
5355The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5356option performs the converse operation of the mkimage's second form (the "-d"
5357option). Given an image built by mkimage, the dumpimage extracts a "data file"
5358from the image:
5359
5360	tools/dumpimage -i image -p position data_file
5361	  -i ==> extract from the 'image' a specific 'data_file', \
5362	   indexed by 'position'
5363
5364
5365Installing a Linux Image:
5366-------------------------
5367
5368To downloading a U-Boot image over the serial (console) interface,
5369you must convert the image to S-Record format:
5370
5371	objcopy -I binary -O srec examples/image examples/image.srec
5372
5373The 'objcopy' does not understand the information in the U-Boot
5374image header, so the resulting S-Record file will be relative to
5375address 0x00000000. To load it to a given address, you need to
5376specify the target address as 'offset' parameter with the 'loads'
5377command.
5378
5379Example: install the image to address 0x40100000 (which on the
5380TQM8xxL is in the first Flash bank):
5381
5382	=> erase 40100000 401FFFFF
5383
5384	.......... done
5385	Erased 8 sectors
5386
5387	=> loads 40100000
5388	## Ready for S-Record download ...
5389	~>examples/image.srec
5390	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5391	...
5392	15989 15990 15991 15992
5393	[file transfer complete]
5394	[connected]
5395	## Start Addr = 0x00000000
5396
5397
5398You can check the success of the download using the 'iminfo' command;
5399this includes a checksum verification so you can be sure no data
5400corruption happened:
5401
5402	=> imi 40100000
5403
5404	## Checking Image at 40100000 ...
5405	   Image Name:	 2.2.13 for initrd on TQM850L
5406	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5407	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5408	   Load Address: 00000000
5409	   Entry Point:	 0000000c
5410	   Verifying Checksum ... OK
5411
5412
5413Boot Linux:
5414-----------
5415
5416The "bootm" command is used to boot an application that is stored in
5417memory (RAM or Flash). In case of a Linux kernel image, the contents
5418of the "bootargs" environment variable is passed to the kernel as
5419parameters. You can check and modify this variable using the
5420"printenv" and "setenv" commands:
5421
5422
5423	=> printenv bootargs
5424	bootargs=root=/dev/ram
5425
5426	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5427
5428	=> printenv bootargs
5429	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5430
5431	=> bootm 40020000
5432	## Booting Linux kernel at 40020000 ...
5433	   Image Name:	 2.2.13 for NFS on TQM850L
5434	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5435	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5436	   Load Address: 00000000
5437	   Entry Point:	 0000000c
5438	   Verifying Checksum ... OK
5439	   Uncompressing Kernel Image ... OK
5440	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
5441	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5442	time_init: decrementer frequency = 187500000/60
5443	Calibrating delay loop... 49.77 BogoMIPS
5444	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5445	...
5446
5447If you want to boot a Linux kernel with initial RAM disk, you pass
5448the memory addresses of both the kernel and the initrd image (PPBCOOT
5449format!) to the "bootm" command:
5450
5451	=> imi 40100000 40200000
5452
5453	## Checking Image at 40100000 ...
5454	   Image Name:	 2.2.13 for initrd on TQM850L
5455	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5456	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5457	   Load Address: 00000000
5458	   Entry Point:	 0000000c
5459	   Verifying Checksum ... OK
5460
5461	## Checking Image at 40200000 ...
5462	   Image Name:	 Simple Ramdisk Image
5463	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5464	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5465	   Load Address: 00000000
5466	   Entry Point:	 00000000
5467	   Verifying Checksum ... OK
5468
5469	=> bootm 40100000 40200000
5470	## Booting Linux kernel at 40100000 ...
5471	   Image Name:	 2.2.13 for initrd on TQM850L
5472	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5473	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5474	   Load Address: 00000000
5475	   Entry Point:	 0000000c
5476	   Verifying Checksum ... OK
5477	   Uncompressing Kernel Image ... OK
5478	## Loading RAMDisk Image at 40200000 ...
5479	   Image Name:	 Simple Ramdisk Image
5480	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5481	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5482	   Load Address: 00000000
5483	   Entry Point:	 00000000
5484	   Verifying Checksum ... OK
5485	   Loading Ramdisk ... OK
5486	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
5487	Boot arguments: root=/dev/ram
5488	time_init: decrementer frequency = 187500000/60
5489	Calibrating delay loop... 49.77 BogoMIPS
5490	...
5491	RAMDISK: Compressed image found at block 0
5492	VFS: Mounted root (ext2 filesystem).
5493
5494	bash#
5495
5496Boot Linux and pass a flat device tree:
5497-----------
5498
5499First, U-Boot must be compiled with the appropriate defines. See the section
5500titled "Linux Kernel Interface" above for a more in depth explanation. The
5501following is an example of how to start a kernel and pass an updated
5502flat device tree:
5503
5504=> print oftaddr
5505oftaddr=0x300000
5506=> print oft
5507oft=oftrees/mpc8540ads.dtb
5508=> tftp $oftaddr $oft
5509Speed: 1000, full duplex
5510Using TSEC0 device
5511TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5512Filename 'oftrees/mpc8540ads.dtb'.
5513Load address: 0x300000
5514Loading: #
5515done
5516Bytes transferred = 4106 (100a hex)
5517=> tftp $loadaddr $bootfile
5518Speed: 1000, full duplex
5519Using TSEC0 device
5520TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5521Filename 'uImage'.
5522Load address: 0x200000
5523Loading:############
5524done
5525Bytes transferred = 1029407 (fb51f hex)
5526=> print loadaddr
5527loadaddr=200000
5528=> print oftaddr
5529oftaddr=0x300000
5530=> bootm $loadaddr - $oftaddr
5531## Booting image at 00200000 ...
5532   Image Name:	 Linux-2.6.17-dirty
5533   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5534   Data Size:	 1029343 Bytes = 1005.2 kB
5535   Load Address: 00000000
5536   Entry Point:	 00000000
5537   Verifying Checksum ... OK
5538   Uncompressing Kernel Image ... OK
5539Booting using flat device tree at 0x300000
5540Using MPC85xx ADS machine description
5541Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5542[snip]
5543
5544
5545More About U-Boot Image Types:
5546------------------------------
5547
5548U-Boot supports the following image types:
5549
5550   "Standalone Programs" are directly runnable in the environment
5551	provided by U-Boot; it is expected that (if they behave
5552	well) you can continue to work in U-Boot after return from
5553	the Standalone Program.
5554   "OS Kernel Images" are usually images of some Embedded OS which
5555	will take over control completely. Usually these programs
5556	will install their own set of exception handlers, device
5557	drivers, set up the MMU, etc. - this means, that you cannot
5558	expect to re-enter U-Boot except by resetting the CPU.
5559   "RAMDisk Images" are more or less just data blocks, and their
5560	parameters (address, size) are passed to an OS kernel that is
5561	being started.
5562   "Multi-File Images" contain several images, typically an OS
5563	(Linux) kernel image and one or more data images like
5564	RAMDisks. This construct is useful for instance when you want
5565	to boot over the network using BOOTP etc., where the boot
5566	server provides just a single image file, but you want to get
5567	for instance an OS kernel and a RAMDisk image.
5568
5569	"Multi-File Images" start with a list of image sizes, each
5570	image size (in bytes) specified by an "uint32_t" in network
5571	byte order. This list is terminated by an "(uint32_t)0".
5572	Immediately after the terminating 0 follow the images, one by
5573	one, all aligned on "uint32_t" boundaries (size rounded up to
5574	a multiple of 4 bytes).
5575
5576   "Firmware Images" are binary images containing firmware (like
5577	U-Boot or FPGA images) which usually will be programmed to
5578	flash memory.
5579
5580   "Script files" are command sequences that will be executed by
5581	U-Boot's command interpreter; this feature is especially
5582	useful when you configure U-Boot to use a real shell (hush)
5583	as command interpreter.
5584
5585Booting the Linux zImage:
5586-------------------------
5587
5588On some platforms, it's possible to boot Linux zImage. This is done
5589using the "bootz" command. The syntax of "bootz" command is the same
5590as the syntax of "bootm" command.
5591
5592Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5593kernel with raw initrd images. The syntax is slightly different, the
5594address of the initrd must be augmented by it's size, in the following
5595format: "<initrd addres>:<initrd size>".
5596
5597
5598Standalone HOWTO:
5599=================
5600
5601One of the features of U-Boot is that you can dynamically load and
5602run "standalone" applications, which can use some resources of
5603U-Boot like console I/O functions or interrupt services.
5604
5605Two simple examples are included with the sources:
5606
5607"Hello World" Demo:
5608-------------------
5609
5610'examples/hello_world.c' contains a small "Hello World" Demo
5611application; it is automatically compiled when you build U-Boot.
5612It's configured to run at address 0x00040004, so you can play with it
5613like that:
5614
5615	=> loads
5616	## Ready for S-Record download ...
5617	~>examples/hello_world.srec
5618	1 2 3 4 5 6 7 8 9 10 11 ...
5619	[file transfer complete]
5620	[connected]
5621	## Start Addr = 0x00040004
5622
5623	=> go 40004 Hello World! This is a test.
5624	## Starting application at 0x00040004 ...
5625	Hello World
5626	argc = 7
5627	argv[0] = "40004"
5628	argv[1] = "Hello"
5629	argv[2] = "World!"
5630	argv[3] = "This"
5631	argv[4] = "is"
5632	argv[5] = "a"
5633	argv[6] = "test."
5634	argv[7] = "<NULL>"
5635	Hit any key to exit ...
5636
5637	## Application terminated, rc = 0x0
5638
5639Another example, which demonstrates how to register a CPM interrupt
5640handler with the U-Boot code, can be found in 'examples/timer.c'.
5641Here, a CPM timer is set up to generate an interrupt every second.
5642The interrupt service routine is trivial, just printing a '.'
5643character, but this is just a demo program. The application can be
5644controlled by the following keys:
5645
5646	? - print current values og the CPM Timer registers
5647	b - enable interrupts and start timer
5648	e - stop timer and disable interrupts
5649	q - quit application
5650
5651	=> loads
5652	## Ready for S-Record download ...
5653	~>examples/timer.srec
5654	1 2 3 4 5 6 7 8 9 10 11 ...
5655	[file transfer complete]
5656	[connected]
5657	## Start Addr = 0x00040004
5658
5659	=> go 40004
5660	## Starting application at 0x00040004 ...
5661	TIMERS=0xfff00980
5662	Using timer 1
5663	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5664
5665Hit 'b':
5666	[q, b, e, ?] Set interval 1000000 us
5667	Enabling timer
5668Hit '?':
5669	[q, b, e, ?] ........
5670	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5671Hit '?':
5672	[q, b, e, ?] .
5673	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5674Hit '?':
5675	[q, b, e, ?] .
5676	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5677Hit '?':
5678	[q, b, e, ?] .
5679	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5680Hit 'e':
5681	[q, b, e, ?] ...Stopping timer
5682Hit 'q':
5683	[q, b, e, ?] ## Application terminated, rc = 0x0
5684
5685
5686Minicom warning:
5687================
5688
5689Over time, many people have reported problems when trying to use the
5690"minicom" terminal emulation program for serial download. I (wd)
5691consider minicom to be broken, and recommend not to use it. Under
5692Unix, I recommend to use C-Kermit for general purpose use (and
5693especially for kermit binary protocol download ("loadb" command), and
5694use "cu" for S-Record download ("loads" command).  See
5695http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5696for help with kermit.
5697
5698
5699Nevertheless, if you absolutely want to use it try adding this
5700configuration to your "File transfer protocols" section:
5701
5702	   Name	   Program			Name U/D FullScr IO-Red. Multi
5703	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5704	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5705
5706
5707NetBSD Notes:
5708=============
5709
5710Starting at version 0.9.2, U-Boot supports NetBSD both as host
5711(build U-Boot) and target system (boots NetBSD/mpc8xx).
5712
5713Building requires a cross environment; it is known to work on
5714NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5715need gmake since the Makefiles are not compatible with BSD make).
5716Note that the cross-powerpc package does not install include files;
5717attempting to build U-Boot will fail because <machine/ansi.h> is
5718missing.  This file has to be installed and patched manually:
5719
5720	# cd /usr/pkg/cross/powerpc-netbsd/include
5721	# mkdir powerpc
5722	# ln -s powerpc machine
5723	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5724	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5725
5726Native builds *don't* work due to incompatibilities between native
5727and U-Boot include files.
5728
5729Booting assumes that (the first part of) the image booted is a
5730stage-2 loader which in turn loads and then invokes the kernel
5731proper. Loader sources will eventually appear in the NetBSD source
5732tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5733meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5734
5735
5736Implementation Internals:
5737=========================
5738
5739The following is not intended to be a complete description of every
5740implementation detail. However, it should help to understand the
5741inner workings of U-Boot and make it easier to port it to custom
5742hardware.
5743
5744
5745Initial Stack, Global Data:
5746---------------------------
5747
5748The implementation of U-Boot is complicated by the fact that U-Boot
5749starts running out of ROM (flash memory), usually without access to
5750system RAM (because the memory controller is not initialized yet).
5751This means that we don't have writable Data or BSS segments, and BSS
5752is not initialized as zero. To be able to get a C environment working
5753at all, we have to allocate at least a minimal stack. Implementation
5754options for this are defined and restricted by the CPU used: Some CPU
5755models provide on-chip memory (like the IMMR area on MPC8xx and
5756MPC826x processors), on others (parts of) the data cache can be
5757locked as (mis-) used as memory, etc.
5758
5759	Chris Hallinan posted a good summary of these issues to the
5760	U-Boot mailing list:
5761
5762	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5763	From: "Chris Hallinan" <clh@net1plus.com>
5764	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5765	...
5766
5767	Correct me if I'm wrong, folks, but the way I understand it
5768	is this: Using DCACHE as initial RAM for Stack, etc, does not
5769	require any physical RAM backing up the cache. The cleverness
5770	is that the cache is being used as a temporary supply of
5771	necessary storage before the SDRAM controller is setup. It's
5772	beyond the scope of this list to explain the details, but you
5773	can see how this works by studying the cache architecture and
5774	operation in the architecture and processor-specific manuals.
5775
5776	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5777	is another option for the system designer to use as an
5778	initial stack/RAM area prior to SDRAM being available. Either
5779	option should work for you. Using CS 4 should be fine if your
5780	board designers haven't used it for something that would
5781	cause you grief during the initial boot! It is frequently not
5782	used.
5783
5784	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5785	with your processor/board/system design. The default value
5786	you will find in any recent u-boot distribution in
5787	walnut.h should work for you. I'd set it to a value larger
5788	than your SDRAM module. If you have a 64MB SDRAM module, set
5789	it above 400_0000. Just make sure your board has no resources
5790	that are supposed to respond to that address! That code in
5791	start.S has been around a while and should work as is when
5792	you get the config right.
5793
5794	-Chris Hallinan
5795	DS4.COM, Inc.
5796
5797It is essential to remember this, since it has some impact on the C
5798code for the initialization procedures:
5799
5800* Initialized global data (data segment) is read-only. Do not attempt
5801  to write it.
5802
5803* Do not use any uninitialized global data (or implicitely initialized
5804  as zero data - BSS segment) at all - this is undefined, initiali-
5805  zation is performed later (when relocating to RAM).
5806
5807* Stack space is very limited. Avoid big data buffers or things like
5808  that.
5809
5810Having only the stack as writable memory limits means we cannot use
5811normal global data to share information beween the code. But it
5812turned out that the implementation of U-Boot can be greatly
5813simplified by making a global data structure (gd_t) available to all
5814functions. We could pass a pointer to this data as argument to _all_
5815functions, but this would bloat the code. Instead we use a feature of
5816the GCC compiler (Global Register Variables) to share the data: we
5817place a pointer (gd) to the global data into a register which we
5818reserve for this purpose.
5819
5820When choosing a register for such a purpose we are restricted by the
5821relevant  (E)ABI  specifications for the current architecture, and by
5822GCC's implementation.
5823
5824For PowerPC, the following registers have specific use:
5825	R1:	stack pointer
5826	R2:	reserved for system use
5827	R3-R4:	parameter passing and return values
5828	R5-R10: parameter passing
5829	R13:	small data area pointer
5830	R30:	GOT pointer
5831	R31:	frame pointer
5832
5833	(U-Boot also uses R12 as internal GOT pointer. r12
5834	is a volatile register so r12 needs to be reset when
5835	going back and forth between asm and C)
5836
5837    ==> U-Boot will use R2 to hold a pointer to the global data
5838
5839    Note: on PPC, we could use a static initializer (since the
5840    address of the global data structure is known at compile time),
5841    but it turned out that reserving a register results in somewhat
5842    smaller code - although the code savings are not that big (on
5843    average for all boards 752 bytes for the whole U-Boot image,
5844    624 text + 127 data).
5845
5846On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5847	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5848
5849    ==> U-Boot will use P3 to hold a pointer to the global data
5850
5851On ARM, the following registers are used:
5852
5853	R0:	function argument word/integer result
5854	R1-R3:	function argument word
5855	R9:	platform specific
5856	R10:	stack limit (used only if stack checking is enabled)
5857	R11:	argument (frame) pointer
5858	R12:	temporary workspace
5859	R13:	stack pointer
5860	R14:	link register
5861	R15:	program counter
5862
5863    ==> U-Boot will use R9 to hold a pointer to the global data
5864
5865    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5866
5867On Nios II, the ABI is documented here:
5868	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5869
5870    ==> U-Boot will use gp to hold a pointer to the global data
5871
5872    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5873    to access small data sections, so gp is free.
5874
5875On NDS32, the following registers are used:
5876
5877	R0-R1:	argument/return
5878	R2-R5:	argument
5879	R15:	temporary register for assembler
5880	R16:	trampoline register
5881	R28:	frame pointer (FP)
5882	R29:	global pointer (GP)
5883	R30:	link register (LP)
5884	R31:	stack pointer (SP)
5885	PC:	program counter (PC)
5886
5887    ==> U-Boot will use R10 to hold a pointer to the global data
5888
5889NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5890or current versions of GCC may "optimize" the code too much.
5891
5892Memory Management:
5893------------------
5894
5895U-Boot runs in system state and uses physical addresses, i.e. the
5896MMU is not used either for address mapping nor for memory protection.
5897
5898The available memory is mapped to fixed addresses using the memory
5899controller. In this process, a contiguous block is formed for each
5900memory type (Flash, SDRAM, SRAM), even when it consists of several
5901physical memory banks.
5902
5903U-Boot is installed in the first 128 kB of the first Flash bank (on
5904TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5905booting and sizing and initializing DRAM, the code relocates itself
5906to the upper end of DRAM. Immediately below the U-Boot code some
5907memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5908configuration setting]. Below that, a structure with global Board
5909Info data is placed, followed by the stack (growing downward).
5910
5911Additionally, some exception handler code is copied to the low 8 kB
5912of DRAM (0x00000000 ... 0x00001FFF).
5913
5914So a typical memory configuration with 16 MB of DRAM could look like
5915this:
5916
5917	0x0000 0000	Exception Vector code
5918	      :
5919	0x0000 1FFF
5920	0x0000 2000	Free for Application Use
5921	      :
5922	      :
5923
5924	      :
5925	      :
5926	0x00FB FF20	Monitor Stack (Growing downward)
5927	0x00FB FFAC	Board Info Data and permanent copy of global data
5928	0x00FC 0000	Malloc Arena
5929	      :
5930	0x00FD FFFF
5931	0x00FE 0000	RAM Copy of Monitor Code
5932	...		eventually: LCD or video framebuffer
5933	...		eventually: pRAM (Protected RAM - unchanged by reset)
5934	0x00FF FFFF	[End of RAM]
5935
5936
5937System Initialization:
5938----------------------
5939
5940In the reset configuration, U-Boot starts at the reset entry point
5941(on most PowerPC systems at address 0x00000100). Because of the reset
5942configuration for CS0# this is a mirror of the onboard Flash memory.
5943To be able to re-map memory U-Boot then jumps to its link address.
5944To be able to implement the initialization code in C, a (small!)
5945initial stack is set up in the internal Dual Ported RAM (in case CPUs
5946which provide such a feature like MPC8xx or MPC8260), or in a locked
5947part of the data cache. After that, U-Boot initializes the CPU core,
5948the caches and the SIU.
5949
5950Next, all (potentially) available memory banks are mapped using a
5951preliminary mapping. For example, we put them on 512 MB boundaries
5952(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5953on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5954programmed for SDRAM access. Using the temporary configuration, a
5955simple memory test is run that determines the size of the SDRAM
5956banks.
5957
5958When there is more than one SDRAM bank, and the banks are of
5959different size, the largest is mapped first. For equal size, the first
5960bank (CS2#) is mapped first. The first mapping is always for address
59610x00000000, with any additional banks following immediately to create
5962contiguous memory starting from 0.
5963
5964Then, the monitor installs itself at the upper end of the SDRAM area
5965and allocates memory for use by malloc() and for the global Board
5966Info data; also, the exception vector code is copied to the low RAM
5967pages, and the final stack is set up.
5968
5969Only after this relocation will you have a "normal" C environment;
5970until that you are restricted in several ways, mostly because you are
5971running from ROM, and because the code will have to be relocated to a
5972new address in RAM.
5973
5974
5975U-Boot Porting Guide:
5976----------------------
5977
5978[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5979list, October 2002]
5980
5981
5982int main(int argc, char *argv[])
5983{
5984	sighandler_t no_more_time;
5985
5986	signal(SIGALRM, no_more_time);
5987	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5988
5989	if (available_money > available_manpower) {
5990		Pay consultant to port U-Boot;
5991		return 0;
5992	}
5993
5994	Download latest U-Boot source;
5995
5996	Subscribe to u-boot mailing list;
5997
5998	if (clueless)
5999		email("Hi, I am new to U-Boot, how do I get started?");
6000
6001	while (learning) {
6002		Read the README file in the top level directory;
6003		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6004		Read applicable doc/*.README;
6005		Read the source, Luke;
6006		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6007	}
6008
6009	if (available_money > toLocalCurrency ($2500))
6010		Buy a BDI3000;
6011	else
6012		Add a lot of aggravation and time;
6013
6014	if (a similar board exists) {	/* hopefully... */
6015		cp -a board/<similar> board/<myboard>
6016		cp include/configs/<similar>.h include/configs/<myboard>.h
6017	} else {
6018		Create your own board support subdirectory;
6019		Create your own board include/configs/<myboard>.h file;
6020	}
6021	Edit new board/<myboard> files
6022	Edit new include/configs/<myboard>.h
6023
6024	while (!accepted) {
6025		while (!running) {
6026			do {
6027				Add / modify source code;
6028			} until (compiles);
6029			Debug;
6030			if (clueless)
6031				email("Hi, I am having problems...");
6032		}
6033		Send patch file to the U-Boot email list;
6034		if (reasonable critiques)
6035			Incorporate improvements from email list code review;
6036		else
6037			Defend code as written;
6038	}
6039
6040	return 0;
6041}
6042
6043void no_more_time (int sig)
6044{
6045      hire_a_guru();
6046}
6047
6048
6049Coding Standards:
6050-----------------
6051
6052All contributions to U-Boot should conform to the Linux kernel
6053coding style; see the file "Documentation/CodingStyle" and the script
6054"scripts/Lindent" in your Linux kernel source directory.
6055
6056Source files originating from a different project (for example the
6057MTD subsystem) are generally exempt from these guidelines and are not
6058reformated to ease subsequent migration to newer versions of those
6059sources.
6060
6061Please note that U-Boot is implemented in C (and to some small parts in
6062Assembler); no C++ is used, so please do not use C++ style comments (//)
6063in your code.
6064
6065Please also stick to the following formatting rules:
6066- remove any trailing white space
6067- use TAB characters for indentation and vertical alignment, not spaces
6068- make sure NOT to use DOS '\r\n' line feeds
6069- do not add more than 2 consecutive empty lines to source files
6070- do not add trailing empty lines to source files
6071
6072Submissions which do not conform to the standards may be returned
6073with a request to reformat the changes.
6074
6075
6076Submitting Patches:
6077-------------------
6078
6079Since the number of patches for U-Boot is growing, we need to
6080establish some rules. Submissions which do not conform to these rules
6081may be rejected, even when they contain important and valuable stuff.
6082
6083Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6084
6085Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6086see http://lists.denx.de/mailman/listinfo/u-boot
6087
6088When you send a patch, please include the following information with
6089it:
6090
6091* For bug fixes: a description of the bug and how your patch fixes
6092  this bug. Please try to include a way of demonstrating that the
6093  patch actually fixes something.
6094
6095* For new features: a description of the feature and your
6096  implementation.
6097
6098* A CHANGELOG entry as plaintext (separate from the patch)
6099
6100* For major contributions, your entry to the CREDITS file
6101
6102* When you add support for a new board, don't forget to add a
6103  maintainer e-mail address to the boards.cfg file, too.
6104
6105* If your patch adds new configuration options, don't forget to
6106  document these in the README file.
6107
6108* The patch itself. If you are using git (which is *strongly*
6109  recommended) you can easily generate the patch using the
6110  "git format-patch". If you then use "git send-email" to send it to
6111  the U-Boot mailing list, you will avoid most of the common problems
6112  with some other mail clients.
6113
6114  If you cannot use git, use "diff -purN OLD NEW". If your version of
6115  diff does not support these options, then get the latest version of
6116  GNU diff.
6117
6118  The current directory when running this command shall be the parent
6119  directory of the U-Boot source tree (i. e. please make sure that
6120  your patch includes sufficient directory information for the
6121  affected files).
6122
6123  We prefer patches as plain text. MIME attachments are discouraged,
6124  and compressed attachments must not be used.
6125
6126* If one logical set of modifications affects or creates several
6127  files, all these changes shall be submitted in a SINGLE patch file.
6128
6129* Changesets that contain different, unrelated modifications shall be
6130  submitted as SEPARATE patches, one patch per changeset.
6131
6132
6133Notes:
6134
6135* Before sending the patch, run the MAKEALL script on your patched
6136  source tree and make sure that no errors or warnings are reported
6137  for any of the boards.
6138
6139* Keep your modifications to the necessary minimum: A patch
6140  containing several unrelated changes or arbitrary reformats will be
6141  returned with a request to re-formatting / split it.
6142
6143* If you modify existing code, make sure that your new code does not
6144  add to the memory footprint of the code ;-) Small is beautiful!
6145  When adding new features, these should compile conditionally only
6146  (using #ifdef), and the resulting code with the new feature
6147  disabled must not need more memory than the old code without your
6148  modification.
6149
6150* Remember that there is a size limit of 100 kB per message on the
6151  u-boot mailing list. Bigger patches will be moderated. If they are
6152  reasonable and not too big, they will be acknowledged. But patches
6153  bigger than the size limit should be avoided.
6154