xref: /openbmc/u-boot/README (revision 34e026f9b1eb3bcffb38e7787c2e6eac0e88ba85)
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- Generic CPU options:
435		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
436
437		Defines the endianess of the CPU. Implementation of those
438		values is arch specific.
439
440		CONFIG_SYS_FSL_DDR
441		Freescale DDR driver in use. This type of DDR controller is
442		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
443		SoCs.
444
445		CONFIG_SYS_FSL_DDR_ADDR
446		Freescale DDR memory-mapped register base.
447
448		CONFIG_SYS_FSL_DDR_EMU
449		Specify emulator support for DDR. Some DDR features such as
450		deskew training are not available.
451
452		CONFIG_SYS_FSL_DDRC_GEN1
453		Freescale DDR1 controller.
454
455		CONFIG_SYS_FSL_DDRC_GEN2
456		Freescale DDR2 controller.
457
458		CONFIG_SYS_FSL_DDRC_GEN3
459		Freescale DDR3 controller.
460
461		CONFIG_SYS_FSL_DDRC_GEN4
462		Freescale DDR4 controller.
463
464		CONFIG_SYS_FSL_DDRC_ARM_GEN3
465		Freescale DDR3 controller for ARM-based SoCs.
466
467		CONFIG_SYS_FSL_DDR1
468		Board config to use DDR1. It can be enabled for SoCs with
469		Freescale DDR1 or DDR2 controllers, depending on the board
470		implemetation.
471
472		CONFIG_SYS_FSL_DDR2
473		Board config to use DDR2. It can be eanbeld for SoCs with
474		Freescale DDR2 or DDR3 controllers, depending on the board
475		implementation.
476
477		CONFIG_SYS_FSL_DDR3
478		Board config to use DDR3. It can be enabled for SoCs with
479		Freescale DDR3 or DDR3L controllers.
480
481		CONFIG_SYS_FSL_DDR3L
482		Board config to use DDR3L. It can be enabled for SoCs with
483		DDR3L controllers.
484
485		CONFIG_SYS_FSL_DDR4
486		Board config to use DDR4. It can be enabled for SoCs with
487		DDR4 controllers.
488
489		CONFIG_SYS_FSL_IFC_BE
490		Defines the IFC controller register space as Big Endian
491
492		CONFIG_SYS_FSL_IFC_LE
493		Defines the IFC controller register space as Little Endian
494
495		CONFIG_SYS_FSL_PBL_PBI
496		It enables addition of RCW (Power on reset configuration) in built image.
497		Please refer doc/README.pblimage for more details
498
499		CONFIG_SYS_FSL_PBL_RCW
500		It adds PBI(pre-boot instructions) commands in u-boot build image.
501		PBI commands can be used to configure SoC before it starts the execution.
502		Please refer doc/README.pblimage for more details
503
504		CONFIG_SYS_FSL_DDR_BE
505		Defines the DDR controller register space as Big Endian
506
507		CONFIG_SYS_FSL_DDR_LE
508		Defines the DDR controller register space as Little Endian
509
510		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
511		Physical address from the view of DDR controllers. It is the
512		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
513		it could be different for ARM SoCs.
514
515		CONFIG_SYS_FSL_DDR_INTLV_256B
516		DDR controller interleaving on 256-byte. This is a special
517		interleaving mode, handled by Dickens for Freescale layerscape
518		SoCs with ARM core.
519
520- Intel Monahans options:
521		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
522
523		Defines the Monahans run mode to oscillator
524		ratio. Valid values are 8, 16, 24, 31. The core
525		frequency is this value multiplied by 13 MHz.
526
527		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
528
529		Defines the Monahans turbo mode to oscillator
530		ratio. Valid values are 1 (default if undefined) and
531		2. The core frequency as calculated above is multiplied
532		by this value.
533
534- MIPS CPU options:
535		CONFIG_SYS_INIT_SP_OFFSET
536
537		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
538		pointer. This is needed for the temporary stack before
539		relocation.
540
541		CONFIG_SYS_MIPS_CACHE_MODE
542
543		Cache operation mode for the MIPS CPU.
544		See also arch/mips/include/asm/mipsregs.h.
545		Possible values are:
546			CONF_CM_CACHABLE_NO_WA
547			CONF_CM_CACHABLE_WA
548			CONF_CM_UNCACHED
549			CONF_CM_CACHABLE_NONCOHERENT
550			CONF_CM_CACHABLE_CE
551			CONF_CM_CACHABLE_COW
552			CONF_CM_CACHABLE_CUW
553			CONF_CM_CACHABLE_ACCELERATED
554
555		CONFIG_SYS_XWAY_EBU_BOOTCFG
556
557		Special option for Lantiq XWAY SoCs for booting from NOR flash.
558		See also arch/mips/cpu/mips32/start.S.
559
560		CONFIG_XWAY_SWAP_BYTES
561
562		Enable compilation of tools/xway-swap-bytes needed for Lantiq
563		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
564		be swapped if a flash programmer is used.
565
566- ARM options:
567		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
568
569		Select high exception vectors of the ARM core, e.g., do not
570		clear the V bit of the c1 register of CP15.
571
572		CONFIG_SYS_THUMB_BUILD
573
574		Use this flag to build U-Boot using the Thumb instruction
575		set for ARM architectures. Thumb instruction set provides
576		better code density. For ARM architectures that support
577		Thumb2 this flag will result in Thumb2 code generated by
578		GCC.
579
580		CONFIG_ARM_ERRATA_716044
581		CONFIG_ARM_ERRATA_742230
582		CONFIG_ARM_ERRATA_743622
583		CONFIG_ARM_ERRATA_751472
584		CONFIG_ARM_ERRATA_794072
585		CONFIG_ARM_ERRATA_761320
586
587		If set, the workarounds for these ARM errata are applied early
588		during U-Boot startup. Note that these options force the
589		workarounds to be applied; no CPU-type/version detection
590		exists, unlike the similar options in the Linux kernel. Do not
591		set these options unless they apply!
592
593- CPU timer options:
594		CONFIG_SYS_HZ
595
596		The frequency of the timer returned by get_timer().
597		get_timer() must operate in milliseconds and this CONFIG
598		option must be set to 1000.
599
600- Linux Kernel Interface:
601		CONFIG_CLOCKS_IN_MHZ
602
603		U-Boot stores all clock information in Hz
604		internally. For binary compatibility with older Linux
605		kernels (which expect the clocks passed in the
606		bd_info data to be in MHz) the environment variable
607		"clocks_in_mhz" can be defined so that U-Boot
608		converts clock data to MHZ before passing it to the
609		Linux kernel.
610		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
611		"clocks_in_mhz=1" is automatically included in the
612		default environment.
613
614		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
615
616		When transferring memsize parameter to linux, some versions
617		expect it to be in bytes, others in MB.
618		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
619
620		CONFIG_OF_LIBFDT
621
622		New kernel versions are expecting firmware settings to be
623		passed using flattened device trees (based on open firmware
624		concepts).
625
626		CONFIG_OF_LIBFDT
627		 * New libfdt-based support
628		 * Adds the "fdt" command
629		 * The bootm command automatically updates the fdt
630
631		OF_CPU - The proper name of the cpus node (only required for
632			MPC512X and MPC5xxx based boards).
633		OF_SOC - The proper name of the soc node (only required for
634			MPC512X and MPC5xxx based boards).
635		OF_TBCLK - The timebase frequency.
636		OF_STDOUT_PATH - The path to the console device
637
638		boards with QUICC Engines require OF_QE to set UCC MAC
639		addresses
640
641		CONFIG_OF_BOARD_SETUP
642
643		Board code has addition modification that it wants to make
644		to the flat device tree before handing it off to the kernel
645
646		CONFIG_OF_BOOT_CPU
647
648		This define fills in the correct boot CPU in the boot
649		param header, the default value is zero if undefined.
650
651		CONFIG_OF_IDE_FIXUP
652
653		U-Boot can detect if an IDE device is present or not.
654		If not, and this new config option is activated, U-Boot
655		removes the ATA node from the DTS before booting Linux,
656		so the Linux IDE driver does not probe the device and
657		crash. This is needed for buggy hardware (uc101) where
658		no pull down resistor is connected to the signal IDE5V_DD7.
659
660		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
661
662		This setting is mandatory for all boards that have only one
663		machine type and must be used to specify the machine type
664		number as it appears in the ARM machine registry
665		(see http://www.arm.linux.org.uk/developer/machines/).
666		Only boards that have multiple machine types supported
667		in a single configuration file and the machine type is
668		runtime discoverable, do not have to use this setting.
669
670- vxWorks boot parameters:
671
672		bootvx constructs a valid bootline using the following
673		environments variables: bootfile, ipaddr, serverip, hostname.
674		It loads the vxWorks image pointed bootfile.
675
676		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
677		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
678		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
679		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
680
681		CONFIG_SYS_VXWORKS_ADD_PARAMS
682
683		Add it at the end of the bootline. E.g "u=username pw=secret"
684
685		Note: If a "bootargs" environment is defined, it will overwride
686		the defaults discussed just above.
687
688- Cache Configuration:
689		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
690		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
691		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
692
693- Cache Configuration for ARM:
694		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
695				      controller
696		CONFIG_SYS_PL310_BASE - Physical base address of PL310
697					controller register space
698
699- Serial Ports:
700		CONFIG_PL010_SERIAL
701
702		Define this if you want support for Amba PrimeCell PL010 UARTs.
703
704		CONFIG_PL011_SERIAL
705
706		Define this if you want support for Amba PrimeCell PL011 UARTs.
707
708		CONFIG_PL011_CLOCK
709
710		If you have Amba PrimeCell PL011 UARTs, set this variable to
711		the clock speed of the UARTs.
712
713		CONFIG_PL01x_PORTS
714
715		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
716		define this to a list of base addresses for each (supported)
717		port. See e.g. include/configs/versatile.h
718
719		CONFIG_PL011_SERIAL_RLCR
720
721		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
722		have separate receive and transmit line control registers.  Set
723		this variable to initialize the extra register.
724
725		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
726
727		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
728		boot loader that has already initialized the UART.  Define this
729		variable to flush the UART at init time.
730
731
732- Console Interface:
733		Depending on board, define exactly one serial port
734		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
735		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
736		console by defining CONFIG_8xx_CONS_NONE
737
738		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
739		port routines must be defined elsewhere
740		(i.e. serial_init(), serial_getc(), ...)
741
742		CONFIG_CFB_CONSOLE
743		Enables console device for a color framebuffer. Needs following
744		defines (cf. smiLynxEM, i8042)
745			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
746						(default big endian)
747			VIDEO_HW_RECTFILL	graphic chip supports
748						rectangle fill
749						(cf. smiLynxEM)
750			VIDEO_HW_BITBLT		graphic chip supports
751						bit-blit (cf. smiLynxEM)
752			VIDEO_VISIBLE_COLS	visible pixel columns
753						(cols=pitch)
754			VIDEO_VISIBLE_ROWS	visible pixel rows
755			VIDEO_PIXEL_SIZE	bytes per pixel
756			VIDEO_DATA_FORMAT	graphic data format
757						(0-5, cf. cfb_console.c)
758			VIDEO_FB_ADRS		framebuffer address
759			VIDEO_KBD_INIT_FCT	keyboard int fct
760						(i.e. i8042_kbd_init())
761			VIDEO_TSTC_FCT		test char fct
762						(i.e. i8042_tstc)
763			VIDEO_GETC_FCT		get char fct
764						(i.e. i8042_getc)
765			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
766						(requires blink timer
767						cf. i8042.c)
768			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
769			CONFIG_CONSOLE_TIME	display time/date info in
770						upper right corner
771						(requires CONFIG_CMD_DATE)
772			CONFIG_VIDEO_LOGO	display Linux logo in
773						upper left corner
774			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
775						linux_logo.h for logo.
776						Requires CONFIG_VIDEO_LOGO
777			CONFIG_CONSOLE_EXTRA_INFO
778						additional board info beside
779						the logo
780
781		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
782		a limited number of ANSI escape sequences (cursor control,
783		erase functions and limited graphics rendition control).
784
785		When CONFIG_CFB_CONSOLE is defined, video console is
786		default i/o. Serial console can be forced with
787		environment 'console=serial'.
788
789		When CONFIG_SILENT_CONSOLE is defined, all console
790		messages (by U-Boot and Linux!) can be silenced with
791		the "silent" environment variable. See
792		doc/README.silent for more information.
793
794		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
795			is 0x00.
796		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
797			is 0xa0.
798
799- Console Baudrate:
800		CONFIG_BAUDRATE - in bps
801		Select one of the baudrates listed in
802		CONFIG_SYS_BAUDRATE_TABLE, see below.
803		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
804
805- Console Rx buffer length
806		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
807		the maximum receive buffer length for the SMC.
808		This option is actual only for 82xx and 8xx possible.
809		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
810		must be defined, to setup the maximum idle timeout for
811		the SMC.
812
813- Pre-Console Buffer:
814		Prior to the console being initialised (i.e. serial UART
815		initialised etc) all console output is silently discarded.
816		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
817		buffer any console messages prior to the console being
818		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
819		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
820		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
821		bytes are output before the console is initialised, the
822		earlier bytes are discarded.
823
824		'Sane' compilers will generate smaller code if
825		CONFIG_PRE_CON_BUF_SZ is a power of 2
826
827- Safe printf() functions
828		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
829		the printf() functions. These are defined in
830		include/vsprintf.h and include snprintf(), vsnprintf() and
831		so on. Code size increase is approximately 300-500 bytes.
832		If this option is not given then these functions will
833		silently discard their buffer size argument - this means
834		you are not getting any overflow checking in this case.
835
836- Boot Delay:	CONFIG_BOOTDELAY - in seconds
837		Delay before automatically booting the default image;
838		set to -1 to disable autoboot.
839		set to -2 to autoboot with no delay and not check for abort
840		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
841
842		See doc/README.autoboot for these options that
843		work with CONFIG_BOOTDELAY. None are required.
844		CONFIG_BOOT_RETRY_TIME
845		CONFIG_BOOT_RETRY_MIN
846		CONFIG_AUTOBOOT_KEYED
847		CONFIG_AUTOBOOT_PROMPT
848		CONFIG_AUTOBOOT_DELAY_STR
849		CONFIG_AUTOBOOT_STOP_STR
850		CONFIG_AUTOBOOT_DELAY_STR2
851		CONFIG_AUTOBOOT_STOP_STR2
852		CONFIG_ZERO_BOOTDELAY_CHECK
853		CONFIG_RESET_TO_RETRY
854
855- Autoboot Command:
856		CONFIG_BOOTCOMMAND
857		Only needed when CONFIG_BOOTDELAY is enabled;
858		define a command string that is automatically executed
859		when no character is read on the console interface
860		within "Boot Delay" after reset.
861
862		CONFIG_BOOTARGS
863		This can be used to pass arguments to the bootm
864		command. The value of CONFIG_BOOTARGS goes into the
865		environment value "bootargs".
866
867		CONFIG_RAMBOOT and CONFIG_NFSBOOT
868		The value of these goes into the environment as
869		"ramboot" and "nfsboot" respectively, and can be used
870		as a convenience, when switching between booting from
871		RAM and NFS.
872
873- Bootcount:
874		CONFIG_BOOTCOUNT_LIMIT
875		Implements a mechanism for detecting a repeating reboot
876		cycle, see:
877		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
878
879		CONFIG_BOOTCOUNT_ENV
880		If no softreset save registers are found on the hardware
881		"bootcount" is stored in the environment. To prevent a
882		saveenv on all reboots, the environment variable
883		"upgrade_available" is used. If "upgrade_available" is
884		0, "bootcount" is always 0, if "upgrade_available" is
885		1 "bootcount" is incremented in the environment.
886		So the Userspace Applikation must set the "upgrade_available"
887		and "bootcount" variable to 0, if a boot was successfully.
888
889- Pre-Boot Commands:
890		CONFIG_PREBOOT
891
892		When this option is #defined, the existence of the
893		environment variable "preboot" will be checked
894		immediately before starting the CONFIG_BOOTDELAY
895		countdown and/or running the auto-boot command resp.
896		entering interactive mode.
897
898		This feature is especially useful when "preboot" is
899		automatically generated or modified. For an example
900		see the LWMON board specific code: here "preboot" is
901		modified when the user holds down a certain
902		combination of keys on the (special) keyboard when
903		booting the systems
904
905- Serial Download Echo Mode:
906		CONFIG_LOADS_ECHO
907		If defined to 1, all characters received during a
908		serial download (using the "loads" command) are
909		echoed back. This might be needed by some terminal
910		emulations (like "cu"), but may as well just take
911		time on others. This setting #define's the initial
912		value of the "loads_echo" environment variable.
913
914- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
915		CONFIG_KGDB_BAUDRATE
916		Select one of the baudrates listed in
917		CONFIG_SYS_BAUDRATE_TABLE, see below.
918
919- Monitor Functions:
920		Monitor commands can be included or excluded
921		from the build by using the #include files
922		<config_cmd_all.h> and #undef'ing unwanted
923		commands, or using <config_cmd_default.h>
924		and augmenting with additional #define's
925		for wanted commands.
926
927		The default command configuration includes all commands
928		except those marked below with a "*".
929
930		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
931		CONFIG_CMD_ASKENV	* ask for env variable
932		CONFIG_CMD_BDI		  bdinfo
933		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
934		CONFIG_CMD_BMP		* BMP support
935		CONFIG_CMD_BSP		* Board specific commands
936		CONFIG_CMD_BOOTD	  bootd
937		CONFIG_CMD_CACHE	* icache, dcache
938		CONFIG_CMD_CLK   	* clock command support
939		CONFIG_CMD_CONSOLE	  coninfo
940		CONFIG_CMD_CRC32	* crc32
941		CONFIG_CMD_DATE		* support for RTC, date/time...
942		CONFIG_CMD_DHCP		* DHCP support
943		CONFIG_CMD_DIAG		* Diagnostics
944		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
945		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
946		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
947		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
948		CONFIG_CMD_DTT		* Digital Therm and Thermostat
949		CONFIG_CMD_ECHO		  echo arguments
950		CONFIG_CMD_EDITENV	  edit env variable
951		CONFIG_CMD_EEPROM	* EEPROM read/write support
952		CONFIG_CMD_ELF		* bootelf, bootvx
953		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
954		CONFIG_CMD_ENV_FLAGS	* display details about env flags
955		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
956		CONFIG_CMD_EXPORTENV	* export the environment
957		CONFIG_CMD_EXT2		* ext2 command support
958		CONFIG_CMD_EXT4		* ext4 command support
959		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
960					  that work for multiple fs types
961		CONFIG_CMD_SAVEENV	  saveenv
962		CONFIG_CMD_FDC		* Floppy Disk Support
963		CONFIG_CMD_FAT		* FAT command support
964		CONFIG_CMD_FLASH	  flinfo, erase, protect
965		CONFIG_CMD_FPGA		  FPGA device initialization support
966		CONFIG_CMD_FUSE		* Device fuse support
967		CONFIG_CMD_GETTIME	* Get time since boot
968		CONFIG_CMD_GO		* the 'go' command (exec code)
969		CONFIG_CMD_GREPENV	* search environment
970		CONFIG_CMD_HASH		* calculate hash / digest
971		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
972		CONFIG_CMD_I2C		* I2C serial bus support
973		CONFIG_CMD_IDE		* IDE harddisk support
974		CONFIG_CMD_IMI		  iminfo
975		CONFIG_CMD_IMLS		  List all images found in NOR flash
976		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
977		CONFIG_CMD_IMMAP	* IMMR dump support
978		CONFIG_CMD_IMPORTENV	* import an environment
979		CONFIG_CMD_INI		* import data from an ini file into the env
980		CONFIG_CMD_IRQ		* irqinfo
981		CONFIG_CMD_ITEST	  Integer/string test of 2 values
982		CONFIG_CMD_JFFS2	* JFFS2 Support
983		CONFIG_CMD_KGDB		* kgdb
984		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
985		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
986					  (169.254.*.*)
987		CONFIG_CMD_LOADB	  loadb
988		CONFIG_CMD_LOADS	  loads
989		CONFIG_CMD_MD5SUM	* print md5 message digest
990					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
991		CONFIG_CMD_MEMINFO	* Display detailed memory information
992		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
993					  loop, loopw
994		CONFIG_CMD_MEMTEST	* mtest
995		CONFIG_CMD_MISC		  Misc functions like sleep etc
996		CONFIG_CMD_MMC		* MMC memory mapped support
997		CONFIG_CMD_MII		* MII utility commands
998		CONFIG_CMD_MTDPARTS	* MTD partition support
999		CONFIG_CMD_NAND		* NAND support
1000		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1001		CONFIG_CMD_NFS		  NFS support
1002		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1003		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1004		CONFIG_CMD_PCI		* pciinfo
1005		CONFIG_CMD_PCMCIA		* PCMCIA support
1006		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1007					  host
1008		CONFIG_CMD_PORTIO	* Port I/O
1009		CONFIG_CMD_READ		* Read raw data from partition
1010		CONFIG_CMD_REGINFO	* Register dump
1011		CONFIG_CMD_RUN		  run command in env variable
1012		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1013		CONFIG_CMD_SAVES	* save S record dump
1014		CONFIG_CMD_SCSI		* SCSI Support
1015		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1016					  (requires CONFIG_CMD_I2C)
1017		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1018					  (4xx only)
1019		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1020		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1021					  (requires CONFIG_CMD_MEMORY)
1022		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1023		CONFIG_CMD_SOURCE	  "source" command Support
1024		CONFIG_CMD_SPI		* SPI serial bus support
1025		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1026		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1027		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1028		CONFIG_CMD_TIMER	* access to the system tick timer
1029		CONFIG_CMD_USB		* USB support
1030		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1031		CONFIG_CMD_MFSL		* Microblaze FSL support
1032		CONFIG_CMD_XIMG		  Load part of Multi Image
1033		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1034
1035		EXAMPLE: If you want all functions except of network
1036		support you can write:
1037
1038		#include "config_cmd_all.h"
1039		#undef CONFIG_CMD_NET
1040
1041	Other Commands:
1042		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1043
1044	Note:	Don't enable the "icache" and "dcache" commands
1045		(configuration option CONFIG_CMD_CACHE) unless you know
1046		what you (and your U-Boot users) are doing. Data
1047		cache cannot be enabled on systems like the 8xx or
1048		8260 (where accesses to the IMMR region must be
1049		uncached), and it cannot be disabled on all other
1050		systems where we (mis-) use the data cache to hold an
1051		initial stack and some data.
1052
1053
1054		XXX - this list needs to get updated!
1055
1056- Regular expression support:
1057		CONFIG_REGEX
1058		If this variable is defined, U-Boot is linked against
1059		the SLRE (Super Light Regular Expression) library,
1060		which adds regex support to some commands, as for
1061		example "env grep" and "setexpr".
1062
1063- Device tree:
1064		CONFIG_OF_CONTROL
1065		If this variable is defined, U-Boot will use a device tree
1066		to configure its devices, instead of relying on statically
1067		compiled #defines in the board file. This option is
1068		experimental and only available on a few boards. The device
1069		tree is available in the global data as gd->fdt_blob.
1070
1071		U-Boot needs to get its device tree from somewhere. This can
1072		be done using one of the two options below:
1073
1074		CONFIG_OF_EMBED
1075		If this variable is defined, U-Boot will embed a device tree
1076		binary in its image. This device tree file should be in the
1077		board directory and called <soc>-<board>.dts. The binary file
1078		is then picked up in board_init_f() and made available through
1079		the global data structure as gd->blob.
1080
1081		CONFIG_OF_SEPARATE
1082		If this variable is defined, U-Boot will build a device tree
1083		binary. It will be called u-boot.dtb. Architecture-specific
1084		code will locate it at run-time. Generally this works by:
1085
1086			cat u-boot.bin u-boot.dtb >image.bin
1087
1088		and in fact, U-Boot does this for you, creating a file called
1089		u-boot-dtb.bin which is useful in the common case. You can
1090		still use the individual files if you need something more
1091		exotic.
1092
1093- Watchdog:
1094		CONFIG_WATCHDOG
1095		If this variable is defined, it enables watchdog
1096		support for the SoC. There must be support in the SoC
1097		specific code for a watchdog. For the 8xx and 8260
1098		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1099		register.  When supported for a specific SoC is
1100		available, then no further board specific code should
1101		be needed to use it.
1102
1103		CONFIG_HW_WATCHDOG
1104		When using a watchdog circuitry external to the used
1105		SoC, then define this variable and provide board
1106		specific code for the "hw_watchdog_reset" function.
1107
1108- U-Boot Version:
1109		CONFIG_VERSION_VARIABLE
1110		If this variable is defined, an environment variable
1111		named "ver" is created by U-Boot showing the U-Boot
1112		version as printed by the "version" command.
1113		Any change to this variable will be reverted at the
1114		next reset.
1115
1116- Real-Time Clock:
1117
1118		When CONFIG_CMD_DATE is selected, the type of the RTC
1119		has to be selected, too. Define exactly one of the
1120		following options:
1121
1122		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1123		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1124		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1125		CONFIG_RTC_MC146818	- use MC146818 RTC
1126		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1127		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1128		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1129		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1130		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1131		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1132		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1133		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1134					  RV3029 RTC.
1135
1136		Note that if the RTC uses I2C, then the I2C interface
1137		must also be configured. See I2C Support, below.
1138
1139- GPIO Support:
1140		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1141
1142		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1143		chip-ngpio pairs that tell the PCA953X driver the number of
1144		pins supported by a particular chip.
1145
1146		Note that if the GPIO device uses I2C, then the I2C interface
1147		must also be configured. See I2C Support, below.
1148
1149- Timestamp Support:
1150
1151		When CONFIG_TIMESTAMP is selected, the timestamp
1152		(date and time) of an image is printed by image
1153		commands like bootm or iminfo. This option is
1154		automatically enabled when you select CONFIG_CMD_DATE .
1155
1156- Partition Labels (disklabels) Supported:
1157		Zero or more of the following:
1158		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1159		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1160				       Intel architecture, USB sticks, etc.
1161		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1162		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1163				       bootloader.  Note 2TB partition limit; see
1164				       disk/part_efi.c
1165		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1166
1167		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1168		CONFIG_CMD_SCSI) you must configure support for at
1169		least one non-MTD partition type as well.
1170
1171- IDE Reset method:
1172		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1173		board configurations files but used nowhere!
1174
1175		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1176		be performed by calling the function
1177			ide_set_reset(int reset)
1178		which has to be defined in a board specific file
1179
1180- ATAPI Support:
1181		CONFIG_ATAPI
1182
1183		Set this to enable ATAPI support.
1184
1185- LBA48 Support
1186		CONFIG_LBA48
1187
1188		Set this to enable support for disks larger than 137GB
1189		Also look at CONFIG_SYS_64BIT_LBA.
1190		Whithout these , LBA48 support uses 32bit variables and will 'only'
1191		support disks up to 2.1TB.
1192
1193		CONFIG_SYS_64BIT_LBA:
1194			When enabled, makes the IDE subsystem use 64bit sector addresses.
1195			Default is 32bit.
1196
1197- SCSI Support:
1198		At the moment only there is only support for the
1199		SYM53C8XX SCSI controller; define
1200		CONFIG_SCSI_SYM53C8XX to enable it.
1201
1202		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1203		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1204		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1205		maximum numbers of LUNs, SCSI ID's and target
1206		devices.
1207		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1208
1209		The environment variable 'scsidevs' is set to the number of
1210		SCSI devices found during the last scan.
1211
1212- NETWORK Support (PCI):
1213		CONFIG_E1000
1214		Support for Intel 8254x/8257x gigabit chips.
1215
1216		CONFIG_E1000_SPI
1217		Utility code for direct access to the SPI bus on Intel 8257x.
1218		This does not do anything useful unless you set at least one
1219		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1220
1221		CONFIG_E1000_SPI_GENERIC
1222		Allow generic access to the SPI bus on the Intel 8257x, for
1223		example with the "sspi" command.
1224
1225		CONFIG_CMD_E1000
1226		Management command for E1000 devices.  When used on devices
1227		with SPI support you can reprogram the EEPROM from U-Boot.
1228
1229		CONFIG_E1000_FALLBACK_MAC
1230		default MAC for empty EEPROM after production.
1231
1232		CONFIG_EEPRO100
1233		Support for Intel 82557/82559/82559ER chips.
1234		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1235		write routine for first time initialisation.
1236
1237		CONFIG_TULIP
1238		Support for Digital 2114x chips.
1239		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1240		modem chip initialisation (KS8761/QS6611).
1241
1242		CONFIG_NATSEMI
1243		Support for National dp83815 chips.
1244
1245		CONFIG_NS8382X
1246		Support for National dp8382[01] gigabit chips.
1247
1248- NETWORK Support (other):
1249
1250		CONFIG_DRIVER_AT91EMAC
1251		Support for AT91RM9200 EMAC.
1252
1253			CONFIG_RMII
1254			Define this to use reduced MII inteface
1255
1256			CONFIG_DRIVER_AT91EMAC_QUIET
1257			If this defined, the driver is quiet.
1258			The driver doen't show link status messages.
1259
1260		CONFIG_CALXEDA_XGMAC
1261		Support for the Calxeda XGMAC device
1262
1263		CONFIG_LAN91C96
1264		Support for SMSC's LAN91C96 chips.
1265
1266			CONFIG_LAN91C96_BASE
1267			Define this to hold the physical address
1268			of the LAN91C96's I/O space
1269
1270			CONFIG_LAN91C96_USE_32_BIT
1271			Define this to enable 32 bit addressing
1272
1273		CONFIG_SMC91111
1274		Support for SMSC's LAN91C111 chip
1275
1276			CONFIG_SMC91111_BASE
1277			Define this to hold the physical address
1278			of the device (I/O space)
1279
1280			CONFIG_SMC_USE_32_BIT
1281			Define this if data bus is 32 bits
1282
1283			CONFIG_SMC_USE_IOFUNCS
1284			Define this to use i/o functions instead of macros
1285			(some hardware wont work with macros)
1286
1287		CONFIG_DRIVER_TI_EMAC
1288		Support for davinci emac
1289
1290			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1291			Define this if you have more then 3 PHYs.
1292
1293		CONFIG_FTGMAC100
1294		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1295
1296			CONFIG_FTGMAC100_EGIGA
1297			Define this to use GE link update with gigabit PHY.
1298			Define this if FTGMAC100 is connected to gigabit PHY.
1299			If your system has 10/100 PHY only, it might not occur
1300			wrong behavior. Because PHY usually return timeout or
1301			useless data when polling gigabit status and gigabit
1302			control registers. This behavior won't affect the
1303			correctnessof 10/100 link speed update.
1304
1305		CONFIG_SMC911X
1306		Support for SMSC's LAN911x and LAN921x chips
1307
1308			CONFIG_SMC911X_BASE
1309			Define this to hold the physical address
1310			of the device (I/O space)
1311
1312			CONFIG_SMC911X_32_BIT
1313			Define this if data bus is 32 bits
1314
1315			CONFIG_SMC911X_16_BIT
1316			Define this if data bus is 16 bits. If your processor
1317			automatically converts one 32 bit word to two 16 bit
1318			words you may also try CONFIG_SMC911X_32_BIT.
1319
1320		CONFIG_SH_ETHER
1321		Support for Renesas on-chip Ethernet controller
1322
1323			CONFIG_SH_ETHER_USE_PORT
1324			Define the number of ports to be used
1325
1326			CONFIG_SH_ETHER_PHY_ADDR
1327			Define the ETH PHY's address
1328
1329			CONFIG_SH_ETHER_CACHE_WRITEBACK
1330			If this option is set, the driver enables cache flush.
1331
1332- TPM Support:
1333		CONFIG_TPM
1334		Support TPM devices.
1335
1336		CONFIG_TPM_TIS_I2C
1337		Support for i2c bus TPM devices. Only one device
1338		per system is supported at this time.
1339
1340			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1341			Define the the i2c bus number for the TPM device
1342
1343			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1344			Define the TPM's address on the i2c bus
1345
1346			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1347			Define the burst count bytes upper limit
1348
1349		CONFIG_TPM_ATMEL_TWI
1350		Support for Atmel TWI TPM device. Requires I2C support.
1351
1352		CONFIG_TPM_TIS_LPC
1353		Support for generic parallel port TPM devices. Only one device
1354		per system is supported at this time.
1355
1356			CONFIG_TPM_TIS_BASE_ADDRESS
1357			Base address where the generic TPM device is mapped
1358			to. Contemporary x86 systems usually map it at
1359			0xfed40000.
1360
1361		CONFIG_CMD_TPM
1362		Add tpm monitor functions.
1363		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1364		provides monitor access to authorized functions.
1365
1366		CONFIG_TPM
1367		Define this to enable the TPM support library which provides
1368		functional interfaces to some TPM commands.
1369		Requires support for a TPM device.
1370
1371		CONFIG_TPM_AUTH_SESSIONS
1372		Define this to enable authorized functions in the TPM library.
1373		Requires CONFIG_TPM and CONFIG_SHA1.
1374
1375- USB Support:
1376		At the moment only the UHCI host controller is
1377		supported (PIP405, MIP405, MPC5200); define
1378		CONFIG_USB_UHCI to enable it.
1379		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1380		and define CONFIG_USB_STORAGE to enable the USB
1381		storage devices.
1382		Note:
1383		Supported are USB Keyboards and USB Floppy drives
1384		(TEAC FD-05PUB).
1385		MPC5200 USB requires additional defines:
1386			CONFIG_USB_CLOCK
1387				for 528 MHz Clock: 0x0001bbbb
1388			CONFIG_PSC3_USB
1389				for USB on PSC3
1390			CONFIG_USB_CONFIG
1391				for differential drivers: 0x00001000
1392				for single ended drivers: 0x00005000
1393				for differential drivers on PSC3: 0x00000100
1394				for single ended drivers on PSC3: 0x00004100
1395			CONFIG_SYS_USB_EVENT_POLL
1396				May be defined to allow interrupt polling
1397				instead of using asynchronous interrupts
1398
1399		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1400		txfilltuning field in the EHCI controller on reset.
1401
1402		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1403		interval for usb hub power-on delay.(minimum 100msec)
1404
1405- USB Device:
1406		Define the below if you wish to use the USB console.
1407		Once firmware is rebuilt from a serial console issue the
1408		command "setenv stdin usbtty; setenv stdout usbtty" and
1409		attach your USB cable. The Unix command "dmesg" should print
1410		it has found a new device. The environment variable usbtty
1411		can be set to gserial or cdc_acm to enable your device to
1412		appear to a USB host as a Linux gserial device or a
1413		Common Device Class Abstract Control Model serial device.
1414		If you select usbtty = gserial you should be able to enumerate
1415		a Linux host by
1416		# modprobe usbserial vendor=0xVendorID product=0xProductID
1417		else if using cdc_acm, simply setting the environment
1418		variable usbtty to be cdc_acm should suffice. The following
1419		might be defined in YourBoardName.h
1420
1421			CONFIG_USB_DEVICE
1422			Define this to build a UDC device
1423
1424			CONFIG_USB_TTY
1425			Define this to have a tty type of device available to
1426			talk to the UDC device
1427
1428			CONFIG_USBD_HS
1429			Define this to enable the high speed support for usb
1430			device and usbtty. If this feature is enabled, a routine
1431			int is_usbd_high_speed(void)
1432			also needs to be defined by the driver to dynamically poll
1433			whether the enumeration has succeded at high speed or full
1434			speed.
1435
1436			CONFIG_SYS_CONSOLE_IS_IN_ENV
1437			Define this if you want stdin, stdout &/or stderr to
1438			be set to usbtty.
1439
1440			mpc8xx:
1441				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1442				Derive USB clock from external clock "blah"
1443				- CONFIG_SYS_USB_EXTC_CLK 0x02
1444
1445				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1446				Derive USB clock from brgclk
1447				- CONFIG_SYS_USB_BRG_CLK 0x04
1448
1449		If you have a USB-IF assigned VendorID then you may wish to
1450		define your own vendor specific values either in BoardName.h
1451		or directly in usbd_vendor_info.h. If you don't define
1452		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1453		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1454		should pretend to be a Linux device to it's target host.
1455
1456			CONFIG_USBD_MANUFACTURER
1457			Define this string as the name of your company for
1458			- CONFIG_USBD_MANUFACTURER "my company"
1459
1460			CONFIG_USBD_PRODUCT_NAME
1461			Define this string as the name of your product
1462			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1463
1464			CONFIG_USBD_VENDORID
1465			Define this as your assigned Vendor ID from the USB
1466			Implementors Forum. This *must* be a genuine Vendor ID
1467			to avoid polluting the USB namespace.
1468			- CONFIG_USBD_VENDORID 0xFFFF
1469
1470			CONFIG_USBD_PRODUCTID
1471			Define this as the unique Product ID
1472			for your device
1473			- CONFIG_USBD_PRODUCTID 0xFFFF
1474
1475		Some USB device drivers may need to check USB cable attachment.
1476		In this case you can enable following config in BoardName.h:
1477			CONFIG_USB_CABLE_CHECK
1478			This enables function definition:
1479			- usb_cable_connected() in include/usb.h
1480			Implementation of this function is board-specific.
1481
1482- ULPI Layer Support:
1483		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1484		the generic ULPI layer. The generic layer accesses the ULPI PHY
1485		via the platform viewport, so you need both the genric layer and
1486		the viewport enabled. Currently only Chipidea/ARC based
1487		viewport is supported.
1488		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1489		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1490		If your ULPI phy needs a different reference clock than the
1491		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1492		the appropriate value in Hz.
1493
1494- MMC Support:
1495		The MMC controller on the Intel PXA is supported. To
1496		enable this define CONFIG_MMC. The MMC can be
1497		accessed from the boot prompt by mapping the device
1498		to physical memory similar to flash. Command line is
1499		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1500		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1501
1502		CONFIG_SH_MMCIF
1503		Support for Renesas on-chip MMCIF controller
1504
1505			CONFIG_SH_MMCIF_ADDR
1506			Define the base address of MMCIF registers
1507
1508			CONFIG_SH_MMCIF_CLK
1509			Define the clock frequency for MMCIF
1510
1511- USB Device Firmware Update (DFU) class support:
1512		CONFIG_DFU_FUNCTION
1513		This enables the USB portion of the DFU USB class
1514
1515		CONFIG_CMD_DFU
1516		This enables the command "dfu" which is used to have
1517		U-Boot create a DFU class device via USB.  This command
1518		requires that the "dfu_alt_info" environment variable be
1519		set and define the alt settings to expose to the host.
1520
1521		CONFIG_DFU_MMC
1522		This enables support for exposing (e)MMC devices via DFU.
1523
1524		CONFIG_DFU_NAND
1525		This enables support for exposing NAND devices via DFU.
1526
1527		CONFIG_DFU_RAM
1528		This enables support for exposing RAM via DFU.
1529		Note: DFU spec refer to non-volatile memory usage, but
1530		allow usages beyond the scope of spec - here RAM usage,
1531		one that would help mostly the developer.
1532
1533		CONFIG_SYS_DFU_DATA_BUF_SIZE
1534		Dfu transfer uses a buffer before writing data to the
1535		raw storage device. Make the size (in bytes) of this buffer
1536		configurable. The size of this buffer is also configurable
1537		through the "dfu_bufsiz" environment variable.
1538
1539		CONFIG_SYS_DFU_MAX_FILE_SIZE
1540		When updating files rather than the raw storage device,
1541		we use a static buffer to copy the file into and then write
1542		the buffer once we've been given the whole file.  Define
1543		this to the maximum filesize (in bytes) for the buffer.
1544		Default is 4 MiB if undefined.
1545
1546		DFU_DEFAULT_POLL_TIMEOUT
1547		Poll timeout [ms], is the timeout a device can send to the
1548		host. The host must wait for this timeout before sending
1549		a subsequent DFU_GET_STATUS request to the device.
1550
1551		DFU_MANIFEST_POLL_TIMEOUT
1552		Poll timeout [ms], which the device sends to the host when
1553		entering dfuMANIFEST state. Host waits this timeout, before
1554		sending again an USB request to the device.
1555
1556- Journaling Flash filesystem support:
1557		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1558		CONFIG_JFFS2_NAND_DEV
1559		Define these for a default partition on a NAND device
1560
1561		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1562		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1563		Define these for a default partition on a NOR device
1564
1565		CONFIG_SYS_JFFS_CUSTOM_PART
1566		Define this to create an own partition. You have to provide a
1567		function struct part_info* jffs2_part_info(int part_num)
1568
1569		If you define only one JFFS2 partition you may also want to
1570		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1571		to disable the command chpart. This is the default when you
1572		have not defined a custom partition
1573
1574- FAT(File Allocation Table) filesystem write function support:
1575		CONFIG_FAT_WRITE
1576
1577		Define this to enable support for saving memory data as a
1578		file in FAT formatted partition.
1579
1580		This will also enable the command "fatwrite" enabling the
1581		user to write files to FAT.
1582
1583CBFS (Coreboot Filesystem) support
1584		CONFIG_CMD_CBFS
1585
1586		Define this to enable support for reading from a Coreboot
1587		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1588		and cbfsload.
1589
1590- Keyboard Support:
1591		CONFIG_ISA_KEYBOARD
1592
1593		Define this to enable standard (PC-Style) keyboard
1594		support
1595
1596		CONFIG_I8042_KBD
1597		Standard PC keyboard driver with US (is default) and
1598		GERMAN key layout (switch via environment 'keymap=de') support.
1599		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1600		for cfb_console. Supports cursor blinking.
1601
1602		CONFIG_CROS_EC_KEYB
1603		Enables a Chrome OS keyboard using the CROS_EC interface.
1604		This uses CROS_EC to communicate with a second microcontroller
1605		which provides key scans on request.
1606
1607- Video support:
1608		CONFIG_VIDEO
1609
1610		Define this to enable video support (for output to
1611		video).
1612
1613		CONFIG_VIDEO_CT69000
1614
1615		Enable Chips & Technologies 69000 Video chip
1616
1617		CONFIG_VIDEO_SMI_LYNXEM
1618		Enable Silicon Motion SMI 712/710/810 Video chip. The
1619		video output is selected via environment 'videoout'
1620		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1621		assumed.
1622
1623		For the CT69000 and SMI_LYNXEM drivers, videomode is
1624		selected via environment 'videomode'. Two different ways
1625		are possible:
1626		- "videomode=num"   'num' is a standard LiLo mode numbers.
1627		Following standard modes are supported	(* is default):
1628
1629		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1630		-------------+---------------------------------------------
1631		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1632		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1633		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1634		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1635		-------------+---------------------------------------------
1636		(i.e. setenv videomode 317; saveenv; reset;)
1637
1638		- "videomode=bootargs" all the video parameters are parsed
1639		from the bootargs. (See drivers/video/videomodes.c)
1640
1641
1642		CONFIG_VIDEO_SED13806
1643		Enable Epson SED13806 driver. This driver supports 8bpp
1644		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1645		or CONFIG_VIDEO_SED13806_16BPP
1646
1647		CONFIG_FSL_DIU_FB
1648		Enable the Freescale DIU video driver.	Reference boards for
1649		SOCs that have a DIU should define this macro to enable DIU
1650		support, and should also define these other macros:
1651
1652			CONFIG_SYS_DIU_ADDR
1653			CONFIG_VIDEO
1654			CONFIG_CMD_BMP
1655			CONFIG_CFB_CONSOLE
1656			CONFIG_VIDEO_SW_CURSOR
1657			CONFIG_VGA_AS_SINGLE_DEVICE
1658			CONFIG_VIDEO_LOGO
1659			CONFIG_VIDEO_BMP_LOGO
1660
1661		The DIU driver will look for the 'video-mode' environment
1662		variable, and if defined, enable the DIU as a console during
1663		boot.  See the documentation file README.video for a
1664		description of this variable.
1665
1666		CONFIG_VIDEO_VGA
1667
1668		Enable the VGA video / BIOS for x86. The alternative if you
1669		are using coreboot is to use the coreboot frame buffer
1670		driver.
1671
1672
1673- Keyboard Support:
1674		CONFIG_KEYBOARD
1675
1676		Define this to enable a custom keyboard support.
1677		This simply calls drv_keyboard_init() which must be
1678		defined in your board-specific files.
1679		The only board using this so far is RBC823.
1680
1681- LCD Support:	CONFIG_LCD
1682
1683		Define this to enable LCD support (for output to LCD
1684		display); also select one of the supported displays
1685		by defining one of these:
1686
1687		CONFIG_ATMEL_LCD:
1688
1689			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1690
1691		CONFIG_NEC_NL6448AC33:
1692
1693			NEC NL6448AC33-18. Active, color, single scan.
1694
1695		CONFIG_NEC_NL6448BC20
1696
1697			NEC NL6448BC20-08. 6.5", 640x480.
1698			Active, color, single scan.
1699
1700		CONFIG_NEC_NL6448BC33_54
1701
1702			NEC NL6448BC33-54. 10.4", 640x480.
1703			Active, color, single scan.
1704
1705		CONFIG_SHARP_16x9
1706
1707			Sharp 320x240. Active, color, single scan.
1708			It isn't 16x9, and I am not sure what it is.
1709
1710		CONFIG_SHARP_LQ64D341
1711
1712			Sharp LQ64D341 display, 640x480.
1713			Active, color, single scan.
1714
1715		CONFIG_HLD1045
1716
1717			HLD1045 display, 640x480.
1718			Active, color, single scan.
1719
1720		CONFIG_OPTREX_BW
1721
1722			Optrex	 CBL50840-2 NF-FW 99 22 M5
1723			or
1724			Hitachi	 LMG6912RPFC-00T
1725			or
1726			Hitachi	 SP14Q002
1727
1728			320x240. Black & white.
1729
1730		Normally display is black on white background; define
1731		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1732
1733		CONFIG_LCD_ALIGNMENT
1734
1735		Normally the LCD is page-aligned (tyically 4KB). If this is
1736		defined then the LCD will be aligned to this value instead.
1737		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1738		here, since it is cheaper to change data cache settings on
1739		a per-section basis.
1740
1741		CONFIG_CONSOLE_SCROLL_LINES
1742
1743		When the console need to be scrolled, this is the number of
1744		lines to scroll by. It defaults to 1. Increasing this makes
1745		the console jump but can help speed up operation when scrolling
1746		is slow.
1747
1748		CONFIG_LCD_BMP_RLE8
1749
1750		Support drawing of RLE8-compressed bitmaps on the LCD.
1751
1752		CONFIG_I2C_EDID
1753
1754		Enables an 'i2c edid' command which can read EDID
1755		information over I2C from an attached LCD display.
1756
1757- Splash Screen Support: CONFIG_SPLASH_SCREEN
1758
1759		If this option is set, the environment is checked for
1760		a variable "splashimage". If found, the usual display
1761		of logo, copyright and system information on the LCD
1762		is suppressed and the BMP image at the address
1763		specified in "splashimage" is loaded instead. The
1764		console is redirected to the "nulldev", too. This
1765		allows for a "silent" boot where a splash screen is
1766		loaded very quickly after power-on.
1767
1768		CONFIG_SPLASHIMAGE_GUARD
1769
1770		If this option is set, then U-Boot will prevent the environment
1771		variable "splashimage" from being set to a problematic address
1772		(see README.displaying-bmps).
1773		This option is useful for targets where, due to alignment
1774		restrictions, an improperly aligned BMP image will cause a data
1775		abort. If you think you will not have problems with unaligned
1776		accesses (for example because your toolchain prevents them)
1777		there is no need to set this option.
1778
1779		CONFIG_SPLASH_SCREEN_ALIGN
1780
1781		If this option is set the splash image can be freely positioned
1782		on the screen. Environment variable "splashpos" specifies the
1783		position as "x,y". If a positive number is given it is used as
1784		number of pixel from left/top. If a negative number is given it
1785		is used as number of pixel from right/bottom. You can also
1786		specify 'm' for centering the image.
1787
1788		Example:
1789		setenv splashpos m,m
1790			=> image at center of screen
1791
1792		setenv splashpos 30,20
1793			=> image at x = 30 and y = 20
1794
1795		setenv splashpos -10,m
1796			=> vertically centered image
1797			   at x = dspWidth - bmpWidth - 9
1798
1799- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1800
1801		If this option is set, additionally to standard BMP
1802		images, gzipped BMP images can be displayed via the
1803		splashscreen support or the bmp command.
1804
1805- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1806
1807		If this option is set, 8-bit RLE compressed BMP images
1808		can be displayed via the splashscreen support or the
1809		bmp command.
1810
1811- Do compresssing for memory range:
1812		CONFIG_CMD_ZIP
1813
1814		If this option is set, it would use zlib deflate method
1815		to compress the specified memory at its best effort.
1816
1817- Compression support:
1818		CONFIG_GZIP
1819
1820		Enabled by default to support gzip compressed images.
1821
1822		CONFIG_BZIP2
1823
1824		If this option is set, support for bzip2 compressed
1825		images is included. If not, only uncompressed and gzip
1826		compressed images are supported.
1827
1828		NOTE: the bzip2 algorithm requires a lot of RAM, so
1829		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1830		be at least 4MB.
1831
1832		CONFIG_LZMA
1833
1834		If this option is set, support for lzma compressed
1835		images is included.
1836
1837		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1838		requires an amount of dynamic memory that is given by the
1839		formula:
1840
1841			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1842
1843		Where lc and lp stand for, respectively, Literal context bits
1844		and Literal pos bits.
1845
1846		This value is upper-bounded by 14MB in the worst case. Anyway,
1847		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1848		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1849		a very small buffer.
1850
1851		Use the lzmainfo tool to determinate the lc and lp values and
1852		then calculate the amount of needed dynamic memory (ensuring
1853		the appropriate CONFIG_SYS_MALLOC_LEN value).
1854
1855		CONFIG_LZO
1856
1857		If this option is set, support for LZO compressed images
1858		is included.
1859
1860- MII/PHY support:
1861		CONFIG_PHY_ADDR
1862
1863		The address of PHY on MII bus.
1864
1865		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1866
1867		The clock frequency of the MII bus
1868
1869		CONFIG_PHY_GIGE
1870
1871		If this option is set, support for speed/duplex
1872		detection of gigabit PHY is included.
1873
1874		CONFIG_PHY_RESET_DELAY
1875
1876		Some PHY like Intel LXT971A need extra delay after
1877		reset before any MII register access is possible.
1878		For such PHY, set this option to the usec delay
1879		required. (minimum 300usec for LXT971A)
1880
1881		CONFIG_PHY_CMD_DELAY (ppc4xx)
1882
1883		Some PHY like Intel LXT971A need extra delay after
1884		command issued before MII status register can be read
1885
1886- Ethernet address:
1887		CONFIG_ETHADDR
1888		CONFIG_ETH1ADDR
1889		CONFIG_ETH2ADDR
1890		CONFIG_ETH3ADDR
1891		CONFIG_ETH4ADDR
1892		CONFIG_ETH5ADDR
1893
1894		Define a default value for Ethernet address to use
1895		for the respective Ethernet interface, in case this
1896		is not determined automatically.
1897
1898- IP address:
1899		CONFIG_IPADDR
1900
1901		Define a default value for the IP address to use for
1902		the default Ethernet interface, in case this is not
1903		determined through e.g. bootp.
1904		(Environment variable "ipaddr")
1905
1906- Server IP address:
1907		CONFIG_SERVERIP
1908
1909		Defines a default value for the IP address of a TFTP
1910		server to contact when using the "tftboot" command.
1911		(Environment variable "serverip")
1912
1913		CONFIG_KEEP_SERVERADDR
1914
1915		Keeps the server's MAC address, in the env 'serveraddr'
1916		for passing to bootargs (like Linux's netconsole option)
1917
1918- Gateway IP address:
1919		CONFIG_GATEWAYIP
1920
1921		Defines a default value for the IP address of the
1922		default router where packets to other networks are
1923		sent to.
1924		(Environment variable "gatewayip")
1925
1926- Subnet mask:
1927		CONFIG_NETMASK
1928
1929		Defines a default value for the subnet mask (or
1930		routing prefix) which is used to determine if an IP
1931		address belongs to the local subnet or needs to be
1932		forwarded through a router.
1933		(Environment variable "netmask")
1934
1935- Multicast TFTP Mode:
1936		CONFIG_MCAST_TFTP
1937
1938		Defines whether you want to support multicast TFTP as per
1939		rfc-2090; for example to work with atftp.  Lets lots of targets
1940		tftp down the same boot image concurrently.  Note: the Ethernet
1941		driver in use must provide a function: mcast() to join/leave a
1942		multicast group.
1943
1944- BOOTP Recovery Mode:
1945		CONFIG_BOOTP_RANDOM_DELAY
1946
1947		If you have many targets in a network that try to
1948		boot using BOOTP, you may want to avoid that all
1949		systems send out BOOTP requests at precisely the same
1950		moment (which would happen for instance at recovery
1951		from a power failure, when all systems will try to
1952		boot, thus flooding the BOOTP server. Defining
1953		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1954		inserted before sending out BOOTP requests. The
1955		following delays are inserted then:
1956
1957		1st BOOTP request:	delay 0 ... 1 sec
1958		2nd BOOTP request:	delay 0 ... 2 sec
1959		3rd BOOTP request:	delay 0 ... 4 sec
1960		4th and following
1961		BOOTP requests:		delay 0 ... 8 sec
1962
1963- DHCP Advanced Options:
1964		You can fine tune the DHCP functionality by defining
1965		CONFIG_BOOTP_* symbols:
1966
1967		CONFIG_BOOTP_SUBNETMASK
1968		CONFIG_BOOTP_GATEWAY
1969		CONFIG_BOOTP_HOSTNAME
1970		CONFIG_BOOTP_NISDOMAIN
1971		CONFIG_BOOTP_BOOTPATH
1972		CONFIG_BOOTP_BOOTFILESIZE
1973		CONFIG_BOOTP_DNS
1974		CONFIG_BOOTP_DNS2
1975		CONFIG_BOOTP_SEND_HOSTNAME
1976		CONFIG_BOOTP_NTPSERVER
1977		CONFIG_BOOTP_TIMEOFFSET
1978		CONFIG_BOOTP_VENDOREX
1979		CONFIG_BOOTP_MAY_FAIL
1980
1981		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1982		environment variable, not the BOOTP server.
1983
1984		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1985		after the configured retry count, the call will fail
1986		instead of starting over.  This can be used to fail over
1987		to Link-local IP address configuration if the DHCP server
1988		is not available.
1989
1990		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1991		serverip from a DHCP server, it is possible that more
1992		than one DNS serverip is offered to the client.
1993		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1994		serverip will be stored in the additional environment
1995		variable "dnsip2". The first DNS serverip is always
1996		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1997		is defined.
1998
1999		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2000		to do a dynamic update of a DNS server. To do this, they
2001		need the hostname of the DHCP requester.
2002		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2003		of the "hostname" environment variable is passed as
2004		option 12 to the DHCP server.
2005
2006		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2007
2008		A 32bit value in microseconds for a delay between
2009		receiving a "DHCP Offer" and sending the "DHCP Request".
2010		This fixes a problem with certain DHCP servers that don't
2011		respond 100% of the time to a "DHCP request". E.g. On an
2012		AT91RM9200 processor running at 180MHz, this delay needed
2013		to be *at least* 15,000 usec before a Windows Server 2003
2014		DHCP server would reply 100% of the time. I recommend at
2015		least 50,000 usec to be safe. The alternative is to hope
2016		that one of the retries will be successful but note that
2017		the DHCP timeout and retry process takes a longer than
2018		this delay.
2019
2020 - Link-local IP address negotiation:
2021		Negotiate with other link-local clients on the local network
2022		for an address that doesn't require explicit configuration.
2023		This is especially useful if a DHCP server cannot be guaranteed
2024		to exist in all environments that the device must operate.
2025
2026		See doc/README.link-local for more information.
2027
2028 - CDP Options:
2029		CONFIG_CDP_DEVICE_ID
2030
2031		The device id used in CDP trigger frames.
2032
2033		CONFIG_CDP_DEVICE_ID_PREFIX
2034
2035		A two character string which is prefixed to the MAC address
2036		of the device.
2037
2038		CONFIG_CDP_PORT_ID
2039
2040		A printf format string which contains the ascii name of
2041		the port. Normally is set to "eth%d" which sets
2042		eth0 for the first Ethernet, eth1 for the second etc.
2043
2044		CONFIG_CDP_CAPABILITIES
2045
2046		A 32bit integer which indicates the device capabilities;
2047		0x00000010 for a normal host which does not forwards.
2048
2049		CONFIG_CDP_VERSION
2050
2051		An ascii string containing the version of the software.
2052
2053		CONFIG_CDP_PLATFORM
2054
2055		An ascii string containing the name of the platform.
2056
2057		CONFIG_CDP_TRIGGER
2058
2059		A 32bit integer sent on the trigger.
2060
2061		CONFIG_CDP_POWER_CONSUMPTION
2062
2063		A 16bit integer containing the power consumption of the
2064		device in .1 of milliwatts.
2065
2066		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2067
2068		A byte containing the id of the VLAN.
2069
2070- Status LED:	CONFIG_STATUS_LED
2071
2072		Several configurations allow to display the current
2073		status using a LED. For instance, the LED will blink
2074		fast while running U-Boot code, stop blinking as
2075		soon as a reply to a BOOTP request was received, and
2076		start blinking slow once the Linux kernel is running
2077		(supported by a status LED driver in the Linux
2078		kernel). Defining CONFIG_STATUS_LED enables this
2079		feature in U-Boot.
2080
2081		Additional options:
2082
2083		CONFIG_GPIO_LED
2084		The status LED can be connected to a GPIO pin.
2085		In such cases, the gpio_led driver can be used as a
2086		status LED backend implementation. Define CONFIG_GPIO_LED
2087		to include the gpio_led driver in the U-Boot binary.
2088
2089		CONFIG_GPIO_LED_INVERTED_TABLE
2090		Some GPIO connected LEDs may have inverted polarity in which
2091		case the GPIO high value corresponds to LED off state and
2092		GPIO low value corresponds to LED on state.
2093		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2094		with a list of GPIO LEDs that have inverted polarity.
2095
2096- CAN Support:	CONFIG_CAN_DRIVER
2097
2098		Defining CONFIG_CAN_DRIVER enables CAN driver support
2099		on those systems that support this (optional)
2100		feature, like the TQM8xxL modules.
2101
2102- I2C Support:	CONFIG_SYS_I2C
2103
2104		This enable the NEW i2c subsystem, and will allow you to use
2105		i2c commands at the u-boot command line (as long as you set
2106		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2107		based realtime clock chips or other i2c devices. See
2108		common/cmd_i2c.c for a description of the command line
2109		interface.
2110
2111		ported i2c driver to the new framework:
2112		- drivers/i2c/soft_i2c.c:
2113		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2114		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2115		    for defining speed and slave address
2116		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2117		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2118		    for defining speed and slave address
2119		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2120		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2121		    for defining speed and slave address
2122		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2123		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2124		    for defining speed and slave address
2125
2126		- drivers/i2c/fsl_i2c.c:
2127		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2128		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2129		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2130		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2131		    bus.
2132		  - If your board supports a second fsl i2c bus, define
2133		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2134		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2135		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2136		    second bus.
2137
2138		- drivers/i2c/tegra_i2c.c:
2139		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2140		  - This driver adds 4 i2c buses with a fix speed from
2141		    100000 and the slave addr 0!
2142
2143		- drivers/i2c/ppc4xx_i2c.c
2144		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2145		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2146		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2147
2148		- drivers/i2c/i2c_mxc.c
2149		  - activate this driver with CONFIG_SYS_I2C_MXC
2150		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2151		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2152		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2153		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2154		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2155		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2156		If thoses defines are not set, default value is 100000
2157		for speed, and 0 for slave.
2158
2159		- drivers/i2c/rcar_i2c.c:
2160		  - activate this driver with CONFIG_SYS_I2C_RCAR
2161		  - This driver adds 4 i2c buses
2162
2163		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2164		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2165		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2166		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2167		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2168		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2169		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2170		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2171		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2172
2173		- drivers/i2c/sh_i2c.c:
2174		  - activate this driver with CONFIG_SYS_I2C_SH
2175		  - This driver adds from 2 to 5 i2c buses
2176
2177		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2178		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2179		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2180		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2181		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2182		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2183		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2184		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2185		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2186		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2187		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2188		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2189		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2190
2191		- drivers/i2c/omap24xx_i2c.c
2192		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2193		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2194		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2195		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2196		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2197		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2198		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2199		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2200		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2201		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2202		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2203
2204		- drivers/i2c/zynq_i2c.c
2205		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2206		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2207		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2208
2209		- drivers/i2c/s3c24x0_i2c.c:
2210		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2211		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2212		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2213		    with a fix speed from 100000 and the slave addr 0!
2214
2215		additional defines:
2216
2217		CONFIG_SYS_NUM_I2C_BUSES
2218		Hold the number of i2c busses you want to use. If you
2219		don't use/have i2c muxes on your i2c bus, this
2220		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2221		omit this define.
2222
2223		CONFIG_SYS_I2C_DIRECT_BUS
2224		define this, if you don't use i2c muxes on your hardware.
2225		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2226		omit this define.
2227
2228		CONFIG_SYS_I2C_MAX_HOPS
2229		define how many muxes are maximal consecutively connected
2230		on one i2c bus. If you not use i2c muxes, omit this
2231		define.
2232
2233		CONFIG_SYS_I2C_BUSES
2234		hold a list of busses you want to use, only used if
2235		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2236		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2237		CONFIG_SYS_NUM_I2C_BUSES = 9:
2238
2239		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2240					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2241					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2242					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2243					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2244					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2245					{1, {I2C_NULL_HOP}}, \
2246					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2247					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2248					}
2249
2250		which defines
2251			bus 0 on adapter 0 without a mux
2252			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2253			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2254			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2255			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2256			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2257			bus 6 on adapter 1 without a mux
2258			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2259			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2260
2261		If you do not have i2c muxes on your board, omit this define.
2262
2263- Legacy I2C Support:	CONFIG_HARD_I2C
2264
2265		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2266		provides the following compelling advantages:
2267
2268		- more than one i2c adapter is usable
2269		- approved multibus support
2270		- better i2c mux support
2271
2272		** Please consider updating your I2C driver now. **
2273
2274		These enable legacy I2C serial bus commands. Defining
2275		CONFIG_HARD_I2C will include the appropriate I2C driver
2276		for the selected CPU.
2277
2278		This will allow you to use i2c commands at the u-boot
2279		command line (as long as you set CONFIG_CMD_I2C in
2280		CONFIG_COMMANDS) and communicate with i2c based realtime
2281		clock chips. See common/cmd_i2c.c for a description of the
2282		command line interface.
2283
2284		CONFIG_HARD_I2C selects a hardware I2C controller.
2285
2286		There are several other quantities that must also be
2287		defined when you define CONFIG_HARD_I2C.
2288
2289		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2290		to be the frequency (in Hz) at which you wish your i2c bus
2291		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2292		the CPU's i2c node address).
2293
2294		Now, the u-boot i2c code for the mpc8xx
2295		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2296		and so its address should therefore be cleared to 0 (See,
2297		eg, MPC823e User's Manual p.16-473). So, set
2298		CONFIG_SYS_I2C_SLAVE to 0.
2299
2300		CONFIG_SYS_I2C_INIT_MPC5XXX
2301
2302		When a board is reset during an i2c bus transfer
2303		chips might think that the current transfer is still
2304		in progress.  Reset the slave devices by sending start
2305		commands until the slave device responds.
2306
2307		That's all that's required for CONFIG_HARD_I2C.
2308
2309		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2310		then the following macros need to be defined (examples are
2311		from include/configs/lwmon.h):
2312
2313		I2C_INIT
2314
2315		(Optional). Any commands necessary to enable the I2C
2316		controller or configure ports.
2317
2318		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2319
2320		I2C_PORT
2321
2322		(Only for MPC8260 CPU). The I/O port to use (the code
2323		assumes both bits are on the same port). Valid values
2324		are 0..3 for ports A..D.
2325
2326		I2C_ACTIVE
2327
2328		The code necessary to make the I2C data line active
2329		(driven).  If the data line is open collector, this
2330		define can be null.
2331
2332		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2333
2334		I2C_TRISTATE
2335
2336		The code necessary to make the I2C data line tri-stated
2337		(inactive).  If the data line is open collector, this
2338		define can be null.
2339
2340		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2341
2342		I2C_READ
2343
2344		Code that returns true if the I2C data line is high,
2345		false if it is low.
2346
2347		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2348
2349		I2C_SDA(bit)
2350
2351		If <bit> is true, sets the I2C data line high. If it
2352		is false, it clears it (low).
2353
2354		eg: #define I2C_SDA(bit) \
2355			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2356			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2357
2358		I2C_SCL(bit)
2359
2360		If <bit> is true, sets the I2C clock line high. If it
2361		is false, it clears it (low).
2362
2363		eg: #define I2C_SCL(bit) \
2364			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2365			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2366
2367		I2C_DELAY
2368
2369		This delay is invoked four times per clock cycle so this
2370		controls the rate of data transfer.  The data rate thus
2371		is 1 / (I2C_DELAY * 4). Often defined to be something
2372		like:
2373
2374		#define I2C_DELAY  udelay(2)
2375
2376		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2377
2378		If your arch supports the generic GPIO framework (asm/gpio.h),
2379		then you may alternatively define the two GPIOs that are to be
2380		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2381		have GPIO-based defaults assigned to them as appropriate.
2382
2383		You should define these to the GPIO value as given directly to
2384		the generic GPIO functions.
2385
2386		CONFIG_SYS_I2C_INIT_BOARD
2387
2388		When a board is reset during an i2c bus transfer
2389		chips might think that the current transfer is still
2390		in progress. On some boards it is possible to access
2391		the i2c SCLK line directly, either by using the
2392		processor pin as a GPIO or by having a second pin
2393		connected to the bus. If this option is defined a
2394		custom i2c_init_board() routine in boards/xxx/board.c
2395		is run early in the boot sequence.
2396
2397		CONFIG_SYS_I2C_BOARD_LATE_INIT
2398
2399		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2400		defined a custom i2c_board_late_init() routine in
2401		boards/xxx/board.c is run AFTER the operations in i2c_init()
2402		is completed. This callpoint can be used to unreset i2c bus
2403		using CPU i2c controller register accesses for CPUs whose i2c
2404		controller provide such a method. It is called at the end of
2405		i2c_init() to allow i2c_init operations to setup the i2c bus
2406		controller on the CPU (e.g. setting bus speed & slave address).
2407
2408		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2409
2410		This option enables configuration of bi_iic_fast[] flags
2411		in u-boot bd_info structure based on u-boot environment
2412		variable "i2cfast". (see also i2cfast)
2413
2414		CONFIG_I2C_MULTI_BUS
2415
2416		This option allows the use of multiple I2C buses, each of which
2417		must have a controller.	 At any point in time, only one bus is
2418		active.	 To switch to a different bus, use the 'i2c dev' command.
2419		Note that bus numbering is zero-based.
2420
2421		CONFIG_SYS_I2C_NOPROBES
2422
2423		This option specifies a list of I2C devices that will be skipped
2424		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2425		is set, specify a list of bus-device pairs.  Otherwise, specify
2426		a 1D array of device addresses
2427
2428		e.g.
2429			#undef	CONFIG_I2C_MULTI_BUS
2430			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2431
2432		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2433
2434			#define CONFIG_I2C_MULTI_BUS
2435			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2436
2437		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2438
2439		CONFIG_SYS_SPD_BUS_NUM
2440
2441		If defined, then this indicates the I2C bus number for DDR SPD.
2442		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2443
2444		CONFIG_SYS_RTC_BUS_NUM
2445
2446		If defined, then this indicates the I2C bus number for the RTC.
2447		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2448
2449		CONFIG_SYS_DTT_BUS_NUM
2450
2451		If defined, then this indicates the I2C bus number for the DTT.
2452		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2453
2454		CONFIG_SYS_I2C_DTT_ADDR:
2455
2456		If defined, specifies the I2C address of the DTT device.
2457		If not defined, then U-Boot uses predefined value for
2458		specified DTT device.
2459
2460		CONFIG_SOFT_I2C_READ_REPEATED_START
2461
2462		defining this will force the i2c_read() function in
2463		the soft_i2c driver to perform an I2C repeated start
2464		between writing the address pointer and reading the
2465		data.  If this define is omitted the default behaviour
2466		of doing a stop-start sequence will be used.  Most I2C
2467		devices can use either method, but some require one or
2468		the other.
2469
2470- SPI Support:	CONFIG_SPI
2471
2472		Enables SPI driver (so far only tested with
2473		SPI EEPROM, also an instance works with Crystal A/D and
2474		D/As on the SACSng board)
2475
2476		CONFIG_SH_SPI
2477
2478		Enables the driver for SPI controller on SuperH. Currently
2479		only SH7757 is supported.
2480
2481		CONFIG_SPI_X
2482
2483		Enables extended (16-bit) SPI EEPROM addressing.
2484		(symmetrical to CONFIG_I2C_X)
2485
2486		CONFIG_SOFT_SPI
2487
2488		Enables a software (bit-bang) SPI driver rather than
2489		using hardware support. This is a general purpose
2490		driver that only requires three general I/O port pins
2491		(two outputs, one input) to function. If this is
2492		defined, the board configuration must define several
2493		SPI configuration items (port pins to use, etc). For
2494		an example, see include/configs/sacsng.h.
2495
2496		CONFIG_HARD_SPI
2497
2498		Enables a hardware SPI driver for general-purpose reads
2499		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2500		must define a list of chip-select function pointers.
2501		Currently supported on some MPC8xxx processors.	 For an
2502		example, see include/configs/mpc8349emds.h.
2503
2504		CONFIG_MXC_SPI
2505
2506		Enables the driver for the SPI controllers on i.MX and MXC
2507		SoCs. Currently i.MX31/35/51 are supported.
2508
2509- FPGA Support: CONFIG_FPGA
2510
2511		Enables FPGA subsystem.
2512
2513		CONFIG_FPGA_<vendor>
2514
2515		Enables support for specific chip vendors.
2516		(ALTERA, XILINX)
2517
2518		CONFIG_FPGA_<family>
2519
2520		Enables support for FPGA family.
2521		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2522
2523		CONFIG_FPGA_COUNT
2524
2525		Specify the number of FPGA devices to support.
2526
2527		CONFIG_SYS_FPGA_PROG_FEEDBACK
2528
2529		Enable printing of hash marks during FPGA configuration.
2530
2531		CONFIG_SYS_FPGA_CHECK_BUSY
2532
2533		Enable checks on FPGA configuration interface busy
2534		status by the configuration function. This option
2535		will require a board or device specific function to
2536		be written.
2537
2538		CONFIG_FPGA_DELAY
2539
2540		If defined, a function that provides delays in the FPGA
2541		configuration driver.
2542
2543		CONFIG_SYS_FPGA_CHECK_CTRLC
2544		Allow Control-C to interrupt FPGA configuration
2545
2546		CONFIG_SYS_FPGA_CHECK_ERROR
2547
2548		Check for configuration errors during FPGA bitfile
2549		loading. For example, abort during Virtex II
2550		configuration if the INIT_B line goes low (which
2551		indicated a CRC error).
2552
2553		CONFIG_SYS_FPGA_WAIT_INIT
2554
2555		Maximum time to wait for the INIT_B line to deassert
2556		after PROB_B has been deasserted during a Virtex II
2557		FPGA configuration sequence. The default time is 500
2558		ms.
2559
2560		CONFIG_SYS_FPGA_WAIT_BUSY
2561
2562		Maximum time to wait for BUSY to deassert during
2563		Virtex II FPGA configuration. The default is 5 ms.
2564
2565		CONFIG_SYS_FPGA_WAIT_CONFIG
2566
2567		Time to wait after FPGA configuration. The default is
2568		200 ms.
2569
2570- Configuration Management:
2571		CONFIG_IDENT_STRING
2572
2573		If defined, this string will be added to the U-Boot
2574		version information (U_BOOT_VERSION)
2575
2576- Vendor Parameter Protection:
2577
2578		U-Boot considers the values of the environment
2579		variables "serial#" (Board Serial Number) and
2580		"ethaddr" (Ethernet Address) to be parameters that
2581		are set once by the board vendor / manufacturer, and
2582		protects these variables from casual modification by
2583		the user. Once set, these variables are read-only,
2584		and write or delete attempts are rejected. You can
2585		change this behaviour:
2586
2587		If CONFIG_ENV_OVERWRITE is #defined in your config
2588		file, the write protection for vendor parameters is
2589		completely disabled. Anybody can change or delete
2590		these parameters.
2591
2592		Alternatively, if you #define _both_ CONFIG_ETHADDR
2593		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2594		Ethernet address is installed in the environment,
2595		which can be changed exactly ONCE by the user. [The
2596		serial# is unaffected by this, i. e. it remains
2597		read-only.]
2598
2599		The same can be accomplished in a more flexible way
2600		for any variable by configuring the type of access
2601		to allow for those variables in the ".flags" variable
2602		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2603
2604- Protected RAM:
2605		CONFIG_PRAM
2606
2607		Define this variable to enable the reservation of
2608		"protected RAM", i. e. RAM which is not overwritten
2609		by U-Boot. Define CONFIG_PRAM to hold the number of
2610		kB you want to reserve for pRAM. You can overwrite
2611		this default value by defining an environment
2612		variable "pram" to the number of kB you want to
2613		reserve. Note that the board info structure will
2614		still show the full amount of RAM. If pRAM is
2615		reserved, a new environment variable "mem" will
2616		automatically be defined to hold the amount of
2617		remaining RAM in a form that can be passed as boot
2618		argument to Linux, for instance like that:
2619
2620			setenv bootargs ... mem=\${mem}
2621			saveenv
2622
2623		This way you can tell Linux not to use this memory,
2624		either, which results in a memory region that will
2625		not be affected by reboots.
2626
2627		*WARNING* If your board configuration uses automatic
2628		detection of the RAM size, you must make sure that
2629		this memory test is non-destructive. So far, the
2630		following board configurations are known to be
2631		"pRAM-clean":
2632
2633			IVMS8, IVML24, SPD8xx, TQM8xxL,
2634			HERMES, IP860, RPXlite, LWMON,
2635			FLAGADM, TQM8260
2636
2637- Access to physical memory region (> 4GB)
2638		Some basic support is provided for operations on memory not
2639		normally accessible to U-Boot - e.g. some architectures
2640		support access to more than 4GB of memory on 32-bit
2641		machines using physical address extension or similar.
2642		Define CONFIG_PHYSMEM to access this basic support, which
2643		currently only supports clearing the memory.
2644
2645- Error Recovery:
2646		CONFIG_PANIC_HANG
2647
2648		Define this variable to stop the system in case of a
2649		fatal error, so that you have to reset it manually.
2650		This is probably NOT a good idea for an embedded
2651		system where you want the system to reboot
2652		automatically as fast as possible, but it may be
2653		useful during development since you can try to debug
2654		the conditions that lead to the situation.
2655
2656		CONFIG_NET_RETRY_COUNT
2657
2658		This variable defines the number of retries for
2659		network operations like ARP, RARP, TFTP, or BOOTP
2660		before giving up the operation. If not defined, a
2661		default value of 5 is used.
2662
2663		CONFIG_ARP_TIMEOUT
2664
2665		Timeout waiting for an ARP reply in milliseconds.
2666
2667		CONFIG_NFS_TIMEOUT
2668
2669		Timeout in milliseconds used in NFS protocol.
2670		If you encounter "ERROR: Cannot umount" in nfs command,
2671		try longer timeout such as
2672		#define CONFIG_NFS_TIMEOUT 10000UL
2673
2674- Command Interpreter:
2675		CONFIG_AUTO_COMPLETE
2676
2677		Enable auto completion of commands using TAB.
2678
2679		Note that this feature has NOT been implemented yet
2680		for the "hush" shell.
2681
2682
2683		CONFIG_SYS_HUSH_PARSER
2684
2685		Define this variable to enable the "hush" shell (from
2686		Busybox) as command line interpreter, thus enabling
2687		powerful command line syntax like
2688		if...then...else...fi conditionals or `&&' and '||'
2689		constructs ("shell scripts").
2690
2691		If undefined, you get the old, much simpler behaviour
2692		with a somewhat smaller memory footprint.
2693
2694
2695		CONFIG_SYS_PROMPT_HUSH_PS2
2696
2697		This defines the secondary prompt string, which is
2698		printed when the command interpreter needs more input
2699		to complete a command. Usually "> ".
2700
2701	Note:
2702
2703		In the current implementation, the local variables
2704		space and global environment variables space are
2705		separated. Local variables are those you define by
2706		simply typing `name=value'. To access a local
2707		variable later on, you have write `$name' or
2708		`${name}'; to execute the contents of a variable
2709		directly type `$name' at the command prompt.
2710
2711		Global environment variables are those you use
2712		setenv/printenv to work with. To run a command stored
2713		in such a variable, you need to use the run command,
2714		and you must not use the '$' sign to access them.
2715
2716		To store commands and special characters in a
2717		variable, please use double quotation marks
2718		surrounding the whole text of the variable, instead
2719		of the backslashes before semicolons and special
2720		symbols.
2721
2722- Commandline Editing and History:
2723		CONFIG_CMDLINE_EDITING
2724
2725		Enable editing and History functions for interactive
2726		commandline input operations
2727
2728- Default Environment:
2729		CONFIG_EXTRA_ENV_SETTINGS
2730
2731		Define this to contain any number of null terminated
2732		strings (variable = value pairs) that will be part of
2733		the default environment compiled into the boot image.
2734
2735		For example, place something like this in your
2736		board's config file:
2737
2738		#define CONFIG_EXTRA_ENV_SETTINGS \
2739			"myvar1=value1\0" \
2740			"myvar2=value2\0"
2741
2742		Warning: This method is based on knowledge about the
2743		internal format how the environment is stored by the
2744		U-Boot code. This is NOT an official, exported
2745		interface! Although it is unlikely that this format
2746		will change soon, there is no guarantee either.
2747		You better know what you are doing here.
2748
2749		Note: overly (ab)use of the default environment is
2750		discouraged. Make sure to check other ways to preset
2751		the environment like the "source" command or the
2752		boot command first.
2753
2754		CONFIG_ENV_VARS_UBOOT_CONFIG
2755
2756		Define this in order to add variables describing the
2757		U-Boot build configuration to the default environment.
2758		These will be named arch, cpu, board, vendor, and soc.
2759
2760		Enabling this option will cause the following to be defined:
2761
2762		- CONFIG_SYS_ARCH
2763		- CONFIG_SYS_CPU
2764		- CONFIG_SYS_BOARD
2765		- CONFIG_SYS_VENDOR
2766		- CONFIG_SYS_SOC
2767
2768		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2769
2770		Define this in order to add variables describing certain
2771		run-time determined information about the hardware to the
2772		environment.  These will be named board_name, board_rev.
2773
2774		CONFIG_DELAY_ENVIRONMENT
2775
2776		Normally the environment is loaded when the board is
2777		intialised so that it is available to U-Boot. This inhibits
2778		that so that the environment is not available until
2779		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2780		this is instead controlled by the value of
2781		/config/load-environment.
2782
2783- DataFlash Support:
2784		CONFIG_HAS_DATAFLASH
2785
2786		Defining this option enables DataFlash features and
2787		allows to read/write in Dataflash via the standard
2788		commands cp, md...
2789
2790- Serial Flash support
2791		CONFIG_CMD_SF
2792
2793		Defining this option enables SPI flash commands
2794		'sf probe/read/write/erase/update'.
2795
2796		Usage requires an initial 'probe' to define the serial
2797		flash parameters, followed by read/write/erase/update
2798		commands.
2799
2800		The following defaults may be provided by the platform
2801		to handle the common case when only a single serial
2802		flash is present on the system.
2803
2804		CONFIG_SF_DEFAULT_BUS		Bus identifier
2805		CONFIG_SF_DEFAULT_CS		Chip-select
2806		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2807		CONFIG_SF_DEFAULT_SPEED		in Hz
2808
2809		CONFIG_CMD_SF_TEST
2810
2811		Define this option to include a destructive SPI flash
2812		test ('sf test').
2813
2814		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2815
2816		Define this option to use the Bank addr/Extended addr
2817		support on SPI flashes which has size > 16Mbytes.
2818
2819		CONFIG_SF_DUAL_FLASH		Dual flash memories
2820
2821		Define this option to use dual flash support where two flash
2822		memories can be connected with a given cs line.
2823		currently Xilinx Zynq qspi support these type of connections.
2824
2825- SystemACE Support:
2826		CONFIG_SYSTEMACE
2827
2828		Adding this option adds support for Xilinx SystemACE
2829		chips attached via some sort of local bus. The address
2830		of the chip must also be defined in the
2831		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2832
2833		#define CONFIG_SYSTEMACE
2834		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2835
2836		When SystemACE support is added, the "ace" device type
2837		becomes available to the fat commands, i.e. fatls.
2838
2839- TFTP Fixed UDP Port:
2840		CONFIG_TFTP_PORT
2841
2842		If this is defined, the environment variable tftpsrcp
2843		is used to supply the TFTP UDP source port value.
2844		If tftpsrcp isn't defined, the normal pseudo-random port
2845		number generator is used.
2846
2847		Also, the environment variable tftpdstp is used to supply
2848		the TFTP UDP destination port value.  If tftpdstp isn't
2849		defined, the normal port 69 is used.
2850
2851		The purpose for tftpsrcp is to allow a TFTP server to
2852		blindly start the TFTP transfer using the pre-configured
2853		target IP address and UDP port. This has the effect of
2854		"punching through" the (Windows XP) firewall, allowing
2855		the remainder of the TFTP transfer to proceed normally.
2856		A better solution is to properly configure the firewall,
2857		but sometimes that is not allowed.
2858
2859- Hashing support:
2860		CONFIG_CMD_HASH
2861
2862		This enables a generic 'hash' command which can produce
2863		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2864
2865		CONFIG_HASH_VERIFY
2866
2867		Enable the hash verify command (hash -v). This adds to code
2868		size a little.
2869
2870		CONFIG_SHA1 - support SHA1 hashing
2871		CONFIG_SHA256 - support SHA256 hashing
2872
2873		Note: There is also a sha1sum command, which should perhaps
2874		be deprecated in favour of 'hash sha1'.
2875
2876- Freescale i.MX specific commands:
2877		CONFIG_CMD_HDMIDETECT
2878		This enables 'hdmidet' command which returns true if an
2879		HDMI monitor is detected.  This command is i.MX 6 specific.
2880
2881		CONFIG_CMD_BMODE
2882		This enables the 'bmode' (bootmode) command for forcing
2883		a boot from specific media.
2884
2885		This is useful for forcing the ROM's usb downloader to
2886		activate upon a watchdog reset which is nice when iterating
2887		on U-Boot.  Using the reset button or running bmode normal
2888		will set it back to normal.  This command currently
2889		supports i.MX53 and i.MX6.
2890
2891- Signing support:
2892		CONFIG_RSA
2893
2894		This enables the RSA algorithm used for FIT image verification
2895		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2896
2897		The signing part is build into mkimage regardless of this
2898		option.
2899
2900- bootcount support:
2901		CONFIG_BOOTCOUNT_LIMIT
2902
2903		This enables the bootcounter support, see:
2904		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2905
2906		CONFIG_AT91SAM9XE
2907		enable special bootcounter support on at91sam9xe based boards.
2908		CONFIG_BLACKFIN
2909		enable special bootcounter support on blackfin based boards.
2910		CONFIG_SOC_DA8XX
2911		enable special bootcounter support on da850 based boards.
2912		CONFIG_BOOTCOUNT_RAM
2913		enable support for the bootcounter in RAM
2914		CONFIG_BOOTCOUNT_I2C
2915		enable support for the bootcounter on an i2c (like RTC) device.
2916			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2917			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2918						    the bootcounter.
2919			CONFIG_BOOTCOUNT_ALEN = address len
2920
2921- Show boot progress:
2922		CONFIG_SHOW_BOOT_PROGRESS
2923
2924		Defining this option allows to add some board-
2925		specific code (calling a user-provided function
2926		"show_boot_progress(int)") that enables you to show
2927		the system's boot progress on some display (for
2928		example, some LED's) on your board. At the moment,
2929		the following checkpoints are implemented:
2930
2931- Detailed boot stage timing
2932		CONFIG_BOOTSTAGE
2933		Define this option to get detailed timing of each stage
2934		of the boot process.
2935
2936		CONFIG_BOOTSTAGE_USER_COUNT
2937		This is the number of available user bootstage records.
2938		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2939		a new ID will be allocated from this stash. If you exceed
2940		the limit, recording will stop.
2941
2942		CONFIG_BOOTSTAGE_REPORT
2943		Define this to print a report before boot, similar to this:
2944
2945		Timer summary in microseconds:
2946		       Mark    Elapsed  Stage
2947			  0          0  reset
2948		  3,575,678  3,575,678  board_init_f start
2949		  3,575,695         17  arch_cpu_init A9
2950		  3,575,777         82  arch_cpu_init done
2951		  3,659,598     83,821  board_init_r start
2952		  3,910,375    250,777  main_loop
2953		 29,916,167 26,005,792  bootm_start
2954		 30,361,327    445,160  start_kernel
2955
2956		CONFIG_CMD_BOOTSTAGE
2957		Add a 'bootstage' command which supports printing a report
2958		and un/stashing of bootstage data.
2959
2960		CONFIG_BOOTSTAGE_FDT
2961		Stash the bootstage information in the FDT. A root 'bootstage'
2962		node is created with each bootstage id as a child. Each child
2963		has a 'name' property and either 'mark' containing the
2964		mark time in microsecond, or 'accum' containing the
2965		accumulated time for that bootstage id in microseconds.
2966		For example:
2967
2968		bootstage {
2969			154 {
2970				name = "board_init_f";
2971				mark = <3575678>;
2972			};
2973			170 {
2974				name = "lcd";
2975				accum = <33482>;
2976			};
2977		};
2978
2979		Code in the Linux kernel can find this in /proc/devicetree.
2980
2981Legacy uImage format:
2982
2983  Arg	Where			When
2984    1	common/cmd_bootm.c	before attempting to boot an image
2985   -1	common/cmd_bootm.c	Image header has bad	 magic number
2986    2	common/cmd_bootm.c	Image header has correct magic number
2987   -2	common/cmd_bootm.c	Image header has bad	 checksum
2988    3	common/cmd_bootm.c	Image header has correct checksum
2989   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2990    4	common/cmd_bootm.c	Image data   has correct checksum
2991   -4	common/cmd_bootm.c	Image is for unsupported architecture
2992    5	common/cmd_bootm.c	Architecture check OK
2993   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2994    6	common/cmd_bootm.c	Image Type check OK
2995   -6	common/cmd_bootm.c	gunzip uncompression error
2996   -7	common/cmd_bootm.c	Unimplemented compression type
2997    7	common/cmd_bootm.c	Uncompression OK
2998    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2999   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3000
3001    9	common/image.c		Start initial ramdisk verification
3002  -10	common/image.c		Ramdisk header has bad	   magic number
3003  -11	common/image.c		Ramdisk header has bad	   checksum
3004   10	common/image.c		Ramdisk header is OK
3005  -12	common/image.c		Ramdisk data   has bad	   checksum
3006   11	common/image.c		Ramdisk data   has correct checksum
3007   12	common/image.c		Ramdisk verification complete, start loading
3008  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3009   13	common/image.c		Start multifile image verification
3010   14	common/image.c		No initial ramdisk, no multifile, continue.
3011
3012   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3013
3014  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3015  -31	post/post.c		POST test failed, detected by post_output_backlog()
3016  -32	post/post.c		POST test failed, detected by post_run_single()
3017
3018   34	common/cmd_doc.c	before loading a Image from a DOC device
3019  -35	common/cmd_doc.c	Bad usage of "doc" command
3020   35	common/cmd_doc.c	correct usage of "doc" command
3021  -36	common/cmd_doc.c	No boot device
3022   36	common/cmd_doc.c	correct boot device
3023  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3024   37	common/cmd_doc.c	correct chip ID found, device available
3025  -38	common/cmd_doc.c	Read Error on boot device
3026   38	common/cmd_doc.c	reading Image header from DOC device OK
3027  -39	common/cmd_doc.c	Image header has bad magic number
3028   39	common/cmd_doc.c	Image header has correct magic number
3029  -40	common/cmd_doc.c	Error reading Image from DOC device
3030   40	common/cmd_doc.c	Image header has correct magic number
3031   41	common/cmd_ide.c	before loading a Image from a IDE device
3032  -42	common/cmd_ide.c	Bad usage of "ide" command
3033   42	common/cmd_ide.c	correct usage of "ide" command
3034  -43	common/cmd_ide.c	No boot device
3035   43	common/cmd_ide.c	boot device found
3036  -44	common/cmd_ide.c	Device not available
3037   44	common/cmd_ide.c	Device available
3038  -45	common/cmd_ide.c	wrong partition selected
3039   45	common/cmd_ide.c	partition selected
3040  -46	common/cmd_ide.c	Unknown partition table
3041   46	common/cmd_ide.c	valid partition table found
3042  -47	common/cmd_ide.c	Invalid partition type
3043   47	common/cmd_ide.c	correct partition type
3044  -48	common/cmd_ide.c	Error reading Image Header on boot device
3045   48	common/cmd_ide.c	reading Image Header from IDE device OK
3046  -49	common/cmd_ide.c	Image header has bad magic number
3047   49	common/cmd_ide.c	Image header has correct magic number
3048  -50	common/cmd_ide.c	Image header has bad	 checksum
3049   50	common/cmd_ide.c	Image header has correct checksum
3050  -51	common/cmd_ide.c	Error reading Image from IDE device
3051   51	common/cmd_ide.c	reading Image from IDE device OK
3052   52	common/cmd_nand.c	before loading a Image from a NAND device
3053  -53	common/cmd_nand.c	Bad usage of "nand" command
3054   53	common/cmd_nand.c	correct usage of "nand" command
3055  -54	common/cmd_nand.c	No boot device
3056   54	common/cmd_nand.c	boot device found
3057  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3058   55	common/cmd_nand.c	correct chip ID found, device available
3059  -56	common/cmd_nand.c	Error reading Image Header on boot device
3060   56	common/cmd_nand.c	reading Image Header from NAND device OK
3061  -57	common/cmd_nand.c	Image header has bad magic number
3062   57	common/cmd_nand.c	Image header has correct magic number
3063  -58	common/cmd_nand.c	Error reading Image from NAND device
3064   58	common/cmd_nand.c	reading Image from NAND device OK
3065
3066  -60	common/env_common.c	Environment has a bad CRC, using default
3067
3068   64	net/eth.c		starting with Ethernet configuration.
3069  -64	net/eth.c		no Ethernet found.
3070   65	net/eth.c		Ethernet found.
3071
3072  -80	common/cmd_net.c	usage wrong
3073   80	common/cmd_net.c	before calling NetLoop()
3074  -81	common/cmd_net.c	some error in NetLoop() occurred
3075   81	common/cmd_net.c	NetLoop() back without error
3076  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3077   82	common/cmd_net.c	trying automatic boot
3078   83	common/cmd_net.c	running "source" command
3079  -83	common/cmd_net.c	some error in automatic boot or "source" command
3080   84	common/cmd_net.c	end without errors
3081
3082FIT uImage format:
3083
3084  Arg	Where			When
3085  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3086 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3087  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3088 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3089  102	common/cmd_bootm.c	Kernel unit name specified
3090 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3091  103	common/cmd_bootm.c	Found configuration node
3092  104	common/cmd_bootm.c	Got kernel subimage node offset
3093 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3094  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3095 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3096  106	common/cmd_bootm.c	Architecture check OK
3097 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3098  107	common/cmd_bootm.c	Kernel subimage type OK
3099 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3100  108	common/cmd_bootm.c	Got kernel subimage data/size
3101 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3102 -109	common/cmd_bootm.c	Can't get kernel subimage type
3103 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3104 -111	common/cmd_bootm.c	Can't get kernel subimage os
3105 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3106 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3107
3108  120	common/image.c		Start initial ramdisk verification
3109 -120	common/image.c		Ramdisk FIT image has incorrect format
3110  121	common/image.c		Ramdisk FIT image has correct format
3111  122	common/image.c		No ramdisk subimage unit name, using configuration
3112 -122	common/image.c		Can't get configuration for ramdisk subimage
3113  123	common/image.c		Ramdisk unit name specified
3114 -124	common/image.c		Can't get ramdisk subimage node offset
3115  125	common/image.c		Got ramdisk subimage node offset
3116 -125	common/image.c		Ramdisk subimage hash verification failed
3117  126	common/image.c		Ramdisk subimage hash verification OK
3118 -126	common/image.c		Ramdisk subimage for unsupported architecture
3119  127	common/image.c		Architecture check OK
3120 -127	common/image.c		Can't get ramdisk subimage data/size
3121  128	common/image.c		Got ramdisk subimage data/size
3122  129	common/image.c		Can't get ramdisk load address
3123 -129	common/image.c		Got ramdisk load address
3124
3125 -130	common/cmd_doc.c	Incorrect FIT image format
3126  131	common/cmd_doc.c	FIT image format OK
3127
3128 -140	common/cmd_ide.c	Incorrect FIT image format
3129  141	common/cmd_ide.c	FIT image format OK
3130
3131 -150	common/cmd_nand.c	Incorrect FIT image format
3132  151	common/cmd_nand.c	FIT image format OK
3133
3134- FIT image support:
3135		CONFIG_FIT
3136		Enable support for the FIT uImage format.
3137
3138		CONFIG_FIT_BEST_MATCH
3139		When no configuration is explicitly selected, default to the
3140		one whose fdt's compatibility field best matches that of
3141		U-Boot itself. A match is considered "best" if it matches the
3142		most specific compatibility entry of U-Boot's fdt's root node.
3143		The order of entries in the configuration's fdt is ignored.
3144
3145		CONFIG_FIT_SIGNATURE
3146		This option enables signature verification of FIT uImages,
3147		using a hash signed and verified using RSA. See
3148		doc/uImage.FIT/signature.txt for more details.
3149
3150- Standalone program support:
3151		CONFIG_STANDALONE_LOAD_ADDR
3152
3153		This option defines a board specific value for the
3154		address where standalone program gets loaded, thus
3155		overwriting the architecture dependent default
3156		settings.
3157
3158- Frame Buffer Address:
3159		CONFIG_FB_ADDR
3160
3161		Define CONFIG_FB_ADDR if you want to use specific
3162		address for frame buffer.  This is typically the case
3163		when using a graphics controller has separate video
3164		memory.  U-Boot will then place the frame buffer at
3165		the given address instead of dynamically reserving it
3166		in system RAM by calling lcd_setmem(), which grabs
3167		the memory for the frame buffer depending on the
3168		configured panel size.
3169
3170		Please see board_init_f function.
3171
3172- Automatic software updates via TFTP server
3173		CONFIG_UPDATE_TFTP
3174		CONFIG_UPDATE_TFTP_CNT_MAX
3175		CONFIG_UPDATE_TFTP_MSEC_MAX
3176
3177		These options enable and control the auto-update feature;
3178		for a more detailed description refer to doc/README.update.
3179
3180- MTD Support (mtdparts command, UBI support)
3181		CONFIG_MTD_DEVICE
3182
3183		Adds the MTD device infrastructure from the Linux kernel.
3184		Needed for mtdparts command support.
3185
3186		CONFIG_MTD_PARTITIONS
3187
3188		Adds the MTD partitioning infrastructure from the Linux
3189		kernel. Needed for UBI support.
3190
3191- UBI support
3192		CONFIG_CMD_UBI
3193
3194		Adds commands for interacting with MTD partitions formatted
3195		with the UBI flash translation layer
3196
3197		Requires also defining CONFIG_RBTREE
3198
3199		CONFIG_UBI_SILENCE_MSG
3200
3201		Make the verbose messages from UBI stop printing.  This leaves
3202		warnings and errors enabled.
3203
3204- UBIFS support
3205		CONFIG_CMD_UBIFS
3206
3207		Adds commands for interacting with UBI volumes formatted as
3208		UBIFS.  UBIFS is read-only in u-boot.
3209
3210		Requires UBI support as well as CONFIG_LZO
3211
3212		CONFIG_UBIFS_SILENCE_MSG
3213
3214		Make the verbose messages from UBIFS stop printing.  This leaves
3215		warnings and errors enabled.
3216
3217- SPL framework
3218		CONFIG_SPL
3219		Enable building of SPL globally.
3220
3221		CONFIG_SPL_LDSCRIPT
3222		LDSCRIPT for linking the SPL binary.
3223
3224		CONFIG_SPL_MAX_FOOTPRINT
3225		Maximum size in memory allocated to the SPL, BSS included.
3226		When defined, the linker checks that the actual memory
3227		used by SPL from _start to __bss_end does not exceed it.
3228		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3229		must not be both defined at the same time.
3230
3231		CONFIG_SPL_MAX_SIZE
3232		Maximum size of the SPL image (text, data, rodata, and
3233		linker lists sections), BSS excluded.
3234		When defined, the linker checks that the actual size does
3235		not exceed it.
3236
3237		CONFIG_SPL_TEXT_BASE
3238		TEXT_BASE for linking the SPL binary.
3239
3240		CONFIG_SPL_RELOC_TEXT_BASE
3241		Address to relocate to.  If unspecified, this is equal to
3242		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3243
3244		CONFIG_SPL_BSS_START_ADDR
3245		Link address for the BSS within the SPL binary.
3246
3247		CONFIG_SPL_BSS_MAX_SIZE
3248		Maximum size in memory allocated to the SPL BSS.
3249		When defined, the linker checks that the actual memory used
3250		by SPL from __bss_start to __bss_end does not exceed it.
3251		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3252		must not be both defined at the same time.
3253
3254		CONFIG_SPL_STACK
3255		Adress of the start of the stack SPL will use
3256
3257		CONFIG_SPL_RELOC_STACK
3258		Adress of the start of the stack SPL will use after
3259		relocation.  If unspecified, this is equal to
3260		CONFIG_SPL_STACK.
3261
3262		CONFIG_SYS_SPL_MALLOC_START
3263		Starting address of the malloc pool used in SPL.
3264
3265		CONFIG_SYS_SPL_MALLOC_SIZE
3266		The size of the malloc pool used in SPL.
3267
3268		CONFIG_SPL_FRAMEWORK
3269		Enable the SPL framework under common/.  This framework
3270		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3271		NAND loading of the Linux Kernel.
3272
3273		CONFIG_SPL_DISPLAY_PRINT
3274		For ARM, enable an optional function to print more information
3275		about the running system.
3276
3277		CONFIG_SPL_INIT_MINIMAL
3278		Arch init code should be built for a very small image
3279
3280		CONFIG_SPL_LIBCOMMON_SUPPORT
3281		Support for common/libcommon.o in SPL binary
3282
3283		CONFIG_SPL_LIBDISK_SUPPORT
3284		Support for disk/libdisk.o in SPL binary
3285
3286		CONFIG_SPL_I2C_SUPPORT
3287		Support for drivers/i2c/libi2c.o in SPL binary
3288
3289		CONFIG_SPL_GPIO_SUPPORT
3290		Support for drivers/gpio/libgpio.o in SPL binary
3291
3292		CONFIG_SPL_MMC_SUPPORT
3293		Support for drivers/mmc/libmmc.o in SPL binary
3294
3295		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3296		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3297		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3298		Address, size and partition on the MMC to load U-Boot from
3299		when the MMC is being used in raw mode.
3300
3301		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3302		Sector to load kernel uImage from when MMC is being
3303		used in raw mode (for Falcon mode)
3304
3305		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3306		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3307		Sector and number of sectors to load kernel argument
3308		parameters from when MMC is being used in raw mode
3309		(for falcon mode)
3310
3311		CONFIG_SPL_FAT_SUPPORT
3312		Support for fs/fat/libfat.o in SPL binary
3313
3314		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3315		Filename to read to load U-Boot when reading from FAT
3316
3317		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3318		Filename to read to load kernel uImage when reading
3319		from FAT (for Falcon mode)
3320
3321		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3322		Filename to read to load kernel argument parameters
3323		when reading from FAT (for Falcon mode)
3324
3325		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3326		Set this for NAND SPL on PPC mpc83xx targets, so that
3327		start.S waits for the rest of the SPL to load before
3328		continuing (the hardware starts execution after just
3329		loading the first page rather than the full 4K).
3330
3331		CONFIG_SPL_NAND_BASE
3332		Include nand_base.c in the SPL.  Requires
3333		CONFIG_SPL_NAND_DRIVERS.
3334
3335		CONFIG_SPL_NAND_DRIVERS
3336		SPL uses normal NAND drivers, not minimal drivers.
3337
3338		CONFIG_SPL_NAND_ECC
3339		Include standard software ECC in the SPL
3340
3341		CONFIG_SPL_NAND_SIMPLE
3342		Support for NAND boot using simple NAND drivers that
3343		expose the cmd_ctrl() interface.
3344
3345		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3346		Set for the SPL on PPC mpc8xxx targets, support for
3347		drivers/ddr/fsl/libddr.o in SPL binary.
3348
3349		CONFIG_SPL_COMMON_INIT_DDR
3350		Set for common ddr init with serial presence detect in
3351		SPL binary.
3352
3353		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3354		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3355		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3356		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3357		CONFIG_SYS_NAND_ECCBYTES
3358		Defines the size and behavior of the NAND that SPL uses
3359		to read U-Boot
3360
3361		CONFIG_SPL_NAND_BOOT
3362		Add support NAND boot
3363
3364		CONFIG_SYS_NAND_U_BOOT_OFFS
3365		Location in NAND to read U-Boot from
3366
3367		CONFIG_SYS_NAND_U_BOOT_DST
3368		Location in memory to load U-Boot to
3369
3370		CONFIG_SYS_NAND_U_BOOT_SIZE
3371		Size of image to load
3372
3373		CONFIG_SYS_NAND_U_BOOT_START
3374		Entry point in loaded image to jump to
3375
3376		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3377		Define this if you need to first read the OOB and then the
3378		data. This is used for example on davinci plattforms.
3379
3380		CONFIG_SPL_OMAP3_ID_NAND
3381		Support for an OMAP3-specific set of functions to return the
3382		ID and MFR of the first attached NAND chip, if present.
3383
3384		CONFIG_SPL_SERIAL_SUPPORT
3385		Support for drivers/serial/libserial.o in SPL binary
3386
3387		CONFIG_SPL_SPI_FLASH_SUPPORT
3388		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3389
3390		CONFIG_SPL_SPI_SUPPORT
3391		Support for drivers/spi/libspi.o in SPL binary
3392
3393		CONFIG_SPL_RAM_DEVICE
3394		Support for running image already present in ram, in SPL binary
3395
3396		CONFIG_SPL_LIBGENERIC_SUPPORT
3397		Support for lib/libgeneric.o in SPL binary
3398
3399		CONFIG_SPL_ENV_SUPPORT
3400		Support for the environment operating in SPL binary
3401
3402		CONFIG_SPL_NET_SUPPORT
3403		Support for the net/libnet.o in SPL binary.
3404		It conflicts with SPL env from storage medium specified by
3405		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3406
3407		CONFIG_SPL_PAD_TO
3408		Image offset to which the SPL should be padded before appending
3409		the SPL payload. By default, this is defined as
3410		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3411		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3412		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3413
3414		CONFIG_SPL_TARGET
3415		Final target image containing SPL and payload.  Some SPLs
3416		use an arch-specific makefile fragment instead, for
3417		example if more than one image needs to be produced.
3418
3419		CONFIG_FIT_SPL_PRINT
3420		Printing information about a FIT image adds quite a bit of
3421		code to SPL. So this is normally disabled in SPL. Use this
3422		option to re-enable it. This will affect the output of the
3423		bootm command when booting a FIT image.
3424
3425- TPL framework
3426		CONFIG_TPL
3427		Enable building of TPL globally.
3428
3429		CONFIG_TPL_PAD_TO
3430		Image offset to which the TPL should be padded before appending
3431		the TPL payload. By default, this is defined as
3432		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3433		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3434		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3435
3436Modem Support:
3437--------------
3438
3439[so far only for SMDK2400 boards]
3440
3441- Modem support enable:
3442		CONFIG_MODEM_SUPPORT
3443
3444- RTS/CTS Flow control enable:
3445		CONFIG_HWFLOW
3446
3447- Modem debug support:
3448		CONFIG_MODEM_SUPPORT_DEBUG
3449
3450		Enables debugging stuff (char screen[1024], dbg())
3451		for modem support. Useful only with BDI2000.
3452
3453- Interrupt support (PPC):
3454
3455		There are common interrupt_init() and timer_interrupt()
3456		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3457		for CPU specific initialization. interrupt_init_cpu()
3458		should set decrementer_count to appropriate value. If
3459		CPU resets decrementer automatically after interrupt
3460		(ppc4xx) it should set decrementer_count to zero.
3461		timer_interrupt() calls timer_interrupt_cpu() for CPU
3462		specific handling. If board has watchdog / status_led
3463		/ other_activity_monitor it works automatically from
3464		general timer_interrupt().
3465
3466- General:
3467
3468		In the target system modem support is enabled when a
3469		specific key (key combination) is pressed during
3470		power-on. Otherwise U-Boot will boot normally
3471		(autoboot). The key_pressed() function is called from
3472		board_init(). Currently key_pressed() is a dummy
3473		function, returning 1 and thus enabling modem
3474		initialization.
3475
3476		If there are no modem init strings in the
3477		environment, U-Boot proceed to autoboot; the
3478		previous output (banner, info printfs) will be
3479		suppressed, though.
3480
3481		See also: doc/README.Modem
3482
3483Board initialization settings:
3484------------------------------
3485
3486During Initialization u-boot calls a number of board specific functions
3487to allow the preparation of board specific prerequisites, e.g. pin setup
3488before drivers are initialized. To enable these callbacks the
3489following configuration macros have to be defined. Currently this is
3490architecture specific, so please check arch/your_architecture/lib/board.c
3491typically in board_init_f() and board_init_r().
3492
3493- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3494- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3495- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3496- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3497
3498Configuration Settings:
3499-----------------------
3500
3501- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3502		Optionally it can be defined to support 64-bit memory commands.
3503
3504- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3505		undefine this when you're short of memory.
3506
3507- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3508		width of the commands listed in the 'help' command output.
3509
3510- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3511		prompt for user input.
3512
3513- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3514
3515- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3516
3517- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3518
3519- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3520		the application (usually a Linux kernel) when it is
3521		booted
3522
3523- CONFIG_SYS_BAUDRATE_TABLE:
3524		List of legal baudrate settings for this board.
3525
3526- CONFIG_SYS_CONSOLE_INFO_QUIET
3527		Suppress display of console information at boot.
3528
3529- CONFIG_SYS_CONSOLE_IS_IN_ENV
3530		If the board specific function
3531			extern int overwrite_console (void);
3532		returns 1, the stdin, stderr and stdout are switched to the
3533		serial port, else the settings in the environment are used.
3534
3535- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3536		Enable the call to overwrite_console().
3537
3538- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3539		Enable overwrite of previous console environment settings.
3540
3541- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3542		Begin and End addresses of the area used by the
3543		simple memory test.
3544
3545- CONFIG_SYS_ALT_MEMTEST:
3546		Enable an alternate, more extensive memory test.
3547
3548- CONFIG_SYS_MEMTEST_SCRATCH:
3549		Scratch address used by the alternate memory test
3550		You only need to set this if address zero isn't writeable
3551
3552- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3553		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3554		this specified memory area will get subtracted from the top
3555		(end) of RAM and won't get "touched" at all by U-Boot. By
3556		fixing up gd->ram_size the Linux kernel should gets passed
3557		the now "corrected" memory size and won't touch it either.
3558		This should work for arch/ppc and arch/powerpc. Only Linux
3559		board ports in arch/powerpc with bootwrapper support that
3560		recalculate the memory size from the SDRAM controller setup
3561		will have to get fixed in Linux additionally.
3562
3563		This option can be used as a workaround for the 440EPx/GRx
3564		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3565		be touched.
3566
3567		WARNING: Please make sure that this value is a multiple of
3568		the Linux page size (normally 4k). If this is not the case,
3569		then the end address of the Linux memory will be located at a
3570		non page size aligned address and this could cause major
3571		problems.
3572
3573- CONFIG_SYS_LOADS_BAUD_CHANGE:
3574		Enable temporary baudrate change while serial download
3575
3576- CONFIG_SYS_SDRAM_BASE:
3577		Physical start address of SDRAM. _Must_ be 0 here.
3578
3579- CONFIG_SYS_MBIO_BASE:
3580		Physical start address of Motherboard I/O (if using a
3581		Cogent motherboard)
3582
3583- CONFIG_SYS_FLASH_BASE:
3584		Physical start address of Flash memory.
3585
3586- CONFIG_SYS_MONITOR_BASE:
3587		Physical start address of boot monitor code (set by
3588		make config files to be same as the text base address
3589		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3590		CONFIG_SYS_FLASH_BASE when booting from flash.
3591
3592- CONFIG_SYS_MONITOR_LEN:
3593		Size of memory reserved for monitor code, used to
3594		determine _at_compile_time_ (!) if the environment is
3595		embedded within the U-Boot image, or in a separate
3596		flash sector.
3597
3598- CONFIG_SYS_MALLOC_LEN:
3599		Size of DRAM reserved for malloc() use.
3600
3601- CONFIG_SYS_BOOTM_LEN:
3602		Normally compressed uImages are limited to an
3603		uncompressed size of 8 MBytes. If this is not enough,
3604		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3605		to adjust this setting to your needs.
3606
3607- CONFIG_SYS_BOOTMAPSZ:
3608		Maximum size of memory mapped by the startup code of
3609		the Linux kernel; all data that must be processed by
3610		the Linux kernel (bd_info, boot arguments, FDT blob if
3611		used) must be put below this limit, unless "bootm_low"
3612		environment variable is defined and non-zero. In such case
3613		all data for the Linux kernel must be between "bootm_low"
3614		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3615		variable "bootm_mapsize" will override the value of
3616		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3617		then the value in "bootm_size" will be used instead.
3618
3619- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3620		Enable initrd_high functionality.  If defined then the
3621		initrd_high feature is enabled and the bootm ramdisk subcommand
3622		is enabled.
3623
3624- CONFIG_SYS_BOOT_GET_CMDLINE:
3625		Enables allocating and saving kernel cmdline in space between
3626		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3627
3628- CONFIG_SYS_BOOT_GET_KBD:
3629		Enables allocating and saving a kernel copy of the bd_info in
3630		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3631
3632- CONFIG_SYS_MAX_FLASH_BANKS:
3633		Max number of Flash memory banks
3634
3635- CONFIG_SYS_MAX_FLASH_SECT:
3636		Max number of sectors on a Flash chip
3637
3638- CONFIG_SYS_FLASH_ERASE_TOUT:
3639		Timeout for Flash erase operations (in ms)
3640
3641- CONFIG_SYS_FLASH_WRITE_TOUT:
3642		Timeout for Flash write operations (in ms)
3643
3644- CONFIG_SYS_FLASH_LOCK_TOUT
3645		Timeout for Flash set sector lock bit operation (in ms)
3646
3647- CONFIG_SYS_FLASH_UNLOCK_TOUT
3648		Timeout for Flash clear lock bits operation (in ms)
3649
3650- CONFIG_SYS_FLASH_PROTECTION
3651		If defined, hardware flash sectors protection is used
3652		instead of U-Boot software protection.
3653
3654- CONFIG_SYS_DIRECT_FLASH_TFTP:
3655
3656		Enable TFTP transfers directly to flash memory;
3657		without this option such a download has to be
3658		performed in two steps: (1) download to RAM, and (2)
3659		copy from RAM to flash.
3660
3661		The two-step approach is usually more reliable, since
3662		you can check if the download worked before you erase
3663		the flash, but in some situations (when system RAM is
3664		too limited to allow for a temporary copy of the
3665		downloaded image) this option may be very useful.
3666
3667- CONFIG_SYS_FLASH_CFI:
3668		Define if the flash driver uses extra elements in the
3669		common flash structure for storing flash geometry.
3670
3671- CONFIG_FLASH_CFI_DRIVER
3672		This option also enables the building of the cfi_flash driver
3673		in the drivers directory
3674
3675- CONFIG_FLASH_CFI_MTD
3676		This option enables the building of the cfi_mtd driver
3677		in the drivers directory. The driver exports CFI flash
3678		to the MTD layer.
3679
3680- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3681		Use buffered writes to flash.
3682
3683- CONFIG_FLASH_SPANSION_S29WS_N
3684		s29ws-n MirrorBit flash has non-standard addresses for buffered
3685		write commands.
3686
3687- CONFIG_SYS_FLASH_QUIET_TEST
3688		If this option is defined, the common CFI flash doesn't
3689		print it's warning upon not recognized FLASH banks. This
3690		is useful, if some of the configured banks are only
3691		optionally available.
3692
3693- CONFIG_FLASH_SHOW_PROGRESS
3694		If defined (must be an integer), print out countdown
3695		digits and dots.  Recommended value: 45 (9..1) for 80
3696		column displays, 15 (3..1) for 40 column displays.
3697
3698- CONFIG_FLASH_VERIFY
3699		If defined, the content of the flash (destination) is compared
3700		against the source after the write operation. An error message
3701		will be printed when the contents are not identical.
3702		Please note that this option is useless in nearly all cases,
3703		since such flash programming errors usually are detected earlier
3704		while unprotecting/erasing/programming. Please only enable
3705		this option if you really know what you are doing.
3706
3707- CONFIG_SYS_RX_ETH_BUFFER:
3708		Defines the number of Ethernet receive buffers. On some
3709		Ethernet controllers it is recommended to set this value
3710		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3711		buffers can be full shortly after enabling the interface
3712		on high Ethernet traffic.
3713		Defaults to 4 if not defined.
3714
3715- CONFIG_ENV_MAX_ENTRIES
3716
3717	Maximum number of entries in the hash table that is used
3718	internally to store the environment settings. The default
3719	setting is supposed to be generous and should work in most
3720	cases. This setting can be used to tune behaviour; see
3721	lib/hashtable.c for details.
3722
3723- CONFIG_ENV_FLAGS_LIST_DEFAULT
3724- CONFIG_ENV_FLAGS_LIST_STATIC
3725	Enable validation of the values given to environment variables when
3726	calling env set.  Variables can be restricted to only decimal,
3727	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3728	the variables can also be restricted to IP address or MAC address.
3729
3730	The format of the list is:
3731		type_attribute = [s|d|x|b|i|m]
3732		access_atribute = [a|r|o|c]
3733		attributes = type_attribute[access_atribute]
3734		entry = variable_name[:attributes]
3735		list = entry[,list]
3736
3737	The type attributes are:
3738		s - String (default)
3739		d - Decimal
3740		x - Hexadecimal
3741		b - Boolean ([1yYtT|0nNfF])
3742		i - IP address
3743		m - MAC address
3744
3745	The access attributes are:
3746		a - Any (default)
3747		r - Read-only
3748		o - Write-once
3749		c - Change-default
3750
3751	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3752		Define this to a list (string) to define the ".flags"
3753		envirnoment variable in the default or embedded environment.
3754
3755	- CONFIG_ENV_FLAGS_LIST_STATIC
3756		Define this to a list (string) to define validation that
3757		should be done if an entry is not found in the ".flags"
3758		environment variable.  To override a setting in the static
3759		list, simply add an entry for the same variable name to the
3760		".flags" variable.
3761
3762- CONFIG_ENV_ACCESS_IGNORE_FORCE
3763	If defined, don't allow the -f switch to env set override variable
3764	access flags.
3765
3766- CONFIG_SYS_GENERIC_BOARD
3767	This selects the architecture-generic board system instead of the
3768	architecture-specific board files. It is intended to move boards
3769	to this new framework over time. Defining this will disable the
3770	arch/foo/lib/board.c file and use common/board_f.c and
3771	common/board_r.c instead. To use this option your architecture
3772	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3773	its config.mk file). If you find problems enabling this option on
3774	your board please report the problem and send patches!
3775
3776- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3777	This is set by OMAP boards for the max time that reset should
3778	be asserted. See doc/README.omap-reset-time for details on how
3779	the value can be calulated on a given board.
3780
3781The following definitions that deal with the placement and management
3782of environment data (variable area); in general, we support the
3783following configurations:
3784
3785- CONFIG_BUILD_ENVCRC:
3786
3787	Builds up envcrc with the target environment so that external utils
3788	may easily extract it and embed it in final U-Boot images.
3789
3790- CONFIG_ENV_IS_IN_FLASH:
3791
3792	Define this if the environment is in flash memory.
3793
3794	a) The environment occupies one whole flash sector, which is
3795	   "embedded" in the text segment with the U-Boot code. This
3796	   happens usually with "bottom boot sector" or "top boot
3797	   sector" type flash chips, which have several smaller
3798	   sectors at the start or the end. For instance, such a
3799	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3800	   such a case you would place the environment in one of the
3801	   4 kB sectors - with U-Boot code before and after it. With
3802	   "top boot sector" type flash chips, you would put the
3803	   environment in one of the last sectors, leaving a gap
3804	   between U-Boot and the environment.
3805
3806	- CONFIG_ENV_OFFSET:
3807
3808	   Offset of environment data (variable area) to the
3809	   beginning of flash memory; for instance, with bottom boot
3810	   type flash chips the second sector can be used: the offset
3811	   for this sector is given here.
3812
3813	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3814
3815	- CONFIG_ENV_ADDR:
3816
3817	   This is just another way to specify the start address of
3818	   the flash sector containing the environment (instead of
3819	   CONFIG_ENV_OFFSET).
3820
3821	- CONFIG_ENV_SECT_SIZE:
3822
3823	   Size of the sector containing the environment.
3824
3825
3826	b) Sometimes flash chips have few, equal sized, BIG sectors.
3827	   In such a case you don't want to spend a whole sector for
3828	   the environment.
3829
3830	- CONFIG_ENV_SIZE:
3831
3832	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3833	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3834	   of this flash sector for the environment. This saves
3835	   memory for the RAM copy of the environment.
3836
3837	   It may also save flash memory if you decide to use this
3838	   when your environment is "embedded" within U-Boot code,
3839	   since then the remainder of the flash sector could be used
3840	   for U-Boot code. It should be pointed out that this is
3841	   STRONGLY DISCOURAGED from a robustness point of view:
3842	   updating the environment in flash makes it always
3843	   necessary to erase the WHOLE sector. If something goes
3844	   wrong before the contents has been restored from a copy in
3845	   RAM, your target system will be dead.
3846
3847	- CONFIG_ENV_ADDR_REDUND
3848	  CONFIG_ENV_SIZE_REDUND
3849
3850	   These settings describe a second storage area used to hold
3851	   a redundant copy of the environment data, so that there is
3852	   a valid backup copy in case there is a power failure during
3853	   a "saveenv" operation.
3854
3855BE CAREFUL! Any changes to the flash layout, and some changes to the
3856source code will make it necessary to adapt <board>/u-boot.lds*
3857accordingly!
3858
3859
3860- CONFIG_ENV_IS_IN_NVRAM:
3861
3862	Define this if you have some non-volatile memory device
3863	(NVRAM, battery buffered SRAM) which you want to use for the
3864	environment.
3865
3866	- CONFIG_ENV_ADDR:
3867	- CONFIG_ENV_SIZE:
3868
3869	  These two #defines are used to determine the memory area you
3870	  want to use for environment. It is assumed that this memory
3871	  can just be read and written to, without any special
3872	  provision.
3873
3874BE CAREFUL! The first access to the environment happens quite early
3875in U-Boot initalization (when we try to get the setting of for the
3876console baudrate). You *MUST* have mapped your NVRAM area then, or
3877U-Boot will hang.
3878
3879Please note that even with NVRAM we still use a copy of the
3880environment in RAM: we could work on NVRAM directly, but we want to
3881keep settings there always unmodified except somebody uses "saveenv"
3882to save the current settings.
3883
3884
3885- CONFIG_ENV_IS_IN_EEPROM:
3886
3887	Use this if you have an EEPROM or similar serial access
3888	device and a driver for it.
3889
3890	- CONFIG_ENV_OFFSET:
3891	- CONFIG_ENV_SIZE:
3892
3893	  These two #defines specify the offset and size of the
3894	  environment area within the total memory of your EEPROM.
3895
3896	- CONFIG_SYS_I2C_EEPROM_ADDR:
3897	  If defined, specified the chip address of the EEPROM device.
3898	  The default address is zero.
3899
3900	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3901	  If defined, the number of bits used to address bytes in a
3902	  single page in the EEPROM device.  A 64 byte page, for example
3903	  would require six bits.
3904
3905	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3906	  If defined, the number of milliseconds to delay between
3907	  page writes.	The default is zero milliseconds.
3908
3909	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3910	  The length in bytes of the EEPROM memory array address.  Note
3911	  that this is NOT the chip address length!
3912
3913	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3914	  EEPROM chips that implement "address overflow" are ones
3915	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3916	  address and the extra bits end up in the "chip address" bit
3917	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3918	  byte chips.
3919
3920	  Note that we consider the length of the address field to
3921	  still be one byte because the extra address bits are hidden
3922	  in the chip address.
3923
3924	- CONFIG_SYS_EEPROM_SIZE:
3925	  The size in bytes of the EEPROM device.
3926
3927	- CONFIG_ENV_EEPROM_IS_ON_I2C
3928	  define this, if you have I2C and SPI activated, and your
3929	  EEPROM, which holds the environment, is on the I2C bus.
3930
3931	- CONFIG_I2C_ENV_EEPROM_BUS
3932	  if you have an Environment on an EEPROM reached over
3933	  I2C muxes, you can define here, how to reach this
3934	  EEPROM. For example:
3935
3936	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3937
3938	  EEPROM which holds the environment, is reached over
3939	  a pca9547 i2c mux with address 0x70, channel 3.
3940
3941- CONFIG_ENV_IS_IN_DATAFLASH:
3942
3943	Define this if you have a DataFlash memory device which you
3944	want to use for the environment.
3945
3946	- CONFIG_ENV_OFFSET:
3947	- CONFIG_ENV_ADDR:
3948	- CONFIG_ENV_SIZE:
3949
3950	  These three #defines specify the offset and size of the
3951	  environment area within the total memory of your DataFlash placed
3952	  at the specified address.
3953
3954- CONFIG_ENV_IS_IN_REMOTE:
3955
3956	Define this if you have a remote memory space which you
3957	want to use for the local device's environment.
3958
3959	- CONFIG_ENV_ADDR:
3960	- CONFIG_ENV_SIZE:
3961
3962	  These two #defines specify the address and size of the
3963	  environment area within the remote memory space. The
3964	  local device can get the environment from remote memory
3965	  space by SRIO or PCIE links.
3966
3967BE CAREFUL! For some special cases, the local device can not use
3968"saveenv" command. For example, the local device will get the
3969environment stored in a remote NOR flash by SRIO or PCIE link,
3970but it can not erase, write this NOR flash by SRIO or PCIE interface.
3971
3972- CONFIG_ENV_IS_IN_NAND:
3973
3974	Define this if you have a NAND device which you want to use
3975	for the environment.
3976
3977	- CONFIG_ENV_OFFSET:
3978	- CONFIG_ENV_SIZE:
3979
3980	  These two #defines specify the offset and size of the environment
3981	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3982	  aligned to an erase block boundary.
3983
3984	- CONFIG_ENV_OFFSET_REDUND (optional):
3985
3986	  This setting describes a second storage area of CONFIG_ENV_SIZE
3987	  size used to hold a redundant copy of the environment data, so
3988	  that there is a valid backup copy in case there is a power failure
3989	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3990	  aligned to an erase block boundary.
3991
3992	- CONFIG_ENV_RANGE (optional):
3993
3994	  Specifies the length of the region in which the environment
3995	  can be written.  This should be a multiple of the NAND device's
3996	  block size.  Specifying a range with more erase blocks than
3997	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3998	  the range to be avoided.
3999
4000	- CONFIG_ENV_OFFSET_OOB (optional):
4001
4002	  Enables support for dynamically retrieving the offset of the
4003	  environment from block zero's out-of-band data.  The
4004	  "nand env.oob" command can be used to record this offset.
4005	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4006	  using CONFIG_ENV_OFFSET_OOB.
4007
4008- CONFIG_NAND_ENV_DST
4009
4010	Defines address in RAM to which the nand_spl code should copy the
4011	environment. If redundant environment is used, it will be copied to
4012	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4013
4014- CONFIG_ENV_IS_IN_UBI:
4015
4016	Define this if you have an UBI volume that you want to use for the
4017	environment.  This has the benefit of wear-leveling the environment
4018	accesses, which is important on NAND.
4019
4020	- CONFIG_ENV_UBI_PART:
4021
4022	  Define this to a string that is the mtd partition containing the UBI.
4023
4024	- CONFIG_ENV_UBI_VOLUME:
4025
4026	  Define this to the name of the volume that you want to store the
4027	  environment in.
4028
4029	- CONFIG_ENV_UBI_VOLUME_REDUND:
4030
4031	  Define this to the name of another volume to store a second copy of
4032	  the environment in.  This will enable redundant environments in UBI.
4033	  It is assumed that both volumes are in the same MTD partition.
4034
4035	- CONFIG_UBI_SILENCE_MSG
4036	- CONFIG_UBIFS_SILENCE_MSG
4037
4038	  You will probably want to define these to avoid a really noisy system
4039	  when storing the env in UBI.
4040
4041- CONFIG_ENV_IS_IN_MMC:
4042
4043	Define this if you have an MMC device which you want to use for the
4044	environment.
4045
4046	- CONFIG_SYS_MMC_ENV_DEV:
4047
4048	  Specifies which MMC device the environment is stored in.
4049
4050	- CONFIG_SYS_MMC_ENV_PART (optional):
4051
4052	  Specifies which MMC partition the environment is stored in. If not
4053	  set, defaults to partition 0, the user area. Common values might be
4054	  1 (first MMC boot partition), 2 (second MMC boot partition).
4055
4056	- CONFIG_ENV_OFFSET:
4057	- CONFIG_ENV_SIZE:
4058
4059	  These two #defines specify the offset and size of the environment
4060	  area within the specified MMC device.
4061
4062	  If offset is positive (the usual case), it is treated as relative to
4063	  the start of the MMC partition. If offset is negative, it is treated
4064	  as relative to the end of the MMC partition. This can be useful if
4065	  your board may be fitted with different MMC devices, which have
4066	  different sizes for the MMC partitions, and you always want the
4067	  environment placed at the very end of the partition, to leave the
4068	  maximum possible space before it, to store other data.
4069
4070	  These two values are in units of bytes, but must be aligned to an
4071	  MMC sector boundary.
4072
4073	- CONFIG_ENV_OFFSET_REDUND (optional):
4074
4075	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4076	  hold a redundant copy of the environment data. This provides a
4077	  valid backup copy in case the other copy is corrupted, e.g. due
4078	  to a power failure during a "saveenv" operation.
4079
4080	  This value may also be positive or negative; this is handled in the
4081	  same way as CONFIG_ENV_OFFSET.
4082
4083	  This value is also in units of bytes, but must also be aligned to
4084	  an MMC sector boundary.
4085
4086	- CONFIG_ENV_SIZE_REDUND (optional):
4087
4088	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4089	  set. If this value is set, it must be set to the same value as
4090	  CONFIG_ENV_SIZE.
4091
4092- CONFIG_SYS_SPI_INIT_OFFSET
4093
4094	Defines offset to the initial SPI buffer area in DPRAM. The
4095	area is used at an early stage (ROM part) if the environment
4096	is configured to reside in the SPI EEPROM: We need a 520 byte
4097	scratch DPRAM area. It is used between the two initialization
4098	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4099	to be a good choice since it makes it far enough from the
4100	start of the data area as well as from the stack pointer.
4101
4102Please note that the environment is read-only until the monitor
4103has been relocated to RAM and a RAM copy of the environment has been
4104created; also, when using EEPROM you will have to use getenv_f()
4105until then to read environment variables.
4106
4107The environment is protected by a CRC32 checksum. Before the monitor
4108is relocated into RAM, as a result of a bad CRC you will be working
4109with the compiled-in default environment - *silently*!!! [This is
4110necessary, because the first environment variable we need is the
4111"baudrate" setting for the console - if we have a bad CRC, we don't
4112have any device yet where we could complain.]
4113
4114Note: once the monitor has been relocated, then it will complain if
4115the default environment is used; a new CRC is computed as soon as you
4116use the "saveenv" command to store a valid environment.
4117
4118- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4119		Echo the inverted Ethernet link state to the fault LED.
4120
4121		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4122		      also needs to be defined.
4123
4124- CONFIG_SYS_FAULT_MII_ADDR:
4125		MII address of the PHY to check for the Ethernet link state.
4126
4127- CONFIG_NS16550_MIN_FUNCTIONS:
4128		Define this if you desire to only have use of the NS16550_init
4129		and NS16550_putc functions for the serial driver located at
4130		drivers/serial/ns16550.c.  This option is useful for saving
4131		space for already greatly restricted images, including but not
4132		limited to NAND_SPL configurations.
4133
4134- CONFIG_DISPLAY_BOARDINFO
4135		Display information about the board that U-Boot is running on
4136		when U-Boot starts up. The board function checkboard() is called
4137		to do this.
4138
4139- CONFIG_DISPLAY_BOARDINFO_LATE
4140		Similar to the previous option, but display this information
4141		later, once stdio is running and output goes to the LCD, if
4142		present.
4143
4144Low Level (hardware related) configuration options:
4145---------------------------------------------------
4146
4147- CONFIG_SYS_CACHELINE_SIZE:
4148		Cache Line Size of the CPU.
4149
4150- CONFIG_SYS_DEFAULT_IMMR:
4151		Default address of the IMMR after system reset.
4152
4153		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4154		and RPXsuper) to be able to adjust the position of
4155		the IMMR register after a reset.
4156
4157- CONFIG_SYS_CCSRBAR_DEFAULT:
4158		Default (power-on reset) physical address of CCSR on Freescale
4159		PowerPC SOCs.
4160
4161- CONFIG_SYS_CCSRBAR:
4162		Virtual address of CCSR.  On a 32-bit build, this is typically
4163		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4164
4165		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4166		for cross-platform code that uses that macro instead.
4167
4168- CONFIG_SYS_CCSRBAR_PHYS:
4169		Physical address of CCSR.  CCSR can be relocated to a new
4170		physical address, if desired.  In this case, this macro should
4171		be set to that address.	 Otherwise, it should be set to the
4172		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4173		is typically relocated on 36-bit builds.  It is recommended
4174		that this macro be defined via the _HIGH and _LOW macros:
4175
4176		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4177			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4178
4179- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4180		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4181		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4182		used in assembly code, so it must not contain typecasts or
4183		integer size suffixes (e.g. "ULL").
4184
4185- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4186		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4187		used in assembly code, so it must not contain typecasts or
4188		integer size suffixes (e.g. "ULL").
4189
4190- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4191		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4192		forced to a value that ensures that CCSR is not relocated.
4193
4194- Floppy Disk Support:
4195		CONFIG_SYS_FDC_DRIVE_NUMBER
4196
4197		the default drive number (default value 0)
4198
4199		CONFIG_SYS_ISA_IO_STRIDE
4200
4201		defines the spacing between FDC chipset registers
4202		(default value 1)
4203
4204		CONFIG_SYS_ISA_IO_OFFSET
4205
4206		defines the offset of register from address. It
4207		depends on which part of the data bus is connected to
4208		the FDC chipset. (default value 0)
4209
4210		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4211		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4212		default value.
4213
4214		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4215		fdc_hw_init() is called at the beginning of the FDC
4216		setup. fdc_hw_init() must be provided by the board
4217		source code. It is used to make hardware dependant
4218		initializations.
4219
4220- CONFIG_IDE_AHB:
4221		Most IDE controllers were designed to be connected with PCI
4222		interface. Only few of them were designed for AHB interface.
4223		When software is doing ATA command and data transfer to
4224		IDE devices through IDE-AHB controller, some additional
4225		registers accessing to these kind of IDE-AHB controller
4226		is requierd.
4227
4228- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4229		DO NOT CHANGE unless you know exactly what you're
4230		doing! (11-4) [MPC8xx/82xx systems only]
4231
4232- CONFIG_SYS_INIT_RAM_ADDR:
4233
4234		Start address of memory area that can be used for
4235		initial data and stack; please note that this must be
4236		writable memory that is working WITHOUT special
4237		initialization, i. e. you CANNOT use normal RAM which
4238		will become available only after programming the
4239		memory controller and running certain initialization
4240		sequences.
4241
4242		U-Boot uses the following memory types:
4243		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4244		- MPC824X: data cache
4245		- PPC4xx:  data cache
4246
4247- CONFIG_SYS_GBL_DATA_OFFSET:
4248
4249		Offset of the initial data structure in the memory
4250		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4251		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4252		data is located at the end of the available space
4253		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4254		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4255		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4256		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4257
4258	Note:
4259		On the MPC824X (or other systems that use the data
4260		cache for initial memory) the address chosen for
4261		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4262		point to an otherwise UNUSED address space between
4263		the top of RAM and the start of the PCI space.
4264
4265- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4266
4267- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4268
4269- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4270
4271- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4272
4273- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4274
4275- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4276
4277- CONFIG_SYS_OR_TIMING_SDRAM:
4278		SDRAM timing
4279
4280- CONFIG_SYS_MAMR_PTA:
4281		periodic timer for refresh
4282
4283- CONFIG_SYS_DER:	Debug Event Register (37-47)
4284
4285- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4286  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4287  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4288  CONFIG_SYS_BR1_PRELIM:
4289		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4290
4291- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4292  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4293  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4294		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4295
4296- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4297  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4298		Machine Mode Register and Memory Periodic Timer
4299		Prescaler definitions (SDRAM timing)
4300
4301- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4302		enable I2C microcode relocation patch (MPC8xx);
4303		define relocation offset in DPRAM [DSP2]
4304
4305- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4306		enable SMC microcode relocation patch (MPC8xx);
4307		define relocation offset in DPRAM [SMC1]
4308
4309- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4310		enable SPI microcode relocation patch (MPC8xx);
4311		define relocation offset in DPRAM [SCC4]
4312
4313- CONFIG_SYS_USE_OSCCLK:
4314		Use OSCM clock mode on MBX8xx board. Be careful,
4315		wrong setting might damage your board. Read
4316		doc/README.MBX before setting this variable!
4317
4318- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4319		Offset of the bootmode word in DPRAM used by post
4320		(Power On Self Tests). This definition overrides
4321		#define'd default value in commproc.h resp.
4322		cpm_8260.h.
4323
4324- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4325  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4326  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4327  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4328  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4329  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4330  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4331  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4332		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4333
4334- CONFIG_PCI_DISABLE_PCIE:
4335		Disable PCI-Express on systems where it is supported but not
4336		required.
4337
4338- CONFIG_PCI_ENUM_ONLY
4339		Only scan through and get the devices on the busses.
4340		Don't do any setup work, presumably because someone or
4341		something has already done it, and we don't need to do it
4342		a second time.	Useful for platforms that are pre-booted
4343		by coreboot or similar.
4344
4345- CONFIG_PCI_INDIRECT_BRIDGE:
4346		Enable support for indirect PCI bridges.
4347
4348- CONFIG_SYS_SRIO:
4349		Chip has SRIO or not
4350
4351- CONFIG_SRIO1:
4352		Board has SRIO 1 port available
4353
4354- CONFIG_SRIO2:
4355		Board has SRIO 2 port available
4356
4357- CONFIG_SRIO_PCIE_BOOT_MASTER
4358		Board can support master function for Boot from SRIO and PCIE
4359
4360- CONFIG_SYS_SRIOn_MEM_VIRT:
4361		Virtual Address of SRIO port 'n' memory region
4362
4363- CONFIG_SYS_SRIOn_MEM_PHYS:
4364		Physical Address of SRIO port 'n' memory region
4365
4366- CONFIG_SYS_SRIOn_MEM_SIZE:
4367		Size of SRIO port 'n' memory region
4368
4369- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4370		Defined to tell the NAND controller that the NAND chip is using
4371		a 16 bit bus.
4372		Not all NAND drivers use this symbol.
4373		Example of drivers that use it:
4374		- drivers/mtd/nand/ndfc.c
4375		- drivers/mtd/nand/mxc_nand.c
4376
4377- CONFIG_SYS_NDFC_EBC0_CFG
4378		Sets the EBC0_CFG register for the NDFC. If not defined
4379		a default value will be used.
4380
4381- CONFIG_SPD_EEPROM
4382		Get DDR timing information from an I2C EEPROM. Common
4383		with pluggable memory modules such as SODIMMs
4384
4385  SPD_EEPROM_ADDRESS
4386		I2C address of the SPD EEPROM
4387
4388- CONFIG_SYS_SPD_BUS_NUM
4389		If SPD EEPROM is on an I2C bus other than the first
4390		one, specify here. Note that the value must resolve
4391		to something your driver can deal with.
4392
4393- CONFIG_SYS_DDR_RAW_TIMING
4394		Get DDR timing information from other than SPD. Common with
4395		soldered DDR chips onboard without SPD. DDR raw timing
4396		parameters are extracted from datasheet and hard-coded into
4397		header files or board specific files.
4398
4399- CONFIG_FSL_DDR_INTERACTIVE
4400		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4401
4402- CONFIG_SYS_83XX_DDR_USES_CS0
4403		Only for 83xx systems. If specified, then DDR should
4404		be configured using CS0 and CS1 instead of CS2 and CS3.
4405
4406- CONFIG_ETHER_ON_FEC[12]
4407		Define to enable FEC[12] on a 8xx series processor.
4408
4409- CONFIG_FEC[12]_PHY
4410		Define to the hardcoded PHY address which corresponds
4411		to the given FEC; i. e.
4412			#define CONFIG_FEC1_PHY 4
4413		means that the PHY with address 4 is connected to FEC1
4414
4415		When set to -1, means to probe for first available.
4416
4417- CONFIG_FEC[12]_PHY_NORXERR
4418		The PHY does not have a RXERR line (RMII only).
4419		(so program the FEC to ignore it).
4420
4421- CONFIG_RMII
4422		Enable RMII mode for all FECs.
4423		Note that this is a global option, we can't
4424		have one FEC in standard MII mode and another in RMII mode.
4425
4426- CONFIG_CRC32_VERIFY
4427		Add a verify option to the crc32 command.
4428		The syntax is:
4429
4430		=> crc32 -v <address> <count> <crc32>
4431
4432		Where address/count indicate a memory area
4433		and crc32 is the correct crc32 which the
4434		area should have.
4435
4436- CONFIG_LOOPW
4437		Add the "loopw" memory command. This only takes effect if
4438		the memory commands are activated globally (CONFIG_CMD_MEM).
4439
4440- CONFIG_MX_CYCLIC
4441		Add the "mdc" and "mwc" memory commands. These are cyclic
4442		"md/mw" commands.
4443		Examples:
4444
4445		=> mdc.b 10 4 500
4446		This command will print 4 bytes (10,11,12,13) each 500 ms.
4447
4448		=> mwc.l 100 12345678 10
4449		This command will write 12345678 to address 100 all 10 ms.
4450
4451		This only takes effect if the memory commands are activated
4452		globally (CONFIG_CMD_MEM).
4453
4454- CONFIG_SKIP_LOWLEVEL_INIT
4455		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4456		low level initializations (like setting up the memory
4457		controller) are omitted and/or U-Boot does not
4458		relocate itself into RAM.
4459
4460		Normally this variable MUST NOT be defined. The only
4461		exception is when U-Boot is loaded (to RAM) by some
4462		other boot loader or by a debugger which performs
4463		these initializations itself.
4464
4465- CONFIG_SPL_BUILD
4466		Modifies the behaviour of start.S when compiling a loader
4467		that is executed before the actual U-Boot. E.g. when
4468		compiling a NAND SPL.
4469
4470- CONFIG_TPL_BUILD
4471		Modifies the behaviour of start.S  when compiling a loader
4472		that is executed after the SPL and before the actual U-Boot.
4473		It is loaded by the SPL.
4474
4475- CONFIG_SYS_MPC85XX_NO_RESETVEC
4476		Only for 85xx systems. If this variable is specified, the section
4477		.resetvec is not kept and the section .bootpg is placed in the
4478		previous 4k of the .text section.
4479
4480- CONFIG_ARCH_MAP_SYSMEM
4481		Generally U-Boot (and in particular the md command) uses
4482		effective address. It is therefore not necessary to regard
4483		U-Boot address as virtual addresses that need to be translated
4484		to physical addresses. However, sandbox requires this, since
4485		it maintains its own little RAM buffer which contains all
4486		addressable memory. This option causes some memory accesses
4487		to be mapped through map_sysmem() / unmap_sysmem().
4488
4489- CONFIG_USE_ARCH_MEMCPY
4490  CONFIG_USE_ARCH_MEMSET
4491		If these options are used a optimized version of memcpy/memset will
4492		be used if available. These functions may be faster under some
4493		conditions but may increase the binary size.
4494
4495- CONFIG_X86_RESET_VECTOR
4496		If defined, the x86 reset vector code is included. This is not
4497		needed when U-Boot is running from Coreboot.
4498
4499- CONFIG_SYS_MPUCLK
4500		Defines the MPU clock speed (in MHz).
4501
4502		NOTE : currently only supported on AM335x platforms.
4503
4504- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4505		Enables the RTC32K OSC on AM33xx based plattforms
4506
4507Freescale QE/FMAN Firmware Support:
4508-----------------------------------
4509
4510The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4511loading of "firmware", which is encoded in the QE firmware binary format.
4512This firmware often needs to be loaded during U-Boot booting, so macros
4513are used to identify the storage device (NOR flash, SPI, etc) and the address
4514within that device.
4515
4516- CONFIG_SYS_FMAN_FW_ADDR
4517	The address in the storage device where the FMAN microcode is located.  The
4518	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4519	is also specified.
4520
4521- CONFIG_SYS_QE_FW_ADDR
4522	The address in the storage device where the QE microcode is located.  The
4523	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4524	is also specified.
4525
4526- CONFIG_SYS_QE_FMAN_FW_LENGTH
4527	The maximum possible size of the firmware.  The firmware binary format
4528	has a field that specifies the actual size of the firmware, but it
4529	might not be possible to read any part of the firmware unless some
4530	local storage is allocated to hold the entire firmware first.
4531
4532- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4533	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4534	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4535	virtual address in NOR flash.
4536
4537- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4538	Specifies that QE/FMAN firmware is located in NAND flash.
4539	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4540
4541- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4542	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4543	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4544
4545- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4546	Specifies that QE/FMAN firmware is located on the primary SPI
4547	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4548
4549- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4550	Specifies that QE/FMAN firmware is located in the remote (master)
4551	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4552	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4553	window->master inbound window->master LAW->the ucode address in
4554	master's memory space.
4555
4556Building the Software:
4557======================
4558
4559Building U-Boot has been tested in several native build environments
4560and in many different cross environments. Of course we cannot support
4561all possibly existing versions of cross development tools in all
4562(potentially obsolete) versions. In case of tool chain problems we
4563recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4564which is extensively used to build and test U-Boot.
4565
4566If you are not using a native environment, it is assumed that you
4567have GNU cross compiling tools available in your path. In this case,
4568you must set the environment variable CROSS_COMPILE in your shell.
4569Note that no changes to the Makefile or any other source files are
4570necessary. For example using the ELDK on a 4xx CPU, please enter:
4571
4572	$ CROSS_COMPILE=ppc_4xx-
4573	$ export CROSS_COMPILE
4574
4575Note: If you wish to generate Windows versions of the utilities in
4576      the tools directory you can use the MinGW toolchain
4577      (http://www.mingw.org).  Set your HOST tools to the MinGW
4578      toolchain and execute 'make tools'.  For example:
4579
4580       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4581
4582      Binaries such as tools/mkimage.exe will be created which can
4583      be executed on computers running Windows.
4584
4585U-Boot is intended to be simple to build. After installing the
4586sources you must configure U-Boot for one specific board type. This
4587is done by typing:
4588
4589	make NAME_config
4590
4591where "NAME_config" is the name of one of the existing configu-
4592rations; see boards.cfg for supported names.
4593
4594Note: for some board special configuration names may exist; check if
4595      additional information is available from the board vendor; for
4596      instance, the TQM823L systems are available without (standard)
4597      or with LCD support. You can select such additional "features"
4598      when choosing the configuration, i. e.
4599
4600      make TQM823L_config
4601	- will configure for a plain TQM823L, i. e. no LCD support
4602
4603      make TQM823L_LCD_config
4604	- will configure for a TQM823L with U-Boot console on LCD
4605
4606      etc.
4607
4608
4609Finally, type "make all", and you should get some working U-Boot
4610images ready for download to / installation on your system:
4611
4612- "u-boot.bin" is a raw binary image
4613- "u-boot" is an image in ELF binary format
4614- "u-boot.srec" is in Motorola S-Record format
4615
4616By default the build is performed locally and the objects are saved
4617in the source directory. One of the two methods can be used to change
4618this behavior and build U-Boot to some external directory:
4619
46201. Add O= to the make command line invocations:
4621
4622	make O=/tmp/build distclean
4623	make O=/tmp/build NAME_config
4624	make O=/tmp/build all
4625
46262. Set environment variable BUILD_DIR to point to the desired location:
4627
4628	export BUILD_DIR=/tmp/build
4629	make distclean
4630	make NAME_config
4631	make all
4632
4633Note that the command line "O=" setting overrides the BUILD_DIR environment
4634variable.
4635
4636
4637Please be aware that the Makefiles assume you are using GNU make, so
4638for instance on NetBSD you might need to use "gmake" instead of
4639native "make".
4640
4641
4642If the system board that you have is not listed, then you will need
4643to port U-Boot to your hardware platform. To do this, follow these
4644steps:
4645
46461.  Add a new configuration option for your board to the toplevel
4647    "boards.cfg" file, using the existing entries as examples.
4648    Follow the instructions there to keep the boards in order.
46492.  Create a new directory to hold your board specific code. Add any
4650    files you need. In your board directory, you will need at least
4651    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46523.  Create a new configuration file "include/configs/<board>.h" for
4653    your board
46543.  If you're porting U-Boot to a new CPU, then also create a new
4655    directory to hold your CPU specific code. Add any files you need.
46564.  Run "make <board>_config" with your new name.
46575.  Type "make", and you should get a working "u-boot.srec" file
4658    to be installed on your target system.
46596.  Debug and solve any problems that might arise.
4660    [Of course, this last step is much harder than it sounds.]
4661
4662
4663Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4664==============================================================
4665
4666If you have modified U-Boot sources (for instance added a new board
4667or support for new devices, a new CPU, etc.) you are expected to
4668provide feedback to the other developers. The feedback normally takes
4669the form of a "patch", i. e. a context diff against a certain (latest
4670official or latest in the git repository) version of U-Boot sources.
4671
4672But before you submit such a patch, please verify that your modifi-
4673cation did not break existing code. At least make sure that *ALL* of
4674the supported boards compile WITHOUT ANY compiler warnings. To do so,
4675just run the "MAKEALL" script, which will configure and build U-Boot
4676for ALL supported system. Be warned, this will take a while. You can
4677select which (cross) compiler to use by passing a `CROSS_COMPILE'
4678environment variable to the script, i. e. to use the ELDK cross tools
4679you can type
4680
4681	CROSS_COMPILE=ppc_8xx- MAKEALL
4682
4683or to build on a native PowerPC system you can type
4684
4685	CROSS_COMPILE=' ' MAKEALL
4686
4687When using the MAKEALL script, the default behaviour is to build
4688U-Boot in the source directory. This location can be changed by
4689setting the BUILD_DIR environment variable. Also, for each target
4690built, the MAKEALL script saves two log files (<target>.ERR and
4691<target>.MAKEALL) in the <source dir>/LOG directory. This default
4692location can be changed by setting the MAKEALL_LOGDIR environment
4693variable. For example:
4694
4695	export BUILD_DIR=/tmp/build
4696	export MAKEALL_LOGDIR=/tmp/log
4697	CROSS_COMPILE=ppc_8xx- MAKEALL
4698
4699With the above settings build objects are saved in the /tmp/build,
4700log files are saved in the /tmp/log and the source tree remains clean
4701during the whole build process.
4702
4703
4704See also "U-Boot Porting Guide" below.
4705
4706
4707Monitor Commands - Overview:
4708============================
4709
4710go	- start application at address 'addr'
4711run	- run commands in an environment variable
4712bootm	- boot application image from memory
4713bootp	- boot image via network using BootP/TFTP protocol
4714bootz   - boot zImage from memory
4715tftpboot- boot image via network using TFTP protocol
4716	       and env variables "ipaddr" and "serverip"
4717	       (and eventually "gatewayip")
4718tftpput - upload a file via network using TFTP protocol
4719rarpboot- boot image via network using RARP/TFTP protocol
4720diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4721loads	- load S-Record file over serial line
4722loadb	- load binary file over serial line (kermit mode)
4723md	- memory display
4724mm	- memory modify (auto-incrementing)
4725nm	- memory modify (constant address)
4726mw	- memory write (fill)
4727cp	- memory copy
4728cmp	- memory compare
4729crc32	- checksum calculation
4730i2c	- I2C sub-system
4731sspi	- SPI utility commands
4732base	- print or set address offset
4733printenv- print environment variables
4734setenv	- set environment variables
4735saveenv - save environment variables to persistent storage
4736protect - enable or disable FLASH write protection
4737erase	- erase FLASH memory
4738flinfo	- print FLASH memory information
4739nand	- NAND memory operations (see doc/README.nand)
4740bdinfo	- print Board Info structure
4741iminfo	- print header information for application image
4742coninfo - print console devices and informations
4743ide	- IDE sub-system
4744loop	- infinite loop on address range
4745loopw	- infinite write loop on address range
4746mtest	- simple RAM test
4747icache	- enable or disable instruction cache
4748dcache	- enable or disable data cache
4749reset	- Perform RESET of the CPU
4750echo	- echo args to console
4751version - print monitor version
4752help	- print online help
4753?	- alias for 'help'
4754
4755
4756Monitor Commands - Detailed Description:
4757========================================
4758
4759TODO.
4760
4761For now: just type "help <command>".
4762
4763
4764Environment Variables:
4765======================
4766
4767U-Boot supports user configuration using Environment Variables which
4768can be made persistent by saving to Flash memory.
4769
4770Environment Variables are set using "setenv", printed using
4771"printenv", and saved to Flash using "saveenv". Using "setenv"
4772without a value can be used to delete a variable from the
4773environment. As long as you don't save the environment you are
4774working with an in-memory copy. In case the Flash area containing the
4775environment is erased by accident, a default environment is provided.
4776
4777Some configuration options can be set using Environment Variables.
4778
4779List of environment variables (most likely not complete):
4780
4781  baudrate	- see CONFIG_BAUDRATE
4782
4783  bootdelay	- see CONFIG_BOOTDELAY
4784
4785  bootcmd	- see CONFIG_BOOTCOMMAND
4786
4787  bootargs	- Boot arguments when booting an RTOS image
4788
4789  bootfile	- Name of the image to load with TFTP
4790
4791  bootm_low	- Memory range available for image processing in the bootm
4792		  command can be restricted. This variable is given as
4793		  a hexadecimal number and defines lowest address allowed
4794		  for use by the bootm command. See also "bootm_size"
4795		  environment variable. Address defined by "bootm_low" is
4796		  also the base of the initial memory mapping for the Linux
4797		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4798		  bootm_mapsize.
4799
4800  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4801		  This variable is given as a hexadecimal number and it
4802		  defines the size of the memory region starting at base
4803		  address bootm_low that is accessible by the Linux kernel
4804		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4805		  as the default value if it is defined, and bootm_size is
4806		  used otherwise.
4807
4808  bootm_size	- Memory range available for image processing in the bootm
4809		  command can be restricted. This variable is given as
4810		  a hexadecimal number and defines the size of the region
4811		  allowed for use by the bootm command. See also "bootm_low"
4812		  environment variable.
4813
4814  updatefile	- Location of the software update file on a TFTP server, used
4815		  by the automatic software update feature. Please refer to
4816		  documentation in doc/README.update for more details.
4817
4818  autoload	- if set to "no" (any string beginning with 'n'),
4819		  "bootp" will just load perform a lookup of the
4820		  configuration from the BOOTP server, but not try to
4821		  load any image using TFTP
4822
4823  autostart	- if set to "yes", an image loaded using the "bootp",
4824		  "rarpboot", "tftpboot" or "diskboot" commands will
4825		  be automatically started (by internally calling
4826		  "bootm")
4827
4828		  If set to "no", a standalone image passed to the
4829		  "bootm" command will be copied to the load address
4830		  (and eventually uncompressed), but NOT be started.
4831		  This can be used to load and uncompress arbitrary
4832		  data.
4833
4834  fdt_high	- if set this restricts the maximum address that the
4835		  flattened device tree will be copied into upon boot.
4836		  For example, if you have a system with 1 GB memory
4837		  at physical address 0x10000000, while Linux kernel
4838		  only recognizes the first 704 MB as low memory, you
4839		  may need to set fdt_high as 0x3C000000 to have the
4840		  device tree blob be copied to the maximum address
4841		  of the 704 MB low memory, so that Linux kernel can
4842		  access it during the boot procedure.
4843
4844		  If this is set to the special value 0xFFFFFFFF then
4845		  the fdt will not be copied at all on boot.  For this
4846		  to work it must reside in writable memory, have
4847		  sufficient padding on the end of it for u-boot to
4848		  add the information it needs into it, and the memory
4849		  must be accessible by the kernel.
4850
4851  fdtcontroladdr- if set this is the address of the control flattened
4852		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4853		  defined.
4854
4855  i2cfast	- (PPC405GP|PPC405EP only)
4856		  if set to 'y' configures Linux I2C driver for fast
4857		  mode (400kHZ). This environment variable is used in
4858		  initialization code. So, for changes to be effective
4859		  it must be saved and board must be reset.
4860
4861  initrd_high	- restrict positioning of initrd images:
4862		  If this variable is not set, initrd images will be
4863		  copied to the highest possible address in RAM; this
4864		  is usually what you want since it allows for
4865		  maximum initrd size. If for some reason you want to
4866		  make sure that the initrd image is loaded below the
4867		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4868		  variable to a value of "no" or "off" or "0".
4869		  Alternatively, you can set it to a maximum upper
4870		  address to use (U-Boot will still check that it
4871		  does not overwrite the U-Boot stack and data).
4872
4873		  For instance, when you have a system with 16 MB
4874		  RAM, and want to reserve 4 MB from use by Linux,
4875		  you can do this by adding "mem=12M" to the value of
4876		  the "bootargs" variable. However, now you must make
4877		  sure that the initrd image is placed in the first
4878		  12 MB as well - this can be done with
4879
4880		  setenv initrd_high 00c00000
4881
4882		  If you set initrd_high to 0xFFFFFFFF, this is an
4883		  indication to U-Boot that all addresses are legal
4884		  for the Linux kernel, including addresses in flash
4885		  memory. In this case U-Boot will NOT COPY the
4886		  ramdisk at all. This may be useful to reduce the
4887		  boot time on your system, but requires that this
4888		  feature is supported by your Linux kernel.
4889
4890  ipaddr	- IP address; needed for tftpboot command
4891
4892  loadaddr	- Default load address for commands like "bootp",
4893		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4894
4895  loads_echo	- see CONFIG_LOADS_ECHO
4896
4897  serverip	- TFTP server IP address; needed for tftpboot command
4898
4899  bootretry	- see CONFIG_BOOT_RETRY_TIME
4900
4901  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4902
4903  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4904
4905  ethprime	- controls which interface is used first.
4906
4907  ethact	- controls which interface is currently active.
4908		  For example you can do the following
4909
4910		  => setenv ethact FEC
4911		  => ping 192.168.0.1 # traffic sent on FEC
4912		  => setenv ethact SCC
4913		  => ping 10.0.0.1 # traffic sent on SCC
4914
4915  ethrotate	- When set to "no" U-Boot does not go through all
4916		  available network interfaces.
4917		  It just stays at the currently selected interface.
4918
4919  netretry	- When set to "no" each network operation will
4920		  either succeed or fail without retrying.
4921		  When set to "once" the network operation will
4922		  fail when all the available network interfaces
4923		  are tried once without success.
4924		  Useful on scripts which control the retry operation
4925		  themselves.
4926
4927  npe_ucode	- set load address for the NPE microcode
4928
4929  silent_linux  - If set then linux will be told to boot silently, by
4930		  changing the console to be empty. If "yes" it will be
4931		  made silent. If "no" it will not be made silent. If
4932		  unset, then it will be made silent if the U-Boot console
4933		  is silent.
4934
4935  tftpsrcport	- If this is set, the value is used for TFTP's
4936		  UDP source port.
4937
4938  tftpdstport	- If this is set, the value is used for TFTP's UDP
4939		  destination port instead of the Well Know Port 69.
4940
4941  tftpblocksize - Block size to use for TFTP transfers; if not set,
4942		  we use the TFTP server's default block size
4943
4944  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4945		  seconds, minimum value is 1000 = 1 second). Defines
4946		  when a packet is considered to be lost so it has to
4947		  be retransmitted. The default is 5000 = 5 seconds.
4948		  Lowering this value may make downloads succeed
4949		  faster in networks with high packet loss rates or
4950		  with unreliable TFTP servers.
4951
4952  vlan		- When set to a value < 4095 the traffic over
4953		  Ethernet is encapsulated/received over 802.1q
4954		  VLAN tagged frames.
4955
4956The following image location variables contain the location of images
4957used in booting. The "Image" column gives the role of the image and is
4958not an environment variable name. The other columns are environment
4959variable names. "File Name" gives the name of the file on a TFTP
4960server, "RAM Address" gives the location in RAM the image will be
4961loaded to, and "Flash Location" gives the image's address in NOR
4962flash or offset in NAND flash.
4963
4964*Note* - these variables don't have to be defined for all boards, some
4965boards currenlty use other variables for these purposes, and some
4966boards use these variables for other purposes.
4967
4968Image		    File Name	     RAM Address       Flash Location
4969-----		    ---------	     -----------       --------------
4970u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4971Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4972device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4973ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4974
4975The following environment variables may be used and automatically
4976updated by the network boot commands ("bootp" and "rarpboot"),
4977depending the information provided by your boot server:
4978
4979  bootfile	- see above
4980  dnsip		- IP address of your Domain Name Server
4981  dnsip2	- IP address of your secondary Domain Name Server
4982  gatewayip	- IP address of the Gateway (Router) to use
4983  hostname	- Target hostname
4984  ipaddr	- see above
4985  netmask	- Subnet Mask
4986  rootpath	- Pathname of the root filesystem on the NFS server
4987  serverip	- see above
4988
4989
4990There are two special Environment Variables:
4991
4992  serial#	- contains hardware identification information such
4993		  as type string and/or serial number
4994  ethaddr	- Ethernet address
4995
4996These variables can be set only once (usually during manufacturing of
4997the board). U-Boot refuses to delete or overwrite these variables
4998once they have been set once.
4999
5000
5001Further special Environment Variables:
5002
5003  ver		- Contains the U-Boot version string as printed
5004		  with the "version" command. This variable is
5005		  readonly (see CONFIG_VERSION_VARIABLE).
5006
5007
5008Please note that changes to some configuration parameters may take
5009only effect after the next boot (yes, that's just like Windoze :-).
5010
5011
5012Callback functions for environment variables:
5013---------------------------------------------
5014
5015For some environment variables, the behavior of u-boot needs to change
5016when their values are changed.  This functionailty allows functions to
5017be associated with arbitrary variables.  On creation, overwrite, or
5018deletion, the callback will provide the opportunity for some side
5019effect to happen or for the change to be rejected.
5020
5021The callbacks are named and associated with a function using the
5022U_BOOT_ENV_CALLBACK macro in your board or driver code.
5023
5024These callbacks are associated with variables in one of two ways.  The
5025static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5026in the board configuration to a string that defines a list of
5027associations.  The list must be in the following format:
5028
5029	entry = variable_name[:callback_name]
5030	list = entry[,list]
5031
5032If the callback name is not specified, then the callback is deleted.
5033Spaces are also allowed anywhere in the list.
5034
5035Callbacks can also be associated by defining the ".callbacks" variable
5036with the same list format above.  Any association in ".callbacks" will
5037override any association in the static list. You can define
5038CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5039".callbacks" envirnoment variable in the default or embedded environment.
5040
5041
5042Command Line Parsing:
5043=====================
5044
5045There are two different command line parsers available with U-Boot:
5046the old "simple" one, and the much more powerful "hush" shell:
5047
5048Old, simple command line parser:
5049--------------------------------
5050
5051- supports environment variables (through setenv / saveenv commands)
5052- several commands on one line, separated by ';'
5053- variable substitution using "... ${name} ..." syntax
5054- special characters ('$', ';') can be escaped by prefixing with '\',
5055  for example:
5056	setenv bootcmd bootm \${address}
5057- You can also escape text by enclosing in single apostrophes, for example:
5058	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5059
5060Hush shell:
5061-----------
5062
5063- similar to Bourne shell, with control structures like
5064  if...then...else...fi, for...do...done; while...do...done,
5065  until...do...done, ...
5066- supports environment ("global") variables (through setenv / saveenv
5067  commands) and local shell variables (through standard shell syntax
5068  "name=value"); only environment variables can be used with "run"
5069  command
5070
5071General rules:
5072--------------
5073
5074(1) If a command line (or an environment variable executed by a "run"
5075    command) contains several commands separated by semicolon, and
5076    one of these commands fails, then the remaining commands will be
5077    executed anyway.
5078
5079(2) If you execute several variables with one call to run (i. e.
5080    calling run with a list of variables as arguments), any failing
5081    command will cause "run" to terminate, i. e. the remaining
5082    variables are not executed.
5083
5084Note for Redundant Ethernet Interfaces:
5085=======================================
5086
5087Some boards come with redundant Ethernet interfaces; U-Boot supports
5088such configurations and is capable of automatic selection of a
5089"working" interface when needed. MAC assignment works as follows:
5090
5091Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5092MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5093"eth1addr" (=>eth1), "eth2addr", ...
5094
5095If the network interface stores some valid MAC address (for instance
5096in SROM), this is used as default address if there is NO correspon-
5097ding setting in the environment; if the corresponding environment
5098variable is set, this overrides the settings in the card; that means:
5099
5100o If the SROM has a valid MAC address, and there is no address in the
5101  environment, the SROM's address is used.
5102
5103o If there is no valid address in the SROM, and a definition in the
5104  environment exists, then the value from the environment variable is
5105  used.
5106
5107o If both the SROM and the environment contain a MAC address, and
5108  both addresses are the same, this MAC address is used.
5109
5110o If both the SROM and the environment contain a MAC address, and the
5111  addresses differ, the value from the environment is used and a
5112  warning is printed.
5113
5114o If neither SROM nor the environment contain a MAC address, an error
5115  is raised.
5116
5117If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5118will be programmed into hardware as part of the initialization process.	 This
5119may be skipped by setting the appropriate 'ethmacskip' environment variable.
5120The naming convention is as follows:
5121"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5122
5123Image Formats:
5124==============
5125
5126U-Boot is capable of booting (and performing other auxiliary operations on)
5127images in two formats:
5128
5129New uImage format (FIT)
5130-----------------------
5131
5132Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5133to Flattened Device Tree). It allows the use of images with multiple
5134components (several kernels, ramdisks, etc.), with contents protected by
5135SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5136
5137
5138Old uImage format
5139-----------------
5140
5141Old image format is based on binary files which can be basically anything,
5142preceded by a special header; see the definitions in include/image.h for
5143details; basically, the header defines the following image properties:
5144
5145* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5146  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5147  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5148  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5149  INTEGRITY).
5150* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5151  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5152  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5153* Compression Type (uncompressed, gzip, bzip2)
5154* Load Address
5155* Entry Point
5156* Image Name
5157* Image Timestamp
5158
5159The header is marked by a special Magic Number, and both the header
5160and the data portions of the image are secured against corruption by
5161CRC32 checksums.
5162
5163
5164Linux Support:
5165==============
5166
5167Although U-Boot should support any OS or standalone application
5168easily, the main focus has always been on Linux during the design of
5169U-Boot.
5170
5171U-Boot includes many features that so far have been part of some
5172special "boot loader" code within the Linux kernel. Also, any
5173"initrd" images to be used are no longer part of one big Linux image;
5174instead, kernel and "initrd" are separate images. This implementation
5175serves several purposes:
5176
5177- the same features can be used for other OS or standalone
5178  applications (for instance: using compressed images to reduce the
5179  Flash memory footprint)
5180
5181- it becomes much easier to port new Linux kernel versions because
5182  lots of low-level, hardware dependent stuff are done by U-Boot
5183
5184- the same Linux kernel image can now be used with different "initrd"
5185  images; of course this also means that different kernel images can
5186  be run with the same "initrd". This makes testing easier (you don't
5187  have to build a new "zImage.initrd" Linux image when you just
5188  change a file in your "initrd"). Also, a field-upgrade of the
5189  software is easier now.
5190
5191
5192Linux HOWTO:
5193============
5194
5195Porting Linux to U-Boot based systems:
5196---------------------------------------
5197
5198U-Boot cannot save you from doing all the necessary modifications to
5199configure the Linux device drivers for use with your target hardware
5200(no, we don't intend to provide a full virtual machine interface to
5201Linux :-).
5202
5203But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5204
5205Just make sure your machine specific header file (for instance
5206include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5207Information structure as we define in include/asm-<arch>/u-boot.h,
5208and make sure that your definition of IMAP_ADDR uses the same value
5209as your U-Boot configuration in CONFIG_SYS_IMMR.
5210
5211
5212Configuring the Linux kernel:
5213-----------------------------
5214
5215No specific requirements for U-Boot. Make sure you have some root
5216device (initial ramdisk, NFS) for your target system.
5217
5218
5219Building a Linux Image:
5220-----------------------
5221
5222With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5223not used. If you use recent kernel source, a new build target
5224"uImage" will exist which automatically builds an image usable by
5225U-Boot. Most older kernels also have support for a "pImage" target,
5226which was introduced for our predecessor project PPCBoot and uses a
5227100% compatible format.
5228
5229Example:
5230
5231	make TQM850L_config
5232	make oldconfig
5233	make dep
5234	make uImage
5235
5236The "uImage" build target uses a special tool (in 'tools/mkimage') to
5237encapsulate a compressed Linux kernel image with header	 information,
5238CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5239
5240* build a standard "vmlinux" kernel image (in ELF binary format):
5241
5242* convert the kernel into a raw binary image:
5243
5244	${CROSS_COMPILE}-objcopy -O binary \
5245				 -R .note -R .comment \
5246				 -S vmlinux linux.bin
5247
5248* compress the binary image:
5249
5250	gzip -9 linux.bin
5251
5252* package compressed binary image for U-Boot:
5253
5254	mkimage -A ppc -O linux -T kernel -C gzip \
5255		-a 0 -e 0 -n "Linux Kernel Image" \
5256		-d linux.bin.gz uImage
5257
5258
5259The "mkimage" tool can also be used to create ramdisk images for use
5260with U-Boot, either separated from the Linux kernel image, or
5261combined into one file. "mkimage" encapsulates the images with a 64
5262byte header containing information about target architecture,
5263operating system, image type, compression method, entry points, time
5264stamp, CRC32 checksums, etc.
5265
5266"mkimage" can be called in two ways: to verify existing images and
5267print the header information, or to build new images.
5268
5269In the first form (with "-l" option) mkimage lists the information
5270contained in the header of an existing U-Boot image; this includes
5271checksum verification:
5272
5273	tools/mkimage -l image
5274	  -l ==> list image header information
5275
5276The second form (with "-d" option) is used to build a U-Boot image
5277from a "data file" which is used as image payload:
5278
5279	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5280		      -n name -d data_file image
5281	  -A ==> set architecture to 'arch'
5282	  -O ==> set operating system to 'os'
5283	  -T ==> set image type to 'type'
5284	  -C ==> set compression type 'comp'
5285	  -a ==> set load address to 'addr' (hex)
5286	  -e ==> set entry point to 'ep' (hex)
5287	  -n ==> set image name to 'name'
5288	  -d ==> use image data from 'datafile'
5289
5290Right now, all Linux kernels for PowerPC systems use the same load
5291address (0x00000000), but the entry point address depends on the
5292kernel version:
5293
5294- 2.2.x kernels have the entry point at 0x0000000C,
5295- 2.3.x and later kernels have the entry point at 0x00000000.
5296
5297So a typical call to build a U-Boot image would read:
5298
5299	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5300	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5301	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5302	> examples/uImage.TQM850L
5303	Image Name:   2.4.4 kernel for TQM850L
5304	Created:      Wed Jul 19 02:34:59 2000
5305	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5306	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5307	Load Address: 0x00000000
5308	Entry Point:  0x00000000
5309
5310To verify the contents of the image (or check for corruption):
5311
5312	-> tools/mkimage -l examples/uImage.TQM850L
5313	Image Name:   2.4.4 kernel for TQM850L
5314	Created:      Wed Jul 19 02:34:59 2000
5315	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5316	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5317	Load Address: 0x00000000
5318	Entry Point:  0x00000000
5319
5320NOTE: for embedded systems where boot time is critical you can trade
5321speed for memory and install an UNCOMPRESSED image instead: this
5322needs more space in Flash, but boots much faster since it does not
5323need to be uncompressed:
5324
5325	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5326	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5327	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5328	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5329	> examples/uImage.TQM850L-uncompressed
5330	Image Name:   2.4.4 kernel for TQM850L
5331	Created:      Wed Jul 19 02:34:59 2000
5332	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5333	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5334	Load Address: 0x00000000
5335	Entry Point:  0x00000000
5336
5337
5338Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5339when your kernel is intended to use an initial ramdisk:
5340
5341	-> tools/mkimage -n 'Simple Ramdisk Image' \
5342	> -A ppc -O linux -T ramdisk -C gzip \
5343	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5344	Image Name:   Simple Ramdisk Image
5345	Created:      Wed Jan 12 14:01:50 2000
5346	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5347	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5348	Load Address: 0x00000000
5349	Entry Point:  0x00000000
5350
5351The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5352option performs the converse operation of the mkimage's second form (the "-d"
5353option). Given an image built by mkimage, the dumpimage extracts a "data file"
5354from the image:
5355
5356	tools/dumpimage -i image -p position data_file
5357	  -i ==> extract from the 'image' a specific 'data_file', \
5358	   indexed by 'position'
5359
5360
5361Installing a Linux Image:
5362-------------------------
5363
5364To downloading a U-Boot image over the serial (console) interface,
5365you must convert the image to S-Record format:
5366
5367	objcopy -I binary -O srec examples/image examples/image.srec
5368
5369The 'objcopy' does not understand the information in the U-Boot
5370image header, so the resulting S-Record file will be relative to
5371address 0x00000000. To load it to a given address, you need to
5372specify the target address as 'offset' parameter with the 'loads'
5373command.
5374
5375Example: install the image to address 0x40100000 (which on the
5376TQM8xxL is in the first Flash bank):
5377
5378	=> erase 40100000 401FFFFF
5379
5380	.......... done
5381	Erased 8 sectors
5382
5383	=> loads 40100000
5384	## Ready for S-Record download ...
5385	~>examples/image.srec
5386	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5387	...
5388	15989 15990 15991 15992
5389	[file transfer complete]
5390	[connected]
5391	## Start Addr = 0x00000000
5392
5393
5394You can check the success of the download using the 'iminfo' command;
5395this includes a checksum verification so you can be sure no data
5396corruption happened:
5397
5398	=> imi 40100000
5399
5400	## Checking Image at 40100000 ...
5401	   Image Name:	 2.2.13 for initrd on TQM850L
5402	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5403	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5404	   Load Address: 00000000
5405	   Entry Point:	 0000000c
5406	   Verifying Checksum ... OK
5407
5408
5409Boot Linux:
5410-----------
5411
5412The "bootm" command is used to boot an application that is stored in
5413memory (RAM or Flash). In case of a Linux kernel image, the contents
5414of the "bootargs" environment variable is passed to the kernel as
5415parameters. You can check and modify this variable using the
5416"printenv" and "setenv" commands:
5417
5418
5419	=> printenv bootargs
5420	bootargs=root=/dev/ram
5421
5422	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5423
5424	=> printenv bootargs
5425	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5426
5427	=> bootm 40020000
5428	## Booting Linux kernel at 40020000 ...
5429	   Image Name:	 2.2.13 for NFS on TQM850L
5430	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5431	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5432	   Load Address: 00000000
5433	   Entry Point:	 0000000c
5434	   Verifying Checksum ... OK
5435	   Uncompressing Kernel Image ... OK
5436	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
5437	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5438	time_init: decrementer frequency = 187500000/60
5439	Calibrating delay loop... 49.77 BogoMIPS
5440	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5441	...
5442
5443If you want to boot a Linux kernel with initial RAM disk, you pass
5444the memory addresses of both the kernel and the initrd image (PPBCOOT
5445format!) to the "bootm" command:
5446
5447	=> imi 40100000 40200000
5448
5449	## Checking Image at 40100000 ...
5450	   Image Name:	 2.2.13 for initrd on TQM850L
5451	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5452	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5453	   Load Address: 00000000
5454	   Entry Point:	 0000000c
5455	   Verifying Checksum ... OK
5456
5457	## Checking Image at 40200000 ...
5458	   Image Name:	 Simple Ramdisk Image
5459	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5460	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5461	   Load Address: 00000000
5462	   Entry Point:	 00000000
5463	   Verifying Checksum ... OK
5464
5465	=> bootm 40100000 40200000
5466	## Booting Linux kernel at 40100000 ...
5467	   Image Name:	 2.2.13 for initrd on TQM850L
5468	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5469	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5470	   Load Address: 00000000
5471	   Entry Point:	 0000000c
5472	   Verifying Checksum ... OK
5473	   Uncompressing Kernel Image ... OK
5474	## Loading RAMDisk Image at 40200000 ...
5475	   Image Name:	 Simple Ramdisk Image
5476	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5477	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5478	   Load Address: 00000000
5479	   Entry Point:	 00000000
5480	   Verifying Checksum ... OK
5481	   Loading Ramdisk ... OK
5482	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
5483	Boot arguments: root=/dev/ram
5484	time_init: decrementer frequency = 187500000/60
5485	Calibrating delay loop... 49.77 BogoMIPS
5486	...
5487	RAMDISK: Compressed image found at block 0
5488	VFS: Mounted root (ext2 filesystem).
5489
5490	bash#
5491
5492Boot Linux and pass a flat device tree:
5493-----------
5494
5495First, U-Boot must be compiled with the appropriate defines. See the section
5496titled "Linux Kernel Interface" above for a more in depth explanation. The
5497following is an example of how to start a kernel and pass an updated
5498flat device tree:
5499
5500=> print oftaddr
5501oftaddr=0x300000
5502=> print oft
5503oft=oftrees/mpc8540ads.dtb
5504=> tftp $oftaddr $oft
5505Speed: 1000, full duplex
5506Using TSEC0 device
5507TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5508Filename 'oftrees/mpc8540ads.dtb'.
5509Load address: 0x300000
5510Loading: #
5511done
5512Bytes transferred = 4106 (100a hex)
5513=> tftp $loadaddr $bootfile
5514Speed: 1000, full duplex
5515Using TSEC0 device
5516TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5517Filename 'uImage'.
5518Load address: 0x200000
5519Loading:############
5520done
5521Bytes transferred = 1029407 (fb51f hex)
5522=> print loadaddr
5523loadaddr=200000
5524=> print oftaddr
5525oftaddr=0x300000
5526=> bootm $loadaddr - $oftaddr
5527## Booting image at 00200000 ...
5528   Image Name:	 Linux-2.6.17-dirty
5529   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5530   Data Size:	 1029343 Bytes = 1005.2 kB
5531   Load Address: 00000000
5532   Entry Point:	 00000000
5533   Verifying Checksum ... OK
5534   Uncompressing Kernel Image ... OK
5535Booting using flat device tree at 0x300000
5536Using MPC85xx ADS machine description
5537Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5538[snip]
5539
5540
5541More About U-Boot Image Types:
5542------------------------------
5543
5544U-Boot supports the following image types:
5545
5546   "Standalone Programs" are directly runnable in the environment
5547	provided by U-Boot; it is expected that (if they behave
5548	well) you can continue to work in U-Boot after return from
5549	the Standalone Program.
5550   "OS Kernel Images" are usually images of some Embedded OS which
5551	will take over control completely. Usually these programs
5552	will install their own set of exception handlers, device
5553	drivers, set up the MMU, etc. - this means, that you cannot
5554	expect to re-enter U-Boot except by resetting the CPU.
5555   "RAMDisk Images" are more or less just data blocks, and their
5556	parameters (address, size) are passed to an OS kernel that is
5557	being started.
5558   "Multi-File Images" contain several images, typically an OS
5559	(Linux) kernel image and one or more data images like
5560	RAMDisks. This construct is useful for instance when you want
5561	to boot over the network using BOOTP etc., where the boot
5562	server provides just a single image file, but you want to get
5563	for instance an OS kernel and a RAMDisk image.
5564
5565	"Multi-File Images" start with a list of image sizes, each
5566	image size (in bytes) specified by an "uint32_t" in network
5567	byte order. This list is terminated by an "(uint32_t)0".
5568	Immediately after the terminating 0 follow the images, one by
5569	one, all aligned on "uint32_t" boundaries (size rounded up to
5570	a multiple of 4 bytes).
5571
5572   "Firmware Images" are binary images containing firmware (like
5573	U-Boot or FPGA images) which usually will be programmed to
5574	flash memory.
5575
5576   "Script files" are command sequences that will be executed by
5577	U-Boot's command interpreter; this feature is especially
5578	useful when you configure U-Boot to use a real shell (hush)
5579	as command interpreter.
5580
5581Booting the Linux zImage:
5582-------------------------
5583
5584On some platforms, it's possible to boot Linux zImage. This is done
5585using the "bootz" command. The syntax of "bootz" command is the same
5586as the syntax of "bootm" command.
5587
5588Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5589kernel with raw initrd images. The syntax is slightly different, the
5590address of the initrd must be augmented by it's size, in the following
5591format: "<initrd addres>:<initrd size>".
5592
5593
5594Standalone HOWTO:
5595=================
5596
5597One of the features of U-Boot is that you can dynamically load and
5598run "standalone" applications, which can use some resources of
5599U-Boot like console I/O functions or interrupt services.
5600
5601Two simple examples are included with the sources:
5602
5603"Hello World" Demo:
5604-------------------
5605
5606'examples/hello_world.c' contains a small "Hello World" Demo
5607application; it is automatically compiled when you build U-Boot.
5608It's configured to run at address 0x00040004, so you can play with it
5609like that:
5610
5611	=> loads
5612	## Ready for S-Record download ...
5613	~>examples/hello_world.srec
5614	1 2 3 4 5 6 7 8 9 10 11 ...
5615	[file transfer complete]
5616	[connected]
5617	## Start Addr = 0x00040004
5618
5619	=> go 40004 Hello World! This is a test.
5620	## Starting application at 0x00040004 ...
5621	Hello World
5622	argc = 7
5623	argv[0] = "40004"
5624	argv[1] = "Hello"
5625	argv[2] = "World!"
5626	argv[3] = "This"
5627	argv[4] = "is"
5628	argv[5] = "a"
5629	argv[6] = "test."
5630	argv[7] = "<NULL>"
5631	Hit any key to exit ...
5632
5633	## Application terminated, rc = 0x0
5634
5635Another example, which demonstrates how to register a CPM interrupt
5636handler with the U-Boot code, can be found in 'examples/timer.c'.
5637Here, a CPM timer is set up to generate an interrupt every second.
5638The interrupt service routine is trivial, just printing a '.'
5639character, but this is just a demo program. The application can be
5640controlled by the following keys:
5641
5642	? - print current values og the CPM Timer registers
5643	b - enable interrupts and start timer
5644	e - stop timer and disable interrupts
5645	q - quit application
5646
5647	=> loads
5648	## Ready for S-Record download ...
5649	~>examples/timer.srec
5650	1 2 3 4 5 6 7 8 9 10 11 ...
5651	[file transfer complete]
5652	[connected]
5653	## Start Addr = 0x00040004
5654
5655	=> go 40004
5656	## Starting application at 0x00040004 ...
5657	TIMERS=0xfff00980
5658	Using timer 1
5659	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5660
5661Hit 'b':
5662	[q, b, e, ?] Set interval 1000000 us
5663	Enabling timer
5664Hit '?':
5665	[q, b, e, ?] ........
5666	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5667Hit '?':
5668	[q, b, e, ?] .
5669	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5670Hit '?':
5671	[q, b, e, ?] .
5672	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5673Hit '?':
5674	[q, b, e, ?] .
5675	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5676Hit 'e':
5677	[q, b, e, ?] ...Stopping timer
5678Hit 'q':
5679	[q, b, e, ?] ## Application terminated, rc = 0x0
5680
5681
5682Minicom warning:
5683================
5684
5685Over time, many people have reported problems when trying to use the
5686"minicom" terminal emulation program for serial download. I (wd)
5687consider minicom to be broken, and recommend not to use it. Under
5688Unix, I recommend to use C-Kermit for general purpose use (and
5689especially for kermit binary protocol download ("loadb" command), and
5690use "cu" for S-Record download ("loads" command).  See
5691http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5692for help with kermit.
5693
5694
5695Nevertheless, if you absolutely want to use it try adding this
5696configuration to your "File transfer protocols" section:
5697
5698	   Name	   Program			Name U/D FullScr IO-Red. Multi
5699	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5700	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5701
5702
5703NetBSD Notes:
5704=============
5705
5706Starting at version 0.9.2, U-Boot supports NetBSD both as host
5707(build U-Boot) and target system (boots NetBSD/mpc8xx).
5708
5709Building requires a cross environment; it is known to work on
5710NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5711need gmake since the Makefiles are not compatible with BSD make).
5712Note that the cross-powerpc package does not install include files;
5713attempting to build U-Boot will fail because <machine/ansi.h> is
5714missing.  This file has to be installed and patched manually:
5715
5716	# cd /usr/pkg/cross/powerpc-netbsd/include
5717	# mkdir powerpc
5718	# ln -s powerpc machine
5719	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5720	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5721
5722Native builds *don't* work due to incompatibilities between native
5723and U-Boot include files.
5724
5725Booting assumes that (the first part of) the image booted is a
5726stage-2 loader which in turn loads and then invokes the kernel
5727proper. Loader sources will eventually appear in the NetBSD source
5728tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5729meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5730
5731
5732Implementation Internals:
5733=========================
5734
5735The following is not intended to be a complete description of every
5736implementation detail. However, it should help to understand the
5737inner workings of U-Boot and make it easier to port it to custom
5738hardware.
5739
5740
5741Initial Stack, Global Data:
5742---------------------------
5743
5744The implementation of U-Boot is complicated by the fact that U-Boot
5745starts running out of ROM (flash memory), usually without access to
5746system RAM (because the memory controller is not initialized yet).
5747This means that we don't have writable Data or BSS segments, and BSS
5748is not initialized as zero. To be able to get a C environment working
5749at all, we have to allocate at least a minimal stack. Implementation
5750options for this are defined and restricted by the CPU used: Some CPU
5751models provide on-chip memory (like the IMMR area on MPC8xx and
5752MPC826x processors), on others (parts of) the data cache can be
5753locked as (mis-) used as memory, etc.
5754
5755	Chris Hallinan posted a good summary of these issues to the
5756	U-Boot mailing list:
5757
5758	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5759	From: "Chris Hallinan" <clh@net1plus.com>
5760	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5761	...
5762
5763	Correct me if I'm wrong, folks, but the way I understand it
5764	is this: Using DCACHE as initial RAM for Stack, etc, does not
5765	require any physical RAM backing up the cache. The cleverness
5766	is that the cache is being used as a temporary supply of
5767	necessary storage before the SDRAM controller is setup. It's
5768	beyond the scope of this list to explain the details, but you
5769	can see how this works by studying the cache architecture and
5770	operation in the architecture and processor-specific manuals.
5771
5772	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5773	is another option for the system designer to use as an
5774	initial stack/RAM area prior to SDRAM being available. Either
5775	option should work for you. Using CS 4 should be fine if your
5776	board designers haven't used it for something that would
5777	cause you grief during the initial boot! It is frequently not
5778	used.
5779
5780	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5781	with your processor/board/system design. The default value
5782	you will find in any recent u-boot distribution in
5783	walnut.h should work for you. I'd set it to a value larger
5784	than your SDRAM module. If you have a 64MB SDRAM module, set
5785	it above 400_0000. Just make sure your board has no resources
5786	that are supposed to respond to that address! That code in
5787	start.S has been around a while and should work as is when
5788	you get the config right.
5789
5790	-Chris Hallinan
5791	DS4.COM, Inc.
5792
5793It is essential to remember this, since it has some impact on the C
5794code for the initialization procedures:
5795
5796* Initialized global data (data segment) is read-only. Do not attempt
5797  to write it.
5798
5799* Do not use any uninitialized global data (or implicitely initialized
5800  as zero data - BSS segment) at all - this is undefined, initiali-
5801  zation is performed later (when relocating to RAM).
5802
5803* Stack space is very limited. Avoid big data buffers or things like
5804  that.
5805
5806Having only the stack as writable memory limits means we cannot use
5807normal global data to share information beween the code. But it
5808turned out that the implementation of U-Boot can be greatly
5809simplified by making a global data structure (gd_t) available to all
5810functions. We could pass a pointer to this data as argument to _all_
5811functions, but this would bloat the code. Instead we use a feature of
5812the GCC compiler (Global Register Variables) to share the data: we
5813place a pointer (gd) to the global data into a register which we
5814reserve for this purpose.
5815
5816When choosing a register for such a purpose we are restricted by the
5817relevant  (E)ABI  specifications for the current architecture, and by
5818GCC's implementation.
5819
5820For PowerPC, the following registers have specific use:
5821	R1:	stack pointer
5822	R2:	reserved for system use
5823	R3-R4:	parameter passing and return values
5824	R5-R10: parameter passing
5825	R13:	small data area pointer
5826	R30:	GOT pointer
5827	R31:	frame pointer
5828
5829	(U-Boot also uses R12 as internal GOT pointer. r12
5830	is a volatile register so r12 needs to be reset when
5831	going back and forth between asm and C)
5832
5833    ==> U-Boot will use R2 to hold a pointer to the global data
5834
5835    Note: on PPC, we could use a static initializer (since the
5836    address of the global data structure is known at compile time),
5837    but it turned out that reserving a register results in somewhat
5838    smaller code - although the code savings are not that big (on
5839    average for all boards 752 bytes for the whole U-Boot image,
5840    624 text + 127 data).
5841
5842On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5843	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5844
5845    ==> U-Boot will use P3 to hold a pointer to the global data
5846
5847On ARM, the following registers are used:
5848
5849	R0:	function argument word/integer result
5850	R1-R3:	function argument word
5851	R9:	platform specific
5852	R10:	stack limit (used only if stack checking is enabled)
5853	R11:	argument (frame) pointer
5854	R12:	temporary workspace
5855	R13:	stack pointer
5856	R14:	link register
5857	R15:	program counter
5858
5859    ==> U-Boot will use R9 to hold a pointer to the global data
5860
5861    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5862
5863On Nios II, the ABI is documented here:
5864	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5865
5866    ==> U-Boot will use gp to hold a pointer to the global data
5867
5868    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5869    to access small data sections, so gp is free.
5870
5871On NDS32, the following registers are used:
5872
5873	R0-R1:	argument/return
5874	R2-R5:	argument
5875	R15:	temporary register for assembler
5876	R16:	trampoline register
5877	R28:	frame pointer (FP)
5878	R29:	global pointer (GP)
5879	R30:	link register (LP)
5880	R31:	stack pointer (SP)
5881	PC:	program counter (PC)
5882
5883    ==> U-Boot will use R10 to hold a pointer to the global data
5884
5885NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5886or current versions of GCC may "optimize" the code too much.
5887
5888Memory Management:
5889------------------
5890
5891U-Boot runs in system state and uses physical addresses, i.e. the
5892MMU is not used either for address mapping nor for memory protection.
5893
5894The available memory is mapped to fixed addresses using the memory
5895controller. In this process, a contiguous block is formed for each
5896memory type (Flash, SDRAM, SRAM), even when it consists of several
5897physical memory banks.
5898
5899U-Boot is installed in the first 128 kB of the first Flash bank (on
5900TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5901booting and sizing and initializing DRAM, the code relocates itself
5902to the upper end of DRAM. Immediately below the U-Boot code some
5903memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5904configuration setting]. Below that, a structure with global Board
5905Info data is placed, followed by the stack (growing downward).
5906
5907Additionally, some exception handler code is copied to the low 8 kB
5908of DRAM (0x00000000 ... 0x00001FFF).
5909
5910So a typical memory configuration with 16 MB of DRAM could look like
5911this:
5912
5913	0x0000 0000	Exception Vector code
5914	      :
5915	0x0000 1FFF
5916	0x0000 2000	Free for Application Use
5917	      :
5918	      :
5919
5920	      :
5921	      :
5922	0x00FB FF20	Monitor Stack (Growing downward)
5923	0x00FB FFAC	Board Info Data and permanent copy of global data
5924	0x00FC 0000	Malloc Arena
5925	      :
5926	0x00FD FFFF
5927	0x00FE 0000	RAM Copy of Monitor Code
5928	...		eventually: LCD or video framebuffer
5929	...		eventually: pRAM (Protected RAM - unchanged by reset)
5930	0x00FF FFFF	[End of RAM]
5931
5932
5933System Initialization:
5934----------------------
5935
5936In the reset configuration, U-Boot starts at the reset entry point
5937(on most PowerPC systems at address 0x00000100). Because of the reset
5938configuration for CS0# this is a mirror of the onboard Flash memory.
5939To be able to re-map memory U-Boot then jumps to its link address.
5940To be able to implement the initialization code in C, a (small!)
5941initial stack is set up in the internal Dual Ported RAM (in case CPUs
5942which provide such a feature like MPC8xx or MPC8260), or in a locked
5943part of the data cache. After that, U-Boot initializes the CPU core,
5944the caches and the SIU.
5945
5946Next, all (potentially) available memory banks are mapped using a
5947preliminary mapping. For example, we put them on 512 MB boundaries
5948(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5949on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5950programmed for SDRAM access. Using the temporary configuration, a
5951simple memory test is run that determines the size of the SDRAM
5952banks.
5953
5954When there is more than one SDRAM bank, and the banks are of
5955different size, the largest is mapped first. For equal size, the first
5956bank (CS2#) is mapped first. The first mapping is always for address
59570x00000000, with any additional banks following immediately to create
5958contiguous memory starting from 0.
5959
5960Then, the monitor installs itself at the upper end of the SDRAM area
5961and allocates memory for use by malloc() and for the global Board
5962Info data; also, the exception vector code is copied to the low RAM
5963pages, and the final stack is set up.
5964
5965Only after this relocation will you have a "normal" C environment;
5966until that you are restricted in several ways, mostly because you are
5967running from ROM, and because the code will have to be relocated to a
5968new address in RAM.
5969
5970
5971U-Boot Porting Guide:
5972----------------------
5973
5974[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5975list, October 2002]
5976
5977
5978int main(int argc, char *argv[])
5979{
5980	sighandler_t no_more_time;
5981
5982	signal(SIGALRM, no_more_time);
5983	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5984
5985	if (available_money > available_manpower) {
5986		Pay consultant to port U-Boot;
5987		return 0;
5988	}
5989
5990	Download latest U-Boot source;
5991
5992	Subscribe to u-boot mailing list;
5993
5994	if (clueless)
5995		email("Hi, I am new to U-Boot, how do I get started?");
5996
5997	while (learning) {
5998		Read the README file in the top level directory;
5999		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6000		Read applicable doc/*.README;
6001		Read the source, Luke;
6002		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6003	}
6004
6005	if (available_money > toLocalCurrency ($2500))
6006		Buy a BDI3000;
6007	else
6008		Add a lot of aggravation and time;
6009
6010	if (a similar board exists) {	/* hopefully... */
6011		cp -a board/<similar> board/<myboard>
6012		cp include/configs/<similar>.h include/configs/<myboard>.h
6013	} else {
6014		Create your own board support subdirectory;
6015		Create your own board include/configs/<myboard>.h file;
6016	}
6017	Edit new board/<myboard> files
6018	Edit new include/configs/<myboard>.h
6019
6020	while (!accepted) {
6021		while (!running) {
6022			do {
6023				Add / modify source code;
6024			} until (compiles);
6025			Debug;
6026			if (clueless)
6027				email("Hi, I am having problems...");
6028		}
6029		Send patch file to the U-Boot email list;
6030		if (reasonable critiques)
6031			Incorporate improvements from email list code review;
6032		else
6033			Defend code as written;
6034	}
6035
6036	return 0;
6037}
6038
6039void no_more_time (int sig)
6040{
6041      hire_a_guru();
6042}
6043
6044
6045Coding Standards:
6046-----------------
6047
6048All contributions to U-Boot should conform to the Linux kernel
6049coding style; see the file "Documentation/CodingStyle" and the script
6050"scripts/Lindent" in your Linux kernel source directory.
6051
6052Source files originating from a different project (for example the
6053MTD subsystem) are generally exempt from these guidelines and are not
6054reformated to ease subsequent migration to newer versions of those
6055sources.
6056
6057Please note that U-Boot is implemented in C (and to some small parts in
6058Assembler); no C++ is used, so please do not use C++ style comments (//)
6059in your code.
6060
6061Please also stick to the following formatting rules:
6062- remove any trailing white space
6063- use TAB characters for indentation and vertical alignment, not spaces
6064- make sure NOT to use DOS '\r\n' line feeds
6065- do not add more than 2 consecutive empty lines to source files
6066- do not add trailing empty lines to source files
6067
6068Submissions which do not conform to the standards may be returned
6069with a request to reformat the changes.
6070
6071
6072Submitting Patches:
6073-------------------
6074
6075Since the number of patches for U-Boot is growing, we need to
6076establish some rules. Submissions which do not conform to these rules
6077may be rejected, even when they contain important and valuable stuff.
6078
6079Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6080
6081Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6082see http://lists.denx.de/mailman/listinfo/u-boot
6083
6084When you send a patch, please include the following information with
6085it:
6086
6087* For bug fixes: a description of the bug and how your patch fixes
6088  this bug. Please try to include a way of demonstrating that the
6089  patch actually fixes something.
6090
6091* For new features: a description of the feature and your
6092  implementation.
6093
6094* A CHANGELOG entry as plaintext (separate from the patch)
6095
6096* For major contributions, your entry to the CREDITS file
6097
6098* When you add support for a new board, don't forget to add a
6099  maintainer e-mail address to the boards.cfg file, too.
6100
6101* If your patch adds new configuration options, don't forget to
6102  document these in the README file.
6103
6104* The patch itself. If you are using git (which is *strongly*
6105  recommended) you can easily generate the patch using the
6106  "git format-patch". If you then use "git send-email" to send it to
6107  the U-Boot mailing list, you will avoid most of the common problems
6108  with some other mail clients.
6109
6110  If you cannot use git, use "diff -purN OLD NEW". If your version of
6111  diff does not support these options, then get the latest version of
6112  GNU diff.
6113
6114  The current directory when running this command shall be the parent
6115  directory of the U-Boot source tree (i. e. please make sure that
6116  your patch includes sufficient directory information for the
6117  affected files).
6118
6119  We prefer patches as plain text. MIME attachments are discouraged,
6120  and compressed attachments must not be used.
6121
6122* If one logical set of modifications affects or creates several
6123  files, all these changes shall be submitted in a SINGLE patch file.
6124
6125* Changesets that contain different, unrelated modifications shall be
6126  submitted as SEPARATE patches, one patch per changeset.
6127
6128
6129Notes:
6130
6131* Before sending the patch, run the MAKEALL script on your patched
6132  source tree and make sure that no errors or warnings are reported
6133  for any of the boards.
6134
6135* Keep your modifications to the necessary minimum: A patch
6136  containing several unrelated changes or arbitrary reformats will be
6137  returned with a request to re-formatting / split it.
6138
6139* If you modify existing code, make sure that your new code does not
6140  add to the memory footprint of the code ;-) Small is beautiful!
6141  When adding new features, these should compile conditionally only
6142  (using #ifdef), and the resulting code with the new feature
6143  disabled must not need more memory than the old code without your
6144  modification.
6145
6146* Remember that there is a size limit of 100 kB per message on the
6147  u-boot mailing list. Bigger patches will be moderated. If they are
6148  reasonable and not too big, they will be acknowledged. But patches
6149  bigger than the size limit should be avoided.
6150