xref: /rk3399_rockchip-uboot/README (revision 6b3d588efee911db65f9deb319488cfe1499c835)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG and CREDITS files to find out
38who contributed the specific port. The boards.cfg file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arm			Files generic to ARM architecture
136    /cpu		CPU specific files
137      /arm720t		Files specific to ARM 720 CPUs
138      /arm920t		Files specific to ARM 920 CPUs
139	/at91		Files specific to Atmel AT91RM9200 CPU
140	/imx		Files specific to Freescale MC9328 i.MX CPUs
141	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
142      /arm926ejs	Files specific to ARM 926 CPUs
143      /arm1136		Files specific to ARM 1136 CPUs
144      /pxa		Files specific to Intel XScale PXA CPUs
145      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
146    /lib		Architecture specific library files
147  /avr32		Files generic to AVR32 architecture
148    /cpu		CPU specific files
149    /lib		Architecture specific library files
150  /blackfin		Files generic to Analog Devices Blackfin architecture
151    /cpu		CPU specific files
152    /lib		Architecture specific library files
153  /m68k			Files generic to m68k architecture
154    /cpu		CPU specific files
155      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
156      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
157      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
158      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
159      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
160    /lib		Architecture specific library files
161  /microblaze		Files generic to microblaze architecture
162    /cpu		CPU specific files
163    /lib		Architecture specific library files
164  /mips			Files generic to MIPS architecture
165    /cpu		CPU specific files
166      /mips32		Files specific to MIPS32 CPUs
167      /xburst		Files specific to Ingenic XBurst CPUs
168    /lib		Architecture specific library files
169  /nds32		Files generic to NDS32 architecture
170    /cpu		CPU specific files
171      /n1213		Files specific to Andes Technology N1213 CPUs
172    /lib		Architecture specific library files
173  /nios2		Files generic to Altera NIOS2 architecture
174    /cpu		CPU specific files
175    /lib		Architecture specific library files
176  /openrisc		Files generic to OpenRISC architecture
177    /cpu		CPU specific files
178    /lib		Architecture specific library files
179  /powerpc		Files generic to PowerPC architecture
180    /cpu		CPU specific files
181      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
182      /mpc5xx		Files specific to Freescale MPC5xx CPUs
183      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
184      /mpc8xx		Files specific to Freescale MPC8xx CPUs
185      /mpc824x		Files specific to Freescale MPC824x CPUs
186      /mpc8260		Files specific to Freescale MPC8260 CPUs
187      /mpc85xx		Files specific to Freescale MPC85xx CPUs
188      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
189    /lib		Architecture specific library files
190  /sh			Files generic to SH architecture
191    /cpu		CPU specific files
192      /sh2		Files specific to sh2 CPUs
193      /sh3		Files specific to sh3 CPUs
194      /sh4		Files specific to sh4 CPUs
195    /lib		Architecture specific library files
196  /sparc		Files generic to SPARC architecture
197    /cpu		CPU specific files
198      /leon2		Files specific to Gaisler LEON2 SPARC CPU
199      /leon3		Files specific to Gaisler LEON3 SPARC CPU
200    /lib		Architecture specific library files
201  /x86			Files generic to x86 architecture
202    /cpu		CPU specific files
203    /lib		Architecture specific library files
204/api			Machine/arch independent API for external apps
205/board			Board dependent files
206/common			Misc architecture independent functions
207/disk			Code for disk drive partition handling
208/doc			Documentation (don't expect too much)
209/drivers		Commonly used device drivers
210/dts			Contains Makefile for building internal U-Boot fdt.
211/examples		Example code for standalone applications, etc.
212/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
213/include		Header Files
214/lib			Files generic to all architectures
215  /libfdt		Library files to support flattened device trees
216  /lzma			Library files to support LZMA decompression
217  /lzo			Library files to support LZO decompression
218/net			Networking code
219/post			Power On Self Test
220/spl			Secondary Program Loader framework
221/tools			Tools to build S-Record or U-Boot images, etc.
222
223Software Configuration:
224=======================
225
226Configuration is usually done using C preprocessor defines; the
227rationale behind that is to avoid dead code whenever possible.
228
229There are two classes of configuration variables:
230
231* Configuration _OPTIONS_:
232  These are selectable by the user and have names beginning with
233  "CONFIG_".
234
235* Configuration _SETTINGS_:
236  These depend on the hardware etc. and should not be meddled with if
237  you don't know what you're doing; they have names beginning with
238  "CONFIG_SYS_".
239
240Later we will add a configuration tool - probably similar to or even
241identical to what's used for the Linux kernel. Right now, we have to
242do the configuration by hand, which means creating some symbolic
243links and editing some configuration files. We use the TQM8xxL boards
244as an example here.
245
246
247Selection of Processor Architecture and Board Type:
248---------------------------------------------------
249
250For all supported boards there are ready-to-use default
251configurations available; just type "make <board_name>_config".
252
253Example: For a TQM823L module type:
254
255	cd u-boot
256	make TQM823L_config
257
258For the Cogent platform, you need to specify the CPU type as well;
259e.g. "make cogent_mpc8xx_config". And also configure the cogent
260directory according to the instructions in cogent/README.
261
262
263Configuration Options:
264----------------------
265
266Configuration depends on the combination of board and CPU type; all
267such information is kept in a configuration file
268"include/configs/<board_name>.h".
269
270Example: For a TQM823L module, all configuration settings are in
271"include/configs/TQM823L.h".
272
273
274Many of the options are named exactly as the corresponding Linux
275kernel configuration options. The intention is to make it easier to
276build a config tool - later.
277
278
279The following options need to be configured:
280
281- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
282
283- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
284
285- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
286		Define exactly one, e.g. CONFIG_ATSTK1002
287
288- CPU Module Type: (if CONFIG_COGENT is defined)
289		Define exactly one of
290		CONFIG_CMA286_60_OLD
291--- FIXME --- not tested yet:
292		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
293		CONFIG_CMA287_23, CONFIG_CMA287_50
294
295- Motherboard Type: (if CONFIG_COGENT is defined)
296		Define exactly one of
297		CONFIG_CMA101, CONFIG_CMA102
298
299- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
300		Define one or more of
301		CONFIG_CMA302
302
303- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
304		Define one or more of
305		CONFIG_LCD_HEARTBEAT	- update a character position on
306					  the LCD display every second with
307					  a "rotator" |\-/|\-/
308
309- Board flavour: (if CONFIG_MPC8260ADS is defined)
310		CONFIG_ADSTYPE
311		Possible values are:
312			CONFIG_SYS_8260ADS	- original MPC8260ADS
313			CONFIG_SYS_8266ADS	- MPC8266ADS
314			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
315			CONFIG_SYS_8272ADS	- MPC8272ADS
316
317- Marvell Family Member
318		CONFIG_SYS_MVFS		- define it if you want to enable
319					  multiple fs option at one time
320					  for marvell soc family
321
322- MPC824X Family Member (if CONFIG_MPC824X is defined)
323		Define exactly one of
324		CONFIG_MPC8240, CONFIG_MPC8245
325
326- 8xx CPU Options: (if using an MPC8xx CPU)
327		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
328					  get_gclk_freq() cannot work
329					  e.g. if there is no 32KHz
330					  reference PIT/RTC clock
331		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
332					  or XTAL/EXTAL)
333
334- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
335		CONFIG_SYS_8xx_CPUCLK_MIN
336		CONFIG_SYS_8xx_CPUCLK_MAX
337		CONFIG_8xx_CPUCLK_DEFAULT
338			See doc/README.MPC866
339
340		CONFIG_SYS_MEASURE_CPUCLK
341
342		Define this to measure the actual CPU clock instead
343		of relying on the correctness of the configured
344		values. Mostly useful for board bringup to make sure
345		the PLL is locked at the intended frequency. Note
346		that this requires a (stable) reference clock (32 kHz
347		RTC clock or CONFIG_SYS_8XX_XIN)
348
349		CONFIG_SYS_DELAYED_ICACHE
350
351		Define this option if you want to enable the
352		ICache only when Code runs from RAM.
353
354- 85xx CPU Options:
355		CONFIG_SYS_PPC64
356
357		Specifies that the core is a 64-bit PowerPC implementation (implements
358		the "64" category of the Power ISA). This is necessary for ePAPR
359		compliance, among other possible reasons.
360
361		CONFIG_SYS_FSL_TBCLK_DIV
362
363		Defines the core time base clock divider ratio compared to the
364		system clock.  On most PQ3 devices this is 8, on newer QorIQ
365		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
366
367		CONFIG_SYS_FSL_PCIE_COMPAT
368
369		Defines the string to utilize when trying to match PCIe device
370		tree nodes for the given platform.
371
372		CONFIG_SYS_PPC_E500_DEBUG_TLB
373
374		Enables a temporary TLB entry to be used during boot to work
375		around limitations in e500v1 and e500v2 external debugger
376		support. This reduces the portions of the boot code where
377		breakpoints and single stepping do not work.  The value of this
378		symbol should be set to the TLB1 entry to be used for this
379		purpose.
380
381		CONFIG_SYS_FSL_ERRATUM_A004510
382
383		Enables a workaround for erratum A004510.  If set,
384		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
385		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
386
387		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
388		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
389
390		Defines one or two SoC revisions (low 8 bits of SVR)
391		for which the A004510 workaround should be applied.
392
393		The rest of SVR is either not relevant to the decision
394		of whether the erratum is present (e.g. p2040 versus
395		p2041) or is implied by the build target, which controls
396		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
397
398		See Freescale App Note 4493 for more information about
399		this erratum.
400
401		CONFIG_A003399_NOR_WORKAROUND
402		Enables a workaround for IFC erratum A003399. It is only
403		requred during NOR boot.
404
405		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
406
407		This is the value to write into CCSR offset 0x18600
408		according to the A004510 workaround.
409
410		CONFIG_SYS_FSL_DSP_DDR_ADDR
411		This value denotes start offset of DDR memory which is
412		connected exclusively to the DSP cores.
413
414		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
415		This value denotes start offset of M2 memory
416		which is directly connected to the DSP core.
417
418		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
419		This value denotes start offset of M3 memory which is directly
420		connected to the DSP core.
421
422		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
423		This value denotes start offset of DSP CCSR space.
424
425		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
426		Single Source Clock is clocking mode present in some of FSL SoC's.
427		In this mode, a single differential clock is used to supply
428		clocks to the sysclock, ddrclock and usbclock.
429
430		CONFIG_SYS_CPC_REINIT_F
431		This CONFIG is defined when the CPC is configured as SRAM at the
432		time of U-boot entry and is required to be re-initialized.
433
434		CONFIG_DEEP_SLEEP
435		Inidcates this SoC supports deep sleep feature. If deep sleep is
436		supported, core will start to execute uboot when wakes up.
437
438- Generic CPU options:
439		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
440
441		Defines the endianess of the CPU. Implementation of those
442		values is arch specific.
443
444		CONFIG_SYS_FSL_DDR
445		Freescale DDR driver in use. This type of DDR controller is
446		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
447		SoCs.
448
449		CONFIG_SYS_FSL_DDR_ADDR
450		Freescale DDR memory-mapped register base.
451
452		CONFIG_SYS_FSL_DDR_EMU
453		Specify emulator support for DDR. Some DDR features such as
454		deskew training are not available.
455
456		CONFIG_SYS_FSL_DDRC_GEN1
457		Freescale DDR1 controller.
458
459		CONFIG_SYS_FSL_DDRC_GEN2
460		Freescale DDR2 controller.
461
462		CONFIG_SYS_FSL_DDRC_GEN3
463		Freescale DDR3 controller.
464
465		CONFIG_SYS_FSL_DDRC_GEN4
466		Freescale DDR4 controller.
467
468		CONFIG_SYS_FSL_DDRC_ARM_GEN3
469		Freescale DDR3 controller for ARM-based SoCs.
470
471		CONFIG_SYS_FSL_DDR1
472		Board config to use DDR1. It can be enabled for SoCs with
473		Freescale DDR1 or DDR2 controllers, depending on the board
474		implemetation.
475
476		CONFIG_SYS_FSL_DDR2
477		Board config to use DDR2. It can be eanbeld for SoCs with
478		Freescale DDR2 or DDR3 controllers, depending on the board
479		implementation.
480
481		CONFIG_SYS_FSL_DDR3
482		Board config to use DDR3. It can be enabled for SoCs with
483		Freescale DDR3 or DDR3L controllers.
484
485		CONFIG_SYS_FSL_DDR3L
486		Board config to use DDR3L. It can be enabled for SoCs with
487		DDR3L controllers.
488
489		CONFIG_SYS_FSL_DDR4
490		Board config to use DDR4. It can be enabled for SoCs with
491		DDR4 controllers.
492
493		CONFIG_SYS_FSL_IFC_BE
494		Defines the IFC controller register space as Big Endian
495
496		CONFIG_SYS_FSL_IFC_LE
497		Defines the IFC controller register space as Little Endian
498
499		CONFIG_SYS_FSL_PBL_PBI
500		It enables addition of RCW (Power on reset configuration) in built image.
501		Please refer doc/README.pblimage for more details
502
503		CONFIG_SYS_FSL_PBL_RCW
504		It adds PBI(pre-boot instructions) commands in u-boot build image.
505		PBI commands can be used to configure SoC before it starts the execution.
506		Please refer doc/README.pblimage for more details
507
508		CONFIG_SYS_FSL_DDR_BE
509		Defines the DDR controller register space as Big Endian
510
511		CONFIG_SYS_FSL_DDR_LE
512		Defines the DDR controller register space as Little Endian
513
514		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
515		Physical address from the view of DDR controllers. It is the
516		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
517		it could be different for ARM SoCs.
518
519		CONFIG_SYS_FSL_DDR_INTLV_256B
520		DDR controller interleaving on 256-byte. This is a special
521		interleaving mode, handled by Dickens for Freescale layerscape
522		SoCs with ARM core.
523
524- Intel Monahans options:
525		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
526
527		Defines the Monahans run mode to oscillator
528		ratio. Valid values are 8, 16, 24, 31. The core
529		frequency is this value multiplied by 13 MHz.
530
531		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
532
533		Defines the Monahans turbo mode to oscillator
534		ratio. Valid values are 1 (default if undefined) and
535		2. The core frequency as calculated above is multiplied
536		by this value.
537
538- MIPS CPU options:
539		CONFIG_SYS_INIT_SP_OFFSET
540
541		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
542		pointer. This is needed for the temporary stack before
543		relocation.
544
545		CONFIG_SYS_MIPS_CACHE_MODE
546
547		Cache operation mode for the MIPS CPU.
548		See also arch/mips/include/asm/mipsregs.h.
549		Possible values are:
550			CONF_CM_CACHABLE_NO_WA
551			CONF_CM_CACHABLE_WA
552			CONF_CM_UNCACHED
553			CONF_CM_CACHABLE_NONCOHERENT
554			CONF_CM_CACHABLE_CE
555			CONF_CM_CACHABLE_COW
556			CONF_CM_CACHABLE_CUW
557			CONF_CM_CACHABLE_ACCELERATED
558
559		CONFIG_SYS_XWAY_EBU_BOOTCFG
560
561		Special option for Lantiq XWAY SoCs for booting from NOR flash.
562		See also arch/mips/cpu/mips32/start.S.
563
564		CONFIG_XWAY_SWAP_BYTES
565
566		Enable compilation of tools/xway-swap-bytes needed for Lantiq
567		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
568		be swapped if a flash programmer is used.
569
570- ARM options:
571		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
572
573		Select high exception vectors of the ARM core, e.g., do not
574		clear the V bit of the c1 register of CP15.
575
576		CONFIG_SYS_THUMB_BUILD
577
578		Use this flag to build U-Boot using the Thumb instruction
579		set for ARM architectures. Thumb instruction set provides
580		better code density. For ARM architectures that support
581		Thumb2 this flag will result in Thumb2 code generated by
582		GCC.
583
584		CONFIG_ARM_ERRATA_716044
585		CONFIG_ARM_ERRATA_742230
586		CONFIG_ARM_ERRATA_743622
587		CONFIG_ARM_ERRATA_751472
588		CONFIG_ARM_ERRATA_794072
589		CONFIG_ARM_ERRATA_761320
590
591		If set, the workarounds for these ARM errata are applied early
592		during U-Boot startup. Note that these options force the
593		workarounds to be applied; no CPU-type/version detection
594		exists, unlike the similar options in the Linux kernel. Do not
595		set these options unless they apply!
596
597- CPU timer options:
598		CONFIG_SYS_HZ
599
600		The frequency of the timer returned by get_timer().
601		get_timer() must operate in milliseconds and this CONFIG
602		option must be set to 1000.
603
604- Linux Kernel Interface:
605		CONFIG_CLOCKS_IN_MHZ
606
607		U-Boot stores all clock information in Hz
608		internally. For binary compatibility with older Linux
609		kernels (which expect the clocks passed in the
610		bd_info data to be in MHz) the environment variable
611		"clocks_in_mhz" can be defined so that U-Boot
612		converts clock data to MHZ before passing it to the
613		Linux kernel.
614		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
615		"clocks_in_mhz=1" is automatically included in the
616		default environment.
617
618		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
619
620		When transferring memsize parameter to linux, some versions
621		expect it to be in bytes, others in MB.
622		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
623
624		CONFIG_OF_LIBFDT
625
626		New kernel versions are expecting firmware settings to be
627		passed using flattened device trees (based on open firmware
628		concepts).
629
630		CONFIG_OF_LIBFDT
631		 * New libfdt-based support
632		 * Adds the "fdt" command
633		 * The bootm command automatically updates the fdt
634
635		OF_CPU - The proper name of the cpus node (only required for
636			MPC512X and MPC5xxx based boards).
637		OF_SOC - The proper name of the soc node (only required for
638			MPC512X and MPC5xxx based boards).
639		OF_TBCLK - The timebase frequency.
640		OF_STDOUT_PATH - The path to the console device
641
642		boards with QUICC Engines require OF_QE to set UCC MAC
643		addresses
644
645		CONFIG_OF_BOARD_SETUP
646
647		Board code has addition modification that it wants to make
648		to the flat device tree before handing it off to the kernel
649
650		CONFIG_OF_BOOT_CPU
651
652		This define fills in the correct boot CPU in the boot
653		param header, the default value is zero if undefined.
654
655		CONFIG_OF_IDE_FIXUP
656
657		U-Boot can detect if an IDE device is present or not.
658		If not, and this new config option is activated, U-Boot
659		removes the ATA node from the DTS before booting Linux,
660		so the Linux IDE driver does not probe the device and
661		crash. This is needed for buggy hardware (uc101) where
662		no pull down resistor is connected to the signal IDE5V_DD7.
663
664		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
665
666		This setting is mandatory for all boards that have only one
667		machine type and must be used to specify the machine type
668		number as it appears in the ARM machine registry
669		(see http://www.arm.linux.org.uk/developer/machines/).
670		Only boards that have multiple machine types supported
671		in a single configuration file and the machine type is
672		runtime discoverable, do not have to use this setting.
673
674- vxWorks boot parameters:
675
676		bootvx constructs a valid bootline using the following
677		environments variables: bootfile, ipaddr, serverip, hostname.
678		It loads the vxWorks image pointed bootfile.
679
680		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
681		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
682		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
683		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
684
685		CONFIG_SYS_VXWORKS_ADD_PARAMS
686
687		Add it at the end of the bootline. E.g "u=username pw=secret"
688
689		Note: If a "bootargs" environment is defined, it will overwride
690		the defaults discussed just above.
691
692- Cache Configuration:
693		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
694		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
695		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
696
697- Cache Configuration for ARM:
698		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
699				      controller
700		CONFIG_SYS_PL310_BASE - Physical base address of PL310
701					controller register space
702
703- Serial Ports:
704		CONFIG_PL010_SERIAL
705
706		Define this if you want support for Amba PrimeCell PL010 UARTs.
707
708		CONFIG_PL011_SERIAL
709
710		Define this if you want support for Amba PrimeCell PL011 UARTs.
711
712		CONFIG_PL011_CLOCK
713
714		If you have Amba PrimeCell PL011 UARTs, set this variable to
715		the clock speed of the UARTs.
716
717		CONFIG_PL01x_PORTS
718
719		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
720		define this to a list of base addresses for each (supported)
721		port. See e.g. include/configs/versatile.h
722
723		CONFIG_PL011_SERIAL_RLCR
724
725		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
726		have separate receive and transmit line control registers.  Set
727		this variable to initialize the extra register.
728
729		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
730
731		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
732		boot loader that has already initialized the UART.  Define this
733		variable to flush the UART at init time.
734
735
736- Console Interface:
737		Depending on board, define exactly one serial port
738		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
739		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
740		console by defining CONFIG_8xx_CONS_NONE
741
742		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
743		port routines must be defined elsewhere
744		(i.e. serial_init(), serial_getc(), ...)
745
746		CONFIG_CFB_CONSOLE
747		Enables console device for a color framebuffer. Needs following
748		defines (cf. smiLynxEM, i8042)
749			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
750						(default big endian)
751			VIDEO_HW_RECTFILL	graphic chip supports
752						rectangle fill
753						(cf. smiLynxEM)
754			VIDEO_HW_BITBLT		graphic chip supports
755						bit-blit (cf. smiLynxEM)
756			VIDEO_VISIBLE_COLS	visible pixel columns
757						(cols=pitch)
758			VIDEO_VISIBLE_ROWS	visible pixel rows
759			VIDEO_PIXEL_SIZE	bytes per pixel
760			VIDEO_DATA_FORMAT	graphic data format
761						(0-5, cf. cfb_console.c)
762			VIDEO_FB_ADRS		framebuffer address
763			VIDEO_KBD_INIT_FCT	keyboard int fct
764						(i.e. i8042_kbd_init())
765			VIDEO_TSTC_FCT		test char fct
766						(i.e. i8042_tstc)
767			VIDEO_GETC_FCT		get char fct
768						(i.e. i8042_getc)
769			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
770						(requires blink timer
771						cf. i8042.c)
772			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
773			CONFIG_CONSOLE_TIME	display time/date info in
774						upper right corner
775						(requires CONFIG_CMD_DATE)
776			CONFIG_VIDEO_LOGO	display Linux logo in
777						upper left corner
778			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
779						linux_logo.h for logo.
780						Requires CONFIG_VIDEO_LOGO
781			CONFIG_CONSOLE_EXTRA_INFO
782						additional board info beside
783						the logo
784
785		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
786		a limited number of ANSI escape sequences (cursor control,
787		erase functions and limited graphics rendition control).
788
789		When CONFIG_CFB_CONSOLE is defined, video console is
790		default i/o. Serial console can be forced with
791		environment 'console=serial'.
792
793		When CONFIG_SILENT_CONSOLE is defined, all console
794		messages (by U-Boot and Linux!) can be silenced with
795		the "silent" environment variable. See
796		doc/README.silent for more information.
797
798		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
799			is 0x00.
800		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
801			is 0xa0.
802
803- Console Baudrate:
804		CONFIG_BAUDRATE - in bps
805		Select one of the baudrates listed in
806		CONFIG_SYS_BAUDRATE_TABLE, see below.
807		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
808
809- Console Rx buffer length
810		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
811		the maximum receive buffer length for the SMC.
812		This option is actual only for 82xx and 8xx possible.
813		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
814		must be defined, to setup the maximum idle timeout for
815		the SMC.
816
817- Pre-Console Buffer:
818		Prior to the console being initialised (i.e. serial UART
819		initialised etc) all console output is silently discarded.
820		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
821		buffer any console messages prior to the console being
822		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
823		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
824		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
825		bytes are output before the console is initialised, the
826		earlier bytes are discarded.
827
828		'Sane' compilers will generate smaller code if
829		CONFIG_PRE_CON_BUF_SZ is a power of 2
830
831- Safe printf() functions
832		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
833		the printf() functions. These are defined in
834		include/vsprintf.h and include snprintf(), vsnprintf() and
835		so on. Code size increase is approximately 300-500 bytes.
836		If this option is not given then these functions will
837		silently discard their buffer size argument - this means
838		you are not getting any overflow checking in this case.
839
840- Boot Delay:	CONFIG_BOOTDELAY - in seconds
841		Delay before automatically booting the default image;
842		set to -1 to disable autoboot.
843		set to -2 to autoboot with no delay and not check for abort
844		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
845
846		See doc/README.autoboot for these options that
847		work with CONFIG_BOOTDELAY. None are required.
848		CONFIG_BOOT_RETRY_TIME
849		CONFIG_BOOT_RETRY_MIN
850		CONFIG_AUTOBOOT_KEYED
851		CONFIG_AUTOBOOT_PROMPT
852		CONFIG_AUTOBOOT_DELAY_STR
853		CONFIG_AUTOBOOT_STOP_STR
854		CONFIG_AUTOBOOT_DELAY_STR2
855		CONFIG_AUTOBOOT_STOP_STR2
856		CONFIG_ZERO_BOOTDELAY_CHECK
857		CONFIG_RESET_TO_RETRY
858
859- Autoboot Command:
860		CONFIG_BOOTCOMMAND
861		Only needed when CONFIG_BOOTDELAY is enabled;
862		define a command string that is automatically executed
863		when no character is read on the console interface
864		within "Boot Delay" after reset.
865
866		CONFIG_BOOTARGS
867		This can be used to pass arguments to the bootm
868		command. The value of CONFIG_BOOTARGS goes into the
869		environment value "bootargs".
870
871		CONFIG_RAMBOOT and CONFIG_NFSBOOT
872		The value of these goes into the environment as
873		"ramboot" and "nfsboot" respectively, and can be used
874		as a convenience, when switching between booting from
875		RAM and NFS.
876
877- Bootcount:
878		CONFIG_BOOTCOUNT_LIMIT
879		Implements a mechanism for detecting a repeating reboot
880		cycle, see:
881		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
882
883		CONFIG_BOOTCOUNT_ENV
884		If no softreset save registers are found on the hardware
885		"bootcount" is stored in the environment. To prevent a
886		saveenv on all reboots, the environment variable
887		"upgrade_available" is used. If "upgrade_available" is
888		0, "bootcount" is always 0, if "upgrade_available" is
889		1 "bootcount" is incremented in the environment.
890		So the Userspace Applikation must set the "upgrade_available"
891		and "bootcount" variable to 0, if a boot was successfully.
892
893- Pre-Boot Commands:
894		CONFIG_PREBOOT
895
896		When this option is #defined, the existence of the
897		environment variable "preboot" will be checked
898		immediately before starting the CONFIG_BOOTDELAY
899		countdown and/or running the auto-boot command resp.
900		entering interactive mode.
901
902		This feature is especially useful when "preboot" is
903		automatically generated or modified. For an example
904		see the LWMON board specific code: here "preboot" is
905		modified when the user holds down a certain
906		combination of keys on the (special) keyboard when
907		booting the systems
908
909- Serial Download Echo Mode:
910		CONFIG_LOADS_ECHO
911		If defined to 1, all characters received during a
912		serial download (using the "loads" command) are
913		echoed back. This might be needed by some terminal
914		emulations (like "cu"), but may as well just take
915		time on others. This setting #define's the initial
916		value of the "loads_echo" environment variable.
917
918- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
919		CONFIG_KGDB_BAUDRATE
920		Select one of the baudrates listed in
921		CONFIG_SYS_BAUDRATE_TABLE, see below.
922
923- Monitor Functions:
924		Monitor commands can be included or excluded
925		from the build by using the #include files
926		<config_cmd_all.h> and #undef'ing unwanted
927		commands, or using <config_cmd_default.h>
928		and augmenting with additional #define's
929		for wanted commands.
930
931		The default command configuration includes all commands
932		except those marked below with a "*".
933
934		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
935		CONFIG_CMD_ASKENV	* ask for env variable
936		CONFIG_CMD_BDI		  bdinfo
937		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
938		CONFIG_CMD_BMP		* BMP support
939		CONFIG_CMD_BSP		* Board specific commands
940		CONFIG_CMD_BOOTD	  bootd
941		CONFIG_CMD_CACHE	* icache, dcache
942		CONFIG_CMD_CLK   	* clock command support
943		CONFIG_CMD_CONSOLE	  coninfo
944		CONFIG_CMD_CRC32	* crc32
945		CONFIG_CMD_DATE		* support for RTC, date/time...
946		CONFIG_CMD_DHCP		* DHCP support
947		CONFIG_CMD_DIAG		* Diagnostics
948		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
949		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
950		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
951		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
952		CONFIG_CMD_DTT		* Digital Therm and Thermostat
953		CONFIG_CMD_ECHO		  echo arguments
954		CONFIG_CMD_EDITENV	  edit env variable
955		CONFIG_CMD_EEPROM	* EEPROM read/write support
956		CONFIG_CMD_ELF		* bootelf, bootvx
957		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
958		CONFIG_CMD_ENV_FLAGS	* display details about env flags
959		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
960		CONFIG_CMD_EXPORTENV	* export the environment
961		CONFIG_CMD_EXT2		* ext2 command support
962		CONFIG_CMD_EXT4		* ext4 command support
963		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
964					  that work for multiple fs types
965		CONFIG_CMD_SAVEENV	  saveenv
966		CONFIG_CMD_FDC		* Floppy Disk Support
967		CONFIG_CMD_FAT		* FAT command support
968		CONFIG_CMD_FLASH	  flinfo, erase, protect
969		CONFIG_CMD_FPGA		  FPGA device initialization support
970		CONFIG_CMD_FUSE		* Device fuse support
971		CONFIG_CMD_GETTIME	* Get time since boot
972		CONFIG_CMD_GO		* the 'go' command (exec code)
973		CONFIG_CMD_GREPENV	* search environment
974		CONFIG_CMD_HASH		* calculate hash / digest
975		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
976		CONFIG_CMD_I2C		* I2C serial bus support
977		CONFIG_CMD_IDE		* IDE harddisk support
978		CONFIG_CMD_IMI		  iminfo
979		CONFIG_CMD_IMLS		  List all images found in NOR flash
980		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
981		CONFIG_CMD_IMMAP	* IMMR dump support
982		CONFIG_CMD_IMPORTENV	* import an environment
983		CONFIG_CMD_INI		* import data from an ini file into the env
984		CONFIG_CMD_IRQ		* irqinfo
985		CONFIG_CMD_ITEST	  Integer/string test of 2 values
986		CONFIG_CMD_JFFS2	* JFFS2 Support
987		CONFIG_CMD_KGDB		* kgdb
988		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
989		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
990					  (169.254.*.*)
991		CONFIG_CMD_LOADB	  loadb
992		CONFIG_CMD_LOADS	  loads
993		CONFIG_CMD_MD5SUM	* print md5 message digest
994					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
995		CONFIG_CMD_MEMINFO	* Display detailed memory information
996		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
997					  loop, loopw
998		CONFIG_CMD_MEMTEST	* mtest
999		CONFIG_CMD_MISC		  Misc functions like sleep etc
1000		CONFIG_CMD_MMC		* MMC memory mapped support
1001		CONFIG_CMD_MII		* MII utility commands
1002		CONFIG_CMD_MTDPARTS	* MTD partition support
1003		CONFIG_CMD_NAND		* NAND support
1004		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1005		CONFIG_CMD_NFS		  NFS support
1006		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1007		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1008		CONFIG_CMD_PCI		* pciinfo
1009		CONFIG_CMD_PCMCIA		* PCMCIA support
1010		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1011					  host
1012		CONFIG_CMD_PORTIO	* Port I/O
1013		CONFIG_CMD_READ		* Read raw data from partition
1014		CONFIG_CMD_REGINFO	* Register dump
1015		CONFIG_CMD_RUN		  run command in env variable
1016		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1017		CONFIG_CMD_SAVES	* save S record dump
1018		CONFIG_CMD_SCSI		* SCSI Support
1019		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1020					  (requires CONFIG_CMD_I2C)
1021		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1022					  (4xx only)
1023		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1024		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1025					  (requires CONFIG_CMD_MEMORY)
1026		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1027		CONFIG_CMD_SOURCE	  "source" command Support
1028		CONFIG_CMD_SPI		* SPI serial bus support
1029		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1030		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1031		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1032		CONFIG_CMD_TIMER	* access to the system tick timer
1033		CONFIG_CMD_USB		* USB support
1034		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1035		CONFIG_CMD_MFSL		* Microblaze FSL support
1036		CONFIG_CMD_XIMG		  Load part of Multi Image
1037		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1038
1039		EXAMPLE: If you want all functions except of network
1040		support you can write:
1041
1042		#include "config_cmd_all.h"
1043		#undef CONFIG_CMD_NET
1044
1045	Other Commands:
1046		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1047
1048	Note:	Don't enable the "icache" and "dcache" commands
1049		(configuration option CONFIG_CMD_CACHE) unless you know
1050		what you (and your U-Boot users) are doing. Data
1051		cache cannot be enabled on systems like the 8xx or
1052		8260 (where accesses to the IMMR region must be
1053		uncached), and it cannot be disabled on all other
1054		systems where we (mis-) use the data cache to hold an
1055		initial stack and some data.
1056
1057
1058		XXX - this list needs to get updated!
1059
1060- Regular expression support:
1061		CONFIG_REGEX
1062		If this variable is defined, U-Boot is linked against
1063		the SLRE (Super Light Regular Expression) library,
1064		which adds regex support to some commands, as for
1065		example "env grep" and "setexpr".
1066
1067- Device tree:
1068		CONFIG_OF_CONTROL
1069		If this variable is defined, U-Boot will use a device tree
1070		to configure its devices, instead of relying on statically
1071		compiled #defines in the board file. This option is
1072		experimental and only available on a few boards. The device
1073		tree is available in the global data as gd->fdt_blob.
1074
1075		U-Boot needs to get its device tree from somewhere. This can
1076		be done using one of the two options below:
1077
1078		CONFIG_OF_EMBED
1079		If this variable is defined, U-Boot will embed a device tree
1080		binary in its image. This device tree file should be in the
1081		board directory and called <soc>-<board>.dts. The binary file
1082		is then picked up in board_init_f() and made available through
1083		the global data structure as gd->blob.
1084
1085		CONFIG_OF_SEPARATE
1086		If this variable is defined, U-Boot will build a device tree
1087		binary. It will be called u-boot.dtb. Architecture-specific
1088		code will locate it at run-time. Generally this works by:
1089
1090			cat u-boot.bin u-boot.dtb >image.bin
1091
1092		and in fact, U-Boot does this for you, creating a file called
1093		u-boot-dtb.bin which is useful in the common case. You can
1094		still use the individual files if you need something more
1095		exotic.
1096
1097- Watchdog:
1098		CONFIG_WATCHDOG
1099		If this variable is defined, it enables watchdog
1100		support for the SoC. There must be support in the SoC
1101		specific code for a watchdog. For the 8xx and 8260
1102		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1103		register.  When supported for a specific SoC is
1104		available, then no further board specific code should
1105		be needed to use it.
1106
1107		CONFIG_HW_WATCHDOG
1108		When using a watchdog circuitry external to the used
1109		SoC, then define this variable and provide board
1110		specific code for the "hw_watchdog_reset" function.
1111
1112- U-Boot Version:
1113		CONFIG_VERSION_VARIABLE
1114		If this variable is defined, an environment variable
1115		named "ver" is created by U-Boot showing the U-Boot
1116		version as printed by the "version" command.
1117		Any change to this variable will be reverted at the
1118		next reset.
1119
1120- Real-Time Clock:
1121
1122		When CONFIG_CMD_DATE is selected, the type of the RTC
1123		has to be selected, too. Define exactly one of the
1124		following options:
1125
1126		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1127		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1128		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1129		CONFIG_RTC_MC146818	- use MC146818 RTC
1130		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1131		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1132		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1133		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1134		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1135		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1136		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1137		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1138					  RV3029 RTC.
1139
1140		Note that if the RTC uses I2C, then the I2C interface
1141		must also be configured. See I2C Support, below.
1142
1143- GPIO Support:
1144		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1145
1146		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1147		chip-ngpio pairs that tell the PCA953X driver the number of
1148		pins supported by a particular chip.
1149
1150		Note that if the GPIO device uses I2C, then the I2C interface
1151		must also be configured. See I2C Support, below.
1152
1153- Timestamp Support:
1154
1155		When CONFIG_TIMESTAMP is selected, the timestamp
1156		(date and time) of an image is printed by image
1157		commands like bootm or iminfo. This option is
1158		automatically enabled when you select CONFIG_CMD_DATE .
1159
1160- Partition Labels (disklabels) Supported:
1161		Zero or more of the following:
1162		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1163		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1164				       Intel architecture, USB sticks, etc.
1165		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1166		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1167				       bootloader.  Note 2TB partition limit; see
1168				       disk/part_efi.c
1169		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1170
1171		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1172		CONFIG_CMD_SCSI) you must configure support for at
1173		least one non-MTD partition type as well.
1174
1175- IDE Reset method:
1176		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1177		board configurations files but used nowhere!
1178
1179		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1180		be performed by calling the function
1181			ide_set_reset(int reset)
1182		which has to be defined in a board specific file
1183
1184- ATAPI Support:
1185		CONFIG_ATAPI
1186
1187		Set this to enable ATAPI support.
1188
1189- LBA48 Support
1190		CONFIG_LBA48
1191
1192		Set this to enable support for disks larger than 137GB
1193		Also look at CONFIG_SYS_64BIT_LBA.
1194		Whithout these , LBA48 support uses 32bit variables and will 'only'
1195		support disks up to 2.1TB.
1196
1197		CONFIG_SYS_64BIT_LBA:
1198			When enabled, makes the IDE subsystem use 64bit sector addresses.
1199			Default is 32bit.
1200
1201- SCSI Support:
1202		At the moment only there is only support for the
1203		SYM53C8XX SCSI controller; define
1204		CONFIG_SCSI_SYM53C8XX to enable it.
1205
1206		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1207		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1208		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1209		maximum numbers of LUNs, SCSI ID's and target
1210		devices.
1211		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1212
1213		The environment variable 'scsidevs' is set to the number of
1214		SCSI devices found during the last scan.
1215
1216- NETWORK Support (PCI):
1217		CONFIG_E1000
1218		Support for Intel 8254x/8257x gigabit chips.
1219
1220		CONFIG_E1000_SPI
1221		Utility code for direct access to the SPI bus on Intel 8257x.
1222		This does not do anything useful unless you set at least one
1223		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1224
1225		CONFIG_E1000_SPI_GENERIC
1226		Allow generic access to the SPI bus on the Intel 8257x, for
1227		example with the "sspi" command.
1228
1229		CONFIG_CMD_E1000
1230		Management command for E1000 devices.  When used on devices
1231		with SPI support you can reprogram the EEPROM from U-Boot.
1232
1233		CONFIG_E1000_FALLBACK_MAC
1234		default MAC for empty EEPROM after production.
1235
1236		CONFIG_EEPRO100
1237		Support for Intel 82557/82559/82559ER chips.
1238		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1239		write routine for first time initialisation.
1240
1241		CONFIG_TULIP
1242		Support for Digital 2114x chips.
1243		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1244		modem chip initialisation (KS8761/QS6611).
1245
1246		CONFIG_NATSEMI
1247		Support for National dp83815 chips.
1248
1249		CONFIG_NS8382X
1250		Support for National dp8382[01] gigabit chips.
1251
1252- NETWORK Support (other):
1253
1254		CONFIG_DRIVER_AT91EMAC
1255		Support for AT91RM9200 EMAC.
1256
1257			CONFIG_RMII
1258			Define this to use reduced MII inteface
1259
1260			CONFIG_DRIVER_AT91EMAC_QUIET
1261			If this defined, the driver is quiet.
1262			The driver doen't show link status messages.
1263
1264		CONFIG_CALXEDA_XGMAC
1265		Support for the Calxeda XGMAC device
1266
1267		CONFIG_LAN91C96
1268		Support for SMSC's LAN91C96 chips.
1269
1270			CONFIG_LAN91C96_BASE
1271			Define this to hold the physical address
1272			of the LAN91C96's I/O space
1273
1274			CONFIG_LAN91C96_USE_32_BIT
1275			Define this to enable 32 bit addressing
1276
1277		CONFIG_SMC91111
1278		Support for SMSC's LAN91C111 chip
1279
1280			CONFIG_SMC91111_BASE
1281			Define this to hold the physical address
1282			of the device (I/O space)
1283
1284			CONFIG_SMC_USE_32_BIT
1285			Define this if data bus is 32 bits
1286
1287			CONFIG_SMC_USE_IOFUNCS
1288			Define this to use i/o functions instead of macros
1289			(some hardware wont work with macros)
1290
1291		CONFIG_DRIVER_TI_EMAC
1292		Support for davinci emac
1293
1294			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1295			Define this if you have more then 3 PHYs.
1296
1297		CONFIG_FTGMAC100
1298		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1299
1300			CONFIG_FTGMAC100_EGIGA
1301			Define this to use GE link update with gigabit PHY.
1302			Define this if FTGMAC100 is connected to gigabit PHY.
1303			If your system has 10/100 PHY only, it might not occur
1304			wrong behavior. Because PHY usually return timeout or
1305			useless data when polling gigabit status and gigabit
1306			control registers. This behavior won't affect the
1307			correctnessof 10/100 link speed update.
1308
1309		CONFIG_SMC911X
1310		Support for SMSC's LAN911x and LAN921x chips
1311
1312			CONFIG_SMC911X_BASE
1313			Define this to hold the physical address
1314			of the device (I/O space)
1315
1316			CONFIG_SMC911X_32_BIT
1317			Define this if data bus is 32 bits
1318
1319			CONFIG_SMC911X_16_BIT
1320			Define this if data bus is 16 bits. If your processor
1321			automatically converts one 32 bit word to two 16 bit
1322			words you may also try CONFIG_SMC911X_32_BIT.
1323
1324		CONFIG_SH_ETHER
1325		Support for Renesas on-chip Ethernet controller
1326
1327			CONFIG_SH_ETHER_USE_PORT
1328			Define the number of ports to be used
1329
1330			CONFIG_SH_ETHER_PHY_ADDR
1331			Define the ETH PHY's address
1332
1333			CONFIG_SH_ETHER_CACHE_WRITEBACK
1334			If this option is set, the driver enables cache flush.
1335
1336- TPM Support:
1337		CONFIG_TPM
1338		Support TPM devices.
1339
1340		CONFIG_TPM_TIS_I2C
1341		Support for i2c bus TPM devices. Only one device
1342		per system is supported at this time.
1343
1344			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1345			Define the the i2c bus number for the TPM device
1346
1347			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1348			Define the TPM's address on the i2c bus
1349
1350			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1351			Define the burst count bytes upper limit
1352
1353		CONFIG_TPM_ATMEL_TWI
1354		Support for Atmel TWI TPM device. Requires I2C support.
1355
1356		CONFIG_TPM_TIS_LPC
1357		Support for generic parallel port TPM devices. Only one device
1358		per system is supported at this time.
1359
1360			CONFIG_TPM_TIS_BASE_ADDRESS
1361			Base address where the generic TPM device is mapped
1362			to. Contemporary x86 systems usually map it at
1363			0xfed40000.
1364
1365		CONFIG_CMD_TPM
1366		Add tpm monitor functions.
1367		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1368		provides monitor access to authorized functions.
1369
1370		CONFIG_TPM
1371		Define this to enable the TPM support library which provides
1372		functional interfaces to some TPM commands.
1373		Requires support for a TPM device.
1374
1375		CONFIG_TPM_AUTH_SESSIONS
1376		Define this to enable authorized functions in the TPM library.
1377		Requires CONFIG_TPM and CONFIG_SHA1.
1378
1379- USB Support:
1380		At the moment only the UHCI host controller is
1381		supported (PIP405, MIP405, MPC5200); define
1382		CONFIG_USB_UHCI to enable it.
1383		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1384		and define CONFIG_USB_STORAGE to enable the USB
1385		storage devices.
1386		Note:
1387		Supported are USB Keyboards and USB Floppy drives
1388		(TEAC FD-05PUB).
1389		MPC5200 USB requires additional defines:
1390			CONFIG_USB_CLOCK
1391				for 528 MHz Clock: 0x0001bbbb
1392			CONFIG_PSC3_USB
1393				for USB on PSC3
1394			CONFIG_USB_CONFIG
1395				for differential drivers: 0x00001000
1396				for single ended drivers: 0x00005000
1397				for differential drivers on PSC3: 0x00000100
1398				for single ended drivers on PSC3: 0x00004100
1399			CONFIG_SYS_USB_EVENT_POLL
1400				May be defined to allow interrupt polling
1401				instead of using asynchronous interrupts
1402
1403		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1404		txfilltuning field in the EHCI controller on reset.
1405
1406		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1407		interval for usb hub power-on delay.(minimum 100msec)
1408
1409- USB Device:
1410		Define the below if you wish to use the USB console.
1411		Once firmware is rebuilt from a serial console issue the
1412		command "setenv stdin usbtty; setenv stdout usbtty" and
1413		attach your USB cable. The Unix command "dmesg" should print
1414		it has found a new device. The environment variable usbtty
1415		can be set to gserial or cdc_acm to enable your device to
1416		appear to a USB host as a Linux gserial device or a
1417		Common Device Class Abstract Control Model serial device.
1418		If you select usbtty = gserial you should be able to enumerate
1419		a Linux host by
1420		# modprobe usbserial vendor=0xVendorID product=0xProductID
1421		else if using cdc_acm, simply setting the environment
1422		variable usbtty to be cdc_acm should suffice. The following
1423		might be defined in YourBoardName.h
1424
1425			CONFIG_USB_DEVICE
1426			Define this to build a UDC device
1427
1428			CONFIG_USB_TTY
1429			Define this to have a tty type of device available to
1430			talk to the UDC device
1431
1432			CONFIG_USBD_HS
1433			Define this to enable the high speed support for usb
1434			device and usbtty. If this feature is enabled, a routine
1435			int is_usbd_high_speed(void)
1436			also needs to be defined by the driver to dynamically poll
1437			whether the enumeration has succeded at high speed or full
1438			speed.
1439
1440			CONFIG_SYS_CONSOLE_IS_IN_ENV
1441			Define this if you want stdin, stdout &/or stderr to
1442			be set to usbtty.
1443
1444			mpc8xx:
1445				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1446				Derive USB clock from external clock "blah"
1447				- CONFIG_SYS_USB_EXTC_CLK 0x02
1448
1449				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1450				Derive USB clock from brgclk
1451				- CONFIG_SYS_USB_BRG_CLK 0x04
1452
1453		If you have a USB-IF assigned VendorID then you may wish to
1454		define your own vendor specific values either in BoardName.h
1455		or directly in usbd_vendor_info.h. If you don't define
1456		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1457		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1458		should pretend to be a Linux device to it's target host.
1459
1460			CONFIG_USBD_MANUFACTURER
1461			Define this string as the name of your company for
1462			- CONFIG_USBD_MANUFACTURER "my company"
1463
1464			CONFIG_USBD_PRODUCT_NAME
1465			Define this string as the name of your product
1466			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1467
1468			CONFIG_USBD_VENDORID
1469			Define this as your assigned Vendor ID from the USB
1470			Implementors Forum. This *must* be a genuine Vendor ID
1471			to avoid polluting the USB namespace.
1472			- CONFIG_USBD_VENDORID 0xFFFF
1473
1474			CONFIG_USBD_PRODUCTID
1475			Define this as the unique Product ID
1476			for your device
1477			- CONFIG_USBD_PRODUCTID 0xFFFF
1478
1479		Some USB device drivers may need to check USB cable attachment.
1480		In this case you can enable following config in BoardName.h:
1481			CONFIG_USB_CABLE_CHECK
1482			This enables function definition:
1483			- usb_cable_connected() in include/usb.h
1484			Implementation of this function is board-specific.
1485
1486- ULPI Layer Support:
1487		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1488		the generic ULPI layer. The generic layer accesses the ULPI PHY
1489		via the platform viewport, so you need both the genric layer and
1490		the viewport enabled. Currently only Chipidea/ARC based
1491		viewport is supported.
1492		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1493		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1494		If your ULPI phy needs a different reference clock than the
1495		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1496		the appropriate value in Hz.
1497
1498- MMC Support:
1499		The MMC controller on the Intel PXA is supported. To
1500		enable this define CONFIG_MMC. The MMC can be
1501		accessed from the boot prompt by mapping the device
1502		to physical memory similar to flash. Command line is
1503		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1504		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1505
1506		CONFIG_SH_MMCIF
1507		Support for Renesas on-chip MMCIF controller
1508
1509			CONFIG_SH_MMCIF_ADDR
1510			Define the base address of MMCIF registers
1511
1512			CONFIG_SH_MMCIF_CLK
1513			Define the clock frequency for MMCIF
1514
1515- USB Device Firmware Update (DFU) class support:
1516		CONFIG_DFU_FUNCTION
1517		This enables the USB portion of the DFU USB class
1518
1519		CONFIG_CMD_DFU
1520		This enables the command "dfu" which is used to have
1521		U-Boot create a DFU class device via USB.  This command
1522		requires that the "dfu_alt_info" environment variable be
1523		set and define the alt settings to expose to the host.
1524
1525		CONFIG_DFU_MMC
1526		This enables support for exposing (e)MMC devices via DFU.
1527
1528		CONFIG_DFU_NAND
1529		This enables support for exposing NAND devices via DFU.
1530
1531		CONFIG_DFU_RAM
1532		This enables support for exposing RAM via DFU.
1533		Note: DFU spec refer to non-volatile memory usage, but
1534		allow usages beyond the scope of spec - here RAM usage,
1535		one that would help mostly the developer.
1536
1537		CONFIG_SYS_DFU_DATA_BUF_SIZE
1538		Dfu transfer uses a buffer before writing data to the
1539		raw storage device. Make the size (in bytes) of this buffer
1540		configurable. The size of this buffer is also configurable
1541		through the "dfu_bufsiz" environment variable.
1542
1543		CONFIG_SYS_DFU_MAX_FILE_SIZE
1544		When updating files rather than the raw storage device,
1545		we use a static buffer to copy the file into and then write
1546		the buffer once we've been given the whole file.  Define
1547		this to the maximum filesize (in bytes) for the buffer.
1548		Default is 4 MiB if undefined.
1549
1550		DFU_DEFAULT_POLL_TIMEOUT
1551		Poll timeout [ms], is the timeout a device can send to the
1552		host. The host must wait for this timeout before sending
1553		a subsequent DFU_GET_STATUS request to the device.
1554
1555		DFU_MANIFEST_POLL_TIMEOUT
1556		Poll timeout [ms], which the device sends to the host when
1557		entering dfuMANIFEST state. Host waits this timeout, before
1558		sending again an USB request to the device.
1559
1560- Journaling Flash filesystem support:
1561		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1562		CONFIG_JFFS2_NAND_DEV
1563		Define these for a default partition on a NAND device
1564
1565		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1566		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1567		Define these for a default partition on a NOR device
1568
1569		CONFIG_SYS_JFFS_CUSTOM_PART
1570		Define this to create an own partition. You have to provide a
1571		function struct part_info* jffs2_part_info(int part_num)
1572
1573		If you define only one JFFS2 partition you may also want to
1574		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1575		to disable the command chpart. This is the default when you
1576		have not defined a custom partition
1577
1578- FAT(File Allocation Table) filesystem write function support:
1579		CONFIG_FAT_WRITE
1580
1581		Define this to enable support for saving memory data as a
1582		file in FAT formatted partition.
1583
1584		This will also enable the command "fatwrite" enabling the
1585		user to write files to FAT.
1586
1587CBFS (Coreboot Filesystem) support
1588		CONFIG_CMD_CBFS
1589
1590		Define this to enable support for reading from a Coreboot
1591		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1592		and cbfsload.
1593
1594- Keyboard Support:
1595		CONFIG_ISA_KEYBOARD
1596
1597		Define this to enable standard (PC-Style) keyboard
1598		support
1599
1600		CONFIG_I8042_KBD
1601		Standard PC keyboard driver with US (is default) and
1602		GERMAN key layout (switch via environment 'keymap=de') support.
1603		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1604		for cfb_console. Supports cursor blinking.
1605
1606		CONFIG_CROS_EC_KEYB
1607		Enables a Chrome OS keyboard using the CROS_EC interface.
1608		This uses CROS_EC to communicate with a second microcontroller
1609		which provides key scans on request.
1610
1611- Video support:
1612		CONFIG_VIDEO
1613
1614		Define this to enable video support (for output to
1615		video).
1616
1617		CONFIG_VIDEO_CT69000
1618
1619		Enable Chips & Technologies 69000 Video chip
1620
1621		CONFIG_VIDEO_SMI_LYNXEM
1622		Enable Silicon Motion SMI 712/710/810 Video chip. The
1623		video output is selected via environment 'videoout'
1624		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1625		assumed.
1626
1627		For the CT69000 and SMI_LYNXEM drivers, videomode is
1628		selected via environment 'videomode'. Two different ways
1629		are possible:
1630		- "videomode=num"   'num' is a standard LiLo mode numbers.
1631		Following standard modes are supported	(* is default):
1632
1633		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1634		-------------+---------------------------------------------
1635		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1636		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1637		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1638		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1639		-------------+---------------------------------------------
1640		(i.e. setenv videomode 317; saveenv; reset;)
1641
1642		- "videomode=bootargs" all the video parameters are parsed
1643		from the bootargs. (See drivers/video/videomodes.c)
1644
1645
1646		CONFIG_VIDEO_SED13806
1647		Enable Epson SED13806 driver. This driver supports 8bpp
1648		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1649		or CONFIG_VIDEO_SED13806_16BPP
1650
1651		CONFIG_FSL_DIU_FB
1652		Enable the Freescale DIU video driver.	Reference boards for
1653		SOCs that have a DIU should define this macro to enable DIU
1654		support, and should also define these other macros:
1655
1656			CONFIG_SYS_DIU_ADDR
1657			CONFIG_VIDEO
1658			CONFIG_CMD_BMP
1659			CONFIG_CFB_CONSOLE
1660			CONFIG_VIDEO_SW_CURSOR
1661			CONFIG_VGA_AS_SINGLE_DEVICE
1662			CONFIG_VIDEO_LOGO
1663			CONFIG_VIDEO_BMP_LOGO
1664
1665		The DIU driver will look for the 'video-mode' environment
1666		variable, and if defined, enable the DIU as a console during
1667		boot.  See the documentation file README.video for a
1668		description of this variable.
1669
1670		CONFIG_VIDEO_VGA
1671
1672		Enable the VGA video / BIOS for x86. The alternative if you
1673		are using coreboot is to use the coreboot frame buffer
1674		driver.
1675
1676
1677- Keyboard Support:
1678		CONFIG_KEYBOARD
1679
1680		Define this to enable a custom keyboard support.
1681		This simply calls drv_keyboard_init() which must be
1682		defined in your board-specific files.
1683		The only board using this so far is RBC823.
1684
1685- LCD Support:	CONFIG_LCD
1686
1687		Define this to enable LCD support (for output to LCD
1688		display); also select one of the supported displays
1689		by defining one of these:
1690
1691		CONFIG_ATMEL_LCD:
1692
1693			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1694
1695		CONFIG_NEC_NL6448AC33:
1696
1697			NEC NL6448AC33-18. Active, color, single scan.
1698
1699		CONFIG_NEC_NL6448BC20
1700
1701			NEC NL6448BC20-08. 6.5", 640x480.
1702			Active, color, single scan.
1703
1704		CONFIG_NEC_NL6448BC33_54
1705
1706			NEC NL6448BC33-54. 10.4", 640x480.
1707			Active, color, single scan.
1708
1709		CONFIG_SHARP_16x9
1710
1711			Sharp 320x240. Active, color, single scan.
1712			It isn't 16x9, and I am not sure what it is.
1713
1714		CONFIG_SHARP_LQ64D341
1715
1716			Sharp LQ64D341 display, 640x480.
1717			Active, color, single scan.
1718
1719		CONFIG_HLD1045
1720
1721			HLD1045 display, 640x480.
1722			Active, color, single scan.
1723
1724		CONFIG_OPTREX_BW
1725
1726			Optrex	 CBL50840-2 NF-FW 99 22 M5
1727			or
1728			Hitachi	 LMG6912RPFC-00T
1729			or
1730			Hitachi	 SP14Q002
1731
1732			320x240. Black & white.
1733
1734		Normally display is black on white background; define
1735		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1736
1737		CONFIG_LCD_ALIGNMENT
1738
1739		Normally the LCD is page-aligned (tyically 4KB). If this is
1740		defined then the LCD will be aligned to this value instead.
1741		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1742		here, since it is cheaper to change data cache settings on
1743		a per-section basis.
1744
1745		CONFIG_CONSOLE_SCROLL_LINES
1746
1747		When the console need to be scrolled, this is the number of
1748		lines to scroll by. It defaults to 1. Increasing this makes
1749		the console jump but can help speed up operation when scrolling
1750		is slow.
1751
1752		CONFIG_LCD_BMP_RLE8
1753
1754		Support drawing of RLE8-compressed bitmaps on the LCD.
1755
1756		CONFIG_I2C_EDID
1757
1758		Enables an 'i2c edid' command which can read EDID
1759		information over I2C from an attached LCD display.
1760
1761- Splash Screen Support: CONFIG_SPLASH_SCREEN
1762
1763		If this option is set, the environment is checked for
1764		a variable "splashimage". If found, the usual display
1765		of logo, copyright and system information on the LCD
1766		is suppressed and the BMP image at the address
1767		specified in "splashimage" is loaded instead. The
1768		console is redirected to the "nulldev", too. This
1769		allows for a "silent" boot where a splash screen is
1770		loaded very quickly after power-on.
1771
1772		CONFIG_SPLASHIMAGE_GUARD
1773
1774		If this option is set, then U-Boot will prevent the environment
1775		variable "splashimage" from being set to a problematic address
1776		(see README.displaying-bmps).
1777		This option is useful for targets where, due to alignment
1778		restrictions, an improperly aligned BMP image will cause a data
1779		abort. If you think you will not have problems with unaligned
1780		accesses (for example because your toolchain prevents them)
1781		there is no need to set this option.
1782
1783		CONFIG_SPLASH_SCREEN_ALIGN
1784
1785		If this option is set the splash image can be freely positioned
1786		on the screen. Environment variable "splashpos" specifies the
1787		position as "x,y". If a positive number is given it is used as
1788		number of pixel from left/top. If a negative number is given it
1789		is used as number of pixel from right/bottom. You can also
1790		specify 'm' for centering the image.
1791
1792		Example:
1793		setenv splashpos m,m
1794			=> image at center of screen
1795
1796		setenv splashpos 30,20
1797			=> image at x = 30 and y = 20
1798
1799		setenv splashpos -10,m
1800			=> vertically centered image
1801			   at x = dspWidth - bmpWidth - 9
1802
1803- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1804
1805		If this option is set, additionally to standard BMP
1806		images, gzipped BMP images can be displayed via the
1807		splashscreen support or the bmp command.
1808
1809- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1810
1811		If this option is set, 8-bit RLE compressed BMP images
1812		can be displayed via the splashscreen support or the
1813		bmp command.
1814
1815- Do compresssing for memory range:
1816		CONFIG_CMD_ZIP
1817
1818		If this option is set, it would use zlib deflate method
1819		to compress the specified memory at its best effort.
1820
1821- Compression support:
1822		CONFIG_GZIP
1823
1824		Enabled by default to support gzip compressed images.
1825
1826		CONFIG_BZIP2
1827
1828		If this option is set, support for bzip2 compressed
1829		images is included. If not, only uncompressed and gzip
1830		compressed images are supported.
1831
1832		NOTE: the bzip2 algorithm requires a lot of RAM, so
1833		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1834		be at least 4MB.
1835
1836		CONFIG_LZMA
1837
1838		If this option is set, support for lzma compressed
1839		images is included.
1840
1841		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1842		requires an amount of dynamic memory that is given by the
1843		formula:
1844
1845			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1846
1847		Where lc and lp stand for, respectively, Literal context bits
1848		and Literal pos bits.
1849
1850		This value is upper-bounded by 14MB in the worst case. Anyway,
1851		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1852		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1853		a very small buffer.
1854
1855		Use the lzmainfo tool to determinate the lc and lp values and
1856		then calculate the amount of needed dynamic memory (ensuring
1857		the appropriate CONFIG_SYS_MALLOC_LEN value).
1858
1859		CONFIG_LZO
1860
1861		If this option is set, support for LZO compressed images
1862		is included.
1863
1864- MII/PHY support:
1865		CONFIG_PHY_ADDR
1866
1867		The address of PHY on MII bus.
1868
1869		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1870
1871		The clock frequency of the MII bus
1872
1873		CONFIG_PHY_GIGE
1874
1875		If this option is set, support for speed/duplex
1876		detection of gigabit PHY is included.
1877
1878		CONFIG_PHY_RESET_DELAY
1879
1880		Some PHY like Intel LXT971A need extra delay after
1881		reset before any MII register access is possible.
1882		For such PHY, set this option to the usec delay
1883		required. (minimum 300usec for LXT971A)
1884
1885		CONFIG_PHY_CMD_DELAY (ppc4xx)
1886
1887		Some PHY like Intel LXT971A need extra delay after
1888		command issued before MII status register can be read
1889
1890- Ethernet address:
1891		CONFIG_ETHADDR
1892		CONFIG_ETH1ADDR
1893		CONFIG_ETH2ADDR
1894		CONFIG_ETH3ADDR
1895		CONFIG_ETH4ADDR
1896		CONFIG_ETH5ADDR
1897
1898		Define a default value for Ethernet address to use
1899		for the respective Ethernet interface, in case this
1900		is not determined automatically.
1901
1902- IP address:
1903		CONFIG_IPADDR
1904
1905		Define a default value for the IP address to use for
1906		the default Ethernet interface, in case this is not
1907		determined through e.g. bootp.
1908		(Environment variable "ipaddr")
1909
1910- Server IP address:
1911		CONFIG_SERVERIP
1912
1913		Defines a default value for the IP address of a TFTP
1914		server to contact when using the "tftboot" command.
1915		(Environment variable "serverip")
1916
1917		CONFIG_KEEP_SERVERADDR
1918
1919		Keeps the server's MAC address, in the env 'serveraddr'
1920		for passing to bootargs (like Linux's netconsole option)
1921
1922- Gateway IP address:
1923		CONFIG_GATEWAYIP
1924
1925		Defines a default value for the IP address of the
1926		default router where packets to other networks are
1927		sent to.
1928		(Environment variable "gatewayip")
1929
1930- Subnet mask:
1931		CONFIG_NETMASK
1932
1933		Defines a default value for the subnet mask (or
1934		routing prefix) which is used to determine if an IP
1935		address belongs to the local subnet or needs to be
1936		forwarded through a router.
1937		(Environment variable "netmask")
1938
1939- Multicast TFTP Mode:
1940		CONFIG_MCAST_TFTP
1941
1942		Defines whether you want to support multicast TFTP as per
1943		rfc-2090; for example to work with atftp.  Lets lots of targets
1944		tftp down the same boot image concurrently.  Note: the Ethernet
1945		driver in use must provide a function: mcast() to join/leave a
1946		multicast group.
1947
1948- BOOTP Recovery Mode:
1949		CONFIG_BOOTP_RANDOM_DELAY
1950
1951		If you have many targets in a network that try to
1952		boot using BOOTP, you may want to avoid that all
1953		systems send out BOOTP requests at precisely the same
1954		moment (which would happen for instance at recovery
1955		from a power failure, when all systems will try to
1956		boot, thus flooding the BOOTP server. Defining
1957		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1958		inserted before sending out BOOTP requests. The
1959		following delays are inserted then:
1960
1961		1st BOOTP request:	delay 0 ... 1 sec
1962		2nd BOOTP request:	delay 0 ... 2 sec
1963		3rd BOOTP request:	delay 0 ... 4 sec
1964		4th and following
1965		BOOTP requests:		delay 0 ... 8 sec
1966
1967- DHCP Advanced Options:
1968		You can fine tune the DHCP functionality by defining
1969		CONFIG_BOOTP_* symbols:
1970
1971		CONFIG_BOOTP_SUBNETMASK
1972		CONFIG_BOOTP_GATEWAY
1973		CONFIG_BOOTP_HOSTNAME
1974		CONFIG_BOOTP_NISDOMAIN
1975		CONFIG_BOOTP_BOOTPATH
1976		CONFIG_BOOTP_BOOTFILESIZE
1977		CONFIG_BOOTP_DNS
1978		CONFIG_BOOTP_DNS2
1979		CONFIG_BOOTP_SEND_HOSTNAME
1980		CONFIG_BOOTP_NTPSERVER
1981		CONFIG_BOOTP_TIMEOFFSET
1982		CONFIG_BOOTP_VENDOREX
1983		CONFIG_BOOTP_MAY_FAIL
1984
1985		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1986		environment variable, not the BOOTP server.
1987
1988		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1989		after the configured retry count, the call will fail
1990		instead of starting over.  This can be used to fail over
1991		to Link-local IP address configuration if the DHCP server
1992		is not available.
1993
1994		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1995		serverip from a DHCP server, it is possible that more
1996		than one DNS serverip is offered to the client.
1997		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1998		serverip will be stored in the additional environment
1999		variable "dnsip2". The first DNS serverip is always
2000		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2001		is defined.
2002
2003		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2004		to do a dynamic update of a DNS server. To do this, they
2005		need the hostname of the DHCP requester.
2006		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2007		of the "hostname" environment variable is passed as
2008		option 12 to the DHCP server.
2009
2010		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2011
2012		A 32bit value in microseconds for a delay between
2013		receiving a "DHCP Offer" and sending the "DHCP Request".
2014		This fixes a problem with certain DHCP servers that don't
2015		respond 100% of the time to a "DHCP request". E.g. On an
2016		AT91RM9200 processor running at 180MHz, this delay needed
2017		to be *at least* 15,000 usec before a Windows Server 2003
2018		DHCP server would reply 100% of the time. I recommend at
2019		least 50,000 usec to be safe. The alternative is to hope
2020		that one of the retries will be successful but note that
2021		the DHCP timeout and retry process takes a longer than
2022		this delay.
2023
2024 - Link-local IP address negotiation:
2025		Negotiate with other link-local clients on the local network
2026		for an address that doesn't require explicit configuration.
2027		This is especially useful if a DHCP server cannot be guaranteed
2028		to exist in all environments that the device must operate.
2029
2030		See doc/README.link-local for more information.
2031
2032 - CDP Options:
2033		CONFIG_CDP_DEVICE_ID
2034
2035		The device id used in CDP trigger frames.
2036
2037		CONFIG_CDP_DEVICE_ID_PREFIX
2038
2039		A two character string which is prefixed to the MAC address
2040		of the device.
2041
2042		CONFIG_CDP_PORT_ID
2043
2044		A printf format string which contains the ascii name of
2045		the port. Normally is set to "eth%d" which sets
2046		eth0 for the first Ethernet, eth1 for the second etc.
2047
2048		CONFIG_CDP_CAPABILITIES
2049
2050		A 32bit integer which indicates the device capabilities;
2051		0x00000010 for a normal host which does not forwards.
2052
2053		CONFIG_CDP_VERSION
2054
2055		An ascii string containing the version of the software.
2056
2057		CONFIG_CDP_PLATFORM
2058
2059		An ascii string containing the name of the platform.
2060
2061		CONFIG_CDP_TRIGGER
2062
2063		A 32bit integer sent on the trigger.
2064
2065		CONFIG_CDP_POWER_CONSUMPTION
2066
2067		A 16bit integer containing the power consumption of the
2068		device in .1 of milliwatts.
2069
2070		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2071
2072		A byte containing the id of the VLAN.
2073
2074- Status LED:	CONFIG_STATUS_LED
2075
2076		Several configurations allow to display the current
2077		status using a LED. For instance, the LED will blink
2078		fast while running U-Boot code, stop blinking as
2079		soon as a reply to a BOOTP request was received, and
2080		start blinking slow once the Linux kernel is running
2081		(supported by a status LED driver in the Linux
2082		kernel). Defining CONFIG_STATUS_LED enables this
2083		feature in U-Boot.
2084
2085		Additional options:
2086
2087		CONFIG_GPIO_LED
2088		The status LED can be connected to a GPIO pin.
2089		In such cases, the gpio_led driver can be used as a
2090		status LED backend implementation. Define CONFIG_GPIO_LED
2091		to include the gpio_led driver in the U-Boot binary.
2092
2093		CONFIG_GPIO_LED_INVERTED_TABLE
2094		Some GPIO connected LEDs may have inverted polarity in which
2095		case the GPIO high value corresponds to LED off state and
2096		GPIO low value corresponds to LED on state.
2097		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2098		with a list of GPIO LEDs that have inverted polarity.
2099
2100- CAN Support:	CONFIG_CAN_DRIVER
2101
2102		Defining CONFIG_CAN_DRIVER enables CAN driver support
2103		on those systems that support this (optional)
2104		feature, like the TQM8xxL modules.
2105
2106- I2C Support:	CONFIG_SYS_I2C
2107
2108		This enable the NEW i2c subsystem, and will allow you to use
2109		i2c commands at the u-boot command line (as long as you set
2110		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2111		based realtime clock chips or other i2c devices. See
2112		common/cmd_i2c.c for a description of the command line
2113		interface.
2114
2115		ported i2c driver to the new framework:
2116		- drivers/i2c/soft_i2c.c:
2117		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2118		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2119		    for defining speed and slave address
2120		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2121		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2122		    for defining speed and slave address
2123		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2124		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2125		    for defining speed and slave address
2126		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2127		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2128		    for defining speed and slave address
2129
2130		- drivers/i2c/fsl_i2c.c:
2131		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2132		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2133		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2134		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2135		    bus.
2136		  - If your board supports a second fsl i2c bus, define
2137		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2138		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2139		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2140		    second bus.
2141
2142		- drivers/i2c/tegra_i2c.c:
2143		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2144		  - This driver adds 4 i2c buses with a fix speed from
2145		    100000 and the slave addr 0!
2146
2147		- drivers/i2c/ppc4xx_i2c.c
2148		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2149		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2150		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2151
2152		- drivers/i2c/i2c_mxc.c
2153		  - activate this driver with CONFIG_SYS_I2C_MXC
2154		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2155		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2156		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2157		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2158		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2159		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2160		If thoses defines are not set, default value is 100000
2161		for speed, and 0 for slave.
2162
2163		- drivers/i2c/rcar_i2c.c:
2164		  - activate this driver with CONFIG_SYS_I2C_RCAR
2165		  - This driver adds 4 i2c buses
2166
2167		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2168		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2169		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2170		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2171		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2172		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2173		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2174		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2175		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2176
2177		- drivers/i2c/sh_i2c.c:
2178		  - activate this driver with CONFIG_SYS_I2C_SH
2179		  - This driver adds from 2 to 5 i2c buses
2180
2181		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2182		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2183		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2184		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2185		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2186		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2187		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2188		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2189		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2190		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2191		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2192		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2193		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2194
2195		- drivers/i2c/omap24xx_i2c.c
2196		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2197		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2198		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2199		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2200		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2201		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2202		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2203		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2204		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2205		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2206		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2207
2208		- drivers/i2c/zynq_i2c.c
2209		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2210		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2211		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2212
2213		- drivers/i2c/s3c24x0_i2c.c:
2214		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2215		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2216		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2217		    with a fix speed from 100000 and the slave addr 0!
2218
2219		additional defines:
2220
2221		CONFIG_SYS_NUM_I2C_BUSES
2222		Hold the number of i2c busses you want to use. If you
2223		don't use/have i2c muxes on your i2c bus, this
2224		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2225		omit this define.
2226
2227		CONFIG_SYS_I2C_DIRECT_BUS
2228		define this, if you don't use i2c muxes on your hardware.
2229		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2230		omit this define.
2231
2232		CONFIG_SYS_I2C_MAX_HOPS
2233		define how many muxes are maximal consecutively connected
2234		on one i2c bus. If you not use i2c muxes, omit this
2235		define.
2236
2237		CONFIG_SYS_I2C_BUSES
2238		hold a list of busses you want to use, only used if
2239		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2240		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2241		CONFIG_SYS_NUM_I2C_BUSES = 9:
2242
2243		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2244					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2245					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2246					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2247					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2248					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2249					{1, {I2C_NULL_HOP}}, \
2250					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2251					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2252					}
2253
2254		which defines
2255			bus 0 on adapter 0 without a mux
2256			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2257			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2258			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2259			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2260			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2261			bus 6 on adapter 1 without a mux
2262			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2263			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2264
2265		If you do not have i2c muxes on your board, omit this define.
2266
2267- Legacy I2C Support:	CONFIG_HARD_I2C
2268
2269		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2270		provides the following compelling advantages:
2271
2272		- more than one i2c adapter is usable
2273		- approved multibus support
2274		- better i2c mux support
2275
2276		** Please consider updating your I2C driver now. **
2277
2278		These enable legacy I2C serial bus commands. Defining
2279		CONFIG_HARD_I2C will include the appropriate I2C driver
2280		for the selected CPU.
2281
2282		This will allow you to use i2c commands at the u-boot
2283		command line (as long as you set CONFIG_CMD_I2C in
2284		CONFIG_COMMANDS) and communicate with i2c based realtime
2285		clock chips. See common/cmd_i2c.c for a description of the
2286		command line interface.
2287
2288		CONFIG_HARD_I2C selects a hardware I2C controller.
2289
2290		There are several other quantities that must also be
2291		defined when you define CONFIG_HARD_I2C.
2292
2293		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2294		to be the frequency (in Hz) at which you wish your i2c bus
2295		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2296		the CPU's i2c node address).
2297
2298		Now, the u-boot i2c code for the mpc8xx
2299		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2300		and so its address should therefore be cleared to 0 (See,
2301		eg, MPC823e User's Manual p.16-473). So, set
2302		CONFIG_SYS_I2C_SLAVE to 0.
2303
2304		CONFIG_SYS_I2C_INIT_MPC5XXX
2305
2306		When a board is reset during an i2c bus transfer
2307		chips might think that the current transfer is still
2308		in progress.  Reset the slave devices by sending start
2309		commands until the slave device responds.
2310
2311		That's all that's required for CONFIG_HARD_I2C.
2312
2313		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2314		then the following macros need to be defined (examples are
2315		from include/configs/lwmon.h):
2316
2317		I2C_INIT
2318
2319		(Optional). Any commands necessary to enable the I2C
2320		controller or configure ports.
2321
2322		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2323
2324		I2C_PORT
2325
2326		(Only for MPC8260 CPU). The I/O port to use (the code
2327		assumes both bits are on the same port). Valid values
2328		are 0..3 for ports A..D.
2329
2330		I2C_ACTIVE
2331
2332		The code necessary to make the I2C data line active
2333		(driven).  If the data line is open collector, this
2334		define can be null.
2335
2336		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2337
2338		I2C_TRISTATE
2339
2340		The code necessary to make the I2C data line tri-stated
2341		(inactive).  If the data line is open collector, this
2342		define can be null.
2343
2344		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2345
2346		I2C_READ
2347
2348		Code that returns true if the I2C data line is high,
2349		false if it is low.
2350
2351		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2352
2353		I2C_SDA(bit)
2354
2355		If <bit> is true, sets the I2C data line high. If it
2356		is false, it clears it (low).
2357
2358		eg: #define I2C_SDA(bit) \
2359			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2360			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2361
2362		I2C_SCL(bit)
2363
2364		If <bit> is true, sets the I2C clock line high. If it
2365		is false, it clears it (low).
2366
2367		eg: #define I2C_SCL(bit) \
2368			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2369			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2370
2371		I2C_DELAY
2372
2373		This delay is invoked four times per clock cycle so this
2374		controls the rate of data transfer.  The data rate thus
2375		is 1 / (I2C_DELAY * 4). Often defined to be something
2376		like:
2377
2378		#define I2C_DELAY  udelay(2)
2379
2380		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2381
2382		If your arch supports the generic GPIO framework (asm/gpio.h),
2383		then you may alternatively define the two GPIOs that are to be
2384		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2385		have GPIO-based defaults assigned to them as appropriate.
2386
2387		You should define these to the GPIO value as given directly to
2388		the generic GPIO functions.
2389
2390		CONFIG_SYS_I2C_INIT_BOARD
2391
2392		When a board is reset during an i2c bus transfer
2393		chips might think that the current transfer is still
2394		in progress. On some boards it is possible to access
2395		the i2c SCLK line directly, either by using the
2396		processor pin as a GPIO or by having a second pin
2397		connected to the bus. If this option is defined a
2398		custom i2c_init_board() routine in boards/xxx/board.c
2399		is run early in the boot sequence.
2400
2401		CONFIG_SYS_I2C_BOARD_LATE_INIT
2402
2403		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2404		defined a custom i2c_board_late_init() routine in
2405		boards/xxx/board.c is run AFTER the operations in i2c_init()
2406		is completed. This callpoint can be used to unreset i2c bus
2407		using CPU i2c controller register accesses for CPUs whose i2c
2408		controller provide such a method. It is called at the end of
2409		i2c_init() to allow i2c_init operations to setup the i2c bus
2410		controller on the CPU (e.g. setting bus speed & slave address).
2411
2412		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2413
2414		This option enables configuration of bi_iic_fast[] flags
2415		in u-boot bd_info structure based on u-boot environment
2416		variable "i2cfast". (see also i2cfast)
2417
2418		CONFIG_I2C_MULTI_BUS
2419
2420		This option allows the use of multiple I2C buses, each of which
2421		must have a controller.	 At any point in time, only one bus is
2422		active.	 To switch to a different bus, use the 'i2c dev' command.
2423		Note that bus numbering is zero-based.
2424
2425		CONFIG_SYS_I2C_NOPROBES
2426
2427		This option specifies a list of I2C devices that will be skipped
2428		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2429		is set, specify a list of bus-device pairs.  Otherwise, specify
2430		a 1D array of device addresses
2431
2432		e.g.
2433			#undef	CONFIG_I2C_MULTI_BUS
2434			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2435
2436		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2437
2438			#define CONFIG_I2C_MULTI_BUS
2439			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2440
2441		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2442
2443		CONFIG_SYS_SPD_BUS_NUM
2444
2445		If defined, then this indicates the I2C bus number for DDR SPD.
2446		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2447
2448		CONFIG_SYS_RTC_BUS_NUM
2449
2450		If defined, then this indicates the I2C bus number for the RTC.
2451		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2452
2453		CONFIG_SYS_DTT_BUS_NUM
2454
2455		If defined, then this indicates the I2C bus number for the DTT.
2456		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2457
2458		CONFIG_SYS_I2C_DTT_ADDR:
2459
2460		If defined, specifies the I2C address of the DTT device.
2461		If not defined, then U-Boot uses predefined value for
2462		specified DTT device.
2463
2464		CONFIG_SOFT_I2C_READ_REPEATED_START
2465
2466		defining this will force the i2c_read() function in
2467		the soft_i2c driver to perform an I2C repeated start
2468		between writing the address pointer and reading the
2469		data.  If this define is omitted the default behaviour
2470		of doing a stop-start sequence will be used.  Most I2C
2471		devices can use either method, but some require one or
2472		the other.
2473
2474- SPI Support:	CONFIG_SPI
2475
2476		Enables SPI driver (so far only tested with
2477		SPI EEPROM, also an instance works with Crystal A/D and
2478		D/As on the SACSng board)
2479
2480		CONFIG_SH_SPI
2481
2482		Enables the driver for SPI controller on SuperH. Currently
2483		only SH7757 is supported.
2484
2485		CONFIG_SPI_X
2486
2487		Enables extended (16-bit) SPI EEPROM addressing.
2488		(symmetrical to CONFIG_I2C_X)
2489
2490		CONFIG_SOFT_SPI
2491
2492		Enables a software (bit-bang) SPI driver rather than
2493		using hardware support. This is a general purpose
2494		driver that only requires three general I/O port pins
2495		(two outputs, one input) to function. If this is
2496		defined, the board configuration must define several
2497		SPI configuration items (port pins to use, etc). For
2498		an example, see include/configs/sacsng.h.
2499
2500		CONFIG_HARD_SPI
2501
2502		Enables a hardware SPI driver for general-purpose reads
2503		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2504		must define a list of chip-select function pointers.
2505		Currently supported on some MPC8xxx processors.	 For an
2506		example, see include/configs/mpc8349emds.h.
2507
2508		CONFIG_MXC_SPI
2509
2510		Enables the driver for the SPI controllers on i.MX and MXC
2511		SoCs. Currently i.MX31/35/51 are supported.
2512
2513- FPGA Support: CONFIG_FPGA
2514
2515		Enables FPGA subsystem.
2516
2517		CONFIG_FPGA_<vendor>
2518
2519		Enables support for specific chip vendors.
2520		(ALTERA, XILINX)
2521
2522		CONFIG_FPGA_<family>
2523
2524		Enables support for FPGA family.
2525		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2526
2527		CONFIG_FPGA_COUNT
2528
2529		Specify the number of FPGA devices to support.
2530
2531		CONFIG_SYS_FPGA_PROG_FEEDBACK
2532
2533		Enable printing of hash marks during FPGA configuration.
2534
2535		CONFIG_SYS_FPGA_CHECK_BUSY
2536
2537		Enable checks on FPGA configuration interface busy
2538		status by the configuration function. This option
2539		will require a board or device specific function to
2540		be written.
2541
2542		CONFIG_FPGA_DELAY
2543
2544		If defined, a function that provides delays in the FPGA
2545		configuration driver.
2546
2547		CONFIG_SYS_FPGA_CHECK_CTRLC
2548		Allow Control-C to interrupt FPGA configuration
2549
2550		CONFIG_SYS_FPGA_CHECK_ERROR
2551
2552		Check for configuration errors during FPGA bitfile
2553		loading. For example, abort during Virtex II
2554		configuration if the INIT_B line goes low (which
2555		indicated a CRC error).
2556
2557		CONFIG_SYS_FPGA_WAIT_INIT
2558
2559		Maximum time to wait for the INIT_B line to deassert
2560		after PROB_B has been deasserted during a Virtex II
2561		FPGA configuration sequence. The default time is 500
2562		ms.
2563
2564		CONFIG_SYS_FPGA_WAIT_BUSY
2565
2566		Maximum time to wait for BUSY to deassert during
2567		Virtex II FPGA configuration. The default is 5 ms.
2568
2569		CONFIG_SYS_FPGA_WAIT_CONFIG
2570
2571		Time to wait after FPGA configuration. The default is
2572		200 ms.
2573
2574- Configuration Management:
2575		CONFIG_IDENT_STRING
2576
2577		If defined, this string will be added to the U-Boot
2578		version information (U_BOOT_VERSION)
2579
2580- Vendor Parameter Protection:
2581
2582		U-Boot considers the values of the environment
2583		variables "serial#" (Board Serial Number) and
2584		"ethaddr" (Ethernet Address) to be parameters that
2585		are set once by the board vendor / manufacturer, and
2586		protects these variables from casual modification by
2587		the user. Once set, these variables are read-only,
2588		and write or delete attempts are rejected. You can
2589		change this behaviour:
2590
2591		If CONFIG_ENV_OVERWRITE is #defined in your config
2592		file, the write protection for vendor parameters is
2593		completely disabled. Anybody can change or delete
2594		these parameters.
2595
2596		Alternatively, if you #define _both_ CONFIG_ETHADDR
2597		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2598		Ethernet address is installed in the environment,
2599		which can be changed exactly ONCE by the user. [The
2600		serial# is unaffected by this, i. e. it remains
2601		read-only.]
2602
2603		The same can be accomplished in a more flexible way
2604		for any variable by configuring the type of access
2605		to allow for those variables in the ".flags" variable
2606		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2607
2608- Protected RAM:
2609		CONFIG_PRAM
2610
2611		Define this variable to enable the reservation of
2612		"protected RAM", i. e. RAM which is not overwritten
2613		by U-Boot. Define CONFIG_PRAM to hold the number of
2614		kB you want to reserve for pRAM. You can overwrite
2615		this default value by defining an environment
2616		variable "pram" to the number of kB you want to
2617		reserve. Note that the board info structure will
2618		still show the full amount of RAM. If pRAM is
2619		reserved, a new environment variable "mem" will
2620		automatically be defined to hold the amount of
2621		remaining RAM in a form that can be passed as boot
2622		argument to Linux, for instance like that:
2623
2624			setenv bootargs ... mem=\${mem}
2625			saveenv
2626
2627		This way you can tell Linux not to use this memory,
2628		either, which results in a memory region that will
2629		not be affected by reboots.
2630
2631		*WARNING* If your board configuration uses automatic
2632		detection of the RAM size, you must make sure that
2633		this memory test is non-destructive. So far, the
2634		following board configurations are known to be
2635		"pRAM-clean":
2636
2637			IVMS8, IVML24, SPD8xx, TQM8xxL,
2638			HERMES, IP860, RPXlite, LWMON,
2639			FLAGADM, TQM8260
2640
2641- Access to physical memory region (> 4GB)
2642		Some basic support is provided for operations on memory not
2643		normally accessible to U-Boot - e.g. some architectures
2644		support access to more than 4GB of memory on 32-bit
2645		machines using physical address extension or similar.
2646		Define CONFIG_PHYSMEM to access this basic support, which
2647		currently only supports clearing the memory.
2648
2649- Error Recovery:
2650		CONFIG_PANIC_HANG
2651
2652		Define this variable to stop the system in case of a
2653		fatal error, so that you have to reset it manually.
2654		This is probably NOT a good idea for an embedded
2655		system where you want the system to reboot
2656		automatically as fast as possible, but it may be
2657		useful during development since you can try to debug
2658		the conditions that lead to the situation.
2659
2660		CONFIG_NET_RETRY_COUNT
2661
2662		This variable defines the number of retries for
2663		network operations like ARP, RARP, TFTP, or BOOTP
2664		before giving up the operation. If not defined, a
2665		default value of 5 is used.
2666
2667		CONFIG_ARP_TIMEOUT
2668
2669		Timeout waiting for an ARP reply in milliseconds.
2670
2671		CONFIG_NFS_TIMEOUT
2672
2673		Timeout in milliseconds used in NFS protocol.
2674		If you encounter "ERROR: Cannot umount" in nfs command,
2675		try longer timeout such as
2676		#define CONFIG_NFS_TIMEOUT 10000UL
2677
2678- Command Interpreter:
2679		CONFIG_AUTO_COMPLETE
2680
2681		Enable auto completion of commands using TAB.
2682
2683		Note that this feature has NOT been implemented yet
2684		for the "hush" shell.
2685
2686
2687		CONFIG_SYS_HUSH_PARSER
2688
2689		Define this variable to enable the "hush" shell (from
2690		Busybox) as command line interpreter, thus enabling
2691		powerful command line syntax like
2692		if...then...else...fi conditionals or `&&' and '||'
2693		constructs ("shell scripts").
2694
2695		If undefined, you get the old, much simpler behaviour
2696		with a somewhat smaller memory footprint.
2697
2698
2699		CONFIG_SYS_PROMPT_HUSH_PS2
2700
2701		This defines the secondary prompt string, which is
2702		printed when the command interpreter needs more input
2703		to complete a command. Usually "> ".
2704
2705	Note:
2706
2707		In the current implementation, the local variables
2708		space and global environment variables space are
2709		separated. Local variables are those you define by
2710		simply typing `name=value'. To access a local
2711		variable later on, you have write `$name' or
2712		`${name}'; to execute the contents of a variable
2713		directly type `$name' at the command prompt.
2714
2715		Global environment variables are those you use
2716		setenv/printenv to work with. To run a command stored
2717		in such a variable, you need to use the run command,
2718		and you must not use the '$' sign to access them.
2719
2720		To store commands and special characters in a
2721		variable, please use double quotation marks
2722		surrounding the whole text of the variable, instead
2723		of the backslashes before semicolons and special
2724		symbols.
2725
2726- Commandline Editing and History:
2727		CONFIG_CMDLINE_EDITING
2728
2729		Enable editing and History functions for interactive
2730		commandline input operations
2731
2732- Default Environment:
2733		CONFIG_EXTRA_ENV_SETTINGS
2734
2735		Define this to contain any number of null terminated
2736		strings (variable = value pairs) that will be part of
2737		the default environment compiled into the boot image.
2738
2739		For example, place something like this in your
2740		board's config file:
2741
2742		#define CONFIG_EXTRA_ENV_SETTINGS \
2743			"myvar1=value1\0" \
2744			"myvar2=value2\0"
2745
2746		Warning: This method is based on knowledge about the
2747		internal format how the environment is stored by the
2748		U-Boot code. This is NOT an official, exported
2749		interface! Although it is unlikely that this format
2750		will change soon, there is no guarantee either.
2751		You better know what you are doing here.
2752
2753		Note: overly (ab)use of the default environment is
2754		discouraged. Make sure to check other ways to preset
2755		the environment like the "source" command or the
2756		boot command first.
2757
2758		CONFIG_ENV_VARS_UBOOT_CONFIG
2759
2760		Define this in order to add variables describing the
2761		U-Boot build configuration to the default environment.
2762		These will be named arch, cpu, board, vendor, and soc.
2763
2764		Enabling this option will cause the following to be defined:
2765
2766		- CONFIG_SYS_ARCH
2767		- CONFIG_SYS_CPU
2768		- CONFIG_SYS_BOARD
2769		- CONFIG_SYS_VENDOR
2770		- CONFIG_SYS_SOC
2771
2772		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2773
2774		Define this in order to add variables describing certain
2775		run-time determined information about the hardware to the
2776		environment.  These will be named board_name, board_rev.
2777
2778		CONFIG_DELAY_ENVIRONMENT
2779
2780		Normally the environment is loaded when the board is
2781		intialised so that it is available to U-Boot. This inhibits
2782		that so that the environment is not available until
2783		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2784		this is instead controlled by the value of
2785		/config/load-environment.
2786
2787- DataFlash Support:
2788		CONFIG_HAS_DATAFLASH
2789
2790		Defining this option enables DataFlash features and
2791		allows to read/write in Dataflash via the standard
2792		commands cp, md...
2793
2794- Serial Flash support
2795		CONFIG_CMD_SF
2796
2797		Defining this option enables SPI flash commands
2798		'sf probe/read/write/erase/update'.
2799
2800		Usage requires an initial 'probe' to define the serial
2801		flash parameters, followed by read/write/erase/update
2802		commands.
2803
2804		The following defaults may be provided by the platform
2805		to handle the common case when only a single serial
2806		flash is present on the system.
2807
2808		CONFIG_SF_DEFAULT_BUS		Bus identifier
2809		CONFIG_SF_DEFAULT_CS		Chip-select
2810		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2811		CONFIG_SF_DEFAULT_SPEED		in Hz
2812
2813		CONFIG_CMD_SF_TEST
2814
2815		Define this option to include a destructive SPI flash
2816		test ('sf test').
2817
2818		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2819
2820		Define this option to use the Bank addr/Extended addr
2821		support on SPI flashes which has size > 16Mbytes.
2822
2823		CONFIG_SF_DUAL_FLASH		Dual flash memories
2824
2825		Define this option to use dual flash support where two flash
2826		memories can be connected with a given cs line.
2827		currently Xilinx Zynq qspi support these type of connections.
2828
2829- SystemACE Support:
2830		CONFIG_SYSTEMACE
2831
2832		Adding this option adds support for Xilinx SystemACE
2833		chips attached via some sort of local bus. The address
2834		of the chip must also be defined in the
2835		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2836
2837		#define CONFIG_SYSTEMACE
2838		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2839
2840		When SystemACE support is added, the "ace" device type
2841		becomes available to the fat commands, i.e. fatls.
2842
2843- TFTP Fixed UDP Port:
2844		CONFIG_TFTP_PORT
2845
2846		If this is defined, the environment variable tftpsrcp
2847		is used to supply the TFTP UDP source port value.
2848		If tftpsrcp isn't defined, the normal pseudo-random port
2849		number generator is used.
2850
2851		Also, the environment variable tftpdstp is used to supply
2852		the TFTP UDP destination port value.  If tftpdstp isn't
2853		defined, the normal port 69 is used.
2854
2855		The purpose for tftpsrcp is to allow a TFTP server to
2856		blindly start the TFTP transfer using the pre-configured
2857		target IP address and UDP port. This has the effect of
2858		"punching through" the (Windows XP) firewall, allowing
2859		the remainder of the TFTP transfer to proceed normally.
2860		A better solution is to properly configure the firewall,
2861		but sometimes that is not allowed.
2862
2863- Hashing support:
2864		CONFIG_CMD_HASH
2865
2866		This enables a generic 'hash' command which can produce
2867		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2868
2869		CONFIG_HASH_VERIFY
2870
2871		Enable the hash verify command (hash -v). This adds to code
2872		size a little.
2873
2874		CONFIG_SHA1 - support SHA1 hashing
2875		CONFIG_SHA256 - support SHA256 hashing
2876
2877		Note: There is also a sha1sum command, which should perhaps
2878		be deprecated in favour of 'hash sha1'.
2879
2880- Freescale i.MX specific commands:
2881		CONFIG_CMD_HDMIDETECT
2882		This enables 'hdmidet' command which returns true if an
2883		HDMI monitor is detected.  This command is i.MX 6 specific.
2884
2885		CONFIG_CMD_BMODE
2886		This enables the 'bmode' (bootmode) command for forcing
2887		a boot from specific media.
2888
2889		This is useful for forcing the ROM's usb downloader to
2890		activate upon a watchdog reset which is nice when iterating
2891		on U-Boot.  Using the reset button or running bmode normal
2892		will set it back to normal.  This command currently
2893		supports i.MX53 and i.MX6.
2894
2895- Signing support:
2896		CONFIG_RSA
2897
2898		This enables the RSA algorithm used for FIT image verification
2899		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2900
2901		The signing part is build into mkimage regardless of this
2902		option.
2903
2904- bootcount support:
2905		CONFIG_BOOTCOUNT_LIMIT
2906
2907		This enables the bootcounter support, see:
2908		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2909
2910		CONFIG_AT91SAM9XE
2911		enable special bootcounter support on at91sam9xe based boards.
2912		CONFIG_BLACKFIN
2913		enable special bootcounter support on blackfin based boards.
2914		CONFIG_SOC_DA8XX
2915		enable special bootcounter support on da850 based boards.
2916		CONFIG_BOOTCOUNT_RAM
2917		enable support for the bootcounter in RAM
2918		CONFIG_BOOTCOUNT_I2C
2919		enable support for the bootcounter on an i2c (like RTC) device.
2920			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2921			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2922						    the bootcounter.
2923			CONFIG_BOOTCOUNT_ALEN = address len
2924
2925- Show boot progress:
2926		CONFIG_SHOW_BOOT_PROGRESS
2927
2928		Defining this option allows to add some board-
2929		specific code (calling a user-provided function
2930		"show_boot_progress(int)") that enables you to show
2931		the system's boot progress on some display (for
2932		example, some LED's) on your board. At the moment,
2933		the following checkpoints are implemented:
2934
2935- Detailed boot stage timing
2936		CONFIG_BOOTSTAGE
2937		Define this option to get detailed timing of each stage
2938		of the boot process.
2939
2940		CONFIG_BOOTSTAGE_USER_COUNT
2941		This is the number of available user bootstage records.
2942		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2943		a new ID will be allocated from this stash. If you exceed
2944		the limit, recording will stop.
2945
2946		CONFIG_BOOTSTAGE_REPORT
2947		Define this to print a report before boot, similar to this:
2948
2949		Timer summary in microseconds:
2950		       Mark    Elapsed  Stage
2951			  0          0  reset
2952		  3,575,678  3,575,678  board_init_f start
2953		  3,575,695         17  arch_cpu_init A9
2954		  3,575,777         82  arch_cpu_init done
2955		  3,659,598     83,821  board_init_r start
2956		  3,910,375    250,777  main_loop
2957		 29,916,167 26,005,792  bootm_start
2958		 30,361,327    445,160  start_kernel
2959
2960		CONFIG_CMD_BOOTSTAGE
2961		Add a 'bootstage' command which supports printing a report
2962		and un/stashing of bootstage data.
2963
2964		CONFIG_BOOTSTAGE_FDT
2965		Stash the bootstage information in the FDT. A root 'bootstage'
2966		node is created with each bootstage id as a child. Each child
2967		has a 'name' property and either 'mark' containing the
2968		mark time in microsecond, or 'accum' containing the
2969		accumulated time for that bootstage id in microseconds.
2970		For example:
2971
2972		bootstage {
2973			154 {
2974				name = "board_init_f";
2975				mark = <3575678>;
2976			};
2977			170 {
2978				name = "lcd";
2979				accum = <33482>;
2980			};
2981		};
2982
2983		Code in the Linux kernel can find this in /proc/devicetree.
2984
2985Legacy uImage format:
2986
2987  Arg	Where			When
2988    1	common/cmd_bootm.c	before attempting to boot an image
2989   -1	common/cmd_bootm.c	Image header has bad	 magic number
2990    2	common/cmd_bootm.c	Image header has correct magic number
2991   -2	common/cmd_bootm.c	Image header has bad	 checksum
2992    3	common/cmd_bootm.c	Image header has correct checksum
2993   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2994    4	common/cmd_bootm.c	Image data   has correct checksum
2995   -4	common/cmd_bootm.c	Image is for unsupported architecture
2996    5	common/cmd_bootm.c	Architecture check OK
2997   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2998    6	common/cmd_bootm.c	Image Type check OK
2999   -6	common/cmd_bootm.c	gunzip uncompression error
3000   -7	common/cmd_bootm.c	Unimplemented compression type
3001    7	common/cmd_bootm.c	Uncompression OK
3002    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3003   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3004
3005    9	common/image.c		Start initial ramdisk verification
3006  -10	common/image.c		Ramdisk header has bad	   magic number
3007  -11	common/image.c		Ramdisk header has bad	   checksum
3008   10	common/image.c		Ramdisk header is OK
3009  -12	common/image.c		Ramdisk data   has bad	   checksum
3010   11	common/image.c		Ramdisk data   has correct checksum
3011   12	common/image.c		Ramdisk verification complete, start loading
3012  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3013   13	common/image.c		Start multifile image verification
3014   14	common/image.c		No initial ramdisk, no multifile, continue.
3015
3016   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3017
3018  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3019  -31	post/post.c		POST test failed, detected by post_output_backlog()
3020  -32	post/post.c		POST test failed, detected by post_run_single()
3021
3022   34	common/cmd_doc.c	before loading a Image from a DOC device
3023  -35	common/cmd_doc.c	Bad usage of "doc" command
3024   35	common/cmd_doc.c	correct usage of "doc" command
3025  -36	common/cmd_doc.c	No boot device
3026   36	common/cmd_doc.c	correct boot device
3027  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3028   37	common/cmd_doc.c	correct chip ID found, device available
3029  -38	common/cmd_doc.c	Read Error on boot device
3030   38	common/cmd_doc.c	reading Image header from DOC device OK
3031  -39	common/cmd_doc.c	Image header has bad magic number
3032   39	common/cmd_doc.c	Image header has correct magic number
3033  -40	common/cmd_doc.c	Error reading Image from DOC device
3034   40	common/cmd_doc.c	Image header has correct magic number
3035   41	common/cmd_ide.c	before loading a Image from a IDE device
3036  -42	common/cmd_ide.c	Bad usage of "ide" command
3037   42	common/cmd_ide.c	correct usage of "ide" command
3038  -43	common/cmd_ide.c	No boot device
3039   43	common/cmd_ide.c	boot device found
3040  -44	common/cmd_ide.c	Device not available
3041   44	common/cmd_ide.c	Device available
3042  -45	common/cmd_ide.c	wrong partition selected
3043   45	common/cmd_ide.c	partition selected
3044  -46	common/cmd_ide.c	Unknown partition table
3045   46	common/cmd_ide.c	valid partition table found
3046  -47	common/cmd_ide.c	Invalid partition type
3047   47	common/cmd_ide.c	correct partition type
3048  -48	common/cmd_ide.c	Error reading Image Header on boot device
3049   48	common/cmd_ide.c	reading Image Header from IDE device OK
3050  -49	common/cmd_ide.c	Image header has bad magic number
3051   49	common/cmd_ide.c	Image header has correct magic number
3052  -50	common/cmd_ide.c	Image header has bad	 checksum
3053   50	common/cmd_ide.c	Image header has correct checksum
3054  -51	common/cmd_ide.c	Error reading Image from IDE device
3055   51	common/cmd_ide.c	reading Image from IDE device OK
3056   52	common/cmd_nand.c	before loading a Image from a NAND device
3057  -53	common/cmd_nand.c	Bad usage of "nand" command
3058   53	common/cmd_nand.c	correct usage of "nand" command
3059  -54	common/cmd_nand.c	No boot device
3060   54	common/cmd_nand.c	boot device found
3061  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3062   55	common/cmd_nand.c	correct chip ID found, device available
3063  -56	common/cmd_nand.c	Error reading Image Header on boot device
3064   56	common/cmd_nand.c	reading Image Header from NAND device OK
3065  -57	common/cmd_nand.c	Image header has bad magic number
3066   57	common/cmd_nand.c	Image header has correct magic number
3067  -58	common/cmd_nand.c	Error reading Image from NAND device
3068   58	common/cmd_nand.c	reading Image from NAND device OK
3069
3070  -60	common/env_common.c	Environment has a bad CRC, using default
3071
3072   64	net/eth.c		starting with Ethernet configuration.
3073  -64	net/eth.c		no Ethernet found.
3074   65	net/eth.c		Ethernet found.
3075
3076  -80	common/cmd_net.c	usage wrong
3077   80	common/cmd_net.c	before calling NetLoop()
3078  -81	common/cmd_net.c	some error in NetLoop() occurred
3079   81	common/cmd_net.c	NetLoop() back without error
3080  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3081   82	common/cmd_net.c	trying automatic boot
3082   83	common/cmd_net.c	running "source" command
3083  -83	common/cmd_net.c	some error in automatic boot or "source" command
3084   84	common/cmd_net.c	end without errors
3085
3086FIT uImage format:
3087
3088  Arg	Where			When
3089  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3090 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3091  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3092 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3093  102	common/cmd_bootm.c	Kernel unit name specified
3094 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3095  103	common/cmd_bootm.c	Found configuration node
3096  104	common/cmd_bootm.c	Got kernel subimage node offset
3097 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3098  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3099 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3100  106	common/cmd_bootm.c	Architecture check OK
3101 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3102  107	common/cmd_bootm.c	Kernel subimage type OK
3103 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3104  108	common/cmd_bootm.c	Got kernel subimage data/size
3105 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3106 -109	common/cmd_bootm.c	Can't get kernel subimage type
3107 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3108 -111	common/cmd_bootm.c	Can't get kernel subimage os
3109 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3110 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3111
3112  120	common/image.c		Start initial ramdisk verification
3113 -120	common/image.c		Ramdisk FIT image has incorrect format
3114  121	common/image.c		Ramdisk FIT image has correct format
3115  122	common/image.c		No ramdisk subimage unit name, using configuration
3116 -122	common/image.c		Can't get configuration for ramdisk subimage
3117  123	common/image.c		Ramdisk unit name specified
3118 -124	common/image.c		Can't get ramdisk subimage node offset
3119  125	common/image.c		Got ramdisk subimage node offset
3120 -125	common/image.c		Ramdisk subimage hash verification failed
3121  126	common/image.c		Ramdisk subimage hash verification OK
3122 -126	common/image.c		Ramdisk subimage for unsupported architecture
3123  127	common/image.c		Architecture check OK
3124 -127	common/image.c		Can't get ramdisk subimage data/size
3125  128	common/image.c		Got ramdisk subimage data/size
3126  129	common/image.c		Can't get ramdisk load address
3127 -129	common/image.c		Got ramdisk load address
3128
3129 -130	common/cmd_doc.c	Incorrect FIT image format
3130  131	common/cmd_doc.c	FIT image format OK
3131
3132 -140	common/cmd_ide.c	Incorrect FIT image format
3133  141	common/cmd_ide.c	FIT image format OK
3134
3135 -150	common/cmd_nand.c	Incorrect FIT image format
3136  151	common/cmd_nand.c	FIT image format OK
3137
3138- FIT image support:
3139		CONFIG_FIT
3140		Enable support for the FIT uImage format.
3141
3142		CONFIG_FIT_BEST_MATCH
3143		When no configuration is explicitly selected, default to the
3144		one whose fdt's compatibility field best matches that of
3145		U-Boot itself. A match is considered "best" if it matches the
3146		most specific compatibility entry of U-Boot's fdt's root node.
3147		The order of entries in the configuration's fdt is ignored.
3148
3149		CONFIG_FIT_SIGNATURE
3150		This option enables signature verification of FIT uImages,
3151		using a hash signed and verified using RSA. See
3152		doc/uImage.FIT/signature.txt for more details.
3153
3154- Standalone program support:
3155		CONFIG_STANDALONE_LOAD_ADDR
3156
3157		This option defines a board specific value for the
3158		address where standalone program gets loaded, thus
3159		overwriting the architecture dependent default
3160		settings.
3161
3162- Frame Buffer Address:
3163		CONFIG_FB_ADDR
3164
3165		Define CONFIG_FB_ADDR if you want to use specific
3166		address for frame buffer.  This is typically the case
3167		when using a graphics controller has separate video
3168		memory.  U-Boot will then place the frame buffer at
3169		the given address instead of dynamically reserving it
3170		in system RAM by calling lcd_setmem(), which grabs
3171		the memory for the frame buffer depending on the
3172		configured panel size.
3173
3174		Please see board_init_f function.
3175
3176- Automatic software updates via TFTP server
3177		CONFIG_UPDATE_TFTP
3178		CONFIG_UPDATE_TFTP_CNT_MAX
3179		CONFIG_UPDATE_TFTP_MSEC_MAX
3180
3181		These options enable and control the auto-update feature;
3182		for a more detailed description refer to doc/README.update.
3183
3184- MTD Support (mtdparts command, UBI support)
3185		CONFIG_MTD_DEVICE
3186
3187		Adds the MTD device infrastructure from the Linux kernel.
3188		Needed for mtdparts command support.
3189
3190		CONFIG_MTD_PARTITIONS
3191
3192		Adds the MTD partitioning infrastructure from the Linux
3193		kernel. Needed for UBI support.
3194
3195- UBI support
3196		CONFIG_CMD_UBI
3197
3198		Adds commands for interacting with MTD partitions formatted
3199		with the UBI flash translation layer
3200
3201		Requires also defining CONFIG_RBTREE
3202
3203		CONFIG_UBI_SILENCE_MSG
3204
3205		Make the verbose messages from UBI stop printing.  This leaves
3206		warnings and errors enabled.
3207
3208- UBIFS support
3209		CONFIG_CMD_UBIFS
3210
3211		Adds commands for interacting with UBI volumes formatted as
3212		UBIFS.  UBIFS is read-only in u-boot.
3213
3214		Requires UBI support as well as CONFIG_LZO
3215
3216		CONFIG_UBIFS_SILENCE_MSG
3217
3218		Make the verbose messages from UBIFS stop printing.  This leaves
3219		warnings and errors enabled.
3220
3221- SPL framework
3222		CONFIG_SPL
3223		Enable building of SPL globally.
3224
3225		CONFIG_SPL_LDSCRIPT
3226		LDSCRIPT for linking the SPL binary.
3227
3228		CONFIG_SPL_MAX_FOOTPRINT
3229		Maximum size in memory allocated to the SPL, BSS included.
3230		When defined, the linker checks that the actual memory
3231		used by SPL from _start to __bss_end does not exceed it.
3232		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3233		must not be both defined at the same time.
3234
3235		CONFIG_SPL_MAX_SIZE
3236		Maximum size of the SPL image (text, data, rodata, and
3237		linker lists sections), BSS excluded.
3238		When defined, the linker checks that the actual size does
3239		not exceed it.
3240
3241		CONFIG_SPL_TEXT_BASE
3242		TEXT_BASE for linking the SPL binary.
3243
3244		CONFIG_SPL_RELOC_TEXT_BASE
3245		Address to relocate to.  If unspecified, this is equal to
3246		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3247
3248		CONFIG_SPL_BSS_START_ADDR
3249		Link address for the BSS within the SPL binary.
3250
3251		CONFIG_SPL_BSS_MAX_SIZE
3252		Maximum size in memory allocated to the SPL BSS.
3253		When defined, the linker checks that the actual memory used
3254		by SPL from __bss_start to __bss_end does not exceed it.
3255		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3256		must not be both defined at the same time.
3257
3258		CONFIG_SPL_STACK
3259		Adress of the start of the stack SPL will use
3260
3261		CONFIG_SPL_RELOC_STACK
3262		Adress of the start of the stack SPL will use after
3263		relocation.  If unspecified, this is equal to
3264		CONFIG_SPL_STACK.
3265
3266		CONFIG_SYS_SPL_MALLOC_START
3267		Starting address of the malloc pool used in SPL.
3268
3269		CONFIG_SYS_SPL_MALLOC_SIZE
3270		The size of the malloc pool used in SPL.
3271
3272		CONFIG_SPL_FRAMEWORK
3273		Enable the SPL framework under common/.  This framework
3274		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3275		NAND loading of the Linux Kernel.
3276
3277		CONFIG_SPL_DISPLAY_PRINT
3278		For ARM, enable an optional function to print more information
3279		about the running system.
3280
3281		CONFIG_SPL_INIT_MINIMAL
3282		Arch init code should be built for a very small image
3283
3284		CONFIG_SPL_LIBCOMMON_SUPPORT
3285		Support for common/libcommon.o in SPL binary
3286
3287		CONFIG_SPL_LIBDISK_SUPPORT
3288		Support for disk/libdisk.o in SPL binary
3289
3290		CONFIG_SPL_I2C_SUPPORT
3291		Support for drivers/i2c/libi2c.o in SPL binary
3292
3293		CONFIG_SPL_GPIO_SUPPORT
3294		Support for drivers/gpio/libgpio.o in SPL binary
3295
3296		CONFIG_SPL_MMC_SUPPORT
3297		Support for drivers/mmc/libmmc.o in SPL binary
3298
3299		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3300		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3301		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3302		Address, size and partition on the MMC to load U-Boot from
3303		when the MMC is being used in raw mode.
3304
3305		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3306		Sector to load kernel uImage from when MMC is being
3307		used in raw mode (for Falcon mode)
3308
3309		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3310		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3311		Sector and number of sectors to load kernel argument
3312		parameters from when MMC is being used in raw mode
3313		(for falcon mode)
3314
3315		CONFIG_SPL_FAT_SUPPORT
3316		Support for fs/fat/libfat.o in SPL binary
3317
3318		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3319		Filename to read to load U-Boot when reading from FAT
3320
3321		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3322		Filename to read to load kernel uImage when reading
3323		from FAT (for Falcon mode)
3324
3325		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3326		Filename to read to load kernel argument parameters
3327		when reading from FAT (for Falcon mode)
3328
3329		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3330		Set this for NAND SPL on PPC mpc83xx targets, so that
3331		start.S waits for the rest of the SPL to load before
3332		continuing (the hardware starts execution after just
3333		loading the first page rather than the full 4K).
3334
3335		CONFIG_SPL_SKIP_RELOCATE
3336		Avoid SPL relocation
3337
3338		CONFIG_SPL_NAND_BASE
3339		Include nand_base.c in the SPL.  Requires
3340		CONFIG_SPL_NAND_DRIVERS.
3341
3342		CONFIG_SPL_NAND_DRIVERS
3343		SPL uses normal NAND drivers, not minimal drivers.
3344
3345		CONFIG_SPL_NAND_ECC
3346		Include standard software ECC in the SPL
3347
3348		CONFIG_SPL_NAND_SIMPLE
3349		Support for NAND boot using simple NAND drivers that
3350		expose the cmd_ctrl() interface.
3351
3352		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3353		Set for the SPL on PPC mpc8xxx targets, support for
3354		drivers/ddr/fsl/libddr.o in SPL binary.
3355
3356		CONFIG_SPL_COMMON_INIT_DDR
3357		Set for common ddr init with serial presence detect in
3358		SPL binary.
3359
3360		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3361		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3362		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3363		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3364		CONFIG_SYS_NAND_ECCBYTES
3365		Defines the size and behavior of the NAND that SPL uses
3366		to read U-Boot
3367
3368		CONFIG_SPL_NAND_BOOT
3369		Add support NAND boot
3370
3371		CONFIG_SYS_NAND_U_BOOT_OFFS
3372		Location in NAND to read U-Boot from
3373
3374		CONFIG_SYS_NAND_U_BOOT_DST
3375		Location in memory to load U-Boot to
3376
3377		CONFIG_SYS_NAND_U_BOOT_SIZE
3378		Size of image to load
3379
3380		CONFIG_SYS_NAND_U_BOOT_START
3381		Entry point in loaded image to jump to
3382
3383		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3384		Define this if you need to first read the OOB and then the
3385		data. This is used for example on davinci plattforms.
3386
3387		CONFIG_SPL_OMAP3_ID_NAND
3388		Support for an OMAP3-specific set of functions to return the
3389		ID and MFR of the first attached NAND chip, if present.
3390
3391		CONFIG_SPL_SERIAL_SUPPORT
3392		Support for drivers/serial/libserial.o in SPL binary
3393
3394		CONFIG_SPL_SPI_FLASH_SUPPORT
3395		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3396
3397		CONFIG_SPL_SPI_SUPPORT
3398		Support for drivers/spi/libspi.o in SPL binary
3399
3400		CONFIG_SPL_RAM_DEVICE
3401		Support for running image already present in ram, in SPL binary
3402
3403		CONFIG_SPL_LIBGENERIC_SUPPORT
3404		Support for lib/libgeneric.o in SPL binary
3405
3406		CONFIG_SPL_ENV_SUPPORT
3407		Support for the environment operating in SPL binary
3408
3409		CONFIG_SPL_NET_SUPPORT
3410		Support for the net/libnet.o in SPL binary.
3411		It conflicts with SPL env from storage medium specified by
3412		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3413
3414		CONFIG_SPL_PAD_TO
3415		Image offset to which the SPL should be padded before appending
3416		the SPL payload. By default, this is defined as
3417		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3418		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3419		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3420
3421		CONFIG_SPL_TARGET
3422		Final target image containing SPL and payload.  Some SPLs
3423		use an arch-specific makefile fragment instead, for
3424		example if more than one image needs to be produced.
3425
3426		CONFIG_FIT_SPL_PRINT
3427		Printing information about a FIT image adds quite a bit of
3428		code to SPL. So this is normally disabled in SPL. Use this
3429		option to re-enable it. This will affect the output of the
3430		bootm command when booting a FIT image.
3431
3432- TPL framework
3433		CONFIG_TPL
3434		Enable building of TPL globally.
3435
3436		CONFIG_TPL_PAD_TO
3437		Image offset to which the TPL should be padded before appending
3438		the TPL payload. By default, this is defined as
3439		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3440		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3441		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3442
3443Modem Support:
3444--------------
3445
3446[so far only for SMDK2400 boards]
3447
3448- Modem support enable:
3449		CONFIG_MODEM_SUPPORT
3450
3451- RTS/CTS Flow control enable:
3452		CONFIG_HWFLOW
3453
3454- Modem debug support:
3455		CONFIG_MODEM_SUPPORT_DEBUG
3456
3457		Enables debugging stuff (char screen[1024], dbg())
3458		for modem support. Useful only with BDI2000.
3459
3460- Interrupt support (PPC):
3461
3462		There are common interrupt_init() and timer_interrupt()
3463		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3464		for CPU specific initialization. interrupt_init_cpu()
3465		should set decrementer_count to appropriate value. If
3466		CPU resets decrementer automatically after interrupt
3467		(ppc4xx) it should set decrementer_count to zero.
3468		timer_interrupt() calls timer_interrupt_cpu() for CPU
3469		specific handling. If board has watchdog / status_led
3470		/ other_activity_monitor it works automatically from
3471		general timer_interrupt().
3472
3473- General:
3474
3475		In the target system modem support is enabled when a
3476		specific key (key combination) is pressed during
3477		power-on. Otherwise U-Boot will boot normally
3478		(autoboot). The key_pressed() function is called from
3479		board_init(). Currently key_pressed() is a dummy
3480		function, returning 1 and thus enabling modem
3481		initialization.
3482
3483		If there are no modem init strings in the
3484		environment, U-Boot proceed to autoboot; the
3485		previous output (banner, info printfs) will be
3486		suppressed, though.
3487
3488		See also: doc/README.Modem
3489
3490Board initialization settings:
3491------------------------------
3492
3493During Initialization u-boot calls a number of board specific functions
3494to allow the preparation of board specific prerequisites, e.g. pin setup
3495before drivers are initialized. To enable these callbacks the
3496following configuration macros have to be defined. Currently this is
3497architecture specific, so please check arch/your_architecture/lib/board.c
3498typically in board_init_f() and board_init_r().
3499
3500- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3501- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3502- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3503- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3504
3505Configuration Settings:
3506-----------------------
3507
3508- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3509		Optionally it can be defined to support 64-bit memory commands.
3510
3511- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3512		undefine this when you're short of memory.
3513
3514- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3515		width of the commands listed in the 'help' command output.
3516
3517- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3518		prompt for user input.
3519
3520- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3521
3522- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3523
3524- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3525
3526- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3527		the application (usually a Linux kernel) when it is
3528		booted
3529
3530- CONFIG_SYS_BAUDRATE_TABLE:
3531		List of legal baudrate settings for this board.
3532
3533- CONFIG_SYS_CONSOLE_INFO_QUIET
3534		Suppress display of console information at boot.
3535
3536- CONFIG_SYS_CONSOLE_IS_IN_ENV
3537		If the board specific function
3538			extern int overwrite_console (void);
3539		returns 1, the stdin, stderr and stdout are switched to the
3540		serial port, else the settings in the environment are used.
3541
3542- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3543		Enable the call to overwrite_console().
3544
3545- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3546		Enable overwrite of previous console environment settings.
3547
3548- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3549		Begin and End addresses of the area used by the
3550		simple memory test.
3551
3552- CONFIG_SYS_ALT_MEMTEST:
3553		Enable an alternate, more extensive memory test.
3554
3555- CONFIG_SYS_MEMTEST_SCRATCH:
3556		Scratch address used by the alternate memory test
3557		You only need to set this if address zero isn't writeable
3558
3559- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3560		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3561		this specified memory area will get subtracted from the top
3562		(end) of RAM and won't get "touched" at all by U-Boot. By
3563		fixing up gd->ram_size the Linux kernel should gets passed
3564		the now "corrected" memory size and won't touch it either.
3565		This should work for arch/ppc and arch/powerpc. Only Linux
3566		board ports in arch/powerpc with bootwrapper support that
3567		recalculate the memory size from the SDRAM controller setup
3568		will have to get fixed in Linux additionally.
3569
3570		This option can be used as a workaround for the 440EPx/GRx
3571		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3572		be touched.
3573
3574		WARNING: Please make sure that this value is a multiple of
3575		the Linux page size (normally 4k). If this is not the case,
3576		then the end address of the Linux memory will be located at a
3577		non page size aligned address and this could cause major
3578		problems.
3579
3580- CONFIG_SYS_LOADS_BAUD_CHANGE:
3581		Enable temporary baudrate change while serial download
3582
3583- CONFIG_SYS_SDRAM_BASE:
3584		Physical start address of SDRAM. _Must_ be 0 here.
3585
3586- CONFIG_SYS_MBIO_BASE:
3587		Physical start address of Motherboard I/O (if using a
3588		Cogent motherboard)
3589
3590- CONFIG_SYS_FLASH_BASE:
3591		Physical start address of Flash memory.
3592
3593- CONFIG_SYS_MONITOR_BASE:
3594		Physical start address of boot monitor code (set by
3595		make config files to be same as the text base address
3596		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3597		CONFIG_SYS_FLASH_BASE when booting from flash.
3598
3599- CONFIG_SYS_MONITOR_LEN:
3600		Size of memory reserved for monitor code, used to
3601		determine _at_compile_time_ (!) if the environment is
3602		embedded within the U-Boot image, or in a separate
3603		flash sector.
3604
3605- CONFIG_SYS_MALLOC_LEN:
3606		Size of DRAM reserved for malloc() use.
3607
3608- CONFIG_SYS_BOOTM_LEN:
3609		Normally compressed uImages are limited to an
3610		uncompressed size of 8 MBytes. If this is not enough,
3611		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3612		to adjust this setting to your needs.
3613
3614- CONFIG_SYS_BOOTMAPSZ:
3615		Maximum size of memory mapped by the startup code of
3616		the Linux kernel; all data that must be processed by
3617		the Linux kernel (bd_info, boot arguments, FDT blob if
3618		used) must be put below this limit, unless "bootm_low"
3619		environment variable is defined and non-zero. In such case
3620		all data for the Linux kernel must be between "bootm_low"
3621		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3622		variable "bootm_mapsize" will override the value of
3623		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3624		then the value in "bootm_size" will be used instead.
3625
3626- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3627		Enable initrd_high functionality.  If defined then the
3628		initrd_high feature is enabled and the bootm ramdisk subcommand
3629		is enabled.
3630
3631- CONFIG_SYS_BOOT_GET_CMDLINE:
3632		Enables allocating and saving kernel cmdline in space between
3633		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3634
3635- CONFIG_SYS_BOOT_GET_KBD:
3636		Enables allocating and saving a kernel copy of the bd_info in
3637		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3638
3639- CONFIG_SYS_MAX_FLASH_BANKS:
3640		Max number of Flash memory banks
3641
3642- CONFIG_SYS_MAX_FLASH_SECT:
3643		Max number of sectors on a Flash chip
3644
3645- CONFIG_SYS_FLASH_ERASE_TOUT:
3646		Timeout for Flash erase operations (in ms)
3647
3648- CONFIG_SYS_FLASH_WRITE_TOUT:
3649		Timeout for Flash write operations (in ms)
3650
3651- CONFIG_SYS_FLASH_LOCK_TOUT
3652		Timeout for Flash set sector lock bit operation (in ms)
3653
3654- CONFIG_SYS_FLASH_UNLOCK_TOUT
3655		Timeout for Flash clear lock bits operation (in ms)
3656
3657- CONFIG_SYS_FLASH_PROTECTION
3658		If defined, hardware flash sectors protection is used
3659		instead of U-Boot software protection.
3660
3661- CONFIG_SYS_DIRECT_FLASH_TFTP:
3662
3663		Enable TFTP transfers directly to flash memory;
3664		without this option such a download has to be
3665		performed in two steps: (1) download to RAM, and (2)
3666		copy from RAM to flash.
3667
3668		The two-step approach is usually more reliable, since
3669		you can check if the download worked before you erase
3670		the flash, but in some situations (when system RAM is
3671		too limited to allow for a temporary copy of the
3672		downloaded image) this option may be very useful.
3673
3674- CONFIG_SYS_FLASH_CFI:
3675		Define if the flash driver uses extra elements in the
3676		common flash structure for storing flash geometry.
3677
3678- CONFIG_FLASH_CFI_DRIVER
3679		This option also enables the building of the cfi_flash driver
3680		in the drivers directory
3681
3682- CONFIG_FLASH_CFI_MTD
3683		This option enables the building of the cfi_mtd driver
3684		in the drivers directory. The driver exports CFI flash
3685		to the MTD layer.
3686
3687- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3688		Use buffered writes to flash.
3689
3690- CONFIG_FLASH_SPANSION_S29WS_N
3691		s29ws-n MirrorBit flash has non-standard addresses for buffered
3692		write commands.
3693
3694- CONFIG_SYS_FLASH_QUIET_TEST
3695		If this option is defined, the common CFI flash doesn't
3696		print it's warning upon not recognized FLASH banks. This
3697		is useful, if some of the configured banks are only
3698		optionally available.
3699
3700- CONFIG_FLASH_SHOW_PROGRESS
3701		If defined (must be an integer), print out countdown
3702		digits and dots.  Recommended value: 45 (9..1) for 80
3703		column displays, 15 (3..1) for 40 column displays.
3704
3705- CONFIG_FLASH_VERIFY
3706		If defined, the content of the flash (destination) is compared
3707		against the source after the write operation. An error message
3708		will be printed when the contents are not identical.
3709		Please note that this option is useless in nearly all cases,
3710		since such flash programming errors usually are detected earlier
3711		while unprotecting/erasing/programming. Please only enable
3712		this option if you really know what you are doing.
3713
3714- CONFIG_SYS_RX_ETH_BUFFER:
3715		Defines the number of Ethernet receive buffers. On some
3716		Ethernet controllers it is recommended to set this value
3717		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3718		buffers can be full shortly after enabling the interface
3719		on high Ethernet traffic.
3720		Defaults to 4 if not defined.
3721
3722- CONFIG_ENV_MAX_ENTRIES
3723
3724	Maximum number of entries in the hash table that is used
3725	internally to store the environment settings. The default
3726	setting is supposed to be generous and should work in most
3727	cases. This setting can be used to tune behaviour; see
3728	lib/hashtable.c for details.
3729
3730- CONFIG_ENV_FLAGS_LIST_DEFAULT
3731- CONFIG_ENV_FLAGS_LIST_STATIC
3732	Enable validation of the values given to environment variables when
3733	calling env set.  Variables can be restricted to only decimal,
3734	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3735	the variables can also be restricted to IP address or MAC address.
3736
3737	The format of the list is:
3738		type_attribute = [s|d|x|b|i|m]
3739		access_atribute = [a|r|o|c]
3740		attributes = type_attribute[access_atribute]
3741		entry = variable_name[:attributes]
3742		list = entry[,list]
3743
3744	The type attributes are:
3745		s - String (default)
3746		d - Decimal
3747		x - Hexadecimal
3748		b - Boolean ([1yYtT|0nNfF])
3749		i - IP address
3750		m - MAC address
3751
3752	The access attributes are:
3753		a - Any (default)
3754		r - Read-only
3755		o - Write-once
3756		c - Change-default
3757
3758	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3759		Define this to a list (string) to define the ".flags"
3760		envirnoment variable in the default or embedded environment.
3761
3762	- CONFIG_ENV_FLAGS_LIST_STATIC
3763		Define this to a list (string) to define validation that
3764		should be done if an entry is not found in the ".flags"
3765		environment variable.  To override a setting in the static
3766		list, simply add an entry for the same variable name to the
3767		".flags" variable.
3768
3769- CONFIG_ENV_ACCESS_IGNORE_FORCE
3770	If defined, don't allow the -f switch to env set override variable
3771	access flags.
3772
3773- CONFIG_SYS_GENERIC_BOARD
3774	This selects the architecture-generic board system instead of the
3775	architecture-specific board files. It is intended to move boards
3776	to this new framework over time. Defining this will disable the
3777	arch/foo/lib/board.c file and use common/board_f.c and
3778	common/board_r.c instead. To use this option your architecture
3779	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3780	its config.mk file). If you find problems enabling this option on
3781	your board please report the problem and send patches!
3782
3783- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3784	This is set by OMAP boards for the max time that reset should
3785	be asserted. See doc/README.omap-reset-time for details on how
3786	the value can be calulated on a given board.
3787
3788The following definitions that deal with the placement and management
3789of environment data (variable area); in general, we support the
3790following configurations:
3791
3792- CONFIG_BUILD_ENVCRC:
3793
3794	Builds up envcrc with the target environment so that external utils
3795	may easily extract it and embed it in final U-Boot images.
3796
3797- CONFIG_ENV_IS_IN_FLASH:
3798
3799	Define this if the environment is in flash memory.
3800
3801	a) The environment occupies one whole flash sector, which is
3802	   "embedded" in the text segment with the U-Boot code. This
3803	   happens usually with "bottom boot sector" or "top boot
3804	   sector" type flash chips, which have several smaller
3805	   sectors at the start or the end. For instance, such a
3806	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3807	   such a case you would place the environment in one of the
3808	   4 kB sectors - with U-Boot code before and after it. With
3809	   "top boot sector" type flash chips, you would put the
3810	   environment in one of the last sectors, leaving a gap
3811	   between U-Boot and the environment.
3812
3813	- CONFIG_ENV_OFFSET:
3814
3815	   Offset of environment data (variable area) to the
3816	   beginning of flash memory; for instance, with bottom boot
3817	   type flash chips the second sector can be used: the offset
3818	   for this sector is given here.
3819
3820	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3821
3822	- CONFIG_ENV_ADDR:
3823
3824	   This is just another way to specify the start address of
3825	   the flash sector containing the environment (instead of
3826	   CONFIG_ENV_OFFSET).
3827
3828	- CONFIG_ENV_SECT_SIZE:
3829
3830	   Size of the sector containing the environment.
3831
3832
3833	b) Sometimes flash chips have few, equal sized, BIG sectors.
3834	   In such a case you don't want to spend a whole sector for
3835	   the environment.
3836
3837	- CONFIG_ENV_SIZE:
3838
3839	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3840	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3841	   of this flash sector for the environment. This saves
3842	   memory for the RAM copy of the environment.
3843
3844	   It may also save flash memory if you decide to use this
3845	   when your environment is "embedded" within U-Boot code,
3846	   since then the remainder of the flash sector could be used
3847	   for U-Boot code. It should be pointed out that this is
3848	   STRONGLY DISCOURAGED from a robustness point of view:
3849	   updating the environment in flash makes it always
3850	   necessary to erase the WHOLE sector. If something goes
3851	   wrong before the contents has been restored from a copy in
3852	   RAM, your target system will be dead.
3853
3854	- CONFIG_ENV_ADDR_REDUND
3855	  CONFIG_ENV_SIZE_REDUND
3856
3857	   These settings describe a second storage area used to hold
3858	   a redundant copy of the environment data, so that there is
3859	   a valid backup copy in case there is a power failure during
3860	   a "saveenv" operation.
3861
3862BE CAREFUL! Any changes to the flash layout, and some changes to the
3863source code will make it necessary to adapt <board>/u-boot.lds*
3864accordingly!
3865
3866
3867- CONFIG_ENV_IS_IN_NVRAM:
3868
3869	Define this if you have some non-volatile memory device
3870	(NVRAM, battery buffered SRAM) which you want to use for the
3871	environment.
3872
3873	- CONFIG_ENV_ADDR:
3874	- CONFIG_ENV_SIZE:
3875
3876	  These two #defines are used to determine the memory area you
3877	  want to use for environment. It is assumed that this memory
3878	  can just be read and written to, without any special
3879	  provision.
3880
3881BE CAREFUL! The first access to the environment happens quite early
3882in U-Boot initalization (when we try to get the setting of for the
3883console baudrate). You *MUST* have mapped your NVRAM area then, or
3884U-Boot will hang.
3885
3886Please note that even with NVRAM we still use a copy of the
3887environment in RAM: we could work on NVRAM directly, but we want to
3888keep settings there always unmodified except somebody uses "saveenv"
3889to save the current settings.
3890
3891
3892- CONFIG_ENV_IS_IN_EEPROM:
3893
3894	Use this if you have an EEPROM or similar serial access
3895	device and a driver for it.
3896
3897	- CONFIG_ENV_OFFSET:
3898	- CONFIG_ENV_SIZE:
3899
3900	  These two #defines specify the offset and size of the
3901	  environment area within the total memory of your EEPROM.
3902
3903	- CONFIG_SYS_I2C_EEPROM_ADDR:
3904	  If defined, specified the chip address of the EEPROM device.
3905	  The default address is zero.
3906
3907	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3908	  If defined, the number of bits used to address bytes in a
3909	  single page in the EEPROM device.  A 64 byte page, for example
3910	  would require six bits.
3911
3912	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3913	  If defined, the number of milliseconds to delay between
3914	  page writes.	The default is zero milliseconds.
3915
3916	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3917	  The length in bytes of the EEPROM memory array address.  Note
3918	  that this is NOT the chip address length!
3919
3920	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3921	  EEPROM chips that implement "address overflow" are ones
3922	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3923	  address and the extra bits end up in the "chip address" bit
3924	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3925	  byte chips.
3926
3927	  Note that we consider the length of the address field to
3928	  still be one byte because the extra address bits are hidden
3929	  in the chip address.
3930
3931	- CONFIG_SYS_EEPROM_SIZE:
3932	  The size in bytes of the EEPROM device.
3933
3934	- CONFIG_ENV_EEPROM_IS_ON_I2C
3935	  define this, if you have I2C and SPI activated, and your
3936	  EEPROM, which holds the environment, is on the I2C bus.
3937
3938	- CONFIG_I2C_ENV_EEPROM_BUS
3939	  if you have an Environment on an EEPROM reached over
3940	  I2C muxes, you can define here, how to reach this
3941	  EEPROM. For example:
3942
3943	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3944
3945	  EEPROM which holds the environment, is reached over
3946	  a pca9547 i2c mux with address 0x70, channel 3.
3947
3948- CONFIG_ENV_IS_IN_DATAFLASH:
3949
3950	Define this if you have a DataFlash memory device which you
3951	want to use for the environment.
3952
3953	- CONFIG_ENV_OFFSET:
3954	- CONFIG_ENV_ADDR:
3955	- CONFIG_ENV_SIZE:
3956
3957	  These three #defines specify the offset and size of the
3958	  environment area within the total memory of your DataFlash placed
3959	  at the specified address.
3960
3961- CONFIG_ENV_IS_IN_REMOTE:
3962
3963	Define this if you have a remote memory space which you
3964	want to use for the local device's environment.
3965
3966	- CONFIG_ENV_ADDR:
3967	- CONFIG_ENV_SIZE:
3968
3969	  These two #defines specify the address and size of the
3970	  environment area within the remote memory space. The
3971	  local device can get the environment from remote memory
3972	  space by SRIO or PCIE links.
3973
3974BE CAREFUL! For some special cases, the local device can not use
3975"saveenv" command. For example, the local device will get the
3976environment stored in a remote NOR flash by SRIO or PCIE link,
3977but it can not erase, write this NOR flash by SRIO or PCIE interface.
3978
3979- CONFIG_ENV_IS_IN_NAND:
3980
3981	Define this if you have a NAND device which you want to use
3982	for the environment.
3983
3984	- CONFIG_ENV_OFFSET:
3985	- CONFIG_ENV_SIZE:
3986
3987	  These two #defines specify the offset and size of the environment
3988	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3989	  aligned to an erase block boundary.
3990
3991	- CONFIG_ENV_OFFSET_REDUND (optional):
3992
3993	  This setting describes a second storage area of CONFIG_ENV_SIZE
3994	  size used to hold a redundant copy of the environment data, so
3995	  that there is a valid backup copy in case there is a power failure
3996	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3997	  aligned to an erase block boundary.
3998
3999	- CONFIG_ENV_RANGE (optional):
4000
4001	  Specifies the length of the region in which the environment
4002	  can be written.  This should be a multiple of the NAND device's
4003	  block size.  Specifying a range with more erase blocks than
4004	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4005	  the range to be avoided.
4006
4007	- CONFIG_ENV_OFFSET_OOB (optional):
4008
4009	  Enables support for dynamically retrieving the offset of the
4010	  environment from block zero's out-of-band data.  The
4011	  "nand env.oob" command can be used to record this offset.
4012	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4013	  using CONFIG_ENV_OFFSET_OOB.
4014
4015- CONFIG_NAND_ENV_DST
4016
4017	Defines address in RAM to which the nand_spl code should copy the
4018	environment. If redundant environment is used, it will be copied to
4019	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4020
4021- CONFIG_ENV_IS_IN_UBI:
4022
4023	Define this if you have an UBI volume that you want to use for the
4024	environment.  This has the benefit of wear-leveling the environment
4025	accesses, which is important on NAND.
4026
4027	- CONFIG_ENV_UBI_PART:
4028
4029	  Define this to a string that is the mtd partition containing the UBI.
4030
4031	- CONFIG_ENV_UBI_VOLUME:
4032
4033	  Define this to the name of the volume that you want to store the
4034	  environment in.
4035
4036	- CONFIG_ENV_UBI_VOLUME_REDUND:
4037
4038	  Define this to the name of another volume to store a second copy of
4039	  the environment in.  This will enable redundant environments in UBI.
4040	  It is assumed that both volumes are in the same MTD partition.
4041
4042	- CONFIG_UBI_SILENCE_MSG
4043	- CONFIG_UBIFS_SILENCE_MSG
4044
4045	  You will probably want to define these to avoid a really noisy system
4046	  when storing the env in UBI.
4047
4048- CONFIG_ENV_IS_IN_MMC:
4049
4050	Define this if you have an MMC device which you want to use for the
4051	environment.
4052
4053	- CONFIG_SYS_MMC_ENV_DEV:
4054
4055	  Specifies which MMC device the environment is stored in.
4056
4057	- CONFIG_SYS_MMC_ENV_PART (optional):
4058
4059	  Specifies which MMC partition the environment is stored in. If not
4060	  set, defaults to partition 0, the user area. Common values might be
4061	  1 (first MMC boot partition), 2 (second MMC boot partition).
4062
4063	- CONFIG_ENV_OFFSET:
4064	- CONFIG_ENV_SIZE:
4065
4066	  These two #defines specify the offset and size of the environment
4067	  area within the specified MMC device.
4068
4069	  If offset is positive (the usual case), it is treated as relative to
4070	  the start of the MMC partition. If offset is negative, it is treated
4071	  as relative to the end of the MMC partition. This can be useful if
4072	  your board may be fitted with different MMC devices, which have
4073	  different sizes for the MMC partitions, and you always want the
4074	  environment placed at the very end of the partition, to leave the
4075	  maximum possible space before it, to store other data.
4076
4077	  These two values are in units of bytes, but must be aligned to an
4078	  MMC sector boundary.
4079
4080	- CONFIG_ENV_OFFSET_REDUND (optional):
4081
4082	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4083	  hold a redundant copy of the environment data. This provides a
4084	  valid backup copy in case the other copy is corrupted, e.g. due
4085	  to a power failure during a "saveenv" operation.
4086
4087	  This value may also be positive or negative; this is handled in the
4088	  same way as CONFIG_ENV_OFFSET.
4089
4090	  This value is also in units of bytes, but must also be aligned to
4091	  an MMC sector boundary.
4092
4093	- CONFIG_ENV_SIZE_REDUND (optional):
4094
4095	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4096	  set. If this value is set, it must be set to the same value as
4097	  CONFIG_ENV_SIZE.
4098
4099- CONFIG_SYS_SPI_INIT_OFFSET
4100
4101	Defines offset to the initial SPI buffer area in DPRAM. The
4102	area is used at an early stage (ROM part) if the environment
4103	is configured to reside in the SPI EEPROM: We need a 520 byte
4104	scratch DPRAM area. It is used between the two initialization
4105	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4106	to be a good choice since it makes it far enough from the
4107	start of the data area as well as from the stack pointer.
4108
4109Please note that the environment is read-only until the monitor
4110has been relocated to RAM and a RAM copy of the environment has been
4111created; also, when using EEPROM you will have to use getenv_f()
4112until then to read environment variables.
4113
4114The environment is protected by a CRC32 checksum. Before the monitor
4115is relocated into RAM, as a result of a bad CRC you will be working
4116with the compiled-in default environment - *silently*!!! [This is
4117necessary, because the first environment variable we need is the
4118"baudrate" setting for the console - if we have a bad CRC, we don't
4119have any device yet where we could complain.]
4120
4121Note: once the monitor has been relocated, then it will complain if
4122the default environment is used; a new CRC is computed as soon as you
4123use the "saveenv" command to store a valid environment.
4124
4125- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4126		Echo the inverted Ethernet link state to the fault LED.
4127
4128		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4129		      also needs to be defined.
4130
4131- CONFIG_SYS_FAULT_MII_ADDR:
4132		MII address of the PHY to check for the Ethernet link state.
4133
4134- CONFIG_NS16550_MIN_FUNCTIONS:
4135		Define this if you desire to only have use of the NS16550_init
4136		and NS16550_putc functions for the serial driver located at
4137		drivers/serial/ns16550.c.  This option is useful for saving
4138		space for already greatly restricted images, including but not
4139		limited to NAND_SPL configurations.
4140
4141- CONFIG_DISPLAY_BOARDINFO
4142		Display information about the board that U-Boot is running on
4143		when U-Boot starts up. The board function checkboard() is called
4144		to do this.
4145
4146- CONFIG_DISPLAY_BOARDINFO_LATE
4147		Similar to the previous option, but display this information
4148		later, once stdio is running and output goes to the LCD, if
4149		present.
4150
4151Low Level (hardware related) configuration options:
4152---------------------------------------------------
4153
4154- CONFIG_SYS_CACHELINE_SIZE:
4155		Cache Line Size of the CPU.
4156
4157- CONFIG_SYS_DEFAULT_IMMR:
4158		Default address of the IMMR after system reset.
4159
4160		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4161		and RPXsuper) to be able to adjust the position of
4162		the IMMR register after a reset.
4163
4164- CONFIG_SYS_CCSRBAR_DEFAULT:
4165		Default (power-on reset) physical address of CCSR on Freescale
4166		PowerPC SOCs.
4167
4168- CONFIG_SYS_CCSRBAR:
4169		Virtual address of CCSR.  On a 32-bit build, this is typically
4170		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4171
4172		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4173		for cross-platform code that uses that macro instead.
4174
4175- CONFIG_SYS_CCSRBAR_PHYS:
4176		Physical address of CCSR.  CCSR can be relocated to a new
4177		physical address, if desired.  In this case, this macro should
4178		be set to that address.	 Otherwise, it should be set to the
4179		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4180		is typically relocated on 36-bit builds.  It is recommended
4181		that this macro be defined via the _HIGH and _LOW macros:
4182
4183		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4184			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4185
4186- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4187		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4188		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4189		used in assembly code, so it must not contain typecasts or
4190		integer size suffixes (e.g. "ULL").
4191
4192- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4193		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4194		used in assembly code, so it must not contain typecasts or
4195		integer size suffixes (e.g. "ULL").
4196
4197- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4198		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4199		forced to a value that ensures that CCSR is not relocated.
4200
4201- Floppy Disk Support:
4202		CONFIG_SYS_FDC_DRIVE_NUMBER
4203
4204		the default drive number (default value 0)
4205
4206		CONFIG_SYS_ISA_IO_STRIDE
4207
4208		defines the spacing between FDC chipset registers
4209		(default value 1)
4210
4211		CONFIG_SYS_ISA_IO_OFFSET
4212
4213		defines the offset of register from address. It
4214		depends on which part of the data bus is connected to
4215		the FDC chipset. (default value 0)
4216
4217		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4218		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4219		default value.
4220
4221		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4222		fdc_hw_init() is called at the beginning of the FDC
4223		setup. fdc_hw_init() must be provided by the board
4224		source code. It is used to make hardware dependant
4225		initializations.
4226
4227- CONFIG_IDE_AHB:
4228		Most IDE controllers were designed to be connected with PCI
4229		interface. Only few of them were designed for AHB interface.
4230		When software is doing ATA command and data transfer to
4231		IDE devices through IDE-AHB controller, some additional
4232		registers accessing to these kind of IDE-AHB controller
4233		is requierd.
4234
4235- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4236		DO NOT CHANGE unless you know exactly what you're
4237		doing! (11-4) [MPC8xx/82xx systems only]
4238
4239- CONFIG_SYS_INIT_RAM_ADDR:
4240
4241		Start address of memory area that can be used for
4242		initial data and stack; please note that this must be
4243		writable memory that is working WITHOUT special
4244		initialization, i. e. you CANNOT use normal RAM which
4245		will become available only after programming the
4246		memory controller and running certain initialization
4247		sequences.
4248
4249		U-Boot uses the following memory types:
4250		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4251		- MPC824X: data cache
4252		- PPC4xx:  data cache
4253
4254- CONFIG_SYS_GBL_DATA_OFFSET:
4255
4256		Offset of the initial data structure in the memory
4257		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4258		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4259		data is located at the end of the available space
4260		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4261		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4262		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4263		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4264
4265	Note:
4266		On the MPC824X (or other systems that use the data
4267		cache for initial memory) the address chosen for
4268		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4269		point to an otherwise UNUSED address space between
4270		the top of RAM and the start of the PCI space.
4271
4272- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4273
4274- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4275
4276- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4277
4278- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4279
4280- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4281
4282- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4283
4284- CONFIG_SYS_OR_TIMING_SDRAM:
4285		SDRAM timing
4286
4287- CONFIG_SYS_MAMR_PTA:
4288		periodic timer for refresh
4289
4290- CONFIG_SYS_DER:	Debug Event Register (37-47)
4291
4292- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4293  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4294  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4295  CONFIG_SYS_BR1_PRELIM:
4296		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4297
4298- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4299  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4300  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4301		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4302
4303- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4304  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4305		Machine Mode Register and Memory Periodic Timer
4306		Prescaler definitions (SDRAM timing)
4307
4308- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4309		enable I2C microcode relocation patch (MPC8xx);
4310		define relocation offset in DPRAM [DSP2]
4311
4312- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4313		enable SMC microcode relocation patch (MPC8xx);
4314		define relocation offset in DPRAM [SMC1]
4315
4316- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4317		enable SPI microcode relocation patch (MPC8xx);
4318		define relocation offset in DPRAM [SCC4]
4319
4320- CONFIG_SYS_USE_OSCCLK:
4321		Use OSCM clock mode on MBX8xx board. Be careful,
4322		wrong setting might damage your board. Read
4323		doc/README.MBX before setting this variable!
4324
4325- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4326		Offset of the bootmode word in DPRAM used by post
4327		(Power On Self Tests). This definition overrides
4328		#define'd default value in commproc.h resp.
4329		cpm_8260.h.
4330
4331- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4332  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4333  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4334  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4335  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4336  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4337  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4338  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4339		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4340
4341- CONFIG_PCI_DISABLE_PCIE:
4342		Disable PCI-Express on systems where it is supported but not
4343		required.
4344
4345- CONFIG_PCI_ENUM_ONLY
4346		Only scan through and get the devices on the busses.
4347		Don't do any setup work, presumably because someone or
4348		something has already done it, and we don't need to do it
4349		a second time.	Useful for platforms that are pre-booted
4350		by coreboot or similar.
4351
4352- CONFIG_PCI_INDIRECT_BRIDGE:
4353		Enable support for indirect PCI bridges.
4354
4355- CONFIG_SYS_SRIO:
4356		Chip has SRIO or not
4357
4358- CONFIG_SRIO1:
4359		Board has SRIO 1 port available
4360
4361- CONFIG_SRIO2:
4362		Board has SRIO 2 port available
4363
4364- CONFIG_SRIO_PCIE_BOOT_MASTER
4365		Board can support master function for Boot from SRIO and PCIE
4366
4367- CONFIG_SYS_SRIOn_MEM_VIRT:
4368		Virtual Address of SRIO port 'n' memory region
4369
4370- CONFIG_SYS_SRIOn_MEM_PHYS:
4371		Physical Address of SRIO port 'n' memory region
4372
4373- CONFIG_SYS_SRIOn_MEM_SIZE:
4374		Size of SRIO port 'n' memory region
4375
4376- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4377		Defined to tell the NAND controller that the NAND chip is using
4378		a 16 bit bus.
4379		Not all NAND drivers use this symbol.
4380		Example of drivers that use it:
4381		- drivers/mtd/nand/ndfc.c
4382		- drivers/mtd/nand/mxc_nand.c
4383
4384- CONFIG_SYS_NDFC_EBC0_CFG
4385		Sets the EBC0_CFG register for the NDFC. If not defined
4386		a default value will be used.
4387
4388- CONFIG_SPD_EEPROM
4389		Get DDR timing information from an I2C EEPROM. Common
4390		with pluggable memory modules such as SODIMMs
4391
4392  SPD_EEPROM_ADDRESS
4393		I2C address of the SPD EEPROM
4394
4395- CONFIG_SYS_SPD_BUS_NUM
4396		If SPD EEPROM is on an I2C bus other than the first
4397		one, specify here. Note that the value must resolve
4398		to something your driver can deal with.
4399
4400- CONFIG_SYS_DDR_RAW_TIMING
4401		Get DDR timing information from other than SPD. Common with
4402		soldered DDR chips onboard without SPD. DDR raw timing
4403		parameters are extracted from datasheet and hard-coded into
4404		header files or board specific files.
4405
4406- CONFIG_FSL_DDR_INTERACTIVE
4407		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4408
4409- CONFIG_SYS_83XX_DDR_USES_CS0
4410		Only for 83xx systems. If specified, then DDR should
4411		be configured using CS0 and CS1 instead of CS2 and CS3.
4412
4413- CONFIG_ETHER_ON_FEC[12]
4414		Define to enable FEC[12] on a 8xx series processor.
4415
4416- CONFIG_FEC[12]_PHY
4417		Define to the hardcoded PHY address which corresponds
4418		to the given FEC; i. e.
4419			#define CONFIG_FEC1_PHY 4
4420		means that the PHY with address 4 is connected to FEC1
4421
4422		When set to -1, means to probe for first available.
4423
4424- CONFIG_FEC[12]_PHY_NORXERR
4425		The PHY does not have a RXERR line (RMII only).
4426		(so program the FEC to ignore it).
4427
4428- CONFIG_RMII
4429		Enable RMII mode for all FECs.
4430		Note that this is a global option, we can't
4431		have one FEC in standard MII mode and another in RMII mode.
4432
4433- CONFIG_CRC32_VERIFY
4434		Add a verify option to the crc32 command.
4435		The syntax is:
4436
4437		=> crc32 -v <address> <count> <crc32>
4438
4439		Where address/count indicate a memory area
4440		and crc32 is the correct crc32 which the
4441		area should have.
4442
4443- CONFIG_LOOPW
4444		Add the "loopw" memory command. This only takes effect if
4445		the memory commands are activated globally (CONFIG_CMD_MEM).
4446
4447- CONFIG_MX_CYCLIC
4448		Add the "mdc" and "mwc" memory commands. These are cyclic
4449		"md/mw" commands.
4450		Examples:
4451
4452		=> mdc.b 10 4 500
4453		This command will print 4 bytes (10,11,12,13) each 500 ms.
4454
4455		=> mwc.l 100 12345678 10
4456		This command will write 12345678 to address 100 all 10 ms.
4457
4458		This only takes effect if the memory commands are activated
4459		globally (CONFIG_CMD_MEM).
4460
4461- CONFIG_SKIP_LOWLEVEL_INIT
4462		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4463		low level initializations (like setting up the memory
4464		controller) are omitted and/or U-Boot does not
4465		relocate itself into RAM.
4466
4467		Normally this variable MUST NOT be defined. The only
4468		exception is when U-Boot is loaded (to RAM) by some
4469		other boot loader or by a debugger which performs
4470		these initializations itself.
4471
4472- CONFIG_SPL_BUILD
4473		Modifies the behaviour of start.S when compiling a loader
4474		that is executed before the actual U-Boot. E.g. when
4475		compiling a NAND SPL.
4476
4477- CONFIG_TPL_BUILD
4478		Modifies the behaviour of start.S  when compiling a loader
4479		that is executed after the SPL and before the actual U-Boot.
4480		It is loaded by the SPL.
4481
4482- CONFIG_SYS_MPC85XX_NO_RESETVEC
4483		Only for 85xx systems. If this variable is specified, the section
4484		.resetvec is not kept and the section .bootpg is placed in the
4485		previous 4k of the .text section.
4486
4487- CONFIG_ARCH_MAP_SYSMEM
4488		Generally U-Boot (and in particular the md command) uses
4489		effective address. It is therefore not necessary to regard
4490		U-Boot address as virtual addresses that need to be translated
4491		to physical addresses. However, sandbox requires this, since
4492		it maintains its own little RAM buffer which contains all
4493		addressable memory. This option causes some memory accesses
4494		to be mapped through map_sysmem() / unmap_sysmem().
4495
4496- CONFIG_USE_ARCH_MEMCPY
4497  CONFIG_USE_ARCH_MEMSET
4498		If these options are used a optimized version of memcpy/memset will
4499		be used if available. These functions may be faster under some
4500		conditions but may increase the binary size.
4501
4502- CONFIG_X86_RESET_VECTOR
4503		If defined, the x86 reset vector code is included. This is not
4504		needed when U-Boot is running from Coreboot.
4505
4506- CONFIG_SYS_MPUCLK
4507		Defines the MPU clock speed (in MHz).
4508
4509		NOTE : currently only supported on AM335x platforms.
4510
4511- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4512		Enables the RTC32K OSC on AM33xx based plattforms
4513
4514Freescale QE/FMAN Firmware Support:
4515-----------------------------------
4516
4517The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4518loading of "firmware", which is encoded in the QE firmware binary format.
4519This firmware often needs to be loaded during U-Boot booting, so macros
4520are used to identify the storage device (NOR flash, SPI, etc) and the address
4521within that device.
4522
4523- CONFIG_SYS_FMAN_FW_ADDR
4524	The address in the storage device where the FMAN microcode is located.  The
4525	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4526	is also specified.
4527
4528- CONFIG_SYS_QE_FW_ADDR
4529	The address in the storage device where the QE microcode is located.  The
4530	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4531	is also specified.
4532
4533- CONFIG_SYS_QE_FMAN_FW_LENGTH
4534	The maximum possible size of the firmware.  The firmware binary format
4535	has a field that specifies the actual size of the firmware, but it
4536	might not be possible to read any part of the firmware unless some
4537	local storage is allocated to hold the entire firmware first.
4538
4539- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4540	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4541	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4542	virtual address in NOR flash.
4543
4544- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4545	Specifies that QE/FMAN firmware is located in NAND flash.
4546	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4547
4548- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4549	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4550	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4551
4552- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4553	Specifies that QE/FMAN firmware is located on the primary SPI
4554	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4555
4556- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4557	Specifies that QE/FMAN firmware is located in the remote (master)
4558	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4559	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4560	window->master inbound window->master LAW->the ucode address in
4561	master's memory space.
4562
4563Building the Software:
4564======================
4565
4566Building U-Boot has been tested in several native build environments
4567and in many different cross environments. Of course we cannot support
4568all possibly existing versions of cross development tools in all
4569(potentially obsolete) versions. In case of tool chain problems we
4570recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4571which is extensively used to build and test U-Boot.
4572
4573If you are not using a native environment, it is assumed that you
4574have GNU cross compiling tools available in your path. In this case,
4575you must set the environment variable CROSS_COMPILE in your shell.
4576Note that no changes to the Makefile or any other source files are
4577necessary. For example using the ELDK on a 4xx CPU, please enter:
4578
4579	$ CROSS_COMPILE=ppc_4xx-
4580	$ export CROSS_COMPILE
4581
4582Note: If you wish to generate Windows versions of the utilities in
4583      the tools directory you can use the MinGW toolchain
4584      (http://www.mingw.org).  Set your HOST tools to the MinGW
4585      toolchain and execute 'make tools'.  For example:
4586
4587       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4588
4589      Binaries such as tools/mkimage.exe will be created which can
4590      be executed on computers running Windows.
4591
4592U-Boot is intended to be simple to build. After installing the
4593sources you must configure U-Boot for one specific board type. This
4594is done by typing:
4595
4596	make NAME_config
4597
4598where "NAME_config" is the name of one of the existing configu-
4599rations; see boards.cfg for supported names.
4600
4601Note: for some board special configuration names may exist; check if
4602      additional information is available from the board vendor; for
4603      instance, the TQM823L systems are available without (standard)
4604      or with LCD support. You can select such additional "features"
4605      when choosing the configuration, i. e.
4606
4607      make TQM823L_config
4608	- will configure for a plain TQM823L, i. e. no LCD support
4609
4610      make TQM823L_LCD_config
4611	- will configure for a TQM823L with U-Boot console on LCD
4612
4613      etc.
4614
4615
4616Finally, type "make all", and you should get some working U-Boot
4617images ready for download to / installation on your system:
4618
4619- "u-boot.bin" is a raw binary image
4620- "u-boot" is an image in ELF binary format
4621- "u-boot.srec" is in Motorola S-Record format
4622
4623By default the build is performed locally and the objects are saved
4624in the source directory. One of the two methods can be used to change
4625this behavior and build U-Boot to some external directory:
4626
46271. Add O= to the make command line invocations:
4628
4629	make O=/tmp/build distclean
4630	make O=/tmp/build NAME_config
4631	make O=/tmp/build all
4632
46332. Set environment variable BUILD_DIR to point to the desired location:
4634
4635	export BUILD_DIR=/tmp/build
4636	make distclean
4637	make NAME_config
4638	make all
4639
4640Note that the command line "O=" setting overrides the BUILD_DIR environment
4641variable.
4642
4643
4644Please be aware that the Makefiles assume you are using GNU make, so
4645for instance on NetBSD you might need to use "gmake" instead of
4646native "make".
4647
4648
4649If the system board that you have is not listed, then you will need
4650to port U-Boot to your hardware platform. To do this, follow these
4651steps:
4652
46531.  Add a new configuration option for your board to the toplevel
4654    "boards.cfg" file, using the existing entries as examples.
4655    Follow the instructions there to keep the boards in order.
46562.  Create a new directory to hold your board specific code. Add any
4657    files you need. In your board directory, you will need at least
4658    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46593.  Create a new configuration file "include/configs/<board>.h" for
4660    your board
46613.  If you're porting U-Boot to a new CPU, then also create a new
4662    directory to hold your CPU specific code. Add any files you need.
46634.  Run "make <board>_config" with your new name.
46645.  Type "make", and you should get a working "u-boot.srec" file
4665    to be installed on your target system.
46666.  Debug and solve any problems that might arise.
4667    [Of course, this last step is much harder than it sounds.]
4668
4669
4670Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4671==============================================================
4672
4673If you have modified U-Boot sources (for instance added a new board
4674or support for new devices, a new CPU, etc.) you are expected to
4675provide feedback to the other developers. The feedback normally takes
4676the form of a "patch", i. e. a context diff against a certain (latest
4677official or latest in the git repository) version of U-Boot sources.
4678
4679But before you submit such a patch, please verify that your modifi-
4680cation did not break existing code. At least make sure that *ALL* of
4681the supported boards compile WITHOUT ANY compiler warnings. To do so,
4682just run the "MAKEALL" script, which will configure and build U-Boot
4683for ALL supported system. Be warned, this will take a while. You can
4684select which (cross) compiler to use by passing a `CROSS_COMPILE'
4685environment variable to the script, i. e. to use the ELDK cross tools
4686you can type
4687
4688	CROSS_COMPILE=ppc_8xx- MAKEALL
4689
4690or to build on a native PowerPC system you can type
4691
4692	CROSS_COMPILE=' ' MAKEALL
4693
4694When using the MAKEALL script, the default behaviour is to build
4695U-Boot in the source directory. This location can be changed by
4696setting the BUILD_DIR environment variable. Also, for each target
4697built, the MAKEALL script saves two log files (<target>.ERR and
4698<target>.MAKEALL) in the <source dir>/LOG directory. This default
4699location can be changed by setting the MAKEALL_LOGDIR environment
4700variable. For example:
4701
4702	export BUILD_DIR=/tmp/build
4703	export MAKEALL_LOGDIR=/tmp/log
4704	CROSS_COMPILE=ppc_8xx- MAKEALL
4705
4706With the above settings build objects are saved in the /tmp/build,
4707log files are saved in the /tmp/log and the source tree remains clean
4708during the whole build process.
4709
4710
4711See also "U-Boot Porting Guide" below.
4712
4713
4714Monitor Commands - Overview:
4715============================
4716
4717go	- start application at address 'addr'
4718run	- run commands in an environment variable
4719bootm	- boot application image from memory
4720bootp	- boot image via network using BootP/TFTP protocol
4721bootz   - boot zImage from memory
4722tftpboot- boot image via network using TFTP protocol
4723	       and env variables "ipaddr" and "serverip"
4724	       (and eventually "gatewayip")
4725tftpput - upload a file via network using TFTP protocol
4726rarpboot- boot image via network using RARP/TFTP protocol
4727diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4728loads	- load S-Record file over serial line
4729loadb	- load binary file over serial line (kermit mode)
4730md	- memory display
4731mm	- memory modify (auto-incrementing)
4732nm	- memory modify (constant address)
4733mw	- memory write (fill)
4734cp	- memory copy
4735cmp	- memory compare
4736crc32	- checksum calculation
4737i2c	- I2C sub-system
4738sspi	- SPI utility commands
4739base	- print or set address offset
4740printenv- print environment variables
4741setenv	- set environment variables
4742saveenv - save environment variables to persistent storage
4743protect - enable or disable FLASH write protection
4744erase	- erase FLASH memory
4745flinfo	- print FLASH memory information
4746nand	- NAND memory operations (see doc/README.nand)
4747bdinfo	- print Board Info structure
4748iminfo	- print header information for application image
4749coninfo - print console devices and informations
4750ide	- IDE sub-system
4751loop	- infinite loop on address range
4752loopw	- infinite write loop on address range
4753mtest	- simple RAM test
4754icache	- enable or disable instruction cache
4755dcache	- enable or disable data cache
4756reset	- Perform RESET of the CPU
4757echo	- echo args to console
4758version - print monitor version
4759help	- print online help
4760?	- alias for 'help'
4761
4762
4763Monitor Commands - Detailed Description:
4764========================================
4765
4766TODO.
4767
4768For now: just type "help <command>".
4769
4770
4771Environment Variables:
4772======================
4773
4774U-Boot supports user configuration using Environment Variables which
4775can be made persistent by saving to Flash memory.
4776
4777Environment Variables are set using "setenv", printed using
4778"printenv", and saved to Flash using "saveenv". Using "setenv"
4779without a value can be used to delete a variable from the
4780environment. As long as you don't save the environment you are
4781working with an in-memory copy. In case the Flash area containing the
4782environment is erased by accident, a default environment is provided.
4783
4784Some configuration options can be set using Environment Variables.
4785
4786List of environment variables (most likely not complete):
4787
4788  baudrate	- see CONFIG_BAUDRATE
4789
4790  bootdelay	- see CONFIG_BOOTDELAY
4791
4792  bootcmd	- see CONFIG_BOOTCOMMAND
4793
4794  bootargs	- Boot arguments when booting an RTOS image
4795
4796  bootfile	- Name of the image to load with TFTP
4797
4798  bootm_low	- Memory range available for image processing in the bootm
4799		  command can be restricted. This variable is given as
4800		  a hexadecimal number and defines lowest address allowed
4801		  for use by the bootm command. See also "bootm_size"
4802		  environment variable. Address defined by "bootm_low" is
4803		  also the base of the initial memory mapping for the Linux
4804		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4805		  bootm_mapsize.
4806
4807  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4808		  This variable is given as a hexadecimal number and it
4809		  defines the size of the memory region starting at base
4810		  address bootm_low that is accessible by the Linux kernel
4811		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4812		  as the default value if it is defined, and bootm_size is
4813		  used otherwise.
4814
4815  bootm_size	- Memory range available for image processing in the bootm
4816		  command can be restricted. This variable is given as
4817		  a hexadecimal number and defines the size of the region
4818		  allowed for use by the bootm command. See also "bootm_low"
4819		  environment variable.
4820
4821  updatefile	- Location of the software update file on a TFTP server, used
4822		  by the automatic software update feature. Please refer to
4823		  documentation in doc/README.update for more details.
4824
4825  autoload	- if set to "no" (any string beginning with 'n'),
4826		  "bootp" will just load perform a lookup of the
4827		  configuration from the BOOTP server, but not try to
4828		  load any image using TFTP
4829
4830  autostart	- if set to "yes", an image loaded using the "bootp",
4831		  "rarpboot", "tftpboot" or "diskboot" commands will
4832		  be automatically started (by internally calling
4833		  "bootm")
4834
4835		  If set to "no", a standalone image passed to the
4836		  "bootm" command will be copied to the load address
4837		  (and eventually uncompressed), but NOT be started.
4838		  This can be used to load and uncompress arbitrary
4839		  data.
4840
4841  fdt_high	- if set this restricts the maximum address that the
4842		  flattened device tree will be copied into upon boot.
4843		  For example, if you have a system with 1 GB memory
4844		  at physical address 0x10000000, while Linux kernel
4845		  only recognizes the first 704 MB as low memory, you
4846		  may need to set fdt_high as 0x3C000000 to have the
4847		  device tree blob be copied to the maximum address
4848		  of the 704 MB low memory, so that Linux kernel can
4849		  access it during the boot procedure.
4850
4851		  If this is set to the special value 0xFFFFFFFF then
4852		  the fdt will not be copied at all on boot.  For this
4853		  to work it must reside in writable memory, have
4854		  sufficient padding on the end of it for u-boot to
4855		  add the information it needs into it, and the memory
4856		  must be accessible by the kernel.
4857
4858  fdtcontroladdr- if set this is the address of the control flattened
4859		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4860		  defined.
4861
4862  i2cfast	- (PPC405GP|PPC405EP only)
4863		  if set to 'y' configures Linux I2C driver for fast
4864		  mode (400kHZ). This environment variable is used in
4865		  initialization code. So, for changes to be effective
4866		  it must be saved and board must be reset.
4867
4868  initrd_high	- restrict positioning of initrd images:
4869		  If this variable is not set, initrd images will be
4870		  copied to the highest possible address in RAM; this
4871		  is usually what you want since it allows for
4872		  maximum initrd size. If for some reason you want to
4873		  make sure that the initrd image is loaded below the
4874		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4875		  variable to a value of "no" or "off" or "0".
4876		  Alternatively, you can set it to a maximum upper
4877		  address to use (U-Boot will still check that it
4878		  does not overwrite the U-Boot stack and data).
4879
4880		  For instance, when you have a system with 16 MB
4881		  RAM, and want to reserve 4 MB from use by Linux,
4882		  you can do this by adding "mem=12M" to the value of
4883		  the "bootargs" variable. However, now you must make
4884		  sure that the initrd image is placed in the first
4885		  12 MB as well - this can be done with
4886
4887		  setenv initrd_high 00c00000
4888
4889		  If you set initrd_high to 0xFFFFFFFF, this is an
4890		  indication to U-Boot that all addresses are legal
4891		  for the Linux kernel, including addresses in flash
4892		  memory. In this case U-Boot will NOT COPY the
4893		  ramdisk at all. This may be useful to reduce the
4894		  boot time on your system, but requires that this
4895		  feature is supported by your Linux kernel.
4896
4897  ipaddr	- IP address; needed for tftpboot command
4898
4899  loadaddr	- Default load address for commands like "bootp",
4900		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4901
4902  loads_echo	- see CONFIG_LOADS_ECHO
4903
4904  serverip	- TFTP server IP address; needed for tftpboot command
4905
4906  bootretry	- see CONFIG_BOOT_RETRY_TIME
4907
4908  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4909
4910  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4911
4912  ethprime	- controls which interface is used first.
4913
4914  ethact	- controls which interface is currently active.
4915		  For example you can do the following
4916
4917		  => setenv ethact FEC
4918		  => ping 192.168.0.1 # traffic sent on FEC
4919		  => setenv ethact SCC
4920		  => ping 10.0.0.1 # traffic sent on SCC
4921
4922  ethrotate	- When set to "no" U-Boot does not go through all
4923		  available network interfaces.
4924		  It just stays at the currently selected interface.
4925
4926  netretry	- When set to "no" each network operation will
4927		  either succeed or fail without retrying.
4928		  When set to "once" the network operation will
4929		  fail when all the available network interfaces
4930		  are tried once without success.
4931		  Useful on scripts which control the retry operation
4932		  themselves.
4933
4934  npe_ucode	- set load address for the NPE microcode
4935
4936  silent_linux  - If set then linux will be told to boot silently, by
4937		  changing the console to be empty. If "yes" it will be
4938		  made silent. If "no" it will not be made silent. If
4939		  unset, then it will be made silent if the U-Boot console
4940		  is silent.
4941
4942  tftpsrcport	- If this is set, the value is used for TFTP's
4943		  UDP source port.
4944
4945  tftpdstport	- If this is set, the value is used for TFTP's UDP
4946		  destination port instead of the Well Know Port 69.
4947
4948  tftpblocksize - Block size to use for TFTP transfers; if not set,
4949		  we use the TFTP server's default block size
4950
4951  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4952		  seconds, minimum value is 1000 = 1 second). Defines
4953		  when a packet is considered to be lost so it has to
4954		  be retransmitted. The default is 5000 = 5 seconds.
4955		  Lowering this value may make downloads succeed
4956		  faster in networks with high packet loss rates or
4957		  with unreliable TFTP servers.
4958
4959  vlan		- When set to a value < 4095 the traffic over
4960		  Ethernet is encapsulated/received over 802.1q
4961		  VLAN tagged frames.
4962
4963The following image location variables contain the location of images
4964used in booting. The "Image" column gives the role of the image and is
4965not an environment variable name. The other columns are environment
4966variable names. "File Name" gives the name of the file on a TFTP
4967server, "RAM Address" gives the location in RAM the image will be
4968loaded to, and "Flash Location" gives the image's address in NOR
4969flash or offset in NAND flash.
4970
4971*Note* - these variables don't have to be defined for all boards, some
4972boards currenlty use other variables for these purposes, and some
4973boards use these variables for other purposes.
4974
4975Image		    File Name	     RAM Address       Flash Location
4976-----		    ---------	     -----------       --------------
4977u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4978Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4979device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4980ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4981
4982The following environment variables may be used and automatically
4983updated by the network boot commands ("bootp" and "rarpboot"),
4984depending the information provided by your boot server:
4985
4986  bootfile	- see above
4987  dnsip		- IP address of your Domain Name Server
4988  dnsip2	- IP address of your secondary Domain Name Server
4989  gatewayip	- IP address of the Gateway (Router) to use
4990  hostname	- Target hostname
4991  ipaddr	- see above
4992  netmask	- Subnet Mask
4993  rootpath	- Pathname of the root filesystem on the NFS server
4994  serverip	- see above
4995
4996
4997There are two special Environment Variables:
4998
4999  serial#	- contains hardware identification information such
5000		  as type string and/or serial number
5001  ethaddr	- Ethernet address
5002
5003These variables can be set only once (usually during manufacturing of
5004the board). U-Boot refuses to delete or overwrite these variables
5005once they have been set once.
5006
5007
5008Further special Environment Variables:
5009
5010  ver		- Contains the U-Boot version string as printed
5011		  with the "version" command. This variable is
5012		  readonly (see CONFIG_VERSION_VARIABLE).
5013
5014
5015Please note that changes to some configuration parameters may take
5016only effect after the next boot (yes, that's just like Windoze :-).
5017
5018
5019Callback functions for environment variables:
5020---------------------------------------------
5021
5022For some environment variables, the behavior of u-boot needs to change
5023when their values are changed.  This functionailty allows functions to
5024be associated with arbitrary variables.  On creation, overwrite, or
5025deletion, the callback will provide the opportunity for some side
5026effect to happen or for the change to be rejected.
5027
5028The callbacks are named and associated with a function using the
5029U_BOOT_ENV_CALLBACK macro in your board or driver code.
5030
5031These callbacks are associated with variables in one of two ways.  The
5032static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5033in the board configuration to a string that defines a list of
5034associations.  The list must be in the following format:
5035
5036	entry = variable_name[:callback_name]
5037	list = entry[,list]
5038
5039If the callback name is not specified, then the callback is deleted.
5040Spaces are also allowed anywhere in the list.
5041
5042Callbacks can also be associated by defining the ".callbacks" variable
5043with the same list format above.  Any association in ".callbacks" will
5044override any association in the static list. You can define
5045CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5046".callbacks" envirnoment variable in the default or embedded environment.
5047
5048
5049Command Line Parsing:
5050=====================
5051
5052There are two different command line parsers available with U-Boot:
5053the old "simple" one, and the much more powerful "hush" shell:
5054
5055Old, simple command line parser:
5056--------------------------------
5057
5058- supports environment variables (through setenv / saveenv commands)
5059- several commands on one line, separated by ';'
5060- variable substitution using "... ${name} ..." syntax
5061- special characters ('$', ';') can be escaped by prefixing with '\',
5062  for example:
5063	setenv bootcmd bootm \${address}
5064- You can also escape text by enclosing in single apostrophes, for example:
5065	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5066
5067Hush shell:
5068-----------
5069
5070- similar to Bourne shell, with control structures like
5071  if...then...else...fi, for...do...done; while...do...done,
5072  until...do...done, ...
5073- supports environment ("global") variables (through setenv / saveenv
5074  commands) and local shell variables (through standard shell syntax
5075  "name=value"); only environment variables can be used with "run"
5076  command
5077
5078General rules:
5079--------------
5080
5081(1) If a command line (or an environment variable executed by a "run"
5082    command) contains several commands separated by semicolon, and
5083    one of these commands fails, then the remaining commands will be
5084    executed anyway.
5085
5086(2) If you execute several variables with one call to run (i. e.
5087    calling run with a list of variables as arguments), any failing
5088    command will cause "run" to terminate, i. e. the remaining
5089    variables are not executed.
5090
5091Note for Redundant Ethernet Interfaces:
5092=======================================
5093
5094Some boards come with redundant Ethernet interfaces; U-Boot supports
5095such configurations and is capable of automatic selection of a
5096"working" interface when needed. MAC assignment works as follows:
5097
5098Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5099MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5100"eth1addr" (=>eth1), "eth2addr", ...
5101
5102If the network interface stores some valid MAC address (for instance
5103in SROM), this is used as default address if there is NO correspon-
5104ding setting in the environment; if the corresponding environment
5105variable is set, this overrides the settings in the card; that means:
5106
5107o If the SROM has a valid MAC address, and there is no address in the
5108  environment, the SROM's address is used.
5109
5110o If there is no valid address in the SROM, and a definition in the
5111  environment exists, then the value from the environment variable is
5112  used.
5113
5114o If both the SROM and the environment contain a MAC address, and
5115  both addresses are the same, this MAC address is used.
5116
5117o If both the SROM and the environment contain a MAC address, and the
5118  addresses differ, the value from the environment is used and a
5119  warning is printed.
5120
5121o If neither SROM nor the environment contain a MAC address, an error
5122  is raised.
5123
5124If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5125will be programmed into hardware as part of the initialization process.	 This
5126may be skipped by setting the appropriate 'ethmacskip' environment variable.
5127The naming convention is as follows:
5128"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5129
5130Image Formats:
5131==============
5132
5133U-Boot is capable of booting (and performing other auxiliary operations on)
5134images in two formats:
5135
5136New uImage format (FIT)
5137-----------------------
5138
5139Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5140to Flattened Device Tree). It allows the use of images with multiple
5141components (several kernels, ramdisks, etc.), with contents protected by
5142SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5143
5144
5145Old uImage format
5146-----------------
5147
5148Old image format is based on binary files which can be basically anything,
5149preceded by a special header; see the definitions in include/image.h for
5150details; basically, the header defines the following image properties:
5151
5152* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5153  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5154  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5155  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5156  INTEGRITY).
5157* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5158  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5159  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5160* Compression Type (uncompressed, gzip, bzip2)
5161* Load Address
5162* Entry Point
5163* Image Name
5164* Image Timestamp
5165
5166The header is marked by a special Magic Number, and both the header
5167and the data portions of the image are secured against corruption by
5168CRC32 checksums.
5169
5170
5171Linux Support:
5172==============
5173
5174Although U-Boot should support any OS or standalone application
5175easily, the main focus has always been on Linux during the design of
5176U-Boot.
5177
5178U-Boot includes many features that so far have been part of some
5179special "boot loader" code within the Linux kernel. Also, any
5180"initrd" images to be used are no longer part of one big Linux image;
5181instead, kernel and "initrd" are separate images. This implementation
5182serves several purposes:
5183
5184- the same features can be used for other OS or standalone
5185  applications (for instance: using compressed images to reduce the
5186  Flash memory footprint)
5187
5188- it becomes much easier to port new Linux kernel versions because
5189  lots of low-level, hardware dependent stuff are done by U-Boot
5190
5191- the same Linux kernel image can now be used with different "initrd"
5192  images; of course this also means that different kernel images can
5193  be run with the same "initrd". This makes testing easier (you don't
5194  have to build a new "zImage.initrd" Linux image when you just
5195  change a file in your "initrd"). Also, a field-upgrade of the
5196  software is easier now.
5197
5198
5199Linux HOWTO:
5200============
5201
5202Porting Linux to U-Boot based systems:
5203---------------------------------------
5204
5205U-Boot cannot save you from doing all the necessary modifications to
5206configure the Linux device drivers for use with your target hardware
5207(no, we don't intend to provide a full virtual machine interface to
5208Linux :-).
5209
5210But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5211
5212Just make sure your machine specific header file (for instance
5213include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5214Information structure as we define in include/asm-<arch>/u-boot.h,
5215and make sure that your definition of IMAP_ADDR uses the same value
5216as your U-Boot configuration in CONFIG_SYS_IMMR.
5217
5218
5219Configuring the Linux kernel:
5220-----------------------------
5221
5222No specific requirements for U-Boot. Make sure you have some root
5223device (initial ramdisk, NFS) for your target system.
5224
5225
5226Building a Linux Image:
5227-----------------------
5228
5229With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5230not used. If you use recent kernel source, a new build target
5231"uImage" will exist which automatically builds an image usable by
5232U-Boot. Most older kernels also have support for a "pImage" target,
5233which was introduced for our predecessor project PPCBoot and uses a
5234100% compatible format.
5235
5236Example:
5237
5238	make TQM850L_config
5239	make oldconfig
5240	make dep
5241	make uImage
5242
5243The "uImage" build target uses a special tool (in 'tools/mkimage') to
5244encapsulate a compressed Linux kernel image with header	 information,
5245CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5246
5247* build a standard "vmlinux" kernel image (in ELF binary format):
5248
5249* convert the kernel into a raw binary image:
5250
5251	${CROSS_COMPILE}-objcopy -O binary \
5252				 -R .note -R .comment \
5253				 -S vmlinux linux.bin
5254
5255* compress the binary image:
5256
5257	gzip -9 linux.bin
5258
5259* package compressed binary image for U-Boot:
5260
5261	mkimage -A ppc -O linux -T kernel -C gzip \
5262		-a 0 -e 0 -n "Linux Kernel Image" \
5263		-d linux.bin.gz uImage
5264
5265
5266The "mkimage" tool can also be used to create ramdisk images for use
5267with U-Boot, either separated from the Linux kernel image, or
5268combined into one file. "mkimage" encapsulates the images with a 64
5269byte header containing information about target architecture,
5270operating system, image type, compression method, entry points, time
5271stamp, CRC32 checksums, etc.
5272
5273"mkimage" can be called in two ways: to verify existing images and
5274print the header information, or to build new images.
5275
5276In the first form (with "-l" option) mkimage lists the information
5277contained in the header of an existing U-Boot image; this includes
5278checksum verification:
5279
5280	tools/mkimage -l image
5281	  -l ==> list image header information
5282
5283The second form (with "-d" option) is used to build a U-Boot image
5284from a "data file" which is used as image payload:
5285
5286	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5287		      -n name -d data_file image
5288	  -A ==> set architecture to 'arch'
5289	  -O ==> set operating system to 'os'
5290	  -T ==> set image type to 'type'
5291	  -C ==> set compression type 'comp'
5292	  -a ==> set load address to 'addr' (hex)
5293	  -e ==> set entry point to 'ep' (hex)
5294	  -n ==> set image name to 'name'
5295	  -d ==> use image data from 'datafile'
5296
5297Right now, all Linux kernels for PowerPC systems use the same load
5298address (0x00000000), but the entry point address depends on the
5299kernel version:
5300
5301- 2.2.x kernels have the entry point at 0x0000000C,
5302- 2.3.x and later kernels have the entry point at 0x00000000.
5303
5304So a typical call to build a U-Boot image would read:
5305
5306	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5307	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5308	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5309	> examples/uImage.TQM850L
5310	Image Name:   2.4.4 kernel for TQM850L
5311	Created:      Wed Jul 19 02:34:59 2000
5312	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5313	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5314	Load Address: 0x00000000
5315	Entry Point:  0x00000000
5316
5317To verify the contents of the image (or check for corruption):
5318
5319	-> tools/mkimage -l examples/uImage.TQM850L
5320	Image Name:   2.4.4 kernel for TQM850L
5321	Created:      Wed Jul 19 02:34:59 2000
5322	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5323	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5324	Load Address: 0x00000000
5325	Entry Point:  0x00000000
5326
5327NOTE: for embedded systems where boot time is critical you can trade
5328speed for memory and install an UNCOMPRESSED image instead: this
5329needs more space in Flash, but boots much faster since it does not
5330need to be uncompressed:
5331
5332	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5333	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5334	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5335	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5336	> examples/uImage.TQM850L-uncompressed
5337	Image Name:   2.4.4 kernel for TQM850L
5338	Created:      Wed Jul 19 02:34:59 2000
5339	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5340	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5341	Load Address: 0x00000000
5342	Entry Point:  0x00000000
5343
5344
5345Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5346when your kernel is intended to use an initial ramdisk:
5347
5348	-> tools/mkimage -n 'Simple Ramdisk Image' \
5349	> -A ppc -O linux -T ramdisk -C gzip \
5350	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5351	Image Name:   Simple Ramdisk Image
5352	Created:      Wed Jan 12 14:01:50 2000
5353	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5354	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5355	Load Address: 0x00000000
5356	Entry Point:  0x00000000
5357
5358The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5359option performs the converse operation of the mkimage's second form (the "-d"
5360option). Given an image built by mkimage, the dumpimage extracts a "data file"
5361from the image:
5362
5363	tools/dumpimage -i image -p position data_file
5364	  -i ==> extract from the 'image' a specific 'data_file', \
5365	   indexed by 'position'
5366
5367
5368Installing a Linux Image:
5369-------------------------
5370
5371To downloading a U-Boot image over the serial (console) interface,
5372you must convert the image to S-Record format:
5373
5374	objcopy -I binary -O srec examples/image examples/image.srec
5375
5376The 'objcopy' does not understand the information in the U-Boot
5377image header, so the resulting S-Record file will be relative to
5378address 0x00000000. To load it to a given address, you need to
5379specify the target address as 'offset' parameter with the 'loads'
5380command.
5381
5382Example: install the image to address 0x40100000 (which on the
5383TQM8xxL is in the first Flash bank):
5384
5385	=> erase 40100000 401FFFFF
5386
5387	.......... done
5388	Erased 8 sectors
5389
5390	=> loads 40100000
5391	## Ready for S-Record download ...
5392	~>examples/image.srec
5393	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5394	...
5395	15989 15990 15991 15992
5396	[file transfer complete]
5397	[connected]
5398	## Start Addr = 0x00000000
5399
5400
5401You can check the success of the download using the 'iminfo' command;
5402this includes a checksum verification so you can be sure no data
5403corruption happened:
5404
5405	=> imi 40100000
5406
5407	## Checking Image at 40100000 ...
5408	   Image Name:	 2.2.13 for initrd on TQM850L
5409	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5410	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5411	   Load Address: 00000000
5412	   Entry Point:	 0000000c
5413	   Verifying Checksum ... OK
5414
5415
5416Boot Linux:
5417-----------
5418
5419The "bootm" command is used to boot an application that is stored in
5420memory (RAM or Flash). In case of a Linux kernel image, the contents
5421of the "bootargs" environment variable is passed to the kernel as
5422parameters. You can check and modify this variable using the
5423"printenv" and "setenv" commands:
5424
5425
5426	=> printenv bootargs
5427	bootargs=root=/dev/ram
5428
5429	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5430
5431	=> printenv bootargs
5432	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5433
5434	=> bootm 40020000
5435	## Booting Linux kernel at 40020000 ...
5436	   Image Name:	 2.2.13 for NFS on TQM850L
5437	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5438	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5439	   Load Address: 00000000
5440	   Entry Point:	 0000000c
5441	   Verifying Checksum ... OK
5442	   Uncompressing Kernel Image ... OK
5443	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
5444	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5445	time_init: decrementer frequency = 187500000/60
5446	Calibrating delay loop... 49.77 BogoMIPS
5447	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5448	...
5449
5450If you want to boot a Linux kernel with initial RAM disk, you pass
5451the memory addresses of both the kernel and the initrd image (PPBCOOT
5452format!) to the "bootm" command:
5453
5454	=> imi 40100000 40200000
5455
5456	## Checking Image at 40100000 ...
5457	   Image Name:	 2.2.13 for initrd on TQM850L
5458	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5459	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5460	   Load Address: 00000000
5461	   Entry Point:	 0000000c
5462	   Verifying Checksum ... OK
5463
5464	## Checking Image at 40200000 ...
5465	   Image Name:	 Simple Ramdisk Image
5466	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5467	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5468	   Load Address: 00000000
5469	   Entry Point:	 00000000
5470	   Verifying Checksum ... OK
5471
5472	=> bootm 40100000 40200000
5473	## Booting Linux kernel at 40100000 ...
5474	   Image Name:	 2.2.13 for initrd on TQM850L
5475	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5476	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5477	   Load Address: 00000000
5478	   Entry Point:	 0000000c
5479	   Verifying Checksum ... OK
5480	   Uncompressing Kernel Image ... OK
5481	## Loading RAMDisk Image at 40200000 ...
5482	   Image Name:	 Simple Ramdisk Image
5483	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5484	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5485	   Load Address: 00000000
5486	   Entry Point:	 00000000
5487	   Verifying Checksum ... OK
5488	   Loading Ramdisk ... OK
5489	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
5490	Boot arguments: root=/dev/ram
5491	time_init: decrementer frequency = 187500000/60
5492	Calibrating delay loop... 49.77 BogoMIPS
5493	...
5494	RAMDISK: Compressed image found at block 0
5495	VFS: Mounted root (ext2 filesystem).
5496
5497	bash#
5498
5499Boot Linux and pass a flat device tree:
5500-----------
5501
5502First, U-Boot must be compiled with the appropriate defines. See the section
5503titled "Linux Kernel Interface" above for a more in depth explanation. The
5504following is an example of how to start a kernel and pass an updated
5505flat device tree:
5506
5507=> print oftaddr
5508oftaddr=0x300000
5509=> print oft
5510oft=oftrees/mpc8540ads.dtb
5511=> tftp $oftaddr $oft
5512Speed: 1000, full duplex
5513Using TSEC0 device
5514TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5515Filename 'oftrees/mpc8540ads.dtb'.
5516Load address: 0x300000
5517Loading: #
5518done
5519Bytes transferred = 4106 (100a hex)
5520=> tftp $loadaddr $bootfile
5521Speed: 1000, full duplex
5522Using TSEC0 device
5523TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5524Filename 'uImage'.
5525Load address: 0x200000
5526Loading:############
5527done
5528Bytes transferred = 1029407 (fb51f hex)
5529=> print loadaddr
5530loadaddr=200000
5531=> print oftaddr
5532oftaddr=0x300000
5533=> bootm $loadaddr - $oftaddr
5534## Booting image at 00200000 ...
5535   Image Name:	 Linux-2.6.17-dirty
5536   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5537   Data Size:	 1029343 Bytes = 1005.2 kB
5538   Load Address: 00000000
5539   Entry Point:	 00000000
5540   Verifying Checksum ... OK
5541   Uncompressing Kernel Image ... OK
5542Booting using flat device tree at 0x300000
5543Using MPC85xx ADS machine description
5544Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5545[snip]
5546
5547
5548More About U-Boot Image Types:
5549------------------------------
5550
5551U-Boot supports the following image types:
5552
5553   "Standalone Programs" are directly runnable in the environment
5554	provided by U-Boot; it is expected that (if they behave
5555	well) you can continue to work in U-Boot after return from
5556	the Standalone Program.
5557   "OS Kernel Images" are usually images of some Embedded OS which
5558	will take over control completely. Usually these programs
5559	will install their own set of exception handlers, device
5560	drivers, set up the MMU, etc. - this means, that you cannot
5561	expect to re-enter U-Boot except by resetting the CPU.
5562   "RAMDisk Images" are more or less just data blocks, and their
5563	parameters (address, size) are passed to an OS kernel that is
5564	being started.
5565   "Multi-File Images" contain several images, typically an OS
5566	(Linux) kernel image and one or more data images like
5567	RAMDisks. This construct is useful for instance when you want
5568	to boot over the network using BOOTP etc., where the boot
5569	server provides just a single image file, but you want to get
5570	for instance an OS kernel and a RAMDisk image.
5571
5572	"Multi-File Images" start with a list of image sizes, each
5573	image size (in bytes) specified by an "uint32_t" in network
5574	byte order. This list is terminated by an "(uint32_t)0".
5575	Immediately after the terminating 0 follow the images, one by
5576	one, all aligned on "uint32_t" boundaries (size rounded up to
5577	a multiple of 4 bytes).
5578
5579   "Firmware Images" are binary images containing firmware (like
5580	U-Boot or FPGA images) which usually will be programmed to
5581	flash memory.
5582
5583   "Script files" are command sequences that will be executed by
5584	U-Boot's command interpreter; this feature is especially
5585	useful when you configure U-Boot to use a real shell (hush)
5586	as command interpreter.
5587
5588Booting the Linux zImage:
5589-------------------------
5590
5591On some platforms, it's possible to boot Linux zImage. This is done
5592using the "bootz" command. The syntax of "bootz" command is the same
5593as the syntax of "bootm" command.
5594
5595Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5596kernel with raw initrd images. The syntax is slightly different, the
5597address of the initrd must be augmented by it's size, in the following
5598format: "<initrd addres>:<initrd size>".
5599
5600
5601Standalone HOWTO:
5602=================
5603
5604One of the features of U-Boot is that you can dynamically load and
5605run "standalone" applications, which can use some resources of
5606U-Boot like console I/O functions or interrupt services.
5607
5608Two simple examples are included with the sources:
5609
5610"Hello World" Demo:
5611-------------------
5612
5613'examples/hello_world.c' contains a small "Hello World" Demo
5614application; it is automatically compiled when you build U-Boot.
5615It's configured to run at address 0x00040004, so you can play with it
5616like that:
5617
5618	=> loads
5619	## Ready for S-Record download ...
5620	~>examples/hello_world.srec
5621	1 2 3 4 5 6 7 8 9 10 11 ...
5622	[file transfer complete]
5623	[connected]
5624	## Start Addr = 0x00040004
5625
5626	=> go 40004 Hello World! This is a test.
5627	## Starting application at 0x00040004 ...
5628	Hello World
5629	argc = 7
5630	argv[0] = "40004"
5631	argv[1] = "Hello"
5632	argv[2] = "World!"
5633	argv[3] = "This"
5634	argv[4] = "is"
5635	argv[5] = "a"
5636	argv[6] = "test."
5637	argv[7] = "<NULL>"
5638	Hit any key to exit ...
5639
5640	## Application terminated, rc = 0x0
5641
5642Another example, which demonstrates how to register a CPM interrupt
5643handler with the U-Boot code, can be found in 'examples/timer.c'.
5644Here, a CPM timer is set up to generate an interrupt every second.
5645The interrupt service routine is trivial, just printing a '.'
5646character, but this is just a demo program. The application can be
5647controlled by the following keys:
5648
5649	? - print current values og the CPM Timer registers
5650	b - enable interrupts and start timer
5651	e - stop timer and disable interrupts
5652	q - quit application
5653
5654	=> loads
5655	## Ready for S-Record download ...
5656	~>examples/timer.srec
5657	1 2 3 4 5 6 7 8 9 10 11 ...
5658	[file transfer complete]
5659	[connected]
5660	## Start Addr = 0x00040004
5661
5662	=> go 40004
5663	## Starting application at 0x00040004 ...
5664	TIMERS=0xfff00980
5665	Using timer 1
5666	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5667
5668Hit 'b':
5669	[q, b, e, ?] Set interval 1000000 us
5670	Enabling timer
5671Hit '?':
5672	[q, b, e, ?] ........
5673	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5674Hit '?':
5675	[q, b, e, ?] .
5676	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5677Hit '?':
5678	[q, b, e, ?] .
5679	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5680Hit '?':
5681	[q, b, e, ?] .
5682	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5683Hit 'e':
5684	[q, b, e, ?] ...Stopping timer
5685Hit 'q':
5686	[q, b, e, ?] ## Application terminated, rc = 0x0
5687
5688
5689Minicom warning:
5690================
5691
5692Over time, many people have reported problems when trying to use the
5693"minicom" terminal emulation program for serial download. I (wd)
5694consider minicom to be broken, and recommend not to use it. Under
5695Unix, I recommend to use C-Kermit for general purpose use (and
5696especially for kermit binary protocol download ("loadb" command), and
5697use "cu" for S-Record download ("loads" command).  See
5698http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5699for help with kermit.
5700
5701
5702Nevertheless, if you absolutely want to use it try adding this
5703configuration to your "File transfer protocols" section:
5704
5705	   Name	   Program			Name U/D FullScr IO-Red. Multi
5706	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5707	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5708
5709
5710NetBSD Notes:
5711=============
5712
5713Starting at version 0.9.2, U-Boot supports NetBSD both as host
5714(build U-Boot) and target system (boots NetBSD/mpc8xx).
5715
5716Building requires a cross environment; it is known to work on
5717NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5718need gmake since the Makefiles are not compatible with BSD make).
5719Note that the cross-powerpc package does not install include files;
5720attempting to build U-Boot will fail because <machine/ansi.h> is
5721missing.  This file has to be installed and patched manually:
5722
5723	# cd /usr/pkg/cross/powerpc-netbsd/include
5724	# mkdir powerpc
5725	# ln -s powerpc machine
5726	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5727	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5728
5729Native builds *don't* work due to incompatibilities between native
5730and U-Boot include files.
5731
5732Booting assumes that (the first part of) the image booted is a
5733stage-2 loader which in turn loads and then invokes the kernel
5734proper. Loader sources will eventually appear in the NetBSD source
5735tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5736meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5737
5738
5739Implementation Internals:
5740=========================
5741
5742The following is not intended to be a complete description of every
5743implementation detail. However, it should help to understand the
5744inner workings of U-Boot and make it easier to port it to custom
5745hardware.
5746
5747
5748Initial Stack, Global Data:
5749---------------------------
5750
5751The implementation of U-Boot is complicated by the fact that U-Boot
5752starts running out of ROM (flash memory), usually without access to
5753system RAM (because the memory controller is not initialized yet).
5754This means that we don't have writable Data or BSS segments, and BSS
5755is not initialized as zero. To be able to get a C environment working
5756at all, we have to allocate at least a minimal stack. Implementation
5757options for this are defined and restricted by the CPU used: Some CPU
5758models provide on-chip memory (like the IMMR area on MPC8xx and
5759MPC826x processors), on others (parts of) the data cache can be
5760locked as (mis-) used as memory, etc.
5761
5762	Chris Hallinan posted a good summary of these issues to the
5763	U-Boot mailing list:
5764
5765	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5766	From: "Chris Hallinan" <clh@net1plus.com>
5767	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5768	...
5769
5770	Correct me if I'm wrong, folks, but the way I understand it
5771	is this: Using DCACHE as initial RAM for Stack, etc, does not
5772	require any physical RAM backing up the cache. The cleverness
5773	is that the cache is being used as a temporary supply of
5774	necessary storage before the SDRAM controller is setup. It's
5775	beyond the scope of this list to explain the details, but you
5776	can see how this works by studying the cache architecture and
5777	operation in the architecture and processor-specific manuals.
5778
5779	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5780	is another option for the system designer to use as an
5781	initial stack/RAM area prior to SDRAM being available. Either
5782	option should work for you. Using CS 4 should be fine if your
5783	board designers haven't used it for something that would
5784	cause you grief during the initial boot! It is frequently not
5785	used.
5786
5787	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5788	with your processor/board/system design. The default value
5789	you will find in any recent u-boot distribution in
5790	walnut.h should work for you. I'd set it to a value larger
5791	than your SDRAM module. If you have a 64MB SDRAM module, set
5792	it above 400_0000. Just make sure your board has no resources
5793	that are supposed to respond to that address! That code in
5794	start.S has been around a while and should work as is when
5795	you get the config right.
5796
5797	-Chris Hallinan
5798	DS4.COM, Inc.
5799
5800It is essential to remember this, since it has some impact on the C
5801code for the initialization procedures:
5802
5803* Initialized global data (data segment) is read-only. Do not attempt
5804  to write it.
5805
5806* Do not use any uninitialized global data (or implicitely initialized
5807  as zero data - BSS segment) at all - this is undefined, initiali-
5808  zation is performed later (when relocating to RAM).
5809
5810* Stack space is very limited. Avoid big data buffers or things like
5811  that.
5812
5813Having only the stack as writable memory limits means we cannot use
5814normal global data to share information beween the code. But it
5815turned out that the implementation of U-Boot can be greatly
5816simplified by making a global data structure (gd_t) available to all
5817functions. We could pass a pointer to this data as argument to _all_
5818functions, but this would bloat the code. Instead we use a feature of
5819the GCC compiler (Global Register Variables) to share the data: we
5820place a pointer (gd) to the global data into a register which we
5821reserve for this purpose.
5822
5823When choosing a register for such a purpose we are restricted by the
5824relevant  (E)ABI  specifications for the current architecture, and by
5825GCC's implementation.
5826
5827For PowerPC, the following registers have specific use:
5828	R1:	stack pointer
5829	R2:	reserved for system use
5830	R3-R4:	parameter passing and return values
5831	R5-R10: parameter passing
5832	R13:	small data area pointer
5833	R30:	GOT pointer
5834	R31:	frame pointer
5835
5836	(U-Boot also uses R12 as internal GOT pointer. r12
5837	is a volatile register so r12 needs to be reset when
5838	going back and forth between asm and C)
5839
5840    ==> U-Boot will use R2 to hold a pointer to the global data
5841
5842    Note: on PPC, we could use a static initializer (since the
5843    address of the global data structure is known at compile time),
5844    but it turned out that reserving a register results in somewhat
5845    smaller code - although the code savings are not that big (on
5846    average for all boards 752 bytes for the whole U-Boot image,
5847    624 text + 127 data).
5848
5849On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5850	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5851
5852    ==> U-Boot will use P3 to hold a pointer to the global data
5853
5854On ARM, the following registers are used:
5855
5856	R0:	function argument word/integer result
5857	R1-R3:	function argument word
5858	R9:	platform specific
5859	R10:	stack limit (used only if stack checking is enabled)
5860	R11:	argument (frame) pointer
5861	R12:	temporary workspace
5862	R13:	stack pointer
5863	R14:	link register
5864	R15:	program counter
5865
5866    ==> U-Boot will use R9 to hold a pointer to the global data
5867
5868    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5869
5870On Nios II, the ABI is documented here:
5871	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5872
5873    ==> U-Boot will use gp to hold a pointer to the global data
5874
5875    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5876    to access small data sections, so gp is free.
5877
5878On NDS32, the following registers are used:
5879
5880	R0-R1:	argument/return
5881	R2-R5:	argument
5882	R15:	temporary register for assembler
5883	R16:	trampoline register
5884	R28:	frame pointer (FP)
5885	R29:	global pointer (GP)
5886	R30:	link register (LP)
5887	R31:	stack pointer (SP)
5888	PC:	program counter (PC)
5889
5890    ==> U-Boot will use R10 to hold a pointer to the global data
5891
5892NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5893or current versions of GCC may "optimize" the code too much.
5894
5895Memory Management:
5896------------------
5897
5898U-Boot runs in system state and uses physical addresses, i.e. the
5899MMU is not used either for address mapping nor for memory protection.
5900
5901The available memory is mapped to fixed addresses using the memory
5902controller. In this process, a contiguous block is formed for each
5903memory type (Flash, SDRAM, SRAM), even when it consists of several
5904physical memory banks.
5905
5906U-Boot is installed in the first 128 kB of the first Flash bank (on
5907TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5908booting and sizing and initializing DRAM, the code relocates itself
5909to the upper end of DRAM. Immediately below the U-Boot code some
5910memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5911configuration setting]. Below that, a structure with global Board
5912Info data is placed, followed by the stack (growing downward).
5913
5914Additionally, some exception handler code is copied to the low 8 kB
5915of DRAM (0x00000000 ... 0x00001FFF).
5916
5917So a typical memory configuration with 16 MB of DRAM could look like
5918this:
5919
5920	0x0000 0000	Exception Vector code
5921	      :
5922	0x0000 1FFF
5923	0x0000 2000	Free for Application Use
5924	      :
5925	      :
5926
5927	      :
5928	      :
5929	0x00FB FF20	Monitor Stack (Growing downward)
5930	0x00FB FFAC	Board Info Data and permanent copy of global data
5931	0x00FC 0000	Malloc Arena
5932	      :
5933	0x00FD FFFF
5934	0x00FE 0000	RAM Copy of Monitor Code
5935	...		eventually: LCD or video framebuffer
5936	...		eventually: pRAM (Protected RAM - unchanged by reset)
5937	0x00FF FFFF	[End of RAM]
5938
5939
5940System Initialization:
5941----------------------
5942
5943In the reset configuration, U-Boot starts at the reset entry point
5944(on most PowerPC systems at address 0x00000100). Because of the reset
5945configuration for CS0# this is a mirror of the onboard Flash memory.
5946To be able to re-map memory U-Boot then jumps to its link address.
5947To be able to implement the initialization code in C, a (small!)
5948initial stack is set up in the internal Dual Ported RAM (in case CPUs
5949which provide such a feature like MPC8xx or MPC8260), or in a locked
5950part of the data cache. After that, U-Boot initializes the CPU core,
5951the caches and the SIU.
5952
5953Next, all (potentially) available memory banks are mapped using a
5954preliminary mapping. For example, we put them on 512 MB boundaries
5955(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5956on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5957programmed for SDRAM access. Using the temporary configuration, a
5958simple memory test is run that determines the size of the SDRAM
5959banks.
5960
5961When there is more than one SDRAM bank, and the banks are of
5962different size, the largest is mapped first. For equal size, the first
5963bank (CS2#) is mapped first. The first mapping is always for address
59640x00000000, with any additional banks following immediately to create
5965contiguous memory starting from 0.
5966
5967Then, the monitor installs itself at the upper end of the SDRAM area
5968and allocates memory for use by malloc() and for the global Board
5969Info data; also, the exception vector code is copied to the low RAM
5970pages, and the final stack is set up.
5971
5972Only after this relocation will you have a "normal" C environment;
5973until that you are restricted in several ways, mostly because you are
5974running from ROM, and because the code will have to be relocated to a
5975new address in RAM.
5976
5977
5978U-Boot Porting Guide:
5979----------------------
5980
5981[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5982list, October 2002]
5983
5984
5985int main(int argc, char *argv[])
5986{
5987	sighandler_t no_more_time;
5988
5989	signal(SIGALRM, no_more_time);
5990	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5991
5992	if (available_money > available_manpower) {
5993		Pay consultant to port U-Boot;
5994		return 0;
5995	}
5996
5997	Download latest U-Boot source;
5998
5999	Subscribe to u-boot mailing list;
6000
6001	if (clueless)
6002		email("Hi, I am new to U-Boot, how do I get started?");
6003
6004	while (learning) {
6005		Read the README file in the top level directory;
6006		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6007		Read applicable doc/*.README;
6008		Read the source, Luke;
6009		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6010	}
6011
6012	if (available_money > toLocalCurrency ($2500))
6013		Buy a BDI3000;
6014	else
6015		Add a lot of aggravation and time;
6016
6017	if (a similar board exists) {	/* hopefully... */
6018		cp -a board/<similar> board/<myboard>
6019		cp include/configs/<similar>.h include/configs/<myboard>.h
6020	} else {
6021		Create your own board support subdirectory;
6022		Create your own board include/configs/<myboard>.h file;
6023	}
6024	Edit new board/<myboard> files
6025	Edit new include/configs/<myboard>.h
6026
6027	while (!accepted) {
6028		while (!running) {
6029			do {
6030				Add / modify source code;
6031			} until (compiles);
6032			Debug;
6033			if (clueless)
6034				email("Hi, I am having problems...");
6035		}
6036		Send patch file to the U-Boot email list;
6037		if (reasonable critiques)
6038			Incorporate improvements from email list code review;
6039		else
6040			Defend code as written;
6041	}
6042
6043	return 0;
6044}
6045
6046void no_more_time (int sig)
6047{
6048      hire_a_guru();
6049}
6050
6051
6052Coding Standards:
6053-----------------
6054
6055All contributions to U-Boot should conform to the Linux kernel
6056coding style; see the file "Documentation/CodingStyle" and the script
6057"scripts/Lindent" in your Linux kernel source directory.
6058
6059Source files originating from a different project (for example the
6060MTD subsystem) are generally exempt from these guidelines and are not
6061reformated to ease subsequent migration to newer versions of those
6062sources.
6063
6064Please note that U-Boot is implemented in C (and to some small parts in
6065Assembler); no C++ is used, so please do not use C++ style comments (//)
6066in your code.
6067
6068Please also stick to the following formatting rules:
6069- remove any trailing white space
6070- use TAB characters for indentation and vertical alignment, not spaces
6071- make sure NOT to use DOS '\r\n' line feeds
6072- do not add more than 2 consecutive empty lines to source files
6073- do not add trailing empty lines to source files
6074
6075Submissions which do not conform to the standards may be returned
6076with a request to reformat the changes.
6077
6078
6079Submitting Patches:
6080-------------------
6081
6082Since the number of patches for U-Boot is growing, we need to
6083establish some rules. Submissions which do not conform to these rules
6084may be rejected, even when they contain important and valuable stuff.
6085
6086Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6087
6088Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6089see http://lists.denx.de/mailman/listinfo/u-boot
6090
6091When you send a patch, please include the following information with
6092it:
6093
6094* For bug fixes: a description of the bug and how your patch fixes
6095  this bug. Please try to include a way of demonstrating that the
6096  patch actually fixes something.
6097
6098* For new features: a description of the feature and your
6099  implementation.
6100
6101* A CHANGELOG entry as plaintext (separate from the patch)
6102
6103* For major contributions, your entry to the CREDITS file
6104
6105* When you add support for a new board, don't forget to add a
6106  maintainer e-mail address to the boards.cfg file, too.
6107
6108* If your patch adds new configuration options, don't forget to
6109  document these in the README file.
6110
6111* The patch itself. If you are using git (which is *strongly*
6112  recommended) you can easily generate the patch using the
6113  "git format-patch". If you then use "git send-email" to send it to
6114  the U-Boot mailing list, you will avoid most of the common problems
6115  with some other mail clients.
6116
6117  If you cannot use git, use "diff -purN OLD NEW". If your version of
6118  diff does not support these options, then get the latest version of
6119  GNU diff.
6120
6121  The current directory when running this command shall be the parent
6122  directory of the U-Boot source tree (i. e. please make sure that
6123  your patch includes sufficient directory information for the
6124  affected files).
6125
6126  We prefer patches as plain text. MIME attachments are discouraged,
6127  and compressed attachments must not be used.
6128
6129* If one logical set of modifications affects or creates several
6130  files, all these changes shall be submitted in a SINGLE patch file.
6131
6132* Changesets that contain different, unrelated modifications shall be
6133  submitted as SEPARATE patches, one patch per changeset.
6134
6135
6136Notes:
6137
6138* Before sending the patch, run the MAKEALL script on your patched
6139  source tree and make sure that no errors or warnings are reported
6140  for any of the boards.
6141
6142* Keep your modifications to the necessary minimum: A patch
6143  containing several unrelated changes or arbitrary reformats will be
6144  returned with a request to re-formatting / split it.
6145
6146* If you modify existing code, make sure that your new code does not
6147  add to the memory footprint of the code ;-) Small is beautiful!
6148  When adding new features, these should compile conditionally only
6149  (using #ifdef), and the resulting code with the new feature
6150  disabled must not need more memory than the old code without your
6151  modification.
6152
6153* Remember that there is a size limit of 100 kB per message on the
6154  u-boot mailing list. Bigger patches will be moderated. If they are
6155  reasonable and not too big, they will be acknowledged. But patches
6156  bigger than the size limit should be avoided.
6157