xref: /rk3399_rockchip-uboot/README (revision 6dd3b566893a99629771e076dca1ce8db7b77dc1)
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- Generic CPU options:
431		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
432
433		Defines the endianess of the CPU. Implementation of those
434		values is arch specific.
435
436		CONFIG_SYS_FSL_DDR
437		Freescale DDR driver in use. This type of DDR controller is
438		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
439		SoCs.
440
441		CONFIG_SYS_FSL_DDR_ADDR
442		Freescale DDR memory-mapped register base.
443
444		CONFIG_SYS_FSL_DDR_EMU
445		Specify emulator support for DDR. Some DDR features such as
446		deskew training are not available.
447
448		CONFIG_SYS_FSL_DDRC_GEN1
449		Freescale DDR1 controller.
450
451		CONFIG_SYS_FSL_DDRC_GEN2
452		Freescale DDR2 controller.
453
454		CONFIG_SYS_FSL_DDRC_GEN3
455		Freescale DDR3 controller.
456
457		CONFIG_SYS_FSL_DDRC_ARM_GEN3
458		Freescale DDR3 controller for ARM-based SoCs.
459
460		CONFIG_SYS_FSL_DDR1
461		Board config to use DDR1. It can be enabled for SoCs with
462		Freescale DDR1 or DDR2 controllers, depending on the board
463		implemetation.
464
465		CONFIG_SYS_FSL_DDR2
466		Board config to use DDR2. It can be eanbeld for SoCs with
467		Freescale DDR2 or DDR3 controllers, depending on the board
468		implementation.
469
470		CONFIG_SYS_FSL_DDR3
471		Board config to use DDR3. It can be enabled for SoCs with
472		Freescale DDR3 controllers.
473
474		CONFIG_SYS_FSL_IFC_BE
475		Defines the IFC controller register space as Big Endian
476
477		CONFIG_SYS_FSL_IFC_LE
478		Defines the IFC controller register space as Little Endian
479
480		CONFIG_SYS_FSL_PBL_PBI
481		It enables addition of RCW (Power on reset configuration) in built image.
482		Please refer doc/README.pblimage for more details
483
484		CONFIG_SYS_FSL_PBL_RCW
485		It adds PBI(pre-boot instructions) commands in u-boot build image.
486		PBI commands can be used to configure SoC before it starts the execution.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SYS_FSL_DDR_BE
490		Defines the DDR controller register space as Big Endian
491
492		CONFIG_SYS_FSL_DDR_LE
493		Defines the DDR controller register space as Little Endian
494
495		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
496		Physical address from the view of DDR controllers. It is the
497		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
498		it could be different for ARM SoCs.
499
500		CONFIG_SYS_FSL_DDR_INTLV_256B
501		DDR controller interleaving on 256-byte. This is a special
502		interleaving mode, handled by Dickens for Freescale layerscape
503		SoCs with ARM core.
504
505- Intel Monahans options:
506		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
507
508		Defines the Monahans run mode to oscillator
509		ratio. Valid values are 8, 16, 24, 31. The core
510		frequency is this value multiplied by 13 MHz.
511
512		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
513
514		Defines the Monahans turbo mode to oscillator
515		ratio. Valid values are 1 (default if undefined) and
516		2. The core frequency as calculated above is multiplied
517		by this value.
518
519- MIPS CPU options:
520		CONFIG_SYS_INIT_SP_OFFSET
521
522		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
523		pointer. This is needed for the temporary stack before
524		relocation.
525
526		CONFIG_SYS_MIPS_CACHE_MODE
527
528		Cache operation mode for the MIPS CPU.
529		See also arch/mips/include/asm/mipsregs.h.
530		Possible values are:
531			CONF_CM_CACHABLE_NO_WA
532			CONF_CM_CACHABLE_WA
533			CONF_CM_UNCACHED
534			CONF_CM_CACHABLE_NONCOHERENT
535			CONF_CM_CACHABLE_CE
536			CONF_CM_CACHABLE_COW
537			CONF_CM_CACHABLE_CUW
538			CONF_CM_CACHABLE_ACCELERATED
539
540		CONFIG_SYS_XWAY_EBU_BOOTCFG
541
542		Special option for Lantiq XWAY SoCs for booting from NOR flash.
543		See also arch/mips/cpu/mips32/start.S.
544
545		CONFIG_XWAY_SWAP_BYTES
546
547		Enable compilation of tools/xway-swap-bytes needed for Lantiq
548		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
549		be swapped if a flash programmer is used.
550
551- ARM options:
552		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
553
554		Select high exception vectors of the ARM core, e.g., do not
555		clear the V bit of the c1 register of CP15.
556
557		CONFIG_SYS_THUMB_BUILD
558
559		Use this flag to build U-Boot using the Thumb instruction
560		set for ARM architectures. Thumb instruction set provides
561		better code density. For ARM architectures that support
562		Thumb2 this flag will result in Thumb2 code generated by
563		GCC.
564
565		CONFIG_ARM_ERRATA_716044
566		CONFIG_ARM_ERRATA_742230
567		CONFIG_ARM_ERRATA_743622
568		CONFIG_ARM_ERRATA_751472
569		CONFIG_ARM_ERRATA_794072
570		CONFIG_ARM_ERRATA_761320
571
572		If set, the workarounds for these ARM errata are applied early
573		during U-Boot startup. Note that these options force the
574		workarounds to be applied; no CPU-type/version detection
575		exists, unlike the similar options in the Linux kernel. Do not
576		set these options unless they apply!
577
578- CPU timer options:
579		CONFIG_SYS_HZ
580
581		The frequency of the timer returned by get_timer().
582		get_timer() must operate in milliseconds and this CONFIG
583		option must be set to 1000.
584
585- Linux Kernel Interface:
586		CONFIG_CLOCKS_IN_MHZ
587
588		U-Boot stores all clock information in Hz
589		internally. For binary compatibility with older Linux
590		kernels (which expect the clocks passed in the
591		bd_info data to be in MHz) the environment variable
592		"clocks_in_mhz" can be defined so that U-Boot
593		converts clock data to MHZ before passing it to the
594		Linux kernel.
595		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
596		"clocks_in_mhz=1" is automatically included in the
597		default environment.
598
599		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
600
601		When transferring memsize parameter to linux, some versions
602		expect it to be in bytes, others in MB.
603		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
604
605		CONFIG_OF_LIBFDT
606
607		New kernel versions are expecting firmware settings to be
608		passed using flattened device trees (based on open firmware
609		concepts).
610
611		CONFIG_OF_LIBFDT
612		 * New libfdt-based support
613		 * Adds the "fdt" command
614		 * The bootm command automatically updates the fdt
615
616		OF_CPU - The proper name of the cpus node (only required for
617			MPC512X and MPC5xxx based boards).
618		OF_SOC - The proper name of the soc node (only required for
619			MPC512X and MPC5xxx based boards).
620		OF_TBCLK - The timebase frequency.
621		OF_STDOUT_PATH - The path to the console device
622
623		boards with QUICC Engines require OF_QE to set UCC MAC
624		addresses
625
626		CONFIG_OF_BOARD_SETUP
627
628		Board code has addition modification that it wants to make
629		to the flat device tree before handing it off to the kernel
630
631		CONFIG_OF_BOOT_CPU
632
633		This define fills in the correct boot CPU in the boot
634		param header, the default value is zero if undefined.
635
636		CONFIG_OF_IDE_FIXUP
637
638		U-Boot can detect if an IDE device is present or not.
639		If not, and this new config option is activated, U-Boot
640		removes the ATA node from the DTS before booting Linux,
641		so the Linux IDE driver does not probe the device and
642		crash. This is needed for buggy hardware (uc101) where
643		no pull down resistor is connected to the signal IDE5V_DD7.
644
645		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
646
647		This setting is mandatory for all boards that have only one
648		machine type and must be used to specify the machine type
649		number as it appears in the ARM machine registry
650		(see http://www.arm.linux.org.uk/developer/machines/).
651		Only boards that have multiple machine types supported
652		in a single configuration file and the machine type is
653		runtime discoverable, do not have to use this setting.
654
655- vxWorks boot parameters:
656
657		bootvx constructs a valid bootline using the following
658		environments variables: bootfile, ipaddr, serverip, hostname.
659		It loads the vxWorks image pointed bootfile.
660
661		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
662		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
663		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
664		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
665
666		CONFIG_SYS_VXWORKS_ADD_PARAMS
667
668		Add it at the end of the bootline. E.g "u=username pw=secret"
669
670		Note: If a "bootargs" environment is defined, it will overwride
671		the defaults discussed just above.
672
673- Cache Configuration:
674		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
675		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
676		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
677
678- Cache Configuration for ARM:
679		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
680				      controller
681		CONFIG_SYS_PL310_BASE - Physical base address of PL310
682					controller register space
683
684- Serial Ports:
685		CONFIG_PL010_SERIAL
686
687		Define this if you want support for Amba PrimeCell PL010 UARTs.
688
689		CONFIG_PL011_SERIAL
690
691		Define this if you want support for Amba PrimeCell PL011 UARTs.
692
693		CONFIG_PL011_CLOCK
694
695		If you have Amba PrimeCell PL011 UARTs, set this variable to
696		the clock speed of the UARTs.
697
698		CONFIG_PL01x_PORTS
699
700		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
701		define this to a list of base addresses for each (supported)
702		port. See e.g. include/configs/versatile.h
703
704		CONFIG_PL011_SERIAL_RLCR
705
706		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
707		have separate receive and transmit line control registers.  Set
708		this variable to initialize the extra register.
709
710		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
711
712		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
713		boot loader that has already initialized the UART.  Define this
714		variable to flush the UART at init time.
715
716
717- Console Interface:
718		Depending on board, define exactly one serial port
719		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
720		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
721		console by defining CONFIG_8xx_CONS_NONE
722
723		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
724		port routines must be defined elsewhere
725		(i.e. serial_init(), serial_getc(), ...)
726
727		CONFIG_CFB_CONSOLE
728		Enables console device for a color framebuffer. Needs following
729		defines (cf. smiLynxEM, i8042)
730			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
731						(default big endian)
732			VIDEO_HW_RECTFILL	graphic chip supports
733						rectangle fill
734						(cf. smiLynxEM)
735			VIDEO_HW_BITBLT		graphic chip supports
736						bit-blit (cf. smiLynxEM)
737			VIDEO_VISIBLE_COLS	visible pixel columns
738						(cols=pitch)
739			VIDEO_VISIBLE_ROWS	visible pixel rows
740			VIDEO_PIXEL_SIZE	bytes per pixel
741			VIDEO_DATA_FORMAT	graphic data format
742						(0-5, cf. cfb_console.c)
743			VIDEO_FB_ADRS		framebuffer address
744			VIDEO_KBD_INIT_FCT	keyboard int fct
745						(i.e. i8042_kbd_init())
746			VIDEO_TSTC_FCT		test char fct
747						(i.e. i8042_tstc)
748			VIDEO_GETC_FCT		get char fct
749						(i.e. i8042_getc)
750			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
751						(requires blink timer
752						cf. i8042.c)
753			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
754			CONFIG_CONSOLE_TIME	display time/date info in
755						upper right corner
756						(requires CONFIG_CMD_DATE)
757			CONFIG_VIDEO_LOGO	display Linux logo in
758						upper left corner
759			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
760						linux_logo.h for logo.
761						Requires CONFIG_VIDEO_LOGO
762			CONFIG_CONSOLE_EXTRA_INFO
763						additional board info beside
764						the logo
765
766		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
767		a limited number of ANSI escape sequences (cursor control,
768		erase functions and limited graphics rendition control).
769
770		When CONFIG_CFB_CONSOLE is defined, video console is
771		default i/o. Serial console can be forced with
772		environment 'console=serial'.
773
774		When CONFIG_SILENT_CONSOLE is defined, all console
775		messages (by U-Boot and Linux!) can be silenced with
776		the "silent" environment variable. See
777		doc/README.silent for more information.
778
779		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
780			is 0x00.
781		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
782			is 0xa0.
783
784- Console Baudrate:
785		CONFIG_BAUDRATE - in bps
786		Select one of the baudrates listed in
787		CONFIG_SYS_BAUDRATE_TABLE, see below.
788		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
789
790- Console Rx buffer length
791		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
792		the maximum receive buffer length for the SMC.
793		This option is actual only for 82xx and 8xx possible.
794		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
795		must be defined, to setup the maximum idle timeout for
796		the SMC.
797
798- Pre-Console Buffer:
799		Prior to the console being initialised (i.e. serial UART
800		initialised etc) all console output is silently discarded.
801		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
802		buffer any console messages prior to the console being
803		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
804		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
805		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
806		bytes are output before the console is initialised, the
807		earlier bytes are discarded.
808
809		'Sane' compilers will generate smaller code if
810		CONFIG_PRE_CON_BUF_SZ is a power of 2
811
812- Safe printf() functions
813		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
814		the printf() functions. These are defined in
815		include/vsprintf.h and include snprintf(), vsnprintf() and
816		so on. Code size increase is approximately 300-500 bytes.
817		If this option is not given then these functions will
818		silently discard their buffer size argument - this means
819		you are not getting any overflow checking in this case.
820
821- Boot Delay:	CONFIG_BOOTDELAY - in seconds
822		Delay before automatically booting the default image;
823		set to -1 to disable autoboot.
824		set to -2 to autoboot with no delay and not check for abort
825		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
826
827		See doc/README.autoboot for these options that
828		work with CONFIG_BOOTDELAY. None are required.
829		CONFIG_BOOT_RETRY_TIME
830		CONFIG_BOOT_RETRY_MIN
831		CONFIG_AUTOBOOT_KEYED
832		CONFIG_AUTOBOOT_PROMPT
833		CONFIG_AUTOBOOT_DELAY_STR
834		CONFIG_AUTOBOOT_STOP_STR
835		CONFIG_AUTOBOOT_DELAY_STR2
836		CONFIG_AUTOBOOT_STOP_STR2
837		CONFIG_ZERO_BOOTDELAY_CHECK
838		CONFIG_RESET_TO_RETRY
839
840- Autoboot Command:
841		CONFIG_BOOTCOMMAND
842		Only needed when CONFIG_BOOTDELAY is enabled;
843		define a command string that is automatically executed
844		when no character is read on the console interface
845		within "Boot Delay" after reset.
846
847		CONFIG_BOOTARGS
848		This can be used to pass arguments to the bootm
849		command. The value of CONFIG_BOOTARGS goes into the
850		environment value "bootargs".
851
852		CONFIG_RAMBOOT and CONFIG_NFSBOOT
853		The value of these goes into the environment as
854		"ramboot" and "nfsboot" respectively, and can be used
855		as a convenience, when switching between booting from
856		RAM and NFS.
857
858- Bootcount:
859		CONFIG_BOOTCOUNT_LIMIT
860		Implements a mechanism for detecting a repeating reboot
861		cycle, see:
862		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
863
864		CONFIG_BOOTCOUNT_ENV
865		If no softreset save registers are found on the hardware
866		"bootcount" is stored in the environment. To prevent a
867		saveenv on all reboots, the environment variable
868		"upgrade_available" is used. If "upgrade_available" is
869		0, "bootcount" is always 0, if "upgrade_available" is
870		1 "bootcount" is incremented in the environment.
871		So the Userspace Applikation must set the "upgrade_available"
872		and "bootcount" variable to 0, if a boot was successfully.
873
874- Pre-Boot Commands:
875		CONFIG_PREBOOT
876
877		When this option is #defined, the existence of the
878		environment variable "preboot" will be checked
879		immediately before starting the CONFIG_BOOTDELAY
880		countdown and/or running the auto-boot command resp.
881		entering interactive mode.
882
883		This feature is especially useful when "preboot" is
884		automatically generated or modified. For an example
885		see the LWMON board specific code: here "preboot" is
886		modified when the user holds down a certain
887		combination of keys on the (special) keyboard when
888		booting the systems
889
890- Serial Download Echo Mode:
891		CONFIG_LOADS_ECHO
892		If defined to 1, all characters received during a
893		serial download (using the "loads" command) are
894		echoed back. This might be needed by some terminal
895		emulations (like "cu"), but may as well just take
896		time on others. This setting #define's the initial
897		value of the "loads_echo" environment variable.
898
899- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
900		CONFIG_KGDB_BAUDRATE
901		Select one of the baudrates listed in
902		CONFIG_SYS_BAUDRATE_TABLE, see below.
903
904- Monitor Functions:
905		Monitor commands can be included or excluded
906		from the build by using the #include files
907		<config_cmd_all.h> and #undef'ing unwanted
908		commands, or using <config_cmd_default.h>
909		and augmenting with additional #define's
910		for wanted commands.
911
912		The default command configuration includes all commands
913		except those marked below with a "*".
914
915		CONFIG_CMD_ASKENV	* ask for env variable
916		CONFIG_CMD_BDI		  bdinfo
917		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
918		CONFIG_CMD_BMP		* BMP support
919		CONFIG_CMD_BSP		* Board specific commands
920		CONFIG_CMD_BOOTD	  bootd
921		CONFIG_CMD_CACHE	* icache, dcache
922		CONFIG_CMD_CLK   	* clock command support
923		CONFIG_CMD_CONSOLE	  coninfo
924		CONFIG_CMD_CRC32	* crc32
925		CONFIG_CMD_DATE		* support for RTC, date/time...
926		CONFIG_CMD_DHCP		* DHCP support
927		CONFIG_CMD_DIAG		* Diagnostics
928		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
929		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
930		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
931		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
932		CONFIG_CMD_DTT		* Digital Therm and Thermostat
933		CONFIG_CMD_ECHO		  echo arguments
934		CONFIG_CMD_EDITENV	  edit env variable
935		CONFIG_CMD_EEPROM	* EEPROM read/write support
936		CONFIG_CMD_ELF		* bootelf, bootvx
937		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
938		CONFIG_CMD_ENV_FLAGS	* display details about env flags
939		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
940		CONFIG_CMD_EXPORTENV	* export the environment
941		CONFIG_CMD_EXT2		* ext2 command support
942		CONFIG_CMD_EXT4		* ext4 command support
943		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
944					  that work for multiple fs types
945		CONFIG_CMD_SAVEENV	  saveenv
946		CONFIG_CMD_FDC		* Floppy Disk Support
947		CONFIG_CMD_FAT		* FAT command support
948		CONFIG_CMD_FLASH	  flinfo, erase, protect
949		CONFIG_CMD_FPGA		  FPGA device initialization support
950		CONFIG_CMD_FUSE		* Device fuse support
951		CONFIG_CMD_GETTIME	* Get time since boot
952		CONFIG_CMD_GO		* the 'go' command (exec code)
953		CONFIG_CMD_GREPENV	* search environment
954		CONFIG_CMD_HASH		* calculate hash / digest
955		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
956		CONFIG_CMD_I2C		* I2C serial bus support
957		CONFIG_CMD_IDE		* IDE harddisk support
958		CONFIG_CMD_IMI		  iminfo
959		CONFIG_CMD_IMLS		  List all images found in NOR flash
960		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
961		CONFIG_CMD_IMMAP	* IMMR dump support
962		CONFIG_CMD_IMPORTENV	* import an environment
963		CONFIG_CMD_INI		* import data from an ini file into the env
964		CONFIG_CMD_IRQ		* irqinfo
965		CONFIG_CMD_ITEST	  Integer/string test of 2 values
966		CONFIG_CMD_JFFS2	* JFFS2 Support
967		CONFIG_CMD_KGDB		* kgdb
968		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
969		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
970					  (169.254.*.*)
971		CONFIG_CMD_LOADB	  loadb
972		CONFIG_CMD_LOADS	  loads
973		CONFIG_CMD_MD5SUM	* print md5 message digest
974					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
975		CONFIG_CMD_MEMINFO	* Display detailed memory information
976		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
977					  loop, loopw
978		CONFIG_CMD_MEMTEST	* mtest
979		CONFIG_CMD_MISC		  Misc functions like sleep etc
980		CONFIG_CMD_MMC		* MMC memory mapped support
981		CONFIG_CMD_MII		* MII utility commands
982		CONFIG_CMD_MTDPARTS	* MTD partition support
983		CONFIG_CMD_NAND		* NAND support
984		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
985		CONFIG_CMD_NFS		  NFS support
986		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
987		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
988		CONFIG_CMD_PCI		* pciinfo
989		CONFIG_CMD_PCMCIA		* PCMCIA support
990		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
991					  host
992		CONFIG_CMD_PORTIO	* Port I/O
993		CONFIG_CMD_READ		* Read raw data from partition
994		CONFIG_CMD_REGINFO	* Register dump
995		CONFIG_CMD_RUN		  run command in env variable
996		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
997		CONFIG_CMD_SAVES	* save S record dump
998		CONFIG_CMD_SCSI		* SCSI Support
999		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1000					  (requires CONFIG_CMD_I2C)
1001		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1002					  (4xx only)
1003		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1004		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1005					  (requires CONFIG_CMD_MEMORY)
1006		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1007		CONFIG_CMD_SOURCE	  "source" command Support
1008		CONFIG_CMD_SPI		* SPI serial bus support
1009		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1010		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1011		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1012		CONFIG_CMD_TIMER	* access to the system tick timer
1013		CONFIG_CMD_USB		* USB support
1014		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1015		CONFIG_CMD_MFSL		* Microblaze FSL support
1016		CONFIG_CMD_XIMG		  Load part of Multi Image
1017		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1018
1019		EXAMPLE: If you want all functions except of network
1020		support you can write:
1021
1022		#include "config_cmd_all.h"
1023		#undef CONFIG_CMD_NET
1024
1025	Other Commands:
1026		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1027
1028	Note:	Don't enable the "icache" and "dcache" commands
1029		(configuration option CONFIG_CMD_CACHE) unless you know
1030		what you (and your U-Boot users) are doing. Data
1031		cache cannot be enabled on systems like the 8xx or
1032		8260 (where accesses to the IMMR region must be
1033		uncached), and it cannot be disabled on all other
1034		systems where we (mis-) use the data cache to hold an
1035		initial stack and some data.
1036
1037
1038		XXX - this list needs to get updated!
1039
1040- Regular expression support:
1041		CONFIG_REGEX
1042		If this variable is defined, U-Boot is linked against
1043		the SLRE (Super Light Regular Expression) library,
1044		which adds regex support to some commands, as for
1045		example "env grep" and "setexpr".
1046
1047- Device tree:
1048		CONFIG_OF_CONTROL
1049		If this variable is defined, U-Boot will use a device tree
1050		to configure its devices, instead of relying on statically
1051		compiled #defines in the board file. This option is
1052		experimental and only available on a few boards. The device
1053		tree is available in the global data as gd->fdt_blob.
1054
1055		U-Boot needs to get its device tree from somewhere. This can
1056		be done using one of the two options below:
1057
1058		CONFIG_OF_EMBED
1059		If this variable is defined, U-Boot will embed a device tree
1060		binary in its image. This device tree file should be in the
1061		board directory and called <soc>-<board>.dts. The binary file
1062		is then picked up in board_init_f() and made available through
1063		the global data structure as gd->blob.
1064
1065		CONFIG_OF_SEPARATE
1066		If this variable is defined, U-Boot will build a device tree
1067		binary. It will be called u-boot.dtb. Architecture-specific
1068		code will locate it at run-time. Generally this works by:
1069
1070			cat u-boot.bin u-boot.dtb >image.bin
1071
1072		and in fact, U-Boot does this for you, creating a file called
1073		u-boot-dtb.bin which is useful in the common case. You can
1074		still use the individual files if you need something more
1075		exotic.
1076
1077- Watchdog:
1078		CONFIG_WATCHDOG
1079		If this variable is defined, it enables watchdog
1080		support for the SoC. There must be support in the SoC
1081		specific code for a watchdog. For the 8xx and 8260
1082		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1083		register.  When supported for a specific SoC is
1084		available, then no further board specific code should
1085		be needed to use it.
1086
1087		CONFIG_HW_WATCHDOG
1088		When using a watchdog circuitry external to the used
1089		SoC, then define this variable and provide board
1090		specific code for the "hw_watchdog_reset" function.
1091
1092- U-Boot Version:
1093		CONFIG_VERSION_VARIABLE
1094		If this variable is defined, an environment variable
1095		named "ver" is created by U-Boot showing the U-Boot
1096		version as printed by the "version" command.
1097		Any change to this variable will be reverted at the
1098		next reset.
1099
1100- Real-Time Clock:
1101
1102		When CONFIG_CMD_DATE is selected, the type of the RTC
1103		has to be selected, too. Define exactly one of the
1104		following options:
1105
1106		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1107		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1108		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1109		CONFIG_RTC_MC146818	- use MC146818 RTC
1110		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1111		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1112		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1113		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1114		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1115		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1116		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1117		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1118					  RV3029 RTC.
1119
1120		Note that if the RTC uses I2C, then the I2C interface
1121		must also be configured. See I2C Support, below.
1122
1123- GPIO Support:
1124		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1125
1126		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1127		chip-ngpio pairs that tell the PCA953X driver the number of
1128		pins supported by a particular chip.
1129
1130		Note that if the GPIO device uses I2C, then the I2C interface
1131		must also be configured. See I2C Support, below.
1132
1133- Timestamp Support:
1134
1135		When CONFIG_TIMESTAMP is selected, the timestamp
1136		(date and time) of an image is printed by image
1137		commands like bootm or iminfo. This option is
1138		automatically enabled when you select CONFIG_CMD_DATE .
1139
1140- Partition Labels (disklabels) Supported:
1141		Zero or more of the following:
1142		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1143		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1144				       Intel architecture, USB sticks, etc.
1145		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1146		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1147				       bootloader.  Note 2TB partition limit; see
1148				       disk/part_efi.c
1149		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1150
1151		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1152		CONFIG_CMD_SCSI) you must configure support for at
1153		least one non-MTD partition type as well.
1154
1155- IDE Reset method:
1156		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1157		board configurations files but used nowhere!
1158
1159		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1160		be performed by calling the function
1161			ide_set_reset(int reset)
1162		which has to be defined in a board specific file
1163
1164- ATAPI Support:
1165		CONFIG_ATAPI
1166
1167		Set this to enable ATAPI support.
1168
1169- LBA48 Support
1170		CONFIG_LBA48
1171
1172		Set this to enable support for disks larger than 137GB
1173		Also look at CONFIG_SYS_64BIT_LBA.
1174		Whithout these , LBA48 support uses 32bit variables and will 'only'
1175		support disks up to 2.1TB.
1176
1177		CONFIG_SYS_64BIT_LBA:
1178			When enabled, makes the IDE subsystem use 64bit sector addresses.
1179			Default is 32bit.
1180
1181- SCSI Support:
1182		At the moment only there is only support for the
1183		SYM53C8XX SCSI controller; define
1184		CONFIG_SCSI_SYM53C8XX to enable it.
1185
1186		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1187		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1188		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1189		maximum numbers of LUNs, SCSI ID's and target
1190		devices.
1191		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1192
1193		The environment variable 'scsidevs' is set to the number of
1194		SCSI devices found during the last scan.
1195
1196- NETWORK Support (PCI):
1197		CONFIG_E1000
1198		Support for Intel 8254x/8257x gigabit chips.
1199
1200		CONFIG_E1000_SPI
1201		Utility code for direct access to the SPI bus on Intel 8257x.
1202		This does not do anything useful unless you set at least one
1203		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1204
1205		CONFIG_E1000_SPI_GENERIC
1206		Allow generic access to the SPI bus on the Intel 8257x, for
1207		example with the "sspi" command.
1208
1209		CONFIG_CMD_E1000
1210		Management command for E1000 devices.  When used on devices
1211		with SPI support you can reprogram the EEPROM from U-Boot.
1212
1213		CONFIG_E1000_FALLBACK_MAC
1214		default MAC for empty EEPROM after production.
1215
1216		CONFIG_EEPRO100
1217		Support for Intel 82557/82559/82559ER chips.
1218		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1219		write routine for first time initialisation.
1220
1221		CONFIG_TULIP
1222		Support for Digital 2114x chips.
1223		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1224		modem chip initialisation (KS8761/QS6611).
1225
1226		CONFIG_NATSEMI
1227		Support for National dp83815 chips.
1228
1229		CONFIG_NS8382X
1230		Support for National dp8382[01] gigabit chips.
1231
1232- NETWORK Support (other):
1233
1234		CONFIG_DRIVER_AT91EMAC
1235		Support for AT91RM9200 EMAC.
1236
1237			CONFIG_RMII
1238			Define this to use reduced MII inteface
1239
1240			CONFIG_DRIVER_AT91EMAC_QUIET
1241			If this defined, the driver is quiet.
1242			The driver doen't show link status messages.
1243
1244		CONFIG_CALXEDA_XGMAC
1245		Support for the Calxeda XGMAC device
1246
1247		CONFIG_LAN91C96
1248		Support for SMSC's LAN91C96 chips.
1249
1250			CONFIG_LAN91C96_BASE
1251			Define this to hold the physical address
1252			of the LAN91C96's I/O space
1253
1254			CONFIG_LAN91C96_USE_32_BIT
1255			Define this to enable 32 bit addressing
1256
1257		CONFIG_SMC91111
1258		Support for SMSC's LAN91C111 chip
1259
1260			CONFIG_SMC91111_BASE
1261			Define this to hold the physical address
1262			of the device (I/O space)
1263
1264			CONFIG_SMC_USE_32_BIT
1265			Define this if data bus is 32 bits
1266
1267			CONFIG_SMC_USE_IOFUNCS
1268			Define this to use i/o functions instead of macros
1269			(some hardware wont work with macros)
1270
1271		CONFIG_DRIVER_TI_EMAC
1272		Support for davinci emac
1273
1274			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1275			Define this if you have more then 3 PHYs.
1276
1277		CONFIG_FTGMAC100
1278		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1279
1280			CONFIG_FTGMAC100_EGIGA
1281			Define this to use GE link update with gigabit PHY.
1282			Define this if FTGMAC100 is connected to gigabit PHY.
1283			If your system has 10/100 PHY only, it might not occur
1284			wrong behavior. Because PHY usually return timeout or
1285			useless data when polling gigabit status and gigabit
1286			control registers. This behavior won't affect the
1287			correctnessof 10/100 link speed update.
1288
1289		CONFIG_SMC911X
1290		Support for SMSC's LAN911x and LAN921x chips
1291
1292			CONFIG_SMC911X_BASE
1293			Define this to hold the physical address
1294			of the device (I/O space)
1295
1296			CONFIG_SMC911X_32_BIT
1297			Define this if data bus is 32 bits
1298
1299			CONFIG_SMC911X_16_BIT
1300			Define this if data bus is 16 bits. If your processor
1301			automatically converts one 32 bit word to two 16 bit
1302			words you may also try CONFIG_SMC911X_32_BIT.
1303
1304		CONFIG_SH_ETHER
1305		Support for Renesas on-chip Ethernet controller
1306
1307			CONFIG_SH_ETHER_USE_PORT
1308			Define the number of ports to be used
1309
1310			CONFIG_SH_ETHER_PHY_ADDR
1311			Define the ETH PHY's address
1312
1313			CONFIG_SH_ETHER_CACHE_WRITEBACK
1314			If this option is set, the driver enables cache flush.
1315
1316- TPM Support:
1317		CONFIG_TPM
1318		Support TPM devices.
1319
1320		CONFIG_TPM_TIS_I2C
1321		Support for i2c bus TPM devices. Only one device
1322		per system is supported at this time.
1323
1324			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1325			Define the the i2c bus number for the TPM device
1326
1327			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1328			Define the TPM's address on the i2c bus
1329
1330			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1331			Define the burst count bytes upper limit
1332
1333		CONFIG_TPM_ATMEL_TWI
1334		Support for Atmel TWI TPM device. Requires I2C support.
1335
1336		CONFIG_TPM_TIS_LPC
1337		Support for generic parallel port TPM devices. Only one device
1338		per system is supported at this time.
1339
1340			CONFIG_TPM_TIS_BASE_ADDRESS
1341			Base address where the generic TPM device is mapped
1342			to. Contemporary x86 systems usually map it at
1343			0xfed40000.
1344
1345		CONFIG_CMD_TPM
1346		Add tpm monitor functions.
1347		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1348		provides monitor access to authorized functions.
1349
1350		CONFIG_TPM
1351		Define this to enable the TPM support library which provides
1352		functional interfaces to some TPM commands.
1353		Requires support for a TPM device.
1354
1355		CONFIG_TPM_AUTH_SESSIONS
1356		Define this to enable authorized functions in the TPM library.
1357		Requires CONFIG_TPM and CONFIG_SHA1.
1358
1359- USB Support:
1360		At the moment only the UHCI host controller is
1361		supported (PIP405, MIP405, MPC5200); define
1362		CONFIG_USB_UHCI to enable it.
1363		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1364		and define CONFIG_USB_STORAGE to enable the USB
1365		storage devices.
1366		Note:
1367		Supported are USB Keyboards and USB Floppy drives
1368		(TEAC FD-05PUB).
1369		MPC5200 USB requires additional defines:
1370			CONFIG_USB_CLOCK
1371				for 528 MHz Clock: 0x0001bbbb
1372			CONFIG_PSC3_USB
1373				for USB on PSC3
1374			CONFIG_USB_CONFIG
1375				for differential drivers: 0x00001000
1376				for single ended drivers: 0x00005000
1377				for differential drivers on PSC3: 0x00000100
1378				for single ended drivers on PSC3: 0x00004100
1379			CONFIG_SYS_USB_EVENT_POLL
1380				May be defined to allow interrupt polling
1381				instead of using asynchronous interrupts
1382
1383		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1384		txfilltuning field in the EHCI controller on reset.
1385
1386		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1387		interval for usb hub power-on delay.(minimum 100msec)
1388
1389- USB Device:
1390		Define the below if you wish to use the USB console.
1391		Once firmware is rebuilt from a serial console issue the
1392		command "setenv stdin usbtty; setenv stdout usbtty" and
1393		attach your USB cable. The Unix command "dmesg" should print
1394		it has found a new device. The environment variable usbtty
1395		can be set to gserial or cdc_acm to enable your device to
1396		appear to a USB host as a Linux gserial device or a
1397		Common Device Class Abstract Control Model serial device.
1398		If you select usbtty = gserial you should be able to enumerate
1399		a Linux host by
1400		# modprobe usbserial vendor=0xVendorID product=0xProductID
1401		else if using cdc_acm, simply setting the environment
1402		variable usbtty to be cdc_acm should suffice. The following
1403		might be defined in YourBoardName.h
1404
1405			CONFIG_USB_DEVICE
1406			Define this to build a UDC device
1407
1408			CONFIG_USB_TTY
1409			Define this to have a tty type of device available to
1410			talk to the UDC device
1411
1412			CONFIG_USBD_HS
1413			Define this to enable the high speed support for usb
1414			device and usbtty. If this feature is enabled, a routine
1415			int is_usbd_high_speed(void)
1416			also needs to be defined by the driver to dynamically poll
1417			whether the enumeration has succeded at high speed or full
1418			speed.
1419
1420			CONFIG_SYS_CONSOLE_IS_IN_ENV
1421			Define this if you want stdin, stdout &/or stderr to
1422			be set to usbtty.
1423
1424			mpc8xx:
1425				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1426				Derive USB clock from external clock "blah"
1427				- CONFIG_SYS_USB_EXTC_CLK 0x02
1428
1429				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1430				Derive USB clock from brgclk
1431				- CONFIG_SYS_USB_BRG_CLK 0x04
1432
1433		If you have a USB-IF assigned VendorID then you may wish to
1434		define your own vendor specific values either in BoardName.h
1435		or directly in usbd_vendor_info.h. If you don't define
1436		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1437		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1438		should pretend to be a Linux device to it's target host.
1439
1440			CONFIG_USBD_MANUFACTURER
1441			Define this string as the name of your company for
1442			- CONFIG_USBD_MANUFACTURER "my company"
1443
1444			CONFIG_USBD_PRODUCT_NAME
1445			Define this string as the name of your product
1446			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1447
1448			CONFIG_USBD_VENDORID
1449			Define this as your assigned Vendor ID from the USB
1450			Implementors Forum. This *must* be a genuine Vendor ID
1451			to avoid polluting the USB namespace.
1452			- CONFIG_USBD_VENDORID 0xFFFF
1453
1454			CONFIG_USBD_PRODUCTID
1455			Define this as the unique Product ID
1456			for your device
1457			- CONFIG_USBD_PRODUCTID 0xFFFF
1458
1459		Some USB device drivers may need to check USB cable attachment.
1460		In this case you can enable following config in BoardName.h:
1461			CONFIG_USB_CABLE_CHECK
1462			This enables function definition:
1463			- usb_cable_connected() in include/usb.h
1464			Implementation of this function is board-specific.
1465
1466- ULPI Layer Support:
1467		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1468		the generic ULPI layer. The generic layer accesses the ULPI PHY
1469		via the platform viewport, so you need both the genric layer and
1470		the viewport enabled. Currently only Chipidea/ARC based
1471		viewport is supported.
1472		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1473		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1474		If your ULPI phy needs a different reference clock than the
1475		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1476		the appropriate value in Hz.
1477
1478- MMC Support:
1479		The MMC controller on the Intel PXA is supported. To
1480		enable this define CONFIG_MMC. The MMC can be
1481		accessed from the boot prompt by mapping the device
1482		to physical memory similar to flash. Command line is
1483		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1484		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1485
1486		CONFIG_SH_MMCIF
1487		Support for Renesas on-chip MMCIF controller
1488
1489			CONFIG_SH_MMCIF_ADDR
1490			Define the base address of MMCIF registers
1491
1492			CONFIG_SH_MMCIF_CLK
1493			Define the clock frequency for MMCIF
1494
1495- USB Device Firmware Update (DFU) class support:
1496		CONFIG_DFU_FUNCTION
1497		This enables the USB portion of the DFU USB class
1498
1499		CONFIG_CMD_DFU
1500		This enables the command "dfu" which is used to have
1501		U-Boot create a DFU class device via USB.  This command
1502		requires that the "dfu_alt_info" environment variable be
1503		set and define the alt settings to expose to the host.
1504
1505		CONFIG_DFU_MMC
1506		This enables support for exposing (e)MMC devices via DFU.
1507
1508		CONFIG_DFU_NAND
1509		This enables support for exposing NAND devices via DFU.
1510
1511		CONFIG_DFU_RAM
1512		This enables support for exposing RAM via DFU.
1513		Note: DFU spec refer to non-volatile memory usage, but
1514		allow usages beyond the scope of spec - here RAM usage,
1515		one that would help mostly the developer.
1516
1517		CONFIG_SYS_DFU_DATA_BUF_SIZE
1518		Dfu transfer uses a buffer before writing data to the
1519		raw storage device. Make the size (in bytes) of this buffer
1520		configurable. The size of this buffer is also configurable
1521		through the "dfu_bufsiz" environment variable.
1522
1523		CONFIG_SYS_DFU_MAX_FILE_SIZE
1524		When updating files rather than the raw storage device,
1525		we use a static buffer to copy the file into and then write
1526		the buffer once we've been given the whole file.  Define
1527		this to the maximum filesize (in bytes) for the buffer.
1528		Default is 4 MiB if undefined.
1529
1530		DFU_DEFAULT_POLL_TIMEOUT
1531		Poll timeout [ms], is the timeout a device can send to the
1532		host. The host must wait for this timeout before sending
1533		a subsequent DFU_GET_STATUS request to the device.
1534
1535		DFU_MANIFEST_POLL_TIMEOUT
1536		Poll timeout [ms], which the device sends to the host when
1537		entering dfuMANIFEST state. Host waits this timeout, before
1538		sending again an USB request to the device.
1539
1540- Journaling Flash filesystem support:
1541		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1542		CONFIG_JFFS2_NAND_DEV
1543		Define these for a default partition on a NAND device
1544
1545		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1546		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1547		Define these for a default partition on a NOR device
1548
1549		CONFIG_SYS_JFFS_CUSTOM_PART
1550		Define this to create an own partition. You have to provide a
1551		function struct part_info* jffs2_part_info(int part_num)
1552
1553		If you define only one JFFS2 partition you may also want to
1554		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1555		to disable the command chpart. This is the default when you
1556		have not defined a custom partition
1557
1558- FAT(File Allocation Table) filesystem write function support:
1559		CONFIG_FAT_WRITE
1560
1561		Define this to enable support for saving memory data as a
1562		file in FAT formatted partition.
1563
1564		This will also enable the command "fatwrite" enabling the
1565		user to write files to FAT.
1566
1567CBFS (Coreboot Filesystem) support
1568		CONFIG_CMD_CBFS
1569
1570		Define this to enable support for reading from a Coreboot
1571		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1572		and cbfsload.
1573
1574- Keyboard Support:
1575		CONFIG_ISA_KEYBOARD
1576
1577		Define this to enable standard (PC-Style) keyboard
1578		support
1579
1580		CONFIG_I8042_KBD
1581		Standard PC keyboard driver with US (is default) and
1582		GERMAN key layout (switch via environment 'keymap=de') support.
1583		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1584		for cfb_console. Supports cursor blinking.
1585
1586		CONFIG_CROS_EC_KEYB
1587		Enables a Chrome OS keyboard using the CROS_EC interface.
1588		This uses CROS_EC to communicate with a second microcontroller
1589		which provides key scans on request.
1590
1591- Video support:
1592		CONFIG_VIDEO
1593
1594		Define this to enable video support (for output to
1595		video).
1596
1597		CONFIG_VIDEO_CT69000
1598
1599		Enable Chips & Technologies 69000 Video chip
1600
1601		CONFIG_VIDEO_SMI_LYNXEM
1602		Enable Silicon Motion SMI 712/710/810 Video chip. The
1603		video output is selected via environment 'videoout'
1604		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1605		assumed.
1606
1607		For the CT69000 and SMI_LYNXEM drivers, videomode is
1608		selected via environment 'videomode'. Two different ways
1609		are possible:
1610		- "videomode=num"   'num' is a standard LiLo mode numbers.
1611		Following standard modes are supported	(* is default):
1612
1613		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1614		-------------+---------------------------------------------
1615		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1616		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1617		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1618		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1619		-------------+---------------------------------------------
1620		(i.e. setenv videomode 317; saveenv; reset;)
1621
1622		- "videomode=bootargs" all the video parameters are parsed
1623		from the bootargs. (See drivers/video/videomodes.c)
1624
1625
1626		CONFIG_VIDEO_SED13806
1627		Enable Epson SED13806 driver. This driver supports 8bpp
1628		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1629		or CONFIG_VIDEO_SED13806_16BPP
1630
1631		CONFIG_FSL_DIU_FB
1632		Enable the Freescale DIU video driver.	Reference boards for
1633		SOCs that have a DIU should define this macro to enable DIU
1634		support, and should also define these other macros:
1635
1636			CONFIG_SYS_DIU_ADDR
1637			CONFIG_VIDEO
1638			CONFIG_CMD_BMP
1639			CONFIG_CFB_CONSOLE
1640			CONFIG_VIDEO_SW_CURSOR
1641			CONFIG_VGA_AS_SINGLE_DEVICE
1642			CONFIG_VIDEO_LOGO
1643			CONFIG_VIDEO_BMP_LOGO
1644
1645		The DIU driver will look for the 'video-mode' environment
1646		variable, and if defined, enable the DIU as a console during
1647		boot.  See the documentation file README.video for a
1648		description of this variable.
1649
1650		CONFIG_VIDEO_VGA
1651
1652		Enable the VGA video / BIOS for x86. The alternative if you
1653		are using coreboot is to use the coreboot frame buffer
1654		driver.
1655
1656
1657- Keyboard Support:
1658		CONFIG_KEYBOARD
1659
1660		Define this to enable a custom keyboard support.
1661		This simply calls drv_keyboard_init() which must be
1662		defined in your board-specific files.
1663		The only board using this so far is RBC823.
1664
1665- LCD Support:	CONFIG_LCD
1666
1667		Define this to enable LCD support (for output to LCD
1668		display); also select one of the supported displays
1669		by defining one of these:
1670
1671		CONFIG_ATMEL_LCD:
1672
1673			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1674
1675		CONFIG_NEC_NL6448AC33:
1676
1677			NEC NL6448AC33-18. Active, color, single scan.
1678
1679		CONFIG_NEC_NL6448BC20
1680
1681			NEC NL6448BC20-08. 6.5", 640x480.
1682			Active, color, single scan.
1683
1684		CONFIG_NEC_NL6448BC33_54
1685
1686			NEC NL6448BC33-54. 10.4", 640x480.
1687			Active, color, single scan.
1688
1689		CONFIG_SHARP_16x9
1690
1691			Sharp 320x240. Active, color, single scan.
1692			It isn't 16x9, and I am not sure what it is.
1693
1694		CONFIG_SHARP_LQ64D341
1695
1696			Sharp LQ64D341 display, 640x480.
1697			Active, color, single scan.
1698
1699		CONFIG_HLD1045
1700
1701			HLD1045 display, 640x480.
1702			Active, color, single scan.
1703
1704		CONFIG_OPTREX_BW
1705
1706			Optrex	 CBL50840-2 NF-FW 99 22 M5
1707			or
1708			Hitachi	 LMG6912RPFC-00T
1709			or
1710			Hitachi	 SP14Q002
1711
1712			320x240. Black & white.
1713
1714		Normally display is black on white background; define
1715		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1716
1717		CONFIG_LCD_ALIGNMENT
1718
1719		Normally the LCD is page-aligned (tyically 4KB). If this is
1720		defined then the LCD will be aligned to this value instead.
1721		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1722		here, since it is cheaper to change data cache settings on
1723		a per-section basis.
1724
1725		CONFIG_CONSOLE_SCROLL_LINES
1726
1727		When the console need to be scrolled, this is the number of
1728		lines to scroll by. It defaults to 1. Increasing this makes
1729		the console jump but can help speed up operation when scrolling
1730		is slow.
1731
1732		CONFIG_LCD_BMP_RLE8
1733
1734		Support drawing of RLE8-compressed bitmaps on the LCD.
1735
1736		CONFIG_I2C_EDID
1737
1738		Enables an 'i2c edid' command which can read EDID
1739		information over I2C from an attached LCD display.
1740
1741- Splash Screen Support: CONFIG_SPLASH_SCREEN
1742
1743		If this option is set, the environment is checked for
1744		a variable "splashimage". If found, the usual display
1745		of logo, copyright and system information on the LCD
1746		is suppressed and the BMP image at the address
1747		specified in "splashimage" is loaded instead. The
1748		console is redirected to the "nulldev", too. This
1749		allows for a "silent" boot where a splash screen is
1750		loaded very quickly after power-on.
1751
1752		CONFIG_SPLASHIMAGE_GUARD
1753
1754		If this option is set, then U-Boot will prevent the environment
1755		variable "splashimage" from being set to a problematic address
1756		(see README.displaying-bmps).
1757		This option is useful for targets where, due to alignment
1758		restrictions, an improperly aligned BMP image will cause a data
1759		abort. If you think you will not have problems with unaligned
1760		accesses (for example because your toolchain prevents them)
1761		there is no need to set this option.
1762
1763		CONFIG_SPLASH_SCREEN_ALIGN
1764
1765		If this option is set the splash image can be freely positioned
1766		on the screen. Environment variable "splashpos" specifies the
1767		position as "x,y". If a positive number is given it is used as
1768		number of pixel from left/top. If a negative number is given it
1769		is used as number of pixel from right/bottom. You can also
1770		specify 'm' for centering the image.
1771
1772		Example:
1773		setenv splashpos m,m
1774			=> image at center of screen
1775
1776		setenv splashpos 30,20
1777			=> image at x = 30 and y = 20
1778
1779		setenv splashpos -10,m
1780			=> vertically centered image
1781			   at x = dspWidth - bmpWidth - 9
1782
1783- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1784
1785		If this option is set, additionally to standard BMP
1786		images, gzipped BMP images can be displayed via the
1787		splashscreen support or the bmp command.
1788
1789- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1790
1791		If this option is set, 8-bit RLE compressed BMP images
1792		can be displayed via the splashscreen support or the
1793		bmp command.
1794
1795- Do compresssing for memory range:
1796		CONFIG_CMD_ZIP
1797
1798		If this option is set, it would use zlib deflate method
1799		to compress the specified memory at its best effort.
1800
1801- Compression support:
1802		CONFIG_GZIP
1803
1804		Enabled by default to support gzip compressed images.
1805
1806		CONFIG_BZIP2
1807
1808		If this option is set, support for bzip2 compressed
1809		images is included. If not, only uncompressed and gzip
1810		compressed images are supported.
1811
1812		NOTE: the bzip2 algorithm requires a lot of RAM, so
1813		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1814		be at least 4MB.
1815
1816		CONFIG_LZMA
1817
1818		If this option is set, support for lzma compressed
1819		images is included.
1820
1821		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1822		requires an amount of dynamic memory that is given by the
1823		formula:
1824
1825			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1826
1827		Where lc and lp stand for, respectively, Literal context bits
1828		and Literal pos bits.
1829
1830		This value is upper-bounded by 14MB in the worst case. Anyway,
1831		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1832		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1833		a very small buffer.
1834
1835		Use the lzmainfo tool to determinate the lc and lp values and
1836		then calculate the amount of needed dynamic memory (ensuring
1837		the appropriate CONFIG_SYS_MALLOC_LEN value).
1838
1839		CONFIG_LZO
1840
1841		If this option is set, support for LZO compressed images
1842		is included.
1843
1844- MII/PHY support:
1845		CONFIG_PHY_ADDR
1846
1847		The address of PHY on MII bus.
1848
1849		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1850
1851		The clock frequency of the MII bus
1852
1853		CONFIG_PHY_GIGE
1854
1855		If this option is set, support for speed/duplex
1856		detection of gigabit PHY is included.
1857
1858		CONFIG_PHY_RESET_DELAY
1859
1860		Some PHY like Intel LXT971A need extra delay after
1861		reset before any MII register access is possible.
1862		For such PHY, set this option to the usec delay
1863		required. (minimum 300usec for LXT971A)
1864
1865		CONFIG_PHY_CMD_DELAY (ppc4xx)
1866
1867		Some PHY like Intel LXT971A need extra delay after
1868		command issued before MII status register can be read
1869
1870- Ethernet address:
1871		CONFIG_ETHADDR
1872		CONFIG_ETH1ADDR
1873		CONFIG_ETH2ADDR
1874		CONFIG_ETH3ADDR
1875		CONFIG_ETH4ADDR
1876		CONFIG_ETH5ADDR
1877
1878		Define a default value for Ethernet address to use
1879		for the respective Ethernet interface, in case this
1880		is not determined automatically.
1881
1882- IP address:
1883		CONFIG_IPADDR
1884
1885		Define a default value for the IP address to use for
1886		the default Ethernet interface, in case this is not
1887		determined through e.g. bootp.
1888		(Environment variable "ipaddr")
1889
1890- Server IP address:
1891		CONFIG_SERVERIP
1892
1893		Defines a default value for the IP address of a TFTP
1894		server to contact when using the "tftboot" command.
1895		(Environment variable "serverip")
1896
1897		CONFIG_KEEP_SERVERADDR
1898
1899		Keeps the server's MAC address, in the env 'serveraddr'
1900		for passing to bootargs (like Linux's netconsole option)
1901
1902- Gateway IP address:
1903		CONFIG_GATEWAYIP
1904
1905		Defines a default value for the IP address of the
1906		default router where packets to other networks are
1907		sent to.
1908		(Environment variable "gatewayip")
1909
1910- Subnet mask:
1911		CONFIG_NETMASK
1912
1913		Defines a default value for the subnet mask (or
1914		routing prefix) which is used to determine if an IP
1915		address belongs to the local subnet or needs to be
1916		forwarded through a router.
1917		(Environment variable "netmask")
1918
1919- Multicast TFTP Mode:
1920		CONFIG_MCAST_TFTP
1921
1922		Defines whether you want to support multicast TFTP as per
1923		rfc-2090; for example to work with atftp.  Lets lots of targets
1924		tftp down the same boot image concurrently.  Note: the Ethernet
1925		driver in use must provide a function: mcast() to join/leave a
1926		multicast group.
1927
1928- BOOTP Recovery Mode:
1929		CONFIG_BOOTP_RANDOM_DELAY
1930
1931		If you have many targets in a network that try to
1932		boot using BOOTP, you may want to avoid that all
1933		systems send out BOOTP requests at precisely the same
1934		moment (which would happen for instance at recovery
1935		from a power failure, when all systems will try to
1936		boot, thus flooding the BOOTP server. Defining
1937		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1938		inserted before sending out BOOTP requests. The
1939		following delays are inserted then:
1940
1941		1st BOOTP request:	delay 0 ... 1 sec
1942		2nd BOOTP request:	delay 0 ... 2 sec
1943		3rd BOOTP request:	delay 0 ... 4 sec
1944		4th and following
1945		BOOTP requests:		delay 0 ... 8 sec
1946
1947- DHCP Advanced Options:
1948		You can fine tune the DHCP functionality by defining
1949		CONFIG_BOOTP_* symbols:
1950
1951		CONFIG_BOOTP_SUBNETMASK
1952		CONFIG_BOOTP_GATEWAY
1953		CONFIG_BOOTP_HOSTNAME
1954		CONFIG_BOOTP_NISDOMAIN
1955		CONFIG_BOOTP_BOOTPATH
1956		CONFIG_BOOTP_BOOTFILESIZE
1957		CONFIG_BOOTP_DNS
1958		CONFIG_BOOTP_DNS2
1959		CONFIG_BOOTP_SEND_HOSTNAME
1960		CONFIG_BOOTP_NTPSERVER
1961		CONFIG_BOOTP_TIMEOFFSET
1962		CONFIG_BOOTP_VENDOREX
1963		CONFIG_BOOTP_MAY_FAIL
1964
1965		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1966		environment variable, not the BOOTP server.
1967
1968		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1969		after the configured retry count, the call will fail
1970		instead of starting over.  This can be used to fail over
1971		to Link-local IP address configuration if the DHCP server
1972		is not available.
1973
1974		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1975		serverip from a DHCP server, it is possible that more
1976		than one DNS serverip is offered to the client.
1977		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1978		serverip will be stored in the additional environment
1979		variable "dnsip2". The first DNS serverip is always
1980		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1981		is defined.
1982
1983		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1984		to do a dynamic update of a DNS server. To do this, they
1985		need the hostname of the DHCP requester.
1986		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1987		of the "hostname" environment variable is passed as
1988		option 12 to the DHCP server.
1989
1990		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1991
1992		A 32bit value in microseconds for a delay between
1993		receiving a "DHCP Offer" and sending the "DHCP Request".
1994		This fixes a problem with certain DHCP servers that don't
1995		respond 100% of the time to a "DHCP request". E.g. On an
1996		AT91RM9200 processor running at 180MHz, this delay needed
1997		to be *at least* 15,000 usec before a Windows Server 2003
1998		DHCP server would reply 100% of the time. I recommend at
1999		least 50,000 usec to be safe. The alternative is to hope
2000		that one of the retries will be successful but note that
2001		the DHCP timeout and retry process takes a longer than
2002		this delay.
2003
2004 - Link-local IP address negotiation:
2005		Negotiate with other link-local clients on the local network
2006		for an address that doesn't require explicit configuration.
2007		This is especially useful if a DHCP server cannot be guaranteed
2008		to exist in all environments that the device must operate.
2009
2010		See doc/README.link-local for more information.
2011
2012 - CDP Options:
2013		CONFIG_CDP_DEVICE_ID
2014
2015		The device id used in CDP trigger frames.
2016
2017		CONFIG_CDP_DEVICE_ID_PREFIX
2018
2019		A two character string which is prefixed to the MAC address
2020		of the device.
2021
2022		CONFIG_CDP_PORT_ID
2023
2024		A printf format string which contains the ascii name of
2025		the port. Normally is set to "eth%d" which sets
2026		eth0 for the first Ethernet, eth1 for the second etc.
2027
2028		CONFIG_CDP_CAPABILITIES
2029
2030		A 32bit integer which indicates the device capabilities;
2031		0x00000010 for a normal host which does not forwards.
2032
2033		CONFIG_CDP_VERSION
2034
2035		An ascii string containing the version of the software.
2036
2037		CONFIG_CDP_PLATFORM
2038
2039		An ascii string containing the name of the platform.
2040
2041		CONFIG_CDP_TRIGGER
2042
2043		A 32bit integer sent on the trigger.
2044
2045		CONFIG_CDP_POWER_CONSUMPTION
2046
2047		A 16bit integer containing the power consumption of the
2048		device in .1 of milliwatts.
2049
2050		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2051
2052		A byte containing the id of the VLAN.
2053
2054- Status LED:	CONFIG_STATUS_LED
2055
2056		Several configurations allow to display the current
2057		status using a LED. For instance, the LED will blink
2058		fast while running U-Boot code, stop blinking as
2059		soon as a reply to a BOOTP request was received, and
2060		start blinking slow once the Linux kernel is running
2061		(supported by a status LED driver in the Linux
2062		kernel). Defining CONFIG_STATUS_LED enables this
2063		feature in U-Boot.
2064
2065		Additional options:
2066
2067		CONFIG_GPIO_LED
2068		The status LED can be connected to a GPIO pin.
2069		In such cases, the gpio_led driver can be used as a
2070		status LED backend implementation. Define CONFIG_GPIO_LED
2071		to include the gpio_led driver in the U-Boot binary.
2072
2073		CONFIG_GPIO_LED_INVERTED_TABLE
2074		Some GPIO connected LEDs may have inverted polarity in which
2075		case the GPIO high value corresponds to LED off state and
2076		GPIO low value corresponds to LED on state.
2077		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2078		with a list of GPIO LEDs that have inverted polarity.
2079
2080- CAN Support:	CONFIG_CAN_DRIVER
2081
2082		Defining CONFIG_CAN_DRIVER enables CAN driver support
2083		on those systems that support this (optional)
2084		feature, like the TQM8xxL modules.
2085
2086- I2C Support:	CONFIG_SYS_I2C
2087
2088		This enable the NEW i2c subsystem, and will allow you to use
2089		i2c commands at the u-boot command line (as long as you set
2090		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2091		based realtime clock chips or other i2c devices. See
2092		common/cmd_i2c.c for a description of the command line
2093		interface.
2094
2095		ported i2c driver to the new framework:
2096		- drivers/i2c/soft_i2c.c:
2097		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2098		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2099		    for defining speed and slave address
2100		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2101		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2102		    for defining speed and slave address
2103		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2104		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2105		    for defining speed and slave address
2106		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2107		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2108		    for defining speed and slave address
2109
2110		- drivers/i2c/fsl_i2c.c:
2111		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2112		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2113		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2114		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2115		    bus.
2116		  - If your board supports a second fsl i2c bus, define
2117		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2118		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2119		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2120		    second bus.
2121
2122		- drivers/i2c/tegra_i2c.c:
2123		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2124		  - This driver adds 4 i2c buses with a fix speed from
2125		    100000 and the slave addr 0!
2126
2127		- drivers/i2c/ppc4xx_i2c.c
2128		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2129		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2130		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2131
2132		- drivers/i2c/i2c_mxc.c
2133		  - activate this driver with CONFIG_SYS_I2C_MXC
2134		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2135		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2136		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2137		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2138		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2139		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2140		If thoses defines are not set, default value is 100000
2141		for speed, and 0 for slave.
2142
2143		- drivers/i2c/rcar_i2c.c:
2144		  - activate this driver with CONFIG_SYS_I2C_RCAR
2145		  - This driver adds 4 i2c buses
2146
2147		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2148		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2149		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2150		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2151		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2152		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2153		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2154		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2155		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2156
2157		- drivers/i2c/sh_i2c.c:
2158		  - activate this driver with CONFIG_SYS_I2C_SH
2159		  - This driver adds from 2 to 5 i2c buses
2160
2161		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2162		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2163		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2164		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2165		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2166		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2167		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2168		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2169		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2170		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2171		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2172		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2173		  - CONFIF_SYS_I2C_SH_NUM_CONTROLLERS for nummber of i2c buses
2174
2175		- drivers/i2c/omap24xx_i2c.c
2176		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2177		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2178		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2179		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2180		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2181		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2182		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2183		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2184		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2185		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2186		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2187
2188		- drivers/i2c/zynq_i2c.c
2189		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2190		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2191		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2192
2193		- drivers/i2c/s3c24x0_i2c.c:
2194		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2195		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2196		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2197		    with a fix speed from 100000 and the slave addr 0!
2198
2199		additional defines:
2200
2201		CONFIG_SYS_NUM_I2C_BUSES
2202		Hold the number of i2c busses you want to use. If you
2203		don't use/have i2c muxes on your i2c bus, this
2204		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2205		omit this define.
2206
2207		CONFIG_SYS_I2C_DIRECT_BUS
2208		define this, if you don't use i2c muxes on your hardware.
2209		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2210		omit this define.
2211
2212		CONFIG_SYS_I2C_MAX_HOPS
2213		define how many muxes are maximal consecutively connected
2214		on one i2c bus. If you not use i2c muxes, omit this
2215		define.
2216
2217		CONFIG_SYS_I2C_BUSES
2218		hold a list of busses you want to use, only used if
2219		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2220		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2221		CONFIG_SYS_NUM_I2C_BUSES = 9:
2222
2223		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2224					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2225					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2226					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2227					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2228					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2229					{1, {I2C_NULL_HOP}}, \
2230					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2231					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2232					}
2233
2234		which defines
2235			bus 0 on adapter 0 without a mux
2236			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2237			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2238			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2239			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2240			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2241			bus 6 on adapter 1 without a mux
2242			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2243			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2244
2245		If you do not have i2c muxes on your board, omit this define.
2246
2247- Legacy I2C Support:	CONFIG_HARD_I2C
2248
2249		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2250		provides the following compelling advantages:
2251
2252		- more than one i2c adapter is usable
2253		- approved multibus support
2254		- better i2c mux support
2255
2256		** Please consider updating your I2C driver now. **
2257
2258		These enable legacy I2C serial bus commands. Defining
2259		CONFIG_HARD_I2C will include the appropriate I2C driver
2260		for the selected CPU.
2261
2262		This will allow you to use i2c commands at the u-boot
2263		command line (as long as you set CONFIG_CMD_I2C in
2264		CONFIG_COMMANDS) and communicate with i2c based realtime
2265		clock chips. See common/cmd_i2c.c for a description of the
2266		command line interface.
2267
2268		CONFIG_HARD_I2C selects a hardware I2C controller.
2269
2270		There are several other quantities that must also be
2271		defined when you define CONFIG_HARD_I2C.
2272
2273		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2274		to be the frequency (in Hz) at which you wish your i2c bus
2275		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2276		the CPU's i2c node address).
2277
2278		Now, the u-boot i2c code for the mpc8xx
2279		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2280		and so its address should therefore be cleared to 0 (See,
2281		eg, MPC823e User's Manual p.16-473). So, set
2282		CONFIG_SYS_I2C_SLAVE to 0.
2283
2284		CONFIG_SYS_I2C_INIT_MPC5XXX
2285
2286		When a board is reset during an i2c bus transfer
2287		chips might think that the current transfer is still
2288		in progress.  Reset the slave devices by sending start
2289		commands until the slave device responds.
2290
2291		That's all that's required for CONFIG_HARD_I2C.
2292
2293		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2294		then the following macros need to be defined (examples are
2295		from include/configs/lwmon.h):
2296
2297		I2C_INIT
2298
2299		(Optional). Any commands necessary to enable the I2C
2300		controller or configure ports.
2301
2302		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2303
2304		I2C_PORT
2305
2306		(Only for MPC8260 CPU). The I/O port to use (the code
2307		assumes both bits are on the same port). Valid values
2308		are 0..3 for ports A..D.
2309
2310		I2C_ACTIVE
2311
2312		The code necessary to make the I2C data line active
2313		(driven).  If the data line is open collector, this
2314		define can be null.
2315
2316		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2317
2318		I2C_TRISTATE
2319
2320		The code necessary to make the I2C data line tri-stated
2321		(inactive).  If the data line is open collector, this
2322		define can be null.
2323
2324		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2325
2326		I2C_READ
2327
2328		Code that returns true if the I2C data line is high,
2329		false if it is low.
2330
2331		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2332
2333		I2C_SDA(bit)
2334
2335		If <bit> is true, sets the I2C data line high. If it
2336		is false, it clears it (low).
2337
2338		eg: #define I2C_SDA(bit) \
2339			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2340			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2341
2342		I2C_SCL(bit)
2343
2344		If <bit> is true, sets the I2C clock line high. If it
2345		is false, it clears it (low).
2346
2347		eg: #define I2C_SCL(bit) \
2348			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2349			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2350
2351		I2C_DELAY
2352
2353		This delay is invoked four times per clock cycle so this
2354		controls the rate of data transfer.  The data rate thus
2355		is 1 / (I2C_DELAY * 4). Often defined to be something
2356		like:
2357
2358		#define I2C_DELAY  udelay(2)
2359
2360		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2361
2362		If your arch supports the generic GPIO framework (asm/gpio.h),
2363		then you may alternatively define the two GPIOs that are to be
2364		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2365		have GPIO-based defaults assigned to them as appropriate.
2366
2367		You should define these to the GPIO value as given directly to
2368		the generic GPIO functions.
2369
2370		CONFIG_SYS_I2C_INIT_BOARD
2371
2372		When a board is reset during an i2c bus transfer
2373		chips might think that the current transfer is still
2374		in progress. On some boards it is possible to access
2375		the i2c SCLK line directly, either by using the
2376		processor pin as a GPIO or by having a second pin
2377		connected to the bus. If this option is defined a
2378		custom i2c_init_board() routine in boards/xxx/board.c
2379		is run early in the boot sequence.
2380
2381		CONFIG_SYS_I2C_BOARD_LATE_INIT
2382
2383		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2384		defined a custom i2c_board_late_init() routine in
2385		boards/xxx/board.c is run AFTER the operations in i2c_init()
2386		is completed. This callpoint can be used to unreset i2c bus
2387		using CPU i2c controller register accesses for CPUs whose i2c
2388		controller provide such a method. It is called at the end of
2389		i2c_init() to allow i2c_init operations to setup the i2c bus
2390		controller on the CPU (e.g. setting bus speed & slave address).
2391
2392		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2393
2394		This option enables configuration of bi_iic_fast[] flags
2395		in u-boot bd_info structure based on u-boot environment
2396		variable "i2cfast". (see also i2cfast)
2397
2398		CONFIG_I2C_MULTI_BUS
2399
2400		This option allows the use of multiple I2C buses, each of which
2401		must have a controller.	 At any point in time, only one bus is
2402		active.	 To switch to a different bus, use the 'i2c dev' command.
2403		Note that bus numbering is zero-based.
2404
2405		CONFIG_SYS_I2C_NOPROBES
2406
2407		This option specifies a list of I2C devices that will be skipped
2408		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2409		is set, specify a list of bus-device pairs.  Otherwise, specify
2410		a 1D array of device addresses
2411
2412		e.g.
2413			#undef	CONFIG_I2C_MULTI_BUS
2414			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2415
2416		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2417
2418			#define CONFIG_I2C_MULTI_BUS
2419			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2420
2421		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2422
2423		CONFIG_SYS_SPD_BUS_NUM
2424
2425		If defined, then this indicates the I2C bus number for DDR SPD.
2426		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2427
2428		CONFIG_SYS_RTC_BUS_NUM
2429
2430		If defined, then this indicates the I2C bus number for the RTC.
2431		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2432
2433		CONFIG_SYS_DTT_BUS_NUM
2434
2435		If defined, then this indicates the I2C bus number for the DTT.
2436		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2437
2438		CONFIG_SYS_I2C_DTT_ADDR:
2439
2440		If defined, specifies the I2C address of the DTT device.
2441		If not defined, then U-Boot uses predefined value for
2442		specified DTT device.
2443
2444		CONFIG_SOFT_I2C_READ_REPEATED_START
2445
2446		defining this will force the i2c_read() function in
2447		the soft_i2c driver to perform an I2C repeated start
2448		between writing the address pointer and reading the
2449		data.  If this define is omitted the default behaviour
2450		of doing a stop-start sequence will be used.  Most I2C
2451		devices can use either method, but some require one or
2452		the other.
2453
2454- SPI Support:	CONFIG_SPI
2455
2456		Enables SPI driver (so far only tested with
2457		SPI EEPROM, also an instance works with Crystal A/D and
2458		D/As on the SACSng board)
2459
2460		CONFIG_SH_SPI
2461
2462		Enables the driver for SPI controller on SuperH. Currently
2463		only SH7757 is supported.
2464
2465		CONFIG_SPI_X
2466
2467		Enables extended (16-bit) SPI EEPROM addressing.
2468		(symmetrical to CONFIG_I2C_X)
2469
2470		CONFIG_SOFT_SPI
2471
2472		Enables a software (bit-bang) SPI driver rather than
2473		using hardware support. This is a general purpose
2474		driver that only requires three general I/O port pins
2475		(two outputs, one input) to function. If this is
2476		defined, the board configuration must define several
2477		SPI configuration items (port pins to use, etc). For
2478		an example, see include/configs/sacsng.h.
2479
2480		CONFIG_HARD_SPI
2481
2482		Enables a hardware SPI driver for general-purpose reads
2483		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2484		must define a list of chip-select function pointers.
2485		Currently supported on some MPC8xxx processors.	 For an
2486		example, see include/configs/mpc8349emds.h.
2487
2488		CONFIG_MXC_SPI
2489
2490		Enables the driver for the SPI controllers on i.MX and MXC
2491		SoCs. Currently i.MX31/35/51 are supported.
2492
2493- FPGA Support: CONFIG_FPGA
2494
2495		Enables FPGA subsystem.
2496
2497		CONFIG_FPGA_<vendor>
2498
2499		Enables support for specific chip vendors.
2500		(ALTERA, XILINX)
2501
2502		CONFIG_FPGA_<family>
2503
2504		Enables support for FPGA family.
2505		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2506
2507		CONFIG_FPGA_COUNT
2508
2509		Specify the number of FPGA devices to support.
2510
2511		CONFIG_SYS_FPGA_PROG_FEEDBACK
2512
2513		Enable printing of hash marks during FPGA configuration.
2514
2515		CONFIG_SYS_FPGA_CHECK_BUSY
2516
2517		Enable checks on FPGA configuration interface busy
2518		status by the configuration function. This option
2519		will require a board or device specific function to
2520		be written.
2521
2522		CONFIG_FPGA_DELAY
2523
2524		If defined, a function that provides delays in the FPGA
2525		configuration driver.
2526
2527		CONFIG_SYS_FPGA_CHECK_CTRLC
2528		Allow Control-C to interrupt FPGA configuration
2529
2530		CONFIG_SYS_FPGA_CHECK_ERROR
2531
2532		Check for configuration errors during FPGA bitfile
2533		loading. For example, abort during Virtex II
2534		configuration if the INIT_B line goes low (which
2535		indicated a CRC error).
2536
2537		CONFIG_SYS_FPGA_WAIT_INIT
2538
2539		Maximum time to wait for the INIT_B line to deassert
2540		after PROB_B has been deasserted during a Virtex II
2541		FPGA configuration sequence. The default time is 500
2542		ms.
2543
2544		CONFIG_SYS_FPGA_WAIT_BUSY
2545
2546		Maximum time to wait for BUSY to deassert during
2547		Virtex II FPGA configuration. The default is 5 ms.
2548
2549		CONFIG_SYS_FPGA_WAIT_CONFIG
2550
2551		Time to wait after FPGA configuration. The default is
2552		200 ms.
2553
2554- Configuration Management:
2555		CONFIG_IDENT_STRING
2556
2557		If defined, this string will be added to the U-Boot
2558		version information (U_BOOT_VERSION)
2559
2560- Vendor Parameter Protection:
2561
2562		U-Boot considers the values of the environment
2563		variables "serial#" (Board Serial Number) and
2564		"ethaddr" (Ethernet Address) to be parameters that
2565		are set once by the board vendor / manufacturer, and
2566		protects these variables from casual modification by
2567		the user. Once set, these variables are read-only,
2568		and write or delete attempts are rejected. You can
2569		change this behaviour:
2570
2571		If CONFIG_ENV_OVERWRITE is #defined in your config
2572		file, the write protection for vendor parameters is
2573		completely disabled. Anybody can change or delete
2574		these parameters.
2575
2576		Alternatively, if you #define _both_ CONFIG_ETHADDR
2577		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2578		Ethernet address is installed in the environment,
2579		which can be changed exactly ONCE by the user. [The
2580		serial# is unaffected by this, i. e. it remains
2581		read-only.]
2582
2583		The same can be accomplished in a more flexible way
2584		for any variable by configuring the type of access
2585		to allow for those variables in the ".flags" variable
2586		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2587
2588- Protected RAM:
2589		CONFIG_PRAM
2590
2591		Define this variable to enable the reservation of
2592		"protected RAM", i. e. RAM which is not overwritten
2593		by U-Boot. Define CONFIG_PRAM to hold the number of
2594		kB you want to reserve for pRAM. You can overwrite
2595		this default value by defining an environment
2596		variable "pram" to the number of kB you want to
2597		reserve. Note that the board info structure will
2598		still show the full amount of RAM. If pRAM is
2599		reserved, a new environment variable "mem" will
2600		automatically be defined to hold the amount of
2601		remaining RAM in a form that can be passed as boot
2602		argument to Linux, for instance like that:
2603
2604			setenv bootargs ... mem=\${mem}
2605			saveenv
2606
2607		This way you can tell Linux not to use this memory,
2608		either, which results in a memory region that will
2609		not be affected by reboots.
2610
2611		*WARNING* If your board configuration uses automatic
2612		detection of the RAM size, you must make sure that
2613		this memory test is non-destructive. So far, the
2614		following board configurations are known to be
2615		"pRAM-clean":
2616
2617			IVMS8, IVML24, SPD8xx, TQM8xxL,
2618			HERMES, IP860, RPXlite, LWMON,
2619			FLAGADM, TQM8260
2620
2621- Access to physical memory region (> 4GB)
2622		Some basic support is provided for operations on memory not
2623		normally accessible to U-Boot - e.g. some architectures
2624		support access to more than 4GB of memory on 32-bit
2625		machines using physical address extension or similar.
2626		Define CONFIG_PHYSMEM to access this basic support, which
2627		currently only supports clearing the memory.
2628
2629- Error Recovery:
2630		CONFIG_PANIC_HANG
2631
2632		Define this variable to stop the system in case of a
2633		fatal error, so that you have to reset it manually.
2634		This is probably NOT a good idea for an embedded
2635		system where you want the system to reboot
2636		automatically as fast as possible, but it may be
2637		useful during development since you can try to debug
2638		the conditions that lead to the situation.
2639
2640		CONFIG_NET_RETRY_COUNT
2641
2642		This variable defines the number of retries for
2643		network operations like ARP, RARP, TFTP, or BOOTP
2644		before giving up the operation. If not defined, a
2645		default value of 5 is used.
2646
2647		CONFIG_ARP_TIMEOUT
2648
2649		Timeout waiting for an ARP reply in milliseconds.
2650
2651		CONFIG_NFS_TIMEOUT
2652
2653		Timeout in milliseconds used in NFS protocol.
2654		If you encounter "ERROR: Cannot umount" in nfs command,
2655		try longer timeout such as
2656		#define CONFIG_NFS_TIMEOUT 10000UL
2657
2658- Command Interpreter:
2659		CONFIG_AUTO_COMPLETE
2660
2661		Enable auto completion of commands using TAB.
2662
2663		Note that this feature has NOT been implemented yet
2664		for the "hush" shell.
2665
2666
2667		CONFIG_SYS_HUSH_PARSER
2668
2669		Define this variable to enable the "hush" shell (from
2670		Busybox) as command line interpreter, thus enabling
2671		powerful command line syntax like
2672		if...then...else...fi conditionals or `&&' and '||'
2673		constructs ("shell scripts").
2674
2675		If undefined, you get the old, much simpler behaviour
2676		with a somewhat smaller memory footprint.
2677
2678
2679		CONFIG_SYS_PROMPT_HUSH_PS2
2680
2681		This defines the secondary prompt string, which is
2682		printed when the command interpreter needs more input
2683		to complete a command. Usually "> ".
2684
2685	Note:
2686
2687		In the current implementation, the local variables
2688		space and global environment variables space are
2689		separated. Local variables are those you define by
2690		simply typing `name=value'. To access a local
2691		variable later on, you have write `$name' or
2692		`${name}'; to execute the contents of a variable
2693		directly type `$name' at the command prompt.
2694
2695		Global environment variables are those you use
2696		setenv/printenv to work with. To run a command stored
2697		in such a variable, you need to use the run command,
2698		and you must not use the '$' sign to access them.
2699
2700		To store commands and special characters in a
2701		variable, please use double quotation marks
2702		surrounding the whole text of the variable, instead
2703		of the backslashes before semicolons and special
2704		symbols.
2705
2706- Commandline Editing and History:
2707		CONFIG_CMDLINE_EDITING
2708
2709		Enable editing and History functions for interactive
2710		commandline input operations
2711
2712- Default Environment:
2713		CONFIG_EXTRA_ENV_SETTINGS
2714
2715		Define this to contain any number of null terminated
2716		strings (variable = value pairs) that will be part of
2717		the default environment compiled into the boot image.
2718
2719		For example, place something like this in your
2720		board's config file:
2721
2722		#define CONFIG_EXTRA_ENV_SETTINGS \
2723			"myvar1=value1\0" \
2724			"myvar2=value2\0"
2725
2726		Warning: This method is based on knowledge about the
2727		internal format how the environment is stored by the
2728		U-Boot code. This is NOT an official, exported
2729		interface! Although it is unlikely that this format
2730		will change soon, there is no guarantee either.
2731		You better know what you are doing here.
2732
2733		Note: overly (ab)use of the default environment is
2734		discouraged. Make sure to check other ways to preset
2735		the environment like the "source" command or the
2736		boot command first.
2737
2738		CONFIG_ENV_VARS_UBOOT_CONFIG
2739
2740		Define this in order to add variables describing the
2741		U-Boot build configuration to the default environment.
2742		These will be named arch, cpu, board, vendor, and soc.
2743
2744		Enabling this option will cause the following to be defined:
2745
2746		- CONFIG_SYS_ARCH
2747		- CONFIG_SYS_CPU
2748		- CONFIG_SYS_BOARD
2749		- CONFIG_SYS_VENDOR
2750		- CONFIG_SYS_SOC
2751
2752		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2753
2754		Define this in order to add variables describing certain
2755		run-time determined information about the hardware to the
2756		environment.  These will be named board_name, board_rev.
2757
2758		CONFIG_DELAY_ENVIRONMENT
2759
2760		Normally the environment is loaded when the board is
2761		intialised so that it is available to U-Boot. This inhibits
2762		that so that the environment is not available until
2763		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2764		this is instead controlled by the value of
2765		/config/load-environment.
2766
2767- DataFlash Support:
2768		CONFIG_HAS_DATAFLASH
2769
2770		Defining this option enables DataFlash features and
2771		allows to read/write in Dataflash via the standard
2772		commands cp, md...
2773
2774- Serial Flash support
2775		CONFIG_CMD_SF
2776
2777		Defining this option enables SPI flash commands
2778		'sf probe/read/write/erase/update'.
2779
2780		Usage requires an initial 'probe' to define the serial
2781		flash parameters, followed by read/write/erase/update
2782		commands.
2783
2784		The following defaults may be provided by the platform
2785		to handle the common case when only a single serial
2786		flash is present on the system.
2787
2788		CONFIG_SF_DEFAULT_BUS		Bus identifier
2789		CONFIG_SF_DEFAULT_CS		Chip-select
2790		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2791		CONFIG_SF_DEFAULT_SPEED		in Hz
2792
2793		CONFIG_CMD_SF_TEST
2794
2795		Define this option to include a destructive SPI flash
2796		test ('sf test').
2797
2798		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2799
2800		Define this option to use the Bank addr/Extended addr
2801		support on SPI flashes which has size > 16Mbytes.
2802
2803		CONFIG_SF_DUAL_FLASH		Dual flash memories
2804
2805		Define this option to use dual flash support where two flash
2806		memories can be connected with a given cs line.
2807		currently Xilinx Zynq qspi support these type of connections.
2808
2809- SystemACE Support:
2810		CONFIG_SYSTEMACE
2811
2812		Adding this option adds support for Xilinx SystemACE
2813		chips attached via some sort of local bus. The address
2814		of the chip must also be defined in the
2815		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2816
2817		#define CONFIG_SYSTEMACE
2818		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2819
2820		When SystemACE support is added, the "ace" device type
2821		becomes available to the fat commands, i.e. fatls.
2822
2823- TFTP Fixed UDP Port:
2824		CONFIG_TFTP_PORT
2825
2826		If this is defined, the environment variable tftpsrcp
2827		is used to supply the TFTP UDP source port value.
2828		If tftpsrcp isn't defined, the normal pseudo-random port
2829		number generator is used.
2830
2831		Also, the environment variable tftpdstp is used to supply
2832		the TFTP UDP destination port value.  If tftpdstp isn't
2833		defined, the normal port 69 is used.
2834
2835		The purpose for tftpsrcp is to allow a TFTP server to
2836		blindly start the TFTP transfer using the pre-configured
2837		target IP address and UDP port. This has the effect of
2838		"punching through" the (Windows XP) firewall, allowing
2839		the remainder of the TFTP transfer to proceed normally.
2840		A better solution is to properly configure the firewall,
2841		but sometimes that is not allowed.
2842
2843- Hashing support:
2844		CONFIG_CMD_HASH
2845
2846		This enables a generic 'hash' command which can produce
2847		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2848
2849		CONFIG_HASH_VERIFY
2850
2851		Enable the hash verify command (hash -v). This adds to code
2852		size a little.
2853
2854		CONFIG_SHA1 - support SHA1 hashing
2855		CONFIG_SHA256 - support SHA256 hashing
2856
2857		Note: There is also a sha1sum command, which should perhaps
2858		be deprecated in favour of 'hash sha1'.
2859
2860- Freescale i.MX specific commands:
2861		CONFIG_CMD_HDMIDETECT
2862		This enables 'hdmidet' command which returns true if an
2863		HDMI monitor is detected.  This command is i.MX 6 specific.
2864
2865		CONFIG_CMD_BMODE
2866		This enables the 'bmode' (bootmode) command for forcing
2867		a boot from specific media.
2868
2869		This is useful for forcing the ROM's usb downloader to
2870		activate upon a watchdog reset which is nice when iterating
2871		on U-Boot.  Using the reset button or running bmode normal
2872		will set it back to normal.  This command currently
2873		supports i.MX53 and i.MX6.
2874
2875- Signing support:
2876		CONFIG_RSA
2877
2878		This enables the RSA algorithm used for FIT image verification
2879		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
2880
2881		The signing part is build into mkimage regardless of this
2882		option.
2883
2884- bootcount support:
2885		CONFIG_BOOTCOUNT_LIMIT
2886
2887		This enables the bootcounter support, see:
2888		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2889
2890		CONFIG_AT91SAM9XE
2891		enable special bootcounter support on at91sam9xe based boards.
2892		CONFIG_BLACKFIN
2893		enable special bootcounter support on blackfin based boards.
2894		CONFIG_SOC_DA8XX
2895		enable special bootcounter support on da850 based boards.
2896		CONFIG_BOOTCOUNT_RAM
2897		enable support for the bootcounter in RAM
2898		CONFIG_BOOTCOUNT_I2C
2899		enable support for the bootcounter on an i2c (like RTC) device.
2900			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2901			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2902						    the bootcounter.
2903			CONFIG_BOOTCOUNT_ALEN = address len
2904
2905- Show boot progress:
2906		CONFIG_SHOW_BOOT_PROGRESS
2907
2908		Defining this option allows to add some board-
2909		specific code (calling a user-provided function
2910		"show_boot_progress(int)") that enables you to show
2911		the system's boot progress on some display (for
2912		example, some LED's) on your board. At the moment,
2913		the following checkpoints are implemented:
2914
2915- Detailed boot stage timing
2916		CONFIG_BOOTSTAGE
2917		Define this option to get detailed timing of each stage
2918		of the boot process.
2919
2920		CONFIG_BOOTSTAGE_USER_COUNT
2921		This is the number of available user bootstage records.
2922		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2923		a new ID will be allocated from this stash. If you exceed
2924		the limit, recording will stop.
2925
2926		CONFIG_BOOTSTAGE_REPORT
2927		Define this to print a report before boot, similar to this:
2928
2929		Timer summary in microseconds:
2930		       Mark    Elapsed  Stage
2931			  0          0  reset
2932		  3,575,678  3,575,678  board_init_f start
2933		  3,575,695         17  arch_cpu_init A9
2934		  3,575,777         82  arch_cpu_init done
2935		  3,659,598     83,821  board_init_r start
2936		  3,910,375    250,777  main_loop
2937		 29,916,167 26,005,792  bootm_start
2938		 30,361,327    445,160  start_kernel
2939
2940		CONFIG_CMD_BOOTSTAGE
2941		Add a 'bootstage' command which supports printing a report
2942		and un/stashing of bootstage data.
2943
2944		CONFIG_BOOTSTAGE_FDT
2945		Stash the bootstage information in the FDT. A root 'bootstage'
2946		node is created with each bootstage id as a child. Each child
2947		has a 'name' property and either 'mark' containing the
2948		mark time in microsecond, or 'accum' containing the
2949		accumulated time for that bootstage id in microseconds.
2950		For example:
2951
2952		bootstage {
2953			154 {
2954				name = "board_init_f";
2955				mark = <3575678>;
2956			};
2957			170 {
2958				name = "lcd";
2959				accum = <33482>;
2960			};
2961		};
2962
2963		Code in the Linux kernel can find this in /proc/devicetree.
2964
2965Legacy uImage format:
2966
2967  Arg	Where			When
2968    1	common/cmd_bootm.c	before attempting to boot an image
2969   -1	common/cmd_bootm.c	Image header has bad	 magic number
2970    2	common/cmd_bootm.c	Image header has correct magic number
2971   -2	common/cmd_bootm.c	Image header has bad	 checksum
2972    3	common/cmd_bootm.c	Image header has correct checksum
2973   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2974    4	common/cmd_bootm.c	Image data   has correct checksum
2975   -4	common/cmd_bootm.c	Image is for unsupported architecture
2976    5	common/cmd_bootm.c	Architecture check OK
2977   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2978    6	common/cmd_bootm.c	Image Type check OK
2979   -6	common/cmd_bootm.c	gunzip uncompression error
2980   -7	common/cmd_bootm.c	Unimplemented compression type
2981    7	common/cmd_bootm.c	Uncompression OK
2982    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2983   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2984
2985    9	common/image.c		Start initial ramdisk verification
2986  -10	common/image.c		Ramdisk header has bad	   magic number
2987  -11	common/image.c		Ramdisk header has bad	   checksum
2988   10	common/image.c		Ramdisk header is OK
2989  -12	common/image.c		Ramdisk data   has bad	   checksum
2990   11	common/image.c		Ramdisk data   has correct checksum
2991   12	common/image.c		Ramdisk verification complete, start loading
2992  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2993   13	common/image.c		Start multifile image verification
2994   14	common/image.c		No initial ramdisk, no multifile, continue.
2995
2996   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2997
2998  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2999  -31	post/post.c		POST test failed, detected by post_output_backlog()
3000  -32	post/post.c		POST test failed, detected by post_run_single()
3001
3002   34	common/cmd_doc.c	before loading a Image from a DOC device
3003  -35	common/cmd_doc.c	Bad usage of "doc" command
3004   35	common/cmd_doc.c	correct usage of "doc" command
3005  -36	common/cmd_doc.c	No boot device
3006   36	common/cmd_doc.c	correct boot device
3007  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3008   37	common/cmd_doc.c	correct chip ID found, device available
3009  -38	common/cmd_doc.c	Read Error on boot device
3010   38	common/cmd_doc.c	reading Image header from DOC device OK
3011  -39	common/cmd_doc.c	Image header has bad magic number
3012   39	common/cmd_doc.c	Image header has correct magic number
3013  -40	common/cmd_doc.c	Error reading Image from DOC device
3014   40	common/cmd_doc.c	Image header has correct magic number
3015   41	common/cmd_ide.c	before loading a Image from a IDE device
3016  -42	common/cmd_ide.c	Bad usage of "ide" command
3017   42	common/cmd_ide.c	correct usage of "ide" command
3018  -43	common/cmd_ide.c	No boot device
3019   43	common/cmd_ide.c	boot device found
3020  -44	common/cmd_ide.c	Device not available
3021   44	common/cmd_ide.c	Device available
3022  -45	common/cmd_ide.c	wrong partition selected
3023   45	common/cmd_ide.c	partition selected
3024  -46	common/cmd_ide.c	Unknown partition table
3025   46	common/cmd_ide.c	valid partition table found
3026  -47	common/cmd_ide.c	Invalid partition type
3027   47	common/cmd_ide.c	correct partition type
3028  -48	common/cmd_ide.c	Error reading Image Header on boot device
3029   48	common/cmd_ide.c	reading Image Header from IDE device OK
3030  -49	common/cmd_ide.c	Image header has bad magic number
3031   49	common/cmd_ide.c	Image header has correct magic number
3032  -50	common/cmd_ide.c	Image header has bad	 checksum
3033   50	common/cmd_ide.c	Image header has correct checksum
3034  -51	common/cmd_ide.c	Error reading Image from IDE device
3035   51	common/cmd_ide.c	reading Image from IDE device OK
3036   52	common/cmd_nand.c	before loading a Image from a NAND device
3037  -53	common/cmd_nand.c	Bad usage of "nand" command
3038   53	common/cmd_nand.c	correct usage of "nand" command
3039  -54	common/cmd_nand.c	No boot device
3040   54	common/cmd_nand.c	boot device found
3041  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3042   55	common/cmd_nand.c	correct chip ID found, device available
3043  -56	common/cmd_nand.c	Error reading Image Header on boot device
3044   56	common/cmd_nand.c	reading Image Header from NAND device OK
3045  -57	common/cmd_nand.c	Image header has bad magic number
3046   57	common/cmd_nand.c	Image header has correct magic number
3047  -58	common/cmd_nand.c	Error reading Image from NAND device
3048   58	common/cmd_nand.c	reading Image from NAND device OK
3049
3050  -60	common/env_common.c	Environment has a bad CRC, using default
3051
3052   64	net/eth.c		starting with Ethernet configuration.
3053  -64	net/eth.c		no Ethernet found.
3054   65	net/eth.c		Ethernet found.
3055
3056  -80	common/cmd_net.c	usage wrong
3057   80	common/cmd_net.c	before calling NetLoop()
3058  -81	common/cmd_net.c	some error in NetLoop() occurred
3059   81	common/cmd_net.c	NetLoop() back without error
3060  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3061   82	common/cmd_net.c	trying automatic boot
3062   83	common/cmd_net.c	running "source" command
3063  -83	common/cmd_net.c	some error in automatic boot or "source" command
3064   84	common/cmd_net.c	end without errors
3065
3066FIT uImage format:
3067
3068  Arg	Where			When
3069  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3070 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3071  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3072 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3073  102	common/cmd_bootm.c	Kernel unit name specified
3074 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3075  103	common/cmd_bootm.c	Found configuration node
3076  104	common/cmd_bootm.c	Got kernel subimage node offset
3077 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3078  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3079 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3080  106	common/cmd_bootm.c	Architecture check OK
3081 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3082  107	common/cmd_bootm.c	Kernel subimage type OK
3083 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3084  108	common/cmd_bootm.c	Got kernel subimage data/size
3085 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3086 -109	common/cmd_bootm.c	Can't get kernel subimage type
3087 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3088 -111	common/cmd_bootm.c	Can't get kernel subimage os
3089 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3090 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3091
3092  120	common/image.c		Start initial ramdisk verification
3093 -120	common/image.c		Ramdisk FIT image has incorrect format
3094  121	common/image.c		Ramdisk FIT image has correct format
3095  122	common/image.c		No ramdisk subimage unit name, using configuration
3096 -122	common/image.c		Can't get configuration for ramdisk subimage
3097  123	common/image.c		Ramdisk unit name specified
3098 -124	common/image.c		Can't get ramdisk subimage node offset
3099  125	common/image.c		Got ramdisk subimage node offset
3100 -125	common/image.c		Ramdisk subimage hash verification failed
3101  126	common/image.c		Ramdisk subimage hash verification OK
3102 -126	common/image.c		Ramdisk subimage for unsupported architecture
3103  127	common/image.c		Architecture check OK
3104 -127	common/image.c		Can't get ramdisk subimage data/size
3105  128	common/image.c		Got ramdisk subimage data/size
3106  129	common/image.c		Can't get ramdisk load address
3107 -129	common/image.c		Got ramdisk load address
3108
3109 -130	common/cmd_doc.c	Incorrect FIT image format
3110  131	common/cmd_doc.c	FIT image format OK
3111
3112 -140	common/cmd_ide.c	Incorrect FIT image format
3113  141	common/cmd_ide.c	FIT image format OK
3114
3115 -150	common/cmd_nand.c	Incorrect FIT image format
3116  151	common/cmd_nand.c	FIT image format OK
3117
3118- FIT image support:
3119		CONFIG_FIT
3120		Enable support for the FIT uImage format.
3121
3122		CONFIG_FIT_BEST_MATCH
3123		When no configuration is explicitly selected, default to the
3124		one whose fdt's compatibility field best matches that of
3125		U-Boot itself. A match is considered "best" if it matches the
3126		most specific compatibility entry of U-Boot's fdt's root node.
3127		The order of entries in the configuration's fdt is ignored.
3128
3129		CONFIG_FIT_SIGNATURE
3130		This option enables signature verification of FIT uImages,
3131		using a hash signed and verified using RSA. See
3132		doc/uImage.FIT/signature.txt for more details.
3133
3134- Standalone program support:
3135		CONFIG_STANDALONE_LOAD_ADDR
3136
3137		This option defines a board specific value for the
3138		address where standalone program gets loaded, thus
3139		overwriting the architecture dependent default
3140		settings.
3141
3142- Frame Buffer Address:
3143		CONFIG_FB_ADDR
3144
3145		Define CONFIG_FB_ADDR if you want to use specific
3146		address for frame buffer.  This is typically the case
3147		when using a graphics controller has separate video
3148		memory.  U-Boot will then place the frame buffer at
3149		the given address instead of dynamically reserving it
3150		in system RAM by calling lcd_setmem(), which grabs
3151		the memory for the frame buffer depending on the
3152		configured panel size.
3153
3154		Please see board_init_f function.
3155
3156- Automatic software updates via TFTP server
3157		CONFIG_UPDATE_TFTP
3158		CONFIG_UPDATE_TFTP_CNT_MAX
3159		CONFIG_UPDATE_TFTP_MSEC_MAX
3160
3161		These options enable and control the auto-update feature;
3162		for a more detailed description refer to doc/README.update.
3163
3164- MTD Support (mtdparts command, UBI support)
3165		CONFIG_MTD_DEVICE
3166
3167		Adds the MTD device infrastructure from the Linux kernel.
3168		Needed for mtdparts command support.
3169
3170		CONFIG_MTD_PARTITIONS
3171
3172		Adds the MTD partitioning infrastructure from the Linux
3173		kernel. Needed for UBI support.
3174
3175- UBI support
3176		CONFIG_CMD_UBI
3177
3178		Adds commands for interacting with MTD partitions formatted
3179		with the UBI flash translation layer
3180
3181		Requires also defining CONFIG_RBTREE
3182
3183		CONFIG_UBI_SILENCE_MSG
3184
3185		Make the verbose messages from UBI stop printing.  This leaves
3186		warnings and errors enabled.
3187
3188- UBIFS support
3189		CONFIG_CMD_UBIFS
3190
3191		Adds commands for interacting with UBI volumes formatted as
3192		UBIFS.  UBIFS is read-only in u-boot.
3193
3194		Requires UBI support as well as CONFIG_LZO
3195
3196		CONFIG_UBIFS_SILENCE_MSG
3197
3198		Make the verbose messages from UBIFS stop printing.  This leaves
3199		warnings and errors enabled.
3200
3201- SPL framework
3202		CONFIG_SPL
3203		Enable building of SPL globally.
3204
3205		CONFIG_SPL_LDSCRIPT
3206		LDSCRIPT for linking the SPL binary.
3207
3208		CONFIG_SPL_MAX_FOOTPRINT
3209		Maximum size in memory allocated to the SPL, BSS included.
3210		When defined, the linker checks that the actual memory
3211		used by SPL from _start to __bss_end does not exceed it.
3212		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3213		must not be both defined at the same time.
3214
3215		CONFIG_SPL_MAX_SIZE
3216		Maximum size of the SPL image (text, data, rodata, and
3217		linker lists sections), BSS excluded.
3218		When defined, the linker checks that the actual size does
3219		not exceed it.
3220
3221		CONFIG_SPL_TEXT_BASE
3222		TEXT_BASE for linking the SPL binary.
3223
3224		CONFIG_SPL_RELOC_TEXT_BASE
3225		Address to relocate to.  If unspecified, this is equal to
3226		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3227
3228		CONFIG_SPL_BSS_START_ADDR
3229		Link address for the BSS within the SPL binary.
3230
3231		CONFIG_SPL_BSS_MAX_SIZE
3232		Maximum size in memory allocated to the SPL BSS.
3233		When defined, the linker checks that the actual memory used
3234		by SPL from __bss_start to __bss_end does not exceed it.
3235		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3236		must not be both defined at the same time.
3237
3238		CONFIG_SPL_STACK
3239		Adress of the start of the stack SPL will use
3240
3241		CONFIG_SPL_RELOC_STACK
3242		Adress of the start of the stack SPL will use after
3243		relocation.  If unspecified, this is equal to
3244		CONFIG_SPL_STACK.
3245
3246		CONFIG_SYS_SPL_MALLOC_START
3247		Starting address of the malloc pool used in SPL.
3248
3249		CONFIG_SYS_SPL_MALLOC_SIZE
3250		The size of the malloc pool used in SPL.
3251
3252		CONFIG_SPL_FRAMEWORK
3253		Enable the SPL framework under common/.  This framework
3254		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3255		NAND loading of the Linux Kernel.
3256
3257		CONFIG_SPL_DISPLAY_PRINT
3258		For ARM, enable an optional function to print more information
3259		about the running system.
3260
3261		CONFIG_SPL_INIT_MINIMAL
3262		Arch init code should be built for a very small image
3263
3264		CONFIG_SPL_LIBCOMMON_SUPPORT
3265		Support for common/libcommon.o in SPL binary
3266
3267		CONFIG_SPL_LIBDISK_SUPPORT
3268		Support for disk/libdisk.o in SPL binary
3269
3270		CONFIG_SPL_I2C_SUPPORT
3271		Support for drivers/i2c/libi2c.o in SPL binary
3272
3273		CONFIG_SPL_GPIO_SUPPORT
3274		Support for drivers/gpio/libgpio.o in SPL binary
3275
3276		CONFIG_SPL_MMC_SUPPORT
3277		Support for drivers/mmc/libmmc.o in SPL binary
3278
3279		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3280		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3281		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3282		Address, size and partition on the MMC to load U-Boot from
3283		when the MMC is being used in raw mode.
3284
3285		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3286		Sector to load kernel uImage from when MMC is being
3287		used in raw mode (for Falcon mode)
3288
3289		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3290		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3291		Sector and number of sectors to load kernel argument
3292		parameters from when MMC is being used in raw mode
3293		(for falcon mode)
3294
3295		CONFIG_SPL_FAT_SUPPORT
3296		Support for fs/fat/libfat.o in SPL binary
3297
3298		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3299		Filename to read to load U-Boot when reading from FAT
3300
3301		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3302		Filename to read to load kernel uImage when reading
3303		from FAT (for Falcon mode)
3304
3305		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3306		Filename to read to load kernel argument parameters
3307		when reading from FAT (for Falcon mode)
3308
3309		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3310		Set this for NAND SPL on PPC mpc83xx targets, so that
3311		start.S waits for the rest of the SPL to load before
3312		continuing (the hardware starts execution after just
3313		loading the first page rather than the full 4K).
3314
3315		CONFIG_SPL_NAND_BASE
3316		Include nand_base.c in the SPL.  Requires
3317		CONFIG_SPL_NAND_DRIVERS.
3318
3319		CONFIG_SPL_NAND_DRIVERS
3320		SPL uses normal NAND drivers, not minimal drivers.
3321
3322		CONFIG_SPL_NAND_ECC
3323		Include standard software ECC in the SPL
3324
3325		CONFIG_SPL_NAND_SIMPLE
3326		Support for NAND boot using simple NAND drivers that
3327		expose the cmd_ctrl() interface.
3328
3329		CONFIG_SPL_MTD_SUPPORT
3330		Support for the MTD subsystem within SPL.  Useful for
3331		environment on NAND support within SPL.
3332
3333		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3334		Set for the SPL on PPC mpc8xxx targets, support for
3335		drivers/ddr/fsl/libddr.o in SPL binary.
3336
3337		CONFIG_SPL_COMMON_INIT_DDR
3338		Set for common ddr init with serial presence detect in
3339		SPL binary.
3340
3341		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3342		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3343		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3344		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3345		CONFIG_SYS_NAND_ECCBYTES
3346		Defines the size and behavior of the NAND that SPL uses
3347		to read U-Boot
3348
3349		CONFIG_SPL_NAND_BOOT
3350		Add support NAND boot
3351
3352		CONFIG_SYS_NAND_U_BOOT_OFFS
3353		Location in NAND to read U-Boot from
3354
3355		CONFIG_SYS_NAND_U_BOOT_DST
3356		Location in memory to load U-Boot to
3357
3358		CONFIG_SYS_NAND_U_BOOT_SIZE
3359		Size of image to load
3360
3361		CONFIG_SYS_NAND_U_BOOT_START
3362		Entry point in loaded image to jump to
3363
3364		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3365		Define this if you need to first read the OOB and then the
3366		data. This is used for example on davinci plattforms.
3367
3368		CONFIG_SPL_OMAP3_ID_NAND
3369		Support for an OMAP3-specific set of functions to return the
3370		ID and MFR of the first attached NAND chip, if present.
3371
3372		CONFIG_SPL_SERIAL_SUPPORT
3373		Support for drivers/serial/libserial.o in SPL binary
3374
3375		CONFIG_SPL_SPI_FLASH_SUPPORT
3376		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3377
3378		CONFIG_SPL_SPI_SUPPORT
3379		Support for drivers/spi/libspi.o in SPL binary
3380
3381		CONFIG_SPL_RAM_DEVICE
3382		Support for running image already present in ram, in SPL binary
3383
3384		CONFIG_SPL_LIBGENERIC_SUPPORT
3385		Support for lib/libgeneric.o in SPL binary
3386
3387		CONFIG_SPL_ENV_SUPPORT
3388		Support for the environment operating in SPL binary
3389
3390		CONFIG_SPL_NET_SUPPORT
3391		Support for the net/libnet.o in SPL binary.
3392		It conflicts with SPL env from storage medium specified by
3393		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3394
3395		CONFIG_SPL_PAD_TO
3396		Image offset to which the SPL should be padded before appending
3397		the SPL payload. By default, this is defined as
3398		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3399		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3400		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3401
3402		CONFIG_SPL_TARGET
3403		Final target image containing SPL and payload.  Some SPLs
3404		use an arch-specific makefile fragment instead, for
3405		example if more than one image needs to be produced.
3406
3407		CONFIG_FIT_SPL_PRINT
3408		Printing information about a FIT image adds quite a bit of
3409		code to SPL. So this is normally disabled in SPL. Use this
3410		option to re-enable it. This will affect the output of the
3411		bootm command when booting a FIT image.
3412
3413- TPL framework
3414		CONFIG_TPL
3415		Enable building of TPL globally.
3416
3417		CONFIG_TPL_PAD_TO
3418		Image offset to which the TPL should be padded before appending
3419		the TPL payload. By default, this is defined as
3420		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3421		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3422		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3423
3424Modem Support:
3425--------------
3426
3427[so far only for SMDK2400 boards]
3428
3429- Modem support enable:
3430		CONFIG_MODEM_SUPPORT
3431
3432- RTS/CTS Flow control enable:
3433		CONFIG_HWFLOW
3434
3435- Modem debug support:
3436		CONFIG_MODEM_SUPPORT_DEBUG
3437
3438		Enables debugging stuff (char screen[1024], dbg())
3439		for modem support. Useful only with BDI2000.
3440
3441- Interrupt support (PPC):
3442
3443		There are common interrupt_init() and timer_interrupt()
3444		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3445		for CPU specific initialization. interrupt_init_cpu()
3446		should set decrementer_count to appropriate value. If
3447		CPU resets decrementer automatically after interrupt
3448		(ppc4xx) it should set decrementer_count to zero.
3449		timer_interrupt() calls timer_interrupt_cpu() for CPU
3450		specific handling. If board has watchdog / status_led
3451		/ other_activity_monitor it works automatically from
3452		general timer_interrupt().
3453
3454- General:
3455
3456		In the target system modem support is enabled when a
3457		specific key (key combination) is pressed during
3458		power-on. Otherwise U-Boot will boot normally
3459		(autoboot). The key_pressed() function is called from
3460		board_init(). Currently key_pressed() is a dummy
3461		function, returning 1 and thus enabling modem
3462		initialization.
3463
3464		If there are no modem init strings in the
3465		environment, U-Boot proceed to autoboot; the
3466		previous output (banner, info printfs) will be
3467		suppressed, though.
3468
3469		See also: doc/README.Modem
3470
3471Board initialization settings:
3472------------------------------
3473
3474During Initialization u-boot calls a number of board specific functions
3475to allow the preparation of board specific prerequisites, e.g. pin setup
3476before drivers are initialized. To enable these callbacks the
3477following configuration macros have to be defined. Currently this is
3478architecture specific, so please check arch/your_architecture/lib/board.c
3479typically in board_init_f() and board_init_r().
3480
3481- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3482- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3483- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3484- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3485
3486Configuration Settings:
3487-----------------------
3488
3489- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3490		Optionally it can be defined to support 64-bit memory commands.
3491
3492- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3493		undefine this when you're short of memory.
3494
3495- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3496		width of the commands listed in the 'help' command output.
3497
3498- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3499		prompt for user input.
3500
3501- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3502
3503- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3504
3505- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3506
3507- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3508		the application (usually a Linux kernel) when it is
3509		booted
3510
3511- CONFIG_SYS_BAUDRATE_TABLE:
3512		List of legal baudrate settings for this board.
3513
3514- CONFIG_SYS_CONSOLE_INFO_QUIET
3515		Suppress display of console information at boot.
3516
3517- CONFIG_SYS_CONSOLE_IS_IN_ENV
3518		If the board specific function
3519			extern int overwrite_console (void);
3520		returns 1, the stdin, stderr and stdout are switched to the
3521		serial port, else the settings in the environment are used.
3522
3523- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3524		Enable the call to overwrite_console().
3525
3526- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3527		Enable overwrite of previous console environment settings.
3528
3529- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3530		Begin and End addresses of the area used by the
3531		simple memory test.
3532
3533- CONFIG_SYS_ALT_MEMTEST:
3534		Enable an alternate, more extensive memory test.
3535
3536- CONFIG_SYS_MEMTEST_SCRATCH:
3537		Scratch address used by the alternate memory test
3538		You only need to set this if address zero isn't writeable
3539
3540- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3541		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3542		this specified memory area will get subtracted from the top
3543		(end) of RAM and won't get "touched" at all by U-Boot. By
3544		fixing up gd->ram_size the Linux kernel should gets passed
3545		the now "corrected" memory size and won't touch it either.
3546		This should work for arch/ppc and arch/powerpc. Only Linux
3547		board ports in arch/powerpc with bootwrapper support that
3548		recalculate the memory size from the SDRAM controller setup
3549		will have to get fixed in Linux additionally.
3550
3551		This option can be used as a workaround for the 440EPx/GRx
3552		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3553		be touched.
3554
3555		WARNING: Please make sure that this value is a multiple of
3556		the Linux page size (normally 4k). If this is not the case,
3557		then the end address of the Linux memory will be located at a
3558		non page size aligned address and this could cause major
3559		problems.
3560
3561- CONFIG_SYS_LOADS_BAUD_CHANGE:
3562		Enable temporary baudrate change while serial download
3563
3564- CONFIG_SYS_SDRAM_BASE:
3565		Physical start address of SDRAM. _Must_ be 0 here.
3566
3567- CONFIG_SYS_MBIO_BASE:
3568		Physical start address of Motherboard I/O (if using a
3569		Cogent motherboard)
3570
3571- CONFIG_SYS_FLASH_BASE:
3572		Physical start address of Flash memory.
3573
3574- CONFIG_SYS_MONITOR_BASE:
3575		Physical start address of boot monitor code (set by
3576		make config files to be same as the text base address
3577		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3578		CONFIG_SYS_FLASH_BASE when booting from flash.
3579
3580- CONFIG_SYS_MONITOR_LEN:
3581		Size of memory reserved for monitor code, used to
3582		determine _at_compile_time_ (!) if the environment is
3583		embedded within the U-Boot image, or in a separate
3584		flash sector.
3585
3586- CONFIG_SYS_MALLOC_LEN:
3587		Size of DRAM reserved for malloc() use.
3588
3589- CONFIG_SYS_BOOTM_LEN:
3590		Normally compressed uImages are limited to an
3591		uncompressed size of 8 MBytes. If this is not enough,
3592		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3593		to adjust this setting to your needs.
3594
3595- CONFIG_SYS_BOOTMAPSZ:
3596		Maximum size of memory mapped by the startup code of
3597		the Linux kernel; all data that must be processed by
3598		the Linux kernel (bd_info, boot arguments, FDT blob if
3599		used) must be put below this limit, unless "bootm_low"
3600		environment variable is defined and non-zero. In such case
3601		all data for the Linux kernel must be between "bootm_low"
3602		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3603		variable "bootm_mapsize" will override the value of
3604		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3605		then the value in "bootm_size" will be used instead.
3606
3607- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3608		Enable initrd_high functionality.  If defined then the
3609		initrd_high feature is enabled and the bootm ramdisk subcommand
3610		is enabled.
3611
3612- CONFIG_SYS_BOOT_GET_CMDLINE:
3613		Enables allocating and saving kernel cmdline in space between
3614		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3615
3616- CONFIG_SYS_BOOT_GET_KBD:
3617		Enables allocating and saving a kernel copy of the bd_info in
3618		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3619
3620- CONFIG_SYS_MAX_FLASH_BANKS:
3621		Max number of Flash memory banks
3622
3623- CONFIG_SYS_MAX_FLASH_SECT:
3624		Max number of sectors on a Flash chip
3625
3626- CONFIG_SYS_FLASH_ERASE_TOUT:
3627		Timeout for Flash erase operations (in ms)
3628
3629- CONFIG_SYS_FLASH_WRITE_TOUT:
3630		Timeout for Flash write operations (in ms)
3631
3632- CONFIG_SYS_FLASH_LOCK_TOUT
3633		Timeout for Flash set sector lock bit operation (in ms)
3634
3635- CONFIG_SYS_FLASH_UNLOCK_TOUT
3636		Timeout for Flash clear lock bits operation (in ms)
3637
3638- CONFIG_SYS_FLASH_PROTECTION
3639		If defined, hardware flash sectors protection is used
3640		instead of U-Boot software protection.
3641
3642- CONFIG_SYS_DIRECT_FLASH_TFTP:
3643
3644		Enable TFTP transfers directly to flash memory;
3645		without this option such a download has to be
3646		performed in two steps: (1) download to RAM, and (2)
3647		copy from RAM to flash.
3648
3649		The two-step approach is usually more reliable, since
3650		you can check if the download worked before you erase
3651		the flash, but in some situations (when system RAM is
3652		too limited to allow for a temporary copy of the
3653		downloaded image) this option may be very useful.
3654
3655- CONFIG_SYS_FLASH_CFI:
3656		Define if the flash driver uses extra elements in the
3657		common flash structure for storing flash geometry.
3658
3659- CONFIG_FLASH_CFI_DRIVER
3660		This option also enables the building of the cfi_flash driver
3661		in the drivers directory
3662
3663- CONFIG_FLASH_CFI_MTD
3664		This option enables the building of the cfi_mtd driver
3665		in the drivers directory. The driver exports CFI flash
3666		to the MTD layer.
3667
3668- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3669		Use buffered writes to flash.
3670
3671- CONFIG_FLASH_SPANSION_S29WS_N
3672		s29ws-n MirrorBit flash has non-standard addresses for buffered
3673		write commands.
3674
3675- CONFIG_SYS_FLASH_QUIET_TEST
3676		If this option is defined, the common CFI flash doesn't
3677		print it's warning upon not recognized FLASH banks. This
3678		is useful, if some of the configured banks are only
3679		optionally available.
3680
3681- CONFIG_FLASH_SHOW_PROGRESS
3682		If defined (must be an integer), print out countdown
3683		digits and dots.  Recommended value: 45 (9..1) for 80
3684		column displays, 15 (3..1) for 40 column displays.
3685
3686- CONFIG_FLASH_VERIFY
3687		If defined, the content of the flash (destination) is compared
3688		against the source after the write operation. An error message
3689		will be printed when the contents are not identical.
3690		Please note that this option is useless in nearly all cases,
3691		since such flash programming errors usually are detected earlier
3692		while unprotecting/erasing/programming. Please only enable
3693		this option if you really know what you are doing.
3694
3695- CONFIG_SYS_RX_ETH_BUFFER:
3696		Defines the number of Ethernet receive buffers. On some
3697		Ethernet controllers it is recommended to set this value
3698		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3699		buffers can be full shortly after enabling the interface
3700		on high Ethernet traffic.
3701		Defaults to 4 if not defined.
3702
3703- CONFIG_ENV_MAX_ENTRIES
3704
3705	Maximum number of entries in the hash table that is used
3706	internally to store the environment settings. The default
3707	setting is supposed to be generous and should work in most
3708	cases. This setting can be used to tune behaviour; see
3709	lib/hashtable.c for details.
3710
3711- CONFIG_ENV_FLAGS_LIST_DEFAULT
3712- CONFIG_ENV_FLAGS_LIST_STATIC
3713	Enable validation of the values given to environment variables when
3714	calling env set.  Variables can be restricted to only decimal,
3715	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3716	the variables can also be restricted to IP address or MAC address.
3717
3718	The format of the list is:
3719		type_attribute = [s|d|x|b|i|m]
3720		access_atribute = [a|r|o|c]
3721		attributes = type_attribute[access_atribute]
3722		entry = variable_name[:attributes]
3723		list = entry[,list]
3724
3725	The type attributes are:
3726		s - String (default)
3727		d - Decimal
3728		x - Hexadecimal
3729		b - Boolean ([1yYtT|0nNfF])
3730		i - IP address
3731		m - MAC address
3732
3733	The access attributes are:
3734		a - Any (default)
3735		r - Read-only
3736		o - Write-once
3737		c - Change-default
3738
3739	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3740		Define this to a list (string) to define the ".flags"
3741		envirnoment variable in the default or embedded environment.
3742
3743	- CONFIG_ENV_FLAGS_LIST_STATIC
3744		Define this to a list (string) to define validation that
3745		should be done if an entry is not found in the ".flags"
3746		environment variable.  To override a setting in the static
3747		list, simply add an entry for the same variable name to the
3748		".flags" variable.
3749
3750- CONFIG_ENV_ACCESS_IGNORE_FORCE
3751	If defined, don't allow the -f switch to env set override variable
3752	access flags.
3753
3754- CONFIG_SYS_GENERIC_BOARD
3755	This selects the architecture-generic board system instead of the
3756	architecture-specific board files. It is intended to move boards
3757	to this new framework over time. Defining this will disable the
3758	arch/foo/lib/board.c file and use common/board_f.c and
3759	common/board_r.c instead. To use this option your architecture
3760	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3761	its config.mk file). If you find problems enabling this option on
3762	your board please report the problem and send patches!
3763
3764- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3765	This is set by OMAP boards for the max time that reset should
3766	be asserted. See doc/README.omap-reset-time for details on how
3767	the value can be calulated on a given board.
3768
3769The following definitions that deal with the placement and management
3770of environment data (variable area); in general, we support the
3771following configurations:
3772
3773- CONFIG_BUILD_ENVCRC:
3774
3775	Builds up envcrc with the target environment so that external utils
3776	may easily extract it and embed it in final U-Boot images.
3777
3778- CONFIG_ENV_IS_IN_FLASH:
3779
3780	Define this if the environment is in flash memory.
3781
3782	a) The environment occupies one whole flash sector, which is
3783	   "embedded" in the text segment with the U-Boot code. This
3784	   happens usually with "bottom boot sector" or "top boot
3785	   sector" type flash chips, which have several smaller
3786	   sectors at the start or the end. For instance, such a
3787	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3788	   such a case you would place the environment in one of the
3789	   4 kB sectors - with U-Boot code before and after it. With
3790	   "top boot sector" type flash chips, you would put the
3791	   environment in one of the last sectors, leaving a gap
3792	   between U-Boot and the environment.
3793
3794	- CONFIG_ENV_OFFSET:
3795
3796	   Offset of environment data (variable area) to the
3797	   beginning of flash memory; for instance, with bottom boot
3798	   type flash chips the second sector can be used: the offset
3799	   for this sector is given here.
3800
3801	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3802
3803	- CONFIG_ENV_ADDR:
3804
3805	   This is just another way to specify the start address of
3806	   the flash sector containing the environment (instead of
3807	   CONFIG_ENV_OFFSET).
3808
3809	- CONFIG_ENV_SECT_SIZE:
3810
3811	   Size of the sector containing the environment.
3812
3813
3814	b) Sometimes flash chips have few, equal sized, BIG sectors.
3815	   In such a case you don't want to spend a whole sector for
3816	   the environment.
3817
3818	- CONFIG_ENV_SIZE:
3819
3820	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3821	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3822	   of this flash sector for the environment. This saves
3823	   memory for the RAM copy of the environment.
3824
3825	   It may also save flash memory if you decide to use this
3826	   when your environment is "embedded" within U-Boot code,
3827	   since then the remainder of the flash sector could be used
3828	   for U-Boot code. It should be pointed out that this is
3829	   STRONGLY DISCOURAGED from a robustness point of view:
3830	   updating the environment in flash makes it always
3831	   necessary to erase the WHOLE sector. If something goes
3832	   wrong before the contents has been restored from a copy in
3833	   RAM, your target system will be dead.
3834
3835	- CONFIG_ENV_ADDR_REDUND
3836	  CONFIG_ENV_SIZE_REDUND
3837
3838	   These settings describe a second storage area used to hold
3839	   a redundant copy of the environment data, so that there is
3840	   a valid backup copy in case there is a power failure during
3841	   a "saveenv" operation.
3842
3843BE CAREFUL! Any changes to the flash layout, and some changes to the
3844source code will make it necessary to adapt <board>/u-boot.lds*
3845accordingly!
3846
3847
3848- CONFIG_ENV_IS_IN_NVRAM:
3849
3850	Define this if you have some non-volatile memory device
3851	(NVRAM, battery buffered SRAM) which you want to use for the
3852	environment.
3853
3854	- CONFIG_ENV_ADDR:
3855	- CONFIG_ENV_SIZE:
3856
3857	  These two #defines are used to determine the memory area you
3858	  want to use for environment. It is assumed that this memory
3859	  can just be read and written to, without any special
3860	  provision.
3861
3862BE CAREFUL! The first access to the environment happens quite early
3863in U-Boot initalization (when we try to get the setting of for the
3864console baudrate). You *MUST* have mapped your NVRAM area then, or
3865U-Boot will hang.
3866
3867Please note that even with NVRAM we still use a copy of the
3868environment in RAM: we could work on NVRAM directly, but we want to
3869keep settings there always unmodified except somebody uses "saveenv"
3870to save the current settings.
3871
3872
3873- CONFIG_ENV_IS_IN_EEPROM:
3874
3875	Use this if you have an EEPROM or similar serial access
3876	device and a driver for it.
3877
3878	- CONFIG_ENV_OFFSET:
3879	- CONFIG_ENV_SIZE:
3880
3881	  These two #defines specify the offset and size of the
3882	  environment area within the total memory of your EEPROM.
3883
3884	- CONFIG_SYS_I2C_EEPROM_ADDR:
3885	  If defined, specified the chip address of the EEPROM device.
3886	  The default address is zero.
3887
3888	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3889	  If defined, the number of bits used to address bytes in a
3890	  single page in the EEPROM device.  A 64 byte page, for example
3891	  would require six bits.
3892
3893	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3894	  If defined, the number of milliseconds to delay between
3895	  page writes.	The default is zero milliseconds.
3896
3897	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3898	  The length in bytes of the EEPROM memory array address.  Note
3899	  that this is NOT the chip address length!
3900
3901	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3902	  EEPROM chips that implement "address overflow" are ones
3903	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3904	  address and the extra bits end up in the "chip address" bit
3905	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3906	  byte chips.
3907
3908	  Note that we consider the length of the address field to
3909	  still be one byte because the extra address bits are hidden
3910	  in the chip address.
3911
3912	- CONFIG_SYS_EEPROM_SIZE:
3913	  The size in bytes of the EEPROM device.
3914
3915	- CONFIG_ENV_EEPROM_IS_ON_I2C
3916	  define this, if you have I2C and SPI activated, and your
3917	  EEPROM, which holds the environment, is on the I2C bus.
3918
3919	- CONFIG_I2C_ENV_EEPROM_BUS
3920	  if you have an Environment on an EEPROM reached over
3921	  I2C muxes, you can define here, how to reach this
3922	  EEPROM. For example:
3923
3924	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3925
3926	  EEPROM which holds the environment, is reached over
3927	  a pca9547 i2c mux with address 0x70, channel 3.
3928
3929- CONFIG_ENV_IS_IN_DATAFLASH:
3930
3931	Define this if you have a DataFlash memory device which you
3932	want to use for the environment.
3933
3934	- CONFIG_ENV_OFFSET:
3935	- CONFIG_ENV_ADDR:
3936	- CONFIG_ENV_SIZE:
3937
3938	  These three #defines specify the offset and size of the
3939	  environment area within the total memory of your DataFlash placed
3940	  at the specified address.
3941
3942- CONFIG_ENV_IS_IN_REMOTE:
3943
3944	Define this if you have a remote memory space which you
3945	want to use for the local device's environment.
3946
3947	- CONFIG_ENV_ADDR:
3948	- CONFIG_ENV_SIZE:
3949
3950	  These two #defines specify the address and size of the
3951	  environment area within the remote memory space. The
3952	  local device can get the environment from remote memory
3953	  space by SRIO or PCIE links.
3954
3955BE CAREFUL! For some special cases, the local device can not use
3956"saveenv" command. For example, the local device will get the
3957environment stored in a remote NOR flash by SRIO or PCIE link,
3958but it can not erase, write this NOR flash by SRIO or PCIE interface.
3959
3960- CONFIG_ENV_IS_IN_NAND:
3961
3962	Define this if you have a NAND device which you want to use
3963	for the environment.
3964
3965	- CONFIG_ENV_OFFSET:
3966	- CONFIG_ENV_SIZE:
3967
3968	  These two #defines specify the offset and size of the environment
3969	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3970	  aligned to an erase block boundary.
3971
3972	- CONFIG_ENV_OFFSET_REDUND (optional):
3973
3974	  This setting describes a second storage area of CONFIG_ENV_SIZE
3975	  size used to hold a redundant copy of the environment data, so
3976	  that there is a valid backup copy in case there is a power failure
3977	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3978	  aligned to an erase block boundary.
3979
3980	- CONFIG_ENV_RANGE (optional):
3981
3982	  Specifies the length of the region in which the environment
3983	  can be written.  This should be a multiple of the NAND device's
3984	  block size.  Specifying a range with more erase blocks than
3985	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3986	  the range to be avoided.
3987
3988	- CONFIG_ENV_OFFSET_OOB (optional):
3989
3990	  Enables support for dynamically retrieving the offset of the
3991	  environment from block zero's out-of-band data.  The
3992	  "nand env.oob" command can be used to record this offset.
3993	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3994	  using CONFIG_ENV_OFFSET_OOB.
3995
3996- CONFIG_NAND_ENV_DST
3997
3998	Defines address in RAM to which the nand_spl code should copy the
3999	environment. If redundant environment is used, it will be copied to
4000	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4001
4002- CONFIG_ENV_IS_IN_UBI:
4003
4004	Define this if you have an UBI volume that you want to use for the
4005	environment.  This has the benefit of wear-leveling the environment
4006	accesses, which is important on NAND.
4007
4008	- CONFIG_ENV_UBI_PART:
4009
4010	  Define this to a string that is the mtd partition containing the UBI.
4011
4012	- CONFIG_ENV_UBI_VOLUME:
4013
4014	  Define this to the name of the volume that you want to store the
4015	  environment in.
4016
4017	- CONFIG_ENV_UBI_VOLUME_REDUND:
4018
4019	  Define this to the name of another volume to store a second copy of
4020	  the environment in.  This will enable redundant environments in UBI.
4021	  It is assumed that both volumes are in the same MTD partition.
4022
4023	- CONFIG_UBI_SILENCE_MSG
4024	- CONFIG_UBIFS_SILENCE_MSG
4025
4026	  You will probably want to define these to avoid a really noisy system
4027	  when storing the env in UBI.
4028
4029- CONFIG_ENV_IS_IN_MMC:
4030
4031	Define this if you have an MMC device which you want to use for the
4032	environment.
4033
4034	- CONFIG_SYS_MMC_ENV_DEV:
4035
4036	  Specifies which MMC device the environment is stored in.
4037
4038	- CONFIG_SYS_MMC_ENV_PART (optional):
4039
4040	  Specifies which MMC partition the environment is stored in. If not
4041	  set, defaults to partition 0, the user area. Common values might be
4042	  1 (first MMC boot partition), 2 (second MMC boot partition).
4043
4044	- CONFIG_ENV_OFFSET:
4045	- CONFIG_ENV_SIZE:
4046
4047	  These two #defines specify the offset and size of the environment
4048	  area within the specified MMC device.
4049
4050	  If offset is positive (the usual case), it is treated as relative to
4051	  the start of the MMC partition. If offset is negative, it is treated
4052	  as relative to the end of the MMC partition. This can be useful if
4053	  your board may be fitted with different MMC devices, which have
4054	  different sizes for the MMC partitions, and you always want the
4055	  environment placed at the very end of the partition, to leave the
4056	  maximum possible space before it, to store other data.
4057
4058	  These two values are in units of bytes, but must be aligned to an
4059	  MMC sector boundary.
4060
4061	- CONFIG_ENV_OFFSET_REDUND (optional):
4062
4063	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4064	  hold a redundant copy of the environment data. This provides a
4065	  valid backup copy in case the other copy is corrupted, e.g. due
4066	  to a power failure during a "saveenv" operation.
4067
4068	  This value may also be positive or negative; this is handled in the
4069	  same way as CONFIG_ENV_OFFSET.
4070
4071	  This value is also in units of bytes, but must also be aligned to
4072	  an MMC sector boundary.
4073
4074	- CONFIG_ENV_SIZE_REDUND (optional):
4075
4076	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4077	  set. If this value is set, it must be set to the same value as
4078	  CONFIG_ENV_SIZE.
4079
4080- CONFIG_SYS_SPI_INIT_OFFSET
4081
4082	Defines offset to the initial SPI buffer area in DPRAM. The
4083	area is used at an early stage (ROM part) if the environment
4084	is configured to reside in the SPI EEPROM: We need a 520 byte
4085	scratch DPRAM area. It is used between the two initialization
4086	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4087	to be a good choice since it makes it far enough from the
4088	start of the data area as well as from the stack pointer.
4089
4090Please note that the environment is read-only until the monitor
4091has been relocated to RAM and a RAM copy of the environment has been
4092created; also, when using EEPROM you will have to use getenv_f()
4093until then to read environment variables.
4094
4095The environment is protected by a CRC32 checksum. Before the monitor
4096is relocated into RAM, as a result of a bad CRC you will be working
4097with the compiled-in default environment - *silently*!!! [This is
4098necessary, because the first environment variable we need is the
4099"baudrate" setting for the console - if we have a bad CRC, we don't
4100have any device yet where we could complain.]
4101
4102Note: once the monitor has been relocated, then it will complain if
4103the default environment is used; a new CRC is computed as soon as you
4104use the "saveenv" command to store a valid environment.
4105
4106- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4107		Echo the inverted Ethernet link state to the fault LED.
4108
4109		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4110		      also needs to be defined.
4111
4112- CONFIG_SYS_FAULT_MII_ADDR:
4113		MII address of the PHY to check for the Ethernet link state.
4114
4115- CONFIG_NS16550_MIN_FUNCTIONS:
4116		Define this if you desire to only have use of the NS16550_init
4117		and NS16550_putc functions for the serial driver located at
4118		drivers/serial/ns16550.c.  This option is useful for saving
4119		space for already greatly restricted images, including but not
4120		limited to NAND_SPL configurations.
4121
4122- CONFIG_DISPLAY_BOARDINFO
4123		Display information about the board that U-Boot is running on
4124		when U-Boot starts up. The board function checkboard() is called
4125		to do this.
4126
4127- CONFIG_DISPLAY_BOARDINFO_LATE
4128		Similar to the previous option, but display this information
4129		later, once stdio is running and output goes to the LCD, if
4130		present.
4131
4132Low Level (hardware related) configuration options:
4133---------------------------------------------------
4134
4135- CONFIG_SYS_CACHELINE_SIZE:
4136		Cache Line Size of the CPU.
4137
4138- CONFIG_SYS_DEFAULT_IMMR:
4139		Default address of the IMMR after system reset.
4140
4141		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4142		and RPXsuper) to be able to adjust the position of
4143		the IMMR register after a reset.
4144
4145- CONFIG_SYS_CCSRBAR_DEFAULT:
4146		Default (power-on reset) physical address of CCSR on Freescale
4147		PowerPC SOCs.
4148
4149- CONFIG_SYS_CCSRBAR:
4150		Virtual address of CCSR.  On a 32-bit build, this is typically
4151		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4152
4153		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4154		for cross-platform code that uses that macro instead.
4155
4156- CONFIG_SYS_CCSRBAR_PHYS:
4157		Physical address of CCSR.  CCSR can be relocated to a new
4158		physical address, if desired.  In this case, this macro should
4159		be set to that address.	 Otherwise, it should be set to the
4160		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4161		is typically relocated on 36-bit builds.  It is recommended
4162		that this macro be defined via the _HIGH and _LOW macros:
4163
4164		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4165			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4166
4167- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4168		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4169		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4170		used in assembly code, so it must not contain typecasts or
4171		integer size suffixes (e.g. "ULL").
4172
4173- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4174		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4175		used in assembly code, so it must not contain typecasts or
4176		integer size suffixes (e.g. "ULL").
4177
4178- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4179		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4180		forced to a value that ensures that CCSR is not relocated.
4181
4182- Floppy Disk Support:
4183		CONFIG_SYS_FDC_DRIVE_NUMBER
4184
4185		the default drive number (default value 0)
4186
4187		CONFIG_SYS_ISA_IO_STRIDE
4188
4189		defines the spacing between FDC chipset registers
4190		(default value 1)
4191
4192		CONFIG_SYS_ISA_IO_OFFSET
4193
4194		defines the offset of register from address. It
4195		depends on which part of the data bus is connected to
4196		the FDC chipset. (default value 0)
4197
4198		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4199		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4200		default value.
4201
4202		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4203		fdc_hw_init() is called at the beginning of the FDC
4204		setup. fdc_hw_init() must be provided by the board
4205		source code. It is used to make hardware dependant
4206		initializations.
4207
4208- CONFIG_IDE_AHB:
4209		Most IDE controllers were designed to be connected with PCI
4210		interface. Only few of them were designed for AHB interface.
4211		When software is doing ATA command and data transfer to
4212		IDE devices through IDE-AHB controller, some additional
4213		registers accessing to these kind of IDE-AHB controller
4214		is requierd.
4215
4216- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4217		DO NOT CHANGE unless you know exactly what you're
4218		doing! (11-4) [MPC8xx/82xx systems only]
4219
4220- CONFIG_SYS_INIT_RAM_ADDR:
4221
4222		Start address of memory area that can be used for
4223		initial data and stack; please note that this must be
4224		writable memory that is working WITHOUT special
4225		initialization, i. e. you CANNOT use normal RAM which
4226		will become available only after programming the
4227		memory controller and running certain initialization
4228		sequences.
4229
4230		U-Boot uses the following memory types:
4231		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4232		- MPC824X: data cache
4233		- PPC4xx:  data cache
4234
4235- CONFIG_SYS_GBL_DATA_OFFSET:
4236
4237		Offset of the initial data structure in the memory
4238		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4239		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4240		data is located at the end of the available space
4241		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4242		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4243		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4244		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4245
4246	Note:
4247		On the MPC824X (or other systems that use the data
4248		cache for initial memory) the address chosen for
4249		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4250		point to an otherwise UNUSED address space between
4251		the top of RAM and the start of the PCI space.
4252
4253- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4254
4255- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4256
4257- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4258
4259- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4260
4261- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4262
4263- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4264
4265- CONFIG_SYS_OR_TIMING_SDRAM:
4266		SDRAM timing
4267
4268- CONFIG_SYS_MAMR_PTA:
4269		periodic timer for refresh
4270
4271- CONFIG_SYS_DER:	Debug Event Register (37-47)
4272
4273- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4274  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4275  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4276  CONFIG_SYS_BR1_PRELIM:
4277		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4278
4279- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4280  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4281  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4282		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4283
4284- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4285  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4286		Machine Mode Register and Memory Periodic Timer
4287		Prescaler definitions (SDRAM timing)
4288
4289- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4290		enable I2C microcode relocation patch (MPC8xx);
4291		define relocation offset in DPRAM [DSP2]
4292
4293- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4294		enable SMC microcode relocation patch (MPC8xx);
4295		define relocation offset in DPRAM [SMC1]
4296
4297- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4298		enable SPI microcode relocation patch (MPC8xx);
4299		define relocation offset in DPRAM [SCC4]
4300
4301- CONFIG_SYS_USE_OSCCLK:
4302		Use OSCM clock mode on MBX8xx board. Be careful,
4303		wrong setting might damage your board. Read
4304		doc/README.MBX before setting this variable!
4305
4306- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4307		Offset of the bootmode word in DPRAM used by post
4308		(Power On Self Tests). This definition overrides
4309		#define'd default value in commproc.h resp.
4310		cpm_8260.h.
4311
4312- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4313  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4314  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4315  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4316  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4317  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4318  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4319  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4320		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4321
4322- CONFIG_PCI_DISABLE_PCIE:
4323		Disable PCI-Express on systems where it is supported but not
4324		required.
4325
4326- CONFIG_PCI_ENUM_ONLY
4327		Only scan through and get the devices on the busses.
4328		Don't do any setup work, presumably because someone or
4329		something has already done it, and we don't need to do it
4330		a second time.	Useful for platforms that are pre-booted
4331		by coreboot or similar.
4332
4333- CONFIG_PCI_INDIRECT_BRIDGE:
4334		Enable support for indirect PCI bridges.
4335
4336- CONFIG_SYS_SRIO:
4337		Chip has SRIO or not
4338
4339- CONFIG_SRIO1:
4340		Board has SRIO 1 port available
4341
4342- CONFIG_SRIO2:
4343		Board has SRIO 2 port available
4344
4345- CONFIG_SRIO_PCIE_BOOT_MASTER
4346		Board can support master function for Boot from SRIO and PCIE
4347
4348- CONFIG_SYS_SRIOn_MEM_VIRT:
4349		Virtual Address of SRIO port 'n' memory region
4350
4351- CONFIG_SYS_SRIOn_MEM_PHYS:
4352		Physical Address of SRIO port 'n' memory region
4353
4354- CONFIG_SYS_SRIOn_MEM_SIZE:
4355		Size of SRIO port 'n' memory region
4356
4357- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4358		Defined to tell the NAND controller that the NAND chip is using
4359		a 16 bit bus.
4360		Not all NAND drivers use this symbol.
4361		Example of drivers that use it:
4362		- drivers/mtd/nand/ndfc.c
4363		- drivers/mtd/nand/mxc_nand.c
4364
4365- CONFIG_SYS_NDFC_EBC0_CFG
4366		Sets the EBC0_CFG register for the NDFC. If not defined
4367		a default value will be used.
4368
4369- CONFIG_SPD_EEPROM
4370		Get DDR timing information from an I2C EEPROM. Common
4371		with pluggable memory modules such as SODIMMs
4372
4373  SPD_EEPROM_ADDRESS
4374		I2C address of the SPD EEPROM
4375
4376- CONFIG_SYS_SPD_BUS_NUM
4377		If SPD EEPROM is on an I2C bus other than the first
4378		one, specify here. Note that the value must resolve
4379		to something your driver can deal with.
4380
4381- CONFIG_SYS_DDR_RAW_TIMING
4382		Get DDR timing information from other than SPD. Common with
4383		soldered DDR chips onboard without SPD. DDR raw timing
4384		parameters are extracted from datasheet and hard-coded into
4385		header files or board specific files.
4386
4387- CONFIG_FSL_DDR_INTERACTIVE
4388		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4389
4390- CONFIG_SYS_83XX_DDR_USES_CS0
4391		Only for 83xx systems. If specified, then DDR should
4392		be configured using CS0 and CS1 instead of CS2 and CS3.
4393
4394- CONFIG_ETHER_ON_FEC[12]
4395		Define to enable FEC[12] on a 8xx series processor.
4396
4397- CONFIG_FEC[12]_PHY
4398		Define to the hardcoded PHY address which corresponds
4399		to the given FEC; i. e.
4400			#define CONFIG_FEC1_PHY 4
4401		means that the PHY with address 4 is connected to FEC1
4402
4403		When set to -1, means to probe for first available.
4404
4405- CONFIG_FEC[12]_PHY_NORXERR
4406		The PHY does not have a RXERR line (RMII only).
4407		(so program the FEC to ignore it).
4408
4409- CONFIG_RMII
4410		Enable RMII mode for all FECs.
4411		Note that this is a global option, we can't
4412		have one FEC in standard MII mode and another in RMII mode.
4413
4414- CONFIG_CRC32_VERIFY
4415		Add a verify option to the crc32 command.
4416		The syntax is:
4417
4418		=> crc32 -v <address> <count> <crc32>
4419
4420		Where address/count indicate a memory area
4421		and crc32 is the correct crc32 which the
4422		area should have.
4423
4424- CONFIG_LOOPW
4425		Add the "loopw" memory command. This only takes effect if
4426		the memory commands are activated globally (CONFIG_CMD_MEM).
4427
4428- CONFIG_MX_CYCLIC
4429		Add the "mdc" and "mwc" memory commands. These are cyclic
4430		"md/mw" commands.
4431		Examples:
4432
4433		=> mdc.b 10 4 500
4434		This command will print 4 bytes (10,11,12,13) each 500 ms.
4435
4436		=> mwc.l 100 12345678 10
4437		This command will write 12345678 to address 100 all 10 ms.
4438
4439		This only takes effect if the memory commands are activated
4440		globally (CONFIG_CMD_MEM).
4441
4442- CONFIG_SKIP_LOWLEVEL_INIT
4443		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4444		low level initializations (like setting up the memory
4445		controller) are omitted and/or U-Boot does not
4446		relocate itself into RAM.
4447
4448		Normally this variable MUST NOT be defined. The only
4449		exception is when U-Boot is loaded (to RAM) by some
4450		other boot loader or by a debugger which performs
4451		these initializations itself.
4452
4453- CONFIG_SPL_BUILD
4454		Modifies the behaviour of start.S when compiling a loader
4455		that is executed before the actual U-Boot. E.g. when
4456		compiling a NAND SPL.
4457
4458- CONFIG_TPL_BUILD
4459		Modifies the behaviour of start.S  when compiling a loader
4460		that is executed after the SPL and before the actual U-Boot.
4461		It is loaded by the SPL.
4462
4463- CONFIG_SYS_MPC85XX_NO_RESETVEC
4464		Only for 85xx systems. If this variable is specified, the section
4465		.resetvec is not kept and the section .bootpg is placed in the
4466		previous 4k of the .text section.
4467
4468- CONFIG_ARCH_MAP_SYSMEM
4469		Generally U-Boot (and in particular the md command) uses
4470		effective address. It is therefore not necessary to regard
4471		U-Boot address as virtual addresses that need to be translated
4472		to physical addresses. However, sandbox requires this, since
4473		it maintains its own little RAM buffer which contains all
4474		addressable memory. This option causes some memory accesses
4475		to be mapped through map_sysmem() / unmap_sysmem().
4476
4477- CONFIG_USE_ARCH_MEMCPY
4478  CONFIG_USE_ARCH_MEMSET
4479		If these options are used a optimized version of memcpy/memset will
4480		be used if available. These functions may be faster under some
4481		conditions but may increase the binary size.
4482
4483- CONFIG_X86_RESET_VECTOR
4484		If defined, the x86 reset vector code is included. This is not
4485		needed when U-Boot is running from Coreboot.
4486
4487- CONFIG_SYS_MPUCLK
4488		Defines the MPU clock speed (in MHz).
4489
4490		NOTE : currently only supported on AM335x platforms.
4491
4492- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4493		Enables the RTC32K OSC on AM33xx based plattforms
4494
4495Freescale QE/FMAN Firmware Support:
4496-----------------------------------
4497
4498The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4499loading of "firmware", which is encoded in the QE firmware binary format.
4500This firmware often needs to be loaded during U-Boot booting, so macros
4501are used to identify the storage device (NOR flash, SPI, etc) and the address
4502within that device.
4503
4504- CONFIG_SYS_QE_FMAN_FW_ADDR
4505	The address in the storage device where the firmware is located.  The
4506	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4507	is also specified.
4508
4509- CONFIG_SYS_QE_FMAN_FW_LENGTH
4510	The maximum possible size of the firmware.  The firmware binary format
4511	has a field that specifies the actual size of the firmware, but it
4512	might not be possible to read any part of the firmware unless some
4513	local storage is allocated to hold the entire firmware first.
4514
4515- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4516	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4517	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4518	virtual address in NOR flash.
4519
4520- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4521	Specifies that QE/FMAN firmware is located in NAND flash.
4522	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4523
4524- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4525	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4526	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4527
4528- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4529	Specifies that QE/FMAN firmware is located on the primary SPI
4530	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4531
4532- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4533	Specifies that QE/FMAN firmware is located in the remote (master)
4534	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4535	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4536	window->master inbound window->master LAW->the ucode address in
4537	master's memory space.
4538
4539Building the Software:
4540======================
4541
4542Building U-Boot has been tested in several native build environments
4543and in many different cross environments. Of course we cannot support
4544all possibly existing versions of cross development tools in all
4545(potentially obsolete) versions. In case of tool chain problems we
4546recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4547which is extensively used to build and test U-Boot.
4548
4549If you are not using a native environment, it is assumed that you
4550have GNU cross compiling tools available in your path. In this case,
4551you must set the environment variable CROSS_COMPILE in your shell.
4552Note that no changes to the Makefile or any other source files are
4553necessary. For example using the ELDK on a 4xx CPU, please enter:
4554
4555	$ CROSS_COMPILE=ppc_4xx-
4556	$ export CROSS_COMPILE
4557
4558Note: If you wish to generate Windows versions of the utilities in
4559      the tools directory you can use the MinGW toolchain
4560      (http://www.mingw.org).  Set your HOST tools to the MinGW
4561      toolchain and execute 'make tools'.  For example:
4562
4563       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4564
4565      Binaries such as tools/mkimage.exe will be created which can
4566      be executed on computers running Windows.
4567
4568U-Boot is intended to be simple to build. After installing the
4569sources you must configure U-Boot for one specific board type. This
4570is done by typing:
4571
4572	make NAME_config
4573
4574where "NAME_config" is the name of one of the existing configu-
4575rations; see boards.cfg for supported names.
4576
4577Note: for some board special configuration names may exist; check if
4578      additional information is available from the board vendor; for
4579      instance, the TQM823L systems are available without (standard)
4580      or with LCD support. You can select such additional "features"
4581      when choosing the configuration, i. e.
4582
4583      make TQM823L_config
4584	- will configure for a plain TQM823L, i. e. no LCD support
4585
4586      make TQM823L_LCD_config
4587	- will configure for a TQM823L with U-Boot console on LCD
4588
4589      etc.
4590
4591
4592Finally, type "make all", and you should get some working U-Boot
4593images ready for download to / installation on your system:
4594
4595- "u-boot.bin" is a raw binary image
4596- "u-boot" is an image in ELF binary format
4597- "u-boot.srec" is in Motorola S-Record format
4598
4599By default the build is performed locally and the objects are saved
4600in the source directory. One of the two methods can be used to change
4601this behavior and build U-Boot to some external directory:
4602
46031. Add O= to the make command line invocations:
4604
4605	make O=/tmp/build distclean
4606	make O=/tmp/build NAME_config
4607	make O=/tmp/build all
4608
46092. Set environment variable BUILD_DIR to point to the desired location:
4610
4611	export BUILD_DIR=/tmp/build
4612	make distclean
4613	make NAME_config
4614	make all
4615
4616Note that the command line "O=" setting overrides the BUILD_DIR environment
4617variable.
4618
4619
4620Please be aware that the Makefiles assume you are using GNU make, so
4621for instance on NetBSD you might need to use "gmake" instead of
4622native "make".
4623
4624
4625If the system board that you have is not listed, then you will need
4626to port U-Boot to your hardware platform. To do this, follow these
4627steps:
4628
46291.  Add a new configuration option for your board to the toplevel
4630    "boards.cfg" file, using the existing entries as examples.
4631    Follow the instructions there to keep the boards in order.
46322.  Create a new directory to hold your board specific code. Add any
4633    files you need. In your board directory, you will need at least
4634    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
46353.  Create a new configuration file "include/configs/<board>.h" for
4636    your board
46373.  If you're porting U-Boot to a new CPU, then also create a new
4638    directory to hold your CPU specific code. Add any files you need.
46394.  Run "make <board>_config" with your new name.
46405.  Type "make", and you should get a working "u-boot.srec" file
4641    to be installed on your target system.
46426.  Debug and solve any problems that might arise.
4643    [Of course, this last step is much harder than it sounds.]
4644
4645
4646Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4647==============================================================
4648
4649If you have modified U-Boot sources (for instance added a new board
4650or support for new devices, a new CPU, etc.) you are expected to
4651provide feedback to the other developers. The feedback normally takes
4652the form of a "patch", i. e. a context diff against a certain (latest
4653official or latest in the git repository) version of U-Boot sources.
4654
4655But before you submit such a patch, please verify that your modifi-
4656cation did not break existing code. At least make sure that *ALL* of
4657the supported boards compile WITHOUT ANY compiler warnings. To do so,
4658just run the "MAKEALL" script, which will configure and build U-Boot
4659for ALL supported system. Be warned, this will take a while. You can
4660select which (cross) compiler to use by passing a `CROSS_COMPILE'
4661environment variable to the script, i. e. to use the ELDK cross tools
4662you can type
4663
4664	CROSS_COMPILE=ppc_8xx- MAKEALL
4665
4666or to build on a native PowerPC system you can type
4667
4668	CROSS_COMPILE=' ' MAKEALL
4669
4670When using the MAKEALL script, the default behaviour is to build
4671U-Boot in the source directory. This location can be changed by
4672setting the BUILD_DIR environment variable. Also, for each target
4673built, the MAKEALL script saves two log files (<target>.ERR and
4674<target>.MAKEALL) in the <source dir>/LOG directory. This default
4675location can be changed by setting the MAKEALL_LOGDIR environment
4676variable. For example:
4677
4678	export BUILD_DIR=/tmp/build
4679	export MAKEALL_LOGDIR=/tmp/log
4680	CROSS_COMPILE=ppc_8xx- MAKEALL
4681
4682With the above settings build objects are saved in the /tmp/build,
4683log files are saved in the /tmp/log and the source tree remains clean
4684during the whole build process.
4685
4686
4687See also "U-Boot Porting Guide" below.
4688
4689
4690Monitor Commands - Overview:
4691============================
4692
4693go	- start application at address 'addr'
4694run	- run commands in an environment variable
4695bootm	- boot application image from memory
4696bootp	- boot image via network using BootP/TFTP protocol
4697bootz   - boot zImage from memory
4698tftpboot- boot image via network using TFTP protocol
4699	       and env variables "ipaddr" and "serverip"
4700	       (and eventually "gatewayip")
4701tftpput - upload a file via network using TFTP protocol
4702rarpboot- boot image via network using RARP/TFTP protocol
4703diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4704loads	- load S-Record file over serial line
4705loadb	- load binary file over serial line (kermit mode)
4706md	- memory display
4707mm	- memory modify (auto-incrementing)
4708nm	- memory modify (constant address)
4709mw	- memory write (fill)
4710cp	- memory copy
4711cmp	- memory compare
4712crc32	- checksum calculation
4713i2c	- I2C sub-system
4714sspi	- SPI utility commands
4715base	- print or set address offset
4716printenv- print environment variables
4717setenv	- set environment variables
4718saveenv - save environment variables to persistent storage
4719protect - enable or disable FLASH write protection
4720erase	- erase FLASH memory
4721flinfo	- print FLASH memory information
4722nand	- NAND memory operations (see doc/README.nand)
4723bdinfo	- print Board Info structure
4724iminfo	- print header information for application image
4725coninfo - print console devices and informations
4726ide	- IDE sub-system
4727loop	- infinite loop on address range
4728loopw	- infinite write loop on address range
4729mtest	- simple RAM test
4730icache	- enable or disable instruction cache
4731dcache	- enable or disable data cache
4732reset	- Perform RESET of the CPU
4733echo	- echo args to console
4734version - print monitor version
4735help	- print online help
4736?	- alias for 'help'
4737
4738
4739Monitor Commands - Detailed Description:
4740========================================
4741
4742TODO.
4743
4744For now: just type "help <command>".
4745
4746
4747Environment Variables:
4748======================
4749
4750U-Boot supports user configuration using Environment Variables which
4751can be made persistent by saving to Flash memory.
4752
4753Environment Variables are set using "setenv", printed using
4754"printenv", and saved to Flash using "saveenv". Using "setenv"
4755without a value can be used to delete a variable from the
4756environment. As long as you don't save the environment you are
4757working with an in-memory copy. In case the Flash area containing the
4758environment is erased by accident, a default environment is provided.
4759
4760Some configuration options can be set using Environment Variables.
4761
4762List of environment variables (most likely not complete):
4763
4764  baudrate	- see CONFIG_BAUDRATE
4765
4766  bootdelay	- see CONFIG_BOOTDELAY
4767
4768  bootcmd	- see CONFIG_BOOTCOMMAND
4769
4770  bootargs	- Boot arguments when booting an RTOS image
4771
4772  bootfile	- Name of the image to load with TFTP
4773
4774  bootm_low	- Memory range available for image processing in the bootm
4775		  command can be restricted. This variable is given as
4776		  a hexadecimal number and defines lowest address allowed
4777		  for use by the bootm command. See also "bootm_size"
4778		  environment variable. Address defined by "bootm_low" is
4779		  also the base of the initial memory mapping for the Linux
4780		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4781		  bootm_mapsize.
4782
4783  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4784		  This variable is given as a hexadecimal number and it
4785		  defines the size of the memory region starting at base
4786		  address bootm_low that is accessible by the Linux kernel
4787		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4788		  as the default value if it is defined, and bootm_size is
4789		  used otherwise.
4790
4791  bootm_size	- Memory range available for image processing in the bootm
4792		  command can be restricted. This variable is given as
4793		  a hexadecimal number and defines the size of the region
4794		  allowed for use by the bootm command. See also "bootm_low"
4795		  environment variable.
4796
4797  updatefile	- Location of the software update file on a TFTP server, used
4798		  by the automatic software update feature. Please refer to
4799		  documentation in doc/README.update for more details.
4800
4801  autoload	- if set to "no" (any string beginning with 'n'),
4802		  "bootp" will just load perform a lookup of the
4803		  configuration from the BOOTP server, but not try to
4804		  load any image using TFTP
4805
4806  autostart	- if set to "yes", an image loaded using the "bootp",
4807		  "rarpboot", "tftpboot" or "diskboot" commands will
4808		  be automatically started (by internally calling
4809		  "bootm")
4810
4811		  If set to "no", a standalone image passed to the
4812		  "bootm" command will be copied to the load address
4813		  (and eventually uncompressed), but NOT be started.
4814		  This can be used to load and uncompress arbitrary
4815		  data.
4816
4817  fdt_high	- if set this restricts the maximum address that the
4818		  flattened device tree will be copied into upon boot.
4819		  For example, if you have a system with 1 GB memory
4820		  at physical address 0x10000000, while Linux kernel
4821		  only recognizes the first 704 MB as low memory, you
4822		  may need to set fdt_high as 0x3C000000 to have the
4823		  device tree blob be copied to the maximum address
4824		  of the 704 MB low memory, so that Linux kernel can
4825		  access it during the boot procedure.
4826
4827		  If this is set to the special value 0xFFFFFFFF then
4828		  the fdt will not be copied at all on boot.  For this
4829		  to work it must reside in writable memory, have
4830		  sufficient padding on the end of it for u-boot to
4831		  add the information it needs into it, and the memory
4832		  must be accessible by the kernel.
4833
4834  fdtcontroladdr- if set this is the address of the control flattened
4835		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4836		  defined.
4837
4838  i2cfast	- (PPC405GP|PPC405EP only)
4839		  if set to 'y' configures Linux I2C driver for fast
4840		  mode (400kHZ). This environment variable is used in
4841		  initialization code. So, for changes to be effective
4842		  it must be saved and board must be reset.
4843
4844  initrd_high	- restrict positioning of initrd images:
4845		  If this variable is not set, initrd images will be
4846		  copied to the highest possible address in RAM; this
4847		  is usually what you want since it allows for
4848		  maximum initrd size. If for some reason you want to
4849		  make sure that the initrd image is loaded below the
4850		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4851		  variable to a value of "no" or "off" or "0".
4852		  Alternatively, you can set it to a maximum upper
4853		  address to use (U-Boot will still check that it
4854		  does not overwrite the U-Boot stack and data).
4855
4856		  For instance, when you have a system with 16 MB
4857		  RAM, and want to reserve 4 MB from use by Linux,
4858		  you can do this by adding "mem=12M" to the value of
4859		  the "bootargs" variable. However, now you must make
4860		  sure that the initrd image is placed in the first
4861		  12 MB as well - this can be done with
4862
4863		  setenv initrd_high 00c00000
4864
4865		  If you set initrd_high to 0xFFFFFFFF, this is an
4866		  indication to U-Boot that all addresses are legal
4867		  for the Linux kernel, including addresses in flash
4868		  memory. In this case U-Boot will NOT COPY the
4869		  ramdisk at all. This may be useful to reduce the
4870		  boot time on your system, but requires that this
4871		  feature is supported by your Linux kernel.
4872
4873  ipaddr	- IP address; needed for tftpboot command
4874
4875  loadaddr	- Default load address for commands like "bootp",
4876		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4877
4878  loads_echo	- see CONFIG_LOADS_ECHO
4879
4880  serverip	- TFTP server IP address; needed for tftpboot command
4881
4882  bootretry	- see CONFIG_BOOT_RETRY_TIME
4883
4884  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4885
4886  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4887
4888  ethprime	- controls which interface is used first.
4889
4890  ethact	- controls which interface is currently active.
4891		  For example you can do the following
4892
4893		  => setenv ethact FEC
4894		  => ping 192.168.0.1 # traffic sent on FEC
4895		  => setenv ethact SCC
4896		  => ping 10.0.0.1 # traffic sent on SCC
4897
4898  ethrotate	- When set to "no" U-Boot does not go through all
4899		  available network interfaces.
4900		  It just stays at the currently selected interface.
4901
4902  netretry	- When set to "no" each network operation will
4903		  either succeed or fail without retrying.
4904		  When set to "once" the network operation will
4905		  fail when all the available network interfaces
4906		  are tried once without success.
4907		  Useful on scripts which control the retry operation
4908		  themselves.
4909
4910  npe_ucode	- set load address for the NPE microcode
4911
4912  silent_linux  - If set then linux will be told to boot silently, by
4913		  changing the console to be empty. If "yes" it will be
4914		  made silent. If "no" it will not be made silent. If
4915		  unset, then it will be made silent if the U-Boot console
4916		  is silent.
4917
4918  tftpsrcport	- If this is set, the value is used for TFTP's
4919		  UDP source port.
4920
4921  tftpdstport	- If this is set, the value is used for TFTP's UDP
4922		  destination port instead of the Well Know Port 69.
4923
4924  tftpblocksize - Block size to use for TFTP transfers; if not set,
4925		  we use the TFTP server's default block size
4926
4927  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4928		  seconds, minimum value is 1000 = 1 second). Defines
4929		  when a packet is considered to be lost so it has to
4930		  be retransmitted. The default is 5000 = 5 seconds.
4931		  Lowering this value may make downloads succeed
4932		  faster in networks with high packet loss rates or
4933		  with unreliable TFTP servers.
4934
4935  vlan		- When set to a value < 4095 the traffic over
4936		  Ethernet is encapsulated/received over 802.1q
4937		  VLAN tagged frames.
4938
4939The following image location variables contain the location of images
4940used in booting. The "Image" column gives the role of the image and is
4941not an environment variable name. The other columns are environment
4942variable names. "File Name" gives the name of the file on a TFTP
4943server, "RAM Address" gives the location in RAM the image will be
4944loaded to, and "Flash Location" gives the image's address in NOR
4945flash or offset in NAND flash.
4946
4947*Note* - these variables don't have to be defined for all boards, some
4948boards currenlty use other variables for these purposes, and some
4949boards use these variables for other purposes.
4950
4951Image		    File Name	     RAM Address       Flash Location
4952-----		    ---------	     -----------       --------------
4953u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4954Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4955device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4956ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4957
4958The following environment variables may be used and automatically
4959updated by the network boot commands ("bootp" and "rarpboot"),
4960depending the information provided by your boot server:
4961
4962  bootfile	- see above
4963  dnsip		- IP address of your Domain Name Server
4964  dnsip2	- IP address of your secondary Domain Name Server
4965  gatewayip	- IP address of the Gateway (Router) to use
4966  hostname	- Target hostname
4967  ipaddr	- see above
4968  netmask	- Subnet Mask
4969  rootpath	- Pathname of the root filesystem on the NFS server
4970  serverip	- see above
4971
4972
4973There are two special Environment Variables:
4974
4975  serial#	- contains hardware identification information such
4976		  as type string and/or serial number
4977  ethaddr	- Ethernet address
4978
4979These variables can be set only once (usually during manufacturing of
4980the board). U-Boot refuses to delete or overwrite these variables
4981once they have been set once.
4982
4983
4984Further special Environment Variables:
4985
4986  ver		- Contains the U-Boot version string as printed
4987		  with the "version" command. This variable is
4988		  readonly (see CONFIG_VERSION_VARIABLE).
4989
4990
4991Please note that changes to some configuration parameters may take
4992only effect after the next boot (yes, that's just like Windoze :-).
4993
4994
4995Callback functions for environment variables:
4996---------------------------------------------
4997
4998For some environment variables, the behavior of u-boot needs to change
4999when their values are changed.  This functionailty allows functions to
5000be associated with arbitrary variables.  On creation, overwrite, or
5001deletion, the callback will provide the opportunity for some side
5002effect to happen or for the change to be rejected.
5003
5004The callbacks are named and associated with a function using the
5005U_BOOT_ENV_CALLBACK macro in your board or driver code.
5006
5007These callbacks are associated with variables in one of two ways.  The
5008static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5009in the board configuration to a string that defines a list of
5010associations.  The list must be in the following format:
5011
5012	entry = variable_name[:callback_name]
5013	list = entry[,list]
5014
5015If the callback name is not specified, then the callback is deleted.
5016Spaces are also allowed anywhere in the list.
5017
5018Callbacks can also be associated by defining the ".callbacks" variable
5019with the same list format above.  Any association in ".callbacks" will
5020override any association in the static list. You can define
5021CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5022".callbacks" envirnoment variable in the default or embedded environment.
5023
5024
5025Command Line Parsing:
5026=====================
5027
5028There are two different command line parsers available with U-Boot:
5029the old "simple" one, and the much more powerful "hush" shell:
5030
5031Old, simple command line parser:
5032--------------------------------
5033
5034- supports environment variables (through setenv / saveenv commands)
5035- several commands on one line, separated by ';'
5036- variable substitution using "... ${name} ..." syntax
5037- special characters ('$', ';') can be escaped by prefixing with '\',
5038  for example:
5039	setenv bootcmd bootm \${address}
5040- You can also escape text by enclosing in single apostrophes, for example:
5041	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5042
5043Hush shell:
5044-----------
5045
5046- similar to Bourne shell, with control structures like
5047  if...then...else...fi, for...do...done; while...do...done,
5048  until...do...done, ...
5049- supports environment ("global") variables (through setenv / saveenv
5050  commands) and local shell variables (through standard shell syntax
5051  "name=value"); only environment variables can be used with "run"
5052  command
5053
5054General rules:
5055--------------
5056
5057(1) If a command line (or an environment variable executed by a "run"
5058    command) contains several commands separated by semicolon, and
5059    one of these commands fails, then the remaining commands will be
5060    executed anyway.
5061
5062(2) If you execute several variables with one call to run (i. e.
5063    calling run with a list of variables as arguments), any failing
5064    command will cause "run" to terminate, i. e. the remaining
5065    variables are not executed.
5066
5067Note for Redundant Ethernet Interfaces:
5068=======================================
5069
5070Some boards come with redundant Ethernet interfaces; U-Boot supports
5071such configurations and is capable of automatic selection of a
5072"working" interface when needed. MAC assignment works as follows:
5073
5074Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5075MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5076"eth1addr" (=>eth1), "eth2addr", ...
5077
5078If the network interface stores some valid MAC address (for instance
5079in SROM), this is used as default address if there is NO correspon-
5080ding setting in the environment; if the corresponding environment
5081variable is set, this overrides the settings in the card; that means:
5082
5083o If the SROM has a valid MAC address, and there is no address in the
5084  environment, the SROM's address is used.
5085
5086o If there is no valid address in the SROM, and a definition in the
5087  environment exists, then the value from the environment variable is
5088  used.
5089
5090o If both the SROM and the environment contain a MAC address, and
5091  both addresses are the same, this MAC address is used.
5092
5093o If both the SROM and the environment contain a MAC address, and the
5094  addresses differ, the value from the environment is used and a
5095  warning is printed.
5096
5097o If neither SROM nor the environment contain a MAC address, an error
5098  is raised.
5099
5100If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5101will be programmed into hardware as part of the initialization process.	 This
5102may be skipped by setting the appropriate 'ethmacskip' environment variable.
5103The naming convention is as follows:
5104"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5105
5106Image Formats:
5107==============
5108
5109U-Boot is capable of booting (and performing other auxiliary operations on)
5110images in two formats:
5111
5112New uImage format (FIT)
5113-----------------------
5114
5115Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5116to Flattened Device Tree). It allows the use of images with multiple
5117components (several kernels, ramdisks, etc.), with contents protected by
5118SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5119
5120
5121Old uImage format
5122-----------------
5123
5124Old image format is based on binary files which can be basically anything,
5125preceded by a special header; see the definitions in include/image.h for
5126details; basically, the header defines the following image properties:
5127
5128* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5129  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5130  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5131  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5132  INTEGRITY).
5133* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5134  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5135  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5136* Compression Type (uncompressed, gzip, bzip2)
5137* Load Address
5138* Entry Point
5139* Image Name
5140* Image Timestamp
5141
5142The header is marked by a special Magic Number, and both the header
5143and the data portions of the image are secured against corruption by
5144CRC32 checksums.
5145
5146
5147Linux Support:
5148==============
5149
5150Although U-Boot should support any OS or standalone application
5151easily, the main focus has always been on Linux during the design of
5152U-Boot.
5153
5154U-Boot includes many features that so far have been part of some
5155special "boot loader" code within the Linux kernel. Also, any
5156"initrd" images to be used are no longer part of one big Linux image;
5157instead, kernel and "initrd" are separate images. This implementation
5158serves several purposes:
5159
5160- the same features can be used for other OS or standalone
5161  applications (for instance: using compressed images to reduce the
5162  Flash memory footprint)
5163
5164- it becomes much easier to port new Linux kernel versions because
5165  lots of low-level, hardware dependent stuff are done by U-Boot
5166
5167- the same Linux kernel image can now be used with different "initrd"
5168  images; of course this also means that different kernel images can
5169  be run with the same "initrd". This makes testing easier (you don't
5170  have to build a new "zImage.initrd" Linux image when you just
5171  change a file in your "initrd"). Also, a field-upgrade of the
5172  software is easier now.
5173
5174
5175Linux HOWTO:
5176============
5177
5178Porting Linux to U-Boot based systems:
5179---------------------------------------
5180
5181U-Boot cannot save you from doing all the necessary modifications to
5182configure the Linux device drivers for use with your target hardware
5183(no, we don't intend to provide a full virtual machine interface to
5184Linux :-).
5185
5186But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5187
5188Just make sure your machine specific header file (for instance
5189include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5190Information structure as we define in include/asm-<arch>/u-boot.h,
5191and make sure that your definition of IMAP_ADDR uses the same value
5192as your U-Boot configuration in CONFIG_SYS_IMMR.
5193
5194
5195Configuring the Linux kernel:
5196-----------------------------
5197
5198No specific requirements for U-Boot. Make sure you have some root
5199device (initial ramdisk, NFS) for your target system.
5200
5201
5202Building a Linux Image:
5203-----------------------
5204
5205With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5206not used. If you use recent kernel source, a new build target
5207"uImage" will exist which automatically builds an image usable by
5208U-Boot. Most older kernels also have support for a "pImage" target,
5209which was introduced for our predecessor project PPCBoot and uses a
5210100% compatible format.
5211
5212Example:
5213
5214	make TQM850L_config
5215	make oldconfig
5216	make dep
5217	make uImage
5218
5219The "uImage" build target uses a special tool (in 'tools/mkimage') to
5220encapsulate a compressed Linux kernel image with header	 information,
5221CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5222
5223* build a standard "vmlinux" kernel image (in ELF binary format):
5224
5225* convert the kernel into a raw binary image:
5226
5227	${CROSS_COMPILE}-objcopy -O binary \
5228				 -R .note -R .comment \
5229				 -S vmlinux linux.bin
5230
5231* compress the binary image:
5232
5233	gzip -9 linux.bin
5234
5235* package compressed binary image for U-Boot:
5236
5237	mkimage -A ppc -O linux -T kernel -C gzip \
5238		-a 0 -e 0 -n "Linux Kernel Image" \
5239		-d linux.bin.gz uImage
5240
5241
5242The "mkimage" tool can also be used to create ramdisk images for use
5243with U-Boot, either separated from the Linux kernel image, or
5244combined into one file. "mkimage" encapsulates the images with a 64
5245byte header containing information about target architecture,
5246operating system, image type, compression method, entry points, time
5247stamp, CRC32 checksums, etc.
5248
5249"mkimage" can be called in two ways: to verify existing images and
5250print the header information, or to build new images.
5251
5252In the first form (with "-l" option) mkimage lists the information
5253contained in the header of an existing U-Boot image; this includes
5254checksum verification:
5255
5256	tools/mkimage -l image
5257	  -l ==> list image header information
5258
5259The second form (with "-d" option) is used to build a U-Boot image
5260from a "data file" which is used as image payload:
5261
5262	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5263		      -n name -d data_file image
5264	  -A ==> set architecture to 'arch'
5265	  -O ==> set operating system to 'os'
5266	  -T ==> set image type to 'type'
5267	  -C ==> set compression type 'comp'
5268	  -a ==> set load address to 'addr' (hex)
5269	  -e ==> set entry point to 'ep' (hex)
5270	  -n ==> set image name to 'name'
5271	  -d ==> use image data from 'datafile'
5272
5273Right now, all Linux kernels for PowerPC systems use the same load
5274address (0x00000000), but the entry point address depends on the
5275kernel version:
5276
5277- 2.2.x kernels have the entry point at 0x0000000C,
5278- 2.3.x and later kernels have the entry point at 0x00000000.
5279
5280So a typical call to build a U-Boot image would read:
5281
5282	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5283	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5284	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5285	> examples/uImage.TQM850L
5286	Image Name:   2.4.4 kernel for TQM850L
5287	Created:      Wed Jul 19 02:34:59 2000
5288	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5289	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5290	Load Address: 0x00000000
5291	Entry Point:  0x00000000
5292
5293To verify the contents of the image (or check for corruption):
5294
5295	-> tools/mkimage -l examples/uImage.TQM850L
5296	Image Name:   2.4.4 kernel for TQM850L
5297	Created:      Wed Jul 19 02:34:59 2000
5298	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5299	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5300	Load Address: 0x00000000
5301	Entry Point:  0x00000000
5302
5303NOTE: for embedded systems where boot time is critical you can trade
5304speed for memory and install an UNCOMPRESSED image instead: this
5305needs more space in Flash, but boots much faster since it does not
5306need to be uncompressed:
5307
5308	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5309	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5310	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5311	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5312	> examples/uImage.TQM850L-uncompressed
5313	Image Name:   2.4.4 kernel for TQM850L
5314	Created:      Wed Jul 19 02:34:59 2000
5315	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5316	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5317	Load Address: 0x00000000
5318	Entry Point:  0x00000000
5319
5320
5321Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5322when your kernel is intended to use an initial ramdisk:
5323
5324	-> tools/mkimage -n 'Simple Ramdisk Image' \
5325	> -A ppc -O linux -T ramdisk -C gzip \
5326	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5327	Image Name:   Simple Ramdisk Image
5328	Created:      Wed Jan 12 14:01:50 2000
5329	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5330	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5331	Load Address: 0x00000000
5332	Entry Point:  0x00000000
5333
5334The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5335option performs the converse operation of the mkimage's second form (the "-d"
5336option). Given an image built by mkimage, the dumpimage extracts a "data file"
5337from the image:
5338
5339	tools/dumpimage -i image -p position data_file
5340	  -i ==> extract from the 'image' a specific 'data_file', \
5341	   indexed by 'position'
5342
5343
5344Installing a Linux Image:
5345-------------------------
5346
5347To downloading a U-Boot image over the serial (console) interface,
5348you must convert the image to S-Record format:
5349
5350	objcopy -I binary -O srec examples/image examples/image.srec
5351
5352The 'objcopy' does not understand the information in the U-Boot
5353image header, so the resulting S-Record file will be relative to
5354address 0x00000000. To load it to a given address, you need to
5355specify the target address as 'offset' parameter with the 'loads'
5356command.
5357
5358Example: install the image to address 0x40100000 (which on the
5359TQM8xxL is in the first Flash bank):
5360
5361	=> erase 40100000 401FFFFF
5362
5363	.......... done
5364	Erased 8 sectors
5365
5366	=> loads 40100000
5367	## Ready for S-Record download ...
5368	~>examples/image.srec
5369	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5370	...
5371	15989 15990 15991 15992
5372	[file transfer complete]
5373	[connected]
5374	## Start Addr = 0x00000000
5375
5376
5377You can check the success of the download using the 'iminfo' command;
5378this includes a checksum verification so you can be sure no data
5379corruption happened:
5380
5381	=> imi 40100000
5382
5383	## Checking Image at 40100000 ...
5384	   Image Name:	 2.2.13 for initrd on TQM850L
5385	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5386	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5387	   Load Address: 00000000
5388	   Entry Point:	 0000000c
5389	   Verifying Checksum ... OK
5390
5391
5392Boot Linux:
5393-----------
5394
5395The "bootm" command is used to boot an application that is stored in
5396memory (RAM or Flash). In case of a Linux kernel image, the contents
5397of the "bootargs" environment variable is passed to the kernel as
5398parameters. You can check and modify this variable using the
5399"printenv" and "setenv" commands:
5400
5401
5402	=> printenv bootargs
5403	bootargs=root=/dev/ram
5404
5405	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5406
5407	=> printenv bootargs
5408	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5409
5410	=> bootm 40020000
5411	## Booting Linux kernel at 40020000 ...
5412	   Image Name:	 2.2.13 for NFS on TQM850L
5413	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5414	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5415	   Load Address: 00000000
5416	   Entry Point:	 0000000c
5417	   Verifying Checksum ... OK
5418	   Uncompressing Kernel Image ... OK
5419	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
5420	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5421	time_init: decrementer frequency = 187500000/60
5422	Calibrating delay loop... 49.77 BogoMIPS
5423	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5424	...
5425
5426If you want to boot a Linux kernel with initial RAM disk, you pass
5427the memory addresses of both the kernel and the initrd image (PPBCOOT
5428format!) to the "bootm" command:
5429
5430	=> imi 40100000 40200000
5431
5432	## Checking Image at 40100000 ...
5433	   Image Name:	 2.2.13 for initrd on TQM850L
5434	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5435	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5436	   Load Address: 00000000
5437	   Entry Point:	 0000000c
5438	   Verifying Checksum ... OK
5439
5440	## Checking Image at 40200000 ...
5441	   Image Name:	 Simple Ramdisk Image
5442	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5443	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5444	   Load Address: 00000000
5445	   Entry Point:	 00000000
5446	   Verifying Checksum ... OK
5447
5448	=> bootm 40100000 40200000
5449	## Booting Linux kernel at 40100000 ...
5450	   Image Name:	 2.2.13 for initrd on TQM850L
5451	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5452	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5453	   Load Address: 00000000
5454	   Entry Point:	 0000000c
5455	   Verifying Checksum ... OK
5456	   Uncompressing Kernel Image ... OK
5457	## Loading RAMDisk Image at 40200000 ...
5458	   Image Name:	 Simple Ramdisk Image
5459	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5460	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5461	   Load Address: 00000000
5462	   Entry Point:	 00000000
5463	   Verifying Checksum ... OK
5464	   Loading Ramdisk ... OK
5465	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
5466	Boot arguments: root=/dev/ram
5467	time_init: decrementer frequency = 187500000/60
5468	Calibrating delay loop... 49.77 BogoMIPS
5469	...
5470	RAMDISK: Compressed image found at block 0
5471	VFS: Mounted root (ext2 filesystem).
5472
5473	bash#
5474
5475Boot Linux and pass a flat device tree:
5476-----------
5477
5478First, U-Boot must be compiled with the appropriate defines. See the section
5479titled "Linux Kernel Interface" above for a more in depth explanation. The
5480following is an example of how to start a kernel and pass an updated
5481flat device tree:
5482
5483=> print oftaddr
5484oftaddr=0x300000
5485=> print oft
5486oft=oftrees/mpc8540ads.dtb
5487=> tftp $oftaddr $oft
5488Speed: 1000, full duplex
5489Using TSEC0 device
5490TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5491Filename 'oftrees/mpc8540ads.dtb'.
5492Load address: 0x300000
5493Loading: #
5494done
5495Bytes transferred = 4106 (100a hex)
5496=> tftp $loadaddr $bootfile
5497Speed: 1000, full duplex
5498Using TSEC0 device
5499TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5500Filename 'uImage'.
5501Load address: 0x200000
5502Loading:############
5503done
5504Bytes transferred = 1029407 (fb51f hex)
5505=> print loadaddr
5506loadaddr=200000
5507=> print oftaddr
5508oftaddr=0x300000
5509=> bootm $loadaddr - $oftaddr
5510## Booting image at 00200000 ...
5511   Image Name:	 Linux-2.6.17-dirty
5512   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5513   Data Size:	 1029343 Bytes = 1005.2 kB
5514   Load Address: 00000000
5515   Entry Point:	 00000000
5516   Verifying Checksum ... OK
5517   Uncompressing Kernel Image ... OK
5518Booting using flat device tree at 0x300000
5519Using MPC85xx ADS machine description
5520Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5521[snip]
5522
5523
5524More About U-Boot Image Types:
5525------------------------------
5526
5527U-Boot supports the following image types:
5528
5529   "Standalone Programs" are directly runnable in the environment
5530	provided by U-Boot; it is expected that (if they behave
5531	well) you can continue to work in U-Boot after return from
5532	the Standalone Program.
5533   "OS Kernel Images" are usually images of some Embedded OS which
5534	will take over control completely. Usually these programs
5535	will install their own set of exception handlers, device
5536	drivers, set up the MMU, etc. - this means, that you cannot
5537	expect to re-enter U-Boot except by resetting the CPU.
5538   "RAMDisk Images" are more or less just data blocks, and their
5539	parameters (address, size) are passed to an OS kernel that is
5540	being started.
5541   "Multi-File Images" contain several images, typically an OS
5542	(Linux) kernel image and one or more data images like
5543	RAMDisks. This construct is useful for instance when you want
5544	to boot over the network using BOOTP etc., where the boot
5545	server provides just a single image file, but you want to get
5546	for instance an OS kernel and a RAMDisk image.
5547
5548	"Multi-File Images" start with a list of image sizes, each
5549	image size (in bytes) specified by an "uint32_t" in network
5550	byte order. This list is terminated by an "(uint32_t)0".
5551	Immediately after the terminating 0 follow the images, one by
5552	one, all aligned on "uint32_t" boundaries (size rounded up to
5553	a multiple of 4 bytes).
5554
5555   "Firmware Images" are binary images containing firmware (like
5556	U-Boot or FPGA images) which usually will be programmed to
5557	flash memory.
5558
5559   "Script files" are command sequences that will be executed by
5560	U-Boot's command interpreter; this feature is especially
5561	useful when you configure U-Boot to use a real shell (hush)
5562	as command interpreter.
5563
5564Booting the Linux zImage:
5565-------------------------
5566
5567On some platforms, it's possible to boot Linux zImage. This is done
5568using the "bootz" command. The syntax of "bootz" command is the same
5569as the syntax of "bootm" command.
5570
5571Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5572kernel with raw initrd images. The syntax is slightly different, the
5573address of the initrd must be augmented by it's size, in the following
5574format: "<initrd addres>:<initrd size>".
5575
5576
5577Standalone HOWTO:
5578=================
5579
5580One of the features of U-Boot is that you can dynamically load and
5581run "standalone" applications, which can use some resources of
5582U-Boot like console I/O functions or interrupt services.
5583
5584Two simple examples are included with the sources:
5585
5586"Hello World" Demo:
5587-------------------
5588
5589'examples/hello_world.c' contains a small "Hello World" Demo
5590application; it is automatically compiled when you build U-Boot.
5591It's configured to run at address 0x00040004, so you can play with it
5592like that:
5593
5594	=> loads
5595	## Ready for S-Record download ...
5596	~>examples/hello_world.srec
5597	1 2 3 4 5 6 7 8 9 10 11 ...
5598	[file transfer complete]
5599	[connected]
5600	## Start Addr = 0x00040004
5601
5602	=> go 40004 Hello World! This is a test.
5603	## Starting application at 0x00040004 ...
5604	Hello World
5605	argc = 7
5606	argv[0] = "40004"
5607	argv[1] = "Hello"
5608	argv[2] = "World!"
5609	argv[3] = "This"
5610	argv[4] = "is"
5611	argv[5] = "a"
5612	argv[6] = "test."
5613	argv[7] = "<NULL>"
5614	Hit any key to exit ...
5615
5616	## Application terminated, rc = 0x0
5617
5618Another example, which demonstrates how to register a CPM interrupt
5619handler with the U-Boot code, can be found in 'examples/timer.c'.
5620Here, a CPM timer is set up to generate an interrupt every second.
5621The interrupt service routine is trivial, just printing a '.'
5622character, but this is just a demo program. The application can be
5623controlled by the following keys:
5624
5625	? - print current values og the CPM Timer registers
5626	b - enable interrupts and start timer
5627	e - stop timer and disable interrupts
5628	q - quit application
5629
5630	=> loads
5631	## Ready for S-Record download ...
5632	~>examples/timer.srec
5633	1 2 3 4 5 6 7 8 9 10 11 ...
5634	[file transfer complete]
5635	[connected]
5636	## Start Addr = 0x00040004
5637
5638	=> go 40004
5639	## Starting application at 0x00040004 ...
5640	TIMERS=0xfff00980
5641	Using timer 1
5642	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5643
5644Hit 'b':
5645	[q, b, e, ?] Set interval 1000000 us
5646	Enabling timer
5647Hit '?':
5648	[q, b, e, ?] ........
5649	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5650Hit '?':
5651	[q, b, e, ?] .
5652	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5653Hit '?':
5654	[q, b, e, ?] .
5655	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5656Hit '?':
5657	[q, b, e, ?] .
5658	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5659Hit 'e':
5660	[q, b, e, ?] ...Stopping timer
5661Hit 'q':
5662	[q, b, e, ?] ## Application terminated, rc = 0x0
5663
5664
5665Minicom warning:
5666================
5667
5668Over time, many people have reported problems when trying to use the
5669"minicom" terminal emulation program for serial download. I (wd)
5670consider minicom to be broken, and recommend not to use it. Under
5671Unix, I recommend to use C-Kermit for general purpose use (and
5672especially for kermit binary protocol download ("loadb" command), and
5673use "cu" for S-Record download ("loads" command).  See
5674http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5675for help with kermit.
5676
5677
5678Nevertheless, if you absolutely want to use it try adding this
5679configuration to your "File transfer protocols" section:
5680
5681	   Name	   Program			Name U/D FullScr IO-Red. Multi
5682	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5683	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5684
5685
5686NetBSD Notes:
5687=============
5688
5689Starting at version 0.9.2, U-Boot supports NetBSD both as host
5690(build U-Boot) and target system (boots NetBSD/mpc8xx).
5691
5692Building requires a cross environment; it is known to work on
5693NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5694need gmake since the Makefiles are not compatible with BSD make).
5695Note that the cross-powerpc package does not install include files;
5696attempting to build U-Boot will fail because <machine/ansi.h> is
5697missing.  This file has to be installed and patched manually:
5698
5699	# cd /usr/pkg/cross/powerpc-netbsd/include
5700	# mkdir powerpc
5701	# ln -s powerpc machine
5702	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5703	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5704
5705Native builds *don't* work due to incompatibilities between native
5706and U-Boot include files.
5707
5708Booting assumes that (the first part of) the image booted is a
5709stage-2 loader which in turn loads and then invokes the kernel
5710proper. Loader sources will eventually appear in the NetBSD source
5711tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5712meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5713
5714
5715Implementation Internals:
5716=========================
5717
5718The following is not intended to be a complete description of every
5719implementation detail. However, it should help to understand the
5720inner workings of U-Boot and make it easier to port it to custom
5721hardware.
5722
5723
5724Initial Stack, Global Data:
5725---------------------------
5726
5727The implementation of U-Boot is complicated by the fact that U-Boot
5728starts running out of ROM (flash memory), usually without access to
5729system RAM (because the memory controller is not initialized yet).
5730This means that we don't have writable Data or BSS segments, and BSS
5731is not initialized as zero. To be able to get a C environment working
5732at all, we have to allocate at least a minimal stack. Implementation
5733options for this are defined and restricted by the CPU used: Some CPU
5734models provide on-chip memory (like the IMMR area on MPC8xx and
5735MPC826x processors), on others (parts of) the data cache can be
5736locked as (mis-) used as memory, etc.
5737
5738	Chris Hallinan posted a good summary of these issues to the
5739	U-Boot mailing list:
5740
5741	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5742	From: "Chris Hallinan" <clh@net1plus.com>
5743	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5744	...
5745
5746	Correct me if I'm wrong, folks, but the way I understand it
5747	is this: Using DCACHE as initial RAM for Stack, etc, does not
5748	require any physical RAM backing up the cache. The cleverness
5749	is that the cache is being used as a temporary supply of
5750	necessary storage before the SDRAM controller is setup. It's
5751	beyond the scope of this list to explain the details, but you
5752	can see how this works by studying the cache architecture and
5753	operation in the architecture and processor-specific manuals.
5754
5755	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5756	is another option for the system designer to use as an
5757	initial stack/RAM area prior to SDRAM being available. Either
5758	option should work for you. Using CS 4 should be fine if your
5759	board designers haven't used it for something that would
5760	cause you grief during the initial boot! It is frequently not
5761	used.
5762
5763	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5764	with your processor/board/system design. The default value
5765	you will find in any recent u-boot distribution in
5766	walnut.h should work for you. I'd set it to a value larger
5767	than your SDRAM module. If you have a 64MB SDRAM module, set
5768	it above 400_0000. Just make sure your board has no resources
5769	that are supposed to respond to that address! That code in
5770	start.S has been around a while and should work as is when
5771	you get the config right.
5772
5773	-Chris Hallinan
5774	DS4.COM, Inc.
5775
5776It is essential to remember this, since it has some impact on the C
5777code for the initialization procedures:
5778
5779* Initialized global data (data segment) is read-only. Do not attempt
5780  to write it.
5781
5782* Do not use any uninitialized global data (or implicitely initialized
5783  as zero data - BSS segment) at all - this is undefined, initiali-
5784  zation is performed later (when relocating to RAM).
5785
5786* Stack space is very limited. Avoid big data buffers or things like
5787  that.
5788
5789Having only the stack as writable memory limits means we cannot use
5790normal global data to share information beween the code. But it
5791turned out that the implementation of U-Boot can be greatly
5792simplified by making a global data structure (gd_t) available to all
5793functions. We could pass a pointer to this data as argument to _all_
5794functions, but this would bloat the code. Instead we use a feature of
5795the GCC compiler (Global Register Variables) to share the data: we
5796place a pointer (gd) to the global data into a register which we
5797reserve for this purpose.
5798
5799When choosing a register for such a purpose we are restricted by the
5800relevant  (E)ABI  specifications for the current architecture, and by
5801GCC's implementation.
5802
5803For PowerPC, the following registers have specific use:
5804	R1:	stack pointer
5805	R2:	reserved for system use
5806	R3-R4:	parameter passing and return values
5807	R5-R10: parameter passing
5808	R13:	small data area pointer
5809	R30:	GOT pointer
5810	R31:	frame pointer
5811
5812	(U-Boot also uses R12 as internal GOT pointer. r12
5813	is a volatile register so r12 needs to be reset when
5814	going back and forth between asm and C)
5815
5816    ==> U-Boot will use R2 to hold a pointer to the global data
5817
5818    Note: on PPC, we could use a static initializer (since the
5819    address of the global data structure is known at compile time),
5820    but it turned out that reserving a register results in somewhat
5821    smaller code - although the code savings are not that big (on
5822    average for all boards 752 bytes for the whole U-Boot image,
5823    624 text + 127 data).
5824
5825On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5826	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5827
5828    ==> U-Boot will use P3 to hold a pointer to the global data
5829
5830On ARM, the following registers are used:
5831
5832	R0:	function argument word/integer result
5833	R1-R3:	function argument word
5834	R9:	platform specific
5835	R10:	stack limit (used only if stack checking is enabled)
5836	R11:	argument (frame) pointer
5837	R12:	temporary workspace
5838	R13:	stack pointer
5839	R14:	link register
5840	R15:	program counter
5841
5842    ==> U-Boot will use R9 to hold a pointer to the global data
5843
5844    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5845
5846On Nios II, the ABI is documented here:
5847	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5848
5849    ==> U-Boot will use gp to hold a pointer to the global data
5850
5851    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5852    to access small data sections, so gp is free.
5853
5854On NDS32, the following registers are used:
5855
5856	R0-R1:	argument/return
5857	R2-R5:	argument
5858	R15:	temporary register for assembler
5859	R16:	trampoline register
5860	R28:	frame pointer (FP)
5861	R29:	global pointer (GP)
5862	R30:	link register (LP)
5863	R31:	stack pointer (SP)
5864	PC:	program counter (PC)
5865
5866    ==> U-Boot will use R10 to hold a pointer to the global data
5867
5868NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5869or current versions of GCC may "optimize" the code too much.
5870
5871Memory Management:
5872------------------
5873
5874U-Boot runs in system state and uses physical addresses, i.e. the
5875MMU is not used either for address mapping nor for memory protection.
5876
5877The available memory is mapped to fixed addresses using the memory
5878controller. In this process, a contiguous block is formed for each
5879memory type (Flash, SDRAM, SRAM), even when it consists of several
5880physical memory banks.
5881
5882U-Boot is installed in the first 128 kB of the first Flash bank (on
5883TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5884booting and sizing and initializing DRAM, the code relocates itself
5885to the upper end of DRAM. Immediately below the U-Boot code some
5886memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5887configuration setting]. Below that, a structure with global Board
5888Info data is placed, followed by the stack (growing downward).
5889
5890Additionally, some exception handler code is copied to the low 8 kB
5891of DRAM (0x00000000 ... 0x00001FFF).
5892
5893So a typical memory configuration with 16 MB of DRAM could look like
5894this:
5895
5896	0x0000 0000	Exception Vector code
5897	      :
5898	0x0000 1FFF
5899	0x0000 2000	Free for Application Use
5900	      :
5901	      :
5902
5903	      :
5904	      :
5905	0x00FB FF20	Monitor Stack (Growing downward)
5906	0x00FB FFAC	Board Info Data and permanent copy of global data
5907	0x00FC 0000	Malloc Arena
5908	      :
5909	0x00FD FFFF
5910	0x00FE 0000	RAM Copy of Monitor Code
5911	...		eventually: LCD or video framebuffer
5912	...		eventually: pRAM (Protected RAM - unchanged by reset)
5913	0x00FF FFFF	[End of RAM]
5914
5915
5916System Initialization:
5917----------------------
5918
5919In the reset configuration, U-Boot starts at the reset entry point
5920(on most PowerPC systems at address 0x00000100). Because of the reset
5921configuration for CS0# this is a mirror of the onboard Flash memory.
5922To be able to re-map memory U-Boot then jumps to its link address.
5923To be able to implement the initialization code in C, a (small!)
5924initial stack is set up in the internal Dual Ported RAM (in case CPUs
5925which provide such a feature like MPC8xx or MPC8260), or in a locked
5926part of the data cache. After that, U-Boot initializes the CPU core,
5927the caches and the SIU.
5928
5929Next, all (potentially) available memory banks are mapped using a
5930preliminary mapping. For example, we put them on 512 MB boundaries
5931(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5932on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5933programmed for SDRAM access. Using the temporary configuration, a
5934simple memory test is run that determines the size of the SDRAM
5935banks.
5936
5937When there is more than one SDRAM bank, and the banks are of
5938different size, the largest is mapped first. For equal size, the first
5939bank (CS2#) is mapped first. The first mapping is always for address
59400x00000000, with any additional banks following immediately to create
5941contiguous memory starting from 0.
5942
5943Then, the monitor installs itself at the upper end of the SDRAM area
5944and allocates memory for use by malloc() and for the global Board
5945Info data; also, the exception vector code is copied to the low RAM
5946pages, and the final stack is set up.
5947
5948Only after this relocation will you have a "normal" C environment;
5949until that you are restricted in several ways, mostly because you are
5950running from ROM, and because the code will have to be relocated to a
5951new address in RAM.
5952
5953
5954U-Boot Porting Guide:
5955----------------------
5956
5957[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5958list, October 2002]
5959
5960
5961int main(int argc, char *argv[])
5962{
5963	sighandler_t no_more_time;
5964
5965	signal(SIGALRM, no_more_time);
5966	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5967
5968	if (available_money > available_manpower) {
5969		Pay consultant to port U-Boot;
5970		return 0;
5971	}
5972
5973	Download latest U-Boot source;
5974
5975	Subscribe to u-boot mailing list;
5976
5977	if (clueless)
5978		email("Hi, I am new to U-Boot, how do I get started?");
5979
5980	while (learning) {
5981		Read the README file in the top level directory;
5982		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5983		Read applicable doc/*.README;
5984		Read the source, Luke;
5985		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5986	}
5987
5988	if (available_money > toLocalCurrency ($2500))
5989		Buy a BDI3000;
5990	else
5991		Add a lot of aggravation and time;
5992
5993	if (a similar board exists) {	/* hopefully... */
5994		cp -a board/<similar> board/<myboard>
5995		cp include/configs/<similar>.h include/configs/<myboard>.h
5996	} else {
5997		Create your own board support subdirectory;
5998		Create your own board include/configs/<myboard>.h file;
5999	}
6000	Edit new board/<myboard> files
6001	Edit new include/configs/<myboard>.h
6002
6003	while (!accepted) {
6004		while (!running) {
6005			do {
6006				Add / modify source code;
6007			} until (compiles);
6008			Debug;
6009			if (clueless)
6010				email("Hi, I am having problems...");
6011		}
6012		Send patch file to the U-Boot email list;
6013		if (reasonable critiques)
6014			Incorporate improvements from email list code review;
6015		else
6016			Defend code as written;
6017	}
6018
6019	return 0;
6020}
6021
6022void no_more_time (int sig)
6023{
6024      hire_a_guru();
6025}
6026
6027
6028Coding Standards:
6029-----------------
6030
6031All contributions to U-Boot should conform to the Linux kernel
6032coding style; see the file "Documentation/CodingStyle" and the script
6033"scripts/Lindent" in your Linux kernel source directory.
6034
6035Source files originating from a different project (for example the
6036MTD subsystem) are generally exempt from these guidelines and are not
6037reformated to ease subsequent migration to newer versions of those
6038sources.
6039
6040Please note that U-Boot is implemented in C (and to some small parts in
6041Assembler); no C++ is used, so please do not use C++ style comments (//)
6042in your code.
6043
6044Please also stick to the following formatting rules:
6045- remove any trailing white space
6046- use TAB characters for indentation and vertical alignment, not spaces
6047- make sure NOT to use DOS '\r\n' line feeds
6048- do not add more than 2 consecutive empty lines to source files
6049- do not add trailing empty lines to source files
6050
6051Submissions which do not conform to the standards may be returned
6052with a request to reformat the changes.
6053
6054
6055Submitting Patches:
6056-------------------
6057
6058Since the number of patches for U-Boot is growing, we need to
6059establish some rules. Submissions which do not conform to these rules
6060may be rejected, even when they contain important and valuable stuff.
6061
6062Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6063
6064Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6065see http://lists.denx.de/mailman/listinfo/u-boot
6066
6067When you send a patch, please include the following information with
6068it:
6069
6070* For bug fixes: a description of the bug and how your patch fixes
6071  this bug. Please try to include a way of demonstrating that the
6072  patch actually fixes something.
6073
6074* For new features: a description of the feature and your
6075  implementation.
6076
6077* A CHANGELOG entry as plaintext (separate from the patch)
6078
6079* For major contributions, your entry to the CREDITS file
6080
6081* When you add support for a new board, don't forget to add a
6082  maintainer e-mail address to the boards.cfg file, too.
6083
6084* If your patch adds new configuration options, don't forget to
6085  document these in the README file.
6086
6087* The patch itself. If you are using git (which is *strongly*
6088  recommended) you can easily generate the patch using the
6089  "git format-patch". If you then use "git send-email" to send it to
6090  the U-Boot mailing list, you will avoid most of the common problems
6091  with some other mail clients.
6092
6093  If you cannot use git, use "diff -purN OLD NEW". If your version of
6094  diff does not support these options, then get the latest version of
6095  GNU diff.
6096
6097  The current directory when running this command shall be the parent
6098  directory of the U-Boot source tree (i. e. please make sure that
6099  your patch includes sufficient directory information for the
6100  affected files).
6101
6102  We prefer patches as plain text. MIME attachments are discouraged,
6103  and compressed attachments must not be used.
6104
6105* If one logical set of modifications affects or creates several
6106  files, all these changes shall be submitted in a SINGLE patch file.
6107
6108* Changesets that contain different, unrelated modifications shall be
6109  submitted as SEPARATE patches, one patch per changeset.
6110
6111
6112Notes:
6113
6114* Before sending the patch, run the MAKEALL script on your patched
6115  source tree and make sure that no errors or warnings are reported
6116  for any of the boards.
6117
6118* Keep your modifications to the necessary minimum: A patch
6119  containing several unrelated changes or arbitrary reformats will be
6120  returned with a request to re-formatting / split it.
6121
6122* If you modify existing code, make sure that your new code does not
6123  add to the memory footprint of the code ;-) Small is beautiful!
6124  When adding new features, these should compile conditionally only
6125  (using #ifdef), and the resulting code with the new feature
6126  disabled must not need more memory than the old code without your
6127  modification.
6128
6129* Remember that there is a size limit of 100 kB per message on the
6130  u-boot mailing list. Bigger patches will be moderated. If they are
6131  reasonable and not too big, they will be acknowledged. But patches
6132  bigger than the size limit should be avoided.
6133