xref: /openbmc/u-boot/README (revision 92ac520821405e196c920d60921bdfa5ab6b878c)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG and CREDITS files to find out
38who contributed the specific port. The boards.cfg file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136    /cpu		CPU specific files
137      /arc700		Files specific to ARC 700 CPUs
138    /lib		Architecture specific library files
139  /arm			Files generic to ARM architecture
140    /cpu		CPU specific files
141      /arm720t		Files specific to ARM 720 CPUs
142      /arm920t		Files specific to ARM 920 CPUs
143	/at91		Files specific to Atmel AT91RM9200 CPU
144	/imx		Files specific to Freescale MC9328 i.MX CPUs
145	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
146      /arm926ejs	Files specific to ARM 926 CPUs
147      /arm1136		Files specific to ARM 1136 CPUs
148      /pxa		Files specific to Intel XScale PXA CPUs
149      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
150    /lib		Architecture specific library files
151  /avr32		Files generic to AVR32 architecture
152    /cpu		CPU specific files
153    /lib		Architecture specific library files
154  /blackfin		Files generic to Analog Devices Blackfin architecture
155    /cpu		CPU specific files
156    /lib		Architecture specific library files
157  /m68k			Files generic to m68k architecture
158    /cpu		CPU specific files
159      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
160      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
161      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
162      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
163      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
164    /lib		Architecture specific library files
165  /microblaze		Files generic to microblaze architecture
166    /cpu		CPU specific files
167    /lib		Architecture specific library files
168  /mips			Files generic to MIPS architecture
169    /cpu		CPU specific files
170      /mips32		Files specific to MIPS32 CPUs
171      /mips64		Files specific to MIPS64 CPUs
172    /lib		Architecture specific library files
173  /nds32		Files generic to NDS32 architecture
174    /cpu		CPU specific files
175      /n1213		Files specific to Andes Technology N1213 CPUs
176    /lib		Architecture specific library files
177  /nios2		Files generic to Altera NIOS2 architecture
178    /cpu		CPU specific files
179    /lib		Architecture specific library files
180  /openrisc		Files generic to OpenRISC architecture
181    /cpu		CPU specific files
182    /lib		Architecture specific library files
183  /powerpc		Files generic to PowerPC architecture
184    /cpu		CPU specific files
185      /mpc5xx		Files specific to Freescale MPC5xx CPUs
186      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
187      /mpc8xx		Files specific to Freescale MPC8xx CPUs
188      /mpc8260		Files specific to Freescale MPC8260 CPUs
189      /mpc85xx		Files specific to Freescale MPC85xx CPUs
190      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
191    /lib		Architecture specific library files
192  /sh			Files generic to SH architecture
193    /cpu		CPU specific files
194      /sh2		Files specific to sh2 CPUs
195      /sh3		Files specific to sh3 CPUs
196      /sh4		Files specific to sh4 CPUs
197    /lib		Architecture specific library files
198  /sparc		Files generic to SPARC architecture
199    /cpu		CPU specific files
200      /leon2		Files specific to Gaisler LEON2 SPARC CPU
201      /leon3		Files specific to Gaisler LEON3 SPARC CPU
202    /lib		Architecture specific library files
203  /x86			Files generic to x86 architecture
204    /cpu		CPU specific files
205    /lib		Architecture specific library files
206/api			Machine/arch independent API for external apps
207/board			Board dependent files
208/common			Misc architecture independent functions
209/disk			Code for disk drive partition handling
210/doc			Documentation (don't expect too much)
211/drivers		Commonly used device drivers
212/dts			Contains Makefile for building internal U-Boot fdt.
213/examples		Example code for standalone applications, etc.
214/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
215/include		Header Files
216/lib			Files generic to all architectures
217  /libfdt		Library files to support flattened device trees
218  /lzma			Library files to support LZMA decompression
219  /lzo			Library files to support LZO decompression
220/net			Networking code
221/post			Power On Self Test
222/spl			Secondary Program Loader framework
223/tools			Tools to build S-Record or U-Boot images, etc.
224
225Software Configuration:
226=======================
227
228Configuration is usually done using C preprocessor defines; the
229rationale behind that is to avoid dead code whenever possible.
230
231There are two classes of configuration variables:
232
233* Configuration _OPTIONS_:
234  These are selectable by the user and have names beginning with
235  "CONFIG_".
236
237* Configuration _SETTINGS_:
238  These depend on the hardware etc. and should not be meddled with if
239  you don't know what you're doing; they have names beginning with
240  "CONFIG_SYS_".
241
242Later we will add a configuration tool - probably similar to or even
243identical to what's used for the Linux kernel. Right now, we have to
244do the configuration by hand, which means creating some symbolic
245links and editing some configuration files. We use the TQM8xxL boards
246as an example here.
247
248
249Selection of Processor Architecture and Board Type:
250---------------------------------------------------
251
252For all supported boards there are ready-to-use default
253configurations available; just type "make <board_name>_defconfig".
254
255Example: For a TQM823L module type:
256
257	cd u-boot
258	make TQM823L_defconfig
259
260For the Cogent platform, you need to specify the CPU type as well;
261e.g. "make cogent_mpc8xx_defconfig". And also configure the cogent
262directory according to the instructions in cogent/README.
263
264
265Sandbox Environment:
266--------------------
267
268U-Boot can be built natively to run on a Linux host using the 'sandbox'
269board. This allows feature development which is not board- or architecture-
270specific to be undertaken on a native platform. The sandbox is also used to
271run some of U-Boot's tests.
272
273See board/sandbox/README.sandbox for more details.
274
275
276Board Initialisation Flow:
277--------------------------
278
279This is the intended start-up flow for boards. This should apply for both
280SPL and U-Boot proper (i.e. they both follow the same rules). At present SPL
281mostly uses a separate code path, but the funtion names and roles of each
282function are the same. Some boards or architectures may not conform to this.
283At least most ARM boards which use CONFIG_SPL_FRAMEWORK conform to this.
284
285Execution starts with start.S with three functions called during init after
286that. The purpose and limitations of each is described below.
287
288lowlevel_init():
289	- purpose: essential init to permit execution to reach board_init_f()
290	- no global_data or BSS
291	- there is no stack (ARMv7 may have one but it will soon be removed)
292	- must not set up SDRAM or use console
293	- must only do the bare minimum to allow execution to continue to
294		board_init_f()
295	- this is almost never needed
296	- return normally from this function
297
298board_init_f():
299	- purpose: set up the machine ready for running board_init_r():
300		i.e. SDRAM and serial UART
301	- global_data is available
302	- stack is in SRAM
303	- BSS is not available, so you cannot use global/static variables,
304		only stack variables and global_data
305
306	Non-SPL-specific notes:
307	- dram_init() is called to set up DRAM. If already done in SPL this
308		can do nothing
309
310	SPL-specific notes:
311	- you can override the entire board_init_f() function with your own
312		version as needed.
313	- preloader_console_init() can be called here in extremis
314	- should set up SDRAM, and anything needed to make the UART work
315	- these is no need to clear BSS, it will be done by crt0.S
316	- must return normally from this function (don't call board_init_r()
317		directly)
318
319Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
320this point the stack and global_data are relocated to below
321CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
322memory.
323
324board_init_r():
325	- purpose: main execution, common code
326	- global_data is available
327	- SDRAM is available
328	- BSS is available, all static/global variables can be used
329	- execution eventually continues to main_loop()
330
331	Non-SPL-specific notes:
332	- U-Boot is relocated to the top of memory and is now running from
333		there.
334
335	SPL-specific notes:
336	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
337		CONFIG_SPL_STACK_R_ADDR points into SDRAM
338	- preloader_console_init() can be called here - typically this is
339		done by defining CONFIG_SPL_BOARD_INIT and then supplying a
340		spl_board_init() function containing this call
341	- loads U-Boot or (in falcon mode) Linux
342
343
344
345Configuration Options:
346----------------------
347
348Configuration depends on the combination of board and CPU type; all
349such information is kept in a configuration file
350"include/configs/<board_name>.h".
351
352Example: For a TQM823L module, all configuration settings are in
353"include/configs/TQM823L.h".
354
355
356Many of the options are named exactly as the corresponding Linux
357kernel configuration options. The intention is to make it easier to
358build a config tool - later.
359
360
361The following options need to be configured:
362
363- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
364
365- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
366
367- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
368		Define exactly one, e.g. CONFIG_ATSTK1002
369
370- CPU Module Type: (if CONFIG_COGENT is defined)
371		Define exactly one of
372		CONFIG_CMA286_60_OLD
373--- FIXME --- not tested yet:
374		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
375		CONFIG_CMA287_23, CONFIG_CMA287_50
376
377- Motherboard Type: (if CONFIG_COGENT is defined)
378		Define exactly one of
379		CONFIG_CMA101, CONFIG_CMA102
380
381- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
382		Define one or more of
383		CONFIG_CMA302
384
385- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
386		Define one or more of
387		CONFIG_LCD_HEARTBEAT	- update a character position on
388					  the LCD display every second with
389					  a "rotator" |\-/|\-/
390
391- Marvell Family Member
392		CONFIG_SYS_MVFS		- define it if you want to enable
393					  multiple fs option at one time
394					  for marvell soc family
395
396- 8xx CPU Options: (if using an MPC8xx CPU)
397		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
398					  get_gclk_freq() cannot work
399					  e.g. if there is no 32KHz
400					  reference PIT/RTC clock
401		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
402					  or XTAL/EXTAL)
403
404- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
405		CONFIG_SYS_8xx_CPUCLK_MIN
406		CONFIG_SYS_8xx_CPUCLK_MAX
407		CONFIG_8xx_CPUCLK_DEFAULT
408			See doc/README.MPC866
409
410		CONFIG_SYS_MEASURE_CPUCLK
411
412		Define this to measure the actual CPU clock instead
413		of relying on the correctness of the configured
414		values. Mostly useful for board bringup to make sure
415		the PLL is locked at the intended frequency. Note
416		that this requires a (stable) reference clock (32 kHz
417		RTC clock or CONFIG_SYS_8XX_XIN)
418
419		CONFIG_SYS_DELAYED_ICACHE
420
421		Define this option if you want to enable the
422		ICache only when Code runs from RAM.
423
424- 85xx CPU Options:
425		CONFIG_SYS_PPC64
426
427		Specifies that the core is a 64-bit PowerPC implementation (implements
428		the "64" category of the Power ISA). This is necessary for ePAPR
429		compliance, among other possible reasons.
430
431		CONFIG_SYS_FSL_TBCLK_DIV
432
433		Defines the core time base clock divider ratio compared to the
434		system clock.  On most PQ3 devices this is 8, on newer QorIQ
435		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
436
437		CONFIG_SYS_FSL_PCIE_COMPAT
438
439		Defines the string to utilize when trying to match PCIe device
440		tree nodes for the given platform.
441
442		CONFIG_SYS_PPC_E500_DEBUG_TLB
443
444		Enables a temporary TLB entry to be used during boot to work
445		around limitations in e500v1 and e500v2 external debugger
446		support. This reduces the portions of the boot code where
447		breakpoints and single stepping do not work.  The value of this
448		symbol should be set to the TLB1 entry to be used for this
449		purpose.
450
451		CONFIG_SYS_FSL_ERRATUM_A004510
452
453		Enables a workaround for erratum A004510.  If set,
454		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
455		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
456
457		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
458		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
459
460		Defines one or two SoC revisions (low 8 bits of SVR)
461		for which the A004510 workaround should be applied.
462
463		The rest of SVR is either not relevant to the decision
464		of whether the erratum is present (e.g. p2040 versus
465		p2041) or is implied by the build target, which controls
466		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
467
468		See Freescale App Note 4493 for more information about
469		this erratum.
470
471		CONFIG_A003399_NOR_WORKAROUND
472		Enables a workaround for IFC erratum A003399. It is only
473		required during NOR boot.
474
475		CONFIG_A008044_WORKAROUND
476		Enables a workaround for T1040/T1042 erratum A008044. It is only
477		required during NAND boot and valid for Rev 1.0 SoC revision
478
479		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
480
481		This is the value to write into CCSR offset 0x18600
482		according to the A004510 workaround.
483
484		CONFIG_SYS_FSL_DSP_DDR_ADDR
485		This value denotes start offset of DDR memory which is
486		connected exclusively to the DSP cores.
487
488		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
489		This value denotes start offset of M2 memory
490		which is directly connected to the DSP core.
491
492		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
493		This value denotes start offset of M3 memory which is directly
494		connected to the DSP core.
495
496		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
497		This value denotes start offset of DSP CCSR space.
498
499		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
500		Single Source Clock is clocking mode present in some of FSL SoC's.
501		In this mode, a single differential clock is used to supply
502		clocks to the sysclock, ddrclock and usbclock.
503
504		CONFIG_SYS_CPC_REINIT_F
505		This CONFIG is defined when the CPC is configured as SRAM at the
506		time of U-boot entry and is required to be re-initialized.
507
508		CONFIG_DEEP_SLEEP
509		Indicates this SoC supports deep sleep feature. If deep sleep is
510		supported, core will start to execute uboot when wakes up.
511
512- Generic CPU options:
513		CONFIG_SYS_GENERIC_GLOBAL_DATA
514		Defines global data is initialized in generic board board_init_f().
515		If this macro is defined, global data is created and cleared in
516		generic board board_init_f(). Without this macro, architecture/board
517		should initialize global data before calling board_init_f().
518
519		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
520
521		Defines the endianess of the CPU. Implementation of those
522		values is arch specific.
523
524		CONFIG_SYS_FSL_DDR
525		Freescale DDR driver in use. This type of DDR controller is
526		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
527		SoCs.
528
529		CONFIG_SYS_FSL_DDR_ADDR
530		Freescale DDR memory-mapped register base.
531
532		CONFIG_SYS_FSL_DDR_EMU
533		Specify emulator support for DDR. Some DDR features such as
534		deskew training are not available.
535
536		CONFIG_SYS_FSL_DDRC_GEN1
537		Freescale DDR1 controller.
538
539		CONFIG_SYS_FSL_DDRC_GEN2
540		Freescale DDR2 controller.
541
542		CONFIG_SYS_FSL_DDRC_GEN3
543		Freescale DDR3 controller.
544
545		CONFIG_SYS_FSL_DDRC_GEN4
546		Freescale DDR4 controller.
547
548		CONFIG_SYS_FSL_DDRC_ARM_GEN3
549		Freescale DDR3 controller for ARM-based SoCs.
550
551		CONFIG_SYS_FSL_DDR1
552		Board config to use DDR1. It can be enabled for SoCs with
553		Freescale DDR1 or DDR2 controllers, depending on the board
554		implemetation.
555
556		CONFIG_SYS_FSL_DDR2
557		Board config to use DDR2. It can be eanbeld for SoCs with
558		Freescale DDR2 or DDR3 controllers, depending on the board
559		implementation.
560
561		CONFIG_SYS_FSL_DDR3
562		Board config to use DDR3. It can be enabled for SoCs with
563		Freescale DDR3 or DDR3L controllers.
564
565		CONFIG_SYS_FSL_DDR3L
566		Board config to use DDR3L. It can be enabled for SoCs with
567		DDR3L controllers.
568
569		CONFIG_SYS_FSL_DDR4
570		Board config to use DDR4. It can be enabled for SoCs with
571		DDR4 controllers.
572
573		CONFIG_SYS_FSL_IFC_BE
574		Defines the IFC controller register space as Big Endian
575
576		CONFIG_SYS_FSL_IFC_LE
577		Defines the IFC controller register space as Little Endian
578
579		CONFIG_SYS_FSL_PBL_PBI
580		It enables addition of RCW (Power on reset configuration) in built image.
581		Please refer doc/README.pblimage for more details
582
583		CONFIG_SYS_FSL_PBL_RCW
584		It adds PBI(pre-boot instructions) commands in u-boot build image.
585		PBI commands can be used to configure SoC before it starts the execution.
586		Please refer doc/README.pblimage for more details
587
588		CONFIG_SPL_FSL_PBL
589		It adds a target to create boot binary having SPL binary in PBI format
590		concatenated with u-boot binary.
591
592		CONFIG_SYS_FSL_DDR_BE
593		Defines the DDR controller register space as Big Endian
594
595		CONFIG_SYS_FSL_DDR_LE
596		Defines the DDR controller register space as Little Endian
597
598		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
599		Physical address from the view of DDR controllers. It is the
600		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
601		it could be different for ARM SoCs.
602
603		CONFIG_SYS_FSL_DDR_INTLV_256B
604		DDR controller interleaving on 256-byte. This is a special
605		interleaving mode, handled by Dickens for Freescale layerscape
606		SoCs with ARM core.
607
608		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
609		Number of controllers used as main memory.
610
611		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
612		Number of controllers used for other than main memory.
613
614		CONFIG_SYS_FSL_SEC_BE
615		Defines the SEC controller register space as Big Endian
616
617		CONFIG_SYS_FSL_SEC_LE
618		Defines the SEC controller register space as Little Endian
619
620- Intel Monahans options:
621		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
622
623		Defines the Monahans run mode to oscillator
624		ratio. Valid values are 8, 16, 24, 31. The core
625		frequency is this value multiplied by 13 MHz.
626
627		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
628
629		Defines the Monahans turbo mode to oscillator
630		ratio. Valid values are 1 (default if undefined) and
631		2. The core frequency as calculated above is multiplied
632		by this value.
633
634- MIPS CPU options:
635		CONFIG_SYS_INIT_SP_OFFSET
636
637		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
638		pointer. This is needed for the temporary stack before
639		relocation.
640
641		CONFIG_SYS_MIPS_CACHE_MODE
642
643		Cache operation mode for the MIPS CPU.
644		See also arch/mips/include/asm/mipsregs.h.
645		Possible values are:
646			CONF_CM_CACHABLE_NO_WA
647			CONF_CM_CACHABLE_WA
648			CONF_CM_UNCACHED
649			CONF_CM_CACHABLE_NONCOHERENT
650			CONF_CM_CACHABLE_CE
651			CONF_CM_CACHABLE_COW
652			CONF_CM_CACHABLE_CUW
653			CONF_CM_CACHABLE_ACCELERATED
654
655		CONFIG_SYS_XWAY_EBU_BOOTCFG
656
657		Special option for Lantiq XWAY SoCs for booting from NOR flash.
658		See also arch/mips/cpu/mips32/start.S.
659
660		CONFIG_XWAY_SWAP_BYTES
661
662		Enable compilation of tools/xway-swap-bytes needed for Lantiq
663		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
664		be swapped if a flash programmer is used.
665
666- ARM options:
667		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
668
669		Select high exception vectors of the ARM core, e.g., do not
670		clear the V bit of the c1 register of CP15.
671
672		CONFIG_SYS_THUMB_BUILD
673
674		Use this flag to build U-Boot using the Thumb instruction
675		set for ARM architectures. Thumb instruction set provides
676		better code density. For ARM architectures that support
677		Thumb2 this flag will result in Thumb2 code generated by
678		GCC.
679
680		CONFIG_ARM_ERRATA_716044
681		CONFIG_ARM_ERRATA_742230
682		CONFIG_ARM_ERRATA_743622
683		CONFIG_ARM_ERRATA_751472
684		CONFIG_ARM_ERRATA_794072
685		CONFIG_ARM_ERRATA_761320
686
687		If set, the workarounds for these ARM errata are applied early
688		during U-Boot startup. Note that these options force the
689		workarounds to be applied; no CPU-type/version detection
690		exists, unlike the similar options in the Linux kernel. Do not
691		set these options unless they apply!
692
693		COUNTER_FREQUENCY
694		Generic timer clock source frequency.
695
696		COUNTER_FREQUENCY_REAL
697		Generic timer clock source frequency if the real clock is
698		different from COUNTER_FREQUENCY, and can only be determined
699		at run time.
700
701		NOTE: The following can be machine specific errata. These
702		do have ability to provide rudimentary version and machine
703		specific checks, but expect no product checks.
704		CONFIG_ARM_ERRATA_430973
705		CONFIG_ARM_ERRATA_454179
706		CONFIG_ARM_ERRATA_621766
707		CONFIG_ARM_ERRATA_798870
708
709- Tegra SoC options:
710		CONFIG_TEGRA_SUPPORT_NON_SECURE
711
712		Support executing U-Boot in non-secure (NS) mode. Certain
713		impossible actions will be skipped if the CPU is in NS mode,
714		such as ARM architectural timer initialization.
715
716- Linux Kernel Interface:
717		CONFIG_CLOCKS_IN_MHZ
718
719		U-Boot stores all clock information in Hz
720		internally. For binary compatibility with older Linux
721		kernels (which expect the clocks passed in the
722		bd_info data to be in MHz) the environment variable
723		"clocks_in_mhz" can be defined so that U-Boot
724		converts clock data to MHZ before passing it to the
725		Linux kernel.
726		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
727		"clocks_in_mhz=1" is automatically included in the
728		default environment.
729
730		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
731
732		When transferring memsize parameter to Linux, some versions
733		expect it to be in bytes, others in MB.
734		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
735
736		CONFIG_OF_LIBFDT
737
738		New kernel versions are expecting firmware settings to be
739		passed using flattened device trees (based on open firmware
740		concepts).
741
742		CONFIG_OF_LIBFDT
743		 * New libfdt-based support
744		 * Adds the "fdt" command
745		 * The bootm command automatically updates the fdt
746
747		OF_CPU - The proper name of the cpus node (only required for
748			MPC512X and MPC5xxx based boards).
749		OF_SOC - The proper name of the soc node (only required for
750			MPC512X and MPC5xxx based boards).
751		OF_TBCLK - The timebase frequency.
752		OF_STDOUT_PATH - The path to the console device
753
754		boards with QUICC Engines require OF_QE to set UCC MAC
755		addresses
756
757		CONFIG_OF_BOARD_SETUP
758
759		Board code has addition modification that it wants to make
760		to the flat device tree before handing it off to the kernel
761
762		CONFIG_OF_SYSTEM_SETUP
763
764		Other code has addition modification that it wants to make
765		to the flat device tree before handing it off to the kernel.
766		This causes ft_system_setup() to be called before booting
767		the kernel.
768
769		CONFIG_OF_BOOT_CPU
770
771		This define fills in the correct boot CPU in the boot
772		param header, the default value is zero if undefined.
773
774		CONFIG_OF_IDE_FIXUP
775
776		U-Boot can detect if an IDE device is present or not.
777		If not, and this new config option is activated, U-Boot
778		removes the ATA node from the DTS before booting Linux,
779		so the Linux IDE driver does not probe the device and
780		crash. This is needed for buggy hardware (uc101) where
781		no pull down resistor is connected to the signal IDE5V_DD7.
782
783		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
784
785		This setting is mandatory for all boards that have only one
786		machine type and must be used to specify the machine type
787		number as it appears in the ARM machine registry
788		(see http://www.arm.linux.org.uk/developer/machines/).
789		Only boards that have multiple machine types supported
790		in a single configuration file and the machine type is
791		runtime discoverable, do not have to use this setting.
792
793- vxWorks boot parameters:
794
795		bootvx constructs a valid bootline using the following
796		environments variables: bootfile, ipaddr, serverip, hostname.
797		It loads the vxWorks image pointed bootfile.
798
799		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
800		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
801		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
802		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
803
804		CONFIG_SYS_VXWORKS_ADD_PARAMS
805
806		Add it at the end of the bootline. E.g "u=username pw=secret"
807
808		Note: If a "bootargs" environment is defined, it will overwride
809		the defaults discussed just above.
810
811- Cache Configuration:
812		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
813		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
814		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
815
816- Cache Configuration for ARM:
817		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
818				      controller
819		CONFIG_SYS_PL310_BASE - Physical base address of PL310
820					controller register space
821
822- Serial Ports:
823		CONFIG_PL010_SERIAL
824
825		Define this if you want support for Amba PrimeCell PL010 UARTs.
826
827		CONFIG_PL011_SERIAL
828
829		Define this if you want support for Amba PrimeCell PL011 UARTs.
830
831		CONFIG_PL011_CLOCK
832
833		If you have Amba PrimeCell PL011 UARTs, set this variable to
834		the clock speed of the UARTs.
835
836		CONFIG_PL01x_PORTS
837
838		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
839		define this to a list of base addresses for each (supported)
840		port. See e.g. include/configs/versatile.h
841
842		CONFIG_PL011_SERIAL_RLCR
843
844		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
845		have separate receive and transmit line control registers.  Set
846		this variable to initialize the extra register.
847
848		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
849
850		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
851		boot loader that has already initialized the UART.  Define this
852		variable to flush the UART at init time.
853
854		CONFIG_SERIAL_HW_FLOW_CONTROL
855
856		Define this variable to enable hw flow control in serial driver.
857		Current user of this option is drivers/serial/nsl16550.c driver
858
859- Console Interface:
860		Depending on board, define exactly one serial port
861		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
862		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
863		console by defining CONFIG_8xx_CONS_NONE
864
865		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
866		port routines must be defined elsewhere
867		(i.e. serial_init(), serial_getc(), ...)
868
869		CONFIG_CFB_CONSOLE
870		Enables console device for a color framebuffer. Needs following
871		defines (cf. smiLynxEM, i8042)
872			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
873						(default big endian)
874			VIDEO_HW_RECTFILL	graphic chip supports
875						rectangle fill
876						(cf. smiLynxEM)
877			VIDEO_HW_BITBLT		graphic chip supports
878						bit-blit (cf. smiLynxEM)
879			VIDEO_VISIBLE_COLS	visible pixel columns
880						(cols=pitch)
881			VIDEO_VISIBLE_ROWS	visible pixel rows
882			VIDEO_PIXEL_SIZE	bytes per pixel
883			VIDEO_DATA_FORMAT	graphic data format
884						(0-5, cf. cfb_console.c)
885			VIDEO_FB_ADRS		framebuffer address
886			VIDEO_KBD_INIT_FCT	keyboard int fct
887						(i.e. i8042_kbd_init())
888			VIDEO_TSTC_FCT		test char fct
889						(i.e. i8042_tstc)
890			VIDEO_GETC_FCT		get char fct
891						(i.e. i8042_getc)
892			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
893						(requires blink timer
894						cf. i8042.c)
895			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
896			CONFIG_CONSOLE_TIME	display time/date info in
897						upper right corner
898						(requires CONFIG_CMD_DATE)
899			CONFIG_VIDEO_LOGO	display Linux logo in
900						upper left corner
901			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
902						linux_logo.h for logo.
903						Requires CONFIG_VIDEO_LOGO
904			CONFIG_CONSOLE_EXTRA_INFO
905						additional board info beside
906						the logo
907
908		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
909		a limited number of ANSI escape sequences (cursor control,
910		erase functions and limited graphics rendition control).
911
912		When CONFIG_CFB_CONSOLE is defined, video console is
913		default i/o. Serial console can be forced with
914		environment 'console=serial'.
915
916		When CONFIG_SILENT_CONSOLE is defined, all console
917		messages (by U-Boot and Linux!) can be silenced with
918		the "silent" environment variable. See
919		doc/README.silent for more information.
920
921		CONFIG_SYS_CONSOLE_BG_COL: define the backgroundcolor, default
922			is 0x00.
923		CONFIG_SYS_CONSOLE_FG_COL: define the foregroundcolor, default
924			is 0xa0.
925
926- Console Baudrate:
927		CONFIG_BAUDRATE - in bps
928		Select one of the baudrates listed in
929		CONFIG_SYS_BAUDRATE_TABLE, see below.
930		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
931
932- Console Rx buffer length
933		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
934		the maximum receive buffer length for the SMC.
935		This option is actual only for 82xx and 8xx possible.
936		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
937		must be defined, to setup the maximum idle timeout for
938		the SMC.
939
940- Pre-Console Buffer:
941		Prior to the console being initialised (i.e. serial UART
942		initialised etc) all console output is silently discarded.
943		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
944		buffer any console messages prior to the console being
945		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
946		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
947		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
948		bytes are output before the console is initialised, the
949		earlier bytes are discarded.
950
951		'Sane' compilers will generate smaller code if
952		CONFIG_PRE_CON_BUF_SZ is a power of 2
953
954- Safe printf() functions
955		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
956		the printf() functions. These are defined in
957		include/vsprintf.h and include snprintf(), vsnprintf() and
958		so on. Code size increase is approximately 300-500 bytes.
959		If this option is not given then these functions will
960		silently discard their buffer size argument - this means
961		you are not getting any overflow checking in this case.
962
963- Boot Delay:	CONFIG_BOOTDELAY - in seconds
964		Delay before automatically booting the default image;
965		set to -1 to disable autoboot.
966		set to -2 to autoboot with no delay and not check for abort
967		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
968
969		See doc/README.autoboot for these options that
970		work with CONFIG_BOOTDELAY. None are required.
971		CONFIG_BOOT_RETRY_TIME
972		CONFIG_BOOT_RETRY_MIN
973		CONFIG_AUTOBOOT_KEYED
974		CONFIG_AUTOBOOT_PROMPT
975		CONFIG_AUTOBOOT_DELAY_STR
976		CONFIG_AUTOBOOT_STOP_STR
977		CONFIG_AUTOBOOT_DELAY_STR2
978		CONFIG_AUTOBOOT_STOP_STR2
979		CONFIG_ZERO_BOOTDELAY_CHECK
980		CONFIG_RESET_TO_RETRY
981
982- Autoboot Command:
983		CONFIG_BOOTCOMMAND
984		Only needed when CONFIG_BOOTDELAY is enabled;
985		define a command string that is automatically executed
986		when no character is read on the console interface
987		within "Boot Delay" after reset.
988
989		CONFIG_BOOTARGS
990		This can be used to pass arguments to the bootm
991		command. The value of CONFIG_BOOTARGS goes into the
992		environment value "bootargs".
993
994		CONFIG_RAMBOOT and CONFIG_NFSBOOT
995		The value of these goes into the environment as
996		"ramboot" and "nfsboot" respectively, and can be used
997		as a convenience, when switching between booting from
998		RAM and NFS.
999
1000- Bootcount:
1001		CONFIG_BOOTCOUNT_LIMIT
1002		Implements a mechanism for detecting a repeating reboot
1003		cycle, see:
1004		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
1005
1006		CONFIG_BOOTCOUNT_ENV
1007		If no softreset save registers are found on the hardware
1008		"bootcount" is stored in the environment. To prevent a
1009		saveenv on all reboots, the environment variable
1010		"upgrade_available" is used. If "upgrade_available" is
1011		0, "bootcount" is always 0, if "upgrade_available" is
1012		1 "bootcount" is incremented in the environment.
1013		So the Userspace Applikation must set the "upgrade_available"
1014		and "bootcount" variable to 0, if a boot was successfully.
1015
1016- Pre-Boot Commands:
1017		CONFIG_PREBOOT
1018
1019		When this option is #defined, the existence of the
1020		environment variable "preboot" will be checked
1021		immediately before starting the CONFIG_BOOTDELAY
1022		countdown and/or running the auto-boot command resp.
1023		entering interactive mode.
1024
1025		This feature is especially useful when "preboot" is
1026		automatically generated or modified. For an example
1027		see the LWMON board specific code: here "preboot" is
1028		modified when the user holds down a certain
1029		combination of keys on the (special) keyboard when
1030		booting the systems
1031
1032- Serial Download Echo Mode:
1033		CONFIG_LOADS_ECHO
1034		If defined to 1, all characters received during a
1035		serial download (using the "loads" command) are
1036		echoed back. This might be needed by some terminal
1037		emulations (like "cu"), but may as well just take
1038		time on others. This setting #define's the initial
1039		value of the "loads_echo" environment variable.
1040
1041- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
1042		CONFIG_KGDB_BAUDRATE
1043		Select one of the baudrates listed in
1044		CONFIG_SYS_BAUDRATE_TABLE, see below.
1045
1046- Monitor Functions:
1047		Monitor commands can be included or excluded
1048		from the build by using the #include files
1049		<config_cmd_all.h> and #undef'ing unwanted
1050		commands, or using <config_cmd_default.h>
1051		and augmenting with additional #define's
1052		for wanted commands.
1053
1054		The default command configuration includes all commands
1055		except those marked below with a "*".
1056
1057		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
1058		CONFIG_CMD_ASKENV	* ask for env variable
1059		CONFIG_CMD_BDI		  bdinfo
1060		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
1061		CONFIG_CMD_BMP		* BMP support
1062		CONFIG_CMD_BSP		* Board specific commands
1063		CONFIG_CMD_BOOTD	  bootd
1064		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
1065		CONFIG_CMD_CACHE	* icache, dcache
1066		CONFIG_CMD_CLK   	* clock command support
1067		CONFIG_CMD_CONSOLE	  coninfo
1068		CONFIG_CMD_CRC32	* crc32
1069		CONFIG_CMD_DATE		* support for RTC, date/time...
1070		CONFIG_CMD_DHCP		* DHCP support
1071		CONFIG_CMD_DIAG		* Diagnostics
1072		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
1073		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
1074		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
1075		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
1076		CONFIG_CMD_DTT		* Digital Therm and Thermostat
1077		CONFIG_CMD_ECHO		  echo arguments
1078		CONFIG_CMD_EDITENV	  edit env variable
1079		CONFIG_CMD_EEPROM	* EEPROM read/write support
1080		CONFIG_CMD_ELF		* bootelf, bootvx
1081		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
1082		CONFIG_CMD_ENV_FLAGS	* display details about env flags
1083		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
1084		CONFIG_CMD_EXPORTENV	* export the environment
1085		CONFIG_CMD_EXT2		* ext2 command support
1086		CONFIG_CMD_EXT4		* ext4 command support
1087		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
1088					  that work for multiple fs types
1089		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
1090		CONFIG_CMD_SAVEENV	  saveenv
1091		CONFIG_CMD_FDC		* Floppy Disk Support
1092		CONFIG_CMD_FAT		* FAT command support
1093		CONFIG_CMD_FLASH	  flinfo, erase, protect
1094		CONFIG_CMD_FPGA		  FPGA device initialization support
1095		CONFIG_CMD_FUSE		* Device fuse support
1096		CONFIG_CMD_GETTIME	* Get time since boot
1097		CONFIG_CMD_GO		* the 'go' command (exec code)
1098		CONFIG_CMD_GREPENV	* search environment
1099		CONFIG_CMD_HASH		* calculate hash / digest
1100		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
1101		CONFIG_CMD_I2C		* I2C serial bus support
1102		CONFIG_CMD_IDE		* IDE harddisk support
1103		CONFIG_CMD_IMI		  iminfo
1104		CONFIG_CMD_IMLS		  List all images found in NOR flash
1105		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
1106		CONFIG_CMD_IMMAP	* IMMR dump support
1107		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
1108		CONFIG_CMD_IMPORTENV	* import an environment
1109		CONFIG_CMD_INI		* import data from an ini file into the env
1110		CONFIG_CMD_IRQ		* irqinfo
1111		CONFIG_CMD_ITEST	  Integer/string test of 2 values
1112		CONFIG_CMD_JFFS2	* JFFS2 Support
1113		CONFIG_CMD_KGDB		* kgdb
1114		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
1115		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
1116					  (169.254.*.*)
1117		CONFIG_CMD_LOADB	  loadb
1118		CONFIG_CMD_LOADS	  loads
1119		CONFIG_CMD_MD5SUM	* print md5 message digest
1120					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
1121		CONFIG_CMD_MEMINFO	* Display detailed memory information
1122		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
1123					  loop, loopw
1124		CONFIG_CMD_MEMTEST	* mtest
1125		CONFIG_CMD_MISC		  Misc functions like sleep etc
1126		CONFIG_CMD_MMC		* MMC memory mapped support
1127		CONFIG_CMD_MII		* MII utility commands
1128		CONFIG_CMD_MTDPARTS	* MTD partition support
1129		CONFIG_CMD_NAND		* NAND support
1130		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
1131		CONFIG_CMD_NFS		  NFS support
1132		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
1133		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
1134		CONFIG_CMD_PCI		* pciinfo
1135		CONFIG_CMD_PCMCIA		* PCMCIA support
1136		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
1137					  host
1138		CONFIG_CMD_PORTIO	* Port I/O
1139		CONFIG_CMD_READ		* Read raw data from partition
1140		CONFIG_CMD_REGINFO	* Register dump
1141		CONFIG_CMD_RUN		  run command in env variable
1142		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
1143		CONFIG_CMD_SAVES	* save S record dump
1144		CONFIG_CMD_SCSI		* SCSI Support
1145		CONFIG_CMD_SDRAM	* print SDRAM configuration information
1146					  (requires CONFIG_CMD_I2C)
1147		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
1148					  (4xx only)
1149		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
1150		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
1151					  (requires CONFIG_CMD_MEMORY)
1152		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
1153		CONFIG_CMD_SOURCE	  "source" command Support
1154		CONFIG_CMD_SPI		* SPI serial bus support
1155		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
1156		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
1157		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
1158		CONFIG_CMD_TIMER	* access to the system tick timer
1159		CONFIG_CMD_USB		* USB support
1160		CONFIG_CMD_CDP		* Cisco Discover Protocol support
1161		CONFIG_CMD_MFSL		* Microblaze FSL support
1162		CONFIG_CMD_XIMG		  Load part of Multi Image
1163		CONFIG_CMD_UUID		* Generate random UUID or GUID string
1164
1165		EXAMPLE: If you want all functions except of network
1166		support you can write:
1167
1168		#include "config_cmd_all.h"
1169		#undef CONFIG_CMD_NET
1170
1171	Other Commands:
1172		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
1173
1174	Note:	Don't enable the "icache" and "dcache" commands
1175		(configuration option CONFIG_CMD_CACHE) unless you know
1176		what you (and your U-Boot users) are doing. Data
1177		cache cannot be enabled on systems like the 8xx or
1178		8260 (where accesses to the IMMR region must be
1179		uncached), and it cannot be disabled on all other
1180		systems where we (mis-) use the data cache to hold an
1181		initial stack and some data.
1182
1183
1184		XXX - this list needs to get updated!
1185
1186- Regular expression support:
1187		CONFIG_REGEX
1188		If this variable is defined, U-Boot is linked against
1189		the SLRE (Super Light Regular Expression) library,
1190		which adds regex support to some commands, as for
1191		example "env grep" and "setexpr".
1192
1193- Device tree:
1194		CONFIG_OF_CONTROL
1195		If this variable is defined, U-Boot will use a device tree
1196		to configure its devices, instead of relying on statically
1197		compiled #defines in the board file. This option is
1198		experimental and only available on a few boards. The device
1199		tree is available in the global data as gd->fdt_blob.
1200
1201		U-Boot needs to get its device tree from somewhere. This can
1202		be done using one of the two options below:
1203
1204		CONFIG_OF_EMBED
1205		If this variable is defined, U-Boot will embed a device tree
1206		binary in its image. This device tree file should be in the
1207		board directory and called <soc>-<board>.dts. The binary file
1208		is then picked up in board_init_f() and made available through
1209		the global data structure as gd->blob.
1210
1211		CONFIG_OF_SEPARATE
1212		If this variable is defined, U-Boot will build a device tree
1213		binary. It will be called u-boot.dtb. Architecture-specific
1214		code will locate it at run-time. Generally this works by:
1215
1216			cat u-boot.bin u-boot.dtb >image.bin
1217
1218		and in fact, U-Boot does this for you, creating a file called
1219		u-boot-dtb.bin which is useful in the common case. You can
1220		still use the individual files if you need something more
1221		exotic.
1222
1223- Watchdog:
1224		CONFIG_WATCHDOG
1225		If this variable is defined, it enables watchdog
1226		support for the SoC. There must be support in the SoC
1227		specific code for a watchdog. For the 8xx and 8260
1228		CPUs, the SIU Watchdog feature is enabled in the SYPCR
1229		register.  When supported for a specific SoC is
1230		available, then no further board specific code should
1231		be needed to use it.
1232
1233		CONFIG_HW_WATCHDOG
1234		When using a watchdog circuitry external to the used
1235		SoC, then define this variable and provide board
1236		specific code for the "hw_watchdog_reset" function.
1237
1238		CONFIG_AT91_HW_WDT_TIMEOUT
1239		specify the timeout in seconds. default 2 seconds.
1240
1241- U-Boot Version:
1242		CONFIG_VERSION_VARIABLE
1243		If this variable is defined, an environment variable
1244		named "ver" is created by U-Boot showing the U-Boot
1245		version as printed by the "version" command.
1246		Any change to this variable will be reverted at the
1247		next reset.
1248
1249- Real-Time Clock:
1250
1251		When CONFIG_CMD_DATE is selected, the type of the RTC
1252		has to be selected, too. Define exactly one of the
1253		following options:
1254
1255		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1256		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1257		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1258		CONFIG_RTC_MC146818	- use MC146818 RTC
1259		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1260		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1261		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1262		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1263		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1264		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1265		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1266		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1267		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1268					  RV3029 RTC.
1269
1270		Note that if the RTC uses I2C, then the I2C interface
1271		must also be configured. See I2C Support, below.
1272
1273- GPIO Support:
1274		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1275
1276		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1277		chip-ngpio pairs that tell the PCA953X driver the number of
1278		pins supported by a particular chip.
1279
1280		Note that if the GPIO device uses I2C, then the I2C interface
1281		must also be configured. See I2C Support, below.
1282
1283- I/O tracing:
1284		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1285		accesses and can checksum them or write a list of them out
1286		to memory. See the 'iotrace' command for details. This is
1287		useful for testing device drivers since it can confirm that
1288		the driver behaves the same way before and after a code
1289		change. Currently this is supported on sandbox and arm. To
1290		add support for your architecture, add '#include <iotrace.h>'
1291		to the bottom of arch/<arch>/include/asm/io.h and test.
1292
1293		Example output from the 'iotrace stats' command is below.
1294		Note that if the trace buffer is exhausted, the checksum will
1295		still continue to operate.
1296
1297			iotrace is enabled
1298			Start:  10000000	(buffer start address)
1299			Size:   00010000	(buffer size)
1300			Offset: 00000120	(current buffer offset)
1301			Output: 10000120	(start + offset)
1302			Count:  00000018	(number of trace records)
1303			CRC32:  9526fb66	(CRC32 of all trace records)
1304
1305- Timestamp Support:
1306
1307		When CONFIG_TIMESTAMP is selected, the timestamp
1308		(date and time) of an image is printed by image
1309		commands like bootm or iminfo. This option is
1310		automatically enabled when you select CONFIG_CMD_DATE .
1311
1312- Partition Labels (disklabels) Supported:
1313		Zero or more of the following:
1314		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1315		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1316				       Intel architecture, USB sticks, etc.
1317		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1318		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1319				       bootloader.  Note 2TB partition limit; see
1320				       disk/part_efi.c
1321		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1322
1323		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1324		CONFIG_CMD_SCSI) you must configure support for at
1325		least one non-MTD partition type as well.
1326
1327- IDE Reset method:
1328		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1329		board configurations files but used nowhere!
1330
1331		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1332		be performed by calling the function
1333			ide_set_reset(int reset)
1334		which has to be defined in a board specific file
1335
1336- ATAPI Support:
1337		CONFIG_ATAPI
1338
1339		Set this to enable ATAPI support.
1340
1341- LBA48 Support
1342		CONFIG_LBA48
1343
1344		Set this to enable support for disks larger than 137GB
1345		Also look at CONFIG_SYS_64BIT_LBA.
1346		Whithout these , LBA48 support uses 32bit variables and will 'only'
1347		support disks up to 2.1TB.
1348
1349		CONFIG_SYS_64BIT_LBA:
1350			When enabled, makes the IDE subsystem use 64bit sector addresses.
1351			Default is 32bit.
1352
1353- SCSI Support:
1354		At the moment only there is only support for the
1355		SYM53C8XX SCSI controller; define
1356		CONFIG_SCSI_SYM53C8XX to enable it.
1357
1358		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1359		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1360		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1361		maximum numbers of LUNs, SCSI ID's and target
1362		devices.
1363		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1364
1365		The environment variable 'scsidevs' is set to the number of
1366		SCSI devices found during the last scan.
1367
1368- NETWORK Support (PCI):
1369		CONFIG_E1000
1370		Support for Intel 8254x/8257x gigabit chips.
1371
1372		CONFIG_E1000_SPI
1373		Utility code for direct access to the SPI bus on Intel 8257x.
1374		This does not do anything useful unless you set at least one
1375		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1376
1377		CONFIG_E1000_SPI_GENERIC
1378		Allow generic access to the SPI bus on the Intel 8257x, for
1379		example with the "sspi" command.
1380
1381		CONFIG_CMD_E1000
1382		Management command for E1000 devices.  When used on devices
1383		with SPI support you can reprogram the EEPROM from U-Boot.
1384
1385		CONFIG_E1000_FALLBACK_MAC
1386		default MAC for empty EEPROM after production.
1387
1388		CONFIG_EEPRO100
1389		Support for Intel 82557/82559/82559ER chips.
1390		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1391		write routine for first time initialisation.
1392
1393		CONFIG_TULIP
1394		Support for Digital 2114x chips.
1395		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1396		modem chip initialisation (KS8761/QS6611).
1397
1398		CONFIG_NATSEMI
1399		Support for National dp83815 chips.
1400
1401		CONFIG_NS8382X
1402		Support for National dp8382[01] gigabit chips.
1403
1404- NETWORK Support (other):
1405
1406		CONFIG_DRIVER_AT91EMAC
1407		Support for AT91RM9200 EMAC.
1408
1409			CONFIG_RMII
1410			Define this to use reduced MII inteface
1411
1412			CONFIG_DRIVER_AT91EMAC_QUIET
1413			If this defined, the driver is quiet.
1414			The driver doen't show link status messages.
1415
1416		CONFIG_CALXEDA_XGMAC
1417		Support for the Calxeda XGMAC device
1418
1419		CONFIG_LAN91C96
1420		Support for SMSC's LAN91C96 chips.
1421
1422			CONFIG_LAN91C96_BASE
1423			Define this to hold the physical address
1424			of the LAN91C96's I/O space
1425
1426			CONFIG_LAN91C96_USE_32_BIT
1427			Define this to enable 32 bit addressing
1428
1429		CONFIG_SMC91111
1430		Support for SMSC's LAN91C111 chip
1431
1432			CONFIG_SMC91111_BASE
1433			Define this to hold the physical address
1434			of the device (I/O space)
1435
1436			CONFIG_SMC_USE_32_BIT
1437			Define this if data bus is 32 bits
1438
1439			CONFIG_SMC_USE_IOFUNCS
1440			Define this to use i/o functions instead of macros
1441			(some hardware wont work with macros)
1442
1443		CONFIG_DRIVER_TI_EMAC
1444		Support for davinci emac
1445
1446			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1447			Define this if you have more then 3 PHYs.
1448
1449		CONFIG_FTGMAC100
1450		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1451
1452			CONFIG_FTGMAC100_EGIGA
1453			Define this to use GE link update with gigabit PHY.
1454			Define this if FTGMAC100 is connected to gigabit PHY.
1455			If your system has 10/100 PHY only, it might not occur
1456			wrong behavior. Because PHY usually return timeout or
1457			useless data when polling gigabit status and gigabit
1458			control registers. This behavior won't affect the
1459			correctnessof 10/100 link speed update.
1460
1461		CONFIG_SMC911X
1462		Support for SMSC's LAN911x and LAN921x chips
1463
1464			CONFIG_SMC911X_BASE
1465			Define this to hold the physical address
1466			of the device (I/O space)
1467
1468			CONFIG_SMC911X_32_BIT
1469			Define this if data bus is 32 bits
1470
1471			CONFIG_SMC911X_16_BIT
1472			Define this if data bus is 16 bits. If your processor
1473			automatically converts one 32 bit word to two 16 bit
1474			words you may also try CONFIG_SMC911X_32_BIT.
1475
1476		CONFIG_SH_ETHER
1477		Support for Renesas on-chip Ethernet controller
1478
1479			CONFIG_SH_ETHER_USE_PORT
1480			Define the number of ports to be used
1481
1482			CONFIG_SH_ETHER_PHY_ADDR
1483			Define the ETH PHY's address
1484
1485			CONFIG_SH_ETHER_CACHE_WRITEBACK
1486			If this option is set, the driver enables cache flush.
1487
1488- PWM Support:
1489		CONFIG_PWM_IMX
1490		Support for PWM modul on the imx6.
1491
1492- TPM Support:
1493		CONFIG_TPM
1494		Support TPM devices.
1495
1496		CONFIG_TPM_TIS_I2C
1497		Support for i2c bus TPM devices. Only one device
1498		per system is supported at this time.
1499
1500			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1501			Define the the i2c bus number for the TPM device
1502
1503			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1504			Define the TPM's address on the i2c bus
1505
1506			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1507			Define the burst count bytes upper limit
1508
1509		CONFIG_TPM_ATMEL_TWI
1510		Support for Atmel TWI TPM device. Requires I2C support.
1511
1512		CONFIG_TPM_TIS_LPC
1513		Support for generic parallel port TPM devices. Only one device
1514		per system is supported at this time.
1515
1516			CONFIG_TPM_TIS_BASE_ADDRESS
1517			Base address where the generic TPM device is mapped
1518			to. Contemporary x86 systems usually map it at
1519			0xfed40000.
1520
1521		CONFIG_CMD_TPM
1522		Add tpm monitor functions.
1523		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1524		provides monitor access to authorized functions.
1525
1526		CONFIG_TPM
1527		Define this to enable the TPM support library which provides
1528		functional interfaces to some TPM commands.
1529		Requires support for a TPM device.
1530
1531		CONFIG_TPM_AUTH_SESSIONS
1532		Define this to enable authorized functions in the TPM library.
1533		Requires CONFIG_TPM and CONFIG_SHA1.
1534
1535- USB Support:
1536		At the moment only the UHCI host controller is
1537		supported (PIP405, MIP405, MPC5200); define
1538		CONFIG_USB_UHCI to enable it.
1539		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1540		and define CONFIG_USB_STORAGE to enable the USB
1541		storage devices.
1542		Note:
1543		Supported are USB Keyboards and USB Floppy drives
1544		(TEAC FD-05PUB).
1545		MPC5200 USB requires additional defines:
1546			CONFIG_USB_CLOCK
1547				for 528 MHz Clock: 0x0001bbbb
1548			CONFIG_PSC3_USB
1549				for USB on PSC3
1550			CONFIG_USB_CONFIG
1551				for differential drivers: 0x00001000
1552				for single ended drivers: 0x00005000
1553				for differential drivers on PSC3: 0x00000100
1554				for single ended drivers on PSC3: 0x00004100
1555			CONFIG_SYS_USB_EVENT_POLL
1556				May be defined to allow interrupt polling
1557				instead of using asynchronous interrupts
1558
1559		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1560		txfilltuning field in the EHCI controller on reset.
1561
1562		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1563		HW module registers.
1564
1565- USB Device:
1566		Define the below if you wish to use the USB console.
1567		Once firmware is rebuilt from a serial console issue the
1568		command "setenv stdin usbtty; setenv stdout usbtty" and
1569		attach your USB cable. The Unix command "dmesg" should print
1570		it has found a new device. The environment variable usbtty
1571		can be set to gserial or cdc_acm to enable your device to
1572		appear to a USB host as a Linux gserial device or a
1573		Common Device Class Abstract Control Model serial device.
1574		If you select usbtty = gserial you should be able to enumerate
1575		a Linux host by
1576		# modprobe usbserial vendor=0xVendorID product=0xProductID
1577		else if using cdc_acm, simply setting the environment
1578		variable usbtty to be cdc_acm should suffice. The following
1579		might be defined in YourBoardName.h
1580
1581			CONFIG_USB_DEVICE
1582			Define this to build a UDC device
1583
1584			CONFIG_USB_TTY
1585			Define this to have a tty type of device available to
1586			talk to the UDC device
1587
1588			CONFIG_USBD_HS
1589			Define this to enable the high speed support for usb
1590			device and usbtty. If this feature is enabled, a routine
1591			int is_usbd_high_speed(void)
1592			also needs to be defined by the driver to dynamically poll
1593			whether the enumeration has succeded at high speed or full
1594			speed.
1595
1596			CONFIG_SYS_CONSOLE_IS_IN_ENV
1597			Define this if you want stdin, stdout &/or stderr to
1598			be set to usbtty.
1599
1600			mpc8xx:
1601				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1602				Derive USB clock from external clock "blah"
1603				- CONFIG_SYS_USB_EXTC_CLK 0x02
1604
1605				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1606				Derive USB clock from brgclk
1607				- CONFIG_SYS_USB_BRG_CLK 0x04
1608
1609		If you have a USB-IF assigned VendorID then you may wish to
1610		define your own vendor specific values either in BoardName.h
1611		or directly in usbd_vendor_info.h. If you don't define
1612		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1613		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1614		should pretend to be a Linux device to it's target host.
1615
1616			CONFIG_USBD_MANUFACTURER
1617			Define this string as the name of your company for
1618			- CONFIG_USBD_MANUFACTURER "my company"
1619
1620			CONFIG_USBD_PRODUCT_NAME
1621			Define this string as the name of your product
1622			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1623
1624			CONFIG_USBD_VENDORID
1625			Define this as your assigned Vendor ID from the USB
1626			Implementors Forum. This *must* be a genuine Vendor ID
1627			to avoid polluting the USB namespace.
1628			- CONFIG_USBD_VENDORID 0xFFFF
1629
1630			CONFIG_USBD_PRODUCTID
1631			Define this as the unique Product ID
1632			for your device
1633			- CONFIG_USBD_PRODUCTID 0xFFFF
1634
1635- ULPI Layer Support:
1636		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1637		the generic ULPI layer. The generic layer accesses the ULPI PHY
1638		via the platform viewport, so you need both the genric layer and
1639		the viewport enabled. Currently only Chipidea/ARC based
1640		viewport is supported.
1641		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1642		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1643		If your ULPI phy needs a different reference clock than the
1644		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1645		the appropriate value in Hz.
1646
1647- MMC Support:
1648		The MMC controller on the Intel PXA is supported. To
1649		enable this define CONFIG_MMC. The MMC can be
1650		accessed from the boot prompt by mapping the device
1651		to physical memory similar to flash. Command line is
1652		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1653		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1654
1655		CONFIG_SH_MMCIF
1656		Support for Renesas on-chip MMCIF controller
1657
1658			CONFIG_SH_MMCIF_ADDR
1659			Define the base address of MMCIF registers
1660
1661			CONFIG_SH_MMCIF_CLK
1662			Define the clock frequency for MMCIF
1663
1664		CONFIG_GENERIC_MMC
1665		Enable the generic MMC driver
1666
1667		CONFIG_SUPPORT_EMMC_BOOT
1668		Enable some additional features of the eMMC boot partitions.
1669
1670		CONFIG_SUPPORT_EMMC_RPMB
1671		Enable the commands for reading, writing and programming the
1672		key for the Replay Protection Memory Block partition in eMMC.
1673
1674- USB Device Firmware Update (DFU) class support:
1675		CONFIG_DFU_FUNCTION
1676		This enables the USB portion of the DFU USB class
1677
1678		CONFIG_CMD_DFU
1679		This enables the command "dfu" which is used to have
1680		U-Boot create a DFU class device via USB.  This command
1681		requires that the "dfu_alt_info" environment variable be
1682		set and define the alt settings to expose to the host.
1683
1684		CONFIG_DFU_MMC
1685		This enables support for exposing (e)MMC devices via DFU.
1686
1687		CONFIG_DFU_NAND
1688		This enables support for exposing NAND devices via DFU.
1689
1690		CONFIG_DFU_RAM
1691		This enables support for exposing RAM via DFU.
1692		Note: DFU spec refer to non-volatile memory usage, but
1693		allow usages beyond the scope of spec - here RAM usage,
1694		one that would help mostly the developer.
1695
1696		CONFIG_SYS_DFU_DATA_BUF_SIZE
1697		Dfu transfer uses a buffer before writing data to the
1698		raw storage device. Make the size (in bytes) of this buffer
1699		configurable. The size of this buffer is also configurable
1700		through the "dfu_bufsiz" environment variable.
1701
1702		CONFIG_SYS_DFU_MAX_FILE_SIZE
1703		When updating files rather than the raw storage device,
1704		we use a static buffer to copy the file into and then write
1705		the buffer once we've been given the whole file.  Define
1706		this to the maximum filesize (in bytes) for the buffer.
1707		Default is 4 MiB if undefined.
1708
1709		DFU_DEFAULT_POLL_TIMEOUT
1710		Poll timeout [ms], is the timeout a device can send to the
1711		host. The host must wait for this timeout before sending
1712		a subsequent DFU_GET_STATUS request to the device.
1713
1714		DFU_MANIFEST_POLL_TIMEOUT
1715		Poll timeout [ms], which the device sends to the host when
1716		entering dfuMANIFEST state. Host waits this timeout, before
1717		sending again an USB request to the device.
1718
1719- USB Device Android Fastboot support:
1720		CONFIG_CMD_FASTBOOT
1721		This enables the command "fastboot" which enables the Android
1722		fastboot mode for the platform's USB device. Fastboot is a USB
1723		protocol for downloading images, flashing and device control
1724		used on Android devices.
1725		See doc/README.android-fastboot for more information.
1726
1727		CONFIG_ANDROID_BOOT_IMAGE
1728		This enables support for booting images which use the Android
1729		image format header.
1730
1731		CONFIG_USB_FASTBOOT_BUF_ADDR
1732		The fastboot protocol requires a large memory buffer for
1733		downloads. Define this to the starting RAM address to use for
1734		downloaded images.
1735
1736		CONFIG_USB_FASTBOOT_BUF_SIZE
1737		The fastboot protocol requires a large memory buffer for
1738		downloads. This buffer should be as large as possible for a
1739		platform. Define this to the size available RAM for fastboot.
1740
1741		CONFIG_FASTBOOT_FLASH
1742		The fastboot protocol includes a "flash" command for writing
1743		the downloaded image to a non-volatile storage device. Define
1744		this to enable the "fastboot flash" command.
1745
1746		CONFIG_FASTBOOT_FLASH_MMC_DEV
1747		The fastboot "flash" command requires additional information
1748		regarding the non-volatile storage device. Define this to
1749		the eMMC device that fastboot should use to store the image.
1750
1751		CONFIG_FASTBOOT_GPT_NAME
1752		The fastboot "flash" command supports writing the downloaded
1753		image to the Protective MBR and the Primary GUID Partition
1754		Table. (Additionally, this downloaded image is post-processed
1755		to generate and write the Backup GUID Partition Table.)
1756		This occurs when the specified "partition name" on the
1757		"fastboot flash" command line matches this value.
1758		Default is GPT_ENTRY_NAME (currently "gpt") if undefined.
1759
1760- Journaling Flash filesystem support:
1761		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1762		CONFIG_JFFS2_NAND_DEV
1763		Define these for a default partition on a NAND device
1764
1765		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1766		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1767		Define these for a default partition on a NOR device
1768
1769		CONFIG_SYS_JFFS_CUSTOM_PART
1770		Define this to create an own partition. You have to provide a
1771		function struct part_info* jffs2_part_info(int part_num)
1772
1773		If you define only one JFFS2 partition you may also want to
1774		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1775		to disable the command chpart. This is the default when you
1776		have not defined a custom partition
1777
1778- FAT(File Allocation Table) filesystem write function support:
1779		CONFIG_FAT_WRITE
1780
1781		Define this to enable support for saving memory data as a
1782		file in FAT formatted partition.
1783
1784		This will also enable the command "fatwrite" enabling the
1785		user to write files to FAT.
1786
1787CBFS (Coreboot Filesystem) support
1788		CONFIG_CMD_CBFS
1789
1790		Define this to enable support for reading from a Coreboot
1791		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1792		and cbfsload.
1793
1794- FAT(File Allocation Table) filesystem cluster size:
1795		CONFIG_FS_FAT_MAX_CLUSTSIZE
1796
1797		Define the max cluster size for fat operations else
1798		a default value of 65536 will be defined.
1799
1800- Keyboard Support:
1801		CONFIG_ISA_KEYBOARD
1802
1803		Define this to enable standard (PC-Style) keyboard
1804		support
1805
1806		CONFIG_I8042_KBD
1807		Standard PC keyboard driver with US (is default) and
1808		GERMAN key layout (switch via environment 'keymap=de') support.
1809		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1810		for cfb_console. Supports cursor blinking.
1811
1812		CONFIG_CROS_EC_KEYB
1813		Enables a Chrome OS keyboard using the CROS_EC interface.
1814		This uses CROS_EC to communicate with a second microcontroller
1815		which provides key scans on request.
1816
1817- Video support:
1818		CONFIG_VIDEO
1819
1820		Define this to enable video support (for output to
1821		video).
1822
1823		CONFIG_VIDEO_CT69000
1824
1825		Enable Chips & Technologies 69000 Video chip
1826
1827		CONFIG_VIDEO_SMI_LYNXEM
1828		Enable Silicon Motion SMI 712/710/810 Video chip. The
1829		video output is selected via environment 'videoout'
1830		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1831		assumed.
1832
1833		For the CT69000 and SMI_LYNXEM drivers, videomode is
1834		selected via environment 'videomode'. Two different ways
1835		are possible:
1836		- "videomode=num"   'num' is a standard LiLo mode numbers.
1837		Following standard modes are supported	(* is default):
1838
1839		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1840		-------------+---------------------------------------------
1841		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1842		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1843		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1844		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1845		-------------+---------------------------------------------
1846		(i.e. setenv videomode 317; saveenv; reset;)
1847
1848		- "videomode=bootargs" all the video parameters are parsed
1849		from the bootargs. (See drivers/video/videomodes.c)
1850
1851
1852		CONFIG_VIDEO_SED13806
1853		Enable Epson SED13806 driver. This driver supports 8bpp
1854		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1855		or CONFIG_VIDEO_SED13806_16BPP
1856
1857		CONFIG_FSL_DIU_FB
1858		Enable the Freescale DIU video driver.	Reference boards for
1859		SOCs that have a DIU should define this macro to enable DIU
1860		support, and should also define these other macros:
1861
1862			CONFIG_SYS_DIU_ADDR
1863			CONFIG_VIDEO
1864			CONFIG_CMD_BMP
1865			CONFIG_CFB_CONSOLE
1866			CONFIG_VIDEO_SW_CURSOR
1867			CONFIG_VGA_AS_SINGLE_DEVICE
1868			CONFIG_VIDEO_LOGO
1869			CONFIG_VIDEO_BMP_LOGO
1870
1871		The DIU driver will look for the 'video-mode' environment
1872		variable, and if defined, enable the DIU as a console during
1873		boot.  See the documentation file README.video for a
1874		description of this variable.
1875
1876
1877- Keyboard Support:
1878		CONFIG_KEYBOARD
1879
1880		Define this to enable a custom keyboard support.
1881		This simply calls drv_keyboard_init() which must be
1882		defined in your board-specific files.
1883		The only board using this so far is RBC823.
1884
1885- LCD Support:	CONFIG_LCD
1886
1887		Define this to enable LCD support (for output to LCD
1888		display); also select one of the supported displays
1889		by defining one of these:
1890
1891		CONFIG_ATMEL_LCD:
1892
1893			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1894
1895		CONFIG_NEC_NL6448AC33:
1896
1897			NEC NL6448AC33-18. Active, color, single scan.
1898
1899		CONFIG_NEC_NL6448BC20
1900
1901			NEC NL6448BC20-08. 6.5", 640x480.
1902			Active, color, single scan.
1903
1904		CONFIG_NEC_NL6448BC33_54
1905
1906			NEC NL6448BC33-54. 10.4", 640x480.
1907			Active, color, single scan.
1908
1909		CONFIG_SHARP_16x9
1910
1911			Sharp 320x240. Active, color, single scan.
1912			It isn't 16x9, and I am not sure what it is.
1913
1914		CONFIG_SHARP_LQ64D341
1915
1916			Sharp LQ64D341 display, 640x480.
1917			Active, color, single scan.
1918
1919		CONFIG_HLD1045
1920
1921			HLD1045 display, 640x480.
1922			Active, color, single scan.
1923
1924		CONFIG_OPTREX_BW
1925
1926			Optrex	 CBL50840-2 NF-FW 99 22 M5
1927			or
1928			Hitachi	 LMG6912RPFC-00T
1929			or
1930			Hitachi	 SP14Q002
1931
1932			320x240. Black & white.
1933
1934		Normally display is black on white background; define
1935		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1936
1937		CONFIG_LCD_ALIGNMENT
1938
1939		Normally the LCD is page-aligned (typically 4KB). If this is
1940		defined then the LCD will be aligned to this value instead.
1941		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1942		here, since it is cheaper to change data cache settings on
1943		a per-section basis.
1944
1945		CONFIG_CONSOLE_SCROLL_LINES
1946
1947		When the console need to be scrolled, this is the number of
1948		lines to scroll by. It defaults to 1. Increasing this makes
1949		the console jump but can help speed up operation when scrolling
1950		is slow.
1951
1952		CONFIG_LCD_ROTATION
1953
1954		Sometimes, for example if the display is mounted in portrait
1955		mode or even if it's mounted landscape but rotated by 180degree,
1956		we need to rotate our content of the display relative to the
1957		framebuffer, so that user can read the messages which are
1958		printed out.
1959		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1960		initialized with a given rotation from "vl_rot" out of
1961		"vidinfo_t" which is provided by the board specific code.
1962		The value for vl_rot is coded as following (matching to
1963		fbcon=rotate:<n> linux-kernel commandline):
1964		0 = no rotation respectively 0 degree
1965		1 = 90 degree rotation
1966		2 = 180 degree rotation
1967		3 = 270 degree rotation
1968
1969		If CONFIG_LCD_ROTATION is not defined, the console will be
1970		initialized with 0degree rotation.
1971
1972		CONFIG_LCD_BMP_RLE8
1973
1974		Support drawing of RLE8-compressed bitmaps on the LCD.
1975
1976		CONFIG_I2C_EDID
1977
1978		Enables an 'i2c edid' command which can read EDID
1979		information over I2C from an attached LCD display.
1980
1981- Splash Screen Support: CONFIG_SPLASH_SCREEN
1982
1983		If this option is set, the environment is checked for
1984		a variable "splashimage". If found, the usual display
1985		of logo, copyright and system information on the LCD
1986		is suppressed and the BMP image at the address
1987		specified in "splashimage" is loaded instead. The
1988		console is redirected to the "nulldev", too. This
1989		allows for a "silent" boot where a splash screen is
1990		loaded very quickly after power-on.
1991
1992		CONFIG_SPLASHIMAGE_GUARD
1993
1994		If this option is set, then U-Boot will prevent the environment
1995		variable "splashimage" from being set to a problematic address
1996		(see README.displaying-bmps).
1997		This option is useful for targets where, due to alignment
1998		restrictions, an improperly aligned BMP image will cause a data
1999		abort. If you think you will not have problems with unaligned
2000		accesses (for example because your toolchain prevents them)
2001		there is no need to set this option.
2002
2003		CONFIG_SPLASH_SCREEN_ALIGN
2004
2005		If this option is set the splash image can be freely positioned
2006		on the screen. Environment variable "splashpos" specifies the
2007		position as "x,y". If a positive number is given it is used as
2008		number of pixel from left/top. If a negative number is given it
2009		is used as number of pixel from right/bottom. You can also
2010		specify 'm' for centering the image.
2011
2012		Example:
2013		setenv splashpos m,m
2014			=> image at center of screen
2015
2016		setenv splashpos 30,20
2017			=> image at x = 30 and y = 20
2018
2019		setenv splashpos -10,m
2020			=> vertically centered image
2021			   at x = dspWidth - bmpWidth - 9
2022
2023- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
2024
2025		If this option is set, additionally to standard BMP
2026		images, gzipped BMP images can be displayed via the
2027		splashscreen support or the bmp command.
2028
2029- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
2030
2031		If this option is set, 8-bit RLE compressed BMP images
2032		can be displayed via the splashscreen support or the
2033		bmp command.
2034
2035- Do compressing for memory range:
2036		CONFIG_CMD_ZIP
2037
2038		If this option is set, it would use zlib deflate method
2039		to compress the specified memory at its best effort.
2040
2041- Compression support:
2042		CONFIG_GZIP
2043
2044		Enabled by default to support gzip compressed images.
2045
2046		CONFIG_BZIP2
2047
2048		If this option is set, support for bzip2 compressed
2049		images is included. If not, only uncompressed and gzip
2050		compressed images are supported.
2051
2052		NOTE: the bzip2 algorithm requires a lot of RAM, so
2053		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
2054		be at least 4MB.
2055
2056		CONFIG_LZMA
2057
2058		If this option is set, support for lzma compressed
2059		images is included.
2060
2061		Note: The LZMA algorithm adds between 2 and 4KB of code and it
2062		requires an amount of dynamic memory that is given by the
2063		formula:
2064
2065			(1846 + 768 << (lc + lp)) * sizeof(uint16)
2066
2067		Where lc and lp stand for, respectively, Literal context bits
2068		and Literal pos bits.
2069
2070		This value is upper-bounded by 14MB in the worst case. Anyway,
2071		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
2072		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
2073		a very small buffer.
2074
2075		Use the lzmainfo tool to determinate the lc and lp values and
2076		then calculate the amount of needed dynamic memory (ensuring
2077		the appropriate CONFIG_SYS_MALLOC_LEN value).
2078
2079		CONFIG_LZO
2080
2081		If this option is set, support for LZO compressed images
2082		is included.
2083
2084- MII/PHY support:
2085		CONFIG_PHY_ADDR
2086
2087		The address of PHY on MII bus.
2088
2089		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
2090
2091		The clock frequency of the MII bus
2092
2093		CONFIG_PHY_GIGE
2094
2095		If this option is set, support for speed/duplex
2096		detection of gigabit PHY is included.
2097
2098		CONFIG_PHY_RESET_DELAY
2099
2100		Some PHY like Intel LXT971A need extra delay after
2101		reset before any MII register access is possible.
2102		For such PHY, set this option to the usec delay
2103		required. (minimum 300usec for LXT971A)
2104
2105		CONFIG_PHY_CMD_DELAY (ppc4xx)
2106
2107		Some PHY like Intel LXT971A need extra delay after
2108		command issued before MII status register can be read
2109
2110- IP address:
2111		CONFIG_IPADDR
2112
2113		Define a default value for the IP address to use for
2114		the default Ethernet interface, in case this is not
2115		determined through e.g. bootp.
2116		(Environment variable "ipaddr")
2117
2118- Server IP address:
2119		CONFIG_SERVERIP
2120
2121		Defines a default value for the IP address of a TFTP
2122		server to contact when using the "tftboot" command.
2123		(Environment variable "serverip")
2124
2125		CONFIG_KEEP_SERVERADDR
2126
2127		Keeps the server's MAC address, in the env 'serveraddr'
2128		for passing to bootargs (like Linux's netconsole option)
2129
2130- Gateway IP address:
2131		CONFIG_GATEWAYIP
2132
2133		Defines a default value for the IP address of the
2134		default router where packets to other networks are
2135		sent to.
2136		(Environment variable "gatewayip")
2137
2138- Subnet mask:
2139		CONFIG_NETMASK
2140
2141		Defines a default value for the subnet mask (or
2142		routing prefix) which is used to determine if an IP
2143		address belongs to the local subnet or needs to be
2144		forwarded through a router.
2145		(Environment variable "netmask")
2146
2147- Multicast TFTP Mode:
2148		CONFIG_MCAST_TFTP
2149
2150		Defines whether you want to support multicast TFTP as per
2151		rfc-2090; for example to work with atftp.  Lets lots of targets
2152		tftp down the same boot image concurrently.  Note: the Ethernet
2153		driver in use must provide a function: mcast() to join/leave a
2154		multicast group.
2155
2156- BOOTP Recovery Mode:
2157		CONFIG_BOOTP_RANDOM_DELAY
2158
2159		If you have many targets in a network that try to
2160		boot using BOOTP, you may want to avoid that all
2161		systems send out BOOTP requests at precisely the same
2162		moment (which would happen for instance at recovery
2163		from a power failure, when all systems will try to
2164		boot, thus flooding the BOOTP server. Defining
2165		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
2166		inserted before sending out BOOTP requests. The
2167		following delays are inserted then:
2168
2169		1st BOOTP request:	delay 0 ... 1 sec
2170		2nd BOOTP request:	delay 0 ... 2 sec
2171		3rd BOOTP request:	delay 0 ... 4 sec
2172		4th and following
2173		BOOTP requests:		delay 0 ... 8 sec
2174
2175		CONFIG_BOOTP_ID_CACHE_SIZE
2176
2177		BOOTP packets are uniquely identified using a 32-bit ID. The
2178		server will copy the ID from client requests to responses and
2179		U-Boot will use this to determine if it is the destination of
2180		an incoming response. Some servers will check that addresses
2181		aren't in use before handing them out (usually using an ARP
2182		ping) and therefore take up to a few hundred milliseconds to
2183		respond. Network congestion may also influence the time it
2184		takes for a response to make it back to the client. If that
2185		time is too long, U-Boot will retransmit requests. In order
2186		to allow earlier responses to still be accepted after these
2187		retransmissions, U-Boot's BOOTP client keeps a small cache of
2188		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
2189		cache. The default is to keep IDs for up to four outstanding
2190		requests. Increasing this will allow U-Boot to accept offers
2191		from a BOOTP client in networks with unusually high latency.
2192
2193- DHCP Advanced Options:
2194		You can fine tune the DHCP functionality by defining
2195		CONFIG_BOOTP_* symbols:
2196
2197		CONFIG_BOOTP_SUBNETMASK
2198		CONFIG_BOOTP_GATEWAY
2199		CONFIG_BOOTP_HOSTNAME
2200		CONFIG_BOOTP_NISDOMAIN
2201		CONFIG_BOOTP_BOOTPATH
2202		CONFIG_BOOTP_BOOTFILESIZE
2203		CONFIG_BOOTP_DNS
2204		CONFIG_BOOTP_DNS2
2205		CONFIG_BOOTP_SEND_HOSTNAME
2206		CONFIG_BOOTP_NTPSERVER
2207		CONFIG_BOOTP_TIMEOFFSET
2208		CONFIG_BOOTP_VENDOREX
2209		CONFIG_BOOTP_MAY_FAIL
2210
2211		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
2212		environment variable, not the BOOTP server.
2213
2214		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
2215		after the configured retry count, the call will fail
2216		instead of starting over.  This can be used to fail over
2217		to Link-local IP address configuration if the DHCP server
2218		is not available.
2219
2220		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
2221		serverip from a DHCP server, it is possible that more
2222		than one DNS serverip is offered to the client.
2223		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
2224		serverip will be stored in the additional environment
2225		variable "dnsip2". The first DNS serverip is always
2226		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
2227		is defined.
2228
2229		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
2230		to do a dynamic update of a DNS server. To do this, they
2231		need the hostname of the DHCP requester.
2232		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
2233		of the "hostname" environment variable is passed as
2234		option 12 to the DHCP server.
2235
2236		CONFIG_BOOTP_DHCP_REQUEST_DELAY
2237
2238		A 32bit value in microseconds for a delay between
2239		receiving a "DHCP Offer" and sending the "DHCP Request".
2240		This fixes a problem with certain DHCP servers that don't
2241		respond 100% of the time to a "DHCP request". E.g. On an
2242		AT91RM9200 processor running at 180MHz, this delay needed
2243		to be *at least* 15,000 usec before a Windows Server 2003
2244		DHCP server would reply 100% of the time. I recommend at
2245		least 50,000 usec to be safe. The alternative is to hope
2246		that one of the retries will be successful but note that
2247		the DHCP timeout and retry process takes a longer than
2248		this delay.
2249
2250 - Link-local IP address negotiation:
2251		Negotiate with other link-local clients on the local network
2252		for an address that doesn't require explicit configuration.
2253		This is especially useful if a DHCP server cannot be guaranteed
2254		to exist in all environments that the device must operate.
2255
2256		See doc/README.link-local for more information.
2257
2258 - CDP Options:
2259		CONFIG_CDP_DEVICE_ID
2260
2261		The device id used in CDP trigger frames.
2262
2263		CONFIG_CDP_DEVICE_ID_PREFIX
2264
2265		A two character string which is prefixed to the MAC address
2266		of the device.
2267
2268		CONFIG_CDP_PORT_ID
2269
2270		A printf format string which contains the ascii name of
2271		the port. Normally is set to "eth%d" which sets
2272		eth0 for the first Ethernet, eth1 for the second etc.
2273
2274		CONFIG_CDP_CAPABILITIES
2275
2276		A 32bit integer which indicates the device capabilities;
2277		0x00000010 for a normal host which does not forwards.
2278
2279		CONFIG_CDP_VERSION
2280
2281		An ascii string containing the version of the software.
2282
2283		CONFIG_CDP_PLATFORM
2284
2285		An ascii string containing the name of the platform.
2286
2287		CONFIG_CDP_TRIGGER
2288
2289		A 32bit integer sent on the trigger.
2290
2291		CONFIG_CDP_POWER_CONSUMPTION
2292
2293		A 16bit integer containing the power consumption of the
2294		device in .1 of milliwatts.
2295
2296		CONFIG_CDP_APPLIANCE_VLAN_TYPE
2297
2298		A byte containing the id of the VLAN.
2299
2300- Status LED:	CONFIG_STATUS_LED
2301
2302		Several configurations allow to display the current
2303		status using a LED. For instance, the LED will blink
2304		fast while running U-Boot code, stop blinking as
2305		soon as a reply to a BOOTP request was received, and
2306		start blinking slow once the Linux kernel is running
2307		(supported by a status LED driver in the Linux
2308		kernel). Defining CONFIG_STATUS_LED enables this
2309		feature in U-Boot.
2310
2311		Additional options:
2312
2313		CONFIG_GPIO_LED
2314		The status LED can be connected to a GPIO pin.
2315		In such cases, the gpio_led driver can be used as a
2316		status LED backend implementation. Define CONFIG_GPIO_LED
2317		to include the gpio_led driver in the U-Boot binary.
2318
2319		CONFIG_GPIO_LED_INVERTED_TABLE
2320		Some GPIO connected LEDs may have inverted polarity in which
2321		case the GPIO high value corresponds to LED off state and
2322		GPIO low value corresponds to LED on state.
2323		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2324		with a list of GPIO LEDs that have inverted polarity.
2325
2326- CAN Support:	CONFIG_CAN_DRIVER
2327
2328		Defining CONFIG_CAN_DRIVER enables CAN driver support
2329		on those systems that support this (optional)
2330		feature, like the TQM8xxL modules.
2331
2332- I2C Support:	CONFIG_SYS_I2C
2333
2334		This enable the NEW i2c subsystem, and will allow you to use
2335		i2c commands at the u-boot command line (as long as you set
2336		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2337		based realtime clock chips or other i2c devices. See
2338		common/cmd_i2c.c for a description of the command line
2339		interface.
2340
2341		ported i2c driver to the new framework:
2342		- drivers/i2c/soft_i2c.c:
2343		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2344		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2345		    for defining speed and slave address
2346		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2347		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2348		    for defining speed and slave address
2349		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2350		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2351		    for defining speed and slave address
2352		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2353		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2354		    for defining speed and slave address
2355
2356		- drivers/i2c/fsl_i2c.c:
2357		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2358		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2359		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2360		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2361		    bus.
2362		  - If your board supports a second fsl i2c bus, define
2363		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2364		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2365		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2366		    second bus.
2367
2368		- drivers/i2c/tegra_i2c.c:
2369		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2370		  - This driver adds 4 i2c buses with a fix speed from
2371		    100000 and the slave addr 0!
2372
2373		- drivers/i2c/ppc4xx_i2c.c
2374		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2375		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2376		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2377
2378		- drivers/i2c/i2c_mxc.c
2379		  - activate this driver with CONFIG_SYS_I2C_MXC
2380		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2381		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2382		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2383		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2384		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2385		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2386		If those defines are not set, default value is 100000
2387		for speed, and 0 for slave.
2388		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2389		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2390
2391		- drivers/i2c/rcar_i2c.c:
2392		  - activate this driver with CONFIG_SYS_I2C_RCAR
2393		  - This driver adds 4 i2c buses
2394
2395		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2396		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2397		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2398		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2399		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2400		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2401		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2402		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2403		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2404
2405		- drivers/i2c/sh_i2c.c:
2406		  - activate this driver with CONFIG_SYS_I2C_SH
2407		  - This driver adds from 2 to 5 i2c buses
2408
2409		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2410		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2411		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2412		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2413		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2414		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2415		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2416		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2417		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2418		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2419		  - CONFIG_SYS_I2C_SH_BASE5 for setting the register channel 5
2420		  - CONFIG_SYS_I2C_SH_SPEED5 for for the speed channel 5
2421		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2422
2423		- drivers/i2c/omap24xx_i2c.c
2424		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2425		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2426		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2427		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2428		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2429		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2430		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2431		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2432		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2433		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2434		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2435
2436		- drivers/i2c/zynq_i2c.c
2437		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2438		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2439		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2440
2441		- drivers/i2c/s3c24x0_i2c.c:
2442		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2443		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2444		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2445		    with a fix speed from 100000 and the slave addr 0!
2446
2447		- drivers/i2c/ihs_i2c.c
2448		  - activate this driver with CONFIG_SYS_I2C_IHS
2449		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2450		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2451		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2452		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2453		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2454		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2455		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2456		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2457		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2458		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2459		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2460		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2461
2462		additional defines:
2463
2464		CONFIG_SYS_NUM_I2C_BUSES
2465		Hold the number of i2c buses you want to use. If you
2466		don't use/have i2c muxes on your i2c bus, this
2467		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2468		omit this define.
2469
2470		CONFIG_SYS_I2C_DIRECT_BUS
2471		define this, if you don't use i2c muxes on your hardware.
2472		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2473		omit this define.
2474
2475		CONFIG_SYS_I2C_MAX_HOPS
2476		define how many muxes are maximal consecutively connected
2477		on one i2c bus. If you not use i2c muxes, omit this
2478		define.
2479
2480		CONFIG_SYS_I2C_BUSES
2481		hold a list of buses you want to use, only used if
2482		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2483		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2484		CONFIG_SYS_NUM_I2C_BUSES = 9:
2485
2486		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2487					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2488					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2489					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2490					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2491					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2492					{1, {I2C_NULL_HOP}}, \
2493					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2494					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2495					}
2496
2497		which defines
2498			bus 0 on adapter 0 without a mux
2499			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2500			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2501			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2502			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2503			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2504			bus 6 on adapter 1 without a mux
2505			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2506			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2507
2508		If you do not have i2c muxes on your board, omit this define.
2509
2510- Legacy I2C Support:	CONFIG_HARD_I2C
2511
2512		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2513		provides the following compelling advantages:
2514
2515		- more than one i2c adapter is usable
2516		- approved multibus support
2517		- better i2c mux support
2518
2519		** Please consider updating your I2C driver now. **
2520
2521		These enable legacy I2C serial bus commands. Defining
2522		CONFIG_HARD_I2C will include the appropriate I2C driver
2523		for the selected CPU.
2524
2525		This will allow you to use i2c commands at the u-boot
2526		command line (as long as you set CONFIG_CMD_I2C in
2527		CONFIG_COMMANDS) and communicate with i2c based realtime
2528		clock chips. See common/cmd_i2c.c for a description of the
2529		command line interface.
2530
2531		CONFIG_HARD_I2C selects a hardware I2C controller.
2532
2533		There are several other quantities that must also be
2534		defined when you define CONFIG_HARD_I2C.
2535
2536		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2537		to be the frequency (in Hz) at which you wish your i2c bus
2538		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2539		the CPU's i2c node address).
2540
2541		Now, the u-boot i2c code for the mpc8xx
2542		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2543		and so its address should therefore be cleared to 0 (See,
2544		eg, MPC823e User's Manual p.16-473). So, set
2545		CONFIG_SYS_I2C_SLAVE to 0.
2546
2547		CONFIG_SYS_I2C_INIT_MPC5XXX
2548
2549		When a board is reset during an i2c bus transfer
2550		chips might think that the current transfer is still
2551		in progress.  Reset the slave devices by sending start
2552		commands until the slave device responds.
2553
2554		That's all that's required for CONFIG_HARD_I2C.
2555
2556		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2557		then the following macros need to be defined (examples are
2558		from include/configs/lwmon.h):
2559
2560		I2C_INIT
2561
2562		(Optional). Any commands necessary to enable the I2C
2563		controller or configure ports.
2564
2565		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2566
2567		I2C_PORT
2568
2569		(Only for MPC8260 CPU). The I/O port to use (the code
2570		assumes both bits are on the same port). Valid values
2571		are 0..3 for ports A..D.
2572
2573		I2C_ACTIVE
2574
2575		The code necessary to make the I2C data line active
2576		(driven).  If the data line is open collector, this
2577		define can be null.
2578
2579		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2580
2581		I2C_TRISTATE
2582
2583		The code necessary to make the I2C data line tri-stated
2584		(inactive).  If the data line is open collector, this
2585		define can be null.
2586
2587		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2588
2589		I2C_READ
2590
2591		Code that returns true if the I2C data line is high,
2592		false if it is low.
2593
2594		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2595
2596		I2C_SDA(bit)
2597
2598		If <bit> is true, sets the I2C data line high. If it
2599		is false, it clears it (low).
2600
2601		eg: #define I2C_SDA(bit) \
2602			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2603			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2604
2605		I2C_SCL(bit)
2606
2607		If <bit> is true, sets the I2C clock line high. If it
2608		is false, it clears it (low).
2609
2610		eg: #define I2C_SCL(bit) \
2611			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2612			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2613
2614		I2C_DELAY
2615
2616		This delay is invoked four times per clock cycle so this
2617		controls the rate of data transfer.  The data rate thus
2618		is 1 / (I2C_DELAY * 4). Often defined to be something
2619		like:
2620
2621		#define I2C_DELAY  udelay(2)
2622
2623		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2624
2625		If your arch supports the generic GPIO framework (asm/gpio.h),
2626		then you may alternatively define the two GPIOs that are to be
2627		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2628		have GPIO-based defaults assigned to them as appropriate.
2629
2630		You should define these to the GPIO value as given directly to
2631		the generic GPIO functions.
2632
2633		CONFIG_SYS_I2C_INIT_BOARD
2634
2635		When a board is reset during an i2c bus transfer
2636		chips might think that the current transfer is still
2637		in progress. On some boards it is possible to access
2638		the i2c SCLK line directly, either by using the
2639		processor pin as a GPIO or by having a second pin
2640		connected to the bus. If this option is defined a
2641		custom i2c_init_board() routine in boards/xxx/board.c
2642		is run early in the boot sequence.
2643
2644		CONFIG_SYS_I2C_BOARD_LATE_INIT
2645
2646		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2647		defined a custom i2c_board_late_init() routine in
2648		boards/xxx/board.c is run AFTER the operations in i2c_init()
2649		is completed. This callpoint can be used to unreset i2c bus
2650		using CPU i2c controller register accesses for CPUs whose i2c
2651		controller provide such a method. It is called at the end of
2652		i2c_init() to allow i2c_init operations to setup the i2c bus
2653		controller on the CPU (e.g. setting bus speed & slave address).
2654
2655		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2656
2657		This option enables configuration of bi_iic_fast[] flags
2658		in u-boot bd_info structure based on u-boot environment
2659		variable "i2cfast". (see also i2cfast)
2660
2661		CONFIG_I2C_MULTI_BUS
2662
2663		This option allows the use of multiple I2C buses, each of which
2664		must have a controller.	 At any point in time, only one bus is
2665		active.	 To switch to a different bus, use the 'i2c dev' command.
2666		Note that bus numbering is zero-based.
2667
2668		CONFIG_SYS_I2C_NOPROBES
2669
2670		This option specifies a list of I2C devices that will be skipped
2671		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2672		is set, specify a list of bus-device pairs.  Otherwise, specify
2673		a 1D array of device addresses
2674
2675		e.g.
2676			#undef	CONFIG_I2C_MULTI_BUS
2677			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2678
2679		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2680
2681			#define CONFIG_I2C_MULTI_BUS
2682			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2683
2684		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2685
2686		CONFIG_SYS_SPD_BUS_NUM
2687
2688		If defined, then this indicates the I2C bus number for DDR SPD.
2689		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2690
2691		CONFIG_SYS_RTC_BUS_NUM
2692
2693		If defined, then this indicates the I2C bus number for the RTC.
2694		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2695
2696		CONFIG_SYS_DTT_BUS_NUM
2697
2698		If defined, then this indicates the I2C bus number for the DTT.
2699		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2700
2701		CONFIG_SYS_I2C_DTT_ADDR:
2702
2703		If defined, specifies the I2C address of the DTT device.
2704		If not defined, then U-Boot uses predefined value for
2705		specified DTT device.
2706
2707		CONFIG_SOFT_I2C_READ_REPEATED_START
2708
2709		defining this will force the i2c_read() function in
2710		the soft_i2c driver to perform an I2C repeated start
2711		between writing the address pointer and reading the
2712		data.  If this define is omitted the default behaviour
2713		of doing a stop-start sequence will be used.  Most I2C
2714		devices can use either method, but some require one or
2715		the other.
2716
2717- SPI Support:	CONFIG_SPI
2718
2719		Enables SPI driver (so far only tested with
2720		SPI EEPROM, also an instance works with Crystal A/D and
2721		D/As on the SACSng board)
2722
2723		CONFIG_SH_SPI
2724
2725		Enables the driver for SPI controller on SuperH. Currently
2726		only SH7757 is supported.
2727
2728		CONFIG_SPI_X
2729
2730		Enables extended (16-bit) SPI EEPROM addressing.
2731		(symmetrical to CONFIG_I2C_X)
2732
2733		CONFIG_SOFT_SPI
2734
2735		Enables a software (bit-bang) SPI driver rather than
2736		using hardware support. This is a general purpose
2737		driver that only requires three general I/O port pins
2738		(two outputs, one input) to function. If this is
2739		defined, the board configuration must define several
2740		SPI configuration items (port pins to use, etc). For
2741		an example, see include/configs/sacsng.h.
2742
2743		CONFIG_HARD_SPI
2744
2745		Enables a hardware SPI driver for general-purpose reads
2746		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2747		must define a list of chip-select function pointers.
2748		Currently supported on some MPC8xxx processors.	 For an
2749		example, see include/configs/mpc8349emds.h.
2750
2751		CONFIG_MXC_SPI
2752
2753		Enables the driver for the SPI controllers on i.MX and MXC
2754		SoCs. Currently i.MX31/35/51 are supported.
2755
2756		CONFIG_SYS_SPI_MXC_WAIT
2757		Timeout for waiting until spi transfer completed.
2758		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2759
2760- FPGA Support: CONFIG_FPGA
2761
2762		Enables FPGA subsystem.
2763
2764		CONFIG_FPGA_<vendor>
2765
2766		Enables support for specific chip vendors.
2767		(ALTERA, XILINX)
2768
2769		CONFIG_FPGA_<family>
2770
2771		Enables support for FPGA family.
2772		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2773
2774		CONFIG_FPGA_COUNT
2775
2776		Specify the number of FPGA devices to support.
2777
2778		CONFIG_CMD_FPGA_LOADMK
2779
2780		Enable support for fpga loadmk command
2781
2782		CONFIG_CMD_FPGA_LOADP
2783
2784		Enable support for fpga loadp command - load partial bitstream
2785
2786		CONFIG_CMD_FPGA_LOADBP
2787
2788		Enable support for fpga loadbp command - load partial bitstream
2789		(Xilinx only)
2790
2791		CONFIG_SYS_FPGA_PROG_FEEDBACK
2792
2793		Enable printing of hash marks during FPGA configuration.
2794
2795		CONFIG_SYS_FPGA_CHECK_BUSY
2796
2797		Enable checks on FPGA configuration interface busy
2798		status by the configuration function. This option
2799		will require a board or device specific function to
2800		be written.
2801
2802		CONFIG_FPGA_DELAY
2803
2804		If defined, a function that provides delays in the FPGA
2805		configuration driver.
2806
2807		CONFIG_SYS_FPGA_CHECK_CTRLC
2808		Allow Control-C to interrupt FPGA configuration
2809
2810		CONFIG_SYS_FPGA_CHECK_ERROR
2811
2812		Check for configuration errors during FPGA bitfile
2813		loading. For example, abort during Virtex II
2814		configuration if the INIT_B line goes low (which
2815		indicated a CRC error).
2816
2817		CONFIG_SYS_FPGA_WAIT_INIT
2818
2819		Maximum time to wait for the INIT_B line to de-assert
2820		after PROB_B has been de-asserted during a Virtex II
2821		FPGA configuration sequence. The default time is 500
2822		ms.
2823
2824		CONFIG_SYS_FPGA_WAIT_BUSY
2825
2826		Maximum time to wait for BUSY to de-assert during
2827		Virtex II FPGA configuration. The default is 5 ms.
2828
2829		CONFIG_SYS_FPGA_WAIT_CONFIG
2830
2831		Time to wait after FPGA configuration. The default is
2832		200 ms.
2833
2834- Configuration Management:
2835		CONFIG_BUILD_TARGET
2836
2837		Some SoCs need special image types (e.g. U-Boot binary
2838		with a special header) as build targets. By defining
2839		CONFIG_BUILD_TARGET in the SoC / board header, this
2840		special image will be automatically built upon calling
2841		make / MAKEALL.
2842
2843		CONFIG_IDENT_STRING
2844
2845		If defined, this string will be added to the U-Boot
2846		version information (U_BOOT_VERSION)
2847
2848- Vendor Parameter Protection:
2849
2850		U-Boot considers the values of the environment
2851		variables "serial#" (Board Serial Number) and
2852		"ethaddr" (Ethernet Address) to be parameters that
2853		are set once by the board vendor / manufacturer, and
2854		protects these variables from casual modification by
2855		the user. Once set, these variables are read-only,
2856		and write or delete attempts are rejected. You can
2857		change this behaviour:
2858
2859		If CONFIG_ENV_OVERWRITE is #defined in your config
2860		file, the write protection for vendor parameters is
2861		completely disabled. Anybody can change or delete
2862		these parameters.
2863
2864		Alternatively, if you define _both_ an ethaddr in the
2865		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2866		Ethernet address is installed in the environment,
2867		which can be changed exactly ONCE by the user. [The
2868		serial# is unaffected by this, i. e. it remains
2869		read-only.]
2870
2871		The same can be accomplished in a more flexible way
2872		for any variable by configuring the type of access
2873		to allow for those variables in the ".flags" variable
2874		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2875
2876- Protected RAM:
2877		CONFIG_PRAM
2878
2879		Define this variable to enable the reservation of
2880		"protected RAM", i. e. RAM which is not overwritten
2881		by U-Boot. Define CONFIG_PRAM to hold the number of
2882		kB you want to reserve for pRAM. You can overwrite
2883		this default value by defining an environment
2884		variable "pram" to the number of kB you want to
2885		reserve. Note that the board info structure will
2886		still show the full amount of RAM. If pRAM is
2887		reserved, a new environment variable "mem" will
2888		automatically be defined to hold the amount of
2889		remaining RAM in a form that can be passed as boot
2890		argument to Linux, for instance like that:
2891
2892			setenv bootargs ... mem=\${mem}
2893			saveenv
2894
2895		This way you can tell Linux not to use this memory,
2896		either, which results in a memory region that will
2897		not be affected by reboots.
2898
2899		*WARNING* If your board configuration uses automatic
2900		detection of the RAM size, you must make sure that
2901		this memory test is non-destructive. So far, the
2902		following board configurations are known to be
2903		"pRAM-clean":
2904
2905			IVMS8, IVML24, SPD8xx, TQM8xxL,
2906			HERMES, IP860, RPXlite, LWMON,
2907			FLAGADM, TQM8260
2908
2909- Access to physical memory region (> 4GB)
2910		Some basic support is provided for operations on memory not
2911		normally accessible to U-Boot - e.g. some architectures
2912		support access to more than 4GB of memory on 32-bit
2913		machines using physical address extension or similar.
2914		Define CONFIG_PHYSMEM to access this basic support, which
2915		currently only supports clearing the memory.
2916
2917- Error Recovery:
2918		CONFIG_PANIC_HANG
2919
2920		Define this variable to stop the system in case of a
2921		fatal error, so that you have to reset it manually.
2922		This is probably NOT a good idea for an embedded
2923		system where you want the system to reboot
2924		automatically as fast as possible, but it may be
2925		useful during development since you can try to debug
2926		the conditions that lead to the situation.
2927
2928		CONFIG_NET_RETRY_COUNT
2929
2930		This variable defines the number of retries for
2931		network operations like ARP, RARP, TFTP, or BOOTP
2932		before giving up the operation. If not defined, a
2933		default value of 5 is used.
2934
2935		CONFIG_ARP_TIMEOUT
2936
2937		Timeout waiting for an ARP reply in milliseconds.
2938
2939		CONFIG_NFS_TIMEOUT
2940
2941		Timeout in milliseconds used in NFS protocol.
2942		If you encounter "ERROR: Cannot umount" in nfs command,
2943		try longer timeout such as
2944		#define CONFIG_NFS_TIMEOUT 10000UL
2945
2946- Command Interpreter:
2947		CONFIG_AUTO_COMPLETE
2948
2949		Enable auto completion of commands using TAB.
2950
2951		CONFIG_SYS_PROMPT_HUSH_PS2
2952
2953		This defines the secondary prompt string, which is
2954		printed when the command interpreter needs more input
2955		to complete a command. Usually "> ".
2956
2957	Note:
2958
2959		In the current implementation, the local variables
2960		space and global environment variables space are
2961		separated. Local variables are those you define by
2962		simply typing `name=value'. To access a local
2963		variable later on, you have write `$name' or
2964		`${name}'; to execute the contents of a variable
2965		directly type `$name' at the command prompt.
2966
2967		Global environment variables are those you use
2968		setenv/printenv to work with. To run a command stored
2969		in such a variable, you need to use the run command,
2970		and you must not use the '$' sign to access them.
2971
2972		To store commands and special characters in a
2973		variable, please use double quotation marks
2974		surrounding the whole text of the variable, instead
2975		of the backslashes before semicolons and special
2976		symbols.
2977
2978- Command Line Editing and History:
2979		CONFIG_CMDLINE_EDITING
2980
2981		Enable editing and History functions for interactive
2982		command line input operations
2983
2984- Default Environment:
2985		CONFIG_EXTRA_ENV_SETTINGS
2986
2987		Define this to contain any number of null terminated
2988		strings (variable = value pairs) that will be part of
2989		the default environment compiled into the boot image.
2990
2991		For example, place something like this in your
2992		board's config file:
2993
2994		#define CONFIG_EXTRA_ENV_SETTINGS \
2995			"myvar1=value1\0" \
2996			"myvar2=value2\0"
2997
2998		Warning: This method is based on knowledge about the
2999		internal format how the environment is stored by the
3000		U-Boot code. This is NOT an official, exported
3001		interface! Although it is unlikely that this format
3002		will change soon, there is no guarantee either.
3003		You better know what you are doing here.
3004
3005		Note: overly (ab)use of the default environment is
3006		discouraged. Make sure to check other ways to preset
3007		the environment like the "source" command or the
3008		boot command first.
3009
3010		CONFIG_ENV_VARS_UBOOT_CONFIG
3011
3012		Define this in order to add variables describing the
3013		U-Boot build configuration to the default environment.
3014		These will be named arch, cpu, board, vendor, and soc.
3015
3016		Enabling this option will cause the following to be defined:
3017
3018		- CONFIG_SYS_ARCH
3019		- CONFIG_SYS_CPU
3020		- CONFIG_SYS_BOARD
3021		- CONFIG_SYS_VENDOR
3022		- CONFIG_SYS_SOC
3023
3024		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
3025
3026		Define this in order to add variables describing certain
3027		run-time determined information about the hardware to the
3028		environment.  These will be named board_name, board_rev.
3029
3030		CONFIG_DELAY_ENVIRONMENT
3031
3032		Normally the environment is loaded when the board is
3033		initialised so that it is available to U-Boot. This inhibits
3034		that so that the environment is not available until
3035		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
3036		this is instead controlled by the value of
3037		/config/load-environment.
3038
3039- DataFlash Support:
3040		CONFIG_HAS_DATAFLASH
3041
3042		Defining this option enables DataFlash features and
3043		allows to read/write in Dataflash via the standard
3044		commands cp, md...
3045
3046- Serial Flash support
3047		CONFIG_CMD_SF
3048
3049		Defining this option enables SPI flash commands
3050		'sf probe/read/write/erase/update'.
3051
3052		Usage requires an initial 'probe' to define the serial
3053		flash parameters, followed by read/write/erase/update
3054		commands.
3055
3056		The following defaults may be provided by the platform
3057		to handle the common case when only a single serial
3058		flash is present on the system.
3059
3060		CONFIG_SF_DEFAULT_BUS		Bus identifier
3061		CONFIG_SF_DEFAULT_CS		Chip-select
3062		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
3063		CONFIG_SF_DEFAULT_SPEED		in Hz
3064
3065		CONFIG_CMD_SF_TEST
3066
3067		Define this option to include a destructive SPI flash
3068		test ('sf test').
3069
3070		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
3071
3072		Define this option to use the Bank addr/Extended addr
3073		support on SPI flashes which has size > 16Mbytes.
3074
3075		CONFIG_SF_DUAL_FLASH		Dual flash memories
3076
3077		Define this option to use dual flash support where two flash
3078		memories can be connected with a given cs line.
3079		Currently Xilinx Zynq qspi supports these type of connections.
3080
3081- SystemACE Support:
3082		CONFIG_SYSTEMACE
3083
3084		Adding this option adds support for Xilinx SystemACE
3085		chips attached via some sort of local bus. The address
3086		of the chip must also be defined in the
3087		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
3088
3089		#define CONFIG_SYSTEMACE
3090		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
3091
3092		When SystemACE support is added, the "ace" device type
3093		becomes available to the fat commands, i.e. fatls.
3094
3095- TFTP Fixed UDP Port:
3096		CONFIG_TFTP_PORT
3097
3098		If this is defined, the environment variable tftpsrcp
3099		is used to supply the TFTP UDP source port value.
3100		If tftpsrcp isn't defined, the normal pseudo-random port
3101		number generator is used.
3102
3103		Also, the environment variable tftpdstp is used to supply
3104		the TFTP UDP destination port value.  If tftpdstp isn't
3105		defined, the normal port 69 is used.
3106
3107		The purpose for tftpsrcp is to allow a TFTP server to
3108		blindly start the TFTP transfer using the pre-configured
3109		target IP address and UDP port. This has the effect of
3110		"punching through" the (Windows XP) firewall, allowing
3111		the remainder of the TFTP transfer to proceed normally.
3112		A better solution is to properly configure the firewall,
3113		but sometimes that is not allowed.
3114
3115- Hashing support:
3116		CONFIG_CMD_HASH
3117
3118		This enables a generic 'hash' command which can produce
3119		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
3120
3121		CONFIG_HASH_VERIFY
3122
3123		Enable the hash verify command (hash -v). This adds to code
3124		size a little.
3125
3126		CONFIG_SHA1 - This option enables support of hashing using SHA1
3127		algorithm. The hash is calculated in software.
3128		CONFIG_SHA256 - This option enables support of hashing using
3129		SHA256 algorithm. The hash is calculated in software.
3130		CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
3131		for SHA1/SHA256 hashing.
3132		This affects the 'hash' command and also the
3133		hash_lookup_algo() function.
3134		CONFIG_SHA_PROG_HW_ACCEL - This option enables
3135		hardware-acceleration for SHA1/SHA256 progressive hashing.
3136		Data can be streamed in a block at a time and the hashing
3137		is performed in hardware.
3138
3139		Note: There is also a sha1sum command, which should perhaps
3140		be deprecated in favour of 'hash sha1'.
3141
3142- Freescale i.MX specific commands:
3143		CONFIG_CMD_HDMIDETECT
3144		This enables 'hdmidet' command which returns true if an
3145		HDMI monitor is detected.  This command is i.MX 6 specific.
3146
3147		CONFIG_CMD_BMODE
3148		This enables the 'bmode' (bootmode) command for forcing
3149		a boot from specific media.
3150
3151		This is useful for forcing the ROM's usb downloader to
3152		activate upon a watchdog reset which is nice when iterating
3153		on U-Boot.  Using the reset button or running bmode normal
3154		will set it back to normal.  This command currently
3155		supports i.MX53 and i.MX6.
3156
3157- Signing support:
3158		CONFIG_RSA
3159
3160		This enables the RSA algorithm used for FIT image verification
3161		in U-Boot. See doc/uImage.FIT/signature.txt for more information.
3162
3163		The Modular Exponentiation algorithm in RSA is implemented using
3164		driver model. So CONFIG_DM needs to be enabled by default for this
3165		library to function.
3166
3167		The signing part is build into mkimage regardless of this
3168		option. The software based modular exponentiation is built into
3169		mkimage irrespective of this option.
3170
3171- bootcount support:
3172		CONFIG_BOOTCOUNT_LIMIT
3173
3174		This enables the bootcounter support, see:
3175		http://www.denx.de/wiki/DULG/UBootBootCountLimit
3176
3177		CONFIG_AT91SAM9XE
3178		enable special bootcounter support on at91sam9xe based boards.
3179		CONFIG_BLACKFIN
3180		enable special bootcounter support on blackfin based boards.
3181		CONFIG_SOC_DA8XX
3182		enable special bootcounter support on da850 based boards.
3183		CONFIG_BOOTCOUNT_RAM
3184		enable support for the bootcounter in RAM
3185		CONFIG_BOOTCOUNT_I2C
3186		enable support for the bootcounter on an i2c (like RTC) device.
3187			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
3188			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
3189						    the bootcounter.
3190			CONFIG_BOOTCOUNT_ALEN = address len
3191
3192- Show boot progress:
3193		CONFIG_SHOW_BOOT_PROGRESS
3194
3195		Defining this option allows to add some board-
3196		specific code (calling a user-provided function
3197		"show_boot_progress(int)") that enables you to show
3198		the system's boot progress on some display (for
3199		example, some LED's) on your board. At the moment,
3200		the following checkpoints are implemented:
3201
3202
3203Legacy uImage format:
3204
3205  Arg	Where			When
3206    1	common/cmd_bootm.c	before attempting to boot an image
3207   -1	common/cmd_bootm.c	Image header has bad	 magic number
3208    2	common/cmd_bootm.c	Image header has correct magic number
3209   -2	common/cmd_bootm.c	Image header has bad	 checksum
3210    3	common/cmd_bootm.c	Image header has correct checksum
3211   -3	common/cmd_bootm.c	Image data   has bad	 checksum
3212    4	common/cmd_bootm.c	Image data   has correct checksum
3213   -4	common/cmd_bootm.c	Image is for unsupported architecture
3214    5	common/cmd_bootm.c	Architecture check OK
3215   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
3216    6	common/cmd_bootm.c	Image Type check OK
3217   -6	common/cmd_bootm.c	gunzip uncompression error
3218   -7	common/cmd_bootm.c	Unimplemented compression type
3219    7	common/cmd_bootm.c	Uncompression OK
3220    8	common/cmd_bootm.c	No uncompress/copy overwrite error
3221   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
3222
3223    9	common/image.c		Start initial ramdisk verification
3224  -10	common/image.c		Ramdisk header has bad	   magic number
3225  -11	common/image.c		Ramdisk header has bad	   checksum
3226   10	common/image.c		Ramdisk header is OK
3227  -12	common/image.c		Ramdisk data   has bad	   checksum
3228   11	common/image.c		Ramdisk data   has correct checksum
3229   12	common/image.c		Ramdisk verification complete, start loading
3230  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
3231   13	common/image.c		Start multifile image verification
3232   14	common/image.c		No initial ramdisk, no multifile, continue.
3233
3234   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
3235
3236  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
3237  -31	post/post.c		POST test failed, detected by post_output_backlog()
3238  -32	post/post.c		POST test failed, detected by post_run_single()
3239
3240   34	common/cmd_doc.c	before loading a Image from a DOC device
3241  -35	common/cmd_doc.c	Bad usage of "doc" command
3242   35	common/cmd_doc.c	correct usage of "doc" command
3243  -36	common/cmd_doc.c	No boot device
3244   36	common/cmd_doc.c	correct boot device
3245  -37	common/cmd_doc.c	Unknown Chip ID on boot device
3246   37	common/cmd_doc.c	correct chip ID found, device available
3247  -38	common/cmd_doc.c	Read Error on boot device
3248   38	common/cmd_doc.c	reading Image header from DOC device OK
3249  -39	common/cmd_doc.c	Image header has bad magic number
3250   39	common/cmd_doc.c	Image header has correct magic number
3251  -40	common/cmd_doc.c	Error reading Image from DOC device
3252   40	common/cmd_doc.c	Image header has correct magic number
3253   41	common/cmd_ide.c	before loading a Image from a IDE device
3254  -42	common/cmd_ide.c	Bad usage of "ide" command
3255   42	common/cmd_ide.c	correct usage of "ide" command
3256  -43	common/cmd_ide.c	No boot device
3257   43	common/cmd_ide.c	boot device found
3258  -44	common/cmd_ide.c	Device not available
3259   44	common/cmd_ide.c	Device available
3260  -45	common/cmd_ide.c	wrong partition selected
3261   45	common/cmd_ide.c	partition selected
3262  -46	common/cmd_ide.c	Unknown partition table
3263   46	common/cmd_ide.c	valid partition table found
3264  -47	common/cmd_ide.c	Invalid partition type
3265   47	common/cmd_ide.c	correct partition type
3266  -48	common/cmd_ide.c	Error reading Image Header on boot device
3267   48	common/cmd_ide.c	reading Image Header from IDE device OK
3268  -49	common/cmd_ide.c	Image header has bad magic number
3269   49	common/cmd_ide.c	Image header has correct magic number
3270  -50	common/cmd_ide.c	Image header has bad	 checksum
3271   50	common/cmd_ide.c	Image header has correct checksum
3272  -51	common/cmd_ide.c	Error reading Image from IDE device
3273   51	common/cmd_ide.c	reading Image from IDE device OK
3274   52	common/cmd_nand.c	before loading a Image from a NAND device
3275  -53	common/cmd_nand.c	Bad usage of "nand" command
3276   53	common/cmd_nand.c	correct usage of "nand" command
3277  -54	common/cmd_nand.c	No boot device
3278   54	common/cmd_nand.c	boot device found
3279  -55	common/cmd_nand.c	Unknown Chip ID on boot device
3280   55	common/cmd_nand.c	correct chip ID found, device available
3281  -56	common/cmd_nand.c	Error reading Image Header on boot device
3282   56	common/cmd_nand.c	reading Image Header from NAND device OK
3283  -57	common/cmd_nand.c	Image header has bad magic number
3284   57	common/cmd_nand.c	Image header has correct magic number
3285  -58	common/cmd_nand.c	Error reading Image from NAND device
3286   58	common/cmd_nand.c	reading Image from NAND device OK
3287
3288  -60	common/env_common.c	Environment has a bad CRC, using default
3289
3290   64	net/eth.c		starting with Ethernet configuration.
3291  -64	net/eth.c		no Ethernet found.
3292   65	net/eth.c		Ethernet found.
3293
3294  -80	common/cmd_net.c	usage wrong
3295   80	common/cmd_net.c	before calling net_loop()
3296  -81	common/cmd_net.c	some error in net_loop() occurred
3297   81	common/cmd_net.c	net_loop() back without error
3298  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
3299   82	common/cmd_net.c	trying automatic boot
3300   83	common/cmd_net.c	running "source" command
3301  -83	common/cmd_net.c	some error in automatic boot or "source" command
3302   84	common/cmd_net.c	end without errors
3303
3304FIT uImage format:
3305
3306  Arg	Where			When
3307  100	common/cmd_bootm.c	Kernel FIT Image has correct format
3308 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
3309  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
3310 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
3311  102	common/cmd_bootm.c	Kernel unit name specified
3312 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
3313  103	common/cmd_bootm.c	Found configuration node
3314  104	common/cmd_bootm.c	Got kernel subimage node offset
3315 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
3316  105	common/cmd_bootm.c	Kernel subimage hash verification OK
3317 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
3318  106	common/cmd_bootm.c	Architecture check OK
3319 -106	common/cmd_bootm.c	Kernel subimage has wrong type
3320  107	common/cmd_bootm.c	Kernel subimage type OK
3321 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
3322  108	common/cmd_bootm.c	Got kernel subimage data/size
3323 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
3324 -109	common/cmd_bootm.c	Can't get kernel subimage type
3325 -110	common/cmd_bootm.c	Can't get kernel subimage comp
3326 -111	common/cmd_bootm.c	Can't get kernel subimage os
3327 -112	common/cmd_bootm.c	Can't get kernel subimage load address
3328 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
3329
3330  120	common/image.c		Start initial ramdisk verification
3331 -120	common/image.c		Ramdisk FIT image has incorrect format
3332  121	common/image.c		Ramdisk FIT image has correct format
3333  122	common/image.c		No ramdisk subimage unit name, using configuration
3334 -122	common/image.c		Can't get configuration for ramdisk subimage
3335  123	common/image.c		Ramdisk unit name specified
3336 -124	common/image.c		Can't get ramdisk subimage node offset
3337  125	common/image.c		Got ramdisk subimage node offset
3338 -125	common/image.c		Ramdisk subimage hash verification failed
3339  126	common/image.c		Ramdisk subimage hash verification OK
3340 -126	common/image.c		Ramdisk subimage for unsupported architecture
3341  127	common/image.c		Architecture check OK
3342 -127	common/image.c		Can't get ramdisk subimage data/size
3343  128	common/image.c		Got ramdisk subimage data/size
3344  129	common/image.c		Can't get ramdisk load address
3345 -129	common/image.c		Got ramdisk load address
3346
3347 -130	common/cmd_doc.c	Incorrect FIT image format
3348  131	common/cmd_doc.c	FIT image format OK
3349
3350 -140	common/cmd_ide.c	Incorrect FIT image format
3351  141	common/cmd_ide.c	FIT image format OK
3352
3353 -150	common/cmd_nand.c	Incorrect FIT image format
3354  151	common/cmd_nand.c	FIT image format OK
3355
3356- legacy image format:
3357		CONFIG_IMAGE_FORMAT_LEGACY
3358		enables the legacy image format support in U-Boot.
3359
3360		Default:
3361		enabled if CONFIG_FIT_SIGNATURE is not defined.
3362
3363		CONFIG_DISABLE_IMAGE_LEGACY
3364		disable the legacy image format
3365
3366		This define is introduced, as the legacy image format is
3367		enabled per default for backward compatibility.
3368
3369- FIT image support:
3370		CONFIG_FIT
3371		Enable support for the FIT uImage format.
3372
3373		CONFIG_FIT_BEST_MATCH
3374		When no configuration is explicitly selected, default to the
3375		one whose fdt's compatibility field best matches that of
3376		U-Boot itself. A match is considered "best" if it matches the
3377		most specific compatibility entry of U-Boot's fdt's root node.
3378		The order of entries in the configuration's fdt is ignored.
3379
3380		CONFIG_FIT_SIGNATURE
3381		This option enables signature verification of FIT uImages,
3382		using a hash signed and verified using RSA. If
3383		CONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressive
3384		hashing is available using hardware, RSA library will use it.
3385		See doc/uImage.FIT/signature.txt for more details.
3386
3387		WARNING: When relying on signed FIT images with required
3388		signature check the legacy image format is default
3389		disabled. If a board need legacy image format support
3390		enable this through CONFIG_IMAGE_FORMAT_LEGACY
3391
3392		CONFIG_FIT_DISABLE_SHA256
3393		Supporting SHA256 hashes has quite an impact on binary size.
3394		For constrained systems sha256 hash support can be disabled
3395		with this option.
3396
3397- Standalone program support:
3398		CONFIG_STANDALONE_LOAD_ADDR
3399
3400		This option defines a board specific value for the
3401		address where standalone program gets loaded, thus
3402		overwriting the architecture dependent default
3403		settings.
3404
3405- Frame Buffer Address:
3406		CONFIG_FB_ADDR
3407
3408		Define CONFIG_FB_ADDR if you want to use specific
3409		address for frame buffer.  This is typically the case
3410		when using a graphics controller has separate video
3411		memory.  U-Boot will then place the frame buffer at
3412		the given address instead of dynamically reserving it
3413		in system RAM by calling lcd_setmem(), which grabs
3414		the memory for the frame buffer depending on the
3415		configured panel size.
3416
3417		Please see board_init_f function.
3418
3419- Automatic software updates via TFTP server
3420		CONFIG_UPDATE_TFTP
3421		CONFIG_UPDATE_TFTP_CNT_MAX
3422		CONFIG_UPDATE_TFTP_MSEC_MAX
3423
3424		These options enable and control the auto-update feature;
3425		for a more detailed description refer to doc/README.update.
3426
3427- MTD Support (mtdparts command, UBI support)
3428		CONFIG_MTD_DEVICE
3429
3430		Adds the MTD device infrastructure from the Linux kernel.
3431		Needed for mtdparts command support.
3432
3433		CONFIG_MTD_PARTITIONS
3434
3435		Adds the MTD partitioning infrastructure from the Linux
3436		kernel. Needed for UBI support.
3437
3438- UBI support
3439		CONFIG_CMD_UBI
3440
3441		Adds commands for interacting with MTD partitions formatted
3442		with the UBI flash translation layer
3443
3444		Requires also defining CONFIG_RBTREE
3445
3446		CONFIG_UBI_SILENCE_MSG
3447
3448		Make the verbose messages from UBI stop printing.  This leaves
3449		warnings and errors enabled.
3450
3451
3452		CONFIG_MTD_UBI_WL_THRESHOLD
3453		This parameter defines the maximum difference between the highest
3454		erase counter value and the lowest erase counter value of eraseblocks
3455		of UBI devices. When this threshold is exceeded, UBI starts performing
3456		wear leveling by means of moving data from eraseblock with low erase
3457		counter to eraseblocks with high erase counter.
3458
3459		The default value should be OK for SLC NAND flashes, NOR flashes and
3460		other flashes which have eraseblock life-cycle 100000 or more.
3461		However, in case of MLC NAND flashes which typically have eraseblock
3462		life-cycle less than 10000, the threshold should be lessened (e.g.,
3463		to 128 or 256, although it does not have to be power of 2).
3464
3465		default: 4096
3466
3467		CONFIG_MTD_UBI_BEB_LIMIT
3468		This option specifies the maximum bad physical eraseblocks UBI
3469		expects on the MTD device (per 1024 eraseblocks). If the
3470		underlying flash does not admit of bad eraseblocks (e.g. NOR
3471		flash), this value is ignored.
3472
3473		NAND datasheets often specify the minimum and maximum NVM
3474		(Number of Valid Blocks) for the flashes' endurance lifetime.
3475		The maximum expected bad eraseblocks per 1024 eraseblocks
3476		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3477		which gives 20 for most NANDs (MaxNVB is basically the total
3478		count of eraseblocks on the chip).
3479
3480		To put it differently, if this value is 20, UBI will try to
3481		reserve about 1.9% of physical eraseblocks for bad blocks
3482		handling. And that will be 1.9% of eraseblocks on the entire
3483		NAND chip, not just the MTD partition UBI attaches. This means
3484		that if you have, say, a NAND flash chip admits maximum 40 bad
3485		eraseblocks, and it is split on two MTD partitions of the same
3486		size, UBI will reserve 40 eraseblocks when attaching a
3487		partition.
3488
3489		default: 20
3490
3491		CONFIG_MTD_UBI_FASTMAP
3492		Fastmap is a mechanism which allows attaching an UBI device
3493		in nearly constant time. Instead of scanning the whole MTD device it
3494		only has to locate a checkpoint (called fastmap) on the device.
3495		The on-flash fastmap contains all information needed to attach
3496		the device. Using fastmap makes only sense on large devices where
3497		attaching by scanning takes long. UBI will not automatically install
3498		a fastmap on old images, but you can set the UBI parameter
3499		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3500		that fastmap-enabled images are still usable with UBI implementations
3501		without	fastmap support. On typical flash devices the whole fastmap
3502		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3503
3504		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3505		Set this parameter to enable fastmap automatically on images
3506		without a fastmap.
3507		default: 0
3508
3509- UBIFS support
3510		CONFIG_CMD_UBIFS
3511
3512		Adds commands for interacting with UBI volumes formatted as
3513		UBIFS.  UBIFS is read-only in u-boot.
3514
3515		Requires UBI support as well as CONFIG_LZO
3516
3517		CONFIG_UBIFS_SILENCE_MSG
3518
3519		Make the verbose messages from UBIFS stop printing.  This leaves
3520		warnings and errors enabled.
3521
3522- SPL framework
3523		CONFIG_SPL
3524		Enable building of SPL globally.
3525
3526		CONFIG_SPL_LDSCRIPT
3527		LDSCRIPT for linking the SPL binary.
3528
3529		CONFIG_SPL_MAX_FOOTPRINT
3530		Maximum size in memory allocated to the SPL, BSS included.
3531		When defined, the linker checks that the actual memory
3532		used by SPL from _start to __bss_end does not exceed it.
3533		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3534		must not be both defined at the same time.
3535
3536		CONFIG_SPL_MAX_SIZE
3537		Maximum size of the SPL image (text, data, rodata, and
3538		linker lists sections), BSS excluded.
3539		When defined, the linker checks that the actual size does
3540		not exceed it.
3541
3542		CONFIG_SPL_TEXT_BASE
3543		TEXT_BASE for linking the SPL binary.
3544
3545		CONFIG_SPL_RELOC_TEXT_BASE
3546		Address to relocate to.  If unspecified, this is equal to
3547		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3548
3549		CONFIG_SPL_BSS_START_ADDR
3550		Link address for the BSS within the SPL binary.
3551
3552		CONFIG_SPL_BSS_MAX_SIZE
3553		Maximum size in memory allocated to the SPL BSS.
3554		When defined, the linker checks that the actual memory used
3555		by SPL from __bss_start to __bss_end does not exceed it.
3556		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3557		must not be both defined at the same time.
3558
3559		CONFIG_SPL_STACK
3560		Adress of the start of the stack SPL will use
3561
3562		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3563		When defined, SPL will panic() if the image it has
3564		loaded does not have a signature.
3565		Defining this is useful when code which loads images
3566		in SPL cannot guarantee that absolutely all read errors
3567		will be caught.
3568		An example is the LPC32XX MLC NAND driver, which will
3569		consider that a completely unreadable NAND block is bad,
3570		and thus should be skipped silently.
3571
3572		CONFIG_SPL_RELOC_STACK
3573		Adress of the start of the stack SPL will use after
3574		relocation.  If unspecified, this is equal to
3575		CONFIG_SPL_STACK.
3576
3577		CONFIG_SYS_SPL_MALLOC_START
3578		Starting address of the malloc pool used in SPL.
3579
3580		CONFIG_SYS_SPL_MALLOC_SIZE
3581		The size of the malloc pool used in SPL.
3582
3583		CONFIG_SPL_FRAMEWORK
3584		Enable the SPL framework under common/.  This framework
3585		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3586		NAND loading of the Linux Kernel.
3587
3588		CONFIG_SPL_OS_BOOT
3589		Enable booting directly to an OS from SPL.
3590		See also: doc/README.falcon
3591
3592		CONFIG_SPL_DISPLAY_PRINT
3593		For ARM, enable an optional function to print more information
3594		about the running system.
3595
3596		CONFIG_SPL_INIT_MINIMAL
3597		Arch init code should be built for a very small image
3598
3599		CONFIG_SPL_LIBCOMMON_SUPPORT
3600		Support for common/libcommon.o in SPL binary
3601
3602		CONFIG_SPL_LIBDISK_SUPPORT
3603		Support for disk/libdisk.o in SPL binary
3604
3605		CONFIG_SPL_I2C_SUPPORT
3606		Support for drivers/i2c/libi2c.o in SPL binary
3607
3608		CONFIG_SPL_GPIO_SUPPORT
3609		Support for drivers/gpio/libgpio.o in SPL binary
3610
3611		CONFIG_SPL_MMC_SUPPORT
3612		Support for drivers/mmc/libmmc.o in SPL binary
3613
3614		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3615		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3616		Address and partition on the MMC to load U-Boot from
3617		when the MMC is being used in raw mode.
3618
3619		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3620		Partition on the MMC to load U-Boot from when the MMC is being
3621		used in raw mode
3622
3623		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3624		Sector to load kernel uImage from when MMC is being
3625		used in raw mode (for Falcon mode)
3626
3627		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3628		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3629		Sector and number of sectors to load kernel argument
3630		parameters from when MMC is being used in raw mode
3631		(for falcon mode)
3632
3633		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3634		Partition on the MMC to load U-Boot from when the MMC is being
3635		used in fs mode
3636
3637		CONFIG_SPL_FAT_SUPPORT
3638		Support for fs/fat/libfat.o in SPL binary
3639
3640		CONFIG_SPL_EXT_SUPPORT
3641		Support for EXT filesystem in SPL binary
3642
3643		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3644		Filename to read to load U-Boot when reading from filesystem
3645
3646		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3647		Filename to read to load kernel uImage when reading
3648		from filesystem (for Falcon mode)
3649
3650		CONFIG_SPL_FS_LOAD_ARGS_NAME
3651		Filename to read to load kernel argument parameters
3652		when reading from filesystem (for Falcon mode)
3653
3654		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3655		Set this for NAND SPL on PPC mpc83xx targets, so that
3656		start.S waits for the rest of the SPL to load before
3657		continuing (the hardware starts execution after just
3658		loading the first page rather than the full 4K).
3659
3660		CONFIG_SPL_SKIP_RELOCATE
3661		Avoid SPL relocation
3662
3663		CONFIG_SPL_NAND_BASE
3664		Include nand_base.c in the SPL.  Requires
3665		CONFIG_SPL_NAND_DRIVERS.
3666
3667		CONFIG_SPL_NAND_DRIVERS
3668		SPL uses normal NAND drivers, not minimal drivers.
3669
3670		CONFIG_SPL_NAND_ECC
3671		Include standard software ECC in the SPL
3672
3673		CONFIG_SPL_NAND_SIMPLE
3674		Support for NAND boot using simple NAND drivers that
3675		expose the cmd_ctrl() interface.
3676
3677		CONFIG_SPL_MTD_SUPPORT
3678		Support for the MTD subsystem within SPL.  Useful for
3679		environment on NAND support within SPL.
3680
3681		CONFIG_SPL_NAND_RAW_ONLY
3682		Support to boot only raw u-boot.bin images. Use this only
3683		if you need to save space.
3684
3685		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3686		Set for the SPL on PPC mpc8xxx targets, support for
3687		drivers/ddr/fsl/libddr.o in SPL binary.
3688
3689		CONFIG_SPL_COMMON_INIT_DDR
3690		Set for common ddr init with serial presence detect in
3691		SPL binary.
3692
3693		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3694		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3695		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3696		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3697		CONFIG_SYS_NAND_ECCBYTES
3698		Defines the size and behavior of the NAND that SPL uses
3699		to read U-Boot
3700
3701		CONFIG_SPL_NAND_BOOT
3702		Add support NAND boot
3703
3704		CONFIG_SYS_NAND_U_BOOT_OFFS
3705		Location in NAND to read U-Boot from
3706
3707		CONFIG_SYS_NAND_U_BOOT_DST
3708		Location in memory to load U-Boot to
3709
3710		CONFIG_SYS_NAND_U_BOOT_SIZE
3711		Size of image to load
3712
3713		CONFIG_SYS_NAND_U_BOOT_START
3714		Entry point in loaded image to jump to
3715
3716		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3717		Define this if you need to first read the OOB and then the
3718		data. This is used, for example, on davinci platforms.
3719
3720		CONFIG_SPL_OMAP3_ID_NAND
3721		Support for an OMAP3-specific set of functions to return the
3722		ID and MFR of the first attached NAND chip, if present.
3723
3724		CONFIG_SPL_SERIAL_SUPPORT
3725		Support for drivers/serial/libserial.o in SPL binary
3726
3727		CONFIG_SPL_SPI_FLASH_SUPPORT
3728		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3729
3730		CONFIG_SPL_SPI_SUPPORT
3731		Support for drivers/spi/libspi.o in SPL binary
3732
3733		CONFIG_SPL_RAM_DEVICE
3734		Support for running image already present in ram, in SPL binary
3735
3736		CONFIG_SPL_LIBGENERIC_SUPPORT
3737		Support for lib/libgeneric.o in SPL binary
3738
3739		CONFIG_SPL_ENV_SUPPORT
3740		Support for the environment operating in SPL binary
3741
3742		CONFIG_SPL_NET_SUPPORT
3743		Support for the net/libnet.o in SPL binary.
3744		It conflicts with SPL env from storage medium specified by
3745		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3746
3747		CONFIG_SPL_PAD_TO
3748		Image offset to which the SPL should be padded before appending
3749		the SPL payload. By default, this is defined as
3750		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3751		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3752		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3753
3754		CONFIG_SPL_TARGET
3755		Final target image containing SPL and payload.  Some SPLs
3756		use an arch-specific makefile fragment instead, for
3757		example if more than one image needs to be produced.
3758
3759		CONFIG_FIT_SPL_PRINT
3760		Printing information about a FIT image adds quite a bit of
3761		code to SPL. So this is normally disabled in SPL. Use this
3762		option to re-enable it. This will affect the output of the
3763		bootm command when booting a FIT image.
3764
3765- TPL framework
3766		CONFIG_TPL
3767		Enable building of TPL globally.
3768
3769		CONFIG_TPL_PAD_TO
3770		Image offset to which the TPL should be padded before appending
3771		the TPL payload. By default, this is defined as
3772		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3773		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3774		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3775
3776Modem Support:
3777--------------
3778
3779[so far only for SMDK2400 boards]
3780
3781- Modem support enable:
3782		CONFIG_MODEM_SUPPORT
3783
3784- RTS/CTS Flow control enable:
3785		CONFIG_HWFLOW
3786
3787- Modem debug support:
3788		CONFIG_MODEM_SUPPORT_DEBUG
3789
3790		Enables debugging stuff (char screen[1024], dbg())
3791		for modem support. Useful only with BDI2000.
3792
3793- Interrupt support (PPC):
3794
3795		There are common interrupt_init() and timer_interrupt()
3796		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3797		for CPU specific initialization. interrupt_init_cpu()
3798		should set decrementer_count to appropriate value. If
3799		CPU resets decrementer automatically after interrupt
3800		(ppc4xx) it should set decrementer_count to zero.
3801		timer_interrupt() calls timer_interrupt_cpu() for CPU
3802		specific handling. If board has watchdog / status_led
3803		/ other_activity_monitor it works automatically from
3804		general timer_interrupt().
3805
3806- General:
3807
3808		In the target system modem support is enabled when a
3809		specific key (key combination) is pressed during
3810		power-on. Otherwise U-Boot will boot normally
3811		(autoboot). The key_pressed() function is called from
3812		board_init(). Currently key_pressed() is a dummy
3813		function, returning 1 and thus enabling modem
3814		initialization.
3815
3816		If there are no modem init strings in the
3817		environment, U-Boot proceed to autoboot; the
3818		previous output (banner, info printfs) will be
3819		suppressed, though.
3820
3821		See also: doc/README.Modem
3822
3823Board initialization settings:
3824------------------------------
3825
3826During Initialization u-boot calls a number of board specific functions
3827to allow the preparation of board specific prerequisites, e.g. pin setup
3828before drivers are initialized. To enable these callbacks the
3829following configuration macros have to be defined. Currently this is
3830architecture specific, so please check arch/your_architecture/lib/board.c
3831typically in board_init_f() and board_init_r().
3832
3833- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3834- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3835- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3836- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3837
3838Configuration Settings:
3839-----------------------
3840
3841- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3842		Optionally it can be defined to support 64-bit memory commands.
3843
3844- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3845		undefine this when you're short of memory.
3846
3847- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3848		width of the commands listed in the 'help' command output.
3849
3850- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3851		prompt for user input.
3852
3853- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3854
3855- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3856
3857- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3858
3859- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3860		the application (usually a Linux kernel) when it is
3861		booted
3862
3863- CONFIG_SYS_BAUDRATE_TABLE:
3864		List of legal baudrate settings for this board.
3865
3866- CONFIG_SYS_CONSOLE_INFO_QUIET
3867		Suppress display of console information at boot.
3868
3869- CONFIG_SYS_CONSOLE_IS_IN_ENV
3870		If the board specific function
3871			extern int overwrite_console (void);
3872		returns 1, the stdin, stderr and stdout are switched to the
3873		serial port, else the settings in the environment are used.
3874
3875- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3876		Enable the call to overwrite_console().
3877
3878- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3879		Enable overwrite of previous console environment settings.
3880
3881- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3882		Begin and End addresses of the area used by the
3883		simple memory test.
3884
3885- CONFIG_SYS_ALT_MEMTEST:
3886		Enable an alternate, more extensive memory test.
3887
3888- CONFIG_SYS_MEMTEST_SCRATCH:
3889		Scratch address used by the alternate memory test
3890		You only need to set this if address zero isn't writeable
3891
3892- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3893		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3894		this specified memory area will get subtracted from the top
3895		(end) of RAM and won't get "touched" at all by U-Boot. By
3896		fixing up gd->ram_size the Linux kernel should gets passed
3897		the now "corrected" memory size and won't touch it either.
3898		This should work for arch/ppc and arch/powerpc. Only Linux
3899		board ports in arch/powerpc with bootwrapper support that
3900		recalculate the memory size from the SDRAM controller setup
3901		will have to get fixed in Linux additionally.
3902
3903		This option can be used as a workaround for the 440EPx/GRx
3904		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3905		be touched.
3906
3907		WARNING: Please make sure that this value is a multiple of
3908		the Linux page size (normally 4k). If this is not the case,
3909		then the end address of the Linux memory will be located at a
3910		non page size aligned address and this could cause major
3911		problems.
3912
3913- CONFIG_SYS_LOADS_BAUD_CHANGE:
3914		Enable temporary baudrate change while serial download
3915
3916- CONFIG_SYS_SDRAM_BASE:
3917		Physical start address of SDRAM. _Must_ be 0 here.
3918
3919- CONFIG_SYS_MBIO_BASE:
3920		Physical start address of Motherboard I/O (if using a
3921		Cogent motherboard)
3922
3923- CONFIG_SYS_FLASH_BASE:
3924		Physical start address of Flash memory.
3925
3926- CONFIG_SYS_MONITOR_BASE:
3927		Physical start address of boot monitor code (set by
3928		make config files to be same as the text base address
3929		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3930		CONFIG_SYS_FLASH_BASE when booting from flash.
3931
3932- CONFIG_SYS_MONITOR_LEN:
3933		Size of memory reserved for monitor code, used to
3934		determine _at_compile_time_ (!) if the environment is
3935		embedded within the U-Boot image, or in a separate
3936		flash sector.
3937
3938- CONFIG_SYS_MALLOC_LEN:
3939		Size of DRAM reserved for malloc() use.
3940
3941- CONFIG_SYS_MALLOC_F_LEN
3942		Size of the malloc() pool for use before relocation. If
3943		this is defined, then a very simple malloc() implementation
3944		will become available before relocation. The address is just
3945		below the global data, and the stack is moved down to make
3946		space.
3947
3948		This feature allocates regions with increasing addresses
3949		within the region. calloc() is supported, but realloc()
3950		is not available. free() is supported but does nothing.
3951		The memory will be freed (or in fact just forgotten) when
3952		U-Boot relocates itself.
3953
3954		Pre-relocation malloc() is only supported on ARM and sandbox
3955		at present but is fairly easy to enable for other archs.
3956
3957- CONFIG_SYS_MALLOC_SIMPLE
3958		Provides a simple and small malloc() and calloc() for those
3959		boards which do not use the full malloc in SPL (which is
3960		enabled with CONFIG_SYS_SPL_MALLOC_START).
3961
3962- CONFIG_SYS_NONCACHED_MEMORY:
3963		Size of non-cached memory area. This area of memory will be
3964		typically located right below the malloc() area and mapped
3965		uncached in the MMU. This is useful for drivers that would
3966		otherwise require a lot of explicit cache maintenance. For
3967		some drivers it's also impossible to properly maintain the
3968		cache. For example if the regions that need to be flushed
3969		are not a multiple of the cache-line size, *and* padding
3970		cannot be allocated between the regions to align them (i.e.
3971		if the HW requires a contiguous array of regions, and the
3972		size of each region is not cache-aligned), then a flush of
3973		one region may result in overwriting data that hardware has
3974		written to another region in the same cache-line. This can
3975		happen for example in network drivers where descriptors for
3976		buffers are typically smaller than the CPU cache-line (e.g.
3977		16 bytes vs. 32 or 64 bytes).
3978
3979		Non-cached memory is only supported on 32-bit ARM at present.
3980
3981- CONFIG_SYS_BOOTM_LEN:
3982		Normally compressed uImages are limited to an
3983		uncompressed size of 8 MBytes. If this is not enough,
3984		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3985		to adjust this setting to your needs.
3986
3987- CONFIG_SYS_BOOTMAPSZ:
3988		Maximum size of memory mapped by the startup code of
3989		the Linux kernel; all data that must be processed by
3990		the Linux kernel (bd_info, boot arguments, FDT blob if
3991		used) must be put below this limit, unless "bootm_low"
3992		environment variable is defined and non-zero. In such case
3993		all data for the Linux kernel must be between "bootm_low"
3994		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3995		variable "bootm_mapsize" will override the value of
3996		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3997		then the value in "bootm_size" will be used instead.
3998
3999- CONFIG_SYS_BOOT_RAMDISK_HIGH:
4000		Enable initrd_high functionality.  If defined then the
4001		initrd_high feature is enabled and the bootm ramdisk subcommand
4002		is enabled.
4003
4004- CONFIG_SYS_BOOT_GET_CMDLINE:
4005		Enables allocating and saving kernel cmdline in space between
4006		"bootm_low" and "bootm_low" + BOOTMAPSZ.
4007
4008- CONFIG_SYS_BOOT_GET_KBD:
4009		Enables allocating and saving a kernel copy of the bd_info in
4010		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
4011
4012- CONFIG_SYS_MAX_FLASH_BANKS:
4013		Max number of Flash memory banks
4014
4015- CONFIG_SYS_MAX_FLASH_SECT:
4016		Max number of sectors on a Flash chip
4017
4018- CONFIG_SYS_FLASH_ERASE_TOUT:
4019		Timeout for Flash erase operations (in ms)
4020
4021- CONFIG_SYS_FLASH_WRITE_TOUT:
4022		Timeout for Flash write operations (in ms)
4023
4024- CONFIG_SYS_FLASH_LOCK_TOUT
4025		Timeout for Flash set sector lock bit operation (in ms)
4026
4027- CONFIG_SYS_FLASH_UNLOCK_TOUT
4028		Timeout for Flash clear lock bits operation (in ms)
4029
4030- CONFIG_SYS_FLASH_PROTECTION
4031		If defined, hardware flash sectors protection is used
4032		instead of U-Boot software protection.
4033
4034- CONFIG_SYS_DIRECT_FLASH_TFTP:
4035
4036		Enable TFTP transfers directly to flash memory;
4037		without this option such a download has to be
4038		performed in two steps: (1) download to RAM, and (2)
4039		copy from RAM to flash.
4040
4041		The two-step approach is usually more reliable, since
4042		you can check if the download worked before you erase
4043		the flash, but in some situations (when system RAM is
4044		too limited to allow for a temporary copy of the
4045		downloaded image) this option may be very useful.
4046
4047- CONFIG_SYS_FLASH_CFI:
4048		Define if the flash driver uses extra elements in the
4049		common flash structure for storing flash geometry.
4050
4051- CONFIG_FLASH_CFI_DRIVER
4052		This option also enables the building of the cfi_flash driver
4053		in the drivers directory
4054
4055- CONFIG_FLASH_CFI_MTD
4056		This option enables the building of the cfi_mtd driver
4057		in the drivers directory. The driver exports CFI flash
4058		to the MTD layer.
4059
4060- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
4061		Use buffered writes to flash.
4062
4063- CONFIG_FLASH_SPANSION_S29WS_N
4064		s29ws-n MirrorBit flash has non-standard addresses for buffered
4065		write commands.
4066
4067- CONFIG_SYS_FLASH_QUIET_TEST
4068		If this option is defined, the common CFI flash doesn't
4069		print it's warning upon not recognized FLASH banks. This
4070		is useful, if some of the configured banks are only
4071		optionally available.
4072
4073- CONFIG_FLASH_SHOW_PROGRESS
4074		If defined (must be an integer), print out countdown
4075		digits and dots.  Recommended value: 45 (9..1) for 80
4076		column displays, 15 (3..1) for 40 column displays.
4077
4078- CONFIG_FLASH_VERIFY
4079		If defined, the content of the flash (destination) is compared
4080		against the source after the write operation. An error message
4081		will be printed when the contents are not identical.
4082		Please note that this option is useless in nearly all cases,
4083		since such flash programming errors usually are detected earlier
4084		while unprotecting/erasing/programming. Please only enable
4085		this option if you really know what you are doing.
4086
4087- CONFIG_SYS_RX_ETH_BUFFER:
4088		Defines the number of Ethernet receive buffers. On some
4089		Ethernet controllers it is recommended to set this value
4090		to 8 or even higher (EEPRO100 or 405 EMAC), since all
4091		buffers can be full shortly after enabling the interface
4092		on high Ethernet traffic.
4093		Defaults to 4 if not defined.
4094
4095- CONFIG_ENV_MAX_ENTRIES
4096
4097	Maximum number of entries in the hash table that is used
4098	internally to store the environment settings. The default
4099	setting is supposed to be generous and should work in most
4100	cases. This setting can be used to tune behaviour; see
4101	lib/hashtable.c for details.
4102
4103- CONFIG_ENV_FLAGS_LIST_DEFAULT
4104- CONFIG_ENV_FLAGS_LIST_STATIC
4105	Enable validation of the values given to environment variables when
4106	calling env set.  Variables can be restricted to only decimal,
4107	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
4108	the variables can also be restricted to IP address or MAC address.
4109
4110	The format of the list is:
4111		type_attribute = [s|d|x|b|i|m]
4112		access_attribute = [a|r|o|c]
4113		attributes = type_attribute[access_attribute]
4114		entry = variable_name[:attributes]
4115		list = entry[,list]
4116
4117	The type attributes are:
4118		s - String (default)
4119		d - Decimal
4120		x - Hexadecimal
4121		b - Boolean ([1yYtT|0nNfF])
4122		i - IP address
4123		m - MAC address
4124
4125	The access attributes are:
4126		a - Any (default)
4127		r - Read-only
4128		o - Write-once
4129		c - Change-default
4130
4131	- CONFIG_ENV_FLAGS_LIST_DEFAULT
4132		Define this to a list (string) to define the ".flags"
4133		environment variable in the default or embedded environment.
4134
4135	- CONFIG_ENV_FLAGS_LIST_STATIC
4136		Define this to a list (string) to define validation that
4137		should be done if an entry is not found in the ".flags"
4138		environment variable.  To override a setting in the static
4139		list, simply add an entry for the same variable name to the
4140		".flags" variable.
4141
4142- CONFIG_ENV_ACCESS_IGNORE_FORCE
4143	If defined, don't allow the -f switch to env set override variable
4144	access flags.
4145
4146- CONFIG_SYS_GENERIC_BOARD
4147	This selects the architecture-generic board system instead of the
4148	architecture-specific board files. It is intended to move boards
4149	to this new framework over time. Defining this will disable the
4150	arch/foo/lib/board.c file and use common/board_f.c and
4151	common/board_r.c instead. To use this option your architecture
4152	must support it (i.e. must select HAVE_GENERIC_BOARD in arch/Kconfig).
4153	If you find problems enabling this option on your board please report
4154	the problem and send patches!
4155
4156- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
4157	This is set by OMAP boards for the max time that reset should
4158	be asserted. See doc/README.omap-reset-time for details on how
4159	the value can be calculated on a given board.
4160
4161- CONFIG_USE_STDINT
4162	If stdint.h is available with your toolchain you can define this
4163	option to enable it. You can provide option 'USE_STDINT=1' when
4164	building U-Boot to enable this.
4165
4166The following definitions that deal with the placement and management
4167of environment data (variable area); in general, we support the
4168following configurations:
4169
4170- CONFIG_BUILD_ENVCRC:
4171
4172	Builds up envcrc with the target environment so that external utils
4173	may easily extract it and embed it in final U-Boot images.
4174
4175- CONFIG_ENV_IS_IN_FLASH:
4176
4177	Define this if the environment is in flash memory.
4178
4179	a) The environment occupies one whole flash sector, which is
4180	   "embedded" in the text segment with the U-Boot code. This
4181	   happens usually with "bottom boot sector" or "top boot
4182	   sector" type flash chips, which have several smaller
4183	   sectors at the start or the end. For instance, such a
4184	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
4185	   such a case you would place the environment in one of the
4186	   4 kB sectors - with U-Boot code before and after it. With
4187	   "top boot sector" type flash chips, you would put the
4188	   environment in one of the last sectors, leaving a gap
4189	   between U-Boot and the environment.
4190
4191	- CONFIG_ENV_OFFSET:
4192
4193	   Offset of environment data (variable area) to the
4194	   beginning of flash memory; for instance, with bottom boot
4195	   type flash chips the second sector can be used: the offset
4196	   for this sector is given here.
4197
4198	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
4199
4200	- CONFIG_ENV_ADDR:
4201
4202	   This is just another way to specify the start address of
4203	   the flash sector containing the environment (instead of
4204	   CONFIG_ENV_OFFSET).
4205
4206	- CONFIG_ENV_SECT_SIZE:
4207
4208	   Size of the sector containing the environment.
4209
4210
4211	b) Sometimes flash chips have few, equal sized, BIG sectors.
4212	   In such a case you don't want to spend a whole sector for
4213	   the environment.
4214
4215	- CONFIG_ENV_SIZE:
4216
4217	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
4218	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
4219	   of this flash sector for the environment. This saves
4220	   memory for the RAM copy of the environment.
4221
4222	   It may also save flash memory if you decide to use this
4223	   when your environment is "embedded" within U-Boot code,
4224	   since then the remainder of the flash sector could be used
4225	   for U-Boot code. It should be pointed out that this is
4226	   STRONGLY DISCOURAGED from a robustness point of view:
4227	   updating the environment in flash makes it always
4228	   necessary to erase the WHOLE sector. If something goes
4229	   wrong before the contents has been restored from a copy in
4230	   RAM, your target system will be dead.
4231
4232	- CONFIG_ENV_ADDR_REDUND
4233	  CONFIG_ENV_SIZE_REDUND
4234
4235	   These settings describe a second storage area used to hold
4236	   a redundant copy of the environment data, so that there is
4237	   a valid backup copy in case there is a power failure during
4238	   a "saveenv" operation.
4239
4240BE CAREFUL! Any changes to the flash layout, and some changes to the
4241source code will make it necessary to adapt <board>/u-boot.lds*
4242accordingly!
4243
4244
4245- CONFIG_ENV_IS_IN_NVRAM:
4246
4247	Define this if you have some non-volatile memory device
4248	(NVRAM, battery buffered SRAM) which you want to use for the
4249	environment.
4250
4251	- CONFIG_ENV_ADDR:
4252	- CONFIG_ENV_SIZE:
4253
4254	  These two #defines are used to determine the memory area you
4255	  want to use for environment. It is assumed that this memory
4256	  can just be read and written to, without any special
4257	  provision.
4258
4259BE CAREFUL! The first access to the environment happens quite early
4260in U-Boot initialization (when we try to get the setting of for the
4261console baudrate). You *MUST* have mapped your NVRAM area then, or
4262U-Boot will hang.
4263
4264Please note that even with NVRAM we still use a copy of the
4265environment in RAM: we could work on NVRAM directly, but we want to
4266keep settings there always unmodified except somebody uses "saveenv"
4267to save the current settings.
4268
4269
4270- CONFIG_ENV_IS_IN_EEPROM:
4271
4272	Use this if you have an EEPROM or similar serial access
4273	device and a driver for it.
4274
4275	- CONFIG_ENV_OFFSET:
4276	- CONFIG_ENV_SIZE:
4277
4278	  These two #defines specify the offset and size of the
4279	  environment area within the total memory of your EEPROM.
4280
4281	- CONFIG_SYS_I2C_EEPROM_ADDR:
4282	  If defined, specified the chip address of the EEPROM device.
4283	  The default address is zero.
4284
4285	- CONFIG_SYS_I2C_EEPROM_BUS:
4286	  If defined, specified the i2c bus of the EEPROM device.
4287
4288	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
4289	  If defined, the number of bits used to address bytes in a
4290	  single page in the EEPROM device.  A 64 byte page, for example
4291	  would require six bits.
4292
4293	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
4294	  If defined, the number of milliseconds to delay between
4295	  page writes.	The default is zero milliseconds.
4296
4297	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
4298	  The length in bytes of the EEPROM memory array address.  Note
4299	  that this is NOT the chip address length!
4300
4301	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
4302	  EEPROM chips that implement "address overflow" are ones
4303	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
4304	  address and the extra bits end up in the "chip address" bit
4305	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
4306	  byte chips.
4307
4308	  Note that we consider the length of the address field to
4309	  still be one byte because the extra address bits are hidden
4310	  in the chip address.
4311
4312	- CONFIG_SYS_EEPROM_SIZE:
4313	  The size in bytes of the EEPROM device.
4314
4315	- CONFIG_ENV_EEPROM_IS_ON_I2C
4316	  define this, if you have I2C and SPI activated, and your
4317	  EEPROM, which holds the environment, is on the I2C bus.
4318
4319	- CONFIG_I2C_ENV_EEPROM_BUS
4320	  if you have an Environment on an EEPROM reached over
4321	  I2C muxes, you can define here, how to reach this
4322	  EEPROM. For example:
4323
4324	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
4325
4326	  EEPROM which holds the environment, is reached over
4327	  a pca9547 i2c mux with address 0x70, channel 3.
4328
4329- CONFIG_ENV_IS_IN_DATAFLASH:
4330
4331	Define this if you have a DataFlash memory device which you
4332	want to use for the environment.
4333
4334	- CONFIG_ENV_OFFSET:
4335	- CONFIG_ENV_ADDR:
4336	- CONFIG_ENV_SIZE:
4337
4338	  These three #defines specify the offset and size of the
4339	  environment area within the total memory of your DataFlash placed
4340	  at the specified address.
4341
4342- CONFIG_ENV_IS_IN_SPI_FLASH:
4343
4344	Define this if you have a SPI Flash memory device which you
4345	want to use for the environment.
4346
4347	- CONFIG_ENV_OFFSET:
4348	- CONFIG_ENV_SIZE:
4349
4350	  These two #defines specify the offset and size of the
4351	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
4352	  aligned to an erase sector boundary.
4353
4354	- CONFIG_ENV_SECT_SIZE:
4355
4356	  Define the SPI flash's sector size.
4357
4358	- CONFIG_ENV_OFFSET_REDUND (optional):
4359
4360	  This setting describes a second storage area of CONFIG_ENV_SIZE
4361	  size used to hold a redundant copy of the environment data, so
4362	  that there is a valid backup copy in case there is a power failure
4363	  during a "saveenv" operation. CONFIG_ENV_OFFSET_RENDUND must be
4364	  aligned to an erase sector boundary.
4365
4366	- CONFIG_ENV_SPI_BUS (optional):
4367	- CONFIG_ENV_SPI_CS (optional):
4368
4369	  Define the SPI bus and chip select. If not defined they will be 0.
4370
4371	- CONFIG_ENV_SPI_MAX_HZ (optional):
4372
4373	  Define the SPI max work clock. If not defined then use 1MHz.
4374
4375	- CONFIG_ENV_SPI_MODE (optional):
4376
4377	  Define the SPI work mode. If not defined then use SPI_MODE_3.
4378
4379- CONFIG_ENV_IS_IN_REMOTE:
4380
4381	Define this if you have a remote memory space which you
4382	want to use for the local device's environment.
4383
4384	- CONFIG_ENV_ADDR:
4385	- CONFIG_ENV_SIZE:
4386
4387	  These two #defines specify the address and size of the
4388	  environment area within the remote memory space. The
4389	  local device can get the environment from remote memory
4390	  space by SRIO or PCIE links.
4391
4392BE CAREFUL! For some special cases, the local device can not use
4393"saveenv" command. For example, the local device will get the
4394environment stored in a remote NOR flash by SRIO or PCIE link,
4395but it can not erase, write this NOR flash by SRIO or PCIE interface.
4396
4397- CONFIG_ENV_IS_IN_NAND:
4398
4399	Define this if you have a NAND device which you want to use
4400	for the environment.
4401
4402	- CONFIG_ENV_OFFSET:
4403	- CONFIG_ENV_SIZE:
4404
4405	  These two #defines specify the offset and size of the environment
4406	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
4407	  aligned to an erase block boundary.
4408
4409	- CONFIG_ENV_OFFSET_REDUND (optional):
4410
4411	  This setting describes a second storage area of CONFIG_ENV_SIZE
4412	  size used to hold a redundant copy of the environment data, so
4413	  that there is a valid backup copy in case there is a power failure
4414	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
4415	  aligned to an erase block boundary.
4416
4417	- CONFIG_ENV_RANGE (optional):
4418
4419	  Specifies the length of the region in which the environment
4420	  can be written.  This should be a multiple of the NAND device's
4421	  block size.  Specifying a range with more erase blocks than
4422	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
4423	  the range to be avoided.
4424
4425	- CONFIG_ENV_OFFSET_OOB (optional):
4426
4427	  Enables support for dynamically retrieving the offset of the
4428	  environment from block zero's out-of-band data.  The
4429	  "nand env.oob" command can be used to record this offset.
4430	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
4431	  using CONFIG_ENV_OFFSET_OOB.
4432
4433- CONFIG_NAND_ENV_DST
4434
4435	Defines address in RAM to which the nand_spl code should copy the
4436	environment. If redundant environment is used, it will be copied to
4437	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
4438
4439- CONFIG_ENV_IS_IN_UBI:
4440
4441	Define this if you have an UBI volume that you want to use for the
4442	environment.  This has the benefit of wear-leveling the environment
4443	accesses, which is important on NAND.
4444
4445	- CONFIG_ENV_UBI_PART:
4446
4447	  Define this to a string that is the mtd partition containing the UBI.
4448
4449	- CONFIG_ENV_UBI_VOLUME:
4450
4451	  Define this to the name of the volume that you want to store the
4452	  environment in.
4453
4454	- CONFIG_ENV_UBI_VOLUME_REDUND:
4455
4456	  Define this to the name of another volume to store a second copy of
4457	  the environment in.  This will enable redundant environments in UBI.
4458	  It is assumed that both volumes are in the same MTD partition.
4459
4460	- CONFIG_UBI_SILENCE_MSG
4461	- CONFIG_UBIFS_SILENCE_MSG
4462
4463	  You will probably want to define these to avoid a really noisy system
4464	  when storing the env in UBI.
4465
4466- CONFIG_ENV_IS_IN_FAT:
4467       Define this if you want to use the FAT file system for the environment.
4468
4469       - FAT_ENV_INTERFACE:
4470
4471         Define this to a string that is the name of the block device.
4472
4473       - FAT_ENV_DEV_AND_PART:
4474
4475         Define this to a string to specify the partition of the device. It can
4476         be as following:
4477
4478           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
4479               - "D:P": device D partition P. Error occurs if device D has no
4480                        partition table.
4481               - "D:0": device D.
4482               - "D" or "D:": device D partition 1 if device D has partition
4483                              table, or the whole device D if has no partition
4484                              table.
4485               - "D:auto": first partition in device D with bootable flag set.
4486                           If none, first valid partition in device D. If no
4487                           partition table then means device D.
4488
4489       - FAT_ENV_FILE:
4490
4491         It's a string of the FAT file name. This file use to store the
4492         environment.
4493
4494       - CONFIG_FAT_WRITE:
4495         This should be defined. Otherwise it cannot save the environment file.
4496
4497- CONFIG_ENV_IS_IN_MMC:
4498
4499	Define this if you have an MMC device which you want to use for the
4500	environment.
4501
4502	- CONFIG_SYS_MMC_ENV_DEV:
4503
4504	  Specifies which MMC device the environment is stored in.
4505
4506	- CONFIG_SYS_MMC_ENV_PART (optional):
4507
4508	  Specifies which MMC partition the environment is stored in. If not
4509	  set, defaults to partition 0, the user area. Common values might be
4510	  1 (first MMC boot partition), 2 (second MMC boot partition).
4511
4512	- CONFIG_ENV_OFFSET:
4513	- CONFIG_ENV_SIZE:
4514
4515	  These two #defines specify the offset and size of the environment
4516	  area within the specified MMC device.
4517
4518	  If offset is positive (the usual case), it is treated as relative to
4519	  the start of the MMC partition. If offset is negative, it is treated
4520	  as relative to the end of the MMC partition. This can be useful if
4521	  your board may be fitted with different MMC devices, which have
4522	  different sizes for the MMC partitions, and you always want the
4523	  environment placed at the very end of the partition, to leave the
4524	  maximum possible space before it, to store other data.
4525
4526	  These two values are in units of bytes, but must be aligned to an
4527	  MMC sector boundary.
4528
4529	- CONFIG_ENV_OFFSET_REDUND (optional):
4530
4531	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
4532	  hold a redundant copy of the environment data. This provides a
4533	  valid backup copy in case the other copy is corrupted, e.g. due
4534	  to a power failure during a "saveenv" operation.
4535
4536	  This value may also be positive or negative; this is handled in the
4537	  same way as CONFIG_ENV_OFFSET.
4538
4539	  This value is also in units of bytes, but must also be aligned to
4540	  an MMC sector boundary.
4541
4542	- CONFIG_ENV_SIZE_REDUND (optional):
4543
4544	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
4545	  set. If this value is set, it must be set to the same value as
4546	  CONFIG_ENV_SIZE.
4547
4548- CONFIG_SYS_SPI_INIT_OFFSET
4549
4550	Defines offset to the initial SPI buffer area in DPRAM. The
4551	area is used at an early stage (ROM part) if the environment
4552	is configured to reside in the SPI EEPROM: We need a 520 byte
4553	scratch DPRAM area. It is used between the two initialization
4554	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4555	to be a good choice since it makes it far enough from the
4556	start of the data area as well as from the stack pointer.
4557
4558Please note that the environment is read-only until the monitor
4559has been relocated to RAM and a RAM copy of the environment has been
4560created; also, when using EEPROM you will have to use getenv_f()
4561until then to read environment variables.
4562
4563The environment is protected by a CRC32 checksum. Before the monitor
4564is relocated into RAM, as a result of a bad CRC you will be working
4565with the compiled-in default environment - *silently*!!! [This is
4566necessary, because the first environment variable we need is the
4567"baudrate" setting for the console - if we have a bad CRC, we don't
4568have any device yet where we could complain.]
4569
4570Note: once the monitor has been relocated, then it will complain if
4571the default environment is used; a new CRC is computed as soon as you
4572use the "saveenv" command to store a valid environment.
4573
4574- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4575		Echo the inverted Ethernet link state to the fault LED.
4576
4577		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4578		      also needs to be defined.
4579
4580- CONFIG_SYS_FAULT_MII_ADDR:
4581		MII address of the PHY to check for the Ethernet link state.
4582
4583- CONFIG_NS16550_MIN_FUNCTIONS:
4584		Define this if you desire to only have use of the NS16550_init
4585		and NS16550_putc functions for the serial driver located at
4586		drivers/serial/ns16550.c.  This option is useful for saving
4587		space for already greatly restricted images, including but not
4588		limited to NAND_SPL configurations.
4589
4590- CONFIG_DISPLAY_BOARDINFO
4591		Display information about the board that U-Boot is running on
4592		when U-Boot starts up. The board function checkboard() is called
4593		to do this.
4594
4595- CONFIG_DISPLAY_BOARDINFO_LATE
4596		Similar to the previous option, but display this information
4597		later, once stdio is running and output goes to the LCD, if
4598		present.
4599
4600- CONFIG_BOARD_SIZE_LIMIT:
4601		Maximum size of the U-Boot image. When defined, the
4602		build system checks that the actual size does not
4603		exceed it.
4604
4605Low Level (hardware related) configuration options:
4606---------------------------------------------------
4607
4608- CONFIG_SYS_CACHELINE_SIZE:
4609		Cache Line Size of the CPU.
4610
4611- CONFIG_SYS_DEFAULT_IMMR:
4612		Default address of the IMMR after system reset.
4613
4614		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4615		and RPXsuper) to be able to adjust the position of
4616		the IMMR register after a reset.
4617
4618- CONFIG_SYS_CCSRBAR_DEFAULT:
4619		Default (power-on reset) physical address of CCSR on Freescale
4620		PowerPC SOCs.
4621
4622- CONFIG_SYS_CCSRBAR:
4623		Virtual address of CCSR.  On a 32-bit build, this is typically
4624		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4625
4626		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4627		for cross-platform code that uses that macro instead.
4628
4629- CONFIG_SYS_CCSRBAR_PHYS:
4630		Physical address of CCSR.  CCSR can be relocated to a new
4631		physical address, if desired.  In this case, this macro should
4632		be set to that address.	 Otherwise, it should be set to the
4633		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4634		is typically relocated on 36-bit builds.  It is recommended
4635		that this macro be defined via the _HIGH and _LOW macros:
4636
4637		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4638			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4639
4640- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4641		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4642		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4643		used in assembly code, so it must not contain typecasts or
4644		integer size suffixes (e.g. "ULL").
4645
4646- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4647		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4648		used in assembly code, so it must not contain typecasts or
4649		integer size suffixes (e.g. "ULL").
4650
4651- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4652		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4653		forced to a value that ensures that CCSR is not relocated.
4654
4655- Floppy Disk Support:
4656		CONFIG_SYS_FDC_DRIVE_NUMBER
4657
4658		the default drive number (default value 0)
4659
4660		CONFIG_SYS_ISA_IO_STRIDE
4661
4662		defines the spacing between FDC chipset registers
4663		(default value 1)
4664
4665		CONFIG_SYS_ISA_IO_OFFSET
4666
4667		defines the offset of register from address. It
4668		depends on which part of the data bus is connected to
4669		the FDC chipset. (default value 0)
4670
4671		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4672		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4673		default value.
4674
4675		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4676		fdc_hw_init() is called at the beginning of the FDC
4677		setup. fdc_hw_init() must be provided by the board
4678		source code. It is used to make hardware-dependent
4679		initializations.
4680
4681- CONFIG_IDE_AHB:
4682		Most IDE controllers were designed to be connected with PCI
4683		interface. Only few of them were designed for AHB interface.
4684		When software is doing ATA command and data transfer to
4685		IDE devices through IDE-AHB controller, some additional
4686		registers accessing to these kind of IDE-AHB controller
4687		is required.
4688
4689- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4690		DO NOT CHANGE unless you know exactly what you're
4691		doing! (11-4) [MPC8xx/82xx systems only]
4692
4693- CONFIG_SYS_INIT_RAM_ADDR:
4694
4695		Start address of memory area that can be used for
4696		initial data and stack; please note that this must be
4697		writable memory that is working WITHOUT special
4698		initialization, i. e. you CANNOT use normal RAM which
4699		will become available only after programming the
4700		memory controller and running certain initialization
4701		sequences.
4702
4703		U-Boot uses the following memory types:
4704		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4705		- MPC824X: data cache
4706		- PPC4xx:  data cache
4707
4708- CONFIG_SYS_GBL_DATA_OFFSET:
4709
4710		Offset of the initial data structure in the memory
4711		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4712		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4713		data is located at the end of the available space
4714		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4715		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4716		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4717		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4718
4719	Note:
4720		On the MPC824X (or other systems that use the data
4721		cache for initial memory) the address chosen for
4722		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4723		point to an otherwise UNUSED address space between
4724		the top of RAM and the start of the PCI space.
4725
4726- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4727
4728- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4729
4730- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4731
4732- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4733
4734- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4735
4736- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4737
4738- CONFIG_SYS_OR_TIMING_SDRAM:
4739		SDRAM timing
4740
4741- CONFIG_SYS_MAMR_PTA:
4742		periodic timer for refresh
4743
4744- CONFIG_SYS_DER:	Debug Event Register (37-47)
4745
4746- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4747  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4748  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4749  CONFIG_SYS_BR1_PRELIM:
4750		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4751
4752- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4753  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4754  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4755		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4756
4757- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4758  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4759		Machine Mode Register and Memory Periodic Timer
4760		Prescaler definitions (SDRAM timing)
4761
4762- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4763		enable I2C microcode relocation patch (MPC8xx);
4764		define relocation offset in DPRAM [DSP2]
4765
4766- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4767		enable SMC microcode relocation patch (MPC8xx);
4768		define relocation offset in DPRAM [SMC1]
4769
4770- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4771		enable SPI microcode relocation patch (MPC8xx);
4772		define relocation offset in DPRAM [SCC4]
4773
4774- CONFIG_SYS_USE_OSCCLK:
4775		Use OSCM clock mode on MBX8xx board. Be careful,
4776		wrong setting might damage your board. Read
4777		doc/README.MBX before setting this variable!
4778
4779- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4780		Offset of the bootmode word in DPRAM used by post
4781		(Power On Self Tests). This definition overrides
4782		#define'd default value in commproc.h resp.
4783		cpm_8260.h.
4784
4785- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4786  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4787  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4788  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4789  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4790  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4791  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4792  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4793		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4794
4795- CONFIG_PCI_DISABLE_PCIE:
4796		Disable PCI-Express on systems where it is supported but not
4797		required.
4798
4799- CONFIG_PCI_ENUM_ONLY
4800		Only scan through and get the devices on the buses.
4801		Don't do any setup work, presumably because someone or
4802		something has already done it, and we don't need to do it
4803		a second time.	Useful for platforms that are pre-booted
4804		by coreboot or similar.
4805
4806- CONFIG_PCI_INDIRECT_BRIDGE:
4807		Enable support for indirect PCI bridges.
4808
4809- CONFIG_SYS_SRIO:
4810		Chip has SRIO or not
4811
4812- CONFIG_SRIO1:
4813		Board has SRIO 1 port available
4814
4815- CONFIG_SRIO2:
4816		Board has SRIO 2 port available
4817
4818- CONFIG_SRIO_PCIE_BOOT_MASTER
4819		Board can support master function for Boot from SRIO and PCIE
4820
4821- CONFIG_SYS_SRIOn_MEM_VIRT:
4822		Virtual Address of SRIO port 'n' memory region
4823
4824- CONFIG_SYS_SRIOn_MEM_PHYS:
4825		Physical Address of SRIO port 'n' memory region
4826
4827- CONFIG_SYS_SRIOn_MEM_SIZE:
4828		Size of SRIO port 'n' memory region
4829
4830- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4831		Defined to tell the NAND controller that the NAND chip is using
4832		a 16 bit bus.
4833		Not all NAND drivers use this symbol.
4834		Example of drivers that use it:
4835		- drivers/mtd/nand/ndfc.c
4836		- drivers/mtd/nand/mxc_nand.c
4837
4838- CONFIG_SYS_NDFC_EBC0_CFG
4839		Sets the EBC0_CFG register for the NDFC. If not defined
4840		a default value will be used.
4841
4842- CONFIG_SPD_EEPROM
4843		Get DDR timing information from an I2C EEPROM. Common
4844		with pluggable memory modules such as SODIMMs
4845
4846  SPD_EEPROM_ADDRESS
4847		I2C address of the SPD EEPROM
4848
4849- CONFIG_SYS_SPD_BUS_NUM
4850		If SPD EEPROM is on an I2C bus other than the first
4851		one, specify here. Note that the value must resolve
4852		to something your driver can deal with.
4853
4854- CONFIG_SYS_DDR_RAW_TIMING
4855		Get DDR timing information from other than SPD. Common with
4856		soldered DDR chips onboard without SPD. DDR raw timing
4857		parameters are extracted from datasheet and hard-coded into
4858		header files or board specific files.
4859
4860- CONFIG_FSL_DDR_INTERACTIVE
4861		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4862
4863- CONFIG_FSL_DDR_SYNC_REFRESH
4864		Enable sync of refresh for multiple controllers.
4865
4866- CONFIG_FSL_DDR_BIST
4867		Enable built-in memory test for Freescale DDR controllers.
4868
4869- CONFIG_SYS_83XX_DDR_USES_CS0
4870		Only for 83xx systems. If specified, then DDR should
4871		be configured using CS0 and CS1 instead of CS2 and CS3.
4872
4873- CONFIG_ETHER_ON_FEC[12]
4874		Define to enable FEC[12] on a 8xx series processor.
4875
4876- CONFIG_FEC[12]_PHY
4877		Define to the hardcoded PHY address which corresponds
4878		to the given FEC; i. e.
4879			#define CONFIG_FEC1_PHY 4
4880		means that the PHY with address 4 is connected to FEC1
4881
4882		When set to -1, means to probe for first available.
4883
4884- CONFIG_FEC[12]_PHY_NORXERR
4885		The PHY does not have a RXERR line (RMII only).
4886		(so program the FEC to ignore it).
4887
4888- CONFIG_RMII
4889		Enable RMII mode for all FECs.
4890		Note that this is a global option, we can't
4891		have one FEC in standard MII mode and another in RMII mode.
4892
4893- CONFIG_CRC32_VERIFY
4894		Add a verify option to the crc32 command.
4895		The syntax is:
4896
4897		=> crc32 -v <address> <count> <crc32>
4898
4899		Where address/count indicate a memory area
4900		and crc32 is the correct crc32 which the
4901		area should have.
4902
4903- CONFIG_LOOPW
4904		Add the "loopw" memory command. This only takes effect if
4905		the memory commands are activated globally (CONFIG_CMD_MEM).
4906
4907- CONFIG_MX_CYCLIC
4908		Add the "mdc" and "mwc" memory commands. These are cyclic
4909		"md/mw" commands.
4910		Examples:
4911
4912		=> mdc.b 10 4 500
4913		This command will print 4 bytes (10,11,12,13) each 500 ms.
4914
4915		=> mwc.l 100 12345678 10
4916		This command will write 12345678 to address 100 all 10 ms.
4917
4918		This only takes effect if the memory commands are activated
4919		globally (CONFIG_CMD_MEM).
4920
4921- CONFIG_SKIP_LOWLEVEL_INIT
4922		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4923		low level initializations (like setting up the memory
4924		controller) are omitted and/or U-Boot does not
4925		relocate itself into RAM.
4926
4927		Normally this variable MUST NOT be defined. The only
4928		exception is when U-Boot is loaded (to RAM) by some
4929		other boot loader or by a debugger which performs
4930		these initializations itself.
4931
4932- CONFIG_SPL_BUILD
4933		Modifies the behaviour of start.S when compiling a loader
4934		that is executed before the actual U-Boot. E.g. when
4935		compiling a NAND SPL.
4936
4937- CONFIG_TPL_BUILD
4938		Modifies the behaviour of start.S  when compiling a loader
4939		that is executed after the SPL and before the actual U-Boot.
4940		It is loaded by the SPL.
4941
4942- CONFIG_SYS_MPC85XX_NO_RESETVEC
4943		Only for 85xx systems. If this variable is specified, the section
4944		.resetvec is not kept and the section .bootpg is placed in the
4945		previous 4k of the .text section.
4946
4947- CONFIG_ARCH_MAP_SYSMEM
4948		Generally U-Boot (and in particular the md command) uses
4949		effective address. It is therefore not necessary to regard
4950		U-Boot address as virtual addresses that need to be translated
4951		to physical addresses. However, sandbox requires this, since
4952		it maintains its own little RAM buffer which contains all
4953		addressable memory. This option causes some memory accesses
4954		to be mapped through map_sysmem() / unmap_sysmem().
4955
4956- CONFIG_USE_ARCH_MEMCPY
4957  CONFIG_USE_ARCH_MEMSET
4958		If these options are used a optimized version of memcpy/memset will
4959		be used if available. These functions may be faster under some
4960		conditions but may increase the binary size.
4961
4962- CONFIG_X86_RESET_VECTOR
4963		If defined, the x86 reset vector code is included. This is not
4964		needed when U-Boot is running from Coreboot.
4965
4966- CONFIG_SYS_MPUCLK
4967		Defines the MPU clock speed (in MHz).
4968
4969		NOTE : currently only supported on AM335x platforms.
4970
4971- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4972		Enables the RTC32K OSC on AM33xx based plattforms
4973
4974- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4975		Option to disable subpage write in NAND driver
4976		driver that uses this:
4977		drivers/mtd/nand/davinci_nand.c
4978
4979Freescale QE/FMAN Firmware Support:
4980-----------------------------------
4981
4982The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4983loading of "firmware", which is encoded in the QE firmware binary format.
4984This firmware often needs to be loaded during U-Boot booting, so macros
4985are used to identify the storage device (NOR flash, SPI, etc) and the address
4986within that device.
4987
4988- CONFIG_SYS_FMAN_FW_ADDR
4989	The address in the storage device where the FMAN microcode is located.  The
4990	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4991	is also specified.
4992
4993- CONFIG_SYS_QE_FW_ADDR
4994	The address in the storage device where the QE microcode is located.  The
4995	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4996	is also specified.
4997
4998- CONFIG_SYS_QE_FMAN_FW_LENGTH
4999	The maximum possible size of the firmware.  The firmware binary format
5000	has a field that specifies the actual size of the firmware, but it
5001	might not be possible to read any part of the firmware unless some
5002	local storage is allocated to hold the entire firmware first.
5003
5004- CONFIG_SYS_QE_FMAN_FW_IN_NOR
5005	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
5006	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
5007	virtual address in NOR flash.
5008
5009- CONFIG_SYS_QE_FMAN_FW_IN_NAND
5010	Specifies that QE/FMAN firmware is located in NAND flash.
5011	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
5012
5013- CONFIG_SYS_QE_FMAN_FW_IN_MMC
5014	Specifies that QE/FMAN firmware is located on the primary SD/MMC
5015	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5016
5017- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
5018	Specifies that QE/FMAN firmware is located on the primary SPI
5019	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
5020
5021- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
5022	Specifies that QE/FMAN firmware is located in the remote (master)
5023	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
5024	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
5025	window->master inbound window->master LAW->the ucode address in
5026	master's memory space.
5027
5028Freescale Layerscape Management Complex Firmware Support:
5029---------------------------------------------------------
5030The Freescale Layerscape Management Complex (MC) supports the loading of
5031"firmware".
5032This firmware often needs to be loaded during U-Boot booting, so macros
5033are used to identify the storage device (NOR flash, SPI, etc) and the address
5034within that device.
5035
5036- CONFIG_FSL_MC_ENET
5037	Enable the MC driver for Layerscape SoCs.
5038
5039- CONFIG_SYS_LS_MC_FW_ADDR
5040	The address in the storage device where the firmware is located.  The
5041	meaning of this address depends on which CONFIG_SYS_LS_MC_FW_IN_xxx macro
5042	is also specified.
5043
5044- CONFIG_SYS_LS_MC_FW_LENGTH
5045	The maximum possible size of the firmware.  The firmware binary format
5046	has a field that specifies the actual size of the firmware, but it
5047	might not be possible to read any part of the firmware unless some
5048	local storage is allocated to hold the entire firmware first.
5049
5050- CONFIG_SYS_LS_MC_FW_IN_NOR
5051	Specifies that MC firmware is located in NOR flash, mapped as
5052	normal addressable memory via the LBC. CONFIG_SYS_LS_MC_FW_ADDR is the
5053	virtual address in NOR flash.
5054
5055Building the Software:
5056======================
5057
5058Building U-Boot has been tested in several native build environments
5059and in many different cross environments. Of course we cannot support
5060all possibly existing versions of cross development tools in all
5061(potentially obsolete) versions. In case of tool chain problems we
5062recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
5063which is extensively used to build and test U-Boot.
5064
5065If you are not using a native environment, it is assumed that you
5066have GNU cross compiling tools available in your path. In this case,
5067you must set the environment variable CROSS_COMPILE in your shell.
5068Note that no changes to the Makefile or any other source files are
5069necessary. For example using the ELDK on a 4xx CPU, please enter:
5070
5071	$ CROSS_COMPILE=ppc_4xx-
5072	$ export CROSS_COMPILE
5073
5074Note: If you wish to generate Windows versions of the utilities in
5075      the tools directory you can use the MinGW toolchain
5076      (http://www.mingw.org).  Set your HOST tools to the MinGW
5077      toolchain and execute 'make tools'.  For example:
5078
5079       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
5080
5081      Binaries such as tools/mkimage.exe will be created which can
5082      be executed on computers running Windows.
5083
5084U-Boot is intended to be simple to build. After installing the
5085sources you must configure U-Boot for one specific board type. This
5086is done by typing:
5087
5088	make NAME_defconfig
5089
5090where "NAME_defconfig" is the name of one of the existing configu-
5091rations; see boards.cfg for supported names.
5092
5093Note: for some board special configuration names may exist; check if
5094      additional information is available from the board vendor; for
5095      instance, the TQM823L systems are available without (standard)
5096      or with LCD support. You can select such additional "features"
5097      when choosing the configuration, i. e.
5098
5099      make TQM823L_defconfig
5100	- will configure for a plain TQM823L, i. e. no LCD support
5101
5102      make TQM823L_LCD_defconfig
5103	- will configure for a TQM823L with U-Boot console on LCD
5104
5105      etc.
5106
5107
5108Finally, type "make all", and you should get some working U-Boot
5109images ready for download to / installation on your system:
5110
5111- "u-boot.bin" is a raw binary image
5112- "u-boot" is an image in ELF binary format
5113- "u-boot.srec" is in Motorola S-Record format
5114
5115By default the build is performed locally and the objects are saved
5116in the source directory. One of the two methods can be used to change
5117this behavior and build U-Boot to some external directory:
5118
51191. Add O= to the make command line invocations:
5120
5121	make O=/tmp/build distclean
5122	make O=/tmp/build NAME_defconfig
5123	make O=/tmp/build all
5124
51252. Set environment variable KBUILD_OUTPUT to point to the desired location:
5126
5127	export KBUILD_OUTPUT=/tmp/build
5128	make distclean
5129	make NAME_defconfig
5130	make all
5131
5132Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
5133variable.
5134
5135
5136Please be aware that the Makefiles assume you are using GNU make, so
5137for instance on NetBSD you might need to use "gmake" instead of
5138native "make".
5139
5140
5141If the system board that you have is not listed, then you will need
5142to port U-Boot to your hardware platform. To do this, follow these
5143steps:
5144
51451.  Add a new configuration option for your board to the toplevel
5146    "boards.cfg" file, using the existing entries as examples.
5147    Follow the instructions there to keep the boards in order.
51482.  Create a new directory to hold your board specific code. Add any
5149    files you need. In your board directory, you will need at least
5150    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
51513.  Create a new configuration file "include/configs/<board>.h" for
5152    your board
51533.  If you're porting U-Boot to a new CPU, then also create a new
5154    directory to hold your CPU specific code. Add any files you need.
51554.  Run "make <board>_defconfig" with your new name.
51565.  Type "make", and you should get a working "u-boot.srec" file
5157    to be installed on your target system.
51586.  Debug and solve any problems that might arise.
5159    [Of course, this last step is much harder than it sounds.]
5160
5161
5162Testing of U-Boot Modifications, Ports to New Hardware, etc.:
5163==============================================================
5164
5165If you have modified U-Boot sources (for instance added a new board
5166or support for new devices, a new CPU, etc.) you are expected to
5167provide feedback to the other developers. The feedback normally takes
5168the form of a "patch", i. e. a context diff against a certain (latest
5169official or latest in the git repository) version of U-Boot sources.
5170
5171But before you submit such a patch, please verify that your modifi-
5172cation did not break existing code. At least make sure that *ALL* of
5173the supported boards compile WITHOUT ANY compiler warnings. To do so,
5174just run the "MAKEALL" script, which will configure and build U-Boot
5175for ALL supported system. Be warned, this will take a while. You can
5176select which (cross) compiler to use by passing a `CROSS_COMPILE'
5177environment variable to the script, i. e. to use the ELDK cross tools
5178you can type
5179
5180	CROSS_COMPILE=ppc_8xx- MAKEALL
5181
5182or to build on a native PowerPC system you can type
5183
5184	CROSS_COMPILE=' ' MAKEALL
5185
5186When using the MAKEALL script, the default behaviour is to build
5187U-Boot in the source directory. This location can be changed by
5188setting the BUILD_DIR environment variable. Also, for each target
5189built, the MAKEALL script saves two log files (<target>.ERR and
5190<target>.MAKEALL) in the <source dir>/LOG directory. This default
5191location can be changed by setting the MAKEALL_LOGDIR environment
5192variable. For example:
5193
5194	export BUILD_DIR=/tmp/build
5195	export MAKEALL_LOGDIR=/tmp/log
5196	CROSS_COMPILE=ppc_8xx- MAKEALL
5197
5198With the above settings build objects are saved in the /tmp/build,
5199log files are saved in the /tmp/log and the source tree remains clean
5200during the whole build process.
5201
5202
5203See also "U-Boot Porting Guide" below.
5204
5205
5206Monitor Commands - Overview:
5207============================
5208
5209go	- start application at address 'addr'
5210run	- run commands in an environment variable
5211bootm	- boot application image from memory
5212bootp	- boot image via network using BootP/TFTP protocol
5213bootz   - boot zImage from memory
5214tftpboot- boot image via network using TFTP protocol
5215	       and env variables "ipaddr" and "serverip"
5216	       (and eventually "gatewayip")
5217tftpput - upload a file via network using TFTP protocol
5218rarpboot- boot image via network using RARP/TFTP protocol
5219diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
5220loads	- load S-Record file over serial line
5221loadb	- load binary file over serial line (kermit mode)
5222md	- memory display
5223mm	- memory modify (auto-incrementing)
5224nm	- memory modify (constant address)
5225mw	- memory write (fill)
5226cp	- memory copy
5227cmp	- memory compare
5228crc32	- checksum calculation
5229i2c	- I2C sub-system
5230sspi	- SPI utility commands
5231base	- print or set address offset
5232printenv- print environment variables
5233setenv	- set environment variables
5234saveenv - save environment variables to persistent storage
5235protect - enable or disable FLASH write protection
5236erase	- erase FLASH memory
5237flinfo	- print FLASH memory information
5238nand	- NAND memory operations (see doc/README.nand)
5239bdinfo	- print Board Info structure
5240iminfo	- print header information for application image
5241coninfo - print console devices and informations
5242ide	- IDE sub-system
5243loop	- infinite loop on address range
5244loopw	- infinite write loop on address range
5245mtest	- simple RAM test
5246icache	- enable or disable instruction cache
5247dcache	- enable or disable data cache
5248reset	- Perform RESET of the CPU
5249echo	- echo args to console
5250version - print monitor version
5251help	- print online help
5252?	- alias for 'help'
5253
5254
5255Monitor Commands - Detailed Description:
5256========================================
5257
5258TODO.
5259
5260For now: just type "help <command>".
5261
5262
5263Environment Variables:
5264======================
5265
5266U-Boot supports user configuration using Environment Variables which
5267can be made persistent by saving to Flash memory.
5268
5269Environment Variables are set using "setenv", printed using
5270"printenv", and saved to Flash using "saveenv". Using "setenv"
5271without a value can be used to delete a variable from the
5272environment. As long as you don't save the environment you are
5273working with an in-memory copy. In case the Flash area containing the
5274environment is erased by accident, a default environment is provided.
5275
5276Some configuration options can be set using Environment Variables.
5277
5278List of environment variables (most likely not complete):
5279
5280  baudrate	- see CONFIG_BAUDRATE
5281
5282  bootdelay	- see CONFIG_BOOTDELAY
5283
5284  bootcmd	- see CONFIG_BOOTCOMMAND
5285
5286  bootargs	- Boot arguments when booting an RTOS image
5287
5288  bootfile	- Name of the image to load with TFTP
5289
5290  bootm_low	- Memory range available for image processing in the bootm
5291		  command can be restricted. This variable is given as
5292		  a hexadecimal number and defines lowest address allowed
5293		  for use by the bootm command. See also "bootm_size"
5294		  environment variable. Address defined by "bootm_low" is
5295		  also the base of the initial memory mapping for the Linux
5296		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
5297		  bootm_mapsize.
5298
5299  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
5300		  This variable is given as a hexadecimal number and it
5301		  defines the size of the memory region starting at base
5302		  address bootm_low that is accessible by the Linux kernel
5303		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
5304		  as the default value if it is defined, and bootm_size is
5305		  used otherwise.
5306
5307  bootm_size	- Memory range available for image processing in the bootm
5308		  command can be restricted. This variable is given as
5309		  a hexadecimal number and defines the size of the region
5310		  allowed for use by the bootm command. See also "bootm_low"
5311		  environment variable.
5312
5313  updatefile	- Location of the software update file on a TFTP server, used
5314		  by the automatic software update feature. Please refer to
5315		  documentation in doc/README.update for more details.
5316
5317  autoload	- if set to "no" (any string beginning with 'n'),
5318		  "bootp" will just load perform a lookup of the
5319		  configuration from the BOOTP server, but not try to
5320		  load any image using TFTP
5321
5322  autostart	- if set to "yes", an image loaded using the "bootp",
5323		  "rarpboot", "tftpboot" or "diskboot" commands will
5324		  be automatically started (by internally calling
5325		  "bootm")
5326
5327		  If set to "no", a standalone image passed to the
5328		  "bootm" command will be copied to the load address
5329		  (and eventually uncompressed), but NOT be started.
5330		  This can be used to load and uncompress arbitrary
5331		  data.
5332
5333  fdt_high	- if set this restricts the maximum address that the
5334		  flattened device tree will be copied into upon boot.
5335		  For example, if you have a system with 1 GB memory
5336		  at physical address 0x10000000, while Linux kernel
5337		  only recognizes the first 704 MB as low memory, you
5338		  may need to set fdt_high as 0x3C000000 to have the
5339		  device tree blob be copied to the maximum address
5340		  of the 704 MB low memory, so that Linux kernel can
5341		  access it during the boot procedure.
5342
5343		  If this is set to the special value 0xFFFFFFFF then
5344		  the fdt will not be copied at all on boot.  For this
5345		  to work it must reside in writable memory, have
5346		  sufficient padding on the end of it for u-boot to
5347		  add the information it needs into it, and the memory
5348		  must be accessible by the kernel.
5349
5350  fdtcontroladdr- if set this is the address of the control flattened
5351		  device tree used by U-Boot when CONFIG_OF_CONTROL is
5352		  defined.
5353
5354  i2cfast	- (PPC405GP|PPC405EP only)
5355		  if set to 'y' configures Linux I2C driver for fast
5356		  mode (400kHZ). This environment variable is used in
5357		  initialization code. So, for changes to be effective
5358		  it must be saved and board must be reset.
5359
5360  initrd_high	- restrict positioning of initrd images:
5361		  If this variable is not set, initrd images will be
5362		  copied to the highest possible address in RAM; this
5363		  is usually what you want since it allows for
5364		  maximum initrd size. If for some reason you want to
5365		  make sure that the initrd image is loaded below the
5366		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
5367		  variable to a value of "no" or "off" or "0".
5368		  Alternatively, you can set it to a maximum upper
5369		  address to use (U-Boot will still check that it
5370		  does not overwrite the U-Boot stack and data).
5371
5372		  For instance, when you have a system with 16 MB
5373		  RAM, and want to reserve 4 MB from use by Linux,
5374		  you can do this by adding "mem=12M" to the value of
5375		  the "bootargs" variable. However, now you must make
5376		  sure that the initrd image is placed in the first
5377		  12 MB as well - this can be done with
5378
5379		  setenv initrd_high 00c00000
5380
5381		  If you set initrd_high to 0xFFFFFFFF, this is an
5382		  indication to U-Boot that all addresses are legal
5383		  for the Linux kernel, including addresses in flash
5384		  memory. In this case U-Boot will NOT COPY the
5385		  ramdisk at all. This may be useful to reduce the
5386		  boot time on your system, but requires that this
5387		  feature is supported by your Linux kernel.
5388
5389  ipaddr	- IP address; needed for tftpboot command
5390
5391  loadaddr	- Default load address for commands like "bootp",
5392		  "rarpboot", "tftpboot", "loadb" or "diskboot"
5393
5394  loads_echo	- see CONFIG_LOADS_ECHO
5395
5396  serverip	- TFTP server IP address; needed for tftpboot command
5397
5398  bootretry	- see CONFIG_BOOT_RETRY_TIME
5399
5400  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
5401
5402  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
5403
5404  ethprime	- controls which interface is used first.
5405
5406  ethact	- controls which interface is currently active.
5407		  For example you can do the following
5408
5409		  => setenv ethact FEC
5410		  => ping 192.168.0.1 # traffic sent on FEC
5411		  => setenv ethact SCC
5412		  => ping 10.0.0.1 # traffic sent on SCC
5413
5414  ethrotate	- When set to "no" U-Boot does not go through all
5415		  available network interfaces.
5416		  It just stays at the currently selected interface.
5417
5418  netretry	- When set to "no" each network operation will
5419		  either succeed or fail without retrying.
5420		  When set to "once" the network operation will
5421		  fail when all the available network interfaces
5422		  are tried once without success.
5423		  Useful on scripts which control the retry operation
5424		  themselves.
5425
5426  npe_ucode	- set load address for the NPE microcode
5427
5428  silent_linux  - If set then Linux will be told to boot silently, by
5429		  changing the console to be empty. If "yes" it will be
5430		  made silent. If "no" it will not be made silent. If
5431		  unset, then it will be made silent if the U-Boot console
5432		  is silent.
5433
5434  tftpsrcport	- If this is set, the value is used for TFTP's
5435		  UDP source port.
5436
5437  tftpdstport	- If this is set, the value is used for TFTP's UDP
5438		  destination port instead of the Well Know Port 69.
5439
5440  tftpblocksize - Block size to use for TFTP transfers; if not set,
5441		  we use the TFTP server's default block size
5442
5443  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
5444		  seconds, minimum value is 1000 = 1 second). Defines
5445		  when a packet is considered to be lost so it has to
5446		  be retransmitted. The default is 5000 = 5 seconds.
5447		  Lowering this value may make downloads succeed
5448		  faster in networks with high packet loss rates or
5449		  with unreliable TFTP servers.
5450
5451  vlan		- When set to a value < 4095 the traffic over
5452		  Ethernet is encapsulated/received over 802.1q
5453		  VLAN tagged frames.
5454
5455The following image location variables contain the location of images
5456used in booting. The "Image" column gives the role of the image and is
5457not an environment variable name. The other columns are environment
5458variable names. "File Name" gives the name of the file on a TFTP
5459server, "RAM Address" gives the location in RAM the image will be
5460loaded to, and "Flash Location" gives the image's address in NOR
5461flash or offset in NAND flash.
5462
5463*Note* - these variables don't have to be defined for all boards, some
5464boards currently use other variables for these purposes, and some
5465boards use these variables for other purposes.
5466
5467Image		    File Name	     RAM Address       Flash Location
5468-----		    ---------	     -----------       --------------
5469u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
5470Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
5471device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
5472ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
5473
5474The following environment variables may be used and automatically
5475updated by the network boot commands ("bootp" and "rarpboot"),
5476depending the information provided by your boot server:
5477
5478  bootfile	- see above
5479  dnsip		- IP address of your Domain Name Server
5480  dnsip2	- IP address of your secondary Domain Name Server
5481  gatewayip	- IP address of the Gateway (Router) to use
5482  hostname	- Target hostname
5483  ipaddr	- see above
5484  netmask	- Subnet Mask
5485  rootpath	- Pathname of the root filesystem on the NFS server
5486  serverip	- see above
5487
5488
5489There are two special Environment Variables:
5490
5491  serial#	- contains hardware identification information such
5492		  as type string and/or serial number
5493  ethaddr	- Ethernet address
5494
5495These variables can be set only once (usually during manufacturing of
5496the board). U-Boot refuses to delete or overwrite these variables
5497once they have been set once.
5498
5499
5500Further special Environment Variables:
5501
5502  ver		- Contains the U-Boot version string as printed
5503		  with the "version" command. This variable is
5504		  readonly (see CONFIG_VERSION_VARIABLE).
5505
5506
5507Please note that changes to some configuration parameters may take
5508only effect after the next boot (yes, that's just like Windoze :-).
5509
5510
5511Callback functions for environment variables:
5512---------------------------------------------
5513
5514For some environment variables, the behavior of u-boot needs to change
5515when their values are changed.  This functionality allows functions to
5516be associated with arbitrary variables.  On creation, overwrite, or
5517deletion, the callback will provide the opportunity for some side
5518effect to happen or for the change to be rejected.
5519
5520The callbacks are named and associated with a function using the
5521U_BOOT_ENV_CALLBACK macro in your board or driver code.
5522
5523These callbacks are associated with variables in one of two ways.  The
5524static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
5525in the board configuration to a string that defines a list of
5526associations.  The list must be in the following format:
5527
5528	entry = variable_name[:callback_name]
5529	list = entry[,list]
5530
5531If the callback name is not specified, then the callback is deleted.
5532Spaces are also allowed anywhere in the list.
5533
5534Callbacks can also be associated by defining the ".callbacks" variable
5535with the same list format above.  Any association in ".callbacks" will
5536override any association in the static list. You can define
5537CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
5538".callbacks" environment variable in the default or embedded environment.
5539
5540
5541Command Line Parsing:
5542=====================
5543
5544There are two different command line parsers available with U-Boot:
5545the old "simple" one, and the much more powerful "hush" shell:
5546
5547Old, simple command line parser:
5548--------------------------------
5549
5550- supports environment variables (through setenv / saveenv commands)
5551- several commands on one line, separated by ';'
5552- variable substitution using "... ${name} ..." syntax
5553- special characters ('$', ';') can be escaped by prefixing with '\',
5554  for example:
5555	setenv bootcmd bootm \${address}
5556- You can also escape text by enclosing in single apostrophes, for example:
5557	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
5558
5559Hush shell:
5560-----------
5561
5562- similar to Bourne shell, with control structures like
5563  if...then...else...fi, for...do...done; while...do...done,
5564  until...do...done, ...
5565- supports environment ("global") variables (through setenv / saveenv
5566  commands) and local shell variables (through standard shell syntax
5567  "name=value"); only environment variables can be used with "run"
5568  command
5569
5570General rules:
5571--------------
5572
5573(1) If a command line (or an environment variable executed by a "run"
5574    command) contains several commands separated by semicolon, and
5575    one of these commands fails, then the remaining commands will be
5576    executed anyway.
5577
5578(2) If you execute several variables with one call to run (i. e.
5579    calling run with a list of variables as arguments), any failing
5580    command will cause "run" to terminate, i. e. the remaining
5581    variables are not executed.
5582
5583Note for Redundant Ethernet Interfaces:
5584=======================================
5585
5586Some boards come with redundant Ethernet interfaces; U-Boot supports
5587such configurations and is capable of automatic selection of a
5588"working" interface when needed. MAC assignment works as follows:
5589
5590Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5591MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5592"eth1addr" (=>eth1), "eth2addr", ...
5593
5594If the network interface stores some valid MAC address (for instance
5595in SROM), this is used as default address if there is NO correspon-
5596ding setting in the environment; if the corresponding environment
5597variable is set, this overrides the settings in the card; that means:
5598
5599o If the SROM has a valid MAC address, and there is no address in the
5600  environment, the SROM's address is used.
5601
5602o If there is no valid address in the SROM, and a definition in the
5603  environment exists, then the value from the environment variable is
5604  used.
5605
5606o If both the SROM and the environment contain a MAC address, and
5607  both addresses are the same, this MAC address is used.
5608
5609o If both the SROM and the environment contain a MAC address, and the
5610  addresses differ, the value from the environment is used and a
5611  warning is printed.
5612
5613o If neither SROM nor the environment contain a MAC address, an error
5614  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5615  a random, locally-assigned MAC is used.
5616
5617If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5618will be programmed into hardware as part of the initialization process.	 This
5619may be skipped by setting the appropriate 'ethmacskip' environment variable.
5620The naming convention is as follows:
5621"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5622
5623Image Formats:
5624==============
5625
5626U-Boot is capable of booting (and performing other auxiliary operations on)
5627images in two formats:
5628
5629New uImage format (FIT)
5630-----------------------
5631
5632Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5633to Flattened Device Tree). It allows the use of images with multiple
5634components (several kernels, ramdisks, etc.), with contents protected by
5635SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5636
5637
5638Old uImage format
5639-----------------
5640
5641Old image format is based on binary files which can be basically anything,
5642preceded by a special header; see the definitions in include/image.h for
5643details; basically, the header defines the following image properties:
5644
5645* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5646  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5647  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5648  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5649  INTEGRITY).
5650* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5651  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5652  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5653* Compression Type (uncompressed, gzip, bzip2)
5654* Load Address
5655* Entry Point
5656* Image Name
5657* Image Timestamp
5658
5659The header is marked by a special Magic Number, and both the header
5660and the data portions of the image are secured against corruption by
5661CRC32 checksums.
5662
5663
5664Linux Support:
5665==============
5666
5667Although U-Boot should support any OS or standalone application
5668easily, the main focus has always been on Linux during the design of
5669U-Boot.
5670
5671U-Boot includes many features that so far have been part of some
5672special "boot loader" code within the Linux kernel. Also, any
5673"initrd" images to be used are no longer part of one big Linux image;
5674instead, kernel and "initrd" are separate images. This implementation
5675serves several purposes:
5676
5677- the same features can be used for other OS or standalone
5678  applications (for instance: using compressed images to reduce the
5679  Flash memory footprint)
5680
5681- it becomes much easier to port new Linux kernel versions because
5682  lots of low-level, hardware dependent stuff are done by U-Boot
5683
5684- the same Linux kernel image can now be used with different "initrd"
5685  images; of course this also means that different kernel images can
5686  be run with the same "initrd". This makes testing easier (you don't
5687  have to build a new "zImage.initrd" Linux image when you just
5688  change a file in your "initrd"). Also, a field-upgrade of the
5689  software is easier now.
5690
5691
5692Linux HOWTO:
5693============
5694
5695Porting Linux to U-Boot based systems:
5696---------------------------------------
5697
5698U-Boot cannot save you from doing all the necessary modifications to
5699configure the Linux device drivers for use with your target hardware
5700(no, we don't intend to provide a full virtual machine interface to
5701Linux :-).
5702
5703But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5704
5705Just make sure your machine specific header file (for instance
5706include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5707Information structure as we define in include/asm-<arch>/u-boot.h,
5708and make sure that your definition of IMAP_ADDR uses the same value
5709as your U-Boot configuration in CONFIG_SYS_IMMR.
5710
5711Note that U-Boot now has a driver model, a unified model for drivers.
5712If you are adding a new driver, plumb it into driver model. If there
5713is no uclass available, you are encouraged to create one. See
5714doc/driver-model.
5715
5716
5717Configuring the Linux kernel:
5718-----------------------------
5719
5720No specific requirements for U-Boot. Make sure you have some root
5721device (initial ramdisk, NFS) for your target system.
5722
5723
5724Building a Linux Image:
5725-----------------------
5726
5727With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5728not used. If you use recent kernel source, a new build target
5729"uImage" will exist which automatically builds an image usable by
5730U-Boot. Most older kernels also have support for a "pImage" target,
5731which was introduced for our predecessor project PPCBoot and uses a
5732100% compatible format.
5733
5734Example:
5735
5736	make TQM850L_defconfig
5737	make oldconfig
5738	make dep
5739	make uImage
5740
5741The "uImage" build target uses a special tool (in 'tools/mkimage') to
5742encapsulate a compressed Linux kernel image with header	 information,
5743CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5744
5745* build a standard "vmlinux" kernel image (in ELF binary format):
5746
5747* convert the kernel into a raw binary image:
5748
5749	${CROSS_COMPILE}-objcopy -O binary \
5750				 -R .note -R .comment \
5751				 -S vmlinux linux.bin
5752
5753* compress the binary image:
5754
5755	gzip -9 linux.bin
5756
5757* package compressed binary image for U-Boot:
5758
5759	mkimage -A ppc -O linux -T kernel -C gzip \
5760		-a 0 -e 0 -n "Linux Kernel Image" \
5761		-d linux.bin.gz uImage
5762
5763
5764The "mkimage" tool can also be used to create ramdisk images for use
5765with U-Boot, either separated from the Linux kernel image, or
5766combined into one file. "mkimage" encapsulates the images with a 64
5767byte header containing information about target architecture,
5768operating system, image type, compression method, entry points, time
5769stamp, CRC32 checksums, etc.
5770
5771"mkimage" can be called in two ways: to verify existing images and
5772print the header information, or to build new images.
5773
5774In the first form (with "-l" option) mkimage lists the information
5775contained in the header of an existing U-Boot image; this includes
5776checksum verification:
5777
5778	tools/mkimage -l image
5779	  -l ==> list image header information
5780
5781The second form (with "-d" option) is used to build a U-Boot image
5782from a "data file" which is used as image payload:
5783
5784	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5785		      -n name -d data_file image
5786	  -A ==> set architecture to 'arch'
5787	  -O ==> set operating system to 'os'
5788	  -T ==> set image type to 'type'
5789	  -C ==> set compression type 'comp'
5790	  -a ==> set load address to 'addr' (hex)
5791	  -e ==> set entry point to 'ep' (hex)
5792	  -n ==> set image name to 'name'
5793	  -d ==> use image data from 'datafile'
5794
5795Right now, all Linux kernels for PowerPC systems use the same load
5796address (0x00000000), but the entry point address depends on the
5797kernel version:
5798
5799- 2.2.x kernels have the entry point at 0x0000000C,
5800- 2.3.x and later kernels have the entry point at 0x00000000.
5801
5802So a typical call to build a U-Boot image would read:
5803
5804	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5805	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5806	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5807	> examples/uImage.TQM850L
5808	Image Name:   2.4.4 kernel for TQM850L
5809	Created:      Wed Jul 19 02:34:59 2000
5810	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5811	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5812	Load Address: 0x00000000
5813	Entry Point:  0x00000000
5814
5815To verify the contents of the image (or check for corruption):
5816
5817	-> tools/mkimage -l examples/uImage.TQM850L
5818	Image Name:   2.4.4 kernel for TQM850L
5819	Created:      Wed Jul 19 02:34:59 2000
5820	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5821	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5822	Load Address: 0x00000000
5823	Entry Point:  0x00000000
5824
5825NOTE: for embedded systems where boot time is critical you can trade
5826speed for memory and install an UNCOMPRESSED image instead: this
5827needs more space in Flash, but boots much faster since it does not
5828need to be uncompressed:
5829
5830	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5831	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5832	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5833	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5834	> examples/uImage.TQM850L-uncompressed
5835	Image Name:   2.4.4 kernel for TQM850L
5836	Created:      Wed Jul 19 02:34:59 2000
5837	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5838	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5839	Load Address: 0x00000000
5840	Entry Point:  0x00000000
5841
5842
5843Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5844when your kernel is intended to use an initial ramdisk:
5845
5846	-> tools/mkimage -n 'Simple Ramdisk Image' \
5847	> -A ppc -O linux -T ramdisk -C gzip \
5848	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5849	Image Name:   Simple Ramdisk Image
5850	Created:      Wed Jan 12 14:01:50 2000
5851	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5852	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5853	Load Address: 0x00000000
5854	Entry Point:  0x00000000
5855
5856The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5857option performs the converse operation of the mkimage's second form (the "-d"
5858option). Given an image built by mkimage, the dumpimage extracts a "data file"
5859from the image:
5860
5861	tools/dumpimage -i image -T type -p position data_file
5862	  -i ==> extract from the 'image' a specific 'data_file'
5863	  -T ==> set image type to 'type'
5864	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5865
5866
5867Installing a Linux Image:
5868-------------------------
5869
5870To downloading a U-Boot image over the serial (console) interface,
5871you must convert the image to S-Record format:
5872
5873	objcopy -I binary -O srec examples/image examples/image.srec
5874
5875The 'objcopy' does not understand the information in the U-Boot
5876image header, so the resulting S-Record file will be relative to
5877address 0x00000000. To load it to a given address, you need to
5878specify the target address as 'offset' parameter with the 'loads'
5879command.
5880
5881Example: install the image to address 0x40100000 (which on the
5882TQM8xxL is in the first Flash bank):
5883
5884	=> erase 40100000 401FFFFF
5885
5886	.......... done
5887	Erased 8 sectors
5888
5889	=> loads 40100000
5890	## Ready for S-Record download ...
5891	~>examples/image.srec
5892	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5893	...
5894	15989 15990 15991 15992
5895	[file transfer complete]
5896	[connected]
5897	## Start Addr = 0x00000000
5898
5899
5900You can check the success of the download using the 'iminfo' command;
5901this includes a checksum verification so you can be sure no data
5902corruption happened:
5903
5904	=> imi 40100000
5905
5906	## Checking Image at 40100000 ...
5907	   Image Name:	 2.2.13 for initrd on TQM850L
5908	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5909	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5910	   Load Address: 00000000
5911	   Entry Point:	 0000000c
5912	   Verifying Checksum ... OK
5913
5914
5915Boot Linux:
5916-----------
5917
5918The "bootm" command is used to boot an application that is stored in
5919memory (RAM or Flash). In case of a Linux kernel image, the contents
5920of the "bootargs" environment variable is passed to the kernel as
5921parameters. You can check and modify this variable using the
5922"printenv" and "setenv" commands:
5923
5924
5925	=> printenv bootargs
5926	bootargs=root=/dev/ram
5927
5928	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5929
5930	=> printenv bootargs
5931	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5932
5933	=> bootm 40020000
5934	## Booting Linux kernel at 40020000 ...
5935	   Image Name:	 2.2.13 for NFS on TQM850L
5936	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5937	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5938	   Load Address: 00000000
5939	   Entry Point:	 0000000c
5940	   Verifying Checksum ... OK
5941	   Uncompressing Kernel Image ... OK
5942	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
5943	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5944	time_init: decrementer frequency = 187500000/60
5945	Calibrating delay loop... 49.77 BogoMIPS
5946	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5947	...
5948
5949If you want to boot a Linux kernel with initial RAM disk, you pass
5950the memory addresses of both the kernel and the initrd image (PPBCOOT
5951format!) to the "bootm" command:
5952
5953	=> imi 40100000 40200000
5954
5955	## Checking Image at 40100000 ...
5956	   Image Name:	 2.2.13 for initrd on TQM850L
5957	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5958	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5959	   Load Address: 00000000
5960	   Entry Point:	 0000000c
5961	   Verifying Checksum ... OK
5962
5963	## Checking Image at 40200000 ...
5964	   Image Name:	 Simple Ramdisk Image
5965	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5966	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5967	   Load Address: 00000000
5968	   Entry Point:	 00000000
5969	   Verifying Checksum ... OK
5970
5971	=> bootm 40100000 40200000
5972	## Booting Linux kernel at 40100000 ...
5973	   Image Name:	 2.2.13 for initrd on TQM850L
5974	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5975	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5976	   Load Address: 00000000
5977	   Entry Point:	 0000000c
5978	   Verifying Checksum ... OK
5979	   Uncompressing Kernel Image ... OK
5980	## Loading RAMDisk Image at 40200000 ...
5981	   Image Name:	 Simple Ramdisk Image
5982	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5983	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5984	   Load Address: 00000000
5985	   Entry Point:	 00000000
5986	   Verifying Checksum ... OK
5987	   Loading Ramdisk ... OK
5988	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
5989	Boot arguments: root=/dev/ram
5990	time_init: decrementer frequency = 187500000/60
5991	Calibrating delay loop... 49.77 BogoMIPS
5992	...
5993	RAMDISK: Compressed image found at block 0
5994	VFS: Mounted root (ext2 filesystem).
5995
5996	bash#
5997
5998Boot Linux and pass a flat device tree:
5999-----------
6000
6001First, U-Boot must be compiled with the appropriate defines. See the section
6002titled "Linux Kernel Interface" above for a more in depth explanation. The
6003following is an example of how to start a kernel and pass an updated
6004flat device tree:
6005
6006=> print oftaddr
6007oftaddr=0x300000
6008=> print oft
6009oft=oftrees/mpc8540ads.dtb
6010=> tftp $oftaddr $oft
6011Speed: 1000, full duplex
6012Using TSEC0 device
6013TFTP from server 192.168.1.1; our IP address is 192.168.1.101
6014Filename 'oftrees/mpc8540ads.dtb'.
6015Load address: 0x300000
6016Loading: #
6017done
6018Bytes transferred = 4106 (100a hex)
6019=> tftp $loadaddr $bootfile
6020Speed: 1000, full duplex
6021Using TSEC0 device
6022TFTP from server 192.168.1.1; our IP address is 192.168.1.2
6023Filename 'uImage'.
6024Load address: 0x200000
6025Loading:############
6026done
6027Bytes transferred = 1029407 (fb51f hex)
6028=> print loadaddr
6029loadaddr=200000
6030=> print oftaddr
6031oftaddr=0x300000
6032=> bootm $loadaddr - $oftaddr
6033## Booting image at 00200000 ...
6034   Image Name:	 Linux-2.6.17-dirty
6035   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
6036   Data Size:	 1029343 Bytes = 1005.2 kB
6037   Load Address: 00000000
6038   Entry Point:	 00000000
6039   Verifying Checksum ... OK
6040   Uncompressing Kernel Image ... OK
6041Booting using flat device tree at 0x300000
6042Using MPC85xx ADS machine description
6043Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
6044[snip]
6045
6046
6047More About U-Boot Image Types:
6048------------------------------
6049
6050U-Boot supports the following image types:
6051
6052   "Standalone Programs" are directly runnable in the environment
6053	provided by U-Boot; it is expected that (if they behave
6054	well) you can continue to work in U-Boot after return from
6055	the Standalone Program.
6056   "OS Kernel Images" are usually images of some Embedded OS which
6057	will take over control completely. Usually these programs
6058	will install their own set of exception handlers, device
6059	drivers, set up the MMU, etc. - this means, that you cannot
6060	expect to re-enter U-Boot except by resetting the CPU.
6061   "RAMDisk Images" are more or less just data blocks, and their
6062	parameters (address, size) are passed to an OS kernel that is
6063	being started.
6064   "Multi-File Images" contain several images, typically an OS
6065	(Linux) kernel image and one or more data images like
6066	RAMDisks. This construct is useful for instance when you want
6067	to boot over the network using BOOTP etc., where the boot
6068	server provides just a single image file, but you want to get
6069	for instance an OS kernel and a RAMDisk image.
6070
6071	"Multi-File Images" start with a list of image sizes, each
6072	image size (in bytes) specified by an "uint32_t" in network
6073	byte order. This list is terminated by an "(uint32_t)0".
6074	Immediately after the terminating 0 follow the images, one by
6075	one, all aligned on "uint32_t" boundaries (size rounded up to
6076	a multiple of 4 bytes).
6077
6078   "Firmware Images" are binary images containing firmware (like
6079	U-Boot or FPGA images) which usually will be programmed to
6080	flash memory.
6081
6082   "Script files" are command sequences that will be executed by
6083	U-Boot's command interpreter; this feature is especially
6084	useful when you configure U-Boot to use a real shell (hush)
6085	as command interpreter.
6086
6087Booting the Linux zImage:
6088-------------------------
6089
6090On some platforms, it's possible to boot Linux zImage. This is done
6091using the "bootz" command. The syntax of "bootz" command is the same
6092as the syntax of "bootm" command.
6093
6094Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
6095kernel with raw initrd images. The syntax is slightly different, the
6096address of the initrd must be augmented by it's size, in the following
6097format: "<initrd addres>:<initrd size>".
6098
6099
6100Standalone HOWTO:
6101=================
6102
6103One of the features of U-Boot is that you can dynamically load and
6104run "standalone" applications, which can use some resources of
6105U-Boot like console I/O functions or interrupt services.
6106
6107Two simple examples are included with the sources:
6108
6109"Hello World" Demo:
6110-------------------
6111
6112'examples/hello_world.c' contains a small "Hello World" Demo
6113application; it is automatically compiled when you build U-Boot.
6114It's configured to run at address 0x00040004, so you can play with it
6115like that:
6116
6117	=> loads
6118	## Ready for S-Record download ...
6119	~>examples/hello_world.srec
6120	1 2 3 4 5 6 7 8 9 10 11 ...
6121	[file transfer complete]
6122	[connected]
6123	## Start Addr = 0x00040004
6124
6125	=> go 40004 Hello World! This is a test.
6126	## Starting application at 0x00040004 ...
6127	Hello World
6128	argc = 7
6129	argv[0] = "40004"
6130	argv[1] = "Hello"
6131	argv[2] = "World!"
6132	argv[3] = "This"
6133	argv[4] = "is"
6134	argv[5] = "a"
6135	argv[6] = "test."
6136	argv[7] = "<NULL>"
6137	Hit any key to exit ...
6138
6139	## Application terminated, rc = 0x0
6140
6141Another example, which demonstrates how to register a CPM interrupt
6142handler with the U-Boot code, can be found in 'examples/timer.c'.
6143Here, a CPM timer is set up to generate an interrupt every second.
6144The interrupt service routine is trivial, just printing a '.'
6145character, but this is just a demo program. The application can be
6146controlled by the following keys:
6147
6148	? - print current values og the CPM Timer registers
6149	b - enable interrupts and start timer
6150	e - stop timer and disable interrupts
6151	q - quit application
6152
6153	=> loads
6154	## Ready for S-Record download ...
6155	~>examples/timer.srec
6156	1 2 3 4 5 6 7 8 9 10 11 ...
6157	[file transfer complete]
6158	[connected]
6159	## Start Addr = 0x00040004
6160
6161	=> go 40004
6162	## Starting application at 0x00040004 ...
6163	TIMERS=0xfff00980
6164	Using timer 1
6165	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
6166
6167Hit 'b':
6168	[q, b, e, ?] Set interval 1000000 us
6169	Enabling timer
6170Hit '?':
6171	[q, b, e, ?] ........
6172	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
6173Hit '?':
6174	[q, b, e, ?] .
6175	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
6176Hit '?':
6177	[q, b, e, ?] .
6178	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
6179Hit '?':
6180	[q, b, e, ?] .
6181	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
6182Hit 'e':
6183	[q, b, e, ?] ...Stopping timer
6184Hit 'q':
6185	[q, b, e, ?] ## Application terminated, rc = 0x0
6186
6187
6188Minicom warning:
6189================
6190
6191Over time, many people have reported problems when trying to use the
6192"minicom" terminal emulation program for serial download. I (wd)
6193consider minicom to be broken, and recommend not to use it. Under
6194Unix, I recommend to use C-Kermit for general purpose use (and
6195especially for kermit binary protocol download ("loadb" command), and
6196use "cu" for S-Record download ("loads" command).  See
6197http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
6198for help with kermit.
6199
6200
6201Nevertheless, if you absolutely want to use it try adding this
6202configuration to your "File transfer protocols" section:
6203
6204	   Name	   Program			Name U/D FullScr IO-Red. Multi
6205	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
6206	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
6207
6208
6209NetBSD Notes:
6210=============
6211
6212Starting at version 0.9.2, U-Boot supports NetBSD both as host
6213(build U-Boot) and target system (boots NetBSD/mpc8xx).
6214
6215Building requires a cross environment; it is known to work on
6216NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
6217need gmake since the Makefiles are not compatible with BSD make).
6218Note that the cross-powerpc package does not install include files;
6219attempting to build U-Boot will fail because <machine/ansi.h> is
6220missing.  This file has to be installed and patched manually:
6221
6222	# cd /usr/pkg/cross/powerpc-netbsd/include
6223	# mkdir powerpc
6224	# ln -s powerpc machine
6225	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
6226	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
6227
6228Native builds *don't* work due to incompatibilities between native
6229and U-Boot include files.
6230
6231Booting assumes that (the first part of) the image booted is a
6232stage-2 loader which in turn loads and then invokes the kernel
6233proper. Loader sources will eventually appear in the NetBSD source
6234tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
6235meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
6236
6237
6238Implementation Internals:
6239=========================
6240
6241The following is not intended to be a complete description of every
6242implementation detail. However, it should help to understand the
6243inner workings of U-Boot and make it easier to port it to custom
6244hardware.
6245
6246
6247Initial Stack, Global Data:
6248---------------------------
6249
6250The implementation of U-Boot is complicated by the fact that U-Boot
6251starts running out of ROM (flash memory), usually without access to
6252system RAM (because the memory controller is not initialized yet).
6253This means that we don't have writable Data or BSS segments, and BSS
6254is not initialized as zero. To be able to get a C environment working
6255at all, we have to allocate at least a minimal stack. Implementation
6256options for this are defined and restricted by the CPU used: Some CPU
6257models provide on-chip memory (like the IMMR area on MPC8xx and
6258MPC826x processors), on others (parts of) the data cache can be
6259locked as (mis-) used as memory, etc.
6260
6261	Chris Hallinan posted a good summary of these issues to the
6262	U-Boot mailing list:
6263
6264	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
6265	From: "Chris Hallinan" <clh@net1plus.com>
6266	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
6267	...
6268
6269	Correct me if I'm wrong, folks, but the way I understand it
6270	is this: Using DCACHE as initial RAM for Stack, etc, does not
6271	require any physical RAM backing up the cache. The cleverness
6272	is that the cache is being used as a temporary supply of
6273	necessary storage before the SDRAM controller is setup. It's
6274	beyond the scope of this list to explain the details, but you
6275	can see how this works by studying the cache architecture and
6276	operation in the architecture and processor-specific manuals.
6277
6278	OCM is On Chip Memory, which I believe the 405GP has 4K. It
6279	is another option for the system designer to use as an
6280	initial stack/RAM area prior to SDRAM being available. Either
6281	option should work for you. Using CS 4 should be fine if your
6282	board designers haven't used it for something that would
6283	cause you grief during the initial boot! It is frequently not
6284	used.
6285
6286	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
6287	with your processor/board/system design. The default value
6288	you will find in any recent u-boot distribution in
6289	walnut.h should work for you. I'd set it to a value larger
6290	than your SDRAM module. If you have a 64MB SDRAM module, set
6291	it above 400_0000. Just make sure your board has no resources
6292	that are supposed to respond to that address! That code in
6293	start.S has been around a while and should work as is when
6294	you get the config right.
6295
6296	-Chris Hallinan
6297	DS4.COM, Inc.
6298
6299It is essential to remember this, since it has some impact on the C
6300code for the initialization procedures:
6301
6302* Initialized global data (data segment) is read-only. Do not attempt
6303  to write it.
6304
6305* Do not use any uninitialized global data (or implicitly initialized
6306  as zero data - BSS segment) at all - this is undefined, initiali-
6307  zation is performed later (when relocating to RAM).
6308
6309* Stack space is very limited. Avoid big data buffers or things like
6310  that.
6311
6312Having only the stack as writable memory limits means we cannot use
6313normal global data to share information between the code. But it
6314turned out that the implementation of U-Boot can be greatly
6315simplified by making a global data structure (gd_t) available to all
6316functions. We could pass a pointer to this data as argument to _all_
6317functions, but this would bloat the code. Instead we use a feature of
6318the GCC compiler (Global Register Variables) to share the data: we
6319place a pointer (gd) to the global data into a register which we
6320reserve for this purpose.
6321
6322When choosing a register for such a purpose we are restricted by the
6323relevant  (E)ABI  specifications for the current architecture, and by
6324GCC's implementation.
6325
6326For PowerPC, the following registers have specific use:
6327	R1:	stack pointer
6328	R2:	reserved for system use
6329	R3-R4:	parameter passing and return values
6330	R5-R10: parameter passing
6331	R13:	small data area pointer
6332	R30:	GOT pointer
6333	R31:	frame pointer
6334
6335	(U-Boot also uses R12 as internal GOT pointer. r12
6336	is a volatile register so r12 needs to be reset when
6337	going back and forth between asm and C)
6338
6339    ==> U-Boot will use R2 to hold a pointer to the global data
6340
6341    Note: on PPC, we could use a static initializer (since the
6342    address of the global data structure is known at compile time),
6343    but it turned out that reserving a register results in somewhat
6344    smaller code - although the code savings are not that big (on
6345    average for all boards 752 bytes for the whole U-Boot image,
6346    624 text + 127 data).
6347
6348On Blackfin, the normal C ABI (except for P3) is followed as documented here:
6349	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
6350
6351    ==> U-Boot will use P3 to hold a pointer to the global data
6352
6353On ARM, the following registers are used:
6354
6355	R0:	function argument word/integer result
6356	R1-R3:	function argument word
6357	R9:	platform specific
6358	R10:	stack limit (used only if stack checking is enabled)
6359	R11:	argument (frame) pointer
6360	R12:	temporary workspace
6361	R13:	stack pointer
6362	R14:	link register
6363	R15:	program counter
6364
6365    ==> U-Boot will use R9 to hold a pointer to the global data
6366
6367    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
6368
6369On Nios II, the ABI is documented here:
6370	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
6371
6372    ==> U-Boot will use gp to hold a pointer to the global data
6373
6374    Note: on Nios II, we give "-G0" option to gcc and don't use gp
6375    to access small data sections, so gp is free.
6376
6377On NDS32, the following registers are used:
6378
6379	R0-R1:	argument/return
6380	R2-R5:	argument
6381	R15:	temporary register for assembler
6382	R16:	trampoline register
6383	R28:	frame pointer (FP)
6384	R29:	global pointer (GP)
6385	R30:	link register (LP)
6386	R31:	stack pointer (SP)
6387	PC:	program counter (PC)
6388
6389    ==> U-Boot will use R10 to hold a pointer to the global data
6390
6391NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
6392or current versions of GCC may "optimize" the code too much.
6393
6394Memory Management:
6395------------------
6396
6397U-Boot runs in system state and uses physical addresses, i.e. the
6398MMU is not used either for address mapping nor for memory protection.
6399
6400The available memory is mapped to fixed addresses using the memory
6401controller. In this process, a contiguous block is formed for each
6402memory type (Flash, SDRAM, SRAM), even when it consists of several
6403physical memory banks.
6404
6405U-Boot is installed in the first 128 kB of the first Flash bank (on
6406TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
6407booting and sizing and initializing DRAM, the code relocates itself
6408to the upper end of DRAM. Immediately below the U-Boot code some
6409memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
6410configuration setting]. Below that, a structure with global Board
6411Info data is placed, followed by the stack (growing downward).
6412
6413Additionally, some exception handler code is copied to the low 8 kB
6414of DRAM (0x00000000 ... 0x00001FFF).
6415
6416So a typical memory configuration with 16 MB of DRAM could look like
6417this:
6418
6419	0x0000 0000	Exception Vector code
6420	      :
6421	0x0000 1FFF
6422	0x0000 2000	Free for Application Use
6423	      :
6424	      :
6425
6426	      :
6427	      :
6428	0x00FB FF20	Monitor Stack (Growing downward)
6429	0x00FB FFAC	Board Info Data and permanent copy of global data
6430	0x00FC 0000	Malloc Arena
6431	      :
6432	0x00FD FFFF
6433	0x00FE 0000	RAM Copy of Monitor Code
6434	...		eventually: LCD or video framebuffer
6435	...		eventually: pRAM (Protected RAM - unchanged by reset)
6436	0x00FF FFFF	[End of RAM]
6437
6438
6439System Initialization:
6440----------------------
6441
6442In the reset configuration, U-Boot starts at the reset entry point
6443(on most PowerPC systems at address 0x00000100). Because of the reset
6444configuration for CS0# this is a mirror of the on board Flash memory.
6445To be able to re-map memory U-Boot then jumps to its link address.
6446To be able to implement the initialization code in C, a (small!)
6447initial stack is set up in the internal Dual Ported RAM (in case CPUs
6448which provide such a feature like MPC8xx or MPC8260), or in a locked
6449part of the data cache. After that, U-Boot initializes the CPU core,
6450the caches and the SIU.
6451
6452Next, all (potentially) available memory banks are mapped using a
6453preliminary mapping. For example, we put them on 512 MB boundaries
6454(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
6455on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
6456programmed for SDRAM access. Using the temporary configuration, a
6457simple memory test is run that determines the size of the SDRAM
6458banks.
6459
6460When there is more than one SDRAM bank, and the banks are of
6461different size, the largest is mapped first. For equal size, the first
6462bank (CS2#) is mapped first. The first mapping is always for address
64630x00000000, with any additional banks following immediately to create
6464contiguous memory starting from 0.
6465
6466Then, the monitor installs itself at the upper end of the SDRAM area
6467and allocates memory for use by malloc() and for the global Board
6468Info data; also, the exception vector code is copied to the low RAM
6469pages, and the final stack is set up.
6470
6471Only after this relocation will you have a "normal" C environment;
6472until that you are restricted in several ways, mostly because you are
6473running from ROM, and because the code will have to be relocated to a
6474new address in RAM.
6475
6476
6477U-Boot Porting Guide:
6478----------------------
6479
6480[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
6481list, October 2002]
6482
6483
6484int main(int argc, char *argv[])
6485{
6486	sighandler_t no_more_time;
6487
6488	signal(SIGALRM, no_more_time);
6489	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
6490
6491	if (available_money > available_manpower) {
6492		Pay consultant to port U-Boot;
6493		return 0;
6494	}
6495
6496	Download latest U-Boot source;
6497
6498	Subscribe to u-boot mailing list;
6499
6500	if (clueless)
6501		email("Hi, I am new to U-Boot, how do I get started?");
6502
6503	while (learning) {
6504		Read the README file in the top level directory;
6505		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
6506		Read applicable doc/*.README;
6507		Read the source, Luke;
6508		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
6509	}
6510
6511	if (available_money > toLocalCurrency ($2500))
6512		Buy a BDI3000;
6513	else
6514		Add a lot of aggravation and time;
6515
6516	if (a similar board exists) {	/* hopefully... */
6517		cp -a board/<similar> board/<myboard>
6518		cp include/configs/<similar>.h include/configs/<myboard>.h
6519	} else {
6520		Create your own board support subdirectory;
6521		Create your own board include/configs/<myboard>.h file;
6522	}
6523	Edit new board/<myboard> files
6524	Edit new include/configs/<myboard>.h
6525
6526	while (!accepted) {
6527		while (!running) {
6528			do {
6529				Add / modify source code;
6530			} until (compiles);
6531			Debug;
6532			if (clueless)
6533				email("Hi, I am having problems...");
6534		}
6535		Send patch file to the U-Boot email list;
6536		if (reasonable critiques)
6537			Incorporate improvements from email list code review;
6538		else
6539			Defend code as written;
6540	}
6541
6542	return 0;
6543}
6544
6545void no_more_time (int sig)
6546{
6547      hire_a_guru();
6548}
6549
6550
6551Coding Standards:
6552-----------------
6553
6554All contributions to U-Boot should conform to the Linux kernel
6555coding style; see the file "Documentation/CodingStyle" and the script
6556"scripts/Lindent" in your Linux kernel source directory.
6557
6558Source files originating from a different project (for example the
6559MTD subsystem) are generally exempt from these guidelines and are not
6560reformatted to ease subsequent migration to newer versions of those
6561sources.
6562
6563Please note that U-Boot is implemented in C (and to some small parts in
6564Assembler); no C++ is used, so please do not use C++ style comments (//)
6565in your code.
6566
6567Please also stick to the following formatting rules:
6568- remove any trailing white space
6569- use TAB characters for indentation and vertical alignment, not spaces
6570- make sure NOT to use DOS '\r\n' line feeds
6571- do not add more than 2 consecutive empty lines to source files
6572- do not add trailing empty lines to source files
6573
6574Submissions which do not conform to the standards may be returned
6575with a request to reformat the changes.
6576
6577
6578Submitting Patches:
6579-------------------
6580
6581Since the number of patches for U-Boot is growing, we need to
6582establish some rules. Submissions which do not conform to these rules
6583may be rejected, even when they contain important and valuable stuff.
6584
6585Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6586
6587Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6588see http://lists.denx.de/mailman/listinfo/u-boot
6589
6590When you send a patch, please include the following information with
6591it:
6592
6593* For bug fixes: a description of the bug and how your patch fixes
6594  this bug. Please try to include a way of demonstrating that the
6595  patch actually fixes something.
6596
6597* For new features: a description of the feature and your
6598  implementation.
6599
6600* A CHANGELOG entry as plaintext (separate from the patch)
6601
6602* For major contributions, your entry to the CREDITS file
6603
6604* When you add support for a new board, don't forget to add a
6605  maintainer e-mail address to the boards.cfg file, too.
6606
6607* If your patch adds new configuration options, don't forget to
6608  document these in the README file.
6609
6610* The patch itself. If you are using git (which is *strongly*
6611  recommended) you can easily generate the patch using the
6612  "git format-patch". If you then use "git send-email" to send it to
6613  the U-Boot mailing list, you will avoid most of the common problems
6614  with some other mail clients.
6615
6616  If you cannot use git, use "diff -purN OLD NEW". If your version of
6617  diff does not support these options, then get the latest version of
6618  GNU diff.
6619
6620  The current directory when running this command shall be the parent
6621  directory of the U-Boot source tree (i. e. please make sure that
6622  your patch includes sufficient directory information for the
6623  affected files).
6624
6625  We prefer patches as plain text. MIME attachments are discouraged,
6626  and compressed attachments must not be used.
6627
6628* If one logical set of modifications affects or creates several
6629  files, all these changes shall be submitted in a SINGLE patch file.
6630
6631* Changesets that contain different, unrelated modifications shall be
6632  submitted as SEPARATE patches, one patch per changeset.
6633
6634
6635Notes:
6636
6637* Before sending the patch, run the MAKEALL script on your patched
6638  source tree and make sure that no errors or warnings are reported
6639  for any of the boards.
6640
6641* Keep your modifications to the necessary minimum: A patch
6642  containing several unrelated changes or arbitrary reformats will be
6643  returned with a request to re-formatting / split it.
6644
6645* If you modify existing code, make sure that your new code does not
6646  add to the memory footprint of the code ;-) Small is beautiful!
6647  When adding new features, these should compile conditionally only
6648  (using #ifdef), and the resulting code with the new feature
6649  disabled must not need more memory than the old code without your
6650  modification.
6651
6652* Remember that there is a size limit of 100 kB per message on the
6653  u-boot mailing list. Bigger patches will be moderated. If they are
6654  reasonable and not too big, they will be acknowledged. But patches
6655  bigger than the size limit should be avoided.
6656