xref: /openbmc/u-boot/README (revision c0dcece7)
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 MAINTAINERS file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arm			Files generic to ARM architecture
136    /cpu		CPU specific files
137      /arm720t		Files specific to ARM 720 CPUs
138      /arm920t		Files specific to ARM 920 CPUs
139	/at91		Files specific to Atmel AT91RM9200 CPU
140	/imx		Files specific to Freescale MC9328 i.MX CPUs
141	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
142      /arm925t		Files specific to ARM 925 CPUs
143      /arm926ejs	Files specific to ARM 926 CPUs
144      /arm1136		Files specific to ARM 1136 CPUs
145      /ixp		Files specific to Intel XScale IXP CPUs
146      /pxa		Files specific to Intel XScale PXA CPUs
147      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
148      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
149    /lib		Architecture specific library files
150  /avr32		Files generic to AVR32 architecture
151    /cpu		CPU specific files
152    /lib		Architecture specific library files
153  /blackfin		Files generic to Analog Devices Blackfin architecture
154    /cpu		CPU specific files
155    /lib		Architecture specific library files
156  /x86			Files generic to x86 architecture
157    /cpu		CPU specific files
158    /lib		Architecture specific library files
159  /m68k			Files generic to m68k architecture
160    /cpu		CPU specific files
161      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
162      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
163      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
164      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
165      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
166    /lib		Architecture specific library files
167  /microblaze		Files generic to microblaze architecture
168    /cpu		CPU specific files
169    /lib		Architecture specific library files
170  /mips			Files generic to MIPS architecture
171    /cpu		CPU specific files
172      /mips32		Files specific to MIPS32 CPUs
173      /xburst		Files specific to Ingenic XBurst CPUs
174    /lib		Architecture specific library files
175  /nds32		Files generic to NDS32 architecture
176    /cpu		CPU specific files
177      /n1213		Files specific to Andes Technology N1213 CPUs
178    /lib		Architecture specific library files
179  /nios2		Files generic to Altera NIOS2 architecture
180    /cpu		CPU specific files
181    /lib		Architecture specific library files
182  /powerpc		Files generic to PowerPC architecture
183    /cpu		CPU specific files
184      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
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      /mpc824x		Files specific to Freescale MPC824x CPUs
189      /mpc8260		Files specific to Freescale MPC8260 CPUs
190      /mpc85xx		Files specific to Freescale MPC85xx CPUs
191      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
192    /lib		Architecture specific library files
193  /sh			Files generic to SH architecture
194    /cpu		CPU specific files
195      /sh2		Files specific to sh2 CPUs
196      /sh3		Files specific to sh3 CPUs
197      /sh4		Files specific to sh4 CPUs
198    /lib		Architecture specific library files
199  /sparc		Files generic to SPARC architecture
200    /cpu		CPU specific files
201      /leon2		Files specific to Gaisler LEON2 SPARC CPU
202      /leon3		Files specific to Gaisler LEON3 SPARC CPU
203    /lib		Architecture specific library files
204/api			Machine/arch independent API for external apps
205/board			Board dependent files
206/common			Misc architecture independent functions
207/disk			Code for disk drive partition handling
208/doc			Documentation (don't expect too much)
209/drivers		Commonly used device drivers
210/examples		Example code for standalone applications, etc.
211/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
212/include		Header Files
213/lib			Files generic to all architectures
214  /libfdt		Library files to support flattened device trees
215  /lzma			Library files to support LZMA decompression
216  /lzo			Library files to support LZO decompression
217/net			Networking code
218/post			Power On Self Test
219/rtc			Real Time Clock drivers
220/tools			Tools to build S-Record or U-Boot images, etc.
221
222Software Configuration:
223=======================
224
225Configuration is usually done using C preprocessor defines; the
226rationale behind that is to avoid dead code whenever possible.
227
228There are two classes of configuration variables:
229
230* Configuration _OPTIONS_:
231  These are selectable by the user and have names beginning with
232  "CONFIG_".
233
234* Configuration _SETTINGS_:
235  These depend on the hardware etc. and should not be meddled with if
236  you don't know what you're doing; they have names beginning with
237  "CONFIG_SYS_".
238
239Later we will add a configuration tool - probably similar to or even
240identical to what's used for the Linux kernel. Right now, we have to
241do the configuration by hand, which means creating some symbolic
242links and editing some configuration files. We use the TQM8xxL boards
243as an example here.
244
245
246Selection of Processor Architecture and Board Type:
247---------------------------------------------------
248
249For all supported boards there are ready-to-use default
250configurations available; just type "make <board_name>_config".
251
252Example: For a TQM823L module type:
253
254	cd u-boot
255	make TQM823L_config
256
257For the Cogent platform, you need to specify the CPU type as well;
258e.g. "make cogent_mpc8xx_config". And also configure the cogent
259directory according to the instructions in cogent/README.
260
261
262Configuration Options:
263----------------------
264
265Configuration depends on the combination of board and CPU type; all
266such information is kept in a configuration file
267"include/configs/<board_name>.h".
268
269Example: For a TQM823L module, all configuration settings are in
270"include/configs/TQM823L.h".
271
272
273Many of the options are named exactly as the corresponding Linux
274kernel configuration options. The intention is to make it easier to
275build a config tool - later.
276
277
278The following options need to be configured:
279
280- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
281
282- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
283
284- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
285		Define exactly one, e.g. CONFIG_ATSTK1002
286
287- CPU Module Type: (if CONFIG_COGENT is defined)
288		Define exactly one of
289		CONFIG_CMA286_60_OLD
290--- FIXME --- not tested yet:
291		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
292		CONFIG_CMA287_23, CONFIG_CMA287_50
293
294- Motherboard Type: (if CONFIG_COGENT is defined)
295		Define exactly one of
296		CONFIG_CMA101, CONFIG_CMA102
297
298- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
299		Define one or more of
300		CONFIG_CMA302
301
302- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
303		Define one or more of
304		CONFIG_LCD_HEARTBEAT	- update a character position on
305					  the LCD display every second with
306					  a "rotator" |\-/|\-/
307
308- Board flavour: (if CONFIG_MPC8260ADS is defined)
309		CONFIG_ADSTYPE
310		Possible values are:
311			CONFIG_SYS_8260ADS	- original MPC8260ADS
312			CONFIG_SYS_8266ADS	- MPC8266ADS
313			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
314			CONFIG_SYS_8272ADS	- MPC8272ADS
315
316- Marvell Family Member
317		CONFIG_SYS_MVFS		- define it if you want to enable
318					  multiple fs option at one time
319					  for marvell soc family
320
321- MPC824X Family Member (if CONFIG_MPC824X is defined)
322		Define exactly one of
323		CONFIG_MPC8240, CONFIG_MPC8245
324
325- 8xx CPU Options: (if using an MPC8xx CPU)
326		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
327					  get_gclk_freq() cannot work
328					  e.g. if there is no 32KHz
329					  reference PIT/RTC clock
330		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
331					  or XTAL/EXTAL)
332
333- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
334		CONFIG_SYS_8xx_CPUCLK_MIN
335		CONFIG_SYS_8xx_CPUCLK_MAX
336		CONFIG_8xx_CPUCLK_DEFAULT
337			See doc/README.MPC866
338
339		CONFIG_SYS_MEASURE_CPUCLK
340
341		Define this to measure the actual CPU clock instead
342		of relying on the correctness of the configured
343		values. Mostly useful for board bringup to make sure
344		the PLL is locked at the intended frequency. Note
345		that this requires a (stable) reference clock (32 kHz
346		RTC clock or CONFIG_SYS_8XX_XIN)
347
348		CONFIG_SYS_DELAYED_ICACHE
349
350		Define this option if you want to enable the
351		ICache only when Code runs from RAM.
352
353- 85xx CPU Options:
354		CONFIG_SYS_PPC64
355
356		Specifies that the core is a 64-bit PowerPC implementation (implements
357		the "64" category of the Power ISA). This is necessary for ePAPR
358		compliance, among other possible reasons.
359
360		CONFIG_SYS_FSL_TBCLK_DIV
361
362		Defines the core time base clock divider ratio compared to the
363		system clock.  On most PQ3 devices this is 8, on newer QorIQ
364		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
365
366		CONFIG_SYS_FSL_PCIE_COMPAT
367
368		Defines the string to utilize when trying to match PCIe device
369		tree nodes for the given platform.
370
371		CONFIG_SYS_PPC_E500_DEBUG_TLB
372
373		Enables a temporary TLB entry to be used during boot to work
374		around limitations in e500v1 and e500v2 external debugger
375		support. This reduces the portions of the boot code where
376		breakpoints and single stepping do not work.  The value of this
377		symbol should be set to the TLB1 entry to be used for this
378		purpose.
379
380		CONFIG_SYS_FSL_ERRATUM_A004510
381
382		Enables a workaround for erratum A004510.  If set,
383		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
384		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
385
386		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
387		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
388
389		Defines one or two SoC revisions (low 8 bits of SVR)
390		for which the A004510 workaround should be applied.
391
392		The rest of SVR is either not relevant to the decision
393		of whether the erratum is present (e.g. p2040 versus
394		p2041) or is implied by the build target, which controls
395		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
396
397		See Freescale App Note 4493 for more information about
398		this erratum.
399
400		CONFIG_A003399_NOR_WORKAROUND
401		Enables a workaround for IFC erratum A003399. It is only
402		requred during NOR boot.
403
404		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
405
406		This is the value to write into CCSR offset 0x18600
407		according to the A004510 workaround.
408
409		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
410		This value denotes start offset of M2 memory
411		which is directly connected to the DSP core.
412
413		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
414		This value denotes start offset of DSP CCSR space.
415
416- Generic CPU options:
417		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
418
419		Defines the endianess of the CPU. Implementation of those
420		values is arch specific.
421
422- Intel Monahans options:
423		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
424
425		Defines the Monahans run mode to oscillator
426		ratio. Valid values are 8, 16, 24, 31. The core
427		frequency is this value multiplied by 13 MHz.
428
429		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
430
431		Defines the Monahans turbo mode to oscillator
432		ratio. Valid values are 1 (default if undefined) and
433		2. The core frequency as calculated above is multiplied
434		by this value.
435
436- MIPS CPU options:
437		CONFIG_SYS_INIT_SP_OFFSET
438
439		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
440		pointer. This is needed for the temporary stack before
441		relocation.
442
443		CONFIG_SYS_MIPS_CACHE_MODE
444
445		Cache operation mode for the MIPS CPU.
446		See also arch/mips/include/asm/mipsregs.h.
447		Possible values are:
448			CONF_CM_CACHABLE_NO_WA
449			CONF_CM_CACHABLE_WA
450			CONF_CM_UNCACHED
451			CONF_CM_CACHABLE_NONCOHERENT
452			CONF_CM_CACHABLE_CE
453			CONF_CM_CACHABLE_COW
454			CONF_CM_CACHABLE_CUW
455			CONF_CM_CACHABLE_ACCELERATED
456
457		CONFIG_SYS_XWAY_EBU_BOOTCFG
458
459		Special option for Lantiq XWAY SoCs for booting from NOR flash.
460		See also arch/mips/cpu/mips32/start.S.
461
462		CONFIG_XWAY_SWAP_BYTES
463
464		Enable compilation of tools/xway-swap-bytes needed for Lantiq
465		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
466		be swapped if a flash programmer is used.
467
468- ARM options:
469		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
470
471		Select high exception vectors of the ARM core, e.g., do not
472		clear the V bit of the c1 register of CP15.
473
474		CONFIG_SYS_THUMB_BUILD
475
476		Use this flag to build U-Boot using the Thumb instruction
477		set for ARM architectures. Thumb instruction set provides
478		better code density. For ARM architectures that support
479		Thumb2 this flag will result in Thumb2 code generated by
480		GCC.
481
482		CONFIG_ARM_ERRATA_716044
483		CONFIG_ARM_ERRATA_742230
484		CONFIG_ARM_ERRATA_743622
485		CONFIG_ARM_ERRATA_751472
486
487		If set, the workarounds for these ARM errata are applied early
488		during U-Boot startup. Note that these options force the
489		workarounds to be applied; no CPU-type/version detection
490		exists, unlike the similar options in the Linux kernel. Do not
491		set these options unless they apply!
492
493- CPU timer options:
494		CONFIG_SYS_HZ
495
496		The frequency of the timer returned by get_timer().
497		get_timer() must operate in milliseconds and this CONFIG
498		option must be set to 1000.
499
500- Linux Kernel Interface:
501		CONFIG_CLOCKS_IN_MHZ
502
503		U-Boot stores all clock information in Hz
504		internally. For binary compatibility with older Linux
505		kernels (which expect the clocks passed in the
506		bd_info data to be in MHz) the environment variable
507		"clocks_in_mhz" can be defined so that U-Boot
508		converts clock data to MHZ before passing it to the
509		Linux kernel.
510		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
511		"clocks_in_mhz=1" is automatically included in the
512		default environment.
513
514		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
515
516		When transferring memsize parameter to linux, some versions
517		expect it to be in bytes, others in MB.
518		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
519
520		CONFIG_OF_LIBFDT
521
522		New kernel versions are expecting firmware settings to be
523		passed using flattened device trees (based on open firmware
524		concepts).
525
526		CONFIG_OF_LIBFDT
527		 * New libfdt-based support
528		 * Adds the "fdt" command
529		 * The bootm command automatically updates the fdt
530
531		OF_CPU - The proper name of the cpus node (only required for
532			MPC512X and MPC5xxx based boards).
533		OF_SOC - The proper name of the soc node (only required for
534			MPC512X and MPC5xxx based boards).
535		OF_TBCLK - The timebase frequency.
536		OF_STDOUT_PATH - The path to the console device
537
538		boards with QUICC Engines require OF_QE to set UCC MAC
539		addresses
540
541		CONFIG_OF_BOARD_SETUP
542
543		Board code has addition modification that it wants to make
544		to the flat device tree before handing it off to the kernel
545
546		CONFIG_OF_BOOT_CPU
547
548		This define fills in the correct boot CPU in the boot
549		param header, the default value is zero if undefined.
550
551		CONFIG_OF_IDE_FIXUP
552
553		U-Boot can detect if an IDE device is present or not.
554		If not, and this new config option is activated, U-Boot
555		removes the ATA node from the DTS before booting Linux,
556		so the Linux IDE driver does not probe the device and
557		crash. This is needed for buggy hardware (uc101) where
558		no pull down resistor is connected to the signal IDE5V_DD7.
559
560		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
561
562		This setting is mandatory for all boards that have only one
563		machine type and must be used to specify the machine type
564		number as it appears in the ARM machine registry
565		(see http://www.arm.linux.org.uk/developer/machines/).
566		Only boards that have multiple machine types supported
567		in a single configuration file and the machine type is
568		runtime discoverable, do not have to use this setting.
569
570- vxWorks boot parameters:
571
572		bootvx constructs a valid bootline using the following
573		environments variables: bootfile, ipaddr, serverip, hostname.
574		It loads the vxWorks image pointed bootfile.
575
576		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
577		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
578		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
579		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
580
581		CONFIG_SYS_VXWORKS_ADD_PARAMS
582
583		Add it at the end of the bootline. E.g "u=username pw=secret"
584
585		Note: If a "bootargs" environment is defined, it will overwride
586		the defaults discussed just above.
587
588- Cache Configuration:
589		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
590		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
591		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
592
593- Cache Configuration for ARM:
594		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
595				      controller
596		CONFIG_SYS_PL310_BASE - Physical base address of PL310
597					controller register space
598
599- Serial Ports:
600		CONFIG_PL010_SERIAL
601
602		Define this if you want support for Amba PrimeCell PL010 UARTs.
603
604		CONFIG_PL011_SERIAL
605
606		Define this if you want support for Amba PrimeCell PL011 UARTs.
607
608		CONFIG_PL011_CLOCK
609
610		If you have Amba PrimeCell PL011 UARTs, set this variable to
611		the clock speed of the UARTs.
612
613		CONFIG_PL01x_PORTS
614
615		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
616		define this to a list of base addresses for each (supported)
617		port. See e.g. include/configs/versatile.h
618
619		CONFIG_PL011_SERIAL_RLCR
620
621		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
622		have separate receive and transmit line control registers.  Set
623		this variable to initialize the extra register.
624
625		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
626
627		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
628		boot loader that has already initialized the UART.  Define this
629		variable to flush the UART at init time.
630
631
632- Console Interface:
633		Depending on board, define exactly one serial port
634		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
635		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
636		console by defining CONFIG_8xx_CONS_NONE
637
638		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
639		port routines must be defined elsewhere
640		(i.e. serial_init(), serial_getc(), ...)
641
642		CONFIG_CFB_CONSOLE
643		Enables console device for a color framebuffer. Needs following
644		defines (cf. smiLynxEM, i8042)
645			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
646						(default big endian)
647			VIDEO_HW_RECTFILL	graphic chip supports
648						rectangle fill
649						(cf. smiLynxEM)
650			VIDEO_HW_BITBLT		graphic chip supports
651						bit-blit (cf. smiLynxEM)
652			VIDEO_VISIBLE_COLS	visible pixel columns
653						(cols=pitch)
654			VIDEO_VISIBLE_ROWS	visible pixel rows
655			VIDEO_PIXEL_SIZE	bytes per pixel
656			VIDEO_DATA_FORMAT	graphic data format
657						(0-5, cf. cfb_console.c)
658			VIDEO_FB_ADRS		framebuffer address
659			VIDEO_KBD_INIT_FCT	keyboard int fct
660						(i.e. i8042_kbd_init())
661			VIDEO_TSTC_FCT		test char fct
662						(i.e. i8042_tstc)
663			VIDEO_GETC_FCT		get char fct
664						(i.e. i8042_getc)
665			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
666						(requires blink timer
667						cf. i8042.c)
668			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
669			CONFIG_CONSOLE_TIME	display time/date info in
670						upper right corner
671						(requires CONFIG_CMD_DATE)
672			CONFIG_VIDEO_LOGO	display Linux logo in
673						upper left corner
674			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
675						linux_logo.h for logo.
676						Requires CONFIG_VIDEO_LOGO
677			CONFIG_CONSOLE_EXTRA_INFO
678						additional board info beside
679						the logo
680
681		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
682		a limited number of ANSI escape sequences (cursor control,
683		erase functions and limited graphics rendition control).
684
685		When CONFIG_CFB_CONSOLE is defined, video console is
686		default i/o. Serial console can be forced with
687		environment 'console=serial'.
688
689		When CONFIG_SILENT_CONSOLE is defined, all console
690		messages (by U-Boot and Linux!) can be silenced with
691		the "silent" environment variable. See
692		doc/README.silent for more information.
693
694- Console Baudrate:
695		CONFIG_BAUDRATE - in bps
696		Select one of the baudrates listed in
697		CONFIG_SYS_BAUDRATE_TABLE, see below.
698		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
699
700- Console Rx buffer length
701		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
702		the maximum receive buffer length for the SMC.
703		This option is actual only for 82xx and 8xx possible.
704		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
705		must be defined, to setup the maximum idle timeout for
706		the SMC.
707
708- Pre-Console Buffer:
709		Prior to the console being initialised (i.e. serial UART
710		initialised etc) all console output is silently discarded.
711		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
712		buffer any console messages prior to the console being
713		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
714		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
715		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
716		bytes are output before the console is initialised, the
717		earlier bytes are discarded.
718
719		'Sane' compilers will generate smaller code if
720		CONFIG_PRE_CON_BUF_SZ is a power of 2
721
722- Safe printf() functions
723		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
724		the printf() functions. These are defined in
725		include/vsprintf.h and include snprintf(), vsnprintf() and
726		so on. Code size increase is approximately 300-500 bytes.
727		If this option is not given then these functions will
728		silently discard their buffer size argument - this means
729		you are not getting any overflow checking in this case.
730
731- Boot Delay:	CONFIG_BOOTDELAY - in seconds
732		Delay before automatically booting the default image;
733		set to -1 to disable autoboot.
734		set to -2 to autoboot with no delay and not check for abort
735		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
736
737		See doc/README.autoboot for these options that
738		work with CONFIG_BOOTDELAY. None are required.
739		CONFIG_BOOT_RETRY_TIME
740		CONFIG_BOOT_RETRY_MIN
741		CONFIG_AUTOBOOT_KEYED
742		CONFIG_AUTOBOOT_PROMPT
743		CONFIG_AUTOBOOT_DELAY_STR
744		CONFIG_AUTOBOOT_STOP_STR
745		CONFIG_AUTOBOOT_DELAY_STR2
746		CONFIG_AUTOBOOT_STOP_STR2
747		CONFIG_ZERO_BOOTDELAY_CHECK
748		CONFIG_RESET_TO_RETRY
749
750- Autoboot Command:
751		CONFIG_BOOTCOMMAND
752		Only needed when CONFIG_BOOTDELAY is enabled;
753		define a command string that is automatically executed
754		when no character is read on the console interface
755		within "Boot Delay" after reset.
756
757		CONFIG_BOOTARGS
758		This can be used to pass arguments to the bootm
759		command. The value of CONFIG_BOOTARGS goes into the
760		environment value "bootargs".
761
762		CONFIG_RAMBOOT and CONFIG_NFSBOOT
763		The value of these goes into the environment as
764		"ramboot" and "nfsboot" respectively, and can be used
765		as a convenience, when switching between booting from
766		RAM and NFS.
767
768- Pre-Boot Commands:
769		CONFIG_PREBOOT
770
771		When this option is #defined, the existence of the
772		environment variable "preboot" will be checked
773		immediately before starting the CONFIG_BOOTDELAY
774		countdown and/or running the auto-boot command resp.
775		entering interactive mode.
776
777		This feature is especially useful when "preboot" is
778		automatically generated or modified. For an example
779		see the LWMON board specific code: here "preboot" is
780		modified when the user holds down a certain
781		combination of keys on the (special) keyboard when
782		booting the systems
783
784- Serial Download Echo Mode:
785		CONFIG_LOADS_ECHO
786		If defined to 1, all characters received during a
787		serial download (using the "loads" command) are
788		echoed back. This might be needed by some terminal
789		emulations (like "cu"), but may as well just take
790		time on others. This setting #define's the initial
791		value of the "loads_echo" environment variable.
792
793- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
794		CONFIG_KGDB_BAUDRATE
795		Select one of the baudrates listed in
796		CONFIG_SYS_BAUDRATE_TABLE, see below.
797
798- Monitor Functions:
799		Monitor commands can be included or excluded
800		from the build by using the #include files
801		<config_cmd_all.h> and #undef'ing unwanted
802		commands, or using <config_cmd_default.h>
803		and augmenting with additional #define's
804		for wanted commands.
805
806		The default command configuration includes all commands
807		except those marked below with a "*".
808
809		CONFIG_CMD_ASKENV	* ask for env variable
810		CONFIG_CMD_BDI		  bdinfo
811		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
812		CONFIG_CMD_BMP		* BMP support
813		CONFIG_CMD_BSP		* Board specific commands
814		CONFIG_CMD_BOOTD	  bootd
815		CONFIG_CMD_CACHE	* icache, dcache
816		CONFIG_CMD_CONSOLE	  coninfo
817		CONFIG_CMD_CRC32	* crc32
818		CONFIG_CMD_DATE		* support for RTC, date/time...
819		CONFIG_CMD_DHCP		* DHCP support
820		CONFIG_CMD_DIAG		* Diagnostics
821		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
822		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
823		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
824		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
825		CONFIG_CMD_DTT		* Digital Therm and Thermostat
826		CONFIG_CMD_ECHO		  echo arguments
827		CONFIG_CMD_EDITENV	  edit env variable
828		CONFIG_CMD_EEPROM	* EEPROM read/write support
829		CONFIG_CMD_ELF		* bootelf, bootvx
830		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
831		CONFIG_CMD_ENV_FLAGS	* display details about env flags
832		CONFIG_CMD_EXPORTENV	* export the environment
833		CONFIG_CMD_EXT2		* ext2 command support
834		CONFIG_CMD_EXT4		* ext4 command support
835		CONFIG_CMD_SAVEENV	  saveenv
836		CONFIG_CMD_FDC		* Floppy Disk Support
837		CONFIG_CMD_FAT		* FAT command support
838		CONFIG_CMD_FDOS		* Dos diskette Support
839		CONFIG_CMD_FLASH	  flinfo, erase, protect
840		CONFIG_CMD_FPGA		  FPGA device initialization support
841		CONFIG_CMD_FUSE		* Device fuse support
842		CONFIG_CMD_GETTIME	* Get time since boot
843		CONFIG_CMD_GO		* the 'go' command (exec code)
844		CONFIG_CMD_GREPENV	* search environment
845		CONFIG_CMD_HASH		* calculate hash / digest
846		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
847		CONFIG_CMD_I2C		* I2C serial bus support
848		CONFIG_CMD_IDE		* IDE harddisk support
849		CONFIG_CMD_IMI		  iminfo
850		CONFIG_CMD_IMLS		  List all images found in NOR flash
851		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
852		CONFIG_CMD_IMMAP	* IMMR dump support
853		CONFIG_CMD_IMPORTENV	* import an environment
854		CONFIG_CMD_INI		* import data from an ini file into the env
855		CONFIG_CMD_IRQ		* irqinfo
856		CONFIG_CMD_ITEST	  Integer/string test of 2 values
857		CONFIG_CMD_JFFS2	* JFFS2 Support
858		CONFIG_CMD_KGDB		* kgdb
859		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
860		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
861					  (169.254.*.*)
862		CONFIG_CMD_LOADB	  loadb
863		CONFIG_CMD_LOADS	  loads
864		CONFIG_CMD_MD5SUM	* print md5 message digest
865					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
866		CONFIG_CMD_MEMINFO	* Display detailed memory information
867		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
868					  loop, loopw
869		CONFIG_CMD_MEMTEST	* mtest
870		CONFIG_CMD_MISC		  Misc functions like sleep etc
871		CONFIG_CMD_MMC		* MMC memory mapped support
872		CONFIG_CMD_MII		* MII utility commands
873		CONFIG_CMD_MTDPARTS	* MTD partition support
874		CONFIG_CMD_NAND		* NAND support
875		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
876		CONFIG_CMD_NFS		  NFS support
877		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
878		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
879		CONFIG_CMD_PCI		* pciinfo
880		CONFIG_CMD_PCMCIA		* PCMCIA support
881		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
882					  host
883		CONFIG_CMD_PORTIO	* Port I/O
884		CONFIG_CMD_READ		* Read raw data from partition
885		CONFIG_CMD_REGINFO	* Register dump
886		CONFIG_CMD_RUN		  run command in env variable
887		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
888		CONFIG_CMD_SAVES	* save S record dump
889		CONFIG_CMD_SCSI		* SCSI Support
890		CONFIG_CMD_SDRAM	* print SDRAM configuration information
891					  (requires CONFIG_CMD_I2C)
892		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
893					  (4xx only)
894		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
895		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
896					  (requires CONFIG_CMD_MEMORY)
897		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
898		CONFIG_CMD_SOURCE	  "source" command Support
899		CONFIG_CMD_SPI		* SPI serial bus support
900		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
901		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
902		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
903		CONFIG_CMD_TIMER	* access to the system tick timer
904		CONFIG_CMD_USB		* USB support
905		CONFIG_CMD_CDP		* Cisco Discover Protocol support
906		CONFIG_CMD_MFSL		* Microblaze FSL support
907		CONFIG_CMD_XIMG		  Load part of Multi Image
908
909
910		EXAMPLE: If you want all functions except of network
911		support you can write:
912
913		#include "config_cmd_all.h"
914		#undef CONFIG_CMD_NET
915
916	Other Commands:
917		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
918
919	Note:	Don't enable the "icache" and "dcache" commands
920		(configuration option CONFIG_CMD_CACHE) unless you know
921		what you (and your U-Boot users) are doing. Data
922		cache cannot be enabled on systems like the 8xx or
923		8260 (where accesses to the IMMR region must be
924		uncached), and it cannot be disabled on all other
925		systems where we (mis-) use the data cache to hold an
926		initial stack and some data.
927
928
929		XXX - this list needs to get updated!
930
931- Regular expression support:
932		CONFIG_REGEX
933                If this variable is defined, U-Boot is linked against
934                the SLRE (Super Light Regular Expression) library,
935                which adds regex support to some commands, as for
936                example "env grep" and "setexpr".
937
938- Device tree:
939		CONFIG_OF_CONTROL
940		If this variable is defined, U-Boot will use a device tree
941		to configure its devices, instead of relying on statically
942		compiled #defines in the board file. This option is
943		experimental and only available on a few boards. The device
944		tree is available in the global data as gd->fdt_blob.
945
946		U-Boot needs to get its device tree from somewhere. This can
947		be done using one of the two options below:
948
949		CONFIG_OF_EMBED
950		If this variable is defined, U-Boot will embed a device tree
951		binary in its image. This device tree file should be in the
952		board directory and called <soc>-<board>.dts. The binary file
953		is then picked up in board_init_f() and made available through
954		the global data structure as gd->blob.
955
956		CONFIG_OF_SEPARATE
957		If this variable is defined, U-Boot will build a device tree
958		binary. It will be called u-boot.dtb. Architecture-specific
959		code will locate it at run-time. Generally this works by:
960
961			cat u-boot.bin u-boot.dtb >image.bin
962
963		and in fact, U-Boot does this for you, creating a file called
964		u-boot-dtb.bin which is useful in the common case. You can
965		still use the individual files if you need something more
966		exotic.
967
968- Watchdog:
969		CONFIG_WATCHDOG
970		If this variable is defined, it enables watchdog
971		support for the SoC. There must be support in the SoC
972		specific code for a watchdog. For the 8xx and 8260
973		CPUs, the SIU Watchdog feature is enabled in the SYPCR
974		register.  When supported for a specific SoC is
975		available, then no further board specific code should
976		be needed to use it.
977
978		CONFIG_HW_WATCHDOG
979		When using a watchdog circuitry external to the used
980		SoC, then define this variable and provide board
981		specific code for the "hw_watchdog_reset" function.
982
983- U-Boot Version:
984		CONFIG_VERSION_VARIABLE
985		If this variable is defined, an environment variable
986		named "ver" is created by U-Boot showing the U-Boot
987		version as printed by the "version" command.
988		Any change to this variable will be reverted at the
989		next reset.
990
991- Real-Time Clock:
992
993		When CONFIG_CMD_DATE is selected, the type of the RTC
994		has to be selected, too. Define exactly one of the
995		following options:
996
997		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
998		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
999		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1000		CONFIG_RTC_MC146818	- use MC146818 RTC
1001		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1002		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1003		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1004		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1005		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1006		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1007		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1008		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1009					  RV3029 RTC.
1010
1011		Note that if the RTC uses I2C, then the I2C interface
1012		must also be configured. See I2C Support, below.
1013
1014- GPIO Support:
1015		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1016		CONFIG_PCA953X_INFO	- enable pca953x info command
1017
1018		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1019		chip-ngpio pairs that tell the PCA953X driver the number of
1020		pins supported by a particular chip.
1021
1022		Note that if the GPIO device uses I2C, then the I2C interface
1023		must also be configured. See I2C Support, below.
1024
1025- Timestamp Support:
1026
1027		When CONFIG_TIMESTAMP is selected, the timestamp
1028		(date and time) of an image is printed by image
1029		commands like bootm or iminfo. This option is
1030		automatically enabled when you select CONFIG_CMD_DATE .
1031
1032- Partition Labels (disklabels) Supported:
1033		Zero or more of the following:
1034		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1035		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1036				       Intel architecture, USB sticks, etc.
1037		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1038		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1039				       bootloader.  Note 2TB partition limit; see
1040				       disk/part_efi.c
1041		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1042
1043		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1044		CONFIG_CMD_SCSI) you must configure support for at
1045		least one non-MTD partition type as well.
1046
1047- IDE Reset method:
1048		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1049		board configurations files but used nowhere!
1050
1051		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1052		be performed by calling the function
1053			ide_set_reset(int reset)
1054		which has to be defined in a board specific file
1055
1056- ATAPI Support:
1057		CONFIG_ATAPI
1058
1059		Set this to enable ATAPI support.
1060
1061- LBA48 Support
1062		CONFIG_LBA48
1063
1064		Set this to enable support for disks larger than 137GB
1065		Also look at CONFIG_SYS_64BIT_LBA.
1066		Whithout these , LBA48 support uses 32bit variables and will 'only'
1067		support disks up to 2.1TB.
1068
1069		CONFIG_SYS_64BIT_LBA:
1070			When enabled, makes the IDE subsystem use 64bit sector addresses.
1071			Default is 32bit.
1072
1073- SCSI Support:
1074		At the moment only there is only support for the
1075		SYM53C8XX SCSI controller; define
1076		CONFIG_SCSI_SYM53C8XX to enable it.
1077
1078		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1079		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1080		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1081		maximum numbers of LUNs, SCSI ID's and target
1082		devices.
1083		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1084
1085                The environment variable 'scsidevs' is set to the number of
1086                SCSI devices found during the last scan.
1087
1088- NETWORK Support (PCI):
1089		CONFIG_E1000
1090		Support for Intel 8254x/8257x gigabit chips.
1091
1092		CONFIG_E1000_SPI
1093		Utility code for direct access to the SPI bus on Intel 8257x.
1094		This does not do anything useful unless you set at least one
1095		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1096
1097		CONFIG_E1000_SPI_GENERIC
1098		Allow generic access to the SPI bus on the Intel 8257x, for
1099		example with the "sspi" command.
1100
1101		CONFIG_CMD_E1000
1102		Management command for E1000 devices.  When used on devices
1103		with SPI support you can reprogram the EEPROM from U-Boot.
1104
1105		CONFIG_E1000_FALLBACK_MAC
1106		default MAC for empty EEPROM after production.
1107
1108		CONFIG_EEPRO100
1109		Support for Intel 82557/82559/82559ER chips.
1110		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1111		write routine for first time initialisation.
1112
1113		CONFIG_TULIP
1114		Support for Digital 2114x chips.
1115		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1116		modem chip initialisation (KS8761/QS6611).
1117
1118		CONFIG_NATSEMI
1119		Support for National dp83815 chips.
1120
1121		CONFIG_NS8382X
1122		Support for National dp8382[01] gigabit chips.
1123
1124- NETWORK Support (other):
1125
1126		CONFIG_DRIVER_AT91EMAC
1127		Support for AT91RM9200 EMAC.
1128
1129			CONFIG_RMII
1130			Define this to use reduced MII inteface
1131
1132			CONFIG_DRIVER_AT91EMAC_QUIET
1133			If this defined, the driver is quiet.
1134			The driver doen't show link status messages.
1135
1136		CONFIG_CALXEDA_XGMAC
1137		Support for the Calxeda XGMAC device
1138
1139		CONFIG_LAN91C96
1140		Support for SMSC's LAN91C96 chips.
1141
1142			CONFIG_LAN91C96_BASE
1143			Define this to hold the physical address
1144			of the LAN91C96's I/O space
1145
1146			CONFIG_LAN91C96_USE_32_BIT
1147			Define this to enable 32 bit addressing
1148
1149		CONFIG_SMC91111
1150		Support for SMSC's LAN91C111 chip
1151
1152			CONFIG_SMC91111_BASE
1153			Define this to hold the physical address
1154			of the device (I/O space)
1155
1156			CONFIG_SMC_USE_32_BIT
1157			Define this if data bus is 32 bits
1158
1159			CONFIG_SMC_USE_IOFUNCS
1160			Define this to use i/o functions instead of macros
1161			(some hardware wont work with macros)
1162
1163		CONFIG_DRIVER_TI_EMAC
1164		Support for davinci emac
1165
1166			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1167			Define this if you have more then 3 PHYs.
1168
1169		CONFIG_FTGMAC100
1170		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1171
1172			CONFIG_FTGMAC100_EGIGA
1173			Define this to use GE link update with gigabit PHY.
1174			Define this if FTGMAC100 is connected to gigabit PHY.
1175			If your system has 10/100 PHY only, it might not occur
1176			wrong behavior. Because PHY usually return timeout or
1177			useless data when polling gigabit status and gigabit
1178			control registers. This behavior won't affect the
1179			correctnessof 10/100 link speed update.
1180
1181		CONFIG_SMC911X
1182		Support for SMSC's LAN911x and LAN921x chips
1183
1184			CONFIG_SMC911X_BASE
1185			Define this to hold the physical address
1186			of the device (I/O space)
1187
1188			CONFIG_SMC911X_32_BIT
1189			Define this if data bus is 32 bits
1190
1191			CONFIG_SMC911X_16_BIT
1192			Define this if data bus is 16 bits. If your processor
1193			automatically converts one 32 bit word to two 16 bit
1194			words you may also try CONFIG_SMC911X_32_BIT.
1195
1196		CONFIG_SH_ETHER
1197		Support for Renesas on-chip Ethernet controller
1198
1199			CONFIG_SH_ETHER_USE_PORT
1200			Define the number of ports to be used
1201
1202			CONFIG_SH_ETHER_PHY_ADDR
1203			Define the ETH PHY's address
1204
1205			CONFIG_SH_ETHER_CACHE_WRITEBACK
1206			If this option is set, the driver enables cache flush.
1207
1208- TPM Support:
1209		CONFIG_TPM
1210		Support TPM devices.
1211
1212		CONFIG_TPM_TIS_I2C
1213		Support for i2c bus TPM devices. Only one device
1214		per system is supported at this time.
1215
1216			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1217			Define the the i2c bus number for the TPM device
1218
1219			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1220			Define the TPM's address on the i2c bus
1221
1222			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1223			Define the burst count bytes upper limit
1224
1225		CONFIG_TPM_ATMEL_TWI
1226		Support for Atmel TWI TPM device. Requires I2C support.
1227
1228		CONFIG_TPM_TIS_LPC
1229		Support for generic parallel port TPM devices. Only one device
1230		per system is supported at this time.
1231
1232			CONFIG_TPM_TIS_BASE_ADDRESS
1233			Base address where the generic TPM device is mapped
1234			to. Contemporary x86 systems usually map it at
1235			0xfed40000.
1236
1237		CONFIG_CMD_TPM
1238		Add tpm monitor functions.
1239		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1240		provides monitor access to authorized functions.
1241
1242		CONFIG_TPM
1243		Define this to enable the TPM support library which provides
1244		functional interfaces to some TPM commands.
1245		Requires support for a TPM device.
1246
1247		CONFIG_TPM_AUTH_SESSIONS
1248		Define this to enable authorized functions in the TPM library.
1249		Requires CONFIG_TPM and CONFIG_SHA1.
1250
1251- USB Support:
1252		At the moment only the UHCI host controller is
1253		supported (PIP405, MIP405, MPC5200); define
1254		CONFIG_USB_UHCI to enable it.
1255		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1256		and define CONFIG_USB_STORAGE to enable the USB
1257		storage devices.
1258		Note:
1259		Supported are USB Keyboards and USB Floppy drives
1260		(TEAC FD-05PUB).
1261		MPC5200 USB requires additional defines:
1262			CONFIG_USB_CLOCK
1263				for 528 MHz Clock: 0x0001bbbb
1264			CONFIG_PSC3_USB
1265				for USB on PSC3
1266			CONFIG_USB_CONFIG
1267				for differential drivers: 0x00001000
1268				for single ended drivers: 0x00005000
1269				for differential drivers on PSC3: 0x00000100
1270				for single ended drivers on PSC3: 0x00004100
1271			CONFIG_SYS_USB_EVENT_POLL
1272				May be defined to allow interrupt polling
1273				instead of using asynchronous interrupts
1274
1275		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1276		txfilltuning field in the EHCI controller on reset.
1277
1278		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1279		interval for usb hub power-on delay.(minimum 100msec)
1280
1281- USB Device:
1282		Define the below if you wish to use the USB console.
1283		Once firmware is rebuilt from a serial console issue the
1284		command "setenv stdin usbtty; setenv stdout usbtty" and
1285		attach your USB cable. The Unix command "dmesg" should print
1286		it has found a new device. The environment variable usbtty
1287		can be set to gserial or cdc_acm to enable your device to
1288		appear to a USB host as a Linux gserial device or a
1289		Common Device Class Abstract Control Model serial device.
1290		If you select usbtty = gserial you should be able to enumerate
1291		a Linux host by
1292		# modprobe usbserial vendor=0xVendorID product=0xProductID
1293		else if using cdc_acm, simply setting the environment
1294		variable usbtty to be cdc_acm should suffice. The following
1295		might be defined in YourBoardName.h
1296
1297			CONFIG_USB_DEVICE
1298			Define this to build a UDC device
1299
1300			CONFIG_USB_TTY
1301			Define this to have a tty type of device available to
1302			talk to the UDC device
1303
1304			CONFIG_USBD_HS
1305			Define this to enable the high speed support for usb
1306			device and usbtty. If this feature is enabled, a routine
1307			int is_usbd_high_speed(void)
1308			also needs to be defined by the driver to dynamically poll
1309			whether the enumeration has succeded at high speed or full
1310			speed.
1311
1312			CONFIG_SYS_CONSOLE_IS_IN_ENV
1313			Define this if you want stdin, stdout &/or stderr to
1314			be set to usbtty.
1315
1316			mpc8xx:
1317				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1318				Derive USB clock from external clock "blah"
1319				- CONFIG_SYS_USB_EXTC_CLK 0x02
1320
1321				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1322				Derive USB clock from brgclk
1323				- CONFIG_SYS_USB_BRG_CLK 0x04
1324
1325		If you have a USB-IF assigned VendorID then you may wish to
1326		define your own vendor specific values either in BoardName.h
1327		or directly in usbd_vendor_info.h. If you don't define
1328		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1329		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1330		should pretend to be a Linux device to it's target host.
1331
1332			CONFIG_USBD_MANUFACTURER
1333			Define this string as the name of your company for
1334			- CONFIG_USBD_MANUFACTURER "my company"
1335
1336			CONFIG_USBD_PRODUCT_NAME
1337			Define this string as the name of your product
1338			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1339
1340			CONFIG_USBD_VENDORID
1341			Define this as your assigned Vendor ID from the USB
1342			Implementors Forum. This *must* be a genuine Vendor ID
1343			to avoid polluting the USB namespace.
1344			- CONFIG_USBD_VENDORID 0xFFFF
1345
1346			CONFIG_USBD_PRODUCTID
1347			Define this as the unique Product ID
1348			for your device
1349			- CONFIG_USBD_PRODUCTID 0xFFFF
1350
1351- ULPI Layer Support:
1352		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1353		the generic ULPI layer. The generic layer accesses the ULPI PHY
1354		via the platform viewport, so you need both the genric layer and
1355		the viewport enabled. Currently only Chipidea/ARC based
1356		viewport is supported.
1357		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1358		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1359		If your ULPI phy needs a different reference clock than the
1360		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1361		the appropriate value in Hz.
1362
1363- MMC Support:
1364		The MMC controller on the Intel PXA is supported. To
1365		enable this define CONFIG_MMC. The MMC can be
1366		accessed from the boot prompt by mapping the device
1367		to physical memory similar to flash. Command line is
1368		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1369		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1370
1371		CONFIG_SH_MMCIF
1372		Support for Renesas on-chip MMCIF controller
1373
1374			CONFIG_SH_MMCIF_ADDR
1375			Define the base address of MMCIF registers
1376
1377			CONFIG_SH_MMCIF_CLK
1378			Define the clock frequency for MMCIF
1379
1380- USB Device Firmware Update (DFU) class support:
1381		CONFIG_DFU_FUNCTION
1382		This enables the USB portion of the DFU USB class
1383
1384		CONFIG_CMD_DFU
1385		This enables the command "dfu" which is used to have
1386		U-Boot create a DFU class device via USB.  This command
1387		requires that the "dfu_alt_info" environment variable be
1388		set and define the alt settings to expose to the host.
1389
1390		CONFIG_DFU_MMC
1391		This enables support for exposing (e)MMC devices via DFU.
1392
1393		CONFIG_DFU_NAND
1394		This enables support for exposing NAND devices via DFU.
1395
1396		CONFIG_SYS_DFU_DATA_BUF_SIZE
1397		Dfu transfer uses a buffer before writing data to the
1398		raw storage device. Make the size (in bytes) of this buffer
1399		configurable. The size of this buffer is also configurable
1400		through the "dfu_bufsiz" environment variable.
1401
1402		CONFIG_SYS_DFU_MAX_FILE_SIZE
1403		When updating files rather than the raw storage device,
1404		we use a static buffer to copy the file into and then write
1405		the buffer once we've been given the whole file.  Define
1406		this to the maximum filesize (in bytes) for the buffer.
1407		Default is 4 MiB if undefined.
1408
1409- Journaling Flash filesystem support:
1410		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1411		CONFIG_JFFS2_NAND_DEV
1412		Define these for a default partition on a NAND device
1413
1414		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1415		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1416		Define these for a default partition on a NOR device
1417
1418		CONFIG_SYS_JFFS_CUSTOM_PART
1419		Define this to create an own partition. You have to provide a
1420		function struct part_info* jffs2_part_info(int part_num)
1421
1422		If you define only one JFFS2 partition you may also want to
1423		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1424		to disable the command chpart. This is the default when you
1425		have not defined a custom partition
1426
1427- FAT(File Allocation Table) filesystem write function support:
1428		CONFIG_FAT_WRITE
1429
1430		Define this to enable support for saving memory data as a
1431		file in FAT formatted partition.
1432
1433		This will also enable the command "fatwrite" enabling the
1434		user to write files to FAT.
1435
1436CBFS (Coreboot Filesystem) support
1437		CONFIG_CMD_CBFS
1438
1439		Define this to enable support for reading from a Coreboot
1440		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1441		and cbfsload.
1442
1443- Keyboard Support:
1444		CONFIG_ISA_KEYBOARD
1445
1446		Define this to enable standard (PC-Style) keyboard
1447		support
1448
1449		CONFIG_I8042_KBD
1450		Standard PC keyboard driver with US (is default) and
1451		GERMAN key layout (switch via environment 'keymap=de') support.
1452		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1453		for cfb_console. Supports cursor blinking.
1454
1455		CONFIG_CROS_EC_KEYB
1456		Enables a Chrome OS keyboard using the CROS_EC interface.
1457		This uses CROS_EC to communicate with a second microcontroller
1458		which provides key scans on request.
1459
1460- Video support:
1461		CONFIG_VIDEO
1462
1463		Define this to enable video support (for output to
1464		video).
1465
1466		CONFIG_VIDEO_CT69000
1467
1468		Enable Chips & Technologies 69000 Video chip
1469
1470		CONFIG_VIDEO_SMI_LYNXEM
1471		Enable Silicon Motion SMI 712/710/810 Video chip. The
1472		video output is selected via environment 'videoout'
1473		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1474		assumed.
1475
1476		For the CT69000 and SMI_LYNXEM drivers, videomode is
1477		selected via environment 'videomode'. Two different ways
1478		are possible:
1479		- "videomode=num"   'num' is a standard LiLo mode numbers.
1480		Following standard modes are supported	(* is default):
1481
1482		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1483		-------------+---------------------------------------------
1484		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1485		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1486		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1487		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1488		-------------+---------------------------------------------
1489		(i.e. setenv videomode 317; saveenv; reset;)
1490
1491		- "videomode=bootargs" all the video parameters are parsed
1492		from the bootargs. (See drivers/video/videomodes.c)
1493
1494
1495		CONFIG_VIDEO_SED13806
1496		Enable Epson SED13806 driver. This driver supports 8bpp
1497		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1498		or CONFIG_VIDEO_SED13806_16BPP
1499
1500		CONFIG_FSL_DIU_FB
1501		Enable the Freescale DIU video driver.	Reference boards for
1502		SOCs that have a DIU should define this macro to enable DIU
1503		support, and should also define these other macros:
1504
1505			CONFIG_SYS_DIU_ADDR
1506			CONFIG_VIDEO
1507			CONFIG_CMD_BMP
1508			CONFIG_CFB_CONSOLE
1509			CONFIG_VIDEO_SW_CURSOR
1510			CONFIG_VGA_AS_SINGLE_DEVICE
1511			CONFIG_VIDEO_LOGO
1512			CONFIG_VIDEO_BMP_LOGO
1513
1514		The DIU driver will look for the 'video-mode' environment
1515		variable, and if defined, enable the DIU as a console during
1516		boot.  See the documentation file README.video for a
1517		description of this variable.
1518
1519		CONFIG_VIDEO_VGA
1520
1521		Enable the VGA video / BIOS for x86. The alternative if you
1522		are using coreboot is to use the coreboot frame buffer
1523		driver.
1524
1525
1526- Keyboard Support:
1527		CONFIG_KEYBOARD
1528
1529		Define this to enable a custom keyboard support.
1530		This simply calls drv_keyboard_init() which must be
1531		defined in your board-specific files.
1532		The only board using this so far is RBC823.
1533
1534- LCD Support:	CONFIG_LCD
1535
1536		Define this to enable LCD support (for output to LCD
1537		display); also select one of the supported displays
1538		by defining one of these:
1539
1540		CONFIG_ATMEL_LCD:
1541
1542			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1543
1544		CONFIG_NEC_NL6448AC33:
1545
1546			NEC NL6448AC33-18. Active, color, single scan.
1547
1548		CONFIG_NEC_NL6448BC20
1549
1550			NEC NL6448BC20-08. 6.5", 640x480.
1551			Active, color, single scan.
1552
1553		CONFIG_NEC_NL6448BC33_54
1554
1555			NEC NL6448BC33-54. 10.4", 640x480.
1556			Active, color, single scan.
1557
1558		CONFIG_SHARP_16x9
1559
1560			Sharp 320x240. Active, color, single scan.
1561			It isn't 16x9, and I am not sure what it is.
1562
1563		CONFIG_SHARP_LQ64D341
1564
1565			Sharp LQ64D341 display, 640x480.
1566			Active, color, single scan.
1567
1568		CONFIG_HLD1045
1569
1570			HLD1045 display, 640x480.
1571			Active, color, single scan.
1572
1573		CONFIG_OPTREX_BW
1574
1575			Optrex	 CBL50840-2 NF-FW 99 22 M5
1576			or
1577			Hitachi	 LMG6912RPFC-00T
1578			or
1579			Hitachi	 SP14Q002
1580
1581			320x240. Black & white.
1582
1583		Normally display is black on white background; define
1584		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1585
1586		CONFIG_LCD_ALIGNMENT
1587
1588		Normally the LCD is page-aligned (tyically 4KB). If this is
1589		defined then the LCD will be aligned to this value instead.
1590		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1591		here, since it is cheaper to change data cache settings on
1592		a per-section basis.
1593
1594		CONFIG_CONSOLE_SCROLL_LINES
1595
1596		When the console need to be scrolled, this is the number of
1597		lines to scroll by. It defaults to 1. Increasing this makes
1598		the console jump but can help speed up operation when scrolling
1599		is slow.
1600
1601		CONFIG_LCD_BMP_RLE8
1602
1603		Support drawing of RLE8-compressed bitmaps on the LCD.
1604
1605		CONFIG_I2C_EDID
1606
1607		Enables an 'i2c edid' command which can read EDID
1608		information over I2C from an attached LCD display.
1609
1610- Splash Screen Support: CONFIG_SPLASH_SCREEN
1611
1612		If this option is set, the environment is checked for
1613		a variable "splashimage". If found, the usual display
1614		of logo, copyright and system information on the LCD
1615		is suppressed and the BMP image at the address
1616		specified in "splashimage" is loaded instead. The
1617		console is redirected to the "nulldev", too. This
1618		allows for a "silent" boot where a splash screen is
1619		loaded very quickly after power-on.
1620
1621		CONFIG_SPLASHIMAGE_GUARD
1622
1623		If this option is set, then U-Boot will prevent the environment
1624		variable "splashimage" from being set to a problematic address
1625		(see README.displaying-bmps and README.arm-unaligned-accesses).
1626		This option is useful for targets where, due to alignment
1627		restrictions, an improperly aligned BMP image will cause a data
1628		abort. If you think you will not have problems with unaligned
1629		accesses (for example because your toolchain prevents them)
1630		there is no need to set this option.
1631
1632		CONFIG_SPLASH_SCREEN_ALIGN
1633
1634		If this option is set the splash image can be freely positioned
1635		on the screen. Environment variable "splashpos" specifies the
1636		position as "x,y". If a positive number is given it is used as
1637		number of pixel from left/top. If a negative number is given it
1638		is used as number of pixel from right/bottom. You can also
1639		specify 'm' for centering the image.
1640
1641		Example:
1642		setenv splashpos m,m
1643			=> image at center of screen
1644
1645		setenv splashpos 30,20
1646			=> image at x = 30 and y = 20
1647
1648		setenv splashpos -10,m
1649			=> vertically centered image
1650			   at x = dspWidth - bmpWidth - 9
1651
1652- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1653
1654		If this option is set, additionally to standard BMP
1655		images, gzipped BMP images can be displayed via the
1656		splashscreen support or the bmp command.
1657
1658- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1659
1660		If this option is set, 8-bit RLE compressed BMP images
1661		can be displayed via the splashscreen support or the
1662		bmp command.
1663
1664- Do compresssing for memory range:
1665		CONFIG_CMD_ZIP
1666
1667		If this option is set, it would use zlib deflate method
1668		to compress the specified memory at its best effort.
1669
1670- Compression support:
1671		CONFIG_BZIP2
1672
1673		If this option is set, support for bzip2 compressed
1674		images is included. If not, only uncompressed and gzip
1675		compressed images are supported.
1676
1677		NOTE: the bzip2 algorithm requires a lot of RAM, so
1678		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1679		be at least 4MB.
1680
1681		CONFIG_LZMA
1682
1683		If this option is set, support for lzma compressed
1684		images is included.
1685
1686		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1687		requires an amount of dynamic memory that is given by the
1688		formula:
1689
1690			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1691
1692		Where lc and lp stand for, respectively, Literal context bits
1693		and Literal pos bits.
1694
1695		This value is upper-bounded by 14MB in the worst case. Anyway,
1696		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1697		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1698		a very small buffer.
1699
1700		Use the lzmainfo tool to determinate the lc and lp values and
1701		then calculate the amount of needed dynamic memory (ensuring
1702		the appropriate CONFIG_SYS_MALLOC_LEN value).
1703
1704- MII/PHY support:
1705		CONFIG_PHY_ADDR
1706
1707		The address of PHY on MII bus.
1708
1709		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1710
1711		The clock frequency of the MII bus
1712
1713		CONFIG_PHY_GIGE
1714
1715		If this option is set, support for speed/duplex
1716		detection of gigabit PHY is included.
1717
1718		CONFIG_PHY_RESET_DELAY
1719
1720		Some PHY like Intel LXT971A need extra delay after
1721		reset before any MII register access is possible.
1722		For such PHY, set this option to the usec delay
1723		required. (minimum 300usec for LXT971A)
1724
1725		CONFIG_PHY_CMD_DELAY (ppc4xx)
1726
1727		Some PHY like Intel LXT971A need extra delay after
1728		command issued before MII status register can be read
1729
1730- Ethernet address:
1731		CONFIG_ETHADDR
1732		CONFIG_ETH1ADDR
1733		CONFIG_ETH2ADDR
1734		CONFIG_ETH3ADDR
1735		CONFIG_ETH4ADDR
1736		CONFIG_ETH5ADDR
1737
1738		Define a default value for Ethernet address to use
1739		for the respective Ethernet interface, in case this
1740		is not determined automatically.
1741
1742- IP address:
1743		CONFIG_IPADDR
1744
1745		Define a default value for the IP address to use for
1746		the default Ethernet interface, in case this is not
1747		determined through e.g. bootp.
1748		(Environment variable "ipaddr")
1749
1750- Server IP address:
1751		CONFIG_SERVERIP
1752
1753		Defines a default value for the IP address of a TFTP
1754		server to contact when using the "tftboot" command.
1755		(Environment variable "serverip")
1756
1757		CONFIG_KEEP_SERVERADDR
1758
1759		Keeps the server's MAC address, in the env 'serveraddr'
1760		for passing to bootargs (like Linux's netconsole option)
1761
1762- Gateway IP address:
1763		CONFIG_GATEWAYIP
1764
1765		Defines a default value for the IP address of the
1766		default router where packets to other networks are
1767		sent to.
1768		(Environment variable "gatewayip")
1769
1770- Subnet mask:
1771		CONFIG_NETMASK
1772
1773		Defines a default value for the subnet mask (or
1774		routing prefix) which is used to determine if an IP
1775		address belongs to the local subnet or needs to be
1776		forwarded through a router.
1777		(Environment variable "netmask")
1778
1779- Multicast TFTP Mode:
1780		CONFIG_MCAST_TFTP
1781
1782		Defines whether you want to support multicast TFTP as per
1783		rfc-2090; for example to work with atftp.  Lets lots of targets
1784		tftp down the same boot image concurrently.  Note: the Ethernet
1785		driver in use must provide a function: mcast() to join/leave a
1786		multicast group.
1787
1788- BOOTP Recovery Mode:
1789		CONFIG_BOOTP_RANDOM_DELAY
1790
1791		If you have many targets in a network that try to
1792		boot using BOOTP, you may want to avoid that all
1793		systems send out BOOTP requests at precisely the same
1794		moment (which would happen for instance at recovery
1795		from a power failure, when all systems will try to
1796		boot, thus flooding the BOOTP server. Defining
1797		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1798		inserted before sending out BOOTP requests. The
1799		following delays are inserted then:
1800
1801		1st BOOTP request:	delay 0 ... 1 sec
1802		2nd BOOTP request:	delay 0 ... 2 sec
1803		3rd BOOTP request:	delay 0 ... 4 sec
1804		4th and following
1805		BOOTP requests:		delay 0 ... 8 sec
1806
1807- DHCP Advanced Options:
1808		You can fine tune the DHCP functionality by defining
1809		CONFIG_BOOTP_* symbols:
1810
1811		CONFIG_BOOTP_SUBNETMASK
1812		CONFIG_BOOTP_GATEWAY
1813		CONFIG_BOOTP_HOSTNAME
1814		CONFIG_BOOTP_NISDOMAIN
1815		CONFIG_BOOTP_BOOTPATH
1816		CONFIG_BOOTP_BOOTFILESIZE
1817		CONFIG_BOOTP_DNS
1818		CONFIG_BOOTP_DNS2
1819		CONFIG_BOOTP_SEND_HOSTNAME
1820		CONFIG_BOOTP_NTPSERVER
1821		CONFIG_BOOTP_TIMEOFFSET
1822		CONFIG_BOOTP_VENDOREX
1823		CONFIG_BOOTP_MAY_FAIL
1824
1825		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1826		environment variable, not the BOOTP server.
1827
1828		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1829		after the configured retry count, the call will fail
1830		instead of starting over.  This can be used to fail over
1831		to Link-local IP address configuration if the DHCP server
1832		is not available.
1833
1834		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1835		serverip from a DHCP server, it is possible that more
1836		than one DNS serverip is offered to the client.
1837		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1838		serverip will be stored in the additional environment
1839		variable "dnsip2". The first DNS serverip is always
1840		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1841		is defined.
1842
1843		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1844		to do a dynamic update of a DNS server. To do this, they
1845		need the hostname of the DHCP requester.
1846		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1847		of the "hostname" environment variable is passed as
1848		option 12 to the DHCP server.
1849
1850		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1851
1852		A 32bit value in microseconds for a delay between
1853		receiving a "DHCP Offer" and sending the "DHCP Request".
1854		This fixes a problem with certain DHCP servers that don't
1855		respond 100% of the time to a "DHCP request". E.g. On an
1856		AT91RM9200 processor running at 180MHz, this delay needed
1857		to be *at least* 15,000 usec before a Windows Server 2003
1858		DHCP server would reply 100% of the time. I recommend at
1859		least 50,000 usec to be safe. The alternative is to hope
1860		that one of the retries will be successful but note that
1861		the DHCP timeout and retry process takes a longer than
1862		this delay.
1863
1864 - Link-local IP address negotiation:
1865		Negotiate with other link-local clients on the local network
1866		for an address that doesn't require explicit configuration.
1867		This is especially useful if a DHCP server cannot be guaranteed
1868		to exist in all environments that the device must operate.
1869
1870		See doc/README.link-local for more information.
1871
1872 - CDP Options:
1873		CONFIG_CDP_DEVICE_ID
1874
1875		The device id used in CDP trigger frames.
1876
1877		CONFIG_CDP_DEVICE_ID_PREFIX
1878
1879		A two character string which is prefixed to the MAC address
1880		of the device.
1881
1882		CONFIG_CDP_PORT_ID
1883
1884		A printf format string which contains the ascii name of
1885		the port. Normally is set to "eth%d" which sets
1886		eth0 for the first Ethernet, eth1 for the second etc.
1887
1888		CONFIG_CDP_CAPABILITIES
1889
1890		A 32bit integer which indicates the device capabilities;
1891		0x00000010 for a normal host which does not forwards.
1892
1893		CONFIG_CDP_VERSION
1894
1895		An ascii string containing the version of the software.
1896
1897		CONFIG_CDP_PLATFORM
1898
1899		An ascii string containing the name of the platform.
1900
1901		CONFIG_CDP_TRIGGER
1902
1903		A 32bit integer sent on the trigger.
1904
1905		CONFIG_CDP_POWER_CONSUMPTION
1906
1907		A 16bit integer containing the power consumption of the
1908		device in .1 of milliwatts.
1909
1910		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1911
1912		A byte containing the id of the VLAN.
1913
1914- Status LED:	CONFIG_STATUS_LED
1915
1916		Several configurations allow to display the current
1917		status using a LED. For instance, the LED will blink
1918		fast while running U-Boot code, stop blinking as
1919		soon as a reply to a BOOTP request was received, and
1920		start blinking slow once the Linux kernel is running
1921		(supported by a status LED driver in the Linux
1922		kernel). Defining CONFIG_STATUS_LED enables this
1923		feature in U-Boot.
1924
1925- CAN Support:	CONFIG_CAN_DRIVER
1926
1927		Defining CONFIG_CAN_DRIVER enables CAN driver support
1928		on those systems that support this (optional)
1929		feature, like the TQM8xxL modules.
1930
1931- I2C Support:	CONFIG_SYS_I2C
1932
1933		This enable the NEW i2c subsystem, and will allow you to use
1934		i2c commands at the u-boot command line (as long as you set
1935		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1936		based realtime clock chips or other i2c devices. See
1937		common/cmd_i2c.c for a description of the command line
1938		interface.
1939
1940		ported i2c driver to the new framework:
1941		- drivers/i2c/soft_i2c.c:
1942		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1943		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1944		    for defining speed and slave address
1945		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1946		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1947		    for defining speed and slave address
1948		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1949		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1950		    for defining speed and slave address
1951		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1952		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1953		    for defining speed and slave address
1954
1955		- drivers/i2c/fsl_i2c.c:
1956		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1957		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1958		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1959		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1960		    bus.
1961                  - If your board supports a second fsl i2c bus, define
1962		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1963		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1964		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1965		    second bus.
1966
1967		- drivers/i2c/tegra_i2c.c:
1968		 - activate this driver with CONFIG_SYS_I2C_TEGRA
1969		 - This driver adds 4 i2c buses with a fix speed from
1970		   100000 and the slave addr 0!
1971
1972		- drivers/i2c/ppc4xx_i2c.c
1973		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1974		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1975		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1976
1977		additional defines:
1978
1979		CONFIG_SYS_NUM_I2C_BUSES
1980		Hold the number of i2c busses you want to use. If you
1981		don't use/have i2c muxes on your i2c bus, this
1982		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
1983		omit this define.
1984
1985		CONFIG_SYS_I2C_DIRECT_BUS
1986		define this, if you don't use i2c muxes on your hardware.
1987		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1988		omit this define.
1989
1990		CONFIG_SYS_I2C_MAX_HOPS
1991		define how many muxes are maximal consecutively connected
1992		on one i2c bus. If you not use i2c muxes, omit this
1993		define.
1994
1995		CONFIG_SYS_I2C_BUSES
1996		hold a list of busses you want to use, only used if
1997		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1998		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1999		CONFIG_SYS_NUM_I2C_BUSES = 9:
2000
2001		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2002					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2003					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2004					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2005					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2006					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2007					{1, {I2C_NULL_HOP}}, \
2008					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2009					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2010					}
2011
2012		which defines
2013			bus 0 on adapter 0 without a mux
2014			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2015			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2016			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2017			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2018			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2019			bus 6 on adapter 1 without a mux
2020			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2021			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2022
2023		If you do not have i2c muxes on your board, omit this define.
2024
2025- Legacy I2C Support:	CONFIG_HARD_I2C
2026
2027		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2028		provides the following compelling advantages:
2029
2030		- more than one i2c adapter is usable
2031		- approved multibus support
2032		- better i2c mux support
2033
2034		** Please consider updating your I2C driver now. **
2035
2036		These enable legacy I2C serial bus commands. Defining
2037		CONFIG_HARD_I2C will include the appropriate I2C driver
2038		for the selected CPU.
2039
2040		This will allow you to use i2c commands at the u-boot
2041		command line (as long as you set CONFIG_CMD_I2C in
2042		CONFIG_COMMANDS) and communicate with i2c based realtime
2043		clock chips. See common/cmd_i2c.c for a description of the
2044		command line interface.
2045
2046		CONFIG_HARD_I2C selects a hardware I2C controller.
2047
2048		There are several other quantities that must also be
2049		defined when you define CONFIG_HARD_I2C.
2050
2051		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2052		to be the frequency (in Hz) at which you wish your i2c bus
2053		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2054		the CPU's i2c node address).
2055
2056		Now, the u-boot i2c code for the mpc8xx
2057		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2058		and so its address should therefore be cleared to 0 (See,
2059		eg, MPC823e User's Manual p.16-473). So, set
2060		CONFIG_SYS_I2C_SLAVE to 0.
2061
2062		CONFIG_SYS_I2C_INIT_MPC5XXX
2063
2064		When a board is reset during an i2c bus transfer
2065		chips might think that the current transfer is still
2066		in progress.  Reset the slave devices by sending start
2067		commands until the slave device responds.
2068
2069		That's all that's required for CONFIG_HARD_I2C.
2070
2071		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2072		then the following macros need to be defined (examples are
2073		from include/configs/lwmon.h):
2074
2075		I2C_INIT
2076
2077		(Optional). Any commands necessary to enable the I2C
2078		controller or configure ports.
2079
2080		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2081
2082		I2C_PORT
2083
2084		(Only for MPC8260 CPU). The I/O port to use (the code
2085		assumes both bits are on the same port). Valid values
2086		are 0..3 for ports A..D.
2087
2088		I2C_ACTIVE
2089
2090		The code necessary to make the I2C data line active
2091		(driven).  If the data line is open collector, this
2092		define can be null.
2093
2094		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2095
2096		I2C_TRISTATE
2097
2098		The code necessary to make the I2C data line tri-stated
2099		(inactive).  If the data line is open collector, this
2100		define can be null.
2101
2102		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2103
2104		I2C_READ
2105
2106		Code that returns true if the I2C data line is high,
2107		false if it is low.
2108
2109		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2110
2111		I2C_SDA(bit)
2112
2113		If <bit> is true, sets the I2C data line high. If it
2114		is false, it clears it (low).
2115
2116		eg: #define I2C_SDA(bit) \
2117			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2118			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2119
2120		I2C_SCL(bit)
2121
2122		If <bit> is true, sets the I2C clock line high. If it
2123		is false, it clears it (low).
2124
2125		eg: #define I2C_SCL(bit) \
2126			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2127			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2128
2129		I2C_DELAY
2130
2131		This delay is invoked four times per clock cycle so this
2132		controls the rate of data transfer.  The data rate thus
2133		is 1 / (I2C_DELAY * 4). Often defined to be something
2134		like:
2135
2136		#define I2C_DELAY  udelay(2)
2137
2138		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2139
2140		If your arch supports the generic GPIO framework (asm/gpio.h),
2141		then you may alternatively define the two GPIOs that are to be
2142		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2143		have GPIO-based defaults assigned to them as appropriate.
2144
2145		You should define these to the GPIO value as given directly to
2146		the generic GPIO functions.
2147
2148		CONFIG_SYS_I2C_INIT_BOARD
2149
2150		When a board is reset during an i2c bus transfer
2151		chips might think that the current transfer is still
2152		in progress. On some boards it is possible to access
2153		the i2c SCLK line directly, either by using the
2154		processor pin as a GPIO or by having a second pin
2155		connected to the bus. If this option is defined a
2156		custom i2c_init_board() routine in boards/xxx/board.c
2157		is run early in the boot sequence.
2158
2159		CONFIG_SYS_I2C_BOARD_LATE_INIT
2160
2161		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2162		defined a custom i2c_board_late_init() routine in
2163		boards/xxx/board.c is run AFTER the operations in i2c_init()
2164		is completed. This callpoint can be used to unreset i2c bus
2165		using CPU i2c controller register accesses for CPUs whose i2c
2166		controller provide such a method. It is called at the end of
2167		i2c_init() to allow i2c_init operations to setup the i2c bus
2168		controller on the CPU (e.g. setting bus speed & slave address).
2169
2170		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2171
2172		This option enables configuration of bi_iic_fast[] flags
2173		in u-boot bd_info structure based on u-boot environment
2174		variable "i2cfast". (see also i2cfast)
2175
2176		CONFIG_I2C_MULTI_BUS
2177
2178		This option allows the use of multiple I2C buses, each of which
2179		must have a controller.	 At any point in time, only one bus is
2180		active.	 To switch to a different bus, use the 'i2c dev' command.
2181		Note that bus numbering is zero-based.
2182
2183		CONFIG_SYS_I2C_NOPROBES
2184
2185		This option specifies a list of I2C devices that will be skipped
2186		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2187		is set, specify a list of bus-device pairs.  Otherwise, specify
2188		a 1D array of device addresses
2189
2190		e.g.
2191			#undef	CONFIG_I2C_MULTI_BUS
2192			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2193
2194		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2195
2196			#define CONFIG_I2C_MULTI_BUS
2197			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2198
2199		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2200
2201		CONFIG_SYS_SPD_BUS_NUM
2202
2203		If defined, then this indicates the I2C bus number for DDR SPD.
2204		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2205
2206		CONFIG_SYS_RTC_BUS_NUM
2207
2208		If defined, then this indicates the I2C bus number for the RTC.
2209		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2210
2211		CONFIG_SYS_DTT_BUS_NUM
2212
2213		If defined, then this indicates the I2C bus number for the DTT.
2214		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2215
2216		CONFIG_SYS_I2C_DTT_ADDR:
2217
2218		If defined, specifies the I2C address of the DTT device.
2219		If not defined, then U-Boot uses predefined value for
2220		specified DTT device.
2221
2222		CONFIG_SOFT_I2C_READ_REPEATED_START
2223
2224		defining this will force the i2c_read() function in
2225		the soft_i2c driver to perform an I2C repeated start
2226		between writing the address pointer and reading the
2227		data.  If this define is omitted the default behaviour
2228		of doing a stop-start sequence will be used.  Most I2C
2229		devices can use either method, but some require one or
2230		the other.
2231
2232- SPI Support:	CONFIG_SPI
2233
2234		Enables SPI driver (so far only tested with
2235		SPI EEPROM, also an instance works with Crystal A/D and
2236		D/As on the SACSng board)
2237
2238		CONFIG_SH_SPI
2239
2240		Enables the driver for SPI controller on SuperH. Currently
2241		only SH7757 is supported.
2242
2243		CONFIG_SPI_X
2244
2245		Enables extended (16-bit) SPI EEPROM addressing.
2246		(symmetrical to CONFIG_I2C_X)
2247
2248		CONFIG_SOFT_SPI
2249
2250		Enables a software (bit-bang) SPI driver rather than
2251		using hardware support. This is a general purpose
2252		driver that only requires three general I/O port pins
2253		(two outputs, one input) to function. If this is
2254		defined, the board configuration must define several
2255		SPI configuration items (port pins to use, etc). For
2256		an example, see include/configs/sacsng.h.
2257
2258		CONFIG_HARD_SPI
2259
2260		Enables a hardware SPI driver for general-purpose reads
2261		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2262		must define a list of chip-select function pointers.
2263		Currently supported on some MPC8xxx processors.	 For an
2264		example, see include/configs/mpc8349emds.h.
2265
2266		CONFIG_MXC_SPI
2267
2268		Enables the driver for the SPI controllers on i.MX and MXC
2269		SoCs. Currently i.MX31/35/51 are supported.
2270
2271- FPGA Support: CONFIG_FPGA
2272
2273		Enables FPGA subsystem.
2274
2275		CONFIG_FPGA_<vendor>
2276
2277		Enables support for specific chip vendors.
2278		(ALTERA, XILINX)
2279
2280		CONFIG_FPGA_<family>
2281
2282		Enables support for FPGA family.
2283		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2284
2285		CONFIG_FPGA_COUNT
2286
2287		Specify the number of FPGA devices to support.
2288
2289		CONFIG_SYS_FPGA_PROG_FEEDBACK
2290
2291		Enable printing of hash marks during FPGA configuration.
2292
2293		CONFIG_SYS_FPGA_CHECK_BUSY
2294
2295		Enable checks on FPGA configuration interface busy
2296		status by the configuration function. This option
2297		will require a board or device specific function to
2298		be written.
2299
2300		CONFIG_FPGA_DELAY
2301
2302		If defined, a function that provides delays in the FPGA
2303		configuration driver.
2304
2305		CONFIG_SYS_FPGA_CHECK_CTRLC
2306		Allow Control-C to interrupt FPGA configuration
2307
2308		CONFIG_SYS_FPGA_CHECK_ERROR
2309
2310		Check for configuration errors during FPGA bitfile
2311		loading. For example, abort during Virtex II
2312		configuration if the INIT_B line goes low (which
2313		indicated a CRC error).
2314
2315		CONFIG_SYS_FPGA_WAIT_INIT
2316
2317		Maximum time to wait for the INIT_B line to deassert
2318		after PROB_B has been deasserted during a Virtex II
2319		FPGA configuration sequence. The default time is 500
2320		ms.
2321
2322		CONFIG_SYS_FPGA_WAIT_BUSY
2323
2324		Maximum time to wait for BUSY to deassert during
2325		Virtex II FPGA configuration. The default is 5 ms.
2326
2327		CONFIG_SYS_FPGA_WAIT_CONFIG
2328
2329		Time to wait after FPGA configuration. The default is
2330		200 ms.
2331
2332- Configuration Management:
2333		CONFIG_IDENT_STRING
2334
2335		If defined, this string will be added to the U-Boot
2336		version information (U_BOOT_VERSION)
2337
2338- Vendor Parameter Protection:
2339
2340		U-Boot considers the values of the environment
2341		variables "serial#" (Board Serial Number) and
2342		"ethaddr" (Ethernet Address) to be parameters that
2343		are set once by the board vendor / manufacturer, and
2344		protects these variables from casual modification by
2345		the user. Once set, these variables are read-only,
2346		and write or delete attempts are rejected. You can
2347		change this behaviour:
2348
2349		If CONFIG_ENV_OVERWRITE is #defined in your config
2350		file, the write protection for vendor parameters is
2351		completely disabled. Anybody can change or delete
2352		these parameters.
2353
2354		Alternatively, if you #define _both_ CONFIG_ETHADDR
2355		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2356		Ethernet address is installed in the environment,
2357		which can be changed exactly ONCE by the user. [The
2358		serial# is unaffected by this, i. e. it remains
2359		read-only.]
2360
2361		The same can be accomplished in a more flexible way
2362		for any variable by configuring the type of access
2363		to allow for those variables in the ".flags" variable
2364		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2365
2366- Protected RAM:
2367		CONFIG_PRAM
2368
2369		Define this variable to enable the reservation of
2370		"protected RAM", i. e. RAM which is not overwritten
2371		by U-Boot. Define CONFIG_PRAM to hold the number of
2372		kB you want to reserve for pRAM. You can overwrite
2373		this default value by defining an environment
2374		variable "pram" to the number of kB you want to
2375		reserve. Note that the board info structure will
2376		still show the full amount of RAM. If pRAM is
2377		reserved, a new environment variable "mem" will
2378		automatically be defined to hold the amount of
2379		remaining RAM in a form that can be passed as boot
2380		argument to Linux, for instance like that:
2381
2382			setenv bootargs ... mem=\${mem}
2383			saveenv
2384
2385		This way you can tell Linux not to use this memory,
2386		either, which results in a memory region that will
2387		not be affected by reboots.
2388
2389		*WARNING* If your board configuration uses automatic
2390		detection of the RAM size, you must make sure that
2391		this memory test is non-destructive. So far, the
2392		following board configurations are known to be
2393		"pRAM-clean":
2394
2395			IVMS8, IVML24, SPD8xx, TQM8xxL,
2396			HERMES, IP860, RPXlite, LWMON,
2397			FLAGADM, TQM8260
2398
2399- Access to physical memory region (> 4GB)
2400		Some basic support is provided for operations on memory not
2401		normally accessible to U-Boot - e.g. some architectures
2402		support access to more than 4GB of memory on 32-bit
2403		machines using physical address extension or similar.
2404		Define CONFIG_PHYSMEM to access this basic support, which
2405		currently only supports clearing the memory.
2406
2407- Error Recovery:
2408		CONFIG_PANIC_HANG
2409
2410		Define this variable to stop the system in case of a
2411		fatal error, so that you have to reset it manually.
2412		This is probably NOT a good idea for an embedded
2413		system where you want the system to reboot
2414		automatically as fast as possible, but it may be
2415		useful during development since you can try to debug
2416		the conditions that lead to the situation.
2417
2418		CONFIG_NET_RETRY_COUNT
2419
2420		This variable defines the number of retries for
2421		network operations like ARP, RARP, TFTP, or BOOTP
2422		before giving up the operation. If not defined, a
2423		default value of 5 is used.
2424
2425		CONFIG_ARP_TIMEOUT
2426
2427		Timeout waiting for an ARP reply in milliseconds.
2428
2429		CONFIG_NFS_TIMEOUT
2430
2431		Timeout in milliseconds used in NFS protocol.
2432		If you encounter "ERROR: Cannot umount" in nfs command,
2433		try longer timeout such as
2434		#define CONFIG_NFS_TIMEOUT 10000UL
2435
2436- Command Interpreter:
2437		CONFIG_AUTO_COMPLETE
2438
2439		Enable auto completion of commands using TAB.
2440
2441		Note that this feature has NOT been implemented yet
2442		for the "hush" shell.
2443
2444
2445		CONFIG_SYS_HUSH_PARSER
2446
2447		Define this variable to enable the "hush" shell (from
2448		Busybox) as command line interpreter, thus enabling
2449		powerful command line syntax like
2450		if...then...else...fi conditionals or `&&' and '||'
2451		constructs ("shell scripts").
2452
2453		If undefined, you get the old, much simpler behaviour
2454		with a somewhat smaller memory footprint.
2455
2456
2457		CONFIG_SYS_PROMPT_HUSH_PS2
2458
2459		This defines the secondary prompt string, which is
2460		printed when the command interpreter needs more input
2461		to complete a command. Usually "> ".
2462
2463	Note:
2464
2465		In the current implementation, the local variables
2466		space and global environment variables space are
2467		separated. Local variables are those you define by
2468		simply typing `name=value'. To access a local
2469		variable later on, you have write `$name' or
2470		`${name}'; to execute the contents of a variable
2471		directly type `$name' at the command prompt.
2472
2473		Global environment variables are those you use
2474		setenv/printenv to work with. To run a command stored
2475		in such a variable, you need to use the run command,
2476		and you must not use the '$' sign to access them.
2477
2478		To store commands and special characters in a
2479		variable, please use double quotation marks
2480		surrounding the whole text of the variable, instead
2481		of the backslashes before semicolons and special
2482		symbols.
2483
2484- Commandline Editing and History:
2485		CONFIG_CMDLINE_EDITING
2486
2487		Enable editing and History functions for interactive
2488		commandline input operations
2489
2490- Default Environment:
2491		CONFIG_EXTRA_ENV_SETTINGS
2492
2493		Define this to contain any number of null terminated
2494		strings (variable = value pairs) that will be part of
2495		the default environment compiled into the boot image.
2496
2497		For example, place something like this in your
2498		board's config file:
2499
2500		#define CONFIG_EXTRA_ENV_SETTINGS \
2501			"myvar1=value1\0" \
2502			"myvar2=value2\0"
2503
2504		Warning: This method is based on knowledge about the
2505		internal format how the environment is stored by the
2506		U-Boot code. This is NOT an official, exported
2507		interface! Although it is unlikely that this format
2508		will change soon, there is no guarantee either.
2509		You better know what you are doing here.
2510
2511		Note: overly (ab)use of the default environment is
2512		discouraged. Make sure to check other ways to preset
2513		the environment like the "source" command or the
2514		boot command first.
2515
2516		CONFIG_ENV_VARS_UBOOT_CONFIG
2517
2518		Define this in order to add variables describing the
2519		U-Boot build configuration to the default environment.
2520		These will be named arch, cpu, board, vendor, and soc.
2521
2522		Enabling this option will cause the following to be defined:
2523
2524		- CONFIG_SYS_ARCH
2525		- CONFIG_SYS_CPU
2526		- CONFIG_SYS_BOARD
2527		- CONFIG_SYS_VENDOR
2528		- CONFIG_SYS_SOC
2529
2530		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2531
2532		Define this in order to add variables describing certain
2533		run-time determined information about the hardware to the
2534		environment.  These will be named board_name, board_rev.
2535
2536		CONFIG_DELAY_ENVIRONMENT
2537
2538		Normally the environment is loaded when the board is
2539		intialised so that it is available to U-Boot. This inhibits
2540		that so that the environment is not available until
2541		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2542		this is instead controlled by the value of
2543		/config/load-environment.
2544
2545- DataFlash Support:
2546		CONFIG_HAS_DATAFLASH
2547
2548		Defining this option enables DataFlash features and
2549		allows to read/write in Dataflash via the standard
2550		commands cp, md...
2551
2552- Serial Flash support
2553		CONFIG_CMD_SF
2554
2555		Defining this option enables SPI flash commands
2556		'sf probe/read/write/erase/update'.
2557
2558		Usage requires an initial 'probe' to define the serial
2559		flash parameters, followed by read/write/erase/update
2560		commands.
2561
2562		The following defaults may be provided by the platform
2563		to handle the common case when only a single serial
2564		flash is present on the system.
2565
2566		CONFIG_SF_DEFAULT_BUS		Bus identifier
2567		CONFIG_SF_DEFAULT_CS		Chip-select
2568		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2569		CONFIG_SF_DEFAULT_SPEED		in Hz
2570
2571		CONFIG_CMD_SF_TEST
2572
2573		Define this option to include a destructive SPI flash
2574		test ('sf test').
2575
2576		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2577
2578		Define this option to use the Bank addr/Extended addr
2579		support on SPI flashes which has size > 16Mbytes.
2580
2581- SystemACE Support:
2582		CONFIG_SYSTEMACE
2583
2584		Adding this option adds support for Xilinx SystemACE
2585		chips attached via some sort of local bus. The address
2586		of the chip must also be defined in the
2587		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2588
2589		#define CONFIG_SYSTEMACE
2590		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2591
2592		When SystemACE support is added, the "ace" device type
2593		becomes available to the fat commands, i.e. fatls.
2594
2595- TFTP Fixed UDP Port:
2596		CONFIG_TFTP_PORT
2597
2598		If this is defined, the environment variable tftpsrcp
2599		is used to supply the TFTP UDP source port value.
2600		If tftpsrcp isn't defined, the normal pseudo-random port
2601		number generator is used.
2602
2603		Also, the environment variable tftpdstp is used to supply
2604		the TFTP UDP destination port value.  If tftpdstp isn't
2605		defined, the normal port 69 is used.
2606
2607		The purpose for tftpsrcp is to allow a TFTP server to
2608		blindly start the TFTP transfer using the pre-configured
2609		target IP address and UDP port. This has the effect of
2610		"punching through" the (Windows XP) firewall, allowing
2611		the remainder of the TFTP transfer to proceed normally.
2612		A better solution is to properly configure the firewall,
2613		but sometimes that is not allowed.
2614
2615- Hashing support:
2616		CONFIG_CMD_HASH
2617
2618		This enables a generic 'hash' command which can produce
2619		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2620
2621		CONFIG_HASH_VERIFY
2622
2623		Enable the hash verify command (hash -v). This adds to code
2624		size a little.
2625
2626		CONFIG_SHA1 - support SHA1 hashing
2627		CONFIG_SHA256 - support SHA256 hashing
2628
2629		Note: There is also a sha1sum command, which should perhaps
2630		be deprecated in favour of 'hash sha1'.
2631
2632- Freescale i.MX specific commands:
2633		CONFIG_CMD_HDMIDETECT
2634		This enables 'hdmidet' command which returns true if an
2635		HDMI monitor is detected.  This command is i.MX 6 specific.
2636
2637		CONFIG_CMD_BMODE
2638		This enables the 'bmode' (bootmode) command for forcing
2639		a boot from specific media.
2640
2641		This is useful for forcing the ROM's usb downloader to
2642		activate upon a watchdog reset which is nice when iterating
2643		on U-Boot.  Using the reset button or running bmode normal
2644		will set it back to normal.  This command currently
2645		supports i.MX53 and i.MX6.
2646
2647- Signing support:
2648		CONFIG_RSA
2649
2650		This enables the RSA algorithm used for FIT image verification
2651		in U-Boot. See doc/uImage/signature for more information.
2652
2653		The signing part is build into mkimage regardless of this
2654		option.
2655
2656
2657- Show boot progress:
2658		CONFIG_SHOW_BOOT_PROGRESS
2659
2660		Defining this option allows to add some board-
2661		specific code (calling a user-provided function
2662		"show_boot_progress(int)") that enables you to show
2663		the system's boot progress on some display (for
2664		example, some LED's) on your board. At the moment,
2665		the following checkpoints are implemented:
2666
2667- Detailed boot stage timing
2668		CONFIG_BOOTSTAGE
2669		Define this option to get detailed timing of each stage
2670		of the boot process.
2671
2672		CONFIG_BOOTSTAGE_USER_COUNT
2673		This is the number of available user bootstage records.
2674		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2675		a new ID will be allocated from this stash. If you exceed
2676		the limit, recording will stop.
2677
2678		CONFIG_BOOTSTAGE_REPORT
2679		Define this to print a report before boot, similar to this:
2680
2681		Timer summary in microseconds:
2682		       Mark    Elapsed  Stage
2683			  0          0  reset
2684		  3,575,678  3,575,678  board_init_f start
2685		  3,575,695         17  arch_cpu_init A9
2686		  3,575,777         82  arch_cpu_init done
2687		  3,659,598     83,821  board_init_r start
2688		  3,910,375    250,777  main_loop
2689		 29,916,167 26,005,792  bootm_start
2690		 30,361,327    445,160  start_kernel
2691
2692		CONFIG_CMD_BOOTSTAGE
2693		Add a 'bootstage' command which supports printing a report
2694		and un/stashing of bootstage data.
2695
2696		CONFIG_BOOTSTAGE_FDT
2697		Stash the bootstage information in the FDT. A root 'bootstage'
2698		node is created with each bootstage id as a child. Each child
2699		has a 'name' property and either 'mark' containing the
2700		mark time in microsecond, or 'accum' containing the
2701		accumulated time for that bootstage id in microseconds.
2702		For example:
2703
2704		bootstage {
2705			154 {
2706				name = "board_init_f";
2707				mark = <3575678>;
2708			};
2709			170 {
2710				name = "lcd";
2711				accum = <33482>;
2712			};
2713		};
2714
2715		Code in the Linux kernel can find this in /proc/devicetree.
2716
2717Legacy uImage format:
2718
2719  Arg	Where			When
2720    1	common/cmd_bootm.c	before attempting to boot an image
2721   -1	common/cmd_bootm.c	Image header has bad	 magic number
2722    2	common/cmd_bootm.c	Image header has correct magic number
2723   -2	common/cmd_bootm.c	Image header has bad	 checksum
2724    3	common/cmd_bootm.c	Image header has correct checksum
2725   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2726    4	common/cmd_bootm.c	Image data   has correct checksum
2727   -4	common/cmd_bootm.c	Image is for unsupported architecture
2728    5	common/cmd_bootm.c	Architecture check OK
2729   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2730    6	common/cmd_bootm.c	Image Type check OK
2731   -6	common/cmd_bootm.c	gunzip uncompression error
2732   -7	common/cmd_bootm.c	Unimplemented compression type
2733    7	common/cmd_bootm.c	Uncompression OK
2734    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2735   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2736
2737    9	common/image.c		Start initial ramdisk verification
2738  -10	common/image.c		Ramdisk header has bad	   magic number
2739  -11	common/image.c		Ramdisk header has bad	   checksum
2740   10	common/image.c		Ramdisk header is OK
2741  -12	common/image.c		Ramdisk data   has bad	   checksum
2742   11	common/image.c		Ramdisk data   has correct checksum
2743   12	common/image.c		Ramdisk verification complete, start loading
2744  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2745   13	common/image.c		Start multifile image verification
2746   14	common/image.c		No initial ramdisk, no multifile, continue.
2747
2748   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2749
2750  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2751  -31	post/post.c		POST test failed, detected by post_output_backlog()
2752  -32	post/post.c		POST test failed, detected by post_run_single()
2753
2754   34	common/cmd_doc.c	before loading a Image from a DOC device
2755  -35	common/cmd_doc.c	Bad usage of "doc" command
2756   35	common/cmd_doc.c	correct usage of "doc" command
2757  -36	common/cmd_doc.c	No boot device
2758   36	common/cmd_doc.c	correct boot device
2759  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2760   37	common/cmd_doc.c	correct chip ID found, device available
2761  -38	common/cmd_doc.c	Read Error on boot device
2762   38	common/cmd_doc.c	reading Image header from DOC device OK
2763  -39	common/cmd_doc.c	Image header has bad magic number
2764   39	common/cmd_doc.c	Image header has correct magic number
2765  -40	common/cmd_doc.c	Error reading Image from DOC device
2766   40	common/cmd_doc.c	Image header has correct magic number
2767   41	common/cmd_ide.c	before loading a Image from a IDE device
2768  -42	common/cmd_ide.c	Bad usage of "ide" command
2769   42	common/cmd_ide.c	correct usage of "ide" command
2770  -43	common/cmd_ide.c	No boot device
2771   43	common/cmd_ide.c	boot device found
2772  -44	common/cmd_ide.c	Device not available
2773   44	common/cmd_ide.c	Device available
2774  -45	common/cmd_ide.c	wrong partition selected
2775   45	common/cmd_ide.c	partition selected
2776  -46	common/cmd_ide.c	Unknown partition table
2777   46	common/cmd_ide.c	valid partition table found
2778  -47	common/cmd_ide.c	Invalid partition type
2779   47	common/cmd_ide.c	correct partition type
2780  -48	common/cmd_ide.c	Error reading Image Header on boot device
2781   48	common/cmd_ide.c	reading Image Header from IDE device OK
2782  -49	common/cmd_ide.c	Image header has bad magic number
2783   49	common/cmd_ide.c	Image header has correct magic number
2784  -50	common/cmd_ide.c	Image header has bad	 checksum
2785   50	common/cmd_ide.c	Image header has correct checksum
2786  -51	common/cmd_ide.c	Error reading Image from IDE device
2787   51	common/cmd_ide.c	reading Image from IDE device OK
2788   52	common/cmd_nand.c	before loading a Image from a NAND device
2789  -53	common/cmd_nand.c	Bad usage of "nand" command
2790   53	common/cmd_nand.c	correct usage of "nand" command
2791  -54	common/cmd_nand.c	No boot device
2792   54	common/cmd_nand.c	boot device found
2793  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2794   55	common/cmd_nand.c	correct chip ID found, device available
2795  -56	common/cmd_nand.c	Error reading Image Header on boot device
2796   56	common/cmd_nand.c	reading Image Header from NAND device OK
2797  -57	common/cmd_nand.c	Image header has bad magic number
2798   57	common/cmd_nand.c	Image header has correct magic number
2799  -58	common/cmd_nand.c	Error reading Image from NAND device
2800   58	common/cmd_nand.c	reading Image from NAND device OK
2801
2802  -60	common/env_common.c	Environment has a bad CRC, using default
2803
2804   64	net/eth.c		starting with Ethernet configuration.
2805  -64	net/eth.c		no Ethernet found.
2806   65	net/eth.c		Ethernet found.
2807
2808  -80	common/cmd_net.c	usage wrong
2809   80	common/cmd_net.c	before calling NetLoop()
2810  -81	common/cmd_net.c	some error in NetLoop() occurred
2811   81	common/cmd_net.c	NetLoop() back without error
2812  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2813   82	common/cmd_net.c	trying automatic boot
2814   83	common/cmd_net.c	running "source" command
2815  -83	common/cmd_net.c	some error in automatic boot or "source" command
2816   84	common/cmd_net.c	end without errors
2817
2818FIT uImage format:
2819
2820  Arg	Where			When
2821  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2822 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2823  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2824 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2825  102	common/cmd_bootm.c	Kernel unit name specified
2826 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2827  103	common/cmd_bootm.c	Found configuration node
2828  104	common/cmd_bootm.c	Got kernel subimage node offset
2829 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2830  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2831 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2832  106	common/cmd_bootm.c	Architecture check OK
2833 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2834  107	common/cmd_bootm.c	Kernel subimage type OK
2835 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2836  108	common/cmd_bootm.c	Got kernel subimage data/size
2837 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2838 -109	common/cmd_bootm.c	Can't get kernel subimage type
2839 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2840 -111	common/cmd_bootm.c	Can't get kernel subimage os
2841 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2842 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2843
2844  120	common/image.c		Start initial ramdisk verification
2845 -120	common/image.c		Ramdisk FIT image has incorrect format
2846  121	common/image.c		Ramdisk FIT image has correct format
2847  122	common/image.c		No ramdisk subimage unit name, using configuration
2848 -122	common/image.c		Can't get configuration for ramdisk subimage
2849  123	common/image.c		Ramdisk unit name specified
2850 -124	common/image.c		Can't get ramdisk subimage node offset
2851  125	common/image.c		Got ramdisk subimage node offset
2852 -125	common/image.c		Ramdisk subimage hash verification failed
2853  126	common/image.c		Ramdisk subimage hash verification OK
2854 -126	common/image.c		Ramdisk subimage for unsupported architecture
2855  127	common/image.c		Architecture check OK
2856 -127	common/image.c		Can't get ramdisk subimage data/size
2857  128	common/image.c		Got ramdisk subimage data/size
2858  129	common/image.c		Can't get ramdisk load address
2859 -129	common/image.c		Got ramdisk load address
2860
2861 -130	common/cmd_doc.c	Incorrect FIT image format
2862  131	common/cmd_doc.c	FIT image format OK
2863
2864 -140	common/cmd_ide.c	Incorrect FIT image format
2865  141	common/cmd_ide.c	FIT image format OK
2866
2867 -150	common/cmd_nand.c	Incorrect FIT image format
2868  151	common/cmd_nand.c	FIT image format OK
2869
2870- FIT image support:
2871		CONFIG_FIT
2872		Enable support for the FIT uImage format.
2873
2874		CONFIG_FIT_BEST_MATCH
2875		When no configuration is explicitly selected, default to the
2876		one whose fdt's compatibility field best matches that of
2877		U-Boot itself. A match is considered "best" if it matches the
2878		most specific compatibility entry of U-Boot's fdt's root node.
2879		The order of entries in the configuration's fdt is ignored.
2880
2881		CONFIG_FIT_SIGNATURE
2882		This option enables signature verification of FIT uImages,
2883		using a hash signed and verified using RSA. See
2884		doc/uImage.FIT/signature.txt for more details.
2885
2886- Standalone program support:
2887		CONFIG_STANDALONE_LOAD_ADDR
2888
2889		This option defines a board specific value for the
2890		address where standalone program gets loaded, thus
2891		overwriting the architecture dependent default
2892		settings.
2893
2894- Frame Buffer Address:
2895		CONFIG_FB_ADDR
2896
2897		Define CONFIG_FB_ADDR if you want to use specific
2898		address for frame buffer.  This is typically the case
2899		when using a graphics controller has separate video
2900		memory.  U-Boot will then place the frame buffer at
2901		the given address instead of dynamically reserving it
2902		in system RAM by calling lcd_setmem(), which grabs
2903		the memory for the frame buffer depending on the
2904		configured panel size.
2905
2906		Please see board_init_f function.
2907
2908- Automatic software updates via TFTP server
2909		CONFIG_UPDATE_TFTP
2910		CONFIG_UPDATE_TFTP_CNT_MAX
2911		CONFIG_UPDATE_TFTP_MSEC_MAX
2912
2913		These options enable and control the auto-update feature;
2914		for a more detailed description refer to doc/README.update.
2915
2916- MTD Support (mtdparts command, UBI support)
2917		CONFIG_MTD_DEVICE
2918
2919		Adds the MTD device infrastructure from the Linux kernel.
2920		Needed for mtdparts command support.
2921
2922		CONFIG_MTD_PARTITIONS
2923
2924		Adds the MTD partitioning infrastructure from the Linux
2925		kernel. Needed for UBI support.
2926
2927- UBI support
2928		CONFIG_CMD_UBI
2929
2930		Adds commands for interacting with MTD partitions formatted
2931		with the UBI flash translation layer
2932
2933		Requires also defining CONFIG_RBTREE
2934
2935		CONFIG_UBI_SILENCE_MSG
2936
2937		Make the verbose messages from UBI stop printing.  This leaves
2938		warnings and errors enabled.
2939
2940- UBIFS support
2941		CONFIG_CMD_UBIFS
2942
2943		Adds commands for interacting with UBI volumes formatted as
2944		UBIFS.  UBIFS is read-only in u-boot.
2945
2946		Requires UBI support as well as CONFIG_LZO
2947
2948		CONFIG_UBIFS_SILENCE_MSG
2949
2950		Make the verbose messages from UBIFS stop printing.  This leaves
2951		warnings and errors enabled.
2952
2953- SPL framework
2954		CONFIG_SPL
2955		Enable building of SPL globally.
2956
2957		CONFIG_SPL_LDSCRIPT
2958		LDSCRIPT for linking the SPL binary.
2959
2960		CONFIG_SPL_MAX_FOOTPRINT
2961		Maximum size in memory allocated to the SPL, BSS included.
2962		When defined, the linker checks that the actual memory
2963		used by SPL from _start to __bss_end does not exceed it.
2964		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2965		must not be both defined at the same time.
2966
2967		CONFIG_SPL_MAX_SIZE
2968		Maximum size of the SPL image (text, data, rodata, and
2969		linker lists sections), BSS excluded.
2970		When defined, the linker checks that the actual size does
2971		not exceed it.
2972
2973		CONFIG_SPL_TEXT_BASE
2974		TEXT_BASE for linking the SPL binary.
2975
2976		CONFIG_SPL_RELOC_TEXT_BASE
2977		Address to relocate to.  If unspecified, this is equal to
2978		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2979
2980		CONFIG_SPL_BSS_START_ADDR
2981		Link address for the BSS within the SPL binary.
2982
2983		CONFIG_SPL_BSS_MAX_SIZE
2984		Maximum size in memory allocated to the SPL BSS.
2985		When defined, the linker checks that the actual memory used
2986		by SPL from __bss_start to __bss_end does not exceed it.
2987		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2988		must not be both defined at the same time.
2989
2990		CONFIG_SPL_STACK
2991		Adress of the start of the stack SPL will use
2992
2993		CONFIG_SPL_RELOC_STACK
2994		Adress of the start of the stack SPL will use after
2995		relocation.  If unspecified, this is equal to
2996		CONFIG_SPL_STACK.
2997
2998		CONFIG_SYS_SPL_MALLOC_START
2999		Starting address of the malloc pool used in SPL.
3000
3001		CONFIG_SYS_SPL_MALLOC_SIZE
3002		The size of the malloc pool used in SPL.
3003
3004		CONFIG_SPL_FRAMEWORK
3005		Enable the SPL framework under common/.  This framework
3006		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3007		NAND loading of the Linux Kernel.
3008
3009		CONFIG_SPL_DISPLAY_PRINT
3010		For ARM, enable an optional function to print more information
3011		about the running system.
3012
3013		CONFIG_SPL_INIT_MINIMAL
3014		Arch init code should be built for a very small image
3015
3016		CONFIG_SPL_LIBCOMMON_SUPPORT
3017		Support for common/libcommon.o in SPL binary
3018
3019		CONFIG_SPL_LIBDISK_SUPPORT
3020		Support for disk/libdisk.o in SPL binary
3021
3022		CONFIG_SPL_I2C_SUPPORT
3023		Support for drivers/i2c/libi2c.o in SPL binary
3024
3025		CONFIG_SPL_GPIO_SUPPORT
3026		Support for drivers/gpio/libgpio.o in SPL binary
3027
3028		CONFIG_SPL_MMC_SUPPORT
3029		Support for drivers/mmc/libmmc.o in SPL binary
3030
3031		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3032		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3033		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3034		Address, size and partition on the MMC to load U-Boot from
3035		when the MMC is being used in raw mode.
3036
3037		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3038		Sector to load kernel uImage from when MMC is being
3039		used in raw mode (for Falcon mode)
3040
3041		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3042		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3043		Sector and number of sectors to load kernel argument
3044		parameters from when MMC is being used in raw mode
3045		(for falcon mode)
3046
3047		CONFIG_SPL_FAT_SUPPORT
3048		Support for fs/fat/libfat.o in SPL binary
3049
3050		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3051		Filename to read to load U-Boot when reading from FAT
3052
3053		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3054		Filename to read to load kernel uImage when reading
3055		from FAT (for Falcon mode)
3056
3057		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3058		Filename to read to load kernel argument parameters
3059		when reading from FAT (for Falcon mode)
3060
3061		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3062		Set this for NAND SPL on PPC mpc83xx targets, so that
3063		start.S waits for the rest of the SPL to load before
3064		continuing (the hardware starts execution after just
3065		loading the first page rather than the full 4K).
3066
3067		CONFIG_SPL_NAND_BASE
3068		Include nand_base.c in the SPL.  Requires
3069		CONFIG_SPL_NAND_DRIVERS.
3070
3071		CONFIG_SPL_NAND_DRIVERS
3072		SPL uses normal NAND drivers, not minimal drivers.
3073
3074		CONFIG_SPL_NAND_ECC
3075		Include standard software ECC in the SPL
3076
3077		CONFIG_SPL_NAND_SIMPLE
3078		Support for NAND boot using simple NAND drivers that
3079		expose the cmd_ctrl() interface.
3080
3081		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3082		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3083		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3084		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3085		CONFIG_SYS_NAND_ECCBYTES
3086		Defines the size and behavior of the NAND that SPL uses
3087		to read U-Boot
3088
3089		CONFIG_SYS_NAND_U_BOOT_OFFS
3090		Location in NAND to read U-Boot from
3091
3092		CONFIG_SYS_NAND_U_BOOT_DST
3093		Location in memory to load U-Boot to
3094
3095		CONFIG_SYS_NAND_U_BOOT_SIZE
3096		Size of image to load
3097
3098		CONFIG_SYS_NAND_U_BOOT_START
3099		Entry point in loaded image to jump to
3100
3101		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3102		Define this if you need to first read the OOB and then the
3103		data. This is used for example on davinci plattforms.
3104
3105		CONFIG_SPL_OMAP3_ID_NAND
3106		Support for an OMAP3-specific set of functions to return the
3107		ID and MFR of the first attached NAND chip, if present.
3108
3109		CONFIG_SPL_SERIAL_SUPPORT
3110		Support for drivers/serial/libserial.o in SPL binary
3111
3112		CONFIG_SPL_SPI_FLASH_SUPPORT
3113		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3114
3115		CONFIG_SPL_SPI_SUPPORT
3116		Support for drivers/spi/libspi.o in SPL binary
3117
3118		CONFIG_SPL_RAM_DEVICE
3119		Support for running image already present in ram, in SPL binary
3120
3121		CONFIG_SPL_LIBGENERIC_SUPPORT
3122		Support for lib/libgeneric.o in SPL binary
3123
3124		CONFIG_SPL_ENV_SUPPORT
3125		Support for the environment operating in SPL binary
3126
3127		CONFIG_SPL_NET_SUPPORT
3128		Support for the net/libnet.o in SPL binary.
3129		It conflicts with SPL env from storage medium specified by
3130		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3131
3132		CONFIG_SPL_PAD_TO
3133		Image offset to which the SPL should be padded before appending
3134		the SPL payload. By default, this is defined as
3135		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3136		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3137		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3138
3139		CONFIG_SPL_TARGET
3140		Final target image containing SPL and payload.  Some SPLs
3141		use an arch-specific makefile fragment instead, for
3142		example if more than one image needs to be produced.
3143
3144		CONFIG_FIT_SPL_PRINT
3145		Printing information about a FIT image adds quite a bit of
3146		code to SPL. So this is normally disabled in SPL. Use this
3147		option to re-enable it. This will affect the output of the
3148		bootm command when booting a FIT image.
3149
3150Modem Support:
3151--------------
3152
3153[so far only for SMDK2400 boards]
3154
3155- Modem support enable:
3156		CONFIG_MODEM_SUPPORT
3157
3158- RTS/CTS Flow control enable:
3159		CONFIG_HWFLOW
3160
3161- Modem debug support:
3162		CONFIG_MODEM_SUPPORT_DEBUG
3163
3164		Enables debugging stuff (char screen[1024], dbg())
3165		for modem support. Useful only with BDI2000.
3166
3167- Interrupt support (PPC):
3168
3169		There are common interrupt_init() and timer_interrupt()
3170		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3171		for CPU specific initialization. interrupt_init_cpu()
3172		should set decrementer_count to appropriate value. If
3173		CPU resets decrementer automatically after interrupt
3174		(ppc4xx) it should set decrementer_count to zero.
3175		timer_interrupt() calls timer_interrupt_cpu() for CPU
3176		specific handling. If board has watchdog / status_led
3177		/ other_activity_monitor it works automatically from
3178		general timer_interrupt().
3179
3180- General:
3181
3182		In the target system modem support is enabled when a
3183		specific key (key combination) is pressed during
3184		power-on. Otherwise U-Boot will boot normally
3185		(autoboot). The key_pressed() function is called from
3186		board_init(). Currently key_pressed() is a dummy
3187		function, returning 1 and thus enabling modem
3188		initialization.
3189
3190		If there are no modem init strings in the
3191		environment, U-Boot proceed to autoboot; the
3192		previous output (banner, info printfs) will be
3193		suppressed, though.
3194
3195		See also: doc/README.Modem
3196
3197Board initialization settings:
3198------------------------------
3199
3200During Initialization u-boot calls a number of board specific functions
3201to allow the preparation of board specific prerequisites, e.g. pin setup
3202before drivers are initialized. To enable these callbacks the
3203following configuration macros have to be defined. Currently this is
3204architecture specific, so please check arch/your_architecture/lib/board.c
3205typically in board_init_f() and board_init_r().
3206
3207- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3208- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3209- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3210- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3211
3212Configuration Settings:
3213-----------------------
3214
3215- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3216		undefine this when you're short of memory.
3217
3218- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3219		width of the commands listed in the 'help' command output.
3220
3221- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3222		prompt for user input.
3223
3224- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3225
3226- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3227
3228- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3229
3230- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3231		the application (usually a Linux kernel) when it is
3232		booted
3233
3234- CONFIG_SYS_BAUDRATE_TABLE:
3235		List of legal baudrate settings for this board.
3236
3237- CONFIG_SYS_CONSOLE_INFO_QUIET
3238		Suppress display of console information at boot.
3239
3240- CONFIG_SYS_CONSOLE_IS_IN_ENV
3241		If the board specific function
3242			extern int overwrite_console (void);
3243		returns 1, the stdin, stderr and stdout are switched to the
3244		serial port, else the settings in the environment are used.
3245
3246- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3247		Enable the call to overwrite_console().
3248
3249- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3250		Enable overwrite of previous console environment settings.
3251
3252- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3253		Begin and End addresses of the area used by the
3254		simple memory test.
3255
3256- CONFIG_SYS_ALT_MEMTEST:
3257		Enable an alternate, more extensive memory test.
3258
3259- CONFIG_SYS_MEMTEST_SCRATCH:
3260		Scratch address used by the alternate memory test
3261		You only need to set this if address zero isn't writeable
3262
3263- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3264		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3265		this specified memory area will get subtracted from the top
3266		(end) of RAM and won't get "touched" at all by U-Boot. By
3267		fixing up gd->ram_size the Linux kernel should gets passed
3268		the now "corrected" memory size and won't touch it either.
3269		This should work for arch/ppc and arch/powerpc. Only Linux
3270		board ports in arch/powerpc with bootwrapper support that
3271		recalculate the memory size from the SDRAM controller setup
3272		will have to get fixed in Linux additionally.
3273
3274		This option can be used as a workaround for the 440EPx/GRx
3275		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3276		be touched.
3277
3278		WARNING: Please make sure that this value is a multiple of
3279		the Linux page size (normally 4k). If this is not the case,
3280		then the end address of the Linux memory will be located at a
3281		non page size aligned address and this could cause major
3282		problems.
3283
3284- CONFIG_SYS_LOADS_BAUD_CHANGE:
3285		Enable temporary baudrate change while serial download
3286
3287- CONFIG_SYS_SDRAM_BASE:
3288		Physical start address of SDRAM. _Must_ be 0 here.
3289
3290- CONFIG_SYS_MBIO_BASE:
3291		Physical start address of Motherboard I/O (if using a
3292		Cogent motherboard)
3293
3294- CONFIG_SYS_FLASH_BASE:
3295		Physical start address of Flash memory.
3296
3297- CONFIG_SYS_MONITOR_BASE:
3298		Physical start address of boot monitor code (set by
3299		make config files to be same as the text base address
3300		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3301		CONFIG_SYS_FLASH_BASE when booting from flash.
3302
3303- CONFIG_SYS_MONITOR_LEN:
3304		Size of memory reserved for monitor code, used to
3305		determine _at_compile_time_ (!) if the environment is
3306		embedded within the U-Boot image, or in a separate
3307		flash sector.
3308
3309- CONFIG_SYS_MALLOC_LEN:
3310		Size of DRAM reserved for malloc() use.
3311
3312- CONFIG_SYS_BOOTM_LEN:
3313		Normally compressed uImages are limited to an
3314		uncompressed size of 8 MBytes. If this is not enough,
3315		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3316		to adjust this setting to your needs.
3317
3318- CONFIG_SYS_BOOTMAPSZ:
3319		Maximum size of memory mapped by the startup code of
3320		the Linux kernel; all data that must be processed by
3321		the Linux kernel (bd_info, boot arguments, FDT blob if
3322		used) must be put below this limit, unless "bootm_low"
3323		enviroment variable is defined and non-zero. In such case
3324		all data for the Linux kernel must be between "bootm_low"
3325		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3326		variable "bootm_mapsize" will override the value of
3327		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3328		then the value in "bootm_size" will be used instead.
3329
3330- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3331		Enable initrd_high functionality.  If defined then the
3332		initrd_high feature is enabled and the bootm ramdisk subcommand
3333		is enabled.
3334
3335- CONFIG_SYS_BOOT_GET_CMDLINE:
3336		Enables allocating and saving kernel cmdline in space between
3337		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3338
3339- CONFIG_SYS_BOOT_GET_KBD:
3340		Enables allocating and saving a kernel copy of the bd_info in
3341		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3342
3343- CONFIG_SYS_MAX_FLASH_BANKS:
3344		Max number of Flash memory banks
3345
3346- CONFIG_SYS_MAX_FLASH_SECT:
3347		Max number of sectors on a Flash chip
3348
3349- CONFIG_SYS_FLASH_ERASE_TOUT:
3350		Timeout for Flash erase operations (in ms)
3351
3352- CONFIG_SYS_FLASH_WRITE_TOUT:
3353		Timeout for Flash write operations (in ms)
3354
3355- CONFIG_SYS_FLASH_LOCK_TOUT
3356		Timeout for Flash set sector lock bit operation (in ms)
3357
3358- CONFIG_SYS_FLASH_UNLOCK_TOUT
3359		Timeout for Flash clear lock bits operation (in ms)
3360
3361- CONFIG_SYS_FLASH_PROTECTION
3362		If defined, hardware flash sectors protection is used
3363		instead of U-Boot software protection.
3364
3365- CONFIG_SYS_DIRECT_FLASH_TFTP:
3366
3367		Enable TFTP transfers directly to flash memory;
3368		without this option such a download has to be
3369		performed in two steps: (1) download to RAM, and (2)
3370		copy from RAM to flash.
3371
3372		The two-step approach is usually more reliable, since
3373		you can check if the download worked before you erase
3374		the flash, but in some situations (when system RAM is
3375		too limited to allow for a temporary copy of the
3376		downloaded image) this option may be very useful.
3377
3378- CONFIG_SYS_FLASH_CFI:
3379		Define if the flash driver uses extra elements in the
3380		common flash structure for storing flash geometry.
3381
3382- CONFIG_FLASH_CFI_DRIVER
3383		This option also enables the building of the cfi_flash driver
3384		in the drivers directory
3385
3386- CONFIG_FLASH_CFI_MTD
3387		This option enables the building of the cfi_mtd driver
3388		in the drivers directory. The driver exports CFI flash
3389		to the MTD layer.
3390
3391- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3392		Use buffered writes to flash.
3393
3394- CONFIG_FLASH_SPANSION_S29WS_N
3395		s29ws-n MirrorBit flash has non-standard addresses for buffered
3396		write commands.
3397
3398- CONFIG_SYS_FLASH_QUIET_TEST
3399		If this option is defined, the common CFI flash doesn't
3400		print it's warning upon not recognized FLASH banks. This
3401		is useful, if some of the configured banks are only
3402		optionally available.
3403
3404- CONFIG_FLASH_SHOW_PROGRESS
3405		If defined (must be an integer), print out countdown
3406		digits and dots.  Recommended value: 45 (9..1) for 80
3407		column displays, 15 (3..1) for 40 column displays.
3408
3409- CONFIG_FLASH_VERIFY
3410		If defined, the content of the flash (destination) is compared
3411		against the source after the write operation. An error message
3412		will be printed when the contents are not identical.
3413		Please note that this option is useless in nearly all cases,
3414		since such flash programming errors usually are detected earlier
3415		while unprotecting/erasing/programming. Please only enable
3416		this option if you really know what you are doing.
3417
3418- CONFIG_SYS_RX_ETH_BUFFER:
3419		Defines the number of Ethernet receive buffers. On some
3420		Ethernet controllers it is recommended to set this value
3421		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3422		buffers can be full shortly after enabling the interface
3423		on high Ethernet traffic.
3424		Defaults to 4 if not defined.
3425
3426- CONFIG_ENV_MAX_ENTRIES
3427
3428	Maximum number of entries in the hash table that is used
3429	internally to store the environment settings. The default
3430	setting is supposed to be generous and should work in most
3431	cases. This setting can be used to tune behaviour; see
3432	lib/hashtable.c for details.
3433
3434- CONFIG_ENV_FLAGS_LIST_DEFAULT
3435- CONFIG_ENV_FLAGS_LIST_STATIC
3436	Enable validation of the values given to enviroment variables when
3437	calling env set.  Variables can be restricted to only decimal,
3438	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3439	the variables can also be restricted to IP address or MAC address.
3440
3441	The format of the list is:
3442		type_attribute = [s|d|x|b|i|m]
3443		access_atribute = [a|r|o|c]
3444		attributes = type_attribute[access_atribute]
3445		entry = variable_name[:attributes]
3446		list = entry[,list]
3447
3448	The type attributes are:
3449		s - String (default)
3450		d - Decimal
3451		x - Hexadecimal
3452		b - Boolean ([1yYtT|0nNfF])
3453		i - IP address
3454		m - MAC address
3455
3456	The access attributes are:
3457		a - Any (default)
3458		r - Read-only
3459		o - Write-once
3460		c - Change-default
3461
3462	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3463		Define this to a list (string) to define the ".flags"
3464		envirnoment variable in the default or embedded environment.
3465
3466	- CONFIG_ENV_FLAGS_LIST_STATIC
3467		Define this to a list (string) to define validation that
3468		should be done if an entry is not found in the ".flags"
3469		environment variable.  To override a setting in the static
3470		list, simply add an entry for the same variable name to the
3471		".flags" variable.
3472
3473- CONFIG_ENV_ACCESS_IGNORE_FORCE
3474	If defined, don't allow the -f switch to env set override variable
3475	access flags.
3476
3477- CONFIG_SYS_GENERIC_BOARD
3478	This selects the architecture-generic board system instead of the
3479	architecture-specific board files. It is intended to move boards
3480	to this new framework over time. Defining this will disable the
3481	arch/foo/lib/board.c file and use common/board_f.c and
3482	common/board_r.c instead. To use this option your architecture
3483	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3484	its config.mk file). If you find problems enabling this option on
3485	your board please report the problem and send patches!
3486
3487- CONFIG_SYS_SYM_OFFSETS
3488	This is set by architectures that use offsets for link symbols
3489	instead of absolute values. So bss_start is obtained using an
3490	offset _bss_start_ofs from CONFIG_SYS_TEXT_BASE, rather than
3491	directly. You should not need to touch this setting.
3492
3493- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3494	This is set by OMAP boards for the max time that reset should
3495	be asserted. See doc/README.omap-reset-time for details on how
3496	the value can be calulated on a given board.
3497
3498The following definitions that deal with the placement and management
3499of environment data (variable area); in general, we support the
3500following configurations:
3501
3502- CONFIG_BUILD_ENVCRC:
3503
3504	Builds up envcrc with the target environment so that external utils
3505	may easily extract it and embed it in final U-Boot images.
3506
3507- CONFIG_ENV_IS_IN_FLASH:
3508
3509	Define this if the environment is in flash memory.
3510
3511	a) The environment occupies one whole flash sector, which is
3512	   "embedded" in the text segment with the U-Boot code. This
3513	   happens usually with "bottom boot sector" or "top boot
3514	   sector" type flash chips, which have several smaller
3515	   sectors at the start or the end. For instance, such a
3516	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3517	   such a case you would place the environment in one of the
3518	   4 kB sectors - with U-Boot code before and after it. With
3519	   "top boot sector" type flash chips, you would put the
3520	   environment in one of the last sectors, leaving a gap
3521	   between U-Boot and the environment.
3522
3523	- CONFIG_ENV_OFFSET:
3524
3525	   Offset of environment data (variable area) to the
3526	   beginning of flash memory; for instance, with bottom boot
3527	   type flash chips the second sector can be used: the offset
3528	   for this sector is given here.
3529
3530	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3531
3532	- CONFIG_ENV_ADDR:
3533
3534	   This is just another way to specify the start address of
3535	   the flash sector containing the environment (instead of
3536	   CONFIG_ENV_OFFSET).
3537
3538	- CONFIG_ENV_SECT_SIZE:
3539
3540	   Size of the sector containing the environment.
3541
3542
3543	b) Sometimes flash chips have few, equal sized, BIG sectors.
3544	   In such a case you don't want to spend a whole sector for
3545	   the environment.
3546
3547	- CONFIG_ENV_SIZE:
3548
3549	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3550	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3551	   of this flash sector for the environment. This saves
3552	   memory for the RAM copy of the environment.
3553
3554	   It may also save flash memory if you decide to use this
3555	   when your environment is "embedded" within U-Boot code,
3556	   since then the remainder of the flash sector could be used
3557	   for U-Boot code. It should be pointed out that this is
3558	   STRONGLY DISCOURAGED from a robustness point of view:
3559	   updating the environment in flash makes it always
3560	   necessary to erase the WHOLE sector. If something goes
3561	   wrong before the contents has been restored from a copy in
3562	   RAM, your target system will be dead.
3563
3564	- CONFIG_ENV_ADDR_REDUND
3565	  CONFIG_ENV_SIZE_REDUND
3566
3567	   These settings describe a second storage area used to hold
3568	   a redundant copy of the environment data, so that there is
3569	   a valid backup copy in case there is a power failure during
3570	   a "saveenv" operation.
3571
3572BE CAREFUL! Any changes to the flash layout, and some changes to the
3573source code will make it necessary to adapt <board>/u-boot.lds*
3574accordingly!
3575
3576
3577- CONFIG_ENV_IS_IN_NVRAM:
3578
3579	Define this if you have some non-volatile memory device
3580	(NVRAM, battery buffered SRAM) which you want to use for the
3581	environment.
3582
3583	- CONFIG_ENV_ADDR:
3584	- CONFIG_ENV_SIZE:
3585
3586	  These two #defines are used to determine the memory area you
3587	  want to use for environment. It is assumed that this memory
3588	  can just be read and written to, without any special
3589	  provision.
3590
3591BE CAREFUL! The first access to the environment happens quite early
3592in U-Boot initalization (when we try to get the setting of for the
3593console baudrate). You *MUST* have mapped your NVRAM area then, or
3594U-Boot will hang.
3595
3596Please note that even with NVRAM we still use a copy of the
3597environment in RAM: we could work on NVRAM directly, but we want to
3598keep settings there always unmodified except somebody uses "saveenv"
3599to save the current settings.
3600
3601
3602- CONFIG_ENV_IS_IN_EEPROM:
3603
3604	Use this if you have an EEPROM or similar serial access
3605	device and a driver for it.
3606
3607	- CONFIG_ENV_OFFSET:
3608	- CONFIG_ENV_SIZE:
3609
3610	  These two #defines specify the offset and size of the
3611	  environment area within the total memory of your EEPROM.
3612
3613	- CONFIG_SYS_I2C_EEPROM_ADDR:
3614	  If defined, specified the chip address of the EEPROM device.
3615	  The default address is zero.
3616
3617	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3618	  If defined, the number of bits used to address bytes in a
3619	  single page in the EEPROM device.  A 64 byte page, for example
3620	  would require six bits.
3621
3622	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3623	  If defined, the number of milliseconds to delay between
3624	  page writes.	The default is zero milliseconds.
3625
3626	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3627	  The length in bytes of the EEPROM memory array address.  Note
3628	  that this is NOT the chip address length!
3629
3630	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3631	  EEPROM chips that implement "address overflow" are ones
3632	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3633	  address and the extra bits end up in the "chip address" bit
3634	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3635	  byte chips.
3636
3637	  Note that we consider the length of the address field to
3638	  still be one byte because the extra address bits are hidden
3639	  in the chip address.
3640
3641	- CONFIG_SYS_EEPROM_SIZE:
3642	  The size in bytes of the EEPROM device.
3643
3644	- CONFIG_ENV_EEPROM_IS_ON_I2C
3645	  define this, if you have I2C and SPI activated, and your
3646	  EEPROM, which holds the environment, is on the I2C bus.
3647
3648	- CONFIG_I2C_ENV_EEPROM_BUS
3649	  if you have an Environment on an EEPROM reached over
3650	  I2C muxes, you can define here, how to reach this
3651	  EEPROM. For example:
3652
3653	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3654
3655	  EEPROM which holds the environment, is reached over
3656	  a pca9547 i2c mux with address 0x70, channel 3.
3657
3658- CONFIG_ENV_IS_IN_DATAFLASH:
3659
3660	Define this if you have a DataFlash memory device which you
3661	want to use for the environment.
3662
3663	- CONFIG_ENV_OFFSET:
3664	- CONFIG_ENV_ADDR:
3665	- CONFIG_ENV_SIZE:
3666
3667	  These three #defines specify the offset and size of the
3668	  environment area within the total memory of your DataFlash placed
3669	  at the specified address.
3670
3671- CONFIG_ENV_IS_IN_REMOTE:
3672
3673	Define this if you have a remote memory space which you
3674	want to use for the local device's environment.
3675
3676	- CONFIG_ENV_ADDR:
3677	- CONFIG_ENV_SIZE:
3678
3679	  These two #defines specify the address and size of the
3680	  environment area within the remote memory space. The
3681	  local device can get the environment from remote memory
3682	  space by SRIO or PCIE links.
3683
3684BE CAREFUL! For some special cases, the local device can not use
3685"saveenv" command. For example, the local device will get the
3686environment stored in a remote NOR flash by SRIO or PCIE link,
3687but it can not erase, write this NOR flash by SRIO or PCIE interface.
3688
3689- CONFIG_ENV_IS_IN_NAND:
3690
3691	Define this if you have a NAND device which you want to use
3692	for the environment.
3693
3694	- CONFIG_ENV_OFFSET:
3695	- CONFIG_ENV_SIZE:
3696
3697	  These two #defines specify the offset and size of the environment
3698	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3699	  aligned to an erase block boundary.
3700
3701	- CONFIG_ENV_OFFSET_REDUND (optional):
3702
3703	  This setting describes a second storage area of CONFIG_ENV_SIZE
3704	  size used to hold a redundant copy of the environment data, so
3705	  that there is a valid backup copy in case there is a power failure
3706	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3707	  aligned to an erase block boundary.
3708
3709	- CONFIG_ENV_RANGE (optional):
3710
3711	  Specifies the length of the region in which the environment
3712	  can be written.  This should be a multiple of the NAND device's
3713	  block size.  Specifying a range with more erase blocks than
3714	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3715	  the range to be avoided.
3716
3717	- CONFIG_ENV_OFFSET_OOB (optional):
3718
3719	  Enables support for dynamically retrieving the offset of the
3720	  environment from block zero's out-of-band data.  The
3721	  "nand env.oob" command can be used to record this offset.
3722	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3723	  using CONFIG_ENV_OFFSET_OOB.
3724
3725- CONFIG_NAND_ENV_DST
3726
3727	Defines address in RAM to which the nand_spl code should copy the
3728	environment. If redundant environment is used, it will be copied to
3729	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3730
3731- CONFIG_ENV_IS_IN_UBI:
3732
3733	Define this if you have an UBI volume that you want to use for the
3734	environment.  This has the benefit of wear-leveling the environment
3735	accesses, which is important on NAND.
3736
3737	- CONFIG_ENV_UBI_PART:
3738
3739	  Define this to a string that is the mtd partition containing the UBI.
3740
3741	- CONFIG_ENV_UBI_VOLUME:
3742
3743	  Define this to the name of the volume that you want to store the
3744	  environment in.
3745
3746	- CONFIG_ENV_UBI_VOLUME_REDUND:
3747
3748	  Define this to the name of another volume to store a second copy of
3749	  the environment in.  This will enable redundant environments in UBI.
3750	  It is assumed that both volumes are in the same MTD partition.
3751
3752	- CONFIG_UBI_SILENCE_MSG
3753	- CONFIG_UBIFS_SILENCE_MSG
3754
3755	  You will probably want to define these to avoid a really noisy system
3756	  when storing the env in UBI.
3757
3758- CONFIG_ENV_IS_IN_MMC:
3759
3760	Define this if you have an MMC device which you want to use for the
3761	environment.
3762
3763	- CONFIG_SYS_MMC_ENV_DEV:
3764
3765	  Specifies which MMC device the environment is stored in.
3766
3767	- CONFIG_SYS_MMC_ENV_PART (optional):
3768
3769	  Specifies which MMC partition the environment is stored in. If not
3770	  set, defaults to partition 0, the user area. Common values might be
3771	  1 (first MMC boot partition), 2 (second MMC boot partition).
3772
3773	- CONFIG_ENV_OFFSET:
3774	- CONFIG_ENV_SIZE:
3775
3776	  These two #defines specify the offset and size of the environment
3777	  area within the specified MMC device.
3778
3779	  If offset is positive (the usual case), it is treated as relative to
3780	  the start of the MMC partition. If offset is negative, it is treated
3781	  as relative to the end of the MMC partition. This can be useful if
3782	  your board may be fitted with different MMC devices, which have
3783	  different sizes for the MMC partitions, and you always want the
3784	  environment placed at the very end of the partition, to leave the
3785	  maximum possible space before it, to store other data.
3786
3787	  These two values are in units of bytes, but must be aligned to an
3788	  MMC sector boundary.
3789
3790	- CONFIG_ENV_OFFSET_REDUND (optional):
3791
3792	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3793	  hold a redundant copy of the environment data. This provides a
3794	  valid backup copy in case the other copy is corrupted, e.g. due
3795	  to a power failure during a "saveenv" operation.
3796
3797	  This value may also be positive or negative; this is handled in the
3798	  same way as CONFIG_ENV_OFFSET.
3799
3800	  This value is also in units of bytes, but must also be aligned to
3801	  an MMC sector boundary.
3802
3803	- CONFIG_ENV_SIZE_REDUND (optional):
3804
3805	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3806	  set. If this value is set, it must be set to the same value as
3807	  CONFIG_ENV_SIZE.
3808
3809- CONFIG_SYS_SPI_INIT_OFFSET
3810
3811	Defines offset to the initial SPI buffer area in DPRAM. The
3812	area is used at an early stage (ROM part) if the environment
3813	is configured to reside in the SPI EEPROM: We need a 520 byte
3814	scratch DPRAM area. It is used between the two initialization
3815	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3816	to be a good choice since it makes it far enough from the
3817	start of the data area as well as from the stack pointer.
3818
3819Please note that the environment is read-only until the monitor
3820has been relocated to RAM and a RAM copy of the environment has been
3821created; also, when using EEPROM you will have to use getenv_f()
3822until then to read environment variables.
3823
3824The environment is protected by a CRC32 checksum. Before the monitor
3825is relocated into RAM, as a result of a bad CRC you will be working
3826with the compiled-in default environment - *silently*!!! [This is
3827necessary, because the first environment variable we need is the
3828"baudrate" setting for the console - if we have a bad CRC, we don't
3829have any device yet where we could complain.]
3830
3831Note: once the monitor has been relocated, then it will complain if
3832the default environment is used; a new CRC is computed as soon as you
3833use the "saveenv" command to store a valid environment.
3834
3835- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3836		Echo the inverted Ethernet link state to the fault LED.
3837
3838		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3839		      also needs to be defined.
3840
3841- CONFIG_SYS_FAULT_MII_ADDR:
3842		MII address of the PHY to check for the Ethernet link state.
3843
3844- CONFIG_NS16550_MIN_FUNCTIONS:
3845		Define this if you desire to only have use of the NS16550_init
3846		and NS16550_putc functions for the serial driver located at
3847		drivers/serial/ns16550.c.  This option is useful for saving
3848		space for already greatly restricted images, including but not
3849		limited to NAND_SPL configurations.
3850
3851- CONFIG_DISPLAY_BOARDINFO
3852		Display information about the board that U-Boot is running on
3853		when U-Boot starts up. The board function checkboard() is called
3854		to do this.
3855
3856- CONFIG_DISPLAY_BOARDINFO_LATE
3857		Similar to the previous option, but display this information
3858		later, once stdio is running and output goes to the LCD, if
3859		present.
3860
3861Low Level (hardware related) configuration options:
3862---------------------------------------------------
3863
3864- CONFIG_SYS_CACHELINE_SIZE:
3865		Cache Line Size of the CPU.
3866
3867- CONFIG_SYS_DEFAULT_IMMR:
3868		Default address of the IMMR after system reset.
3869
3870		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3871		and RPXsuper) to be able to adjust the position of
3872		the IMMR register after a reset.
3873
3874- CONFIG_SYS_CCSRBAR_DEFAULT:
3875		Default (power-on reset) physical address of CCSR on Freescale
3876		PowerPC SOCs.
3877
3878- CONFIG_SYS_CCSRBAR:
3879		Virtual address of CCSR.  On a 32-bit build, this is typically
3880		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3881
3882		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3883		for cross-platform code that uses that macro instead.
3884
3885- CONFIG_SYS_CCSRBAR_PHYS:
3886		Physical address of CCSR.  CCSR can be relocated to a new
3887		physical address, if desired.  In this case, this macro should
3888		be set to that address.	 Otherwise, it should be set to the
3889		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3890		is typically relocated on 36-bit builds.  It is recommended
3891		that this macro be defined via the _HIGH and _LOW macros:
3892
3893		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3894			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3895
3896- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3897		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3898		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3899		used in assembly code, so it must not contain typecasts or
3900		integer size suffixes (e.g. "ULL").
3901
3902- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3903		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3904		used in assembly code, so it must not contain typecasts or
3905		integer size suffixes (e.g. "ULL").
3906
3907- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3908		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3909		forced to a value that ensures that CCSR is not relocated.
3910
3911- Floppy Disk Support:
3912		CONFIG_SYS_FDC_DRIVE_NUMBER
3913
3914		the default drive number (default value 0)
3915
3916		CONFIG_SYS_ISA_IO_STRIDE
3917
3918		defines the spacing between FDC chipset registers
3919		(default value 1)
3920
3921		CONFIG_SYS_ISA_IO_OFFSET
3922
3923		defines the offset of register from address. It
3924		depends on which part of the data bus is connected to
3925		the FDC chipset. (default value 0)
3926
3927		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3928		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3929		default value.
3930
3931		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3932		fdc_hw_init() is called at the beginning of the FDC
3933		setup. fdc_hw_init() must be provided by the board
3934		source code. It is used to make hardware dependant
3935		initializations.
3936
3937- CONFIG_IDE_AHB:
3938		Most IDE controllers were designed to be connected with PCI
3939		interface. Only few of them were designed for AHB interface.
3940		When software is doing ATA command and data transfer to
3941		IDE devices through IDE-AHB controller, some additional
3942		registers accessing to these kind of IDE-AHB controller
3943		is requierd.
3944
3945- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3946		DO NOT CHANGE unless you know exactly what you're
3947		doing! (11-4) [MPC8xx/82xx systems only]
3948
3949- CONFIG_SYS_INIT_RAM_ADDR:
3950
3951		Start address of memory area that can be used for
3952		initial data and stack; please note that this must be
3953		writable memory that is working WITHOUT special
3954		initialization, i. e. you CANNOT use normal RAM which
3955		will become available only after programming the
3956		memory controller and running certain initialization
3957		sequences.
3958
3959		U-Boot uses the following memory types:
3960		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3961		- MPC824X: data cache
3962		- PPC4xx:  data cache
3963
3964- CONFIG_SYS_GBL_DATA_OFFSET:
3965
3966		Offset of the initial data structure in the memory
3967		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3968		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3969		data is located at the end of the available space
3970		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3971		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3972		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3973		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3974
3975	Note:
3976		On the MPC824X (or other systems that use the data
3977		cache for initial memory) the address chosen for
3978		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3979		point to an otherwise UNUSED address space between
3980		the top of RAM and the start of the PCI space.
3981
3982- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3983
3984- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3985
3986- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3987
3988- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3989
3990- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3991
3992- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3993
3994- CONFIG_SYS_OR_TIMING_SDRAM:
3995		SDRAM timing
3996
3997- CONFIG_SYS_MAMR_PTA:
3998		periodic timer for refresh
3999
4000- CONFIG_SYS_DER:	Debug Event Register (37-47)
4001
4002- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4003  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4004  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4005  CONFIG_SYS_BR1_PRELIM:
4006		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4007
4008- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4009  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4010  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4011		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4012
4013- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4014  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4015		Machine Mode Register and Memory Periodic Timer
4016		Prescaler definitions (SDRAM timing)
4017
4018- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4019		enable I2C microcode relocation patch (MPC8xx);
4020		define relocation offset in DPRAM [DSP2]
4021
4022- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4023		enable SMC microcode relocation patch (MPC8xx);
4024		define relocation offset in DPRAM [SMC1]
4025
4026- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4027		enable SPI microcode relocation patch (MPC8xx);
4028		define relocation offset in DPRAM [SCC4]
4029
4030- CONFIG_SYS_USE_OSCCLK:
4031		Use OSCM clock mode on MBX8xx board. Be careful,
4032		wrong setting might damage your board. Read
4033		doc/README.MBX before setting this variable!
4034
4035- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4036		Offset of the bootmode word in DPRAM used by post
4037		(Power On Self Tests). This definition overrides
4038		#define'd default value in commproc.h resp.
4039		cpm_8260.h.
4040
4041- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4042  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4043  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4044  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4045  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4046  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4047  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4048  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4049		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4050
4051- CONFIG_PCI_DISABLE_PCIE:
4052		Disable PCI-Express on systems where it is supported but not
4053		required.
4054
4055- CONFIG_PCI_ENUM_ONLY
4056		Only scan through and get the devices on the busses.
4057		Don't do any setup work, presumably because someone or
4058		something has already done it, and we don't need to do it
4059		a second time.	Useful for platforms that are pre-booted
4060		by coreboot or similar.
4061
4062- CONFIG_PCI_INDIRECT_BRIDGE:
4063		Enable support for indirect PCI bridges.
4064
4065- CONFIG_SYS_SRIO:
4066		Chip has SRIO or not
4067
4068- CONFIG_SRIO1:
4069		Board has SRIO 1 port available
4070
4071- CONFIG_SRIO2:
4072		Board has SRIO 2 port available
4073
4074- CONFIG_SRIO_PCIE_BOOT_MASTER
4075		Board can support master function for Boot from SRIO and PCIE
4076
4077- CONFIG_SYS_SRIOn_MEM_VIRT:
4078		Virtual Address of SRIO port 'n' memory region
4079
4080- CONFIG_SYS_SRIOn_MEM_PHYS:
4081		Physical Address of SRIO port 'n' memory region
4082
4083- CONFIG_SYS_SRIOn_MEM_SIZE:
4084		Size of SRIO port 'n' memory region
4085
4086- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4087		Defined to tell the NAND controller that the NAND chip is using
4088		a 16 bit bus.
4089		Not all NAND drivers use this symbol.
4090		Example of drivers that use it:
4091		- drivers/mtd/nand/ndfc.c
4092		- drivers/mtd/nand/mxc_nand.c
4093
4094- CONFIG_SYS_NDFC_EBC0_CFG
4095		Sets the EBC0_CFG register for the NDFC. If not defined
4096		a default value will be used.
4097
4098- CONFIG_SPD_EEPROM
4099		Get DDR timing information from an I2C EEPROM. Common
4100		with pluggable memory modules such as SODIMMs
4101
4102  SPD_EEPROM_ADDRESS
4103		I2C address of the SPD EEPROM
4104
4105- CONFIG_SYS_SPD_BUS_NUM
4106		If SPD EEPROM is on an I2C bus other than the first
4107		one, specify here. Note that the value must resolve
4108		to something your driver can deal with.
4109
4110- CONFIG_SYS_DDR_RAW_TIMING
4111		Get DDR timing information from other than SPD. Common with
4112		soldered DDR chips onboard without SPD. DDR raw timing
4113		parameters are extracted from datasheet and hard-coded into
4114		header files or board specific files.
4115
4116- CONFIG_FSL_DDR_INTERACTIVE
4117		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4118
4119- CONFIG_SYS_83XX_DDR_USES_CS0
4120		Only for 83xx systems. If specified, then DDR should
4121		be configured using CS0 and CS1 instead of CS2 and CS3.
4122
4123- CONFIG_ETHER_ON_FEC[12]
4124		Define to enable FEC[12] on a 8xx series processor.
4125
4126- CONFIG_FEC[12]_PHY
4127		Define to the hardcoded PHY address which corresponds
4128		to the given FEC; i. e.
4129			#define CONFIG_FEC1_PHY 4
4130		means that the PHY with address 4 is connected to FEC1
4131
4132		When set to -1, means to probe for first available.
4133
4134- CONFIG_FEC[12]_PHY_NORXERR
4135		The PHY does not have a RXERR line (RMII only).
4136		(so program the FEC to ignore it).
4137
4138- CONFIG_RMII
4139		Enable RMII mode for all FECs.
4140		Note that this is a global option, we can't
4141		have one FEC in standard MII mode and another in RMII mode.
4142
4143- CONFIG_CRC32_VERIFY
4144		Add a verify option to the crc32 command.
4145		The syntax is:
4146
4147		=> crc32 -v <address> <count> <crc32>
4148
4149		Where address/count indicate a memory area
4150		and crc32 is the correct crc32 which the
4151		area should have.
4152
4153- CONFIG_LOOPW
4154		Add the "loopw" memory command. This only takes effect if
4155		the memory commands are activated globally (CONFIG_CMD_MEM).
4156
4157- CONFIG_MX_CYCLIC
4158		Add the "mdc" and "mwc" memory commands. These are cyclic
4159		"md/mw" commands.
4160		Examples:
4161
4162		=> mdc.b 10 4 500
4163		This command will print 4 bytes (10,11,12,13) each 500 ms.
4164
4165		=> mwc.l 100 12345678 10
4166		This command will write 12345678 to address 100 all 10 ms.
4167
4168		This only takes effect if the memory commands are activated
4169		globally (CONFIG_CMD_MEM).
4170
4171- CONFIG_SKIP_LOWLEVEL_INIT
4172		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4173		low level initializations (like setting up the memory
4174		controller) are omitted and/or U-Boot does not
4175		relocate itself into RAM.
4176
4177		Normally this variable MUST NOT be defined. The only
4178		exception is when U-Boot is loaded (to RAM) by some
4179		other boot loader or by a debugger which performs
4180		these initializations itself.
4181
4182- CONFIG_SPL_BUILD
4183		Modifies the behaviour of start.S when compiling a loader
4184		that is executed before the actual U-Boot. E.g. when
4185		compiling a NAND SPL.
4186
4187- CONFIG_SYS_MPC85XX_NO_RESETVEC
4188		Only for 85xx systems. If this variable is specified, the section
4189		.resetvec is not kept and the section .bootpg is placed in the
4190		previous 4k of the .text section.
4191
4192- CONFIG_ARCH_MAP_SYSMEM
4193		Generally U-Boot (and in particular the md command) uses
4194		effective address. It is therefore not necessary to regard
4195		U-Boot address as virtual addresses that need to be translated
4196		to physical addresses. However, sandbox requires this, since
4197		it maintains its own little RAM buffer which contains all
4198		addressable memory. This option causes some memory accesses
4199		to be mapped through map_sysmem() / unmap_sysmem().
4200
4201- CONFIG_USE_ARCH_MEMCPY
4202  CONFIG_USE_ARCH_MEMSET
4203		If these options are used a optimized version of memcpy/memset will
4204		be used if available. These functions may be faster under some
4205		conditions but may increase the binary size.
4206
4207- CONFIG_X86_RESET_VECTOR
4208		If defined, the x86 reset vector code is included. This is not
4209		needed when U-Boot is running from Coreboot.
4210
4211- CONFIG_SYS_MPUCLK
4212		Defines the MPU clock speed (in MHz).
4213
4214		NOTE : currently only supported on AM335x platforms.
4215
4216Freescale QE/FMAN Firmware Support:
4217-----------------------------------
4218
4219The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4220loading of "firmware", which is encoded in the QE firmware binary format.
4221This firmware often needs to be loaded during U-Boot booting, so macros
4222are used to identify the storage device (NOR flash, SPI, etc) and the address
4223within that device.
4224
4225- CONFIG_SYS_QE_FMAN_FW_ADDR
4226	The address in the storage device where the firmware is located.  The
4227	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4228	is also specified.
4229
4230- CONFIG_SYS_QE_FMAN_FW_LENGTH
4231	The maximum possible size of the firmware.  The firmware binary format
4232	has a field that specifies the actual size of the firmware, but it
4233	might not be possible to read any part of the firmware unless some
4234	local storage is allocated to hold the entire firmware first.
4235
4236- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4237	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4238	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4239	virtual address in NOR flash.
4240
4241- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4242	Specifies that QE/FMAN firmware is located in NAND flash.
4243	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4244
4245- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4246	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4247	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4248
4249- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4250	Specifies that QE/FMAN firmware is located on the primary SPI
4251	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4252
4253- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4254	Specifies that QE/FMAN firmware is located in the remote (master)
4255	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4256	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4257	window->master inbound window->master LAW->the ucode address in
4258	master's memory space.
4259
4260Building the Software:
4261======================
4262
4263Building U-Boot has been tested in several native build environments
4264and in many different cross environments. Of course we cannot support
4265all possibly existing versions of cross development tools in all
4266(potentially obsolete) versions. In case of tool chain problems we
4267recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4268which is extensively used to build and test U-Boot.
4269
4270If you are not using a native environment, it is assumed that you
4271have GNU cross compiling tools available in your path. In this case,
4272you must set the environment variable CROSS_COMPILE in your shell.
4273Note that no changes to the Makefile or any other source files are
4274necessary. For example using the ELDK on a 4xx CPU, please enter:
4275
4276	$ CROSS_COMPILE=ppc_4xx-
4277	$ export CROSS_COMPILE
4278
4279Note: If you wish to generate Windows versions of the utilities in
4280      the tools directory you can use the MinGW toolchain
4281      (http://www.mingw.org).  Set your HOST tools to the MinGW
4282      toolchain and execute 'make tools'.  For example:
4283
4284       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4285
4286      Binaries such as tools/mkimage.exe will be created which can
4287      be executed on computers running Windows.
4288
4289U-Boot is intended to be simple to build. After installing the
4290sources you must configure U-Boot for one specific board type. This
4291is done by typing:
4292
4293	make NAME_config
4294
4295where "NAME_config" is the name of one of the existing configu-
4296rations; see boards.cfg for supported names.
4297
4298Note: for some board special configuration names may exist; check if
4299      additional information is available from the board vendor; for
4300      instance, the TQM823L systems are available without (standard)
4301      or with LCD support. You can select such additional "features"
4302      when choosing the configuration, i. e.
4303
4304      make TQM823L_config
4305	- will configure for a plain TQM823L, i. e. no LCD support
4306
4307      make TQM823L_LCD_config
4308	- will configure for a TQM823L with U-Boot console on LCD
4309
4310      etc.
4311
4312
4313Finally, type "make all", and you should get some working U-Boot
4314images ready for download to / installation on your system:
4315
4316- "u-boot.bin" is a raw binary image
4317- "u-boot" is an image in ELF binary format
4318- "u-boot.srec" is in Motorola S-Record format
4319
4320By default the build is performed locally and the objects are saved
4321in the source directory. One of the two methods can be used to change
4322this behavior and build U-Boot to some external directory:
4323
43241. Add O= to the make command line invocations:
4325
4326	make O=/tmp/build distclean
4327	make O=/tmp/build NAME_config
4328	make O=/tmp/build all
4329
43302. Set environment variable BUILD_DIR to point to the desired location:
4331
4332	export BUILD_DIR=/tmp/build
4333	make distclean
4334	make NAME_config
4335	make all
4336
4337Note that the command line "O=" setting overrides the BUILD_DIR environment
4338variable.
4339
4340
4341Please be aware that the Makefiles assume you are using GNU make, so
4342for instance on NetBSD you might need to use "gmake" instead of
4343native "make".
4344
4345
4346If the system board that you have is not listed, then you will need
4347to port U-Boot to your hardware platform. To do this, follow these
4348steps:
4349
43501.  Add a new configuration option for your board to the toplevel
4351    "boards.cfg" file, using the existing entries as examples.
4352    Follow the instructions there to keep the boards in order.
43532.  Create a new directory to hold your board specific code. Add any
4354    files you need. In your board directory, you will need at least
4355    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
43563.  Create a new configuration file "include/configs/<board>.h" for
4357    your board
43583.  If you're porting U-Boot to a new CPU, then also create a new
4359    directory to hold your CPU specific code. Add any files you need.
43604.  Run "make <board>_config" with your new name.
43615.  Type "make", and you should get a working "u-boot.srec" file
4362    to be installed on your target system.
43636.  Debug and solve any problems that might arise.
4364    [Of course, this last step is much harder than it sounds.]
4365
4366
4367Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4368==============================================================
4369
4370If you have modified U-Boot sources (for instance added a new board
4371or support for new devices, a new CPU, etc.) you are expected to
4372provide feedback to the other developers. The feedback normally takes
4373the form of a "patch", i. e. a context diff against a certain (latest
4374official or latest in the git repository) version of U-Boot sources.
4375
4376But before you submit such a patch, please verify that your modifi-
4377cation did not break existing code. At least make sure that *ALL* of
4378the supported boards compile WITHOUT ANY compiler warnings. To do so,
4379just run the "MAKEALL" script, which will configure and build U-Boot
4380for ALL supported system. Be warned, this will take a while. You can
4381select which (cross) compiler to use by passing a `CROSS_COMPILE'
4382environment variable to the script, i. e. to use the ELDK cross tools
4383you can type
4384
4385	CROSS_COMPILE=ppc_8xx- MAKEALL
4386
4387or to build on a native PowerPC system you can type
4388
4389	CROSS_COMPILE=' ' MAKEALL
4390
4391When using the MAKEALL script, the default behaviour is to build
4392U-Boot in the source directory. This location can be changed by
4393setting the BUILD_DIR environment variable. Also, for each target
4394built, the MAKEALL script saves two log files (<target>.ERR and
4395<target>.MAKEALL) in the <source dir>/LOG directory. This default
4396location can be changed by setting the MAKEALL_LOGDIR environment
4397variable. For example:
4398
4399	export BUILD_DIR=/tmp/build
4400	export MAKEALL_LOGDIR=/tmp/log
4401	CROSS_COMPILE=ppc_8xx- MAKEALL
4402
4403With the above settings build objects are saved in the /tmp/build,
4404log files are saved in the /tmp/log and the source tree remains clean
4405during the whole build process.
4406
4407
4408See also "U-Boot Porting Guide" below.
4409
4410
4411Monitor Commands - Overview:
4412============================
4413
4414go	- start application at address 'addr'
4415run	- run commands in an environment variable
4416bootm	- boot application image from memory
4417bootp	- boot image via network using BootP/TFTP protocol
4418bootz   - boot zImage from memory
4419tftpboot- boot image via network using TFTP protocol
4420	       and env variables "ipaddr" and "serverip"
4421	       (and eventually "gatewayip")
4422tftpput - upload a file via network using TFTP protocol
4423rarpboot- boot image via network using RARP/TFTP protocol
4424diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4425loads	- load S-Record file over serial line
4426loadb	- load binary file over serial line (kermit mode)
4427md	- memory display
4428mm	- memory modify (auto-incrementing)
4429nm	- memory modify (constant address)
4430mw	- memory write (fill)
4431cp	- memory copy
4432cmp	- memory compare
4433crc32	- checksum calculation
4434i2c	- I2C sub-system
4435sspi	- SPI utility commands
4436base	- print or set address offset
4437printenv- print environment variables
4438setenv	- set environment variables
4439saveenv - save environment variables to persistent storage
4440protect - enable or disable FLASH write protection
4441erase	- erase FLASH memory
4442flinfo	- print FLASH memory information
4443nand	- NAND memory operations (see doc/README.nand)
4444bdinfo	- print Board Info structure
4445iminfo	- print header information for application image
4446coninfo - print console devices and informations
4447ide	- IDE sub-system
4448loop	- infinite loop on address range
4449loopw	- infinite write loop on address range
4450mtest	- simple RAM test
4451icache	- enable or disable instruction cache
4452dcache	- enable or disable data cache
4453reset	- Perform RESET of the CPU
4454echo	- echo args to console
4455version - print monitor version
4456help	- print online help
4457?	- alias for 'help'
4458
4459
4460Monitor Commands - Detailed Description:
4461========================================
4462
4463TODO.
4464
4465For now: just type "help <command>".
4466
4467
4468Environment Variables:
4469======================
4470
4471U-Boot supports user configuration using Environment Variables which
4472can be made persistent by saving to Flash memory.
4473
4474Environment Variables are set using "setenv", printed using
4475"printenv", and saved to Flash using "saveenv". Using "setenv"
4476without a value can be used to delete a variable from the
4477environment. As long as you don't save the environment you are
4478working with an in-memory copy. In case the Flash area containing the
4479environment is erased by accident, a default environment is provided.
4480
4481Some configuration options can be set using Environment Variables.
4482
4483List of environment variables (most likely not complete):
4484
4485  baudrate	- see CONFIG_BAUDRATE
4486
4487  bootdelay	- see CONFIG_BOOTDELAY
4488
4489  bootcmd	- see CONFIG_BOOTCOMMAND
4490
4491  bootargs	- Boot arguments when booting an RTOS image
4492
4493  bootfile	- Name of the image to load with TFTP
4494
4495  bootm_low	- Memory range available for image processing in the bootm
4496		  command can be restricted. This variable is given as
4497		  a hexadecimal number and defines lowest address allowed
4498		  for use by the bootm command. See also "bootm_size"
4499		  environment variable. Address defined by "bootm_low" is
4500		  also the base of the initial memory mapping for the Linux
4501		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4502		  bootm_mapsize.
4503
4504  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4505		  This variable is given as a hexadecimal number and it
4506		  defines the size of the memory region starting at base
4507		  address bootm_low that is accessible by the Linux kernel
4508		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4509		  as the default value if it is defined, and bootm_size is
4510		  used otherwise.
4511
4512  bootm_size	- Memory range available for image processing in the bootm
4513		  command can be restricted. This variable is given as
4514		  a hexadecimal number and defines the size of the region
4515		  allowed for use by the bootm command. See also "bootm_low"
4516		  environment variable.
4517
4518  updatefile	- Location of the software update file on a TFTP server, used
4519		  by the automatic software update feature. Please refer to
4520		  documentation in doc/README.update for more details.
4521
4522  autoload	- if set to "no" (any string beginning with 'n'),
4523		  "bootp" will just load perform a lookup of the
4524		  configuration from the BOOTP server, but not try to
4525		  load any image using TFTP
4526
4527  autostart	- if set to "yes", an image loaded using the "bootp",
4528		  "rarpboot", "tftpboot" or "diskboot" commands will
4529		  be automatically started (by internally calling
4530		  "bootm")
4531
4532		  If set to "no", a standalone image passed to the
4533		  "bootm" command will be copied to the load address
4534		  (and eventually uncompressed), but NOT be started.
4535		  This can be used to load and uncompress arbitrary
4536		  data.
4537
4538  fdt_high	- if set this restricts the maximum address that the
4539		  flattened device tree will be copied into upon boot.
4540		  For example, if you have a system with 1 GB memory
4541		  at physical address 0x10000000, while Linux kernel
4542		  only recognizes the first 704 MB as low memory, you
4543		  may need to set fdt_high as 0x3C000000 to have the
4544		  device tree blob be copied to the maximum address
4545		  of the 704 MB low memory, so that Linux kernel can
4546		  access it during the boot procedure.
4547
4548		  If this is set to the special value 0xFFFFFFFF then
4549		  the fdt will not be copied at all on boot.  For this
4550		  to work it must reside in writable memory, have
4551		  sufficient padding on the end of it for u-boot to
4552		  add the information it needs into it, and the memory
4553		  must be accessible by the kernel.
4554
4555  fdtcontroladdr- if set this is the address of the control flattened
4556		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4557		  defined.
4558
4559  i2cfast	- (PPC405GP|PPC405EP only)
4560		  if set to 'y' configures Linux I2C driver for fast
4561		  mode (400kHZ). This environment variable is used in
4562		  initialization code. So, for changes to be effective
4563		  it must be saved and board must be reset.
4564
4565  initrd_high	- restrict positioning of initrd images:
4566		  If this variable is not set, initrd images will be
4567		  copied to the highest possible address in RAM; this
4568		  is usually what you want since it allows for
4569		  maximum initrd size. If for some reason you want to
4570		  make sure that the initrd image is loaded below the
4571		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4572		  variable to a value of "no" or "off" or "0".
4573		  Alternatively, you can set it to a maximum upper
4574		  address to use (U-Boot will still check that it
4575		  does not overwrite the U-Boot stack and data).
4576
4577		  For instance, when you have a system with 16 MB
4578		  RAM, and want to reserve 4 MB from use by Linux,
4579		  you can do this by adding "mem=12M" to the value of
4580		  the "bootargs" variable. However, now you must make
4581		  sure that the initrd image is placed in the first
4582		  12 MB as well - this can be done with
4583
4584		  setenv initrd_high 00c00000
4585
4586		  If you set initrd_high to 0xFFFFFFFF, this is an
4587		  indication to U-Boot that all addresses are legal
4588		  for the Linux kernel, including addresses in flash
4589		  memory. In this case U-Boot will NOT COPY the
4590		  ramdisk at all. This may be useful to reduce the
4591		  boot time on your system, but requires that this
4592		  feature is supported by your Linux kernel.
4593
4594  ipaddr	- IP address; needed for tftpboot command
4595
4596  loadaddr	- Default load address for commands like "bootp",
4597		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4598
4599  loads_echo	- see CONFIG_LOADS_ECHO
4600
4601  serverip	- TFTP server IP address; needed for tftpboot command
4602
4603  bootretry	- see CONFIG_BOOT_RETRY_TIME
4604
4605  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4606
4607  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4608
4609  ethprime	- controls which interface is used first.
4610
4611  ethact	- controls which interface is currently active.
4612		  For example you can do the following
4613
4614		  => setenv ethact FEC
4615		  => ping 192.168.0.1 # traffic sent on FEC
4616		  => setenv ethact SCC
4617		  => ping 10.0.0.1 # traffic sent on SCC
4618
4619  ethrotate	- When set to "no" U-Boot does not go through all
4620		  available network interfaces.
4621		  It just stays at the currently selected interface.
4622
4623  netretry	- When set to "no" each network operation will
4624		  either succeed or fail without retrying.
4625		  When set to "once" the network operation will
4626		  fail when all the available network interfaces
4627		  are tried once without success.
4628		  Useful on scripts which control the retry operation
4629		  themselves.
4630
4631  npe_ucode	- set load address for the NPE microcode
4632
4633  tftpsrcport	- If this is set, the value is used for TFTP's
4634		  UDP source port.
4635
4636  tftpdstport	- If this is set, the value is used for TFTP's UDP
4637		  destination port instead of the Well Know Port 69.
4638
4639  tftpblocksize - Block size to use for TFTP transfers; if not set,
4640		  we use the TFTP server's default block size
4641
4642  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4643		  seconds, minimum value is 1000 = 1 second). Defines
4644		  when a packet is considered to be lost so it has to
4645		  be retransmitted. The default is 5000 = 5 seconds.
4646		  Lowering this value may make downloads succeed
4647		  faster in networks with high packet loss rates or
4648		  with unreliable TFTP servers.
4649
4650  vlan		- When set to a value < 4095 the traffic over
4651		  Ethernet is encapsulated/received over 802.1q
4652		  VLAN tagged frames.
4653
4654The following image location variables contain the location of images
4655used in booting. The "Image" column gives the role of the image and is
4656not an environment variable name. The other columns are environment
4657variable names. "File Name" gives the name of the file on a TFTP
4658server, "RAM Address" gives the location in RAM the image will be
4659loaded to, and "Flash Location" gives the image's address in NOR
4660flash or offset in NAND flash.
4661
4662*Note* - these variables don't have to be defined for all boards, some
4663boards currenlty use other variables for these purposes, and some
4664boards use these variables for other purposes.
4665
4666Image		    File Name	     RAM Address       Flash Location
4667-----		    ---------	     -----------       --------------
4668u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4669Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4670device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4671ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4672
4673The following environment variables may be used and automatically
4674updated by the network boot commands ("bootp" and "rarpboot"),
4675depending the information provided by your boot server:
4676
4677  bootfile	- see above
4678  dnsip		- IP address of your Domain Name Server
4679  dnsip2	- IP address of your secondary Domain Name Server
4680  gatewayip	- IP address of the Gateway (Router) to use
4681  hostname	- Target hostname
4682  ipaddr	- see above
4683  netmask	- Subnet Mask
4684  rootpath	- Pathname of the root filesystem on the NFS server
4685  serverip	- see above
4686
4687
4688There are two special Environment Variables:
4689
4690  serial#	- contains hardware identification information such
4691		  as type string and/or serial number
4692  ethaddr	- Ethernet address
4693
4694These variables can be set only once (usually during manufacturing of
4695the board). U-Boot refuses to delete or overwrite these variables
4696once they have been set once.
4697
4698
4699Further special Environment Variables:
4700
4701  ver		- Contains the U-Boot version string as printed
4702		  with the "version" command. This variable is
4703		  readonly (see CONFIG_VERSION_VARIABLE).
4704
4705
4706Please note that changes to some configuration parameters may take
4707only effect after the next boot (yes, that's just like Windoze :-).
4708
4709
4710Callback functions for environment variables:
4711---------------------------------------------
4712
4713For some environment variables, the behavior of u-boot needs to change
4714when their values are changed.  This functionailty allows functions to
4715be associated with arbitrary variables.  On creation, overwrite, or
4716deletion, the callback will provide the opportunity for some side
4717effect to happen or for the change to be rejected.
4718
4719The callbacks are named and associated with a function using the
4720U_BOOT_ENV_CALLBACK macro in your board or driver code.
4721
4722These callbacks are associated with variables in one of two ways.  The
4723static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4724in the board configuration to a string that defines a list of
4725associations.  The list must be in the following format:
4726
4727	entry = variable_name[:callback_name]
4728	list = entry[,list]
4729
4730If the callback name is not specified, then the callback is deleted.
4731Spaces are also allowed anywhere in the list.
4732
4733Callbacks can also be associated by defining the ".callbacks" variable
4734with the same list format above.  Any association in ".callbacks" will
4735override any association in the static list. You can define
4736CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4737".callbacks" envirnoment variable in the default or embedded environment.
4738
4739
4740Command Line Parsing:
4741=====================
4742
4743There are two different command line parsers available with U-Boot:
4744the old "simple" one, and the much more powerful "hush" shell:
4745
4746Old, simple command line parser:
4747--------------------------------
4748
4749- supports environment variables (through setenv / saveenv commands)
4750- several commands on one line, separated by ';'
4751- variable substitution using "... ${name} ..." syntax
4752- special characters ('$', ';') can be escaped by prefixing with '\',
4753  for example:
4754	setenv bootcmd bootm \${address}
4755- You can also escape text by enclosing in single apostrophes, for example:
4756	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4757
4758Hush shell:
4759-----------
4760
4761- similar to Bourne shell, with control structures like
4762  if...then...else...fi, for...do...done; while...do...done,
4763  until...do...done, ...
4764- supports environment ("global") variables (through setenv / saveenv
4765  commands) and local shell variables (through standard shell syntax
4766  "name=value"); only environment variables can be used with "run"
4767  command
4768
4769General rules:
4770--------------
4771
4772(1) If a command line (or an environment variable executed by a "run"
4773    command) contains several commands separated by semicolon, and
4774    one of these commands fails, then the remaining commands will be
4775    executed anyway.
4776
4777(2) If you execute several variables with one call to run (i. e.
4778    calling run with a list of variables as arguments), any failing
4779    command will cause "run" to terminate, i. e. the remaining
4780    variables are not executed.
4781
4782Note for Redundant Ethernet Interfaces:
4783=======================================
4784
4785Some boards come with redundant Ethernet interfaces; U-Boot supports
4786such configurations and is capable of automatic selection of a
4787"working" interface when needed. MAC assignment works as follows:
4788
4789Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4790MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4791"eth1addr" (=>eth1), "eth2addr", ...
4792
4793If the network interface stores some valid MAC address (for instance
4794in SROM), this is used as default address if there is NO correspon-
4795ding setting in the environment; if the corresponding environment
4796variable is set, this overrides the settings in the card; that means:
4797
4798o If the SROM has a valid MAC address, and there is no address in the
4799  environment, the SROM's address is used.
4800
4801o If there is no valid address in the SROM, and a definition in the
4802  environment exists, then the value from the environment variable is
4803  used.
4804
4805o If both the SROM and the environment contain a MAC address, and
4806  both addresses are the same, this MAC address is used.
4807
4808o If both the SROM and the environment contain a MAC address, and the
4809  addresses differ, the value from the environment is used and a
4810  warning is printed.
4811
4812o If neither SROM nor the environment contain a MAC address, an error
4813  is raised.
4814
4815If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4816will be programmed into hardware as part of the initialization process.	 This
4817may be skipped by setting the appropriate 'ethmacskip' environment variable.
4818The naming convention is as follows:
4819"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4820
4821Image Formats:
4822==============
4823
4824U-Boot is capable of booting (and performing other auxiliary operations on)
4825images in two formats:
4826
4827New uImage format (FIT)
4828-----------------------
4829
4830Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4831to Flattened Device Tree). It allows the use of images with multiple
4832components (several kernels, ramdisks, etc.), with contents protected by
4833SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4834
4835
4836Old uImage format
4837-----------------
4838
4839Old image format is based on binary files which can be basically anything,
4840preceded by a special header; see the definitions in include/image.h for
4841details; basically, the header defines the following image properties:
4842
4843* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4844  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4845  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4846  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4847  INTEGRITY).
4848* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4849  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4850  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4851* Compression Type (uncompressed, gzip, bzip2)
4852* Load Address
4853* Entry Point
4854* Image Name
4855* Image Timestamp
4856
4857The header is marked by a special Magic Number, and both the header
4858and the data portions of the image are secured against corruption by
4859CRC32 checksums.
4860
4861
4862Linux Support:
4863==============
4864
4865Although U-Boot should support any OS or standalone application
4866easily, the main focus has always been on Linux during the design of
4867U-Boot.
4868
4869U-Boot includes many features that so far have been part of some
4870special "boot loader" code within the Linux kernel. Also, any
4871"initrd" images to be used are no longer part of one big Linux image;
4872instead, kernel and "initrd" are separate images. This implementation
4873serves several purposes:
4874
4875- the same features can be used for other OS or standalone
4876  applications (for instance: using compressed images to reduce the
4877  Flash memory footprint)
4878
4879- it becomes much easier to port new Linux kernel versions because
4880  lots of low-level, hardware dependent stuff are done by U-Boot
4881
4882- the same Linux kernel image can now be used with different "initrd"
4883  images; of course this also means that different kernel images can
4884  be run with the same "initrd". This makes testing easier (you don't
4885  have to build a new "zImage.initrd" Linux image when you just
4886  change a file in your "initrd"). Also, a field-upgrade of the
4887  software is easier now.
4888
4889
4890Linux HOWTO:
4891============
4892
4893Porting Linux to U-Boot based systems:
4894---------------------------------------
4895
4896U-Boot cannot save you from doing all the necessary modifications to
4897configure the Linux device drivers for use with your target hardware
4898(no, we don't intend to provide a full virtual machine interface to
4899Linux :-).
4900
4901But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4902
4903Just make sure your machine specific header file (for instance
4904include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4905Information structure as we define in include/asm-<arch>/u-boot.h,
4906and make sure that your definition of IMAP_ADDR uses the same value
4907as your U-Boot configuration in CONFIG_SYS_IMMR.
4908
4909
4910Configuring the Linux kernel:
4911-----------------------------
4912
4913No specific requirements for U-Boot. Make sure you have some root
4914device (initial ramdisk, NFS) for your target system.
4915
4916
4917Building a Linux Image:
4918-----------------------
4919
4920With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4921not used. If you use recent kernel source, a new build target
4922"uImage" will exist which automatically builds an image usable by
4923U-Boot. Most older kernels also have support for a "pImage" target,
4924which was introduced for our predecessor project PPCBoot and uses a
4925100% compatible format.
4926
4927Example:
4928
4929	make TQM850L_config
4930	make oldconfig
4931	make dep
4932	make uImage
4933
4934The "uImage" build target uses a special tool (in 'tools/mkimage') to
4935encapsulate a compressed Linux kernel image with header	 information,
4936CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4937
4938* build a standard "vmlinux" kernel image (in ELF binary format):
4939
4940* convert the kernel into a raw binary image:
4941
4942	${CROSS_COMPILE}-objcopy -O binary \
4943				 -R .note -R .comment \
4944				 -S vmlinux linux.bin
4945
4946* compress the binary image:
4947
4948	gzip -9 linux.bin
4949
4950* package compressed binary image for U-Boot:
4951
4952	mkimage -A ppc -O linux -T kernel -C gzip \
4953		-a 0 -e 0 -n "Linux Kernel Image" \
4954		-d linux.bin.gz uImage
4955
4956
4957The "mkimage" tool can also be used to create ramdisk images for use
4958with U-Boot, either separated from the Linux kernel image, or
4959combined into one file. "mkimage" encapsulates the images with a 64
4960byte header containing information about target architecture,
4961operating system, image type, compression method, entry points, time
4962stamp, CRC32 checksums, etc.
4963
4964"mkimage" can be called in two ways: to verify existing images and
4965print the header information, or to build new images.
4966
4967In the first form (with "-l" option) mkimage lists the information
4968contained in the header of an existing U-Boot image; this includes
4969checksum verification:
4970
4971	tools/mkimage -l image
4972	  -l ==> list image header information
4973
4974The second form (with "-d" option) is used to build a U-Boot image
4975from a "data file" which is used as image payload:
4976
4977	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4978		      -n name -d data_file image
4979	  -A ==> set architecture to 'arch'
4980	  -O ==> set operating system to 'os'
4981	  -T ==> set image type to 'type'
4982	  -C ==> set compression type 'comp'
4983	  -a ==> set load address to 'addr' (hex)
4984	  -e ==> set entry point to 'ep' (hex)
4985	  -n ==> set image name to 'name'
4986	  -d ==> use image data from 'datafile'
4987
4988Right now, all Linux kernels for PowerPC systems use the same load
4989address (0x00000000), but the entry point address depends on the
4990kernel version:
4991
4992- 2.2.x kernels have the entry point at 0x0000000C,
4993- 2.3.x and later kernels have the entry point at 0x00000000.
4994
4995So a typical call to build a U-Boot image would read:
4996
4997	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4998	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4999	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5000	> examples/uImage.TQM850L
5001	Image Name:   2.4.4 kernel for TQM850L
5002	Created:      Wed Jul 19 02:34:59 2000
5003	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5004	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5005	Load Address: 0x00000000
5006	Entry Point:  0x00000000
5007
5008To verify the contents of the image (or check for corruption):
5009
5010	-> tools/mkimage -l examples/uImage.TQM850L
5011	Image Name:   2.4.4 kernel for TQM850L
5012	Created:      Wed Jul 19 02:34:59 2000
5013	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5014	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5015	Load Address: 0x00000000
5016	Entry Point:  0x00000000
5017
5018NOTE: for embedded systems where boot time is critical you can trade
5019speed for memory and install an UNCOMPRESSED image instead: this
5020needs more space in Flash, but boots much faster since it does not
5021need to be uncompressed:
5022
5023	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5024	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5025	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5026	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5027	> examples/uImage.TQM850L-uncompressed
5028	Image Name:   2.4.4 kernel for TQM850L
5029	Created:      Wed Jul 19 02:34:59 2000
5030	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5031	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5032	Load Address: 0x00000000
5033	Entry Point:  0x00000000
5034
5035
5036Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5037when your kernel is intended to use an initial ramdisk:
5038
5039	-> tools/mkimage -n 'Simple Ramdisk Image' \
5040	> -A ppc -O linux -T ramdisk -C gzip \
5041	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5042	Image Name:   Simple Ramdisk Image
5043	Created:      Wed Jan 12 14:01:50 2000
5044	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5045	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5046	Load Address: 0x00000000
5047	Entry Point:  0x00000000
5048
5049
5050Installing a Linux Image:
5051-------------------------
5052
5053To downloading a U-Boot image over the serial (console) interface,
5054you must convert the image to S-Record format:
5055
5056	objcopy -I binary -O srec examples/image examples/image.srec
5057
5058The 'objcopy' does not understand the information in the U-Boot
5059image header, so the resulting S-Record file will be relative to
5060address 0x00000000. To load it to a given address, you need to
5061specify the target address as 'offset' parameter with the 'loads'
5062command.
5063
5064Example: install the image to address 0x40100000 (which on the
5065TQM8xxL is in the first Flash bank):
5066
5067	=> erase 40100000 401FFFFF
5068
5069	.......... done
5070	Erased 8 sectors
5071
5072	=> loads 40100000
5073	## Ready for S-Record download ...
5074	~>examples/image.srec
5075	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5076	...
5077	15989 15990 15991 15992
5078	[file transfer complete]
5079	[connected]
5080	## Start Addr = 0x00000000
5081
5082
5083You can check the success of the download using the 'iminfo' command;
5084this includes a checksum verification so you can be sure no data
5085corruption happened:
5086
5087	=> imi 40100000
5088
5089	## Checking Image at 40100000 ...
5090	   Image Name:	 2.2.13 for initrd on TQM850L
5091	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5092	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5093	   Load Address: 00000000
5094	   Entry Point:	 0000000c
5095	   Verifying Checksum ... OK
5096
5097
5098Boot Linux:
5099-----------
5100
5101The "bootm" command is used to boot an application that is stored in
5102memory (RAM or Flash). In case of a Linux kernel image, the contents
5103of the "bootargs" environment variable is passed to the kernel as
5104parameters. You can check and modify this variable using the
5105"printenv" and "setenv" commands:
5106
5107
5108	=> printenv bootargs
5109	bootargs=root=/dev/ram
5110
5111	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5112
5113	=> printenv bootargs
5114	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5115
5116	=> bootm 40020000
5117	## Booting Linux kernel at 40020000 ...
5118	   Image Name:	 2.2.13 for NFS on TQM850L
5119	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5120	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5121	   Load Address: 00000000
5122	   Entry Point:	 0000000c
5123	   Verifying Checksum ... OK
5124	   Uncompressing Kernel Image ... OK
5125	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
5126	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5127	time_init: decrementer frequency = 187500000/60
5128	Calibrating delay loop... 49.77 BogoMIPS
5129	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5130	...
5131
5132If you want to boot a Linux kernel with initial RAM disk, you pass
5133the memory addresses of both the kernel and the initrd image (PPBCOOT
5134format!) to the "bootm" command:
5135
5136	=> imi 40100000 40200000
5137
5138	## Checking Image at 40100000 ...
5139	   Image Name:	 2.2.13 for initrd on TQM850L
5140	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5141	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5142	   Load Address: 00000000
5143	   Entry Point:	 0000000c
5144	   Verifying Checksum ... OK
5145
5146	## Checking Image at 40200000 ...
5147	   Image Name:	 Simple Ramdisk Image
5148	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5149	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5150	   Load Address: 00000000
5151	   Entry Point:	 00000000
5152	   Verifying Checksum ... OK
5153
5154	=> bootm 40100000 40200000
5155	## Booting Linux kernel at 40100000 ...
5156	   Image Name:	 2.2.13 for initrd on TQM850L
5157	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5158	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5159	   Load Address: 00000000
5160	   Entry Point:	 0000000c
5161	   Verifying Checksum ... OK
5162	   Uncompressing Kernel Image ... OK
5163	## Loading RAMDisk Image at 40200000 ...
5164	   Image Name:	 Simple Ramdisk Image
5165	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5166	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5167	   Load Address: 00000000
5168	   Entry Point:	 00000000
5169	   Verifying Checksum ... OK
5170	   Loading Ramdisk ... OK
5171	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
5172	Boot arguments: root=/dev/ram
5173	time_init: decrementer frequency = 187500000/60
5174	Calibrating delay loop... 49.77 BogoMIPS
5175	...
5176	RAMDISK: Compressed image found at block 0
5177	VFS: Mounted root (ext2 filesystem).
5178
5179	bash#
5180
5181Boot Linux and pass a flat device tree:
5182-----------
5183
5184First, U-Boot must be compiled with the appropriate defines. See the section
5185titled "Linux Kernel Interface" above for a more in depth explanation. The
5186following is an example of how to start a kernel and pass an updated
5187flat device tree:
5188
5189=> print oftaddr
5190oftaddr=0x300000
5191=> print oft
5192oft=oftrees/mpc8540ads.dtb
5193=> tftp $oftaddr $oft
5194Speed: 1000, full duplex
5195Using TSEC0 device
5196TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5197Filename 'oftrees/mpc8540ads.dtb'.
5198Load address: 0x300000
5199Loading: #
5200done
5201Bytes transferred = 4106 (100a hex)
5202=> tftp $loadaddr $bootfile
5203Speed: 1000, full duplex
5204Using TSEC0 device
5205TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5206Filename 'uImage'.
5207Load address: 0x200000
5208Loading:############
5209done
5210Bytes transferred = 1029407 (fb51f hex)
5211=> print loadaddr
5212loadaddr=200000
5213=> print oftaddr
5214oftaddr=0x300000
5215=> bootm $loadaddr - $oftaddr
5216## Booting image at 00200000 ...
5217   Image Name:	 Linux-2.6.17-dirty
5218   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5219   Data Size:	 1029343 Bytes = 1005.2 kB
5220   Load Address: 00000000
5221   Entry Point:	 00000000
5222   Verifying Checksum ... OK
5223   Uncompressing Kernel Image ... OK
5224Booting using flat device tree at 0x300000
5225Using MPC85xx ADS machine description
5226Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5227[snip]
5228
5229
5230More About U-Boot Image Types:
5231------------------------------
5232
5233U-Boot supports the following image types:
5234
5235   "Standalone Programs" are directly runnable in the environment
5236	provided by U-Boot; it is expected that (if they behave
5237	well) you can continue to work in U-Boot after return from
5238	the Standalone Program.
5239   "OS Kernel Images" are usually images of some Embedded OS which
5240	will take over control completely. Usually these programs
5241	will install their own set of exception handlers, device
5242	drivers, set up the MMU, etc. - this means, that you cannot
5243	expect to re-enter U-Boot except by resetting the CPU.
5244   "RAMDisk Images" are more or less just data blocks, and their
5245	parameters (address, size) are passed to an OS kernel that is
5246	being started.
5247   "Multi-File Images" contain several images, typically an OS
5248	(Linux) kernel image and one or more data images like
5249	RAMDisks. This construct is useful for instance when you want
5250	to boot over the network using BOOTP etc., where the boot
5251	server provides just a single image file, but you want to get
5252	for instance an OS kernel and a RAMDisk image.
5253
5254	"Multi-File Images" start with a list of image sizes, each
5255	image size (in bytes) specified by an "uint32_t" in network
5256	byte order. This list is terminated by an "(uint32_t)0".
5257	Immediately after the terminating 0 follow the images, one by
5258	one, all aligned on "uint32_t" boundaries (size rounded up to
5259	a multiple of 4 bytes).
5260
5261   "Firmware Images" are binary images containing firmware (like
5262	U-Boot or FPGA images) which usually will be programmed to
5263	flash memory.
5264
5265   "Script files" are command sequences that will be executed by
5266	U-Boot's command interpreter; this feature is especially
5267	useful when you configure U-Boot to use a real shell (hush)
5268	as command interpreter.
5269
5270Booting the Linux zImage:
5271-------------------------
5272
5273On some platforms, it's possible to boot Linux zImage. This is done
5274using the "bootz" command. The syntax of "bootz" command is the same
5275as the syntax of "bootm" command.
5276
5277Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5278kernel with raw initrd images. The syntax is slightly different, the
5279address of the initrd must be augmented by it's size, in the following
5280format: "<initrd addres>:<initrd size>".
5281
5282
5283Standalone HOWTO:
5284=================
5285
5286One of the features of U-Boot is that you can dynamically load and
5287run "standalone" applications, which can use some resources of
5288U-Boot like console I/O functions or interrupt services.
5289
5290Two simple examples are included with the sources:
5291
5292"Hello World" Demo:
5293-------------------
5294
5295'examples/hello_world.c' contains a small "Hello World" Demo
5296application; it is automatically compiled when you build U-Boot.
5297It's configured to run at address 0x00040004, so you can play with it
5298like that:
5299
5300	=> loads
5301	## Ready for S-Record download ...
5302	~>examples/hello_world.srec
5303	1 2 3 4 5 6 7 8 9 10 11 ...
5304	[file transfer complete]
5305	[connected]
5306	## Start Addr = 0x00040004
5307
5308	=> go 40004 Hello World! This is a test.
5309	## Starting application at 0x00040004 ...
5310	Hello World
5311	argc = 7
5312	argv[0] = "40004"
5313	argv[1] = "Hello"
5314	argv[2] = "World!"
5315	argv[3] = "This"
5316	argv[4] = "is"
5317	argv[5] = "a"
5318	argv[6] = "test."
5319	argv[7] = "<NULL>"
5320	Hit any key to exit ...
5321
5322	## Application terminated, rc = 0x0
5323
5324Another example, which demonstrates how to register a CPM interrupt
5325handler with the U-Boot code, can be found in 'examples/timer.c'.
5326Here, a CPM timer is set up to generate an interrupt every second.
5327The interrupt service routine is trivial, just printing a '.'
5328character, but this is just a demo program. The application can be
5329controlled by the following keys:
5330
5331	? - print current values og the CPM Timer registers
5332	b - enable interrupts and start timer
5333	e - stop timer and disable interrupts
5334	q - quit application
5335
5336	=> loads
5337	## Ready for S-Record download ...
5338	~>examples/timer.srec
5339	1 2 3 4 5 6 7 8 9 10 11 ...
5340	[file transfer complete]
5341	[connected]
5342	## Start Addr = 0x00040004
5343
5344	=> go 40004
5345	## Starting application at 0x00040004 ...
5346	TIMERS=0xfff00980
5347	Using timer 1
5348	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5349
5350Hit 'b':
5351	[q, b, e, ?] Set interval 1000000 us
5352	Enabling timer
5353Hit '?':
5354	[q, b, e, ?] ........
5355	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5356Hit '?':
5357	[q, b, e, ?] .
5358	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5359Hit '?':
5360	[q, b, e, ?] .
5361	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5362Hit '?':
5363	[q, b, e, ?] .
5364	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5365Hit 'e':
5366	[q, b, e, ?] ...Stopping timer
5367Hit 'q':
5368	[q, b, e, ?] ## Application terminated, rc = 0x0
5369
5370
5371Minicom warning:
5372================
5373
5374Over time, many people have reported problems when trying to use the
5375"minicom" terminal emulation program for serial download. I (wd)
5376consider minicom to be broken, and recommend not to use it. Under
5377Unix, I recommend to use C-Kermit for general purpose use (and
5378especially for kermit binary protocol download ("loadb" command), and
5379use "cu" for S-Record download ("loads" command).  See
5380http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5381for help with kermit.
5382
5383
5384Nevertheless, if you absolutely want to use it try adding this
5385configuration to your "File transfer protocols" section:
5386
5387	   Name	   Program			Name U/D FullScr IO-Red. Multi
5388	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5389	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5390
5391
5392NetBSD Notes:
5393=============
5394
5395Starting at version 0.9.2, U-Boot supports NetBSD both as host
5396(build U-Boot) and target system (boots NetBSD/mpc8xx).
5397
5398Building requires a cross environment; it is known to work on
5399NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5400need gmake since the Makefiles are not compatible with BSD make).
5401Note that the cross-powerpc package does not install include files;
5402attempting to build U-Boot will fail because <machine/ansi.h> is
5403missing.  This file has to be installed and patched manually:
5404
5405	# cd /usr/pkg/cross/powerpc-netbsd/include
5406	# mkdir powerpc
5407	# ln -s powerpc machine
5408	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5409	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5410
5411Native builds *don't* work due to incompatibilities between native
5412and U-Boot include files.
5413
5414Booting assumes that (the first part of) the image booted is a
5415stage-2 loader which in turn loads and then invokes the kernel
5416proper. Loader sources will eventually appear in the NetBSD source
5417tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5418meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5419
5420
5421Implementation Internals:
5422=========================
5423
5424The following is not intended to be a complete description of every
5425implementation detail. However, it should help to understand the
5426inner workings of U-Boot and make it easier to port it to custom
5427hardware.
5428
5429
5430Initial Stack, Global Data:
5431---------------------------
5432
5433The implementation of U-Boot is complicated by the fact that U-Boot
5434starts running out of ROM (flash memory), usually without access to
5435system RAM (because the memory controller is not initialized yet).
5436This means that we don't have writable Data or BSS segments, and BSS
5437is not initialized as zero. To be able to get a C environment working
5438at all, we have to allocate at least a minimal stack. Implementation
5439options for this are defined and restricted by the CPU used: Some CPU
5440models provide on-chip memory (like the IMMR area on MPC8xx and
5441MPC826x processors), on others (parts of) the data cache can be
5442locked as (mis-) used as memory, etc.
5443
5444	Chris Hallinan posted a good summary of these issues to the
5445	U-Boot mailing list:
5446
5447	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5448	From: "Chris Hallinan" <clh@net1plus.com>
5449	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5450	...
5451
5452	Correct me if I'm wrong, folks, but the way I understand it
5453	is this: Using DCACHE as initial RAM for Stack, etc, does not
5454	require any physical RAM backing up the cache. The cleverness
5455	is that the cache is being used as a temporary supply of
5456	necessary storage before the SDRAM controller is setup. It's
5457	beyond the scope of this list to explain the details, but you
5458	can see how this works by studying the cache architecture and
5459	operation in the architecture and processor-specific manuals.
5460
5461	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5462	is another option for the system designer to use as an
5463	initial stack/RAM area prior to SDRAM being available. Either
5464	option should work for you. Using CS 4 should be fine if your
5465	board designers haven't used it for something that would
5466	cause you grief during the initial boot! It is frequently not
5467	used.
5468
5469	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5470	with your processor/board/system design. The default value
5471	you will find in any recent u-boot distribution in
5472	walnut.h should work for you. I'd set it to a value larger
5473	than your SDRAM module. If you have a 64MB SDRAM module, set
5474	it above 400_0000. Just make sure your board has no resources
5475	that are supposed to respond to that address! That code in
5476	start.S has been around a while and should work as is when
5477	you get the config right.
5478
5479	-Chris Hallinan
5480	DS4.COM, Inc.
5481
5482It is essential to remember this, since it has some impact on the C
5483code for the initialization procedures:
5484
5485* Initialized global data (data segment) is read-only. Do not attempt
5486  to write it.
5487
5488* Do not use any uninitialized global data (or implicitely initialized
5489  as zero data - BSS segment) at all - this is undefined, initiali-
5490  zation is performed later (when relocating to RAM).
5491
5492* Stack space is very limited. Avoid big data buffers or things like
5493  that.
5494
5495Having only the stack as writable memory limits means we cannot use
5496normal global data to share information beween the code. But it
5497turned out that the implementation of U-Boot can be greatly
5498simplified by making a global data structure (gd_t) available to all
5499functions. We could pass a pointer to this data as argument to _all_
5500functions, but this would bloat the code. Instead we use a feature of
5501the GCC compiler (Global Register Variables) to share the data: we
5502place a pointer (gd) to the global data into a register which we
5503reserve for this purpose.
5504
5505When choosing a register for such a purpose we are restricted by the
5506relevant  (E)ABI  specifications for the current architecture, and by
5507GCC's implementation.
5508
5509For PowerPC, the following registers have specific use:
5510	R1:	stack pointer
5511	R2:	reserved for system use
5512	R3-R4:	parameter passing and return values
5513	R5-R10: parameter passing
5514	R13:	small data area pointer
5515	R30:	GOT pointer
5516	R31:	frame pointer
5517
5518	(U-Boot also uses R12 as internal GOT pointer. r12
5519	is a volatile register so r12 needs to be reset when
5520	going back and forth between asm and C)
5521
5522    ==> U-Boot will use R2 to hold a pointer to the global data
5523
5524    Note: on PPC, we could use a static initializer (since the
5525    address of the global data structure is known at compile time),
5526    but it turned out that reserving a register results in somewhat
5527    smaller code - although the code savings are not that big (on
5528    average for all boards 752 bytes for the whole U-Boot image,
5529    624 text + 127 data).
5530
5531On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5532	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5533
5534    ==> U-Boot will use P3 to hold a pointer to the global data
5535
5536On ARM, the following registers are used:
5537
5538	R0:	function argument word/integer result
5539	R1-R3:	function argument word
5540	R9:	GOT pointer
5541	R10:	stack limit (used only if stack checking if enabled)
5542	R11:	argument (frame) pointer
5543	R12:	temporary workspace
5544	R13:	stack pointer
5545	R14:	link register
5546	R15:	program counter
5547
5548    ==> U-Boot will use R8 to hold a pointer to the global data
5549
5550On Nios II, the ABI is documented here:
5551	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5552
5553    ==> U-Boot will use gp to hold a pointer to the global data
5554
5555    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5556    to access small data sections, so gp is free.
5557
5558On NDS32, the following registers are used:
5559
5560	R0-R1:	argument/return
5561	R2-R5:	argument
5562	R15:	temporary register for assembler
5563	R16:	trampoline register
5564	R28:	frame pointer (FP)
5565	R29:	global pointer (GP)
5566	R30:	link register (LP)
5567	R31:	stack pointer (SP)
5568	PC:	program counter (PC)
5569
5570    ==> U-Boot will use R10 to hold a pointer to the global data
5571
5572NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5573or current versions of GCC may "optimize" the code too much.
5574
5575Memory Management:
5576------------------
5577
5578U-Boot runs in system state and uses physical addresses, i.e. the
5579MMU is not used either for address mapping nor for memory protection.
5580
5581The available memory is mapped to fixed addresses using the memory
5582controller. In this process, a contiguous block is formed for each
5583memory type (Flash, SDRAM, SRAM), even when it consists of several
5584physical memory banks.
5585
5586U-Boot is installed in the first 128 kB of the first Flash bank (on
5587TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5588booting and sizing and initializing DRAM, the code relocates itself
5589to the upper end of DRAM. Immediately below the U-Boot code some
5590memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5591configuration setting]. Below that, a structure with global Board
5592Info data is placed, followed by the stack (growing downward).
5593
5594Additionally, some exception handler code is copied to the low 8 kB
5595of DRAM (0x00000000 ... 0x00001FFF).
5596
5597So a typical memory configuration with 16 MB of DRAM could look like
5598this:
5599
5600	0x0000 0000	Exception Vector code
5601	      :
5602	0x0000 1FFF
5603	0x0000 2000	Free for Application Use
5604	      :
5605	      :
5606
5607	      :
5608	      :
5609	0x00FB FF20	Monitor Stack (Growing downward)
5610	0x00FB FFAC	Board Info Data and permanent copy of global data
5611	0x00FC 0000	Malloc Arena
5612	      :
5613	0x00FD FFFF
5614	0x00FE 0000	RAM Copy of Monitor Code
5615	...		eventually: LCD or video framebuffer
5616	...		eventually: pRAM (Protected RAM - unchanged by reset)
5617	0x00FF FFFF	[End of RAM]
5618
5619
5620System Initialization:
5621----------------------
5622
5623In the reset configuration, U-Boot starts at the reset entry point
5624(on most PowerPC systems at address 0x00000100). Because of the reset
5625configuration for CS0# this is a mirror of the onboard Flash memory.
5626To be able to re-map memory U-Boot then jumps to its link address.
5627To be able to implement the initialization code in C, a (small!)
5628initial stack is set up in the internal Dual Ported RAM (in case CPUs
5629which provide such a feature like MPC8xx or MPC8260), or in a locked
5630part of the data cache. After that, U-Boot initializes the CPU core,
5631the caches and the SIU.
5632
5633Next, all (potentially) available memory banks are mapped using a
5634preliminary mapping. For example, we put them on 512 MB boundaries
5635(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5636on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5637programmed for SDRAM access. Using the temporary configuration, a
5638simple memory test is run that determines the size of the SDRAM
5639banks.
5640
5641When there is more than one SDRAM bank, and the banks are of
5642different size, the largest is mapped first. For equal size, the first
5643bank (CS2#) is mapped first. The first mapping is always for address
56440x00000000, with any additional banks following immediately to create
5645contiguous memory starting from 0.
5646
5647Then, the monitor installs itself at the upper end of the SDRAM area
5648and allocates memory for use by malloc() and for the global Board
5649Info data; also, the exception vector code is copied to the low RAM
5650pages, and the final stack is set up.
5651
5652Only after this relocation will you have a "normal" C environment;
5653until that you are restricted in several ways, mostly because you are
5654running from ROM, and because the code will have to be relocated to a
5655new address in RAM.
5656
5657
5658U-Boot Porting Guide:
5659----------------------
5660
5661[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5662list, October 2002]
5663
5664
5665int main(int argc, char *argv[])
5666{
5667	sighandler_t no_more_time;
5668
5669	signal(SIGALRM, no_more_time);
5670	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5671
5672	if (available_money > available_manpower) {
5673		Pay consultant to port U-Boot;
5674		return 0;
5675	}
5676
5677	Download latest U-Boot source;
5678
5679	Subscribe to u-boot mailing list;
5680
5681	if (clueless)
5682		email("Hi, I am new to U-Boot, how do I get started?");
5683
5684	while (learning) {
5685		Read the README file in the top level directory;
5686		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5687		Read applicable doc/*.README;
5688		Read the source, Luke;
5689		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5690	}
5691
5692	if (available_money > toLocalCurrency ($2500))
5693		Buy a BDI3000;
5694	else
5695		Add a lot of aggravation and time;
5696
5697	if (a similar board exists) {	/* hopefully... */
5698		cp -a board/<similar> board/<myboard>
5699		cp include/configs/<similar>.h include/configs/<myboard>.h
5700	} else {
5701		Create your own board support subdirectory;
5702		Create your own board include/configs/<myboard>.h file;
5703	}
5704	Edit new board/<myboard> files
5705	Edit new include/configs/<myboard>.h
5706
5707	while (!accepted) {
5708		while (!running) {
5709			do {
5710				Add / modify source code;
5711			} until (compiles);
5712			Debug;
5713			if (clueless)
5714				email("Hi, I am having problems...");
5715		}
5716		Send patch file to the U-Boot email list;
5717		if (reasonable critiques)
5718			Incorporate improvements from email list code review;
5719		else
5720			Defend code as written;
5721	}
5722
5723	return 0;
5724}
5725
5726void no_more_time (int sig)
5727{
5728      hire_a_guru();
5729}
5730
5731
5732Coding Standards:
5733-----------------
5734
5735All contributions to U-Boot should conform to the Linux kernel
5736coding style; see the file "Documentation/CodingStyle" and the script
5737"scripts/Lindent" in your Linux kernel source directory.
5738
5739Source files originating from a different project (for example the
5740MTD subsystem) are generally exempt from these guidelines and are not
5741reformated to ease subsequent migration to newer versions of those
5742sources.
5743
5744Please note that U-Boot is implemented in C (and to some small parts in
5745Assembler); no C++ is used, so please do not use C++ style comments (//)
5746in your code.
5747
5748Please also stick to the following formatting rules:
5749- remove any trailing white space
5750- use TAB characters for indentation and vertical alignment, not spaces
5751- make sure NOT to use DOS '\r\n' line feeds
5752- do not add more than 2 consecutive empty lines to source files
5753- do not add trailing empty lines to source files
5754
5755Submissions which do not conform to the standards may be returned
5756with a request to reformat the changes.
5757
5758
5759Submitting Patches:
5760-------------------
5761
5762Since the number of patches for U-Boot is growing, we need to
5763establish some rules. Submissions which do not conform to these rules
5764may be rejected, even when they contain important and valuable stuff.
5765
5766Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5767
5768Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5769see http://lists.denx.de/mailman/listinfo/u-boot
5770
5771When you send a patch, please include the following information with
5772it:
5773
5774* For bug fixes: a description of the bug and how your patch fixes
5775  this bug. Please try to include a way of demonstrating that the
5776  patch actually fixes something.
5777
5778* For new features: a description of the feature and your
5779  implementation.
5780
5781* A CHANGELOG entry as plaintext (separate from the patch)
5782
5783* For major contributions, your entry to the CREDITS file
5784
5785* When you add support for a new board, don't forget to add this
5786  board to the MAINTAINERS file, too.
5787
5788* If your patch adds new configuration options, don't forget to
5789  document these in the README file.
5790
5791* The patch itself. If you are using git (which is *strongly*
5792  recommended) you can easily generate the patch using the
5793  "git format-patch". If you then use "git send-email" to send it to
5794  the U-Boot mailing list, you will avoid most of the common problems
5795  with some other mail clients.
5796
5797  If you cannot use git, use "diff -purN OLD NEW". If your version of
5798  diff does not support these options, then get the latest version of
5799  GNU diff.
5800
5801  The current directory when running this command shall be the parent
5802  directory of the U-Boot source tree (i. e. please make sure that
5803  your patch includes sufficient directory information for the
5804  affected files).
5805
5806  We prefer patches as plain text. MIME attachments are discouraged,
5807  and compressed attachments must not be used.
5808
5809* If one logical set of modifications affects or creates several
5810  files, all these changes shall be submitted in a SINGLE patch file.
5811
5812* Changesets that contain different, unrelated modifications shall be
5813  submitted as SEPARATE patches, one patch per changeset.
5814
5815
5816Notes:
5817
5818* Before sending the patch, run the MAKEALL script on your patched
5819  source tree and make sure that no errors or warnings are reported
5820  for any of the boards.
5821
5822* Keep your modifications to the necessary minimum: A patch
5823  containing several unrelated changes or arbitrary reformats will be
5824  returned with a request to re-formatting / split it.
5825
5826* If you modify existing code, make sure that your new code does not
5827  add to the memory footprint of the code ;-) Small is beautiful!
5828  When adding new features, these should compile conditionally only
5829  (using #ifdef), and the resulting code with the new feature
5830  disabled must not need more memory than the old code without your
5831  modification.
5832
5833* Remember that there is a size limit of 100 kB per message on the
5834  u-boot mailing list. Bigger patches will be moderated. If they are
5835  reasonable and not too big, they will be acknowledged. But patches
5836  bigger than the size limit should be avoided.
5837