xref: /rk3399_rockchip-uboot/README (revision 7ad2cc7964d37f3a444a0472bbccda487d51c7f6)
1#
2# (C) Copyright 2000 - 2012
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# See file CREDITS for list of people who contributed to this
6# project.
7#
8# This program is free software; you can redistribute it and/or
9# modify it under the terms of the GNU General Public License as
10# published by the Free Software Foundation; either version 2 of
11# the License, or (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the GNU General Public License
19# along with this program; if not, write to the Free Software
20# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21# MA 02111-1307 USA
22#
23
24Summary:
25========
26
27This directory contains the source code for U-Boot, a boot loader for
28Embedded boards based on PowerPC, ARM, MIPS and several other
29processors, which can be installed in a boot ROM and used to
30initialize and test the hardware or to download and run application
31code.
32
33The development of U-Boot is closely related to Linux: some parts of
34the source code originate in the Linux source tree, we have some
35header files in common, and special provision has been made to
36support booting of Linux images.
37
38Some attention has been paid to make this software easily
39configurable and extendable. For instance, all monitor commands are
40implemented with the same call interface, so that it's very easy to
41add new commands. Also, instead of permanently adding rarely used
42code (for instance hardware test utilities) to the monitor, you can
43load and run it dynamically.
44
45
46Status:
47=======
48
49In general, all boards for which a configuration option exists in the
50Makefile have been tested to some extent and can be considered
51"working". In fact, many of them are used in production systems.
52
53In case of problems see the CHANGELOG and CREDITS files to find out
54who contributed the specific port. The MAINTAINERS file lists board
55maintainers.
56
57Note: There is no CHANGELOG file in the actual U-Boot source tree;
58it can be created dynamically from the Git log using:
59
60	make CHANGELOG
61
62
63Where to get help:
64==================
65
66In case you have questions about, problems with or contributions for
67U-Boot you should send a message to the U-Boot mailing list at
68<u-boot@lists.denx.de>. There is also an archive of previous traffic
69on the mailing list - please search the archive before asking FAQ's.
70Please see http://lists.denx.de/pipermail/u-boot and
71http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
72
73
74Where to get source code:
75=========================
76
77The U-Boot source code is maintained in the git repository at
78git://www.denx.de/git/u-boot.git ; you can browse it online at
79http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
80
81The "snapshot" links on this page allow you to download tarballs of
82any version you might be interested in. Official releases are also
83available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
84directory.
85
86Pre-built (and tested) images are available from
87ftp://ftp.denx.de/pub/u-boot/images/
88
89
90Where we come from:
91===================
92
93- start from 8xxrom sources
94- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
95- clean up code
96- make it easier to add custom boards
97- make it possible to add other [PowerPC] CPUs
98- extend functions, especially:
99  * Provide extended interface to Linux boot loader
100  * S-Record download
101  * network boot
102  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
103- create ARMBoot project (http://sourceforge.net/projects/armboot)
104- add other CPU families (starting with ARM)
105- create U-Boot project (http://sourceforge.net/projects/u-boot)
106- current project page: see http://www.denx.de/wiki/U-Boot
107
108
109Names and Spelling:
110===================
111
112The "official" name of this project is "Das U-Boot". The spelling
113"U-Boot" shall be used in all written text (documentation, comments
114in source files etc.). Example:
115
116	This is the README file for the U-Boot project.
117
118File names etc. shall be based on the string "u-boot". Examples:
119
120	include/asm-ppc/u-boot.h
121
122	#include <asm/u-boot.h>
123
124Variable names, preprocessor constants etc. shall be either based on
125the string "u_boot" or on "U_BOOT". Example:
126
127	U_BOOT_VERSION		u_boot_logo
128	IH_OS_U_BOOT		u_boot_hush_start
129
130
131Versioning:
132===========
133
134Starting with the release in October 2008, the names of the releases
135were changed from numerical release numbers without deeper meaning
136into a time stamp based numbering. Regular releases are identified by
137names consisting of the calendar year and month of the release date.
138Additional fields (if present) indicate release candidates or bug fix
139releases in "stable" maintenance trees.
140
141Examples:
142	U-Boot v2009.11	    - Release November 2009
143	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
144	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
145
146
147Directory Hierarchy:
148====================
149
150/arch			Architecture specific files
151  /arm			Files generic to ARM architecture
152    /cpu		CPU specific files
153      /arm720t		Files specific to ARM 720 CPUs
154      /arm920t		Files specific to ARM 920 CPUs
155	/at91		Files specific to Atmel AT91RM9200 CPU
156	/imx		Files specific to Freescale MC9328 i.MX CPUs
157	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
158      /arm925t		Files specific to ARM 925 CPUs
159      /arm926ejs	Files specific to ARM 926 CPUs
160      /arm1136		Files specific to ARM 1136 CPUs
161      /ixp		Files specific to Intel XScale IXP CPUs
162      /pxa		Files specific to Intel XScale PXA CPUs
163      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
164      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
165    /lib		Architecture specific library files
166  /avr32		Files generic to AVR32 architecture
167    /cpu		CPU specific files
168    /lib		Architecture specific library files
169  /blackfin		Files generic to Analog Devices Blackfin architecture
170    /cpu		CPU specific files
171    /lib		Architecture specific library files
172  /x86			Files generic to x86 architecture
173    /cpu		CPU specific files
174    /lib		Architecture specific library files
175  /m68k			Files generic to m68k architecture
176    /cpu		CPU specific files
177      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
178      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
179      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
180      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
181      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
182    /lib		Architecture specific library files
183  /microblaze		Files generic to microblaze architecture
184    /cpu		CPU specific files
185    /lib		Architecture specific library files
186  /mips			Files generic to MIPS architecture
187    /cpu		CPU specific files
188      /mips32		Files specific to MIPS32 CPUs
189      /xburst		Files specific to Ingenic XBurst CPUs
190    /lib		Architecture specific library files
191  /nds32		Files generic to NDS32 architecture
192    /cpu		CPU specific files
193      /n1213		Files specific to Andes Technology N1213 CPUs
194    /lib		Architecture specific library files
195  /nios2		Files generic to Altera NIOS2 architecture
196    /cpu		CPU specific files
197    /lib		Architecture specific library files
198  /powerpc		Files generic to PowerPC architecture
199    /cpu		CPU specific files
200      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
201      /mpc5xx		Files specific to Freescale MPC5xx CPUs
202      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
203      /mpc8xx		Files specific to Freescale MPC8xx CPUs
204      /mpc824x		Files specific to Freescale MPC824x CPUs
205      /mpc8260		Files specific to Freescale MPC8260 CPUs
206      /mpc85xx		Files specific to Freescale MPC85xx CPUs
207      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
208    /lib		Architecture specific library files
209  /sh			Files generic to SH architecture
210    /cpu		CPU specific files
211      /sh2		Files specific to sh2 CPUs
212      /sh3		Files specific to sh3 CPUs
213      /sh4		Files specific to sh4 CPUs
214    /lib		Architecture specific library files
215  /sparc		Files generic to SPARC architecture
216    /cpu		CPU specific files
217      /leon2		Files specific to Gaisler LEON2 SPARC CPU
218      /leon3		Files specific to Gaisler LEON3 SPARC CPU
219    /lib		Architecture specific library files
220/api			Machine/arch independent API for external apps
221/board			Board dependent files
222/common			Misc architecture independent functions
223/disk			Code for disk drive partition handling
224/doc			Documentation (don't expect too much)
225/drivers		Commonly used device drivers
226/examples		Example code for standalone applications, etc.
227/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
228/include		Header Files
229/lib			Files generic to all architectures
230  /libfdt		Library files to support flattened device trees
231  /lzma			Library files to support LZMA decompression
232  /lzo			Library files to support LZO decompression
233/net			Networking code
234/post			Power On Self Test
235/rtc			Real Time Clock drivers
236/tools			Tools to build S-Record or U-Boot images, etc.
237
238Software Configuration:
239=======================
240
241Configuration is usually done using C preprocessor defines; the
242rationale behind that is to avoid dead code whenever possible.
243
244There are two classes of configuration variables:
245
246* Configuration _OPTIONS_:
247  These are selectable by the user and have names beginning with
248  "CONFIG_".
249
250* Configuration _SETTINGS_:
251  These depend on the hardware etc. and should not be meddled with if
252  you don't know what you're doing; they have names beginning with
253  "CONFIG_SYS_".
254
255Later we will add a configuration tool - probably similar to or even
256identical to what's used for the Linux kernel. Right now, we have to
257do the configuration by hand, which means creating some symbolic
258links and editing some configuration files. We use the TQM8xxL boards
259as an example here.
260
261
262Selection of Processor Architecture and Board Type:
263---------------------------------------------------
264
265For all supported boards there are ready-to-use default
266configurations available; just type "make <board_name>_config".
267
268Example: For a TQM823L module type:
269
270	cd u-boot
271	make TQM823L_config
272
273For the Cogent platform, you need to specify the CPU type as well;
274e.g. "make cogent_mpc8xx_config". And also configure the cogent
275directory according to the instructions in cogent/README.
276
277
278Configuration Options:
279----------------------
280
281Configuration depends on the combination of board and CPU type; all
282such information is kept in a configuration file
283"include/configs/<board_name>.h".
284
285Example: For a TQM823L module, all configuration settings are in
286"include/configs/TQM823L.h".
287
288
289Many of the options are named exactly as the corresponding Linux
290kernel configuration options. The intention is to make it easier to
291build a config tool - later.
292
293
294The following options need to be configured:
295
296- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
297
298- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
299
300- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
301		Define exactly one, e.g. CONFIG_ATSTK1002
302
303- CPU Module Type: (if CONFIG_COGENT is defined)
304		Define exactly one of
305		CONFIG_CMA286_60_OLD
306--- FIXME --- not tested yet:
307		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
308		CONFIG_CMA287_23, CONFIG_CMA287_50
309
310- Motherboard Type: (if CONFIG_COGENT is defined)
311		Define exactly one of
312		CONFIG_CMA101, CONFIG_CMA102
313
314- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
315		Define one or more of
316		CONFIG_CMA302
317
318- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
319		Define one or more of
320		CONFIG_LCD_HEARTBEAT	- update a character position on
321					  the LCD display every second with
322					  a "rotator" |\-/|\-/
323
324- Board flavour: (if CONFIG_MPC8260ADS is defined)
325		CONFIG_ADSTYPE
326		Possible values are:
327			CONFIG_SYS_8260ADS	- original MPC8260ADS
328			CONFIG_SYS_8266ADS	- MPC8266ADS
329			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
330			CONFIG_SYS_8272ADS	- MPC8272ADS
331
332- Marvell Family Member
333		CONFIG_SYS_MVFS		- define it if you want to enable
334					  multiple fs option at one time
335					  for marvell soc family
336
337- MPC824X Family Member (if CONFIG_MPC824X is defined)
338		Define exactly one of
339		CONFIG_MPC8240, CONFIG_MPC8245
340
341- 8xx CPU Options: (if using an MPC8xx CPU)
342		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
343					  get_gclk_freq() cannot work
344					  e.g. if there is no 32KHz
345					  reference PIT/RTC clock
346		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
347					  or XTAL/EXTAL)
348
349- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
350		CONFIG_SYS_8xx_CPUCLK_MIN
351		CONFIG_SYS_8xx_CPUCLK_MAX
352		CONFIG_8xx_CPUCLK_DEFAULT
353			See doc/README.MPC866
354
355		CONFIG_SYS_MEASURE_CPUCLK
356
357		Define this to measure the actual CPU clock instead
358		of relying on the correctness of the configured
359		values. Mostly useful for board bringup to make sure
360		the PLL is locked at the intended frequency. Note
361		that this requires a (stable) reference clock (32 kHz
362		RTC clock or CONFIG_SYS_8XX_XIN)
363
364		CONFIG_SYS_DELAYED_ICACHE
365
366		Define this option if you want to enable the
367		ICache only when Code runs from RAM.
368
369- 85xx CPU Options:
370		CONFIG_SYS_PPC64
371
372		Specifies that the core is a 64-bit PowerPC implementation (implements
373		the "64" category of the Power ISA). This is necessary for ePAPR
374		compliance, among other possible reasons.
375
376		CONFIG_SYS_FSL_TBCLK_DIV
377
378		Defines the core time base clock divider ratio compared to the
379		system clock.  On most PQ3 devices this is 8, on newer QorIQ
380		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
381
382		CONFIG_SYS_FSL_PCIE_COMPAT
383
384		Defines the string to utilize when trying to match PCIe device
385		tree nodes for the given platform.
386
387		CONFIG_SYS_PPC_E500_DEBUG_TLB
388
389		Enables a temporary TLB entry to be used during boot to work
390		around limitations in e500v1 and e500v2 external debugger
391		support. This reduces the portions of the boot code where
392		breakpoints and single stepping do not work.  The value of this
393		symbol should be set to the TLB1 entry to be used for this
394		purpose.
395
396		CONFIG_SYS_FSL_ERRATUM_A004510
397
398		Enables a workaround for erratum A004510.  If set,
399		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
400		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
401
402		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
403		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
404
405		Defines one or two SoC revisions (low 8 bits of SVR)
406		for which the A004510 workaround should be applied.
407
408		The rest of SVR is either not relevant to the decision
409		of whether the erratum is present (e.g. p2040 versus
410		p2041) or is implied by the build target, which controls
411		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
412
413		See Freescale App Note 4493 for more information about
414		this erratum.
415
416		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
417
418		This is the value to write into CCSR offset 0x18600
419		according to the A004510 workaround.
420
421- Generic CPU options:
422		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
423
424		Defines the endianess of the CPU. Implementation of those
425		values is arch specific.
426
427- Intel Monahans options:
428		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
429
430		Defines the Monahans run mode to oscillator
431		ratio. Valid values are 8, 16, 24, 31. The core
432		frequency is this value multiplied by 13 MHz.
433
434		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
435
436		Defines the Monahans turbo mode to oscillator
437		ratio. Valid values are 1 (default if undefined) and
438		2. The core frequency as calculated above is multiplied
439		by this value.
440
441- MIPS CPU options:
442		CONFIG_SYS_INIT_SP_OFFSET
443
444		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
445		pointer. This is needed for the temporary stack before
446		relocation.
447
448		CONFIG_SYS_MIPS_CACHE_MODE
449
450		Cache operation mode for the MIPS CPU.
451		See also arch/mips/include/asm/mipsregs.h.
452		Possible values are:
453			CONF_CM_CACHABLE_NO_WA
454			CONF_CM_CACHABLE_WA
455			CONF_CM_UNCACHED
456			CONF_CM_CACHABLE_NONCOHERENT
457			CONF_CM_CACHABLE_CE
458			CONF_CM_CACHABLE_COW
459			CONF_CM_CACHABLE_CUW
460			CONF_CM_CACHABLE_ACCELERATED
461
462		CONFIG_SYS_XWAY_EBU_BOOTCFG
463
464		Special option for Lantiq XWAY SoCs for booting from NOR flash.
465		See also arch/mips/cpu/mips32/start.S.
466
467		CONFIG_XWAY_SWAP_BYTES
468
469		Enable compilation of tools/xway-swap-bytes needed for Lantiq
470		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
471		be swapped if a flash programmer is used.
472
473- ARM options:
474		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
475
476		Select high exception vectors of the ARM core, e.g., do not
477		clear the V bit of the c1 register of CP15.
478
479		CONFIG_SYS_THUMB_BUILD
480
481		Use this flag to build U-Boot using the Thumb instruction
482		set for ARM architectures. Thumb instruction set provides
483		better code density. For ARM architectures that support
484		Thumb2 this flag will result in Thumb2 code generated by
485		GCC.
486
487		CONFIG_ARM_ERRATA_716044
488		CONFIG_ARM_ERRATA_742230
489		CONFIG_ARM_ERRATA_743622
490		CONFIG_ARM_ERRATA_751472
491
492		If set, the workarounds for these ARM errata are applied early
493		during U-Boot startup. Note that these options force the
494		workarounds to be applied; no CPU-type/version detection
495		exists, unlike the similar options in the Linux kernel. Do not
496		set these options unless they apply!
497
498- CPU timer options:
499		CONFIG_SYS_HZ
500
501		The frequency of the timer returned by get_timer().
502		get_timer() must operate in milliseconds and this CONFIG
503		option must be set to 1000.
504
505- Linux Kernel Interface:
506		CONFIG_CLOCKS_IN_MHZ
507
508		U-Boot stores all clock information in Hz
509		internally. For binary compatibility with older Linux
510		kernels (which expect the clocks passed in the
511		bd_info data to be in MHz) the environment variable
512		"clocks_in_mhz" can be defined so that U-Boot
513		converts clock data to MHZ before passing it to the
514		Linux kernel.
515		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
516		"clocks_in_mhz=1" is automatically included in the
517		default environment.
518
519		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
520
521		When transferring memsize parameter to linux, some versions
522		expect it to be in bytes, others in MB.
523		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
524
525		CONFIG_OF_LIBFDT
526
527		New kernel versions are expecting firmware settings to be
528		passed using flattened device trees (based on open firmware
529		concepts).
530
531		CONFIG_OF_LIBFDT
532		 * New libfdt-based support
533		 * Adds the "fdt" command
534		 * The bootm command automatically updates the fdt
535
536		OF_CPU - The proper name of the cpus node (only required for
537			MPC512X and MPC5xxx based boards).
538		OF_SOC - The proper name of the soc node (only required for
539			MPC512X and MPC5xxx based boards).
540		OF_TBCLK - The timebase frequency.
541		OF_STDOUT_PATH - The path to the console device
542
543		boards with QUICC Engines require OF_QE to set UCC MAC
544		addresses
545
546		CONFIG_OF_BOARD_SETUP
547
548		Board code has addition modification that it wants to make
549		to the flat device tree before handing it off to the kernel
550
551		CONFIG_OF_BOOT_CPU
552
553		This define fills in the correct boot CPU in the boot
554		param header, the default value is zero if undefined.
555
556		CONFIG_OF_IDE_FIXUP
557
558		U-Boot can detect if an IDE device is present or not.
559		If not, and this new config option is activated, U-Boot
560		removes the ATA node from the DTS before booting Linux,
561		so the Linux IDE driver does not probe the device and
562		crash. This is needed for buggy hardware (uc101) where
563		no pull down resistor is connected to the signal IDE5V_DD7.
564
565		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
566
567		This setting is mandatory for all boards that have only one
568		machine type and must be used to specify the machine type
569		number as it appears in the ARM machine registry
570		(see http://www.arm.linux.org.uk/developer/machines/).
571		Only boards that have multiple machine types supported
572		in a single configuration file and the machine type is
573		runtime discoverable, do not have to use this setting.
574
575- vxWorks boot parameters:
576
577		bootvx constructs a valid bootline using the following
578		environments variables: bootfile, ipaddr, serverip, hostname.
579		It loads the vxWorks image pointed bootfile.
580
581		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
582		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
583		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
584		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
585
586		CONFIG_SYS_VXWORKS_ADD_PARAMS
587
588		Add it at the end of the bootline. E.g "u=username pw=secret"
589
590		Note: If a "bootargs" environment is defined, it will overwride
591		the defaults discussed just above.
592
593- Cache Configuration:
594		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
595		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
596		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
597
598- Cache Configuration for ARM:
599		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
600				      controller
601		CONFIG_SYS_PL310_BASE - Physical base address of PL310
602					controller register space
603
604- Serial Ports:
605		CONFIG_PL010_SERIAL
606
607		Define this if you want support for Amba PrimeCell PL010 UARTs.
608
609		CONFIG_PL011_SERIAL
610
611		Define this if you want support for Amba PrimeCell PL011 UARTs.
612
613		CONFIG_PL011_CLOCK
614
615		If you have Amba PrimeCell PL011 UARTs, set this variable to
616		the clock speed of the UARTs.
617
618		CONFIG_PL01x_PORTS
619
620		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
621		define this to a list of base addresses for each (supported)
622		port. See e.g. include/configs/versatile.h
623
624		CONFIG_PL011_SERIAL_RLCR
625
626		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
627		have separate receive and transmit line control registers.  Set
628		this variable to initialize the extra register.
629
630		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
631
632		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
633		boot loader that has already initialized the UART.  Define this
634		variable to flush the UART at init time.
635
636
637- Console Interface:
638		Depending on board, define exactly one serial port
639		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
640		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
641		console by defining CONFIG_8xx_CONS_NONE
642
643		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
644		port routines must be defined elsewhere
645		(i.e. serial_init(), serial_getc(), ...)
646
647		CONFIG_CFB_CONSOLE
648		Enables console device for a color framebuffer. Needs following
649		defines (cf. smiLynxEM, i8042)
650			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
651						(default big endian)
652			VIDEO_HW_RECTFILL	graphic chip supports
653						rectangle fill
654						(cf. smiLynxEM)
655			VIDEO_HW_BITBLT		graphic chip supports
656						bit-blit (cf. smiLynxEM)
657			VIDEO_VISIBLE_COLS	visible pixel columns
658						(cols=pitch)
659			VIDEO_VISIBLE_ROWS	visible pixel rows
660			VIDEO_PIXEL_SIZE	bytes per pixel
661			VIDEO_DATA_FORMAT	graphic data format
662						(0-5, cf. cfb_console.c)
663			VIDEO_FB_ADRS		framebuffer address
664			VIDEO_KBD_INIT_FCT	keyboard int fct
665						(i.e. i8042_kbd_init())
666			VIDEO_TSTC_FCT		test char fct
667						(i.e. i8042_tstc)
668			VIDEO_GETC_FCT		get char fct
669						(i.e. i8042_getc)
670			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
671						(requires blink timer
672						cf. i8042.c)
673			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
674			CONFIG_CONSOLE_TIME	display time/date info in
675						upper right corner
676						(requires CONFIG_CMD_DATE)
677			CONFIG_VIDEO_LOGO	display Linux logo in
678						upper left corner
679			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
680						linux_logo.h for logo.
681						Requires CONFIG_VIDEO_LOGO
682			CONFIG_CONSOLE_EXTRA_INFO
683						additional board info beside
684						the logo
685
686		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
687		a limited number of ANSI escape sequences (cursor control,
688		erase functions and limited graphics rendition control).
689
690		When CONFIG_CFB_CONSOLE is defined, video console is
691		default i/o. Serial console can be forced with
692		environment 'console=serial'.
693
694		When CONFIG_SILENT_CONSOLE is defined, all console
695		messages (by U-Boot and Linux!) can be silenced with
696		the "silent" environment variable. See
697		doc/README.silent for more information.
698
699- Console Baudrate:
700		CONFIG_BAUDRATE - in bps
701		Select one of the baudrates listed in
702		CONFIG_SYS_BAUDRATE_TABLE, see below.
703		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
704
705- Console Rx buffer length
706		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
707		the maximum receive buffer length for the SMC.
708		This option is actual only for 82xx and 8xx possible.
709		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
710		must be defined, to setup the maximum idle timeout for
711		the SMC.
712
713- Pre-Console Buffer:
714		Prior to the console being initialised (i.e. serial UART
715		initialised etc) all console output is silently discarded.
716		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
717		buffer any console messages prior to the console being
718		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
719		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
720		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
721		bytes are output before the console is initialised, the
722		earlier bytes are discarded.
723
724		'Sane' compilers will generate smaller code if
725		CONFIG_PRE_CON_BUF_SZ is a power of 2
726
727- Safe printf() functions
728		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
729		the printf() functions. These are defined in
730		include/vsprintf.h and include snprintf(), vsnprintf() and
731		so on. Code size increase is approximately 300-500 bytes.
732		If this option is not given then these functions will
733		silently discard their buffer size argument - this means
734		you are not getting any overflow checking in this case.
735
736- Boot Delay:	CONFIG_BOOTDELAY - in seconds
737		Delay before automatically booting the default image;
738		set to -1 to disable autoboot.
739		set to -2 to autoboot with no delay and not check for abort
740		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
741
742		See doc/README.autoboot for these options that
743		work with CONFIG_BOOTDELAY. None are required.
744		CONFIG_BOOT_RETRY_TIME
745		CONFIG_BOOT_RETRY_MIN
746		CONFIG_AUTOBOOT_KEYED
747		CONFIG_AUTOBOOT_PROMPT
748		CONFIG_AUTOBOOT_DELAY_STR
749		CONFIG_AUTOBOOT_STOP_STR
750		CONFIG_AUTOBOOT_DELAY_STR2
751		CONFIG_AUTOBOOT_STOP_STR2
752		CONFIG_ZERO_BOOTDELAY_CHECK
753		CONFIG_RESET_TO_RETRY
754
755- Autoboot Command:
756		CONFIG_BOOTCOMMAND
757		Only needed when CONFIG_BOOTDELAY is enabled;
758		define a command string that is automatically executed
759		when no character is read on the console interface
760		within "Boot Delay" after reset.
761
762		CONFIG_BOOTARGS
763		This can be used to pass arguments to the bootm
764		command. The value of CONFIG_BOOTARGS goes into the
765		environment value "bootargs".
766
767		CONFIG_RAMBOOT and CONFIG_NFSBOOT
768		The value of these goes into the environment as
769		"ramboot" and "nfsboot" respectively, and can be used
770		as a convenience, when switching between booting from
771		RAM and NFS.
772
773- Pre-Boot Commands:
774		CONFIG_PREBOOT
775
776		When this option is #defined, the existence of the
777		environment variable "preboot" will be checked
778		immediately before starting the CONFIG_BOOTDELAY
779		countdown and/or running the auto-boot command resp.
780		entering interactive mode.
781
782		This feature is especially useful when "preboot" is
783		automatically generated or modified. For an example
784		see the LWMON board specific code: here "preboot" is
785		modified when the user holds down a certain
786		combination of keys on the (special) keyboard when
787		booting the systems
788
789- Serial Download Echo Mode:
790		CONFIG_LOADS_ECHO
791		If defined to 1, all characters received during a
792		serial download (using the "loads" command) are
793		echoed back. This might be needed by some terminal
794		emulations (like "cu"), but may as well just take
795		time on others. This setting #define's the initial
796		value of the "loads_echo" environment variable.
797
798- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
799		CONFIG_KGDB_BAUDRATE
800		Select one of the baudrates listed in
801		CONFIG_SYS_BAUDRATE_TABLE, see below.
802
803- Monitor Functions:
804		Monitor commands can be included or excluded
805		from the build by using the #include files
806		<config_cmd_all.h> and #undef'ing unwanted
807		commands, or using <config_cmd_default.h>
808		and augmenting with additional #define's
809		for wanted commands.
810
811		The default command configuration includes all commands
812		except those marked below with a "*".
813
814		CONFIG_CMD_ASKENV	* ask for env variable
815		CONFIG_CMD_BDI		  bdinfo
816		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
817		CONFIG_CMD_BMP		* BMP support
818		CONFIG_CMD_BSP		* Board specific commands
819		CONFIG_CMD_BOOTD	  bootd
820		CONFIG_CMD_CACHE	* icache, dcache
821		CONFIG_CMD_CONSOLE	  coninfo
822		CONFIG_CMD_CRC32	* crc32
823		CONFIG_CMD_DATE		* support for RTC, date/time...
824		CONFIG_CMD_DHCP		* DHCP support
825		CONFIG_CMD_DIAG		* Diagnostics
826		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
827		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
828		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
829		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
830		CONFIG_CMD_DTT		* Digital Therm and Thermostat
831		CONFIG_CMD_ECHO		  echo arguments
832		CONFIG_CMD_EDITENV	  edit env variable
833		CONFIG_CMD_EEPROM	* EEPROM read/write support
834		CONFIG_CMD_ELF		* bootelf, bootvx
835		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
836		CONFIG_CMD_ENV_FLAGS	* display details about env flags
837		CONFIG_CMD_EXPORTENV	* export the environment
838		CONFIG_CMD_EXT2		* ext2 command support
839		CONFIG_CMD_EXT4		* ext4 command support
840		CONFIG_CMD_SAVEENV	  saveenv
841		CONFIG_CMD_FDC		* Floppy Disk Support
842		CONFIG_CMD_FAT		* FAT command support
843		CONFIG_CMD_FDOS		* Dos diskette Support
844		CONFIG_CMD_FLASH	  flinfo, erase, protect
845		CONFIG_CMD_FPGA		  FPGA device initialization support
846		CONFIG_CMD_FUSE		  Device fuse support
847		CONFIG_CMD_GETTIME	* Get time since boot
848		CONFIG_CMD_GO		* the 'go' command (exec code)
849		CONFIG_CMD_GREPENV	* search environment
850		CONFIG_CMD_HASH		* calculate hash / digest
851		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
852		CONFIG_CMD_I2C		* I2C serial bus support
853		CONFIG_CMD_IDE		* IDE harddisk support
854		CONFIG_CMD_IMI		  iminfo
855		CONFIG_CMD_IMLS		  List all images found in NOR flash
856		CONFIG_CMD_IMLS_NAND	  List all images found in NAND flash
857		CONFIG_CMD_IMMAP	* IMMR dump support
858		CONFIG_CMD_IMPORTENV	* import an environment
859		CONFIG_CMD_INI		* import data from an ini file into the env
860		CONFIG_CMD_IRQ		* irqinfo
861		CONFIG_CMD_ITEST	  Integer/string test of 2 values
862		CONFIG_CMD_JFFS2	* JFFS2 Support
863		CONFIG_CMD_KGDB		* kgdb
864		CONFIG_CMD_LDRINFO	  ldrinfo (display Blackfin loader)
865		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
866					  (169.254.*.*)
867		CONFIG_CMD_LOADB	  loadb
868		CONFIG_CMD_LOADS	  loads
869		CONFIG_CMD_MD5SUM	  print md5 message digest
870					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
871		CONFIG_CMD_MEMINFO	* Display detailed memory information
872		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
873					  loop, loopw
874		CONFIG_CMD_MEMTEST	  mtest
875		CONFIG_CMD_MISC		  Misc functions like sleep etc
876		CONFIG_CMD_MMC		* MMC memory mapped support
877		CONFIG_CMD_MII		* MII utility commands
878		CONFIG_CMD_MTDPARTS	* MTD partition support
879		CONFIG_CMD_NAND		* NAND support
880		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
881		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
882		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
883		CONFIG_CMD_PCI		* pciinfo
884		CONFIG_CMD_PCMCIA		* PCMCIA support
885		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
886					  host
887		CONFIG_CMD_PORTIO	* Port I/O
888		CONFIG_CMD_READ		* Read raw data from partition
889		CONFIG_CMD_REGINFO	* Register dump
890		CONFIG_CMD_RUN		  run command in env variable
891		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
892		CONFIG_CMD_SAVES	* save S record dump
893		CONFIG_CMD_SCSI		* SCSI Support
894		CONFIG_CMD_SDRAM	* print SDRAM configuration information
895					  (requires CONFIG_CMD_I2C)
896		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
897					  (4xx only)
898		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
899		CONFIG_CMD_SHA1SUM	  print sha1 memory digest
900					  (requires CONFIG_CMD_MEMORY)
901		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
902		CONFIG_CMD_SOURCE	  "source" command Support
903		CONFIG_CMD_SPI		* SPI serial bus support
904		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
905		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
906		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
907		CONFIG_CMD_TIMER	* access to the system tick timer
908		CONFIG_CMD_USB		* USB support
909		CONFIG_CMD_CDP		* Cisco Discover Protocol support
910		CONFIG_CMD_MFSL		* Microblaze FSL support
911
912
913		EXAMPLE: If you want all functions except of network
914		support you can write:
915
916		#include "config_cmd_all.h"
917		#undef CONFIG_CMD_NET
918
919	Other Commands:
920		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
921
922	Note:	Don't enable the "icache" and "dcache" commands
923		(configuration option CONFIG_CMD_CACHE) unless you know
924		what you (and your U-Boot users) are doing. Data
925		cache cannot be enabled on systems like the 8xx or
926		8260 (where accesses to the IMMR region must be
927		uncached), and it cannot be disabled on all other
928		systems where we (mis-) use the data cache to hold an
929		initial stack and some data.
930
931
932		XXX - this list needs to get updated!
933
934- Regular expression support:
935		CONFIG_REGEX
936                If this variable is defined, U-Boot is linked against
937                the SLRE (Super Light Regular Expression) library,
938                which adds regex support to some commands, as for
939                example "env grep" and "setexpr".
940
941- Device tree:
942		CONFIG_OF_CONTROL
943		If this variable is defined, U-Boot will use a device tree
944		to configure its devices, instead of relying on statically
945		compiled #defines in the board file. This option is
946		experimental and only available on a few boards. The device
947		tree is available in the global data as gd->fdt_blob.
948
949		U-Boot needs to get its device tree from somewhere. This can
950		be done using one of the two options below:
951
952		CONFIG_OF_EMBED
953		If this variable is defined, U-Boot will embed a device tree
954		binary in its image. This device tree file should be in the
955		board directory and called <soc>-<board>.dts. The binary file
956		is then picked up in board_init_f() and made available through
957		the global data structure as gd->blob.
958
959		CONFIG_OF_SEPARATE
960		If this variable is defined, U-Boot will build a device tree
961		binary. It will be called u-boot.dtb. Architecture-specific
962		code will locate it at run-time. Generally this works by:
963
964			cat u-boot.bin u-boot.dtb >image.bin
965
966		and in fact, U-Boot does this for you, creating a file called
967		u-boot-dtb.bin which is useful in the common case. You can
968		still use the individual files if you need something more
969		exotic.
970
971- Watchdog:
972		CONFIG_WATCHDOG
973		If this variable is defined, it enables watchdog
974		support for the SoC. There must be support in the SoC
975		specific code for a watchdog. For the 8xx and 8260
976		CPUs, the SIU Watchdog feature is enabled in the SYPCR
977		register.  When supported for a specific SoC is
978		available, then no further board specific code should
979		be needed to use it.
980
981		CONFIG_HW_WATCHDOG
982		When using a watchdog circuitry external to the used
983		SoC, then define this variable and provide board
984		specific code for the "hw_watchdog_reset" function.
985
986- U-Boot Version:
987		CONFIG_VERSION_VARIABLE
988		If this variable is defined, an environment variable
989		named "ver" is created by U-Boot showing the U-Boot
990		version as printed by the "version" command.
991		Any change to this variable will be reverted at the
992		next reset.
993
994- Real-Time Clock:
995
996		When CONFIG_CMD_DATE is selected, the type of the RTC
997		has to be selected, too. Define exactly one of the
998		following options:
999
1000		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1001		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1002		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1003		CONFIG_RTC_MC146818	- use MC146818 RTC
1004		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1005		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1006		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1007		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1008		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1009		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1010		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1011		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1012					  RV3029 RTC.
1013
1014		Note that if the RTC uses I2C, then the I2C interface
1015		must also be configured. See I2C Support, below.
1016
1017- GPIO Support:
1018		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1019		CONFIG_PCA953X_INFO	- enable pca953x info command
1020
1021		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1022		chip-ngpio pairs that tell the PCA953X driver the number of
1023		pins supported by a particular chip.
1024
1025		Note that if the GPIO device uses I2C, then the I2C interface
1026		must also be configured. See I2C Support, below.
1027
1028- Timestamp Support:
1029
1030		When CONFIG_TIMESTAMP is selected, the timestamp
1031		(date and time) of an image is printed by image
1032		commands like bootm or iminfo. This option is
1033		automatically enabled when you select CONFIG_CMD_DATE .
1034
1035- Partition Labels (disklabels) Supported:
1036		Zero or more of the following:
1037		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1038		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1039				       Intel architecture, USB sticks, etc.
1040		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1041		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1042				       bootloader.  Note 2TB partition limit; see
1043				       disk/part_efi.c
1044		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1045
1046		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1047		CONFIG_CMD_SCSI) you must configure support for at
1048		least one non-MTD partition type as well.
1049
1050- IDE Reset method:
1051		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1052		board configurations files but used nowhere!
1053
1054		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1055		be performed by calling the function
1056			ide_set_reset(int reset)
1057		which has to be defined in a board specific file
1058
1059- ATAPI Support:
1060		CONFIG_ATAPI
1061
1062		Set this to enable ATAPI support.
1063
1064- LBA48 Support
1065		CONFIG_LBA48
1066
1067		Set this to enable support for disks larger than 137GB
1068		Also look at CONFIG_SYS_64BIT_LBA.
1069		Whithout these , LBA48 support uses 32bit variables and will 'only'
1070		support disks up to 2.1TB.
1071
1072		CONFIG_SYS_64BIT_LBA:
1073			When enabled, makes the IDE subsystem use 64bit sector addresses.
1074			Default is 32bit.
1075
1076- SCSI Support:
1077		At the moment only there is only support for the
1078		SYM53C8XX SCSI controller; define
1079		CONFIG_SCSI_SYM53C8XX to enable it.
1080
1081		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1082		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1083		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1084		maximum numbers of LUNs, SCSI ID's and target
1085		devices.
1086		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1087
1088                The environment variable 'scsidevs' is set to the number of
1089                SCSI devices found during the last scan.
1090
1091- NETWORK Support (PCI):
1092		CONFIG_E1000
1093		Support for Intel 8254x/8257x gigabit chips.
1094
1095		CONFIG_E1000_SPI
1096		Utility code for direct access to the SPI bus on Intel 8257x.
1097		This does not do anything useful unless you set at least one
1098		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1099
1100		CONFIG_E1000_SPI_GENERIC
1101		Allow generic access to the SPI bus on the Intel 8257x, for
1102		example with the "sspi" command.
1103
1104		CONFIG_CMD_E1000
1105		Management command for E1000 devices.  When used on devices
1106		with SPI support you can reprogram the EEPROM from U-Boot.
1107
1108		CONFIG_E1000_FALLBACK_MAC
1109		default MAC for empty EEPROM after production.
1110
1111		CONFIG_EEPRO100
1112		Support for Intel 82557/82559/82559ER chips.
1113		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1114		write routine for first time initialisation.
1115
1116		CONFIG_TULIP
1117		Support for Digital 2114x chips.
1118		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1119		modem chip initialisation (KS8761/QS6611).
1120
1121		CONFIG_NATSEMI
1122		Support for National dp83815 chips.
1123
1124		CONFIG_NS8382X
1125		Support for National dp8382[01] gigabit chips.
1126
1127- NETWORK Support (other):
1128
1129		CONFIG_DRIVER_AT91EMAC
1130		Support for AT91RM9200 EMAC.
1131
1132			CONFIG_RMII
1133			Define this to use reduced MII inteface
1134
1135			CONFIG_DRIVER_AT91EMAC_QUIET
1136			If this defined, the driver is quiet.
1137			The driver doen't show link status messages.
1138
1139		CONFIG_CALXEDA_XGMAC
1140		Support for the Calxeda XGMAC device
1141
1142		CONFIG_LAN91C96
1143		Support for SMSC's LAN91C96 chips.
1144
1145			CONFIG_LAN91C96_BASE
1146			Define this to hold the physical address
1147			of the LAN91C96's I/O space
1148
1149			CONFIG_LAN91C96_USE_32_BIT
1150			Define this to enable 32 bit addressing
1151
1152		CONFIG_SMC91111
1153		Support for SMSC's LAN91C111 chip
1154
1155			CONFIG_SMC91111_BASE
1156			Define this to hold the physical address
1157			of the device (I/O space)
1158
1159			CONFIG_SMC_USE_32_BIT
1160			Define this if data bus is 32 bits
1161
1162			CONFIG_SMC_USE_IOFUNCS
1163			Define this to use i/o functions instead of macros
1164			(some hardware wont work with macros)
1165
1166		CONFIG_DRIVER_TI_EMAC
1167		Support for davinci emac
1168
1169			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1170			Define this if you have more then 3 PHYs.
1171
1172		CONFIG_FTGMAC100
1173		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1174
1175			CONFIG_FTGMAC100_EGIGA
1176			Define this to use GE link update with gigabit PHY.
1177			Define this if FTGMAC100 is connected to gigabit PHY.
1178			If your system has 10/100 PHY only, it might not occur
1179			wrong behavior. Because PHY usually return timeout or
1180			useless data when polling gigabit status and gigabit
1181			control registers. This behavior won't affect the
1182			correctnessof 10/100 link speed update.
1183
1184		CONFIG_SMC911X
1185		Support for SMSC's LAN911x and LAN921x chips
1186
1187			CONFIG_SMC911X_BASE
1188			Define this to hold the physical address
1189			of the device (I/O space)
1190
1191			CONFIG_SMC911X_32_BIT
1192			Define this if data bus is 32 bits
1193
1194			CONFIG_SMC911X_16_BIT
1195			Define this if data bus is 16 bits. If your processor
1196			automatically converts one 32 bit word to two 16 bit
1197			words you may also try CONFIG_SMC911X_32_BIT.
1198
1199		CONFIG_SH_ETHER
1200		Support for Renesas on-chip Ethernet controller
1201
1202			CONFIG_SH_ETHER_USE_PORT
1203			Define the number of ports to be used
1204
1205			CONFIG_SH_ETHER_PHY_ADDR
1206			Define the ETH PHY's address
1207
1208			CONFIG_SH_ETHER_CACHE_WRITEBACK
1209			If this option is set, the driver enables cache flush.
1210
1211- TPM Support:
1212		CONFIG_TPM
1213		Support TPM devices.
1214
1215		CONFIG_TPM_TIS_I2C
1216		Support for i2c bus TPM devices. Only one device
1217		per system is supported at this time.
1218
1219			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1220			Define the the i2c bus number for the TPM device
1221
1222			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1223			Define the TPM's address on the i2c bus
1224
1225			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1226			Define the burst count bytes upper limit
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- USB Support:
1238		At the moment only the UHCI host controller is
1239		supported (PIP405, MIP405, MPC5200); define
1240		CONFIG_USB_UHCI to enable it.
1241		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1242		and define CONFIG_USB_STORAGE to enable the USB
1243		storage devices.
1244		Note:
1245		Supported are USB Keyboards and USB Floppy drives
1246		(TEAC FD-05PUB).
1247		MPC5200 USB requires additional defines:
1248			CONFIG_USB_CLOCK
1249				for 528 MHz Clock: 0x0001bbbb
1250			CONFIG_PSC3_USB
1251				for USB on PSC3
1252			CONFIG_USB_CONFIG
1253				for differential drivers: 0x00001000
1254				for single ended drivers: 0x00005000
1255				for differential drivers on PSC3: 0x00000100
1256				for single ended drivers on PSC3: 0x00004100
1257			CONFIG_SYS_USB_EVENT_POLL
1258				May be defined to allow interrupt polling
1259				instead of using asynchronous interrupts
1260
1261		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1262		txfilltuning field in the EHCI controller on reset.
1263
1264- USB Device:
1265		Define the below if you wish to use the USB console.
1266		Once firmware is rebuilt from a serial console issue the
1267		command "setenv stdin usbtty; setenv stdout usbtty" and
1268		attach your USB cable. The Unix command "dmesg" should print
1269		it has found a new device. The environment variable usbtty
1270		can be set to gserial or cdc_acm to enable your device to
1271		appear to a USB host as a Linux gserial device or a
1272		Common Device Class Abstract Control Model serial device.
1273		If you select usbtty = gserial you should be able to enumerate
1274		a Linux host by
1275		# modprobe usbserial vendor=0xVendorID product=0xProductID
1276		else if using cdc_acm, simply setting the environment
1277		variable usbtty to be cdc_acm should suffice. The following
1278		might be defined in YourBoardName.h
1279
1280			CONFIG_USB_DEVICE
1281			Define this to build a UDC device
1282
1283			CONFIG_USB_TTY
1284			Define this to have a tty type of device available to
1285			talk to the UDC device
1286
1287			CONFIG_USBD_HS
1288			Define this to enable the high speed support for usb
1289			device and usbtty. If this feature is enabled, a routine
1290			int is_usbd_high_speed(void)
1291			also needs to be defined by the driver to dynamically poll
1292			whether the enumeration has succeded at high speed or full
1293			speed.
1294
1295			CONFIG_SYS_CONSOLE_IS_IN_ENV
1296			Define this if you want stdin, stdout &/or stderr to
1297			be set to usbtty.
1298
1299			mpc8xx:
1300				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1301				Derive USB clock from external clock "blah"
1302				- CONFIG_SYS_USB_EXTC_CLK 0x02
1303
1304				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1305				Derive USB clock from brgclk
1306				- CONFIG_SYS_USB_BRG_CLK 0x04
1307
1308		If you have a USB-IF assigned VendorID then you may wish to
1309		define your own vendor specific values either in BoardName.h
1310		or directly in usbd_vendor_info.h. If you don't define
1311		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1312		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1313		should pretend to be a Linux device to it's target host.
1314
1315			CONFIG_USBD_MANUFACTURER
1316			Define this string as the name of your company for
1317			- CONFIG_USBD_MANUFACTURER "my company"
1318
1319			CONFIG_USBD_PRODUCT_NAME
1320			Define this string as the name of your product
1321			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1322
1323			CONFIG_USBD_VENDORID
1324			Define this as your assigned Vendor ID from the USB
1325			Implementors Forum. This *must* be a genuine Vendor ID
1326			to avoid polluting the USB namespace.
1327			- CONFIG_USBD_VENDORID 0xFFFF
1328
1329			CONFIG_USBD_PRODUCTID
1330			Define this as the unique Product ID
1331			for your device
1332			- CONFIG_USBD_PRODUCTID 0xFFFF
1333
1334- ULPI Layer Support:
1335		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1336		the generic ULPI layer. The generic layer accesses the ULPI PHY
1337		via the platform viewport, so you need both the genric layer and
1338		the viewport enabled. Currently only Chipidea/ARC based
1339		viewport is supported.
1340		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1341		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1342		If your ULPI phy needs a different reference clock than the
1343		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1344		the appropriate value in Hz.
1345
1346- MMC Support:
1347		The MMC controller on the Intel PXA is supported. To
1348		enable this define CONFIG_MMC. The MMC can be
1349		accessed from the boot prompt by mapping the device
1350		to physical memory similar to flash. Command line is
1351		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1352		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1353
1354		CONFIG_SH_MMCIF
1355		Support for Renesas on-chip MMCIF controller
1356
1357			CONFIG_SH_MMCIF_ADDR
1358			Define the base address of MMCIF registers
1359
1360			CONFIG_SH_MMCIF_CLK
1361			Define the clock frequency for MMCIF
1362
1363- USB Device Firmware Update (DFU) class support:
1364		CONFIG_DFU_FUNCTION
1365		This enables the USB portion of the DFU USB class
1366
1367		CONFIG_CMD_DFU
1368		This enables the command "dfu" which is used to have
1369		U-Boot create a DFU class device via USB.  This command
1370		requires that the "dfu_alt_info" environment variable be
1371		set and define the alt settings to expose to the host.
1372
1373		CONFIG_DFU_MMC
1374		This enables support for exposing (e)MMC devices via DFU.
1375
1376		CONFIG_DFU_NAND
1377		This enables support for exposing NAND devices via DFU.
1378
1379		CONFIG_SYS_DFU_MAX_FILE_SIZE
1380		When updating files rather than the raw storage device,
1381		we use a static buffer to copy the file into and then write
1382		the buffer once we've been given the whole file.  Define
1383		this to the maximum filesize (in bytes) for the buffer.
1384		Default is 4 MiB if undefined.
1385
1386- Journaling Flash filesystem support:
1387		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1388		CONFIG_JFFS2_NAND_DEV
1389		Define these for a default partition on a NAND device
1390
1391		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1392		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1393		Define these for a default partition on a NOR device
1394
1395		CONFIG_SYS_JFFS_CUSTOM_PART
1396		Define this to create an own partition. You have to provide a
1397		function struct part_info* jffs2_part_info(int part_num)
1398
1399		If you define only one JFFS2 partition you may also want to
1400		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1401		to disable the command chpart. This is the default when you
1402		have not defined a custom partition
1403
1404- FAT(File Allocation Table) filesystem write function support:
1405		CONFIG_FAT_WRITE
1406
1407		Define this to enable support for saving memory data as a
1408		file in FAT formatted partition.
1409
1410		This will also enable the command "fatwrite" enabling the
1411		user to write files to FAT.
1412
1413CBFS (Coreboot Filesystem) support
1414		CONFIG_CMD_CBFS
1415
1416		Define this to enable support for reading from a Coreboot
1417		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1418		and cbfsload.
1419
1420- Keyboard Support:
1421		CONFIG_ISA_KEYBOARD
1422
1423		Define this to enable standard (PC-Style) keyboard
1424		support
1425
1426		CONFIG_I8042_KBD
1427		Standard PC keyboard driver with US (is default) and
1428		GERMAN key layout (switch via environment 'keymap=de') support.
1429		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1430		for cfb_console. Supports cursor blinking.
1431
1432- Video support:
1433		CONFIG_VIDEO
1434
1435		Define this to enable video support (for output to
1436		video).
1437
1438		CONFIG_VIDEO_CT69000
1439
1440		Enable Chips & Technologies 69000 Video chip
1441
1442		CONFIG_VIDEO_SMI_LYNXEM
1443		Enable Silicon Motion SMI 712/710/810 Video chip. The
1444		video output is selected via environment 'videoout'
1445		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1446		assumed.
1447
1448		For the CT69000 and SMI_LYNXEM drivers, videomode is
1449		selected via environment 'videomode'. Two different ways
1450		are possible:
1451		- "videomode=num"   'num' is a standard LiLo mode numbers.
1452		Following standard modes are supported	(* is default):
1453
1454		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1455		-------------+---------------------------------------------
1456		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1457		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1458		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1459		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1460		-------------+---------------------------------------------
1461		(i.e. setenv videomode 317; saveenv; reset;)
1462
1463		- "videomode=bootargs" all the video parameters are parsed
1464		from the bootargs. (See drivers/video/videomodes.c)
1465
1466
1467		CONFIG_VIDEO_SED13806
1468		Enable Epson SED13806 driver. This driver supports 8bpp
1469		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1470		or CONFIG_VIDEO_SED13806_16BPP
1471
1472		CONFIG_FSL_DIU_FB
1473		Enable the Freescale DIU video driver.	Reference boards for
1474		SOCs that have a DIU should define this macro to enable DIU
1475		support, and should also define these other macros:
1476
1477			CONFIG_SYS_DIU_ADDR
1478			CONFIG_VIDEO
1479			CONFIG_CMD_BMP
1480			CONFIG_CFB_CONSOLE
1481			CONFIG_VIDEO_SW_CURSOR
1482			CONFIG_VGA_AS_SINGLE_DEVICE
1483			CONFIG_VIDEO_LOGO
1484			CONFIG_VIDEO_BMP_LOGO
1485
1486		The DIU driver will look for the 'video-mode' environment
1487		variable, and if defined, enable the DIU as a console during
1488		boot.  See the documentation file README.video for a
1489		description of this variable.
1490
1491		CONFIG_VIDEO_VGA
1492
1493		Enable the VGA video / BIOS for x86. The alternative if you
1494		are using coreboot is to use the coreboot frame buffer
1495		driver.
1496
1497
1498- Keyboard Support:
1499		CONFIG_KEYBOARD
1500
1501		Define this to enable a custom keyboard support.
1502		This simply calls drv_keyboard_init() which must be
1503		defined in your board-specific files.
1504		The only board using this so far is RBC823.
1505
1506- LCD Support:	CONFIG_LCD
1507
1508		Define this to enable LCD support (for output to LCD
1509		display); also select one of the supported displays
1510		by defining one of these:
1511
1512		CONFIG_ATMEL_LCD:
1513
1514			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1515
1516		CONFIG_NEC_NL6448AC33:
1517
1518			NEC NL6448AC33-18. Active, color, single scan.
1519
1520		CONFIG_NEC_NL6448BC20
1521
1522			NEC NL6448BC20-08. 6.5", 640x480.
1523			Active, color, single scan.
1524
1525		CONFIG_NEC_NL6448BC33_54
1526
1527			NEC NL6448BC33-54. 10.4", 640x480.
1528			Active, color, single scan.
1529
1530		CONFIG_SHARP_16x9
1531
1532			Sharp 320x240. Active, color, single scan.
1533			It isn't 16x9, and I am not sure what it is.
1534
1535		CONFIG_SHARP_LQ64D341
1536
1537			Sharp LQ64D341 display, 640x480.
1538			Active, color, single scan.
1539
1540		CONFIG_HLD1045
1541
1542			HLD1045 display, 640x480.
1543			Active, color, single scan.
1544
1545		CONFIG_OPTREX_BW
1546
1547			Optrex	 CBL50840-2 NF-FW 99 22 M5
1548			or
1549			Hitachi	 LMG6912RPFC-00T
1550			or
1551			Hitachi	 SP14Q002
1552
1553			320x240. Black & white.
1554
1555		Normally display is black on white background; define
1556		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1557
1558		CONFIG_LCD_ALIGNMENT
1559
1560		Normally the LCD is page-aligned (tyically 4KB). If this is
1561		defined then the LCD will be aligned to this value instead.
1562		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1563		here, since it is cheaper to change data cache settings on
1564		a per-section basis.
1565
1566		CONFIG_CONSOLE_SCROLL_LINES
1567
1568		When the console need to be scrolled, this is the number of
1569		lines to scroll by. It defaults to 1. Increasing this makes
1570		the console jump but can help speed up operation when scrolling
1571		is slow.
1572
1573		CONFIG_LCD_BMP_RLE8
1574
1575		Support drawing of RLE8-compressed bitmaps on the LCD.
1576
1577		CONFIG_I2C_EDID
1578
1579		Enables an 'i2c edid' command which can read EDID
1580		information over I2C from an attached LCD display.
1581
1582- Splash Screen Support: CONFIG_SPLASH_SCREEN
1583
1584		If this option is set, the environment is checked for
1585		a variable "splashimage". If found, the usual display
1586		of logo, copyright and system information on the LCD
1587		is suppressed and the BMP image at the address
1588		specified in "splashimage" is loaded instead. The
1589		console is redirected to the "nulldev", too. This
1590		allows for a "silent" boot where a splash screen is
1591		loaded very quickly after power-on.
1592
1593		CONFIG_SPLASHIMAGE_GUARD
1594
1595		If this option is set, then U-Boot will prevent the environment
1596		variable "splashimage" from being set to a problematic address
1597		(see README.displaying-bmps and README.arm-unaligned-accesses).
1598		This option is useful for targets where, due to alignment
1599		restrictions, an improperly aligned BMP image will cause a data
1600		abort. If you think you will not have problems with unaligned
1601		accesses (for example because your toolchain prevents them)
1602		there is no need to set this option.
1603
1604		CONFIG_SPLASH_SCREEN_ALIGN
1605
1606		If this option is set the splash image can be freely positioned
1607		on the screen. Environment variable "splashpos" specifies the
1608		position as "x,y". If a positive number is given it is used as
1609		number of pixel from left/top. If a negative number is given it
1610		is used as number of pixel from right/bottom. You can also
1611		specify 'm' for centering the image.
1612
1613		Example:
1614		setenv splashpos m,m
1615			=> image at center of screen
1616
1617		setenv splashpos 30,20
1618			=> image at x = 30 and y = 20
1619
1620		setenv splashpos -10,m
1621			=> vertically centered image
1622			   at x = dspWidth - bmpWidth - 9
1623
1624		CONFIG_SPLASH_SCREEN_PREPARE
1625
1626		If this option is set then the board_splash_screen_prepare()
1627		function, which must be defined in your code, is called as part
1628		of the splash screen display sequence. It gives the board an
1629		opportunity to prepare the splash image data before it is
1630		processed and sent to the frame buffer by U-Boot.
1631
1632- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1633
1634		If this option is set, additionally to standard BMP
1635		images, gzipped BMP images can be displayed via the
1636		splashscreen support or the bmp command.
1637
1638- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1639
1640		If this option is set, 8-bit RLE compressed BMP images
1641		can be displayed via the splashscreen support or the
1642		bmp command.
1643
1644- Do compresssing for memory range:
1645		CONFIG_CMD_ZIP
1646
1647		If this option is set, it would use zlib deflate method
1648		to compress the specified memory at its best effort.
1649
1650- Compression support:
1651		CONFIG_BZIP2
1652
1653		If this option is set, support for bzip2 compressed
1654		images is included. If not, only uncompressed and gzip
1655		compressed images are supported.
1656
1657		NOTE: the bzip2 algorithm requires a lot of RAM, so
1658		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1659		be at least 4MB.
1660
1661		CONFIG_LZMA
1662
1663		If this option is set, support for lzma compressed
1664		images is included.
1665
1666		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1667		requires an amount of dynamic memory that is given by the
1668		formula:
1669
1670			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1671
1672		Where lc and lp stand for, respectively, Literal context bits
1673		and Literal pos bits.
1674
1675		This value is upper-bounded by 14MB in the worst case. Anyway,
1676		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1677		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1678		a very small buffer.
1679
1680		Use the lzmainfo tool to determinate the lc and lp values and
1681		then calculate the amount of needed dynamic memory (ensuring
1682		the appropriate CONFIG_SYS_MALLOC_LEN value).
1683
1684- MII/PHY support:
1685		CONFIG_PHY_ADDR
1686
1687		The address of PHY on MII bus.
1688
1689		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1690
1691		The clock frequency of the MII bus
1692
1693		CONFIG_PHY_GIGE
1694
1695		If this option is set, support for speed/duplex
1696		detection of gigabit PHY is included.
1697
1698		CONFIG_PHY_RESET_DELAY
1699
1700		Some PHY like Intel LXT971A need extra delay after
1701		reset before any MII register access is possible.
1702		For such PHY, set this option to the usec delay
1703		required. (minimum 300usec for LXT971A)
1704
1705		CONFIG_PHY_CMD_DELAY (ppc4xx)
1706
1707		Some PHY like Intel LXT971A need extra delay after
1708		command issued before MII status register can be read
1709
1710- Ethernet address:
1711		CONFIG_ETHADDR
1712		CONFIG_ETH1ADDR
1713		CONFIG_ETH2ADDR
1714		CONFIG_ETH3ADDR
1715		CONFIG_ETH4ADDR
1716		CONFIG_ETH5ADDR
1717
1718		Define a default value for Ethernet address to use
1719		for the respective Ethernet interface, in case this
1720		is not determined automatically.
1721
1722- IP address:
1723		CONFIG_IPADDR
1724
1725		Define a default value for the IP address to use for
1726		the default Ethernet interface, in case this is not
1727		determined through e.g. bootp.
1728		(Environment variable "ipaddr")
1729
1730- Server IP address:
1731		CONFIG_SERVERIP
1732
1733		Defines a default value for the IP address of a TFTP
1734		server to contact when using the "tftboot" command.
1735		(Environment variable "serverip")
1736
1737		CONFIG_KEEP_SERVERADDR
1738
1739		Keeps the server's MAC address, in the env 'serveraddr'
1740		for passing to bootargs (like Linux's netconsole option)
1741
1742- Gateway IP address:
1743		CONFIG_GATEWAYIP
1744
1745		Defines a default value for the IP address of the
1746		default router where packets to other networks are
1747		sent to.
1748		(Environment variable "gatewayip")
1749
1750- Subnet mask:
1751		CONFIG_NETMASK
1752
1753		Defines a default value for the subnet mask (or
1754		routing prefix) which is used to determine if an IP
1755		address belongs to the local subnet or needs to be
1756		forwarded through a router.
1757		(Environment variable "netmask")
1758
1759- Multicast TFTP Mode:
1760		CONFIG_MCAST_TFTP
1761
1762		Defines whether you want to support multicast TFTP as per
1763		rfc-2090; for example to work with atftp.  Lets lots of targets
1764		tftp down the same boot image concurrently.  Note: the Ethernet
1765		driver in use must provide a function: mcast() to join/leave a
1766		multicast group.
1767
1768- BOOTP Recovery Mode:
1769		CONFIG_BOOTP_RANDOM_DELAY
1770
1771		If you have many targets in a network that try to
1772		boot using BOOTP, you may want to avoid that all
1773		systems send out BOOTP requests at precisely the same
1774		moment (which would happen for instance at recovery
1775		from a power failure, when all systems will try to
1776		boot, thus flooding the BOOTP server. Defining
1777		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1778		inserted before sending out BOOTP requests. The
1779		following delays are inserted then:
1780
1781		1st BOOTP request:	delay 0 ... 1 sec
1782		2nd BOOTP request:	delay 0 ... 2 sec
1783		3rd BOOTP request:	delay 0 ... 4 sec
1784		4th and following
1785		BOOTP requests:		delay 0 ... 8 sec
1786
1787- DHCP Advanced Options:
1788		You can fine tune the DHCP functionality by defining
1789		CONFIG_BOOTP_* symbols:
1790
1791		CONFIG_BOOTP_SUBNETMASK
1792		CONFIG_BOOTP_GATEWAY
1793		CONFIG_BOOTP_HOSTNAME
1794		CONFIG_BOOTP_NISDOMAIN
1795		CONFIG_BOOTP_BOOTPATH
1796		CONFIG_BOOTP_BOOTFILESIZE
1797		CONFIG_BOOTP_DNS
1798		CONFIG_BOOTP_DNS2
1799		CONFIG_BOOTP_SEND_HOSTNAME
1800		CONFIG_BOOTP_NTPSERVER
1801		CONFIG_BOOTP_TIMEOFFSET
1802		CONFIG_BOOTP_VENDOREX
1803		CONFIG_BOOTP_MAY_FAIL
1804
1805		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1806		environment variable, not the BOOTP server.
1807
1808		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1809		after the configured retry count, the call will fail
1810		instead of starting over.  This can be used to fail over
1811		to Link-local IP address configuration if the DHCP server
1812		is not available.
1813
1814		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1815		serverip from a DHCP server, it is possible that more
1816		than one DNS serverip is offered to the client.
1817		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1818		serverip will be stored in the additional environment
1819		variable "dnsip2". The first DNS serverip is always
1820		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1821		is defined.
1822
1823		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1824		to do a dynamic update of a DNS server. To do this, they
1825		need the hostname of the DHCP requester.
1826		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1827		of the "hostname" environment variable is passed as
1828		option 12 to the DHCP server.
1829
1830		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1831
1832		A 32bit value in microseconds for a delay between
1833		receiving a "DHCP Offer" and sending the "DHCP Request".
1834		This fixes a problem with certain DHCP servers that don't
1835		respond 100% of the time to a "DHCP request". E.g. On an
1836		AT91RM9200 processor running at 180MHz, this delay needed
1837		to be *at least* 15,000 usec before a Windows Server 2003
1838		DHCP server would reply 100% of the time. I recommend at
1839		least 50,000 usec to be safe. The alternative is to hope
1840		that one of the retries will be successful but note that
1841		the DHCP timeout and retry process takes a longer than
1842		this delay.
1843
1844 - Link-local IP address negotiation:
1845		Negotiate with other link-local clients on the local network
1846		for an address that doesn't require explicit configuration.
1847		This is especially useful if a DHCP server cannot be guaranteed
1848		to exist in all environments that the device must operate.
1849
1850		See doc/README.link-local for more information.
1851
1852 - CDP Options:
1853		CONFIG_CDP_DEVICE_ID
1854
1855		The device id used in CDP trigger frames.
1856
1857		CONFIG_CDP_DEVICE_ID_PREFIX
1858
1859		A two character string which is prefixed to the MAC address
1860		of the device.
1861
1862		CONFIG_CDP_PORT_ID
1863
1864		A printf format string which contains the ascii name of
1865		the port. Normally is set to "eth%d" which sets
1866		eth0 for the first Ethernet, eth1 for the second etc.
1867
1868		CONFIG_CDP_CAPABILITIES
1869
1870		A 32bit integer which indicates the device capabilities;
1871		0x00000010 for a normal host which does not forwards.
1872
1873		CONFIG_CDP_VERSION
1874
1875		An ascii string containing the version of the software.
1876
1877		CONFIG_CDP_PLATFORM
1878
1879		An ascii string containing the name of the platform.
1880
1881		CONFIG_CDP_TRIGGER
1882
1883		A 32bit integer sent on the trigger.
1884
1885		CONFIG_CDP_POWER_CONSUMPTION
1886
1887		A 16bit integer containing the power consumption of the
1888		device in .1 of milliwatts.
1889
1890		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1891
1892		A byte containing the id of the VLAN.
1893
1894- Status LED:	CONFIG_STATUS_LED
1895
1896		Several configurations allow to display the current
1897		status using a LED. For instance, the LED will blink
1898		fast while running U-Boot code, stop blinking as
1899		soon as a reply to a BOOTP request was received, and
1900		start blinking slow once the Linux kernel is running
1901		(supported by a status LED driver in the Linux
1902		kernel). Defining CONFIG_STATUS_LED enables this
1903		feature in U-Boot.
1904
1905- CAN Support:	CONFIG_CAN_DRIVER
1906
1907		Defining CONFIG_CAN_DRIVER enables CAN driver support
1908		on those systems that support this (optional)
1909		feature, like the TQM8xxL modules.
1910
1911- I2C Support:	CONFIG_HARD_I2C | CONFIG_SOFT_I2C
1912
1913		These enable I2C serial bus commands. Defining either of
1914		(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
1915		include the appropriate I2C driver for the selected CPU.
1916
1917		This will allow you to use i2c commands at the u-boot
1918		command line (as long as you set CONFIG_CMD_I2C in
1919		CONFIG_COMMANDS) and communicate with i2c based realtime
1920		clock chips. See common/cmd_i2c.c for a description of the
1921		command line interface.
1922
1923		CONFIG_HARD_I2C selects a hardware I2C controller.
1924
1925		CONFIG_SOFT_I2C configures u-boot to use a software (aka
1926		bit-banging) driver instead of CPM or similar hardware
1927		support for I2C.
1928
1929		There are several other quantities that must also be
1930		defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.
1931
1932		In both cases you will need to define CONFIG_SYS_I2C_SPEED
1933		to be the frequency (in Hz) at which you wish your i2c bus
1934		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
1935		the CPU's i2c node address).
1936
1937		Now, the u-boot i2c code for the mpc8xx
1938		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
1939		and so its address should therefore be cleared to 0 (See,
1940		eg, MPC823e User's Manual p.16-473). So, set
1941		CONFIG_SYS_I2C_SLAVE to 0.
1942
1943		CONFIG_SYS_I2C_INIT_MPC5XXX
1944
1945		When a board is reset during an i2c bus transfer
1946		chips might think that the current transfer is still
1947		in progress.  Reset the slave devices by sending start
1948		commands until the slave device responds.
1949
1950		That's all that's required for CONFIG_HARD_I2C.
1951
1952		If you use the software i2c interface (CONFIG_SOFT_I2C)
1953		then the following macros need to be defined (examples are
1954		from include/configs/lwmon.h):
1955
1956		I2C_INIT
1957
1958		(Optional). Any commands necessary to enable the I2C
1959		controller or configure ports.
1960
1961		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1962
1963		I2C_PORT
1964
1965		(Only for MPC8260 CPU). The I/O port to use (the code
1966		assumes both bits are on the same port). Valid values
1967		are 0..3 for ports A..D.
1968
1969		I2C_ACTIVE
1970
1971		The code necessary to make the I2C data line active
1972		(driven).  If the data line is open collector, this
1973		define can be null.
1974
1975		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1976
1977		I2C_TRISTATE
1978
1979		The code necessary to make the I2C data line tri-stated
1980		(inactive).  If the data line is open collector, this
1981		define can be null.
1982
1983		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1984
1985		I2C_READ
1986
1987		Code that returns true if the I2C data line is high,
1988		false if it is low.
1989
1990		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1991
1992		I2C_SDA(bit)
1993
1994		If <bit> is true, sets the I2C data line high. If it
1995		is false, it clears it (low).
1996
1997		eg: #define I2C_SDA(bit) \
1998			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1999			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2000
2001		I2C_SCL(bit)
2002
2003		If <bit> is true, sets the I2C clock line high. If it
2004		is false, it clears it (low).
2005
2006		eg: #define I2C_SCL(bit) \
2007			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2008			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2009
2010		I2C_DELAY
2011
2012		This delay is invoked four times per clock cycle so this
2013		controls the rate of data transfer.  The data rate thus
2014		is 1 / (I2C_DELAY * 4). Often defined to be something
2015		like:
2016
2017		#define I2C_DELAY  udelay(2)
2018
2019		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2020
2021		If your arch supports the generic GPIO framework (asm/gpio.h),
2022		then you may alternatively define the two GPIOs that are to be
2023		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2024		have GPIO-based defaults assigned to them as appropriate.
2025
2026		You should define these to the GPIO value as given directly to
2027		the generic GPIO functions.
2028
2029		CONFIG_SYS_I2C_INIT_BOARD
2030
2031		When a board is reset during an i2c bus transfer
2032		chips might think that the current transfer is still
2033		in progress. On some boards it is possible to access
2034		the i2c SCLK line directly, either by using the
2035		processor pin as a GPIO or by having a second pin
2036		connected to the bus. If this option is defined a
2037		custom i2c_init_board() routine in boards/xxx/board.c
2038		is run early in the boot sequence.
2039
2040		CONFIG_SYS_I2C_BOARD_LATE_INIT
2041
2042		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2043		defined a custom i2c_board_late_init() routine in
2044		boards/xxx/board.c is run AFTER the operations in i2c_init()
2045		is completed. This callpoint can be used to unreset i2c bus
2046		using CPU i2c controller register accesses for CPUs whose i2c
2047		controller provide such a method. It is called at the end of
2048		i2c_init() to allow i2c_init operations to setup the i2c bus
2049		controller on the CPU (e.g. setting bus speed & slave address).
2050
2051		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2052
2053		This option enables configuration of bi_iic_fast[] flags
2054		in u-boot bd_info structure based on u-boot environment
2055		variable "i2cfast". (see also i2cfast)
2056
2057		CONFIG_I2C_MULTI_BUS
2058
2059		This option allows the use of multiple I2C buses, each of which
2060		must have a controller.	 At any point in time, only one bus is
2061		active.	 To switch to a different bus, use the 'i2c dev' command.
2062		Note that bus numbering is zero-based.
2063
2064		CONFIG_SYS_I2C_NOPROBES
2065
2066		This option specifies a list of I2C devices that will be skipped
2067		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2068		is set, specify a list of bus-device pairs.  Otherwise, specify
2069		a 1D array of device addresses
2070
2071		e.g.
2072			#undef	CONFIG_I2C_MULTI_BUS
2073			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2074
2075		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2076
2077			#define CONFIG_I2C_MULTI_BUS
2078			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2079
2080		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2081
2082		CONFIG_SYS_SPD_BUS_NUM
2083
2084		If defined, then this indicates the I2C bus number for DDR SPD.
2085		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2086
2087		CONFIG_SYS_RTC_BUS_NUM
2088
2089		If defined, then this indicates the I2C bus number for the RTC.
2090		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2091
2092		CONFIG_SYS_DTT_BUS_NUM
2093
2094		If defined, then this indicates the I2C bus number for the DTT.
2095		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2096
2097		CONFIG_SYS_I2C_DTT_ADDR:
2098
2099		If defined, specifies the I2C address of the DTT device.
2100		If not defined, then U-Boot uses predefined value for
2101		specified DTT device.
2102
2103		CONFIG_FSL_I2C
2104
2105		Define this option if you want to use Freescale's I2C driver in
2106		drivers/i2c/fsl_i2c.c.
2107
2108		CONFIG_I2C_MUX
2109
2110		Define this option if you have I2C devices reached over 1 .. n
2111		I2C Muxes like the pca9544a. This option addes a new I2C
2112		Command "i2c bus [muxtype:muxaddr:muxchannel]" which adds a
2113		new I2C Bus to the existing I2C Busses. If you select the
2114		new Bus with "i2c dev", u-bbot sends first the commandos for
2115		the muxes to activate this new "bus".
2116
2117		CONFIG_I2C_MULTI_BUS must be also defined, to use this
2118		feature!
2119
2120		Example:
2121		Adding a new I2C Bus reached over 2 pca9544a muxes
2122			The First mux with address 70 and channel 6
2123			The Second mux with address 71 and channel 4
2124
2125		=> i2c bus pca9544a:70:6:pca9544a:71:4
2126
2127		Use the "i2c bus" command without parameter, to get a list
2128		of I2C Busses with muxes:
2129
2130		=> i2c bus
2131		Busses reached over muxes:
2132		Bus ID: 2
2133		  reached over Mux(es):
2134		    pca9544a@70 ch: 4
2135		Bus ID: 3
2136		  reached over Mux(es):
2137		    pca9544a@70 ch: 6
2138		    pca9544a@71 ch: 4
2139		=>
2140
2141		If you now switch to the new I2C Bus 3 with "i2c dev 3"
2142		u-boot first sends the command to the mux@70 to enable
2143		channel 6, and then the command to the mux@71 to enable
2144		the channel 4.
2145
2146		After that, you can use the "normal" i2c commands as
2147		usual to communicate with your I2C devices behind
2148		the 2 muxes.
2149
2150		This option is actually implemented for the bitbanging
2151		algorithm in common/soft_i2c.c and for the Hardware I2C
2152		Bus on the MPC8260. But it should be not so difficult
2153		to add this option to other architectures.
2154
2155		CONFIG_SOFT_I2C_READ_REPEATED_START
2156
2157		defining this will force the i2c_read() function in
2158		the soft_i2c driver to perform an I2C repeated start
2159		between writing the address pointer and reading the
2160		data.  If this define is omitted the default behaviour
2161		of doing a stop-start sequence will be used.  Most I2C
2162		devices can use either method, but some require one or
2163		the other.
2164
2165- SPI Support:	CONFIG_SPI
2166
2167		Enables SPI driver (so far only tested with
2168		SPI EEPROM, also an instance works with Crystal A/D and
2169		D/As on the SACSng board)
2170
2171		CONFIG_SH_SPI
2172
2173		Enables the driver for SPI controller on SuperH. Currently
2174		only SH7757 is supported.
2175
2176		CONFIG_SPI_X
2177
2178		Enables extended (16-bit) SPI EEPROM addressing.
2179		(symmetrical to CONFIG_I2C_X)
2180
2181		CONFIG_SOFT_SPI
2182
2183		Enables a software (bit-bang) SPI driver rather than
2184		using hardware support. This is a general purpose
2185		driver that only requires three general I/O port pins
2186		(two outputs, one input) to function. If this is
2187		defined, the board configuration must define several
2188		SPI configuration items (port pins to use, etc). For
2189		an example, see include/configs/sacsng.h.
2190
2191		CONFIG_HARD_SPI
2192
2193		Enables a hardware SPI driver for general-purpose reads
2194		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2195		must define a list of chip-select function pointers.
2196		Currently supported on some MPC8xxx processors.	 For an
2197		example, see include/configs/mpc8349emds.h.
2198
2199		CONFIG_MXC_SPI
2200
2201		Enables the driver for the SPI controllers on i.MX and MXC
2202		SoCs. Currently i.MX31/35/51 are supported.
2203
2204- FPGA Support: CONFIG_FPGA
2205
2206		Enables FPGA subsystem.
2207
2208		CONFIG_FPGA_<vendor>
2209
2210		Enables support for specific chip vendors.
2211		(ALTERA, XILINX)
2212
2213		CONFIG_FPGA_<family>
2214
2215		Enables support for FPGA family.
2216		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2217
2218		CONFIG_FPGA_COUNT
2219
2220		Specify the number of FPGA devices to support.
2221
2222		CONFIG_SYS_FPGA_PROG_FEEDBACK
2223
2224		Enable printing of hash marks during FPGA configuration.
2225
2226		CONFIG_SYS_FPGA_CHECK_BUSY
2227
2228		Enable checks on FPGA configuration interface busy
2229		status by the configuration function. This option
2230		will require a board or device specific function to
2231		be written.
2232
2233		CONFIG_FPGA_DELAY
2234
2235		If defined, a function that provides delays in the FPGA
2236		configuration driver.
2237
2238		CONFIG_SYS_FPGA_CHECK_CTRLC
2239		Allow Control-C to interrupt FPGA configuration
2240
2241		CONFIG_SYS_FPGA_CHECK_ERROR
2242
2243		Check for configuration errors during FPGA bitfile
2244		loading. For example, abort during Virtex II
2245		configuration if the INIT_B line goes low (which
2246		indicated a CRC error).
2247
2248		CONFIG_SYS_FPGA_WAIT_INIT
2249
2250		Maximum time to wait for the INIT_B line to deassert
2251		after PROB_B has been deasserted during a Virtex II
2252		FPGA configuration sequence. The default time is 500
2253		ms.
2254
2255		CONFIG_SYS_FPGA_WAIT_BUSY
2256
2257		Maximum time to wait for BUSY to deassert during
2258		Virtex II FPGA configuration. The default is 5 ms.
2259
2260		CONFIG_SYS_FPGA_WAIT_CONFIG
2261
2262		Time to wait after FPGA configuration. The default is
2263		200 ms.
2264
2265- Configuration Management:
2266		CONFIG_IDENT_STRING
2267
2268		If defined, this string will be added to the U-Boot
2269		version information (U_BOOT_VERSION)
2270
2271- Vendor Parameter Protection:
2272
2273		U-Boot considers the values of the environment
2274		variables "serial#" (Board Serial Number) and
2275		"ethaddr" (Ethernet Address) to be parameters that
2276		are set once by the board vendor / manufacturer, and
2277		protects these variables from casual modification by
2278		the user. Once set, these variables are read-only,
2279		and write or delete attempts are rejected. You can
2280		change this behaviour:
2281
2282		If CONFIG_ENV_OVERWRITE is #defined in your config
2283		file, the write protection for vendor parameters is
2284		completely disabled. Anybody can change or delete
2285		these parameters.
2286
2287		Alternatively, if you #define _both_ CONFIG_ETHADDR
2288		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2289		Ethernet address is installed in the environment,
2290		which can be changed exactly ONCE by the user. [The
2291		serial# is unaffected by this, i. e. it remains
2292		read-only.]
2293
2294		The same can be accomplished in a more flexible way
2295		for any variable by configuring the type of access
2296		to allow for those variables in the ".flags" variable
2297		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2298
2299- Protected RAM:
2300		CONFIG_PRAM
2301
2302		Define this variable to enable the reservation of
2303		"protected RAM", i. e. RAM which is not overwritten
2304		by U-Boot. Define CONFIG_PRAM to hold the number of
2305		kB you want to reserve for pRAM. You can overwrite
2306		this default value by defining an environment
2307		variable "pram" to the number of kB you want to
2308		reserve. Note that the board info structure will
2309		still show the full amount of RAM. If pRAM is
2310		reserved, a new environment variable "mem" will
2311		automatically be defined to hold the amount of
2312		remaining RAM in a form that can be passed as boot
2313		argument to Linux, for instance like that:
2314
2315			setenv bootargs ... mem=\${mem}
2316			saveenv
2317
2318		This way you can tell Linux not to use this memory,
2319		either, which results in a memory region that will
2320		not be affected by reboots.
2321
2322		*WARNING* If your board configuration uses automatic
2323		detection of the RAM size, you must make sure that
2324		this memory test is non-destructive. So far, the
2325		following board configurations are known to be
2326		"pRAM-clean":
2327
2328			IVMS8, IVML24, SPD8xx, TQM8xxL,
2329			HERMES, IP860, RPXlite, LWMON,
2330			FLAGADM, TQM8260
2331
2332- Access to physical memory region (> 4GB)
2333		Some basic support is provided for operations on memory not
2334		normally accessible to U-Boot - e.g. some architectures
2335		support access to more than 4GB of memory on 32-bit
2336		machines using physical address extension or similar.
2337		Define CONFIG_PHYSMEM to access this basic support, which
2338		currently only supports clearing the memory.
2339
2340- Error Recovery:
2341		CONFIG_PANIC_HANG
2342
2343		Define this variable to stop the system in case of a
2344		fatal error, so that you have to reset it manually.
2345		This is probably NOT a good idea for an embedded
2346		system where you want the system to reboot
2347		automatically as fast as possible, but it may be
2348		useful during development since you can try to debug
2349		the conditions that lead to the situation.
2350
2351		CONFIG_NET_RETRY_COUNT
2352
2353		This variable defines the number of retries for
2354		network operations like ARP, RARP, TFTP, or BOOTP
2355		before giving up the operation. If not defined, a
2356		default value of 5 is used.
2357
2358		CONFIG_ARP_TIMEOUT
2359
2360		Timeout waiting for an ARP reply in milliseconds.
2361
2362		CONFIG_NFS_TIMEOUT
2363
2364		Timeout in milliseconds used in NFS protocol.
2365		If you encounter "ERROR: Cannot umount" in nfs command,
2366		try longer timeout such as
2367		#define CONFIG_NFS_TIMEOUT 10000UL
2368
2369- Command Interpreter:
2370		CONFIG_AUTO_COMPLETE
2371
2372		Enable auto completion of commands using TAB.
2373
2374		Note that this feature has NOT been implemented yet
2375		for the "hush" shell.
2376
2377
2378		CONFIG_SYS_HUSH_PARSER
2379
2380		Define this variable to enable the "hush" shell (from
2381		Busybox) as command line interpreter, thus enabling
2382		powerful command line syntax like
2383		if...then...else...fi conditionals or `&&' and '||'
2384		constructs ("shell scripts").
2385
2386		If undefined, you get the old, much simpler behaviour
2387		with a somewhat smaller memory footprint.
2388
2389
2390		CONFIG_SYS_PROMPT_HUSH_PS2
2391
2392		This defines the secondary prompt string, which is
2393		printed when the command interpreter needs more input
2394		to complete a command. Usually "> ".
2395
2396	Note:
2397
2398		In the current implementation, the local variables
2399		space and global environment variables space are
2400		separated. Local variables are those you define by
2401		simply typing `name=value'. To access a local
2402		variable later on, you have write `$name' or
2403		`${name}'; to execute the contents of a variable
2404		directly type `$name' at the command prompt.
2405
2406		Global environment variables are those you use
2407		setenv/printenv to work with. To run a command stored
2408		in such a variable, you need to use the run command,
2409		and you must not use the '$' sign to access them.
2410
2411		To store commands and special characters in a
2412		variable, please use double quotation marks
2413		surrounding the whole text of the variable, instead
2414		of the backslashes before semicolons and special
2415		symbols.
2416
2417- Commandline Editing and History:
2418		CONFIG_CMDLINE_EDITING
2419
2420		Enable editing and History functions for interactive
2421		commandline input operations
2422
2423- Default Environment:
2424		CONFIG_EXTRA_ENV_SETTINGS
2425
2426		Define this to contain any number of null terminated
2427		strings (variable = value pairs) that will be part of
2428		the default environment compiled into the boot image.
2429
2430		For example, place something like this in your
2431		board's config file:
2432
2433		#define CONFIG_EXTRA_ENV_SETTINGS \
2434			"myvar1=value1\0" \
2435			"myvar2=value2\0"
2436
2437		Warning: This method is based on knowledge about the
2438		internal format how the environment is stored by the
2439		U-Boot code. This is NOT an official, exported
2440		interface! Although it is unlikely that this format
2441		will change soon, there is no guarantee either.
2442		You better know what you are doing here.
2443
2444		Note: overly (ab)use of the default environment is
2445		discouraged. Make sure to check other ways to preset
2446		the environment like the "source" command or the
2447		boot command first.
2448
2449		CONFIG_ENV_VARS_UBOOT_CONFIG
2450
2451		Define this in order to add variables describing the
2452		U-Boot build configuration to the default environment.
2453		These will be named arch, cpu, board, vendor, and soc.
2454
2455		Enabling this option will cause the following to be defined:
2456
2457		- CONFIG_SYS_ARCH
2458		- CONFIG_SYS_CPU
2459		- CONFIG_SYS_BOARD
2460		- CONFIG_SYS_VENDOR
2461		- CONFIG_SYS_SOC
2462
2463		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2464
2465		Define this in order to add variables describing certain
2466		run-time determined information about the hardware to the
2467		environment.  These will be named board_name, board_rev.
2468
2469		CONFIG_DELAY_ENVIRONMENT
2470
2471		Normally the environment is loaded when the board is
2472		intialised so that it is available to U-Boot. This inhibits
2473		that so that the environment is not available until
2474		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2475		this is instead controlled by the value of
2476		/config/load-environment.
2477
2478- DataFlash Support:
2479		CONFIG_HAS_DATAFLASH
2480
2481		Defining this option enables DataFlash features and
2482		allows to read/write in Dataflash via the standard
2483		commands cp, md...
2484
2485- Serial Flash support
2486		CONFIG_CMD_SF
2487
2488		Defining this option enables SPI flash commands
2489		'sf probe/read/write/erase/update'.
2490
2491		Usage requires an initial 'probe' to define the serial
2492		flash parameters, followed by read/write/erase/update
2493		commands.
2494
2495		The following defaults may be provided by the platform
2496		to handle the common case when only a single serial
2497		flash is present on the system.
2498
2499		CONFIG_SF_DEFAULT_BUS		Bus identifier
2500		CONFIG_SF_DEFAULT_CS		Chip-select
2501		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2502		CONFIG_SF_DEFAULT_SPEED		in Hz
2503
2504		CONFIG_CMD_SF_TEST
2505
2506		Define this option to include a destructive SPI flash
2507		test ('sf test').
2508
2509- SystemACE Support:
2510		CONFIG_SYSTEMACE
2511
2512		Adding this option adds support for Xilinx SystemACE
2513		chips attached via some sort of local bus. The address
2514		of the chip must also be defined in the
2515		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2516
2517		#define CONFIG_SYSTEMACE
2518		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2519
2520		When SystemACE support is added, the "ace" device type
2521		becomes available to the fat commands, i.e. fatls.
2522
2523- TFTP Fixed UDP Port:
2524		CONFIG_TFTP_PORT
2525
2526		If this is defined, the environment variable tftpsrcp
2527		is used to supply the TFTP UDP source port value.
2528		If tftpsrcp isn't defined, the normal pseudo-random port
2529		number generator is used.
2530
2531		Also, the environment variable tftpdstp is used to supply
2532		the TFTP UDP destination port value.  If tftpdstp isn't
2533		defined, the normal port 69 is used.
2534
2535		The purpose for tftpsrcp is to allow a TFTP server to
2536		blindly start the TFTP transfer using the pre-configured
2537		target IP address and UDP port. This has the effect of
2538		"punching through" the (Windows XP) firewall, allowing
2539		the remainder of the TFTP transfer to proceed normally.
2540		A better solution is to properly configure the firewall,
2541		but sometimes that is not allowed.
2542
2543- Hashing support:
2544		CONFIG_CMD_HASH
2545
2546		This enables a generic 'hash' command which can produce
2547		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2548
2549		CONFIG_HASH_VERIFY
2550
2551		Enable the hash verify command (hash -v). This adds to code
2552		size a little.
2553
2554		CONFIG_SHA1 - support SHA1 hashing
2555		CONFIG_SHA256 - support SHA256 hashing
2556
2557		Note: There is also a sha1sum command, which should perhaps
2558		be deprecated in favour of 'hash sha1'.
2559
2560- Show boot progress:
2561		CONFIG_SHOW_BOOT_PROGRESS
2562
2563		Defining this option allows to add some board-
2564		specific code (calling a user-provided function
2565		"show_boot_progress(int)") that enables you to show
2566		the system's boot progress on some display (for
2567		example, some LED's) on your board. At the moment,
2568		the following checkpoints are implemented:
2569
2570- Detailed boot stage timing
2571		CONFIG_BOOTSTAGE
2572		Define this option to get detailed timing of each stage
2573		of the boot process.
2574
2575		CONFIG_BOOTSTAGE_USER_COUNT
2576		This is the number of available user bootstage records.
2577		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2578		a new ID will be allocated from this stash. If you exceed
2579		the limit, recording will stop.
2580
2581		CONFIG_BOOTSTAGE_REPORT
2582		Define this to print a report before boot, similar to this:
2583
2584		Timer summary in microseconds:
2585		       Mark    Elapsed  Stage
2586			  0          0  reset
2587		  3,575,678  3,575,678  board_init_f start
2588		  3,575,695         17  arch_cpu_init A9
2589		  3,575,777         82  arch_cpu_init done
2590		  3,659,598     83,821  board_init_r start
2591		  3,910,375    250,777  main_loop
2592		 29,916,167 26,005,792  bootm_start
2593		 30,361,327    445,160  start_kernel
2594
2595		CONFIG_CMD_BOOTSTAGE
2596		Add a 'bootstage' command which supports printing a report
2597		and un/stashing of bootstage data.
2598
2599		CONFIG_BOOTSTAGE_FDT
2600		Stash the bootstage information in the FDT. A root 'bootstage'
2601		node is created with each bootstage id as a child. Each child
2602		has a 'name' property and either 'mark' containing the
2603		mark time in microsecond, or 'accum' containing the
2604		accumulated time for that bootstage id in microseconds.
2605		For example:
2606
2607		bootstage {
2608			154 {
2609				name = "board_init_f";
2610				mark = <3575678>;
2611			};
2612			170 {
2613				name = "lcd";
2614				accum = <33482>;
2615			};
2616		};
2617
2618		Code in the Linux kernel can find this in /proc/devicetree.
2619
2620Legacy uImage format:
2621
2622  Arg	Where			When
2623    1	common/cmd_bootm.c	before attempting to boot an image
2624   -1	common/cmd_bootm.c	Image header has bad	 magic number
2625    2	common/cmd_bootm.c	Image header has correct magic number
2626   -2	common/cmd_bootm.c	Image header has bad	 checksum
2627    3	common/cmd_bootm.c	Image header has correct checksum
2628   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2629    4	common/cmd_bootm.c	Image data   has correct checksum
2630   -4	common/cmd_bootm.c	Image is for unsupported architecture
2631    5	common/cmd_bootm.c	Architecture check OK
2632   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2633    6	common/cmd_bootm.c	Image Type check OK
2634   -6	common/cmd_bootm.c	gunzip uncompression error
2635   -7	common/cmd_bootm.c	Unimplemented compression type
2636    7	common/cmd_bootm.c	Uncompression OK
2637    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2638   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2639
2640    9	common/image.c		Start initial ramdisk verification
2641  -10	common/image.c		Ramdisk header has bad	   magic number
2642  -11	common/image.c		Ramdisk header has bad	   checksum
2643   10	common/image.c		Ramdisk header is OK
2644  -12	common/image.c		Ramdisk data   has bad	   checksum
2645   11	common/image.c		Ramdisk data   has correct checksum
2646   12	common/image.c		Ramdisk verification complete, start loading
2647  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2648   13	common/image.c		Start multifile image verification
2649   14	common/image.c		No initial ramdisk, no multifile, continue.
2650
2651   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2652
2653  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2654  -31	post/post.c		POST test failed, detected by post_output_backlog()
2655  -32	post/post.c		POST test failed, detected by post_run_single()
2656
2657   34	common/cmd_doc.c	before loading a Image from a DOC device
2658  -35	common/cmd_doc.c	Bad usage of "doc" command
2659   35	common/cmd_doc.c	correct usage of "doc" command
2660  -36	common/cmd_doc.c	No boot device
2661   36	common/cmd_doc.c	correct boot device
2662  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2663   37	common/cmd_doc.c	correct chip ID found, device available
2664  -38	common/cmd_doc.c	Read Error on boot device
2665   38	common/cmd_doc.c	reading Image header from DOC device OK
2666  -39	common/cmd_doc.c	Image header has bad magic number
2667   39	common/cmd_doc.c	Image header has correct magic number
2668  -40	common/cmd_doc.c	Error reading Image from DOC device
2669   40	common/cmd_doc.c	Image header has correct magic number
2670   41	common/cmd_ide.c	before loading a Image from a IDE device
2671  -42	common/cmd_ide.c	Bad usage of "ide" command
2672   42	common/cmd_ide.c	correct usage of "ide" command
2673  -43	common/cmd_ide.c	No boot device
2674   43	common/cmd_ide.c	boot device found
2675  -44	common/cmd_ide.c	Device not available
2676   44	common/cmd_ide.c	Device available
2677  -45	common/cmd_ide.c	wrong partition selected
2678   45	common/cmd_ide.c	partition selected
2679  -46	common/cmd_ide.c	Unknown partition table
2680   46	common/cmd_ide.c	valid partition table found
2681  -47	common/cmd_ide.c	Invalid partition type
2682   47	common/cmd_ide.c	correct partition type
2683  -48	common/cmd_ide.c	Error reading Image Header on boot device
2684   48	common/cmd_ide.c	reading Image Header from IDE device OK
2685  -49	common/cmd_ide.c	Image header has bad magic number
2686   49	common/cmd_ide.c	Image header has correct magic number
2687  -50	common/cmd_ide.c	Image header has bad	 checksum
2688   50	common/cmd_ide.c	Image header has correct checksum
2689  -51	common/cmd_ide.c	Error reading Image from IDE device
2690   51	common/cmd_ide.c	reading Image from IDE device OK
2691   52	common/cmd_nand.c	before loading a Image from a NAND device
2692  -53	common/cmd_nand.c	Bad usage of "nand" command
2693   53	common/cmd_nand.c	correct usage of "nand" command
2694  -54	common/cmd_nand.c	No boot device
2695   54	common/cmd_nand.c	boot device found
2696  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2697   55	common/cmd_nand.c	correct chip ID found, device available
2698  -56	common/cmd_nand.c	Error reading Image Header on boot device
2699   56	common/cmd_nand.c	reading Image Header from NAND device OK
2700  -57	common/cmd_nand.c	Image header has bad magic number
2701   57	common/cmd_nand.c	Image header has correct magic number
2702  -58	common/cmd_nand.c	Error reading Image from NAND device
2703   58	common/cmd_nand.c	reading Image from NAND device OK
2704
2705  -60	common/env_common.c	Environment has a bad CRC, using default
2706
2707   64	net/eth.c		starting with Ethernet configuration.
2708  -64	net/eth.c		no Ethernet found.
2709   65	net/eth.c		Ethernet found.
2710
2711  -80	common/cmd_net.c	usage wrong
2712   80	common/cmd_net.c	before calling NetLoop()
2713  -81	common/cmd_net.c	some error in NetLoop() occurred
2714   81	common/cmd_net.c	NetLoop() back without error
2715  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2716   82	common/cmd_net.c	trying automatic boot
2717   83	common/cmd_net.c	running "source" command
2718  -83	common/cmd_net.c	some error in automatic boot or "source" command
2719   84	common/cmd_net.c	end without errors
2720
2721FIT uImage format:
2722
2723  Arg	Where			When
2724  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2725 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2726  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2727 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2728  102	common/cmd_bootm.c	Kernel unit name specified
2729 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2730  103	common/cmd_bootm.c	Found configuration node
2731  104	common/cmd_bootm.c	Got kernel subimage node offset
2732 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2733  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2734 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2735  106	common/cmd_bootm.c	Architecture check OK
2736 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2737  107	common/cmd_bootm.c	Kernel subimage type OK
2738 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2739  108	common/cmd_bootm.c	Got kernel subimage data/size
2740 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2741 -109	common/cmd_bootm.c	Can't get kernel subimage type
2742 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2743 -111	common/cmd_bootm.c	Can't get kernel subimage os
2744 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2745 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2746
2747  120	common/image.c		Start initial ramdisk verification
2748 -120	common/image.c		Ramdisk FIT image has incorrect format
2749  121	common/image.c		Ramdisk FIT image has correct format
2750  122	common/image.c		No ramdisk subimage unit name, using configuration
2751 -122	common/image.c		Can't get configuration for ramdisk subimage
2752  123	common/image.c		Ramdisk unit name specified
2753 -124	common/image.c		Can't get ramdisk subimage node offset
2754  125	common/image.c		Got ramdisk subimage node offset
2755 -125	common/image.c		Ramdisk subimage hash verification failed
2756  126	common/image.c		Ramdisk subimage hash verification OK
2757 -126	common/image.c		Ramdisk subimage for unsupported architecture
2758  127	common/image.c		Architecture check OK
2759 -127	common/image.c		Can't get ramdisk subimage data/size
2760  128	common/image.c		Got ramdisk subimage data/size
2761  129	common/image.c		Can't get ramdisk load address
2762 -129	common/image.c		Got ramdisk load address
2763
2764 -130	common/cmd_doc.c	Incorrect FIT image format
2765  131	common/cmd_doc.c	FIT image format OK
2766
2767 -140	common/cmd_ide.c	Incorrect FIT image format
2768  141	common/cmd_ide.c	FIT image format OK
2769
2770 -150	common/cmd_nand.c	Incorrect FIT image format
2771  151	common/cmd_nand.c	FIT image format OK
2772
2773- FIT image support:
2774		CONFIG_FIT
2775		Enable support for the FIT uImage format.
2776
2777		CONFIG_FIT_BEST_MATCH
2778		When no configuration is explicitly selected, default to the
2779		one whose fdt's compatibility field best matches that of
2780		U-Boot itself. A match is considered "best" if it matches the
2781		most specific compatibility entry of U-Boot's fdt's root node.
2782		The order of entries in the configuration's fdt is ignored.
2783
2784- Standalone program support:
2785		CONFIG_STANDALONE_LOAD_ADDR
2786
2787		This option defines a board specific value for the
2788		address where standalone program gets loaded, thus
2789		overwriting the architecture dependent default
2790		settings.
2791
2792- Frame Buffer Address:
2793		CONFIG_FB_ADDR
2794
2795		Define CONFIG_FB_ADDR if you want to use specific
2796		address for frame buffer.  This is typically the case
2797		when using a graphics controller has separate video
2798		memory.  U-Boot will then place the frame buffer at
2799		the given address instead of dynamically reserving it
2800		in system RAM by calling lcd_setmem(), which grabs
2801		the memory for the frame buffer depending on the
2802		configured panel size.
2803
2804		Please see board_init_f function.
2805
2806- Automatic software updates via TFTP server
2807		CONFIG_UPDATE_TFTP
2808		CONFIG_UPDATE_TFTP_CNT_MAX
2809		CONFIG_UPDATE_TFTP_MSEC_MAX
2810
2811		These options enable and control the auto-update feature;
2812		for a more detailed description refer to doc/README.update.
2813
2814- MTD Support (mtdparts command, UBI support)
2815		CONFIG_MTD_DEVICE
2816
2817		Adds the MTD device infrastructure from the Linux kernel.
2818		Needed for mtdparts command support.
2819
2820		CONFIG_MTD_PARTITIONS
2821
2822		Adds the MTD partitioning infrastructure from the Linux
2823		kernel. Needed for UBI support.
2824
2825- UBI support
2826		CONFIG_CMD_UBI
2827
2828		Adds commands for interacting with MTD partitions formatted
2829		with the UBI flash translation layer
2830
2831		Requires also defining CONFIG_RBTREE
2832
2833		CONFIG_UBI_SILENCE_MSG
2834
2835		Make the verbose messages from UBI stop printing.  This leaves
2836		warnings and errors enabled.
2837
2838- UBIFS support
2839		CONFIG_CMD_UBIFS
2840
2841		Adds commands for interacting with UBI volumes formatted as
2842		UBIFS.  UBIFS is read-only in u-boot.
2843
2844		Requires UBI support as well as CONFIG_LZO
2845
2846		CONFIG_UBIFS_SILENCE_MSG
2847
2848		Make the verbose messages from UBIFS stop printing.  This leaves
2849		warnings and errors enabled.
2850
2851- SPL framework
2852		CONFIG_SPL
2853		Enable building of SPL globally.
2854
2855		CONFIG_SPL_LDSCRIPT
2856		LDSCRIPT for linking the SPL binary.
2857
2858		CONFIG_SPL_MAX_FOOTPRINT
2859		Maximum size in memory allocated to the SPL, BSS included.
2860		When defined, the linker checks that the actual memory
2861		used by SPL from _start to __bss_end does not exceed it.
2862		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2863		must not be both defined at the same time.
2864
2865		CONFIG_SPL_MAX_SIZE
2866		Maximum size of the SPL image (text, data, rodata, and
2867		linker lists sections), BSS excluded.
2868		When defined, the linker checks that the actual size does
2869		not exceed it.
2870
2871		CONFIG_SPL_TEXT_BASE
2872		TEXT_BASE for linking the SPL binary.
2873
2874		CONFIG_SPL_RELOC_TEXT_BASE
2875		Address to relocate to.  If unspecified, this is equal to
2876		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2877
2878		CONFIG_SPL_BSS_START_ADDR
2879		Link address for the BSS within the SPL binary.
2880
2881		CONFIG_SPL_BSS_MAX_SIZE
2882		Maximum size in memory allocated to the SPL BSS.
2883		When defined, the linker checks that the actual memory used
2884		by SPL from __bss_start to __bss_end does not exceed it.
2885		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2886		must not be both defined at the same time.
2887
2888		CONFIG_SPL_STACK
2889		Adress of the start of the stack SPL will use
2890
2891		CONFIG_SPL_RELOC_STACK
2892		Adress of the start of the stack SPL will use after
2893		relocation.  If unspecified, this is equal to
2894		CONFIG_SPL_STACK.
2895
2896		CONFIG_SYS_SPL_MALLOC_START
2897		Starting address of the malloc pool used in SPL.
2898
2899		CONFIG_SYS_SPL_MALLOC_SIZE
2900		The size of the malloc pool used in SPL.
2901
2902		CONFIG_SPL_FRAMEWORK
2903		Enable the SPL framework under common/.  This framework
2904		supports MMC, NAND and YMODEM loading of U-Boot and NAND
2905		NAND loading of the Linux Kernel.
2906
2907		CONFIG_SPL_DISPLAY_PRINT
2908		For ARM, enable an optional function to print more information
2909		about the running system.
2910
2911		CONFIG_SPL_INIT_MINIMAL
2912		Arch init code should be built for a very small image
2913
2914		CONFIG_SPL_LIBCOMMON_SUPPORT
2915		Support for common/libcommon.o in SPL binary
2916
2917		CONFIG_SPL_LIBDISK_SUPPORT
2918		Support for disk/libdisk.o in SPL binary
2919
2920		CONFIG_SPL_I2C_SUPPORT
2921		Support for drivers/i2c/libi2c.o in SPL binary
2922
2923		CONFIG_SPL_GPIO_SUPPORT
2924		Support for drivers/gpio/libgpio.o in SPL binary
2925
2926		CONFIG_SPL_MMC_SUPPORT
2927		Support for drivers/mmc/libmmc.o in SPL binary
2928
2929		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
2930		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
2931		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
2932		Address, size and partition on the MMC to load U-Boot from
2933		when the MMC is being used in raw mode.
2934
2935		CONFIG_SPL_FAT_SUPPORT
2936		Support for fs/fat/libfat.o in SPL binary
2937
2938		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
2939		Filename to read to load U-Boot when reading from FAT
2940
2941		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
2942		Filename to read to load kernel uImage when reading
2943		from FAT (for Falcon mode)
2944
2945		CONFIG_SPL_FAT_LOAD_ARGS_NAME
2946		Filename to read to load kernel argument parameters
2947		when reading from FAT (for Falcon mode)
2948
2949		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2950		Set this for NAND SPL on PPC mpc83xx targets, so that
2951		start.S waits for the rest of the SPL to load before
2952		continuing (the hardware starts execution after just
2953		loading the first page rather than the full 4K).
2954
2955		CONFIG_SPL_NAND_BASE
2956		Include nand_base.c in the SPL.  Requires
2957		CONFIG_SPL_NAND_DRIVERS.
2958
2959		CONFIG_SPL_NAND_DRIVERS
2960		SPL uses normal NAND drivers, not minimal drivers.
2961
2962		CONFIG_SPL_NAND_ECC
2963		Include standard software ECC in the SPL
2964
2965		CONFIG_SPL_NAND_SIMPLE
2966		Support for NAND boot using simple NAND drivers that
2967		expose the cmd_ctrl() interface.
2968
2969		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2970		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2971		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2972		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2973		CONFIG_SYS_NAND_ECCBYTES
2974		Defines the size and behavior of the NAND that SPL uses
2975		to read U-Boot
2976
2977		CONFIG_SYS_NAND_U_BOOT_OFFS
2978		Location in NAND to read U-Boot from
2979
2980		CONFIG_SYS_NAND_U_BOOT_DST
2981		Location in memory to load U-Boot to
2982
2983		CONFIG_SYS_NAND_U_BOOT_SIZE
2984		Size of image to load
2985
2986		CONFIG_SYS_NAND_U_BOOT_START
2987		Entry point in loaded image to jump to
2988
2989		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2990		Define this if you need to first read the OOB and then the
2991		data. This is used for example on davinci plattforms.
2992
2993		CONFIG_SPL_OMAP3_ID_NAND
2994		Support for an OMAP3-specific set of functions to return the
2995		ID and MFR of the first attached NAND chip, if present.
2996
2997		CONFIG_SPL_SERIAL_SUPPORT
2998		Support for drivers/serial/libserial.o in SPL binary
2999
3000		CONFIG_SPL_SPI_FLASH_SUPPORT
3001		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3002
3003		CONFIG_SPL_SPI_SUPPORT
3004		Support for drivers/spi/libspi.o in SPL binary
3005
3006		CONFIG_SPL_RAM_DEVICE
3007		Support for running image already present in ram, in SPL binary
3008
3009		CONFIG_SPL_LIBGENERIC_SUPPORT
3010		Support for lib/libgeneric.o in SPL binary
3011
3012		CONFIG_SPL_PAD_TO
3013		Image offset to which the SPL should be padded before appending
3014		the SPL payload. By default, this is defined as
3015		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3016		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3017		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3018
3019		CONFIG_SPL_TARGET
3020		Final target image containing SPL and payload.  Some SPLs
3021		use an arch-specific makefile fragment instead, for
3022		example if more than one image needs to be produced.
3023
3024		CONFIG_FIT_SPL_PRINT
3025		Printing information about a FIT image adds quite a bit of
3026		code to SPL. So this is normally disabled in SPL. Use this
3027		option to re-enable it. This will affect the output of the
3028		bootm command when booting a FIT image.
3029
3030Modem Support:
3031--------------
3032
3033[so far only for SMDK2400 boards]
3034
3035- Modem support enable:
3036		CONFIG_MODEM_SUPPORT
3037
3038- RTS/CTS Flow control enable:
3039		CONFIG_HWFLOW
3040
3041- Modem debug support:
3042		CONFIG_MODEM_SUPPORT_DEBUG
3043
3044		Enables debugging stuff (char screen[1024], dbg())
3045		for modem support. Useful only with BDI2000.
3046
3047- Interrupt support (PPC):
3048
3049		There are common interrupt_init() and timer_interrupt()
3050		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3051		for CPU specific initialization. interrupt_init_cpu()
3052		should set decrementer_count to appropriate value. If
3053		CPU resets decrementer automatically after interrupt
3054		(ppc4xx) it should set decrementer_count to zero.
3055		timer_interrupt() calls timer_interrupt_cpu() for CPU
3056		specific handling. If board has watchdog / status_led
3057		/ other_activity_monitor it works automatically from
3058		general timer_interrupt().
3059
3060- General:
3061
3062		In the target system modem support is enabled when a
3063		specific key (key combination) is pressed during
3064		power-on. Otherwise U-Boot will boot normally
3065		(autoboot). The key_pressed() function is called from
3066		board_init(). Currently key_pressed() is a dummy
3067		function, returning 1 and thus enabling modem
3068		initialization.
3069
3070		If there are no modem init strings in the
3071		environment, U-Boot proceed to autoboot; the
3072		previous output (banner, info printfs) will be
3073		suppressed, though.
3074
3075		See also: doc/README.Modem
3076
3077Board initialization settings:
3078------------------------------
3079
3080During Initialization u-boot calls a number of board specific functions
3081to allow the preparation of board specific prerequisites, e.g. pin setup
3082before drivers are initialized. To enable these callbacks the
3083following configuration macros have to be defined. Currently this is
3084architecture specific, so please check arch/your_architecture/lib/board.c
3085typically in board_init_f() and board_init_r().
3086
3087- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3088- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3089- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3090- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3091
3092Configuration Settings:
3093-----------------------
3094
3095- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3096		undefine this when you're short of memory.
3097
3098- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3099		width of the commands listed in the 'help' command output.
3100
3101- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3102		prompt for user input.
3103
3104- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3105
3106- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3107
3108- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3109
3110- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3111		the application (usually a Linux kernel) when it is
3112		booted
3113
3114- CONFIG_SYS_BAUDRATE_TABLE:
3115		List of legal baudrate settings for this board.
3116
3117- CONFIG_SYS_CONSOLE_INFO_QUIET
3118		Suppress display of console information at boot.
3119
3120- CONFIG_SYS_CONSOLE_IS_IN_ENV
3121		If the board specific function
3122			extern int overwrite_console (void);
3123		returns 1, the stdin, stderr and stdout are switched to the
3124		serial port, else the settings in the environment are used.
3125
3126- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3127		Enable the call to overwrite_console().
3128
3129- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3130		Enable overwrite of previous console environment settings.
3131
3132- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3133		Begin and End addresses of the area used by the
3134		simple memory test.
3135
3136- CONFIG_SYS_ALT_MEMTEST:
3137		Enable an alternate, more extensive memory test.
3138
3139- CONFIG_SYS_MEMTEST_SCRATCH:
3140		Scratch address used by the alternate memory test
3141		You only need to set this if address zero isn't writeable
3142
3143- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3144		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3145		this specified memory area will get subtracted from the top
3146		(end) of RAM and won't get "touched" at all by U-Boot. By
3147		fixing up gd->ram_size the Linux kernel should gets passed
3148		the now "corrected" memory size and won't touch it either.
3149		This should work for arch/ppc and arch/powerpc. Only Linux
3150		board ports in arch/powerpc with bootwrapper support that
3151		recalculate the memory size from the SDRAM controller setup
3152		will have to get fixed in Linux additionally.
3153
3154		This option can be used as a workaround for the 440EPx/GRx
3155		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3156		be touched.
3157
3158		WARNING: Please make sure that this value is a multiple of
3159		the Linux page size (normally 4k). If this is not the case,
3160		then the end address of the Linux memory will be located at a
3161		non page size aligned address and this could cause major
3162		problems.
3163
3164- CONFIG_SYS_LOADS_BAUD_CHANGE:
3165		Enable temporary baudrate change while serial download
3166
3167- CONFIG_SYS_SDRAM_BASE:
3168		Physical start address of SDRAM. _Must_ be 0 here.
3169
3170- CONFIG_SYS_MBIO_BASE:
3171		Physical start address of Motherboard I/O (if using a
3172		Cogent motherboard)
3173
3174- CONFIG_SYS_FLASH_BASE:
3175		Physical start address of Flash memory.
3176
3177- CONFIG_SYS_MONITOR_BASE:
3178		Physical start address of boot monitor code (set by
3179		make config files to be same as the text base address
3180		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3181		CONFIG_SYS_FLASH_BASE when booting from flash.
3182
3183- CONFIG_SYS_MONITOR_LEN:
3184		Size of memory reserved for monitor code, used to
3185		determine _at_compile_time_ (!) if the environment is
3186		embedded within the U-Boot image, or in a separate
3187		flash sector.
3188
3189- CONFIG_SYS_MALLOC_LEN:
3190		Size of DRAM reserved for malloc() use.
3191
3192- CONFIG_SYS_BOOTM_LEN:
3193		Normally compressed uImages are limited to an
3194		uncompressed size of 8 MBytes. If this is not enough,
3195		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3196		to adjust this setting to your needs.
3197
3198- CONFIG_SYS_BOOTMAPSZ:
3199		Maximum size of memory mapped by the startup code of
3200		the Linux kernel; all data that must be processed by
3201		the Linux kernel (bd_info, boot arguments, FDT blob if
3202		used) must be put below this limit, unless "bootm_low"
3203		enviroment variable is defined and non-zero. In such case
3204		all data for the Linux kernel must be between "bootm_low"
3205		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3206		variable "bootm_mapsize" will override the value of
3207		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3208		then the value in "bootm_size" will be used instead.
3209
3210- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3211		Enable initrd_high functionality.  If defined then the
3212		initrd_high feature is enabled and the bootm ramdisk subcommand
3213		is enabled.
3214
3215- CONFIG_SYS_BOOT_GET_CMDLINE:
3216		Enables allocating and saving kernel cmdline in space between
3217		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3218
3219- CONFIG_SYS_BOOT_GET_KBD:
3220		Enables allocating and saving a kernel copy of the bd_info in
3221		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3222
3223- CONFIG_SYS_MAX_FLASH_BANKS:
3224		Max number of Flash memory banks
3225
3226- CONFIG_SYS_MAX_FLASH_SECT:
3227		Max number of sectors on a Flash chip
3228
3229- CONFIG_SYS_FLASH_ERASE_TOUT:
3230		Timeout for Flash erase operations (in ms)
3231
3232- CONFIG_SYS_FLASH_WRITE_TOUT:
3233		Timeout for Flash write operations (in ms)
3234
3235- CONFIG_SYS_FLASH_LOCK_TOUT
3236		Timeout for Flash set sector lock bit operation (in ms)
3237
3238- CONFIG_SYS_FLASH_UNLOCK_TOUT
3239		Timeout for Flash clear lock bits operation (in ms)
3240
3241- CONFIG_SYS_FLASH_PROTECTION
3242		If defined, hardware flash sectors protection is used
3243		instead of U-Boot software protection.
3244
3245- CONFIG_SYS_DIRECT_FLASH_TFTP:
3246
3247		Enable TFTP transfers directly to flash memory;
3248		without this option such a download has to be
3249		performed in two steps: (1) download to RAM, and (2)
3250		copy from RAM to flash.
3251
3252		The two-step approach is usually more reliable, since
3253		you can check if the download worked before you erase
3254		the flash, but in some situations (when system RAM is
3255		too limited to allow for a temporary copy of the
3256		downloaded image) this option may be very useful.
3257
3258- CONFIG_SYS_FLASH_CFI:
3259		Define if the flash driver uses extra elements in the
3260		common flash structure for storing flash geometry.
3261
3262- CONFIG_FLASH_CFI_DRIVER
3263		This option also enables the building of the cfi_flash driver
3264		in the drivers directory
3265
3266- CONFIG_FLASH_CFI_MTD
3267		This option enables the building of the cfi_mtd driver
3268		in the drivers directory. The driver exports CFI flash
3269		to the MTD layer.
3270
3271- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3272		Use buffered writes to flash.
3273
3274- CONFIG_FLASH_SPANSION_S29WS_N
3275		s29ws-n MirrorBit flash has non-standard addresses for buffered
3276		write commands.
3277
3278- CONFIG_SYS_FLASH_QUIET_TEST
3279		If this option is defined, the common CFI flash doesn't
3280		print it's warning upon not recognized FLASH banks. This
3281		is useful, if some of the configured banks are only
3282		optionally available.
3283
3284- CONFIG_FLASH_SHOW_PROGRESS
3285		If defined (must be an integer), print out countdown
3286		digits and dots.  Recommended value: 45 (9..1) for 80
3287		column displays, 15 (3..1) for 40 column displays.
3288
3289- CONFIG_FLASH_VERIFY
3290		If defined, the content of the flash (destination) is compared
3291		against the source after the write operation. An error message
3292		will be printed when the contents are not identical.
3293		Please note that this option is useless in nearly all cases,
3294		since such flash programming errors usually are detected earlier
3295		while unprotecting/erasing/programming. Please only enable
3296		this option if you really know what you are doing.
3297
3298- CONFIG_SYS_RX_ETH_BUFFER:
3299		Defines the number of Ethernet receive buffers. On some
3300		Ethernet controllers it is recommended to set this value
3301		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3302		buffers can be full shortly after enabling the interface
3303		on high Ethernet traffic.
3304		Defaults to 4 if not defined.
3305
3306- CONFIG_ENV_MAX_ENTRIES
3307
3308	Maximum number of entries in the hash table that is used
3309	internally to store the environment settings. The default
3310	setting is supposed to be generous and should work in most
3311	cases. This setting can be used to tune behaviour; see
3312	lib/hashtable.c for details.
3313
3314- CONFIG_ENV_FLAGS_LIST_DEFAULT
3315- CONFIG_ENV_FLAGS_LIST_STATIC
3316	Enable validation of the values given to enviroment variables when
3317	calling env set.  Variables can be restricted to only decimal,
3318	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3319	the variables can also be restricted to IP address or MAC address.
3320
3321	The format of the list is:
3322		type_attribute = [s|d|x|b|i|m]
3323		access_atribute = [a|r|o|c]
3324		attributes = type_attribute[access_atribute]
3325		entry = variable_name[:attributes]
3326		list = entry[,list]
3327
3328	The type attributes are:
3329		s - String (default)
3330		d - Decimal
3331		x - Hexadecimal
3332		b - Boolean ([1yYtT|0nNfF])
3333		i - IP address
3334		m - MAC address
3335
3336	The access attributes are:
3337		a - Any (default)
3338		r - Read-only
3339		o - Write-once
3340		c - Change-default
3341
3342	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3343		Define this to a list (string) to define the ".flags"
3344		envirnoment variable in the default or embedded environment.
3345
3346	- CONFIG_ENV_FLAGS_LIST_STATIC
3347		Define this to a list (string) to define validation that
3348		should be done if an entry is not found in the ".flags"
3349		environment variable.  To override a setting in the static
3350		list, simply add an entry for the same variable name to the
3351		".flags" variable.
3352
3353- CONFIG_ENV_ACCESS_IGNORE_FORCE
3354	If defined, don't allow the -f switch to env set override variable
3355	access flags.
3356
3357- CONFIG_SYS_GENERIC_BOARD
3358	This selects the architecture-generic board system instead of the
3359	architecture-specific board files. It is intended to move boards
3360	to this new framework over time. Defining this will disable the
3361	arch/foo/lib/board.c file and use common/board_f.c and
3362	common/board_r.c instead. To use this option your architecture
3363	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3364	its config.mk file). If you find problems enabling this option on
3365	your board please report the problem and send patches!
3366
3367- CONFIG_SYS_SYM_OFFSETS
3368	This is set by architectures that use offsets for link symbols
3369	instead of absolute values. So bss_start is obtained using an
3370	offset _bss_start_ofs from CONFIG_SYS_TEXT_BASE, rather than
3371	directly. You should not need to touch this setting.
3372
3373- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3374	This is set by OMAP boards for the max time that reset should
3375	be asserted. See doc/README.omap-reset-time for details on how
3376	the value can be calulated on a given board.
3377
3378The following definitions that deal with the placement and management
3379of environment data (variable area); in general, we support the
3380following configurations:
3381
3382- CONFIG_BUILD_ENVCRC:
3383
3384	Builds up envcrc with the target environment so that external utils
3385	may easily extract it and embed it in final U-Boot images.
3386
3387- CONFIG_ENV_IS_IN_FLASH:
3388
3389	Define this if the environment is in flash memory.
3390
3391	a) The environment occupies one whole flash sector, which is
3392	   "embedded" in the text segment with the U-Boot code. This
3393	   happens usually with "bottom boot sector" or "top boot
3394	   sector" type flash chips, which have several smaller
3395	   sectors at the start or the end. For instance, such a
3396	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3397	   such a case you would place the environment in one of the
3398	   4 kB sectors - with U-Boot code before and after it. With
3399	   "top boot sector" type flash chips, you would put the
3400	   environment in one of the last sectors, leaving a gap
3401	   between U-Boot and the environment.
3402
3403	- CONFIG_ENV_OFFSET:
3404
3405	   Offset of environment data (variable area) to the
3406	   beginning of flash memory; for instance, with bottom boot
3407	   type flash chips the second sector can be used: the offset
3408	   for this sector is given here.
3409
3410	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3411
3412	- CONFIG_ENV_ADDR:
3413
3414	   This is just another way to specify the start address of
3415	   the flash sector containing the environment (instead of
3416	   CONFIG_ENV_OFFSET).
3417
3418	- CONFIG_ENV_SECT_SIZE:
3419
3420	   Size of the sector containing the environment.
3421
3422
3423	b) Sometimes flash chips have few, equal sized, BIG sectors.
3424	   In such a case you don't want to spend a whole sector for
3425	   the environment.
3426
3427	- CONFIG_ENV_SIZE:
3428
3429	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3430	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3431	   of this flash sector for the environment. This saves
3432	   memory for the RAM copy of the environment.
3433
3434	   It may also save flash memory if you decide to use this
3435	   when your environment is "embedded" within U-Boot code,
3436	   since then the remainder of the flash sector could be used
3437	   for U-Boot code. It should be pointed out that this is
3438	   STRONGLY DISCOURAGED from a robustness point of view:
3439	   updating the environment in flash makes it always
3440	   necessary to erase the WHOLE sector. If something goes
3441	   wrong before the contents has been restored from a copy in
3442	   RAM, your target system will be dead.
3443
3444	- CONFIG_ENV_ADDR_REDUND
3445	  CONFIG_ENV_SIZE_REDUND
3446
3447	   These settings describe a second storage area used to hold
3448	   a redundant copy of the environment data, so that there is
3449	   a valid backup copy in case there is a power failure during
3450	   a "saveenv" operation.
3451
3452BE CAREFUL! Any changes to the flash layout, and some changes to the
3453source code will make it necessary to adapt <board>/u-boot.lds*
3454accordingly!
3455
3456
3457- CONFIG_ENV_IS_IN_NVRAM:
3458
3459	Define this if you have some non-volatile memory device
3460	(NVRAM, battery buffered SRAM) which you want to use for the
3461	environment.
3462
3463	- CONFIG_ENV_ADDR:
3464	- CONFIG_ENV_SIZE:
3465
3466	  These two #defines are used to determine the memory area you
3467	  want to use for environment. It is assumed that this memory
3468	  can just be read and written to, without any special
3469	  provision.
3470
3471BE CAREFUL! The first access to the environment happens quite early
3472in U-Boot initalization (when we try to get the setting of for the
3473console baudrate). You *MUST* have mapped your NVRAM area then, or
3474U-Boot will hang.
3475
3476Please note that even with NVRAM we still use a copy of the
3477environment in RAM: we could work on NVRAM directly, but we want to
3478keep settings there always unmodified except somebody uses "saveenv"
3479to save the current settings.
3480
3481
3482- CONFIG_ENV_IS_IN_EEPROM:
3483
3484	Use this if you have an EEPROM or similar serial access
3485	device and a driver for it.
3486
3487	- CONFIG_ENV_OFFSET:
3488	- CONFIG_ENV_SIZE:
3489
3490	  These two #defines specify the offset and size of the
3491	  environment area within the total memory of your EEPROM.
3492
3493	- CONFIG_SYS_I2C_EEPROM_ADDR:
3494	  If defined, specified the chip address of the EEPROM device.
3495	  The default address is zero.
3496
3497	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3498	  If defined, the number of bits used to address bytes in a
3499	  single page in the EEPROM device.  A 64 byte page, for example
3500	  would require six bits.
3501
3502	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3503	  If defined, the number of milliseconds to delay between
3504	  page writes.	The default is zero milliseconds.
3505
3506	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3507	  The length in bytes of the EEPROM memory array address.  Note
3508	  that this is NOT the chip address length!
3509
3510	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3511	  EEPROM chips that implement "address overflow" are ones
3512	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3513	  address and the extra bits end up in the "chip address" bit
3514	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3515	  byte chips.
3516
3517	  Note that we consider the length of the address field to
3518	  still be one byte because the extra address bits are hidden
3519	  in the chip address.
3520
3521	- CONFIG_SYS_EEPROM_SIZE:
3522	  The size in bytes of the EEPROM device.
3523
3524	- CONFIG_ENV_EEPROM_IS_ON_I2C
3525	  define this, if you have I2C and SPI activated, and your
3526	  EEPROM, which holds the environment, is on the I2C bus.
3527
3528	- CONFIG_I2C_ENV_EEPROM_BUS
3529	  if you have an Environment on an EEPROM reached over
3530	  I2C muxes, you can define here, how to reach this
3531	  EEPROM. For example:
3532
3533	  #define CONFIG_I2C_ENV_EEPROM_BUS	  "pca9547:70:d\0"
3534
3535	  EEPROM which holds the environment, is reached over
3536	  a pca9547 i2c mux with address 0x70, channel 3.
3537
3538- CONFIG_ENV_IS_IN_DATAFLASH:
3539
3540	Define this if you have a DataFlash memory device which you
3541	want to use for the environment.
3542
3543	- CONFIG_ENV_OFFSET:
3544	- CONFIG_ENV_ADDR:
3545	- CONFIG_ENV_SIZE:
3546
3547	  These three #defines specify the offset and size of the
3548	  environment area within the total memory of your DataFlash placed
3549	  at the specified address.
3550
3551- CONFIG_ENV_IS_IN_REMOTE:
3552
3553	Define this if you have a remote memory space which you
3554	want to use for the local device's environment.
3555
3556	- CONFIG_ENV_ADDR:
3557	- CONFIG_ENV_SIZE:
3558
3559	  These two #defines specify the address and size of the
3560	  environment area within the remote memory space. The
3561	  local device can get the environment from remote memory
3562	  space by SRIO or PCIE links.
3563
3564BE CAREFUL! For some special cases, the local device can not use
3565"saveenv" command. For example, the local device will get the
3566environment stored in a remote NOR flash by SRIO or PCIE link,
3567but it can not erase, write this NOR flash by SRIO or PCIE interface.
3568
3569- CONFIG_ENV_IS_IN_NAND:
3570
3571	Define this if you have a NAND device which you want to use
3572	for the environment.
3573
3574	- CONFIG_ENV_OFFSET:
3575	- CONFIG_ENV_SIZE:
3576
3577	  These two #defines specify the offset and size of the environment
3578	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3579	  aligned to an erase block boundary.
3580
3581	- CONFIG_ENV_OFFSET_REDUND (optional):
3582
3583	  This setting describes a second storage area of CONFIG_ENV_SIZE
3584	  size used to hold a redundant copy of the environment data, so
3585	  that there is a valid backup copy in case there is a power failure
3586	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3587	  aligned to an erase block boundary.
3588
3589	- CONFIG_ENV_RANGE (optional):
3590
3591	  Specifies the length of the region in which the environment
3592	  can be written.  This should be a multiple of the NAND device's
3593	  block size.  Specifying a range with more erase blocks than
3594	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3595	  the range to be avoided.
3596
3597	- CONFIG_ENV_OFFSET_OOB (optional):
3598
3599	  Enables support for dynamically retrieving the offset of the
3600	  environment from block zero's out-of-band data.  The
3601	  "nand env.oob" command can be used to record this offset.
3602	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3603	  using CONFIG_ENV_OFFSET_OOB.
3604
3605- CONFIG_NAND_ENV_DST
3606
3607	Defines address in RAM to which the nand_spl code should copy the
3608	environment. If redundant environment is used, it will be copied to
3609	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3610
3611- CONFIG_ENV_IS_IN_UBI:
3612
3613	Define this if you have an UBI volume that you want to use for the
3614	environment.  This has the benefit of wear-leveling the environment
3615	accesses, which is important on NAND.
3616
3617	- CONFIG_ENV_UBI_PART:
3618
3619	  Define this to a string that is the mtd partition containing the UBI.
3620
3621	- CONFIG_ENV_UBI_VOLUME:
3622
3623	  Define this to the name of the volume that you want to store the
3624	  environment in.
3625
3626	- CONFIG_ENV_UBI_VOLUME_REDUND:
3627
3628	  Define this to the name of another volume to store a second copy of
3629	  the environment in.  This will enable redundant environments in UBI.
3630	  It is assumed that both volumes are in the same MTD partition.
3631
3632	- CONFIG_UBI_SILENCE_MSG
3633	- CONFIG_UBIFS_SILENCE_MSG
3634
3635	  You will probably want to define these to avoid a really noisy system
3636	  when storing the env in UBI.
3637
3638- CONFIG_SYS_SPI_INIT_OFFSET
3639
3640	Defines offset to the initial SPI buffer area in DPRAM. The
3641	area is used at an early stage (ROM part) if the environment
3642	is configured to reside in the SPI EEPROM: We need a 520 byte
3643	scratch DPRAM area. It is used between the two initialization
3644	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3645	to be a good choice since it makes it far enough from the
3646	start of the data area as well as from the stack pointer.
3647
3648Please note that the environment is read-only until the monitor
3649has been relocated to RAM and a RAM copy of the environment has been
3650created; also, when using EEPROM you will have to use getenv_f()
3651until then to read environment variables.
3652
3653The environment is protected by a CRC32 checksum. Before the monitor
3654is relocated into RAM, as a result of a bad CRC you will be working
3655with the compiled-in default environment - *silently*!!! [This is
3656necessary, because the first environment variable we need is the
3657"baudrate" setting for the console - if we have a bad CRC, we don't
3658have any device yet where we could complain.]
3659
3660Note: once the monitor has been relocated, then it will complain if
3661the default environment is used; a new CRC is computed as soon as you
3662use the "saveenv" command to store a valid environment.
3663
3664- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3665		Echo the inverted Ethernet link state to the fault LED.
3666
3667		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3668		      also needs to be defined.
3669
3670- CONFIG_SYS_FAULT_MII_ADDR:
3671		MII address of the PHY to check for the Ethernet link state.
3672
3673- CONFIG_NS16550_MIN_FUNCTIONS:
3674		Define this if you desire to only have use of the NS16550_init
3675		and NS16550_putc functions for the serial driver located at
3676		drivers/serial/ns16550.c.  This option is useful for saving
3677		space for already greatly restricted images, including but not
3678		limited to NAND_SPL configurations.
3679
3680- CONFIG_DISPLAY_BOARDINFO
3681		Display information about the board that U-Boot is running on
3682		when U-Boot starts up. The board function checkboard() is called
3683		to do this.
3684
3685- CONFIG_DISPLAY_BOARDINFO_LATE
3686		Similar to the previous option, but display this information
3687		later, once stdio is running and output goes to the LCD, if
3688		present.
3689
3690Low Level (hardware related) configuration options:
3691---------------------------------------------------
3692
3693- CONFIG_SYS_CACHELINE_SIZE:
3694		Cache Line Size of the CPU.
3695
3696- CONFIG_SYS_DEFAULT_IMMR:
3697		Default address of the IMMR after system reset.
3698
3699		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3700		and RPXsuper) to be able to adjust the position of
3701		the IMMR register after a reset.
3702
3703- CONFIG_SYS_CCSRBAR_DEFAULT:
3704		Default (power-on reset) physical address of CCSR on Freescale
3705		PowerPC SOCs.
3706
3707- CONFIG_SYS_CCSRBAR:
3708		Virtual address of CCSR.  On a 32-bit build, this is typically
3709		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3710
3711		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3712		for cross-platform code that uses that macro instead.
3713
3714- CONFIG_SYS_CCSRBAR_PHYS:
3715		Physical address of CCSR.  CCSR can be relocated to a new
3716		physical address, if desired.  In this case, this macro should
3717		be set to that address.	 Otherwise, it should be set to the
3718		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3719		is typically relocated on 36-bit builds.  It is recommended
3720		that this macro be defined via the _HIGH and _LOW macros:
3721
3722		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3723			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3724
3725- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3726		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3727		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3728		used in assembly code, so it must not contain typecasts or
3729		integer size suffixes (e.g. "ULL").
3730
3731- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3732		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3733		used in assembly code, so it must not contain typecasts or
3734		integer size suffixes (e.g. "ULL").
3735
3736- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3737		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3738		forced to a value that ensures that CCSR is not relocated.
3739
3740- Floppy Disk Support:
3741		CONFIG_SYS_FDC_DRIVE_NUMBER
3742
3743		the default drive number (default value 0)
3744
3745		CONFIG_SYS_ISA_IO_STRIDE
3746
3747		defines the spacing between FDC chipset registers
3748		(default value 1)
3749
3750		CONFIG_SYS_ISA_IO_OFFSET
3751
3752		defines the offset of register from address. It
3753		depends on which part of the data bus is connected to
3754		the FDC chipset. (default value 0)
3755
3756		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3757		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3758		default value.
3759
3760		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3761		fdc_hw_init() is called at the beginning of the FDC
3762		setup. fdc_hw_init() must be provided by the board
3763		source code. It is used to make hardware dependant
3764		initializations.
3765
3766- CONFIG_IDE_AHB:
3767		Most IDE controllers were designed to be connected with PCI
3768		interface. Only few of them were designed for AHB interface.
3769		When software is doing ATA command and data transfer to
3770		IDE devices through IDE-AHB controller, some additional
3771		registers accessing to these kind of IDE-AHB controller
3772		is requierd.
3773
3774- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3775		DO NOT CHANGE unless you know exactly what you're
3776		doing! (11-4) [MPC8xx/82xx systems only]
3777
3778- CONFIG_SYS_INIT_RAM_ADDR:
3779
3780		Start address of memory area that can be used for
3781		initial data and stack; please note that this must be
3782		writable memory that is working WITHOUT special
3783		initialization, i. e. you CANNOT use normal RAM which
3784		will become available only after programming the
3785		memory controller and running certain initialization
3786		sequences.
3787
3788		U-Boot uses the following memory types:
3789		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
3790		- MPC824X: data cache
3791		- PPC4xx:  data cache
3792
3793- CONFIG_SYS_GBL_DATA_OFFSET:
3794
3795		Offset of the initial data structure in the memory
3796		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3797		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3798		data is located at the end of the available space
3799		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3800		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
3801		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3802		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3803
3804	Note:
3805		On the MPC824X (or other systems that use the data
3806		cache for initial memory) the address chosen for
3807		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3808		point to an otherwise UNUSED address space between
3809		the top of RAM and the start of the PCI space.
3810
3811- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
3812
3813- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
3814
3815- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
3816
3817- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
3818
3819- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
3820
3821- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3822
3823- CONFIG_SYS_OR_TIMING_SDRAM:
3824		SDRAM timing
3825
3826- CONFIG_SYS_MAMR_PTA:
3827		periodic timer for refresh
3828
3829- CONFIG_SYS_DER:	Debug Event Register (37-47)
3830
3831- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3832  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3833  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3834  CONFIG_SYS_BR1_PRELIM:
3835		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3836
3837- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3838  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3839  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3840		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3841
3842- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
3843  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
3844		Machine Mode Register and Memory Periodic Timer
3845		Prescaler definitions (SDRAM timing)
3846
3847- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
3848		enable I2C microcode relocation patch (MPC8xx);
3849		define relocation offset in DPRAM [DSP2]
3850
3851- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
3852		enable SMC microcode relocation patch (MPC8xx);
3853		define relocation offset in DPRAM [SMC1]
3854
3855- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
3856		enable SPI microcode relocation patch (MPC8xx);
3857		define relocation offset in DPRAM [SCC4]
3858
3859- CONFIG_SYS_USE_OSCCLK:
3860		Use OSCM clock mode on MBX8xx board. Be careful,
3861		wrong setting might damage your board. Read
3862		doc/README.MBX before setting this variable!
3863
3864- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
3865		Offset of the bootmode word in DPRAM used by post
3866		(Power On Self Tests). This definition overrides
3867		#define'd default value in commproc.h resp.
3868		cpm_8260.h.
3869
3870- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
3871  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
3872  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
3873  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
3874  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
3875  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
3876  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
3877  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
3878		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
3879
3880- CONFIG_PCI_DISABLE_PCIE:
3881		Disable PCI-Express on systems where it is supported but not
3882		required.
3883
3884- CONFIG_PCI_ENUM_ONLY
3885		Only scan through and get the devices on the busses.
3886		Don't do any setup work, presumably because someone or
3887		something has already done it, and we don't need to do it
3888		a second time.	Useful for platforms that are pre-booted
3889		by coreboot or similar.
3890
3891- CONFIG_SYS_SRIO:
3892		Chip has SRIO or not
3893
3894- CONFIG_SRIO1:
3895		Board has SRIO 1 port available
3896
3897- CONFIG_SRIO2:
3898		Board has SRIO 2 port available
3899
3900- CONFIG_SYS_SRIOn_MEM_VIRT:
3901		Virtual Address of SRIO port 'n' memory region
3902
3903- CONFIG_SYS_SRIOn_MEM_PHYS:
3904		Physical Address of SRIO port 'n' memory region
3905
3906- CONFIG_SYS_SRIOn_MEM_SIZE:
3907		Size of SRIO port 'n' memory region
3908
3909- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3910		Defined to tell the NAND controller that the NAND chip is using
3911		a 16 bit bus.
3912		Not all NAND drivers use this symbol.
3913		Example of drivers that use it:
3914		- drivers/mtd/nand/ndfc.c
3915		- drivers/mtd/nand/mxc_nand.c
3916
3917- CONFIG_SYS_NDFC_EBC0_CFG
3918		Sets the EBC0_CFG register for the NDFC. If not defined
3919		a default value will be used.
3920
3921- CONFIG_SPD_EEPROM
3922		Get DDR timing information from an I2C EEPROM. Common
3923		with pluggable memory modules such as SODIMMs
3924
3925  SPD_EEPROM_ADDRESS
3926		I2C address of the SPD EEPROM
3927
3928- CONFIG_SYS_SPD_BUS_NUM
3929		If SPD EEPROM is on an I2C bus other than the first
3930		one, specify here. Note that the value must resolve
3931		to something your driver can deal with.
3932
3933- CONFIG_SYS_DDR_RAW_TIMING
3934		Get DDR timing information from other than SPD. Common with
3935		soldered DDR chips onboard without SPD. DDR raw timing
3936		parameters are extracted from datasheet and hard-coded into
3937		header files or board specific files.
3938
3939- CONFIG_FSL_DDR_INTERACTIVE
3940		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3941
3942- CONFIG_SYS_83XX_DDR_USES_CS0
3943		Only for 83xx systems. If specified, then DDR should
3944		be configured using CS0 and CS1 instead of CS2 and CS3.
3945
3946- CONFIG_ETHER_ON_FEC[12]
3947		Define to enable FEC[12] on a 8xx series processor.
3948
3949- CONFIG_FEC[12]_PHY
3950		Define to the hardcoded PHY address which corresponds
3951		to the given FEC; i. e.
3952			#define CONFIG_FEC1_PHY 4
3953		means that the PHY with address 4 is connected to FEC1
3954
3955		When set to -1, means to probe for first available.
3956
3957- CONFIG_FEC[12]_PHY_NORXERR
3958		The PHY does not have a RXERR line (RMII only).
3959		(so program the FEC to ignore it).
3960
3961- CONFIG_RMII
3962		Enable RMII mode for all FECs.
3963		Note that this is a global option, we can't
3964		have one FEC in standard MII mode and another in RMII mode.
3965
3966- CONFIG_CRC32_VERIFY
3967		Add a verify option to the crc32 command.
3968		The syntax is:
3969
3970		=> crc32 -v <address> <count> <crc32>
3971
3972		Where address/count indicate a memory area
3973		and crc32 is the correct crc32 which the
3974		area should have.
3975
3976- CONFIG_LOOPW
3977		Add the "loopw" memory command. This only takes effect if
3978		the memory commands are activated globally (CONFIG_CMD_MEM).
3979
3980- CONFIG_MX_CYCLIC
3981		Add the "mdc" and "mwc" memory commands. These are cyclic
3982		"md/mw" commands.
3983		Examples:
3984
3985		=> mdc.b 10 4 500
3986		This command will print 4 bytes (10,11,12,13) each 500 ms.
3987
3988		=> mwc.l 100 12345678 10
3989		This command will write 12345678 to address 100 all 10 ms.
3990
3991		This only takes effect if the memory commands are activated
3992		globally (CONFIG_CMD_MEM).
3993
3994- CONFIG_SKIP_LOWLEVEL_INIT
3995		[ARM, NDS32, MIPS only] If this variable is defined, then certain
3996		low level initializations (like setting up the memory
3997		controller) are omitted and/or U-Boot does not
3998		relocate itself into RAM.
3999
4000		Normally this variable MUST NOT be defined. The only
4001		exception is when U-Boot is loaded (to RAM) by some
4002		other boot loader or by a debugger which performs
4003		these initializations itself.
4004
4005- CONFIG_SPL_BUILD
4006		Modifies the behaviour of start.S when compiling a loader
4007		that is executed before the actual U-Boot. E.g. when
4008		compiling a NAND SPL.
4009
4010- CONFIG_ARCH_MAP_SYSMEM
4011		Generally U-Boot (and in particular the md command) uses
4012		effective address. It is therefore not necessary to regard
4013		U-Boot address as virtual addresses that need to be translated
4014		to physical addresses. However, sandbox requires this, since
4015		it maintains its own little RAM buffer which contains all
4016		addressable memory. This option causes some memory accesses
4017		to be mapped through map_sysmem() / unmap_sysmem().
4018
4019- CONFIG_USE_ARCH_MEMCPY
4020  CONFIG_USE_ARCH_MEMSET
4021		If these options are used a optimized version of memcpy/memset will
4022		be used if available. These functions may be faster under some
4023		conditions but may increase the binary size.
4024
4025- CONFIG_X86_RESET_VECTOR
4026		If defined, the x86 reset vector code is included. This is not
4027		needed when U-Boot is running from Coreboot.
4028
4029- CONFIG_SYS_MPUCLK
4030		Defines the MPU clock speed (in MHz).
4031
4032		NOTE : currently only supported on AM335x platforms.
4033
4034Freescale QE/FMAN Firmware Support:
4035-----------------------------------
4036
4037The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4038loading of "firmware", which is encoded in the QE firmware binary format.
4039This firmware often needs to be loaded during U-Boot booting, so macros
4040are used to identify the storage device (NOR flash, SPI, etc) and the address
4041within that device.
4042
4043- CONFIG_SYS_QE_FMAN_FW_ADDR
4044	The address in the storage device where the firmware is located.  The
4045	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4046	is also specified.
4047
4048- CONFIG_SYS_QE_FMAN_FW_LENGTH
4049	The maximum possible size of the firmware.  The firmware binary format
4050	has a field that specifies the actual size of the firmware, but it
4051	might not be possible to read any part of the firmware unless some
4052	local storage is allocated to hold the entire firmware first.
4053
4054- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4055	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4056	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4057	virtual address in NOR flash.
4058
4059- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4060	Specifies that QE/FMAN firmware is located in NAND flash.
4061	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4062
4063- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4064	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4065	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4066
4067- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4068	Specifies that QE/FMAN firmware is located on the primary SPI
4069	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4070
4071- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4072	Specifies that QE/FMAN firmware is located in the remote (master)
4073	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4074	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4075	window->master inbound window->master LAW->the ucode address in
4076	master's memory space.
4077
4078Building the Software:
4079======================
4080
4081Building U-Boot has been tested in several native build environments
4082and in many different cross environments. Of course we cannot support
4083all possibly existing versions of cross development tools in all
4084(potentially obsolete) versions. In case of tool chain problems we
4085recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4086which is extensively used to build and test U-Boot.
4087
4088If you are not using a native environment, it is assumed that you
4089have GNU cross compiling tools available in your path. In this case,
4090you must set the environment variable CROSS_COMPILE in your shell.
4091Note that no changes to the Makefile or any other source files are
4092necessary. For example using the ELDK on a 4xx CPU, please enter:
4093
4094	$ CROSS_COMPILE=ppc_4xx-
4095	$ export CROSS_COMPILE
4096
4097Note: If you wish to generate Windows versions of the utilities in
4098      the tools directory you can use the MinGW toolchain
4099      (http://www.mingw.org).  Set your HOST tools to the MinGW
4100      toolchain and execute 'make tools'.  For example:
4101
4102       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4103
4104      Binaries such as tools/mkimage.exe will be created which can
4105      be executed on computers running Windows.
4106
4107U-Boot is intended to be simple to build. After installing the
4108sources you must configure U-Boot for one specific board type. This
4109is done by typing:
4110
4111	make NAME_config
4112
4113where "NAME_config" is the name of one of the existing configu-
4114rations; see boards.cfg for supported names.
4115
4116Note: for some board special configuration names may exist; check if
4117      additional information is available from the board vendor; for
4118      instance, the TQM823L systems are available without (standard)
4119      or with LCD support. You can select such additional "features"
4120      when choosing the configuration, i. e.
4121
4122      make TQM823L_config
4123	- will configure for a plain TQM823L, i. e. no LCD support
4124
4125      make TQM823L_LCD_config
4126	- will configure for a TQM823L with U-Boot console on LCD
4127
4128      etc.
4129
4130
4131Finally, type "make all", and you should get some working U-Boot
4132images ready for download to / installation on your system:
4133
4134- "u-boot.bin" is a raw binary image
4135- "u-boot" is an image in ELF binary format
4136- "u-boot.srec" is in Motorola S-Record format
4137
4138By default the build is performed locally and the objects are saved
4139in the source directory. One of the two methods can be used to change
4140this behavior and build U-Boot to some external directory:
4141
41421. Add O= to the make command line invocations:
4143
4144	make O=/tmp/build distclean
4145	make O=/tmp/build NAME_config
4146	make O=/tmp/build all
4147
41482. Set environment variable BUILD_DIR to point to the desired location:
4149
4150	export BUILD_DIR=/tmp/build
4151	make distclean
4152	make NAME_config
4153	make all
4154
4155Note that the command line "O=" setting overrides the BUILD_DIR environment
4156variable.
4157
4158
4159Please be aware that the Makefiles assume you are using GNU make, so
4160for instance on NetBSD you might need to use "gmake" instead of
4161native "make".
4162
4163
4164If the system board that you have is not listed, then you will need
4165to port U-Boot to your hardware platform. To do this, follow these
4166steps:
4167
41681.  Add a new configuration option for your board to the toplevel
4169    "boards.cfg" file, using the existing entries as examples.
4170    Follow the instructions there to keep the boards in order.
41712.  Create a new directory to hold your board specific code. Add any
4172    files you need. In your board directory, you will need at least
4173    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
41743.  Create a new configuration file "include/configs/<board>.h" for
4175    your board
41763.  If you're porting U-Boot to a new CPU, then also create a new
4177    directory to hold your CPU specific code. Add any files you need.
41784.  Run "make <board>_config" with your new name.
41795.  Type "make", and you should get a working "u-boot.srec" file
4180    to be installed on your target system.
41816.  Debug and solve any problems that might arise.
4182    [Of course, this last step is much harder than it sounds.]
4183
4184
4185Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4186==============================================================
4187
4188If you have modified U-Boot sources (for instance added a new board
4189or support for new devices, a new CPU, etc.) you are expected to
4190provide feedback to the other developers. The feedback normally takes
4191the form of a "patch", i. e. a context diff against a certain (latest
4192official or latest in the git repository) version of U-Boot sources.
4193
4194But before you submit such a patch, please verify that your modifi-
4195cation did not break existing code. At least make sure that *ALL* of
4196the supported boards compile WITHOUT ANY compiler warnings. To do so,
4197just run the "MAKEALL" script, which will configure and build U-Boot
4198for ALL supported system. Be warned, this will take a while. You can
4199select which (cross) compiler to use by passing a `CROSS_COMPILE'
4200environment variable to the script, i. e. to use the ELDK cross tools
4201you can type
4202
4203	CROSS_COMPILE=ppc_8xx- MAKEALL
4204
4205or to build on a native PowerPC system you can type
4206
4207	CROSS_COMPILE=' ' MAKEALL
4208
4209When using the MAKEALL script, the default behaviour is to build
4210U-Boot in the source directory. This location can be changed by
4211setting the BUILD_DIR environment variable. Also, for each target
4212built, the MAKEALL script saves two log files (<target>.ERR and
4213<target>.MAKEALL) in the <source dir>/LOG directory. This default
4214location can be changed by setting the MAKEALL_LOGDIR environment
4215variable. For example:
4216
4217	export BUILD_DIR=/tmp/build
4218	export MAKEALL_LOGDIR=/tmp/log
4219	CROSS_COMPILE=ppc_8xx- MAKEALL
4220
4221With the above settings build objects are saved in the /tmp/build,
4222log files are saved in the /tmp/log and the source tree remains clean
4223during the whole build process.
4224
4225
4226See also "U-Boot Porting Guide" below.
4227
4228
4229Monitor Commands - Overview:
4230============================
4231
4232go	- start application at address 'addr'
4233run	- run commands in an environment variable
4234bootm	- boot application image from memory
4235bootp	- boot image via network using BootP/TFTP protocol
4236bootz   - boot zImage from memory
4237tftpboot- boot image via network using TFTP protocol
4238	       and env variables "ipaddr" and "serverip"
4239	       (and eventually "gatewayip")
4240tftpput - upload a file via network using TFTP protocol
4241rarpboot- boot image via network using RARP/TFTP protocol
4242diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4243loads	- load S-Record file over serial line
4244loadb	- load binary file over serial line (kermit mode)
4245md	- memory display
4246mm	- memory modify (auto-incrementing)
4247nm	- memory modify (constant address)
4248mw	- memory write (fill)
4249cp	- memory copy
4250cmp	- memory compare
4251crc32	- checksum calculation
4252i2c	- I2C sub-system
4253sspi	- SPI utility commands
4254base	- print or set address offset
4255printenv- print environment variables
4256setenv	- set environment variables
4257saveenv - save environment variables to persistent storage
4258protect - enable or disable FLASH write protection
4259erase	- erase FLASH memory
4260flinfo	- print FLASH memory information
4261nand	- NAND memory operations (see doc/README.nand)
4262bdinfo	- print Board Info structure
4263iminfo	- print header information for application image
4264coninfo - print console devices and informations
4265ide	- IDE sub-system
4266loop	- infinite loop on address range
4267loopw	- infinite write loop on address range
4268mtest	- simple RAM test
4269icache	- enable or disable instruction cache
4270dcache	- enable or disable data cache
4271reset	- Perform RESET of the CPU
4272echo	- echo args to console
4273version - print monitor version
4274help	- print online help
4275?	- alias for 'help'
4276
4277
4278Monitor Commands - Detailed Description:
4279========================================
4280
4281TODO.
4282
4283For now: just type "help <command>".
4284
4285
4286Environment Variables:
4287======================
4288
4289U-Boot supports user configuration using Environment Variables which
4290can be made persistent by saving to Flash memory.
4291
4292Environment Variables are set using "setenv", printed using
4293"printenv", and saved to Flash using "saveenv". Using "setenv"
4294without a value can be used to delete a variable from the
4295environment. As long as you don't save the environment you are
4296working with an in-memory copy. In case the Flash area containing the
4297environment is erased by accident, a default environment is provided.
4298
4299Some configuration options can be set using Environment Variables.
4300
4301List of environment variables (most likely not complete):
4302
4303  baudrate	- see CONFIG_BAUDRATE
4304
4305  bootdelay	- see CONFIG_BOOTDELAY
4306
4307  bootcmd	- see CONFIG_BOOTCOMMAND
4308
4309  bootargs	- Boot arguments when booting an RTOS image
4310
4311  bootfile	- Name of the image to load with TFTP
4312
4313  bootm_low	- Memory range available for image processing in the bootm
4314		  command can be restricted. This variable is given as
4315		  a hexadecimal number and defines lowest address allowed
4316		  for use by the bootm command. See also "bootm_size"
4317		  environment variable. Address defined by "bootm_low" is
4318		  also the base of the initial memory mapping for the Linux
4319		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4320		  bootm_mapsize.
4321
4322  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4323		  This variable is given as a hexadecimal number and it
4324		  defines the size of the memory region starting at base
4325		  address bootm_low that is accessible by the Linux kernel
4326		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4327		  as the default value if it is defined, and bootm_size is
4328		  used otherwise.
4329
4330  bootm_size	- Memory range available for image processing in the bootm
4331		  command can be restricted. This variable is given as
4332		  a hexadecimal number and defines the size of the region
4333		  allowed for use by the bootm command. See also "bootm_low"
4334		  environment variable.
4335
4336  updatefile	- Location of the software update file on a TFTP server, used
4337		  by the automatic software update feature. Please refer to
4338		  documentation in doc/README.update for more details.
4339
4340  autoload	- if set to "no" (any string beginning with 'n'),
4341		  "bootp" will just load perform a lookup of the
4342		  configuration from the BOOTP server, but not try to
4343		  load any image using TFTP
4344
4345  autostart	- if set to "yes", an image loaded using the "bootp",
4346		  "rarpboot", "tftpboot" or "diskboot" commands will
4347		  be automatically started (by internally calling
4348		  "bootm")
4349
4350		  If set to "no", a standalone image passed to the
4351		  "bootm" command will be copied to the load address
4352		  (and eventually uncompressed), but NOT be started.
4353		  This can be used to load and uncompress arbitrary
4354		  data.
4355
4356  fdt_high	- if set this restricts the maximum address that the
4357		  flattened device tree will be copied into upon boot.
4358		  For example, if you have a system with 1 GB memory
4359		  at physical address 0x10000000, while Linux kernel
4360		  only recognizes the first 704 MB as low memory, you
4361		  may need to set fdt_high as 0x3C000000 to have the
4362		  device tree blob be copied to the maximum address
4363		  of the 704 MB low memory, so that Linux kernel can
4364		  access it during the boot procedure.
4365
4366		  If this is set to the special value 0xFFFFFFFF then
4367		  the fdt will not be copied at all on boot.  For this
4368		  to work it must reside in writable memory, have
4369		  sufficient padding on the end of it for u-boot to
4370		  add the information it needs into it, and the memory
4371		  must be accessible by the kernel.
4372
4373  fdtcontroladdr- if set this is the address of the control flattened
4374		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4375		  defined.
4376
4377  i2cfast	- (PPC405GP|PPC405EP only)
4378		  if set to 'y' configures Linux I2C driver for fast
4379		  mode (400kHZ). This environment variable is used in
4380		  initialization code. So, for changes to be effective
4381		  it must be saved and board must be reset.
4382
4383  initrd_high	- restrict positioning of initrd images:
4384		  If this variable is not set, initrd images will be
4385		  copied to the highest possible address in RAM; this
4386		  is usually what you want since it allows for
4387		  maximum initrd size. If for some reason you want to
4388		  make sure that the initrd image is loaded below the
4389		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4390		  variable to a value of "no" or "off" or "0".
4391		  Alternatively, you can set it to a maximum upper
4392		  address to use (U-Boot will still check that it
4393		  does not overwrite the U-Boot stack and data).
4394
4395		  For instance, when you have a system with 16 MB
4396		  RAM, and want to reserve 4 MB from use by Linux,
4397		  you can do this by adding "mem=12M" to the value of
4398		  the "bootargs" variable. However, now you must make
4399		  sure that the initrd image is placed in the first
4400		  12 MB as well - this can be done with
4401
4402		  setenv initrd_high 00c00000
4403
4404		  If you set initrd_high to 0xFFFFFFFF, this is an
4405		  indication to U-Boot that all addresses are legal
4406		  for the Linux kernel, including addresses in flash
4407		  memory. In this case U-Boot will NOT COPY the
4408		  ramdisk at all. This may be useful to reduce the
4409		  boot time on your system, but requires that this
4410		  feature is supported by your Linux kernel.
4411
4412  ipaddr	- IP address; needed for tftpboot command
4413
4414  loadaddr	- Default load address for commands like "bootp",
4415		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4416
4417  loads_echo	- see CONFIG_LOADS_ECHO
4418
4419  serverip	- TFTP server IP address; needed for tftpboot command
4420
4421  bootretry	- see CONFIG_BOOT_RETRY_TIME
4422
4423  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4424
4425  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4426
4427  ethprime	- controls which interface is used first.
4428
4429  ethact	- controls which interface is currently active.
4430		  For example you can do the following
4431
4432		  => setenv ethact FEC
4433		  => ping 192.168.0.1 # traffic sent on FEC
4434		  => setenv ethact SCC
4435		  => ping 10.0.0.1 # traffic sent on SCC
4436
4437  ethrotate	- When set to "no" U-Boot does not go through all
4438		  available network interfaces.
4439		  It just stays at the currently selected interface.
4440
4441  netretry	- When set to "no" each network operation will
4442		  either succeed or fail without retrying.
4443		  When set to "once" the network operation will
4444		  fail when all the available network interfaces
4445		  are tried once without success.
4446		  Useful on scripts which control the retry operation
4447		  themselves.
4448
4449  npe_ucode	- set load address for the NPE microcode
4450
4451  tftpsrcport	- If this is set, the value is used for TFTP's
4452		  UDP source port.
4453
4454  tftpdstport	- If this is set, the value is used for TFTP's UDP
4455		  destination port instead of the Well Know Port 69.
4456
4457  tftpblocksize - Block size to use for TFTP transfers; if not set,
4458		  we use the TFTP server's default block size
4459
4460  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4461		  seconds, minimum value is 1000 = 1 second). Defines
4462		  when a packet is considered to be lost so it has to
4463		  be retransmitted. The default is 5000 = 5 seconds.
4464		  Lowering this value may make downloads succeed
4465		  faster in networks with high packet loss rates or
4466		  with unreliable TFTP servers.
4467
4468  vlan		- When set to a value < 4095 the traffic over
4469		  Ethernet is encapsulated/received over 802.1q
4470		  VLAN tagged frames.
4471
4472The following image location variables contain the location of images
4473used in booting. The "Image" column gives the role of the image and is
4474not an environment variable name. The other columns are environment
4475variable names. "File Name" gives the name of the file on a TFTP
4476server, "RAM Address" gives the location in RAM the image will be
4477loaded to, and "Flash Location" gives the image's address in NOR
4478flash or offset in NAND flash.
4479
4480*Note* - these variables don't have to be defined for all boards, some
4481boards currenlty use other variables for these purposes, and some
4482boards use these variables for other purposes.
4483
4484Image		    File Name	     RAM Address       Flash Location
4485-----		    ---------	     -----------       --------------
4486u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4487Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4488device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4489ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4490
4491The following environment variables may be used and automatically
4492updated by the network boot commands ("bootp" and "rarpboot"),
4493depending the information provided by your boot server:
4494
4495  bootfile	- see above
4496  dnsip		- IP address of your Domain Name Server
4497  dnsip2	- IP address of your secondary Domain Name Server
4498  gatewayip	- IP address of the Gateway (Router) to use
4499  hostname	- Target hostname
4500  ipaddr	- see above
4501  netmask	- Subnet Mask
4502  rootpath	- Pathname of the root filesystem on the NFS server
4503  serverip	- see above
4504
4505
4506There are two special Environment Variables:
4507
4508  serial#	- contains hardware identification information such
4509		  as type string and/or serial number
4510  ethaddr	- Ethernet address
4511
4512These variables can be set only once (usually during manufacturing of
4513the board). U-Boot refuses to delete or overwrite these variables
4514once they have been set once.
4515
4516
4517Further special Environment Variables:
4518
4519  ver		- Contains the U-Boot version string as printed
4520		  with the "version" command. This variable is
4521		  readonly (see CONFIG_VERSION_VARIABLE).
4522
4523
4524Please note that changes to some configuration parameters may take
4525only effect after the next boot (yes, that's just like Windoze :-).
4526
4527
4528Callback functions for environment variables:
4529---------------------------------------------
4530
4531For some environment variables, the behavior of u-boot needs to change
4532when their values are changed.  This functionailty allows functions to
4533be associated with arbitrary variables.  On creation, overwrite, or
4534deletion, the callback will provide the opportunity for some side
4535effect to happen or for the change to be rejected.
4536
4537The callbacks are named and associated with a function using the
4538U_BOOT_ENV_CALLBACK macro in your board or driver code.
4539
4540These callbacks are associated with variables in one of two ways.  The
4541static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4542in the board configuration to a string that defines a list of
4543associations.  The list must be in the following format:
4544
4545	entry = variable_name[:callback_name]
4546	list = entry[,list]
4547
4548If the callback name is not specified, then the callback is deleted.
4549Spaces are also allowed anywhere in the list.
4550
4551Callbacks can also be associated by defining the ".callbacks" variable
4552with the same list format above.  Any association in ".callbacks" will
4553override any association in the static list. You can define
4554CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4555".callbacks" envirnoment variable in the default or embedded environment.
4556
4557
4558Command Line Parsing:
4559=====================
4560
4561There are two different command line parsers available with U-Boot:
4562the old "simple" one, and the much more powerful "hush" shell:
4563
4564Old, simple command line parser:
4565--------------------------------
4566
4567- supports environment variables (through setenv / saveenv commands)
4568- several commands on one line, separated by ';'
4569- variable substitution using "... ${name} ..." syntax
4570- special characters ('$', ';') can be escaped by prefixing with '\',
4571  for example:
4572	setenv bootcmd bootm \${address}
4573- You can also escape text by enclosing in single apostrophes, for example:
4574	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4575
4576Hush shell:
4577-----------
4578
4579- similar to Bourne shell, with control structures like
4580  if...then...else...fi, for...do...done; while...do...done,
4581  until...do...done, ...
4582- supports environment ("global") variables (through setenv / saveenv
4583  commands) and local shell variables (through standard shell syntax
4584  "name=value"); only environment variables can be used with "run"
4585  command
4586
4587General rules:
4588--------------
4589
4590(1) If a command line (or an environment variable executed by a "run"
4591    command) contains several commands separated by semicolon, and
4592    one of these commands fails, then the remaining commands will be
4593    executed anyway.
4594
4595(2) If you execute several variables with one call to run (i. e.
4596    calling run with a list of variables as arguments), any failing
4597    command will cause "run" to terminate, i. e. the remaining
4598    variables are not executed.
4599
4600Note for Redundant Ethernet Interfaces:
4601=======================================
4602
4603Some boards come with redundant Ethernet interfaces; U-Boot supports
4604such configurations and is capable of automatic selection of a
4605"working" interface when needed. MAC assignment works as follows:
4606
4607Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4608MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4609"eth1addr" (=>eth1), "eth2addr", ...
4610
4611If the network interface stores some valid MAC address (for instance
4612in SROM), this is used as default address if there is NO correspon-
4613ding setting in the environment; if the corresponding environment
4614variable is set, this overrides the settings in the card; that means:
4615
4616o If the SROM has a valid MAC address, and there is no address in the
4617  environment, the SROM's address is used.
4618
4619o If there is no valid address in the SROM, and a definition in the
4620  environment exists, then the value from the environment variable is
4621  used.
4622
4623o If both the SROM and the environment contain a MAC address, and
4624  both addresses are the same, this MAC address is used.
4625
4626o If both the SROM and the environment contain a MAC address, and the
4627  addresses differ, the value from the environment is used and a
4628  warning is printed.
4629
4630o If neither SROM nor the environment contain a MAC address, an error
4631  is raised.
4632
4633If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4634will be programmed into hardware as part of the initialization process.	 This
4635may be skipped by setting the appropriate 'ethmacskip' environment variable.
4636The naming convention is as follows:
4637"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4638
4639Image Formats:
4640==============
4641
4642U-Boot is capable of booting (and performing other auxiliary operations on)
4643images in two formats:
4644
4645New uImage format (FIT)
4646-----------------------
4647
4648Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4649to Flattened Device Tree). It allows the use of images with multiple
4650components (several kernels, ramdisks, etc.), with contents protected by
4651SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4652
4653
4654Old uImage format
4655-----------------
4656
4657Old image format is based on binary files which can be basically anything,
4658preceded by a special header; see the definitions in include/image.h for
4659details; basically, the header defines the following image properties:
4660
4661* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4662  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4663  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4664  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4665  INTEGRITY).
4666* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4667  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4668  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4669* Compression Type (uncompressed, gzip, bzip2)
4670* Load Address
4671* Entry Point
4672* Image Name
4673* Image Timestamp
4674
4675The header is marked by a special Magic Number, and both the header
4676and the data portions of the image are secured against corruption by
4677CRC32 checksums.
4678
4679
4680Linux Support:
4681==============
4682
4683Although U-Boot should support any OS or standalone application
4684easily, the main focus has always been on Linux during the design of
4685U-Boot.
4686
4687U-Boot includes many features that so far have been part of some
4688special "boot loader" code within the Linux kernel. Also, any
4689"initrd" images to be used are no longer part of one big Linux image;
4690instead, kernel and "initrd" are separate images. This implementation
4691serves several purposes:
4692
4693- the same features can be used for other OS or standalone
4694  applications (for instance: using compressed images to reduce the
4695  Flash memory footprint)
4696
4697- it becomes much easier to port new Linux kernel versions because
4698  lots of low-level, hardware dependent stuff are done by U-Boot
4699
4700- the same Linux kernel image can now be used with different "initrd"
4701  images; of course this also means that different kernel images can
4702  be run with the same "initrd". This makes testing easier (you don't
4703  have to build a new "zImage.initrd" Linux image when you just
4704  change a file in your "initrd"). Also, a field-upgrade of the
4705  software is easier now.
4706
4707
4708Linux HOWTO:
4709============
4710
4711Porting Linux to U-Boot based systems:
4712---------------------------------------
4713
4714U-Boot cannot save you from doing all the necessary modifications to
4715configure the Linux device drivers for use with your target hardware
4716(no, we don't intend to provide a full virtual machine interface to
4717Linux :-).
4718
4719But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4720
4721Just make sure your machine specific header file (for instance
4722include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4723Information structure as we define in include/asm-<arch>/u-boot.h,
4724and make sure that your definition of IMAP_ADDR uses the same value
4725as your U-Boot configuration in CONFIG_SYS_IMMR.
4726
4727
4728Configuring the Linux kernel:
4729-----------------------------
4730
4731No specific requirements for U-Boot. Make sure you have some root
4732device (initial ramdisk, NFS) for your target system.
4733
4734
4735Building a Linux Image:
4736-----------------------
4737
4738With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4739not used. If you use recent kernel source, a new build target
4740"uImage" will exist which automatically builds an image usable by
4741U-Boot. Most older kernels also have support for a "pImage" target,
4742which was introduced for our predecessor project PPCBoot and uses a
4743100% compatible format.
4744
4745Example:
4746
4747	make TQM850L_config
4748	make oldconfig
4749	make dep
4750	make uImage
4751
4752The "uImage" build target uses a special tool (in 'tools/mkimage') to
4753encapsulate a compressed Linux kernel image with header	 information,
4754CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4755
4756* build a standard "vmlinux" kernel image (in ELF binary format):
4757
4758* convert the kernel into a raw binary image:
4759
4760	${CROSS_COMPILE}-objcopy -O binary \
4761				 -R .note -R .comment \
4762				 -S vmlinux linux.bin
4763
4764* compress the binary image:
4765
4766	gzip -9 linux.bin
4767
4768* package compressed binary image for U-Boot:
4769
4770	mkimage -A ppc -O linux -T kernel -C gzip \
4771		-a 0 -e 0 -n "Linux Kernel Image" \
4772		-d linux.bin.gz uImage
4773
4774
4775The "mkimage" tool can also be used to create ramdisk images for use
4776with U-Boot, either separated from the Linux kernel image, or
4777combined into one file. "mkimage" encapsulates the images with a 64
4778byte header containing information about target architecture,
4779operating system, image type, compression method, entry points, time
4780stamp, CRC32 checksums, etc.
4781
4782"mkimage" can be called in two ways: to verify existing images and
4783print the header information, or to build new images.
4784
4785In the first form (with "-l" option) mkimage lists the information
4786contained in the header of an existing U-Boot image; this includes
4787checksum verification:
4788
4789	tools/mkimage -l image
4790	  -l ==> list image header information
4791
4792The second form (with "-d" option) is used to build a U-Boot image
4793from a "data file" which is used as image payload:
4794
4795	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4796		      -n name -d data_file image
4797	  -A ==> set architecture to 'arch'
4798	  -O ==> set operating system to 'os'
4799	  -T ==> set image type to 'type'
4800	  -C ==> set compression type 'comp'
4801	  -a ==> set load address to 'addr' (hex)
4802	  -e ==> set entry point to 'ep' (hex)
4803	  -n ==> set image name to 'name'
4804	  -d ==> use image data from 'datafile'
4805
4806Right now, all Linux kernels for PowerPC systems use the same load
4807address (0x00000000), but the entry point address depends on the
4808kernel version:
4809
4810- 2.2.x kernels have the entry point at 0x0000000C,
4811- 2.3.x and later kernels have the entry point at 0x00000000.
4812
4813So a typical call to build a U-Boot image would read:
4814
4815	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4816	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4817	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4818	> examples/uImage.TQM850L
4819	Image Name:   2.4.4 kernel for TQM850L
4820	Created:      Wed Jul 19 02:34:59 2000
4821	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4822	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4823	Load Address: 0x00000000
4824	Entry Point:  0x00000000
4825
4826To verify the contents of the image (or check for corruption):
4827
4828	-> tools/mkimage -l examples/uImage.TQM850L
4829	Image Name:   2.4.4 kernel for TQM850L
4830	Created:      Wed Jul 19 02:34:59 2000
4831	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4832	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4833	Load Address: 0x00000000
4834	Entry Point:  0x00000000
4835
4836NOTE: for embedded systems where boot time is critical you can trade
4837speed for memory and install an UNCOMPRESSED image instead: this
4838needs more space in Flash, but boots much faster since it does not
4839need to be uncompressed:
4840
4841	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4842	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4843	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4844	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4845	> examples/uImage.TQM850L-uncompressed
4846	Image Name:   2.4.4 kernel for TQM850L
4847	Created:      Wed Jul 19 02:34:59 2000
4848	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4849	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4850	Load Address: 0x00000000
4851	Entry Point:  0x00000000
4852
4853
4854Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4855when your kernel is intended to use an initial ramdisk:
4856
4857	-> tools/mkimage -n 'Simple Ramdisk Image' \
4858	> -A ppc -O linux -T ramdisk -C gzip \
4859	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4860	Image Name:   Simple Ramdisk Image
4861	Created:      Wed Jan 12 14:01:50 2000
4862	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4863	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4864	Load Address: 0x00000000
4865	Entry Point:  0x00000000
4866
4867
4868Installing a Linux Image:
4869-------------------------
4870
4871To downloading a U-Boot image over the serial (console) interface,
4872you must convert the image to S-Record format:
4873
4874	objcopy -I binary -O srec examples/image examples/image.srec
4875
4876The 'objcopy' does not understand the information in the U-Boot
4877image header, so the resulting S-Record file will be relative to
4878address 0x00000000. To load it to a given address, you need to
4879specify the target address as 'offset' parameter with the 'loads'
4880command.
4881
4882Example: install the image to address 0x40100000 (which on the
4883TQM8xxL is in the first Flash bank):
4884
4885	=> erase 40100000 401FFFFF
4886
4887	.......... done
4888	Erased 8 sectors
4889
4890	=> loads 40100000
4891	## Ready for S-Record download ...
4892	~>examples/image.srec
4893	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4894	...
4895	15989 15990 15991 15992
4896	[file transfer complete]
4897	[connected]
4898	## Start Addr = 0x00000000
4899
4900
4901You can check the success of the download using the 'iminfo' command;
4902this includes a checksum verification so you can be sure no data
4903corruption happened:
4904
4905	=> imi 40100000
4906
4907	## Checking Image at 40100000 ...
4908	   Image Name:	 2.2.13 for initrd on TQM850L
4909	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4910	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4911	   Load Address: 00000000
4912	   Entry Point:	 0000000c
4913	   Verifying Checksum ... OK
4914
4915
4916Boot Linux:
4917-----------
4918
4919The "bootm" command is used to boot an application that is stored in
4920memory (RAM or Flash). In case of a Linux kernel image, the contents
4921of the "bootargs" environment variable is passed to the kernel as
4922parameters. You can check and modify this variable using the
4923"printenv" and "setenv" commands:
4924
4925
4926	=> printenv bootargs
4927	bootargs=root=/dev/ram
4928
4929	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4930
4931	=> printenv bootargs
4932	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4933
4934	=> bootm 40020000
4935	## Booting Linux kernel at 40020000 ...
4936	   Image Name:	 2.2.13 for NFS on TQM850L
4937	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4938	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4939	   Load Address: 00000000
4940	   Entry Point:	 0000000c
4941	   Verifying Checksum ... OK
4942	   Uncompressing Kernel Image ... OK
4943	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
4944	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4945	time_init: decrementer frequency = 187500000/60
4946	Calibrating delay loop... 49.77 BogoMIPS
4947	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4948	...
4949
4950If you want to boot a Linux kernel with initial RAM disk, you pass
4951the memory addresses of both the kernel and the initrd image (PPBCOOT
4952format!) to the "bootm" command:
4953
4954	=> imi 40100000 40200000
4955
4956	## Checking Image at 40100000 ...
4957	   Image Name:	 2.2.13 for initrd on TQM850L
4958	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4959	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4960	   Load Address: 00000000
4961	   Entry Point:	 0000000c
4962	   Verifying Checksum ... OK
4963
4964	## Checking Image at 40200000 ...
4965	   Image Name:	 Simple Ramdisk Image
4966	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4967	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4968	   Load Address: 00000000
4969	   Entry Point:	 00000000
4970	   Verifying Checksum ... OK
4971
4972	=> bootm 40100000 40200000
4973	## Booting Linux kernel at 40100000 ...
4974	   Image Name:	 2.2.13 for initrd on TQM850L
4975	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4976	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4977	   Load Address: 00000000
4978	   Entry Point:	 0000000c
4979	   Verifying Checksum ... OK
4980	   Uncompressing Kernel Image ... OK
4981	## Loading RAMDisk Image at 40200000 ...
4982	   Image Name:	 Simple Ramdisk Image
4983	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4984	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4985	   Load Address: 00000000
4986	   Entry Point:	 00000000
4987	   Verifying Checksum ... OK
4988	   Loading Ramdisk ... OK
4989	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
4990	Boot arguments: root=/dev/ram
4991	time_init: decrementer frequency = 187500000/60
4992	Calibrating delay loop... 49.77 BogoMIPS
4993	...
4994	RAMDISK: Compressed image found at block 0
4995	VFS: Mounted root (ext2 filesystem).
4996
4997	bash#
4998
4999Boot Linux and pass a flat device tree:
5000-----------
5001
5002First, U-Boot must be compiled with the appropriate defines. See the section
5003titled "Linux Kernel Interface" above for a more in depth explanation. The
5004following is an example of how to start a kernel and pass an updated
5005flat device tree:
5006
5007=> print oftaddr
5008oftaddr=0x300000
5009=> print oft
5010oft=oftrees/mpc8540ads.dtb
5011=> tftp $oftaddr $oft
5012Speed: 1000, full duplex
5013Using TSEC0 device
5014TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5015Filename 'oftrees/mpc8540ads.dtb'.
5016Load address: 0x300000
5017Loading: #
5018done
5019Bytes transferred = 4106 (100a hex)
5020=> tftp $loadaddr $bootfile
5021Speed: 1000, full duplex
5022Using TSEC0 device
5023TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5024Filename 'uImage'.
5025Load address: 0x200000
5026Loading:############
5027done
5028Bytes transferred = 1029407 (fb51f hex)
5029=> print loadaddr
5030loadaddr=200000
5031=> print oftaddr
5032oftaddr=0x300000
5033=> bootm $loadaddr - $oftaddr
5034## Booting image at 00200000 ...
5035   Image Name:	 Linux-2.6.17-dirty
5036   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5037   Data Size:	 1029343 Bytes = 1005.2 kB
5038   Load Address: 00000000
5039   Entry Point:	 00000000
5040   Verifying Checksum ... OK
5041   Uncompressing Kernel Image ... OK
5042Booting using flat device tree at 0x300000
5043Using MPC85xx ADS machine description
5044Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5045[snip]
5046
5047
5048More About U-Boot Image Types:
5049------------------------------
5050
5051U-Boot supports the following image types:
5052
5053   "Standalone Programs" are directly runnable in the environment
5054	provided by U-Boot; it is expected that (if they behave
5055	well) you can continue to work in U-Boot after return from
5056	the Standalone Program.
5057   "OS Kernel Images" are usually images of some Embedded OS which
5058	will take over control completely. Usually these programs
5059	will install their own set of exception handlers, device
5060	drivers, set up the MMU, etc. - this means, that you cannot
5061	expect to re-enter U-Boot except by resetting the CPU.
5062   "RAMDisk Images" are more or less just data blocks, and their
5063	parameters (address, size) are passed to an OS kernel that is
5064	being started.
5065   "Multi-File Images" contain several images, typically an OS
5066	(Linux) kernel image and one or more data images like
5067	RAMDisks. This construct is useful for instance when you want
5068	to boot over the network using BOOTP etc., where the boot
5069	server provides just a single image file, but you want to get
5070	for instance an OS kernel and a RAMDisk image.
5071
5072	"Multi-File Images" start with a list of image sizes, each
5073	image size (in bytes) specified by an "uint32_t" in network
5074	byte order. This list is terminated by an "(uint32_t)0".
5075	Immediately after the terminating 0 follow the images, one by
5076	one, all aligned on "uint32_t" boundaries (size rounded up to
5077	a multiple of 4 bytes).
5078
5079   "Firmware Images" are binary images containing firmware (like
5080	U-Boot or FPGA images) which usually will be programmed to
5081	flash memory.
5082
5083   "Script files" are command sequences that will be executed by
5084	U-Boot's command interpreter; this feature is especially
5085	useful when you configure U-Boot to use a real shell (hush)
5086	as command interpreter.
5087
5088Booting the Linux zImage:
5089-------------------------
5090
5091On some platforms, it's possible to boot Linux zImage. This is done
5092using the "bootz" command. The syntax of "bootz" command is the same
5093as the syntax of "bootm" command.
5094
5095Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5096kernel with raw initrd images. The syntax is slightly different, the
5097address of the initrd must be augmented by it's size, in the following
5098format: "<initrd addres>:<initrd size>".
5099
5100
5101Standalone HOWTO:
5102=================
5103
5104One of the features of U-Boot is that you can dynamically load and
5105run "standalone" applications, which can use some resources of
5106U-Boot like console I/O functions or interrupt services.
5107
5108Two simple examples are included with the sources:
5109
5110"Hello World" Demo:
5111-------------------
5112
5113'examples/hello_world.c' contains a small "Hello World" Demo
5114application; it is automatically compiled when you build U-Boot.
5115It's configured to run at address 0x00040004, so you can play with it
5116like that:
5117
5118	=> loads
5119	## Ready for S-Record download ...
5120	~>examples/hello_world.srec
5121	1 2 3 4 5 6 7 8 9 10 11 ...
5122	[file transfer complete]
5123	[connected]
5124	## Start Addr = 0x00040004
5125
5126	=> go 40004 Hello World! This is a test.
5127	## Starting application at 0x00040004 ...
5128	Hello World
5129	argc = 7
5130	argv[0] = "40004"
5131	argv[1] = "Hello"
5132	argv[2] = "World!"
5133	argv[3] = "This"
5134	argv[4] = "is"
5135	argv[5] = "a"
5136	argv[6] = "test."
5137	argv[7] = "<NULL>"
5138	Hit any key to exit ...
5139
5140	## Application terminated, rc = 0x0
5141
5142Another example, which demonstrates how to register a CPM interrupt
5143handler with the U-Boot code, can be found in 'examples/timer.c'.
5144Here, a CPM timer is set up to generate an interrupt every second.
5145The interrupt service routine is trivial, just printing a '.'
5146character, but this is just a demo program. The application can be
5147controlled by the following keys:
5148
5149	? - print current values og the CPM Timer registers
5150	b - enable interrupts and start timer
5151	e - stop timer and disable interrupts
5152	q - quit application
5153
5154	=> loads
5155	## Ready for S-Record download ...
5156	~>examples/timer.srec
5157	1 2 3 4 5 6 7 8 9 10 11 ...
5158	[file transfer complete]
5159	[connected]
5160	## Start Addr = 0x00040004
5161
5162	=> go 40004
5163	## Starting application at 0x00040004 ...
5164	TIMERS=0xfff00980
5165	Using timer 1
5166	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5167
5168Hit 'b':
5169	[q, b, e, ?] Set interval 1000000 us
5170	Enabling timer
5171Hit '?':
5172	[q, b, e, ?] ........
5173	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5174Hit '?':
5175	[q, b, e, ?] .
5176	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5177Hit '?':
5178	[q, b, e, ?] .
5179	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5180Hit '?':
5181	[q, b, e, ?] .
5182	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5183Hit 'e':
5184	[q, b, e, ?] ...Stopping timer
5185Hit 'q':
5186	[q, b, e, ?] ## Application terminated, rc = 0x0
5187
5188
5189Minicom warning:
5190================
5191
5192Over time, many people have reported problems when trying to use the
5193"minicom" terminal emulation program for serial download. I (wd)
5194consider minicom to be broken, and recommend not to use it. Under
5195Unix, I recommend to use C-Kermit for general purpose use (and
5196especially for kermit binary protocol download ("loadb" command), and
5197use "cu" for S-Record download ("loads" command).  See
5198http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5199for help with kermit.
5200
5201
5202Nevertheless, if you absolutely want to use it try adding this
5203configuration to your "File transfer protocols" section:
5204
5205	   Name	   Program			Name U/D FullScr IO-Red. Multi
5206	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5207	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5208
5209
5210NetBSD Notes:
5211=============
5212
5213Starting at version 0.9.2, U-Boot supports NetBSD both as host
5214(build U-Boot) and target system (boots NetBSD/mpc8xx).
5215
5216Building requires a cross environment; it is known to work on
5217NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5218need gmake since the Makefiles are not compatible with BSD make).
5219Note that the cross-powerpc package does not install include files;
5220attempting to build U-Boot will fail because <machine/ansi.h> is
5221missing.  This file has to be installed and patched manually:
5222
5223	# cd /usr/pkg/cross/powerpc-netbsd/include
5224	# mkdir powerpc
5225	# ln -s powerpc machine
5226	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5227	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5228
5229Native builds *don't* work due to incompatibilities between native
5230and U-Boot include files.
5231
5232Booting assumes that (the first part of) the image booted is a
5233stage-2 loader which in turn loads and then invokes the kernel
5234proper. Loader sources will eventually appear in the NetBSD source
5235tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5236meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5237
5238
5239Implementation Internals:
5240=========================
5241
5242The following is not intended to be a complete description of every
5243implementation detail. However, it should help to understand the
5244inner workings of U-Boot and make it easier to port it to custom
5245hardware.
5246
5247
5248Initial Stack, Global Data:
5249---------------------------
5250
5251The implementation of U-Boot is complicated by the fact that U-Boot
5252starts running out of ROM (flash memory), usually without access to
5253system RAM (because the memory controller is not initialized yet).
5254This means that we don't have writable Data or BSS segments, and BSS
5255is not initialized as zero. To be able to get a C environment working
5256at all, we have to allocate at least a minimal stack. Implementation
5257options for this are defined and restricted by the CPU used: Some CPU
5258models provide on-chip memory (like the IMMR area on MPC8xx and
5259MPC826x processors), on others (parts of) the data cache can be
5260locked as (mis-) used as memory, etc.
5261
5262	Chris Hallinan posted a good summary of these issues to the
5263	U-Boot mailing list:
5264
5265	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5266	From: "Chris Hallinan" <clh@net1plus.com>
5267	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5268	...
5269
5270	Correct me if I'm wrong, folks, but the way I understand it
5271	is this: Using DCACHE as initial RAM for Stack, etc, does not
5272	require any physical RAM backing up the cache. The cleverness
5273	is that the cache is being used as a temporary supply of
5274	necessary storage before the SDRAM controller is setup. It's
5275	beyond the scope of this list to explain the details, but you
5276	can see how this works by studying the cache architecture and
5277	operation in the architecture and processor-specific manuals.
5278
5279	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5280	is another option for the system designer to use as an
5281	initial stack/RAM area prior to SDRAM being available. Either
5282	option should work for you. Using CS 4 should be fine if your
5283	board designers haven't used it for something that would
5284	cause you grief during the initial boot! It is frequently not
5285	used.
5286
5287	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5288	with your processor/board/system design. The default value
5289	you will find in any recent u-boot distribution in
5290	walnut.h should work for you. I'd set it to a value larger
5291	than your SDRAM module. If you have a 64MB SDRAM module, set
5292	it above 400_0000. Just make sure your board has no resources
5293	that are supposed to respond to that address! That code in
5294	start.S has been around a while and should work as is when
5295	you get the config right.
5296
5297	-Chris Hallinan
5298	DS4.COM, Inc.
5299
5300It is essential to remember this, since it has some impact on the C
5301code for the initialization procedures:
5302
5303* Initialized global data (data segment) is read-only. Do not attempt
5304  to write it.
5305
5306* Do not use any uninitialized global data (or implicitely initialized
5307  as zero data - BSS segment) at all - this is undefined, initiali-
5308  zation is performed later (when relocating to RAM).
5309
5310* Stack space is very limited. Avoid big data buffers or things like
5311  that.
5312
5313Having only the stack as writable memory limits means we cannot use
5314normal global data to share information beween the code. But it
5315turned out that the implementation of U-Boot can be greatly
5316simplified by making a global data structure (gd_t) available to all
5317functions. We could pass a pointer to this data as argument to _all_
5318functions, but this would bloat the code. Instead we use a feature of
5319the GCC compiler (Global Register Variables) to share the data: we
5320place a pointer (gd) to the global data into a register which we
5321reserve for this purpose.
5322
5323When choosing a register for such a purpose we are restricted by the
5324relevant  (E)ABI  specifications for the current architecture, and by
5325GCC's implementation.
5326
5327For PowerPC, the following registers have specific use:
5328	R1:	stack pointer
5329	R2:	reserved for system use
5330	R3-R4:	parameter passing and return values
5331	R5-R10: parameter passing
5332	R13:	small data area pointer
5333	R30:	GOT pointer
5334	R31:	frame pointer
5335
5336	(U-Boot also uses R12 as internal GOT pointer. r12
5337	is a volatile register so r12 needs to be reset when
5338	going back and forth between asm and C)
5339
5340    ==> U-Boot will use R2 to hold a pointer to the global data
5341
5342    Note: on PPC, we could use a static initializer (since the
5343    address of the global data structure is known at compile time),
5344    but it turned out that reserving a register results in somewhat
5345    smaller code - although the code savings are not that big (on
5346    average for all boards 752 bytes for the whole U-Boot image,
5347    624 text + 127 data).
5348
5349On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5350	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5351
5352    ==> U-Boot will use P3 to hold a pointer to the global data
5353
5354On ARM, the following registers are used:
5355
5356	R0:	function argument word/integer result
5357	R1-R3:	function argument word
5358	R9:	GOT pointer
5359	R10:	stack limit (used only if stack checking if enabled)
5360	R11:	argument (frame) pointer
5361	R12:	temporary workspace
5362	R13:	stack pointer
5363	R14:	link register
5364	R15:	program counter
5365
5366    ==> U-Boot will use R8 to hold a pointer to the global data
5367
5368On Nios II, the ABI is documented here:
5369	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5370
5371    ==> U-Boot will use gp to hold a pointer to the global data
5372
5373    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5374    to access small data sections, so gp is free.
5375
5376On NDS32, the following registers are used:
5377
5378	R0-R1:	argument/return
5379	R2-R5:	argument
5380	R15:	temporary register for assembler
5381	R16:	trampoline register
5382	R28:	frame pointer (FP)
5383	R29:	global pointer (GP)
5384	R30:	link register (LP)
5385	R31:	stack pointer (SP)
5386	PC:	program counter (PC)
5387
5388    ==> U-Boot will use R10 to hold a pointer to the global data
5389
5390NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5391or current versions of GCC may "optimize" the code too much.
5392
5393Memory Management:
5394------------------
5395
5396U-Boot runs in system state and uses physical addresses, i.e. the
5397MMU is not used either for address mapping nor for memory protection.
5398
5399The available memory is mapped to fixed addresses using the memory
5400controller. In this process, a contiguous block is formed for each
5401memory type (Flash, SDRAM, SRAM), even when it consists of several
5402physical memory banks.
5403
5404U-Boot is installed in the first 128 kB of the first Flash bank (on
5405TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5406booting and sizing and initializing DRAM, the code relocates itself
5407to the upper end of DRAM. Immediately below the U-Boot code some
5408memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5409configuration setting]. Below that, a structure with global Board
5410Info data is placed, followed by the stack (growing downward).
5411
5412Additionally, some exception handler code is copied to the low 8 kB
5413of DRAM (0x00000000 ... 0x00001FFF).
5414
5415So a typical memory configuration with 16 MB of DRAM could look like
5416this:
5417
5418	0x0000 0000	Exception Vector code
5419	      :
5420	0x0000 1FFF
5421	0x0000 2000	Free for Application Use
5422	      :
5423	      :
5424
5425	      :
5426	      :
5427	0x00FB FF20	Monitor Stack (Growing downward)
5428	0x00FB FFAC	Board Info Data and permanent copy of global data
5429	0x00FC 0000	Malloc Arena
5430	      :
5431	0x00FD FFFF
5432	0x00FE 0000	RAM Copy of Monitor Code
5433	...		eventually: LCD or video framebuffer
5434	...		eventually: pRAM (Protected RAM - unchanged by reset)
5435	0x00FF FFFF	[End of RAM]
5436
5437
5438System Initialization:
5439----------------------
5440
5441In the reset configuration, U-Boot starts at the reset entry point
5442(on most PowerPC systems at address 0x00000100). Because of the reset
5443configuration for CS0# this is a mirror of the onboard Flash memory.
5444To be able to re-map memory U-Boot then jumps to its link address.
5445To be able to implement the initialization code in C, a (small!)
5446initial stack is set up in the internal Dual Ported RAM (in case CPUs
5447which provide such a feature like MPC8xx or MPC8260), or in a locked
5448part of the data cache. After that, U-Boot initializes the CPU core,
5449the caches and the SIU.
5450
5451Next, all (potentially) available memory banks are mapped using a
5452preliminary mapping. For example, we put them on 512 MB boundaries
5453(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5454on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5455programmed for SDRAM access. Using the temporary configuration, a
5456simple memory test is run that determines the size of the SDRAM
5457banks.
5458
5459When there is more than one SDRAM bank, and the banks are of
5460different size, the largest is mapped first. For equal size, the first
5461bank (CS2#) is mapped first. The first mapping is always for address
54620x00000000, with any additional banks following immediately to create
5463contiguous memory starting from 0.
5464
5465Then, the monitor installs itself at the upper end of the SDRAM area
5466and allocates memory for use by malloc() and for the global Board
5467Info data; also, the exception vector code is copied to the low RAM
5468pages, and the final stack is set up.
5469
5470Only after this relocation will you have a "normal" C environment;
5471until that you are restricted in several ways, mostly because you are
5472running from ROM, and because the code will have to be relocated to a
5473new address in RAM.
5474
5475
5476U-Boot Porting Guide:
5477----------------------
5478
5479[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5480list, October 2002]
5481
5482
5483int main(int argc, char *argv[])
5484{
5485	sighandler_t no_more_time;
5486
5487	signal(SIGALRM, no_more_time);
5488	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5489
5490	if (available_money > available_manpower) {
5491		Pay consultant to port U-Boot;
5492		return 0;
5493	}
5494
5495	Download latest U-Boot source;
5496
5497	Subscribe to u-boot mailing list;
5498
5499	if (clueless)
5500		email("Hi, I am new to U-Boot, how do I get started?");
5501
5502	while (learning) {
5503		Read the README file in the top level directory;
5504		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5505		Read applicable doc/*.README;
5506		Read the source, Luke;
5507		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5508	}
5509
5510	if (available_money > toLocalCurrency ($2500))
5511		Buy a BDI3000;
5512	else
5513		Add a lot of aggravation and time;
5514
5515	if (a similar board exists) {	/* hopefully... */
5516		cp -a board/<similar> board/<myboard>
5517		cp include/configs/<similar>.h include/configs/<myboard>.h
5518	} else {
5519		Create your own board support subdirectory;
5520		Create your own board include/configs/<myboard>.h file;
5521	}
5522	Edit new board/<myboard> files
5523	Edit new include/configs/<myboard>.h
5524
5525	while (!accepted) {
5526		while (!running) {
5527			do {
5528				Add / modify source code;
5529			} until (compiles);
5530			Debug;
5531			if (clueless)
5532				email("Hi, I am having problems...");
5533		}
5534		Send patch file to the U-Boot email list;
5535		if (reasonable critiques)
5536			Incorporate improvements from email list code review;
5537		else
5538			Defend code as written;
5539	}
5540
5541	return 0;
5542}
5543
5544void no_more_time (int sig)
5545{
5546      hire_a_guru();
5547}
5548
5549
5550Coding Standards:
5551-----------------
5552
5553All contributions to U-Boot should conform to the Linux kernel
5554coding style; see the file "Documentation/CodingStyle" and the script
5555"scripts/Lindent" in your Linux kernel source directory.
5556
5557Source files originating from a different project (for example the
5558MTD subsystem) are generally exempt from these guidelines and are not
5559reformated to ease subsequent migration to newer versions of those
5560sources.
5561
5562Please note that U-Boot is implemented in C (and to some small parts in
5563Assembler); no C++ is used, so please do not use C++ style comments (//)
5564in your code.
5565
5566Please also stick to the following formatting rules:
5567- remove any trailing white space
5568- use TAB characters for indentation and vertical alignment, not spaces
5569- make sure NOT to use DOS '\r\n' line feeds
5570- do not add more than 2 consecutive empty lines to source files
5571- do not add trailing empty lines to source files
5572
5573Submissions which do not conform to the standards may be returned
5574with a request to reformat the changes.
5575
5576
5577Submitting Patches:
5578-------------------
5579
5580Since the number of patches for U-Boot is growing, we need to
5581establish some rules. Submissions which do not conform to these rules
5582may be rejected, even when they contain important and valuable stuff.
5583
5584Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5585
5586Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5587see http://lists.denx.de/mailman/listinfo/u-boot
5588
5589When you send a patch, please include the following information with
5590it:
5591
5592* For bug fixes: a description of the bug and how your patch fixes
5593  this bug. Please try to include a way of demonstrating that the
5594  patch actually fixes something.
5595
5596* For new features: a description of the feature and your
5597  implementation.
5598
5599* A CHANGELOG entry as plaintext (separate from the patch)
5600
5601* For major contributions, your entry to the CREDITS file
5602
5603* When you add support for a new board, don't forget to add this
5604  board to the MAINTAINERS file, too.
5605
5606* If your patch adds new configuration options, don't forget to
5607  document these in the README file.
5608
5609* The patch itself. If you are using git (which is *strongly*
5610  recommended) you can easily generate the patch using the
5611  "git format-patch". If you then use "git send-email" to send it to
5612  the U-Boot mailing list, you will avoid most of the common problems
5613  with some other mail clients.
5614
5615  If you cannot use git, use "diff -purN OLD NEW". If your version of
5616  diff does not support these options, then get the latest version of
5617  GNU diff.
5618
5619  The current directory when running this command shall be the parent
5620  directory of the U-Boot source tree (i. e. please make sure that
5621  your patch includes sufficient directory information for the
5622  affected files).
5623
5624  We prefer patches as plain text. MIME attachments are discouraged,
5625  and compressed attachments must not be used.
5626
5627* If one logical set of modifications affects or creates several
5628  files, all these changes shall be submitted in a SINGLE patch file.
5629
5630* Changesets that contain different, unrelated modifications shall be
5631  submitted as SEPARATE patches, one patch per changeset.
5632
5633
5634Notes:
5635
5636* Before sending the patch, run the MAKEALL script on your patched
5637  source tree and make sure that no errors or warnings are reported
5638  for any of the boards.
5639
5640* Keep your modifications to the necessary minimum: A patch
5641  containing several unrelated changes or arbitrary reformats will be
5642  returned with a request to re-formatting / split it.
5643
5644* If you modify existing code, make sure that your new code does not
5645  add to the memory footprint of the code ;-) Small is beautiful!
5646  When adding new features, these should compile conditionally only
5647  (using #ifdef), and the resulting code with the new feature
5648  disabled must not need more memory than the old code without your
5649  modification.
5650
5651* Remember that there is a size limit of 100 kB per message on the
5652  u-boot mailing list. Bigger patches will be moderated. If they are
5653  reasonable and not too big, they will be acknowledged. But patches
5654  bigger than the size limit should be avoided.
5655