xref: /rk3399_rockchip-uboot/README (revision 69d6cbe748ae13e6b728d2c28616a8c54b07f9c2)
1#
2# (C) Copyright 2000 - 2013
3# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
4#
5# SPDX-License-Identifier:	GPL-2.0+
6#
7
8Summary:
9========
10
11This directory contains the source code for U-Boot, a boot loader for
12Embedded boards based on PowerPC, ARM, MIPS and several other
13processors, which can be installed in a boot ROM and used to
14initialize and test the hardware or to download and run application
15code.
16
17The development of U-Boot is closely related to Linux: some parts of
18the source code originate in the Linux source tree, we have some
19header files in common, and special provision has been made to
20support booting of Linux images.
21
22Some attention has been paid to make this software easily
23configurable and extendable. For instance, all monitor commands are
24implemented with the same call interface, so that it's very easy to
25add new commands. Also, instead of permanently adding rarely used
26code (for instance hardware test utilities) to the monitor, you can
27load and run it dynamically.
28
29
30Status:
31=======
32
33In general, all boards for which a configuration option exists in the
34Makefile have been tested to some extent and can be considered
35"working". In fact, many of them are used in production systems.
36
37In case of problems see the CHANGELOG and CREDITS files to find out
38who contributed the specific port. The boards.cfg file lists board
39maintainers.
40
41Note: There is no CHANGELOG file in the actual U-Boot source tree;
42it can be created dynamically from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arm			Files generic to ARM architecture
136    /cpu		CPU specific files
137      /arm720t		Files specific to ARM 720 CPUs
138      /arm920t		Files specific to ARM 920 CPUs
139	/at91		Files specific to Atmel AT91RM9200 CPU
140	/imx		Files specific to Freescale MC9328 i.MX CPUs
141	/s3c24x0	Files specific to Samsung S3C24X0 CPUs
142      /arm925t		Files specific to ARM 925 CPUs
143      /arm926ejs	Files specific to ARM 926 CPUs
144      /arm1136		Files specific to ARM 1136 CPUs
145      /ixp		Files specific to Intel XScale IXP CPUs
146      /pxa		Files specific to Intel XScale PXA CPUs
147      /s3c44b0		Files specific to Samsung S3C44B0 CPUs
148      /sa1100		Files specific to Intel StrongARM SA1100 CPUs
149    /lib		Architecture specific library files
150  /avr32		Files generic to AVR32 architecture
151    /cpu		CPU specific files
152    /lib		Architecture specific library files
153  /blackfin		Files generic to Analog Devices Blackfin architecture
154    /cpu		CPU specific files
155    /lib		Architecture specific library files
156  /m68k			Files generic to m68k architecture
157    /cpu		CPU specific files
158      /mcf52x2		Files specific to Freescale ColdFire MCF52x2 CPUs
159      /mcf5227x		Files specific to Freescale ColdFire MCF5227x CPUs
160      /mcf532x		Files specific to Freescale ColdFire MCF5329 CPUs
161      /mcf5445x		Files specific to Freescale ColdFire MCF5445x CPUs
162      /mcf547x_8x	Files specific to Freescale ColdFire MCF547x_8x CPUs
163    /lib		Architecture specific library files
164  /microblaze		Files generic to microblaze architecture
165    /cpu		CPU specific files
166    /lib		Architecture specific library files
167  /mips			Files generic to MIPS architecture
168    /cpu		CPU specific files
169      /mips32		Files specific to MIPS32 CPUs
170      /xburst		Files specific to Ingenic XBurst CPUs
171    /lib		Architecture specific library files
172  /nds32		Files generic to NDS32 architecture
173    /cpu		CPU specific files
174      /n1213		Files specific to Andes Technology N1213 CPUs
175    /lib		Architecture specific library files
176  /nios2		Files generic to Altera NIOS2 architecture
177    /cpu		CPU specific files
178    /lib		Architecture specific library files
179  /openrisc		Files generic to OpenRISC architecture
180    /cpu		CPU specific files
181    /lib		Architecture specific library files
182  /powerpc		Files generic to PowerPC architecture
183    /cpu		CPU specific files
184      /74xx_7xx		Files specific to Freescale MPC74xx and 7xx CPUs
185      /mpc5xx		Files specific to Freescale MPC5xx CPUs
186      /mpc5xxx		Files specific to Freescale MPC5xxx CPUs
187      /mpc8xx		Files specific to Freescale MPC8xx CPUs
188      /mpc824x		Files specific to Freescale MPC824x CPUs
189      /mpc8260		Files specific to Freescale MPC8260 CPUs
190      /mpc85xx		Files specific to Freescale MPC85xx CPUs
191      /ppc4xx		Files specific to AMCC PowerPC 4xx CPUs
192    /lib		Architecture specific library files
193  /sh			Files generic to SH architecture
194    /cpu		CPU specific files
195      /sh2		Files specific to sh2 CPUs
196      /sh3		Files specific to sh3 CPUs
197      /sh4		Files specific to sh4 CPUs
198    /lib		Architecture specific library files
199  /sparc		Files generic to SPARC architecture
200    /cpu		CPU specific files
201      /leon2		Files specific to Gaisler LEON2 SPARC CPU
202      /leon3		Files specific to Gaisler LEON3 SPARC CPU
203    /lib		Architecture specific library files
204  /x86			Files generic to x86 architecture
205    /cpu		CPU specific files
206    /lib		Architecture specific library files
207/api			Machine/arch independent API for external apps
208/board			Board dependent files
209/common			Misc architecture independent functions
210/disk			Code for disk drive partition handling
211/doc			Documentation (don't expect too much)
212/drivers		Commonly used device drivers
213/dts			Contains Makefile for building internal U-Boot fdt.
214/examples		Example code for standalone applications, etc.
215/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
216/include		Header Files
217/lib			Files generic to all architectures
218  /libfdt		Library files to support flattened device trees
219  /lzma			Library files to support LZMA decompression
220  /lzo			Library files to support LZO decompression
221/net			Networking code
222/post			Power On Self Test
223/spl			Secondary Program Loader framework
224/tools			Tools to build S-Record or U-Boot images, etc.
225
226Software Configuration:
227=======================
228
229Configuration is usually done using C preprocessor defines; the
230rationale behind that is to avoid dead code whenever possible.
231
232There are two classes of configuration variables:
233
234* Configuration _OPTIONS_:
235  These are selectable by the user and have names beginning with
236  "CONFIG_".
237
238* Configuration _SETTINGS_:
239  These depend on the hardware etc. and should not be meddled with if
240  you don't know what you're doing; they have names beginning with
241  "CONFIG_SYS_".
242
243Later we will add a configuration tool - probably similar to or even
244identical to what's used for the Linux kernel. Right now, we have to
245do the configuration by hand, which means creating some symbolic
246links and editing some configuration files. We use the TQM8xxL boards
247as an example here.
248
249
250Selection of Processor Architecture and Board Type:
251---------------------------------------------------
252
253For all supported boards there are ready-to-use default
254configurations available; just type "make <board_name>_config".
255
256Example: For a TQM823L module type:
257
258	cd u-boot
259	make TQM823L_config
260
261For the Cogent platform, you need to specify the CPU type as well;
262e.g. "make cogent_mpc8xx_config". And also configure the cogent
263directory according to the instructions in cogent/README.
264
265
266Configuration Options:
267----------------------
268
269Configuration depends on the combination of board and CPU type; all
270such information is kept in a configuration file
271"include/configs/<board_name>.h".
272
273Example: For a TQM823L module, all configuration settings are in
274"include/configs/TQM823L.h".
275
276
277Many of the options are named exactly as the corresponding Linux
278kernel configuration options. The intention is to make it easier to
279build a config tool - later.
280
281
282The following options need to be configured:
283
284- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
285
286- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
287
288- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
289		Define exactly one, e.g. CONFIG_ATSTK1002
290
291- CPU Module Type: (if CONFIG_COGENT is defined)
292		Define exactly one of
293		CONFIG_CMA286_60_OLD
294--- FIXME --- not tested yet:
295		CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
296		CONFIG_CMA287_23, CONFIG_CMA287_50
297
298- Motherboard Type: (if CONFIG_COGENT is defined)
299		Define exactly one of
300		CONFIG_CMA101, CONFIG_CMA102
301
302- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
303		Define one or more of
304		CONFIG_CMA302
305
306- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
307		Define one or more of
308		CONFIG_LCD_HEARTBEAT	- update a character position on
309					  the LCD display every second with
310					  a "rotator" |\-/|\-/
311
312- Board flavour: (if CONFIG_MPC8260ADS is defined)
313		CONFIG_ADSTYPE
314		Possible values are:
315			CONFIG_SYS_8260ADS	- original MPC8260ADS
316			CONFIG_SYS_8266ADS	- MPC8266ADS
317			CONFIG_SYS_PQ2FADS	- PQ2FADS-ZU or PQ2FADS-VR
318			CONFIG_SYS_8272ADS	- MPC8272ADS
319
320- Marvell Family Member
321		CONFIG_SYS_MVFS		- define it if you want to enable
322					  multiple fs option at one time
323					  for marvell soc family
324
325- MPC824X Family Member (if CONFIG_MPC824X is defined)
326		Define exactly one of
327		CONFIG_MPC8240, CONFIG_MPC8245
328
329- 8xx CPU Options: (if using an MPC8xx CPU)
330		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
331					  get_gclk_freq() cannot work
332					  e.g. if there is no 32KHz
333					  reference PIT/RTC clock
334		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
335					  or XTAL/EXTAL)
336
337- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
338		CONFIG_SYS_8xx_CPUCLK_MIN
339		CONFIG_SYS_8xx_CPUCLK_MAX
340		CONFIG_8xx_CPUCLK_DEFAULT
341			See doc/README.MPC866
342
343		CONFIG_SYS_MEASURE_CPUCLK
344
345		Define this to measure the actual CPU clock instead
346		of relying on the correctness of the configured
347		values. Mostly useful for board bringup to make sure
348		the PLL is locked at the intended frequency. Note
349		that this requires a (stable) reference clock (32 kHz
350		RTC clock or CONFIG_SYS_8XX_XIN)
351
352		CONFIG_SYS_DELAYED_ICACHE
353
354		Define this option if you want to enable the
355		ICache only when Code runs from RAM.
356
357- 85xx CPU Options:
358		CONFIG_SYS_PPC64
359
360		Specifies that the core is a 64-bit PowerPC implementation (implements
361		the "64" category of the Power ISA). This is necessary for ePAPR
362		compliance, among other possible reasons.
363
364		CONFIG_SYS_FSL_TBCLK_DIV
365
366		Defines the core time base clock divider ratio compared to the
367		system clock.  On most PQ3 devices this is 8, on newer QorIQ
368		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
369
370		CONFIG_SYS_FSL_PCIE_COMPAT
371
372		Defines the string to utilize when trying to match PCIe device
373		tree nodes for the given platform.
374
375		CONFIG_SYS_PPC_E500_DEBUG_TLB
376
377		Enables a temporary TLB entry to be used during boot to work
378		around limitations in e500v1 and e500v2 external debugger
379		support. This reduces the portions of the boot code where
380		breakpoints and single stepping do not work.  The value of this
381		symbol should be set to the TLB1 entry to be used for this
382		purpose.
383
384		CONFIG_SYS_FSL_ERRATUM_A004510
385
386		Enables a workaround for erratum A004510.  If set,
387		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
388		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
389
390		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
391		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
392
393		Defines one or two SoC revisions (low 8 bits of SVR)
394		for which the A004510 workaround should be applied.
395
396		The rest of SVR is either not relevant to the decision
397		of whether the erratum is present (e.g. p2040 versus
398		p2041) or is implied by the build target, which controls
399		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
400
401		See Freescale App Note 4493 for more information about
402		this erratum.
403
404		CONFIG_A003399_NOR_WORKAROUND
405		Enables a workaround for IFC erratum A003399. It is only
406		requred during NOR boot.
407
408		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
409
410		This is the value to write into CCSR offset 0x18600
411		according to the A004510 workaround.
412
413		CONFIG_SYS_FSL_DSP_DDR_ADDR
414		This value denotes start offset of DDR memory which is
415		connected exclusively to the DSP cores.
416
417		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
418		This value denotes start offset of M2 memory
419		which is directly connected to the DSP core.
420
421		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
422		This value denotes start offset of M3 memory which is directly
423		connected to the DSP core.
424
425		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
426		This value denotes start offset of DSP CCSR space.
427
428		CONFIG_SYS_FSL_DDR_EMU
429		Specify emulator support for DDR. Some DDR features such as
430		deskew training are not available.
431
432- Generic CPU options:
433		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
434
435		Defines the endianess of the CPU. Implementation of those
436		values is arch specific.
437
438- Intel Monahans options:
439		CONFIG_SYS_MONAHANS_RUN_MODE_OSC_RATIO
440
441		Defines the Monahans run mode to oscillator
442		ratio. Valid values are 8, 16, 24, 31. The core
443		frequency is this value multiplied by 13 MHz.
444
445		CONFIG_SYS_MONAHANS_TURBO_RUN_MODE_RATIO
446
447		Defines the Monahans turbo mode to oscillator
448		ratio. Valid values are 1 (default if undefined) and
449		2. The core frequency as calculated above is multiplied
450		by this value.
451
452- MIPS CPU options:
453		CONFIG_SYS_INIT_SP_OFFSET
454
455		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
456		pointer. This is needed for the temporary stack before
457		relocation.
458
459		CONFIG_SYS_MIPS_CACHE_MODE
460
461		Cache operation mode for the MIPS CPU.
462		See also arch/mips/include/asm/mipsregs.h.
463		Possible values are:
464			CONF_CM_CACHABLE_NO_WA
465			CONF_CM_CACHABLE_WA
466			CONF_CM_UNCACHED
467			CONF_CM_CACHABLE_NONCOHERENT
468			CONF_CM_CACHABLE_CE
469			CONF_CM_CACHABLE_COW
470			CONF_CM_CACHABLE_CUW
471			CONF_CM_CACHABLE_ACCELERATED
472
473		CONFIG_SYS_XWAY_EBU_BOOTCFG
474
475		Special option for Lantiq XWAY SoCs for booting from NOR flash.
476		See also arch/mips/cpu/mips32/start.S.
477
478		CONFIG_XWAY_SWAP_BYTES
479
480		Enable compilation of tools/xway-swap-bytes needed for Lantiq
481		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
482		be swapped if a flash programmer is used.
483
484- ARM options:
485		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
486
487		Select high exception vectors of the ARM core, e.g., do not
488		clear the V bit of the c1 register of CP15.
489
490		CONFIG_SYS_THUMB_BUILD
491
492		Use this flag to build U-Boot using the Thumb instruction
493		set for ARM architectures. Thumb instruction set provides
494		better code density. For ARM architectures that support
495		Thumb2 this flag will result in Thumb2 code generated by
496		GCC.
497
498		CONFIG_ARM_ERRATA_716044
499		CONFIG_ARM_ERRATA_742230
500		CONFIG_ARM_ERRATA_743622
501		CONFIG_ARM_ERRATA_751472
502
503		If set, the workarounds for these ARM errata are applied early
504		during U-Boot startup. Note that these options force the
505		workarounds to be applied; no CPU-type/version detection
506		exists, unlike the similar options in the Linux kernel. Do not
507		set these options unless they apply!
508
509- CPU timer options:
510		CONFIG_SYS_HZ
511
512		The frequency of the timer returned by get_timer().
513		get_timer() must operate in milliseconds and this CONFIG
514		option must be set to 1000.
515
516- Linux Kernel Interface:
517		CONFIG_CLOCKS_IN_MHZ
518
519		U-Boot stores all clock information in Hz
520		internally. For binary compatibility with older Linux
521		kernels (which expect the clocks passed in the
522		bd_info data to be in MHz) the environment variable
523		"clocks_in_mhz" can be defined so that U-Boot
524		converts clock data to MHZ before passing it to the
525		Linux kernel.
526		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
527		"clocks_in_mhz=1" is automatically included in the
528		default environment.
529
530		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
531
532		When transferring memsize parameter to linux, some versions
533		expect it to be in bytes, others in MB.
534		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
535
536		CONFIG_OF_LIBFDT
537
538		New kernel versions are expecting firmware settings to be
539		passed using flattened device trees (based on open firmware
540		concepts).
541
542		CONFIG_OF_LIBFDT
543		 * New libfdt-based support
544		 * Adds the "fdt" command
545		 * The bootm command automatically updates the fdt
546
547		OF_CPU - The proper name of the cpus node (only required for
548			MPC512X and MPC5xxx based boards).
549		OF_SOC - The proper name of the soc node (only required for
550			MPC512X and MPC5xxx based boards).
551		OF_TBCLK - The timebase frequency.
552		OF_STDOUT_PATH - The path to the console device
553
554		boards with QUICC Engines require OF_QE to set UCC MAC
555		addresses
556
557		CONFIG_OF_BOARD_SETUP
558
559		Board code has addition modification that it wants to make
560		to the flat device tree before handing it off to the kernel
561
562		CONFIG_OF_BOOT_CPU
563
564		This define fills in the correct boot CPU in the boot
565		param header, the default value is zero if undefined.
566
567		CONFIG_OF_IDE_FIXUP
568
569		U-Boot can detect if an IDE device is present or not.
570		If not, and this new config option is activated, U-Boot
571		removes the ATA node from the DTS before booting Linux,
572		so the Linux IDE driver does not probe the device and
573		crash. This is needed for buggy hardware (uc101) where
574		no pull down resistor is connected to the signal IDE5V_DD7.
575
576		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
577
578		This setting is mandatory for all boards that have only one
579		machine type and must be used to specify the machine type
580		number as it appears in the ARM machine registry
581		(see http://www.arm.linux.org.uk/developer/machines/).
582		Only boards that have multiple machine types supported
583		in a single configuration file and the machine type is
584		runtime discoverable, do not have to use this setting.
585
586- vxWorks boot parameters:
587
588		bootvx constructs a valid bootline using the following
589		environments variables: bootfile, ipaddr, serverip, hostname.
590		It loads the vxWorks image pointed bootfile.
591
592		CONFIG_SYS_VXWORKS_BOOT_DEVICE - The vxworks device name
593		CONFIG_SYS_VXWORKS_MAC_PTR - Ethernet 6 byte MA -address
594		CONFIG_SYS_VXWORKS_SERVERNAME - Name of the server
595		CONFIG_SYS_VXWORKS_BOOT_ADDR - Address of boot parameters
596
597		CONFIG_SYS_VXWORKS_ADD_PARAMS
598
599		Add it at the end of the bootline. E.g "u=username pw=secret"
600
601		Note: If a "bootargs" environment is defined, it will overwride
602		the defaults discussed just above.
603
604- Cache Configuration:
605		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
606		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
607		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
608
609- Cache Configuration for ARM:
610		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
611				      controller
612		CONFIG_SYS_PL310_BASE - Physical base address of PL310
613					controller register space
614
615- Serial Ports:
616		CONFIG_PL010_SERIAL
617
618		Define this if you want support for Amba PrimeCell PL010 UARTs.
619
620		CONFIG_PL011_SERIAL
621
622		Define this if you want support for Amba PrimeCell PL011 UARTs.
623
624		CONFIG_PL011_CLOCK
625
626		If you have Amba PrimeCell PL011 UARTs, set this variable to
627		the clock speed of the UARTs.
628
629		CONFIG_PL01x_PORTS
630
631		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
632		define this to a list of base addresses for each (supported)
633		port. See e.g. include/configs/versatile.h
634
635		CONFIG_PL011_SERIAL_RLCR
636
637		Some vendor versions of PL011 serial ports (e.g. ST-Ericsson U8500)
638		have separate receive and transmit line control registers.  Set
639		this variable to initialize the extra register.
640
641		CONFIG_PL011_SERIAL_FLUSH_ON_INIT
642
643		On some platforms (e.g. U8500) U-Boot is loaded by a second stage
644		boot loader that has already initialized the UART.  Define this
645		variable to flush the UART at init time.
646
647
648- Console Interface:
649		Depending on board, define exactly one serial port
650		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
651		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
652		console by defining CONFIG_8xx_CONS_NONE
653
654		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
655		port routines must be defined elsewhere
656		(i.e. serial_init(), serial_getc(), ...)
657
658		CONFIG_CFB_CONSOLE
659		Enables console device for a color framebuffer. Needs following
660		defines (cf. smiLynxEM, i8042)
661			VIDEO_FB_LITTLE_ENDIAN	graphic memory organisation
662						(default big endian)
663			VIDEO_HW_RECTFILL	graphic chip supports
664						rectangle fill
665						(cf. smiLynxEM)
666			VIDEO_HW_BITBLT		graphic chip supports
667						bit-blit (cf. smiLynxEM)
668			VIDEO_VISIBLE_COLS	visible pixel columns
669						(cols=pitch)
670			VIDEO_VISIBLE_ROWS	visible pixel rows
671			VIDEO_PIXEL_SIZE	bytes per pixel
672			VIDEO_DATA_FORMAT	graphic data format
673						(0-5, cf. cfb_console.c)
674			VIDEO_FB_ADRS		framebuffer address
675			VIDEO_KBD_INIT_FCT	keyboard int fct
676						(i.e. i8042_kbd_init())
677			VIDEO_TSTC_FCT		test char fct
678						(i.e. i8042_tstc)
679			VIDEO_GETC_FCT		get char fct
680						(i.e. i8042_getc)
681			CONFIG_CONSOLE_CURSOR	cursor drawing on/off
682						(requires blink timer
683						cf. i8042.c)
684			CONFIG_SYS_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
685			CONFIG_CONSOLE_TIME	display time/date info in
686						upper right corner
687						(requires CONFIG_CMD_DATE)
688			CONFIG_VIDEO_LOGO	display Linux logo in
689						upper left corner
690			CONFIG_VIDEO_BMP_LOGO	use bmp_logo.h instead of
691						linux_logo.h for logo.
692						Requires CONFIG_VIDEO_LOGO
693			CONFIG_CONSOLE_EXTRA_INFO
694						additional board info beside
695						the logo
696
697		When CONFIG_CFB_CONSOLE_ANSI is defined, console will support
698		a limited number of ANSI escape sequences (cursor control,
699		erase functions and limited graphics rendition control).
700
701		When CONFIG_CFB_CONSOLE is defined, video console is
702		default i/o. Serial console can be forced with
703		environment 'console=serial'.
704
705		When CONFIG_SILENT_CONSOLE is defined, all console
706		messages (by U-Boot and Linux!) can be silenced with
707		the "silent" environment variable. See
708		doc/README.silent for more information.
709
710- Console Baudrate:
711		CONFIG_BAUDRATE - in bps
712		Select one of the baudrates listed in
713		CONFIG_SYS_BAUDRATE_TABLE, see below.
714		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
715
716- Console Rx buffer length
717		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
718		the maximum receive buffer length for the SMC.
719		This option is actual only for 82xx and 8xx possible.
720		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
721		must be defined, to setup the maximum idle timeout for
722		the SMC.
723
724- Pre-Console Buffer:
725		Prior to the console being initialised (i.e. serial UART
726		initialised etc) all console output is silently discarded.
727		Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
728		buffer any console messages prior to the console being
729		initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
730		bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
731		a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
732		bytes are output before the console is initialised, the
733		earlier bytes are discarded.
734
735		'Sane' compilers will generate smaller code if
736		CONFIG_PRE_CON_BUF_SZ is a power of 2
737
738- Safe printf() functions
739		Define CONFIG_SYS_VSNPRINTF to compile in safe versions of
740		the printf() functions. These are defined in
741		include/vsprintf.h and include snprintf(), vsnprintf() and
742		so on. Code size increase is approximately 300-500 bytes.
743		If this option is not given then these functions will
744		silently discard their buffer size argument - this means
745		you are not getting any overflow checking in this case.
746
747- Boot Delay:	CONFIG_BOOTDELAY - in seconds
748		Delay before automatically booting the default image;
749		set to -1 to disable autoboot.
750		set to -2 to autoboot with no delay and not check for abort
751		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
752
753		See doc/README.autoboot for these options that
754		work with CONFIG_BOOTDELAY. None are required.
755		CONFIG_BOOT_RETRY_TIME
756		CONFIG_BOOT_RETRY_MIN
757		CONFIG_AUTOBOOT_KEYED
758		CONFIG_AUTOBOOT_PROMPT
759		CONFIG_AUTOBOOT_DELAY_STR
760		CONFIG_AUTOBOOT_STOP_STR
761		CONFIG_AUTOBOOT_DELAY_STR2
762		CONFIG_AUTOBOOT_STOP_STR2
763		CONFIG_ZERO_BOOTDELAY_CHECK
764		CONFIG_RESET_TO_RETRY
765
766- Autoboot Command:
767		CONFIG_BOOTCOMMAND
768		Only needed when CONFIG_BOOTDELAY is enabled;
769		define a command string that is automatically executed
770		when no character is read on the console interface
771		within "Boot Delay" after reset.
772
773		CONFIG_BOOTARGS
774		This can be used to pass arguments to the bootm
775		command. The value of CONFIG_BOOTARGS goes into the
776		environment value "bootargs".
777
778		CONFIG_RAMBOOT and CONFIG_NFSBOOT
779		The value of these goes into the environment as
780		"ramboot" and "nfsboot" respectively, and can be used
781		as a convenience, when switching between booting from
782		RAM and NFS.
783
784- Pre-Boot Commands:
785		CONFIG_PREBOOT
786
787		When this option is #defined, the existence of the
788		environment variable "preboot" will be checked
789		immediately before starting the CONFIG_BOOTDELAY
790		countdown and/or running the auto-boot command resp.
791		entering interactive mode.
792
793		This feature is especially useful when "preboot" is
794		automatically generated or modified. For an example
795		see the LWMON board specific code: here "preboot" is
796		modified when the user holds down a certain
797		combination of keys on the (special) keyboard when
798		booting the systems
799
800- Serial Download Echo Mode:
801		CONFIG_LOADS_ECHO
802		If defined to 1, all characters received during a
803		serial download (using the "loads" command) are
804		echoed back. This might be needed by some terminal
805		emulations (like "cu"), but may as well just take
806		time on others. This setting #define's the initial
807		value of the "loads_echo" environment variable.
808
809- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
810		CONFIG_KGDB_BAUDRATE
811		Select one of the baudrates listed in
812		CONFIG_SYS_BAUDRATE_TABLE, see below.
813
814- Monitor Functions:
815		Monitor commands can be included or excluded
816		from the build by using the #include files
817		<config_cmd_all.h> and #undef'ing unwanted
818		commands, or using <config_cmd_default.h>
819		and augmenting with additional #define's
820		for wanted commands.
821
822		The default command configuration includes all commands
823		except those marked below with a "*".
824
825		CONFIG_CMD_ASKENV	* ask for env variable
826		CONFIG_CMD_BDI		  bdinfo
827		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
828		CONFIG_CMD_BMP		* BMP support
829		CONFIG_CMD_BSP		* Board specific commands
830		CONFIG_CMD_BOOTD	  bootd
831		CONFIG_CMD_CACHE	* icache, dcache
832		CONFIG_CMD_CONSOLE	  coninfo
833		CONFIG_CMD_CRC32	* crc32
834		CONFIG_CMD_DATE		* support for RTC, date/time...
835		CONFIG_CMD_DHCP		* DHCP support
836		CONFIG_CMD_DIAG		* Diagnostics
837		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
838		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
839		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
840		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
841		CONFIG_CMD_DTT		* Digital Therm and Thermostat
842		CONFIG_CMD_ECHO		  echo arguments
843		CONFIG_CMD_EDITENV	  edit env variable
844		CONFIG_CMD_EEPROM	* EEPROM read/write support
845		CONFIG_CMD_ELF		* bootelf, bootvx
846		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
847		CONFIG_CMD_ENV_FLAGS	* display details about env flags
848		CONFIG_CMD_EXPORTENV	* export the environment
849		CONFIG_CMD_EXT2		* ext2 command support
850		CONFIG_CMD_EXT4		* ext4 command support
851		CONFIG_CMD_SAVEENV	  saveenv
852		CONFIG_CMD_FDC		* Floppy Disk Support
853		CONFIG_CMD_FAT		* FAT command support
854		CONFIG_CMD_FDOS		* Dos diskette Support
855		CONFIG_CMD_FLASH	  flinfo, erase, protect
856		CONFIG_CMD_FPGA		  FPGA device initialization support
857		CONFIG_CMD_FUSE		* Device fuse support
858		CONFIG_CMD_GETTIME	* Get time since boot
859		CONFIG_CMD_GO		* the 'go' command (exec code)
860		CONFIG_CMD_GREPENV	* search environment
861		CONFIG_CMD_HASH		* calculate hash / digest
862		CONFIG_CMD_HWFLOW	* RTS/CTS hw flow control
863		CONFIG_CMD_I2C		* I2C serial bus support
864		CONFIG_CMD_IDE		* IDE harddisk support
865		CONFIG_CMD_IMI		  iminfo
866		CONFIG_CMD_IMLS		  List all images found in NOR flash
867		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
868		CONFIG_CMD_IMMAP	* IMMR dump support
869		CONFIG_CMD_IMPORTENV	* import an environment
870		CONFIG_CMD_INI		* import data from an ini file into the env
871		CONFIG_CMD_IRQ		* irqinfo
872		CONFIG_CMD_ITEST	  Integer/string test of 2 values
873		CONFIG_CMD_JFFS2	* JFFS2 Support
874		CONFIG_CMD_KGDB		* kgdb
875		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
876		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
877					  (169.254.*.*)
878		CONFIG_CMD_LOADB	  loadb
879		CONFIG_CMD_LOADS	  loads
880		CONFIG_CMD_MD5SUM	* print md5 message digest
881					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
882		CONFIG_CMD_MEMINFO	* Display detailed memory information
883		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
884					  loop, loopw
885		CONFIG_CMD_MEMTEST	* mtest
886		CONFIG_CMD_MISC		  Misc functions like sleep etc
887		CONFIG_CMD_MMC		* MMC memory mapped support
888		CONFIG_CMD_MII		* MII utility commands
889		CONFIG_CMD_MTDPARTS	* MTD partition support
890		CONFIG_CMD_NAND		* NAND support
891		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
892		CONFIG_CMD_NFS		  NFS support
893		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
894		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
895		CONFIG_CMD_PCI		* pciinfo
896		CONFIG_CMD_PCMCIA		* PCMCIA support
897		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
898					  host
899		CONFIG_CMD_PORTIO	* Port I/O
900		CONFIG_CMD_READ		* Read raw data from partition
901		CONFIG_CMD_REGINFO	* Register dump
902		CONFIG_CMD_RUN		  run command in env variable
903		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
904		CONFIG_CMD_SAVES	* save S record dump
905		CONFIG_CMD_SCSI		* SCSI Support
906		CONFIG_CMD_SDRAM	* print SDRAM configuration information
907					  (requires CONFIG_CMD_I2C)
908		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
909					  (4xx only)
910		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
911		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
912					  (requires CONFIG_CMD_MEMORY)
913		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
914		CONFIG_CMD_SOURCE	  "source" command Support
915		CONFIG_CMD_SPI		* SPI serial bus support
916		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
917		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
918		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
919		CONFIG_CMD_TIMER	* access to the system tick timer
920		CONFIG_CMD_USB		* USB support
921		CONFIG_CMD_CDP		* Cisco Discover Protocol support
922		CONFIG_CMD_MFSL		* Microblaze FSL support
923		CONFIG_CMD_XIMG		  Load part of Multi Image
924
925
926		EXAMPLE: If you want all functions except of network
927		support you can write:
928
929		#include "config_cmd_all.h"
930		#undef CONFIG_CMD_NET
931
932	Other Commands:
933		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
934
935	Note:	Don't enable the "icache" and "dcache" commands
936		(configuration option CONFIG_CMD_CACHE) unless you know
937		what you (and your U-Boot users) are doing. Data
938		cache cannot be enabled on systems like the 8xx or
939		8260 (where accesses to the IMMR region must be
940		uncached), and it cannot be disabled on all other
941		systems where we (mis-) use the data cache to hold an
942		initial stack and some data.
943
944
945		XXX - this list needs to get updated!
946
947- Regular expression support:
948		CONFIG_REGEX
949                If this variable is defined, U-Boot is linked against
950                the SLRE (Super Light Regular Expression) library,
951                which adds regex support to some commands, as for
952                example "env grep" and "setexpr".
953
954- Device tree:
955		CONFIG_OF_CONTROL
956		If this variable is defined, U-Boot will use a device tree
957		to configure its devices, instead of relying on statically
958		compiled #defines in the board file. This option is
959		experimental and only available on a few boards. The device
960		tree is available in the global data as gd->fdt_blob.
961
962		U-Boot needs to get its device tree from somewhere. This can
963		be done using one of the two options below:
964
965		CONFIG_OF_EMBED
966		If this variable is defined, U-Boot will embed a device tree
967		binary in its image. This device tree file should be in the
968		board directory and called <soc>-<board>.dts. The binary file
969		is then picked up in board_init_f() and made available through
970		the global data structure as gd->blob.
971
972		CONFIG_OF_SEPARATE
973		If this variable is defined, U-Boot will build a device tree
974		binary. It will be called u-boot.dtb. Architecture-specific
975		code will locate it at run-time. Generally this works by:
976
977			cat u-boot.bin u-boot.dtb >image.bin
978
979		and in fact, U-Boot does this for you, creating a file called
980		u-boot-dtb.bin which is useful in the common case. You can
981		still use the individual files if you need something more
982		exotic.
983
984- Watchdog:
985		CONFIG_WATCHDOG
986		If this variable is defined, it enables watchdog
987		support for the SoC. There must be support in the SoC
988		specific code for a watchdog. For the 8xx and 8260
989		CPUs, the SIU Watchdog feature is enabled in the SYPCR
990		register.  When supported for a specific SoC is
991		available, then no further board specific code should
992		be needed to use it.
993
994		CONFIG_HW_WATCHDOG
995		When using a watchdog circuitry external to the used
996		SoC, then define this variable and provide board
997		specific code for the "hw_watchdog_reset" function.
998
999- U-Boot Version:
1000		CONFIG_VERSION_VARIABLE
1001		If this variable is defined, an environment variable
1002		named "ver" is created by U-Boot showing the U-Boot
1003		version as printed by the "version" command.
1004		Any change to this variable will be reverted at the
1005		next reset.
1006
1007- Real-Time Clock:
1008
1009		When CONFIG_CMD_DATE is selected, the type of the RTC
1010		has to be selected, too. Define exactly one of the
1011		following options:
1012
1013		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1014		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1015		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1016		CONFIG_RTC_MC146818	- use MC146818 RTC
1017		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1018		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1019		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1020		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1021		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1022		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1023		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1024		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1025					  RV3029 RTC.
1026
1027		Note that if the RTC uses I2C, then the I2C interface
1028		must also be configured. See I2C Support, below.
1029
1030- GPIO Support:
1031		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1032		CONFIG_PCA953X_INFO	- enable pca953x info command
1033
1034		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1035		chip-ngpio pairs that tell the PCA953X driver the number of
1036		pins supported by a particular chip.
1037
1038		Note that if the GPIO device uses I2C, then the I2C interface
1039		must also be configured. See I2C Support, below.
1040
1041- Timestamp Support:
1042
1043		When CONFIG_TIMESTAMP is selected, the timestamp
1044		(date and time) of an image is printed by image
1045		commands like bootm or iminfo. This option is
1046		automatically enabled when you select CONFIG_CMD_DATE .
1047
1048- Partition Labels (disklabels) Supported:
1049		Zero or more of the following:
1050		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1051		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1052				       Intel architecture, USB sticks, etc.
1053		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1054		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1055				       bootloader.  Note 2TB partition limit; see
1056				       disk/part_efi.c
1057		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1058
1059		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1060		CONFIG_CMD_SCSI) you must configure support for at
1061		least one non-MTD partition type as well.
1062
1063- IDE Reset method:
1064		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1065		board configurations files but used nowhere!
1066
1067		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1068		be performed by calling the function
1069			ide_set_reset(int reset)
1070		which has to be defined in a board specific file
1071
1072- ATAPI Support:
1073		CONFIG_ATAPI
1074
1075		Set this to enable ATAPI support.
1076
1077- LBA48 Support
1078		CONFIG_LBA48
1079
1080		Set this to enable support for disks larger than 137GB
1081		Also look at CONFIG_SYS_64BIT_LBA.
1082		Whithout these , LBA48 support uses 32bit variables and will 'only'
1083		support disks up to 2.1TB.
1084
1085		CONFIG_SYS_64BIT_LBA:
1086			When enabled, makes the IDE subsystem use 64bit sector addresses.
1087			Default is 32bit.
1088
1089- SCSI Support:
1090		At the moment only there is only support for the
1091		SYM53C8XX SCSI controller; define
1092		CONFIG_SCSI_SYM53C8XX to enable it.
1093
1094		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1095		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1096		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1097		maximum numbers of LUNs, SCSI ID's and target
1098		devices.
1099		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1100
1101                The environment variable 'scsidevs' is set to the number of
1102                SCSI devices found during the last scan.
1103
1104- NETWORK Support (PCI):
1105		CONFIG_E1000
1106		Support for Intel 8254x/8257x gigabit chips.
1107
1108		CONFIG_E1000_SPI
1109		Utility code for direct access to the SPI bus on Intel 8257x.
1110		This does not do anything useful unless you set at least one
1111		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1112
1113		CONFIG_E1000_SPI_GENERIC
1114		Allow generic access to the SPI bus on the Intel 8257x, for
1115		example with the "sspi" command.
1116
1117		CONFIG_CMD_E1000
1118		Management command for E1000 devices.  When used on devices
1119		with SPI support you can reprogram the EEPROM from U-Boot.
1120
1121		CONFIG_E1000_FALLBACK_MAC
1122		default MAC for empty EEPROM after production.
1123
1124		CONFIG_EEPRO100
1125		Support for Intel 82557/82559/82559ER chips.
1126		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1127		write routine for first time initialisation.
1128
1129		CONFIG_TULIP
1130		Support for Digital 2114x chips.
1131		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1132		modem chip initialisation (KS8761/QS6611).
1133
1134		CONFIG_NATSEMI
1135		Support for National dp83815 chips.
1136
1137		CONFIG_NS8382X
1138		Support for National dp8382[01] gigabit chips.
1139
1140- NETWORK Support (other):
1141
1142		CONFIG_DRIVER_AT91EMAC
1143		Support for AT91RM9200 EMAC.
1144
1145			CONFIG_RMII
1146			Define this to use reduced MII inteface
1147
1148			CONFIG_DRIVER_AT91EMAC_QUIET
1149			If this defined, the driver is quiet.
1150			The driver doen't show link status messages.
1151
1152		CONFIG_CALXEDA_XGMAC
1153		Support for the Calxeda XGMAC device
1154
1155		CONFIG_LAN91C96
1156		Support for SMSC's LAN91C96 chips.
1157
1158			CONFIG_LAN91C96_BASE
1159			Define this to hold the physical address
1160			of the LAN91C96's I/O space
1161
1162			CONFIG_LAN91C96_USE_32_BIT
1163			Define this to enable 32 bit addressing
1164
1165		CONFIG_SMC91111
1166		Support for SMSC's LAN91C111 chip
1167
1168			CONFIG_SMC91111_BASE
1169			Define this to hold the physical address
1170			of the device (I/O space)
1171
1172			CONFIG_SMC_USE_32_BIT
1173			Define this if data bus is 32 bits
1174
1175			CONFIG_SMC_USE_IOFUNCS
1176			Define this to use i/o functions instead of macros
1177			(some hardware wont work with macros)
1178
1179		CONFIG_DRIVER_TI_EMAC
1180		Support for davinci emac
1181
1182			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1183			Define this if you have more then 3 PHYs.
1184
1185		CONFIG_FTGMAC100
1186		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1187
1188			CONFIG_FTGMAC100_EGIGA
1189			Define this to use GE link update with gigabit PHY.
1190			Define this if FTGMAC100 is connected to gigabit PHY.
1191			If your system has 10/100 PHY only, it might not occur
1192			wrong behavior. Because PHY usually return timeout or
1193			useless data when polling gigabit status and gigabit
1194			control registers. This behavior won't affect the
1195			correctnessof 10/100 link speed update.
1196
1197		CONFIG_SMC911X
1198		Support for SMSC's LAN911x and LAN921x chips
1199
1200			CONFIG_SMC911X_BASE
1201			Define this to hold the physical address
1202			of the device (I/O space)
1203
1204			CONFIG_SMC911X_32_BIT
1205			Define this if data bus is 32 bits
1206
1207			CONFIG_SMC911X_16_BIT
1208			Define this if data bus is 16 bits. If your processor
1209			automatically converts one 32 bit word to two 16 bit
1210			words you may also try CONFIG_SMC911X_32_BIT.
1211
1212		CONFIG_SH_ETHER
1213		Support for Renesas on-chip Ethernet controller
1214
1215			CONFIG_SH_ETHER_USE_PORT
1216			Define the number of ports to be used
1217
1218			CONFIG_SH_ETHER_PHY_ADDR
1219			Define the ETH PHY's address
1220
1221			CONFIG_SH_ETHER_CACHE_WRITEBACK
1222			If this option is set, the driver enables cache flush.
1223
1224- TPM Support:
1225		CONFIG_TPM
1226		Support TPM devices.
1227
1228		CONFIG_TPM_TIS_I2C
1229		Support for i2c bus TPM devices. Only one device
1230		per system is supported at this time.
1231
1232			CONFIG_TPM_TIS_I2C_BUS_NUMBER
1233			Define the the i2c bus number for the TPM device
1234
1235			CONFIG_TPM_TIS_I2C_SLAVE_ADDRESS
1236			Define the TPM's address on the i2c bus
1237
1238			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1239			Define the burst count bytes upper limit
1240
1241		CONFIG_TPM_ATMEL_TWI
1242		Support for Atmel TWI TPM device. Requires I2C support.
1243
1244		CONFIG_TPM_TIS_LPC
1245		Support for generic parallel port TPM devices. Only one device
1246		per system is supported at this time.
1247
1248			CONFIG_TPM_TIS_BASE_ADDRESS
1249			Base address where the generic TPM device is mapped
1250			to. Contemporary x86 systems usually map it at
1251			0xfed40000.
1252
1253		CONFIG_CMD_TPM
1254		Add tpm monitor functions.
1255		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1256		provides monitor access to authorized functions.
1257
1258		CONFIG_TPM
1259		Define this to enable the TPM support library which provides
1260		functional interfaces to some TPM commands.
1261		Requires support for a TPM device.
1262
1263		CONFIG_TPM_AUTH_SESSIONS
1264		Define this to enable authorized functions in the TPM library.
1265		Requires CONFIG_TPM and CONFIG_SHA1.
1266
1267- USB Support:
1268		At the moment only the UHCI host controller is
1269		supported (PIP405, MIP405, MPC5200); define
1270		CONFIG_USB_UHCI to enable it.
1271		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1272		and define CONFIG_USB_STORAGE to enable the USB
1273		storage devices.
1274		Note:
1275		Supported are USB Keyboards and USB Floppy drives
1276		(TEAC FD-05PUB).
1277		MPC5200 USB requires additional defines:
1278			CONFIG_USB_CLOCK
1279				for 528 MHz Clock: 0x0001bbbb
1280			CONFIG_PSC3_USB
1281				for USB on PSC3
1282			CONFIG_USB_CONFIG
1283				for differential drivers: 0x00001000
1284				for single ended drivers: 0x00005000
1285				for differential drivers on PSC3: 0x00000100
1286				for single ended drivers on PSC3: 0x00004100
1287			CONFIG_SYS_USB_EVENT_POLL
1288				May be defined to allow interrupt polling
1289				instead of using asynchronous interrupts
1290
1291		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1292		txfilltuning field in the EHCI controller on reset.
1293
1294		CONFIG_USB_HUB_MIN_POWER_ON_DELAY defines the minimum
1295		interval for usb hub power-on delay.(minimum 100msec)
1296
1297- USB Device:
1298		Define the below if you wish to use the USB console.
1299		Once firmware is rebuilt from a serial console issue the
1300		command "setenv stdin usbtty; setenv stdout usbtty" and
1301		attach your USB cable. The Unix command "dmesg" should print
1302		it has found a new device. The environment variable usbtty
1303		can be set to gserial or cdc_acm to enable your device to
1304		appear to a USB host as a Linux gserial device or a
1305		Common Device Class Abstract Control Model serial device.
1306		If you select usbtty = gserial you should be able to enumerate
1307		a Linux host by
1308		# modprobe usbserial vendor=0xVendorID product=0xProductID
1309		else if using cdc_acm, simply setting the environment
1310		variable usbtty to be cdc_acm should suffice. The following
1311		might be defined in YourBoardName.h
1312
1313			CONFIG_USB_DEVICE
1314			Define this to build a UDC device
1315
1316			CONFIG_USB_TTY
1317			Define this to have a tty type of device available to
1318			talk to the UDC device
1319
1320			CONFIG_USBD_HS
1321			Define this to enable the high speed support for usb
1322			device and usbtty. If this feature is enabled, a routine
1323			int is_usbd_high_speed(void)
1324			also needs to be defined by the driver to dynamically poll
1325			whether the enumeration has succeded at high speed or full
1326			speed.
1327
1328			CONFIG_SYS_CONSOLE_IS_IN_ENV
1329			Define this if you want stdin, stdout &/or stderr to
1330			be set to usbtty.
1331
1332			mpc8xx:
1333				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1334				Derive USB clock from external clock "blah"
1335				- CONFIG_SYS_USB_EXTC_CLK 0x02
1336
1337				CONFIG_SYS_USB_BRG_CLK 0xBLAH
1338				Derive USB clock from brgclk
1339				- CONFIG_SYS_USB_BRG_CLK 0x04
1340
1341		If you have a USB-IF assigned VendorID then you may wish to
1342		define your own vendor specific values either in BoardName.h
1343		or directly in usbd_vendor_info.h. If you don't define
1344		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1345		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1346		should pretend to be a Linux device to it's target host.
1347
1348			CONFIG_USBD_MANUFACTURER
1349			Define this string as the name of your company for
1350			- CONFIG_USBD_MANUFACTURER "my company"
1351
1352			CONFIG_USBD_PRODUCT_NAME
1353			Define this string as the name of your product
1354			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1355
1356			CONFIG_USBD_VENDORID
1357			Define this as your assigned Vendor ID from the USB
1358			Implementors Forum. This *must* be a genuine Vendor ID
1359			to avoid polluting the USB namespace.
1360			- CONFIG_USBD_VENDORID 0xFFFF
1361
1362			CONFIG_USBD_PRODUCTID
1363			Define this as the unique Product ID
1364			for your device
1365			- CONFIG_USBD_PRODUCTID 0xFFFF
1366
1367- ULPI Layer Support:
1368		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1369		the generic ULPI layer. The generic layer accesses the ULPI PHY
1370		via the platform viewport, so you need both the genric layer and
1371		the viewport enabled. Currently only Chipidea/ARC based
1372		viewport is supported.
1373		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1374		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1375		If your ULPI phy needs a different reference clock than the
1376		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1377		the appropriate value in Hz.
1378
1379- MMC Support:
1380		The MMC controller on the Intel PXA is supported. To
1381		enable this define CONFIG_MMC. The MMC can be
1382		accessed from the boot prompt by mapping the device
1383		to physical memory similar to flash. Command line is
1384		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1385		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1386
1387		CONFIG_SH_MMCIF
1388		Support for Renesas on-chip MMCIF controller
1389
1390			CONFIG_SH_MMCIF_ADDR
1391			Define the base address of MMCIF registers
1392
1393			CONFIG_SH_MMCIF_CLK
1394			Define the clock frequency for MMCIF
1395
1396- USB Device Firmware Update (DFU) class support:
1397		CONFIG_DFU_FUNCTION
1398		This enables the USB portion of the DFU USB class
1399
1400		CONFIG_CMD_DFU
1401		This enables the command "dfu" which is used to have
1402		U-Boot create a DFU class device via USB.  This command
1403		requires that the "dfu_alt_info" environment variable be
1404		set and define the alt settings to expose to the host.
1405
1406		CONFIG_DFU_MMC
1407		This enables support for exposing (e)MMC devices via DFU.
1408
1409		CONFIG_DFU_NAND
1410		This enables support for exposing NAND devices via DFU.
1411
1412		CONFIG_DFU_RAM
1413		This enables support for exposing RAM via DFU.
1414		Note: DFU spec refer to non-volatile memory usage, but
1415		allow usages beyond the scope of spec - here RAM usage,
1416		one that would help mostly the developer.
1417
1418		CONFIG_SYS_DFU_DATA_BUF_SIZE
1419		Dfu transfer uses a buffer before writing data to the
1420		raw storage device. Make the size (in bytes) of this buffer
1421		configurable. The size of this buffer is also configurable
1422		through the "dfu_bufsiz" environment variable.
1423
1424		CONFIG_SYS_DFU_MAX_FILE_SIZE
1425		When updating files rather than the raw storage device,
1426		we use a static buffer to copy the file into and then write
1427		the buffer once we've been given the whole file.  Define
1428		this to the maximum filesize (in bytes) for the buffer.
1429		Default is 4 MiB if undefined.
1430
1431- Journaling Flash filesystem support:
1432		CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
1433		CONFIG_JFFS2_NAND_DEV
1434		Define these for a default partition on a NAND device
1435
1436		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1437		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1438		Define these for a default partition on a NOR device
1439
1440		CONFIG_SYS_JFFS_CUSTOM_PART
1441		Define this to create an own partition. You have to provide a
1442		function struct part_info* jffs2_part_info(int part_num)
1443
1444		If you define only one JFFS2 partition you may also want to
1445		#define CONFIG_SYS_JFFS_SINGLE_PART	1
1446		to disable the command chpart. This is the default when you
1447		have not defined a custom partition
1448
1449- FAT(File Allocation Table) filesystem write function support:
1450		CONFIG_FAT_WRITE
1451
1452		Define this to enable support for saving memory data as a
1453		file in FAT formatted partition.
1454
1455		This will also enable the command "fatwrite" enabling the
1456		user to write files to FAT.
1457
1458CBFS (Coreboot Filesystem) support
1459		CONFIG_CMD_CBFS
1460
1461		Define this to enable support for reading from a Coreboot
1462		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
1463		and cbfsload.
1464
1465- Keyboard Support:
1466		CONFIG_ISA_KEYBOARD
1467
1468		Define this to enable standard (PC-Style) keyboard
1469		support
1470
1471		CONFIG_I8042_KBD
1472		Standard PC keyboard driver with US (is default) and
1473		GERMAN key layout (switch via environment 'keymap=de') support.
1474		Export function i8042_kbd_init, i8042_tstc and i8042_getc
1475		for cfb_console. Supports cursor blinking.
1476
1477		CONFIG_CROS_EC_KEYB
1478		Enables a Chrome OS keyboard using the CROS_EC interface.
1479		This uses CROS_EC to communicate with a second microcontroller
1480		which provides key scans on request.
1481
1482- Video support:
1483		CONFIG_VIDEO
1484
1485		Define this to enable video support (for output to
1486		video).
1487
1488		CONFIG_VIDEO_CT69000
1489
1490		Enable Chips & Technologies 69000 Video chip
1491
1492		CONFIG_VIDEO_SMI_LYNXEM
1493		Enable Silicon Motion SMI 712/710/810 Video chip. The
1494		video output is selected via environment 'videoout'
1495		(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
1496		assumed.
1497
1498		For the CT69000 and SMI_LYNXEM drivers, videomode is
1499		selected via environment 'videomode'. Two different ways
1500		are possible:
1501		- "videomode=num"   'num' is a standard LiLo mode numbers.
1502		Following standard modes are supported	(* is default):
1503
1504		      Colors	640x480 800x600 1024x768 1152x864 1280x1024
1505		-------------+---------------------------------------------
1506		      8 bits |	0x301*	0x303	 0x305	  0x161	    0x307
1507		     15 bits |	0x310	0x313	 0x316	  0x162	    0x319
1508		     16 bits |	0x311	0x314	 0x317	  0x163	    0x31A
1509		     24 bits |	0x312	0x315	 0x318	    ?	    0x31B
1510		-------------+---------------------------------------------
1511		(i.e. setenv videomode 317; saveenv; reset;)
1512
1513		- "videomode=bootargs" all the video parameters are parsed
1514		from the bootargs. (See drivers/video/videomodes.c)
1515
1516
1517		CONFIG_VIDEO_SED13806
1518		Enable Epson SED13806 driver. This driver supports 8bpp
1519		and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
1520		or CONFIG_VIDEO_SED13806_16BPP
1521
1522		CONFIG_FSL_DIU_FB
1523		Enable the Freescale DIU video driver.	Reference boards for
1524		SOCs that have a DIU should define this macro to enable DIU
1525		support, and should also define these other macros:
1526
1527			CONFIG_SYS_DIU_ADDR
1528			CONFIG_VIDEO
1529			CONFIG_CMD_BMP
1530			CONFIG_CFB_CONSOLE
1531			CONFIG_VIDEO_SW_CURSOR
1532			CONFIG_VGA_AS_SINGLE_DEVICE
1533			CONFIG_VIDEO_LOGO
1534			CONFIG_VIDEO_BMP_LOGO
1535
1536		The DIU driver will look for the 'video-mode' environment
1537		variable, and if defined, enable the DIU as a console during
1538		boot.  See the documentation file README.video for a
1539		description of this variable.
1540
1541		CONFIG_VIDEO_VGA
1542
1543		Enable the VGA video / BIOS for x86. The alternative if you
1544		are using coreboot is to use the coreboot frame buffer
1545		driver.
1546
1547
1548- Keyboard Support:
1549		CONFIG_KEYBOARD
1550
1551		Define this to enable a custom keyboard support.
1552		This simply calls drv_keyboard_init() which must be
1553		defined in your board-specific files.
1554		The only board using this so far is RBC823.
1555
1556- LCD Support:	CONFIG_LCD
1557
1558		Define this to enable LCD support (for output to LCD
1559		display); also select one of the supported displays
1560		by defining one of these:
1561
1562		CONFIG_ATMEL_LCD:
1563
1564			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1565
1566		CONFIG_NEC_NL6448AC33:
1567
1568			NEC NL6448AC33-18. Active, color, single scan.
1569
1570		CONFIG_NEC_NL6448BC20
1571
1572			NEC NL6448BC20-08. 6.5", 640x480.
1573			Active, color, single scan.
1574
1575		CONFIG_NEC_NL6448BC33_54
1576
1577			NEC NL6448BC33-54. 10.4", 640x480.
1578			Active, color, single scan.
1579
1580		CONFIG_SHARP_16x9
1581
1582			Sharp 320x240. Active, color, single scan.
1583			It isn't 16x9, and I am not sure what it is.
1584
1585		CONFIG_SHARP_LQ64D341
1586
1587			Sharp LQ64D341 display, 640x480.
1588			Active, color, single scan.
1589
1590		CONFIG_HLD1045
1591
1592			HLD1045 display, 640x480.
1593			Active, color, single scan.
1594
1595		CONFIG_OPTREX_BW
1596
1597			Optrex	 CBL50840-2 NF-FW 99 22 M5
1598			or
1599			Hitachi	 LMG6912RPFC-00T
1600			or
1601			Hitachi	 SP14Q002
1602
1603			320x240. Black & white.
1604
1605		Normally display is black on white background; define
1606		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
1607
1608		CONFIG_LCD_ALIGNMENT
1609
1610		Normally the LCD is page-aligned (tyically 4KB). If this is
1611		defined then the LCD will be aligned to this value instead.
1612		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1613		here, since it is cheaper to change data cache settings on
1614		a per-section basis.
1615
1616		CONFIG_CONSOLE_SCROLL_LINES
1617
1618		When the console need to be scrolled, this is the number of
1619		lines to scroll by. It defaults to 1. Increasing this makes
1620		the console jump but can help speed up operation when scrolling
1621		is slow.
1622
1623		CONFIG_LCD_BMP_RLE8
1624
1625		Support drawing of RLE8-compressed bitmaps on the LCD.
1626
1627		CONFIG_I2C_EDID
1628
1629		Enables an 'i2c edid' command which can read EDID
1630		information over I2C from an attached LCD display.
1631
1632- Splash Screen Support: CONFIG_SPLASH_SCREEN
1633
1634		If this option is set, the environment is checked for
1635		a variable "splashimage". If found, the usual display
1636		of logo, copyright and system information on the LCD
1637		is suppressed and the BMP image at the address
1638		specified in "splashimage" is loaded instead. The
1639		console is redirected to the "nulldev", too. This
1640		allows for a "silent" boot where a splash screen is
1641		loaded very quickly after power-on.
1642
1643		CONFIG_SPLASHIMAGE_GUARD
1644
1645		If this option is set, then U-Boot will prevent the environment
1646		variable "splashimage" from being set to a problematic address
1647		(see README.displaying-bmps and README.arm-unaligned-accesses).
1648		This option is useful for targets where, due to alignment
1649		restrictions, an improperly aligned BMP image will cause a data
1650		abort. If you think you will not have problems with unaligned
1651		accesses (for example because your toolchain prevents them)
1652		there is no need to set this option.
1653
1654		CONFIG_SPLASH_SCREEN_ALIGN
1655
1656		If this option is set the splash image can be freely positioned
1657		on the screen. Environment variable "splashpos" specifies the
1658		position as "x,y". If a positive number is given it is used as
1659		number of pixel from left/top. If a negative number is given it
1660		is used as number of pixel from right/bottom. You can also
1661		specify 'm' for centering the image.
1662
1663		Example:
1664		setenv splashpos m,m
1665			=> image at center of screen
1666
1667		setenv splashpos 30,20
1668			=> image at x = 30 and y = 20
1669
1670		setenv splashpos -10,m
1671			=> vertically centered image
1672			   at x = dspWidth - bmpWidth - 9
1673
1674- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1675
1676		If this option is set, additionally to standard BMP
1677		images, gzipped BMP images can be displayed via the
1678		splashscreen support or the bmp command.
1679
1680- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1681
1682		If this option is set, 8-bit RLE compressed BMP images
1683		can be displayed via the splashscreen support or the
1684		bmp command.
1685
1686- Do compresssing for memory range:
1687		CONFIG_CMD_ZIP
1688
1689		If this option is set, it would use zlib deflate method
1690		to compress the specified memory at its best effort.
1691
1692- Compression support:
1693		CONFIG_GZIP
1694
1695		Enabled by default to support gzip compressed images.
1696
1697		CONFIG_BZIP2
1698
1699		If this option is set, support for bzip2 compressed
1700		images is included. If not, only uncompressed and gzip
1701		compressed images are supported.
1702
1703		NOTE: the bzip2 algorithm requires a lot of RAM, so
1704		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1705		be at least 4MB.
1706
1707		CONFIG_LZMA
1708
1709		If this option is set, support for lzma compressed
1710		images is included.
1711
1712		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1713		requires an amount of dynamic memory that is given by the
1714		formula:
1715
1716			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1717
1718		Where lc and lp stand for, respectively, Literal context bits
1719		and Literal pos bits.
1720
1721		This value is upper-bounded by 14MB in the worst case. Anyway,
1722		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1723		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1724		a very small buffer.
1725
1726		Use the lzmainfo tool to determinate the lc and lp values and
1727		then calculate the amount of needed dynamic memory (ensuring
1728		the appropriate CONFIG_SYS_MALLOC_LEN value).
1729
1730		CONFIG_LZO
1731
1732		If this option is set, support for LZO compressed images
1733		is included.
1734
1735- MII/PHY support:
1736		CONFIG_PHY_ADDR
1737
1738		The address of PHY on MII bus.
1739
1740		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1741
1742		The clock frequency of the MII bus
1743
1744		CONFIG_PHY_GIGE
1745
1746		If this option is set, support for speed/duplex
1747		detection of gigabit PHY is included.
1748
1749		CONFIG_PHY_RESET_DELAY
1750
1751		Some PHY like Intel LXT971A need extra delay after
1752		reset before any MII register access is possible.
1753		For such PHY, set this option to the usec delay
1754		required. (minimum 300usec for LXT971A)
1755
1756		CONFIG_PHY_CMD_DELAY (ppc4xx)
1757
1758		Some PHY like Intel LXT971A need extra delay after
1759		command issued before MII status register can be read
1760
1761- Ethernet address:
1762		CONFIG_ETHADDR
1763		CONFIG_ETH1ADDR
1764		CONFIG_ETH2ADDR
1765		CONFIG_ETH3ADDR
1766		CONFIG_ETH4ADDR
1767		CONFIG_ETH5ADDR
1768
1769		Define a default value for Ethernet address to use
1770		for the respective Ethernet interface, in case this
1771		is not determined automatically.
1772
1773- IP address:
1774		CONFIG_IPADDR
1775
1776		Define a default value for the IP address to use for
1777		the default Ethernet interface, in case this is not
1778		determined through e.g. bootp.
1779		(Environment variable "ipaddr")
1780
1781- Server IP address:
1782		CONFIG_SERVERIP
1783
1784		Defines a default value for the IP address of a TFTP
1785		server to contact when using the "tftboot" command.
1786		(Environment variable "serverip")
1787
1788		CONFIG_KEEP_SERVERADDR
1789
1790		Keeps the server's MAC address, in the env 'serveraddr'
1791		for passing to bootargs (like Linux's netconsole option)
1792
1793- Gateway IP address:
1794		CONFIG_GATEWAYIP
1795
1796		Defines a default value for the IP address of the
1797		default router where packets to other networks are
1798		sent to.
1799		(Environment variable "gatewayip")
1800
1801- Subnet mask:
1802		CONFIG_NETMASK
1803
1804		Defines a default value for the subnet mask (or
1805		routing prefix) which is used to determine if an IP
1806		address belongs to the local subnet or needs to be
1807		forwarded through a router.
1808		(Environment variable "netmask")
1809
1810- Multicast TFTP Mode:
1811		CONFIG_MCAST_TFTP
1812
1813		Defines whether you want to support multicast TFTP as per
1814		rfc-2090; for example to work with atftp.  Lets lots of targets
1815		tftp down the same boot image concurrently.  Note: the Ethernet
1816		driver in use must provide a function: mcast() to join/leave a
1817		multicast group.
1818
1819- BOOTP Recovery Mode:
1820		CONFIG_BOOTP_RANDOM_DELAY
1821
1822		If you have many targets in a network that try to
1823		boot using BOOTP, you may want to avoid that all
1824		systems send out BOOTP requests at precisely the same
1825		moment (which would happen for instance at recovery
1826		from a power failure, when all systems will try to
1827		boot, thus flooding the BOOTP server. Defining
1828		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1829		inserted before sending out BOOTP requests. The
1830		following delays are inserted then:
1831
1832		1st BOOTP request:	delay 0 ... 1 sec
1833		2nd BOOTP request:	delay 0 ... 2 sec
1834		3rd BOOTP request:	delay 0 ... 4 sec
1835		4th and following
1836		BOOTP requests:		delay 0 ... 8 sec
1837
1838- DHCP Advanced Options:
1839		You can fine tune the DHCP functionality by defining
1840		CONFIG_BOOTP_* symbols:
1841
1842		CONFIG_BOOTP_SUBNETMASK
1843		CONFIG_BOOTP_GATEWAY
1844		CONFIG_BOOTP_HOSTNAME
1845		CONFIG_BOOTP_NISDOMAIN
1846		CONFIG_BOOTP_BOOTPATH
1847		CONFIG_BOOTP_BOOTFILESIZE
1848		CONFIG_BOOTP_DNS
1849		CONFIG_BOOTP_DNS2
1850		CONFIG_BOOTP_SEND_HOSTNAME
1851		CONFIG_BOOTP_NTPSERVER
1852		CONFIG_BOOTP_TIMEOFFSET
1853		CONFIG_BOOTP_VENDOREX
1854		CONFIG_BOOTP_MAY_FAIL
1855
1856		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1857		environment variable, not the BOOTP server.
1858
1859		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1860		after the configured retry count, the call will fail
1861		instead of starting over.  This can be used to fail over
1862		to Link-local IP address configuration if the DHCP server
1863		is not available.
1864
1865		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1866		serverip from a DHCP server, it is possible that more
1867		than one DNS serverip is offered to the client.
1868		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1869		serverip will be stored in the additional environment
1870		variable "dnsip2". The first DNS serverip is always
1871		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1872		is defined.
1873
1874		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1875		to do a dynamic update of a DNS server. To do this, they
1876		need the hostname of the DHCP requester.
1877		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1878		of the "hostname" environment variable is passed as
1879		option 12 to the DHCP server.
1880
1881		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1882
1883		A 32bit value in microseconds for a delay between
1884		receiving a "DHCP Offer" and sending the "DHCP Request".
1885		This fixes a problem with certain DHCP servers that don't
1886		respond 100% of the time to a "DHCP request". E.g. On an
1887		AT91RM9200 processor running at 180MHz, this delay needed
1888		to be *at least* 15,000 usec before a Windows Server 2003
1889		DHCP server would reply 100% of the time. I recommend at
1890		least 50,000 usec to be safe. The alternative is to hope
1891		that one of the retries will be successful but note that
1892		the DHCP timeout and retry process takes a longer than
1893		this delay.
1894
1895 - Link-local IP address negotiation:
1896		Negotiate with other link-local clients on the local network
1897		for an address that doesn't require explicit configuration.
1898		This is especially useful if a DHCP server cannot be guaranteed
1899		to exist in all environments that the device must operate.
1900
1901		See doc/README.link-local for more information.
1902
1903 - CDP Options:
1904		CONFIG_CDP_DEVICE_ID
1905
1906		The device id used in CDP trigger frames.
1907
1908		CONFIG_CDP_DEVICE_ID_PREFIX
1909
1910		A two character string which is prefixed to the MAC address
1911		of the device.
1912
1913		CONFIG_CDP_PORT_ID
1914
1915		A printf format string which contains the ascii name of
1916		the port. Normally is set to "eth%d" which sets
1917		eth0 for the first Ethernet, eth1 for the second etc.
1918
1919		CONFIG_CDP_CAPABILITIES
1920
1921		A 32bit integer which indicates the device capabilities;
1922		0x00000010 for a normal host which does not forwards.
1923
1924		CONFIG_CDP_VERSION
1925
1926		An ascii string containing the version of the software.
1927
1928		CONFIG_CDP_PLATFORM
1929
1930		An ascii string containing the name of the platform.
1931
1932		CONFIG_CDP_TRIGGER
1933
1934		A 32bit integer sent on the trigger.
1935
1936		CONFIG_CDP_POWER_CONSUMPTION
1937
1938		A 16bit integer containing the power consumption of the
1939		device in .1 of milliwatts.
1940
1941		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1942
1943		A byte containing the id of the VLAN.
1944
1945- Status LED:	CONFIG_STATUS_LED
1946
1947		Several configurations allow to display the current
1948		status using a LED. For instance, the LED will blink
1949		fast while running U-Boot code, stop blinking as
1950		soon as a reply to a BOOTP request was received, and
1951		start blinking slow once the Linux kernel is running
1952		(supported by a status LED driver in the Linux
1953		kernel). Defining CONFIG_STATUS_LED enables this
1954		feature in U-Boot.
1955
1956- CAN Support:	CONFIG_CAN_DRIVER
1957
1958		Defining CONFIG_CAN_DRIVER enables CAN driver support
1959		on those systems that support this (optional)
1960		feature, like the TQM8xxL modules.
1961
1962- I2C Support:	CONFIG_SYS_I2C
1963
1964		This enable the NEW i2c subsystem, and will allow you to use
1965		i2c commands at the u-boot command line (as long as you set
1966		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1967		based realtime clock chips or other i2c devices. See
1968		common/cmd_i2c.c for a description of the command line
1969		interface.
1970
1971		ported i2c driver to the new framework:
1972		- drivers/i2c/soft_i2c.c:
1973		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1974		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1975		    for defining speed and slave address
1976		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1977		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1978		    for defining speed and slave address
1979		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1980		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1981		    for defining speed and slave address
1982		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1983		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1984		    for defining speed and slave address
1985
1986		- drivers/i2c/fsl_i2c.c:
1987		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1988		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1989		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1990		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1991		    bus.
1992                  - If your board supports a second fsl i2c bus, define
1993		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1994		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1995		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1996		    second bus.
1997
1998		- drivers/i2c/tegra_i2c.c:
1999		 - activate this driver with CONFIG_SYS_I2C_TEGRA
2000		 - This driver adds 4 i2c buses with a fix speed from
2001		   100000 and the slave addr 0!
2002
2003		- drivers/i2c/ppc4xx_i2c.c
2004		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2005		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2006		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2007
2008		additional defines:
2009
2010		CONFIG_SYS_NUM_I2C_BUSES
2011		Hold the number of i2c busses you want to use. If you
2012		don't use/have i2c muxes on your i2c bus, this
2013		is equal to CONFIG_SYS_NUM_I2C_ADAPTERS, and you can
2014		omit this define.
2015
2016		CONFIG_SYS_I2C_DIRECT_BUS
2017		define this, if you don't use i2c muxes on your hardware.
2018		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2019		omit this define.
2020
2021		CONFIG_SYS_I2C_MAX_HOPS
2022		define how many muxes are maximal consecutively connected
2023		on one i2c bus. If you not use i2c muxes, omit this
2024		define.
2025
2026		CONFIG_SYS_I2C_BUSES
2027		hold a list of busses you want to use, only used if
2028		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2029		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2030		CONFIG_SYS_NUM_I2C_BUSES = 9:
2031
2032		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2033					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2034					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2035					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2036					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2037					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2038					{1, {I2C_NULL_HOP}}, \
2039					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2040					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2041					}
2042
2043		which defines
2044			bus 0 on adapter 0 without a mux
2045			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2046			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2047			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2048			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2049			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2050			bus 6 on adapter 1 without a mux
2051			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2052			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2053
2054		If you do not have i2c muxes on your board, omit this define.
2055
2056- Legacy I2C Support:	CONFIG_HARD_I2C
2057
2058		NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
2059		provides the following compelling advantages:
2060
2061		- more than one i2c adapter is usable
2062		- approved multibus support
2063		- better i2c mux support
2064
2065		** Please consider updating your I2C driver now. **
2066
2067		These enable legacy I2C serial bus commands. Defining
2068		CONFIG_HARD_I2C will include the appropriate I2C driver
2069		for the selected CPU.
2070
2071		This will allow you to use i2c commands at the u-boot
2072		command line (as long as you set CONFIG_CMD_I2C in
2073		CONFIG_COMMANDS) and communicate with i2c based realtime
2074		clock chips. See common/cmd_i2c.c for a description of the
2075		command line interface.
2076
2077		CONFIG_HARD_I2C selects a hardware I2C controller.
2078
2079		There are several other quantities that must also be
2080		defined when you define CONFIG_HARD_I2C.
2081
2082		In both cases you will need to define CONFIG_SYS_I2C_SPEED
2083		to be the frequency (in Hz) at which you wish your i2c bus
2084		to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
2085		the CPU's i2c node address).
2086
2087		Now, the u-boot i2c code for the mpc8xx
2088		(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
2089		and so its address should therefore be cleared to 0 (See,
2090		eg, MPC823e User's Manual p.16-473). So, set
2091		CONFIG_SYS_I2C_SLAVE to 0.
2092
2093		CONFIG_SYS_I2C_INIT_MPC5XXX
2094
2095		When a board is reset during an i2c bus transfer
2096		chips might think that the current transfer is still
2097		in progress.  Reset the slave devices by sending start
2098		commands until the slave device responds.
2099
2100		That's all that's required for CONFIG_HARD_I2C.
2101
2102		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2103		then the following macros need to be defined (examples are
2104		from include/configs/lwmon.h):
2105
2106		I2C_INIT
2107
2108		(Optional). Any commands necessary to enable the I2C
2109		controller or configure ports.
2110
2111		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2112
2113		I2C_PORT
2114
2115		(Only for MPC8260 CPU). The I/O port to use (the code
2116		assumes both bits are on the same port). Valid values
2117		are 0..3 for ports A..D.
2118
2119		I2C_ACTIVE
2120
2121		The code necessary to make the I2C data line active
2122		(driven).  If the data line is open collector, this
2123		define can be null.
2124
2125		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2126
2127		I2C_TRISTATE
2128
2129		The code necessary to make the I2C data line tri-stated
2130		(inactive).  If the data line is open collector, this
2131		define can be null.
2132
2133		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2134
2135		I2C_READ
2136
2137		Code that returns true if the I2C data line is high,
2138		false if it is low.
2139
2140		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2141
2142		I2C_SDA(bit)
2143
2144		If <bit> is true, sets the I2C data line high. If it
2145		is false, it clears it (low).
2146
2147		eg: #define I2C_SDA(bit) \
2148			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2149			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2150
2151		I2C_SCL(bit)
2152
2153		If <bit> is true, sets the I2C clock line high. If it
2154		is false, it clears it (low).
2155
2156		eg: #define I2C_SCL(bit) \
2157			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2158			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2159
2160		I2C_DELAY
2161
2162		This delay is invoked four times per clock cycle so this
2163		controls the rate of data transfer.  The data rate thus
2164		is 1 / (I2C_DELAY * 4). Often defined to be something
2165		like:
2166
2167		#define I2C_DELAY  udelay(2)
2168
2169		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2170
2171		If your arch supports the generic GPIO framework (asm/gpio.h),
2172		then you may alternatively define the two GPIOs that are to be
2173		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2174		have GPIO-based defaults assigned to them as appropriate.
2175
2176		You should define these to the GPIO value as given directly to
2177		the generic GPIO functions.
2178
2179		CONFIG_SYS_I2C_INIT_BOARD
2180
2181		When a board is reset during an i2c bus transfer
2182		chips might think that the current transfer is still
2183		in progress. On some boards it is possible to access
2184		the i2c SCLK line directly, either by using the
2185		processor pin as a GPIO or by having a second pin
2186		connected to the bus. If this option is defined a
2187		custom i2c_init_board() routine in boards/xxx/board.c
2188		is run early in the boot sequence.
2189
2190		CONFIG_SYS_I2C_BOARD_LATE_INIT
2191
2192		An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
2193		defined a custom i2c_board_late_init() routine in
2194		boards/xxx/board.c is run AFTER the operations in i2c_init()
2195		is completed. This callpoint can be used to unreset i2c bus
2196		using CPU i2c controller register accesses for CPUs whose i2c
2197		controller provide such a method. It is called at the end of
2198		i2c_init() to allow i2c_init operations to setup the i2c bus
2199		controller on the CPU (e.g. setting bus speed & slave address).
2200
2201		CONFIG_I2CFAST (PPC405GP|PPC405EP only)
2202
2203		This option enables configuration of bi_iic_fast[] flags
2204		in u-boot bd_info structure based on u-boot environment
2205		variable "i2cfast". (see also i2cfast)
2206
2207		CONFIG_I2C_MULTI_BUS
2208
2209		This option allows the use of multiple I2C buses, each of which
2210		must have a controller.	 At any point in time, only one bus is
2211		active.	 To switch to a different bus, use the 'i2c dev' command.
2212		Note that bus numbering is zero-based.
2213
2214		CONFIG_SYS_I2C_NOPROBES
2215
2216		This option specifies a list of I2C devices that will be skipped
2217		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2218		is set, specify a list of bus-device pairs.  Otherwise, specify
2219		a 1D array of device addresses
2220
2221		e.g.
2222			#undef	CONFIG_I2C_MULTI_BUS
2223			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2224
2225		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2226
2227			#define CONFIG_I2C_MULTI_BUS
2228			#define CONFIG_SYS_I2C_MULTI_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2229
2230		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2231
2232		CONFIG_SYS_SPD_BUS_NUM
2233
2234		If defined, then this indicates the I2C bus number for DDR SPD.
2235		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2236
2237		CONFIG_SYS_RTC_BUS_NUM
2238
2239		If defined, then this indicates the I2C bus number for the RTC.
2240		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2241
2242		CONFIG_SYS_DTT_BUS_NUM
2243
2244		If defined, then this indicates the I2C bus number for the DTT.
2245		If not defined, then U-Boot assumes that DTT is on I2C bus 0.
2246
2247		CONFIG_SYS_I2C_DTT_ADDR:
2248
2249		If defined, specifies the I2C address of the DTT device.
2250		If not defined, then U-Boot uses predefined value for
2251		specified DTT device.
2252
2253		CONFIG_SOFT_I2C_READ_REPEATED_START
2254
2255		defining this will force the i2c_read() function in
2256		the soft_i2c driver to perform an I2C repeated start
2257		between writing the address pointer and reading the
2258		data.  If this define is omitted the default behaviour
2259		of doing a stop-start sequence will be used.  Most I2C
2260		devices can use either method, but some require one or
2261		the other.
2262
2263- SPI Support:	CONFIG_SPI
2264
2265		Enables SPI driver (so far only tested with
2266		SPI EEPROM, also an instance works with Crystal A/D and
2267		D/As on the SACSng board)
2268
2269		CONFIG_SH_SPI
2270
2271		Enables the driver for SPI controller on SuperH. Currently
2272		only SH7757 is supported.
2273
2274		CONFIG_SPI_X
2275
2276		Enables extended (16-bit) SPI EEPROM addressing.
2277		(symmetrical to CONFIG_I2C_X)
2278
2279		CONFIG_SOFT_SPI
2280
2281		Enables a software (bit-bang) SPI driver rather than
2282		using hardware support. This is a general purpose
2283		driver that only requires three general I/O port pins
2284		(two outputs, one input) to function. If this is
2285		defined, the board configuration must define several
2286		SPI configuration items (port pins to use, etc). For
2287		an example, see include/configs/sacsng.h.
2288
2289		CONFIG_HARD_SPI
2290
2291		Enables a hardware SPI driver for general-purpose reads
2292		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2293		must define a list of chip-select function pointers.
2294		Currently supported on some MPC8xxx processors.	 For an
2295		example, see include/configs/mpc8349emds.h.
2296
2297		CONFIG_MXC_SPI
2298
2299		Enables the driver for the SPI controllers on i.MX and MXC
2300		SoCs. Currently i.MX31/35/51 are supported.
2301
2302- FPGA Support: CONFIG_FPGA
2303
2304		Enables FPGA subsystem.
2305
2306		CONFIG_FPGA_<vendor>
2307
2308		Enables support for specific chip vendors.
2309		(ALTERA, XILINX)
2310
2311		CONFIG_FPGA_<family>
2312
2313		Enables support for FPGA family.
2314		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2315
2316		CONFIG_FPGA_COUNT
2317
2318		Specify the number of FPGA devices to support.
2319
2320		CONFIG_SYS_FPGA_PROG_FEEDBACK
2321
2322		Enable printing of hash marks during FPGA configuration.
2323
2324		CONFIG_SYS_FPGA_CHECK_BUSY
2325
2326		Enable checks on FPGA configuration interface busy
2327		status by the configuration function. This option
2328		will require a board or device specific function to
2329		be written.
2330
2331		CONFIG_FPGA_DELAY
2332
2333		If defined, a function that provides delays in the FPGA
2334		configuration driver.
2335
2336		CONFIG_SYS_FPGA_CHECK_CTRLC
2337		Allow Control-C to interrupt FPGA configuration
2338
2339		CONFIG_SYS_FPGA_CHECK_ERROR
2340
2341		Check for configuration errors during FPGA bitfile
2342		loading. For example, abort during Virtex II
2343		configuration if the INIT_B line goes low (which
2344		indicated a CRC error).
2345
2346		CONFIG_SYS_FPGA_WAIT_INIT
2347
2348		Maximum time to wait for the INIT_B line to deassert
2349		after PROB_B has been deasserted during a Virtex II
2350		FPGA configuration sequence. The default time is 500
2351		ms.
2352
2353		CONFIG_SYS_FPGA_WAIT_BUSY
2354
2355		Maximum time to wait for BUSY to deassert during
2356		Virtex II FPGA configuration. The default is 5 ms.
2357
2358		CONFIG_SYS_FPGA_WAIT_CONFIG
2359
2360		Time to wait after FPGA configuration. The default is
2361		200 ms.
2362
2363- Configuration Management:
2364		CONFIG_IDENT_STRING
2365
2366		If defined, this string will be added to the U-Boot
2367		version information (U_BOOT_VERSION)
2368
2369- Vendor Parameter Protection:
2370
2371		U-Boot considers the values of the environment
2372		variables "serial#" (Board Serial Number) and
2373		"ethaddr" (Ethernet Address) to be parameters that
2374		are set once by the board vendor / manufacturer, and
2375		protects these variables from casual modification by
2376		the user. Once set, these variables are read-only,
2377		and write or delete attempts are rejected. You can
2378		change this behaviour:
2379
2380		If CONFIG_ENV_OVERWRITE is #defined in your config
2381		file, the write protection for vendor parameters is
2382		completely disabled. Anybody can change or delete
2383		these parameters.
2384
2385		Alternatively, if you #define _both_ CONFIG_ETHADDR
2386		_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2387		Ethernet address is installed in the environment,
2388		which can be changed exactly ONCE by the user. [The
2389		serial# is unaffected by this, i. e. it remains
2390		read-only.]
2391
2392		The same can be accomplished in a more flexible way
2393		for any variable by configuring the type of access
2394		to allow for those variables in the ".flags" variable
2395		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2396
2397- Protected RAM:
2398		CONFIG_PRAM
2399
2400		Define this variable to enable the reservation of
2401		"protected RAM", i. e. RAM which is not overwritten
2402		by U-Boot. Define CONFIG_PRAM to hold the number of
2403		kB you want to reserve for pRAM. You can overwrite
2404		this default value by defining an environment
2405		variable "pram" to the number of kB you want to
2406		reserve. Note that the board info structure will
2407		still show the full amount of RAM. If pRAM is
2408		reserved, a new environment variable "mem" will
2409		automatically be defined to hold the amount of
2410		remaining RAM in a form that can be passed as boot
2411		argument to Linux, for instance like that:
2412
2413			setenv bootargs ... mem=\${mem}
2414			saveenv
2415
2416		This way you can tell Linux not to use this memory,
2417		either, which results in a memory region that will
2418		not be affected by reboots.
2419
2420		*WARNING* If your board configuration uses automatic
2421		detection of the RAM size, you must make sure that
2422		this memory test is non-destructive. So far, the
2423		following board configurations are known to be
2424		"pRAM-clean":
2425
2426			IVMS8, IVML24, SPD8xx, TQM8xxL,
2427			HERMES, IP860, RPXlite, LWMON,
2428			FLAGADM, TQM8260
2429
2430- Access to physical memory region (> 4GB)
2431		Some basic support is provided for operations on memory not
2432		normally accessible to U-Boot - e.g. some architectures
2433		support access to more than 4GB of memory on 32-bit
2434		machines using physical address extension or similar.
2435		Define CONFIG_PHYSMEM to access this basic support, which
2436		currently only supports clearing the memory.
2437
2438- Error Recovery:
2439		CONFIG_PANIC_HANG
2440
2441		Define this variable to stop the system in case of a
2442		fatal error, so that you have to reset it manually.
2443		This is probably NOT a good idea for an embedded
2444		system where you want the system to reboot
2445		automatically as fast as possible, but it may be
2446		useful during development since you can try to debug
2447		the conditions that lead to the situation.
2448
2449		CONFIG_NET_RETRY_COUNT
2450
2451		This variable defines the number of retries for
2452		network operations like ARP, RARP, TFTP, or BOOTP
2453		before giving up the operation. If not defined, a
2454		default value of 5 is used.
2455
2456		CONFIG_ARP_TIMEOUT
2457
2458		Timeout waiting for an ARP reply in milliseconds.
2459
2460		CONFIG_NFS_TIMEOUT
2461
2462		Timeout in milliseconds used in NFS protocol.
2463		If you encounter "ERROR: Cannot umount" in nfs command,
2464		try longer timeout such as
2465		#define CONFIG_NFS_TIMEOUT 10000UL
2466
2467- Command Interpreter:
2468		CONFIG_AUTO_COMPLETE
2469
2470		Enable auto completion of commands using TAB.
2471
2472		Note that this feature has NOT been implemented yet
2473		for the "hush" shell.
2474
2475
2476		CONFIG_SYS_HUSH_PARSER
2477
2478		Define this variable to enable the "hush" shell (from
2479		Busybox) as command line interpreter, thus enabling
2480		powerful command line syntax like
2481		if...then...else...fi conditionals or `&&' and '||'
2482		constructs ("shell scripts").
2483
2484		If undefined, you get the old, much simpler behaviour
2485		with a somewhat smaller memory footprint.
2486
2487
2488		CONFIG_SYS_PROMPT_HUSH_PS2
2489
2490		This defines the secondary prompt string, which is
2491		printed when the command interpreter needs more input
2492		to complete a command. Usually "> ".
2493
2494	Note:
2495
2496		In the current implementation, the local variables
2497		space and global environment variables space are
2498		separated. Local variables are those you define by
2499		simply typing `name=value'. To access a local
2500		variable later on, you have write `$name' or
2501		`${name}'; to execute the contents of a variable
2502		directly type `$name' at the command prompt.
2503
2504		Global environment variables are those you use
2505		setenv/printenv to work with. To run a command stored
2506		in such a variable, you need to use the run command,
2507		and you must not use the '$' sign to access them.
2508
2509		To store commands and special characters in a
2510		variable, please use double quotation marks
2511		surrounding the whole text of the variable, instead
2512		of the backslashes before semicolons and special
2513		symbols.
2514
2515- Commandline Editing and History:
2516		CONFIG_CMDLINE_EDITING
2517
2518		Enable editing and History functions for interactive
2519		commandline input operations
2520
2521- Default Environment:
2522		CONFIG_EXTRA_ENV_SETTINGS
2523
2524		Define this to contain any number of null terminated
2525		strings (variable = value pairs) that will be part of
2526		the default environment compiled into the boot image.
2527
2528		For example, place something like this in your
2529		board's config file:
2530
2531		#define CONFIG_EXTRA_ENV_SETTINGS \
2532			"myvar1=value1\0" \
2533			"myvar2=value2\0"
2534
2535		Warning: This method is based on knowledge about the
2536		internal format how the environment is stored by the
2537		U-Boot code. This is NOT an official, exported
2538		interface! Although it is unlikely that this format
2539		will change soon, there is no guarantee either.
2540		You better know what you are doing here.
2541
2542		Note: overly (ab)use of the default environment is
2543		discouraged. Make sure to check other ways to preset
2544		the environment like the "source" command or the
2545		boot command first.
2546
2547		CONFIG_ENV_VARS_UBOOT_CONFIG
2548
2549		Define this in order to add variables describing the
2550		U-Boot build configuration to the default environment.
2551		These will be named arch, cpu, board, vendor, and soc.
2552
2553		Enabling this option will cause the following to be defined:
2554
2555		- CONFIG_SYS_ARCH
2556		- CONFIG_SYS_CPU
2557		- CONFIG_SYS_BOARD
2558		- CONFIG_SYS_VENDOR
2559		- CONFIG_SYS_SOC
2560
2561		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2562
2563		Define this in order to add variables describing certain
2564		run-time determined information about the hardware to the
2565		environment.  These will be named board_name, board_rev.
2566
2567		CONFIG_DELAY_ENVIRONMENT
2568
2569		Normally the environment is loaded when the board is
2570		intialised so that it is available to U-Boot. This inhibits
2571		that so that the environment is not available until
2572		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2573		this is instead controlled by the value of
2574		/config/load-environment.
2575
2576- DataFlash Support:
2577		CONFIG_HAS_DATAFLASH
2578
2579		Defining this option enables DataFlash features and
2580		allows to read/write in Dataflash via the standard
2581		commands cp, md...
2582
2583- Serial Flash support
2584		CONFIG_CMD_SF
2585
2586		Defining this option enables SPI flash commands
2587		'sf probe/read/write/erase/update'.
2588
2589		Usage requires an initial 'probe' to define the serial
2590		flash parameters, followed by read/write/erase/update
2591		commands.
2592
2593		The following defaults may be provided by the platform
2594		to handle the common case when only a single serial
2595		flash is present on the system.
2596
2597		CONFIG_SF_DEFAULT_BUS		Bus identifier
2598		CONFIG_SF_DEFAULT_CS		Chip-select
2599		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2600		CONFIG_SF_DEFAULT_SPEED		in Hz
2601
2602		CONFIG_CMD_SF_TEST
2603
2604		Define this option to include a destructive SPI flash
2605		test ('sf test').
2606
2607		CONFIG_SPI_FLASH_BAR		Ban/Extended Addr Reg
2608
2609		Define this option to use the Bank addr/Extended addr
2610		support on SPI flashes which has size > 16Mbytes.
2611
2612- SystemACE Support:
2613		CONFIG_SYSTEMACE
2614
2615		Adding this option adds support for Xilinx SystemACE
2616		chips attached via some sort of local bus. The address
2617		of the chip must also be defined in the
2618		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2619
2620		#define CONFIG_SYSTEMACE
2621		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2622
2623		When SystemACE support is added, the "ace" device type
2624		becomes available to the fat commands, i.e. fatls.
2625
2626- TFTP Fixed UDP Port:
2627		CONFIG_TFTP_PORT
2628
2629		If this is defined, the environment variable tftpsrcp
2630		is used to supply the TFTP UDP source port value.
2631		If tftpsrcp isn't defined, the normal pseudo-random port
2632		number generator is used.
2633
2634		Also, the environment variable tftpdstp is used to supply
2635		the TFTP UDP destination port value.  If tftpdstp isn't
2636		defined, the normal port 69 is used.
2637
2638		The purpose for tftpsrcp is to allow a TFTP server to
2639		blindly start the TFTP transfer using the pre-configured
2640		target IP address and UDP port. This has the effect of
2641		"punching through" the (Windows XP) firewall, allowing
2642		the remainder of the TFTP transfer to proceed normally.
2643		A better solution is to properly configure the firewall,
2644		but sometimes that is not allowed.
2645
2646- Hashing support:
2647		CONFIG_CMD_HASH
2648
2649		This enables a generic 'hash' command which can produce
2650		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2651
2652		CONFIG_HASH_VERIFY
2653
2654		Enable the hash verify command (hash -v). This adds to code
2655		size a little.
2656
2657		CONFIG_SHA1 - support SHA1 hashing
2658		CONFIG_SHA256 - support SHA256 hashing
2659
2660		Note: There is also a sha1sum command, which should perhaps
2661		be deprecated in favour of 'hash sha1'.
2662
2663- Freescale i.MX specific commands:
2664		CONFIG_CMD_HDMIDETECT
2665		This enables 'hdmidet' command which returns true if an
2666		HDMI monitor is detected.  This command is i.MX 6 specific.
2667
2668		CONFIG_CMD_BMODE
2669		This enables the 'bmode' (bootmode) command for forcing
2670		a boot from specific media.
2671
2672		This is useful for forcing the ROM's usb downloader to
2673		activate upon a watchdog reset which is nice when iterating
2674		on U-Boot.  Using the reset button or running bmode normal
2675		will set it back to normal.  This command currently
2676		supports i.MX53 and i.MX6.
2677
2678- Signing support:
2679		CONFIG_RSA
2680
2681		This enables the RSA algorithm used for FIT image verification
2682		in U-Boot. See doc/uImage/signature for more information.
2683
2684		The signing part is build into mkimage regardless of this
2685		option.
2686
2687
2688- Show boot progress:
2689		CONFIG_SHOW_BOOT_PROGRESS
2690
2691		Defining this option allows to add some board-
2692		specific code (calling a user-provided function
2693		"show_boot_progress(int)") that enables you to show
2694		the system's boot progress on some display (for
2695		example, some LED's) on your board. At the moment,
2696		the following checkpoints are implemented:
2697
2698- Detailed boot stage timing
2699		CONFIG_BOOTSTAGE
2700		Define this option to get detailed timing of each stage
2701		of the boot process.
2702
2703		CONFIG_BOOTSTAGE_USER_COUNT
2704		This is the number of available user bootstage records.
2705		Each time you call bootstage_mark(BOOTSTAGE_ID_ALLOC, ...)
2706		a new ID will be allocated from this stash. If you exceed
2707		the limit, recording will stop.
2708
2709		CONFIG_BOOTSTAGE_REPORT
2710		Define this to print a report before boot, similar to this:
2711
2712		Timer summary in microseconds:
2713		       Mark    Elapsed  Stage
2714			  0          0  reset
2715		  3,575,678  3,575,678  board_init_f start
2716		  3,575,695         17  arch_cpu_init A9
2717		  3,575,777         82  arch_cpu_init done
2718		  3,659,598     83,821  board_init_r start
2719		  3,910,375    250,777  main_loop
2720		 29,916,167 26,005,792  bootm_start
2721		 30,361,327    445,160  start_kernel
2722
2723		CONFIG_CMD_BOOTSTAGE
2724		Add a 'bootstage' command which supports printing a report
2725		and un/stashing of bootstage data.
2726
2727		CONFIG_BOOTSTAGE_FDT
2728		Stash the bootstage information in the FDT. A root 'bootstage'
2729		node is created with each bootstage id as a child. Each child
2730		has a 'name' property and either 'mark' containing the
2731		mark time in microsecond, or 'accum' containing the
2732		accumulated time for that bootstage id in microseconds.
2733		For example:
2734
2735		bootstage {
2736			154 {
2737				name = "board_init_f";
2738				mark = <3575678>;
2739			};
2740			170 {
2741				name = "lcd";
2742				accum = <33482>;
2743			};
2744		};
2745
2746		Code in the Linux kernel can find this in /proc/devicetree.
2747
2748Legacy uImage format:
2749
2750  Arg	Where			When
2751    1	common/cmd_bootm.c	before attempting to boot an image
2752   -1	common/cmd_bootm.c	Image header has bad	 magic number
2753    2	common/cmd_bootm.c	Image header has correct magic number
2754   -2	common/cmd_bootm.c	Image header has bad	 checksum
2755    3	common/cmd_bootm.c	Image header has correct checksum
2756   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2757    4	common/cmd_bootm.c	Image data   has correct checksum
2758   -4	common/cmd_bootm.c	Image is for unsupported architecture
2759    5	common/cmd_bootm.c	Architecture check OK
2760   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2761    6	common/cmd_bootm.c	Image Type check OK
2762   -6	common/cmd_bootm.c	gunzip uncompression error
2763   -7	common/cmd_bootm.c	Unimplemented compression type
2764    7	common/cmd_bootm.c	Uncompression OK
2765    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2766   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2767
2768    9	common/image.c		Start initial ramdisk verification
2769  -10	common/image.c		Ramdisk header has bad	   magic number
2770  -11	common/image.c		Ramdisk header has bad	   checksum
2771   10	common/image.c		Ramdisk header is OK
2772  -12	common/image.c		Ramdisk data   has bad	   checksum
2773   11	common/image.c		Ramdisk data   has correct checksum
2774   12	common/image.c		Ramdisk verification complete, start loading
2775  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2776   13	common/image.c		Start multifile image verification
2777   14	common/image.c		No initial ramdisk, no multifile, continue.
2778
2779   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2780
2781  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2782  -31	post/post.c		POST test failed, detected by post_output_backlog()
2783  -32	post/post.c		POST test failed, detected by post_run_single()
2784
2785   34	common/cmd_doc.c	before loading a Image from a DOC device
2786  -35	common/cmd_doc.c	Bad usage of "doc" command
2787   35	common/cmd_doc.c	correct usage of "doc" command
2788  -36	common/cmd_doc.c	No boot device
2789   36	common/cmd_doc.c	correct boot device
2790  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2791   37	common/cmd_doc.c	correct chip ID found, device available
2792  -38	common/cmd_doc.c	Read Error on boot device
2793   38	common/cmd_doc.c	reading Image header from DOC device OK
2794  -39	common/cmd_doc.c	Image header has bad magic number
2795   39	common/cmd_doc.c	Image header has correct magic number
2796  -40	common/cmd_doc.c	Error reading Image from DOC device
2797   40	common/cmd_doc.c	Image header has correct magic number
2798   41	common/cmd_ide.c	before loading a Image from a IDE device
2799  -42	common/cmd_ide.c	Bad usage of "ide" command
2800   42	common/cmd_ide.c	correct usage of "ide" command
2801  -43	common/cmd_ide.c	No boot device
2802   43	common/cmd_ide.c	boot device found
2803  -44	common/cmd_ide.c	Device not available
2804   44	common/cmd_ide.c	Device available
2805  -45	common/cmd_ide.c	wrong partition selected
2806   45	common/cmd_ide.c	partition selected
2807  -46	common/cmd_ide.c	Unknown partition table
2808   46	common/cmd_ide.c	valid partition table found
2809  -47	common/cmd_ide.c	Invalid partition type
2810   47	common/cmd_ide.c	correct partition type
2811  -48	common/cmd_ide.c	Error reading Image Header on boot device
2812   48	common/cmd_ide.c	reading Image Header from IDE device OK
2813  -49	common/cmd_ide.c	Image header has bad magic number
2814   49	common/cmd_ide.c	Image header has correct magic number
2815  -50	common/cmd_ide.c	Image header has bad	 checksum
2816   50	common/cmd_ide.c	Image header has correct checksum
2817  -51	common/cmd_ide.c	Error reading Image from IDE device
2818   51	common/cmd_ide.c	reading Image from IDE device OK
2819   52	common/cmd_nand.c	before loading a Image from a NAND device
2820  -53	common/cmd_nand.c	Bad usage of "nand" command
2821   53	common/cmd_nand.c	correct usage of "nand" command
2822  -54	common/cmd_nand.c	No boot device
2823   54	common/cmd_nand.c	boot device found
2824  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2825   55	common/cmd_nand.c	correct chip ID found, device available
2826  -56	common/cmd_nand.c	Error reading Image Header on boot device
2827   56	common/cmd_nand.c	reading Image Header from NAND device OK
2828  -57	common/cmd_nand.c	Image header has bad magic number
2829   57	common/cmd_nand.c	Image header has correct magic number
2830  -58	common/cmd_nand.c	Error reading Image from NAND device
2831   58	common/cmd_nand.c	reading Image from NAND device OK
2832
2833  -60	common/env_common.c	Environment has a bad CRC, using default
2834
2835   64	net/eth.c		starting with Ethernet configuration.
2836  -64	net/eth.c		no Ethernet found.
2837   65	net/eth.c		Ethernet found.
2838
2839  -80	common/cmd_net.c	usage wrong
2840   80	common/cmd_net.c	before calling NetLoop()
2841  -81	common/cmd_net.c	some error in NetLoop() occurred
2842   81	common/cmd_net.c	NetLoop() back without error
2843  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2844   82	common/cmd_net.c	trying automatic boot
2845   83	common/cmd_net.c	running "source" command
2846  -83	common/cmd_net.c	some error in automatic boot or "source" command
2847   84	common/cmd_net.c	end without errors
2848
2849FIT uImage format:
2850
2851  Arg	Where			When
2852  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2853 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2854  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2855 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2856  102	common/cmd_bootm.c	Kernel unit name specified
2857 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2858  103	common/cmd_bootm.c	Found configuration node
2859  104	common/cmd_bootm.c	Got kernel subimage node offset
2860 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2861  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2862 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2863  106	common/cmd_bootm.c	Architecture check OK
2864 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2865  107	common/cmd_bootm.c	Kernel subimage type OK
2866 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2867  108	common/cmd_bootm.c	Got kernel subimage data/size
2868 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2869 -109	common/cmd_bootm.c	Can't get kernel subimage type
2870 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2871 -111	common/cmd_bootm.c	Can't get kernel subimage os
2872 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2873 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2874
2875  120	common/image.c		Start initial ramdisk verification
2876 -120	common/image.c		Ramdisk FIT image has incorrect format
2877  121	common/image.c		Ramdisk FIT image has correct format
2878  122	common/image.c		No ramdisk subimage unit name, using configuration
2879 -122	common/image.c		Can't get configuration for ramdisk subimage
2880  123	common/image.c		Ramdisk unit name specified
2881 -124	common/image.c		Can't get ramdisk subimage node offset
2882  125	common/image.c		Got ramdisk subimage node offset
2883 -125	common/image.c		Ramdisk subimage hash verification failed
2884  126	common/image.c		Ramdisk subimage hash verification OK
2885 -126	common/image.c		Ramdisk subimage for unsupported architecture
2886  127	common/image.c		Architecture check OK
2887 -127	common/image.c		Can't get ramdisk subimage data/size
2888  128	common/image.c		Got ramdisk subimage data/size
2889  129	common/image.c		Can't get ramdisk load address
2890 -129	common/image.c		Got ramdisk load address
2891
2892 -130	common/cmd_doc.c	Incorrect FIT image format
2893  131	common/cmd_doc.c	FIT image format OK
2894
2895 -140	common/cmd_ide.c	Incorrect FIT image format
2896  141	common/cmd_ide.c	FIT image format OK
2897
2898 -150	common/cmd_nand.c	Incorrect FIT image format
2899  151	common/cmd_nand.c	FIT image format OK
2900
2901- FIT image support:
2902		CONFIG_FIT
2903		Enable support for the FIT uImage format.
2904
2905		CONFIG_FIT_BEST_MATCH
2906		When no configuration is explicitly selected, default to the
2907		one whose fdt's compatibility field best matches that of
2908		U-Boot itself. A match is considered "best" if it matches the
2909		most specific compatibility entry of U-Boot's fdt's root node.
2910		The order of entries in the configuration's fdt is ignored.
2911
2912		CONFIG_FIT_SIGNATURE
2913		This option enables signature verification of FIT uImages,
2914		using a hash signed and verified using RSA. See
2915		doc/uImage.FIT/signature.txt for more details.
2916
2917- Standalone program support:
2918		CONFIG_STANDALONE_LOAD_ADDR
2919
2920		This option defines a board specific value for the
2921		address where standalone program gets loaded, thus
2922		overwriting the architecture dependent default
2923		settings.
2924
2925- Frame Buffer Address:
2926		CONFIG_FB_ADDR
2927
2928		Define CONFIG_FB_ADDR if you want to use specific
2929		address for frame buffer.  This is typically the case
2930		when using a graphics controller has separate video
2931		memory.  U-Boot will then place the frame buffer at
2932		the given address instead of dynamically reserving it
2933		in system RAM by calling lcd_setmem(), which grabs
2934		the memory for the frame buffer depending on the
2935		configured panel size.
2936
2937		Please see board_init_f function.
2938
2939- Automatic software updates via TFTP server
2940		CONFIG_UPDATE_TFTP
2941		CONFIG_UPDATE_TFTP_CNT_MAX
2942		CONFIG_UPDATE_TFTP_MSEC_MAX
2943
2944		These options enable and control the auto-update feature;
2945		for a more detailed description refer to doc/README.update.
2946
2947- MTD Support (mtdparts command, UBI support)
2948		CONFIG_MTD_DEVICE
2949
2950		Adds the MTD device infrastructure from the Linux kernel.
2951		Needed for mtdparts command support.
2952
2953		CONFIG_MTD_PARTITIONS
2954
2955		Adds the MTD partitioning infrastructure from the Linux
2956		kernel. Needed for UBI support.
2957
2958- UBI support
2959		CONFIG_CMD_UBI
2960
2961		Adds commands for interacting with MTD partitions formatted
2962		with the UBI flash translation layer
2963
2964		Requires also defining CONFIG_RBTREE
2965
2966		CONFIG_UBI_SILENCE_MSG
2967
2968		Make the verbose messages from UBI stop printing.  This leaves
2969		warnings and errors enabled.
2970
2971- UBIFS support
2972		CONFIG_CMD_UBIFS
2973
2974		Adds commands for interacting with UBI volumes formatted as
2975		UBIFS.  UBIFS is read-only in u-boot.
2976
2977		Requires UBI support as well as CONFIG_LZO
2978
2979		CONFIG_UBIFS_SILENCE_MSG
2980
2981		Make the verbose messages from UBIFS stop printing.  This leaves
2982		warnings and errors enabled.
2983
2984- SPL framework
2985		CONFIG_SPL
2986		Enable building of SPL globally.
2987
2988		CONFIG_SPL_LDSCRIPT
2989		LDSCRIPT for linking the SPL binary.
2990
2991		CONFIG_SPL_MAX_FOOTPRINT
2992		Maximum size in memory allocated to the SPL, BSS included.
2993		When defined, the linker checks that the actual memory
2994		used by SPL from _start to __bss_end does not exceed it.
2995		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2996		must not be both defined at the same time.
2997
2998		CONFIG_SPL_MAX_SIZE
2999		Maximum size of the SPL image (text, data, rodata, and
3000		linker lists sections), BSS excluded.
3001		When defined, the linker checks that the actual size does
3002		not exceed it.
3003
3004		CONFIG_SPL_TEXT_BASE
3005		TEXT_BASE for linking the SPL binary.
3006
3007		CONFIG_SPL_RELOC_TEXT_BASE
3008		Address to relocate to.  If unspecified, this is equal to
3009		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3010
3011		CONFIG_SPL_BSS_START_ADDR
3012		Link address for the BSS within the SPL binary.
3013
3014		CONFIG_SPL_BSS_MAX_SIZE
3015		Maximum size in memory allocated to the SPL BSS.
3016		When defined, the linker checks that the actual memory used
3017		by SPL from __bss_start to __bss_end does not exceed it.
3018		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3019		must not be both defined at the same time.
3020
3021		CONFIG_SPL_STACK
3022		Adress of the start of the stack SPL will use
3023
3024		CONFIG_SPL_RELOC_STACK
3025		Adress of the start of the stack SPL will use after
3026		relocation.  If unspecified, this is equal to
3027		CONFIG_SPL_STACK.
3028
3029		CONFIG_SYS_SPL_MALLOC_START
3030		Starting address of the malloc pool used in SPL.
3031
3032		CONFIG_SYS_SPL_MALLOC_SIZE
3033		The size of the malloc pool used in SPL.
3034
3035		CONFIG_SPL_FRAMEWORK
3036		Enable the SPL framework under common/.  This framework
3037		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3038		NAND loading of the Linux Kernel.
3039
3040		CONFIG_SPL_DISPLAY_PRINT
3041		For ARM, enable an optional function to print more information
3042		about the running system.
3043
3044		CONFIG_SPL_INIT_MINIMAL
3045		Arch init code should be built for a very small image
3046
3047		CONFIG_SPL_LIBCOMMON_SUPPORT
3048		Support for common/libcommon.o in SPL binary
3049
3050		CONFIG_SPL_LIBDISK_SUPPORT
3051		Support for disk/libdisk.o in SPL binary
3052
3053		CONFIG_SPL_I2C_SUPPORT
3054		Support for drivers/i2c/libi2c.o in SPL binary
3055
3056		CONFIG_SPL_GPIO_SUPPORT
3057		Support for drivers/gpio/libgpio.o in SPL binary
3058
3059		CONFIG_SPL_MMC_SUPPORT
3060		Support for drivers/mmc/libmmc.o in SPL binary
3061
3062		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR,
3063		CONFIG_SYS_U_BOOT_MAX_SIZE_SECTORS,
3064		CONFIG_SYS_MMC_SD_FAT_BOOT_PARTITION
3065		Address, size and partition on the MMC to load U-Boot from
3066		when the MMC is being used in raw mode.
3067
3068		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3069		Sector to load kernel uImage from when MMC is being
3070		used in raw mode (for Falcon mode)
3071
3072		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3073		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3074		Sector and number of sectors to load kernel argument
3075		parameters from when MMC is being used in raw mode
3076		(for falcon mode)
3077
3078		CONFIG_SPL_FAT_SUPPORT
3079		Support for fs/fat/libfat.o in SPL binary
3080
3081		CONFIG_SPL_FAT_LOAD_PAYLOAD_NAME
3082		Filename to read to load U-Boot when reading from FAT
3083
3084		CONFIG_SPL_FAT_LOAD_KERNEL_NAME
3085		Filename to read to load kernel uImage when reading
3086		from FAT (for Falcon mode)
3087
3088		CONFIG_SPL_FAT_LOAD_ARGS_NAME
3089		Filename to read to load kernel argument parameters
3090		when reading from FAT (for Falcon mode)
3091
3092		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3093		Set this for NAND SPL on PPC mpc83xx targets, so that
3094		start.S waits for the rest of the SPL to load before
3095		continuing (the hardware starts execution after just
3096		loading the first page rather than the full 4K).
3097
3098		CONFIG_SPL_NAND_BASE
3099		Include nand_base.c in the SPL.  Requires
3100		CONFIG_SPL_NAND_DRIVERS.
3101
3102		CONFIG_SPL_NAND_DRIVERS
3103		SPL uses normal NAND drivers, not minimal drivers.
3104
3105		CONFIG_SPL_NAND_ECC
3106		Include standard software ECC in the SPL
3107
3108		CONFIG_SPL_NAND_SIMPLE
3109		Support for NAND boot using simple NAND drivers that
3110		expose the cmd_ctrl() interface.
3111
3112		CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT
3113		Set for the SPL on PPC mpc8xxx targets, support for
3114		arch/powerpc/cpu/mpc8xxx/ddr/libddr.o in SPL binary.
3115
3116		CONFIG_SPL_COMMON_INIT_DDR
3117		Set for common ddr init with serial presence detect in
3118		SPL binary.
3119
3120		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3121		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3122		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3123		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3124		CONFIG_SYS_NAND_ECCBYTES
3125		Defines the size and behavior of the NAND that SPL uses
3126		to read U-Boot
3127
3128		CONFIG_SYS_NAND_U_BOOT_OFFS
3129		Location in NAND to read U-Boot from
3130
3131		CONFIG_SYS_NAND_U_BOOT_DST
3132		Location in memory to load U-Boot to
3133
3134		CONFIG_SYS_NAND_U_BOOT_SIZE
3135		Size of image to load
3136
3137		CONFIG_SYS_NAND_U_BOOT_START
3138		Entry point in loaded image to jump to
3139
3140		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3141		Define this if you need to first read the OOB and then the
3142		data. This is used for example on davinci plattforms.
3143
3144		CONFIG_SPL_OMAP3_ID_NAND
3145		Support for an OMAP3-specific set of functions to return the
3146		ID and MFR of the first attached NAND chip, if present.
3147
3148		CONFIG_SPL_SERIAL_SUPPORT
3149		Support for drivers/serial/libserial.o in SPL binary
3150
3151		CONFIG_SPL_SPI_FLASH_SUPPORT
3152		Support for drivers/mtd/spi/libspi_flash.o in SPL binary
3153
3154		CONFIG_SPL_SPI_SUPPORT
3155		Support for drivers/spi/libspi.o in SPL binary
3156
3157		CONFIG_SPL_RAM_DEVICE
3158		Support for running image already present in ram, in SPL binary
3159
3160		CONFIG_SPL_LIBGENERIC_SUPPORT
3161		Support for lib/libgeneric.o in SPL binary
3162
3163		CONFIG_SPL_ENV_SUPPORT
3164		Support for the environment operating in SPL binary
3165
3166		CONFIG_SPL_NET_SUPPORT
3167		Support for the net/libnet.o in SPL binary.
3168		It conflicts with SPL env from storage medium specified by
3169		CONFIG_ENV_IS_xxx but CONFIG_ENV_IS_NOWHERE
3170
3171		CONFIG_SPL_PAD_TO
3172		Image offset to which the SPL should be padded before appending
3173		the SPL payload. By default, this is defined as
3174		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3175		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3176		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3177
3178		CONFIG_SPL_TARGET
3179		Final target image containing SPL and payload.  Some SPLs
3180		use an arch-specific makefile fragment instead, for
3181		example if more than one image needs to be produced.
3182
3183		CONFIG_FIT_SPL_PRINT
3184		Printing information about a FIT image adds quite a bit of
3185		code to SPL. So this is normally disabled in SPL. Use this
3186		option to re-enable it. This will affect the output of the
3187		bootm command when booting a FIT image.
3188
3189- TPL framework
3190		CONFIG_TPL
3191		Enable building of TPL globally.
3192
3193		CONFIG_TPL_PAD_TO
3194		Image offset to which the TPL should be padded before appending
3195		the TPL payload. By default, this is defined as
3196                CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3197                CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3198                payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3199
3200Modem Support:
3201--------------
3202
3203[so far only for SMDK2400 boards]
3204
3205- Modem support enable:
3206		CONFIG_MODEM_SUPPORT
3207
3208- RTS/CTS Flow control enable:
3209		CONFIG_HWFLOW
3210
3211- Modem debug support:
3212		CONFIG_MODEM_SUPPORT_DEBUG
3213
3214		Enables debugging stuff (char screen[1024], dbg())
3215		for modem support. Useful only with BDI2000.
3216
3217- Interrupt support (PPC):
3218
3219		There are common interrupt_init() and timer_interrupt()
3220		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3221		for CPU specific initialization. interrupt_init_cpu()
3222		should set decrementer_count to appropriate value. If
3223		CPU resets decrementer automatically after interrupt
3224		(ppc4xx) it should set decrementer_count to zero.
3225		timer_interrupt() calls timer_interrupt_cpu() for CPU
3226		specific handling. If board has watchdog / status_led
3227		/ other_activity_monitor it works automatically from
3228		general timer_interrupt().
3229
3230- General:
3231
3232		In the target system modem support is enabled when a
3233		specific key (key combination) is pressed during
3234		power-on. Otherwise U-Boot will boot normally
3235		(autoboot). The key_pressed() function is called from
3236		board_init(). Currently key_pressed() is a dummy
3237		function, returning 1 and thus enabling modem
3238		initialization.
3239
3240		If there are no modem init strings in the
3241		environment, U-Boot proceed to autoboot; the
3242		previous output (banner, info printfs) will be
3243		suppressed, though.
3244
3245		See also: doc/README.Modem
3246
3247Board initialization settings:
3248------------------------------
3249
3250During Initialization u-boot calls a number of board specific functions
3251to allow the preparation of board specific prerequisites, e.g. pin setup
3252before drivers are initialized. To enable these callbacks the
3253following configuration macros have to be defined. Currently this is
3254architecture specific, so please check arch/your_architecture/lib/board.c
3255typically in board_init_f() and board_init_r().
3256
3257- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3258- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3259- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3260- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3261
3262Configuration Settings:
3263-----------------------
3264
3265- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3266		undefine this when you're short of memory.
3267
3268- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3269		width of the commands listed in the 'help' command output.
3270
3271- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3272		prompt for user input.
3273
3274- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3275
3276- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3277
3278- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3279
3280- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3281		the application (usually a Linux kernel) when it is
3282		booted
3283
3284- CONFIG_SYS_BAUDRATE_TABLE:
3285		List of legal baudrate settings for this board.
3286
3287- CONFIG_SYS_CONSOLE_INFO_QUIET
3288		Suppress display of console information at boot.
3289
3290- CONFIG_SYS_CONSOLE_IS_IN_ENV
3291		If the board specific function
3292			extern int overwrite_console (void);
3293		returns 1, the stdin, stderr and stdout are switched to the
3294		serial port, else the settings in the environment are used.
3295
3296- CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE
3297		Enable the call to overwrite_console().
3298
3299- CONFIG_SYS_CONSOLE_ENV_OVERWRITE
3300		Enable overwrite of previous console environment settings.
3301
3302- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3303		Begin and End addresses of the area used by the
3304		simple memory test.
3305
3306- CONFIG_SYS_ALT_MEMTEST:
3307		Enable an alternate, more extensive memory test.
3308
3309- CONFIG_SYS_MEMTEST_SCRATCH:
3310		Scratch address used by the alternate memory test
3311		You only need to set this if address zero isn't writeable
3312
3313- CONFIG_SYS_MEM_TOP_HIDE (PPC only):
3314		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3315		this specified memory area will get subtracted from the top
3316		(end) of RAM and won't get "touched" at all by U-Boot. By
3317		fixing up gd->ram_size the Linux kernel should gets passed
3318		the now "corrected" memory size and won't touch it either.
3319		This should work for arch/ppc and arch/powerpc. Only Linux
3320		board ports in arch/powerpc with bootwrapper support that
3321		recalculate the memory size from the SDRAM controller setup
3322		will have to get fixed in Linux additionally.
3323
3324		This option can be used as a workaround for the 440EPx/GRx
3325		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3326		be touched.
3327
3328		WARNING: Please make sure that this value is a multiple of
3329		the Linux page size (normally 4k). If this is not the case,
3330		then the end address of the Linux memory will be located at a
3331		non page size aligned address and this could cause major
3332		problems.
3333
3334- CONFIG_SYS_LOADS_BAUD_CHANGE:
3335		Enable temporary baudrate change while serial download
3336
3337- CONFIG_SYS_SDRAM_BASE:
3338		Physical start address of SDRAM. _Must_ be 0 here.
3339
3340- CONFIG_SYS_MBIO_BASE:
3341		Physical start address of Motherboard I/O (if using a
3342		Cogent motherboard)
3343
3344- CONFIG_SYS_FLASH_BASE:
3345		Physical start address of Flash memory.
3346
3347- CONFIG_SYS_MONITOR_BASE:
3348		Physical start address of boot monitor code (set by
3349		make config files to be same as the text base address
3350		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3351		CONFIG_SYS_FLASH_BASE when booting from flash.
3352
3353- CONFIG_SYS_MONITOR_LEN:
3354		Size of memory reserved for monitor code, used to
3355		determine _at_compile_time_ (!) if the environment is
3356		embedded within the U-Boot image, or in a separate
3357		flash sector.
3358
3359- CONFIG_SYS_MALLOC_LEN:
3360		Size of DRAM reserved for malloc() use.
3361
3362- CONFIG_SYS_BOOTM_LEN:
3363		Normally compressed uImages are limited to an
3364		uncompressed size of 8 MBytes. If this is not enough,
3365		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3366		to adjust this setting to your needs.
3367
3368- CONFIG_SYS_BOOTMAPSZ:
3369		Maximum size of memory mapped by the startup code of
3370		the Linux kernel; all data that must be processed by
3371		the Linux kernel (bd_info, boot arguments, FDT blob if
3372		used) must be put below this limit, unless "bootm_low"
3373		environment variable is defined and non-zero. In such case
3374		all data for the Linux kernel must be between "bootm_low"
3375		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3376		variable "bootm_mapsize" will override the value of
3377		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3378		then the value in "bootm_size" will be used instead.
3379
3380- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3381		Enable initrd_high functionality.  If defined then the
3382		initrd_high feature is enabled and the bootm ramdisk subcommand
3383		is enabled.
3384
3385- CONFIG_SYS_BOOT_GET_CMDLINE:
3386		Enables allocating and saving kernel cmdline in space between
3387		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3388
3389- CONFIG_SYS_BOOT_GET_KBD:
3390		Enables allocating and saving a kernel copy of the bd_info in
3391		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3392
3393- CONFIG_SYS_MAX_FLASH_BANKS:
3394		Max number of Flash memory banks
3395
3396- CONFIG_SYS_MAX_FLASH_SECT:
3397		Max number of sectors on a Flash chip
3398
3399- CONFIG_SYS_FLASH_ERASE_TOUT:
3400		Timeout for Flash erase operations (in ms)
3401
3402- CONFIG_SYS_FLASH_WRITE_TOUT:
3403		Timeout for Flash write operations (in ms)
3404
3405- CONFIG_SYS_FLASH_LOCK_TOUT
3406		Timeout for Flash set sector lock bit operation (in ms)
3407
3408- CONFIG_SYS_FLASH_UNLOCK_TOUT
3409		Timeout for Flash clear lock bits operation (in ms)
3410
3411- CONFIG_SYS_FLASH_PROTECTION
3412		If defined, hardware flash sectors protection is used
3413		instead of U-Boot software protection.
3414
3415- CONFIG_SYS_DIRECT_FLASH_TFTP:
3416
3417		Enable TFTP transfers directly to flash memory;
3418		without this option such a download has to be
3419		performed in two steps: (1) download to RAM, and (2)
3420		copy from RAM to flash.
3421
3422		The two-step approach is usually more reliable, since
3423		you can check if the download worked before you erase
3424		the flash, but in some situations (when system RAM is
3425		too limited to allow for a temporary copy of the
3426		downloaded image) this option may be very useful.
3427
3428- CONFIG_SYS_FLASH_CFI:
3429		Define if the flash driver uses extra elements in the
3430		common flash structure for storing flash geometry.
3431
3432- CONFIG_FLASH_CFI_DRIVER
3433		This option also enables the building of the cfi_flash driver
3434		in the drivers directory
3435
3436- CONFIG_FLASH_CFI_MTD
3437		This option enables the building of the cfi_mtd driver
3438		in the drivers directory. The driver exports CFI flash
3439		to the MTD layer.
3440
3441- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3442		Use buffered writes to flash.
3443
3444- CONFIG_FLASH_SPANSION_S29WS_N
3445		s29ws-n MirrorBit flash has non-standard addresses for buffered
3446		write commands.
3447
3448- CONFIG_SYS_FLASH_QUIET_TEST
3449		If this option is defined, the common CFI flash doesn't
3450		print it's warning upon not recognized FLASH banks. This
3451		is useful, if some of the configured banks are only
3452		optionally available.
3453
3454- CONFIG_FLASH_SHOW_PROGRESS
3455		If defined (must be an integer), print out countdown
3456		digits and dots.  Recommended value: 45 (9..1) for 80
3457		column displays, 15 (3..1) for 40 column displays.
3458
3459- CONFIG_FLASH_VERIFY
3460		If defined, the content of the flash (destination) is compared
3461		against the source after the write operation. An error message
3462		will be printed when the contents are not identical.
3463		Please note that this option is useless in nearly all cases,
3464		since such flash programming errors usually are detected earlier
3465		while unprotecting/erasing/programming. Please only enable
3466		this option if you really know what you are doing.
3467
3468- CONFIG_SYS_RX_ETH_BUFFER:
3469		Defines the number of Ethernet receive buffers. On some
3470		Ethernet controllers it is recommended to set this value
3471		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3472		buffers can be full shortly after enabling the interface
3473		on high Ethernet traffic.
3474		Defaults to 4 if not defined.
3475
3476- CONFIG_ENV_MAX_ENTRIES
3477
3478	Maximum number of entries in the hash table that is used
3479	internally to store the environment settings. The default
3480	setting is supposed to be generous and should work in most
3481	cases. This setting can be used to tune behaviour; see
3482	lib/hashtable.c for details.
3483
3484- CONFIG_ENV_FLAGS_LIST_DEFAULT
3485- CONFIG_ENV_FLAGS_LIST_STATIC
3486	Enable validation of the values given to environment variables when
3487	calling env set.  Variables can be restricted to only decimal,
3488	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3489	the variables can also be restricted to IP address or MAC address.
3490
3491	The format of the list is:
3492		type_attribute = [s|d|x|b|i|m]
3493		access_atribute = [a|r|o|c]
3494		attributes = type_attribute[access_atribute]
3495		entry = variable_name[:attributes]
3496		list = entry[,list]
3497
3498	The type attributes are:
3499		s - String (default)
3500		d - Decimal
3501		x - Hexadecimal
3502		b - Boolean ([1yYtT|0nNfF])
3503		i - IP address
3504		m - MAC address
3505
3506	The access attributes are:
3507		a - Any (default)
3508		r - Read-only
3509		o - Write-once
3510		c - Change-default
3511
3512	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3513		Define this to a list (string) to define the ".flags"
3514		envirnoment variable in the default or embedded environment.
3515
3516	- CONFIG_ENV_FLAGS_LIST_STATIC
3517		Define this to a list (string) to define validation that
3518		should be done if an entry is not found in the ".flags"
3519		environment variable.  To override a setting in the static
3520		list, simply add an entry for the same variable name to the
3521		".flags" variable.
3522
3523- CONFIG_ENV_ACCESS_IGNORE_FORCE
3524	If defined, don't allow the -f switch to env set override variable
3525	access flags.
3526
3527- CONFIG_SYS_GENERIC_BOARD
3528	This selects the architecture-generic board system instead of the
3529	architecture-specific board files. It is intended to move boards
3530	to this new framework over time. Defining this will disable the
3531	arch/foo/lib/board.c file and use common/board_f.c and
3532	common/board_r.c instead. To use this option your architecture
3533	must support it (i.e. must define __HAVE_ARCH_GENERIC_BOARD in
3534	its config.mk file). If you find problems enabling this option on
3535	your board please report the problem and send patches!
3536
3537- CONFIG_SYS_SYM_OFFSETS
3538	This is set by architectures that use offsets for link symbols
3539	instead of absolute values. So bss_start is obtained using an
3540	offset _bss_start_ofs from CONFIG_SYS_TEXT_BASE, rather than
3541	directly. You should not need to touch this setting.
3542
3543- CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC (OMAP only)
3544	This is set by OMAP boards for the max time that reset should
3545	be asserted. See doc/README.omap-reset-time for details on how
3546	the value can be calulated on a given board.
3547
3548The following definitions that deal with the placement and management
3549of environment data (variable area); in general, we support the
3550following configurations:
3551
3552- CONFIG_BUILD_ENVCRC:
3553
3554	Builds up envcrc with the target environment so that external utils
3555	may easily extract it and embed it in final U-Boot images.
3556
3557- CONFIG_ENV_IS_IN_FLASH:
3558
3559	Define this if the environment is in flash memory.
3560
3561	a) The environment occupies one whole flash sector, which is
3562	   "embedded" in the text segment with the U-Boot code. This
3563	   happens usually with "bottom boot sector" or "top boot
3564	   sector" type flash chips, which have several smaller
3565	   sectors at the start or the end. For instance, such a
3566	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3567	   such a case you would place the environment in one of the
3568	   4 kB sectors - with U-Boot code before and after it. With
3569	   "top boot sector" type flash chips, you would put the
3570	   environment in one of the last sectors, leaving a gap
3571	   between U-Boot and the environment.
3572
3573	- CONFIG_ENV_OFFSET:
3574
3575	   Offset of environment data (variable area) to the
3576	   beginning of flash memory; for instance, with bottom boot
3577	   type flash chips the second sector can be used: the offset
3578	   for this sector is given here.
3579
3580	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3581
3582	- CONFIG_ENV_ADDR:
3583
3584	   This is just another way to specify the start address of
3585	   the flash sector containing the environment (instead of
3586	   CONFIG_ENV_OFFSET).
3587
3588	- CONFIG_ENV_SECT_SIZE:
3589
3590	   Size of the sector containing the environment.
3591
3592
3593	b) Sometimes flash chips have few, equal sized, BIG sectors.
3594	   In such a case you don't want to spend a whole sector for
3595	   the environment.
3596
3597	- CONFIG_ENV_SIZE:
3598
3599	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3600	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3601	   of this flash sector for the environment. This saves
3602	   memory for the RAM copy of the environment.
3603
3604	   It may also save flash memory if you decide to use this
3605	   when your environment is "embedded" within U-Boot code,
3606	   since then the remainder of the flash sector could be used
3607	   for U-Boot code. It should be pointed out that this is
3608	   STRONGLY DISCOURAGED from a robustness point of view:
3609	   updating the environment in flash makes it always
3610	   necessary to erase the WHOLE sector. If something goes
3611	   wrong before the contents has been restored from a copy in
3612	   RAM, your target system will be dead.
3613
3614	- CONFIG_ENV_ADDR_REDUND
3615	  CONFIG_ENV_SIZE_REDUND
3616
3617	   These settings describe a second storage area used to hold
3618	   a redundant copy of the environment data, so that there is
3619	   a valid backup copy in case there is a power failure during
3620	   a "saveenv" operation.
3621
3622BE CAREFUL! Any changes to the flash layout, and some changes to the
3623source code will make it necessary to adapt <board>/u-boot.lds*
3624accordingly!
3625
3626
3627- CONFIG_ENV_IS_IN_NVRAM:
3628
3629	Define this if you have some non-volatile memory device
3630	(NVRAM, battery buffered SRAM) which you want to use for the
3631	environment.
3632
3633	- CONFIG_ENV_ADDR:
3634	- CONFIG_ENV_SIZE:
3635
3636	  These two #defines are used to determine the memory area you
3637	  want to use for environment. It is assumed that this memory
3638	  can just be read and written to, without any special
3639	  provision.
3640
3641BE CAREFUL! The first access to the environment happens quite early
3642in U-Boot initalization (when we try to get the setting of for the
3643console baudrate). You *MUST* have mapped your NVRAM area then, or
3644U-Boot will hang.
3645
3646Please note that even with NVRAM we still use a copy of the
3647environment in RAM: we could work on NVRAM directly, but we want to
3648keep settings there always unmodified except somebody uses "saveenv"
3649to save the current settings.
3650
3651
3652- CONFIG_ENV_IS_IN_EEPROM:
3653
3654	Use this if you have an EEPROM or similar serial access
3655	device and a driver for it.
3656
3657	- CONFIG_ENV_OFFSET:
3658	- CONFIG_ENV_SIZE:
3659
3660	  These two #defines specify the offset and size of the
3661	  environment area within the total memory of your EEPROM.
3662
3663	- CONFIG_SYS_I2C_EEPROM_ADDR:
3664	  If defined, specified the chip address of the EEPROM device.
3665	  The default address is zero.
3666
3667	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3668	  If defined, the number of bits used to address bytes in a
3669	  single page in the EEPROM device.  A 64 byte page, for example
3670	  would require six bits.
3671
3672	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3673	  If defined, the number of milliseconds to delay between
3674	  page writes.	The default is zero milliseconds.
3675
3676	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3677	  The length in bytes of the EEPROM memory array address.  Note
3678	  that this is NOT the chip address length!
3679
3680	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3681	  EEPROM chips that implement "address overflow" are ones
3682	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3683	  address and the extra bits end up in the "chip address" bit
3684	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3685	  byte chips.
3686
3687	  Note that we consider the length of the address field to
3688	  still be one byte because the extra address bits are hidden
3689	  in the chip address.
3690
3691	- CONFIG_SYS_EEPROM_SIZE:
3692	  The size in bytes of the EEPROM device.
3693
3694	- CONFIG_ENV_EEPROM_IS_ON_I2C
3695	  define this, if you have I2C and SPI activated, and your
3696	  EEPROM, which holds the environment, is on the I2C bus.
3697
3698	- CONFIG_I2C_ENV_EEPROM_BUS
3699	  if you have an Environment on an EEPROM reached over
3700	  I2C muxes, you can define here, how to reach this
3701	  EEPROM. For example:
3702
3703	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3704
3705	  EEPROM which holds the environment, is reached over
3706	  a pca9547 i2c mux with address 0x70, channel 3.
3707
3708- CONFIG_ENV_IS_IN_DATAFLASH:
3709
3710	Define this if you have a DataFlash memory device which you
3711	want to use for the environment.
3712
3713	- CONFIG_ENV_OFFSET:
3714	- CONFIG_ENV_ADDR:
3715	- CONFIG_ENV_SIZE:
3716
3717	  These three #defines specify the offset and size of the
3718	  environment area within the total memory of your DataFlash placed
3719	  at the specified address.
3720
3721- CONFIG_ENV_IS_IN_REMOTE:
3722
3723	Define this if you have a remote memory space which you
3724	want to use for the local device's environment.
3725
3726	- CONFIG_ENV_ADDR:
3727	- CONFIG_ENV_SIZE:
3728
3729	  These two #defines specify the address and size of the
3730	  environment area within the remote memory space. The
3731	  local device can get the environment from remote memory
3732	  space by SRIO or PCIE links.
3733
3734BE CAREFUL! For some special cases, the local device can not use
3735"saveenv" command. For example, the local device will get the
3736environment stored in a remote NOR flash by SRIO or PCIE link,
3737but it can not erase, write this NOR flash by SRIO or PCIE interface.
3738
3739- CONFIG_ENV_IS_IN_NAND:
3740
3741	Define this if you have a NAND device which you want to use
3742	for the environment.
3743
3744	- CONFIG_ENV_OFFSET:
3745	- CONFIG_ENV_SIZE:
3746
3747	  These two #defines specify the offset and size of the environment
3748	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3749	  aligned to an erase block boundary.
3750
3751	- CONFIG_ENV_OFFSET_REDUND (optional):
3752
3753	  This setting describes a second storage area of CONFIG_ENV_SIZE
3754	  size used to hold a redundant copy of the environment data, so
3755	  that there is a valid backup copy in case there is a power failure
3756	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_RENDUND must be
3757	  aligned to an erase block boundary.
3758
3759	- CONFIG_ENV_RANGE (optional):
3760
3761	  Specifies the length of the region in which the environment
3762	  can be written.  This should be a multiple of the NAND device's
3763	  block size.  Specifying a range with more erase blocks than
3764	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3765	  the range to be avoided.
3766
3767	- CONFIG_ENV_OFFSET_OOB (optional):
3768
3769	  Enables support for dynamically retrieving the offset of the
3770	  environment from block zero's out-of-band data.  The
3771	  "nand env.oob" command can be used to record this offset.
3772	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3773	  using CONFIG_ENV_OFFSET_OOB.
3774
3775- CONFIG_NAND_ENV_DST
3776
3777	Defines address in RAM to which the nand_spl code should copy the
3778	environment. If redundant environment is used, it will be copied to
3779	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3780
3781- CONFIG_ENV_IS_IN_UBI:
3782
3783	Define this if you have an UBI volume that you want to use for the
3784	environment.  This has the benefit of wear-leveling the environment
3785	accesses, which is important on NAND.
3786
3787	- CONFIG_ENV_UBI_PART:
3788
3789	  Define this to a string that is the mtd partition containing the UBI.
3790
3791	- CONFIG_ENV_UBI_VOLUME:
3792
3793	  Define this to the name of the volume that you want to store the
3794	  environment in.
3795
3796	- CONFIG_ENV_UBI_VOLUME_REDUND:
3797
3798	  Define this to the name of another volume to store a second copy of
3799	  the environment in.  This will enable redundant environments in UBI.
3800	  It is assumed that both volumes are in the same MTD partition.
3801
3802	- CONFIG_UBI_SILENCE_MSG
3803	- CONFIG_UBIFS_SILENCE_MSG
3804
3805	  You will probably want to define these to avoid a really noisy system
3806	  when storing the env in UBI.
3807
3808- CONFIG_ENV_IS_IN_MMC:
3809
3810	Define this if you have an MMC device which you want to use for the
3811	environment.
3812
3813	- CONFIG_SYS_MMC_ENV_DEV:
3814
3815	  Specifies which MMC device the environment is stored in.
3816
3817	- CONFIG_SYS_MMC_ENV_PART (optional):
3818
3819	  Specifies which MMC partition the environment is stored in. If not
3820	  set, defaults to partition 0, the user area. Common values might be
3821	  1 (first MMC boot partition), 2 (second MMC boot partition).
3822
3823	- CONFIG_ENV_OFFSET:
3824	- CONFIG_ENV_SIZE:
3825
3826	  These two #defines specify the offset and size of the environment
3827	  area within the specified MMC device.
3828
3829	  If offset is positive (the usual case), it is treated as relative to
3830	  the start of the MMC partition. If offset is negative, it is treated
3831	  as relative to the end of the MMC partition. This can be useful if
3832	  your board may be fitted with different MMC devices, which have
3833	  different sizes for the MMC partitions, and you always want the
3834	  environment placed at the very end of the partition, to leave the
3835	  maximum possible space before it, to store other data.
3836
3837	  These two values are in units of bytes, but must be aligned to an
3838	  MMC sector boundary.
3839
3840	- CONFIG_ENV_OFFSET_REDUND (optional):
3841
3842	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3843	  hold a redundant copy of the environment data. This provides a
3844	  valid backup copy in case the other copy is corrupted, e.g. due
3845	  to a power failure during a "saveenv" operation.
3846
3847	  This value may also be positive or negative; this is handled in the
3848	  same way as CONFIG_ENV_OFFSET.
3849
3850	  This value is also in units of bytes, but must also be aligned to
3851	  an MMC sector boundary.
3852
3853	- CONFIG_ENV_SIZE_REDUND (optional):
3854
3855	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3856	  set. If this value is set, it must be set to the same value as
3857	  CONFIG_ENV_SIZE.
3858
3859- CONFIG_SYS_SPI_INIT_OFFSET
3860
3861	Defines offset to the initial SPI buffer area in DPRAM. The
3862	area is used at an early stage (ROM part) if the environment
3863	is configured to reside in the SPI EEPROM: We need a 520 byte
3864	scratch DPRAM area. It is used between the two initialization
3865	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3866	to be a good choice since it makes it far enough from the
3867	start of the data area as well as from the stack pointer.
3868
3869Please note that the environment is read-only until the monitor
3870has been relocated to RAM and a RAM copy of the environment has been
3871created; also, when using EEPROM you will have to use getenv_f()
3872until then to read environment variables.
3873
3874The environment is protected by a CRC32 checksum. Before the monitor
3875is relocated into RAM, as a result of a bad CRC you will be working
3876with the compiled-in default environment - *silently*!!! [This is
3877necessary, because the first environment variable we need is the
3878"baudrate" setting for the console - if we have a bad CRC, we don't
3879have any device yet where we could complain.]
3880
3881Note: once the monitor has been relocated, then it will complain if
3882the default environment is used; a new CRC is computed as soon as you
3883use the "saveenv" command to store a valid environment.
3884
3885- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3886		Echo the inverted Ethernet link state to the fault LED.
3887
3888		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3889		      also needs to be defined.
3890
3891- CONFIG_SYS_FAULT_MII_ADDR:
3892		MII address of the PHY to check for the Ethernet link state.
3893
3894- CONFIG_NS16550_MIN_FUNCTIONS:
3895		Define this if you desire to only have use of the NS16550_init
3896		and NS16550_putc functions for the serial driver located at
3897		drivers/serial/ns16550.c.  This option is useful for saving
3898		space for already greatly restricted images, including but not
3899		limited to NAND_SPL configurations.
3900
3901- CONFIG_DISPLAY_BOARDINFO
3902		Display information about the board that U-Boot is running on
3903		when U-Boot starts up. The board function checkboard() is called
3904		to do this.
3905
3906- CONFIG_DISPLAY_BOARDINFO_LATE
3907		Similar to the previous option, but display this information
3908		later, once stdio is running and output goes to the LCD, if
3909		present.
3910
3911Low Level (hardware related) configuration options:
3912---------------------------------------------------
3913
3914- CONFIG_SYS_CACHELINE_SIZE:
3915		Cache Line Size of the CPU.
3916
3917- CONFIG_SYS_DEFAULT_IMMR:
3918		Default address of the IMMR after system reset.
3919
3920		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3921		and RPXsuper) to be able to adjust the position of
3922		the IMMR register after a reset.
3923
3924- CONFIG_SYS_CCSRBAR_DEFAULT:
3925		Default (power-on reset) physical address of CCSR on Freescale
3926		PowerPC SOCs.
3927
3928- CONFIG_SYS_CCSRBAR:
3929		Virtual address of CCSR.  On a 32-bit build, this is typically
3930		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3931
3932		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
3933		for cross-platform code that uses that macro instead.
3934
3935- CONFIG_SYS_CCSRBAR_PHYS:
3936		Physical address of CCSR.  CCSR can be relocated to a new
3937		physical address, if desired.  In this case, this macro should
3938		be set to that address.	 Otherwise, it should be set to the
3939		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3940		is typically relocated on 36-bit builds.  It is recommended
3941		that this macro be defined via the _HIGH and _LOW macros:
3942
3943		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3944			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3945
3946- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3947		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3948		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3949		used in assembly code, so it must not contain typecasts or
3950		integer size suffixes (e.g. "ULL").
3951
3952- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3953		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3954		used in assembly code, so it must not contain typecasts or
3955		integer size suffixes (e.g. "ULL").
3956
3957- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3958		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3959		forced to a value that ensures that CCSR is not relocated.
3960
3961- Floppy Disk Support:
3962		CONFIG_SYS_FDC_DRIVE_NUMBER
3963
3964		the default drive number (default value 0)
3965
3966		CONFIG_SYS_ISA_IO_STRIDE
3967
3968		defines the spacing between FDC chipset registers
3969		(default value 1)
3970
3971		CONFIG_SYS_ISA_IO_OFFSET
3972
3973		defines the offset of register from address. It
3974		depends on which part of the data bus is connected to
3975		the FDC chipset. (default value 0)
3976
3977		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3978		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3979		default value.
3980
3981		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3982		fdc_hw_init() is called at the beginning of the FDC
3983		setup. fdc_hw_init() must be provided by the board
3984		source code. It is used to make hardware dependant
3985		initializations.
3986
3987- CONFIG_IDE_AHB:
3988		Most IDE controllers were designed to be connected with PCI
3989		interface. Only few of them were designed for AHB interface.
3990		When software is doing ATA command and data transfer to
3991		IDE devices through IDE-AHB controller, some additional
3992		registers accessing to these kind of IDE-AHB controller
3993		is requierd.
3994
3995- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3996		DO NOT CHANGE unless you know exactly what you're
3997		doing! (11-4) [MPC8xx/82xx systems only]
3998
3999- CONFIG_SYS_INIT_RAM_ADDR:
4000
4001		Start address of memory area that can be used for
4002		initial data and stack; please note that this must be
4003		writable memory that is working WITHOUT special
4004		initialization, i. e. you CANNOT use normal RAM which
4005		will become available only after programming the
4006		memory controller and running certain initialization
4007		sequences.
4008
4009		U-Boot uses the following memory types:
4010		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4011		- MPC824X: data cache
4012		- PPC4xx:  data cache
4013
4014- CONFIG_SYS_GBL_DATA_OFFSET:
4015
4016		Offset of the initial data structure in the memory
4017		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4018		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4019		data is located at the end of the available space
4020		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4021		CONFIG_SYS_INIT_DATA_SIZE), and the initial stack is just
4022		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4023		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4024
4025	Note:
4026		On the MPC824X (or other systems that use the data
4027		cache for initial memory) the address chosen for
4028		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4029		point to an otherwise UNUSED address space between
4030		the top of RAM and the start of the PCI space.
4031
4032- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4033
4034- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4035
4036- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4037
4038- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4039
4040- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4041
4042- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4043
4044- CONFIG_SYS_OR_TIMING_SDRAM:
4045		SDRAM timing
4046
4047- CONFIG_SYS_MAMR_PTA:
4048		periodic timer for refresh
4049
4050- CONFIG_SYS_DER:	Debug Event Register (37-47)
4051
4052- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4053  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4054  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4055  CONFIG_SYS_BR1_PRELIM:
4056		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4057
4058- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4059  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4060  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4061		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4062
4063- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4064  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4065		Machine Mode Register and Memory Periodic Timer
4066		Prescaler definitions (SDRAM timing)
4067
4068- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4069		enable I2C microcode relocation patch (MPC8xx);
4070		define relocation offset in DPRAM [DSP2]
4071
4072- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4073		enable SMC microcode relocation patch (MPC8xx);
4074		define relocation offset in DPRAM [SMC1]
4075
4076- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4077		enable SPI microcode relocation patch (MPC8xx);
4078		define relocation offset in DPRAM [SCC4]
4079
4080- CONFIG_SYS_USE_OSCCLK:
4081		Use OSCM clock mode on MBX8xx board. Be careful,
4082		wrong setting might damage your board. Read
4083		doc/README.MBX before setting this variable!
4084
4085- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4086		Offset of the bootmode word in DPRAM used by post
4087		(Power On Self Tests). This definition overrides
4088		#define'd default value in commproc.h resp.
4089		cpm_8260.h.
4090
4091- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4092  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4093  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4094  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4095  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4096  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4097  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4098  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4099		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4100
4101- CONFIG_PCI_DISABLE_PCIE:
4102		Disable PCI-Express on systems where it is supported but not
4103		required.
4104
4105- CONFIG_PCI_ENUM_ONLY
4106		Only scan through and get the devices on the busses.
4107		Don't do any setup work, presumably because someone or
4108		something has already done it, and we don't need to do it
4109		a second time.	Useful for platforms that are pre-booted
4110		by coreboot or similar.
4111
4112- CONFIG_PCI_INDIRECT_BRIDGE:
4113		Enable support for indirect PCI bridges.
4114
4115- CONFIG_SYS_SRIO:
4116		Chip has SRIO or not
4117
4118- CONFIG_SRIO1:
4119		Board has SRIO 1 port available
4120
4121- CONFIG_SRIO2:
4122		Board has SRIO 2 port available
4123
4124- CONFIG_SRIO_PCIE_BOOT_MASTER
4125		Board can support master function for Boot from SRIO and PCIE
4126
4127- CONFIG_SYS_SRIOn_MEM_VIRT:
4128		Virtual Address of SRIO port 'n' memory region
4129
4130- CONFIG_SYS_SRIOn_MEM_PHYS:
4131		Physical Address of SRIO port 'n' memory region
4132
4133- CONFIG_SYS_SRIOn_MEM_SIZE:
4134		Size of SRIO port 'n' memory region
4135
4136- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4137		Defined to tell the NAND controller that the NAND chip is using
4138		a 16 bit bus.
4139		Not all NAND drivers use this symbol.
4140		Example of drivers that use it:
4141		- drivers/mtd/nand/ndfc.c
4142		- drivers/mtd/nand/mxc_nand.c
4143
4144- CONFIG_SYS_NDFC_EBC0_CFG
4145		Sets the EBC0_CFG register for the NDFC. If not defined
4146		a default value will be used.
4147
4148- CONFIG_SPD_EEPROM
4149		Get DDR timing information from an I2C EEPROM. Common
4150		with pluggable memory modules such as SODIMMs
4151
4152  SPD_EEPROM_ADDRESS
4153		I2C address of the SPD EEPROM
4154
4155- CONFIG_SYS_SPD_BUS_NUM
4156		If SPD EEPROM is on an I2C bus other than the first
4157		one, specify here. Note that the value must resolve
4158		to something your driver can deal with.
4159
4160- CONFIG_SYS_DDR_RAW_TIMING
4161		Get DDR timing information from other than SPD. Common with
4162		soldered DDR chips onboard without SPD. DDR raw timing
4163		parameters are extracted from datasheet and hard-coded into
4164		header files or board specific files.
4165
4166- CONFIG_FSL_DDR_INTERACTIVE
4167		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4168
4169- CONFIG_SYS_83XX_DDR_USES_CS0
4170		Only for 83xx systems. If specified, then DDR should
4171		be configured using CS0 and CS1 instead of CS2 and CS3.
4172
4173- CONFIG_ETHER_ON_FEC[12]
4174		Define to enable FEC[12] on a 8xx series processor.
4175
4176- CONFIG_FEC[12]_PHY
4177		Define to the hardcoded PHY address which corresponds
4178		to the given FEC; i. e.
4179			#define CONFIG_FEC1_PHY 4
4180		means that the PHY with address 4 is connected to FEC1
4181
4182		When set to -1, means to probe for first available.
4183
4184- CONFIG_FEC[12]_PHY_NORXERR
4185		The PHY does not have a RXERR line (RMII only).
4186		(so program the FEC to ignore it).
4187
4188- CONFIG_RMII
4189		Enable RMII mode for all FECs.
4190		Note that this is a global option, we can't
4191		have one FEC in standard MII mode and another in RMII mode.
4192
4193- CONFIG_CRC32_VERIFY
4194		Add a verify option to the crc32 command.
4195		The syntax is:
4196
4197		=> crc32 -v <address> <count> <crc32>
4198
4199		Where address/count indicate a memory area
4200		and crc32 is the correct crc32 which the
4201		area should have.
4202
4203- CONFIG_LOOPW
4204		Add the "loopw" memory command. This only takes effect if
4205		the memory commands are activated globally (CONFIG_CMD_MEM).
4206
4207- CONFIG_MX_CYCLIC
4208		Add the "mdc" and "mwc" memory commands. These are cyclic
4209		"md/mw" commands.
4210		Examples:
4211
4212		=> mdc.b 10 4 500
4213		This command will print 4 bytes (10,11,12,13) each 500 ms.
4214
4215		=> mwc.l 100 12345678 10
4216		This command will write 12345678 to address 100 all 10 ms.
4217
4218		This only takes effect if the memory commands are activated
4219		globally (CONFIG_CMD_MEM).
4220
4221- CONFIG_SKIP_LOWLEVEL_INIT
4222		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4223		low level initializations (like setting up the memory
4224		controller) are omitted and/or U-Boot does not
4225		relocate itself into RAM.
4226
4227		Normally this variable MUST NOT be defined. The only
4228		exception is when U-Boot is loaded (to RAM) by some
4229		other boot loader or by a debugger which performs
4230		these initializations itself.
4231
4232- CONFIG_SPL_BUILD
4233		Modifies the behaviour of start.S when compiling a loader
4234		that is executed before the actual U-Boot. E.g. when
4235		compiling a NAND SPL.
4236
4237- CONFIG_TPL_BUILD
4238		Modifies the behaviour of start.S  when compiling a loader
4239		that is executed after the SPL and before the actual U-Boot.
4240		It is loaded by the SPL.
4241
4242- CONFIG_SYS_MPC85XX_NO_RESETVEC
4243		Only for 85xx systems. If this variable is specified, the section
4244		.resetvec is not kept and the section .bootpg is placed in the
4245		previous 4k of the .text section.
4246
4247- CONFIG_ARCH_MAP_SYSMEM
4248		Generally U-Boot (and in particular the md command) uses
4249		effective address. It is therefore not necessary to regard
4250		U-Boot address as virtual addresses that need to be translated
4251		to physical addresses. However, sandbox requires this, since
4252		it maintains its own little RAM buffer which contains all
4253		addressable memory. This option causes some memory accesses
4254		to be mapped through map_sysmem() / unmap_sysmem().
4255
4256- CONFIG_USE_ARCH_MEMCPY
4257  CONFIG_USE_ARCH_MEMSET
4258		If these options are used a optimized version of memcpy/memset will
4259		be used if available. These functions may be faster under some
4260		conditions but may increase the binary size.
4261
4262- CONFIG_X86_RESET_VECTOR
4263		If defined, the x86 reset vector code is included. This is not
4264		needed when U-Boot is running from Coreboot.
4265
4266- CONFIG_SYS_MPUCLK
4267		Defines the MPU clock speed (in MHz).
4268
4269		NOTE : currently only supported on AM335x platforms.
4270
4271Freescale QE/FMAN Firmware Support:
4272-----------------------------------
4273
4274The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4275loading of "firmware", which is encoded in the QE firmware binary format.
4276This firmware often needs to be loaded during U-Boot booting, so macros
4277are used to identify the storage device (NOR flash, SPI, etc) and the address
4278within that device.
4279
4280- CONFIG_SYS_QE_FMAN_FW_ADDR
4281	The address in the storage device where the firmware is located.  The
4282	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4283	is also specified.
4284
4285- CONFIG_SYS_QE_FMAN_FW_LENGTH
4286	The maximum possible size of the firmware.  The firmware binary format
4287	has a field that specifies the actual size of the firmware, but it
4288	might not be possible to read any part of the firmware unless some
4289	local storage is allocated to hold the entire firmware first.
4290
4291- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4292	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4293	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4294	virtual address in NOR flash.
4295
4296- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4297	Specifies that QE/FMAN firmware is located in NAND flash.
4298	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4299
4300- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4301	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4302	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4303
4304- CONFIG_SYS_QE_FMAN_FW_IN_SPIFLASH
4305	Specifies that QE/FMAN firmware is located on the primary SPI
4306	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4307
4308- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4309	Specifies that QE/FMAN firmware is located in the remote (master)
4310	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4311	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4312	window->master inbound window->master LAW->the ucode address in
4313	master's memory space.
4314
4315Building the Software:
4316======================
4317
4318Building U-Boot has been tested in several native build environments
4319and in many different cross environments. Of course we cannot support
4320all possibly existing versions of cross development tools in all
4321(potentially obsolete) versions. In case of tool chain problems we
4322recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4323which is extensively used to build and test U-Boot.
4324
4325If you are not using a native environment, it is assumed that you
4326have GNU cross compiling tools available in your path. In this case,
4327you must set the environment variable CROSS_COMPILE in your shell.
4328Note that no changes to the Makefile or any other source files are
4329necessary. For example using the ELDK on a 4xx CPU, please enter:
4330
4331	$ CROSS_COMPILE=ppc_4xx-
4332	$ export CROSS_COMPILE
4333
4334Note: If you wish to generate Windows versions of the utilities in
4335      the tools directory you can use the MinGW toolchain
4336      (http://www.mingw.org).  Set your HOST tools to the MinGW
4337      toolchain and execute 'make tools'.  For example:
4338
4339       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4340
4341      Binaries such as tools/mkimage.exe will be created which can
4342      be executed on computers running Windows.
4343
4344U-Boot is intended to be simple to build. After installing the
4345sources you must configure U-Boot for one specific board type. This
4346is done by typing:
4347
4348	make NAME_config
4349
4350where "NAME_config" is the name of one of the existing configu-
4351rations; see boards.cfg for supported names.
4352
4353Note: for some board special configuration names may exist; check if
4354      additional information is available from the board vendor; for
4355      instance, the TQM823L systems are available without (standard)
4356      or with LCD support. You can select such additional "features"
4357      when choosing the configuration, i. e.
4358
4359      make TQM823L_config
4360	- will configure for a plain TQM823L, i. e. no LCD support
4361
4362      make TQM823L_LCD_config
4363	- will configure for a TQM823L with U-Boot console on LCD
4364
4365      etc.
4366
4367
4368Finally, type "make all", and you should get some working U-Boot
4369images ready for download to / installation on your system:
4370
4371- "u-boot.bin" is a raw binary image
4372- "u-boot" is an image in ELF binary format
4373- "u-boot.srec" is in Motorola S-Record format
4374
4375By default the build is performed locally and the objects are saved
4376in the source directory. One of the two methods can be used to change
4377this behavior and build U-Boot to some external directory:
4378
43791. Add O= to the make command line invocations:
4380
4381	make O=/tmp/build distclean
4382	make O=/tmp/build NAME_config
4383	make O=/tmp/build all
4384
43852. Set environment variable BUILD_DIR to point to the desired location:
4386
4387	export BUILD_DIR=/tmp/build
4388	make distclean
4389	make NAME_config
4390	make all
4391
4392Note that the command line "O=" setting overrides the BUILD_DIR environment
4393variable.
4394
4395
4396Please be aware that the Makefiles assume you are using GNU make, so
4397for instance on NetBSD you might need to use "gmake" instead of
4398native "make".
4399
4400
4401If the system board that you have is not listed, then you will need
4402to port U-Boot to your hardware platform. To do this, follow these
4403steps:
4404
44051.  Add a new configuration option for your board to the toplevel
4406    "boards.cfg" file, using the existing entries as examples.
4407    Follow the instructions there to keep the boards in order.
44082.  Create a new directory to hold your board specific code. Add any
4409    files you need. In your board directory, you will need at least
4410    the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
44113.  Create a new configuration file "include/configs/<board>.h" for
4412    your board
44133.  If you're porting U-Boot to a new CPU, then also create a new
4414    directory to hold your CPU specific code. Add any files you need.
44154.  Run "make <board>_config" with your new name.
44165.  Type "make", and you should get a working "u-boot.srec" file
4417    to be installed on your target system.
44186.  Debug and solve any problems that might arise.
4419    [Of course, this last step is much harder than it sounds.]
4420
4421
4422Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4423==============================================================
4424
4425If you have modified U-Boot sources (for instance added a new board
4426or support for new devices, a new CPU, etc.) you are expected to
4427provide feedback to the other developers. The feedback normally takes
4428the form of a "patch", i. e. a context diff against a certain (latest
4429official or latest in the git repository) version of U-Boot sources.
4430
4431But before you submit such a patch, please verify that your modifi-
4432cation did not break existing code. At least make sure that *ALL* of
4433the supported boards compile WITHOUT ANY compiler warnings. To do so,
4434just run the "MAKEALL" script, which will configure and build U-Boot
4435for ALL supported system. Be warned, this will take a while. You can
4436select which (cross) compiler to use by passing a `CROSS_COMPILE'
4437environment variable to the script, i. e. to use the ELDK cross tools
4438you can type
4439
4440	CROSS_COMPILE=ppc_8xx- MAKEALL
4441
4442or to build on a native PowerPC system you can type
4443
4444	CROSS_COMPILE=' ' MAKEALL
4445
4446When using the MAKEALL script, the default behaviour is to build
4447U-Boot in the source directory. This location can be changed by
4448setting the BUILD_DIR environment variable. Also, for each target
4449built, the MAKEALL script saves two log files (<target>.ERR and
4450<target>.MAKEALL) in the <source dir>/LOG directory. This default
4451location can be changed by setting the MAKEALL_LOGDIR environment
4452variable. For example:
4453
4454	export BUILD_DIR=/tmp/build
4455	export MAKEALL_LOGDIR=/tmp/log
4456	CROSS_COMPILE=ppc_8xx- MAKEALL
4457
4458With the above settings build objects are saved in the /tmp/build,
4459log files are saved in the /tmp/log and the source tree remains clean
4460during the whole build process.
4461
4462
4463See also "U-Boot Porting Guide" below.
4464
4465
4466Monitor Commands - Overview:
4467============================
4468
4469go	- start application at address 'addr'
4470run	- run commands in an environment variable
4471bootm	- boot application image from memory
4472bootp	- boot image via network using BootP/TFTP protocol
4473bootz   - boot zImage from memory
4474tftpboot- boot image via network using TFTP protocol
4475	       and env variables "ipaddr" and "serverip"
4476	       (and eventually "gatewayip")
4477tftpput - upload a file via network using TFTP protocol
4478rarpboot- boot image via network using RARP/TFTP protocol
4479diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4480loads	- load S-Record file over serial line
4481loadb	- load binary file over serial line (kermit mode)
4482md	- memory display
4483mm	- memory modify (auto-incrementing)
4484nm	- memory modify (constant address)
4485mw	- memory write (fill)
4486cp	- memory copy
4487cmp	- memory compare
4488crc32	- checksum calculation
4489i2c	- I2C sub-system
4490sspi	- SPI utility commands
4491base	- print or set address offset
4492printenv- print environment variables
4493setenv	- set environment variables
4494saveenv - save environment variables to persistent storage
4495protect - enable or disable FLASH write protection
4496erase	- erase FLASH memory
4497flinfo	- print FLASH memory information
4498nand	- NAND memory operations (see doc/README.nand)
4499bdinfo	- print Board Info structure
4500iminfo	- print header information for application image
4501coninfo - print console devices and informations
4502ide	- IDE sub-system
4503loop	- infinite loop on address range
4504loopw	- infinite write loop on address range
4505mtest	- simple RAM test
4506icache	- enable or disable instruction cache
4507dcache	- enable or disable data cache
4508reset	- Perform RESET of the CPU
4509echo	- echo args to console
4510version - print monitor version
4511help	- print online help
4512?	- alias for 'help'
4513
4514
4515Monitor Commands - Detailed Description:
4516========================================
4517
4518TODO.
4519
4520For now: just type "help <command>".
4521
4522
4523Environment Variables:
4524======================
4525
4526U-Boot supports user configuration using Environment Variables which
4527can be made persistent by saving to Flash memory.
4528
4529Environment Variables are set using "setenv", printed using
4530"printenv", and saved to Flash using "saveenv". Using "setenv"
4531without a value can be used to delete a variable from the
4532environment. As long as you don't save the environment you are
4533working with an in-memory copy. In case the Flash area containing the
4534environment is erased by accident, a default environment is provided.
4535
4536Some configuration options can be set using Environment Variables.
4537
4538List of environment variables (most likely not complete):
4539
4540  baudrate	- see CONFIG_BAUDRATE
4541
4542  bootdelay	- see CONFIG_BOOTDELAY
4543
4544  bootcmd	- see CONFIG_BOOTCOMMAND
4545
4546  bootargs	- Boot arguments when booting an RTOS image
4547
4548  bootfile	- Name of the image to load with TFTP
4549
4550  bootm_low	- Memory range available for image processing in the bootm
4551		  command can be restricted. This variable is given as
4552		  a hexadecimal number and defines lowest address allowed
4553		  for use by the bootm command. See also "bootm_size"
4554		  environment variable. Address defined by "bootm_low" is
4555		  also the base of the initial memory mapping for the Linux
4556		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4557		  bootm_mapsize.
4558
4559  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4560		  This variable is given as a hexadecimal number and it
4561		  defines the size of the memory region starting at base
4562		  address bootm_low that is accessible by the Linux kernel
4563		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4564		  as the default value if it is defined, and bootm_size is
4565		  used otherwise.
4566
4567  bootm_size	- Memory range available for image processing in the bootm
4568		  command can be restricted. This variable is given as
4569		  a hexadecimal number and defines the size of the region
4570		  allowed for use by the bootm command. See also "bootm_low"
4571		  environment variable.
4572
4573  updatefile	- Location of the software update file on a TFTP server, used
4574		  by the automatic software update feature. Please refer to
4575		  documentation in doc/README.update for more details.
4576
4577  autoload	- if set to "no" (any string beginning with 'n'),
4578		  "bootp" will just load perform a lookup of the
4579		  configuration from the BOOTP server, but not try to
4580		  load any image using TFTP
4581
4582  autostart	- if set to "yes", an image loaded using the "bootp",
4583		  "rarpboot", "tftpboot" or "diskboot" commands will
4584		  be automatically started (by internally calling
4585		  "bootm")
4586
4587		  If set to "no", a standalone image passed to the
4588		  "bootm" command will be copied to the load address
4589		  (and eventually uncompressed), but NOT be started.
4590		  This can be used to load and uncompress arbitrary
4591		  data.
4592
4593  fdt_high	- if set this restricts the maximum address that the
4594		  flattened device tree will be copied into upon boot.
4595		  For example, if you have a system with 1 GB memory
4596		  at physical address 0x10000000, while Linux kernel
4597		  only recognizes the first 704 MB as low memory, you
4598		  may need to set fdt_high as 0x3C000000 to have the
4599		  device tree blob be copied to the maximum address
4600		  of the 704 MB low memory, so that Linux kernel can
4601		  access it during the boot procedure.
4602
4603		  If this is set to the special value 0xFFFFFFFF then
4604		  the fdt will not be copied at all on boot.  For this
4605		  to work it must reside in writable memory, have
4606		  sufficient padding on the end of it for u-boot to
4607		  add the information it needs into it, and the memory
4608		  must be accessible by the kernel.
4609
4610  fdtcontroladdr- if set this is the address of the control flattened
4611		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4612		  defined.
4613
4614  i2cfast	- (PPC405GP|PPC405EP only)
4615		  if set to 'y' configures Linux I2C driver for fast
4616		  mode (400kHZ). This environment variable is used in
4617		  initialization code. So, for changes to be effective
4618		  it must be saved and board must be reset.
4619
4620  initrd_high	- restrict positioning of initrd images:
4621		  If this variable is not set, initrd images will be
4622		  copied to the highest possible address in RAM; this
4623		  is usually what you want since it allows for
4624		  maximum initrd size. If for some reason you want to
4625		  make sure that the initrd image is loaded below the
4626		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4627		  variable to a value of "no" or "off" or "0".
4628		  Alternatively, you can set it to a maximum upper
4629		  address to use (U-Boot will still check that it
4630		  does not overwrite the U-Boot stack and data).
4631
4632		  For instance, when you have a system with 16 MB
4633		  RAM, and want to reserve 4 MB from use by Linux,
4634		  you can do this by adding "mem=12M" to the value of
4635		  the "bootargs" variable. However, now you must make
4636		  sure that the initrd image is placed in the first
4637		  12 MB as well - this can be done with
4638
4639		  setenv initrd_high 00c00000
4640
4641		  If you set initrd_high to 0xFFFFFFFF, this is an
4642		  indication to U-Boot that all addresses are legal
4643		  for the Linux kernel, including addresses in flash
4644		  memory. In this case U-Boot will NOT COPY the
4645		  ramdisk at all. This may be useful to reduce the
4646		  boot time on your system, but requires that this
4647		  feature is supported by your Linux kernel.
4648
4649  ipaddr	- IP address; needed for tftpboot command
4650
4651  loadaddr	- Default load address for commands like "bootp",
4652		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4653
4654  loads_echo	- see CONFIG_LOADS_ECHO
4655
4656  serverip	- TFTP server IP address; needed for tftpboot command
4657
4658  bootretry	- see CONFIG_BOOT_RETRY_TIME
4659
4660  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4661
4662  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4663
4664  ethprime	- controls which interface is used first.
4665
4666  ethact	- controls which interface is currently active.
4667		  For example you can do the following
4668
4669		  => setenv ethact FEC
4670		  => ping 192.168.0.1 # traffic sent on FEC
4671		  => setenv ethact SCC
4672		  => ping 10.0.0.1 # traffic sent on SCC
4673
4674  ethrotate	- When set to "no" U-Boot does not go through all
4675		  available network interfaces.
4676		  It just stays at the currently selected interface.
4677
4678  netretry	- When set to "no" each network operation will
4679		  either succeed or fail without retrying.
4680		  When set to "once" the network operation will
4681		  fail when all the available network interfaces
4682		  are tried once without success.
4683		  Useful on scripts which control the retry operation
4684		  themselves.
4685
4686  npe_ucode	- set load address for the NPE microcode
4687
4688  silent_linux  - If set then linux will be told to boot silently, by
4689		  changing the console to be empty. If "yes" it will be
4690		  made silent. If "no" it will not be made silent. If
4691		  unset, then it will be made silent if the U-Boot console
4692		  is silent.
4693
4694  tftpsrcport	- If this is set, the value is used for TFTP's
4695		  UDP source port.
4696
4697  tftpdstport	- If this is set, the value is used for TFTP's UDP
4698		  destination port instead of the Well Know Port 69.
4699
4700  tftpblocksize - Block size to use for TFTP transfers; if not set,
4701		  we use the TFTP server's default block size
4702
4703  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4704		  seconds, minimum value is 1000 = 1 second). Defines
4705		  when a packet is considered to be lost so it has to
4706		  be retransmitted. The default is 5000 = 5 seconds.
4707		  Lowering this value may make downloads succeed
4708		  faster in networks with high packet loss rates or
4709		  with unreliable TFTP servers.
4710
4711  vlan		- When set to a value < 4095 the traffic over
4712		  Ethernet is encapsulated/received over 802.1q
4713		  VLAN tagged frames.
4714
4715The following image location variables contain the location of images
4716used in booting. The "Image" column gives the role of the image and is
4717not an environment variable name. The other columns are environment
4718variable names. "File Name" gives the name of the file on a TFTP
4719server, "RAM Address" gives the location in RAM the image will be
4720loaded to, and "Flash Location" gives the image's address in NOR
4721flash or offset in NAND flash.
4722
4723*Note* - these variables don't have to be defined for all boards, some
4724boards currenlty use other variables for these purposes, and some
4725boards use these variables for other purposes.
4726
4727Image		    File Name	     RAM Address       Flash Location
4728-----		    ---------	     -----------       --------------
4729u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4730Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4731device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4732ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4733
4734The following environment variables may be used and automatically
4735updated by the network boot commands ("bootp" and "rarpboot"),
4736depending the information provided by your boot server:
4737
4738  bootfile	- see above
4739  dnsip		- IP address of your Domain Name Server
4740  dnsip2	- IP address of your secondary Domain Name Server
4741  gatewayip	- IP address of the Gateway (Router) to use
4742  hostname	- Target hostname
4743  ipaddr	- see above
4744  netmask	- Subnet Mask
4745  rootpath	- Pathname of the root filesystem on the NFS server
4746  serverip	- see above
4747
4748
4749There are two special Environment Variables:
4750
4751  serial#	- contains hardware identification information such
4752		  as type string and/or serial number
4753  ethaddr	- Ethernet address
4754
4755These variables can be set only once (usually during manufacturing of
4756the board). U-Boot refuses to delete or overwrite these variables
4757once they have been set once.
4758
4759
4760Further special Environment Variables:
4761
4762  ver		- Contains the U-Boot version string as printed
4763		  with the "version" command. This variable is
4764		  readonly (see CONFIG_VERSION_VARIABLE).
4765
4766
4767Please note that changes to some configuration parameters may take
4768only effect after the next boot (yes, that's just like Windoze :-).
4769
4770
4771Callback functions for environment variables:
4772---------------------------------------------
4773
4774For some environment variables, the behavior of u-boot needs to change
4775when their values are changed.  This functionailty allows functions to
4776be associated with arbitrary variables.  On creation, overwrite, or
4777deletion, the callback will provide the opportunity for some side
4778effect to happen or for the change to be rejected.
4779
4780The callbacks are named and associated with a function using the
4781U_BOOT_ENV_CALLBACK macro in your board or driver code.
4782
4783These callbacks are associated with variables in one of two ways.  The
4784static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4785in the board configuration to a string that defines a list of
4786associations.  The list must be in the following format:
4787
4788	entry = variable_name[:callback_name]
4789	list = entry[,list]
4790
4791If the callback name is not specified, then the callback is deleted.
4792Spaces are also allowed anywhere in the list.
4793
4794Callbacks can also be associated by defining the ".callbacks" variable
4795with the same list format above.  Any association in ".callbacks" will
4796override any association in the static list. You can define
4797CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4798".callbacks" envirnoment variable in the default or embedded environment.
4799
4800
4801Command Line Parsing:
4802=====================
4803
4804There are two different command line parsers available with U-Boot:
4805the old "simple" one, and the much more powerful "hush" shell:
4806
4807Old, simple command line parser:
4808--------------------------------
4809
4810- supports environment variables (through setenv / saveenv commands)
4811- several commands on one line, separated by ';'
4812- variable substitution using "... ${name} ..." syntax
4813- special characters ('$', ';') can be escaped by prefixing with '\',
4814  for example:
4815	setenv bootcmd bootm \${address}
4816- You can also escape text by enclosing in single apostrophes, for example:
4817	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4818
4819Hush shell:
4820-----------
4821
4822- similar to Bourne shell, with control structures like
4823  if...then...else...fi, for...do...done; while...do...done,
4824  until...do...done, ...
4825- supports environment ("global") variables (through setenv / saveenv
4826  commands) and local shell variables (through standard shell syntax
4827  "name=value"); only environment variables can be used with "run"
4828  command
4829
4830General rules:
4831--------------
4832
4833(1) If a command line (or an environment variable executed by a "run"
4834    command) contains several commands separated by semicolon, and
4835    one of these commands fails, then the remaining commands will be
4836    executed anyway.
4837
4838(2) If you execute several variables with one call to run (i. e.
4839    calling run with a list of variables as arguments), any failing
4840    command will cause "run" to terminate, i. e. the remaining
4841    variables are not executed.
4842
4843Note for Redundant Ethernet Interfaces:
4844=======================================
4845
4846Some boards come with redundant Ethernet interfaces; U-Boot supports
4847such configurations and is capable of automatic selection of a
4848"working" interface when needed. MAC assignment works as follows:
4849
4850Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4851MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4852"eth1addr" (=>eth1), "eth2addr", ...
4853
4854If the network interface stores some valid MAC address (for instance
4855in SROM), this is used as default address if there is NO correspon-
4856ding setting in the environment; if the corresponding environment
4857variable is set, this overrides the settings in the card; that means:
4858
4859o If the SROM has a valid MAC address, and there is no address in the
4860  environment, the SROM's address is used.
4861
4862o If there is no valid address in the SROM, and a definition in the
4863  environment exists, then the value from the environment variable is
4864  used.
4865
4866o If both the SROM and the environment contain a MAC address, and
4867  both addresses are the same, this MAC address is used.
4868
4869o If both the SROM and the environment contain a MAC address, and the
4870  addresses differ, the value from the environment is used and a
4871  warning is printed.
4872
4873o If neither SROM nor the environment contain a MAC address, an error
4874  is raised.
4875
4876If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4877will be programmed into hardware as part of the initialization process.	 This
4878may be skipped by setting the appropriate 'ethmacskip' environment variable.
4879The naming convention is as follows:
4880"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4881
4882Image Formats:
4883==============
4884
4885U-Boot is capable of booting (and performing other auxiliary operations on)
4886images in two formats:
4887
4888New uImage format (FIT)
4889-----------------------
4890
4891Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4892to Flattened Device Tree). It allows the use of images with multiple
4893components (several kernels, ramdisks, etc.), with contents protected by
4894SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4895
4896
4897Old uImage format
4898-----------------
4899
4900Old image format is based on binary files which can be basically anything,
4901preceded by a special header; see the definitions in include/image.h for
4902details; basically, the header defines the following image properties:
4903
4904* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4905  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4906  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4907  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4908  INTEGRITY).
4909* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
4910  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4911  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4912* Compression Type (uncompressed, gzip, bzip2)
4913* Load Address
4914* Entry Point
4915* Image Name
4916* Image Timestamp
4917
4918The header is marked by a special Magic Number, and both the header
4919and the data portions of the image are secured against corruption by
4920CRC32 checksums.
4921
4922
4923Linux Support:
4924==============
4925
4926Although U-Boot should support any OS or standalone application
4927easily, the main focus has always been on Linux during the design of
4928U-Boot.
4929
4930U-Boot includes many features that so far have been part of some
4931special "boot loader" code within the Linux kernel. Also, any
4932"initrd" images to be used are no longer part of one big Linux image;
4933instead, kernel and "initrd" are separate images. This implementation
4934serves several purposes:
4935
4936- the same features can be used for other OS or standalone
4937  applications (for instance: using compressed images to reduce the
4938  Flash memory footprint)
4939
4940- it becomes much easier to port new Linux kernel versions because
4941  lots of low-level, hardware dependent stuff are done by U-Boot
4942
4943- the same Linux kernel image can now be used with different "initrd"
4944  images; of course this also means that different kernel images can
4945  be run with the same "initrd". This makes testing easier (you don't
4946  have to build a new "zImage.initrd" Linux image when you just
4947  change a file in your "initrd"). Also, a field-upgrade of the
4948  software is easier now.
4949
4950
4951Linux HOWTO:
4952============
4953
4954Porting Linux to U-Boot based systems:
4955---------------------------------------
4956
4957U-Boot cannot save you from doing all the necessary modifications to
4958configure the Linux device drivers for use with your target hardware
4959(no, we don't intend to provide a full virtual machine interface to
4960Linux :-).
4961
4962But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4963
4964Just make sure your machine specific header file (for instance
4965include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4966Information structure as we define in include/asm-<arch>/u-boot.h,
4967and make sure that your definition of IMAP_ADDR uses the same value
4968as your U-Boot configuration in CONFIG_SYS_IMMR.
4969
4970
4971Configuring the Linux kernel:
4972-----------------------------
4973
4974No specific requirements for U-Boot. Make sure you have some root
4975device (initial ramdisk, NFS) for your target system.
4976
4977
4978Building a Linux Image:
4979-----------------------
4980
4981With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4982not used. If you use recent kernel source, a new build target
4983"uImage" will exist which automatically builds an image usable by
4984U-Boot. Most older kernels also have support for a "pImage" target,
4985which was introduced for our predecessor project PPCBoot and uses a
4986100% compatible format.
4987
4988Example:
4989
4990	make TQM850L_config
4991	make oldconfig
4992	make dep
4993	make uImage
4994
4995The "uImage" build target uses a special tool (in 'tools/mkimage') to
4996encapsulate a compressed Linux kernel image with header	 information,
4997CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4998
4999* build a standard "vmlinux" kernel image (in ELF binary format):
5000
5001* convert the kernel into a raw binary image:
5002
5003	${CROSS_COMPILE}-objcopy -O binary \
5004				 -R .note -R .comment \
5005				 -S vmlinux linux.bin
5006
5007* compress the binary image:
5008
5009	gzip -9 linux.bin
5010
5011* package compressed binary image for U-Boot:
5012
5013	mkimage -A ppc -O linux -T kernel -C gzip \
5014		-a 0 -e 0 -n "Linux Kernel Image" \
5015		-d linux.bin.gz uImage
5016
5017
5018The "mkimage" tool can also be used to create ramdisk images for use
5019with U-Boot, either separated from the Linux kernel image, or
5020combined into one file. "mkimage" encapsulates the images with a 64
5021byte header containing information about target architecture,
5022operating system, image type, compression method, entry points, time
5023stamp, CRC32 checksums, etc.
5024
5025"mkimage" can be called in two ways: to verify existing images and
5026print the header information, or to build new images.
5027
5028In the first form (with "-l" option) mkimage lists the information
5029contained in the header of an existing U-Boot image; this includes
5030checksum verification:
5031
5032	tools/mkimage -l image
5033	  -l ==> list image header information
5034
5035The second form (with "-d" option) is used to build a U-Boot image
5036from a "data file" which is used as image payload:
5037
5038	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5039		      -n name -d data_file image
5040	  -A ==> set architecture to 'arch'
5041	  -O ==> set operating system to 'os'
5042	  -T ==> set image type to 'type'
5043	  -C ==> set compression type 'comp'
5044	  -a ==> set load address to 'addr' (hex)
5045	  -e ==> set entry point to 'ep' (hex)
5046	  -n ==> set image name to 'name'
5047	  -d ==> use image data from 'datafile'
5048
5049Right now, all Linux kernels for PowerPC systems use the same load
5050address (0x00000000), but the entry point address depends on the
5051kernel version:
5052
5053- 2.2.x kernels have the entry point at 0x0000000C,
5054- 2.3.x and later kernels have the entry point at 0x00000000.
5055
5056So a typical call to build a U-Boot image would read:
5057
5058	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5059	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5060	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5061	> examples/uImage.TQM850L
5062	Image Name:   2.4.4 kernel for TQM850L
5063	Created:      Wed Jul 19 02:34:59 2000
5064	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5065	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5066	Load Address: 0x00000000
5067	Entry Point:  0x00000000
5068
5069To verify the contents of the image (or check for corruption):
5070
5071	-> tools/mkimage -l examples/uImage.TQM850L
5072	Image Name:   2.4.4 kernel for TQM850L
5073	Created:      Wed Jul 19 02:34:59 2000
5074	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5075	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5076	Load Address: 0x00000000
5077	Entry Point:  0x00000000
5078
5079NOTE: for embedded systems where boot time is critical you can trade
5080speed for memory and install an UNCOMPRESSED image instead: this
5081needs more space in Flash, but boots much faster since it does not
5082need to be uncompressed:
5083
5084	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5085	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5086	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5087	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5088	> examples/uImage.TQM850L-uncompressed
5089	Image Name:   2.4.4 kernel for TQM850L
5090	Created:      Wed Jul 19 02:34:59 2000
5091	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5092	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5093	Load Address: 0x00000000
5094	Entry Point:  0x00000000
5095
5096
5097Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5098when your kernel is intended to use an initial ramdisk:
5099
5100	-> tools/mkimage -n 'Simple Ramdisk Image' \
5101	> -A ppc -O linux -T ramdisk -C gzip \
5102	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5103	Image Name:   Simple Ramdisk Image
5104	Created:      Wed Jan 12 14:01:50 2000
5105	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5106	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5107	Load Address: 0x00000000
5108	Entry Point:  0x00000000
5109
5110
5111Installing a Linux Image:
5112-------------------------
5113
5114To downloading a U-Boot image over the serial (console) interface,
5115you must convert the image to S-Record format:
5116
5117	objcopy -I binary -O srec examples/image examples/image.srec
5118
5119The 'objcopy' does not understand the information in the U-Boot
5120image header, so the resulting S-Record file will be relative to
5121address 0x00000000. To load it to a given address, you need to
5122specify the target address as 'offset' parameter with the 'loads'
5123command.
5124
5125Example: install the image to address 0x40100000 (which on the
5126TQM8xxL is in the first Flash bank):
5127
5128	=> erase 40100000 401FFFFF
5129
5130	.......... done
5131	Erased 8 sectors
5132
5133	=> loads 40100000
5134	## Ready for S-Record download ...
5135	~>examples/image.srec
5136	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5137	...
5138	15989 15990 15991 15992
5139	[file transfer complete]
5140	[connected]
5141	## Start Addr = 0x00000000
5142
5143
5144You can check the success of the download using the 'iminfo' command;
5145this includes a checksum verification so you can be sure no data
5146corruption happened:
5147
5148	=> imi 40100000
5149
5150	## Checking Image at 40100000 ...
5151	   Image Name:	 2.2.13 for initrd on TQM850L
5152	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5153	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5154	   Load Address: 00000000
5155	   Entry Point:	 0000000c
5156	   Verifying Checksum ... OK
5157
5158
5159Boot Linux:
5160-----------
5161
5162The "bootm" command is used to boot an application that is stored in
5163memory (RAM or Flash). In case of a Linux kernel image, the contents
5164of the "bootargs" environment variable is passed to the kernel as
5165parameters. You can check and modify this variable using the
5166"printenv" and "setenv" commands:
5167
5168
5169	=> printenv bootargs
5170	bootargs=root=/dev/ram
5171
5172	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5173
5174	=> printenv bootargs
5175	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5176
5177	=> bootm 40020000
5178	## Booting Linux kernel at 40020000 ...
5179	   Image Name:	 2.2.13 for NFS on TQM850L
5180	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5181	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5182	   Load Address: 00000000
5183	   Entry Point:	 0000000c
5184	   Verifying Checksum ... OK
5185	   Uncompressing Kernel Image ... OK
5186	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
5187	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5188	time_init: decrementer frequency = 187500000/60
5189	Calibrating delay loop... 49.77 BogoMIPS
5190	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5191	...
5192
5193If you want to boot a Linux kernel with initial RAM disk, you pass
5194the memory addresses of both the kernel and the initrd image (PPBCOOT
5195format!) to the "bootm" command:
5196
5197	=> imi 40100000 40200000
5198
5199	## Checking Image at 40100000 ...
5200	   Image Name:	 2.2.13 for initrd on TQM850L
5201	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5202	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5203	   Load Address: 00000000
5204	   Entry Point:	 0000000c
5205	   Verifying Checksum ... OK
5206
5207	## Checking Image at 40200000 ...
5208	   Image Name:	 Simple Ramdisk Image
5209	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5210	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5211	   Load Address: 00000000
5212	   Entry Point:	 00000000
5213	   Verifying Checksum ... OK
5214
5215	=> bootm 40100000 40200000
5216	## Booting Linux kernel at 40100000 ...
5217	   Image Name:	 2.2.13 for initrd on TQM850L
5218	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5219	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5220	   Load Address: 00000000
5221	   Entry Point:	 0000000c
5222	   Verifying Checksum ... OK
5223	   Uncompressing Kernel Image ... OK
5224	## Loading RAMDisk Image at 40200000 ...
5225	   Image Name:	 Simple Ramdisk Image
5226	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5227	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5228	   Load Address: 00000000
5229	   Entry Point:	 00000000
5230	   Verifying Checksum ... OK
5231	   Loading Ramdisk ... OK
5232	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
5233	Boot arguments: root=/dev/ram
5234	time_init: decrementer frequency = 187500000/60
5235	Calibrating delay loop... 49.77 BogoMIPS
5236	...
5237	RAMDISK: Compressed image found at block 0
5238	VFS: Mounted root (ext2 filesystem).
5239
5240	bash#
5241
5242Boot Linux and pass a flat device tree:
5243-----------
5244
5245First, U-Boot must be compiled with the appropriate defines. See the section
5246titled "Linux Kernel Interface" above for a more in depth explanation. The
5247following is an example of how to start a kernel and pass an updated
5248flat device tree:
5249
5250=> print oftaddr
5251oftaddr=0x300000
5252=> print oft
5253oft=oftrees/mpc8540ads.dtb
5254=> tftp $oftaddr $oft
5255Speed: 1000, full duplex
5256Using TSEC0 device
5257TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5258Filename 'oftrees/mpc8540ads.dtb'.
5259Load address: 0x300000
5260Loading: #
5261done
5262Bytes transferred = 4106 (100a hex)
5263=> tftp $loadaddr $bootfile
5264Speed: 1000, full duplex
5265Using TSEC0 device
5266TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5267Filename 'uImage'.
5268Load address: 0x200000
5269Loading:############
5270done
5271Bytes transferred = 1029407 (fb51f hex)
5272=> print loadaddr
5273loadaddr=200000
5274=> print oftaddr
5275oftaddr=0x300000
5276=> bootm $loadaddr - $oftaddr
5277## Booting image at 00200000 ...
5278   Image Name:	 Linux-2.6.17-dirty
5279   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5280   Data Size:	 1029343 Bytes = 1005.2 kB
5281   Load Address: 00000000
5282   Entry Point:	 00000000
5283   Verifying Checksum ... OK
5284   Uncompressing Kernel Image ... OK
5285Booting using flat device tree at 0x300000
5286Using MPC85xx ADS machine description
5287Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5288[snip]
5289
5290
5291More About U-Boot Image Types:
5292------------------------------
5293
5294U-Boot supports the following image types:
5295
5296   "Standalone Programs" are directly runnable in the environment
5297	provided by U-Boot; it is expected that (if they behave
5298	well) you can continue to work in U-Boot after return from
5299	the Standalone Program.
5300   "OS Kernel Images" are usually images of some Embedded OS which
5301	will take over control completely. Usually these programs
5302	will install their own set of exception handlers, device
5303	drivers, set up the MMU, etc. - this means, that you cannot
5304	expect to re-enter U-Boot except by resetting the CPU.
5305   "RAMDisk Images" are more or less just data blocks, and their
5306	parameters (address, size) are passed to an OS kernel that is
5307	being started.
5308   "Multi-File Images" contain several images, typically an OS
5309	(Linux) kernel image and one or more data images like
5310	RAMDisks. This construct is useful for instance when you want
5311	to boot over the network using BOOTP etc., where the boot
5312	server provides just a single image file, but you want to get
5313	for instance an OS kernel and a RAMDisk image.
5314
5315	"Multi-File Images" start with a list of image sizes, each
5316	image size (in bytes) specified by an "uint32_t" in network
5317	byte order. This list is terminated by an "(uint32_t)0".
5318	Immediately after the terminating 0 follow the images, one by
5319	one, all aligned on "uint32_t" boundaries (size rounded up to
5320	a multiple of 4 bytes).
5321
5322   "Firmware Images" are binary images containing firmware (like
5323	U-Boot or FPGA images) which usually will be programmed to
5324	flash memory.
5325
5326   "Script files" are command sequences that will be executed by
5327	U-Boot's command interpreter; this feature is especially
5328	useful when you configure U-Boot to use a real shell (hush)
5329	as command interpreter.
5330
5331Booting the Linux zImage:
5332-------------------------
5333
5334On some platforms, it's possible to boot Linux zImage. This is done
5335using the "bootz" command. The syntax of "bootz" command is the same
5336as the syntax of "bootm" command.
5337
5338Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5339kernel with raw initrd images. The syntax is slightly different, the
5340address of the initrd must be augmented by it's size, in the following
5341format: "<initrd addres>:<initrd size>".
5342
5343
5344Standalone HOWTO:
5345=================
5346
5347One of the features of U-Boot is that you can dynamically load and
5348run "standalone" applications, which can use some resources of
5349U-Boot like console I/O functions or interrupt services.
5350
5351Two simple examples are included with the sources:
5352
5353"Hello World" Demo:
5354-------------------
5355
5356'examples/hello_world.c' contains a small "Hello World" Demo
5357application; it is automatically compiled when you build U-Boot.
5358It's configured to run at address 0x00040004, so you can play with it
5359like that:
5360
5361	=> loads
5362	## Ready for S-Record download ...
5363	~>examples/hello_world.srec
5364	1 2 3 4 5 6 7 8 9 10 11 ...
5365	[file transfer complete]
5366	[connected]
5367	## Start Addr = 0x00040004
5368
5369	=> go 40004 Hello World! This is a test.
5370	## Starting application at 0x00040004 ...
5371	Hello World
5372	argc = 7
5373	argv[0] = "40004"
5374	argv[1] = "Hello"
5375	argv[2] = "World!"
5376	argv[3] = "This"
5377	argv[4] = "is"
5378	argv[5] = "a"
5379	argv[6] = "test."
5380	argv[7] = "<NULL>"
5381	Hit any key to exit ...
5382
5383	## Application terminated, rc = 0x0
5384
5385Another example, which demonstrates how to register a CPM interrupt
5386handler with the U-Boot code, can be found in 'examples/timer.c'.
5387Here, a CPM timer is set up to generate an interrupt every second.
5388The interrupt service routine is trivial, just printing a '.'
5389character, but this is just a demo program. The application can be
5390controlled by the following keys:
5391
5392	? - print current values og the CPM Timer registers
5393	b - enable interrupts and start timer
5394	e - stop timer and disable interrupts
5395	q - quit application
5396
5397	=> loads
5398	## Ready for S-Record download ...
5399	~>examples/timer.srec
5400	1 2 3 4 5 6 7 8 9 10 11 ...
5401	[file transfer complete]
5402	[connected]
5403	## Start Addr = 0x00040004
5404
5405	=> go 40004
5406	## Starting application at 0x00040004 ...
5407	TIMERS=0xfff00980
5408	Using timer 1
5409	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5410
5411Hit 'b':
5412	[q, b, e, ?] Set interval 1000000 us
5413	Enabling timer
5414Hit '?':
5415	[q, b, e, ?] ........
5416	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5417Hit '?':
5418	[q, b, e, ?] .
5419	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5420Hit '?':
5421	[q, b, e, ?] .
5422	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5423Hit '?':
5424	[q, b, e, ?] .
5425	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5426Hit 'e':
5427	[q, b, e, ?] ...Stopping timer
5428Hit 'q':
5429	[q, b, e, ?] ## Application terminated, rc = 0x0
5430
5431
5432Minicom warning:
5433================
5434
5435Over time, many people have reported problems when trying to use the
5436"minicom" terminal emulation program for serial download. I (wd)
5437consider minicom to be broken, and recommend not to use it. Under
5438Unix, I recommend to use C-Kermit for general purpose use (and
5439especially for kermit binary protocol download ("loadb" command), and
5440use "cu" for S-Record download ("loads" command).  See
5441http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5442for help with kermit.
5443
5444
5445Nevertheless, if you absolutely want to use it try adding this
5446configuration to your "File transfer protocols" section:
5447
5448	   Name	   Program			Name U/D FullScr IO-Red. Multi
5449	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5450	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5451
5452
5453NetBSD Notes:
5454=============
5455
5456Starting at version 0.9.2, U-Boot supports NetBSD both as host
5457(build U-Boot) and target system (boots NetBSD/mpc8xx).
5458
5459Building requires a cross environment; it is known to work on
5460NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5461need gmake since the Makefiles are not compatible with BSD make).
5462Note that the cross-powerpc package does not install include files;
5463attempting to build U-Boot will fail because <machine/ansi.h> is
5464missing.  This file has to be installed and patched manually:
5465
5466	# cd /usr/pkg/cross/powerpc-netbsd/include
5467	# mkdir powerpc
5468	# ln -s powerpc machine
5469	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5470	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5471
5472Native builds *don't* work due to incompatibilities between native
5473and U-Boot include files.
5474
5475Booting assumes that (the first part of) the image booted is a
5476stage-2 loader which in turn loads and then invokes the kernel
5477proper. Loader sources will eventually appear in the NetBSD source
5478tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5479meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5480
5481
5482Implementation Internals:
5483=========================
5484
5485The following is not intended to be a complete description of every
5486implementation detail. However, it should help to understand the
5487inner workings of U-Boot and make it easier to port it to custom
5488hardware.
5489
5490
5491Initial Stack, Global Data:
5492---------------------------
5493
5494The implementation of U-Boot is complicated by the fact that U-Boot
5495starts running out of ROM (flash memory), usually without access to
5496system RAM (because the memory controller is not initialized yet).
5497This means that we don't have writable Data or BSS segments, and BSS
5498is not initialized as zero. To be able to get a C environment working
5499at all, we have to allocate at least a minimal stack. Implementation
5500options for this are defined and restricted by the CPU used: Some CPU
5501models provide on-chip memory (like the IMMR area on MPC8xx and
5502MPC826x processors), on others (parts of) the data cache can be
5503locked as (mis-) used as memory, etc.
5504
5505	Chris Hallinan posted a good summary of these issues to the
5506	U-Boot mailing list:
5507
5508	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5509	From: "Chris Hallinan" <clh@net1plus.com>
5510	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5511	...
5512
5513	Correct me if I'm wrong, folks, but the way I understand it
5514	is this: Using DCACHE as initial RAM for Stack, etc, does not
5515	require any physical RAM backing up the cache. The cleverness
5516	is that the cache is being used as a temporary supply of
5517	necessary storage before the SDRAM controller is setup. It's
5518	beyond the scope of this list to explain the details, but you
5519	can see how this works by studying the cache architecture and
5520	operation in the architecture and processor-specific manuals.
5521
5522	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5523	is another option for the system designer to use as an
5524	initial stack/RAM area prior to SDRAM being available. Either
5525	option should work for you. Using CS 4 should be fine if your
5526	board designers haven't used it for something that would
5527	cause you grief during the initial boot! It is frequently not
5528	used.
5529
5530	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5531	with your processor/board/system design. The default value
5532	you will find in any recent u-boot distribution in
5533	walnut.h should work for you. I'd set it to a value larger
5534	than your SDRAM module. If you have a 64MB SDRAM module, set
5535	it above 400_0000. Just make sure your board has no resources
5536	that are supposed to respond to that address! That code in
5537	start.S has been around a while and should work as is when
5538	you get the config right.
5539
5540	-Chris Hallinan
5541	DS4.COM, Inc.
5542
5543It is essential to remember this, since it has some impact on the C
5544code for the initialization procedures:
5545
5546* Initialized global data (data segment) is read-only. Do not attempt
5547  to write it.
5548
5549* Do not use any uninitialized global data (or implicitely initialized
5550  as zero data - BSS segment) at all - this is undefined, initiali-
5551  zation is performed later (when relocating to RAM).
5552
5553* Stack space is very limited. Avoid big data buffers or things like
5554  that.
5555
5556Having only the stack as writable memory limits means we cannot use
5557normal global data to share information beween the code. But it
5558turned out that the implementation of U-Boot can be greatly
5559simplified by making a global data structure (gd_t) available to all
5560functions. We could pass a pointer to this data as argument to _all_
5561functions, but this would bloat the code. Instead we use a feature of
5562the GCC compiler (Global Register Variables) to share the data: we
5563place a pointer (gd) to the global data into a register which we
5564reserve for this purpose.
5565
5566When choosing a register for such a purpose we are restricted by the
5567relevant  (E)ABI  specifications for the current architecture, and by
5568GCC's implementation.
5569
5570For PowerPC, the following registers have specific use:
5571	R1:	stack pointer
5572	R2:	reserved for system use
5573	R3-R4:	parameter passing and return values
5574	R5-R10: parameter passing
5575	R13:	small data area pointer
5576	R30:	GOT pointer
5577	R31:	frame pointer
5578
5579	(U-Boot also uses R12 as internal GOT pointer. r12
5580	is a volatile register so r12 needs to be reset when
5581	going back and forth between asm and C)
5582
5583    ==> U-Boot will use R2 to hold a pointer to the global data
5584
5585    Note: on PPC, we could use a static initializer (since the
5586    address of the global data structure is known at compile time),
5587    but it turned out that reserving a register results in somewhat
5588    smaller code - although the code savings are not that big (on
5589    average for all boards 752 bytes for the whole U-Boot image,
5590    624 text + 127 data).
5591
5592On Blackfin, the normal C ABI (except for P3) is followed as documented here:
5593	http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface
5594
5595    ==> U-Boot will use P3 to hold a pointer to the global data
5596
5597On ARM, the following registers are used:
5598
5599	R0:	function argument word/integer result
5600	R1-R3:	function argument word
5601	R9:	GOT pointer
5602	R10:	stack limit (used only if stack checking if enabled)
5603	R11:	argument (frame) pointer
5604	R12:	temporary workspace
5605	R13:	stack pointer
5606	R14:	link register
5607	R15:	program counter
5608
5609    ==> U-Boot will use R8 to hold a pointer to the global data
5610
5611On Nios II, the ABI is documented here:
5612	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5613
5614    ==> U-Boot will use gp to hold a pointer to the global data
5615
5616    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5617    to access small data sections, so gp is free.
5618
5619On NDS32, the following registers are used:
5620
5621	R0-R1:	argument/return
5622	R2-R5:	argument
5623	R15:	temporary register for assembler
5624	R16:	trampoline register
5625	R28:	frame pointer (FP)
5626	R29:	global pointer (GP)
5627	R30:	link register (LP)
5628	R31:	stack pointer (SP)
5629	PC:	program counter (PC)
5630
5631    ==> U-Boot will use R10 to hold a pointer to the global data
5632
5633NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5634or current versions of GCC may "optimize" the code too much.
5635
5636Memory Management:
5637------------------
5638
5639U-Boot runs in system state and uses physical addresses, i.e. the
5640MMU is not used either for address mapping nor for memory protection.
5641
5642The available memory is mapped to fixed addresses using the memory
5643controller. In this process, a contiguous block is formed for each
5644memory type (Flash, SDRAM, SRAM), even when it consists of several
5645physical memory banks.
5646
5647U-Boot is installed in the first 128 kB of the first Flash bank (on
5648TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5649booting and sizing and initializing DRAM, the code relocates itself
5650to the upper end of DRAM. Immediately below the U-Boot code some
5651memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5652configuration setting]. Below that, a structure with global Board
5653Info data is placed, followed by the stack (growing downward).
5654
5655Additionally, some exception handler code is copied to the low 8 kB
5656of DRAM (0x00000000 ... 0x00001FFF).
5657
5658So a typical memory configuration with 16 MB of DRAM could look like
5659this:
5660
5661	0x0000 0000	Exception Vector code
5662	      :
5663	0x0000 1FFF
5664	0x0000 2000	Free for Application Use
5665	      :
5666	      :
5667
5668	      :
5669	      :
5670	0x00FB FF20	Monitor Stack (Growing downward)
5671	0x00FB FFAC	Board Info Data and permanent copy of global data
5672	0x00FC 0000	Malloc Arena
5673	      :
5674	0x00FD FFFF
5675	0x00FE 0000	RAM Copy of Monitor Code
5676	...		eventually: LCD or video framebuffer
5677	...		eventually: pRAM (Protected RAM - unchanged by reset)
5678	0x00FF FFFF	[End of RAM]
5679
5680
5681System Initialization:
5682----------------------
5683
5684In the reset configuration, U-Boot starts at the reset entry point
5685(on most PowerPC systems at address 0x00000100). Because of the reset
5686configuration for CS0# this is a mirror of the onboard Flash memory.
5687To be able to re-map memory U-Boot then jumps to its link address.
5688To be able to implement the initialization code in C, a (small!)
5689initial stack is set up in the internal Dual Ported RAM (in case CPUs
5690which provide such a feature like MPC8xx or MPC8260), or in a locked
5691part of the data cache. After that, U-Boot initializes the CPU core,
5692the caches and the SIU.
5693
5694Next, all (potentially) available memory banks are mapped using a
5695preliminary mapping. For example, we put them on 512 MB boundaries
5696(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5697on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5698programmed for SDRAM access. Using the temporary configuration, a
5699simple memory test is run that determines the size of the SDRAM
5700banks.
5701
5702When there is more than one SDRAM bank, and the banks are of
5703different size, the largest is mapped first. For equal size, the first
5704bank (CS2#) is mapped first. The first mapping is always for address
57050x00000000, with any additional banks following immediately to create
5706contiguous memory starting from 0.
5707
5708Then, the monitor installs itself at the upper end of the SDRAM area
5709and allocates memory for use by malloc() and for the global Board
5710Info data; also, the exception vector code is copied to the low RAM
5711pages, and the final stack is set up.
5712
5713Only after this relocation will you have a "normal" C environment;
5714until that you are restricted in several ways, mostly because you are
5715running from ROM, and because the code will have to be relocated to a
5716new address in RAM.
5717
5718
5719U-Boot Porting Guide:
5720----------------------
5721
5722[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5723list, October 2002]
5724
5725
5726int main(int argc, char *argv[])
5727{
5728	sighandler_t no_more_time;
5729
5730	signal(SIGALRM, no_more_time);
5731	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5732
5733	if (available_money > available_manpower) {
5734		Pay consultant to port U-Boot;
5735		return 0;
5736	}
5737
5738	Download latest U-Boot source;
5739
5740	Subscribe to u-boot mailing list;
5741
5742	if (clueless)
5743		email("Hi, I am new to U-Boot, how do I get started?");
5744
5745	while (learning) {
5746		Read the README file in the top level directory;
5747		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5748		Read applicable doc/*.README;
5749		Read the source, Luke;
5750		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5751	}
5752
5753	if (available_money > toLocalCurrency ($2500))
5754		Buy a BDI3000;
5755	else
5756		Add a lot of aggravation and time;
5757
5758	if (a similar board exists) {	/* hopefully... */
5759		cp -a board/<similar> board/<myboard>
5760		cp include/configs/<similar>.h include/configs/<myboard>.h
5761	} else {
5762		Create your own board support subdirectory;
5763		Create your own board include/configs/<myboard>.h file;
5764	}
5765	Edit new board/<myboard> files
5766	Edit new include/configs/<myboard>.h
5767
5768	while (!accepted) {
5769		while (!running) {
5770			do {
5771				Add / modify source code;
5772			} until (compiles);
5773			Debug;
5774			if (clueless)
5775				email("Hi, I am having problems...");
5776		}
5777		Send patch file to the U-Boot email list;
5778		if (reasonable critiques)
5779			Incorporate improvements from email list code review;
5780		else
5781			Defend code as written;
5782	}
5783
5784	return 0;
5785}
5786
5787void no_more_time (int sig)
5788{
5789      hire_a_guru();
5790}
5791
5792
5793Coding Standards:
5794-----------------
5795
5796All contributions to U-Boot should conform to the Linux kernel
5797coding style; see the file "Documentation/CodingStyle" and the script
5798"scripts/Lindent" in your Linux kernel source directory.
5799
5800Source files originating from a different project (for example the
5801MTD subsystem) are generally exempt from these guidelines and are not
5802reformated to ease subsequent migration to newer versions of those
5803sources.
5804
5805Please note that U-Boot is implemented in C (and to some small parts in
5806Assembler); no C++ is used, so please do not use C++ style comments (//)
5807in your code.
5808
5809Please also stick to the following formatting rules:
5810- remove any trailing white space
5811- use TAB characters for indentation and vertical alignment, not spaces
5812- make sure NOT to use DOS '\r\n' line feeds
5813- do not add more than 2 consecutive empty lines to source files
5814- do not add trailing empty lines to source files
5815
5816Submissions which do not conform to the standards may be returned
5817with a request to reformat the changes.
5818
5819
5820Submitting Patches:
5821-------------------
5822
5823Since the number of patches for U-Boot is growing, we need to
5824establish some rules. Submissions which do not conform to these rules
5825may be rejected, even when they contain important and valuable stuff.
5826
5827Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5828
5829Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5830see http://lists.denx.de/mailman/listinfo/u-boot
5831
5832When you send a patch, please include the following information with
5833it:
5834
5835* For bug fixes: a description of the bug and how your patch fixes
5836  this bug. Please try to include a way of demonstrating that the
5837  patch actually fixes something.
5838
5839* For new features: a description of the feature and your
5840  implementation.
5841
5842* A CHANGELOG entry as plaintext (separate from the patch)
5843
5844* For major contributions, your entry to the CREDITS file
5845
5846* When you add support for a new board, don't forget to add a
5847  maintainer e-mail address to the boards.cfg file, too.
5848
5849* If your patch adds new configuration options, don't forget to
5850  document these in the README file.
5851
5852* The patch itself. If you are using git (which is *strongly*
5853  recommended) you can easily generate the patch using the
5854  "git format-patch". If you then use "git send-email" to send it to
5855  the U-Boot mailing list, you will avoid most of the common problems
5856  with some other mail clients.
5857
5858  If you cannot use git, use "diff -purN OLD NEW". If your version of
5859  diff does not support these options, then get the latest version of
5860  GNU diff.
5861
5862  The current directory when running this command shall be the parent
5863  directory of the U-Boot source tree (i. e. please make sure that
5864  your patch includes sufficient directory information for the
5865  affected files).
5866
5867  We prefer patches as plain text. MIME attachments are discouraged,
5868  and compressed attachments must not be used.
5869
5870* If one logical set of modifications affects or creates several
5871  files, all these changes shall be submitted in a SINGLE patch file.
5872
5873* Changesets that contain different, unrelated modifications shall be
5874  submitted as SEPARATE patches, one patch per changeset.
5875
5876
5877Notes:
5878
5879* Before sending the patch, run the MAKEALL script on your patched
5880  source tree and make sure that no errors or warnings are reported
5881  for any of the boards.
5882
5883* Keep your modifications to the necessary minimum: A patch
5884  containing several unrelated changes or arbitrary reformats will be
5885  returned with a request to re-formatting / split it.
5886
5887* If you modify existing code, make sure that your new code does not
5888  add to the memory footprint of the code ;-) Small is beautiful!
5889  When adding new features, these should compile conditionally only
5890  (using #ifdef), and the resulting code with the new feature
5891  disabled must not need more memory than the old code without your
5892  modification.
5893
5894* Remember that there is a size limit of 100 kB per message on the
5895  u-boot mailing list. Bigger patches will be moderated. If they are
5896  reasonable and not too big, they will be acknowledged. But patches
5897  bigger than the size limit should be avoided.
5898