xref: /openbmc/u-boot/README (revision 9d922450)
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 file to find out who contributed
38the specific port. In addition, there are various MAINTAINERS files
39scattered throughout the U-Boot source identifying the people or
40companies responsible for various boards and subsystems.
41
42Note: As of August, 2010, there is no longer a CHANGELOG file in the
43actual U-Boot source tree; however, it can be created dynamically
44from the Git log using:
45
46	make CHANGELOG
47
48
49Where to get help:
50==================
51
52In case you have questions about, problems with or contributions for
53U-Boot, you should send a message to the U-Boot mailing list at
54<u-boot@lists.denx.de>. There is also an archive of previous traffic
55on the mailing list - please search the archive before asking FAQ's.
56Please see http://lists.denx.de/pipermail/u-boot and
57http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
58
59
60Where to get source code:
61=========================
62
63The U-Boot source code is maintained in the Git repository at
64git://www.denx.de/git/u-boot.git ; you can browse it online at
65http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
66
67The "snapshot" links on this page allow you to download tarballs of
68any version you might be interested in. Official releases are also
69available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
70directory.
71
72Pre-built (and tested) images are available from
73ftp://ftp.denx.de/pub/u-boot/images/
74
75
76Where we come from:
77===================
78
79- start from 8xxrom sources
80- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
81- clean up code
82- make it easier to add custom boards
83- make it possible to add other [PowerPC] CPUs
84- extend functions, especially:
85  * Provide extended interface to Linux boot loader
86  * S-Record download
87  * network boot
88  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
89- create ARMBoot project (http://sourceforge.net/projects/armboot)
90- add other CPU families (starting with ARM)
91- create U-Boot project (http://sourceforge.net/projects/u-boot)
92- current project page: see http://www.denx.de/wiki/U-Boot
93
94
95Names and Spelling:
96===================
97
98The "official" name of this project is "Das U-Boot". The spelling
99"U-Boot" shall be used in all written text (documentation, comments
100in source files etc.). Example:
101
102	This is the README file for the U-Boot project.
103
104File names etc. shall be based on the string "u-boot". Examples:
105
106	include/asm-ppc/u-boot.h
107
108	#include <asm/u-boot.h>
109
110Variable names, preprocessor constants etc. shall be either based on
111the string "u_boot" or on "U_BOOT". Example:
112
113	U_BOOT_VERSION		u_boot_logo
114	IH_OS_U_BOOT		u_boot_hush_start
115
116
117Versioning:
118===========
119
120Starting with the release in October 2008, the names of the releases
121were changed from numerical release numbers without deeper meaning
122into a time stamp based numbering. Regular releases are identified by
123names consisting of the calendar year and month of the release date.
124Additional fields (if present) indicate release candidates or bug fix
125releases in "stable" maintenance trees.
126
127Examples:
128	U-Boot v2009.11	    - Release November 2009
129	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
130	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
131
132
133Directory Hierarchy:
134====================
135
136/arch			Architecture specific files
137  /arc			Files generic to ARC architecture
138  /arm			Files generic to ARM architecture
139  /avr32		Files generic to AVR32 architecture
140  /m68k			Files generic to m68k architecture
141  /microblaze		Files generic to microblaze architecture
142  /mips			Files generic to MIPS architecture
143  /nds32		Files generic to NDS32 architecture
144  /nios2		Files generic to Altera NIOS2 architecture
145  /openrisc		Files generic to OpenRISC architecture
146  /powerpc		Files generic to PowerPC architecture
147  /sandbox		Files generic to HW-independent "sandbox"
148  /sh			Files generic to SH architecture
149  /x86			Files generic to x86 architecture
150/api			Machine/arch independent API for external apps
151/board			Board dependent files
152/cmd			U-Boot commands functions
153/common			Misc architecture independent functions
154/configs		Board default configuration files
155/disk			Code for disk drive partition handling
156/doc			Documentation (don't expect too much)
157/drivers		Commonly used device drivers
158/dts			Contains Makefile for building internal U-Boot fdt.
159/examples		Example code for standalone applications, etc.
160/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
161/include		Header Files
162/lib			Library routines generic to all architectures
163/Licenses		Various license files
164/net			Networking code
165/post			Power On Self Test
166/scripts		Various build scripts and Makefiles
167/test			Various unit test files
168/tools			Tools to build S-Record or U-Boot images, etc.
169
170Software Configuration:
171=======================
172
173Configuration is usually done using C preprocessor defines; the
174rationale behind that is to avoid dead code whenever possible.
175
176There are two classes of configuration variables:
177
178* Configuration _OPTIONS_:
179  These are selectable by the user and have names beginning with
180  "CONFIG_".
181
182* Configuration _SETTINGS_:
183  These depend on the hardware etc. and should not be meddled with if
184  you don't know what you're doing; they have names beginning with
185  "CONFIG_SYS_".
186
187Previously, all configuration was done by hand, which involved creating
188symbolic links and editing configuration files manually. More recently,
189U-Boot has added the Kbuild infrastructure used by the Linux kernel,
190allowing you to use the "make menuconfig" command to configure your
191build.
192
193
194Selection of Processor Architecture and Board Type:
195---------------------------------------------------
196
197For all supported boards there are ready-to-use default
198configurations available; just type "make <board_name>_defconfig".
199
200Example: For a TQM823L module type:
201
202	cd u-boot
203	make TQM823L_defconfig
204
205Note: If you're looking for the default configuration file for a board
206you're sure used to be there but is now missing, check the file
207doc/README.scrapyard for a list of no longer supported boards.
208
209Sandbox Environment:
210--------------------
211
212U-Boot can be built natively to run on a Linux host using the 'sandbox'
213board. This allows feature development which is not board- or architecture-
214specific to be undertaken on a native platform. The sandbox is also used to
215run some of U-Boot's tests.
216
217See board/sandbox/README.sandbox for more details.
218
219
220Board Initialisation Flow:
221--------------------------
222
223This is the intended start-up flow for boards. This should apply for both
224SPL and U-Boot proper (i.e. they both follow the same rules).
225
226Note: "SPL" stands for "Secondary Program Loader," which is explained in
227more detail later in this file.
228
229At present, SPL mostly uses a separate code path, but the function names
230and roles of each function are the same. Some boards or architectures
231may not conform to this.  At least most ARM boards which use
232CONFIG_SPL_FRAMEWORK conform to this.
233
234Execution typically starts with an architecture-specific (and possibly
235CPU-specific) start.S file, such as:
236
237	- arch/arm/cpu/armv7/start.S
238	- arch/powerpc/cpu/mpc83xx/start.S
239	- arch/mips/cpu/start.S
240
241and so on. From there, three functions are called; the purpose and
242limitations of each of these functions are described below.
243
244lowlevel_init():
245	- purpose: essential init to permit execution to reach board_init_f()
246	- no global_data or BSS
247	- there is no stack (ARMv7 may have one but it will soon be removed)
248	- must not set up SDRAM or use console
249	- must only do the bare minimum to allow execution to continue to
250		board_init_f()
251	- this is almost never needed
252	- return normally from this function
253
254board_init_f():
255	- purpose: set up the machine ready for running board_init_r():
256		i.e. SDRAM and serial UART
257	- global_data is available
258	- stack is in SRAM
259	- BSS is not available, so you cannot use global/static variables,
260		only stack variables and global_data
261
262	Non-SPL-specific notes:
263	- dram_init() is called to set up DRAM. If already done in SPL this
264		can do nothing
265
266	SPL-specific notes:
267	- you can override the entire board_init_f() function with your own
268		version as needed.
269	- preloader_console_init() can be called here in extremis
270	- should set up SDRAM, and anything needed to make the UART work
271	- these is no need to clear BSS, it will be done by crt0.S
272	- must return normally from this function (don't call board_init_r()
273		directly)
274
275Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
276this point the stack and global_data are relocated to below
277CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
278memory.
279
280board_init_r():
281	- purpose: main execution, common code
282	- global_data is available
283	- SDRAM is available
284	- BSS is available, all static/global variables can be used
285	- execution eventually continues to main_loop()
286
287	Non-SPL-specific notes:
288	- U-Boot is relocated to the top of memory and is now running from
289		there.
290
291	SPL-specific notes:
292	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
293		CONFIG_SPL_STACK_R_ADDR points into SDRAM
294	- preloader_console_init() can be called here - typically this is
295		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
296		spl_board_init() function containing this call
297	- loads U-Boot or (in falcon mode) Linux
298
299
300
301Configuration Options:
302----------------------
303
304Configuration depends on the combination of board and CPU type; all
305such information is kept in a configuration file
306"include/configs/<board_name>.h".
307
308Example: For a TQM823L module, all configuration settings are in
309"include/configs/TQM823L.h".
310
311
312Many of the options are named exactly as the corresponding Linux
313kernel configuration options. The intention is to make it easier to
314build a config tool - later.
315
316
317The following options need to be configured:
318
319- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
320
321- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
322
323- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
324		Define exactly one, e.g. CONFIG_ATSTK1002
325
326- Marvell Family Member
327		CONFIG_SYS_MVFS		- define it if you want to enable
328					  multiple fs option at one time
329					  for marvell soc family
330
331- 8xx CPU Options: (if using an MPC8xx CPU)
332		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
333					  get_gclk_freq() cannot work
334					  e.g. if there is no 32KHz
335					  reference PIT/RTC clock
336		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
337					  or XTAL/EXTAL)
338
339- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
340		CONFIG_SYS_8xx_CPUCLK_MIN
341		CONFIG_SYS_8xx_CPUCLK_MAX
342		CONFIG_8xx_CPUCLK_DEFAULT
343			See doc/README.MPC866
344
345		CONFIG_SYS_MEASURE_CPUCLK
346
347		Define this to measure the actual CPU clock instead
348		of relying on the correctness of the configured
349		values. Mostly useful for board bringup to make sure
350		the PLL is locked at the intended frequency. Note
351		that this requires a (stable) reference clock (32 kHz
352		RTC clock or CONFIG_SYS_8XX_XIN)
353
354		CONFIG_SYS_DELAYED_ICACHE
355
356		Define this option if you want to enable the
357		ICache only when Code runs from RAM.
358
359- 85xx CPU Options:
360		CONFIG_SYS_PPC64
361
362		Specifies that the core is a 64-bit PowerPC implementation (implements
363		the "64" category of the Power ISA). This is necessary for ePAPR
364		compliance, among other possible reasons.
365
366		CONFIG_SYS_FSL_TBCLK_DIV
367
368		Defines the core time base clock divider ratio compared to the
369		system clock.  On most PQ3 devices this is 8, on newer QorIQ
370		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
371
372		CONFIG_SYS_FSL_PCIE_COMPAT
373
374		Defines the string to utilize when trying to match PCIe device
375		tree nodes for the given platform.
376
377		CONFIG_SYS_FSL_ERRATUM_A004510
378
379		Enables a workaround for erratum A004510.  If set,
380		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
381		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
382
383		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
384		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
385
386		Defines one or two SoC revisions (low 8 bits of SVR)
387		for which the A004510 workaround should be applied.
388
389		The rest of SVR is either not relevant to the decision
390		of whether the erratum is present (e.g. p2040 versus
391		p2041) or is implied by the build target, which controls
392		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
393
394		See Freescale App Note 4493 for more information about
395		this erratum.
396
397		CONFIG_A003399_NOR_WORKAROUND
398		Enables a workaround for IFC erratum A003399. It is only
399		required during NOR boot.
400
401		CONFIG_A008044_WORKAROUND
402		Enables a workaround for T1040/T1042 erratum A008044. It is only
403		required during NAND boot and valid for Rev 1.0 SoC revision
404
405		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
406
407		This is the value to write into CCSR offset 0x18600
408		according to the A004510 workaround.
409
410		CONFIG_SYS_FSL_DSP_DDR_ADDR
411		This value denotes start offset of DDR memory which is
412		connected exclusively to the DSP cores.
413
414		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
415		This value denotes start offset of M2 memory
416		which is directly connected to the DSP core.
417
418		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
419		This value denotes start offset of M3 memory which is directly
420		connected to the DSP core.
421
422		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
423		This value denotes start offset of DSP CCSR space.
424
425		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
426		Single Source Clock is clocking mode present in some of FSL SoC's.
427		In this mode, a single differential clock is used to supply
428		clocks to the sysclock, ddrclock and usbclock.
429
430		CONFIG_SYS_CPC_REINIT_F
431		This CONFIG is defined when the CPC is configured as SRAM at the
432		time of U-Boot entry and is required to be re-initialized.
433
434		CONFIG_DEEP_SLEEP
435		Indicates this SoC supports deep sleep feature. If deep sleep is
436		supported, core will start to execute uboot when wakes up.
437
438- Generic CPU options:
439		CONFIG_SYS_GENERIC_GLOBAL_DATA
440		Defines global data is initialized in generic board board_init_f().
441		If this macro is defined, global data is created and cleared in
442		generic board board_init_f(). Without this macro, architecture/board
443		should initialize global data before calling board_init_f().
444
445		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
446
447		Defines the endianess of the CPU. Implementation of those
448		values is arch specific.
449
450		CONFIG_SYS_FSL_DDR
451		Freescale DDR driver in use. This type of DDR controller is
452		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
453		SoCs.
454
455		CONFIG_SYS_FSL_DDR_ADDR
456		Freescale DDR memory-mapped register base.
457
458		CONFIG_SYS_FSL_DDR_EMU
459		Specify emulator support for DDR. Some DDR features such as
460		deskew training are not available.
461
462		CONFIG_SYS_FSL_DDRC_GEN1
463		Freescale DDR1 controller.
464
465		CONFIG_SYS_FSL_DDRC_GEN2
466		Freescale DDR2 controller.
467
468		CONFIG_SYS_FSL_DDRC_GEN3
469		Freescale DDR3 controller.
470
471		CONFIG_SYS_FSL_DDRC_GEN4
472		Freescale DDR4 controller.
473
474		CONFIG_SYS_FSL_DDRC_ARM_GEN3
475		Freescale DDR3 controller for ARM-based SoCs.
476
477		CONFIG_SYS_FSL_DDR1
478		Board config to use DDR1. It can be enabled for SoCs with
479		Freescale DDR1 or DDR2 controllers, depending on the board
480		implemetation.
481
482		CONFIG_SYS_FSL_DDR2
483		Board config to use DDR2. It can be enabled for SoCs with
484		Freescale DDR2 or DDR3 controllers, depending on the board
485		implementation.
486
487		CONFIG_SYS_FSL_DDR3
488		Board config to use DDR3. It can be enabled for SoCs with
489		Freescale DDR3 or DDR3L controllers.
490
491		CONFIG_SYS_FSL_DDR3L
492		Board config to use DDR3L. It can be enabled for SoCs with
493		DDR3L controllers.
494
495		CONFIG_SYS_FSL_DDR4
496		Board config to use DDR4. It can be enabled for SoCs with
497		DDR4 controllers.
498
499		CONFIG_SYS_FSL_IFC_BE
500		Defines the IFC controller register space as Big Endian
501
502		CONFIG_SYS_FSL_IFC_LE
503		Defines the IFC controller register space as Little Endian
504
505		CONFIG_SYS_FSL_IFC_CLK_DIV
506		Defines divider of platform clock(clock input to IFC controller).
507
508		CONFIG_SYS_FSL_LBC_CLK_DIV
509		Defines divider of platform clock(clock input to eLBC controller).
510
511		CONFIG_SYS_FSL_PBL_PBI
512		It enables addition of RCW (Power on reset configuration) in built image.
513		Please refer doc/README.pblimage for more details
514
515		CONFIG_SYS_FSL_PBL_RCW
516		It adds PBI(pre-boot instructions) commands in u-boot build image.
517		PBI commands can be used to configure SoC before it starts the execution.
518		Please refer doc/README.pblimage for more details
519
520		CONFIG_SPL_FSL_PBL
521		It adds a target to create boot binary having SPL binary in PBI format
522		concatenated with u-boot binary.
523
524		CONFIG_SYS_FSL_DDR_BE
525		Defines the DDR controller register space as Big Endian
526
527		CONFIG_SYS_FSL_DDR_LE
528		Defines the DDR controller register space as Little Endian
529
530		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
531		Physical address from the view of DDR controllers. It is the
532		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
533		it could be different for ARM SoCs.
534
535		CONFIG_SYS_FSL_DDR_INTLV_256B
536		DDR controller interleaving on 256-byte. This is a special
537		interleaving mode, handled by Dickens for Freescale layerscape
538		SoCs with ARM core.
539
540		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
541		Number of controllers used as main memory.
542
543		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
544		Number of controllers used for other than main memory.
545
546		CONFIG_SYS_FSL_HAS_DP_DDR
547		Defines the SoC has DP-DDR used for DPAA.
548
549		CONFIG_SYS_FSL_SEC_BE
550		Defines the SEC controller register space as Big Endian
551
552		CONFIG_SYS_FSL_SEC_LE
553		Defines the SEC controller register space as Little Endian
554
555- MIPS CPU options:
556		CONFIG_SYS_INIT_SP_OFFSET
557
558		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
559		pointer. This is needed for the temporary stack before
560		relocation.
561
562		CONFIG_SYS_MIPS_CACHE_MODE
563
564		Cache operation mode for the MIPS CPU.
565		See also arch/mips/include/asm/mipsregs.h.
566		Possible values are:
567			CONF_CM_CACHABLE_NO_WA
568			CONF_CM_CACHABLE_WA
569			CONF_CM_UNCACHED
570			CONF_CM_CACHABLE_NONCOHERENT
571			CONF_CM_CACHABLE_CE
572			CONF_CM_CACHABLE_COW
573			CONF_CM_CACHABLE_CUW
574			CONF_CM_CACHABLE_ACCELERATED
575
576		CONFIG_SYS_XWAY_EBU_BOOTCFG
577
578		Special option for Lantiq XWAY SoCs for booting from NOR flash.
579		See also arch/mips/cpu/mips32/start.S.
580
581		CONFIG_XWAY_SWAP_BYTES
582
583		Enable compilation of tools/xway-swap-bytes needed for Lantiq
584		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
585		be swapped if a flash programmer is used.
586
587- ARM options:
588		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
589
590		Select high exception vectors of the ARM core, e.g., do not
591		clear the V bit of the c1 register of CP15.
592
593		COUNTER_FREQUENCY
594		Generic timer clock source frequency.
595
596		COUNTER_FREQUENCY_REAL
597		Generic timer clock source frequency if the real clock is
598		different from COUNTER_FREQUENCY, and can only be determined
599		at run time.
600
601- Tegra SoC options:
602		CONFIG_TEGRA_SUPPORT_NON_SECURE
603
604		Support executing U-Boot in non-secure (NS) mode. Certain
605		impossible actions will be skipped if the CPU is in NS mode,
606		such as ARM architectural timer initialization.
607
608- Linux Kernel Interface:
609		CONFIG_CLOCKS_IN_MHZ
610
611		U-Boot stores all clock information in Hz
612		internally. For binary compatibility with older Linux
613		kernels (which expect the clocks passed in the
614		bd_info data to be in MHz) the environment variable
615		"clocks_in_mhz" can be defined so that U-Boot
616		converts clock data to MHZ before passing it to the
617		Linux kernel.
618		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
619		"clocks_in_mhz=1" is automatically included in the
620		default environment.
621
622		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
623
624		When transferring memsize parameter to Linux, some versions
625		expect it to be in bytes, others in MB.
626		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
627
628		CONFIG_OF_LIBFDT
629
630		New kernel versions are expecting firmware settings to be
631		passed using flattened device trees (based on open firmware
632		concepts).
633
634		CONFIG_OF_LIBFDT
635		 * New libfdt-based support
636		 * Adds the "fdt" command
637		 * The bootm command automatically updates the fdt
638
639		OF_CPU - The proper name of the cpus node (only required for
640			MPC512X and MPC5xxx based boards).
641		OF_SOC - The proper name of the soc node (only required for
642			MPC512X and MPC5xxx based boards).
643		OF_TBCLK - The timebase frequency.
644		OF_STDOUT_PATH - The path to the console device
645
646		boards with QUICC Engines require OF_QE to set UCC MAC
647		addresses
648
649		CONFIG_OF_BOARD_SETUP
650
651		Board code has addition modification that it wants to make
652		to the flat device tree before handing it off to the kernel
653
654		CONFIG_OF_SYSTEM_SETUP
655
656		Other code has addition modification that it wants to make
657		to the flat device tree before handing it off to the kernel.
658		This causes ft_system_setup() to be called before booting
659		the kernel.
660
661		CONFIG_OF_IDE_FIXUP
662
663		U-Boot can detect if an IDE device is present or not.
664		If not, and this new config option is activated, U-Boot
665		removes the ATA node from the DTS before booting Linux,
666		so the Linux IDE driver does not probe the device and
667		crash. This is needed for buggy hardware (uc101) where
668		no pull down resistor is connected to the signal IDE5V_DD7.
669
670		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
671
672		This setting is mandatory for all boards that have only one
673		machine type and must be used to specify the machine type
674		number as it appears in the ARM machine registry
675		(see http://www.arm.linux.org.uk/developer/machines/).
676		Only boards that have multiple machine types supported
677		in a single configuration file and the machine type is
678		runtime discoverable, do not have to use this setting.
679
680- vxWorks boot parameters:
681
682		bootvx constructs a valid bootline using the following
683		environments variables: bootdev, bootfile, ipaddr, netmask,
684		serverip, gatewayip, hostname, othbootargs.
685		It loads the vxWorks image pointed bootfile.
686
687		Note: If a "bootargs" environment is defined, it will overwride
688		the defaults discussed just above.
689
690- Cache Configuration:
691		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
692		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
693		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
694
695- Cache Configuration for ARM:
696		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
697				      controller
698		CONFIG_SYS_PL310_BASE - Physical base address of PL310
699					controller register space
700
701- Serial Ports:
702		CONFIG_PL010_SERIAL
703
704		Define this if you want support for Amba PrimeCell PL010 UARTs.
705
706		CONFIG_PL011_SERIAL
707
708		Define this if you want support for Amba PrimeCell PL011 UARTs.
709
710		CONFIG_PL011_CLOCK
711
712		If you have Amba PrimeCell PL011 UARTs, set this variable to
713		the clock speed of the UARTs.
714
715		CONFIG_PL01x_PORTS
716
717		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
718		define this to a list of base addresses for each (supported)
719		port. See e.g. include/configs/versatile.h
720
721		CONFIG_SERIAL_HW_FLOW_CONTROL
722
723		Define this variable to enable hw flow control in serial driver.
724		Current user of this option is drivers/serial/nsl16550.c driver
725
726- Console Interface:
727		Depending on board, define exactly one serial port
728		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
729		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
730		console by defining CONFIG_8xx_CONS_NONE
731
732		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
733		port routines must be defined elsewhere
734		(i.e. serial_init(), serial_getc(), ...)
735
736- Console Baudrate:
737		CONFIG_BAUDRATE - in bps
738		Select one of the baudrates listed in
739		CONFIG_SYS_BAUDRATE_TABLE, see below.
740		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
741
742- Console Rx buffer length
743		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
744		the maximum receive buffer length for the SMC.
745		This option is actual only for 82xx and 8xx possible.
746		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
747		must be defined, to setup the maximum idle timeout for
748		the SMC.
749
750- Autoboot Command:
751		CONFIG_BOOTCOMMAND
752		Only needed when CONFIG_BOOTDELAY is enabled;
753		define a command string that is automatically executed
754		when no character is read on the console interface
755		within "Boot Delay" after reset.
756
757		CONFIG_BOOTARGS
758		This can be used to pass arguments to the bootm
759		command. The value of CONFIG_BOOTARGS goes into the
760		environment value "bootargs".
761
762		CONFIG_RAMBOOT and CONFIG_NFSBOOT
763		The value of these goes into the environment as
764		"ramboot" and "nfsboot" respectively, and can be used
765		as a convenience, when switching between booting from
766		RAM and NFS.
767
768- Bootcount:
769		CONFIG_BOOTCOUNT_LIMIT
770		Implements a mechanism for detecting a repeating reboot
771		cycle, see:
772		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit
773
774		CONFIG_BOOTCOUNT_ENV
775		If no softreset save registers are found on the hardware
776		"bootcount" is stored in the environment. To prevent a
777		saveenv on all reboots, the environment variable
778		"upgrade_available" is used. If "upgrade_available" is
779		0, "bootcount" is always 0, if "upgrade_available" is
780		1 "bootcount" is incremented in the environment.
781		So the Userspace Applikation must set the "upgrade_available"
782		and "bootcount" variable to 0, if a boot was successfully.
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 adding #define's for wanted commands.
819
820		The default command configuration includes all commands
821		except those marked below with a "*".
822
823		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
824		CONFIG_CMD_ASKENV	* ask for env variable
825		CONFIG_CMD_BDI		  bdinfo
826		CONFIG_CMD_BOOTD	  bootd
827		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
828		CONFIG_CMD_CACHE	* icache, dcache
829		CONFIG_CMD_CONSOLE	  coninfo
830		CONFIG_CMD_DHCP		* DHCP support
831		CONFIG_CMD_DIAG		* Diagnostics
832		CONFIG_CMD_ECHO		  echo arguments
833		CONFIG_CMD_EDITENV	  edit env variable
834		CONFIG_CMD_ELF		* bootelf, bootvx
835		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
836		CONFIG_CMD_EXPORTENV	* export the environment
837		CONFIG_CMD_EXT2		* ext2 command support
838		CONFIG_CMD_EXT4		* ext4 command support
839		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
840					  that work for multiple fs types
841		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
842		CONFIG_CMD_SAVEENV	  saveenv
843		CONFIG_CMD_FAT		* FAT command support
844		CONFIG_CMD_FLASH	  flinfo, erase, protect
845		CONFIG_CMD_FPGA		  FPGA device initialization support
846		CONFIG_CMD_GO		* the 'go' command (exec code)
847		CONFIG_CMD_GREPENV	* search environment
848		CONFIG_CMD_I2C		* I2C serial bus support
849		CONFIG_CMD_IMI		  iminfo
850		CONFIG_CMD_IMLS		  List all images found in NOR flash
851		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
852		CONFIG_CMD_IMPORTENV	* import an environment
853		CONFIG_CMD_INI		* import data from an ini file into the env
854		CONFIG_CMD_ITEST	  Integer/string test of 2 values
855		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
856		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
857					  (169.254.*.*)
858		CONFIG_CMD_LOADB	  loadb
859		CONFIG_CMD_LOADS	  loads
860		CONFIG_CMD_MD5SUM	* print md5 message digest
861					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
862		CONFIG_CMD_MEMINFO	* Display detailed memory information
863		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
864					  loop, loopw
865		CONFIG_CMD_MEMTEST	* mtest
866		CONFIG_CMD_MISC		  Misc functions like sleep etc
867		CONFIG_CMD_MMC		* MMC memory mapped support
868		CONFIG_CMD_MII		* MII utility commands
869		CONFIG_CMD_MTDPARTS	* MTD partition support
870		CONFIG_CMD_NAND		* NAND support
871		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
872		CONFIG_CMD_NFS		  NFS support
873		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
874		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
875		CONFIG_CMD_PCI		* pciinfo
876		CONFIG_CMD_PCMCIA		* PCMCIA support
877		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
878					  host
879		CONFIG_CMD_PORTIO	* Port I/O
880		CONFIG_CMD_READ		* Read raw data from partition
881		CONFIG_CMD_REGINFO	* Register dump
882		CONFIG_CMD_RUN		  run command in env variable
883		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
884		CONFIG_CMD_SAVES	* save S record dump
885		CONFIG_SCSI		* SCSI Support
886		CONFIG_CMD_SDRAM	* print SDRAM configuration information
887					  (requires CONFIG_CMD_I2C)
888		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
889					  (4xx only)
890		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
891		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
892		CONFIG_CMD_SOURCE	  "source" command Support
893		CONFIG_CMD_SPI		* SPI serial bus support
894		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
895		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
896		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
897		CONFIG_CMD_TIMER	* access to the system tick timer
898		CONFIG_CMD_USB		* USB support
899		CONFIG_CMD_CDP		* Cisco Discover Protocol support
900		CONFIG_CMD_MFSL		* Microblaze FSL support
901		CONFIG_CMD_XIMG		  Load part of Multi Image
902		CONFIG_CMD_UUID		* Generate random UUID or GUID string
903
904		EXAMPLE: If you want all functions except of network
905		support you can write:
906
907		#include "config_cmd_all.h"
908		#undef CONFIG_CMD_NET
909
910	Other Commands:
911		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
912
913	Note:	Don't enable the "icache" and "dcache" commands
914		(configuration option CONFIG_CMD_CACHE) unless you know
915		what you (and your U-Boot users) are doing. Data
916		cache cannot be enabled on systems like the 8xx or
917		8260 (where accesses to the IMMR region must be
918		uncached), and it cannot be disabled on all other
919		systems where we (mis-) use the data cache to hold an
920		initial stack and some data.
921
922
923		XXX - this list needs to get updated!
924
925- Removal of commands
926		If no commands are needed to boot, you can disable
927		CONFIG_CMDLINE to remove them. In this case, the command line
928		will not be available, and when U-Boot wants to execute the
929		boot command (on start-up) it will call board_run_command()
930		instead. This can reduce image size significantly for very
931		simple boot procedures.
932
933- Regular expression support:
934		CONFIG_REGEX
935		If this variable is defined, U-Boot is linked against
936		the SLRE (Super Light Regular Expression) library,
937		which adds regex support to some commands, as for
938		example "env grep" and "setexpr".
939
940- Device tree:
941		CONFIG_OF_CONTROL
942		If this variable is defined, U-Boot will use a device tree
943		to configure its devices, instead of relying on statically
944		compiled #defines in the board file. This option is
945		experimental and only available on a few boards. The device
946		tree is available in the global data as gd->fdt_blob.
947
948		U-Boot needs to get its device tree from somewhere. This can
949		be done using one of the three options below:
950
951		CONFIG_OF_EMBED
952		If this variable is defined, U-Boot will embed a device tree
953		binary in its image. This device tree file should be in the
954		board directory and called <soc>-<board>.dts. The binary file
955		is then picked up in board_init_f() and made available through
956		the global data structure as gd->blob.
957
958		CONFIG_OF_SEPARATE
959		If this variable is defined, U-Boot will build a device tree
960		binary. It will be called u-boot.dtb. Architecture-specific
961		code will locate it at run-time. Generally this works by:
962
963			cat u-boot.bin u-boot.dtb >image.bin
964
965		and in fact, U-Boot does this for you, creating a file called
966		u-boot-dtb.bin which is useful in the common case. You can
967		still use the individual files if you need something more
968		exotic.
969
970		CONFIG_OF_BOARD
971		If this variable is defined, U-Boot will use the device tree
972		provided by the board at runtime instead of embedding one with
973		the image. Only boards defining board_fdt_blob_setup() support
974		this option (see include/fdtdec.h file).
975
976- Watchdog:
977		CONFIG_WATCHDOG
978		If this variable is defined, it enables watchdog
979		support for the SoC. There must be support in the SoC
980		specific code for a watchdog. For the 8xx and 8260
981		CPUs, the SIU Watchdog feature is enabled in the SYPCR
982		register.  When supported for a specific SoC is
983		available, then no further board specific code should
984		be needed to use it.
985
986		CONFIG_HW_WATCHDOG
987		When using a watchdog circuitry external to the used
988		SoC, then define this variable and provide board
989		specific code for the "hw_watchdog_reset" function.
990
991		CONFIG_AT91_HW_WDT_TIMEOUT
992		specify the timeout in seconds. default 2 seconds.
993
994- U-Boot Version:
995		CONFIG_VERSION_VARIABLE
996		If this variable is defined, an environment variable
997		named "ver" is created by U-Boot showing the U-Boot
998		version as printed by the "version" command.
999		Any change to this variable will be reverted at the
1000		next reset.
1001
1002- Real-Time Clock:
1003
1004		When CONFIG_CMD_DATE is selected, the type of the RTC
1005		has to be selected, too. Define exactly one of the
1006		following options:
1007
1008		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1009		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1010		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1011		CONFIG_RTC_MC146818	- use MC146818 RTC
1012		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1013		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1014		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1015		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1016		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1017		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1018		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1019		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1020		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1021					  RV3029 RTC.
1022
1023		Note that if the RTC uses I2C, then the I2C interface
1024		must also be configured. See I2C Support, below.
1025
1026- GPIO Support:
1027		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1028
1029		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1030		chip-ngpio pairs that tell the PCA953X driver the number of
1031		pins supported by a particular chip.
1032
1033		Note that if the GPIO device uses I2C, then the I2C interface
1034		must also be configured. See I2C Support, below.
1035
1036- I/O tracing:
1037		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1038		accesses and can checksum them or write a list of them out
1039		to memory. See the 'iotrace' command for details. This is
1040		useful for testing device drivers since it can confirm that
1041		the driver behaves the same way before and after a code
1042		change. Currently this is supported on sandbox and arm. To
1043		add support for your architecture, add '#include <iotrace.h>'
1044		to the bottom of arch/<arch>/include/asm/io.h and test.
1045
1046		Example output from the 'iotrace stats' command is below.
1047		Note that if the trace buffer is exhausted, the checksum will
1048		still continue to operate.
1049
1050			iotrace is enabled
1051			Start:  10000000	(buffer start address)
1052			Size:   00010000	(buffer size)
1053			Offset: 00000120	(current buffer offset)
1054			Output: 10000120	(start + offset)
1055			Count:  00000018	(number of trace records)
1056			CRC32:  9526fb66	(CRC32 of all trace records)
1057
1058- Timestamp Support:
1059
1060		When CONFIG_TIMESTAMP is selected, the timestamp
1061		(date and time) of an image is printed by image
1062		commands like bootm or iminfo. This option is
1063		automatically enabled when you select CONFIG_CMD_DATE .
1064
1065- Partition Labels (disklabels) Supported:
1066		Zero or more of the following:
1067		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1068		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1069				       Intel architecture, USB sticks, etc.
1070		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1071		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1072				       bootloader.  Note 2TB partition limit; see
1073				       disk/part_efi.c
1074		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1075
1076		If IDE or SCSI support is enabled (CONFIG_IDE or
1077		CONFIG_SCSI) you must configure support for at
1078		least one non-MTD partition type as well.
1079
1080- IDE Reset method:
1081		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1082		board configurations files but used nowhere!
1083
1084		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1085		be performed by calling the function
1086			ide_set_reset(int reset)
1087		which has to be defined in a board specific file
1088
1089- ATAPI Support:
1090		CONFIG_ATAPI
1091
1092		Set this to enable ATAPI support.
1093
1094- LBA48 Support
1095		CONFIG_LBA48
1096
1097		Set this to enable support for disks larger than 137GB
1098		Also look at CONFIG_SYS_64BIT_LBA.
1099		Whithout these , LBA48 support uses 32bit variables and will 'only'
1100		support disks up to 2.1TB.
1101
1102		CONFIG_SYS_64BIT_LBA:
1103			When enabled, makes the IDE subsystem use 64bit sector addresses.
1104			Default is 32bit.
1105
1106- SCSI Support:
1107		At the moment only there is only support for the
1108		SYM53C8XX SCSI controller; define
1109		CONFIG_SCSI_SYM53C8XX to enable it.
1110
1111		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1112		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1113		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1114		maximum numbers of LUNs, SCSI ID's and target
1115		devices.
1116		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1117
1118		The environment variable 'scsidevs' is set to the number of
1119		SCSI devices found during the last scan.
1120
1121- NETWORK Support (PCI):
1122		CONFIG_E1000
1123		Support for Intel 8254x/8257x gigabit chips.
1124
1125		CONFIG_E1000_SPI
1126		Utility code for direct access to the SPI bus on Intel 8257x.
1127		This does not do anything useful unless you set at least one
1128		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1129
1130		CONFIG_E1000_SPI_GENERIC
1131		Allow generic access to the SPI bus on the Intel 8257x, for
1132		example with the "sspi" command.
1133
1134		CONFIG_CMD_E1000
1135		Management command for E1000 devices.  When used on devices
1136		with SPI support you can reprogram the EEPROM from U-Boot.
1137
1138		CONFIG_EEPRO100
1139		Support for Intel 82557/82559/82559ER chips.
1140		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1141		write routine for first time initialisation.
1142
1143		CONFIG_TULIP
1144		Support for Digital 2114x chips.
1145		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1146		modem chip initialisation (KS8761/QS6611).
1147
1148		CONFIG_NATSEMI
1149		Support for National dp83815 chips.
1150
1151		CONFIG_NS8382X
1152		Support for National dp8382[01] gigabit chips.
1153
1154- NETWORK Support (other):
1155
1156		CONFIG_DRIVER_AT91EMAC
1157		Support for AT91RM9200 EMAC.
1158
1159			CONFIG_RMII
1160			Define this to use reduced MII inteface
1161
1162			CONFIG_DRIVER_AT91EMAC_QUIET
1163			If this defined, the driver is quiet.
1164			The driver doen't show link status messages.
1165
1166		CONFIG_CALXEDA_XGMAC
1167		Support for the Calxeda XGMAC device
1168
1169		CONFIG_LAN91C96
1170		Support for SMSC's LAN91C96 chips.
1171
1172			CONFIG_LAN91C96_USE_32_BIT
1173			Define this to enable 32 bit addressing
1174
1175		CONFIG_SMC91111
1176		Support for SMSC's LAN91C111 chip
1177
1178			CONFIG_SMC91111_BASE
1179			Define this to hold the physical address
1180			of the device (I/O space)
1181
1182			CONFIG_SMC_USE_32_BIT
1183			Define this if data bus is 32 bits
1184
1185			CONFIG_SMC_USE_IOFUNCS
1186			Define this to use i/o functions instead of macros
1187			(some hardware wont work with macros)
1188
1189		CONFIG_DRIVER_TI_EMAC
1190		Support for davinci emac
1191
1192			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1193			Define this if you have more then 3 PHYs.
1194
1195		CONFIG_FTGMAC100
1196		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1197
1198			CONFIG_FTGMAC100_EGIGA
1199			Define this to use GE link update with gigabit PHY.
1200			Define this if FTGMAC100 is connected to gigabit PHY.
1201			If your system has 10/100 PHY only, it might not occur
1202			wrong behavior. Because PHY usually return timeout or
1203			useless data when polling gigabit status and gigabit
1204			control registers. This behavior won't affect the
1205			correctnessof 10/100 link speed update.
1206
1207		CONFIG_SMC911X
1208		Support for SMSC's LAN911x and LAN921x chips
1209
1210			CONFIG_SMC911X_BASE
1211			Define this to hold the physical address
1212			of the device (I/O space)
1213
1214			CONFIG_SMC911X_32_BIT
1215			Define this if data bus is 32 bits
1216
1217			CONFIG_SMC911X_16_BIT
1218			Define this if data bus is 16 bits. If your processor
1219			automatically converts one 32 bit word to two 16 bit
1220			words you may also try CONFIG_SMC911X_32_BIT.
1221
1222		CONFIG_SH_ETHER
1223		Support for Renesas on-chip Ethernet controller
1224
1225			CONFIG_SH_ETHER_USE_PORT
1226			Define the number of ports to be used
1227
1228			CONFIG_SH_ETHER_PHY_ADDR
1229			Define the ETH PHY's address
1230
1231			CONFIG_SH_ETHER_CACHE_WRITEBACK
1232			If this option is set, the driver enables cache flush.
1233
1234- PWM Support:
1235		CONFIG_PWM_IMX
1236		Support for PWM module on the imx6.
1237
1238- TPM Support:
1239		CONFIG_TPM
1240		Support TPM devices.
1241
1242		CONFIG_TPM_TIS_INFINEON
1243		Support for Infineon i2c bus TPM devices. Only one device
1244		per system is supported at this time.
1245
1246			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1247			Define the burst count bytes upper limit
1248
1249		CONFIG_TPM_ST33ZP24
1250		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1251
1252			CONFIG_TPM_ST33ZP24_I2C
1253			Support for STMicroelectronics ST33ZP24 I2C devices.
1254			Requires TPM_ST33ZP24 and I2C.
1255
1256			CONFIG_TPM_ST33ZP24_SPI
1257			Support for STMicroelectronics ST33ZP24 SPI devices.
1258			Requires TPM_ST33ZP24 and SPI.
1259
1260		CONFIG_TPM_ATMEL_TWI
1261		Support for Atmel TWI TPM device. Requires I2C support.
1262
1263		CONFIG_TPM_TIS_LPC
1264		Support for generic parallel port TPM devices. Only one device
1265		per system is supported at this time.
1266
1267			CONFIG_TPM_TIS_BASE_ADDRESS
1268			Base address where the generic TPM device is mapped
1269			to. Contemporary x86 systems usually map it at
1270			0xfed40000.
1271
1272		CONFIG_CMD_TPM
1273		Add tpm monitor functions.
1274		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1275		provides monitor access to authorized functions.
1276
1277		CONFIG_TPM
1278		Define this to enable the TPM support library which provides
1279		functional interfaces to some TPM commands.
1280		Requires support for a TPM device.
1281
1282		CONFIG_TPM_AUTH_SESSIONS
1283		Define this to enable authorized functions in the TPM library.
1284		Requires CONFIG_TPM and CONFIG_SHA1.
1285
1286- USB Support:
1287		At the moment only the UHCI host controller is
1288		supported (PIP405, MIP405, MPC5200); define
1289		CONFIG_USB_UHCI to enable it.
1290		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1291		and define CONFIG_USB_STORAGE to enable the USB
1292		storage devices.
1293		Note:
1294		Supported are USB Keyboards and USB Floppy drives
1295		(TEAC FD-05PUB).
1296		MPC5200 USB requires additional defines:
1297			CONFIG_USB_CLOCK
1298				for 528 MHz Clock: 0x0001bbbb
1299			CONFIG_PSC3_USB
1300				for USB on PSC3
1301			CONFIG_USB_CONFIG
1302				for differential drivers: 0x00001000
1303				for single ended drivers: 0x00005000
1304				for differential drivers on PSC3: 0x00000100
1305				for single ended drivers on PSC3: 0x00004100
1306			CONFIG_SYS_USB_EVENT_POLL
1307				May be defined to allow interrupt polling
1308				instead of using asynchronous interrupts
1309
1310		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1311		txfilltuning field in the EHCI controller on reset.
1312
1313		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1314		HW module registers.
1315
1316- USB Device:
1317		Define the below if you wish to use the USB console.
1318		Once firmware is rebuilt from a serial console issue the
1319		command "setenv stdin usbtty; setenv stdout usbtty" and
1320		attach your USB cable. The Unix command "dmesg" should print
1321		it has found a new device. The environment variable usbtty
1322		can be set to gserial or cdc_acm to enable your device to
1323		appear to a USB host as a Linux gserial device or a
1324		Common Device Class Abstract Control Model serial device.
1325		If you select usbtty = gserial you should be able to enumerate
1326		a Linux host by
1327		# modprobe usbserial vendor=0xVendorID product=0xProductID
1328		else if using cdc_acm, simply setting the environment
1329		variable usbtty to be cdc_acm should suffice. The following
1330		might be defined in YourBoardName.h
1331
1332			CONFIG_USB_DEVICE
1333			Define this to build a UDC device
1334
1335			CONFIG_USB_TTY
1336			Define this to have a tty type of device available to
1337			talk to the UDC device
1338
1339			CONFIG_USBD_HS
1340			Define this to enable the high speed support for usb
1341			device and usbtty. If this feature is enabled, a routine
1342			int is_usbd_high_speed(void)
1343			also needs to be defined by the driver to dynamically poll
1344			whether the enumeration has succeded at high speed or full
1345			speed.
1346
1347			CONFIG_SYS_CONSOLE_IS_IN_ENV
1348			Define this if you want stdin, stdout &/or stderr to
1349			be set to usbtty.
1350
1351			mpc8xx:
1352				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1353				Derive USB clock from external clock "blah"
1354				- CONFIG_SYS_USB_EXTC_CLK 0x02
1355
1356		If you have a USB-IF assigned VendorID then you may wish to
1357		define your own vendor specific values either in BoardName.h
1358		or directly in usbd_vendor_info.h. If you don't define
1359		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1360		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1361		should pretend to be a Linux device to it's target host.
1362
1363			CONFIG_USBD_MANUFACTURER
1364			Define this string as the name of your company for
1365			- CONFIG_USBD_MANUFACTURER "my company"
1366
1367			CONFIG_USBD_PRODUCT_NAME
1368			Define this string as the name of your product
1369			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1370
1371			CONFIG_USBD_VENDORID
1372			Define this as your assigned Vendor ID from the USB
1373			Implementors Forum. This *must* be a genuine Vendor ID
1374			to avoid polluting the USB namespace.
1375			- CONFIG_USBD_VENDORID 0xFFFF
1376
1377			CONFIG_USBD_PRODUCTID
1378			Define this as the unique Product ID
1379			for your device
1380			- CONFIG_USBD_PRODUCTID 0xFFFF
1381
1382- ULPI Layer Support:
1383		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1384		the generic ULPI layer. The generic layer accesses the ULPI PHY
1385		via the platform viewport, so you need both the genric layer and
1386		the viewport enabled. Currently only Chipidea/ARC based
1387		viewport is supported.
1388		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1389		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1390		If your ULPI phy needs a different reference clock than the
1391		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1392		the appropriate value in Hz.
1393
1394- MMC Support:
1395		The MMC controller on the Intel PXA is supported. To
1396		enable this define CONFIG_MMC. The MMC can be
1397		accessed from the boot prompt by mapping the device
1398		to physical memory similar to flash. Command line is
1399		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1400		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1401
1402		CONFIG_SH_MMCIF
1403		Support for Renesas on-chip MMCIF controller
1404
1405			CONFIG_SH_MMCIF_ADDR
1406			Define the base address of MMCIF registers
1407
1408			CONFIG_SH_MMCIF_CLK
1409			Define the clock frequency for MMCIF
1410
1411		CONFIG_SUPPORT_EMMC_BOOT
1412		Enable some additional features of the eMMC boot partitions.
1413
1414		CONFIG_SUPPORT_EMMC_RPMB
1415		Enable the commands for reading, writing and programming the
1416		key for the Replay Protection Memory Block partition in eMMC.
1417
1418- USB Device Firmware Update (DFU) class support:
1419		CONFIG_USB_FUNCTION_DFU
1420		This enables the USB portion of the DFU USB class
1421
1422		CONFIG_CMD_DFU
1423		This enables the command "dfu" which is used to have
1424		U-Boot create a DFU class device via USB.  This command
1425		requires that the "dfu_alt_info" environment variable be
1426		set and define the alt settings to expose to the host.
1427
1428		CONFIG_DFU_MMC
1429		This enables support for exposing (e)MMC devices via DFU.
1430
1431		CONFIG_DFU_NAND
1432		This enables support for exposing NAND devices via DFU.
1433
1434		CONFIG_DFU_RAM
1435		This enables support for exposing RAM via DFU.
1436		Note: DFU spec refer to non-volatile memory usage, but
1437		allow usages beyond the scope of spec - here RAM usage,
1438		one that would help mostly the developer.
1439
1440		CONFIG_SYS_DFU_DATA_BUF_SIZE
1441		Dfu transfer uses a buffer before writing data to the
1442		raw storage device. Make the size (in bytes) of this buffer
1443		configurable. The size of this buffer is also configurable
1444		through the "dfu_bufsiz" environment variable.
1445
1446		CONFIG_SYS_DFU_MAX_FILE_SIZE
1447		When updating files rather than the raw storage device,
1448		we use a static buffer to copy the file into and then write
1449		the buffer once we've been given the whole file.  Define
1450		this to the maximum filesize (in bytes) for the buffer.
1451		Default is 4 MiB if undefined.
1452
1453		DFU_DEFAULT_POLL_TIMEOUT
1454		Poll timeout [ms], is the timeout a device can send to the
1455		host. The host must wait for this timeout before sending
1456		a subsequent DFU_GET_STATUS request to the device.
1457
1458		DFU_MANIFEST_POLL_TIMEOUT
1459		Poll timeout [ms], which the device sends to the host when
1460		entering dfuMANIFEST state. Host waits this timeout, before
1461		sending again an USB request to the device.
1462
1463- USB Device Android Fastboot support:
1464		CONFIG_USB_FUNCTION_FASTBOOT
1465		This enables the USB part of the fastboot gadget
1466
1467		CONFIG_CMD_FASTBOOT
1468		This enables the command "fastboot" which enables the Android
1469		fastboot mode for the platform's USB device. Fastboot is a USB
1470		protocol for downloading images, flashing and device control
1471		used on Android devices.
1472		See doc/README.android-fastboot for more information.
1473
1474		CONFIG_ANDROID_BOOT_IMAGE
1475		This enables support for booting images which use the Android
1476		image format header.
1477
1478		CONFIG_FASTBOOT_BUF_ADDR
1479		The fastboot protocol requires a large memory buffer for
1480		downloads. Define this to the starting RAM address to use for
1481		downloaded images.
1482
1483		CONFIG_FASTBOOT_BUF_SIZE
1484		The fastboot protocol requires a large memory buffer for
1485		downloads. This buffer should be as large as possible for a
1486		platform. Define this to the size available RAM for fastboot.
1487
1488		CONFIG_FASTBOOT_FLASH
1489		The fastboot protocol includes a "flash" command for writing
1490		the downloaded image to a non-volatile storage device. Define
1491		this to enable the "fastboot flash" command.
1492
1493		CONFIG_FASTBOOT_FLASH_MMC_DEV
1494		The fastboot "flash" command requires additional information
1495		regarding the non-volatile storage device. Define this to
1496		the eMMC device that fastboot should use to store the image.
1497
1498		CONFIG_FASTBOOT_GPT_NAME
1499		The fastboot "flash" command supports writing the downloaded
1500		image to the Protective MBR and the Primary GUID Partition
1501		Table. (Additionally, this downloaded image is post-processed
1502		to generate and write the Backup GUID Partition Table.)
1503		This occurs when the specified "partition name" on the
1504		"fastboot flash" command line matches this value.
1505		The default is "gpt" if undefined.
1506
1507		CONFIG_FASTBOOT_MBR_NAME
1508		The fastboot "flash" command supports writing the downloaded
1509		image to DOS MBR.
1510		This occurs when the "partition name" specified on the
1511		"fastboot flash" command line matches this value.
1512		If not defined the default value "mbr" is used.
1513
1514- Journaling Flash filesystem support:
1515		CONFIG_JFFS2_NAND
1516		Define these for a default partition on a NAND device
1517
1518		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1519		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1520		Define these for a default partition on a NOR device
1521
1522- FAT(File Allocation Table) filesystem write function support:
1523		CONFIG_FAT_WRITE
1524
1525		Define this to enable support for saving memory data as a
1526		file in FAT formatted partition.
1527
1528		This will also enable the command "fatwrite" enabling the
1529		user to write files to FAT.
1530
1531- FAT(File Allocation Table) filesystem cluster size:
1532		CONFIG_FS_FAT_MAX_CLUSTSIZE
1533
1534		Define the max cluster size for fat operations else
1535		a default value of 65536 will be defined.
1536
1537- Keyboard Support:
1538		See Kconfig help for available keyboard drivers.
1539
1540		CONFIG_KEYBOARD
1541
1542		Define this to enable a custom keyboard support.
1543		This simply calls drv_keyboard_init() which must be
1544		defined in your board-specific files. This option is deprecated
1545		and is only used by novena. For new boards, use driver model
1546		instead.
1547
1548- Video support:
1549		CONFIG_FSL_DIU_FB
1550		Enable the Freescale DIU video driver.	Reference boards for
1551		SOCs that have a DIU should define this macro to enable DIU
1552		support, and should also define these other macros:
1553
1554			CONFIG_SYS_DIU_ADDR
1555			CONFIG_VIDEO
1556			CONFIG_CFB_CONSOLE
1557			CONFIG_VIDEO_SW_CURSOR
1558			CONFIG_VGA_AS_SINGLE_DEVICE
1559			CONFIG_VIDEO_LOGO
1560			CONFIG_VIDEO_BMP_LOGO
1561
1562		The DIU driver will look for the 'video-mode' environment
1563		variable, and if defined, enable the DIU as a console during
1564		boot.  See the documentation file doc/README.video for a
1565		description of this variable.
1566
1567- LCD Support:	CONFIG_LCD
1568
1569		Define this to enable LCD support (for output to LCD
1570		display); also select one of the supported displays
1571		by defining one of these:
1572
1573		CONFIG_ATMEL_LCD:
1574
1575			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1576
1577		CONFIG_NEC_NL6448AC33:
1578
1579			NEC NL6448AC33-18. Active, color, single scan.
1580
1581		CONFIG_NEC_NL6448BC20
1582
1583			NEC NL6448BC20-08. 6.5", 640x480.
1584			Active, color, single scan.
1585
1586		CONFIG_NEC_NL6448BC33_54
1587
1588			NEC NL6448BC33-54. 10.4", 640x480.
1589			Active, color, single scan.
1590
1591		CONFIG_SHARP_16x9
1592
1593			Sharp 320x240. Active, color, single scan.
1594			It isn't 16x9, and I am not sure what it is.
1595
1596		CONFIG_SHARP_LQ64D341
1597
1598			Sharp LQ64D341 display, 640x480.
1599			Active, color, single scan.
1600
1601		CONFIG_HLD1045
1602
1603			HLD1045 display, 640x480.
1604			Active, color, single scan.
1605
1606		CONFIG_OPTREX_BW
1607
1608			Optrex	 CBL50840-2 NF-FW 99 22 M5
1609			or
1610			Hitachi	 LMG6912RPFC-00T
1611			or
1612			Hitachi	 SP14Q002
1613
1614			320x240. Black & white.
1615
1616		CONFIG_LCD_ALIGNMENT
1617
1618		Normally the LCD is page-aligned (typically 4KB). If this is
1619		defined then the LCD will be aligned to this value instead.
1620		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1621		here, since it is cheaper to change data cache settings on
1622		a per-section basis.
1623
1624
1625		CONFIG_LCD_ROTATION
1626
1627		Sometimes, for example if the display is mounted in portrait
1628		mode or even if it's mounted landscape but rotated by 180degree,
1629		we need to rotate our content of the display relative to the
1630		framebuffer, so that user can read the messages which are
1631		printed out.
1632		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1633		initialized with a given rotation from "vl_rot" out of
1634		"vidinfo_t" which is provided by the board specific code.
1635		The value for vl_rot is coded as following (matching to
1636		fbcon=rotate:<n> linux-kernel commandline):
1637		0 = no rotation respectively 0 degree
1638		1 = 90 degree rotation
1639		2 = 180 degree rotation
1640		3 = 270 degree rotation
1641
1642		If CONFIG_LCD_ROTATION is not defined, the console will be
1643		initialized with 0degree rotation.
1644
1645		CONFIG_LCD_BMP_RLE8
1646
1647		Support drawing of RLE8-compressed bitmaps on the LCD.
1648
1649		CONFIG_I2C_EDID
1650
1651		Enables an 'i2c edid' command which can read EDID
1652		information over I2C from an attached LCD display.
1653
1654- Splash Screen Support: CONFIG_SPLASH_SCREEN
1655
1656		If this option is set, the environment is checked for
1657		a variable "splashimage". If found, the usual display
1658		of logo, copyright and system information on the LCD
1659		is suppressed and the BMP image at the address
1660		specified in "splashimage" is loaded instead. The
1661		console is redirected to the "nulldev", too. This
1662		allows for a "silent" boot where a splash screen is
1663		loaded very quickly after power-on.
1664
1665		CONFIG_SPLASHIMAGE_GUARD
1666
1667		If this option is set, then U-Boot will prevent the environment
1668		variable "splashimage" from being set to a problematic address
1669		(see doc/README.displaying-bmps).
1670		This option is useful for targets where, due to alignment
1671		restrictions, an improperly aligned BMP image will cause a data
1672		abort. If you think you will not have problems with unaligned
1673		accesses (for example because your toolchain prevents them)
1674		there is no need to set this option.
1675
1676		CONFIG_SPLASH_SCREEN_ALIGN
1677
1678		If this option is set the splash image can be freely positioned
1679		on the screen. Environment variable "splashpos" specifies the
1680		position as "x,y". If a positive number is given it is used as
1681		number of pixel from left/top. If a negative number is given it
1682		is used as number of pixel from right/bottom. You can also
1683		specify 'm' for centering the image.
1684
1685		Example:
1686		setenv splashpos m,m
1687			=> image at center of screen
1688
1689		setenv splashpos 30,20
1690			=> image at x = 30 and y = 20
1691
1692		setenv splashpos -10,m
1693			=> vertically centered image
1694			   at x = dspWidth - bmpWidth - 9
1695
1696- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1697
1698		If this option is set, additionally to standard BMP
1699		images, gzipped BMP images can be displayed via the
1700		splashscreen support or the bmp command.
1701
1702- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1703
1704		If this option is set, 8-bit RLE compressed BMP images
1705		can be displayed via the splashscreen support or the
1706		bmp command.
1707
1708- Compression support:
1709		CONFIG_GZIP
1710
1711		Enabled by default to support gzip compressed images.
1712
1713		CONFIG_BZIP2
1714
1715		If this option is set, support for bzip2 compressed
1716		images is included. If not, only uncompressed and gzip
1717		compressed images are supported.
1718
1719		NOTE: the bzip2 algorithm requires a lot of RAM, so
1720		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1721		be at least 4MB.
1722
1723		CONFIG_LZO
1724
1725		If this option is set, support for LZO compressed images
1726		is included.
1727
1728- MII/PHY support:
1729		CONFIG_PHY_ADDR
1730
1731		The address of PHY on MII bus.
1732
1733		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1734
1735		The clock frequency of the MII bus
1736
1737		CONFIG_PHY_GIGE
1738
1739		If this option is set, support for speed/duplex
1740		detection of gigabit PHY is included.
1741
1742		CONFIG_PHY_RESET_DELAY
1743
1744		Some PHY like Intel LXT971A need extra delay after
1745		reset before any MII register access is possible.
1746		For such PHY, set this option to the usec delay
1747		required. (minimum 300usec for LXT971A)
1748
1749		CONFIG_PHY_CMD_DELAY (ppc4xx)
1750
1751		Some PHY like Intel LXT971A need extra delay after
1752		command issued before MII status register can be read
1753
1754- IP address:
1755		CONFIG_IPADDR
1756
1757		Define a default value for the IP address to use for
1758		the default Ethernet interface, in case this is not
1759		determined through e.g. bootp.
1760		(Environment variable "ipaddr")
1761
1762- Server IP address:
1763		CONFIG_SERVERIP
1764
1765		Defines a default value for the IP address of a TFTP
1766		server to contact when using the "tftboot" command.
1767		(Environment variable "serverip")
1768
1769		CONFIG_KEEP_SERVERADDR
1770
1771		Keeps the server's MAC address, in the env 'serveraddr'
1772		for passing to bootargs (like Linux's netconsole option)
1773
1774- Gateway IP address:
1775		CONFIG_GATEWAYIP
1776
1777		Defines a default value for the IP address of the
1778		default router where packets to other networks are
1779		sent to.
1780		(Environment variable "gatewayip")
1781
1782- Subnet mask:
1783		CONFIG_NETMASK
1784
1785		Defines a default value for the subnet mask (or
1786		routing prefix) which is used to determine if an IP
1787		address belongs to the local subnet or needs to be
1788		forwarded through a router.
1789		(Environment variable "netmask")
1790
1791- Multicast TFTP Mode:
1792		CONFIG_MCAST_TFTP
1793
1794		Defines whether you want to support multicast TFTP as per
1795		rfc-2090; for example to work with atftp.  Lets lots of targets
1796		tftp down the same boot image concurrently.  Note: the Ethernet
1797		driver in use must provide a function: mcast() to join/leave a
1798		multicast group.
1799
1800- BOOTP Recovery Mode:
1801		CONFIG_BOOTP_RANDOM_DELAY
1802
1803		If you have many targets in a network that try to
1804		boot using BOOTP, you may want to avoid that all
1805		systems send out BOOTP requests at precisely the same
1806		moment (which would happen for instance at recovery
1807		from a power failure, when all systems will try to
1808		boot, thus flooding the BOOTP server. Defining
1809		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1810		inserted before sending out BOOTP requests. The
1811		following delays are inserted then:
1812
1813		1st BOOTP request:	delay 0 ... 1 sec
1814		2nd BOOTP request:	delay 0 ... 2 sec
1815		3rd BOOTP request:	delay 0 ... 4 sec
1816		4th and following
1817		BOOTP requests:		delay 0 ... 8 sec
1818
1819		CONFIG_BOOTP_ID_CACHE_SIZE
1820
1821		BOOTP packets are uniquely identified using a 32-bit ID. The
1822		server will copy the ID from client requests to responses and
1823		U-Boot will use this to determine if it is the destination of
1824		an incoming response. Some servers will check that addresses
1825		aren't in use before handing them out (usually using an ARP
1826		ping) and therefore take up to a few hundred milliseconds to
1827		respond. Network congestion may also influence the time it
1828		takes for a response to make it back to the client. If that
1829		time is too long, U-Boot will retransmit requests. In order
1830		to allow earlier responses to still be accepted after these
1831		retransmissions, U-Boot's BOOTP client keeps a small cache of
1832		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1833		cache. The default is to keep IDs for up to four outstanding
1834		requests. Increasing this will allow U-Boot to accept offers
1835		from a BOOTP client in networks with unusually high latency.
1836
1837- DHCP Advanced Options:
1838		You can fine tune the DHCP functionality by defining
1839		CONFIG_BOOTP_* symbols:
1840
1841		CONFIG_BOOTP_SUBNETMASK
1842		CONFIG_BOOTP_GATEWAY
1843		CONFIG_BOOTP_HOSTNAME
1844		CONFIG_BOOTP_NISDOMAIN
1845		CONFIG_BOOTP_BOOTPATH
1846		CONFIG_BOOTP_BOOTFILESIZE
1847		CONFIG_BOOTP_DNS
1848		CONFIG_BOOTP_DNS2
1849		CONFIG_BOOTP_SEND_HOSTNAME
1850		CONFIG_BOOTP_NTPSERVER
1851		CONFIG_BOOTP_TIMEOFFSET
1852		CONFIG_BOOTP_VENDOREX
1853		CONFIG_BOOTP_MAY_FAIL
1854
1855		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1856		environment variable, not the BOOTP server.
1857
1858		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1859		after the configured retry count, the call will fail
1860		instead of starting over.  This can be used to fail over
1861		to Link-local IP address configuration if the DHCP server
1862		is not available.
1863
1864		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1865		serverip from a DHCP server, it is possible that more
1866		than one DNS serverip is offered to the client.
1867		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1868		serverip will be stored in the additional environment
1869		variable "dnsip2". The first DNS serverip is always
1870		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1871		is defined.
1872
1873		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1874		to do a dynamic update of a DNS server. To do this, they
1875		need the hostname of the DHCP requester.
1876		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1877		of the "hostname" environment variable is passed as
1878		option 12 to the DHCP server.
1879
1880		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1881
1882		A 32bit value in microseconds for a delay between
1883		receiving a "DHCP Offer" and sending the "DHCP Request".
1884		This fixes a problem with certain DHCP servers that don't
1885		respond 100% of the time to a "DHCP request". E.g. On an
1886		AT91RM9200 processor running at 180MHz, this delay needed
1887		to be *at least* 15,000 usec before a Windows Server 2003
1888		DHCP server would reply 100% of the time. I recommend at
1889		least 50,000 usec to be safe. The alternative is to hope
1890		that one of the retries will be successful but note that
1891		the DHCP timeout and retry process takes a longer than
1892		this delay.
1893
1894 - Link-local IP address negotiation:
1895		Negotiate with other link-local clients on the local network
1896		for an address that doesn't require explicit configuration.
1897		This is especially useful if a DHCP server cannot be guaranteed
1898		to exist in all environments that the device must operate.
1899
1900		See doc/README.link-local for more information.
1901
1902 - CDP Options:
1903		CONFIG_CDP_DEVICE_ID
1904
1905		The device id used in CDP trigger frames.
1906
1907		CONFIG_CDP_DEVICE_ID_PREFIX
1908
1909		A two character string which is prefixed to the MAC address
1910		of the device.
1911
1912		CONFIG_CDP_PORT_ID
1913
1914		A printf format string which contains the ascii name of
1915		the port. Normally is set to "eth%d" which sets
1916		eth0 for the first Ethernet, eth1 for the second etc.
1917
1918		CONFIG_CDP_CAPABILITIES
1919
1920		A 32bit integer which indicates the device capabilities;
1921		0x00000010 for a normal host which does not forwards.
1922
1923		CONFIG_CDP_VERSION
1924
1925		An ascii string containing the version of the software.
1926
1927		CONFIG_CDP_PLATFORM
1928
1929		An ascii string containing the name of the platform.
1930
1931		CONFIG_CDP_TRIGGER
1932
1933		A 32bit integer sent on the trigger.
1934
1935		CONFIG_CDP_POWER_CONSUMPTION
1936
1937		A 16bit integer containing the power consumption of the
1938		device in .1 of milliwatts.
1939
1940		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1941
1942		A byte containing the id of the VLAN.
1943
1944- Status LED:	CONFIG_LED_STATUS
1945
1946		Several configurations allow to display the current
1947		status using a LED. For instance, the LED will blink
1948		fast while running U-Boot code, stop blinking as
1949		soon as a reply to a BOOTP request was received, and
1950		start blinking slow once the Linux kernel is running
1951		(supported by a status LED driver in the Linux
1952		kernel). Defining CONFIG_LED_STATUS enables this
1953		feature in U-Boot.
1954
1955		Additional options:
1956
1957		CONFIG_LED_STATUS_GPIO
1958		The status LED can be connected to a GPIO pin.
1959		In such cases, the gpio_led driver can be used as a
1960		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1961		to include the gpio_led driver in the U-Boot binary.
1962
1963		CONFIG_GPIO_LED_INVERTED_TABLE
1964		Some GPIO connected LEDs may have inverted polarity in which
1965		case the GPIO high value corresponds to LED off state and
1966		GPIO low value corresponds to LED on state.
1967		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1968		with a list of GPIO LEDs that have inverted polarity.
1969
1970- CAN Support:	CONFIG_CAN_DRIVER
1971
1972		Defining CONFIG_CAN_DRIVER enables CAN driver support
1973		on those systems that support this (optional)
1974		feature, like the TQM8xxL modules.
1975
1976- I2C Support:	CONFIG_SYS_I2C
1977
1978		This enable the NEW i2c subsystem, and will allow you to use
1979		i2c commands at the u-boot command line (as long as you set
1980		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1981		based realtime clock chips or other i2c devices. See
1982		common/cmd_i2c.c for a description of the command line
1983		interface.
1984
1985		ported i2c driver to the new framework:
1986		- drivers/i2c/soft_i2c.c:
1987		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1988		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1989		    for defining speed and slave address
1990		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1991		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1992		    for defining speed and slave address
1993		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1994		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1995		    for defining speed and slave address
1996		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1997		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1998		    for defining speed and slave address
1999
2000		- drivers/i2c/fsl_i2c.c:
2001		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2002		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2003		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2004		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2005		    bus.
2006		  - If your board supports a second fsl i2c bus, define
2007		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2008		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2009		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2010		    second bus.
2011
2012		- drivers/i2c/tegra_i2c.c:
2013		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2014		  - This driver adds 4 i2c buses with a fix speed from
2015		    100000 and the slave addr 0!
2016
2017		- drivers/i2c/ppc4xx_i2c.c
2018		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2019		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2020		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2021
2022		- drivers/i2c/i2c_mxc.c
2023		  - activate this driver with CONFIG_SYS_I2C_MXC
2024		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2025		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2026		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2027		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2028		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2029		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2030		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2031		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2032		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2033		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2034		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2035		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2036		If those defines are not set, default value is 100000
2037		for speed, and 0 for slave.
2038
2039		- drivers/i2c/rcar_i2c.c:
2040		  - activate this driver with CONFIG_SYS_I2C_RCAR
2041		  - This driver adds 4 i2c buses
2042
2043		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2044		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2045		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2046		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2047		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2048		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2049		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2050		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2051		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2052
2053		- drivers/i2c/sh_i2c.c:
2054		  - activate this driver with CONFIG_SYS_I2C_SH
2055		  - This driver adds from 2 to 5 i2c buses
2056
2057		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2058		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2059		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2060		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2061		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2062		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2063		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2064		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2065		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2066		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2067		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2068
2069		- drivers/i2c/omap24xx_i2c.c
2070		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2071		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2072		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2073		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2074		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2075		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2076		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2077		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2078		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2079		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2080		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2081
2082		- drivers/i2c/zynq_i2c.c
2083		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2084		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2085		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2086
2087		- drivers/i2c/s3c24x0_i2c.c:
2088		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2089		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2090		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2091		    with a fix speed from 100000 and the slave addr 0!
2092
2093		- drivers/i2c/ihs_i2c.c
2094		  - activate this driver with CONFIG_SYS_I2C_IHS
2095		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2096		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2097		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2098		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2099		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2100		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2101		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2102		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2103		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2104		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2105		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2106		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2107		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2108		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2109		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2110		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2111		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2112		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2113		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2114		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2115		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2116
2117		additional defines:
2118
2119		CONFIG_SYS_NUM_I2C_BUSES
2120		Hold the number of i2c buses you want to use.
2121
2122		CONFIG_SYS_I2C_DIRECT_BUS
2123		define this, if you don't use i2c muxes on your hardware.
2124		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2125		omit this define.
2126
2127		CONFIG_SYS_I2C_MAX_HOPS
2128		define how many muxes are maximal consecutively connected
2129		on one i2c bus. If you not use i2c muxes, omit this
2130		define.
2131
2132		CONFIG_SYS_I2C_BUSES
2133		hold a list of buses you want to use, only used if
2134		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2135		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2136		CONFIG_SYS_NUM_I2C_BUSES = 9:
2137
2138		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2139					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2140					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2141					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2142					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2143					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2144					{1, {I2C_NULL_HOP}}, \
2145					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2146					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2147					}
2148
2149		which defines
2150			bus 0 on adapter 0 without a mux
2151			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2152			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2153			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2154			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2155			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2156			bus 6 on adapter 1 without a mux
2157			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2158			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2159
2160		If you do not have i2c muxes on your board, omit this define.
2161
2162- Legacy I2C Support:
2163		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2164		then the following macros need to be defined (examples are
2165		from include/configs/lwmon.h):
2166
2167		I2C_INIT
2168
2169		(Optional). Any commands necessary to enable the I2C
2170		controller or configure ports.
2171
2172		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2173
2174		I2C_PORT
2175
2176		(Only for MPC8260 CPU). The I/O port to use (the code
2177		assumes both bits are on the same port). Valid values
2178		are 0..3 for ports A..D.
2179
2180		I2C_ACTIVE
2181
2182		The code necessary to make the I2C data line active
2183		(driven).  If the data line is open collector, this
2184		define can be null.
2185
2186		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2187
2188		I2C_TRISTATE
2189
2190		The code necessary to make the I2C data line tri-stated
2191		(inactive).  If the data line is open collector, this
2192		define can be null.
2193
2194		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2195
2196		I2C_READ
2197
2198		Code that returns true if the I2C data line is high,
2199		false if it is low.
2200
2201		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2202
2203		I2C_SDA(bit)
2204
2205		If <bit> is true, sets the I2C data line high. If it
2206		is false, it clears it (low).
2207
2208		eg: #define I2C_SDA(bit) \
2209			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2210			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2211
2212		I2C_SCL(bit)
2213
2214		If <bit> is true, sets the I2C clock line high. If it
2215		is false, it clears it (low).
2216
2217		eg: #define I2C_SCL(bit) \
2218			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2219			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2220
2221		I2C_DELAY
2222
2223		This delay is invoked four times per clock cycle so this
2224		controls the rate of data transfer.  The data rate thus
2225		is 1 / (I2C_DELAY * 4). Often defined to be something
2226		like:
2227
2228		#define I2C_DELAY  udelay(2)
2229
2230		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2231
2232		If your arch supports the generic GPIO framework (asm/gpio.h),
2233		then you may alternatively define the two GPIOs that are to be
2234		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2235		have GPIO-based defaults assigned to them as appropriate.
2236
2237		You should define these to the GPIO value as given directly to
2238		the generic GPIO functions.
2239
2240		CONFIG_SYS_I2C_INIT_BOARD
2241
2242		When a board is reset during an i2c bus transfer
2243		chips might think that the current transfer is still
2244		in progress. On some boards it is possible to access
2245		the i2c SCLK line directly, either by using the
2246		processor pin as a GPIO or by having a second pin
2247		connected to the bus. If this option is defined a
2248		custom i2c_init_board() routine in boards/xxx/board.c
2249		is run early in the boot sequence.
2250
2251		CONFIG_I2C_MULTI_BUS
2252
2253		This option allows the use of multiple I2C buses, each of which
2254		must have a controller.	 At any point in time, only one bus is
2255		active.	 To switch to a different bus, use the 'i2c dev' command.
2256		Note that bus numbering is zero-based.
2257
2258		CONFIG_SYS_I2C_NOPROBES
2259
2260		This option specifies a list of I2C devices that will be skipped
2261		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2262		is set, specify a list of bus-device pairs.  Otherwise, specify
2263		a 1D array of device addresses
2264
2265		e.g.
2266			#undef	CONFIG_I2C_MULTI_BUS
2267			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2268
2269		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2270
2271			#define CONFIG_I2C_MULTI_BUS
2272			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2273
2274		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2275
2276		CONFIG_SYS_SPD_BUS_NUM
2277
2278		If defined, then this indicates the I2C bus number for DDR SPD.
2279		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2280
2281		CONFIG_SYS_RTC_BUS_NUM
2282
2283		If defined, then this indicates the I2C bus number for the RTC.
2284		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2285
2286		CONFIG_SOFT_I2C_READ_REPEATED_START
2287
2288		defining this will force the i2c_read() function in
2289		the soft_i2c driver to perform an I2C repeated start
2290		between writing the address pointer and reading the
2291		data.  If this define is omitted the default behaviour
2292		of doing a stop-start sequence will be used.  Most I2C
2293		devices can use either method, but some require one or
2294		the other.
2295
2296- SPI Support:	CONFIG_SPI
2297
2298		Enables SPI driver (so far only tested with
2299		SPI EEPROM, also an instance works with Crystal A/D and
2300		D/As on the SACSng board)
2301
2302		CONFIG_SH_SPI
2303
2304		Enables the driver for SPI controller on SuperH. Currently
2305		only SH7757 is supported.
2306
2307		CONFIG_SOFT_SPI
2308
2309		Enables a software (bit-bang) SPI driver rather than
2310		using hardware support. This is a general purpose
2311		driver that only requires three general I/O port pins
2312		(two outputs, one input) to function. If this is
2313		defined, the board configuration must define several
2314		SPI configuration items (port pins to use, etc). For
2315		an example, see include/configs/sacsng.h.
2316
2317		CONFIG_HARD_SPI
2318
2319		Enables a hardware SPI driver for general-purpose reads
2320		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2321		must define a list of chip-select function pointers.
2322		Currently supported on some MPC8xxx processors.	 For an
2323		example, see include/configs/mpc8349emds.h.
2324
2325		CONFIG_MXC_SPI
2326
2327		Enables the driver for the SPI controllers on i.MX and MXC
2328		SoCs. Currently i.MX31/35/51 are supported.
2329
2330		CONFIG_SYS_SPI_MXC_WAIT
2331		Timeout for waiting until spi transfer completed.
2332		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2333
2334- FPGA Support: CONFIG_FPGA
2335
2336		Enables FPGA subsystem.
2337
2338		CONFIG_FPGA_<vendor>
2339
2340		Enables support for specific chip vendors.
2341		(ALTERA, XILINX)
2342
2343		CONFIG_FPGA_<family>
2344
2345		Enables support for FPGA family.
2346		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2347
2348		CONFIG_FPGA_COUNT
2349
2350		Specify the number of FPGA devices to support.
2351
2352		CONFIG_SYS_FPGA_PROG_FEEDBACK
2353
2354		Enable printing of hash marks during FPGA configuration.
2355
2356		CONFIG_SYS_FPGA_CHECK_BUSY
2357
2358		Enable checks on FPGA configuration interface busy
2359		status by the configuration function. This option
2360		will require a board or device specific function to
2361		be written.
2362
2363		CONFIG_FPGA_DELAY
2364
2365		If defined, a function that provides delays in the FPGA
2366		configuration driver.
2367
2368		CONFIG_SYS_FPGA_CHECK_CTRLC
2369		Allow Control-C to interrupt FPGA configuration
2370
2371		CONFIG_SYS_FPGA_CHECK_ERROR
2372
2373		Check for configuration errors during FPGA bitfile
2374		loading. For example, abort during Virtex II
2375		configuration if the INIT_B line goes low (which
2376		indicated a CRC error).
2377
2378		CONFIG_SYS_FPGA_WAIT_INIT
2379
2380		Maximum time to wait for the INIT_B line to de-assert
2381		after PROB_B has been de-asserted during a Virtex II
2382		FPGA configuration sequence. The default time is 500
2383		ms.
2384
2385		CONFIG_SYS_FPGA_WAIT_BUSY
2386
2387		Maximum time to wait for BUSY to de-assert during
2388		Virtex II FPGA configuration. The default is 5 ms.
2389
2390		CONFIG_SYS_FPGA_WAIT_CONFIG
2391
2392		Time to wait after FPGA configuration. The default is
2393		200 ms.
2394
2395- Configuration Management:
2396		CONFIG_BUILD_TARGET
2397
2398		Some SoCs need special image types (e.g. U-Boot binary
2399		with a special header) as build targets. By defining
2400		CONFIG_BUILD_TARGET in the SoC / board header, this
2401		special image will be automatically built upon calling
2402		make / buildman.
2403
2404		CONFIG_IDENT_STRING
2405
2406		If defined, this string will be added to the U-Boot
2407		version information (U_BOOT_VERSION)
2408
2409- Vendor Parameter Protection:
2410
2411		U-Boot considers the values of the environment
2412		variables "serial#" (Board Serial Number) and
2413		"ethaddr" (Ethernet Address) to be parameters that
2414		are set once by the board vendor / manufacturer, and
2415		protects these variables from casual modification by
2416		the user. Once set, these variables are read-only,
2417		and write or delete attempts are rejected. You can
2418		change this behaviour:
2419
2420		If CONFIG_ENV_OVERWRITE is #defined in your config
2421		file, the write protection for vendor parameters is
2422		completely disabled. Anybody can change or delete
2423		these parameters.
2424
2425		Alternatively, if you define _both_ an ethaddr in the
2426		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2427		Ethernet address is installed in the environment,
2428		which can be changed exactly ONCE by the user. [The
2429		serial# is unaffected by this, i. e. it remains
2430		read-only.]
2431
2432		The same can be accomplished in a more flexible way
2433		for any variable by configuring the type of access
2434		to allow for those variables in the ".flags" variable
2435		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2436
2437- Protected RAM:
2438		CONFIG_PRAM
2439
2440		Define this variable to enable the reservation of
2441		"protected RAM", i. e. RAM which is not overwritten
2442		by U-Boot. Define CONFIG_PRAM to hold the number of
2443		kB you want to reserve for pRAM. You can overwrite
2444		this default value by defining an environment
2445		variable "pram" to the number of kB you want to
2446		reserve. Note that the board info structure will
2447		still show the full amount of RAM. If pRAM is
2448		reserved, a new environment variable "mem" will
2449		automatically be defined to hold the amount of
2450		remaining RAM in a form that can be passed as boot
2451		argument to Linux, for instance like that:
2452
2453			setenv bootargs ... mem=\${mem}
2454			saveenv
2455
2456		This way you can tell Linux not to use this memory,
2457		either, which results in a memory region that will
2458		not be affected by reboots.
2459
2460		*WARNING* If your board configuration uses automatic
2461		detection of the RAM size, you must make sure that
2462		this memory test is non-destructive. So far, the
2463		following board configurations are known to be
2464		"pRAM-clean":
2465
2466			IVMS8, IVML24, SPD8xx, TQM8xxL,
2467			HERMES, IP860, RPXlite, LWMON,
2468			FLAGADM, TQM8260
2469
2470- Access to physical memory region (> 4GB)
2471		Some basic support is provided for operations on memory not
2472		normally accessible to U-Boot - e.g. some architectures
2473		support access to more than 4GB of memory on 32-bit
2474		machines using physical address extension or similar.
2475		Define CONFIG_PHYSMEM to access this basic support, which
2476		currently only supports clearing the memory.
2477
2478- Error Recovery:
2479		CONFIG_PANIC_HANG
2480
2481		Define this variable to stop the system in case of a
2482		fatal error, so that you have to reset it manually.
2483		This is probably NOT a good idea for an embedded
2484		system where you want the system to reboot
2485		automatically as fast as possible, but it may be
2486		useful during development since you can try to debug
2487		the conditions that lead to the situation.
2488
2489		CONFIG_NET_RETRY_COUNT
2490
2491		This variable defines the number of retries for
2492		network operations like ARP, RARP, TFTP, or BOOTP
2493		before giving up the operation. If not defined, a
2494		default value of 5 is used.
2495
2496		CONFIG_ARP_TIMEOUT
2497
2498		Timeout waiting for an ARP reply in milliseconds.
2499
2500		CONFIG_NFS_TIMEOUT
2501
2502		Timeout in milliseconds used in NFS protocol.
2503		If you encounter "ERROR: Cannot umount" in nfs command,
2504		try longer timeout such as
2505		#define CONFIG_NFS_TIMEOUT 10000UL
2506
2507- Command Interpreter:
2508		CONFIG_AUTO_COMPLETE
2509
2510		Enable auto completion of commands using TAB.
2511
2512		CONFIG_SYS_PROMPT_HUSH_PS2
2513
2514		This defines the secondary prompt string, which is
2515		printed when the command interpreter needs more input
2516		to complete a command. Usually "> ".
2517
2518	Note:
2519
2520		In the current implementation, the local variables
2521		space and global environment variables space are
2522		separated. Local variables are those you define by
2523		simply typing `name=value'. To access a local
2524		variable later on, you have write `$name' or
2525		`${name}'; to execute the contents of a variable
2526		directly type `$name' at the command prompt.
2527
2528		Global environment variables are those you use
2529		setenv/printenv to work with. To run a command stored
2530		in such a variable, you need to use the run command,
2531		and you must not use the '$' sign to access them.
2532
2533		To store commands and special characters in a
2534		variable, please use double quotation marks
2535		surrounding the whole text of the variable, instead
2536		of the backslashes before semicolons and special
2537		symbols.
2538
2539- Command Line Editing and History:
2540		CONFIG_CMDLINE_EDITING
2541
2542		Enable editing and History functions for interactive
2543		command line input operations
2544
2545- Command Line PS1/PS2 support:
2546		CONFIG_CMDLINE_PS_SUPPORT
2547
2548		Enable support for changing the command prompt string
2549		at run-time. Only static string is supported so far.
2550		The string is obtained from environment variables PS1
2551		and PS2.
2552
2553- Default Environment:
2554		CONFIG_EXTRA_ENV_SETTINGS
2555
2556		Define this to contain any number of null terminated
2557		strings (variable = value pairs) that will be part of
2558		the default environment compiled into the boot image.
2559
2560		For example, place something like this in your
2561		board's config file:
2562
2563		#define CONFIG_EXTRA_ENV_SETTINGS \
2564			"myvar1=value1\0" \
2565			"myvar2=value2\0"
2566
2567		Warning: This method is based on knowledge about the
2568		internal format how the environment is stored by the
2569		U-Boot code. This is NOT an official, exported
2570		interface! Although it is unlikely that this format
2571		will change soon, there is no guarantee either.
2572		You better know what you are doing here.
2573
2574		Note: overly (ab)use of the default environment is
2575		discouraged. Make sure to check other ways to preset
2576		the environment like the "source" command or the
2577		boot command first.
2578
2579		CONFIG_ENV_VARS_UBOOT_CONFIG
2580
2581		Define this in order to add variables describing the
2582		U-Boot build configuration to the default environment.
2583		These will be named arch, cpu, board, vendor, and soc.
2584
2585		Enabling this option will cause the following to be defined:
2586
2587		- CONFIG_SYS_ARCH
2588		- CONFIG_SYS_CPU
2589		- CONFIG_SYS_BOARD
2590		- CONFIG_SYS_VENDOR
2591		- CONFIG_SYS_SOC
2592
2593		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2594
2595		Define this in order to add variables describing certain
2596		run-time determined information about the hardware to the
2597		environment.  These will be named board_name, board_rev.
2598
2599		CONFIG_DELAY_ENVIRONMENT
2600
2601		Normally the environment is loaded when the board is
2602		initialised so that it is available to U-Boot. This inhibits
2603		that so that the environment is not available until
2604		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2605		this is instead controlled by the value of
2606		/config/load-environment.
2607
2608- DataFlash Support:
2609		CONFIG_HAS_DATAFLASH
2610
2611		Defining this option enables DataFlash features and
2612		allows to read/write in Dataflash via the standard
2613		commands cp, md...
2614
2615- Serial Flash support
2616		CONFIG_CMD_SF
2617
2618		Defining this option enables SPI flash commands
2619		'sf probe/read/write/erase/update'.
2620
2621		Usage requires an initial 'probe' to define the serial
2622		flash parameters, followed by read/write/erase/update
2623		commands.
2624
2625		The following defaults may be provided by the platform
2626		to handle the common case when only a single serial
2627		flash is present on the system.
2628
2629		CONFIG_SF_DEFAULT_BUS		Bus identifier
2630		CONFIG_SF_DEFAULT_CS		Chip-select
2631		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2632		CONFIG_SF_DEFAULT_SPEED		in Hz
2633
2634		CONFIG_CMD_SF_TEST
2635
2636		Define this option to include a destructive SPI flash
2637		test ('sf test').
2638
2639		CONFIG_SF_DUAL_FLASH		Dual flash memories
2640
2641		Define this option to use dual flash support where two flash
2642		memories can be connected with a given cs line.
2643		Currently Xilinx Zynq qspi supports these type of connections.
2644
2645- SystemACE Support:
2646		CONFIG_SYSTEMACE
2647
2648		Adding this option adds support for Xilinx SystemACE
2649		chips attached via some sort of local bus. The address
2650		of the chip must also be defined in the
2651		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2652
2653		#define CONFIG_SYSTEMACE
2654		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2655
2656		When SystemACE support is added, the "ace" device type
2657		becomes available to the fat commands, i.e. fatls.
2658
2659- TFTP Fixed UDP Port:
2660		CONFIG_TFTP_PORT
2661
2662		If this is defined, the environment variable tftpsrcp
2663		is used to supply the TFTP UDP source port value.
2664		If tftpsrcp isn't defined, the normal pseudo-random port
2665		number generator is used.
2666
2667		Also, the environment variable tftpdstp is used to supply
2668		the TFTP UDP destination port value.  If tftpdstp isn't
2669		defined, the normal port 69 is used.
2670
2671		The purpose for tftpsrcp is to allow a TFTP server to
2672		blindly start the TFTP transfer using the pre-configured
2673		target IP address and UDP port. This has the effect of
2674		"punching through" the (Windows XP) firewall, allowing
2675		the remainder of the TFTP transfer to proceed normally.
2676		A better solution is to properly configure the firewall,
2677		but sometimes that is not allowed.
2678
2679- bootcount support:
2680		CONFIG_BOOTCOUNT_LIMIT
2681
2682		This enables the bootcounter support, see:
2683		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2684
2685		CONFIG_AT91SAM9XE
2686		enable special bootcounter support on at91sam9xe based boards.
2687		CONFIG_SOC_DA8XX
2688		enable special bootcounter support on da850 based boards.
2689		CONFIG_BOOTCOUNT_RAM
2690		enable support for the bootcounter in RAM
2691		CONFIG_BOOTCOUNT_I2C
2692		enable support for the bootcounter on an i2c (like RTC) device.
2693			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2694			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2695						    the bootcounter.
2696			CONFIG_BOOTCOUNT_ALEN = address len
2697
2698- Show boot progress:
2699		CONFIG_SHOW_BOOT_PROGRESS
2700
2701		Defining this option allows to add some board-
2702		specific code (calling a user-provided function
2703		"show_boot_progress(int)") that enables you to show
2704		the system's boot progress on some display (for
2705		example, some LED's) on your board. At the moment,
2706		the following checkpoints are implemented:
2707
2708
2709Legacy uImage format:
2710
2711  Arg	Where			When
2712    1	common/cmd_bootm.c	before attempting to boot an image
2713   -1	common/cmd_bootm.c	Image header has bad	 magic number
2714    2	common/cmd_bootm.c	Image header has correct magic number
2715   -2	common/cmd_bootm.c	Image header has bad	 checksum
2716    3	common/cmd_bootm.c	Image header has correct checksum
2717   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2718    4	common/cmd_bootm.c	Image data   has correct checksum
2719   -4	common/cmd_bootm.c	Image is for unsupported architecture
2720    5	common/cmd_bootm.c	Architecture check OK
2721   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2722    6	common/cmd_bootm.c	Image Type check OK
2723   -6	common/cmd_bootm.c	gunzip uncompression error
2724   -7	common/cmd_bootm.c	Unimplemented compression type
2725    7	common/cmd_bootm.c	Uncompression OK
2726    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2727   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2728
2729    9	common/image.c		Start initial ramdisk verification
2730  -10	common/image.c		Ramdisk header has bad	   magic number
2731  -11	common/image.c		Ramdisk header has bad	   checksum
2732   10	common/image.c		Ramdisk header is OK
2733  -12	common/image.c		Ramdisk data   has bad	   checksum
2734   11	common/image.c		Ramdisk data   has correct checksum
2735   12	common/image.c		Ramdisk verification complete, start loading
2736  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2737   13	common/image.c		Start multifile image verification
2738   14	common/image.c		No initial ramdisk, no multifile, continue.
2739
2740   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2741
2742  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2743  -31	post/post.c		POST test failed, detected by post_output_backlog()
2744  -32	post/post.c		POST test failed, detected by post_run_single()
2745
2746   34	common/cmd_doc.c	before loading a Image from a DOC device
2747  -35	common/cmd_doc.c	Bad usage of "doc" command
2748   35	common/cmd_doc.c	correct usage of "doc" command
2749  -36	common/cmd_doc.c	No boot device
2750   36	common/cmd_doc.c	correct boot device
2751  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2752   37	common/cmd_doc.c	correct chip ID found, device available
2753  -38	common/cmd_doc.c	Read Error on boot device
2754   38	common/cmd_doc.c	reading Image header from DOC device OK
2755  -39	common/cmd_doc.c	Image header has bad magic number
2756   39	common/cmd_doc.c	Image header has correct magic number
2757  -40	common/cmd_doc.c	Error reading Image from DOC device
2758   40	common/cmd_doc.c	Image header has correct magic number
2759   41	common/cmd_ide.c	before loading a Image from a IDE device
2760  -42	common/cmd_ide.c	Bad usage of "ide" command
2761   42	common/cmd_ide.c	correct usage of "ide" command
2762  -43	common/cmd_ide.c	No boot device
2763   43	common/cmd_ide.c	boot device found
2764  -44	common/cmd_ide.c	Device not available
2765   44	common/cmd_ide.c	Device available
2766  -45	common/cmd_ide.c	wrong partition selected
2767   45	common/cmd_ide.c	partition selected
2768  -46	common/cmd_ide.c	Unknown partition table
2769   46	common/cmd_ide.c	valid partition table found
2770  -47	common/cmd_ide.c	Invalid partition type
2771   47	common/cmd_ide.c	correct partition type
2772  -48	common/cmd_ide.c	Error reading Image Header on boot device
2773   48	common/cmd_ide.c	reading Image Header from IDE device OK
2774  -49	common/cmd_ide.c	Image header has bad magic number
2775   49	common/cmd_ide.c	Image header has correct magic number
2776  -50	common/cmd_ide.c	Image header has bad	 checksum
2777   50	common/cmd_ide.c	Image header has correct checksum
2778  -51	common/cmd_ide.c	Error reading Image from IDE device
2779   51	common/cmd_ide.c	reading Image from IDE device OK
2780   52	common/cmd_nand.c	before loading a Image from a NAND device
2781  -53	common/cmd_nand.c	Bad usage of "nand" command
2782   53	common/cmd_nand.c	correct usage of "nand" command
2783  -54	common/cmd_nand.c	No boot device
2784   54	common/cmd_nand.c	boot device found
2785  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2786   55	common/cmd_nand.c	correct chip ID found, device available
2787  -56	common/cmd_nand.c	Error reading Image Header on boot device
2788   56	common/cmd_nand.c	reading Image Header from NAND device OK
2789  -57	common/cmd_nand.c	Image header has bad magic number
2790   57	common/cmd_nand.c	Image header has correct magic number
2791  -58	common/cmd_nand.c	Error reading Image from NAND device
2792   58	common/cmd_nand.c	reading Image from NAND device OK
2793
2794  -60	common/env_common.c	Environment has a bad CRC, using default
2795
2796   64	net/eth.c		starting with Ethernet configuration.
2797  -64	net/eth.c		no Ethernet found.
2798   65	net/eth.c		Ethernet found.
2799
2800  -80	common/cmd_net.c	usage wrong
2801   80	common/cmd_net.c	before calling net_loop()
2802  -81	common/cmd_net.c	some error in net_loop() occurred
2803   81	common/cmd_net.c	net_loop() back without error
2804  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2805   82	common/cmd_net.c	trying automatic boot
2806   83	common/cmd_net.c	running "source" command
2807  -83	common/cmd_net.c	some error in automatic boot or "source" command
2808   84	common/cmd_net.c	end without errors
2809
2810FIT uImage format:
2811
2812  Arg	Where			When
2813  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2814 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2815  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2816 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2817  102	common/cmd_bootm.c	Kernel unit name specified
2818 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2819  103	common/cmd_bootm.c	Found configuration node
2820  104	common/cmd_bootm.c	Got kernel subimage node offset
2821 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2822  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2823 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2824  106	common/cmd_bootm.c	Architecture check OK
2825 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2826  107	common/cmd_bootm.c	Kernel subimage type OK
2827 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2828  108	common/cmd_bootm.c	Got kernel subimage data/size
2829 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2830 -109	common/cmd_bootm.c	Can't get kernel subimage type
2831 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2832 -111	common/cmd_bootm.c	Can't get kernel subimage os
2833 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2834 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2835
2836  120	common/image.c		Start initial ramdisk verification
2837 -120	common/image.c		Ramdisk FIT image has incorrect format
2838  121	common/image.c		Ramdisk FIT image has correct format
2839  122	common/image.c		No ramdisk subimage unit name, using configuration
2840 -122	common/image.c		Can't get configuration for ramdisk subimage
2841  123	common/image.c		Ramdisk unit name specified
2842 -124	common/image.c		Can't get ramdisk subimage node offset
2843  125	common/image.c		Got ramdisk subimage node offset
2844 -125	common/image.c		Ramdisk subimage hash verification failed
2845  126	common/image.c		Ramdisk subimage hash verification OK
2846 -126	common/image.c		Ramdisk subimage for unsupported architecture
2847  127	common/image.c		Architecture check OK
2848 -127	common/image.c		Can't get ramdisk subimage data/size
2849  128	common/image.c		Got ramdisk subimage data/size
2850  129	common/image.c		Can't get ramdisk load address
2851 -129	common/image.c		Got ramdisk load address
2852
2853 -130	common/cmd_doc.c	Incorrect FIT image format
2854  131	common/cmd_doc.c	FIT image format OK
2855
2856 -140	common/cmd_ide.c	Incorrect FIT image format
2857  141	common/cmd_ide.c	FIT image format OK
2858
2859 -150	common/cmd_nand.c	Incorrect FIT image format
2860  151	common/cmd_nand.c	FIT image format OK
2861
2862- legacy image format:
2863		CONFIG_IMAGE_FORMAT_LEGACY
2864		enables the legacy image format support in U-Boot.
2865
2866		Default:
2867		enabled if CONFIG_FIT_SIGNATURE is not defined.
2868
2869		CONFIG_DISABLE_IMAGE_LEGACY
2870		disable the legacy image format
2871
2872		This define is introduced, as the legacy image format is
2873		enabled per default for backward compatibility.
2874
2875- Standalone program support:
2876		CONFIG_STANDALONE_LOAD_ADDR
2877
2878		This option defines a board specific value for the
2879		address where standalone program gets loaded, thus
2880		overwriting the architecture dependent default
2881		settings.
2882
2883- Frame Buffer Address:
2884		CONFIG_FB_ADDR
2885
2886		Define CONFIG_FB_ADDR if you want to use specific
2887		address for frame buffer.  This is typically the case
2888		when using a graphics controller has separate video
2889		memory.  U-Boot will then place the frame buffer at
2890		the given address instead of dynamically reserving it
2891		in system RAM by calling lcd_setmem(), which grabs
2892		the memory for the frame buffer depending on the
2893		configured panel size.
2894
2895		Please see board_init_f function.
2896
2897- Automatic software updates via TFTP server
2898		CONFIG_UPDATE_TFTP
2899		CONFIG_UPDATE_TFTP_CNT_MAX
2900		CONFIG_UPDATE_TFTP_MSEC_MAX
2901
2902		These options enable and control the auto-update feature;
2903		for a more detailed description refer to doc/README.update.
2904
2905- MTD Support (mtdparts command, UBI support)
2906		CONFIG_MTD_DEVICE
2907
2908		Adds the MTD device infrastructure from the Linux kernel.
2909		Needed for mtdparts command support.
2910
2911		CONFIG_MTD_PARTITIONS
2912
2913		Adds the MTD partitioning infrastructure from the Linux
2914		kernel. Needed for UBI support.
2915
2916- UBI support
2917		CONFIG_CMD_UBI
2918
2919		Adds commands for interacting with MTD partitions formatted
2920		with the UBI flash translation layer
2921
2922		Requires also defining CONFIG_RBTREE
2923
2924		CONFIG_UBI_SILENCE_MSG
2925
2926		Make the verbose messages from UBI stop printing.  This leaves
2927		warnings and errors enabled.
2928
2929
2930		CONFIG_MTD_UBI_WL_THRESHOLD
2931		This parameter defines the maximum difference between the highest
2932		erase counter value and the lowest erase counter value of eraseblocks
2933		of UBI devices. When this threshold is exceeded, UBI starts performing
2934		wear leveling by means of moving data from eraseblock with low erase
2935		counter to eraseblocks with high erase counter.
2936
2937		The default value should be OK for SLC NAND flashes, NOR flashes and
2938		other flashes which have eraseblock life-cycle 100000 or more.
2939		However, in case of MLC NAND flashes which typically have eraseblock
2940		life-cycle less than 10000, the threshold should be lessened (e.g.,
2941		to 128 or 256, although it does not have to be power of 2).
2942
2943		default: 4096
2944
2945		CONFIG_MTD_UBI_BEB_LIMIT
2946		This option specifies the maximum bad physical eraseblocks UBI
2947		expects on the MTD device (per 1024 eraseblocks). If the
2948		underlying flash does not admit of bad eraseblocks (e.g. NOR
2949		flash), this value is ignored.
2950
2951		NAND datasheets often specify the minimum and maximum NVM
2952		(Number of Valid Blocks) for the flashes' endurance lifetime.
2953		The maximum expected bad eraseblocks per 1024 eraseblocks
2954		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2955		which gives 20 for most NANDs (MaxNVB is basically the total
2956		count of eraseblocks on the chip).
2957
2958		To put it differently, if this value is 20, UBI will try to
2959		reserve about 1.9% of physical eraseblocks for bad blocks
2960		handling. And that will be 1.9% of eraseblocks on the entire
2961		NAND chip, not just the MTD partition UBI attaches. This means
2962		that if you have, say, a NAND flash chip admits maximum 40 bad
2963		eraseblocks, and it is split on two MTD partitions of the same
2964		size, UBI will reserve 40 eraseblocks when attaching a
2965		partition.
2966
2967		default: 20
2968
2969		CONFIG_MTD_UBI_FASTMAP
2970		Fastmap is a mechanism which allows attaching an UBI device
2971		in nearly constant time. Instead of scanning the whole MTD device it
2972		only has to locate a checkpoint (called fastmap) on the device.
2973		The on-flash fastmap contains all information needed to attach
2974		the device. Using fastmap makes only sense on large devices where
2975		attaching by scanning takes long. UBI will not automatically install
2976		a fastmap on old images, but you can set the UBI parameter
2977		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2978		that fastmap-enabled images are still usable with UBI implementations
2979		without	fastmap support. On typical flash devices the whole fastmap
2980		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2981
2982		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2983		Set this parameter to enable fastmap automatically on images
2984		without a fastmap.
2985		default: 0
2986
2987		CONFIG_MTD_UBI_FM_DEBUG
2988		Enable UBI fastmap debug
2989		default: 0
2990
2991- UBIFS support
2992		CONFIG_CMD_UBIFS
2993
2994		Adds commands for interacting with UBI volumes formatted as
2995		UBIFS.  UBIFS is read-only in u-boot.
2996
2997		Requires UBI support as well as CONFIG_LZO
2998
2999		CONFIG_UBIFS_SILENCE_MSG
3000
3001		Make the verbose messages from UBIFS stop printing.  This leaves
3002		warnings and errors enabled.
3003
3004- SPL framework
3005		CONFIG_SPL
3006		Enable building of SPL globally.
3007
3008		CONFIG_SPL_LDSCRIPT
3009		LDSCRIPT for linking the SPL binary.
3010
3011		CONFIG_SPL_MAX_FOOTPRINT
3012		Maximum size in memory allocated to the SPL, BSS included.
3013		When defined, the linker checks that the actual memory
3014		used by SPL from _start to __bss_end does not exceed it.
3015		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3016		must not be both defined at the same time.
3017
3018		CONFIG_SPL_MAX_SIZE
3019		Maximum size of the SPL image (text, data, rodata, and
3020		linker lists sections), BSS excluded.
3021		When defined, the linker checks that the actual size does
3022		not exceed it.
3023
3024		CONFIG_SPL_TEXT_BASE
3025		TEXT_BASE for linking the SPL binary.
3026
3027		CONFIG_SPL_RELOC_TEXT_BASE
3028		Address to relocate to.  If unspecified, this is equal to
3029		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3030
3031		CONFIG_SPL_BSS_START_ADDR
3032		Link address for the BSS within the SPL binary.
3033
3034		CONFIG_SPL_BSS_MAX_SIZE
3035		Maximum size in memory allocated to the SPL BSS.
3036		When defined, the linker checks that the actual memory used
3037		by SPL from __bss_start to __bss_end does not exceed it.
3038		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3039		must not be both defined at the same time.
3040
3041		CONFIG_SPL_STACK
3042		Adress of the start of the stack SPL will use
3043
3044		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3045		When defined, SPL will panic() if the image it has
3046		loaded does not have a signature.
3047		Defining this is useful when code which loads images
3048		in SPL cannot guarantee that absolutely all read errors
3049		will be caught.
3050		An example is the LPC32XX MLC NAND driver, which will
3051		consider that a completely unreadable NAND block is bad,
3052		and thus should be skipped silently.
3053
3054		CONFIG_SPL_RELOC_STACK
3055		Adress of the start of the stack SPL will use after
3056		relocation.  If unspecified, this is equal to
3057		CONFIG_SPL_STACK.
3058
3059		CONFIG_SYS_SPL_MALLOC_START
3060		Starting address of the malloc pool used in SPL.
3061		When this option is set the full malloc is used in SPL and
3062		it is set up by spl_init() and before that, the simple malloc()
3063		can be used if CONFIG_SYS_MALLOC_F is defined.
3064
3065		CONFIG_SYS_SPL_MALLOC_SIZE
3066		The size of the malloc pool used in SPL.
3067
3068		CONFIG_SPL_FRAMEWORK
3069		Enable the SPL framework under common/.  This framework
3070		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3071		NAND loading of the Linux Kernel.
3072
3073		CONFIG_SPL_OS_BOOT
3074		Enable booting directly to an OS from SPL.
3075		See also: doc/README.falcon
3076
3077		CONFIG_SPL_DISPLAY_PRINT
3078		For ARM, enable an optional function to print more information
3079		about the running system.
3080
3081		CONFIG_SPL_INIT_MINIMAL
3082		Arch init code should be built for a very small image
3083
3084		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3085		Partition on the MMC to load U-Boot from when the MMC is being
3086		used in raw mode
3087
3088		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3089		Sector to load kernel uImage from when MMC is being
3090		used in raw mode (for Falcon mode)
3091
3092		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3093		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3094		Sector and number of sectors to load kernel argument
3095		parameters from when MMC is being used in raw mode
3096		(for falcon mode)
3097
3098		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3099		Partition on the MMC to load U-Boot from when the MMC is being
3100		used in fs mode
3101
3102		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3103		Filename to read to load U-Boot when reading from filesystem
3104
3105		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3106		Filename to read to load kernel uImage when reading
3107		from filesystem (for Falcon mode)
3108
3109		CONFIG_SPL_FS_LOAD_ARGS_NAME
3110		Filename to read to load kernel argument parameters
3111		when reading from filesystem (for Falcon mode)
3112
3113		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3114		Set this for NAND SPL on PPC mpc83xx targets, so that
3115		start.S waits for the rest of the SPL to load before
3116		continuing (the hardware starts execution after just
3117		loading the first page rather than the full 4K).
3118
3119		CONFIG_SPL_SKIP_RELOCATE
3120		Avoid SPL relocation
3121
3122		CONFIG_SPL_NAND_BASE
3123		Include nand_base.c in the SPL.  Requires
3124		CONFIG_SPL_NAND_DRIVERS.
3125
3126		CONFIG_SPL_NAND_DRIVERS
3127		SPL uses normal NAND drivers, not minimal drivers.
3128
3129		CONFIG_SPL_NAND_ECC
3130		Include standard software ECC in the SPL
3131
3132		CONFIG_SPL_NAND_SIMPLE
3133		Support for NAND boot using simple NAND drivers that
3134		expose the cmd_ctrl() interface.
3135
3136		CONFIG_SPL_UBI
3137		Support for a lightweight UBI (fastmap) scanner and
3138		loader
3139
3140		CONFIG_SPL_NAND_RAW_ONLY
3141		Support to boot only raw u-boot.bin images. Use this only
3142		if you need to save space.
3143
3144		CONFIG_SPL_COMMON_INIT_DDR
3145		Set for common ddr init with serial presence detect in
3146		SPL binary.
3147
3148		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3149		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3150		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3151		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3152		CONFIG_SYS_NAND_ECCBYTES
3153		Defines the size and behavior of the NAND that SPL uses
3154		to read U-Boot
3155
3156		CONFIG_SPL_NAND_BOOT
3157		Add support NAND boot
3158
3159		CONFIG_SYS_NAND_U_BOOT_OFFS
3160		Location in NAND to read U-Boot from
3161
3162		CONFIG_SYS_NAND_U_BOOT_DST
3163		Location in memory to load U-Boot to
3164
3165		CONFIG_SYS_NAND_U_BOOT_SIZE
3166		Size of image to load
3167
3168		CONFIG_SYS_NAND_U_BOOT_START
3169		Entry point in loaded image to jump to
3170
3171		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3172		Define this if you need to first read the OOB and then the
3173		data. This is used, for example, on davinci platforms.
3174
3175		CONFIG_SPL_OMAP3_ID_NAND
3176		Support for an OMAP3-specific set of functions to return the
3177		ID and MFR of the first attached NAND chip, if present.
3178
3179		CONFIG_SPL_RAM_DEVICE
3180		Support for running image already present in ram, in SPL binary
3181
3182		CONFIG_SPL_PAD_TO
3183		Image offset to which the SPL should be padded before appending
3184		the SPL payload. By default, this is defined as
3185		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3186		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3187		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3188
3189		CONFIG_SPL_TARGET
3190		Final target image containing SPL and payload.  Some SPLs
3191		use an arch-specific makefile fragment instead, for
3192		example if more than one image needs to be produced.
3193
3194		CONFIG_FIT_SPL_PRINT
3195		Printing information about a FIT image adds quite a bit of
3196		code to SPL. So this is normally disabled in SPL. Use this
3197		option to re-enable it. This will affect the output of the
3198		bootm command when booting a FIT image.
3199
3200- TPL framework
3201		CONFIG_TPL
3202		Enable building of TPL globally.
3203
3204		CONFIG_TPL_PAD_TO
3205		Image offset to which the TPL should be padded before appending
3206		the TPL payload. By default, this is defined as
3207		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3208		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3209		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3210
3211- Interrupt support (PPC):
3212
3213		There are common interrupt_init() and timer_interrupt()
3214		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3215		for CPU specific initialization. interrupt_init_cpu()
3216		should set decrementer_count to appropriate value. If
3217		CPU resets decrementer automatically after interrupt
3218		(ppc4xx) it should set decrementer_count to zero.
3219		timer_interrupt() calls timer_interrupt_cpu() for CPU
3220		specific handling. If board has watchdog / status_led
3221		/ other_activity_monitor it works automatically from
3222		general timer_interrupt().
3223
3224
3225Board initialization settings:
3226------------------------------
3227
3228During Initialization u-boot calls a number of board specific functions
3229to allow the preparation of board specific prerequisites, e.g. pin setup
3230before drivers are initialized. To enable these callbacks the
3231following configuration macros have to be defined. Currently this is
3232architecture specific, so please check arch/your_architecture/lib/board.c
3233typically in board_init_f() and board_init_r().
3234
3235- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3236- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3237- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3238- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3239
3240Configuration Settings:
3241-----------------------
3242
3243- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3244		Optionally it can be defined to support 64-bit memory commands.
3245
3246- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3247		undefine this when you're short of memory.
3248
3249- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3250		width of the commands listed in the 'help' command output.
3251
3252- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3253		prompt for user input.
3254
3255- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3256
3257- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3258
3259- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3260
3261- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3262		the application (usually a Linux kernel) when it is
3263		booted
3264
3265- CONFIG_SYS_BAUDRATE_TABLE:
3266		List of legal baudrate settings for this board.
3267
3268- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3269		Begin and End addresses of the area used by the
3270		simple memory test.
3271
3272- CONFIG_SYS_ALT_MEMTEST:
3273		Enable an alternate, more extensive memory test.
3274
3275- CONFIG_SYS_MEMTEST_SCRATCH:
3276		Scratch address used by the alternate memory test
3277		You only need to set this if address zero isn't writeable
3278
3279- CONFIG_SYS_MEM_RESERVE_SECURE
3280		Only implemented for ARMv8 for now.
3281		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3282		is substracted from total RAM and won't be reported to OS.
3283		This memory can be used as secure memory. A variable
3284		gd->arch.secure_ram is used to track the location. In systems
3285		the RAM base is not zero, or RAM is divided into banks,
3286		this variable needs to be recalcuated to get the address.
3287
3288- CONFIG_SYS_MEM_TOP_HIDE:
3289		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3290		this specified memory area will get subtracted from the top
3291		(end) of RAM and won't get "touched" at all by U-Boot. By
3292		fixing up gd->ram_size the Linux kernel should gets passed
3293		the now "corrected" memory size and won't touch it either.
3294		This should work for arch/ppc and arch/powerpc. Only Linux
3295		board ports in arch/powerpc with bootwrapper support that
3296		recalculate the memory size from the SDRAM controller setup
3297		will have to get fixed in Linux additionally.
3298
3299		This option can be used as a workaround for the 440EPx/GRx
3300		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3301		be touched.
3302
3303		WARNING: Please make sure that this value is a multiple of
3304		the Linux page size (normally 4k). If this is not the case,
3305		then the end address of the Linux memory will be located at a
3306		non page size aligned address and this could cause major
3307		problems.
3308
3309- CONFIG_SYS_LOADS_BAUD_CHANGE:
3310		Enable temporary baudrate change while serial download
3311
3312- CONFIG_SYS_SDRAM_BASE:
3313		Physical start address of SDRAM. _Must_ be 0 here.
3314
3315- CONFIG_SYS_FLASH_BASE:
3316		Physical start address of Flash memory.
3317
3318- CONFIG_SYS_MONITOR_BASE:
3319		Physical start address of boot monitor code (set by
3320		make config files to be same as the text base address
3321		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3322		CONFIG_SYS_FLASH_BASE when booting from flash.
3323
3324- CONFIG_SYS_MONITOR_LEN:
3325		Size of memory reserved for monitor code, used to
3326		determine _at_compile_time_ (!) if the environment is
3327		embedded within the U-Boot image, or in a separate
3328		flash sector.
3329
3330- CONFIG_SYS_MALLOC_LEN:
3331		Size of DRAM reserved for malloc() use.
3332
3333- CONFIG_SYS_MALLOC_F_LEN
3334		Size of the malloc() pool for use before relocation. If
3335		this is defined, then a very simple malloc() implementation
3336		will become available before relocation. The address is just
3337		below the global data, and the stack is moved down to make
3338		space.
3339
3340		This feature allocates regions with increasing addresses
3341		within the region. calloc() is supported, but realloc()
3342		is not available. free() is supported but does nothing.
3343		The memory will be freed (or in fact just forgotten) when
3344		U-Boot relocates itself.
3345
3346- CONFIG_SYS_MALLOC_SIMPLE
3347		Provides a simple and small malloc() and calloc() for those
3348		boards which do not use the full malloc in SPL (which is
3349		enabled with CONFIG_SYS_SPL_MALLOC_START).
3350
3351- CONFIG_SYS_NONCACHED_MEMORY:
3352		Size of non-cached memory area. This area of memory will be
3353		typically located right below the malloc() area and mapped
3354		uncached in the MMU. This is useful for drivers that would
3355		otherwise require a lot of explicit cache maintenance. For
3356		some drivers it's also impossible to properly maintain the
3357		cache. For example if the regions that need to be flushed
3358		are not a multiple of the cache-line size, *and* padding
3359		cannot be allocated between the regions to align them (i.e.
3360		if the HW requires a contiguous array of regions, and the
3361		size of each region is not cache-aligned), then a flush of
3362		one region may result in overwriting data that hardware has
3363		written to another region in the same cache-line. This can
3364		happen for example in network drivers where descriptors for
3365		buffers are typically smaller than the CPU cache-line (e.g.
3366		16 bytes vs. 32 or 64 bytes).
3367
3368		Non-cached memory is only supported on 32-bit ARM at present.
3369
3370- CONFIG_SYS_BOOTM_LEN:
3371		Normally compressed uImages are limited to an
3372		uncompressed size of 8 MBytes. If this is not enough,
3373		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3374		to adjust this setting to your needs.
3375
3376- CONFIG_SYS_BOOTMAPSZ:
3377		Maximum size of memory mapped by the startup code of
3378		the Linux kernel; all data that must be processed by
3379		the Linux kernel (bd_info, boot arguments, FDT blob if
3380		used) must be put below this limit, unless "bootm_low"
3381		environment variable is defined and non-zero. In such case
3382		all data for the Linux kernel must be between "bootm_low"
3383		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3384		variable "bootm_mapsize" will override the value of
3385		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3386		then the value in "bootm_size" will be used instead.
3387
3388- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3389		Enable initrd_high functionality.  If defined then the
3390		initrd_high feature is enabled and the bootm ramdisk subcommand
3391		is enabled.
3392
3393- CONFIG_SYS_BOOT_GET_CMDLINE:
3394		Enables allocating and saving kernel cmdline in space between
3395		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3396
3397- CONFIG_SYS_BOOT_GET_KBD:
3398		Enables allocating and saving a kernel copy of the bd_info in
3399		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3400
3401- CONFIG_SYS_MAX_FLASH_BANKS:
3402		Max number of Flash memory banks
3403
3404- CONFIG_SYS_MAX_FLASH_SECT:
3405		Max number of sectors on a Flash chip
3406
3407- CONFIG_SYS_FLASH_ERASE_TOUT:
3408		Timeout for Flash erase operations (in ms)
3409
3410- CONFIG_SYS_FLASH_WRITE_TOUT:
3411		Timeout for Flash write operations (in ms)
3412
3413- CONFIG_SYS_FLASH_LOCK_TOUT
3414		Timeout for Flash set sector lock bit operation (in ms)
3415
3416- CONFIG_SYS_FLASH_UNLOCK_TOUT
3417		Timeout for Flash clear lock bits operation (in ms)
3418
3419- CONFIG_SYS_FLASH_PROTECTION
3420		If defined, hardware flash sectors protection is used
3421		instead of U-Boot software protection.
3422
3423- CONFIG_SYS_DIRECT_FLASH_TFTP:
3424
3425		Enable TFTP transfers directly to flash memory;
3426		without this option such a download has to be
3427		performed in two steps: (1) download to RAM, and (2)
3428		copy from RAM to flash.
3429
3430		The two-step approach is usually more reliable, since
3431		you can check if the download worked before you erase
3432		the flash, but in some situations (when system RAM is
3433		too limited to allow for a temporary copy of the
3434		downloaded image) this option may be very useful.
3435
3436- CONFIG_SYS_FLASH_CFI:
3437		Define if the flash driver uses extra elements in the
3438		common flash structure for storing flash geometry.
3439
3440- CONFIG_FLASH_CFI_DRIVER
3441		This option also enables the building of the cfi_flash driver
3442		in the drivers directory
3443
3444- CONFIG_FLASH_CFI_MTD
3445		This option enables the building of the cfi_mtd driver
3446		in the drivers directory. The driver exports CFI flash
3447		to the MTD layer.
3448
3449- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3450		Use buffered writes to flash.
3451
3452- CONFIG_FLASH_SPANSION_S29WS_N
3453		s29ws-n MirrorBit flash has non-standard addresses for buffered
3454		write commands.
3455
3456- CONFIG_SYS_FLASH_QUIET_TEST
3457		If this option is defined, the common CFI flash doesn't
3458		print it's warning upon not recognized FLASH banks. This
3459		is useful, if some of the configured banks are only
3460		optionally available.
3461
3462- CONFIG_FLASH_SHOW_PROGRESS
3463		If defined (must be an integer), print out countdown
3464		digits and dots.  Recommended value: 45 (9..1) for 80
3465		column displays, 15 (3..1) for 40 column displays.
3466
3467- CONFIG_FLASH_VERIFY
3468		If defined, the content of the flash (destination) is compared
3469		against the source after the write operation. An error message
3470		will be printed when the contents are not identical.
3471		Please note that this option is useless in nearly all cases,
3472		since such flash programming errors usually are detected earlier
3473		while unprotecting/erasing/programming. Please only enable
3474		this option if you really know what you are doing.
3475
3476- CONFIG_SYS_RX_ETH_BUFFER:
3477		Defines the number of Ethernet receive buffers. On some
3478		Ethernet controllers it is recommended to set this value
3479		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3480		buffers can be full shortly after enabling the interface
3481		on high Ethernet traffic.
3482		Defaults to 4 if not defined.
3483
3484- CONFIG_ENV_MAX_ENTRIES
3485
3486	Maximum number of entries in the hash table that is used
3487	internally to store the environment settings. The default
3488	setting is supposed to be generous and should work in most
3489	cases. This setting can be used to tune behaviour; see
3490	lib/hashtable.c for details.
3491
3492- CONFIG_ENV_FLAGS_LIST_DEFAULT
3493- CONFIG_ENV_FLAGS_LIST_STATIC
3494	Enable validation of the values given to environment variables when
3495	calling env set.  Variables can be restricted to only decimal,
3496	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3497	the variables can also be restricted to IP address or MAC address.
3498
3499	The format of the list is:
3500		type_attribute = [s|d|x|b|i|m]
3501		access_attribute = [a|r|o|c]
3502		attributes = type_attribute[access_attribute]
3503		entry = variable_name[:attributes]
3504		list = entry[,list]
3505
3506	The type attributes are:
3507		s - String (default)
3508		d - Decimal
3509		x - Hexadecimal
3510		b - Boolean ([1yYtT|0nNfF])
3511		i - IP address
3512		m - MAC address
3513
3514	The access attributes are:
3515		a - Any (default)
3516		r - Read-only
3517		o - Write-once
3518		c - Change-default
3519
3520	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3521		Define this to a list (string) to define the ".flags"
3522		environment variable in the default or embedded environment.
3523
3524	- CONFIG_ENV_FLAGS_LIST_STATIC
3525		Define this to a list (string) to define validation that
3526		should be done if an entry is not found in the ".flags"
3527		environment variable.  To override a setting in the static
3528		list, simply add an entry for the same variable name to the
3529		".flags" variable.
3530
3531	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3532	regular expression. This allows multiple variables to define the same
3533	flags without explicitly listing them for each variable.
3534
3535- CONFIG_ENV_ACCESS_IGNORE_FORCE
3536	If defined, don't allow the -f switch to env set override variable
3537	access flags.
3538
3539- CONFIG_USE_STDINT
3540	If stdint.h is available with your toolchain you can define this
3541	option to enable it. You can provide option 'USE_STDINT=1' when
3542	building U-Boot to enable this.
3543
3544The following definitions that deal with the placement and management
3545of environment data (variable area); in general, we support the
3546following configurations:
3547
3548- CONFIG_BUILD_ENVCRC:
3549
3550	Builds up envcrc with the target environment so that external utils
3551	may easily extract it and embed it in final U-Boot images.
3552
3553- CONFIG_ENV_IS_IN_FLASH:
3554
3555	Define this if the environment is in flash memory.
3556
3557	a) The environment occupies one whole flash sector, which is
3558	   "embedded" in the text segment with the U-Boot code. This
3559	   happens usually with "bottom boot sector" or "top boot
3560	   sector" type flash chips, which have several smaller
3561	   sectors at the start or the end. For instance, such a
3562	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3563	   such a case you would place the environment in one of the
3564	   4 kB sectors - with U-Boot code before and after it. With
3565	   "top boot sector" type flash chips, you would put the
3566	   environment in one of the last sectors, leaving a gap
3567	   between U-Boot and the environment.
3568
3569	- CONFIG_ENV_OFFSET:
3570
3571	   Offset of environment data (variable area) to the
3572	   beginning of flash memory; for instance, with bottom boot
3573	   type flash chips the second sector can be used: the offset
3574	   for this sector is given here.
3575
3576	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3577
3578	- CONFIG_ENV_ADDR:
3579
3580	   This is just another way to specify the start address of
3581	   the flash sector containing the environment (instead of
3582	   CONFIG_ENV_OFFSET).
3583
3584	- CONFIG_ENV_SECT_SIZE:
3585
3586	   Size of the sector containing the environment.
3587
3588
3589	b) Sometimes flash chips have few, equal sized, BIG sectors.
3590	   In such a case you don't want to spend a whole sector for
3591	   the environment.
3592
3593	- CONFIG_ENV_SIZE:
3594
3595	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3596	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3597	   of this flash sector for the environment. This saves
3598	   memory for the RAM copy of the environment.
3599
3600	   It may also save flash memory if you decide to use this
3601	   when your environment is "embedded" within U-Boot code,
3602	   since then the remainder of the flash sector could be used
3603	   for U-Boot code. It should be pointed out that this is
3604	   STRONGLY DISCOURAGED from a robustness point of view:
3605	   updating the environment in flash makes it always
3606	   necessary to erase the WHOLE sector. If something goes
3607	   wrong before the contents has been restored from a copy in
3608	   RAM, your target system will be dead.
3609
3610	- CONFIG_ENV_ADDR_REDUND
3611	  CONFIG_ENV_SIZE_REDUND
3612
3613	   These settings describe a second storage area used to hold
3614	   a redundant copy of the environment data, so that there is
3615	   a valid backup copy in case there is a power failure during
3616	   a "saveenv" operation.
3617
3618BE CAREFUL! Any changes to the flash layout, and some changes to the
3619source code will make it necessary to adapt <board>/u-boot.lds*
3620accordingly!
3621
3622
3623- CONFIG_ENV_IS_IN_NVRAM:
3624
3625	Define this if you have some non-volatile memory device
3626	(NVRAM, battery buffered SRAM) which you want to use for the
3627	environment.
3628
3629	- CONFIG_ENV_ADDR:
3630	- CONFIG_ENV_SIZE:
3631
3632	  These two #defines are used to determine the memory area you
3633	  want to use for environment. It is assumed that this memory
3634	  can just be read and written to, without any special
3635	  provision.
3636
3637BE CAREFUL! The first access to the environment happens quite early
3638in U-Boot initialization (when we try to get the setting of for the
3639console baudrate). You *MUST* have mapped your NVRAM area then, or
3640U-Boot will hang.
3641
3642Please note that even with NVRAM we still use a copy of the
3643environment in RAM: we could work on NVRAM directly, but we want to
3644keep settings there always unmodified except somebody uses "saveenv"
3645to save the current settings.
3646
3647
3648- CONFIG_ENV_IS_IN_EEPROM:
3649
3650	Use this if you have an EEPROM or similar serial access
3651	device and a driver for it.
3652
3653	- CONFIG_ENV_OFFSET:
3654	- CONFIG_ENV_SIZE:
3655
3656	  These two #defines specify the offset and size of the
3657	  environment area within the total memory of your EEPROM.
3658
3659	- CONFIG_SYS_I2C_EEPROM_ADDR:
3660	  If defined, specified the chip address of the EEPROM device.
3661	  The default address is zero.
3662
3663	- CONFIG_SYS_I2C_EEPROM_BUS:
3664	  If defined, specified the i2c bus of the EEPROM device.
3665
3666	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3667	  If defined, the number of bits used to address bytes in a
3668	  single page in the EEPROM device.  A 64 byte page, for example
3669	  would require six bits.
3670
3671	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3672	  If defined, the number of milliseconds to delay between
3673	  page writes.	The default is zero milliseconds.
3674
3675	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3676	  The length in bytes of the EEPROM memory array address.  Note
3677	  that this is NOT the chip address length!
3678
3679	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3680	  EEPROM chips that implement "address overflow" are ones
3681	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3682	  address and the extra bits end up in the "chip address" bit
3683	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3684	  byte chips.
3685
3686	  Note that we consider the length of the address field to
3687	  still be one byte because the extra address bits are hidden
3688	  in the chip address.
3689
3690	- CONFIG_SYS_EEPROM_SIZE:
3691	  The size in bytes of the EEPROM device.
3692
3693	- CONFIG_ENV_EEPROM_IS_ON_I2C
3694	  define this, if you have I2C and SPI activated, and your
3695	  EEPROM, which holds the environment, is on the I2C bus.
3696
3697	- CONFIG_I2C_ENV_EEPROM_BUS
3698	  if you have an Environment on an EEPROM reached over
3699	  I2C muxes, you can define here, how to reach this
3700	  EEPROM. For example:
3701
3702	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3703
3704	  EEPROM which holds the environment, is reached over
3705	  a pca9547 i2c mux with address 0x70, channel 3.
3706
3707- CONFIG_ENV_IS_IN_DATAFLASH:
3708
3709	Define this if you have a DataFlash memory device which you
3710	want to use for the environment.
3711
3712	- CONFIG_ENV_OFFSET:
3713	- CONFIG_ENV_ADDR:
3714	- CONFIG_ENV_SIZE:
3715
3716	  These three #defines specify the offset and size of the
3717	  environment area within the total memory of your DataFlash placed
3718	  at the specified address.
3719
3720- CONFIG_ENV_IS_IN_SPI_FLASH:
3721
3722	Define this if you have a SPI Flash memory device which you
3723	want to use for the environment.
3724
3725	- CONFIG_ENV_OFFSET:
3726	- CONFIG_ENV_SIZE:
3727
3728	  These two #defines specify the offset and size of the
3729	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
3730	  aligned to an erase sector boundary.
3731
3732	- CONFIG_ENV_SECT_SIZE:
3733
3734	  Define the SPI flash's sector size.
3735
3736	- CONFIG_ENV_OFFSET_REDUND (optional):
3737
3738	  This setting describes a second storage area of CONFIG_ENV_SIZE
3739	  size used to hold a redundant copy of the environment data, so
3740	  that there is a valid backup copy in case there is a power failure
3741	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
3742	  aligned to an erase sector boundary.
3743
3744	- CONFIG_ENV_SPI_BUS (optional):
3745	- CONFIG_ENV_SPI_CS (optional):
3746
3747	  Define the SPI bus and chip select. If not defined they will be 0.
3748
3749	- CONFIG_ENV_SPI_MAX_HZ (optional):
3750
3751	  Define the SPI max work clock. If not defined then use 1MHz.
3752
3753	- CONFIG_ENV_SPI_MODE (optional):
3754
3755	  Define the SPI work mode. If not defined then use SPI_MODE_3.
3756
3757- CONFIG_ENV_IS_IN_REMOTE:
3758
3759	Define this if you have a remote memory space which you
3760	want to use for the local device's environment.
3761
3762	- CONFIG_ENV_ADDR:
3763	- CONFIG_ENV_SIZE:
3764
3765	  These two #defines specify the address and size of the
3766	  environment area within the remote memory space. The
3767	  local device can get the environment from remote memory
3768	  space by SRIO or PCIE links.
3769
3770BE CAREFUL! For some special cases, the local device can not use
3771"saveenv" command. For example, the local device will get the
3772environment stored in a remote NOR flash by SRIO or PCIE link,
3773but it can not erase, write this NOR flash by SRIO or PCIE interface.
3774
3775- CONFIG_ENV_IS_IN_NAND:
3776
3777	Define this if you have a NAND device which you want to use
3778	for the environment.
3779
3780	- CONFIG_ENV_OFFSET:
3781	- CONFIG_ENV_SIZE:
3782
3783	  These two #defines specify the offset and size of the environment
3784	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3785	  aligned to an erase block boundary.
3786
3787	- CONFIG_ENV_OFFSET_REDUND (optional):
3788
3789	  This setting describes a second storage area of CONFIG_ENV_SIZE
3790	  size used to hold a redundant copy of the environment data, so
3791	  that there is a valid backup copy in case there is a power failure
3792	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
3793	  aligned to an erase block boundary.
3794
3795	- CONFIG_ENV_RANGE (optional):
3796
3797	  Specifies the length of the region in which the environment
3798	  can be written.  This should be a multiple of the NAND device's
3799	  block size.  Specifying a range with more erase blocks than
3800	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3801	  the range to be avoided.
3802
3803	- CONFIG_ENV_OFFSET_OOB (optional):
3804
3805	  Enables support for dynamically retrieving the offset of the
3806	  environment from block zero's out-of-band data.  The
3807	  "nand env.oob" command can be used to record this offset.
3808	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3809	  using CONFIG_ENV_OFFSET_OOB.
3810
3811- CONFIG_NAND_ENV_DST
3812
3813	Defines address in RAM to which the nand_spl code should copy the
3814	environment. If redundant environment is used, it will be copied to
3815	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3816
3817- CONFIG_ENV_IS_IN_UBI:
3818
3819	Define this if you have an UBI volume that you want to use for the
3820	environment.  This has the benefit of wear-leveling the environment
3821	accesses, which is important on NAND.
3822
3823	- CONFIG_ENV_UBI_PART:
3824
3825	  Define this to a string that is the mtd partition containing the UBI.
3826
3827	- CONFIG_ENV_UBI_VOLUME:
3828
3829	  Define this to the name of the volume that you want to store the
3830	  environment in.
3831
3832	- CONFIG_ENV_UBI_VOLUME_REDUND:
3833
3834	  Define this to the name of another volume to store a second copy of
3835	  the environment in.  This will enable redundant environments in UBI.
3836	  It is assumed that both volumes are in the same MTD partition.
3837
3838	- CONFIG_UBI_SILENCE_MSG
3839	- CONFIG_UBIFS_SILENCE_MSG
3840
3841	  You will probably want to define these to avoid a really noisy system
3842	  when storing the env in UBI.
3843
3844- CONFIG_ENV_IS_IN_FAT:
3845       Define this if you want to use the FAT file system for the environment.
3846
3847       - FAT_ENV_INTERFACE:
3848
3849         Define this to a string that is the name of the block device.
3850
3851       - FAT_ENV_DEVICE_AND_PART:
3852
3853         Define this to a string to specify the partition of the device. It can
3854         be as following:
3855
3856           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
3857               - "D:P": device D partition P. Error occurs if device D has no
3858                        partition table.
3859               - "D:0": device D.
3860               - "D" or "D:": device D partition 1 if device D has partition
3861                              table, or the whole device D if has no partition
3862                              table.
3863               - "D:auto": first partition in device D with bootable flag set.
3864                           If none, first valid partition in device D. If no
3865                           partition table then means device D.
3866
3867       - FAT_ENV_FILE:
3868
3869         It's a string of the FAT file name. This file use to store the
3870         environment.
3871
3872       - CONFIG_FAT_WRITE:
3873         This should be defined. Otherwise it cannot save the environment file.
3874
3875- CONFIG_ENV_IS_IN_MMC:
3876
3877	Define this if you have an MMC device which you want to use for the
3878	environment.
3879
3880	- CONFIG_SYS_MMC_ENV_DEV:
3881
3882	  Specifies which MMC device the environment is stored in.
3883
3884	- CONFIG_SYS_MMC_ENV_PART (optional):
3885
3886	  Specifies which MMC partition the environment is stored in. If not
3887	  set, defaults to partition 0, the user area. Common values might be
3888	  1 (first MMC boot partition), 2 (second MMC boot partition).
3889
3890	- CONFIG_ENV_OFFSET:
3891	- CONFIG_ENV_SIZE:
3892
3893	  These two #defines specify the offset and size of the environment
3894	  area within the specified MMC device.
3895
3896	  If offset is positive (the usual case), it is treated as relative to
3897	  the start of the MMC partition. If offset is negative, it is treated
3898	  as relative to the end of the MMC partition. This can be useful if
3899	  your board may be fitted with different MMC devices, which have
3900	  different sizes for the MMC partitions, and you always want the
3901	  environment placed at the very end of the partition, to leave the
3902	  maximum possible space before it, to store other data.
3903
3904	  These two values are in units of bytes, but must be aligned to an
3905	  MMC sector boundary.
3906
3907	- CONFIG_ENV_OFFSET_REDUND (optional):
3908
3909	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3910	  hold a redundant copy of the environment data. This provides a
3911	  valid backup copy in case the other copy is corrupted, e.g. due
3912	  to a power failure during a "saveenv" operation.
3913
3914	  This value may also be positive or negative; this is handled in the
3915	  same way as CONFIG_ENV_OFFSET.
3916
3917	  This value is also in units of bytes, but must also be aligned to
3918	  an MMC sector boundary.
3919
3920	- CONFIG_ENV_SIZE_REDUND (optional):
3921
3922	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3923	  set. If this value is set, it must be set to the same value as
3924	  CONFIG_ENV_SIZE.
3925
3926- CONFIG_SYS_SPI_INIT_OFFSET
3927
3928	Defines offset to the initial SPI buffer area in DPRAM. The
3929	area is used at an early stage (ROM part) if the environment
3930	is configured to reside in the SPI EEPROM: We need a 520 byte
3931	scratch DPRAM area. It is used between the two initialization
3932	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
3933	to be a good choice since it makes it far enough from the
3934	start of the data area as well as from the stack pointer.
3935
3936Please note that the environment is read-only until the monitor
3937has been relocated to RAM and a RAM copy of the environment has been
3938created; also, when using EEPROM you will have to use getenv_f()
3939until then to read environment variables.
3940
3941The environment is protected by a CRC32 checksum. Before the monitor
3942is relocated into RAM, as a result of a bad CRC you will be working
3943with the compiled-in default environment - *silently*!!! [This is
3944necessary, because the first environment variable we need is the
3945"baudrate" setting for the console - if we have a bad CRC, we don't
3946have any device yet where we could complain.]
3947
3948Note: once the monitor has been relocated, then it will complain if
3949the default environment is used; a new CRC is computed as soon as you
3950use the "saveenv" command to store a valid environment.
3951
3952- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3953		Echo the inverted Ethernet link state to the fault LED.
3954
3955		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3956		      also needs to be defined.
3957
3958- CONFIG_SYS_FAULT_MII_ADDR:
3959		MII address of the PHY to check for the Ethernet link state.
3960
3961- CONFIG_NS16550_MIN_FUNCTIONS:
3962		Define this if you desire to only have use of the NS16550_init
3963		and NS16550_putc functions for the serial driver located at
3964		drivers/serial/ns16550.c.  This option is useful for saving
3965		space for already greatly restricted images, including but not
3966		limited to NAND_SPL configurations.
3967
3968- CONFIG_DISPLAY_BOARDINFO
3969		Display information about the board that U-Boot is running on
3970		when U-Boot starts up. The board function checkboard() is called
3971		to do this.
3972
3973- CONFIG_DISPLAY_BOARDINFO_LATE
3974		Similar to the previous option, but display this information
3975		later, once stdio is running and output goes to the LCD, if
3976		present.
3977
3978- CONFIG_BOARD_SIZE_LIMIT:
3979		Maximum size of the U-Boot image. When defined, the
3980		build system checks that the actual size does not
3981		exceed it.
3982
3983Low Level (hardware related) configuration options:
3984---------------------------------------------------
3985
3986- CONFIG_SYS_CACHELINE_SIZE:
3987		Cache Line Size of the CPU.
3988
3989- CONFIG_SYS_DEFAULT_IMMR:
3990		Default address of the IMMR after system reset.
3991
3992		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
3993		and RPXsuper) to be able to adjust the position of
3994		the IMMR register after a reset.
3995
3996- CONFIG_SYS_CCSRBAR_DEFAULT:
3997		Default (power-on reset) physical address of CCSR on Freescale
3998		PowerPC SOCs.
3999
4000- CONFIG_SYS_CCSRBAR:
4001		Virtual address of CCSR.  On a 32-bit build, this is typically
4002		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4003
4004		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4005		for cross-platform code that uses that macro instead.
4006
4007- CONFIG_SYS_CCSRBAR_PHYS:
4008		Physical address of CCSR.  CCSR can be relocated to a new
4009		physical address, if desired.  In this case, this macro should
4010		be set to that address.	 Otherwise, it should be set to the
4011		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4012		is typically relocated on 36-bit builds.  It is recommended
4013		that this macro be defined via the _HIGH and _LOW macros:
4014
4015		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4016			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4017
4018- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4019		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4020		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4021		used in assembly code, so it must not contain typecasts or
4022		integer size suffixes (e.g. "ULL").
4023
4024- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4025		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4026		used in assembly code, so it must not contain typecasts or
4027		integer size suffixes (e.g. "ULL").
4028
4029- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4030		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4031		forced to a value that ensures that CCSR is not relocated.
4032
4033- Floppy Disk Support:
4034		CONFIG_SYS_FDC_DRIVE_NUMBER
4035
4036		the default drive number (default value 0)
4037
4038		CONFIG_SYS_ISA_IO_STRIDE
4039
4040		defines the spacing between FDC chipset registers
4041		(default value 1)
4042
4043		CONFIG_SYS_ISA_IO_OFFSET
4044
4045		defines the offset of register from address. It
4046		depends on which part of the data bus is connected to
4047		the FDC chipset. (default value 0)
4048
4049		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4050		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4051		default value.
4052
4053		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4054		fdc_hw_init() is called at the beginning of the FDC
4055		setup. fdc_hw_init() must be provided by the board
4056		source code. It is used to make hardware-dependent
4057		initializations.
4058
4059- CONFIG_IDE_AHB:
4060		Most IDE controllers were designed to be connected with PCI
4061		interface. Only few of them were designed for AHB interface.
4062		When software is doing ATA command and data transfer to
4063		IDE devices through IDE-AHB controller, some additional
4064		registers accessing to these kind of IDE-AHB controller
4065		is required.
4066
4067- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4068		DO NOT CHANGE unless you know exactly what you're
4069		doing! (11-4) [MPC8xx/82xx systems only]
4070
4071- CONFIG_SYS_INIT_RAM_ADDR:
4072
4073		Start address of memory area that can be used for
4074		initial data and stack; please note that this must be
4075		writable memory that is working WITHOUT special
4076		initialization, i. e. you CANNOT use normal RAM which
4077		will become available only after programming the
4078		memory controller and running certain initialization
4079		sequences.
4080
4081		U-Boot uses the following memory types:
4082		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4083		- MPC824X: data cache
4084		- PPC4xx:  data cache
4085
4086- CONFIG_SYS_GBL_DATA_OFFSET:
4087
4088		Offset of the initial data structure in the memory
4089		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4090		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4091		data is located at the end of the available space
4092		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4093		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4094		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4095		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4096
4097	Note:
4098		On the MPC824X (or other systems that use the data
4099		cache for initial memory) the address chosen for
4100		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4101		point to an otherwise UNUSED address space between
4102		the top of RAM and the start of the PCI space.
4103
4104- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4105
4106- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4107
4108- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4109
4110- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4111
4112- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4113
4114- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4115
4116- CONFIG_SYS_OR_TIMING_SDRAM:
4117		SDRAM timing
4118
4119- CONFIG_SYS_MAMR_PTA:
4120		periodic timer for refresh
4121
4122- CONFIG_SYS_DER:	Debug Event Register (37-47)
4123
4124- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4125  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4126  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4127  CONFIG_SYS_BR1_PRELIM:
4128		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4129
4130- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4131  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4132  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4133		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4134
4135- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4136  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4137		Machine Mode Register and Memory Periodic Timer
4138		Prescaler definitions (SDRAM timing)
4139
4140- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4141		enable I2C microcode relocation patch (MPC8xx);
4142		define relocation offset in DPRAM [DSP2]
4143
4144- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4145		enable SMC microcode relocation patch (MPC8xx);
4146		define relocation offset in DPRAM [SMC1]
4147
4148- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4149		enable SPI microcode relocation patch (MPC8xx);
4150		define relocation offset in DPRAM [SCC4]
4151
4152- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4153		Offset of the bootmode word in DPRAM used by post
4154		(Power On Self Tests). This definition overrides
4155		#define'd default value in commproc.h resp.
4156		cpm_8260.h.
4157
4158- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4159  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4160  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4161  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4162  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4163  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4164  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4165  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4166		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4167
4168- CONFIG_PCI_DISABLE_PCIE:
4169		Disable PCI-Express on systems where it is supported but not
4170		required.
4171
4172- CONFIG_PCI_ENUM_ONLY
4173		Only scan through and get the devices on the buses.
4174		Don't do any setup work, presumably because someone or
4175		something has already done it, and we don't need to do it
4176		a second time.	Useful for platforms that are pre-booted
4177		by coreboot or similar.
4178
4179- CONFIG_PCI_INDIRECT_BRIDGE:
4180		Enable support for indirect PCI bridges.
4181
4182- CONFIG_SYS_SRIO:
4183		Chip has SRIO or not
4184
4185- CONFIG_SRIO1:
4186		Board has SRIO 1 port available
4187
4188- CONFIG_SRIO2:
4189		Board has SRIO 2 port available
4190
4191- CONFIG_SRIO_PCIE_BOOT_MASTER
4192		Board can support master function for Boot from SRIO and PCIE
4193
4194- CONFIG_SYS_SRIOn_MEM_VIRT:
4195		Virtual Address of SRIO port 'n' memory region
4196
4197- CONFIG_SYS_SRIOn_MEM_PHYS:
4198		Physical Address of SRIO port 'n' memory region
4199
4200- CONFIG_SYS_SRIOn_MEM_SIZE:
4201		Size of SRIO port 'n' memory region
4202
4203- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4204		Defined to tell the NAND controller that the NAND chip is using
4205		a 16 bit bus.
4206		Not all NAND drivers use this symbol.
4207		Example of drivers that use it:
4208		- drivers/mtd/nand/ndfc.c
4209		- drivers/mtd/nand/mxc_nand.c
4210
4211- CONFIG_SYS_NDFC_EBC0_CFG
4212		Sets the EBC0_CFG register for the NDFC. If not defined
4213		a default value will be used.
4214
4215- CONFIG_SPD_EEPROM
4216		Get DDR timing information from an I2C EEPROM. Common
4217		with pluggable memory modules such as SODIMMs
4218
4219  SPD_EEPROM_ADDRESS
4220		I2C address of the SPD EEPROM
4221
4222- CONFIG_SYS_SPD_BUS_NUM
4223		If SPD EEPROM is on an I2C bus other than the first
4224		one, specify here. Note that the value must resolve
4225		to something your driver can deal with.
4226
4227- CONFIG_SYS_DDR_RAW_TIMING
4228		Get DDR timing information from other than SPD. Common with
4229		soldered DDR chips onboard without SPD. DDR raw timing
4230		parameters are extracted from datasheet and hard-coded into
4231		header files or board specific files.
4232
4233- CONFIG_FSL_DDR_INTERACTIVE
4234		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4235
4236- CONFIG_FSL_DDR_SYNC_REFRESH
4237		Enable sync of refresh for multiple controllers.
4238
4239- CONFIG_FSL_DDR_BIST
4240		Enable built-in memory test for Freescale DDR controllers.
4241
4242- CONFIG_SYS_83XX_DDR_USES_CS0
4243		Only for 83xx systems. If specified, then DDR should
4244		be configured using CS0 and CS1 instead of CS2 and CS3.
4245
4246- CONFIG_ETHER_ON_FEC[12]
4247		Define to enable FEC[12] on a 8xx series processor.
4248
4249- CONFIG_FEC[12]_PHY
4250		Define to the hardcoded PHY address which corresponds
4251		to the given FEC; i. e.
4252			#define CONFIG_FEC1_PHY 4
4253		means that the PHY with address 4 is connected to FEC1
4254
4255		When set to -1, means to probe for first available.
4256
4257- CONFIG_FEC[12]_PHY_NORXERR
4258		The PHY does not have a RXERR line (RMII only).
4259		(so program the FEC to ignore it).
4260
4261- CONFIG_RMII
4262		Enable RMII mode for all FECs.
4263		Note that this is a global option, we can't
4264		have one FEC in standard MII mode and another in RMII mode.
4265
4266- CONFIG_CRC32_VERIFY
4267		Add a verify option to the crc32 command.
4268		The syntax is:
4269
4270		=> crc32 -v <address> <count> <crc32>
4271
4272		Where address/count indicate a memory area
4273		and crc32 is the correct crc32 which the
4274		area should have.
4275
4276- CONFIG_LOOPW
4277		Add the "loopw" memory command. This only takes effect if
4278		the memory commands are activated globally (CONFIG_CMD_MEM).
4279
4280- CONFIG_MX_CYCLIC
4281		Add the "mdc" and "mwc" memory commands. These are cyclic
4282		"md/mw" commands.
4283		Examples:
4284
4285		=> mdc.b 10 4 500
4286		This command will print 4 bytes (10,11,12,13) each 500 ms.
4287
4288		=> mwc.l 100 12345678 10
4289		This command will write 12345678 to address 100 all 10 ms.
4290
4291		This only takes effect if the memory commands are activated
4292		globally (CONFIG_CMD_MEM).
4293
4294- CONFIG_SKIP_LOWLEVEL_INIT
4295		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4296		low level initializations (like setting up the memory
4297		controller) are omitted and/or U-Boot does not
4298		relocate itself into RAM.
4299
4300		Normally this variable MUST NOT be defined. The only
4301		exception is when U-Boot is loaded (to RAM) by some
4302		other boot loader or by a debugger which performs
4303		these initializations itself.
4304
4305- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4306		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4307		to be skipped. The normal CP15 init (such as enabling the
4308		instruction cache) is still performed.
4309
4310- CONFIG_SPL_BUILD
4311		Modifies the behaviour of start.S when compiling a loader
4312		that is executed before the actual U-Boot. E.g. when
4313		compiling a NAND SPL.
4314
4315- CONFIG_TPL_BUILD
4316		Modifies the behaviour of start.S  when compiling a loader
4317		that is executed after the SPL and before the actual U-Boot.
4318		It is loaded by the SPL.
4319
4320- CONFIG_SYS_MPC85XX_NO_RESETVEC
4321		Only for 85xx systems. If this variable is specified, the section
4322		.resetvec is not kept and the section .bootpg is placed in the
4323		previous 4k of the .text section.
4324
4325- CONFIG_ARCH_MAP_SYSMEM
4326		Generally U-Boot (and in particular the md command) uses
4327		effective address. It is therefore not necessary to regard
4328		U-Boot address as virtual addresses that need to be translated
4329		to physical addresses. However, sandbox requires this, since
4330		it maintains its own little RAM buffer which contains all
4331		addressable memory. This option causes some memory accesses
4332		to be mapped through map_sysmem() / unmap_sysmem().
4333
4334- CONFIG_X86_RESET_VECTOR
4335		If defined, the x86 reset vector code is included. This is not
4336		needed when U-Boot is running from Coreboot.
4337
4338- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4339		Enables the RTC32K OSC on AM33xx based plattforms
4340
4341- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4342		Option to disable subpage write in NAND driver
4343		driver that uses this:
4344		drivers/mtd/nand/davinci_nand.c
4345
4346Freescale QE/FMAN Firmware Support:
4347-----------------------------------
4348
4349The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4350loading of "firmware", which is encoded in the QE firmware binary format.
4351This firmware often needs to be loaded during U-Boot booting, so macros
4352are used to identify the storage device (NOR flash, SPI, etc) and the address
4353within that device.
4354
4355- CONFIG_SYS_FMAN_FW_ADDR
4356	The address in the storage device where the FMAN microcode is located.  The
4357	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4358	is also specified.
4359
4360- CONFIG_SYS_QE_FW_ADDR
4361	The address in the storage device where the QE microcode is located.  The
4362	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4363	is also specified.
4364
4365- CONFIG_SYS_QE_FMAN_FW_LENGTH
4366	The maximum possible size of the firmware.  The firmware binary format
4367	has a field that specifies the actual size of the firmware, but it
4368	might not be possible to read any part of the firmware unless some
4369	local storage is allocated to hold the entire firmware first.
4370
4371- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4372	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4373	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4374	virtual address in NOR flash.
4375
4376- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4377	Specifies that QE/FMAN firmware is located in NAND flash.
4378	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4379
4380- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4381	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4382	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4383
4384- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4385	Specifies that QE/FMAN firmware is located in the remote (master)
4386	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4387	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4388	window->master inbound window->master LAW->the ucode address in
4389	master's memory space.
4390
4391Freescale Layerscape Management Complex Firmware Support:
4392---------------------------------------------------------
4393The Freescale Layerscape Management Complex (MC) supports the loading of
4394"firmware".
4395This firmware often needs to be loaded during U-Boot booting, so macros
4396are used to identify the storage device (NOR flash, SPI, etc) and the address
4397within that device.
4398
4399- CONFIG_FSL_MC_ENET
4400	Enable the MC driver for Layerscape SoCs.
4401
4402Freescale Layerscape Debug Server Support:
4403-------------------------------------------
4404The Freescale Layerscape Debug Server Support supports the loading of
4405"Debug Server firmware" and triggering SP boot-rom.
4406This firmware often needs to be loaded during U-Boot booting.
4407
4408- CONFIG_SYS_MC_RSV_MEM_ALIGN
4409	Define alignment of reserved memory MC requires
4410
4411Reproducible builds
4412-------------------
4413
4414In order to achieve reproducible builds, timestamps used in the U-Boot build
4415process have to be set to a fixed value.
4416
4417This is done using the SOURCE_DATE_EPOCH environment variable.
4418SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4419option for U-Boot or an environment variable in U-Boot.
4420
4421SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4422
4423Building the Software:
4424======================
4425
4426Building U-Boot has been tested in several native build environments
4427and in many different cross environments. Of course we cannot support
4428all possibly existing versions of cross development tools in all
4429(potentially obsolete) versions. In case of tool chain problems we
4430recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4431which is extensively used to build and test U-Boot.
4432
4433If you are not using a native environment, it is assumed that you
4434have GNU cross compiling tools available in your path. In this case,
4435you must set the environment variable CROSS_COMPILE in your shell.
4436Note that no changes to the Makefile or any other source files are
4437necessary. For example using the ELDK on a 4xx CPU, please enter:
4438
4439	$ CROSS_COMPILE=ppc_4xx-
4440	$ export CROSS_COMPILE
4441
4442Note: If you wish to generate Windows versions of the utilities in
4443      the tools directory you can use the MinGW toolchain
4444      (http://www.mingw.org).  Set your HOST tools to the MinGW
4445      toolchain and execute 'make tools'.  For example:
4446
4447       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4448
4449      Binaries such as tools/mkimage.exe will be created which can
4450      be executed on computers running Windows.
4451
4452U-Boot is intended to be simple to build. After installing the
4453sources you must configure U-Boot for one specific board type. This
4454is done by typing:
4455
4456	make NAME_defconfig
4457
4458where "NAME_defconfig" is the name of one of the existing configu-
4459rations; see boards.cfg for supported names.
4460
4461Note: for some board special configuration names may exist; check if
4462      additional information is available from the board vendor; for
4463      instance, the TQM823L systems are available without (standard)
4464      or with LCD support. You can select such additional "features"
4465      when choosing the configuration, i. e.
4466
4467      make TQM823L_defconfig
4468	- will configure for a plain TQM823L, i. e. no LCD support
4469
4470      make TQM823L_LCD_defconfig
4471	- will configure for a TQM823L with U-Boot console on LCD
4472
4473      etc.
4474
4475
4476Finally, type "make all", and you should get some working U-Boot
4477images ready for download to / installation on your system:
4478
4479- "u-boot.bin" is a raw binary image
4480- "u-boot" is an image in ELF binary format
4481- "u-boot.srec" is in Motorola S-Record format
4482
4483By default the build is performed locally and the objects are saved
4484in the source directory. One of the two methods can be used to change
4485this behavior and build U-Boot to some external directory:
4486
44871. Add O= to the make command line invocations:
4488
4489	make O=/tmp/build distclean
4490	make O=/tmp/build NAME_defconfig
4491	make O=/tmp/build all
4492
44932. Set environment variable KBUILD_OUTPUT to point to the desired location:
4494
4495	export KBUILD_OUTPUT=/tmp/build
4496	make distclean
4497	make NAME_defconfig
4498	make all
4499
4500Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4501variable.
4502
4503
4504Please be aware that the Makefiles assume you are using GNU make, so
4505for instance on NetBSD you might need to use "gmake" instead of
4506native "make".
4507
4508
4509If the system board that you have is not listed, then you will need
4510to port U-Boot to your hardware platform. To do this, follow these
4511steps:
4512
45131.  Create a new directory to hold your board specific code. Add any
4514    files you need. In your board directory, you will need at least
4515    the "Makefile" and a "<board>.c".
45162.  Create a new configuration file "include/configs/<board>.h" for
4517    your board.
45183.  If you're porting U-Boot to a new CPU, then also create a new
4519    directory to hold your CPU specific code. Add any files you need.
45204.  Run "make <board>_defconfig" with your new name.
45215.  Type "make", and you should get a working "u-boot.srec" file
4522    to be installed on your target system.
45236.  Debug and solve any problems that might arise.
4524    [Of course, this last step is much harder than it sounds.]
4525
4526
4527Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4528==============================================================
4529
4530If you have modified U-Boot sources (for instance added a new board
4531or support for new devices, a new CPU, etc.) you are expected to
4532provide feedback to the other developers. The feedback normally takes
4533the form of a "patch", i. e. a context diff against a certain (latest
4534official or latest in the git repository) version of U-Boot sources.
4535
4536But before you submit such a patch, please verify that your modifi-
4537cation did not break existing code. At least make sure that *ALL* of
4538the supported boards compile WITHOUT ANY compiler warnings. To do so,
4539just run the buildman script (tools/buildman/buildman), which will
4540configure and build U-Boot for ALL supported system. Be warned, this
4541will take a while. Please see the buildman README, or run 'buildman -H'
4542for documentation.
4543
4544
4545See also "U-Boot Porting Guide" below.
4546
4547
4548Monitor Commands - Overview:
4549============================
4550
4551go	- start application at address 'addr'
4552run	- run commands in an environment variable
4553bootm	- boot application image from memory
4554bootp	- boot image via network using BootP/TFTP protocol
4555bootz   - boot zImage from memory
4556tftpboot- boot image via network using TFTP protocol
4557	       and env variables "ipaddr" and "serverip"
4558	       (and eventually "gatewayip")
4559tftpput - upload a file via network using TFTP protocol
4560rarpboot- boot image via network using RARP/TFTP protocol
4561diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4562loads	- load S-Record file over serial line
4563loadb	- load binary file over serial line (kermit mode)
4564md	- memory display
4565mm	- memory modify (auto-incrementing)
4566nm	- memory modify (constant address)
4567mw	- memory write (fill)
4568cp	- memory copy
4569cmp	- memory compare
4570crc32	- checksum calculation
4571i2c	- I2C sub-system
4572sspi	- SPI utility commands
4573base	- print or set address offset
4574printenv- print environment variables
4575setenv	- set environment variables
4576saveenv - save environment variables to persistent storage
4577protect - enable or disable FLASH write protection
4578erase	- erase FLASH memory
4579flinfo	- print FLASH memory information
4580nand	- NAND memory operations (see doc/README.nand)
4581bdinfo	- print Board Info structure
4582iminfo	- print header information for application image
4583coninfo - print console devices and informations
4584ide	- IDE sub-system
4585loop	- infinite loop on address range
4586loopw	- infinite write loop on address range
4587mtest	- simple RAM test
4588icache	- enable or disable instruction cache
4589dcache	- enable or disable data cache
4590reset	- Perform RESET of the CPU
4591echo	- echo args to console
4592version - print monitor version
4593help	- print online help
4594?	- alias for 'help'
4595
4596
4597Monitor Commands - Detailed Description:
4598========================================
4599
4600TODO.
4601
4602For now: just type "help <command>".
4603
4604
4605Environment Variables:
4606======================
4607
4608U-Boot supports user configuration using Environment Variables which
4609can be made persistent by saving to Flash memory.
4610
4611Environment Variables are set using "setenv", printed using
4612"printenv", and saved to Flash using "saveenv". Using "setenv"
4613without a value can be used to delete a variable from the
4614environment. As long as you don't save the environment you are
4615working with an in-memory copy. In case the Flash area containing the
4616environment is erased by accident, a default environment is provided.
4617
4618Some configuration options can be set using Environment Variables.
4619
4620List of environment variables (most likely not complete):
4621
4622  baudrate	- see CONFIG_BAUDRATE
4623
4624  bootdelay	- see CONFIG_BOOTDELAY
4625
4626  bootcmd	- see CONFIG_BOOTCOMMAND
4627
4628  bootargs	- Boot arguments when booting an RTOS image
4629
4630  bootfile	- Name of the image to load with TFTP
4631
4632  bootm_low	- Memory range available for image processing in the bootm
4633		  command can be restricted. This variable is given as
4634		  a hexadecimal number and defines lowest address allowed
4635		  for use by the bootm command. See also "bootm_size"
4636		  environment variable. Address defined by "bootm_low" is
4637		  also the base of the initial memory mapping for the Linux
4638		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4639		  bootm_mapsize.
4640
4641  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4642		  This variable is given as a hexadecimal number and it
4643		  defines the size of the memory region starting at base
4644		  address bootm_low that is accessible by the Linux kernel
4645		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4646		  as the default value if it is defined, and bootm_size is
4647		  used otherwise.
4648
4649  bootm_size	- Memory range available for image processing in the bootm
4650		  command can be restricted. This variable is given as
4651		  a hexadecimal number and defines the size of the region
4652		  allowed for use by the bootm command. See also "bootm_low"
4653		  environment variable.
4654
4655  updatefile	- Location of the software update file on a TFTP server, used
4656		  by the automatic software update feature. Please refer to
4657		  documentation in doc/README.update for more details.
4658
4659  autoload	- if set to "no" (any string beginning with 'n'),
4660		  "bootp" will just load perform a lookup of the
4661		  configuration from the BOOTP server, but not try to
4662		  load any image using TFTP
4663
4664  autostart	- if set to "yes", an image loaded using the "bootp",
4665		  "rarpboot", "tftpboot" or "diskboot" commands will
4666		  be automatically started (by internally calling
4667		  "bootm")
4668
4669		  If set to "no", a standalone image passed to the
4670		  "bootm" command will be copied to the load address
4671		  (and eventually uncompressed), but NOT be started.
4672		  This can be used to load and uncompress arbitrary
4673		  data.
4674
4675  fdt_high	- if set this restricts the maximum address that the
4676		  flattened device tree will be copied into upon boot.
4677		  For example, if you have a system with 1 GB memory
4678		  at physical address 0x10000000, while Linux kernel
4679		  only recognizes the first 704 MB as low memory, you
4680		  may need to set fdt_high as 0x3C000000 to have the
4681		  device tree blob be copied to the maximum address
4682		  of the 704 MB low memory, so that Linux kernel can
4683		  access it during the boot procedure.
4684
4685		  If this is set to the special value 0xFFFFFFFF then
4686		  the fdt will not be copied at all on boot.  For this
4687		  to work it must reside in writable memory, have
4688		  sufficient padding on the end of it for u-boot to
4689		  add the information it needs into it, and the memory
4690		  must be accessible by the kernel.
4691
4692  fdtcontroladdr- if set this is the address of the control flattened
4693		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4694		  defined.
4695
4696  i2cfast	- (PPC405GP|PPC405EP only)
4697		  if set to 'y' configures Linux I2C driver for fast
4698		  mode (400kHZ). This environment variable is used in
4699		  initialization code. So, for changes to be effective
4700		  it must be saved and board must be reset.
4701
4702  initrd_high	- restrict positioning of initrd images:
4703		  If this variable is not set, initrd images will be
4704		  copied to the highest possible address in RAM; this
4705		  is usually what you want since it allows for
4706		  maximum initrd size. If for some reason you want to
4707		  make sure that the initrd image is loaded below the
4708		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4709		  variable to a value of "no" or "off" or "0".
4710		  Alternatively, you can set it to a maximum upper
4711		  address to use (U-Boot will still check that it
4712		  does not overwrite the U-Boot stack and data).
4713
4714		  For instance, when you have a system with 16 MB
4715		  RAM, and want to reserve 4 MB from use by Linux,
4716		  you can do this by adding "mem=12M" to the value of
4717		  the "bootargs" variable. However, now you must make
4718		  sure that the initrd image is placed in the first
4719		  12 MB as well - this can be done with
4720
4721		  setenv initrd_high 00c00000
4722
4723		  If you set initrd_high to 0xFFFFFFFF, this is an
4724		  indication to U-Boot that all addresses are legal
4725		  for the Linux kernel, including addresses in flash
4726		  memory. In this case U-Boot will NOT COPY the
4727		  ramdisk at all. This may be useful to reduce the
4728		  boot time on your system, but requires that this
4729		  feature is supported by your Linux kernel.
4730
4731  ipaddr	- IP address; needed for tftpboot command
4732
4733  loadaddr	- Default load address for commands like "bootp",
4734		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4735
4736  loads_echo	- see CONFIG_LOADS_ECHO
4737
4738  serverip	- TFTP server IP address; needed for tftpboot command
4739
4740  bootretry	- see CONFIG_BOOT_RETRY_TIME
4741
4742  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4743
4744  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4745
4746  ethprime	- controls which interface is used first.
4747
4748  ethact	- controls which interface is currently active.
4749		  For example you can do the following
4750
4751		  => setenv ethact FEC
4752		  => ping 192.168.0.1 # traffic sent on FEC
4753		  => setenv ethact SCC
4754		  => ping 10.0.0.1 # traffic sent on SCC
4755
4756  ethrotate	- When set to "no" U-Boot does not go through all
4757		  available network interfaces.
4758		  It just stays at the currently selected interface.
4759
4760  netretry	- When set to "no" each network operation will
4761		  either succeed or fail without retrying.
4762		  When set to "once" the network operation will
4763		  fail when all the available network interfaces
4764		  are tried once without success.
4765		  Useful on scripts which control the retry operation
4766		  themselves.
4767
4768  npe_ucode	- set load address for the NPE microcode
4769
4770  silent_linux  - If set then Linux will be told to boot silently, by
4771		  changing the console to be empty. If "yes" it will be
4772		  made silent. If "no" it will not be made silent. If
4773		  unset, then it will be made silent if the U-Boot console
4774		  is silent.
4775
4776  tftpsrcp	- If this is set, the value is used for TFTP's
4777		  UDP source port.
4778
4779  tftpdstp	- If this is set, the value is used for TFTP's UDP
4780		  destination port instead of the Well Know Port 69.
4781
4782  tftpblocksize - Block size to use for TFTP transfers; if not set,
4783		  we use the TFTP server's default block size
4784
4785  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4786		  seconds, minimum value is 1000 = 1 second). Defines
4787		  when a packet is considered to be lost so it has to
4788		  be retransmitted. The default is 5000 = 5 seconds.
4789		  Lowering this value may make downloads succeed
4790		  faster in networks with high packet loss rates or
4791		  with unreliable TFTP servers.
4792
4793  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4794		  unit, minimum value = 0). Defines how many timeouts
4795		  can happen during a single file transfer before that
4796		  transfer is aborted. The default is 10, and 0 means
4797		  'no timeouts allowed'. Increasing this value may help
4798		  downloads succeed with high packet loss rates, or with
4799		  unreliable TFTP servers or client hardware.
4800
4801  vlan		- When set to a value < 4095 the traffic over
4802		  Ethernet is encapsulated/received over 802.1q
4803		  VLAN tagged frames.
4804
4805  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4806		  Unsigned value, in milliseconds. If not set, the period will
4807		  be either the default (28000), or a value based on
4808		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4809		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4810
4811The following image location variables contain the location of images
4812used in booting. The "Image" column gives the role of the image and is
4813not an environment variable name. The other columns are environment
4814variable names. "File Name" gives the name of the file on a TFTP
4815server, "RAM Address" gives the location in RAM the image will be
4816loaded to, and "Flash Location" gives the image's address in NOR
4817flash or offset in NAND flash.
4818
4819*Note* - these variables don't have to be defined for all boards, some
4820boards currently use other variables for these purposes, and some
4821boards use these variables for other purposes.
4822
4823Image		    File Name	     RAM Address       Flash Location
4824-----		    ---------	     -----------       --------------
4825u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4826Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4827device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4828ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4829
4830The following environment variables may be used and automatically
4831updated by the network boot commands ("bootp" and "rarpboot"),
4832depending the information provided by your boot server:
4833
4834  bootfile	- see above
4835  dnsip		- IP address of your Domain Name Server
4836  dnsip2	- IP address of your secondary Domain Name Server
4837  gatewayip	- IP address of the Gateway (Router) to use
4838  hostname	- Target hostname
4839  ipaddr	- see above
4840  netmask	- Subnet Mask
4841  rootpath	- Pathname of the root filesystem on the NFS server
4842  serverip	- see above
4843
4844
4845There are two special Environment Variables:
4846
4847  serial#	- contains hardware identification information such
4848		  as type string and/or serial number
4849  ethaddr	- Ethernet address
4850
4851These variables can be set only once (usually during manufacturing of
4852the board). U-Boot refuses to delete or overwrite these variables
4853once they have been set once.
4854
4855
4856Further special Environment Variables:
4857
4858  ver		- Contains the U-Boot version string as printed
4859		  with the "version" command. This variable is
4860		  readonly (see CONFIG_VERSION_VARIABLE).
4861
4862
4863Please note that changes to some configuration parameters may take
4864only effect after the next boot (yes, that's just like Windoze :-).
4865
4866
4867Callback functions for environment variables:
4868---------------------------------------------
4869
4870For some environment variables, the behavior of u-boot needs to change
4871when their values are changed.  This functionality allows functions to
4872be associated with arbitrary variables.  On creation, overwrite, or
4873deletion, the callback will provide the opportunity for some side
4874effect to happen or for the change to be rejected.
4875
4876The callbacks are named and associated with a function using the
4877U_BOOT_ENV_CALLBACK macro in your board or driver code.
4878
4879These callbacks are associated with variables in one of two ways.  The
4880static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4881in the board configuration to a string that defines a list of
4882associations.  The list must be in the following format:
4883
4884	entry = variable_name[:callback_name]
4885	list = entry[,list]
4886
4887If the callback name is not specified, then the callback is deleted.
4888Spaces are also allowed anywhere in the list.
4889
4890Callbacks can also be associated by defining the ".callbacks" variable
4891with the same list format above.  Any association in ".callbacks" will
4892override any association in the static list. You can define
4893CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4894".callbacks" environment variable in the default or embedded environment.
4895
4896If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4897regular expression. This allows multiple variables to be connected to
4898the same callback without explicitly listing them all out.
4899
4900
4901Command Line Parsing:
4902=====================
4903
4904There are two different command line parsers available with U-Boot:
4905the old "simple" one, and the much more powerful "hush" shell:
4906
4907Old, simple command line parser:
4908--------------------------------
4909
4910- supports environment variables (through setenv / saveenv commands)
4911- several commands on one line, separated by ';'
4912- variable substitution using "... ${name} ..." syntax
4913- special characters ('$', ';') can be escaped by prefixing with '\',
4914  for example:
4915	setenv bootcmd bootm \${address}
4916- You can also escape text by enclosing in single apostrophes, for example:
4917	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4918
4919Hush shell:
4920-----------
4921
4922- similar to Bourne shell, with control structures like
4923  if...then...else...fi, for...do...done; while...do...done,
4924  until...do...done, ...
4925- supports environment ("global") variables (through setenv / saveenv
4926  commands) and local shell variables (through standard shell syntax
4927  "name=value"); only environment variables can be used with "run"
4928  command
4929
4930General rules:
4931--------------
4932
4933(1) If a command line (or an environment variable executed by a "run"
4934    command) contains several commands separated by semicolon, and
4935    one of these commands fails, then the remaining commands will be
4936    executed anyway.
4937
4938(2) If you execute several variables with one call to run (i. e.
4939    calling run with a list of variables as arguments), any failing
4940    command will cause "run" to terminate, i. e. the remaining
4941    variables are not executed.
4942
4943Note for Redundant Ethernet Interfaces:
4944=======================================
4945
4946Some boards come with redundant Ethernet interfaces; U-Boot supports
4947such configurations and is capable of automatic selection of a
4948"working" interface when needed. MAC assignment works as follows:
4949
4950Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4951MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4952"eth1addr" (=>eth1), "eth2addr", ...
4953
4954If the network interface stores some valid MAC address (for instance
4955in SROM), this is used as default address if there is NO correspon-
4956ding setting in the environment; if the corresponding environment
4957variable is set, this overrides the settings in the card; that means:
4958
4959o If the SROM has a valid MAC address, and there is no address in the
4960  environment, the SROM's address is used.
4961
4962o If there is no valid address in the SROM, and a definition in the
4963  environment exists, then the value from the environment variable is
4964  used.
4965
4966o If both the SROM and the environment contain a MAC address, and
4967  both addresses are the same, this MAC address is used.
4968
4969o If both the SROM and the environment contain a MAC address, and the
4970  addresses differ, the value from the environment is used and a
4971  warning is printed.
4972
4973o If neither SROM nor the environment contain a MAC address, an error
4974  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4975  a random, locally-assigned MAC is used.
4976
4977If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4978will be programmed into hardware as part of the initialization process.	 This
4979may be skipped by setting the appropriate 'ethmacskip' environment variable.
4980The naming convention is as follows:
4981"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4982
4983Image Formats:
4984==============
4985
4986U-Boot is capable of booting (and performing other auxiliary operations on)
4987images in two formats:
4988
4989New uImage format (FIT)
4990-----------------------
4991
4992Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4993to Flattened Device Tree). It allows the use of images with multiple
4994components (several kernels, ramdisks, etc.), with contents protected by
4995SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4996
4997
4998Old uImage format
4999-----------------
5000
5001Old image format is based on binary files which can be basically anything,
5002preceded by a special header; see the definitions in include/image.h for
5003details; basically, the header defines the following image properties:
5004
5005* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5006  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5007  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5008  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5009  INTEGRITY).
5010* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5011  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5012  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5013* Compression Type (uncompressed, gzip, bzip2)
5014* Load Address
5015* Entry Point
5016* Image Name
5017* Image Timestamp
5018
5019The header is marked by a special Magic Number, and both the header
5020and the data portions of the image are secured against corruption by
5021CRC32 checksums.
5022
5023
5024Linux Support:
5025==============
5026
5027Although U-Boot should support any OS or standalone application
5028easily, the main focus has always been on Linux during the design of
5029U-Boot.
5030
5031U-Boot includes many features that so far have been part of some
5032special "boot loader" code within the Linux kernel. Also, any
5033"initrd" images to be used are no longer part of one big Linux image;
5034instead, kernel and "initrd" are separate images. This implementation
5035serves several purposes:
5036
5037- the same features can be used for other OS or standalone
5038  applications (for instance: using compressed images to reduce the
5039  Flash memory footprint)
5040
5041- it becomes much easier to port new Linux kernel versions because
5042  lots of low-level, hardware dependent stuff are done by U-Boot
5043
5044- the same Linux kernel image can now be used with different "initrd"
5045  images; of course this also means that different kernel images can
5046  be run with the same "initrd". This makes testing easier (you don't
5047  have to build a new "zImage.initrd" Linux image when you just
5048  change a file in your "initrd"). Also, a field-upgrade of the
5049  software is easier now.
5050
5051
5052Linux HOWTO:
5053============
5054
5055Porting Linux to U-Boot based systems:
5056---------------------------------------
5057
5058U-Boot cannot save you from doing all the necessary modifications to
5059configure the Linux device drivers for use with your target hardware
5060(no, we don't intend to provide a full virtual machine interface to
5061Linux :-).
5062
5063But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5064
5065Just make sure your machine specific header file (for instance
5066include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5067Information structure as we define in include/asm-<arch>/u-boot.h,
5068and make sure that your definition of IMAP_ADDR uses the same value
5069as your U-Boot configuration in CONFIG_SYS_IMMR.
5070
5071Note that U-Boot now has a driver model, a unified model for drivers.
5072If you are adding a new driver, plumb it into driver model. If there
5073is no uclass available, you are encouraged to create one. See
5074doc/driver-model.
5075
5076
5077Configuring the Linux kernel:
5078-----------------------------
5079
5080No specific requirements for U-Boot. Make sure you have some root
5081device (initial ramdisk, NFS) for your target system.
5082
5083
5084Building a Linux Image:
5085-----------------------
5086
5087With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5088not used. If you use recent kernel source, a new build target
5089"uImage" will exist which automatically builds an image usable by
5090U-Boot. Most older kernels also have support for a "pImage" target,
5091which was introduced for our predecessor project PPCBoot and uses a
5092100% compatible format.
5093
5094Example:
5095
5096	make TQM850L_defconfig
5097	make oldconfig
5098	make dep
5099	make uImage
5100
5101The "uImage" build target uses a special tool (in 'tools/mkimage') to
5102encapsulate a compressed Linux kernel image with header	 information,
5103CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5104
5105* build a standard "vmlinux" kernel image (in ELF binary format):
5106
5107* convert the kernel into a raw binary image:
5108
5109	${CROSS_COMPILE}-objcopy -O binary \
5110				 -R .note -R .comment \
5111				 -S vmlinux linux.bin
5112
5113* compress the binary image:
5114
5115	gzip -9 linux.bin
5116
5117* package compressed binary image for U-Boot:
5118
5119	mkimage -A ppc -O linux -T kernel -C gzip \
5120		-a 0 -e 0 -n "Linux Kernel Image" \
5121		-d linux.bin.gz uImage
5122
5123
5124The "mkimage" tool can also be used to create ramdisk images for use
5125with U-Boot, either separated from the Linux kernel image, or
5126combined into one file. "mkimage" encapsulates the images with a 64
5127byte header containing information about target architecture,
5128operating system, image type, compression method, entry points, time
5129stamp, CRC32 checksums, etc.
5130
5131"mkimage" can be called in two ways: to verify existing images and
5132print the header information, or to build new images.
5133
5134In the first form (with "-l" option) mkimage lists the information
5135contained in the header of an existing U-Boot image; this includes
5136checksum verification:
5137
5138	tools/mkimage -l image
5139	  -l ==> list image header information
5140
5141The second form (with "-d" option) is used to build a U-Boot image
5142from a "data file" which is used as image payload:
5143
5144	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5145		      -n name -d data_file image
5146	  -A ==> set architecture to 'arch'
5147	  -O ==> set operating system to 'os'
5148	  -T ==> set image type to 'type'
5149	  -C ==> set compression type 'comp'
5150	  -a ==> set load address to 'addr' (hex)
5151	  -e ==> set entry point to 'ep' (hex)
5152	  -n ==> set image name to 'name'
5153	  -d ==> use image data from 'datafile'
5154
5155Right now, all Linux kernels for PowerPC systems use the same load
5156address (0x00000000), but the entry point address depends on the
5157kernel version:
5158
5159- 2.2.x kernels have the entry point at 0x0000000C,
5160- 2.3.x and later kernels have the entry point at 0x00000000.
5161
5162So a typical call to build a U-Boot image would read:
5163
5164	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5165	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5166	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5167	> examples/uImage.TQM850L
5168	Image Name:   2.4.4 kernel for TQM850L
5169	Created:      Wed Jul 19 02:34:59 2000
5170	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5171	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5172	Load Address: 0x00000000
5173	Entry Point:  0x00000000
5174
5175To verify the contents of the image (or check for corruption):
5176
5177	-> tools/mkimage -l examples/uImage.TQM850L
5178	Image Name:   2.4.4 kernel for TQM850L
5179	Created:      Wed Jul 19 02:34:59 2000
5180	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5181	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5182	Load Address: 0x00000000
5183	Entry Point:  0x00000000
5184
5185NOTE: for embedded systems where boot time is critical you can trade
5186speed for memory and install an UNCOMPRESSED image instead: this
5187needs more space in Flash, but boots much faster since it does not
5188need to be uncompressed:
5189
5190	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5191	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5192	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5193	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5194	> examples/uImage.TQM850L-uncompressed
5195	Image Name:   2.4.4 kernel for TQM850L
5196	Created:      Wed Jul 19 02:34:59 2000
5197	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5198	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5199	Load Address: 0x00000000
5200	Entry Point:  0x00000000
5201
5202
5203Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5204when your kernel is intended to use an initial ramdisk:
5205
5206	-> tools/mkimage -n 'Simple Ramdisk Image' \
5207	> -A ppc -O linux -T ramdisk -C gzip \
5208	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5209	Image Name:   Simple Ramdisk Image
5210	Created:      Wed Jan 12 14:01:50 2000
5211	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5212	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5213	Load Address: 0x00000000
5214	Entry Point:  0x00000000
5215
5216The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5217option performs the converse operation of the mkimage's second form (the "-d"
5218option). Given an image built by mkimage, the dumpimage extracts a "data file"
5219from the image:
5220
5221	tools/dumpimage -i image -T type -p position data_file
5222	  -i ==> extract from the 'image' a specific 'data_file'
5223	  -T ==> set image type to 'type'
5224	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5225
5226
5227Installing a Linux Image:
5228-------------------------
5229
5230To downloading a U-Boot image over the serial (console) interface,
5231you must convert the image to S-Record format:
5232
5233	objcopy -I binary -O srec examples/image examples/image.srec
5234
5235The 'objcopy' does not understand the information in the U-Boot
5236image header, so the resulting S-Record file will be relative to
5237address 0x00000000. To load it to a given address, you need to
5238specify the target address as 'offset' parameter with the 'loads'
5239command.
5240
5241Example: install the image to address 0x40100000 (which on the
5242TQM8xxL is in the first Flash bank):
5243
5244	=> erase 40100000 401FFFFF
5245
5246	.......... done
5247	Erased 8 sectors
5248
5249	=> loads 40100000
5250	## Ready for S-Record download ...
5251	~>examples/image.srec
5252	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5253	...
5254	15989 15990 15991 15992
5255	[file transfer complete]
5256	[connected]
5257	## Start Addr = 0x00000000
5258
5259
5260You can check the success of the download using the 'iminfo' command;
5261this includes a checksum verification so you can be sure no data
5262corruption happened:
5263
5264	=> imi 40100000
5265
5266	## Checking Image at 40100000 ...
5267	   Image Name:	 2.2.13 for initrd on TQM850L
5268	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5269	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5270	   Load Address: 00000000
5271	   Entry Point:	 0000000c
5272	   Verifying Checksum ... OK
5273
5274
5275Boot Linux:
5276-----------
5277
5278The "bootm" command is used to boot an application that is stored in
5279memory (RAM or Flash). In case of a Linux kernel image, the contents
5280of the "bootargs" environment variable is passed to the kernel as
5281parameters. You can check and modify this variable using the
5282"printenv" and "setenv" commands:
5283
5284
5285	=> printenv bootargs
5286	bootargs=root=/dev/ram
5287
5288	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5289
5290	=> printenv bootargs
5291	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5292
5293	=> bootm 40020000
5294	## Booting Linux kernel at 40020000 ...
5295	   Image Name:	 2.2.13 for NFS on TQM850L
5296	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5297	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5298	   Load Address: 00000000
5299	   Entry Point:	 0000000c
5300	   Verifying Checksum ... OK
5301	   Uncompressing Kernel Image ... OK
5302	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
5303	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5304	time_init: decrementer frequency = 187500000/60
5305	Calibrating delay loop... 49.77 BogoMIPS
5306	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5307	...
5308
5309If you want to boot a Linux kernel with initial RAM disk, you pass
5310the memory addresses of both the kernel and the initrd image (PPBCOOT
5311format!) to the "bootm" command:
5312
5313	=> imi 40100000 40200000
5314
5315	## Checking Image at 40100000 ...
5316	   Image Name:	 2.2.13 for initrd on TQM850L
5317	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5318	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5319	   Load Address: 00000000
5320	   Entry Point:	 0000000c
5321	   Verifying Checksum ... OK
5322
5323	## Checking Image at 40200000 ...
5324	   Image Name:	 Simple Ramdisk Image
5325	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5326	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5327	   Load Address: 00000000
5328	   Entry Point:	 00000000
5329	   Verifying Checksum ... OK
5330
5331	=> bootm 40100000 40200000
5332	## Booting Linux kernel at 40100000 ...
5333	   Image Name:	 2.2.13 for initrd on TQM850L
5334	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5335	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5336	   Load Address: 00000000
5337	   Entry Point:	 0000000c
5338	   Verifying Checksum ... OK
5339	   Uncompressing Kernel Image ... OK
5340	## Loading RAMDisk Image at 40200000 ...
5341	   Image Name:	 Simple Ramdisk Image
5342	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5343	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5344	   Load Address: 00000000
5345	   Entry Point:	 00000000
5346	   Verifying Checksum ... OK
5347	   Loading Ramdisk ... OK
5348	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
5349	Boot arguments: root=/dev/ram
5350	time_init: decrementer frequency = 187500000/60
5351	Calibrating delay loop... 49.77 BogoMIPS
5352	...
5353	RAMDISK: Compressed image found at block 0
5354	VFS: Mounted root (ext2 filesystem).
5355
5356	bash#
5357
5358Boot Linux and pass a flat device tree:
5359-----------
5360
5361First, U-Boot must be compiled with the appropriate defines. See the section
5362titled "Linux Kernel Interface" above for a more in depth explanation. The
5363following is an example of how to start a kernel and pass an updated
5364flat device tree:
5365
5366=> print oftaddr
5367oftaddr=0x300000
5368=> print oft
5369oft=oftrees/mpc8540ads.dtb
5370=> tftp $oftaddr $oft
5371Speed: 1000, full duplex
5372Using TSEC0 device
5373TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5374Filename 'oftrees/mpc8540ads.dtb'.
5375Load address: 0x300000
5376Loading: #
5377done
5378Bytes transferred = 4106 (100a hex)
5379=> tftp $loadaddr $bootfile
5380Speed: 1000, full duplex
5381Using TSEC0 device
5382TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5383Filename 'uImage'.
5384Load address: 0x200000
5385Loading:############
5386done
5387Bytes transferred = 1029407 (fb51f hex)
5388=> print loadaddr
5389loadaddr=200000
5390=> print oftaddr
5391oftaddr=0x300000
5392=> bootm $loadaddr - $oftaddr
5393## Booting image at 00200000 ...
5394   Image Name:	 Linux-2.6.17-dirty
5395   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5396   Data Size:	 1029343 Bytes = 1005.2 kB
5397   Load Address: 00000000
5398   Entry Point:	 00000000
5399   Verifying Checksum ... OK
5400   Uncompressing Kernel Image ... OK
5401Booting using flat device tree at 0x300000
5402Using MPC85xx ADS machine description
5403Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5404[snip]
5405
5406
5407More About U-Boot Image Types:
5408------------------------------
5409
5410U-Boot supports the following image types:
5411
5412   "Standalone Programs" are directly runnable in the environment
5413	provided by U-Boot; it is expected that (if they behave
5414	well) you can continue to work in U-Boot after return from
5415	the Standalone Program.
5416   "OS Kernel Images" are usually images of some Embedded OS which
5417	will take over control completely. Usually these programs
5418	will install their own set of exception handlers, device
5419	drivers, set up the MMU, etc. - this means, that you cannot
5420	expect to re-enter U-Boot except by resetting the CPU.
5421   "RAMDisk Images" are more or less just data blocks, and their
5422	parameters (address, size) are passed to an OS kernel that is
5423	being started.
5424   "Multi-File Images" contain several images, typically an OS
5425	(Linux) kernel image and one or more data images like
5426	RAMDisks. This construct is useful for instance when you want
5427	to boot over the network using BOOTP etc., where the boot
5428	server provides just a single image file, but you want to get
5429	for instance an OS kernel and a RAMDisk image.
5430
5431	"Multi-File Images" start with a list of image sizes, each
5432	image size (in bytes) specified by an "uint32_t" in network
5433	byte order. This list is terminated by an "(uint32_t)0".
5434	Immediately after the terminating 0 follow the images, one by
5435	one, all aligned on "uint32_t" boundaries (size rounded up to
5436	a multiple of 4 bytes).
5437
5438   "Firmware Images" are binary images containing firmware (like
5439	U-Boot or FPGA images) which usually will be programmed to
5440	flash memory.
5441
5442   "Script files" are command sequences that will be executed by
5443	U-Boot's command interpreter; this feature is especially
5444	useful when you configure U-Boot to use a real shell (hush)
5445	as command interpreter.
5446
5447Booting the Linux zImage:
5448-------------------------
5449
5450On some platforms, it's possible to boot Linux zImage. This is done
5451using the "bootz" command. The syntax of "bootz" command is the same
5452as the syntax of "bootm" command.
5453
5454Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5455kernel with raw initrd images. The syntax is slightly different, the
5456address of the initrd must be augmented by it's size, in the following
5457format: "<initrd addres>:<initrd size>".
5458
5459
5460Standalone HOWTO:
5461=================
5462
5463One of the features of U-Boot is that you can dynamically load and
5464run "standalone" applications, which can use some resources of
5465U-Boot like console I/O functions or interrupt services.
5466
5467Two simple examples are included with the sources:
5468
5469"Hello World" Demo:
5470-------------------
5471
5472'examples/hello_world.c' contains a small "Hello World" Demo
5473application; it is automatically compiled when you build U-Boot.
5474It's configured to run at address 0x00040004, so you can play with it
5475like that:
5476
5477	=> loads
5478	## Ready for S-Record download ...
5479	~>examples/hello_world.srec
5480	1 2 3 4 5 6 7 8 9 10 11 ...
5481	[file transfer complete]
5482	[connected]
5483	## Start Addr = 0x00040004
5484
5485	=> go 40004 Hello World! This is a test.
5486	## Starting application at 0x00040004 ...
5487	Hello World
5488	argc = 7
5489	argv[0] = "40004"
5490	argv[1] = "Hello"
5491	argv[2] = "World!"
5492	argv[3] = "This"
5493	argv[4] = "is"
5494	argv[5] = "a"
5495	argv[6] = "test."
5496	argv[7] = "<NULL>"
5497	Hit any key to exit ...
5498
5499	## Application terminated, rc = 0x0
5500
5501Another example, which demonstrates how to register a CPM interrupt
5502handler with the U-Boot code, can be found in 'examples/timer.c'.
5503Here, a CPM timer is set up to generate an interrupt every second.
5504The interrupt service routine is trivial, just printing a '.'
5505character, but this is just a demo program. The application can be
5506controlled by the following keys:
5507
5508	? - print current values og the CPM Timer registers
5509	b - enable interrupts and start timer
5510	e - stop timer and disable interrupts
5511	q - quit application
5512
5513	=> loads
5514	## Ready for S-Record download ...
5515	~>examples/timer.srec
5516	1 2 3 4 5 6 7 8 9 10 11 ...
5517	[file transfer complete]
5518	[connected]
5519	## Start Addr = 0x00040004
5520
5521	=> go 40004
5522	## Starting application at 0x00040004 ...
5523	TIMERS=0xfff00980
5524	Using timer 1
5525	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5526
5527Hit 'b':
5528	[q, b, e, ?] Set interval 1000000 us
5529	Enabling timer
5530Hit '?':
5531	[q, b, e, ?] ........
5532	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5533Hit '?':
5534	[q, b, e, ?] .
5535	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5536Hit '?':
5537	[q, b, e, ?] .
5538	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5539Hit '?':
5540	[q, b, e, ?] .
5541	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5542Hit 'e':
5543	[q, b, e, ?] ...Stopping timer
5544Hit 'q':
5545	[q, b, e, ?] ## Application terminated, rc = 0x0
5546
5547
5548Minicom warning:
5549================
5550
5551Over time, many people have reported problems when trying to use the
5552"minicom" terminal emulation program for serial download. I (wd)
5553consider minicom to be broken, and recommend not to use it. Under
5554Unix, I recommend to use C-Kermit for general purpose use (and
5555especially for kermit binary protocol download ("loadb" command), and
5556use "cu" for S-Record download ("loads" command).  See
5557http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5558for help with kermit.
5559
5560
5561Nevertheless, if you absolutely want to use it try adding this
5562configuration to your "File transfer protocols" section:
5563
5564	   Name	   Program			Name U/D FullScr IO-Red. Multi
5565	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5566	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5567
5568
5569NetBSD Notes:
5570=============
5571
5572Starting at version 0.9.2, U-Boot supports NetBSD both as host
5573(build U-Boot) and target system (boots NetBSD/mpc8xx).
5574
5575Building requires a cross environment; it is known to work on
5576NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5577need gmake since the Makefiles are not compatible with BSD make).
5578Note that the cross-powerpc package does not install include files;
5579attempting to build U-Boot will fail because <machine/ansi.h> is
5580missing.  This file has to be installed and patched manually:
5581
5582	# cd /usr/pkg/cross/powerpc-netbsd/include
5583	# mkdir powerpc
5584	# ln -s powerpc machine
5585	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5586	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5587
5588Native builds *don't* work due to incompatibilities between native
5589and U-Boot include files.
5590
5591Booting assumes that (the first part of) the image booted is a
5592stage-2 loader which in turn loads and then invokes the kernel
5593proper. Loader sources will eventually appear in the NetBSD source
5594tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5595meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5596
5597
5598Implementation Internals:
5599=========================
5600
5601The following is not intended to be a complete description of every
5602implementation detail. However, it should help to understand the
5603inner workings of U-Boot and make it easier to port it to custom
5604hardware.
5605
5606
5607Initial Stack, Global Data:
5608---------------------------
5609
5610The implementation of U-Boot is complicated by the fact that U-Boot
5611starts running out of ROM (flash memory), usually without access to
5612system RAM (because the memory controller is not initialized yet).
5613This means that we don't have writable Data or BSS segments, and BSS
5614is not initialized as zero. To be able to get a C environment working
5615at all, we have to allocate at least a minimal stack. Implementation
5616options for this are defined and restricted by the CPU used: Some CPU
5617models provide on-chip memory (like the IMMR area on MPC8xx and
5618MPC826x processors), on others (parts of) the data cache can be
5619locked as (mis-) used as memory, etc.
5620
5621	Chris Hallinan posted a good summary of these issues to the
5622	U-Boot mailing list:
5623
5624	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5625	From: "Chris Hallinan" <clh@net1plus.com>
5626	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5627	...
5628
5629	Correct me if I'm wrong, folks, but the way I understand it
5630	is this: Using DCACHE as initial RAM for Stack, etc, does not
5631	require any physical RAM backing up the cache. The cleverness
5632	is that the cache is being used as a temporary supply of
5633	necessary storage before the SDRAM controller is setup. It's
5634	beyond the scope of this list to explain the details, but you
5635	can see how this works by studying the cache architecture and
5636	operation in the architecture and processor-specific manuals.
5637
5638	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5639	is another option for the system designer to use as an
5640	initial stack/RAM area prior to SDRAM being available. Either
5641	option should work for you. Using CS 4 should be fine if your
5642	board designers haven't used it for something that would
5643	cause you grief during the initial boot! It is frequently not
5644	used.
5645
5646	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5647	with your processor/board/system design. The default value
5648	you will find in any recent u-boot distribution in
5649	walnut.h should work for you. I'd set it to a value larger
5650	than your SDRAM module. If you have a 64MB SDRAM module, set
5651	it above 400_0000. Just make sure your board has no resources
5652	that are supposed to respond to that address! That code in
5653	start.S has been around a while and should work as is when
5654	you get the config right.
5655
5656	-Chris Hallinan
5657	DS4.COM, Inc.
5658
5659It is essential to remember this, since it has some impact on the C
5660code for the initialization procedures:
5661
5662* Initialized global data (data segment) is read-only. Do not attempt
5663  to write it.
5664
5665* Do not use any uninitialized global data (or implicitly initialized
5666  as zero data - BSS segment) at all - this is undefined, initiali-
5667  zation is performed later (when relocating to RAM).
5668
5669* Stack space is very limited. Avoid big data buffers or things like
5670  that.
5671
5672Having only the stack as writable memory limits means we cannot use
5673normal global data to share information between the code. But it
5674turned out that the implementation of U-Boot can be greatly
5675simplified by making a global data structure (gd_t) available to all
5676functions. We could pass a pointer to this data as argument to _all_
5677functions, but this would bloat the code. Instead we use a feature of
5678the GCC compiler (Global Register Variables) to share the data: we
5679place a pointer (gd) to the global data into a register which we
5680reserve for this purpose.
5681
5682When choosing a register for such a purpose we are restricted by the
5683relevant  (E)ABI  specifications for the current architecture, and by
5684GCC's implementation.
5685
5686For PowerPC, the following registers have specific use:
5687	R1:	stack pointer
5688	R2:	reserved for system use
5689	R3-R4:	parameter passing and return values
5690	R5-R10: parameter passing
5691	R13:	small data area pointer
5692	R30:	GOT pointer
5693	R31:	frame pointer
5694
5695	(U-Boot also uses R12 as internal GOT pointer. r12
5696	is a volatile register so r12 needs to be reset when
5697	going back and forth between asm and C)
5698
5699    ==> U-Boot will use R2 to hold a pointer to the global data
5700
5701    Note: on PPC, we could use a static initializer (since the
5702    address of the global data structure is known at compile time),
5703    but it turned out that reserving a register results in somewhat
5704    smaller code - although the code savings are not that big (on
5705    average for all boards 752 bytes for the whole U-Boot image,
5706    624 text + 127 data).
5707
5708On ARM, the following registers are used:
5709
5710	R0:	function argument word/integer result
5711	R1-R3:	function argument word
5712	R9:	platform specific
5713	R10:	stack limit (used only if stack checking is enabled)
5714	R11:	argument (frame) pointer
5715	R12:	temporary workspace
5716	R13:	stack pointer
5717	R14:	link register
5718	R15:	program counter
5719
5720    ==> U-Boot will use R9 to hold a pointer to the global data
5721
5722    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5723
5724On Nios II, the ABI is documented here:
5725	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5726
5727    ==> U-Boot will use gp to hold a pointer to the global data
5728
5729    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5730    to access small data sections, so gp is free.
5731
5732On NDS32, the following registers are used:
5733
5734	R0-R1:	argument/return
5735	R2-R5:	argument
5736	R15:	temporary register for assembler
5737	R16:	trampoline register
5738	R28:	frame pointer (FP)
5739	R29:	global pointer (GP)
5740	R30:	link register (LP)
5741	R31:	stack pointer (SP)
5742	PC:	program counter (PC)
5743
5744    ==> U-Boot will use R10 to hold a pointer to the global data
5745
5746NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5747or current versions of GCC may "optimize" the code too much.
5748
5749Memory Management:
5750------------------
5751
5752U-Boot runs in system state and uses physical addresses, i.e. the
5753MMU is not used either for address mapping nor for memory protection.
5754
5755The available memory is mapped to fixed addresses using the memory
5756controller. In this process, a contiguous block is formed for each
5757memory type (Flash, SDRAM, SRAM), even when it consists of several
5758physical memory banks.
5759
5760U-Boot is installed in the first 128 kB of the first Flash bank (on
5761TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5762booting and sizing and initializing DRAM, the code relocates itself
5763to the upper end of DRAM. Immediately below the U-Boot code some
5764memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5765configuration setting]. Below that, a structure with global Board
5766Info data is placed, followed by the stack (growing downward).
5767
5768Additionally, some exception handler code is copied to the low 8 kB
5769of DRAM (0x00000000 ... 0x00001FFF).
5770
5771So a typical memory configuration with 16 MB of DRAM could look like
5772this:
5773
5774	0x0000 0000	Exception Vector code
5775	      :
5776	0x0000 1FFF
5777	0x0000 2000	Free for Application Use
5778	      :
5779	      :
5780
5781	      :
5782	      :
5783	0x00FB FF20	Monitor Stack (Growing downward)
5784	0x00FB FFAC	Board Info Data and permanent copy of global data
5785	0x00FC 0000	Malloc Arena
5786	      :
5787	0x00FD FFFF
5788	0x00FE 0000	RAM Copy of Monitor Code
5789	...		eventually: LCD or video framebuffer
5790	...		eventually: pRAM (Protected RAM - unchanged by reset)
5791	0x00FF FFFF	[End of RAM]
5792
5793
5794System Initialization:
5795----------------------
5796
5797In the reset configuration, U-Boot starts at the reset entry point
5798(on most PowerPC systems at address 0x00000100). Because of the reset
5799configuration for CS0# this is a mirror of the on board Flash memory.
5800To be able to re-map memory U-Boot then jumps to its link address.
5801To be able to implement the initialization code in C, a (small!)
5802initial stack is set up in the internal Dual Ported RAM (in case CPUs
5803which provide such a feature like MPC8xx or MPC8260), or in a locked
5804part of the data cache. After that, U-Boot initializes the CPU core,
5805the caches and the SIU.
5806
5807Next, all (potentially) available memory banks are mapped using a
5808preliminary mapping. For example, we put them on 512 MB boundaries
5809(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5810on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5811programmed for SDRAM access. Using the temporary configuration, a
5812simple memory test is run that determines the size of the SDRAM
5813banks.
5814
5815When there is more than one SDRAM bank, and the banks are of
5816different size, the largest is mapped first. For equal size, the first
5817bank (CS2#) is mapped first. The first mapping is always for address
58180x00000000, with any additional banks following immediately to create
5819contiguous memory starting from 0.
5820
5821Then, the monitor installs itself at the upper end of the SDRAM area
5822and allocates memory for use by malloc() and for the global Board
5823Info data; also, the exception vector code is copied to the low RAM
5824pages, and the final stack is set up.
5825
5826Only after this relocation will you have a "normal" C environment;
5827until that you are restricted in several ways, mostly because you are
5828running from ROM, and because the code will have to be relocated to a
5829new address in RAM.
5830
5831
5832U-Boot Porting Guide:
5833----------------------
5834
5835[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5836list, October 2002]
5837
5838
5839int main(int argc, char *argv[])
5840{
5841	sighandler_t no_more_time;
5842
5843	signal(SIGALRM, no_more_time);
5844	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5845
5846	if (available_money > available_manpower) {
5847		Pay consultant to port U-Boot;
5848		return 0;
5849	}
5850
5851	Download latest U-Boot source;
5852
5853	Subscribe to u-boot mailing list;
5854
5855	if (clueless)
5856		email("Hi, I am new to U-Boot, how do I get started?");
5857
5858	while (learning) {
5859		Read the README file in the top level directory;
5860		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5861		Read applicable doc/*.README;
5862		Read the source, Luke;
5863		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5864	}
5865
5866	if (available_money > toLocalCurrency ($2500))
5867		Buy a BDI3000;
5868	else
5869		Add a lot of aggravation and time;
5870
5871	if (a similar board exists) {	/* hopefully... */
5872		cp -a board/<similar> board/<myboard>
5873		cp include/configs/<similar>.h include/configs/<myboard>.h
5874	} else {
5875		Create your own board support subdirectory;
5876		Create your own board include/configs/<myboard>.h file;
5877	}
5878	Edit new board/<myboard> files
5879	Edit new include/configs/<myboard>.h
5880
5881	while (!accepted) {
5882		while (!running) {
5883			do {
5884				Add / modify source code;
5885			} until (compiles);
5886			Debug;
5887			if (clueless)
5888				email("Hi, I am having problems...");
5889		}
5890		Send patch file to the U-Boot email list;
5891		if (reasonable critiques)
5892			Incorporate improvements from email list code review;
5893		else
5894			Defend code as written;
5895	}
5896
5897	return 0;
5898}
5899
5900void no_more_time (int sig)
5901{
5902      hire_a_guru();
5903}
5904
5905
5906Coding Standards:
5907-----------------
5908
5909All contributions to U-Boot should conform to the Linux kernel
5910coding style; see the file "Documentation/CodingStyle" and the script
5911"scripts/Lindent" in your Linux kernel source directory.
5912
5913Source files originating from a different project (for example the
5914MTD subsystem) are generally exempt from these guidelines and are not
5915reformatted to ease subsequent migration to newer versions of those
5916sources.
5917
5918Please note that U-Boot is implemented in C (and to some small parts in
5919Assembler); no C++ is used, so please do not use C++ style comments (//)
5920in your code.
5921
5922Please also stick to the following formatting rules:
5923- remove any trailing white space
5924- use TAB characters for indentation and vertical alignment, not spaces
5925- make sure NOT to use DOS '\r\n' line feeds
5926- do not add more than 2 consecutive empty lines to source files
5927- do not add trailing empty lines to source files
5928
5929Submissions which do not conform to the standards may be returned
5930with a request to reformat the changes.
5931
5932
5933Submitting Patches:
5934-------------------
5935
5936Since the number of patches for U-Boot is growing, we need to
5937establish some rules. Submissions which do not conform to these rules
5938may be rejected, even when they contain important and valuable stuff.
5939
5940Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5941
5942Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5943see http://lists.denx.de/mailman/listinfo/u-boot
5944
5945When you send a patch, please include the following information with
5946it:
5947
5948* For bug fixes: a description of the bug and how your patch fixes
5949  this bug. Please try to include a way of demonstrating that the
5950  patch actually fixes something.
5951
5952* For new features: a description of the feature and your
5953  implementation.
5954
5955* A CHANGELOG entry as plaintext (separate from the patch)
5956
5957* For major contributions, add a MAINTAINERS file with your
5958  information and associated file and directory references.
5959
5960* When you add support for a new board, don't forget to add a
5961  maintainer e-mail address to the boards.cfg file, too.
5962
5963* If your patch adds new configuration options, don't forget to
5964  document these in the README file.
5965
5966* The patch itself. If you are using git (which is *strongly*
5967  recommended) you can easily generate the patch using the
5968  "git format-patch". If you then use "git send-email" to send it to
5969  the U-Boot mailing list, you will avoid most of the common problems
5970  with some other mail clients.
5971
5972  If you cannot use git, use "diff -purN OLD NEW". If your version of
5973  diff does not support these options, then get the latest version of
5974  GNU diff.
5975
5976  The current directory when running this command shall be the parent
5977  directory of the U-Boot source tree (i. e. please make sure that
5978  your patch includes sufficient directory information for the
5979  affected files).
5980
5981  We prefer patches as plain text. MIME attachments are discouraged,
5982  and compressed attachments must not be used.
5983
5984* If one logical set of modifications affects or creates several
5985  files, all these changes shall be submitted in a SINGLE patch file.
5986
5987* Changesets that contain different, unrelated modifications shall be
5988  submitted as SEPARATE patches, one patch per changeset.
5989
5990
5991Notes:
5992
5993* Before sending the patch, run the buildman script on your patched
5994  source tree and make sure that no errors or warnings are reported
5995  for any of the boards.
5996
5997* Keep your modifications to the necessary minimum: A patch
5998  containing several unrelated changes or arbitrary reformats will be
5999  returned with a request to re-formatting / split it.
6000
6001* If you modify existing code, make sure that your new code does not
6002  add to the memory footprint of the code ;-) Small is beautiful!
6003  When adding new features, these should compile conditionally only
6004  (using #ifdef), and the resulting code with the new feature
6005  disabled must not need more memory than the old code without your
6006  modification.
6007
6008* Remember that there is a size limit of 100 kB per message on the
6009  u-boot mailing list. Bigger patches will be moderated. If they are
6010  reasonable and not too big, they will be acknowledged. But patches
6011  bigger than the size limit should be avoided.
6012