xref: /openbmc/u-boot/README (revision ffc76589)
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_CRC32	* crc32
831		CONFIG_CMD_DHCP		* DHCP support
832		CONFIG_CMD_DIAG		* Diagnostics
833		CONFIG_CMD_ECHO		  echo arguments
834		CONFIG_CMD_EDITENV	  edit env variable
835		CONFIG_CMD_ELF		* bootelf, bootvx
836		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
837		CONFIG_CMD_EXPORTENV	* export the environment
838		CONFIG_CMD_EXT2		* ext2 command support
839		CONFIG_CMD_EXT4		* ext4 command support
840		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
841					  that work for multiple fs types
842		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
843		CONFIG_CMD_SAVEENV	  saveenv
844		CONFIG_CMD_FDC		* Floppy Disk Support
845		CONFIG_CMD_FAT		* FAT command support
846		CONFIG_CMD_FLASH	  flinfo, erase, protect
847		CONFIG_CMD_FPGA		  FPGA device initialization support
848		CONFIG_CMD_FUSE		* Device fuse support
849		CONFIG_CMD_GETTIME	* Get time since boot
850		CONFIG_CMD_GO		* the 'go' command (exec code)
851		CONFIG_CMD_GREPENV	* search environment
852		CONFIG_CMD_HASH		* calculate hash / digest
853		CONFIG_CMD_I2C		* I2C serial bus support
854		CONFIG_CMD_IDE		* IDE harddisk support
855		CONFIG_CMD_IMI		  iminfo
856		CONFIG_CMD_IMLS		  List all images found in NOR flash
857		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
858		CONFIG_CMD_IMMAP	* IMMR dump support
859		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
860		CONFIG_CMD_IMPORTENV	* import an environment
861		CONFIG_CMD_INI		* import data from an ini file into the env
862		CONFIG_CMD_IRQ		* irqinfo
863		CONFIG_CMD_ITEST	  Integer/string test of 2 values
864		CONFIG_CMD_JFFS2	* JFFS2 Support
865		CONFIG_CMD_KGDB		* kgdb
866		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
867		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
868					  (169.254.*.*)
869		CONFIG_CMD_LOADB	  loadb
870		CONFIG_CMD_LOADS	  loads
871		CONFIG_CMD_MD5SUM	* print md5 message digest
872					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
873		CONFIG_CMD_MEMINFO	* Display detailed memory information
874		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
875					  loop, loopw
876		CONFIG_CMD_MEMTEST	* mtest
877		CONFIG_CMD_MISC		  Misc functions like sleep etc
878		CONFIG_CMD_MMC		* MMC memory mapped support
879		CONFIG_CMD_MII		* MII utility commands
880		CONFIG_CMD_MTDPARTS	* MTD partition support
881		CONFIG_CMD_NAND		* NAND support
882		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
883		CONFIG_CMD_NFS		  NFS support
884		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
885		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
886		CONFIG_CMD_PCI		* pciinfo
887		CONFIG_CMD_PCMCIA		* PCMCIA support
888		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
889					  host
890		CONFIG_CMD_PORTIO	* Port I/O
891		CONFIG_CMD_READ		* Read raw data from partition
892		CONFIG_CMD_REGINFO	* Register dump
893		CONFIG_CMD_RUN		  run command in env variable
894		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
895		CONFIG_CMD_SAVES	* save S record dump
896		CONFIG_SCSI		* SCSI Support
897		CONFIG_CMD_SDRAM	* print SDRAM configuration information
898					  (requires CONFIG_CMD_I2C)
899		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
900					  (4xx only)
901		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
902		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
903					  (requires CONFIG_CMD_MEMORY)
904		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
905		CONFIG_CMD_SOURCE	  "source" command Support
906		CONFIG_CMD_SPI		* SPI serial bus support
907		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
908		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
909		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
910		CONFIG_CMD_TIMER	* access to the system tick timer
911		CONFIG_CMD_USB		* USB support
912		CONFIG_CMD_CDP		* Cisco Discover Protocol support
913		CONFIG_CMD_MFSL		* Microblaze FSL support
914		CONFIG_CMD_XIMG		  Load part of Multi Image
915		CONFIG_CMD_UUID		* Generate random UUID or GUID string
916
917		EXAMPLE: If you want all functions except of network
918		support you can write:
919
920		#include "config_cmd_all.h"
921		#undef CONFIG_CMD_NET
922
923	Other Commands:
924		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
925
926	Note:	Don't enable the "icache" and "dcache" commands
927		(configuration option CONFIG_CMD_CACHE) unless you know
928		what you (and your U-Boot users) are doing. Data
929		cache cannot be enabled on systems like the 8xx or
930		8260 (where accesses to the IMMR region must be
931		uncached), and it cannot be disabled on all other
932		systems where we (mis-) use the data cache to hold an
933		initial stack and some data.
934
935
936		XXX - this list needs to get updated!
937
938- Removal of commands
939		If no commands are needed to boot, you can disable
940		CONFIG_CMDLINE to remove them. In this case, the command line
941		will not be available, and when U-Boot wants to execute the
942		boot command (on start-up) it will call board_run_command()
943		instead. This can reduce image size significantly for very
944		simple boot procedures.
945
946- Regular expression support:
947		CONFIG_REGEX
948		If this variable is defined, U-Boot is linked against
949		the SLRE (Super Light Regular Expression) library,
950		which adds regex support to some commands, as for
951		example "env grep" and "setexpr".
952
953- Device tree:
954		CONFIG_OF_CONTROL
955		If this variable is defined, U-Boot will use a device tree
956		to configure its devices, instead of relying on statically
957		compiled #defines in the board file. This option is
958		experimental and only available on a few boards. The device
959		tree is available in the global data as gd->fdt_blob.
960
961		U-Boot needs to get its device tree from somewhere. This can
962		be done using one of the three options below:
963
964		CONFIG_OF_EMBED
965		If this variable is defined, U-Boot will embed a device tree
966		binary in its image. This device tree file should be in the
967		board directory and called <soc>-<board>.dts. The binary file
968		is then picked up in board_init_f() and made available through
969		the global data structure as gd->blob.
970
971		CONFIG_OF_SEPARATE
972		If this variable is defined, U-Boot will build a device tree
973		binary. It will be called u-boot.dtb. Architecture-specific
974		code will locate it at run-time. Generally this works by:
975
976			cat u-boot.bin u-boot.dtb >image.bin
977
978		and in fact, U-Boot does this for you, creating a file called
979		u-boot-dtb.bin which is useful in the common case. You can
980		still use the individual files if you need something more
981		exotic.
982
983		CONFIG_OF_BOARD
984		If this variable is defined, U-Boot will use the device tree
985		provided by the board at runtime instead of embedding one with
986		the image. Only boards defining board_fdt_blob_setup() support
987		this option (see include/fdtdec.h file).
988
989- Watchdog:
990		CONFIG_WATCHDOG
991		If this variable is defined, it enables watchdog
992		support for the SoC. There must be support in the SoC
993		specific code for a watchdog. For the 8xx and 8260
994		CPUs, the SIU Watchdog feature is enabled in the SYPCR
995		register.  When supported for a specific SoC is
996		available, then no further board specific code should
997		be needed to use it.
998
999		CONFIG_HW_WATCHDOG
1000		When using a watchdog circuitry external to the used
1001		SoC, then define this variable and provide board
1002		specific code for the "hw_watchdog_reset" function.
1003
1004		CONFIG_AT91_HW_WDT_TIMEOUT
1005		specify the timeout in seconds. default 2 seconds.
1006
1007- U-Boot Version:
1008		CONFIG_VERSION_VARIABLE
1009		If this variable is defined, an environment variable
1010		named "ver" is created by U-Boot showing the U-Boot
1011		version as printed by the "version" command.
1012		Any change to this variable will be reverted at the
1013		next reset.
1014
1015- Real-Time Clock:
1016
1017		When CONFIG_CMD_DATE is selected, the type of the RTC
1018		has to be selected, too. Define exactly one of the
1019		following options:
1020
1021		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
1022		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
1023		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
1024		CONFIG_RTC_MC146818	- use MC146818 RTC
1025		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
1026		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
1027		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
1028		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
1029		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
1030		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
1031		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
1032		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
1033		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
1034					  RV3029 RTC.
1035
1036		Note that if the RTC uses I2C, then the I2C interface
1037		must also be configured. See I2C Support, below.
1038
1039- GPIO Support:
1040		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
1041
1042		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
1043		chip-ngpio pairs that tell the PCA953X driver the number of
1044		pins supported by a particular chip.
1045
1046		Note that if the GPIO device uses I2C, then the I2C interface
1047		must also be configured. See I2C Support, below.
1048
1049- I/O tracing:
1050		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
1051		accesses and can checksum them or write a list of them out
1052		to memory. See the 'iotrace' command for details. This is
1053		useful for testing device drivers since it can confirm that
1054		the driver behaves the same way before and after a code
1055		change. Currently this is supported on sandbox and arm. To
1056		add support for your architecture, add '#include <iotrace.h>'
1057		to the bottom of arch/<arch>/include/asm/io.h and test.
1058
1059		Example output from the 'iotrace stats' command is below.
1060		Note that if the trace buffer is exhausted, the checksum will
1061		still continue to operate.
1062
1063			iotrace is enabled
1064			Start:  10000000	(buffer start address)
1065			Size:   00010000	(buffer size)
1066			Offset: 00000120	(current buffer offset)
1067			Output: 10000120	(start + offset)
1068			Count:  00000018	(number of trace records)
1069			CRC32:  9526fb66	(CRC32 of all trace records)
1070
1071- Timestamp Support:
1072
1073		When CONFIG_TIMESTAMP is selected, the timestamp
1074		(date and time) of an image is printed by image
1075		commands like bootm or iminfo. This option is
1076		automatically enabled when you select CONFIG_CMD_DATE .
1077
1078- Partition Labels (disklabels) Supported:
1079		Zero or more of the following:
1080		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
1081		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
1082				       Intel architecture, USB sticks, etc.
1083		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
1084		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
1085				       bootloader.  Note 2TB partition limit; see
1086				       disk/part_efi.c
1087		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
1088
1089		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
1090		CONFIG_SCSI) you must configure support for at
1091		least one non-MTD partition type as well.
1092
1093- IDE Reset method:
1094		CONFIG_IDE_RESET_ROUTINE - this is defined in several
1095		board configurations files but used nowhere!
1096
1097		CONFIG_IDE_RESET - is this is defined, IDE Reset will
1098		be performed by calling the function
1099			ide_set_reset(int reset)
1100		which has to be defined in a board specific file
1101
1102- ATAPI Support:
1103		CONFIG_ATAPI
1104
1105		Set this to enable ATAPI support.
1106
1107- LBA48 Support
1108		CONFIG_LBA48
1109
1110		Set this to enable support for disks larger than 137GB
1111		Also look at CONFIG_SYS_64BIT_LBA.
1112		Whithout these , LBA48 support uses 32bit variables and will 'only'
1113		support disks up to 2.1TB.
1114
1115		CONFIG_SYS_64BIT_LBA:
1116			When enabled, makes the IDE subsystem use 64bit sector addresses.
1117			Default is 32bit.
1118
1119- SCSI Support:
1120		At the moment only there is only support for the
1121		SYM53C8XX SCSI controller; define
1122		CONFIG_SCSI_SYM53C8XX to enable it.
1123
1124		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
1125		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
1126		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
1127		maximum numbers of LUNs, SCSI ID's and target
1128		devices.
1129		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
1130
1131		The environment variable 'scsidevs' is set to the number of
1132		SCSI devices found during the last scan.
1133
1134- NETWORK Support (PCI):
1135		CONFIG_E1000
1136		Support for Intel 8254x/8257x gigabit chips.
1137
1138		CONFIG_E1000_SPI
1139		Utility code for direct access to the SPI bus on Intel 8257x.
1140		This does not do anything useful unless you set at least one
1141		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
1142
1143		CONFIG_E1000_SPI_GENERIC
1144		Allow generic access to the SPI bus on the Intel 8257x, for
1145		example with the "sspi" command.
1146
1147		CONFIG_CMD_E1000
1148		Management command for E1000 devices.  When used on devices
1149		with SPI support you can reprogram the EEPROM from U-Boot.
1150
1151		CONFIG_EEPRO100
1152		Support for Intel 82557/82559/82559ER chips.
1153		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
1154		write routine for first time initialisation.
1155
1156		CONFIG_TULIP
1157		Support for Digital 2114x chips.
1158		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
1159		modem chip initialisation (KS8761/QS6611).
1160
1161		CONFIG_NATSEMI
1162		Support for National dp83815 chips.
1163
1164		CONFIG_NS8382X
1165		Support for National dp8382[01] gigabit chips.
1166
1167- NETWORK Support (other):
1168
1169		CONFIG_DRIVER_AT91EMAC
1170		Support for AT91RM9200 EMAC.
1171
1172			CONFIG_RMII
1173			Define this to use reduced MII inteface
1174
1175			CONFIG_DRIVER_AT91EMAC_QUIET
1176			If this defined, the driver is quiet.
1177			The driver doen't show link status messages.
1178
1179		CONFIG_CALXEDA_XGMAC
1180		Support for the Calxeda XGMAC device
1181
1182		CONFIG_LAN91C96
1183		Support for SMSC's LAN91C96 chips.
1184
1185			CONFIG_LAN91C96_USE_32_BIT
1186			Define this to enable 32 bit addressing
1187
1188		CONFIG_SMC91111
1189		Support for SMSC's LAN91C111 chip
1190
1191			CONFIG_SMC91111_BASE
1192			Define this to hold the physical address
1193			of the device (I/O space)
1194
1195			CONFIG_SMC_USE_32_BIT
1196			Define this if data bus is 32 bits
1197
1198			CONFIG_SMC_USE_IOFUNCS
1199			Define this to use i/o functions instead of macros
1200			(some hardware wont work with macros)
1201
1202		CONFIG_DRIVER_TI_EMAC
1203		Support for davinci emac
1204
1205			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
1206			Define this if you have more then 3 PHYs.
1207
1208		CONFIG_FTGMAC100
1209		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
1210
1211			CONFIG_FTGMAC100_EGIGA
1212			Define this to use GE link update with gigabit PHY.
1213			Define this if FTGMAC100 is connected to gigabit PHY.
1214			If your system has 10/100 PHY only, it might not occur
1215			wrong behavior. Because PHY usually return timeout or
1216			useless data when polling gigabit status and gigabit
1217			control registers. This behavior won't affect the
1218			correctnessof 10/100 link speed update.
1219
1220		CONFIG_SMC911X
1221		Support for SMSC's LAN911x and LAN921x chips
1222
1223			CONFIG_SMC911X_BASE
1224			Define this to hold the physical address
1225			of the device (I/O space)
1226
1227			CONFIG_SMC911X_32_BIT
1228			Define this if data bus is 32 bits
1229
1230			CONFIG_SMC911X_16_BIT
1231			Define this if data bus is 16 bits. If your processor
1232			automatically converts one 32 bit word to two 16 bit
1233			words you may also try CONFIG_SMC911X_32_BIT.
1234
1235		CONFIG_SH_ETHER
1236		Support for Renesas on-chip Ethernet controller
1237
1238			CONFIG_SH_ETHER_USE_PORT
1239			Define the number of ports to be used
1240
1241			CONFIG_SH_ETHER_PHY_ADDR
1242			Define the ETH PHY's address
1243
1244			CONFIG_SH_ETHER_CACHE_WRITEBACK
1245			If this option is set, the driver enables cache flush.
1246
1247- PWM Support:
1248		CONFIG_PWM_IMX
1249		Support for PWM module on the imx6.
1250
1251- TPM Support:
1252		CONFIG_TPM
1253		Support TPM devices.
1254
1255		CONFIG_TPM_TIS_INFINEON
1256		Support for Infineon i2c bus TPM devices. Only one device
1257		per system is supported at this time.
1258
1259			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1260			Define the burst count bytes upper limit
1261
1262		CONFIG_TPM_ST33ZP24
1263		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1264
1265			CONFIG_TPM_ST33ZP24_I2C
1266			Support for STMicroelectronics ST33ZP24 I2C devices.
1267			Requires TPM_ST33ZP24 and I2C.
1268
1269			CONFIG_TPM_ST33ZP24_SPI
1270			Support for STMicroelectronics ST33ZP24 SPI devices.
1271			Requires TPM_ST33ZP24 and SPI.
1272
1273		CONFIG_TPM_ATMEL_TWI
1274		Support for Atmel TWI TPM device. Requires I2C support.
1275
1276		CONFIG_TPM_TIS_LPC
1277		Support for generic parallel port TPM devices. Only one device
1278		per system is supported at this time.
1279
1280			CONFIG_TPM_TIS_BASE_ADDRESS
1281			Base address where the generic TPM device is mapped
1282			to. Contemporary x86 systems usually map it at
1283			0xfed40000.
1284
1285		CONFIG_CMD_TPM
1286		Add tpm monitor functions.
1287		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
1288		provides monitor access to authorized functions.
1289
1290		CONFIG_TPM
1291		Define this to enable the TPM support library which provides
1292		functional interfaces to some TPM commands.
1293		Requires support for a TPM device.
1294
1295		CONFIG_TPM_AUTH_SESSIONS
1296		Define this to enable authorized functions in the TPM library.
1297		Requires CONFIG_TPM and CONFIG_SHA1.
1298
1299- USB Support:
1300		At the moment only the UHCI host controller is
1301		supported (PIP405, MIP405, MPC5200); define
1302		CONFIG_USB_UHCI to enable it.
1303		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1304		and define CONFIG_USB_STORAGE to enable the USB
1305		storage devices.
1306		Note:
1307		Supported are USB Keyboards and USB Floppy drives
1308		(TEAC FD-05PUB).
1309		MPC5200 USB requires additional defines:
1310			CONFIG_USB_CLOCK
1311				for 528 MHz Clock: 0x0001bbbb
1312			CONFIG_PSC3_USB
1313				for USB on PSC3
1314			CONFIG_USB_CONFIG
1315				for differential drivers: 0x00001000
1316				for single ended drivers: 0x00005000
1317				for differential drivers on PSC3: 0x00000100
1318				for single ended drivers on PSC3: 0x00004100
1319			CONFIG_SYS_USB_EVENT_POLL
1320				May be defined to allow interrupt polling
1321				instead of using asynchronous interrupts
1322
1323		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1324		txfilltuning field in the EHCI controller on reset.
1325
1326		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1327		HW module registers.
1328
1329- USB Device:
1330		Define the below if you wish to use the USB console.
1331		Once firmware is rebuilt from a serial console issue the
1332		command "setenv stdin usbtty; setenv stdout usbtty" and
1333		attach your USB cable. The Unix command "dmesg" should print
1334		it has found a new device. The environment variable usbtty
1335		can be set to gserial or cdc_acm to enable your device to
1336		appear to a USB host as a Linux gserial device or a
1337		Common Device Class Abstract Control Model serial device.
1338		If you select usbtty = gserial you should be able to enumerate
1339		a Linux host by
1340		# modprobe usbserial vendor=0xVendorID product=0xProductID
1341		else if using cdc_acm, simply setting the environment
1342		variable usbtty to be cdc_acm should suffice. The following
1343		might be defined in YourBoardName.h
1344
1345			CONFIG_USB_DEVICE
1346			Define this to build a UDC device
1347
1348			CONFIG_USB_TTY
1349			Define this to have a tty type of device available to
1350			talk to the UDC device
1351
1352			CONFIG_USBD_HS
1353			Define this to enable the high speed support for usb
1354			device and usbtty. If this feature is enabled, a routine
1355			int is_usbd_high_speed(void)
1356			also needs to be defined by the driver to dynamically poll
1357			whether the enumeration has succeded at high speed or full
1358			speed.
1359
1360			CONFIG_SYS_CONSOLE_IS_IN_ENV
1361			Define this if you want stdin, stdout &/or stderr to
1362			be set to usbtty.
1363
1364			mpc8xx:
1365				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
1366				Derive USB clock from external clock "blah"
1367				- CONFIG_SYS_USB_EXTC_CLK 0x02
1368
1369		If you have a USB-IF assigned VendorID then you may wish to
1370		define your own vendor specific values either in BoardName.h
1371		or directly in usbd_vendor_info.h. If you don't define
1372		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1373		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1374		should pretend to be a Linux device to it's target host.
1375
1376			CONFIG_USBD_MANUFACTURER
1377			Define this string as the name of your company for
1378			- CONFIG_USBD_MANUFACTURER "my company"
1379
1380			CONFIG_USBD_PRODUCT_NAME
1381			Define this string as the name of your product
1382			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1383
1384			CONFIG_USBD_VENDORID
1385			Define this as your assigned Vendor ID from the USB
1386			Implementors Forum. This *must* be a genuine Vendor ID
1387			to avoid polluting the USB namespace.
1388			- CONFIG_USBD_VENDORID 0xFFFF
1389
1390			CONFIG_USBD_PRODUCTID
1391			Define this as the unique Product ID
1392			for your device
1393			- CONFIG_USBD_PRODUCTID 0xFFFF
1394
1395- ULPI Layer Support:
1396		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1397		the generic ULPI layer. The generic layer accesses the ULPI PHY
1398		via the platform viewport, so you need both the genric layer and
1399		the viewport enabled. Currently only Chipidea/ARC based
1400		viewport is supported.
1401		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1402		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1403		If your ULPI phy needs a different reference clock than the
1404		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1405		the appropriate value in Hz.
1406
1407- MMC Support:
1408		The MMC controller on the Intel PXA is supported. To
1409		enable this define CONFIG_MMC. The MMC can be
1410		accessed from the boot prompt by mapping the device
1411		to physical memory similar to flash. Command line is
1412		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1413		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1414
1415		CONFIG_SH_MMCIF
1416		Support for Renesas on-chip MMCIF controller
1417
1418			CONFIG_SH_MMCIF_ADDR
1419			Define the base address of MMCIF registers
1420
1421			CONFIG_SH_MMCIF_CLK
1422			Define the clock frequency for MMCIF
1423
1424		CONFIG_SUPPORT_EMMC_BOOT
1425		Enable some additional features of the eMMC boot partitions.
1426
1427		CONFIG_SUPPORT_EMMC_RPMB
1428		Enable the commands for reading, writing and programming the
1429		key for the Replay Protection Memory Block partition in eMMC.
1430
1431- USB Device Firmware Update (DFU) class support:
1432		CONFIG_USB_FUNCTION_DFU
1433		This enables the USB portion of the DFU USB class
1434
1435		CONFIG_CMD_DFU
1436		This enables the command "dfu" which is used to have
1437		U-Boot create a DFU class device via USB.  This command
1438		requires that the "dfu_alt_info" environment variable be
1439		set and define the alt settings to expose to the host.
1440
1441		CONFIG_DFU_MMC
1442		This enables support for exposing (e)MMC devices via DFU.
1443
1444		CONFIG_DFU_NAND
1445		This enables support for exposing NAND devices via DFU.
1446
1447		CONFIG_DFU_RAM
1448		This enables support for exposing RAM via DFU.
1449		Note: DFU spec refer to non-volatile memory usage, but
1450		allow usages beyond the scope of spec - here RAM usage,
1451		one that would help mostly the developer.
1452
1453		CONFIG_SYS_DFU_DATA_BUF_SIZE
1454		Dfu transfer uses a buffer before writing data to the
1455		raw storage device. Make the size (in bytes) of this buffer
1456		configurable. The size of this buffer is also configurable
1457		through the "dfu_bufsiz" environment variable.
1458
1459		CONFIG_SYS_DFU_MAX_FILE_SIZE
1460		When updating files rather than the raw storage device,
1461		we use a static buffer to copy the file into and then write
1462		the buffer once we've been given the whole file.  Define
1463		this to the maximum filesize (in bytes) for the buffer.
1464		Default is 4 MiB if undefined.
1465
1466		DFU_DEFAULT_POLL_TIMEOUT
1467		Poll timeout [ms], is the timeout a device can send to the
1468		host. The host must wait for this timeout before sending
1469		a subsequent DFU_GET_STATUS request to the device.
1470
1471		DFU_MANIFEST_POLL_TIMEOUT
1472		Poll timeout [ms], which the device sends to the host when
1473		entering dfuMANIFEST state. Host waits this timeout, before
1474		sending again an USB request to the device.
1475
1476- USB Device Android Fastboot support:
1477		CONFIG_USB_FUNCTION_FASTBOOT
1478		This enables the USB part of the fastboot gadget
1479
1480		CONFIG_CMD_FASTBOOT
1481		This enables the command "fastboot" which enables the Android
1482		fastboot mode for the platform's USB device. Fastboot is a USB
1483		protocol for downloading images, flashing and device control
1484		used on Android devices.
1485		See doc/README.android-fastboot for more information.
1486
1487		CONFIG_ANDROID_BOOT_IMAGE
1488		This enables support for booting images which use the Android
1489		image format header.
1490
1491		CONFIG_FASTBOOT_BUF_ADDR
1492		The fastboot protocol requires a large memory buffer for
1493		downloads. Define this to the starting RAM address to use for
1494		downloaded images.
1495
1496		CONFIG_FASTBOOT_BUF_SIZE
1497		The fastboot protocol requires a large memory buffer for
1498		downloads. This buffer should be as large as possible for a
1499		platform. Define this to the size available RAM for fastboot.
1500
1501		CONFIG_FASTBOOT_FLASH
1502		The fastboot protocol includes a "flash" command for writing
1503		the downloaded image to a non-volatile storage device. Define
1504		this to enable the "fastboot flash" command.
1505
1506		CONFIG_FASTBOOT_FLASH_MMC_DEV
1507		The fastboot "flash" command requires additional information
1508		regarding the non-volatile storage device. Define this to
1509		the eMMC device that fastboot should use to store the image.
1510
1511		CONFIG_FASTBOOT_GPT_NAME
1512		The fastboot "flash" command supports writing the downloaded
1513		image to the Protective MBR and the Primary GUID Partition
1514		Table. (Additionally, this downloaded image is post-processed
1515		to generate and write the Backup GUID Partition Table.)
1516		This occurs when the specified "partition name" on the
1517		"fastboot flash" command line matches this value.
1518		The default is "gpt" if undefined.
1519
1520		CONFIG_FASTBOOT_MBR_NAME
1521		The fastboot "flash" command supports writing the downloaded
1522		image to DOS MBR.
1523		This occurs when the "partition name" specified on the
1524		"fastboot flash" command line matches this value.
1525		If not defined the default value "mbr" is used.
1526
1527- Journaling Flash filesystem support:
1528		CONFIG_JFFS2_NAND
1529		Define these for a default partition on a NAND device
1530
1531		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1532		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1533		Define these for a default partition on a NOR device
1534
1535- FAT(File Allocation Table) filesystem write function support:
1536		CONFIG_FAT_WRITE
1537
1538		Define this to enable support for saving memory data as a
1539		file in FAT formatted partition.
1540
1541		This will also enable the command "fatwrite" enabling the
1542		user to write files to FAT.
1543
1544- FAT(File Allocation Table) filesystem cluster size:
1545		CONFIG_FS_FAT_MAX_CLUSTSIZE
1546
1547		Define the max cluster size for fat operations else
1548		a default value of 65536 will be defined.
1549
1550- Keyboard Support:
1551		See Kconfig help for available keyboard drivers.
1552
1553		CONFIG_KEYBOARD
1554
1555		Define this to enable a custom keyboard support.
1556		This simply calls drv_keyboard_init() which must be
1557		defined in your board-specific files. This option is deprecated
1558		and is only used by novena. For new boards, use driver model
1559		instead.
1560
1561- Video support:
1562		CONFIG_FSL_DIU_FB
1563		Enable the Freescale DIU video driver.	Reference boards for
1564		SOCs that have a DIU should define this macro to enable DIU
1565		support, and should also define these other macros:
1566
1567			CONFIG_SYS_DIU_ADDR
1568			CONFIG_VIDEO
1569			CONFIG_CFB_CONSOLE
1570			CONFIG_VIDEO_SW_CURSOR
1571			CONFIG_VGA_AS_SINGLE_DEVICE
1572			CONFIG_VIDEO_LOGO
1573			CONFIG_VIDEO_BMP_LOGO
1574
1575		The DIU driver will look for the 'video-mode' environment
1576		variable, and if defined, enable the DIU as a console during
1577		boot.  See the documentation file doc/README.video for a
1578		description of this variable.
1579
1580- LCD Support:	CONFIG_LCD
1581
1582		Define this to enable LCD support (for output to LCD
1583		display); also select one of the supported displays
1584		by defining one of these:
1585
1586		CONFIG_ATMEL_LCD:
1587
1588			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1589
1590		CONFIG_NEC_NL6448AC33:
1591
1592			NEC NL6448AC33-18. Active, color, single scan.
1593
1594		CONFIG_NEC_NL6448BC20
1595
1596			NEC NL6448BC20-08. 6.5", 640x480.
1597			Active, color, single scan.
1598
1599		CONFIG_NEC_NL6448BC33_54
1600
1601			NEC NL6448BC33-54. 10.4", 640x480.
1602			Active, color, single scan.
1603
1604		CONFIG_SHARP_16x9
1605
1606			Sharp 320x240. Active, color, single scan.
1607			It isn't 16x9, and I am not sure what it is.
1608
1609		CONFIG_SHARP_LQ64D341
1610
1611			Sharp LQ64D341 display, 640x480.
1612			Active, color, single scan.
1613
1614		CONFIG_HLD1045
1615
1616			HLD1045 display, 640x480.
1617			Active, color, single scan.
1618
1619		CONFIG_OPTREX_BW
1620
1621			Optrex	 CBL50840-2 NF-FW 99 22 M5
1622			or
1623			Hitachi	 LMG6912RPFC-00T
1624			or
1625			Hitachi	 SP14Q002
1626
1627			320x240. Black & white.
1628
1629		CONFIG_LCD_ALIGNMENT
1630
1631		Normally the LCD is page-aligned (typically 4KB). If this is
1632		defined then the LCD will be aligned to this value instead.
1633		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1634		here, since it is cheaper to change data cache settings on
1635		a per-section basis.
1636
1637
1638		CONFIG_LCD_ROTATION
1639
1640		Sometimes, for example if the display is mounted in portrait
1641		mode or even if it's mounted landscape but rotated by 180degree,
1642		we need to rotate our content of the display relative to the
1643		framebuffer, so that user can read the messages which are
1644		printed out.
1645		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1646		initialized with a given rotation from "vl_rot" out of
1647		"vidinfo_t" which is provided by the board specific code.
1648		The value for vl_rot is coded as following (matching to
1649		fbcon=rotate:<n> linux-kernel commandline):
1650		0 = no rotation respectively 0 degree
1651		1 = 90 degree rotation
1652		2 = 180 degree rotation
1653		3 = 270 degree rotation
1654
1655		If CONFIG_LCD_ROTATION is not defined, the console will be
1656		initialized with 0degree rotation.
1657
1658		CONFIG_LCD_BMP_RLE8
1659
1660		Support drawing of RLE8-compressed bitmaps on the LCD.
1661
1662		CONFIG_I2C_EDID
1663
1664		Enables an 'i2c edid' command which can read EDID
1665		information over I2C from an attached LCD display.
1666
1667- Splash Screen Support: CONFIG_SPLASH_SCREEN
1668
1669		If this option is set, the environment is checked for
1670		a variable "splashimage". If found, the usual display
1671		of logo, copyright and system information on the LCD
1672		is suppressed and the BMP image at the address
1673		specified in "splashimage" is loaded instead. The
1674		console is redirected to the "nulldev", too. This
1675		allows for a "silent" boot where a splash screen is
1676		loaded very quickly after power-on.
1677
1678		CONFIG_SPLASHIMAGE_GUARD
1679
1680		If this option is set, then U-Boot will prevent the environment
1681		variable "splashimage" from being set to a problematic address
1682		(see doc/README.displaying-bmps).
1683		This option is useful for targets where, due to alignment
1684		restrictions, an improperly aligned BMP image will cause a data
1685		abort. If you think you will not have problems with unaligned
1686		accesses (for example because your toolchain prevents them)
1687		there is no need to set this option.
1688
1689		CONFIG_SPLASH_SCREEN_ALIGN
1690
1691		If this option is set the splash image can be freely positioned
1692		on the screen. Environment variable "splashpos" specifies the
1693		position as "x,y". If a positive number is given it is used as
1694		number of pixel from left/top. If a negative number is given it
1695		is used as number of pixel from right/bottom. You can also
1696		specify 'm' for centering the image.
1697
1698		Example:
1699		setenv splashpos m,m
1700			=> image at center of screen
1701
1702		setenv splashpos 30,20
1703			=> image at x = 30 and y = 20
1704
1705		setenv splashpos -10,m
1706			=> vertically centered image
1707			   at x = dspWidth - bmpWidth - 9
1708
1709- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1710
1711		If this option is set, additionally to standard BMP
1712		images, gzipped BMP images can be displayed via the
1713		splashscreen support or the bmp command.
1714
1715- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1716
1717		If this option is set, 8-bit RLE compressed BMP images
1718		can be displayed via the splashscreen support or the
1719		bmp command.
1720
1721- Compression support:
1722		CONFIG_GZIP
1723
1724		Enabled by default to support gzip compressed images.
1725
1726		CONFIG_BZIP2
1727
1728		If this option is set, support for bzip2 compressed
1729		images is included. If not, only uncompressed and gzip
1730		compressed images are supported.
1731
1732		NOTE: the bzip2 algorithm requires a lot of RAM, so
1733		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1734		be at least 4MB.
1735
1736		CONFIG_LZMA
1737
1738		If this option is set, support for lzma compressed
1739		images is included.
1740
1741		Note: The LZMA algorithm adds between 2 and 4KB of code and it
1742		requires an amount of dynamic memory that is given by the
1743		formula:
1744
1745			(1846 + 768 << (lc + lp)) * sizeof(uint16)
1746
1747		Where lc and lp stand for, respectively, Literal context bits
1748		and Literal pos bits.
1749
1750		This value is upper-bounded by 14MB in the worst case. Anyway,
1751		for a ~4MB large kernel image, we have lc=3 and lp=0 for a
1752		total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
1753		a very small buffer.
1754
1755		Use the lzmainfo tool to determinate the lc and lp values and
1756		then calculate the amount of needed dynamic memory (ensuring
1757		the appropriate CONFIG_SYS_MALLOC_LEN value).
1758
1759		CONFIG_LZO
1760
1761		If this option is set, support for LZO compressed images
1762		is included.
1763
1764- MII/PHY support:
1765		CONFIG_PHY_ADDR
1766
1767		The address of PHY on MII bus.
1768
1769		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1770
1771		The clock frequency of the MII bus
1772
1773		CONFIG_PHY_GIGE
1774
1775		If this option is set, support for speed/duplex
1776		detection of gigabit PHY is included.
1777
1778		CONFIG_PHY_RESET_DELAY
1779
1780		Some PHY like Intel LXT971A need extra delay after
1781		reset before any MII register access is possible.
1782		For such PHY, set this option to the usec delay
1783		required. (minimum 300usec for LXT971A)
1784
1785		CONFIG_PHY_CMD_DELAY (ppc4xx)
1786
1787		Some PHY like Intel LXT971A need extra delay after
1788		command issued before MII status register can be read
1789
1790- IP address:
1791		CONFIG_IPADDR
1792
1793		Define a default value for the IP address to use for
1794		the default Ethernet interface, in case this is not
1795		determined through e.g. bootp.
1796		(Environment variable "ipaddr")
1797
1798- Server IP address:
1799		CONFIG_SERVERIP
1800
1801		Defines a default value for the IP address of a TFTP
1802		server to contact when using the "tftboot" command.
1803		(Environment variable "serverip")
1804
1805		CONFIG_KEEP_SERVERADDR
1806
1807		Keeps the server's MAC address, in the env 'serveraddr'
1808		for passing to bootargs (like Linux's netconsole option)
1809
1810- Gateway IP address:
1811		CONFIG_GATEWAYIP
1812
1813		Defines a default value for the IP address of the
1814		default router where packets to other networks are
1815		sent to.
1816		(Environment variable "gatewayip")
1817
1818- Subnet mask:
1819		CONFIG_NETMASK
1820
1821		Defines a default value for the subnet mask (or
1822		routing prefix) which is used to determine if an IP
1823		address belongs to the local subnet or needs to be
1824		forwarded through a router.
1825		(Environment variable "netmask")
1826
1827- Multicast TFTP Mode:
1828		CONFIG_MCAST_TFTP
1829
1830		Defines whether you want to support multicast TFTP as per
1831		rfc-2090; for example to work with atftp.  Lets lots of targets
1832		tftp down the same boot image concurrently.  Note: the Ethernet
1833		driver in use must provide a function: mcast() to join/leave a
1834		multicast group.
1835
1836- BOOTP Recovery Mode:
1837		CONFIG_BOOTP_RANDOM_DELAY
1838
1839		If you have many targets in a network that try to
1840		boot using BOOTP, you may want to avoid that all
1841		systems send out BOOTP requests at precisely the same
1842		moment (which would happen for instance at recovery
1843		from a power failure, when all systems will try to
1844		boot, thus flooding the BOOTP server. Defining
1845		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1846		inserted before sending out BOOTP requests. The
1847		following delays are inserted then:
1848
1849		1st BOOTP request:	delay 0 ... 1 sec
1850		2nd BOOTP request:	delay 0 ... 2 sec
1851		3rd BOOTP request:	delay 0 ... 4 sec
1852		4th and following
1853		BOOTP requests:		delay 0 ... 8 sec
1854
1855		CONFIG_BOOTP_ID_CACHE_SIZE
1856
1857		BOOTP packets are uniquely identified using a 32-bit ID. The
1858		server will copy the ID from client requests to responses and
1859		U-Boot will use this to determine if it is the destination of
1860		an incoming response. Some servers will check that addresses
1861		aren't in use before handing them out (usually using an ARP
1862		ping) and therefore take up to a few hundred milliseconds to
1863		respond. Network congestion may also influence the time it
1864		takes for a response to make it back to the client. If that
1865		time is too long, U-Boot will retransmit requests. In order
1866		to allow earlier responses to still be accepted after these
1867		retransmissions, U-Boot's BOOTP client keeps a small cache of
1868		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1869		cache. The default is to keep IDs for up to four outstanding
1870		requests. Increasing this will allow U-Boot to accept offers
1871		from a BOOTP client in networks with unusually high latency.
1872
1873- DHCP Advanced Options:
1874		You can fine tune the DHCP functionality by defining
1875		CONFIG_BOOTP_* symbols:
1876
1877		CONFIG_BOOTP_SUBNETMASK
1878		CONFIG_BOOTP_GATEWAY
1879		CONFIG_BOOTP_HOSTNAME
1880		CONFIG_BOOTP_NISDOMAIN
1881		CONFIG_BOOTP_BOOTPATH
1882		CONFIG_BOOTP_BOOTFILESIZE
1883		CONFIG_BOOTP_DNS
1884		CONFIG_BOOTP_DNS2
1885		CONFIG_BOOTP_SEND_HOSTNAME
1886		CONFIG_BOOTP_NTPSERVER
1887		CONFIG_BOOTP_TIMEOFFSET
1888		CONFIG_BOOTP_VENDOREX
1889		CONFIG_BOOTP_MAY_FAIL
1890
1891		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1892		environment variable, not the BOOTP server.
1893
1894		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1895		after the configured retry count, the call will fail
1896		instead of starting over.  This can be used to fail over
1897		to Link-local IP address configuration if the DHCP server
1898		is not available.
1899
1900		CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
1901		serverip from a DHCP server, it is possible that more
1902		than one DNS serverip is offered to the client.
1903		If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
1904		serverip will be stored in the additional environment
1905		variable "dnsip2". The first DNS serverip is always
1906		stored in the variable "dnsip", when CONFIG_BOOTP_DNS
1907		is defined.
1908
1909		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1910		to do a dynamic update of a DNS server. To do this, they
1911		need the hostname of the DHCP requester.
1912		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1913		of the "hostname" environment variable is passed as
1914		option 12 to the DHCP server.
1915
1916		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1917
1918		A 32bit value in microseconds for a delay between
1919		receiving a "DHCP Offer" and sending the "DHCP Request".
1920		This fixes a problem with certain DHCP servers that don't
1921		respond 100% of the time to a "DHCP request". E.g. On an
1922		AT91RM9200 processor running at 180MHz, this delay needed
1923		to be *at least* 15,000 usec before a Windows Server 2003
1924		DHCP server would reply 100% of the time. I recommend at
1925		least 50,000 usec to be safe. The alternative is to hope
1926		that one of the retries will be successful but note that
1927		the DHCP timeout and retry process takes a longer than
1928		this delay.
1929
1930 - Link-local IP address negotiation:
1931		Negotiate with other link-local clients on the local network
1932		for an address that doesn't require explicit configuration.
1933		This is especially useful if a DHCP server cannot be guaranteed
1934		to exist in all environments that the device must operate.
1935
1936		See doc/README.link-local for more information.
1937
1938 - CDP Options:
1939		CONFIG_CDP_DEVICE_ID
1940
1941		The device id used in CDP trigger frames.
1942
1943		CONFIG_CDP_DEVICE_ID_PREFIX
1944
1945		A two character string which is prefixed to the MAC address
1946		of the device.
1947
1948		CONFIG_CDP_PORT_ID
1949
1950		A printf format string which contains the ascii name of
1951		the port. Normally is set to "eth%d" which sets
1952		eth0 for the first Ethernet, eth1 for the second etc.
1953
1954		CONFIG_CDP_CAPABILITIES
1955
1956		A 32bit integer which indicates the device capabilities;
1957		0x00000010 for a normal host which does not forwards.
1958
1959		CONFIG_CDP_VERSION
1960
1961		An ascii string containing the version of the software.
1962
1963		CONFIG_CDP_PLATFORM
1964
1965		An ascii string containing the name of the platform.
1966
1967		CONFIG_CDP_TRIGGER
1968
1969		A 32bit integer sent on the trigger.
1970
1971		CONFIG_CDP_POWER_CONSUMPTION
1972
1973		A 16bit integer containing the power consumption of the
1974		device in .1 of milliwatts.
1975
1976		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1977
1978		A byte containing the id of the VLAN.
1979
1980- Status LED:	CONFIG_LED_STATUS
1981
1982		Several configurations allow to display the current
1983		status using a LED. For instance, the LED will blink
1984		fast while running U-Boot code, stop blinking as
1985		soon as a reply to a BOOTP request was received, and
1986		start blinking slow once the Linux kernel is running
1987		(supported by a status LED driver in the Linux
1988		kernel). Defining CONFIG_LED_STATUS enables this
1989		feature in U-Boot.
1990
1991		Additional options:
1992
1993		CONFIG_LED_STATUS_GPIO
1994		The status LED can be connected to a GPIO pin.
1995		In such cases, the gpio_led driver can be used as a
1996		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1997		to include the gpio_led driver in the U-Boot binary.
1998
1999		CONFIG_GPIO_LED_INVERTED_TABLE
2000		Some GPIO connected LEDs may have inverted polarity in which
2001		case the GPIO high value corresponds to LED off state and
2002		GPIO low value corresponds to LED on state.
2003		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
2004		with a list of GPIO LEDs that have inverted polarity.
2005
2006- CAN Support:	CONFIG_CAN_DRIVER
2007
2008		Defining CONFIG_CAN_DRIVER enables CAN driver support
2009		on those systems that support this (optional)
2010		feature, like the TQM8xxL modules.
2011
2012- I2C Support:	CONFIG_SYS_I2C
2013
2014		This enable the NEW i2c subsystem, and will allow you to use
2015		i2c commands at the u-boot command line (as long as you set
2016		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
2017		based realtime clock chips or other i2c devices. See
2018		common/cmd_i2c.c for a description of the command line
2019		interface.
2020
2021		ported i2c driver to the new framework:
2022		- drivers/i2c/soft_i2c.c:
2023		  - activate first bus with CONFIG_SYS_I2C_SOFT define
2024		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
2025		    for defining speed and slave address
2026		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
2027		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
2028		    for defining speed and slave address
2029		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
2030		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
2031		    for defining speed and slave address
2032		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
2033		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
2034		    for defining speed and slave address
2035
2036		- drivers/i2c/fsl_i2c.c:
2037		  - activate i2c driver with CONFIG_SYS_I2C_FSL
2038		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
2039		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
2040		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
2041		    bus.
2042		  - If your board supports a second fsl i2c bus, define
2043		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
2044		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
2045		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
2046		    second bus.
2047
2048		- drivers/i2c/tegra_i2c.c:
2049		  - activate this driver with CONFIG_SYS_I2C_TEGRA
2050		  - This driver adds 4 i2c buses with a fix speed from
2051		    100000 and the slave addr 0!
2052
2053		- drivers/i2c/ppc4xx_i2c.c
2054		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
2055		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
2056		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
2057
2058		- drivers/i2c/i2c_mxc.c
2059		  - activate this driver with CONFIG_SYS_I2C_MXC
2060		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
2061		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
2062		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
2063		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
2064		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
2065		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
2066		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
2067		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
2068		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
2069		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
2070		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
2071		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
2072		If those defines are not set, default value is 100000
2073		for speed, and 0 for slave.
2074
2075		- drivers/i2c/rcar_i2c.c:
2076		  - activate this driver with CONFIG_SYS_I2C_RCAR
2077		  - This driver adds 4 i2c buses
2078
2079		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
2080		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
2081		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
2082		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
2083		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
2084		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
2085		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
2086		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
2087		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
2088
2089		- drivers/i2c/sh_i2c.c:
2090		  - activate this driver with CONFIG_SYS_I2C_SH
2091		  - This driver adds from 2 to 5 i2c buses
2092
2093		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
2094		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
2095		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
2096		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
2097		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
2098		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
2099		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
2100		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
2101		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
2102		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
2103		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
2104
2105		- drivers/i2c/omap24xx_i2c.c
2106		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
2107		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
2108		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
2109		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
2110		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
2111		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
2112		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
2113		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
2114		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
2115		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
2116		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
2117
2118		- drivers/i2c/zynq_i2c.c
2119		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
2120		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
2121		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
2122
2123		- drivers/i2c/s3c24x0_i2c.c:
2124		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
2125		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
2126		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
2127		    with a fix speed from 100000 and the slave addr 0!
2128
2129		- drivers/i2c/ihs_i2c.c
2130		  - activate this driver with CONFIG_SYS_I2C_IHS
2131		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
2132		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
2133		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
2134		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
2135		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
2136		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
2137		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
2138		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
2139		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
2140		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
2141		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
2142		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
2143		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
2144		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
2145		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
2146		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
2147		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
2148		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
2149		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
2150		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
2151		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
2152
2153		additional defines:
2154
2155		CONFIG_SYS_NUM_I2C_BUSES
2156		Hold the number of i2c buses you want to use.
2157
2158		CONFIG_SYS_I2C_DIRECT_BUS
2159		define this, if you don't use i2c muxes on your hardware.
2160		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
2161		omit this define.
2162
2163		CONFIG_SYS_I2C_MAX_HOPS
2164		define how many muxes are maximal consecutively connected
2165		on one i2c bus. If you not use i2c muxes, omit this
2166		define.
2167
2168		CONFIG_SYS_I2C_BUSES
2169		hold a list of buses you want to use, only used if
2170		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
2171		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
2172		CONFIG_SYS_NUM_I2C_BUSES = 9:
2173
2174		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
2175					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
2176					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
2177					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
2178					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
2179					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
2180					{1, {I2C_NULL_HOP}}, \
2181					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
2182					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
2183					}
2184
2185		which defines
2186			bus 0 on adapter 0 without a mux
2187			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
2188			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
2189			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
2190			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
2191			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
2192			bus 6 on adapter 1 without a mux
2193			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
2194			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
2195
2196		If you do not have i2c muxes on your board, omit this define.
2197
2198- Legacy I2C Support:
2199		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
2200		then the following macros need to be defined (examples are
2201		from include/configs/lwmon.h):
2202
2203		I2C_INIT
2204
2205		(Optional). Any commands necessary to enable the I2C
2206		controller or configure ports.
2207
2208		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
2209
2210		I2C_PORT
2211
2212		(Only for MPC8260 CPU). The I/O port to use (the code
2213		assumes both bits are on the same port). Valid values
2214		are 0..3 for ports A..D.
2215
2216		I2C_ACTIVE
2217
2218		The code necessary to make the I2C data line active
2219		(driven).  If the data line is open collector, this
2220		define can be null.
2221
2222		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
2223
2224		I2C_TRISTATE
2225
2226		The code necessary to make the I2C data line tri-stated
2227		(inactive).  If the data line is open collector, this
2228		define can be null.
2229
2230		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
2231
2232		I2C_READ
2233
2234		Code that returns true if the I2C data line is high,
2235		false if it is low.
2236
2237		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
2238
2239		I2C_SDA(bit)
2240
2241		If <bit> is true, sets the I2C data line high. If it
2242		is false, it clears it (low).
2243
2244		eg: #define I2C_SDA(bit) \
2245			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
2246			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
2247
2248		I2C_SCL(bit)
2249
2250		If <bit> is true, sets the I2C clock line high. If it
2251		is false, it clears it (low).
2252
2253		eg: #define I2C_SCL(bit) \
2254			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
2255			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
2256
2257		I2C_DELAY
2258
2259		This delay is invoked four times per clock cycle so this
2260		controls the rate of data transfer.  The data rate thus
2261		is 1 / (I2C_DELAY * 4). Often defined to be something
2262		like:
2263
2264		#define I2C_DELAY  udelay(2)
2265
2266		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
2267
2268		If your arch supports the generic GPIO framework (asm/gpio.h),
2269		then you may alternatively define the two GPIOs that are to be
2270		used as SCL / SDA.  Any of the previous I2C_xxx macros will
2271		have GPIO-based defaults assigned to them as appropriate.
2272
2273		You should define these to the GPIO value as given directly to
2274		the generic GPIO functions.
2275
2276		CONFIG_SYS_I2C_INIT_BOARD
2277
2278		When a board is reset during an i2c bus transfer
2279		chips might think that the current transfer is still
2280		in progress. On some boards it is possible to access
2281		the i2c SCLK line directly, either by using the
2282		processor pin as a GPIO or by having a second pin
2283		connected to the bus. If this option is defined a
2284		custom i2c_init_board() routine in boards/xxx/board.c
2285		is run early in the boot sequence.
2286
2287		CONFIG_I2C_MULTI_BUS
2288
2289		This option allows the use of multiple I2C buses, each of which
2290		must have a controller.	 At any point in time, only one bus is
2291		active.	 To switch to a different bus, use the 'i2c dev' command.
2292		Note that bus numbering is zero-based.
2293
2294		CONFIG_SYS_I2C_NOPROBES
2295
2296		This option specifies a list of I2C devices that will be skipped
2297		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
2298		is set, specify a list of bus-device pairs.  Otherwise, specify
2299		a 1D array of device addresses
2300
2301		e.g.
2302			#undef	CONFIG_I2C_MULTI_BUS
2303			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
2304
2305		will skip addresses 0x50 and 0x68 on a board with one I2C bus
2306
2307			#define CONFIG_I2C_MULTI_BUS
2308			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
2309
2310		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
2311
2312		CONFIG_SYS_SPD_BUS_NUM
2313
2314		If defined, then this indicates the I2C bus number for DDR SPD.
2315		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
2316
2317		CONFIG_SYS_RTC_BUS_NUM
2318
2319		If defined, then this indicates the I2C bus number for the RTC.
2320		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
2321
2322		CONFIG_SOFT_I2C_READ_REPEATED_START
2323
2324		defining this will force the i2c_read() function in
2325		the soft_i2c driver to perform an I2C repeated start
2326		between writing the address pointer and reading the
2327		data.  If this define is omitted the default behaviour
2328		of doing a stop-start sequence will be used.  Most I2C
2329		devices can use either method, but some require one or
2330		the other.
2331
2332- SPI Support:	CONFIG_SPI
2333
2334		Enables SPI driver (so far only tested with
2335		SPI EEPROM, also an instance works with Crystal A/D and
2336		D/As on the SACSng board)
2337
2338		CONFIG_SH_SPI
2339
2340		Enables the driver for SPI controller on SuperH. Currently
2341		only SH7757 is supported.
2342
2343		CONFIG_SOFT_SPI
2344
2345		Enables a software (bit-bang) SPI driver rather than
2346		using hardware support. This is a general purpose
2347		driver that only requires three general I/O port pins
2348		(two outputs, one input) to function. If this is
2349		defined, the board configuration must define several
2350		SPI configuration items (port pins to use, etc). For
2351		an example, see include/configs/sacsng.h.
2352
2353		CONFIG_HARD_SPI
2354
2355		Enables a hardware SPI driver for general-purpose reads
2356		and writes.  As with CONFIG_SOFT_SPI, the board configuration
2357		must define a list of chip-select function pointers.
2358		Currently supported on some MPC8xxx processors.	 For an
2359		example, see include/configs/mpc8349emds.h.
2360
2361		CONFIG_MXC_SPI
2362
2363		Enables the driver for the SPI controllers on i.MX and MXC
2364		SoCs. Currently i.MX31/35/51 are supported.
2365
2366		CONFIG_SYS_SPI_MXC_WAIT
2367		Timeout for waiting until spi transfer completed.
2368		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
2369
2370- FPGA Support: CONFIG_FPGA
2371
2372		Enables FPGA subsystem.
2373
2374		CONFIG_FPGA_<vendor>
2375
2376		Enables support for specific chip vendors.
2377		(ALTERA, XILINX)
2378
2379		CONFIG_FPGA_<family>
2380
2381		Enables support for FPGA family.
2382		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
2383
2384		CONFIG_FPGA_COUNT
2385
2386		Specify the number of FPGA devices to support.
2387
2388		CONFIG_CMD_FPGA_LOADMK
2389
2390		Enable support for fpga loadmk command
2391
2392		CONFIG_CMD_FPGA_LOADP
2393
2394		Enable support for fpga loadp command - load partial bitstream
2395
2396		CONFIG_CMD_FPGA_LOADBP
2397
2398		Enable support for fpga loadbp command - load partial bitstream
2399		(Xilinx only)
2400
2401		CONFIG_SYS_FPGA_PROG_FEEDBACK
2402
2403		Enable printing of hash marks during FPGA configuration.
2404
2405		CONFIG_SYS_FPGA_CHECK_BUSY
2406
2407		Enable checks on FPGA configuration interface busy
2408		status by the configuration function. This option
2409		will require a board or device specific function to
2410		be written.
2411
2412		CONFIG_FPGA_DELAY
2413
2414		If defined, a function that provides delays in the FPGA
2415		configuration driver.
2416
2417		CONFIG_SYS_FPGA_CHECK_CTRLC
2418		Allow Control-C to interrupt FPGA configuration
2419
2420		CONFIG_SYS_FPGA_CHECK_ERROR
2421
2422		Check for configuration errors during FPGA bitfile
2423		loading. For example, abort during Virtex II
2424		configuration if the INIT_B line goes low (which
2425		indicated a CRC error).
2426
2427		CONFIG_SYS_FPGA_WAIT_INIT
2428
2429		Maximum time to wait for the INIT_B line to de-assert
2430		after PROB_B has been de-asserted during a Virtex II
2431		FPGA configuration sequence. The default time is 500
2432		ms.
2433
2434		CONFIG_SYS_FPGA_WAIT_BUSY
2435
2436		Maximum time to wait for BUSY to de-assert during
2437		Virtex II FPGA configuration. The default is 5 ms.
2438
2439		CONFIG_SYS_FPGA_WAIT_CONFIG
2440
2441		Time to wait after FPGA configuration. The default is
2442		200 ms.
2443
2444- Configuration Management:
2445		CONFIG_BUILD_TARGET
2446
2447		Some SoCs need special image types (e.g. U-Boot binary
2448		with a special header) as build targets. By defining
2449		CONFIG_BUILD_TARGET in the SoC / board header, this
2450		special image will be automatically built upon calling
2451		make / buildman.
2452
2453		CONFIG_IDENT_STRING
2454
2455		If defined, this string will be added to the U-Boot
2456		version information (U_BOOT_VERSION)
2457
2458- Vendor Parameter Protection:
2459
2460		U-Boot considers the values of the environment
2461		variables "serial#" (Board Serial Number) and
2462		"ethaddr" (Ethernet Address) to be parameters that
2463		are set once by the board vendor / manufacturer, and
2464		protects these variables from casual modification by
2465		the user. Once set, these variables are read-only,
2466		and write or delete attempts are rejected. You can
2467		change this behaviour:
2468
2469		If CONFIG_ENV_OVERWRITE is #defined in your config
2470		file, the write protection for vendor parameters is
2471		completely disabled. Anybody can change or delete
2472		these parameters.
2473
2474		Alternatively, if you define _both_ an ethaddr in the
2475		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2476		Ethernet address is installed in the environment,
2477		which can be changed exactly ONCE by the user. [The
2478		serial# is unaffected by this, i. e. it remains
2479		read-only.]
2480
2481		The same can be accomplished in a more flexible way
2482		for any variable by configuring the type of access
2483		to allow for those variables in the ".flags" variable
2484		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2485
2486- Protected RAM:
2487		CONFIG_PRAM
2488
2489		Define this variable to enable the reservation of
2490		"protected RAM", i. e. RAM which is not overwritten
2491		by U-Boot. Define CONFIG_PRAM to hold the number of
2492		kB you want to reserve for pRAM. You can overwrite
2493		this default value by defining an environment
2494		variable "pram" to the number of kB you want to
2495		reserve. Note that the board info structure will
2496		still show the full amount of RAM. If pRAM is
2497		reserved, a new environment variable "mem" will
2498		automatically be defined to hold the amount of
2499		remaining RAM in a form that can be passed as boot
2500		argument to Linux, for instance like that:
2501
2502			setenv bootargs ... mem=\${mem}
2503			saveenv
2504
2505		This way you can tell Linux not to use this memory,
2506		either, which results in a memory region that will
2507		not be affected by reboots.
2508
2509		*WARNING* If your board configuration uses automatic
2510		detection of the RAM size, you must make sure that
2511		this memory test is non-destructive. So far, the
2512		following board configurations are known to be
2513		"pRAM-clean":
2514
2515			IVMS8, IVML24, SPD8xx, TQM8xxL,
2516			HERMES, IP860, RPXlite, LWMON,
2517			FLAGADM, TQM8260
2518
2519- Access to physical memory region (> 4GB)
2520		Some basic support is provided for operations on memory not
2521		normally accessible to U-Boot - e.g. some architectures
2522		support access to more than 4GB of memory on 32-bit
2523		machines using physical address extension or similar.
2524		Define CONFIG_PHYSMEM to access this basic support, which
2525		currently only supports clearing the memory.
2526
2527- Error Recovery:
2528		CONFIG_PANIC_HANG
2529
2530		Define this variable to stop the system in case of a
2531		fatal error, so that you have to reset it manually.
2532		This is probably NOT a good idea for an embedded
2533		system where you want the system to reboot
2534		automatically as fast as possible, but it may be
2535		useful during development since you can try to debug
2536		the conditions that lead to the situation.
2537
2538		CONFIG_NET_RETRY_COUNT
2539
2540		This variable defines the number of retries for
2541		network operations like ARP, RARP, TFTP, or BOOTP
2542		before giving up the operation. If not defined, a
2543		default value of 5 is used.
2544
2545		CONFIG_ARP_TIMEOUT
2546
2547		Timeout waiting for an ARP reply in milliseconds.
2548
2549		CONFIG_NFS_TIMEOUT
2550
2551		Timeout in milliseconds used in NFS protocol.
2552		If you encounter "ERROR: Cannot umount" in nfs command,
2553		try longer timeout such as
2554		#define CONFIG_NFS_TIMEOUT 10000UL
2555
2556- Command Interpreter:
2557		CONFIG_AUTO_COMPLETE
2558
2559		Enable auto completion of commands using TAB.
2560
2561		CONFIG_SYS_PROMPT_HUSH_PS2
2562
2563		This defines the secondary prompt string, which is
2564		printed when the command interpreter needs more input
2565		to complete a command. Usually "> ".
2566
2567	Note:
2568
2569		In the current implementation, the local variables
2570		space and global environment variables space are
2571		separated. Local variables are those you define by
2572		simply typing `name=value'. To access a local
2573		variable later on, you have write `$name' or
2574		`${name}'; to execute the contents of a variable
2575		directly type `$name' at the command prompt.
2576
2577		Global environment variables are those you use
2578		setenv/printenv to work with. To run a command stored
2579		in such a variable, you need to use the run command,
2580		and you must not use the '$' sign to access them.
2581
2582		To store commands and special characters in a
2583		variable, please use double quotation marks
2584		surrounding the whole text of the variable, instead
2585		of the backslashes before semicolons and special
2586		symbols.
2587
2588- Command Line Editing and History:
2589		CONFIG_CMDLINE_EDITING
2590
2591		Enable editing and History functions for interactive
2592		command line input operations
2593
2594- Command Line PS1/PS2 support:
2595		CONFIG_CMDLINE_PS_SUPPORT
2596
2597		Enable support for changing the command prompt string
2598		at run-time. Only static string is supported so far.
2599		The string is obtained from environment variables PS1
2600		and PS2.
2601
2602- Default Environment:
2603		CONFIG_EXTRA_ENV_SETTINGS
2604
2605		Define this to contain any number of null terminated
2606		strings (variable = value pairs) that will be part of
2607		the default environment compiled into the boot image.
2608
2609		For example, place something like this in your
2610		board's config file:
2611
2612		#define CONFIG_EXTRA_ENV_SETTINGS \
2613			"myvar1=value1\0" \
2614			"myvar2=value2\0"
2615
2616		Warning: This method is based on knowledge about the
2617		internal format how the environment is stored by the
2618		U-Boot code. This is NOT an official, exported
2619		interface! Although it is unlikely that this format
2620		will change soon, there is no guarantee either.
2621		You better know what you are doing here.
2622
2623		Note: overly (ab)use of the default environment is
2624		discouraged. Make sure to check other ways to preset
2625		the environment like the "source" command or the
2626		boot command first.
2627
2628		CONFIG_ENV_VARS_UBOOT_CONFIG
2629
2630		Define this in order to add variables describing the
2631		U-Boot build configuration to the default environment.
2632		These will be named arch, cpu, board, vendor, and soc.
2633
2634		Enabling this option will cause the following to be defined:
2635
2636		- CONFIG_SYS_ARCH
2637		- CONFIG_SYS_CPU
2638		- CONFIG_SYS_BOARD
2639		- CONFIG_SYS_VENDOR
2640		- CONFIG_SYS_SOC
2641
2642		CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
2643
2644		Define this in order to add variables describing certain
2645		run-time determined information about the hardware to the
2646		environment.  These will be named board_name, board_rev.
2647
2648		CONFIG_DELAY_ENVIRONMENT
2649
2650		Normally the environment is loaded when the board is
2651		initialised so that it is available to U-Boot. This inhibits
2652		that so that the environment is not available until
2653		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2654		this is instead controlled by the value of
2655		/config/load-environment.
2656
2657- DataFlash Support:
2658		CONFIG_HAS_DATAFLASH
2659
2660		Defining this option enables DataFlash features and
2661		allows to read/write in Dataflash via the standard
2662		commands cp, md...
2663
2664- Serial Flash support
2665		CONFIG_CMD_SF
2666
2667		Defining this option enables SPI flash commands
2668		'sf probe/read/write/erase/update'.
2669
2670		Usage requires an initial 'probe' to define the serial
2671		flash parameters, followed by read/write/erase/update
2672		commands.
2673
2674		The following defaults may be provided by the platform
2675		to handle the common case when only a single serial
2676		flash is present on the system.
2677
2678		CONFIG_SF_DEFAULT_BUS		Bus identifier
2679		CONFIG_SF_DEFAULT_CS		Chip-select
2680		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2681		CONFIG_SF_DEFAULT_SPEED		in Hz
2682
2683		CONFIG_CMD_SF_TEST
2684
2685		Define this option to include a destructive SPI flash
2686		test ('sf test').
2687
2688		CONFIG_SF_DUAL_FLASH		Dual flash memories
2689
2690		Define this option to use dual flash support where two flash
2691		memories can be connected with a given cs line.
2692		Currently Xilinx Zynq qspi supports these type of connections.
2693
2694- SystemACE Support:
2695		CONFIG_SYSTEMACE
2696
2697		Adding this option adds support for Xilinx SystemACE
2698		chips attached via some sort of local bus. The address
2699		of the chip must also be defined in the
2700		CONFIG_SYS_SYSTEMACE_BASE macro. For example:
2701
2702		#define CONFIG_SYSTEMACE
2703		#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
2704
2705		When SystemACE support is added, the "ace" device type
2706		becomes available to the fat commands, i.e. fatls.
2707
2708- TFTP Fixed UDP Port:
2709		CONFIG_TFTP_PORT
2710
2711		If this is defined, the environment variable tftpsrcp
2712		is used to supply the TFTP UDP source port value.
2713		If tftpsrcp isn't defined, the normal pseudo-random port
2714		number generator is used.
2715
2716		Also, the environment variable tftpdstp is used to supply
2717		the TFTP UDP destination port value.  If tftpdstp isn't
2718		defined, the normal port 69 is used.
2719
2720		The purpose for tftpsrcp is to allow a TFTP server to
2721		blindly start the TFTP transfer using the pre-configured
2722		target IP address and UDP port. This has the effect of
2723		"punching through" the (Windows XP) firewall, allowing
2724		the remainder of the TFTP transfer to proceed normally.
2725		A better solution is to properly configure the firewall,
2726		but sometimes that is not allowed.
2727
2728- Hashing support:
2729		CONFIG_CMD_HASH
2730
2731		This enables a generic 'hash' command which can produce
2732		hashes / digests from a few algorithms (e.g. SHA1, SHA256).
2733
2734		CONFIG_HASH_VERIFY
2735
2736		Enable the hash verify command (hash -v). This adds to code
2737		size a little.
2738
2739		Note: There is also a sha1sum command, which should perhaps
2740		be deprecated in favour of 'hash sha1'.
2741
2742- Freescale i.MX specific commands:
2743		CONFIG_CMD_HDMIDETECT
2744		This enables 'hdmidet' command which returns true if an
2745		HDMI monitor is detected.  This command is i.MX 6 specific.
2746
2747- bootcount support:
2748		CONFIG_BOOTCOUNT_LIMIT
2749
2750		This enables the bootcounter support, see:
2751		http://www.denx.de/wiki/DULG/UBootBootCountLimit
2752
2753		CONFIG_AT91SAM9XE
2754		enable special bootcounter support on at91sam9xe based boards.
2755		CONFIG_SOC_DA8XX
2756		enable special bootcounter support on da850 based boards.
2757		CONFIG_BOOTCOUNT_RAM
2758		enable support for the bootcounter in RAM
2759		CONFIG_BOOTCOUNT_I2C
2760		enable support for the bootcounter on an i2c (like RTC) device.
2761			CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
2762			CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
2763						    the bootcounter.
2764			CONFIG_BOOTCOUNT_ALEN = address len
2765
2766- Show boot progress:
2767		CONFIG_SHOW_BOOT_PROGRESS
2768
2769		Defining this option allows to add some board-
2770		specific code (calling a user-provided function
2771		"show_boot_progress(int)") that enables you to show
2772		the system's boot progress on some display (for
2773		example, some LED's) on your board. At the moment,
2774		the following checkpoints are implemented:
2775
2776
2777Legacy uImage format:
2778
2779  Arg	Where			When
2780    1	common/cmd_bootm.c	before attempting to boot an image
2781   -1	common/cmd_bootm.c	Image header has bad	 magic number
2782    2	common/cmd_bootm.c	Image header has correct magic number
2783   -2	common/cmd_bootm.c	Image header has bad	 checksum
2784    3	common/cmd_bootm.c	Image header has correct checksum
2785   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2786    4	common/cmd_bootm.c	Image data   has correct checksum
2787   -4	common/cmd_bootm.c	Image is for unsupported architecture
2788    5	common/cmd_bootm.c	Architecture check OK
2789   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2790    6	common/cmd_bootm.c	Image Type check OK
2791   -6	common/cmd_bootm.c	gunzip uncompression error
2792   -7	common/cmd_bootm.c	Unimplemented compression type
2793    7	common/cmd_bootm.c	Uncompression OK
2794    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2795   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2796
2797    9	common/image.c		Start initial ramdisk verification
2798  -10	common/image.c		Ramdisk header has bad	   magic number
2799  -11	common/image.c		Ramdisk header has bad	   checksum
2800   10	common/image.c		Ramdisk header is OK
2801  -12	common/image.c		Ramdisk data   has bad	   checksum
2802   11	common/image.c		Ramdisk data   has correct checksum
2803   12	common/image.c		Ramdisk verification complete, start loading
2804  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2805   13	common/image.c		Start multifile image verification
2806   14	common/image.c		No initial ramdisk, no multifile, continue.
2807
2808   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2809
2810  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2811  -31	post/post.c		POST test failed, detected by post_output_backlog()
2812  -32	post/post.c		POST test failed, detected by post_run_single()
2813
2814   34	common/cmd_doc.c	before loading a Image from a DOC device
2815  -35	common/cmd_doc.c	Bad usage of "doc" command
2816   35	common/cmd_doc.c	correct usage of "doc" command
2817  -36	common/cmd_doc.c	No boot device
2818   36	common/cmd_doc.c	correct boot device
2819  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2820   37	common/cmd_doc.c	correct chip ID found, device available
2821  -38	common/cmd_doc.c	Read Error on boot device
2822   38	common/cmd_doc.c	reading Image header from DOC device OK
2823  -39	common/cmd_doc.c	Image header has bad magic number
2824   39	common/cmd_doc.c	Image header has correct magic number
2825  -40	common/cmd_doc.c	Error reading Image from DOC device
2826   40	common/cmd_doc.c	Image header has correct magic number
2827   41	common/cmd_ide.c	before loading a Image from a IDE device
2828  -42	common/cmd_ide.c	Bad usage of "ide" command
2829   42	common/cmd_ide.c	correct usage of "ide" command
2830  -43	common/cmd_ide.c	No boot device
2831   43	common/cmd_ide.c	boot device found
2832  -44	common/cmd_ide.c	Device not available
2833   44	common/cmd_ide.c	Device available
2834  -45	common/cmd_ide.c	wrong partition selected
2835   45	common/cmd_ide.c	partition selected
2836  -46	common/cmd_ide.c	Unknown partition table
2837   46	common/cmd_ide.c	valid partition table found
2838  -47	common/cmd_ide.c	Invalid partition type
2839   47	common/cmd_ide.c	correct partition type
2840  -48	common/cmd_ide.c	Error reading Image Header on boot device
2841   48	common/cmd_ide.c	reading Image Header from IDE device OK
2842  -49	common/cmd_ide.c	Image header has bad magic number
2843   49	common/cmd_ide.c	Image header has correct magic number
2844  -50	common/cmd_ide.c	Image header has bad	 checksum
2845   50	common/cmd_ide.c	Image header has correct checksum
2846  -51	common/cmd_ide.c	Error reading Image from IDE device
2847   51	common/cmd_ide.c	reading Image from IDE device OK
2848   52	common/cmd_nand.c	before loading a Image from a NAND device
2849  -53	common/cmd_nand.c	Bad usage of "nand" command
2850   53	common/cmd_nand.c	correct usage of "nand" command
2851  -54	common/cmd_nand.c	No boot device
2852   54	common/cmd_nand.c	boot device found
2853  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2854   55	common/cmd_nand.c	correct chip ID found, device available
2855  -56	common/cmd_nand.c	Error reading Image Header on boot device
2856   56	common/cmd_nand.c	reading Image Header from NAND device OK
2857  -57	common/cmd_nand.c	Image header has bad magic number
2858   57	common/cmd_nand.c	Image header has correct magic number
2859  -58	common/cmd_nand.c	Error reading Image from NAND device
2860   58	common/cmd_nand.c	reading Image from NAND device OK
2861
2862  -60	common/env_common.c	Environment has a bad CRC, using default
2863
2864   64	net/eth.c		starting with Ethernet configuration.
2865  -64	net/eth.c		no Ethernet found.
2866   65	net/eth.c		Ethernet found.
2867
2868  -80	common/cmd_net.c	usage wrong
2869   80	common/cmd_net.c	before calling net_loop()
2870  -81	common/cmd_net.c	some error in net_loop() occurred
2871   81	common/cmd_net.c	net_loop() back without error
2872  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2873   82	common/cmd_net.c	trying automatic boot
2874   83	common/cmd_net.c	running "source" command
2875  -83	common/cmd_net.c	some error in automatic boot or "source" command
2876   84	common/cmd_net.c	end without errors
2877
2878FIT uImage format:
2879
2880  Arg	Where			When
2881  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2882 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2883  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2884 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2885  102	common/cmd_bootm.c	Kernel unit name specified
2886 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2887  103	common/cmd_bootm.c	Found configuration node
2888  104	common/cmd_bootm.c	Got kernel subimage node offset
2889 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2890  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2891 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2892  106	common/cmd_bootm.c	Architecture check OK
2893 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2894  107	common/cmd_bootm.c	Kernel subimage type OK
2895 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2896  108	common/cmd_bootm.c	Got kernel subimage data/size
2897 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2898 -109	common/cmd_bootm.c	Can't get kernel subimage type
2899 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2900 -111	common/cmd_bootm.c	Can't get kernel subimage os
2901 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2902 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2903
2904  120	common/image.c		Start initial ramdisk verification
2905 -120	common/image.c		Ramdisk FIT image has incorrect format
2906  121	common/image.c		Ramdisk FIT image has correct format
2907  122	common/image.c		No ramdisk subimage unit name, using configuration
2908 -122	common/image.c		Can't get configuration for ramdisk subimage
2909  123	common/image.c		Ramdisk unit name specified
2910 -124	common/image.c		Can't get ramdisk subimage node offset
2911  125	common/image.c		Got ramdisk subimage node offset
2912 -125	common/image.c		Ramdisk subimage hash verification failed
2913  126	common/image.c		Ramdisk subimage hash verification OK
2914 -126	common/image.c		Ramdisk subimage for unsupported architecture
2915  127	common/image.c		Architecture check OK
2916 -127	common/image.c		Can't get ramdisk subimage data/size
2917  128	common/image.c		Got ramdisk subimage data/size
2918  129	common/image.c		Can't get ramdisk load address
2919 -129	common/image.c		Got ramdisk load address
2920
2921 -130	common/cmd_doc.c	Incorrect FIT image format
2922  131	common/cmd_doc.c	FIT image format OK
2923
2924 -140	common/cmd_ide.c	Incorrect FIT image format
2925  141	common/cmd_ide.c	FIT image format OK
2926
2927 -150	common/cmd_nand.c	Incorrect FIT image format
2928  151	common/cmd_nand.c	FIT image format OK
2929
2930- legacy image format:
2931		CONFIG_IMAGE_FORMAT_LEGACY
2932		enables the legacy image format support in U-Boot.
2933
2934		Default:
2935		enabled if CONFIG_FIT_SIGNATURE is not defined.
2936
2937		CONFIG_DISABLE_IMAGE_LEGACY
2938		disable the legacy image format
2939
2940		This define is introduced, as the legacy image format is
2941		enabled per default for backward compatibility.
2942
2943- Standalone program support:
2944		CONFIG_STANDALONE_LOAD_ADDR
2945
2946		This option defines a board specific value for the
2947		address where standalone program gets loaded, thus
2948		overwriting the architecture dependent default
2949		settings.
2950
2951- Frame Buffer Address:
2952		CONFIG_FB_ADDR
2953
2954		Define CONFIG_FB_ADDR if you want to use specific
2955		address for frame buffer.  This is typically the case
2956		when using a graphics controller has separate video
2957		memory.  U-Boot will then place the frame buffer at
2958		the given address instead of dynamically reserving it
2959		in system RAM by calling lcd_setmem(), which grabs
2960		the memory for the frame buffer depending on the
2961		configured panel size.
2962
2963		Please see board_init_f function.
2964
2965- Automatic software updates via TFTP server
2966		CONFIG_UPDATE_TFTP
2967		CONFIG_UPDATE_TFTP_CNT_MAX
2968		CONFIG_UPDATE_TFTP_MSEC_MAX
2969
2970		These options enable and control the auto-update feature;
2971		for a more detailed description refer to doc/README.update.
2972
2973- MTD Support (mtdparts command, UBI support)
2974		CONFIG_MTD_DEVICE
2975
2976		Adds the MTD device infrastructure from the Linux kernel.
2977		Needed for mtdparts command support.
2978
2979		CONFIG_MTD_PARTITIONS
2980
2981		Adds the MTD partitioning infrastructure from the Linux
2982		kernel. Needed for UBI support.
2983
2984- UBI support
2985		CONFIG_CMD_UBI
2986
2987		Adds commands for interacting with MTD partitions formatted
2988		with the UBI flash translation layer
2989
2990		Requires also defining CONFIG_RBTREE
2991
2992		CONFIG_UBI_SILENCE_MSG
2993
2994		Make the verbose messages from UBI stop printing.  This leaves
2995		warnings and errors enabled.
2996
2997
2998		CONFIG_MTD_UBI_WL_THRESHOLD
2999		This parameter defines the maximum difference between the highest
3000		erase counter value and the lowest erase counter value of eraseblocks
3001		of UBI devices. When this threshold is exceeded, UBI starts performing
3002		wear leveling by means of moving data from eraseblock with low erase
3003		counter to eraseblocks with high erase counter.
3004
3005		The default value should be OK for SLC NAND flashes, NOR flashes and
3006		other flashes which have eraseblock life-cycle 100000 or more.
3007		However, in case of MLC NAND flashes which typically have eraseblock
3008		life-cycle less than 10000, the threshold should be lessened (e.g.,
3009		to 128 or 256, although it does not have to be power of 2).
3010
3011		default: 4096
3012
3013		CONFIG_MTD_UBI_BEB_LIMIT
3014		This option specifies the maximum bad physical eraseblocks UBI
3015		expects on the MTD device (per 1024 eraseblocks). If the
3016		underlying flash does not admit of bad eraseblocks (e.g. NOR
3017		flash), this value is ignored.
3018
3019		NAND datasheets often specify the minimum and maximum NVM
3020		(Number of Valid Blocks) for the flashes' endurance lifetime.
3021		The maximum expected bad eraseblocks per 1024 eraseblocks
3022		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
3023		which gives 20 for most NANDs (MaxNVB is basically the total
3024		count of eraseblocks on the chip).
3025
3026		To put it differently, if this value is 20, UBI will try to
3027		reserve about 1.9% of physical eraseblocks for bad blocks
3028		handling. And that will be 1.9% of eraseblocks on the entire
3029		NAND chip, not just the MTD partition UBI attaches. This means
3030		that if you have, say, a NAND flash chip admits maximum 40 bad
3031		eraseblocks, and it is split on two MTD partitions of the same
3032		size, UBI will reserve 40 eraseblocks when attaching a
3033		partition.
3034
3035		default: 20
3036
3037		CONFIG_MTD_UBI_FASTMAP
3038		Fastmap is a mechanism which allows attaching an UBI device
3039		in nearly constant time. Instead of scanning the whole MTD device it
3040		only has to locate a checkpoint (called fastmap) on the device.
3041		The on-flash fastmap contains all information needed to attach
3042		the device. Using fastmap makes only sense on large devices where
3043		attaching by scanning takes long. UBI will not automatically install
3044		a fastmap on old images, but you can set the UBI parameter
3045		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
3046		that fastmap-enabled images are still usable with UBI implementations
3047		without	fastmap support. On typical flash devices the whole fastmap
3048		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
3049
3050		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
3051		Set this parameter to enable fastmap automatically on images
3052		without a fastmap.
3053		default: 0
3054
3055		CONFIG_MTD_UBI_FM_DEBUG
3056		Enable UBI fastmap debug
3057		default: 0
3058
3059- UBIFS support
3060		CONFIG_CMD_UBIFS
3061
3062		Adds commands for interacting with UBI volumes formatted as
3063		UBIFS.  UBIFS is read-only in u-boot.
3064
3065		Requires UBI support as well as CONFIG_LZO
3066
3067		CONFIG_UBIFS_SILENCE_MSG
3068
3069		Make the verbose messages from UBIFS stop printing.  This leaves
3070		warnings and errors enabled.
3071
3072- SPL framework
3073		CONFIG_SPL
3074		Enable building of SPL globally.
3075
3076		CONFIG_SPL_LDSCRIPT
3077		LDSCRIPT for linking the SPL binary.
3078
3079		CONFIG_SPL_MAX_FOOTPRINT
3080		Maximum size in memory allocated to the SPL, BSS included.
3081		When defined, the linker checks that the actual memory
3082		used by SPL from _start to __bss_end does not exceed it.
3083		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3084		must not be both defined at the same time.
3085
3086		CONFIG_SPL_MAX_SIZE
3087		Maximum size of the SPL image (text, data, rodata, and
3088		linker lists sections), BSS excluded.
3089		When defined, the linker checks that the actual size does
3090		not exceed it.
3091
3092		CONFIG_SPL_TEXT_BASE
3093		TEXT_BASE for linking the SPL binary.
3094
3095		CONFIG_SPL_RELOC_TEXT_BASE
3096		Address to relocate to.  If unspecified, this is equal to
3097		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
3098
3099		CONFIG_SPL_BSS_START_ADDR
3100		Link address for the BSS within the SPL binary.
3101
3102		CONFIG_SPL_BSS_MAX_SIZE
3103		Maximum size in memory allocated to the SPL BSS.
3104		When defined, the linker checks that the actual memory used
3105		by SPL from __bss_start to __bss_end does not exceed it.
3106		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
3107		must not be both defined at the same time.
3108
3109		CONFIG_SPL_STACK
3110		Adress of the start of the stack SPL will use
3111
3112		CONFIG_SPL_PANIC_ON_RAW_IMAGE
3113		When defined, SPL will panic() if the image it has
3114		loaded does not have a signature.
3115		Defining this is useful when code which loads images
3116		in SPL cannot guarantee that absolutely all read errors
3117		will be caught.
3118		An example is the LPC32XX MLC NAND driver, which will
3119		consider that a completely unreadable NAND block is bad,
3120		and thus should be skipped silently.
3121
3122		CONFIG_SPL_RELOC_STACK
3123		Adress of the start of the stack SPL will use after
3124		relocation.  If unspecified, this is equal to
3125		CONFIG_SPL_STACK.
3126
3127		CONFIG_SYS_SPL_MALLOC_START
3128		Starting address of the malloc pool used in SPL.
3129		When this option is set the full malloc is used in SPL and
3130		it is set up by spl_init() and before that, the simple malloc()
3131		can be used if CONFIG_SYS_MALLOC_F is defined.
3132
3133		CONFIG_SYS_SPL_MALLOC_SIZE
3134		The size of the malloc pool used in SPL.
3135
3136		CONFIG_SPL_FRAMEWORK
3137		Enable the SPL framework under common/.  This framework
3138		supports MMC, NAND and YMODEM loading of U-Boot and NAND
3139		NAND loading of the Linux Kernel.
3140
3141		CONFIG_SPL_OS_BOOT
3142		Enable booting directly to an OS from SPL.
3143		See also: doc/README.falcon
3144
3145		CONFIG_SPL_DISPLAY_PRINT
3146		For ARM, enable an optional function to print more information
3147		about the running system.
3148
3149		CONFIG_SPL_INIT_MINIMAL
3150		Arch init code should be built for a very small image
3151
3152		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
3153		Partition on the MMC to load U-Boot from when the MMC is being
3154		used in raw mode
3155
3156		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
3157		Sector to load kernel uImage from when MMC is being
3158		used in raw mode (for Falcon mode)
3159
3160		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
3161		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
3162		Sector and number of sectors to load kernel argument
3163		parameters from when MMC is being used in raw mode
3164		(for falcon mode)
3165
3166		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
3167		Partition on the MMC to load U-Boot from when the MMC is being
3168		used in fs mode
3169
3170		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
3171		Filename to read to load U-Boot when reading from filesystem
3172
3173		CONFIG_SPL_FS_LOAD_KERNEL_NAME
3174		Filename to read to load kernel uImage when reading
3175		from filesystem (for Falcon mode)
3176
3177		CONFIG_SPL_FS_LOAD_ARGS_NAME
3178		Filename to read to load kernel argument parameters
3179		when reading from filesystem (for Falcon mode)
3180
3181		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
3182		Set this for NAND SPL on PPC mpc83xx targets, so that
3183		start.S waits for the rest of the SPL to load before
3184		continuing (the hardware starts execution after just
3185		loading the first page rather than the full 4K).
3186
3187		CONFIG_SPL_SKIP_RELOCATE
3188		Avoid SPL relocation
3189
3190		CONFIG_SPL_NAND_BASE
3191		Include nand_base.c in the SPL.  Requires
3192		CONFIG_SPL_NAND_DRIVERS.
3193
3194		CONFIG_SPL_NAND_DRIVERS
3195		SPL uses normal NAND drivers, not minimal drivers.
3196
3197		CONFIG_SPL_NAND_ECC
3198		Include standard software ECC in the SPL
3199
3200		CONFIG_SPL_NAND_SIMPLE
3201		Support for NAND boot using simple NAND drivers that
3202		expose the cmd_ctrl() interface.
3203
3204		CONFIG_SPL_UBI
3205		Support for a lightweight UBI (fastmap) scanner and
3206		loader
3207
3208		CONFIG_SPL_NAND_RAW_ONLY
3209		Support to boot only raw u-boot.bin images. Use this only
3210		if you need to save space.
3211
3212		CONFIG_SPL_COMMON_INIT_DDR
3213		Set for common ddr init with serial presence detect in
3214		SPL binary.
3215
3216		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
3217		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
3218		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
3219		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
3220		CONFIG_SYS_NAND_ECCBYTES
3221		Defines the size and behavior of the NAND that SPL uses
3222		to read U-Boot
3223
3224		CONFIG_SPL_NAND_BOOT
3225		Add support NAND boot
3226
3227		CONFIG_SYS_NAND_U_BOOT_OFFS
3228		Location in NAND to read U-Boot from
3229
3230		CONFIG_SYS_NAND_U_BOOT_DST
3231		Location in memory to load U-Boot to
3232
3233		CONFIG_SYS_NAND_U_BOOT_SIZE
3234		Size of image to load
3235
3236		CONFIG_SYS_NAND_U_BOOT_START
3237		Entry point in loaded image to jump to
3238
3239		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
3240		Define this if you need to first read the OOB and then the
3241		data. This is used, for example, on davinci platforms.
3242
3243		CONFIG_SPL_OMAP3_ID_NAND
3244		Support for an OMAP3-specific set of functions to return the
3245		ID and MFR of the first attached NAND chip, if present.
3246
3247		CONFIG_SPL_RAM_DEVICE
3248		Support for running image already present in ram, in SPL binary
3249
3250		CONFIG_SPL_PAD_TO
3251		Image offset to which the SPL should be padded before appending
3252		the SPL payload. By default, this is defined as
3253		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3254		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3255		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3256
3257		CONFIG_SPL_TARGET
3258		Final target image containing SPL and payload.  Some SPLs
3259		use an arch-specific makefile fragment instead, for
3260		example if more than one image needs to be produced.
3261
3262		CONFIG_FIT_SPL_PRINT
3263		Printing information about a FIT image adds quite a bit of
3264		code to SPL. So this is normally disabled in SPL. Use this
3265		option to re-enable it. This will affect the output of the
3266		bootm command when booting a FIT image.
3267
3268- TPL framework
3269		CONFIG_TPL
3270		Enable building of TPL globally.
3271
3272		CONFIG_TPL_PAD_TO
3273		Image offset to which the TPL should be padded before appending
3274		the TPL payload. By default, this is defined as
3275		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
3276		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
3277		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
3278
3279- Interrupt support (PPC):
3280
3281		There are common interrupt_init() and timer_interrupt()
3282		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
3283		for CPU specific initialization. interrupt_init_cpu()
3284		should set decrementer_count to appropriate value. If
3285		CPU resets decrementer automatically after interrupt
3286		(ppc4xx) it should set decrementer_count to zero.
3287		timer_interrupt() calls timer_interrupt_cpu() for CPU
3288		specific handling. If board has watchdog / status_led
3289		/ other_activity_monitor it works automatically from
3290		general timer_interrupt().
3291
3292
3293Board initialization settings:
3294------------------------------
3295
3296During Initialization u-boot calls a number of board specific functions
3297to allow the preparation of board specific prerequisites, e.g. pin setup
3298before drivers are initialized. To enable these callbacks the
3299following configuration macros have to be defined. Currently this is
3300architecture specific, so please check arch/your_architecture/lib/board.c
3301typically in board_init_f() and board_init_r().
3302
3303- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
3304- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
3305- CONFIG_BOARD_LATE_INIT: Call board_late_init()
3306- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
3307
3308Configuration Settings:
3309-----------------------
3310
3311- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
3312		Optionally it can be defined to support 64-bit memory commands.
3313
3314- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
3315		undefine this when you're short of memory.
3316
3317- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
3318		width of the commands listed in the 'help' command output.
3319
3320- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
3321		prompt for user input.
3322
3323- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
3324
3325- CONFIG_SYS_PBSIZE:	Buffer size for Console output
3326
3327- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
3328
3329- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
3330		the application (usually a Linux kernel) when it is
3331		booted
3332
3333- CONFIG_SYS_BAUDRATE_TABLE:
3334		List of legal baudrate settings for this board.
3335
3336- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
3337		Begin and End addresses of the area used by the
3338		simple memory test.
3339
3340- CONFIG_SYS_ALT_MEMTEST:
3341		Enable an alternate, more extensive memory test.
3342
3343- CONFIG_SYS_MEMTEST_SCRATCH:
3344		Scratch address used by the alternate memory test
3345		You only need to set this if address zero isn't writeable
3346
3347- CONFIG_SYS_MEM_RESERVE_SECURE
3348		Only implemented for ARMv8 for now.
3349		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
3350		is substracted from total RAM and won't be reported to OS.
3351		This memory can be used as secure memory. A variable
3352		gd->arch.secure_ram is used to track the location. In systems
3353		the RAM base is not zero, or RAM is divided into banks,
3354		this variable needs to be recalcuated to get the address.
3355
3356- CONFIG_SYS_MEM_TOP_HIDE:
3357		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
3358		this specified memory area will get subtracted from the top
3359		(end) of RAM and won't get "touched" at all by U-Boot. By
3360		fixing up gd->ram_size the Linux kernel should gets passed
3361		the now "corrected" memory size and won't touch it either.
3362		This should work for arch/ppc and arch/powerpc. Only Linux
3363		board ports in arch/powerpc with bootwrapper support that
3364		recalculate the memory size from the SDRAM controller setup
3365		will have to get fixed in Linux additionally.
3366
3367		This option can be used as a workaround for the 440EPx/GRx
3368		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
3369		be touched.
3370
3371		WARNING: Please make sure that this value is a multiple of
3372		the Linux page size (normally 4k). If this is not the case,
3373		then the end address of the Linux memory will be located at a
3374		non page size aligned address and this could cause major
3375		problems.
3376
3377- CONFIG_SYS_LOADS_BAUD_CHANGE:
3378		Enable temporary baudrate change while serial download
3379
3380- CONFIG_SYS_SDRAM_BASE:
3381		Physical start address of SDRAM. _Must_ be 0 here.
3382
3383- CONFIG_SYS_FLASH_BASE:
3384		Physical start address of Flash memory.
3385
3386- CONFIG_SYS_MONITOR_BASE:
3387		Physical start address of boot monitor code (set by
3388		make config files to be same as the text base address
3389		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
3390		CONFIG_SYS_FLASH_BASE when booting from flash.
3391
3392- CONFIG_SYS_MONITOR_LEN:
3393		Size of memory reserved for monitor code, used to
3394		determine _at_compile_time_ (!) if the environment is
3395		embedded within the U-Boot image, or in a separate
3396		flash sector.
3397
3398- CONFIG_SYS_MALLOC_LEN:
3399		Size of DRAM reserved for malloc() use.
3400
3401- CONFIG_SYS_MALLOC_F_LEN
3402		Size of the malloc() pool for use before relocation. If
3403		this is defined, then a very simple malloc() implementation
3404		will become available before relocation. The address is just
3405		below the global data, and the stack is moved down to make
3406		space.
3407
3408		This feature allocates regions with increasing addresses
3409		within the region. calloc() is supported, but realloc()
3410		is not available. free() is supported but does nothing.
3411		The memory will be freed (or in fact just forgotten) when
3412		U-Boot relocates itself.
3413
3414- CONFIG_SYS_MALLOC_SIMPLE
3415		Provides a simple and small malloc() and calloc() for those
3416		boards which do not use the full malloc in SPL (which is
3417		enabled with CONFIG_SYS_SPL_MALLOC_START).
3418
3419- CONFIG_SYS_NONCACHED_MEMORY:
3420		Size of non-cached memory area. This area of memory will be
3421		typically located right below the malloc() area and mapped
3422		uncached in the MMU. This is useful for drivers that would
3423		otherwise require a lot of explicit cache maintenance. For
3424		some drivers it's also impossible to properly maintain the
3425		cache. For example if the regions that need to be flushed
3426		are not a multiple of the cache-line size, *and* padding
3427		cannot be allocated between the regions to align them (i.e.
3428		if the HW requires a contiguous array of regions, and the
3429		size of each region is not cache-aligned), then a flush of
3430		one region may result in overwriting data that hardware has
3431		written to another region in the same cache-line. This can
3432		happen for example in network drivers where descriptors for
3433		buffers are typically smaller than the CPU cache-line (e.g.
3434		16 bytes vs. 32 or 64 bytes).
3435
3436		Non-cached memory is only supported on 32-bit ARM at present.
3437
3438- CONFIG_SYS_BOOTM_LEN:
3439		Normally compressed uImages are limited to an
3440		uncompressed size of 8 MBytes. If this is not enough,
3441		you can define CONFIG_SYS_BOOTM_LEN in your board config file
3442		to adjust this setting to your needs.
3443
3444- CONFIG_SYS_BOOTMAPSZ:
3445		Maximum size of memory mapped by the startup code of
3446		the Linux kernel; all data that must be processed by
3447		the Linux kernel (bd_info, boot arguments, FDT blob if
3448		used) must be put below this limit, unless "bootm_low"
3449		environment variable is defined and non-zero. In such case
3450		all data for the Linux kernel must be between "bootm_low"
3451		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
3452		variable "bootm_mapsize" will override the value of
3453		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
3454		then the value in "bootm_size" will be used instead.
3455
3456- CONFIG_SYS_BOOT_RAMDISK_HIGH:
3457		Enable initrd_high functionality.  If defined then the
3458		initrd_high feature is enabled and the bootm ramdisk subcommand
3459		is enabled.
3460
3461- CONFIG_SYS_BOOT_GET_CMDLINE:
3462		Enables allocating and saving kernel cmdline in space between
3463		"bootm_low" and "bootm_low" + BOOTMAPSZ.
3464
3465- CONFIG_SYS_BOOT_GET_KBD:
3466		Enables allocating and saving a kernel copy of the bd_info in
3467		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
3468
3469- CONFIG_SYS_MAX_FLASH_BANKS:
3470		Max number of Flash memory banks
3471
3472- CONFIG_SYS_MAX_FLASH_SECT:
3473		Max number of sectors on a Flash chip
3474
3475- CONFIG_SYS_FLASH_ERASE_TOUT:
3476		Timeout for Flash erase operations (in ms)
3477
3478- CONFIG_SYS_FLASH_WRITE_TOUT:
3479		Timeout for Flash write operations (in ms)
3480
3481- CONFIG_SYS_FLASH_LOCK_TOUT
3482		Timeout for Flash set sector lock bit operation (in ms)
3483
3484- CONFIG_SYS_FLASH_UNLOCK_TOUT
3485		Timeout for Flash clear lock bits operation (in ms)
3486
3487- CONFIG_SYS_FLASH_PROTECTION
3488		If defined, hardware flash sectors protection is used
3489		instead of U-Boot software protection.
3490
3491- CONFIG_SYS_DIRECT_FLASH_TFTP:
3492
3493		Enable TFTP transfers directly to flash memory;
3494		without this option such a download has to be
3495		performed in two steps: (1) download to RAM, and (2)
3496		copy from RAM to flash.
3497
3498		The two-step approach is usually more reliable, since
3499		you can check if the download worked before you erase
3500		the flash, but in some situations (when system RAM is
3501		too limited to allow for a temporary copy of the
3502		downloaded image) this option may be very useful.
3503
3504- CONFIG_SYS_FLASH_CFI:
3505		Define if the flash driver uses extra elements in the
3506		common flash structure for storing flash geometry.
3507
3508- CONFIG_FLASH_CFI_DRIVER
3509		This option also enables the building of the cfi_flash driver
3510		in the drivers directory
3511
3512- CONFIG_FLASH_CFI_MTD
3513		This option enables the building of the cfi_mtd driver
3514		in the drivers directory. The driver exports CFI flash
3515		to the MTD layer.
3516
3517- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
3518		Use buffered writes to flash.
3519
3520- CONFIG_FLASH_SPANSION_S29WS_N
3521		s29ws-n MirrorBit flash has non-standard addresses for buffered
3522		write commands.
3523
3524- CONFIG_SYS_FLASH_QUIET_TEST
3525		If this option is defined, the common CFI flash doesn't
3526		print it's warning upon not recognized FLASH banks. This
3527		is useful, if some of the configured banks are only
3528		optionally available.
3529
3530- CONFIG_FLASH_SHOW_PROGRESS
3531		If defined (must be an integer), print out countdown
3532		digits and dots.  Recommended value: 45 (9..1) for 80
3533		column displays, 15 (3..1) for 40 column displays.
3534
3535- CONFIG_FLASH_VERIFY
3536		If defined, the content of the flash (destination) is compared
3537		against the source after the write operation. An error message
3538		will be printed when the contents are not identical.
3539		Please note that this option is useless in nearly all cases,
3540		since such flash programming errors usually are detected earlier
3541		while unprotecting/erasing/programming. Please only enable
3542		this option if you really know what you are doing.
3543
3544- CONFIG_SYS_RX_ETH_BUFFER:
3545		Defines the number of Ethernet receive buffers. On some
3546		Ethernet controllers it is recommended to set this value
3547		to 8 or even higher (EEPRO100 or 405 EMAC), since all
3548		buffers can be full shortly after enabling the interface
3549		on high Ethernet traffic.
3550		Defaults to 4 if not defined.
3551
3552- CONFIG_ENV_MAX_ENTRIES
3553
3554	Maximum number of entries in the hash table that is used
3555	internally to store the environment settings. The default
3556	setting is supposed to be generous and should work in most
3557	cases. This setting can be used to tune behaviour; see
3558	lib/hashtable.c for details.
3559
3560- CONFIG_ENV_FLAGS_LIST_DEFAULT
3561- CONFIG_ENV_FLAGS_LIST_STATIC
3562	Enable validation of the values given to environment variables when
3563	calling env set.  Variables can be restricted to only decimal,
3564	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
3565	the variables can also be restricted to IP address or MAC address.
3566
3567	The format of the list is:
3568		type_attribute = [s|d|x|b|i|m]
3569		access_attribute = [a|r|o|c]
3570		attributes = type_attribute[access_attribute]
3571		entry = variable_name[:attributes]
3572		list = entry[,list]
3573
3574	The type attributes are:
3575		s - String (default)
3576		d - Decimal
3577		x - Hexadecimal
3578		b - Boolean ([1yYtT|0nNfF])
3579		i - IP address
3580		m - MAC address
3581
3582	The access attributes are:
3583		a - Any (default)
3584		r - Read-only
3585		o - Write-once
3586		c - Change-default
3587
3588	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3589		Define this to a list (string) to define the ".flags"
3590		environment variable in the default or embedded environment.
3591
3592	- CONFIG_ENV_FLAGS_LIST_STATIC
3593		Define this to a list (string) to define validation that
3594		should be done if an entry is not found in the ".flags"
3595		environment variable.  To override a setting in the static
3596		list, simply add an entry for the same variable name to the
3597		".flags" variable.
3598
3599	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3600	regular expression. This allows multiple variables to define the same
3601	flags without explicitly listing them for each variable.
3602
3603- CONFIG_ENV_ACCESS_IGNORE_FORCE
3604	If defined, don't allow the -f switch to env set override variable
3605	access flags.
3606
3607- CONFIG_USE_STDINT
3608	If stdint.h is available with your toolchain you can define this
3609	option to enable it. You can provide option 'USE_STDINT=1' when
3610	building U-Boot to enable this.
3611
3612The following definitions that deal with the placement and management
3613of environment data (variable area); in general, we support the
3614following configurations:
3615
3616- CONFIG_BUILD_ENVCRC:
3617
3618	Builds up envcrc with the target environment so that external utils
3619	may easily extract it and embed it in final U-Boot images.
3620
3621- CONFIG_ENV_IS_IN_FLASH:
3622
3623	Define this if the environment is in flash memory.
3624
3625	a) The environment occupies one whole flash sector, which is
3626	   "embedded" in the text segment with the U-Boot code. This
3627	   happens usually with "bottom boot sector" or "top boot
3628	   sector" type flash chips, which have several smaller
3629	   sectors at the start or the end. For instance, such a
3630	   layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
3631	   such a case you would place the environment in one of the
3632	   4 kB sectors - with U-Boot code before and after it. With
3633	   "top boot sector" type flash chips, you would put the
3634	   environment in one of the last sectors, leaving a gap
3635	   between U-Boot and the environment.
3636
3637	- CONFIG_ENV_OFFSET:
3638
3639	   Offset of environment data (variable area) to the
3640	   beginning of flash memory; for instance, with bottom boot
3641	   type flash chips the second sector can be used: the offset
3642	   for this sector is given here.
3643
3644	   CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE.
3645
3646	- CONFIG_ENV_ADDR:
3647
3648	   This is just another way to specify the start address of
3649	   the flash sector containing the environment (instead of
3650	   CONFIG_ENV_OFFSET).
3651
3652	- CONFIG_ENV_SECT_SIZE:
3653
3654	   Size of the sector containing the environment.
3655
3656
3657	b) Sometimes flash chips have few, equal sized, BIG sectors.
3658	   In such a case you don't want to spend a whole sector for
3659	   the environment.
3660
3661	- CONFIG_ENV_SIZE:
3662
3663	   If you use this in combination with CONFIG_ENV_IS_IN_FLASH
3664	   and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
3665	   of this flash sector for the environment. This saves
3666	   memory for the RAM copy of the environment.
3667
3668	   It may also save flash memory if you decide to use this
3669	   when your environment is "embedded" within U-Boot code,
3670	   since then the remainder of the flash sector could be used
3671	   for U-Boot code. It should be pointed out that this is
3672	   STRONGLY DISCOURAGED from a robustness point of view:
3673	   updating the environment in flash makes it always
3674	   necessary to erase the WHOLE sector. If something goes
3675	   wrong before the contents has been restored from a copy in
3676	   RAM, your target system will be dead.
3677
3678	- CONFIG_ENV_ADDR_REDUND
3679	  CONFIG_ENV_SIZE_REDUND
3680
3681	   These settings describe a second storage area used to hold
3682	   a redundant copy of the environment data, so that there is
3683	   a valid backup copy in case there is a power failure during
3684	   a "saveenv" operation.
3685
3686BE CAREFUL! Any changes to the flash layout, and some changes to the
3687source code will make it necessary to adapt <board>/u-boot.lds*
3688accordingly!
3689
3690
3691- CONFIG_ENV_IS_IN_NVRAM:
3692
3693	Define this if you have some non-volatile memory device
3694	(NVRAM, battery buffered SRAM) which you want to use for the
3695	environment.
3696
3697	- CONFIG_ENV_ADDR:
3698	- CONFIG_ENV_SIZE:
3699
3700	  These two #defines are used to determine the memory area you
3701	  want to use for environment. It is assumed that this memory
3702	  can just be read and written to, without any special
3703	  provision.
3704
3705BE CAREFUL! The first access to the environment happens quite early
3706in U-Boot initialization (when we try to get the setting of for the
3707console baudrate). You *MUST* have mapped your NVRAM area then, or
3708U-Boot will hang.
3709
3710Please note that even with NVRAM we still use a copy of the
3711environment in RAM: we could work on NVRAM directly, but we want to
3712keep settings there always unmodified except somebody uses "saveenv"
3713to save the current settings.
3714
3715
3716- CONFIG_ENV_IS_IN_EEPROM:
3717
3718	Use this if you have an EEPROM or similar serial access
3719	device and a driver for it.
3720
3721	- CONFIG_ENV_OFFSET:
3722	- CONFIG_ENV_SIZE:
3723
3724	  These two #defines specify the offset and size of the
3725	  environment area within the total memory of your EEPROM.
3726
3727	- CONFIG_SYS_I2C_EEPROM_ADDR:
3728	  If defined, specified the chip address of the EEPROM device.
3729	  The default address is zero.
3730
3731	- CONFIG_SYS_I2C_EEPROM_BUS:
3732	  If defined, specified the i2c bus of the EEPROM device.
3733
3734	- CONFIG_SYS_EEPROM_PAGE_WRITE_BITS:
3735	  If defined, the number of bits used to address bytes in a
3736	  single page in the EEPROM device.  A 64 byte page, for example
3737	  would require six bits.
3738
3739	- CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS:
3740	  If defined, the number of milliseconds to delay between
3741	  page writes.	The default is zero milliseconds.
3742
3743	- CONFIG_SYS_I2C_EEPROM_ADDR_LEN:
3744	  The length in bytes of the EEPROM memory array address.  Note
3745	  that this is NOT the chip address length!
3746
3747	- CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW:
3748	  EEPROM chips that implement "address overflow" are ones
3749	  like Catalyst 24WC04/08/16 which has 9/10/11 bits of
3750	  address and the extra bits end up in the "chip address" bit
3751	  slots. This makes a 24WC08 (1Kbyte) chip look like four 256
3752	  byte chips.
3753
3754	  Note that we consider the length of the address field to
3755	  still be one byte because the extra address bits are hidden
3756	  in the chip address.
3757
3758	- CONFIG_SYS_EEPROM_SIZE:
3759	  The size in bytes of the EEPROM device.
3760
3761	- CONFIG_ENV_EEPROM_IS_ON_I2C
3762	  define this, if you have I2C and SPI activated, and your
3763	  EEPROM, which holds the environment, is on the I2C bus.
3764
3765	- CONFIG_I2C_ENV_EEPROM_BUS
3766	  if you have an Environment on an EEPROM reached over
3767	  I2C muxes, you can define here, how to reach this
3768	  EEPROM. For example:
3769
3770	  #define CONFIG_I2C_ENV_EEPROM_BUS	  1
3771
3772	  EEPROM which holds the environment, is reached over
3773	  a pca9547 i2c mux with address 0x70, channel 3.
3774
3775- CONFIG_ENV_IS_IN_DATAFLASH:
3776
3777	Define this if you have a DataFlash memory device which you
3778	want to use for the environment.
3779
3780	- CONFIG_ENV_OFFSET:
3781	- CONFIG_ENV_ADDR:
3782	- CONFIG_ENV_SIZE:
3783
3784	  These three #defines specify the offset and size of the
3785	  environment area within the total memory of your DataFlash placed
3786	  at the specified address.
3787
3788- CONFIG_ENV_IS_IN_SPI_FLASH:
3789
3790	Define this if you have a SPI Flash memory device which you
3791	want to use for the environment.
3792
3793	- CONFIG_ENV_OFFSET:
3794	- CONFIG_ENV_SIZE:
3795
3796	  These two #defines specify the offset and size of the
3797	  environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
3798	  aligned to an erase sector boundary.
3799
3800	- CONFIG_ENV_SECT_SIZE:
3801
3802	  Define the SPI flash's sector size.
3803
3804	- CONFIG_ENV_OFFSET_REDUND (optional):
3805
3806	  This setting describes a second storage area of CONFIG_ENV_SIZE
3807	  size used to hold a redundant copy of the environment data, so
3808	  that there is a valid backup copy in case there is a power failure
3809	  during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
3810	  aligned to an erase sector boundary.
3811
3812	- CONFIG_ENV_SPI_BUS (optional):
3813	- CONFIG_ENV_SPI_CS (optional):
3814
3815	  Define the SPI bus and chip select. If not defined they will be 0.
3816
3817	- CONFIG_ENV_SPI_MAX_HZ (optional):
3818
3819	  Define the SPI max work clock. If not defined then use 1MHz.
3820
3821	- CONFIG_ENV_SPI_MODE (optional):
3822
3823	  Define the SPI work mode. If not defined then use SPI_MODE_3.
3824
3825- CONFIG_ENV_IS_IN_REMOTE:
3826
3827	Define this if you have a remote memory space which you
3828	want to use for the local device's environment.
3829
3830	- CONFIG_ENV_ADDR:
3831	- CONFIG_ENV_SIZE:
3832
3833	  These two #defines specify the address and size of the
3834	  environment area within the remote memory space. The
3835	  local device can get the environment from remote memory
3836	  space by SRIO or PCIE links.
3837
3838BE CAREFUL! For some special cases, the local device can not use
3839"saveenv" command. For example, the local device will get the
3840environment stored in a remote NOR flash by SRIO or PCIE link,
3841but it can not erase, write this NOR flash by SRIO or PCIE interface.
3842
3843- CONFIG_ENV_IS_IN_NAND:
3844
3845	Define this if you have a NAND device which you want to use
3846	for the environment.
3847
3848	- CONFIG_ENV_OFFSET:
3849	- CONFIG_ENV_SIZE:
3850
3851	  These two #defines specify the offset and size of the environment
3852	  area within the first NAND device.  CONFIG_ENV_OFFSET must be
3853	  aligned to an erase block boundary.
3854
3855	- CONFIG_ENV_OFFSET_REDUND (optional):
3856
3857	  This setting describes a second storage area of CONFIG_ENV_SIZE
3858	  size used to hold a redundant copy of the environment data, so
3859	  that there is a valid backup copy in case there is a power failure
3860	  during a "saveenv" operation.	 CONFIG_ENV_OFFSET_REDUND must be
3861	  aligned to an erase block boundary.
3862
3863	- CONFIG_ENV_RANGE (optional):
3864
3865	  Specifies the length of the region in which the environment
3866	  can be written.  This should be a multiple of the NAND device's
3867	  block size.  Specifying a range with more erase blocks than
3868	  are needed to hold CONFIG_ENV_SIZE allows bad blocks within
3869	  the range to be avoided.
3870
3871	- CONFIG_ENV_OFFSET_OOB (optional):
3872
3873	  Enables support for dynamically retrieving the offset of the
3874	  environment from block zero's out-of-band data.  The
3875	  "nand env.oob" command can be used to record this offset.
3876	  Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
3877	  using CONFIG_ENV_OFFSET_OOB.
3878
3879- CONFIG_NAND_ENV_DST
3880
3881	Defines address in RAM to which the nand_spl code should copy the
3882	environment. If redundant environment is used, it will be copied to
3883	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3884
3885- CONFIG_ENV_IS_IN_UBI:
3886
3887	Define this if you have an UBI volume that you want to use for the
3888	environment.  This has the benefit of wear-leveling the environment
3889	accesses, which is important on NAND.
3890
3891	- CONFIG_ENV_UBI_PART:
3892
3893	  Define this to a string that is the mtd partition containing the UBI.
3894
3895	- CONFIG_ENV_UBI_VOLUME:
3896
3897	  Define this to the name of the volume that you want to store the
3898	  environment in.
3899
3900	- CONFIG_ENV_UBI_VOLUME_REDUND:
3901
3902	  Define this to the name of another volume to store a second copy of
3903	  the environment in.  This will enable redundant environments in UBI.
3904	  It is assumed that both volumes are in the same MTD partition.
3905
3906	- CONFIG_UBI_SILENCE_MSG
3907	- CONFIG_UBIFS_SILENCE_MSG
3908
3909	  You will probably want to define these to avoid a really noisy system
3910	  when storing the env in UBI.
3911
3912- CONFIG_ENV_IS_IN_FAT:
3913       Define this if you want to use the FAT file system for the environment.
3914
3915       - FAT_ENV_INTERFACE:
3916
3917         Define this to a string that is the name of the block device.
3918
3919       - FAT_ENV_DEVICE_AND_PART:
3920
3921         Define this to a string to specify the partition of the device. It can
3922         be as following:
3923
3924           "D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
3925               - "D:P": device D partition P. Error occurs if device D has no
3926                        partition table.
3927               - "D:0": device D.
3928               - "D" or "D:": device D partition 1 if device D has partition
3929                              table, or the whole device D if has no partition
3930                              table.
3931               - "D:auto": first partition in device D with bootable flag set.
3932                           If none, first valid partition in device D. If no
3933                           partition table then means device D.
3934
3935       - FAT_ENV_FILE:
3936
3937         It's a string of the FAT file name. This file use to store the
3938         environment.
3939
3940       - CONFIG_FAT_WRITE:
3941         This should be defined. Otherwise it cannot save the environment file.
3942
3943- CONFIG_ENV_IS_IN_MMC:
3944
3945	Define this if you have an MMC device which you want to use for the
3946	environment.
3947
3948	- CONFIG_SYS_MMC_ENV_DEV:
3949
3950	  Specifies which MMC device the environment is stored in.
3951
3952	- CONFIG_SYS_MMC_ENV_PART (optional):
3953
3954	  Specifies which MMC partition the environment is stored in. If not
3955	  set, defaults to partition 0, the user area. Common values might be
3956	  1 (first MMC boot partition), 2 (second MMC boot partition).
3957
3958	- CONFIG_ENV_OFFSET:
3959	- CONFIG_ENV_SIZE:
3960
3961	  These two #defines specify the offset and size of the environment
3962	  area within the specified MMC device.
3963
3964	  If offset is positive (the usual case), it is treated as relative to
3965	  the start of the MMC partition. If offset is negative, it is treated
3966	  as relative to the end of the MMC partition. This can be useful if
3967	  your board may be fitted with different MMC devices, which have
3968	  different sizes for the MMC partitions, and you always want the
3969	  environment placed at the very end of the partition, to leave the
3970	  maximum possible space before it, to store other data.
3971
3972	  These two values are in units of bytes, but must be aligned to an
3973	  MMC sector boundary.
3974
3975	- CONFIG_ENV_OFFSET_REDUND (optional):
3976
3977	  Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
3978	  hold a redundant copy of the environment data. This provides a
3979	  valid backup copy in case the other copy is corrupted, e.g. due
3980	  to a power failure during a "saveenv" operation.
3981
3982	  This value may also be positive or negative; this is handled in the
3983	  same way as CONFIG_ENV_OFFSET.
3984
3985	  This value is also in units of bytes, but must also be aligned to
3986	  an MMC sector boundary.
3987
3988	- CONFIG_ENV_SIZE_REDUND (optional):
3989
3990	  This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
3991	  set. If this value is set, it must be set to the same value as
3992	  CONFIG_ENV_SIZE.
3993
3994- CONFIG_SYS_SPI_INIT_OFFSET
3995
3996	Defines offset to the initial SPI buffer area in DPRAM. The
3997	area is used at an early stage (ROM part) if the environment
3998	is configured to reside in the SPI EEPROM: We need a 520 byte
3999	scratch DPRAM area. It is used between the two initialization
4000	calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
4001	to be a good choice since it makes it far enough from the
4002	start of the data area as well as from the stack pointer.
4003
4004Please note that the environment is read-only until the monitor
4005has been relocated to RAM and a RAM copy of the environment has been
4006created; also, when using EEPROM you will have to use getenv_f()
4007until then to read environment variables.
4008
4009The environment is protected by a CRC32 checksum. Before the monitor
4010is relocated into RAM, as a result of a bad CRC you will be working
4011with the compiled-in default environment - *silently*!!! [This is
4012necessary, because the first environment variable we need is the
4013"baudrate" setting for the console - if we have a bad CRC, we don't
4014have any device yet where we could complain.]
4015
4016Note: once the monitor has been relocated, then it will complain if
4017the default environment is used; a new CRC is computed as soon as you
4018use the "saveenv" command to store a valid environment.
4019
4020- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
4021		Echo the inverted Ethernet link state to the fault LED.
4022
4023		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
4024		      also needs to be defined.
4025
4026- CONFIG_SYS_FAULT_MII_ADDR:
4027		MII address of the PHY to check for the Ethernet link state.
4028
4029- CONFIG_NS16550_MIN_FUNCTIONS:
4030		Define this if you desire to only have use of the NS16550_init
4031		and NS16550_putc functions for the serial driver located at
4032		drivers/serial/ns16550.c.  This option is useful for saving
4033		space for already greatly restricted images, including but not
4034		limited to NAND_SPL configurations.
4035
4036- CONFIG_DISPLAY_BOARDINFO
4037		Display information about the board that U-Boot is running on
4038		when U-Boot starts up. The board function checkboard() is called
4039		to do this.
4040
4041- CONFIG_DISPLAY_BOARDINFO_LATE
4042		Similar to the previous option, but display this information
4043		later, once stdio is running and output goes to the LCD, if
4044		present.
4045
4046- CONFIG_BOARD_SIZE_LIMIT:
4047		Maximum size of the U-Boot image. When defined, the
4048		build system checks that the actual size does not
4049		exceed it.
4050
4051Low Level (hardware related) configuration options:
4052---------------------------------------------------
4053
4054- CONFIG_SYS_CACHELINE_SIZE:
4055		Cache Line Size of the CPU.
4056
4057- CONFIG_SYS_DEFAULT_IMMR:
4058		Default address of the IMMR after system reset.
4059
4060		Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
4061		and RPXsuper) to be able to adjust the position of
4062		the IMMR register after a reset.
4063
4064- CONFIG_SYS_CCSRBAR_DEFAULT:
4065		Default (power-on reset) physical address of CCSR on Freescale
4066		PowerPC SOCs.
4067
4068- CONFIG_SYS_CCSRBAR:
4069		Virtual address of CCSR.  On a 32-bit build, this is typically
4070		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
4071
4072		CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
4073		for cross-platform code that uses that macro instead.
4074
4075- CONFIG_SYS_CCSRBAR_PHYS:
4076		Physical address of CCSR.  CCSR can be relocated to a new
4077		physical address, if desired.  In this case, this macro should
4078		be set to that address.	 Otherwise, it should be set to the
4079		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
4080		is typically relocated on 36-bit builds.  It is recommended
4081		that this macro be defined via the _HIGH and _LOW macros:
4082
4083		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
4084			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
4085
4086- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
4087		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
4088		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
4089		used in assembly code, so it must not contain typecasts or
4090		integer size suffixes (e.g. "ULL").
4091
4092- CONFIG_SYS_CCSRBAR_PHYS_LOW:
4093		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
4094		used in assembly code, so it must not contain typecasts or
4095		integer size suffixes (e.g. "ULL").
4096
4097- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
4098		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
4099		forced to a value that ensures that CCSR is not relocated.
4100
4101- Floppy Disk Support:
4102		CONFIG_SYS_FDC_DRIVE_NUMBER
4103
4104		the default drive number (default value 0)
4105
4106		CONFIG_SYS_ISA_IO_STRIDE
4107
4108		defines the spacing between FDC chipset registers
4109		(default value 1)
4110
4111		CONFIG_SYS_ISA_IO_OFFSET
4112
4113		defines the offset of register from address. It
4114		depends on which part of the data bus is connected to
4115		the FDC chipset. (default value 0)
4116
4117		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
4118		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
4119		default value.
4120
4121		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
4122		fdc_hw_init() is called at the beginning of the FDC
4123		setup. fdc_hw_init() must be provided by the board
4124		source code. It is used to make hardware-dependent
4125		initializations.
4126
4127- CONFIG_IDE_AHB:
4128		Most IDE controllers were designed to be connected with PCI
4129		interface. Only few of them were designed for AHB interface.
4130		When software is doing ATA command and data transfer to
4131		IDE devices through IDE-AHB controller, some additional
4132		registers accessing to these kind of IDE-AHB controller
4133		is required.
4134
4135- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
4136		DO NOT CHANGE unless you know exactly what you're
4137		doing! (11-4) [MPC8xx/82xx systems only]
4138
4139- CONFIG_SYS_INIT_RAM_ADDR:
4140
4141		Start address of memory area that can be used for
4142		initial data and stack; please note that this must be
4143		writable memory that is working WITHOUT special
4144		initialization, i. e. you CANNOT use normal RAM which
4145		will become available only after programming the
4146		memory controller and running certain initialization
4147		sequences.
4148
4149		U-Boot uses the following memory types:
4150		- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
4151		- MPC824X: data cache
4152		- PPC4xx:  data cache
4153
4154- CONFIG_SYS_GBL_DATA_OFFSET:
4155
4156		Offset of the initial data structure in the memory
4157		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
4158		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
4159		data is located at the end of the available space
4160		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
4161		GENERATED_GBL_DATA_SIZE), and the initial stack is just
4162		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
4163		CONFIG_SYS_GBL_DATA_OFFSET) downward.
4164
4165	Note:
4166		On the MPC824X (or other systems that use the data
4167		cache for initial memory) the address chosen for
4168		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
4169		point to an otherwise UNUSED address space between
4170		the top of RAM and the start of the PCI space.
4171
4172- CONFIG_SYS_SIUMCR:	SIU Module Configuration (11-6)
4173
4174- CONFIG_SYS_SYPCR:	System Protection Control (11-9)
4175
4176- CONFIG_SYS_TBSCR:	Time Base Status and Control (11-26)
4177
4178- CONFIG_SYS_PISCR:	Periodic Interrupt Status and Control (11-31)
4179
4180- CONFIG_SYS_PLPRCR:	PLL, Low-Power, and Reset Control Register (15-30)
4181
4182- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
4183
4184- CONFIG_SYS_OR_TIMING_SDRAM:
4185		SDRAM timing
4186
4187- CONFIG_SYS_MAMR_PTA:
4188		periodic timer for refresh
4189
4190- CONFIG_SYS_DER:	Debug Event Register (37-47)
4191
4192- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
4193  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
4194  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
4195  CONFIG_SYS_BR1_PRELIM:
4196		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
4197
4198- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
4199  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
4200  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
4201		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
4202
4203- CONFIG_SYS_MAMR_PTA, CONFIG_SYS_MPTPR_2BK_4K, CONFIG_SYS_MPTPR_1BK_4K, CONFIG_SYS_MPTPR_2BK_8K,
4204  CONFIG_SYS_MPTPR_1BK_8K, CONFIG_SYS_MAMR_8COL, CONFIG_SYS_MAMR_9COL:
4205		Machine Mode Register and Memory Periodic Timer
4206		Prescaler definitions (SDRAM timing)
4207
4208- CONFIG_SYS_I2C_UCODE_PATCH, CONFIG_SYS_I2C_DPMEM_OFFSET [0x1FC0]:
4209		enable I2C microcode relocation patch (MPC8xx);
4210		define relocation offset in DPRAM [DSP2]
4211
4212- CONFIG_SYS_SMC_UCODE_PATCH, CONFIG_SYS_SMC_DPMEM_OFFSET [0x1FC0]:
4213		enable SMC microcode relocation patch (MPC8xx);
4214		define relocation offset in DPRAM [SMC1]
4215
4216- CONFIG_SYS_SPI_UCODE_PATCH, CONFIG_SYS_SPI_DPMEM_OFFSET [0x1FC0]:
4217		enable SPI microcode relocation patch (MPC8xx);
4218		define relocation offset in DPRAM [SCC4]
4219
4220- CONFIG_SYS_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
4221		Offset of the bootmode word in DPRAM used by post
4222		(Power On Self Tests). This definition overrides
4223		#define'd default value in commproc.h resp.
4224		cpm_8260.h.
4225
4226- CONFIG_SYS_PCI_SLV_MEM_LOCAL, CONFIG_SYS_PCI_SLV_MEM_BUS, CONFIG_SYS_PICMR0_MASK_ATTRIB,
4227  CONFIG_SYS_PCI_MSTR0_LOCAL, CONFIG_SYS_PCIMSK0_MASK, CONFIG_SYS_PCI_MSTR1_LOCAL,
4228  CONFIG_SYS_PCIMSK1_MASK, CONFIG_SYS_PCI_MSTR_MEM_LOCAL, CONFIG_SYS_PCI_MSTR_MEM_BUS,
4229  CONFIG_SYS_CPU_PCI_MEM_START, CONFIG_SYS_PCI_MSTR_MEM_SIZE, CONFIG_SYS_POCMR0_MASK_ATTRIB,
4230  CONFIG_SYS_PCI_MSTR_MEMIO_LOCAL, CONFIG_SYS_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
4231  CONFIG_SYS_PCI_MSTR_MEMIO_SIZE, CONFIG_SYS_POCMR1_MASK_ATTRIB, CONFIG_SYS_PCI_MSTR_IO_LOCAL,
4232  CONFIG_SYS_PCI_MSTR_IO_BUS, CONFIG_SYS_CPU_PCI_IO_START, CONFIG_SYS_PCI_MSTR_IO_SIZE,
4233  CONFIG_SYS_POCMR2_MASK_ATTRIB: (MPC826x only)
4234		Overrides the default PCI memory map in arch/powerpc/cpu/mpc8260/pci.c if set.
4235
4236- CONFIG_PCI_DISABLE_PCIE:
4237		Disable PCI-Express on systems where it is supported but not
4238		required.
4239
4240- CONFIG_PCI_ENUM_ONLY
4241		Only scan through and get the devices on the buses.
4242		Don't do any setup work, presumably because someone or
4243		something has already done it, and we don't need to do it
4244		a second time.	Useful for platforms that are pre-booted
4245		by coreboot or similar.
4246
4247- CONFIG_PCI_INDIRECT_BRIDGE:
4248		Enable support for indirect PCI bridges.
4249
4250- CONFIG_SYS_SRIO:
4251		Chip has SRIO or not
4252
4253- CONFIG_SRIO1:
4254		Board has SRIO 1 port available
4255
4256- CONFIG_SRIO2:
4257		Board has SRIO 2 port available
4258
4259- CONFIG_SRIO_PCIE_BOOT_MASTER
4260		Board can support master function for Boot from SRIO and PCIE
4261
4262- CONFIG_SYS_SRIOn_MEM_VIRT:
4263		Virtual Address of SRIO port 'n' memory region
4264
4265- CONFIG_SYS_SRIOn_MEM_PHYS:
4266		Physical Address of SRIO port 'n' memory region
4267
4268- CONFIG_SYS_SRIOn_MEM_SIZE:
4269		Size of SRIO port 'n' memory region
4270
4271- CONFIG_SYS_NAND_BUSWIDTH_16BIT
4272		Defined to tell the NAND controller that the NAND chip is using
4273		a 16 bit bus.
4274		Not all NAND drivers use this symbol.
4275		Example of drivers that use it:
4276		- drivers/mtd/nand/ndfc.c
4277		- drivers/mtd/nand/mxc_nand.c
4278
4279- CONFIG_SYS_NDFC_EBC0_CFG
4280		Sets the EBC0_CFG register for the NDFC. If not defined
4281		a default value will be used.
4282
4283- CONFIG_SPD_EEPROM
4284		Get DDR timing information from an I2C EEPROM. Common
4285		with pluggable memory modules such as SODIMMs
4286
4287  SPD_EEPROM_ADDRESS
4288		I2C address of the SPD EEPROM
4289
4290- CONFIG_SYS_SPD_BUS_NUM
4291		If SPD EEPROM is on an I2C bus other than the first
4292		one, specify here. Note that the value must resolve
4293		to something your driver can deal with.
4294
4295- CONFIG_SYS_DDR_RAW_TIMING
4296		Get DDR timing information from other than SPD. Common with
4297		soldered DDR chips onboard without SPD. DDR raw timing
4298		parameters are extracted from datasheet and hard-coded into
4299		header files or board specific files.
4300
4301- CONFIG_FSL_DDR_INTERACTIVE
4302		Enable interactive DDR debugging. See doc/README.fsl-ddr.
4303
4304- CONFIG_FSL_DDR_SYNC_REFRESH
4305		Enable sync of refresh for multiple controllers.
4306
4307- CONFIG_FSL_DDR_BIST
4308		Enable built-in memory test for Freescale DDR controllers.
4309
4310- CONFIG_SYS_83XX_DDR_USES_CS0
4311		Only for 83xx systems. If specified, then DDR should
4312		be configured using CS0 and CS1 instead of CS2 and CS3.
4313
4314- CONFIG_ETHER_ON_FEC[12]
4315		Define to enable FEC[12] on a 8xx series processor.
4316
4317- CONFIG_FEC[12]_PHY
4318		Define to the hardcoded PHY address which corresponds
4319		to the given FEC; i. e.
4320			#define CONFIG_FEC1_PHY 4
4321		means that the PHY with address 4 is connected to FEC1
4322
4323		When set to -1, means to probe for first available.
4324
4325- CONFIG_FEC[12]_PHY_NORXERR
4326		The PHY does not have a RXERR line (RMII only).
4327		(so program the FEC to ignore it).
4328
4329- CONFIG_RMII
4330		Enable RMII mode for all FECs.
4331		Note that this is a global option, we can't
4332		have one FEC in standard MII mode and another in RMII mode.
4333
4334- CONFIG_CRC32_VERIFY
4335		Add a verify option to the crc32 command.
4336		The syntax is:
4337
4338		=> crc32 -v <address> <count> <crc32>
4339
4340		Where address/count indicate a memory area
4341		and crc32 is the correct crc32 which the
4342		area should have.
4343
4344- CONFIG_LOOPW
4345		Add the "loopw" memory command. This only takes effect if
4346		the memory commands are activated globally (CONFIG_CMD_MEM).
4347
4348- CONFIG_MX_CYCLIC
4349		Add the "mdc" and "mwc" memory commands. These are cyclic
4350		"md/mw" commands.
4351		Examples:
4352
4353		=> mdc.b 10 4 500
4354		This command will print 4 bytes (10,11,12,13) each 500 ms.
4355
4356		=> mwc.l 100 12345678 10
4357		This command will write 12345678 to address 100 all 10 ms.
4358
4359		This only takes effect if the memory commands are activated
4360		globally (CONFIG_CMD_MEM).
4361
4362- CONFIG_SKIP_LOWLEVEL_INIT
4363		[ARM, NDS32, MIPS only] If this variable is defined, then certain
4364		low level initializations (like setting up the memory
4365		controller) are omitted and/or U-Boot does not
4366		relocate itself into RAM.
4367
4368		Normally this variable MUST NOT be defined. The only
4369		exception is when U-Boot is loaded (to RAM) by some
4370		other boot loader or by a debugger which performs
4371		these initializations itself.
4372
4373- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
4374		[ARM926EJ-S only] This allows just the call to lowlevel_init()
4375		to be skipped. The normal CP15 init (such as enabling the
4376		instruction cache) is still performed.
4377
4378- CONFIG_SPL_BUILD
4379		Modifies the behaviour of start.S when compiling a loader
4380		that is executed before the actual U-Boot. E.g. when
4381		compiling a NAND SPL.
4382
4383- CONFIG_TPL_BUILD
4384		Modifies the behaviour of start.S  when compiling a loader
4385		that is executed after the SPL and before the actual U-Boot.
4386		It is loaded by the SPL.
4387
4388- CONFIG_SYS_MPC85XX_NO_RESETVEC
4389		Only for 85xx systems. If this variable is specified, the section
4390		.resetvec is not kept and the section .bootpg is placed in the
4391		previous 4k of the .text section.
4392
4393- CONFIG_ARCH_MAP_SYSMEM
4394		Generally U-Boot (and in particular the md command) uses
4395		effective address. It is therefore not necessary to regard
4396		U-Boot address as virtual addresses that need to be translated
4397		to physical addresses. However, sandbox requires this, since
4398		it maintains its own little RAM buffer which contains all
4399		addressable memory. This option causes some memory accesses
4400		to be mapped through map_sysmem() / unmap_sysmem().
4401
4402- CONFIG_X86_RESET_VECTOR
4403		If defined, the x86 reset vector code is included. This is not
4404		needed when U-Boot is running from Coreboot.
4405
4406- CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC:
4407		Enables the RTC32K OSC on AM33xx based plattforms
4408
4409- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
4410		Option to disable subpage write in NAND driver
4411		driver that uses this:
4412		drivers/mtd/nand/davinci_nand.c
4413
4414Freescale QE/FMAN Firmware Support:
4415-----------------------------------
4416
4417The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
4418loading of "firmware", which is encoded in the QE firmware binary format.
4419This firmware often needs to be loaded during U-Boot booting, so macros
4420are used to identify the storage device (NOR flash, SPI, etc) and the address
4421within that device.
4422
4423- CONFIG_SYS_FMAN_FW_ADDR
4424	The address in the storage device where the FMAN microcode is located.  The
4425	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4426	is also specified.
4427
4428- CONFIG_SYS_QE_FW_ADDR
4429	The address in the storage device where the QE microcode is located.  The
4430	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
4431	is also specified.
4432
4433- CONFIG_SYS_QE_FMAN_FW_LENGTH
4434	The maximum possible size of the firmware.  The firmware binary format
4435	has a field that specifies the actual size of the firmware, but it
4436	might not be possible to read any part of the firmware unless some
4437	local storage is allocated to hold the entire firmware first.
4438
4439- CONFIG_SYS_QE_FMAN_FW_IN_NOR
4440	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
4441	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
4442	virtual address in NOR flash.
4443
4444- CONFIG_SYS_QE_FMAN_FW_IN_NAND
4445	Specifies that QE/FMAN firmware is located in NAND flash.
4446	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
4447
4448- CONFIG_SYS_QE_FMAN_FW_IN_MMC
4449	Specifies that QE/FMAN firmware is located on the primary SD/MMC
4450	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
4451
4452- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
4453	Specifies that QE/FMAN firmware is located in the remote (master)
4454	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
4455	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
4456	window->master inbound window->master LAW->the ucode address in
4457	master's memory space.
4458
4459Freescale Layerscape Management Complex Firmware Support:
4460---------------------------------------------------------
4461The Freescale Layerscape Management Complex (MC) supports the loading of
4462"firmware".
4463This firmware often needs to be loaded during U-Boot booting, so macros
4464are used to identify the storage device (NOR flash, SPI, etc) and the address
4465within that device.
4466
4467- CONFIG_FSL_MC_ENET
4468	Enable the MC driver for Layerscape SoCs.
4469
4470Freescale Layerscape Debug Server Support:
4471-------------------------------------------
4472The Freescale Layerscape Debug Server Support supports the loading of
4473"Debug Server firmware" and triggering SP boot-rom.
4474This firmware often needs to be loaded during U-Boot booting.
4475
4476- CONFIG_SYS_MC_RSV_MEM_ALIGN
4477	Define alignment of reserved memory MC requires
4478
4479Reproducible builds
4480-------------------
4481
4482In order to achieve reproducible builds, timestamps used in the U-Boot build
4483process have to be set to a fixed value.
4484
4485This is done using the SOURCE_DATE_EPOCH environment variable.
4486SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
4487option for U-Boot or an environment variable in U-Boot.
4488
4489SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
4490
4491Building the Software:
4492======================
4493
4494Building U-Boot has been tested in several native build environments
4495and in many different cross environments. Of course we cannot support
4496all possibly existing versions of cross development tools in all
4497(potentially obsolete) versions. In case of tool chain problems we
4498recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
4499which is extensively used to build and test U-Boot.
4500
4501If you are not using a native environment, it is assumed that you
4502have GNU cross compiling tools available in your path. In this case,
4503you must set the environment variable CROSS_COMPILE in your shell.
4504Note that no changes to the Makefile or any other source files are
4505necessary. For example using the ELDK on a 4xx CPU, please enter:
4506
4507	$ CROSS_COMPILE=ppc_4xx-
4508	$ export CROSS_COMPILE
4509
4510Note: If you wish to generate Windows versions of the utilities in
4511      the tools directory you can use the MinGW toolchain
4512      (http://www.mingw.org).  Set your HOST tools to the MinGW
4513      toolchain and execute 'make tools'.  For example:
4514
4515       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
4516
4517      Binaries such as tools/mkimage.exe will be created which can
4518      be executed on computers running Windows.
4519
4520U-Boot is intended to be simple to build. After installing the
4521sources you must configure U-Boot for one specific board type. This
4522is done by typing:
4523
4524	make NAME_defconfig
4525
4526where "NAME_defconfig" is the name of one of the existing configu-
4527rations; see boards.cfg for supported names.
4528
4529Note: for some board special configuration names may exist; check if
4530      additional information is available from the board vendor; for
4531      instance, the TQM823L systems are available without (standard)
4532      or with LCD support. You can select such additional "features"
4533      when choosing the configuration, i. e.
4534
4535      make TQM823L_defconfig
4536	- will configure for a plain TQM823L, i. e. no LCD support
4537
4538      make TQM823L_LCD_defconfig
4539	- will configure for a TQM823L with U-Boot console on LCD
4540
4541      etc.
4542
4543
4544Finally, type "make all", and you should get some working U-Boot
4545images ready for download to / installation on your system:
4546
4547- "u-boot.bin" is a raw binary image
4548- "u-boot" is an image in ELF binary format
4549- "u-boot.srec" is in Motorola S-Record format
4550
4551By default the build is performed locally and the objects are saved
4552in the source directory. One of the two methods can be used to change
4553this behavior and build U-Boot to some external directory:
4554
45551. Add O= to the make command line invocations:
4556
4557	make O=/tmp/build distclean
4558	make O=/tmp/build NAME_defconfig
4559	make O=/tmp/build all
4560
45612. Set environment variable KBUILD_OUTPUT to point to the desired location:
4562
4563	export KBUILD_OUTPUT=/tmp/build
4564	make distclean
4565	make NAME_defconfig
4566	make all
4567
4568Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
4569variable.
4570
4571
4572Please be aware that the Makefiles assume you are using GNU make, so
4573for instance on NetBSD you might need to use "gmake" instead of
4574native "make".
4575
4576
4577If the system board that you have is not listed, then you will need
4578to port U-Boot to your hardware platform. To do this, follow these
4579steps:
4580
45811.  Create a new directory to hold your board specific code. Add any
4582    files you need. In your board directory, you will need at least
4583    the "Makefile" and a "<board>.c".
45842.  Create a new configuration file "include/configs/<board>.h" for
4585    your board.
45863.  If you're porting U-Boot to a new CPU, then also create a new
4587    directory to hold your CPU specific code. Add any files you need.
45884.  Run "make <board>_defconfig" with your new name.
45895.  Type "make", and you should get a working "u-boot.srec" file
4590    to be installed on your target system.
45916.  Debug and solve any problems that might arise.
4592    [Of course, this last step is much harder than it sounds.]
4593
4594
4595Testing of U-Boot Modifications, Ports to New Hardware, etc.:
4596==============================================================
4597
4598If you have modified U-Boot sources (for instance added a new board
4599or support for new devices, a new CPU, etc.) you are expected to
4600provide feedback to the other developers. The feedback normally takes
4601the form of a "patch", i. e. a context diff against a certain (latest
4602official or latest in the git repository) version of U-Boot sources.
4603
4604But before you submit such a patch, please verify that your modifi-
4605cation did not break existing code. At least make sure that *ALL* of
4606the supported boards compile WITHOUT ANY compiler warnings. To do so,
4607just run the buildman script (tools/buildman/buildman), which will
4608configure and build U-Boot for ALL supported system. Be warned, this
4609will take a while. Please see the buildman README, or run 'buildman -H'
4610for documentation.
4611
4612
4613See also "U-Boot Porting Guide" below.
4614
4615
4616Monitor Commands - Overview:
4617============================
4618
4619go	- start application at address 'addr'
4620run	- run commands in an environment variable
4621bootm	- boot application image from memory
4622bootp	- boot image via network using BootP/TFTP protocol
4623bootz   - boot zImage from memory
4624tftpboot- boot image via network using TFTP protocol
4625	       and env variables "ipaddr" and "serverip"
4626	       (and eventually "gatewayip")
4627tftpput - upload a file via network using TFTP protocol
4628rarpboot- boot image via network using RARP/TFTP protocol
4629diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
4630loads	- load S-Record file over serial line
4631loadb	- load binary file over serial line (kermit mode)
4632md	- memory display
4633mm	- memory modify (auto-incrementing)
4634nm	- memory modify (constant address)
4635mw	- memory write (fill)
4636cp	- memory copy
4637cmp	- memory compare
4638crc32	- checksum calculation
4639i2c	- I2C sub-system
4640sspi	- SPI utility commands
4641base	- print or set address offset
4642printenv- print environment variables
4643setenv	- set environment variables
4644saveenv - save environment variables to persistent storage
4645protect - enable or disable FLASH write protection
4646erase	- erase FLASH memory
4647flinfo	- print FLASH memory information
4648nand	- NAND memory operations (see doc/README.nand)
4649bdinfo	- print Board Info structure
4650iminfo	- print header information for application image
4651coninfo - print console devices and informations
4652ide	- IDE sub-system
4653loop	- infinite loop on address range
4654loopw	- infinite write loop on address range
4655mtest	- simple RAM test
4656icache	- enable or disable instruction cache
4657dcache	- enable or disable data cache
4658reset	- Perform RESET of the CPU
4659echo	- echo args to console
4660version - print monitor version
4661help	- print online help
4662?	- alias for 'help'
4663
4664
4665Monitor Commands - Detailed Description:
4666========================================
4667
4668TODO.
4669
4670For now: just type "help <command>".
4671
4672
4673Environment Variables:
4674======================
4675
4676U-Boot supports user configuration using Environment Variables which
4677can be made persistent by saving to Flash memory.
4678
4679Environment Variables are set using "setenv", printed using
4680"printenv", and saved to Flash using "saveenv". Using "setenv"
4681without a value can be used to delete a variable from the
4682environment. As long as you don't save the environment you are
4683working with an in-memory copy. In case the Flash area containing the
4684environment is erased by accident, a default environment is provided.
4685
4686Some configuration options can be set using Environment Variables.
4687
4688List of environment variables (most likely not complete):
4689
4690  baudrate	- see CONFIG_BAUDRATE
4691
4692  bootdelay	- see CONFIG_BOOTDELAY
4693
4694  bootcmd	- see CONFIG_BOOTCOMMAND
4695
4696  bootargs	- Boot arguments when booting an RTOS image
4697
4698  bootfile	- Name of the image to load with TFTP
4699
4700  bootm_low	- Memory range available for image processing in the bootm
4701		  command can be restricted. This variable is given as
4702		  a hexadecimal number and defines lowest address allowed
4703		  for use by the bootm command. See also "bootm_size"
4704		  environment variable. Address defined by "bootm_low" is
4705		  also the base of the initial memory mapping for the Linux
4706		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
4707		  bootm_mapsize.
4708
4709  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
4710		  This variable is given as a hexadecimal number and it
4711		  defines the size of the memory region starting at base
4712		  address bootm_low that is accessible by the Linux kernel
4713		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
4714		  as the default value if it is defined, and bootm_size is
4715		  used otherwise.
4716
4717  bootm_size	- Memory range available for image processing in the bootm
4718		  command can be restricted. This variable is given as
4719		  a hexadecimal number and defines the size of the region
4720		  allowed for use by the bootm command. See also "bootm_low"
4721		  environment variable.
4722
4723  updatefile	- Location of the software update file on a TFTP server, used
4724		  by the automatic software update feature. Please refer to
4725		  documentation in doc/README.update for more details.
4726
4727  autoload	- if set to "no" (any string beginning with 'n'),
4728		  "bootp" will just load perform a lookup of the
4729		  configuration from the BOOTP server, but not try to
4730		  load any image using TFTP
4731
4732  autostart	- if set to "yes", an image loaded using the "bootp",
4733		  "rarpboot", "tftpboot" or "diskboot" commands will
4734		  be automatically started (by internally calling
4735		  "bootm")
4736
4737		  If set to "no", a standalone image passed to the
4738		  "bootm" command will be copied to the load address
4739		  (and eventually uncompressed), but NOT be started.
4740		  This can be used to load and uncompress arbitrary
4741		  data.
4742
4743  fdt_high	- if set this restricts the maximum address that the
4744		  flattened device tree will be copied into upon boot.
4745		  For example, if you have a system with 1 GB memory
4746		  at physical address 0x10000000, while Linux kernel
4747		  only recognizes the first 704 MB as low memory, you
4748		  may need to set fdt_high as 0x3C000000 to have the
4749		  device tree blob be copied to the maximum address
4750		  of the 704 MB low memory, so that Linux kernel can
4751		  access it during the boot procedure.
4752
4753		  If this is set to the special value 0xFFFFFFFF then
4754		  the fdt will not be copied at all on boot.  For this
4755		  to work it must reside in writable memory, have
4756		  sufficient padding on the end of it for u-boot to
4757		  add the information it needs into it, and the memory
4758		  must be accessible by the kernel.
4759
4760  fdtcontroladdr- if set this is the address of the control flattened
4761		  device tree used by U-Boot when CONFIG_OF_CONTROL is
4762		  defined.
4763
4764  i2cfast	- (PPC405GP|PPC405EP only)
4765		  if set to 'y' configures Linux I2C driver for fast
4766		  mode (400kHZ). This environment variable is used in
4767		  initialization code. So, for changes to be effective
4768		  it must be saved and board must be reset.
4769
4770  initrd_high	- restrict positioning of initrd images:
4771		  If this variable is not set, initrd images will be
4772		  copied to the highest possible address in RAM; this
4773		  is usually what you want since it allows for
4774		  maximum initrd size. If for some reason you want to
4775		  make sure that the initrd image is loaded below the
4776		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
4777		  variable to a value of "no" or "off" or "0".
4778		  Alternatively, you can set it to a maximum upper
4779		  address to use (U-Boot will still check that it
4780		  does not overwrite the U-Boot stack and data).
4781
4782		  For instance, when you have a system with 16 MB
4783		  RAM, and want to reserve 4 MB from use by Linux,
4784		  you can do this by adding "mem=12M" to the value of
4785		  the "bootargs" variable. However, now you must make
4786		  sure that the initrd image is placed in the first
4787		  12 MB as well - this can be done with
4788
4789		  setenv initrd_high 00c00000
4790
4791		  If you set initrd_high to 0xFFFFFFFF, this is an
4792		  indication to U-Boot that all addresses are legal
4793		  for the Linux kernel, including addresses in flash
4794		  memory. In this case U-Boot will NOT COPY the
4795		  ramdisk at all. This may be useful to reduce the
4796		  boot time on your system, but requires that this
4797		  feature is supported by your Linux kernel.
4798
4799  ipaddr	- IP address; needed for tftpboot command
4800
4801  loadaddr	- Default load address for commands like "bootp",
4802		  "rarpboot", "tftpboot", "loadb" or "diskboot"
4803
4804  loads_echo	- see CONFIG_LOADS_ECHO
4805
4806  serverip	- TFTP server IP address; needed for tftpboot command
4807
4808  bootretry	- see CONFIG_BOOT_RETRY_TIME
4809
4810  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
4811
4812  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
4813
4814  ethprime	- controls which interface is used first.
4815
4816  ethact	- controls which interface is currently active.
4817		  For example you can do the following
4818
4819		  => setenv ethact FEC
4820		  => ping 192.168.0.1 # traffic sent on FEC
4821		  => setenv ethact SCC
4822		  => ping 10.0.0.1 # traffic sent on SCC
4823
4824  ethrotate	- When set to "no" U-Boot does not go through all
4825		  available network interfaces.
4826		  It just stays at the currently selected interface.
4827
4828  netretry	- When set to "no" each network operation will
4829		  either succeed or fail without retrying.
4830		  When set to "once" the network operation will
4831		  fail when all the available network interfaces
4832		  are tried once without success.
4833		  Useful on scripts which control the retry operation
4834		  themselves.
4835
4836  npe_ucode	- set load address for the NPE microcode
4837
4838  silent_linux  - If set then Linux will be told to boot silently, by
4839		  changing the console to be empty. If "yes" it will be
4840		  made silent. If "no" it will not be made silent. If
4841		  unset, then it will be made silent if the U-Boot console
4842		  is silent.
4843
4844  tftpsrcp	- If this is set, the value is used for TFTP's
4845		  UDP source port.
4846
4847  tftpdstp	- If this is set, the value is used for TFTP's UDP
4848		  destination port instead of the Well Know Port 69.
4849
4850  tftpblocksize - Block size to use for TFTP transfers; if not set,
4851		  we use the TFTP server's default block size
4852
4853  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
4854		  seconds, minimum value is 1000 = 1 second). Defines
4855		  when a packet is considered to be lost so it has to
4856		  be retransmitted. The default is 5000 = 5 seconds.
4857		  Lowering this value may make downloads succeed
4858		  faster in networks with high packet loss rates or
4859		  with unreliable TFTP servers.
4860
4861  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
4862		  unit, minimum value = 0). Defines how many timeouts
4863		  can happen during a single file transfer before that
4864		  transfer is aborted. The default is 10, and 0 means
4865		  'no timeouts allowed'. Increasing this value may help
4866		  downloads succeed with high packet loss rates, or with
4867		  unreliable TFTP servers or client hardware.
4868
4869  vlan		- When set to a value < 4095 the traffic over
4870		  Ethernet is encapsulated/received over 802.1q
4871		  VLAN tagged frames.
4872
4873  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
4874		  Unsigned value, in milliseconds. If not set, the period will
4875		  be either the default (28000), or a value based on
4876		  CONFIG_NET_RETRY_COUNT, if defined. This value has
4877		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
4878
4879The following image location variables contain the location of images
4880used in booting. The "Image" column gives the role of the image and is
4881not an environment variable name. The other columns are environment
4882variable names. "File Name" gives the name of the file on a TFTP
4883server, "RAM Address" gives the location in RAM the image will be
4884loaded to, and "Flash Location" gives the image's address in NOR
4885flash or offset in NAND flash.
4886
4887*Note* - these variables don't have to be defined for all boards, some
4888boards currently use other variables for these purposes, and some
4889boards use these variables for other purposes.
4890
4891Image		    File Name	     RAM Address       Flash Location
4892-----		    ---------	     -----------       --------------
4893u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
4894Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
4895device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
4896ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
4897
4898The following environment variables may be used and automatically
4899updated by the network boot commands ("bootp" and "rarpboot"),
4900depending the information provided by your boot server:
4901
4902  bootfile	- see above
4903  dnsip		- IP address of your Domain Name Server
4904  dnsip2	- IP address of your secondary Domain Name Server
4905  gatewayip	- IP address of the Gateway (Router) to use
4906  hostname	- Target hostname
4907  ipaddr	- see above
4908  netmask	- Subnet Mask
4909  rootpath	- Pathname of the root filesystem on the NFS server
4910  serverip	- see above
4911
4912
4913There are two special Environment Variables:
4914
4915  serial#	- contains hardware identification information such
4916		  as type string and/or serial number
4917  ethaddr	- Ethernet address
4918
4919These variables can be set only once (usually during manufacturing of
4920the board). U-Boot refuses to delete or overwrite these variables
4921once they have been set once.
4922
4923
4924Further special Environment Variables:
4925
4926  ver		- Contains the U-Boot version string as printed
4927		  with the "version" command. This variable is
4928		  readonly (see CONFIG_VERSION_VARIABLE).
4929
4930
4931Please note that changes to some configuration parameters may take
4932only effect after the next boot (yes, that's just like Windoze :-).
4933
4934
4935Callback functions for environment variables:
4936---------------------------------------------
4937
4938For some environment variables, the behavior of u-boot needs to change
4939when their values are changed.  This functionality allows functions to
4940be associated with arbitrary variables.  On creation, overwrite, or
4941deletion, the callback will provide the opportunity for some side
4942effect to happen or for the change to be rejected.
4943
4944The callbacks are named and associated with a function using the
4945U_BOOT_ENV_CALLBACK macro in your board or driver code.
4946
4947These callbacks are associated with variables in one of two ways.  The
4948static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
4949in the board configuration to a string that defines a list of
4950associations.  The list must be in the following format:
4951
4952	entry = variable_name[:callback_name]
4953	list = entry[,list]
4954
4955If the callback name is not specified, then the callback is deleted.
4956Spaces are also allowed anywhere in the list.
4957
4958Callbacks can also be associated by defining the ".callbacks" variable
4959with the same list format above.  Any association in ".callbacks" will
4960override any association in the static list. You can define
4961CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
4962".callbacks" environment variable in the default or embedded environment.
4963
4964If CONFIG_REGEX is defined, the variable_name above is evaluated as a
4965regular expression. This allows multiple variables to be connected to
4966the same callback without explicitly listing them all out.
4967
4968
4969Command Line Parsing:
4970=====================
4971
4972There are two different command line parsers available with U-Boot:
4973the old "simple" one, and the much more powerful "hush" shell:
4974
4975Old, simple command line parser:
4976--------------------------------
4977
4978- supports environment variables (through setenv / saveenv commands)
4979- several commands on one line, separated by ';'
4980- variable substitution using "... ${name} ..." syntax
4981- special characters ('$', ';') can be escaped by prefixing with '\',
4982  for example:
4983	setenv bootcmd bootm \${address}
4984- You can also escape text by enclosing in single apostrophes, for example:
4985	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
4986
4987Hush shell:
4988-----------
4989
4990- similar to Bourne shell, with control structures like
4991  if...then...else...fi, for...do...done; while...do...done,
4992  until...do...done, ...
4993- supports environment ("global") variables (through setenv / saveenv
4994  commands) and local shell variables (through standard shell syntax
4995  "name=value"); only environment variables can be used with "run"
4996  command
4997
4998General rules:
4999--------------
5000
5001(1) If a command line (or an environment variable executed by a "run"
5002    command) contains several commands separated by semicolon, and
5003    one of these commands fails, then the remaining commands will be
5004    executed anyway.
5005
5006(2) If you execute several variables with one call to run (i. e.
5007    calling run with a list of variables as arguments), any failing
5008    command will cause "run" to terminate, i. e. the remaining
5009    variables are not executed.
5010
5011Note for Redundant Ethernet Interfaces:
5012=======================================
5013
5014Some boards come with redundant Ethernet interfaces; U-Boot supports
5015such configurations and is capable of automatic selection of a
5016"working" interface when needed. MAC assignment works as follows:
5017
5018Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
5019MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
5020"eth1addr" (=>eth1), "eth2addr", ...
5021
5022If the network interface stores some valid MAC address (for instance
5023in SROM), this is used as default address if there is NO correspon-
5024ding setting in the environment; if the corresponding environment
5025variable is set, this overrides the settings in the card; that means:
5026
5027o If the SROM has a valid MAC address, and there is no address in the
5028  environment, the SROM's address is used.
5029
5030o If there is no valid address in the SROM, and a definition in the
5031  environment exists, then the value from the environment variable is
5032  used.
5033
5034o If both the SROM and the environment contain a MAC address, and
5035  both addresses are the same, this MAC address is used.
5036
5037o If both the SROM and the environment contain a MAC address, and the
5038  addresses differ, the value from the environment is used and a
5039  warning is printed.
5040
5041o If neither SROM nor the environment contain a MAC address, an error
5042  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
5043  a random, locally-assigned MAC is used.
5044
5045If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
5046will be programmed into hardware as part of the initialization process.	 This
5047may be skipped by setting the appropriate 'ethmacskip' environment variable.
5048The naming convention is as follows:
5049"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
5050
5051Image Formats:
5052==============
5053
5054U-Boot is capable of booting (and performing other auxiliary operations on)
5055images in two formats:
5056
5057New uImage format (FIT)
5058-----------------------
5059
5060Flexible and powerful format based on Flattened Image Tree -- FIT (similar
5061to Flattened Device Tree). It allows the use of images with multiple
5062components (several kernels, ramdisks, etc.), with contents protected by
5063SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
5064
5065
5066Old uImage format
5067-----------------
5068
5069Old image format is based on binary files which can be basically anything,
5070preceded by a special header; see the definitions in include/image.h for
5071details; basically, the header defines the following image properties:
5072
5073* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
5074  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
5075  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
5076  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
5077  INTEGRITY).
5078* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
5079  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
5080  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
5081* Compression Type (uncompressed, gzip, bzip2)
5082* Load Address
5083* Entry Point
5084* Image Name
5085* Image Timestamp
5086
5087The header is marked by a special Magic Number, and both the header
5088and the data portions of the image are secured against corruption by
5089CRC32 checksums.
5090
5091
5092Linux Support:
5093==============
5094
5095Although U-Boot should support any OS or standalone application
5096easily, the main focus has always been on Linux during the design of
5097U-Boot.
5098
5099U-Boot includes many features that so far have been part of some
5100special "boot loader" code within the Linux kernel. Also, any
5101"initrd" images to be used are no longer part of one big Linux image;
5102instead, kernel and "initrd" are separate images. This implementation
5103serves several purposes:
5104
5105- the same features can be used for other OS or standalone
5106  applications (for instance: using compressed images to reduce the
5107  Flash memory footprint)
5108
5109- it becomes much easier to port new Linux kernel versions because
5110  lots of low-level, hardware dependent stuff are done by U-Boot
5111
5112- the same Linux kernel image can now be used with different "initrd"
5113  images; of course this also means that different kernel images can
5114  be run with the same "initrd". This makes testing easier (you don't
5115  have to build a new "zImage.initrd" Linux image when you just
5116  change a file in your "initrd"). Also, a field-upgrade of the
5117  software is easier now.
5118
5119
5120Linux HOWTO:
5121============
5122
5123Porting Linux to U-Boot based systems:
5124---------------------------------------
5125
5126U-Boot cannot save you from doing all the necessary modifications to
5127configure the Linux device drivers for use with your target hardware
5128(no, we don't intend to provide a full virtual machine interface to
5129Linux :-).
5130
5131But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
5132
5133Just make sure your machine specific header file (for instance
5134include/asm-ppc/tqm8xx.h) includes the same definition of the Board
5135Information structure as we define in include/asm-<arch>/u-boot.h,
5136and make sure that your definition of IMAP_ADDR uses the same value
5137as your U-Boot configuration in CONFIG_SYS_IMMR.
5138
5139Note that U-Boot now has a driver model, a unified model for drivers.
5140If you are adding a new driver, plumb it into driver model. If there
5141is no uclass available, you are encouraged to create one. See
5142doc/driver-model.
5143
5144
5145Configuring the Linux kernel:
5146-----------------------------
5147
5148No specific requirements for U-Boot. Make sure you have some root
5149device (initial ramdisk, NFS) for your target system.
5150
5151
5152Building a Linux Image:
5153-----------------------
5154
5155With U-Boot, "normal" build targets like "zImage" or "bzImage" are
5156not used. If you use recent kernel source, a new build target
5157"uImage" will exist which automatically builds an image usable by
5158U-Boot. Most older kernels also have support for a "pImage" target,
5159which was introduced for our predecessor project PPCBoot and uses a
5160100% compatible format.
5161
5162Example:
5163
5164	make TQM850L_defconfig
5165	make oldconfig
5166	make dep
5167	make uImage
5168
5169The "uImage" build target uses a special tool (in 'tools/mkimage') to
5170encapsulate a compressed Linux kernel image with header	 information,
5171CRC32 checksum etc. for use with U-Boot. This is what we are doing:
5172
5173* build a standard "vmlinux" kernel image (in ELF binary format):
5174
5175* convert the kernel into a raw binary image:
5176
5177	${CROSS_COMPILE}-objcopy -O binary \
5178				 -R .note -R .comment \
5179				 -S vmlinux linux.bin
5180
5181* compress the binary image:
5182
5183	gzip -9 linux.bin
5184
5185* package compressed binary image for U-Boot:
5186
5187	mkimage -A ppc -O linux -T kernel -C gzip \
5188		-a 0 -e 0 -n "Linux Kernel Image" \
5189		-d linux.bin.gz uImage
5190
5191
5192The "mkimage" tool can also be used to create ramdisk images for use
5193with U-Boot, either separated from the Linux kernel image, or
5194combined into one file. "mkimage" encapsulates the images with a 64
5195byte header containing information about target architecture,
5196operating system, image type, compression method, entry points, time
5197stamp, CRC32 checksums, etc.
5198
5199"mkimage" can be called in two ways: to verify existing images and
5200print the header information, or to build new images.
5201
5202In the first form (with "-l" option) mkimage lists the information
5203contained in the header of an existing U-Boot image; this includes
5204checksum verification:
5205
5206	tools/mkimage -l image
5207	  -l ==> list image header information
5208
5209The second form (with "-d" option) is used to build a U-Boot image
5210from a "data file" which is used as image payload:
5211
5212	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
5213		      -n name -d data_file image
5214	  -A ==> set architecture to 'arch'
5215	  -O ==> set operating system to 'os'
5216	  -T ==> set image type to 'type'
5217	  -C ==> set compression type 'comp'
5218	  -a ==> set load address to 'addr' (hex)
5219	  -e ==> set entry point to 'ep' (hex)
5220	  -n ==> set image name to 'name'
5221	  -d ==> use image data from 'datafile'
5222
5223Right now, all Linux kernels for PowerPC systems use the same load
5224address (0x00000000), but the entry point address depends on the
5225kernel version:
5226
5227- 2.2.x kernels have the entry point at 0x0000000C,
5228- 2.3.x and later kernels have the entry point at 0x00000000.
5229
5230So a typical call to build a U-Boot image would read:
5231
5232	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5233	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
5234	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
5235	> examples/uImage.TQM850L
5236	Image Name:   2.4.4 kernel for TQM850L
5237	Created:      Wed Jul 19 02:34:59 2000
5238	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5239	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5240	Load Address: 0x00000000
5241	Entry Point:  0x00000000
5242
5243To verify the contents of the image (or check for corruption):
5244
5245	-> tools/mkimage -l examples/uImage.TQM850L
5246	Image Name:   2.4.4 kernel for TQM850L
5247	Created:      Wed Jul 19 02:34:59 2000
5248	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
5249	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
5250	Load Address: 0x00000000
5251	Entry Point:  0x00000000
5252
5253NOTE: for embedded systems where boot time is critical you can trade
5254speed for memory and install an UNCOMPRESSED image instead: this
5255needs more space in Flash, but boots much faster since it does not
5256need to be uncompressed:
5257
5258	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
5259	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
5260	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
5261	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
5262	> examples/uImage.TQM850L-uncompressed
5263	Image Name:   2.4.4 kernel for TQM850L
5264	Created:      Wed Jul 19 02:34:59 2000
5265	Image Type:   PowerPC Linux Kernel Image (uncompressed)
5266	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
5267	Load Address: 0x00000000
5268	Entry Point:  0x00000000
5269
5270
5271Similar you can build U-Boot images from a 'ramdisk.image.gz' file
5272when your kernel is intended to use an initial ramdisk:
5273
5274	-> tools/mkimage -n 'Simple Ramdisk Image' \
5275	> -A ppc -O linux -T ramdisk -C gzip \
5276	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
5277	Image Name:   Simple Ramdisk Image
5278	Created:      Wed Jan 12 14:01:50 2000
5279	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
5280	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
5281	Load Address: 0x00000000
5282	Entry Point:  0x00000000
5283
5284The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
5285option performs the converse operation of the mkimage's second form (the "-d"
5286option). Given an image built by mkimage, the dumpimage extracts a "data file"
5287from the image:
5288
5289	tools/dumpimage -i image -T type -p position data_file
5290	  -i ==> extract from the 'image' a specific 'data_file'
5291	  -T ==> set image type to 'type'
5292	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
5293
5294
5295Installing a Linux Image:
5296-------------------------
5297
5298To downloading a U-Boot image over the serial (console) interface,
5299you must convert the image to S-Record format:
5300
5301	objcopy -I binary -O srec examples/image examples/image.srec
5302
5303The 'objcopy' does not understand the information in the U-Boot
5304image header, so the resulting S-Record file will be relative to
5305address 0x00000000. To load it to a given address, you need to
5306specify the target address as 'offset' parameter with the 'loads'
5307command.
5308
5309Example: install the image to address 0x40100000 (which on the
5310TQM8xxL is in the first Flash bank):
5311
5312	=> erase 40100000 401FFFFF
5313
5314	.......... done
5315	Erased 8 sectors
5316
5317	=> loads 40100000
5318	## Ready for S-Record download ...
5319	~>examples/image.srec
5320	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
5321	...
5322	15989 15990 15991 15992
5323	[file transfer complete]
5324	[connected]
5325	## Start Addr = 0x00000000
5326
5327
5328You can check the success of the download using the 'iminfo' command;
5329this includes a checksum verification so you can be sure no data
5330corruption happened:
5331
5332	=> imi 40100000
5333
5334	## Checking Image at 40100000 ...
5335	   Image Name:	 2.2.13 for initrd on TQM850L
5336	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5337	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5338	   Load Address: 00000000
5339	   Entry Point:	 0000000c
5340	   Verifying Checksum ... OK
5341
5342
5343Boot Linux:
5344-----------
5345
5346The "bootm" command is used to boot an application that is stored in
5347memory (RAM or Flash). In case of a Linux kernel image, the contents
5348of the "bootargs" environment variable is passed to the kernel as
5349parameters. You can check and modify this variable using the
5350"printenv" and "setenv" commands:
5351
5352
5353	=> printenv bootargs
5354	bootargs=root=/dev/ram
5355
5356	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5357
5358	=> printenv bootargs
5359	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5360
5361	=> bootm 40020000
5362	## Booting Linux kernel at 40020000 ...
5363	   Image Name:	 2.2.13 for NFS on TQM850L
5364	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5365	   Data Size:	 381681 Bytes = 372 kB = 0 MB
5366	   Load Address: 00000000
5367	   Entry Point:	 0000000c
5368	   Verifying Checksum ... OK
5369	   Uncompressing Kernel Image ... OK
5370	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
5371	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
5372	time_init: decrementer frequency = 187500000/60
5373	Calibrating delay loop... 49.77 BogoMIPS
5374	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
5375	...
5376
5377If you want to boot a Linux kernel with initial RAM disk, you pass
5378the memory addresses of both the kernel and the initrd image (PPBCOOT
5379format!) to the "bootm" command:
5380
5381	=> imi 40100000 40200000
5382
5383	## Checking Image at 40100000 ...
5384	   Image Name:	 2.2.13 for initrd on TQM850L
5385	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5386	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5387	   Load Address: 00000000
5388	   Entry Point:	 0000000c
5389	   Verifying Checksum ... OK
5390
5391	## Checking Image at 40200000 ...
5392	   Image Name:	 Simple Ramdisk Image
5393	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5394	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5395	   Load Address: 00000000
5396	   Entry Point:	 00000000
5397	   Verifying Checksum ... OK
5398
5399	=> bootm 40100000 40200000
5400	## Booting Linux kernel at 40100000 ...
5401	   Image Name:	 2.2.13 for initrd on TQM850L
5402	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5403	   Data Size:	 335725 Bytes = 327 kB = 0 MB
5404	   Load Address: 00000000
5405	   Entry Point:	 0000000c
5406	   Verifying Checksum ... OK
5407	   Uncompressing Kernel Image ... OK
5408	## Loading RAMDisk Image at 40200000 ...
5409	   Image Name:	 Simple Ramdisk Image
5410	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
5411	   Data Size:	 566530 Bytes = 553 kB = 0 MB
5412	   Load Address: 00000000
5413	   Entry Point:	 00000000
5414	   Verifying Checksum ... OK
5415	   Loading Ramdisk ... OK
5416	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
5417	Boot arguments: root=/dev/ram
5418	time_init: decrementer frequency = 187500000/60
5419	Calibrating delay loop... 49.77 BogoMIPS
5420	...
5421	RAMDISK: Compressed image found at block 0
5422	VFS: Mounted root (ext2 filesystem).
5423
5424	bash#
5425
5426Boot Linux and pass a flat device tree:
5427-----------
5428
5429First, U-Boot must be compiled with the appropriate defines. See the section
5430titled "Linux Kernel Interface" above for a more in depth explanation. The
5431following is an example of how to start a kernel and pass an updated
5432flat device tree:
5433
5434=> print oftaddr
5435oftaddr=0x300000
5436=> print oft
5437oft=oftrees/mpc8540ads.dtb
5438=> tftp $oftaddr $oft
5439Speed: 1000, full duplex
5440Using TSEC0 device
5441TFTP from server 192.168.1.1; our IP address is 192.168.1.101
5442Filename 'oftrees/mpc8540ads.dtb'.
5443Load address: 0x300000
5444Loading: #
5445done
5446Bytes transferred = 4106 (100a hex)
5447=> tftp $loadaddr $bootfile
5448Speed: 1000, full duplex
5449Using TSEC0 device
5450TFTP from server 192.168.1.1; our IP address is 192.168.1.2
5451Filename 'uImage'.
5452Load address: 0x200000
5453Loading:############
5454done
5455Bytes transferred = 1029407 (fb51f hex)
5456=> print loadaddr
5457loadaddr=200000
5458=> print oftaddr
5459oftaddr=0x300000
5460=> bootm $loadaddr - $oftaddr
5461## Booting image at 00200000 ...
5462   Image Name:	 Linux-2.6.17-dirty
5463   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
5464   Data Size:	 1029343 Bytes = 1005.2 kB
5465   Load Address: 00000000
5466   Entry Point:	 00000000
5467   Verifying Checksum ... OK
5468   Uncompressing Kernel Image ... OK
5469Booting using flat device tree at 0x300000
5470Using MPC85xx ADS machine description
5471Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
5472[snip]
5473
5474
5475More About U-Boot Image Types:
5476------------------------------
5477
5478U-Boot supports the following image types:
5479
5480   "Standalone Programs" are directly runnable in the environment
5481	provided by U-Boot; it is expected that (if they behave
5482	well) you can continue to work in U-Boot after return from
5483	the Standalone Program.
5484   "OS Kernel Images" are usually images of some Embedded OS which
5485	will take over control completely. Usually these programs
5486	will install their own set of exception handlers, device
5487	drivers, set up the MMU, etc. - this means, that you cannot
5488	expect to re-enter U-Boot except by resetting the CPU.
5489   "RAMDisk Images" are more or less just data blocks, and their
5490	parameters (address, size) are passed to an OS kernel that is
5491	being started.
5492   "Multi-File Images" contain several images, typically an OS
5493	(Linux) kernel image and one or more data images like
5494	RAMDisks. This construct is useful for instance when you want
5495	to boot over the network using BOOTP etc., where the boot
5496	server provides just a single image file, but you want to get
5497	for instance an OS kernel and a RAMDisk image.
5498
5499	"Multi-File Images" start with a list of image sizes, each
5500	image size (in bytes) specified by an "uint32_t" in network
5501	byte order. This list is terminated by an "(uint32_t)0".
5502	Immediately after the terminating 0 follow the images, one by
5503	one, all aligned on "uint32_t" boundaries (size rounded up to
5504	a multiple of 4 bytes).
5505
5506   "Firmware Images" are binary images containing firmware (like
5507	U-Boot or FPGA images) which usually will be programmed to
5508	flash memory.
5509
5510   "Script files" are command sequences that will be executed by
5511	U-Boot's command interpreter; this feature is especially
5512	useful when you configure U-Boot to use a real shell (hush)
5513	as command interpreter.
5514
5515Booting the Linux zImage:
5516-------------------------
5517
5518On some platforms, it's possible to boot Linux zImage. This is done
5519using the "bootz" command. The syntax of "bootz" command is the same
5520as the syntax of "bootm" command.
5521
5522Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
5523kernel with raw initrd images. The syntax is slightly different, the
5524address of the initrd must be augmented by it's size, in the following
5525format: "<initrd addres>:<initrd size>".
5526
5527
5528Standalone HOWTO:
5529=================
5530
5531One of the features of U-Boot is that you can dynamically load and
5532run "standalone" applications, which can use some resources of
5533U-Boot like console I/O functions or interrupt services.
5534
5535Two simple examples are included with the sources:
5536
5537"Hello World" Demo:
5538-------------------
5539
5540'examples/hello_world.c' contains a small "Hello World" Demo
5541application; it is automatically compiled when you build U-Boot.
5542It's configured to run at address 0x00040004, so you can play with it
5543like that:
5544
5545	=> loads
5546	## Ready for S-Record download ...
5547	~>examples/hello_world.srec
5548	1 2 3 4 5 6 7 8 9 10 11 ...
5549	[file transfer complete]
5550	[connected]
5551	## Start Addr = 0x00040004
5552
5553	=> go 40004 Hello World! This is a test.
5554	## Starting application at 0x00040004 ...
5555	Hello World
5556	argc = 7
5557	argv[0] = "40004"
5558	argv[1] = "Hello"
5559	argv[2] = "World!"
5560	argv[3] = "This"
5561	argv[4] = "is"
5562	argv[5] = "a"
5563	argv[6] = "test."
5564	argv[7] = "<NULL>"
5565	Hit any key to exit ...
5566
5567	## Application terminated, rc = 0x0
5568
5569Another example, which demonstrates how to register a CPM interrupt
5570handler with the U-Boot code, can be found in 'examples/timer.c'.
5571Here, a CPM timer is set up to generate an interrupt every second.
5572The interrupt service routine is trivial, just printing a '.'
5573character, but this is just a demo program. The application can be
5574controlled by the following keys:
5575
5576	? - print current values og the CPM Timer registers
5577	b - enable interrupts and start timer
5578	e - stop timer and disable interrupts
5579	q - quit application
5580
5581	=> loads
5582	## Ready for S-Record download ...
5583	~>examples/timer.srec
5584	1 2 3 4 5 6 7 8 9 10 11 ...
5585	[file transfer complete]
5586	[connected]
5587	## Start Addr = 0x00040004
5588
5589	=> go 40004
5590	## Starting application at 0x00040004 ...
5591	TIMERS=0xfff00980
5592	Using timer 1
5593	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
5594
5595Hit 'b':
5596	[q, b, e, ?] Set interval 1000000 us
5597	Enabling timer
5598Hit '?':
5599	[q, b, e, ?] ........
5600	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
5601Hit '?':
5602	[q, b, e, ?] .
5603	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
5604Hit '?':
5605	[q, b, e, ?] .
5606	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
5607Hit '?':
5608	[q, b, e, ?] .
5609	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
5610Hit 'e':
5611	[q, b, e, ?] ...Stopping timer
5612Hit 'q':
5613	[q, b, e, ?] ## Application terminated, rc = 0x0
5614
5615
5616Minicom warning:
5617================
5618
5619Over time, many people have reported problems when trying to use the
5620"minicom" terminal emulation program for serial download. I (wd)
5621consider minicom to be broken, and recommend not to use it. Under
5622Unix, I recommend to use C-Kermit for general purpose use (and
5623especially for kermit binary protocol download ("loadb" command), and
5624use "cu" for S-Record download ("loads" command).  See
5625http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
5626for help with kermit.
5627
5628
5629Nevertheless, if you absolutely want to use it try adding this
5630configuration to your "File transfer protocols" section:
5631
5632	   Name	   Program			Name U/D FullScr IO-Red. Multi
5633	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
5634	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
5635
5636
5637NetBSD Notes:
5638=============
5639
5640Starting at version 0.9.2, U-Boot supports NetBSD both as host
5641(build U-Boot) and target system (boots NetBSD/mpc8xx).
5642
5643Building requires a cross environment; it is known to work on
5644NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
5645need gmake since the Makefiles are not compatible with BSD make).
5646Note that the cross-powerpc package does not install include files;
5647attempting to build U-Boot will fail because <machine/ansi.h> is
5648missing.  This file has to be installed and patched manually:
5649
5650	# cd /usr/pkg/cross/powerpc-netbsd/include
5651	# mkdir powerpc
5652	# ln -s powerpc machine
5653	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
5654	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
5655
5656Native builds *don't* work due to incompatibilities between native
5657and U-Boot include files.
5658
5659Booting assumes that (the first part of) the image booted is a
5660stage-2 loader which in turn loads and then invokes the kernel
5661proper. Loader sources will eventually appear in the NetBSD source
5662tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
5663meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
5664
5665
5666Implementation Internals:
5667=========================
5668
5669The following is not intended to be a complete description of every
5670implementation detail. However, it should help to understand the
5671inner workings of U-Boot and make it easier to port it to custom
5672hardware.
5673
5674
5675Initial Stack, Global Data:
5676---------------------------
5677
5678The implementation of U-Boot is complicated by the fact that U-Boot
5679starts running out of ROM (flash memory), usually without access to
5680system RAM (because the memory controller is not initialized yet).
5681This means that we don't have writable Data or BSS segments, and BSS
5682is not initialized as zero. To be able to get a C environment working
5683at all, we have to allocate at least a minimal stack. Implementation
5684options for this are defined and restricted by the CPU used: Some CPU
5685models provide on-chip memory (like the IMMR area on MPC8xx and
5686MPC826x processors), on others (parts of) the data cache can be
5687locked as (mis-) used as memory, etc.
5688
5689	Chris Hallinan posted a good summary of these issues to the
5690	U-Boot mailing list:
5691
5692	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
5693	From: "Chris Hallinan" <clh@net1plus.com>
5694	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
5695	...
5696
5697	Correct me if I'm wrong, folks, but the way I understand it
5698	is this: Using DCACHE as initial RAM for Stack, etc, does not
5699	require any physical RAM backing up the cache. The cleverness
5700	is that the cache is being used as a temporary supply of
5701	necessary storage before the SDRAM controller is setup. It's
5702	beyond the scope of this list to explain the details, but you
5703	can see how this works by studying the cache architecture and
5704	operation in the architecture and processor-specific manuals.
5705
5706	OCM is On Chip Memory, which I believe the 405GP has 4K. It
5707	is another option for the system designer to use as an
5708	initial stack/RAM area prior to SDRAM being available. Either
5709	option should work for you. Using CS 4 should be fine if your
5710	board designers haven't used it for something that would
5711	cause you grief during the initial boot! It is frequently not
5712	used.
5713
5714	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
5715	with your processor/board/system design. The default value
5716	you will find in any recent u-boot distribution in
5717	walnut.h should work for you. I'd set it to a value larger
5718	than your SDRAM module. If you have a 64MB SDRAM module, set
5719	it above 400_0000. Just make sure your board has no resources
5720	that are supposed to respond to that address! That code in
5721	start.S has been around a while and should work as is when
5722	you get the config right.
5723
5724	-Chris Hallinan
5725	DS4.COM, Inc.
5726
5727It is essential to remember this, since it has some impact on the C
5728code for the initialization procedures:
5729
5730* Initialized global data (data segment) is read-only. Do not attempt
5731  to write it.
5732
5733* Do not use any uninitialized global data (or implicitly initialized
5734  as zero data - BSS segment) at all - this is undefined, initiali-
5735  zation is performed later (when relocating to RAM).
5736
5737* Stack space is very limited. Avoid big data buffers or things like
5738  that.
5739
5740Having only the stack as writable memory limits means we cannot use
5741normal global data to share information between the code. But it
5742turned out that the implementation of U-Boot can be greatly
5743simplified by making a global data structure (gd_t) available to all
5744functions. We could pass a pointer to this data as argument to _all_
5745functions, but this would bloat the code. Instead we use a feature of
5746the GCC compiler (Global Register Variables) to share the data: we
5747place a pointer (gd) to the global data into a register which we
5748reserve for this purpose.
5749
5750When choosing a register for such a purpose we are restricted by the
5751relevant  (E)ABI  specifications for the current architecture, and by
5752GCC's implementation.
5753
5754For PowerPC, the following registers have specific use:
5755	R1:	stack pointer
5756	R2:	reserved for system use
5757	R3-R4:	parameter passing and return values
5758	R5-R10: parameter passing
5759	R13:	small data area pointer
5760	R30:	GOT pointer
5761	R31:	frame pointer
5762
5763	(U-Boot also uses R12 as internal GOT pointer. r12
5764	is a volatile register so r12 needs to be reset when
5765	going back and forth between asm and C)
5766
5767    ==> U-Boot will use R2 to hold a pointer to the global data
5768
5769    Note: on PPC, we could use a static initializer (since the
5770    address of the global data structure is known at compile time),
5771    but it turned out that reserving a register results in somewhat
5772    smaller code - although the code savings are not that big (on
5773    average for all boards 752 bytes for the whole U-Boot image,
5774    624 text + 127 data).
5775
5776On ARM, the following registers are used:
5777
5778	R0:	function argument word/integer result
5779	R1-R3:	function argument word
5780	R9:	platform specific
5781	R10:	stack limit (used only if stack checking is enabled)
5782	R11:	argument (frame) pointer
5783	R12:	temporary workspace
5784	R13:	stack pointer
5785	R14:	link register
5786	R15:	program counter
5787
5788    ==> U-Boot will use R9 to hold a pointer to the global data
5789
5790    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
5791
5792On Nios II, the ABI is documented here:
5793	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
5794
5795    ==> U-Boot will use gp to hold a pointer to the global data
5796
5797    Note: on Nios II, we give "-G0" option to gcc and don't use gp
5798    to access small data sections, so gp is free.
5799
5800On NDS32, the following registers are used:
5801
5802	R0-R1:	argument/return
5803	R2-R5:	argument
5804	R15:	temporary register for assembler
5805	R16:	trampoline register
5806	R28:	frame pointer (FP)
5807	R29:	global pointer (GP)
5808	R30:	link register (LP)
5809	R31:	stack pointer (SP)
5810	PC:	program counter (PC)
5811
5812    ==> U-Boot will use R10 to hold a pointer to the global data
5813
5814NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
5815or current versions of GCC may "optimize" the code too much.
5816
5817Memory Management:
5818------------------
5819
5820U-Boot runs in system state and uses physical addresses, i.e. the
5821MMU is not used either for address mapping nor for memory protection.
5822
5823The available memory is mapped to fixed addresses using the memory
5824controller. In this process, a contiguous block is formed for each
5825memory type (Flash, SDRAM, SRAM), even when it consists of several
5826physical memory banks.
5827
5828U-Boot is installed in the first 128 kB of the first Flash bank (on
5829TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
5830booting and sizing and initializing DRAM, the code relocates itself
5831to the upper end of DRAM. Immediately below the U-Boot code some
5832memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
5833configuration setting]. Below that, a structure with global Board
5834Info data is placed, followed by the stack (growing downward).
5835
5836Additionally, some exception handler code is copied to the low 8 kB
5837of DRAM (0x00000000 ... 0x00001FFF).
5838
5839So a typical memory configuration with 16 MB of DRAM could look like
5840this:
5841
5842	0x0000 0000	Exception Vector code
5843	      :
5844	0x0000 1FFF
5845	0x0000 2000	Free for Application Use
5846	      :
5847	      :
5848
5849	      :
5850	      :
5851	0x00FB FF20	Monitor Stack (Growing downward)
5852	0x00FB FFAC	Board Info Data and permanent copy of global data
5853	0x00FC 0000	Malloc Arena
5854	      :
5855	0x00FD FFFF
5856	0x00FE 0000	RAM Copy of Monitor Code
5857	...		eventually: LCD or video framebuffer
5858	...		eventually: pRAM (Protected RAM - unchanged by reset)
5859	0x00FF FFFF	[End of RAM]
5860
5861
5862System Initialization:
5863----------------------
5864
5865In the reset configuration, U-Boot starts at the reset entry point
5866(on most PowerPC systems at address 0x00000100). Because of the reset
5867configuration for CS0# this is a mirror of the on board Flash memory.
5868To be able to re-map memory U-Boot then jumps to its link address.
5869To be able to implement the initialization code in C, a (small!)
5870initial stack is set up in the internal Dual Ported RAM (in case CPUs
5871which provide such a feature like MPC8xx or MPC8260), or in a locked
5872part of the data cache. After that, U-Boot initializes the CPU core,
5873the caches and the SIU.
5874
5875Next, all (potentially) available memory banks are mapped using a
5876preliminary mapping. For example, we put them on 512 MB boundaries
5877(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
5878on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
5879programmed for SDRAM access. Using the temporary configuration, a
5880simple memory test is run that determines the size of the SDRAM
5881banks.
5882
5883When there is more than one SDRAM bank, and the banks are of
5884different size, the largest is mapped first. For equal size, the first
5885bank (CS2#) is mapped first. The first mapping is always for address
58860x00000000, with any additional banks following immediately to create
5887contiguous memory starting from 0.
5888
5889Then, the monitor installs itself at the upper end of the SDRAM area
5890and allocates memory for use by malloc() and for the global Board
5891Info data; also, the exception vector code is copied to the low RAM
5892pages, and the final stack is set up.
5893
5894Only after this relocation will you have a "normal" C environment;
5895until that you are restricted in several ways, mostly because you are
5896running from ROM, and because the code will have to be relocated to a
5897new address in RAM.
5898
5899
5900U-Boot Porting Guide:
5901----------------------
5902
5903[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
5904list, October 2002]
5905
5906
5907int main(int argc, char *argv[])
5908{
5909	sighandler_t no_more_time;
5910
5911	signal(SIGALRM, no_more_time);
5912	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
5913
5914	if (available_money > available_manpower) {
5915		Pay consultant to port U-Boot;
5916		return 0;
5917	}
5918
5919	Download latest U-Boot source;
5920
5921	Subscribe to u-boot mailing list;
5922
5923	if (clueless)
5924		email("Hi, I am new to U-Boot, how do I get started?");
5925
5926	while (learning) {
5927		Read the README file in the top level directory;
5928		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
5929		Read applicable doc/*.README;
5930		Read the source, Luke;
5931		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
5932	}
5933
5934	if (available_money > toLocalCurrency ($2500))
5935		Buy a BDI3000;
5936	else
5937		Add a lot of aggravation and time;
5938
5939	if (a similar board exists) {	/* hopefully... */
5940		cp -a board/<similar> board/<myboard>
5941		cp include/configs/<similar>.h include/configs/<myboard>.h
5942	} else {
5943		Create your own board support subdirectory;
5944		Create your own board include/configs/<myboard>.h file;
5945	}
5946	Edit new board/<myboard> files
5947	Edit new include/configs/<myboard>.h
5948
5949	while (!accepted) {
5950		while (!running) {
5951			do {
5952				Add / modify source code;
5953			} until (compiles);
5954			Debug;
5955			if (clueless)
5956				email("Hi, I am having problems...");
5957		}
5958		Send patch file to the U-Boot email list;
5959		if (reasonable critiques)
5960			Incorporate improvements from email list code review;
5961		else
5962			Defend code as written;
5963	}
5964
5965	return 0;
5966}
5967
5968void no_more_time (int sig)
5969{
5970      hire_a_guru();
5971}
5972
5973
5974Coding Standards:
5975-----------------
5976
5977All contributions to U-Boot should conform to the Linux kernel
5978coding style; see the file "Documentation/CodingStyle" and the script
5979"scripts/Lindent" in your Linux kernel source directory.
5980
5981Source files originating from a different project (for example the
5982MTD subsystem) are generally exempt from these guidelines and are not
5983reformatted to ease subsequent migration to newer versions of those
5984sources.
5985
5986Please note that U-Boot is implemented in C (and to some small parts in
5987Assembler); no C++ is used, so please do not use C++ style comments (//)
5988in your code.
5989
5990Please also stick to the following formatting rules:
5991- remove any trailing white space
5992- use TAB characters for indentation and vertical alignment, not spaces
5993- make sure NOT to use DOS '\r\n' line feeds
5994- do not add more than 2 consecutive empty lines to source files
5995- do not add trailing empty lines to source files
5996
5997Submissions which do not conform to the standards may be returned
5998with a request to reformat the changes.
5999
6000
6001Submitting Patches:
6002-------------------
6003
6004Since the number of patches for U-Boot is growing, we need to
6005establish some rules. Submissions which do not conform to these rules
6006may be rejected, even when they contain important and valuable stuff.
6007
6008Please see http://www.denx.de/wiki/U-Boot/Patches for details.
6009
6010Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
6011see http://lists.denx.de/mailman/listinfo/u-boot
6012
6013When you send a patch, please include the following information with
6014it:
6015
6016* For bug fixes: a description of the bug and how your patch fixes
6017  this bug. Please try to include a way of demonstrating that the
6018  patch actually fixes something.
6019
6020* For new features: a description of the feature and your
6021  implementation.
6022
6023* A CHANGELOG entry as plaintext (separate from the patch)
6024
6025* For major contributions, add a MAINTAINERS file with your
6026  information and associated file and directory references.
6027
6028* When you add support for a new board, don't forget to add a
6029  maintainer e-mail address to the boards.cfg file, too.
6030
6031* If your patch adds new configuration options, don't forget to
6032  document these in the README file.
6033
6034* The patch itself. If you are using git (which is *strongly*
6035  recommended) you can easily generate the patch using the
6036  "git format-patch". If you then use "git send-email" to send it to
6037  the U-Boot mailing list, you will avoid most of the common problems
6038  with some other mail clients.
6039
6040  If you cannot use git, use "diff -purN OLD NEW". If your version of
6041  diff does not support these options, then get the latest version of
6042  GNU diff.
6043
6044  The current directory when running this command shall be the parent
6045  directory of the U-Boot source tree (i. e. please make sure that
6046  your patch includes sufficient directory information for the
6047  affected files).
6048
6049  We prefer patches as plain text. MIME attachments are discouraged,
6050  and compressed attachments must not be used.
6051
6052* If one logical set of modifications affects or creates several
6053  files, all these changes shall be submitted in a SINGLE patch file.
6054
6055* Changesets that contain different, unrelated modifications shall be
6056  submitted as SEPARATE patches, one patch per changeset.
6057
6058
6059Notes:
6060
6061* Before sending the patch, run the buildman script on your patched
6062  source tree and make sure that no errors or warnings are reported
6063  for any of the boards.
6064
6065* Keep your modifications to the necessary minimum: A patch
6066  containing several unrelated changes or arbitrary reformats will be
6067  returned with a request to re-formatting / split it.
6068
6069* If you modify existing code, make sure that your new code does not
6070  add to the memory footprint of the code ;-) Small is beautiful!
6071  When adding new features, these should compile conditionally only
6072  (using #ifdef), and the resulting code with the new feature
6073  disabled must not need more memory than the old code without your
6074  modification.
6075
6076* Remember that there is a size limit of 100 kB per message on the
6077  u-boot mailing list. Bigger patches will be moderated. If they are
6078  reasonable and not too big, they will be acknowledged. But patches
6079  bigger than the size limit should be avoided.
6080