xref: /openbmc/u-boot/README (revision 1494cc89)
1# SPDX-License-Identifier: GPL-2.0+
2#
3# (C) Copyright 2000 - 2013
4# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5
6Summary:
7========
8
9This directory contains the source code for U-Boot, a boot loader for
10Embedded boards based on PowerPC, ARM, MIPS and several other
11processors, which can be installed in a boot ROM and used to
12initialize and test the hardware or to download and run application
13code.
14
15The development of U-Boot is closely related to Linux: some parts of
16the source code originate in the Linux source tree, we have some
17header files in common, and special provision has been made to
18support booting of Linux images.
19
20Some attention has been paid to make this software easily
21configurable and extendable. For instance, all monitor commands are
22implemented with the same call interface, so that it's very easy to
23add new commands. Also, instead of permanently adding rarely used
24code (for instance hardware test utilities) to the monitor, you can
25load and run it dynamically.
26
27
28Status:
29=======
30
31In general, all boards for which a configuration option exists in the
32Makefile have been tested to some extent and can be considered
33"working". In fact, many of them are used in production systems.
34
35In case of problems see the CHANGELOG file to find out who contributed
36the specific port. In addition, there are various MAINTAINERS files
37scattered throughout the U-Boot source identifying the people or
38companies responsible for various boards and subsystems.
39
40Note: As of August, 2010, there is no longer a CHANGELOG file in the
41actual U-Boot source tree; however, it can be created dynamically
42from the Git log using:
43
44	make CHANGELOG
45
46
47Where to get help:
48==================
49
50In case you have questions about, problems with or contributions for
51U-Boot, you should send a message to the U-Boot mailing list at
52<u-boot@lists.denx.de>. There is also an archive of previous traffic
53on the mailing list - please search the archive before asking FAQ's.
54Please see http://lists.denx.de/pipermail/u-boot and
55http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
56
57
58Where to get source code:
59=========================
60
61The U-Boot source code is maintained in the Git repository at
62git://www.denx.de/git/u-boot.git ; you can browse it online at
63http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary
64
65The "snapshot" links on this page allow you to download tarballs of
66any version you might be interested in. Official releases are also
67available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
68directory.
69
70Pre-built (and tested) images are available from
71ftp://ftp.denx.de/pub/u-boot/images/
72
73
74Where we come from:
75===================
76
77- start from 8xxrom sources
78- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
79- clean up code
80- make it easier to add custom boards
81- make it possible to add other [PowerPC] CPUs
82- extend functions, especially:
83  * Provide extended interface to Linux boot loader
84  * S-Record download
85  * network boot
86  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
87- create ARMBoot project (http://sourceforge.net/projects/armboot)
88- add other CPU families (starting with ARM)
89- create U-Boot project (http://sourceforge.net/projects/u-boot)
90- current project page: see http://www.denx.de/wiki/U-Boot
91
92
93Names and Spelling:
94===================
95
96The "official" name of this project is "Das U-Boot". The spelling
97"U-Boot" shall be used in all written text (documentation, comments
98in source files etc.). Example:
99
100	This is the README file for the U-Boot project.
101
102File names etc. shall be based on the string "u-boot". Examples:
103
104	include/asm-ppc/u-boot.h
105
106	#include <asm/u-boot.h>
107
108Variable names, preprocessor constants etc. shall be either based on
109the string "u_boot" or on "U_BOOT". Example:
110
111	U_BOOT_VERSION		u_boot_logo
112	IH_OS_U_BOOT		u_boot_hush_start
113
114
115Versioning:
116===========
117
118Starting with the release in October 2008, the names of the releases
119were changed from numerical release numbers without deeper meaning
120into a time stamp based numbering. Regular releases are identified by
121names consisting of the calendar year and month of the release date.
122Additional fields (if present) indicate release candidates or bug fix
123releases in "stable" maintenance trees.
124
125Examples:
126	U-Boot v2009.11	    - Release November 2009
127	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
128	U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
129
130
131Directory Hierarchy:
132====================
133
134/arch			Architecture specific files
135  /arc			Files generic to ARC architecture
136  /arm			Files generic to ARM architecture
137  /m68k			Files generic to m68k architecture
138  /microblaze		Files generic to microblaze architecture
139  /mips			Files generic to MIPS architecture
140  /nds32		Files generic to NDS32 architecture
141  /nios2		Files generic to Altera NIOS2 architecture
142  /openrisc		Files generic to OpenRISC architecture
143  /powerpc		Files generic to PowerPC architecture
144  /riscv		Files generic to RISC-V architecture
145  /sandbox		Files generic to HW-independent "sandbox"
146  /sh			Files generic to SH architecture
147  /x86			Files generic to x86 architecture
148/api			Machine/arch independent API for external apps
149/board			Board dependent files
150/cmd			U-Boot commands functions
151/common			Misc architecture independent functions
152/configs		Board default configuration files
153/disk			Code for disk drive partition handling
154/doc			Documentation (don't expect too much)
155/drivers		Commonly used device drivers
156/dts			Contains Makefile for building internal U-Boot fdt.
157/examples		Example code for standalone applications, etc.
158/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
159/include		Header Files
160/lib			Library routines generic to all architectures
161/Licenses		Various license files
162/net			Networking code
163/post			Power On Self Test
164/scripts		Various build scripts and Makefiles
165/test			Various unit test files
166/tools			Tools to build S-Record or U-Boot images, etc.
167
168Software Configuration:
169=======================
170
171Configuration is usually done using C preprocessor defines; the
172rationale behind that is to avoid dead code whenever possible.
173
174There are two classes of configuration variables:
175
176* Configuration _OPTIONS_:
177  These are selectable by the user and have names beginning with
178  "CONFIG_".
179
180* Configuration _SETTINGS_:
181  These depend on the hardware etc. and should not be meddled with if
182  you don't know what you're doing; they have names beginning with
183  "CONFIG_SYS_".
184
185Previously, all configuration was done by hand, which involved creating
186symbolic links and editing configuration files manually. More recently,
187U-Boot has added the Kbuild infrastructure used by the Linux kernel,
188allowing you to use the "make menuconfig" command to configure your
189build.
190
191
192Selection of Processor Architecture and Board Type:
193---------------------------------------------------
194
195For all supported boards there are ready-to-use default
196configurations available; just type "make <board_name>_defconfig".
197
198Example: For a TQM823L module type:
199
200	cd u-boot
201	make TQM823L_defconfig
202
203Note: If you're looking for the default configuration file for a board
204you're sure used to be there but is now missing, check the file
205doc/README.scrapyard for a list of no longer supported boards.
206
207Sandbox Environment:
208--------------------
209
210U-Boot can be built natively to run on a Linux host using the 'sandbox'
211board. This allows feature development which is not board- or architecture-
212specific to be undertaken on a native platform. The sandbox is also used to
213run some of U-Boot's tests.
214
215See board/sandbox/README.sandbox for more details.
216
217
218Board Initialisation Flow:
219--------------------------
220
221This is the intended start-up flow for boards. This should apply for both
222SPL and U-Boot proper (i.e. they both follow the same rules).
223
224Note: "SPL" stands for "Secondary Program Loader," which is explained in
225more detail later in this file.
226
227At present, SPL mostly uses a separate code path, but the function names
228and roles of each function are the same. Some boards or architectures
229may not conform to this.  At least most ARM boards which use
230CONFIG_SPL_FRAMEWORK conform to this.
231
232Execution typically starts with an architecture-specific (and possibly
233CPU-specific) start.S file, such as:
234
235	- arch/arm/cpu/armv7/start.S
236	- arch/powerpc/cpu/mpc83xx/start.S
237	- arch/mips/cpu/start.S
238
239and so on. From there, three functions are called; the purpose and
240limitations of each of these functions are described below.
241
242lowlevel_init():
243	- purpose: essential init to permit execution to reach board_init_f()
244	- no global_data or BSS
245	- there is no stack (ARMv7 may have one but it will soon be removed)
246	- must not set up SDRAM or use console
247	- must only do the bare minimum to allow execution to continue to
248		board_init_f()
249	- this is almost never needed
250	- return normally from this function
251
252board_init_f():
253	- purpose: set up the machine ready for running board_init_r():
254		i.e. SDRAM and serial UART
255	- global_data is available
256	- stack is in SRAM
257	- BSS is not available, so you cannot use global/static variables,
258		only stack variables and global_data
259
260	Non-SPL-specific notes:
261	- dram_init() is called to set up DRAM. If already done in SPL this
262		can do nothing
263
264	SPL-specific notes:
265	- you can override the entire board_init_f() function with your own
266		version as needed.
267	- preloader_console_init() can be called here in extremis
268	- should set up SDRAM, and anything needed to make the UART work
269	- these is no need to clear BSS, it will be done by crt0.S
270	- must return normally from this function (don't call board_init_r()
271		directly)
272
273Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
274this point the stack and global_data are relocated to below
275CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
276memory.
277
278board_init_r():
279	- purpose: main execution, common code
280	- global_data is available
281	- SDRAM is available
282	- BSS is available, all static/global variables can be used
283	- execution eventually continues to main_loop()
284
285	Non-SPL-specific notes:
286	- U-Boot is relocated to the top of memory and is now running from
287		there.
288
289	SPL-specific notes:
290	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
291		CONFIG_SPL_STACK_R_ADDR points into SDRAM
292	- preloader_console_init() can be called here - typically this is
293		done by selecting CONFIG_SPL_BOARD_INIT and then supplying a
294		spl_board_init() function containing this call
295	- loads U-Boot or (in falcon mode) Linux
296
297
298
299Configuration Options:
300----------------------
301
302Configuration depends on the combination of board and CPU type; all
303such information is kept in a configuration file
304"include/configs/<board_name>.h".
305
306Example: For a TQM823L module, all configuration settings are in
307"include/configs/TQM823L.h".
308
309
310Many of the options are named exactly as the corresponding Linux
311kernel configuration options. The intention is to make it easier to
312build a config tool - later.
313
314- ARM Platform Bus Type(CCI):
315		CoreLink Cache Coherent Interconnect (CCI) is ARM BUS which
316		provides full cache coherency between two clusters of multi-core
317		CPUs and I/O coherency for devices and I/O masters
318
319		CONFIG_SYS_FSL_HAS_CCI400
320
321		Defined For SoC that has cache coherent interconnect
322		CCN-400
323
324		CONFIG_SYS_FSL_HAS_CCN504
325
326		Defined for SoC that has cache coherent interconnect CCN-504
327
328The following options need to be configured:
329
330- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.
331
332- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
333
334- Marvell Family Member
335		CONFIG_SYS_MVFS		- define it if you want to enable
336					  multiple fs option at one time
337					  for marvell soc family
338
339- 85xx CPU Options:
340		CONFIG_SYS_PPC64
341
342		Specifies that the core is a 64-bit PowerPC implementation (implements
343		the "64" category of the Power ISA). This is necessary for ePAPR
344		compliance, among other possible reasons.
345
346		CONFIG_SYS_FSL_TBCLK_DIV
347
348		Defines the core time base clock divider ratio compared to the
349		system clock.  On most PQ3 devices this is 8, on newer QorIQ
350		devices it can be 16 or 32.  The ratio varies from SoC to Soc.
351
352		CONFIG_SYS_FSL_PCIE_COMPAT
353
354		Defines the string to utilize when trying to match PCIe device
355		tree nodes for the given platform.
356
357		CONFIG_SYS_FSL_ERRATUM_A004510
358
359		Enables a workaround for erratum A004510.  If set,
360		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
361		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.
362
363		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
364		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)
365
366		Defines one or two SoC revisions (low 8 bits of SVR)
367		for which the A004510 workaround should be applied.
368
369		The rest of SVR is either not relevant to the decision
370		of whether the erratum is present (e.g. p2040 versus
371		p2041) or is implied by the build target, which controls
372		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
373
374		See Freescale App Note 4493 for more information about
375		this erratum.
376
377		CONFIG_A003399_NOR_WORKAROUND
378		Enables a workaround for IFC erratum A003399. It is only
379		required during NOR boot.
380
381		CONFIG_A008044_WORKAROUND
382		Enables a workaround for T1040/T1042 erratum A008044. It is only
383		required during NAND boot and valid for Rev 1.0 SoC revision
384
385		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY
386
387		This is the value to write into CCSR offset 0x18600
388		according to the A004510 workaround.
389
390		CONFIG_SYS_FSL_DSP_DDR_ADDR
391		This value denotes start offset of DDR memory which is
392		connected exclusively to the DSP cores.
393
394		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
395		This value denotes start offset of M2 memory
396		which is directly connected to the DSP core.
397
398		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
399		This value denotes start offset of M3 memory which is directly
400		connected to the DSP core.
401
402		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
403		This value denotes start offset of DSP CCSR space.
404
405		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
406		Single Source Clock is clocking mode present in some of FSL SoC's.
407		In this mode, a single differential clock is used to supply
408		clocks to the sysclock, ddrclock and usbclock.
409
410		CONFIG_SYS_CPC_REINIT_F
411		This CONFIG is defined when the CPC is configured as SRAM at the
412		time of U-Boot entry and is required to be re-initialized.
413
414		CONFIG_DEEP_SLEEP
415		Indicates this SoC supports deep sleep feature. If deep sleep is
416		supported, core will start to execute uboot when wakes up.
417
418- Generic CPU options:
419		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN
420
421		Defines the endianess of the CPU. Implementation of those
422		values is arch specific.
423
424		CONFIG_SYS_FSL_DDR
425		Freescale DDR driver in use. This type of DDR controller is
426		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
427		SoCs.
428
429		CONFIG_SYS_FSL_DDR_ADDR
430		Freescale DDR memory-mapped register base.
431
432		CONFIG_SYS_FSL_DDR_EMU
433		Specify emulator support for DDR. Some DDR features such as
434		deskew training are not available.
435
436		CONFIG_SYS_FSL_DDRC_GEN1
437		Freescale DDR1 controller.
438
439		CONFIG_SYS_FSL_DDRC_GEN2
440		Freescale DDR2 controller.
441
442		CONFIG_SYS_FSL_DDRC_GEN3
443		Freescale DDR3 controller.
444
445		CONFIG_SYS_FSL_DDRC_GEN4
446		Freescale DDR4 controller.
447
448		CONFIG_SYS_FSL_DDRC_ARM_GEN3
449		Freescale DDR3 controller for ARM-based SoCs.
450
451		CONFIG_SYS_FSL_DDR1
452		Board config to use DDR1. It can be enabled for SoCs with
453		Freescale DDR1 or DDR2 controllers, depending on the board
454		implemetation.
455
456		CONFIG_SYS_FSL_DDR2
457		Board config to use DDR2. It can be enabled for SoCs with
458		Freescale DDR2 or DDR3 controllers, depending on the board
459		implementation.
460
461		CONFIG_SYS_FSL_DDR3
462		Board config to use DDR3. It can be enabled for SoCs with
463		Freescale DDR3 or DDR3L controllers.
464
465		CONFIG_SYS_FSL_DDR3L
466		Board config to use DDR3L. It can be enabled for SoCs with
467		DDR3L controllers.
468
469		CONFIG_SYS_FSL_DDR4
470		Board config to use DDR4. It can be enabled for SoCs with
471		DDR4 controllers.
472
473		CONFIG_SYS_FSL_IFC_BE
474		Defines the IFC controller register space as Big Endian
475
476		CONFIG_SYS_FSL_IFC_LE
477		Defines the IFC controller register space as Little Endian
478
479		CONFIG_SYS_FSL_IFC_CLK_DIV
480		Defines divider of platform clock(clock input to IFC controller).
481
482		CONFIG_SYS_FSL_LBC_CLK_DIV
483		Defines divider of platform clock(clock input to eLBC controller).
484
485		CONFIG_SYS_FSL_PBL_PBI
486		It enables addition of RCW (Power on reset configuration) in built image.
487		Please refer doc/README.pblimage for more details
488
489		CONFIG_SYS_FSL_PBL_RCW
490		It adds PBI(pre-boot instructions) commands in u-boot build image.
491		PBI commands can be used to configure SoC before it starts the execution.
492		Please refer doc/README.pblimage for more details
493
494		CONFIG_SPL_FSL_PBL
495		It adds a target to create boot binary having SPL binary in PBI format
496		concatenated with u-boot binary.
497
498		CONFIG_SYS_FSL_DDR_BE
499		Defines the DDR controller register space as Big Endian
500
501		CONFIG_SYS_FSL_DDR_LE
502		Defines the DDR controller register space as Little Endian
503
504		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
505		Physical address from the view of DDR controllers. It is the
506		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
507		it could be different for ARM SoCs.
508
509		CONFIG_SYS_FSL_DDR_INTLV_256B
510		DDR controller interleaving on 256-byte. This is a special
511		interleaving mode, handled by Dickens for Freescale layerscape
512		SoCs with ARM core.
513
514		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
515		Number of controllers used as main memory.
516
517		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
518		Number of controllers used for other than main memory.
519
520		CONFIG_SYS_FSL_HAS_DP_DDR
521		Defines the SoC has DP-DDR used for DPAA.
522
523		CONFIG_SYS_FSL_SEC_BE
524		Defines the SEC controller register space as Big Endian
525
526		CONFIG_SYS_FSL_SEC_LE
527		Defines the SEC controller register space as Little Endian
528
529- MIPS CPU options:
530		CONFIG_SYS_INIT_SP_OFFSET
531
532		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
533		pointer. This is needed for the temporary stack before
534		relocation.
535
536		CONFIG_SYS_MIPS_CACHE_MODE
537
538		Cache operation mode for the MIPS CPU.
539		See also arch/mips/include/asm/mipsregs.h.
540		Possible values are:
541			CONF_CM_CACHABLE_NO_WA
542			CONF_CM_CACHABLE_WA
543			CONF_CM_UNCACHED
544			CONF_CM_CACHABLE_NONCOHERENT
545			CONF_CM_CACHABLE_CE
546			CONF_CM_CACHABLE_COW
547			CONF_CM_CACHABLE_CUW
548			CONF_CM_CACHABLE_ACCELERATED
549
550		CONFIG_SYS_XWAY_EBU_BOOTCFG
551
552		Special option for Lantiq XWAY SoCs for booting from NOR flash.
553		See also arch/mips/cpu/mips32/start.S.
554
555		CONFIG_XWAY_SWAP_BYTES
556
557		Enable compilation of tools/xway-swap-bytes needed for Lantiq
558		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
559		be swapped if a flash programmer is used.
560
561- ARM options:
562		CONFIG_SYS_EXCEPTION_VECTORS_HIGH
563
564		Select high exception vectors of the ARM core, e.g., do not
565		clear the V bit of the c1 register of CP15.
566
567		COUNTER_FREQUENCY
568		Generic timer clock source frequency.
569
570		COUNTER_FREQUENCY_REAL
571		Generic timer clock source frequency if the real clock is
572		different from COUNTER_FREQUENCY, and can only be determined
573		at run time.
574
575- Tegra SoC options:
576		CONFIG_TEGRA_SUPPORT_NON_SECURE
577
578		Support executing U-Boot in non-secure (NS) mode. Certain
579		impossible actions will be skipped if the CPU is in NS mode,
580		such as ARM architectural timer initialization.
581
582- Linux Kernel Interface:
583		CONFIG_CLOCKS_IN_MHZ
584
585		U-Boot stores all clock information in Hz
586		internally. For binary compatibility with older Linux
587		kernels (which expect the clocks passed in the
588		bd_info data to be in MHz) the environment variable
589		"clocks_in_mhz" can be defined so that U-Boot
590		converts clock data to MHZ before passing it to the
591		Linux kernel.
592		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
593		"clocks_in_mhz=1" is automatically included in the
594		default environment.
595
596		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]
597
598		When transferring memsize parameter to Linux, some versions
599		expect it to be in bytes, others in MB.
600		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
601
602		CONFIG_OF_LIBFDT
603
604		New kernel versions are expecting firmware settings to be
605		passed using flattened device trees (based on open firmware
606		concepts).
607
608		CONFIG_OF_LIBFDT
609		 * New libfdt-based support
610		 * Adds the "fdt" command
611		 * The bootm command automatically updates the fdt
612
613		OF_TBCLK - The timebase frequency.
614		OF_STDOUT_PATH - The path to the console device
615
616		boards with QUICC Engines require OF_QE to set UCC MAC
617		addresses
618
619		CONFIG_OF_BOARD_SETUP
620
621		Board code has addition modification that it wants to make
622		to the flat device tree before handing it off to the kernel
623
624		CONFIG_OF_SYSTEM_SETUP
625
626		Other code has addition modification that it wants to make
627		to the flat device tree before handing it off to the kernel.
628		This causes ft_system_setup() to be called before booting
629		the kernel.
630
631		CONFIG_OF_IDE_FIXUP
632
633		U-Boot can detect if an IDE device is present or not.
634		If not, and this new config option is activated, U-Boot
635		removes the ATA node from the DTS before booting Linux,
636		so the Linux IDE driver does not probe the device and
637		crash. This is needed for buggy hardware (uc101) where
638		no pull down resistor is connected to the signal IDE5V_DD7.
639
640		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]
641
642		This setting is mandatory for all boards that have only one
643		machine type and must be used to specify the machine type
644		number as it appears in the ARM machine registry
645		(see http://www.arm.linux.org.uk/developer/machines/).
646		Only boards that have multiple machine types supported
647		in a single configuration file and the machine type is
648		runtime discoverable, do not have to use this setting.
649
650- vxWorks boot parameters:
651
652		bootvx constructs a valid bootline using the following
653		environments variables: bootdev, bootfile, ipaddr, netmask,
654		serverip, gatewayip, hostname, othbootargs.
655		It loads the vxWorks image pointed bootfile.
656
657		Note: If a "bootargs" environment is defined, it will overwride
658		the defaults discussed just above.
659
660- Cache Configuration:
661		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
662		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
663		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
664
665- Cache Configuration for ARM:
666		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
667				      controller
668		CONFIG_SYS_PL310_BASE - Physical base address of PL310
669					controller register space
670
671- Serial Ports:
672		CONFIG_PL010_SERIAL
673
674		Define this if you want support for Amba PrimeCell PL010 UARTs.
675
676		CONFIG_PL011_SERIAL
677
678		Define this if you want support for Amba PrimeCell PL011 UARTs.
679
680		CONFIG_PL011_CLOCK
681
682		If you have Amba PrimeCell PL011 UARTs, set this variable to
683		the clock speed of the UARTs.
684
685		CONFIG_PL01x_PORTS
686
687		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
688		define this to a list of base addresses for each (supported)
689		port. See e.g. include/configs/versatile.h
690
691		CONFIG_SERIAL_HW_FLOW_CONTROL
692
693		Define this variable to enable hw flow control in serial driver.
694		Current user of this option is drivers/serial/nsl16550.c driver
695
696- Console Baudrate:
697		CONFIG_BAUDRATE - in bps
698		Select one of the baudrates listed in
699		CONFIG_SYS_BAUDRATE_TABLE, see below.
700
701- Autoboot Command:
702		CONFIG_BOOTCOMMAND
703		Only needed when CONFIG_BOOTDELAY is enabled;
704		define a command string that is automatically executed
705		when no character is read on the console interface
706		within "Boot Delay" after reset.
707
708		CONFIG_RAMBOOT and CONFIG_NFSBOOT
709		The value of these goes into the environment as
710		"ramboot" and "nfsboot" respectively, and can be used
711		as a convenience, when switching between booting from
712		RAM and NFS.
713
714- Pre-Boot Commands:
715		CONFIG_PREBOOT
716
717		When this option is #defined, the existence of the
718		environment variable "preboot" will be checked
719		immediately before starting the CONFIG_BOOTDELAY
720		countdown and/or running the auto-boot command resp.
721		entering interactive mode.
722
723		This feature is especially useful when "preboot" is
724		automatically generated or modified. For an example
725		see the LWMON board specific code: here "preboot" is
726		modified when the user holds down a certain
727		combination of keys on the (special) keyboard when
728		booting the systems
729
730- Serial Download Echo Mode:
731		CONFIG_LOADS_ECHO
732		If defined to 1, all characters received during a
733		serial download (using the "loads" command) are
734		echoed back. This might be needed by some terminal
735		emulations (like "cu"), but may as well just take
736		time on others. This setting #define's the initial
737		value of the "loads_echo" environment variable.
738
739- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
740		CONFIG_KGDB_BAUDRATE
741		Select one of the baudrates listed in
742		CONFIG_SYS_BAUDRATE_TABLE, see below.
743
744- Removal of commands
745		If no commands are needed to boot, you can disable
746		CONFIG_CMDLINE to remove them. In this case, the command line
747		will not be available, and when U-Boot wants to execute the
748		boot command (on start-up) it will call board_run_command()
749		instead. This can reduce image size significantly for very
750		simple boot procedures.
751
752- Regular expression support:
753		CONFIG_REGEX
754		If this variable is defined, U-Boot is linked against
755		the SLRE (Super Light Regular Expression) library,
756		which adds regex support to some commands, as for
757		example "env grep" and "setexpr".
758
759- Device tree:
760		CONFIG_OF_CONTROL
761		If this variable is defined, U-Boot will use a device tree
762		to configure its devices, instead of relying on statically
763		compiled #defines in the board file. This option is
764		experimental and only available on a few boards. The device
765		tree is available in the global data as gd->fdt_blob.
766
767		U-Boot needs to get its device tree from somewhere. This can
768		be done using one of the three options below:
769
770		CONFIG_OF_EMBED
771		If this variable is defined, U-Boot will embed a device tree
772		binary in its image. This device tree file should be in the
773		board directory and called <soc>-<board>.dts. The binary file
774		is then picked up in board_init_f() and made available through
775		the global data structure as gd->fdt_blob.
776
777		CONFIG_OF_SEPARATE
778		If this variable is defined, U-Boot will build a device tree
779		binary. It will be called u-boot.dtb. Architecture-specific
780		code will locate it at run-time. Generally this works by:
781
782			cat u-boot.bin u-boot.dtb >image.bin
783
784		and in fact, U-Boot does this for you, creating a file called
785		u-boot-dtb.bin which is useful in the common case. You can
786		still use the individual files if you need something more
787		exotic.
788
789		CONFIG_OF_BOARD
790		If this variable is defined, U-Boot will use the device tree
791		provided by the board at runtime instead of embedding one with
792		the image. Only boards defining board_fdt_blob_setup() support
793		this option (see include/fdtdec.h file).
794
795- Watchdog:
796		CONFIG_WATCHDOG
797		If this variable is defined, it enables watchdog
798		support for the SoC. There must be support in the SoC
799		specific code for a watchdog. For the 8xx
800		CPUs, the SIU Watchdog feature is enabled in the SYPCR
801		register.  When supported for a specific SoC is
802		available, then no further board specific code should
803		be needed to use it.
804
805		CONFIG_HW_WATCHDOG
806		When using a watchdog circuitry external to the used
807		SoC, then define this variable and provide board
808		specific code for the "hw_watchdog_reset" function.
809
810		CONFIG_AT91_HW_WDT_TIMEOUT
811		specify the timeout in seconds. default 2 seconds.
812
813- Real-Time Clock:
814
815		When CONFIG_CMD_DATE is selected, the type of the RTC
816		has to be selected, too. Define exactly one of the
817		following options:
818
819		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
820		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
821		CONFIG_RTC_MC146818	- use MC146818 RTC
822		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
823		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
824		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
825		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
826		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
827		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
828		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
829		CONFIG_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
830		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
831					  RV3029 RTC.
832
833		Note that if the RTC uses I2C, then the I2C interface
834		must also be configured. See I2C Support, below.
835
836- GPIO Support:
837		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO
838
839		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
840		chip-ngpio pairs that tell the PCA953X driver the number of
841		pins supported by a particular chip.
842
843		Note that if the GPIO device uses I2C, then the I2C interface
844		must also be configured. See I2C Support, below.
845
846- I/O tracing:
847		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
848		accesses and can checksum them or write a list of them out
849		to memory. See the 'iotrace' command for details. This is
850		useful for testing device drivers since it can confirm that
851		the driver behaves the same way before and after a code
852		change. Currently this is supported on sandbox and arm. To
853		add support for your architecture, add '#include <iotrace.h>'
854		to the bottom of arch/<arch>/include/asm/io.h and test.
855
856		Example output from the 'iotrace stats' command is below.
857		Note that if the trace buffer is exhausted, the checksum will
858		still continue to operate.
859
860			iotrace is enabled
861			Start:  10000000	(buffer start address)
862			Size:   00010000	(buffer size)
863			Offset: 00000120	(current buffer offset)
864			Output: 10000120	(start + offset)
865			Count:  00000018	(number of trace records)
866			CRC32:  9526fb66	(CRC32 of all trace records)
867
868- Timestamp Support:
869
870		When CONFIG_TIMESTAMP is selected, the timestamp
871		(date and time) of an image is printed by image
872		commands like bootm or iminfo. This option is
873		automatically enabled when you select CONFIG_CMD_DATE .
874
875- Partition Labels (disklabels) Supported:
876		Zero or more of the following:
877		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
878		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
879		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
880				       bootloader.  Note 2TB partition limit; see
881				       disk/part_efi.c
882		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
883
884		If IDE or SCSI support is enabled (CONFIG_IDE or
885		CONFIG_SCSI) you must configure support for at
886		least one non-MTD partition type as well.
887
888- IDE Reset method:
889		CONFIG_IDE_RESET_ROUTINE - this is defined in several
890		board configurations files but used nowhere!
891
892		CONFIG_IDE_RESET - is this is defined, IDE Reset will
893		be performed by calling the function
894			ide_set_reset(int reset)
895		which has to be defined in a board specific file
896
897- ATAPI Support:
898		CONFIG_ATAPI
899
900		Set this to enable ATAPI support.
901
902- LBA48 Support
903		CONFIG_LBA48
904
905		Set this to enable support for disks larger than 137GB
906		Also look at CONFIG_SYS_64BIT_LBA.
907		Whithout these , LBA48 support uses 32bit variables and will 'only'
908		support disks up to 2.1TB.
909
910		CONFIG_SYS_64BIT_LBA:
911			When enabled, makes the IDE subsystem use 64bit sector addresses.
912			Default is 32bit.
913
914- SCSI Support:
915		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
916		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
917		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
918		maximum numbers of LUNs, SCSI ID's and target
919		devices.
920
921		The environment variable 'scsidevs' is set to the number of
922		SCSI devices found during the last scan.
923
924- NETWORK Support (PCI):
925		CONFIG_E1000
926		Support for Intel 8254x/8257x gigabit chips.
927
928		CONFIG_E1000_SPI
929		Utility code for direct access to the SPI bus on Intel 8257x.
930		This does not do anything useful unless you set at least one
931		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.
932
933		CONFIG_E1000_SPI_GENERIC
934		Allow generic access to the SPI bus on the Intel 8257x, for
935		example with the "sspi" command.
936
937		CONFIG_EEPRO100
938		Support for Intel 82557/82559/82559ER chips.
939		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
940		write routine for first time initialisation.
941
942		CONFIG_TULIP
943		Support for Digital 2114x chips.
944		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
945		modem chip initialisation (KS8761/QS6611).
946
947		CONFIG_NATSEMI
948		Support for National dp83815 chips.
949
950		CONFIG_NS8382X
951		Support for National dp8382[01] gigabit chips.
952
953- NETWORK Support (other):
954
955		CONFIG_DRIVER_AT91EMAC
956		Support for AT91RM9200 EMAC.
957
958			CONFIG_RMII
959			Define this to use reduced MII inteface
960
961			CONFIG_DRIVER_AT91EMAC_QUIET
962			If this defined, the driver is quiet.
963			The driver doen't show link status messages.
964
965		CONFIG_CALXEDA_XGMAC
966		Support for the Calxeda XGMAC device
967
968		CONFIG_LAN91C96
969		Support for SMSC's LAN91C96 chips.
970
971			CONFIG_LAN91C96_USE_32_BIT
972			Define this to enable 32 bit addressing
973
974		CONFIG_SMC91111
975		Support for SMSC's LAN91C111 chip
976
977			CONFIG_SMC91111_BASE
978			Define this to hold the physical address
979			of the device (I/O space)
980
981			CONFIG_SMC_USE_32_BIT
982			Define this if data bus is 32 bits
983
984			CONFIG_SMC_USE_IOFUNCS
985			Define this to use i/o functions instead of macros
986			(some hardware wont work with macros)
987
988		CONFIG_DRIVER_TI_EMAC
989		Support for davinci emac
990
991			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
992			Define this if you have more then 3 PHYs.
993
994		CONFIG_FTGMAC100
995		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
996
997			CONFIG_FTGMAC100_EGIGA
998			Define this to use GE link update with gigabit PHY.
999			Define this if FTGMAC100 is connected to gigabit PHY.
1000			If your system has 10/100 PHY only, it might not occur
1001			wrong behavior. Because PHY usually return timeout or
1002			useless data when polling gigabit status and gigabit
1003			control registers. This behavior won't affect the
1004			correctnessof 10/100 link speed update.
1005
1006		CONFIG_SH_ETHER
1007		Support for Renesas on-chip Ethernet controller
1008
1009			CONFIG_SH_ETHER_USE_PORT
1010			Define the number of ports to be used
1011
1012			CONFIG_SH_ETHER_PHY_ADDR
1013			Define the ETH PHY's address
1014
1015			CONFIG_SH_ETHER_CACHE_WRITEBACK
1016			If this option is set, the driver enables cache flush.
1017
1018- PWM Support:
1019		CONFIG_PWM_IMX
1020		Support for PWM module on the imx6.
1021
1022- TPM Support:
1023		CONFIG_TPM
1024		Support TPM devices.
1025
1026		CONFIG_TPM_TIS_INFINEON
1027		Support for Infineon i2c bus TPM devices. Only one device
1028		per system is supported at this time.
1029
1030			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
1031			Define the burst count bytes upper limit
1032
1033		CONFIG_TPM_ST33ZP24
1034		Support for STMicroelectronics TPM devices. Requires DM_TPM support.
1035
1036			CONFIG_TPM_ST33ZP24_I2C
1037			Support for STMicroelectronics ST33ZP24 I2C devices.
1038			Requires TPM_ST33ZP24 and I2C.
1039
1040			CONFIG_TPM_ST33ZP24_SPI
1041			Support for STMicroelectronics ST33ZP24 SPI devices.
1042			Requires TPM_ST33ZP24 and SPI.
1043
1044		CONFIG_TPM_ATMEL_TWI
1045		Support for Atmel TWI TPM device. Requires I2C support.
1046
1047		CONFIG_TPM_TIS_LPC
1048		Support for generic parallel port TPM devices. Only one device
1049		per system is supported at this time.
1050
1051			CONFIG_TPM_TIS_BASE_ADDRESS
1052			Base address where the generic TPM device is mapped
1053			to. Contemporary x86 systems usually map it at
1054			0xfed40000.
1055
1056		CONFIG_TPM
1057		Define this to enable the TPM support library which provides
1058		functional interfaces to some TPM commands.
1059		Requires support for a TPM device.
1060
1061		CONFIG_TPM_AUTH_SESSIONS
1062		Define this to enable authorized functions in the TPM library.
1063		Requires CONFIG_TPM and CONFIG_SHA1.
1064
1065- USB Support:
1066		At the moment only the UHCI host controller is
1067		supported (PIP405, MIP405); define
1068		CONFIG_USB_UHCI to enable it.
1069		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
1070		and define CONFIG_USB_STORAGE to enable the USB
1071		storage devices.
1072		Note:
1073		Supported are USB Keyboards and USB Floppy drives
1074		(TEAC FD-05PUB).
1075
1076		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
1077		txfilltuning field in the EHCI controller on reset.
1078
1079		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
1080		HW module registers.
1081
1082- USB Device:
1083		Define the below if you wish to use the USB console.
1084		Once firmware is rebuilt from a serial console issue the
1085		command "setenv stdin usbtty; setenv stdout usbtty" and
1086		attach your USB cable. The Unix command "dmesg" should print
1087		it has found a new device. The environment variable usbtty
1088		can be set to gserial or cdc_acm to enable your device to
1089		appear to a USB host as a Linux gserial device or a
1090		Common Device Class Abstract Control Model serial device.
1091		If you select usbtty = gserial you should be able to enumerate
1092		a Linux host by
1093		# modprobe usbserial vendor=0xVendorID product=0xProductID
1094		else if using cdc_acm, simply setting the environment
1095		variable usbtty to be cdc_acm should suffice. The following
1096		might be defined in YourBoardName.h
1097
1098			CONFIG_USB_DEVICE
1099			Define this to build a UDC device
1100
1101			CONFIG_USB_TTY
1102			Define this to have a tty type of device available to
1103			talk to the UDC device
1104
1105			CONFIG_USBD_HS
1106			Define this to enable the high speed support for usb
1107			device and usbtty. If this feature is enabled, a routine
1108			int is_usbd_high_speed(void)
1109			also needs to be defined by the driver to dynamically poll
1110			whether the enumeration has succeded at high speed or full
1111			speed.
1112
1113			CONFIG_SYS_CONSOLE_IS_IN_ENV
1114			Define this if you want stdin, stdout &/or stderr to
1115			be set to usbtty.
1116
1117		If you have a USB-IF assigned VendorID then you may wish to
1118		define your own vendor specific values either in BoardName.h
1119		or directly in usbd_vendor_info.h. If you don't define
1120		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
1121		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
1122		should pretend to be a Linux device to it's target host.
1123
1124			CONFIG_USBD_MANUFACTURER
1125			Define this string as the name of your company for
1126			- CONFIG_USBD_MANUFACTURER "my company"
1127
1128			CONFIG_USBD_PRODUCT_NAME
1129			Define this string as the name of your product
1130			- CONFIG_USBD_PRODUCT_NAME "acme usb device"
1131
1132			CONFIG_USBD_VENDORID
1133			Define this as your assigned Vendor ID from the USB
1134			Implementors Forum. This *must* be a genuine Vendor ID
1135			to avoid polluting the USB namespace.
1136			- CONFIG_USBD_VENDORID 0xFFFF
1137
1138			CONFIG_USBD_PRODUCTID
1139			Define this as the unique Product ID
1140			for your device
1141			- CONFIG_USBD_PRODUCTID 0xFFFF
1142
1143- ULPI Layer Support:
1144		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
1145		the generic ULPI layer. The generic layer accesses the ULPI PHY
1146		via the platform viewport, so you need both the genric layer and
1147		the viewport enabled. Currently only Chipidea/ARC based
1148		viewport is supported.
1149		To enable the ULPI layer support, define CONFIG_USB_ULPI and
1150		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
1151		If your ULPI phy needs a different reference clock than the
1152		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
1153		the appropriate value in Hz.
1154
1155- MMC Support:
1156		The MMC controller on the Intel PXA is supported. To
1157		enable this define CONFIG_MMC. The MMC can be
1158		accessed from the boot prompt by mapping the device
1159		to physical memory similar to flash. Command line is
1160		enabled with CONFIG_CMD_MMC. The MMC driver also works with
1161		the FAT fs. This is enabled with CONFIG_CMD_FAT.
1162
1163		CONFIG_SH_MMCIF
1164		Support for Renesas on-chip MMCIF controller
1165
1166			CONFIG_SH_MMCIF_ADDR
1167			Define the base address of MMCIF registers
1168
1169			CONFIG_SH_MMCIF_CLK
1170			Define the clock frequency for MMCIF
1171
1172		CONFIG_SUPPORT_EMMC_BOOT
1173		Enable some additional features of the eMMC boot partitions.
1174
1175		CONFIG_SUPPORT_EMMC_RPMB
1176		Enable the commands for reading, writing and programming the
1177		key for the Replay Protection Memory Block partition in eMMC.
1178
1179- USB Device Firmware Update (DFU) class support:
1180		CONFIG_DFU_OVER_USB
1181		This enables the USB portion of the DFU USB class
1182
1183		CONFIG_DFU_MMC
1184		This enables support for exposing (e)MMC devices via DFU.
1185
1186		CONFIG_DFU_NAND
1187		This enables support for exposing NAND devices via DFU.
1188
1189		CONFIG_DFU_RAM
1190		This enables support for exposing RAM via DFU.
1191		Note: DFU spec refer to non-volatile memory usage, but
1192		allow usages beyond the scope of spec - here RAM usage,
1193		one that would help mostly the developer.
1194
1195		CONFIG_SYS_DFU_DATA_BUF_SIZE
1196		Dfu transfer uses a buffer before writing data to the
1197		raw storage device. Make the size (in bytes) of this buffer
1198		configurable. The size of this buffer is also configurable
1199		through the "dfu_bufsiz" environment variable.
1200
1201		CONFIG_SYS_DFU_MAX_FILE_SIZE
1202		When updating files rather than the raw storage device,
1203		we use a static buffer to copy the file into and then write
1204		the buffer once we've been given the whole file.  Define
1205		this to the maximum filesize (in bytes) for the buffer.
1206		Default is 4 MiB if undefined.
1207
1208		DFU_DEFAULT_POLL_TIMEOUT
1209		Poll timeout [ms], is the timeout a device can send to the
1210		host. The host must wait for this timeout before sending
1211		a subsequent DFU_GET_STATUS request to the device.
1212
1213		DFU_MANIFEST_POLL_TIMEOUT
1214		Poll timeout [ms], which the device sends to the host when
1215		entering dfuMANIFEST state. Host waits this timeout, before
1216		sending again an USB request to the device.
1217
1218- Journaling Flash filesystem support:
1219		CONFIG_JFFS2_NAND
1220		Define these for a default partition on a NAND device
1221
1222		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1223		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1224		Define these for a default partition on a NOR device
1225
1226- Keyboard Support:
1227		See Kconfig help for available keyboard drivers.
1228
1229		CONFIG_KEYBOARD
1230
1231		Define this to enable a custom keyboard support.
1232		This simply calls drv_keyboard_init() which must be
1233		defined in your board-specific files. This option is deprecated
1234		and is only used by novena. For new boards, use driver model
1235		instead.
1236
1237- Video support:
1238		CONFIG_FSL_DIU_FB
1239		Enable the Freescale DIU video driver.	Reference boards for
1240		SOCs that have a DIU should define this macro to enable DIU
1241		support, and should also define these other macros:
1242
1243			CONFIG_SYS_DIU_ADDR
1244			CONFIG_VIDEO
1245			CONFIG_CFB_CONSOLE
1246			CONFIG_VIDEO_SW_CURSOR
1247			CONFIG_VGA_AS_SINGLE_DEVICE
1248			CONFIG_VIDEO_LOGO
1249			CONFIG_VIDEO_BMP_LOGO
1250
1251		The DIU driver will look for the 'video-mode' environment
1252		variable, and if defined, enable the DIU as a console during
1253		boot.  See the documentation file doc/README.video for a
1254		description of this variable.
1255
1256- LCD Support:	CONFIG_LCD
1257
1258		Define this to enable LCD support (for output to LCD
1259		display); also select one of the supported displays
1260		by defining one of these:
1261
1262		CONFIG_ATMEL_LCD:
1263
1264			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1265
1266		CONFIG_NEC_NL6448AC33:
1267
1268			NEC NL6448AC33-18. Active, color, single scan.
1269
1270		CONFIG_NEC_NL6448BC20
1271
1272			NEC NL6448BC20-08. 6.5", 640x480.
1273			Active, color, single scan.
1274
1275		CONFIG_NEC_NL6448BC33_54
1276
1277			NEC NL6448BC33-54. 10.4", 640x480.
1278			Active, color, single scan.
1279
1280		CONFIG_SHARP_16x9
1281
1282			Sharp 320x240. Active, color, single scan.
1283			It isn't 16x9, and I am not sure what it is.
1284
1285		CONFIG_SHARP_LQ64D341
1286
1287			Sharp LQ64D341 display, 640x480.
1288			Active, color, single scan.
1289
1290		CONFIG_HLD1045
1291
1292			HLD1045 display, 640x480.
1293			Active, color, single scan.
1294
1295		CONFIG_OPTREX_BW
1296
1297			Optrex	 CBL50840-2 NF-FW 99 22 M5
1298			or
1299			Hitachi	 LMG6912RPFC-00T
1300			or
1301			Hitachi	 SP14Q002
1302
1303			320x240. Black & white.
1304
1305		CONFIG_LCD_ALIGNMENT
1306
1307		Normally the LCD is page-aligned (typically 4KB). If this is
1308		defined then the LCD will be aligned to this value instead.
1309		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1310		here, since it is cheaper to change data cache settings on
1311		a per-section basis.
1312
1313
1314		CONFIG_LCD_ROTATION
1315
1316		Sometimes, for example if the display is mounted in portrait
1317		mode or even if it's mounted landscape but rotated by 180degree,
1318		we need to rotate our content of the display relative to the
1319		framebuffer, so that user can read the messages which are
1320		printed out.
1321		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1322		initialized with a given rotation from "vl_rot" out of
1323		"vidinfo_t" which is provided by the board specific code.
1324		The value for vl_rot is coded as following (matching to
1325		fbcon=rotate:<n> linux-kernel commandline):
1326		0 = no rotation respectively 0 degree
1327		1 = 90 degree rotation
1328		2 = 180 degree rotation
1329		3 = 270 degree rotation
1330
1331		If CONFIG_LCD_ROTATION is not defined, the console will be
1332		initialized with 0degree rotation.
1333
1334		CONFIG_LCD_BMP_RLE8
1335
1336		Support drawing of RLE8-compressed bitmaps on the LCD.
1337
1338		CONFIG_I2C_EDID
1339
1340		Enables an 'i2c edid' command which can read EDID
1341		information over I2C from an attached LCD display.
1342
1343- Splash Screen Support: CONFIG_SPLASH_SCREEN
1344
1345		If this option is set, the environment is checked for
1346		a variable "splashimage". If found, the usual display
1347		of logo, copyright and system information on the LCD
1348		is suppressed and the BMP image at the address
1349		specified in "splashimage" is loaded instead. The
1350		console is redirected to the "nulldev", too. This
1351		allows for a "silent" boot where a splash screen is
1352		loaded very quickly after power-on.
1353
1354		CONFIG_SPLASHIMAGE_GUARD
1355
1356		If this option is set, then U-Boot will prevent the environment
1357		variable "splashimage" from being set to a problematic address
1358		(see doc/README.displaying-bmps).
1359		This option is useful for targets where, due to alignment
1360		restrictions, an improperly aligned BMP image will cause a data
1361		abort. If you think you will not have problems with unaligned
1362		accesses (for example because your toolchain prevents them)
1363		there is no need to set this option.
1364
1365		CONFIG_SPLASH_SCREEN_ALIGN
1366
1367		If this option is set the splash image can be freely positioned
1368		on the screen. Environment variable "splashpos" specifies the
1369		position as "x,y". If a positive number is given it is used as
1370		number of pixel from left/top. If a negative number is given it
1371		is used as number of pixel from right/bottom. You can also
1372		specify 'm' for centering the image.
1373
1374		Example:
1375		setenv splashpos m,m
1376			=> image at center of screen
1377
1378		setenv splashpos 30,20
1379			=> image at x = 30 and y = 20
1380
1381		setenv splashpos -10,m
1382			=> vertically centered image
1383			   at x = dspWidth - bmpWidth - 9
1384
1385- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1386
1387		If this option is set, additionally to standard BMP
1388		images, gzipped BMP images can be displayed via the
1389		splashscreen support or the bmp command.
1390
1391- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1392
1393		If this option is set, 8-bit RLE compressed BMP images
1394		can be displayed via the splashscreen support or the
1395		bmp command.
1396
1397- Compression support:
1398		CONFIG_GZIP
1399
1400		Enabled by default to support gzip compressed images.
1401
1402		CONFIG_BZIP2
1403
1404		If this option is set, support for bzip2 compressed
1405		images is included. If not, only uncompressed and gzip
1406		compressed images are supported.
1407
1408		NOTE: the bzip2 algorithm requires a lot of RAM, so
1409		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1410		be at least 4MB.
1411
1412- MII/PHY support:
1413		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1414
1415		The clock frequency of the MII bus
1416
1417		CONFIG_PHY_RESET_DELAY
1418
1419		Some PHY like Intel LXT971A need extra delay after
1420		reset before any MII register access is possible.
1421		For such PHY, set this option to the usec delay
1422		required. (minimum 300usec for LXT971A)
1423
1424		CONFIG_PHY_CMD_DELAY (ppc4xx)
1425
1426		Some PHY like Intel LXT971A need extra delay after
1427		command issued before MII status register can be read
1428
1429- IP address:
1430		CONFIG_IPADDR
1431
1432		Define a default value for the IP address to use for
1433		the default Ethernet interface, in case this is not
1434		determined through e.g. bootp.
1435		(Environment variable "ipaddr")
1436
1437- Server IP address:
1438		CONFIG_SERVERIP
1439
1440		Defines a default value for the IP address of a TFTP
1441		server to contact when using the "tftboot" command.
1442		(Environment variable "serverip")
1443
1444		CONFIG_KEEP_SERVERADDR
1445
1446		Keeps the server's MAC address, in the env 'serveraddr'
1447		for passing to bootargs (like Linux's netconsole option)
1448
1449- Gateway IP address:
1450		CONFIG_GATEWAYIP
1451
1452		Defines a default value for the IP address of the
1453		default router where packets to other networks are
1454		sent to.
1455		(Environment variable "gatewayip")
1456
1457- Subnet mask:
1458		CONFIG_NETMASK
1459
1460		Defines a default value for the subnet mask (or
1461		routing prefix) which is used to determine if an IP
1462		address belongs to the local subnet or needs to be
1463		forwarded through a router.
1464		(Environment variable "netmask")
1465
1466- Multicast TFTP Mode:
1467		CONFIG_MCAST_TFTP
1468
1469		Defines whether you want to support multicast TFTP as per
1470		rfc-2090; for example to work with atftp.  Lets lots of targets
1471		tftp down the same boot image concurrently.  Note: the Ethernet
1472		driver in use must provide a function: mcast() to join/leave a
1473		multicast group.
1474
1475- BOOTP Recovery Mode:
1476		CONFIG_BOOTP_RANDOM_DELAY
1477
1478		If you have many targets in a network that try to
1479		boot using BOOTP, you may want to avoid that all
1480		systems send out BOOTP requests at precisely the same
1481		moment (which would happen for instance at recovery
1482		from a power failure, when all systems will try to
1483		boot, thus flooding the BOOTP server. Defining
1484		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1485		inserted before sending out BOOTP requests. The
1486		following delays are inserted then:
1487
1488		1st BOOTP request:	delay 0 ... 1 sec
1489		2nd BOOTP request:	delay 0 ... 2 sec
1490		3rd BOOTP request:	delay 0 ... 4 sec
1491		4th and following
1492		BOOTP requests:		delay 0 ... 8 sec
1493
1494		CONFIG_BOOTP_ID_CACHE_SIZE
1495
1496		BOOTP packets are uniquely identified using a 32-bit ID. The
1497		server will copy the ID from client requests to responses and
1498		U-Boot will use this to determine if it is the destination of
1499		an incoming response. Some servers will check that addresses
1500		aren't in use before handing them out (usually using an ARP
1501		ping) and therefore take up to a few hundred milliseconds to
1502		respond. Network congestion may also influence the time it
1503		takes for a response to make it back to the client. If that
1504		time is too long, U-Boot will retransmit requests. In order
1505		to allow earlier responses to still be accepted after these
1506		retransmissions, U-Boot's BOOTP client keeps a small cache of
1507		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1508		cache. The default is to keep IDs for up to four outstanding
1509		requests. Increasing this will allow U-Boot to accept offers
1510		from a BOOTP client in networks with unusually high latency.
1511
1512- DHCP Advanced Options:
1513		You can fine tune the DHCP functionality by defining
1514		CONFIG_BOOTP_* symbols:
1515
1516		CONFIG_BOOTP_NISDOMAIN
1517		CONFIG_BOOTP_BOOTFILESIZE
1518		CONFIG_BOOTP_SEND_HOSTNAME
1519		CONFIG_BOOTP_NTPSERVER
1520		CONFIG_BOOTP_TIMEOFFSET
1521		CONFIG_BOOTP_VENDOREX
1522		CONFIG_BOOTP_MAY_FAIL
1523
1524		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1525		environment variable, not the BOOTP server.
1526
1527		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1528		after the configured retry count, the call will fail
1529		instead of starting over.  This can be used to fail over
1530		to Link-local IP address configuration if the DHCP server
1531		is not available.
1532
1533		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1534		to do a dynamic update of a DNS server. To do this, they
1535		need the hostname of the DHCP requester.
1536		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1537		of the "hostname" environment variable is passed as
1538		option 12 to the DHCP server.
1539
1540		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1541
1542		A 32bit value in microseconds for a delay between
1543		receiving a "DHCP Offer" and sending the "DHCP Request".
1544		This fixes a problem with certain DHCP servers that don't
1545		respond 100% of the time to a "DHCP request". E.g. On an
1546		AT91RM9200 processor running at 180MHz, this delay needed
1547		to be *at least* 15,000 usec before a Windows Server 2003
1548		DHCP server would reply 100% of the time. I recommend at
1549		least 50,000 usec to be safe. The alternative is to hope
1550		that one of the retries will be successful but note that
1551		the DHCP timeout and retry process takes a longer than
1552		this delay.
1553
1554 - Link-local IP address negotiation:
1555		Negotiate with other link-local clients on the local network
1556		for an address that doesn't require explicit configuration.
1557		This is especially useful if a DHCP server cannot be guaranteed
1558		to exist in all environments that the device must operate.
1559
1560		See doc/README.link-local for more information.
1561
1562 - MAC address from environment variables
1563
1564		FDT_SEQ_MACADDR_FROM_ENV
1565
1566		Fix-up device tree with MAC addresses fetched sequentially from
1567		environment variables. This config work on assumption that
1568		non-usable ethernet node of device-tree are either not present
1569		or their status has been marked as "disabled".
1570
1571 - CDP Options:
1572		CONFIG_CDP_DEVICE_ID
1573
1574		The device id used in CDP trigger frames.
1575
1576		CONFIG_CDP_DEVICE_ID_PREFIX
1577
1578		A two character string which is prefixed to the MAC address
1579		of the device.
1580
1581		CONFIG_CDP_PORT_ID
1582
1583		A printf format string which contains the ascii name of
1584		the port. Normally is set to "eth%d" which sets
1585		eth0 for the first Ethernet, eth1 for the second etc.
1586
1587		CONFIG_CDP_CAPABILITIES
1588
1589		A 32bit integer which indicates the device capabilities;
1590		0x00000010 for a normal host which does not forwards.
1591
1592		CONFIG_CDP_VERSION
1593
1594		An ascii string containing the version of the software.
1595
1596		CONFIG_CDP_PLATFORM
1597
1598		An ascii string containing the name of the platform.
1599
1600		CONFIG_CDP_TRIGGER
1601
1602		A 32bit integer sent on the trigger.
1603
1604		CONFIG_CDP_POWER_CONSUMPTION
1605
1606		A 16bit integer containing the power consumption of the
1607		device in .1 of milliwatts.
1608
1609		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1610
1611		A byte containing the id of the VLAN.
1612
1613- Status LED:	CONFIG_LED_STATUS
1614
1615		Several configurations allow to display the current
1616		status using a LED. For instance, the LED will blink
1617		fast while running U-Boot code, stop blinking as
1618		soon as a reply to a BOOTP request was received, and
1619		start blinking slow once the Linux kernel is running
1620		(supported by a status LED driver in the Linux
1621		kernel). Defining CONFIG_LED_STATUS enables this
1622		feature in U-Boot.
1623
1624		Additional options:
1625
1626		CONFIG_LED_STATUS_GPIO
1627		The status LED can be connected to a GPIO pin.
1628		In such cases, the gpio_led driver can be used as a
1629		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1630		to include the gpio_led driver in the U-Boot binary.
1631
1632		CONFIG_GPIO_LED_INVERTED_TABLE
1633		Some GPIO connected LEDs may have inverted polarity in which
1634		case the GPIO high value corresponds to LED off state and
1635		GPIO low value corresponds to LED on state.
1636		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1637		with a list of GPIO LEDs that have inverted polarity.
1638
1639- I2C Support:	CONFIG_SYS_I2C
1640
1641		This enable the NEW i2c subsystem, and will allow you to use
1642		i2c commands at the u-boot command line (as long as you set
1643		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1644		based realtime clock chips or other i2c devices. See
1645		common/cmd_i2c.c for a description of the command line
1646		interface.
1647
1648		ported i2c driver to the new framework:
1649		- drivers/i2c/soft_i2c.c:
1650		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1651		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1652		    for defining speed and slave address
1653		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1654		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1655		    for defining speed and slave address
1656		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1657		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1658		    for defining speed and slave address
1659		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1660		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1661		    for defining speed and slave address
1662
1663		- drivers/i2c/fsl_i2c.c:
1664		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1665		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1666		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1667		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1668		    bus.
1669		  - If your board supports a second fsl i2c bus, define
1670		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1671		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1672		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1673		    second bus.
1674
1675		- drivers/i2c/tegra_i2c.c:
1676		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1677		  - This driver adds 4 i2c buses with a fix speed from
1678		    100000 and the slave addr 0!
1679
1680		- drivers/i2c/ppc4xx_i2c.c
1681		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1682		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1683		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1684
1685		- drivers/i2c/i2c_mxc.c
1686		  - activate this driver with CONFIG_SYS_I2C_MXC
1687		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1688		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1689		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1690		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1691		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1692		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1693		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1694		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1695		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1696		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1697		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1698		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1699		If those defines are not set, default value is 100000
1700		for speed, and 0 for slave.
1701
1702		- drivers/i2c/rcar_i2c.c:
1703		  - activate this driver with CONFIG_SYS_I2C_RCAR
1704		  - This driver adds 4 i2c buses
1705
1706		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1707		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1708		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1709		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1710		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1711		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1712		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1713		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1714		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1715
1716		- drivers/i2c/sh_i2c.c:
1717		  - activate this driver with CONFIG_SYS_I2C_SH
1718		  - This driver adds from 2 to 5 i2c buses
1719
1720		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1721		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1722		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1723		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1724		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1725		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1726		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1727		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1728		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1729		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1730		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1731
1732		- drivers/i2c/omap24xx_i2c.c
1733		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1734		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1735		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1736		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1737		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1738		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1739		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1740		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1741		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1742		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1743		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1744
1745		- drivers/i2c/zynq_i2c.c
1746		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1747		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1748		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1749
1750		- drivers/i2c/s3c24x0_i2c.c:
1751		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1752		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1753		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1754		    with a fix speed from 100000 and the slave addr 0!
1755
1756		- drivers/i2c/ihs_i2c.c
1757		  - activate this driver with CONFIG_SYS_I2C_IHS
1758		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1759		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1760		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1761		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1762		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1763		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1764		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1765		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1766		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1767		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1768		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1769		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1770		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1771		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1772		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1773		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1774		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1775		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1776		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1777		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1778		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1779
1780		additional defines:
1781
1782		CONFIG_SYS_NUM_I2C_BUSES
1783		Hold the number of i2c buses you want to use.
1784
1785		CONFIG_SYS_I2C_DIRECT_BUS
1786		define this, if you don't use i2c muxes on your hardware.
1787		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1788		omit this define.
1789
1790		CONFIG_SYS_I2C_MAX_HOPS
1791		define how many muxes are maximal consecutively connected
1792		on one i2c bus. If you not use i2c muxes, omit this
1793		define.
1794
1795		CONFIG_SYS_I2C_BUSES
1796		hold a list of buses you want to use, only used if
1797		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1798		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1799		CONFIG_SYS_NUM_I2C_BUSES = 9:
1800
1801		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1802					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1803					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1804					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1805					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1806					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1807					{1, {I2C_NULL_HOP}}, \
1808					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1809					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1810					}
1811
1812		which defines
1813			bus 0 on adapter 0 without a mux
1814			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1815			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1816			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1817			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1818			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1819			bus 6 on adapter 1 without a mux
1820			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1821			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1822
1823		If you do not have i2c muxes on your board, omit this define.
1824
1825- Legacy I2C Support:
1826		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1827		then the following macros need to be defined (examples are
1828		from include/configs/lwmon.h):
1829
1830		I2C_INIT
1831
1832		(Optional). Any commands necessary to enable the I2C
1833		controller or configure ports.
1834
1835		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1836
1837		I2C_ACTIVE
1838
1839		The code necessary to make the I2C data line active
1840		(driven).  If the data line is open collector, this
1841		define can be null.
1842
1843		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1844
1845		I2C_TRISTATE
1846
1847		The code necessary to make the I2C data line tri-stated
1848		(inactive).  If the data line is open collector, this
1849		define can be null.
1850
1851		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1852
1853		I2C_READ
1854
1855		Code that returns true if the I2C data line is high,
1856		false if it is low.
1857
1858		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1859
1860		I2C_SDA(bit)
1861
1862		If <bit> is true, sets the I2C data line high. If it
1863		is false, it clears it (low).
1864
1865		eg: #define I2C_SDA(bit) \
1866			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1867			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1868
1869		I2C_SCL(bit)
1870
1871		If <bit> is true, sets the I2C clock line high. If it
1872		is false, it clears it (low).
1873
1874		eg: #define I2C_SCL(bit) \
1875			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1876			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1877
1878		I2C_DELAY
1879
1880		This delay is invoked four times per clock cycle so this
1881		controls the rate of data transfer.  The data rate thus
1882		is 1 / (I2C_DELAY * 4). Often defined to be something
1883		like:
1884
1885		#define I2C_DELAY  udelay(2)
1886
1887		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1888
1889		If your arch supports the generic GPIO framework (asm/gpio.h),
1890		then you may alternatively define the two GPIOs that are to be
1891		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1892		have GPIO-based defaults assigned to them as appropriate.
1893
1894		You should define these to the GPIO value as given directly to
1895		the generic GPIO functions.
1896
1897		CONFIG_SYS_I2C_INIT_BOARD
1898
1899		When a board is reset during an i2c bus transfer
1900		chips might think that the current transfer is still
1901		in progress. On some boards it is possible to access
1902		the i2c SCLK line directly, either by using the
1903		processor pin as a GPIO or by having a second pin
1904		connected to the bus. If this option is defined a
1905		custom i2c_init_board() routine in boards/xxx/board.c
1906		is run early in the boot sequence.
1907
1908		CONFIG_I2C_MULTI_BUS
1909
1910		This option allows the use of multiple I2C buses, each of which
1911		must have a controller.	 At any point in time, only one bus is
1912		active.	 To switch to a different bus, use the 'i2c dev' command.
1913		Note that bus numbering is zero-based.
1914
1915		CONFIG_SYS_I2C_NOPROBES
1916
1917		This option specifies a list of I2C devices that will be skipped
1918		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1919		is set, specify a list of bus-device pairs.  Otherwise, specify
1920		a 1D array of device addresses
1921
1922		e.g.
1923			#undef	CONFIG_I2C_MULTI_BUS
1924			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1925
1926		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1927
1928			#define CONFIG_I2C_MULTI_BUS
1929			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1930
1931		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1932
1933		CONFIG_SYS_SPD_BUS_NUM
1934
1935		If defined, then this indicates the I2C bus number for DDR SPD.
1936		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1937
1938		CONFIG_SYS_RTC_BUS_NUM
1939
1940		If defined, then this indicates the I2C bus number for the RTC.
1941		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1942
1943		CONFIG_SOFT_I2C_READ_REPEATED_START
1944
1945		defining this will force the i2c_read() function in
1946		the soft_i2c driver to perform an I2C repeated start
1947		between writing the address pointer and reading the
1948		data.  If this define is omitted the default behaviour
1949		of doing a stop-start sequence will be used.  Most I2C
1950		devices can use either method, but some require one or
1951		the other.
1952
1953- SPI Support:	CONFIG_SPI
1954
1955		Enables SPI driver (so far only tested with
1956		SPI EEPROM, also an instance works with Crystal A/D and
1957		D/As on the SACSng board)
1958
1959		CONFIG_SOFT_SPI
1960
1961		Enables a software (bit-bang) SPI driver rather than
1962		using hardware support. This is a general purpose
1963		driver that only requires three general I/O port pins
1964		(two outputs, one input) to function. If this is
1965		defined, the board configuration must define several
1966		SPI configuration items (port pins to use, etc). For
1967		an example, see include/configs/sacsng.h.
1968
1969		CONFIG_HARD_SPI
1970
1971		Enables a hardware SPI driver for general-purpose reads
1972		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1973		must define a list of chip-select function pointers.
1974		Currently supported on some MPC8xxx processors.	 For an
1975		example, see include/configs/mpc8349emds.h.
1976
1977		CONFIG_SYS_SPI_MXC_WAIT
1978		Timeout for waiting until spi transfer completed.
1979		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1980
1981- FPGA Support: CONFIG_FPGA
1982
1983		Enables FPGA subsystem.
1984
1985		CONFIG_FPGA_<vendor>
1986
1987		Enables support for specific chip vendors.
1988		(ALTERA, XILINX)
1989
1990		CONFIG_FPGA_<family>
1991
1992		Enables support for FPGA family.
1993		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1994
1995		CONFIG_FPGA_COUNT
1996
1997		Specify the number of FPGA devices to support.
1998
1999		CONFIG_SYS_FPGA_PROG_FEEDBACK
2000
2001		Enable printing of hash marks during FPGA configuration.
2002
2003		CONFIG_SYS_FPGA_CHECK_BUSY
2004
2005		Enable checks on FPGA configuration interface busy
2006		status by the configuration function. This option
2007		will require a board or device specific function to
2008		be written.
2009
2010		CONFIG_FPGA_DELAY
2011
2012		If defined, a function that provides delays in the FPGA
2013		configuration driver.
2014
2015		CONFIG_SYS_FPGA_CHECK_CTRLC
2016		Allow Control-C to interrupt FPGA configuration
2017
2018		CONFIG_SYS_FPGA_CHECK_ERROR
2019
2020		Check for configuration errors during FPGA bitfile
2021		loading. For example, abort during Virtex II
2022		configuration if the INIT_B line goes low (which
2023		indicated a CRC error).
2024
2025		CONFIG_SYS_FPGA_WAIT_INIT
2026
2027		Maximum time to wait for the INIT_B line to de-assert
2028		after PROB_B has been de-asserted during a Virtex II
2029		FPGA configuration sequence. The default time is 500
2030		ms.
2031
2032		CONFIG_SYS_FPGA_WAIT_BUSY
2033
2034		Maximum time to wait for BUSY to de-assert during
2035		Virtex II FPGA configuration. The default is 5 ms.
2036
2037		CONFIG_SYS_FPGA_WAIT_CONFIG
2038
2039		Time to wait after FPGA configuration. The default is
2040		200 ms.
2041
2042- Configuration Management:
2043		CONFIG_BUILD_TARGET
2044
2045		Some SoCs need special image types (e.g. U-Boot binary
2046		with a special header) as build targets. By defining
2047		CONFIG_BUILD_TARGET in the SoC / board header, this
2048		special image will be automatically built upon calling
2049		make / buildman.
2050
2051		CONFIG_IDENT_STRING
2052
2053		If defined, this string will be added to the U-Boot
2054		version information (U_BOOT_VERSION)
2055
2056- Vendor Parameter Protection:
2057
2058		U-Boot considers the values of the environment
2059		variables "serial#" (Board Serial Number) and
2060		"ethaddr" (Ethernet Address) to be parameters that
2061		are set once by the board vendor / manufacturer, and
2062		protects these variables from casual modification by
2063		the user. Once set, these variables are read-only,
2064		and write or delete attempts are rejected. You can
2065		change this behaviour:
2066
2067		If CONFIG_ENV_OVERWRITE is #defined in your config
2068		file, the write protection for vendor parameters is
2069		completely disabled. Anybody can change or delete
2070		these parameters.
2071
2072		Alternatively, if you define _both_ an ethaddr in the
2073		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2074		Ethernet address is installed in the environment,
2075		which can be changed exactly ONCE by the user. [The
2076		serial# is unaffected by this, i. e. it remains
2077		read-only.]
2078
2079		The same can be accomplished in a more flexible way
2080		for any variable by configuring the type of access
2081		to allow for those variables in the ".flags" variable
2082		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2083
2084- Protected RAM:
2085		CONFIG_PRAM
2086
2087		Define this variable to enable the reservation of
2088		"protected RAM", i. e. RAM which is not overwritten
2089		by U-Boot. Define CONFIG_PRAM to hold the number of
2090		kB you want to reserve for pRAM. You can overwrite
2091		this default value by defining an environment
2092		variable "pram" to the number of kB you want to
2093		reserve. Note that the board info structure will
2094		still show the full amount of RAM. If pRAM is
2095		reserved, a new environment variable "mem" will
2096		automatically be defined to hold the amount of
2097		remaining RAM in a form that can be passed as boot
2098		argument to Linux, for instance like that:
2099
2100			setenv bootargs ... mem=\${mem}
2101			saveenv
2102
2103		This way you can tell Linux not to use this memory,
2104		either, which results in a memory region that will
2105		not be affected by reboots.
2106
2107		*WARNING* If your board configuration uses automatic
2108		detection of the RAM size, you must make sure that
2109		this memory test is non-destructive. So far, the
2110		following board configurations are known to be
2111		"pRAM-clean":
2112
2113			IVMS8, IVML24, SPD8xx,
2114			HERMES, IP860, RPXlite, LWMON,
2115			FLAGADM
2116
2117- Access to physical memory region (> 4GB)
2118		Some basic support is provided for operations on memory not
2119		normally accessible to U-Boot - e.g. some architectures
2120		support access to more than 4GB of memory on 32-bit
2121		machines using physical address extension or similar.
2122		Define CONFIG_PHYSMEM to access this basic support, which
2123		currently only supports clearing the memory.
2124
2125- Error Recovery:
2126		CONFIG_NET_RETRY_COUNT
2127
2128		This variable defines the number of retries for
2129		network operations like ARP, RARP, TFTP, or BOOTP
2130		before giving up the operation. If not defined, a
2131		default value of 5 is used.
2132
2133		CONFIG_ARP_TIMEOUT
2134
2135		Timeout waiting for an ARP reply in milliseconds.
2136
2137		CONFIG_NFS_TIMEOUT
2138
2139		Timeout in milliseconds used in NFS protocol.
2140		If you encounter "ERROR: Cannot umount" in nfs command,
2141		try longer timeout such as
2142		#define CONFIG_NFS_TIMEOUT 10000UL
2143
2144- Command Interpreter:
2145		CONFIG_SYS_PROMPT_HUSH_PS2
2146
2147		This defines the secondary prompt string, which is
2148		printed when the command interpreter needs more input
2149		to complete a command. Usually "> ".
2150
2151	Note:
2152
2153		In the current implementation, the local variables
2154		space and global environment variables space are
2155		separated. Local variables are those you define by
2156		simply typing `name=value'. To access a local
2157		variable later on, you have write `$name' or
2158		`${name}'; to execute the contents of a variable
2159		directly type `$name' at the command prompt.
2160
2161		Global environment variables are those you use
2162		setenv/printenv to work with. To run a command stored
2163		in such a variable, you need to use the run command,
2164		and you must not use the '$' sign to access them.
2165
2166		To store commands and special characters in a
2167		variable, please use double quotation marks
2168		surrounding the whole text of the variable, instead
2169		of the backslashes before semicolons and special
2170		symbols.
2171
2172- Command Line Editing and History:
2173		CONFIG_CMDLINE_PS_SUPPORT
2174
2175		Enable support for changing the command prompt string
2176		at run-time. Only static string is supported so far.
2177		The string is obtained from environment variables PS1
2178		and PS2.
2179
2180- Default Environment:
2181		CONFIG_EXTRA_ENV_SETTINGS
2182
2183		Define this to contain any number of null terminated
2184		strings (variable = value pairs) that will be part of
2185		the default environment compiled into the boot image.
2186
2187		For example, place something like this in your
2188		board's config file:
2189
2190		#define CONFIG_EXTRA_ENV_SETTINGS \
2191			"myvar1=value1\0" \
2192			"myvar2=value2\0"
2193
2194		Warning: This method is based on knowledge about the
2195		internal format how the environment is stored by the
2196		U-Boot code. This is NOT an official, exported
2197		interface! Although it is unlikely that this format
2198		will change soon, there is no guarantee either.
2199		You better know what you are doing here.
2200
2201		Note: overly (ab)use of the default environment is
2202		discouraged. Make sure to check other ways to preset
2203		the environment like the "source" command or the
2204		boot command first.
2205
2206		CONFIG_DELAY_ENVIRONMENT
2207
2208		Normally the environment is loaded when the board is
2209		initialised so that it is available to U-Boot. This inhibits
2210		that so that the environment is not available until
2211		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2212		this is instead controlled by the value of
2213		/config/load-environment.
2214
2215- Serial Flash support
2216		Usage requires an initial 'sf probe' to define the serial
2217		flash parameters, followed by read/write/erase/update
2218		commands.
2219
2220		The following defaults may be provided by the platform
2221		to handle the common case when only a single serial
2222		flash is present on the system.
2223
2224		CONFIG_SF_DEFAULT_BUS		Bus identifier
2225		CONFIG_SF_DEFAULT_CS		Chip-select
2226		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2227		CONFIG_SF_DEFAULT_SPEED		in Hz
2228
2229
2230- TFTP Fixed UDP Port:
2231		CONFIG_TFTP_PORT
2232
2233		If this is defined, the environment variable tftpsrcp
2234		is used to supply the TFTP UDP source port value.
2235		If tftpsrcp isn't defined, the normal pseudo-random port
2236		number generator is used.
2237
2238		Also, the environment variable tftpdstp is used to supply
2239		the TFTP UDP destination port value.  If tftpdstp isn't
2240		defined, the normal port 69 is used.
2241
2242		The purpose for tftpsrcp is to allow a TFTP server to
2243		blindly start the TFTP transfer using the pre-configured
2244		target IP address and UDP port. This has the effect of
2245		"punching through" the (Windows XP) firewall, allowing
2246		the remainder of the TFTP transfer to proceed normally.
2247		A better solution is to properly configure the firewall,
2248		but sometimes that is not allowed.
2249
2250- Show boot progress:
2251		CONFIG_SHOW_BOOT_PROGRESS
2252
2253		Defining this option allows to add some board-
2254		specific code (calling a user-provided function
2255		"show_boot_progress(int)") that enables you to show
2256		the system's boot progress on some display (for
2257		example, some LED's) on your board. At the moment,
2258		the following checkpoints are implemented:
2259
2260
2261Legacy uImage format:
2262
2263  Arg	Where			When
2264    1	common/cmd_bootm.c	before attempting to boot an image
2265   -1	common/cmd_bootm.c	Image header has bad	 magic number
2266    2	common/cmd_bootm.c	Image header has correct magic number
2267   -2	common/cmd_bootm.c	Image header has bad	 checksum
2268    3	common/cmd_bootm.c	Image header has correct checksum
2269   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2270    4	common/cmd_bootm.c	Image data   has correct checksum
2271   -4	common/cmd_bootm.c	Image is for unsupported architecture
2272    5	common/cmd_bootm.c	Architecture check OK
2273   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2274    6	common/cmd_bootm.c	Image Type check OK
2275   -6	common/cmd_bootm.c	gunzip uncompression error
2276   -7	common/cmd_bootm.c	Unimplemented compression type
2277    7	common/cmd_bootm.c	Uncompression OK
2278    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2279   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2280
2281    9	common/image.c		Start initial ramdisk verification
2282  -10	common/image.c		Ramdisk header has bad	   magic number
2283  -11	common/image.c		Ramdisk header has bad	   checksum
2284   10	common/image.c		Ramdisk header is OK
2285  -12	common/image.c		Ramdisk data   has bad	   checksum
2286   11	common/image.c		Ramdisk data   has correct checksum
2287   12	common/image.c		Ramdisk verification complete, start loading
2288  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2289   13	common/image.c		Start multifile image verification
2290   14	common/image.c		No initial ramdisk, no multifile, continue.
2291
2292   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2293
2294  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2295  -31	post/post.c		POST test failed, detected by post_output_backlog()
2296  -32	post/post.c		POST test failed, detected by post_run_single()
2297
2298   34	common/cmd_doc.c	before loading a Image from a DOC device
2299  -35	common/cmd_doc.c	Bad usage of "doc" command
2300   35	common/cmd_doc.c	correct usage of "doc" command
2301  -36	common/cmd_doc.c	No boot device
2302   36	common/cmd_doc.c	correct boot device
2303  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2304   37	common/cmd_doc.c	correct chip ID found, device available
2305  -38	common/cmd_doc.c	Read Error on boot device
2306   38	common/cmd_doc.c	reading Image header from DOC device OK
2307  -39	common/cmd_doc.c	Image header has bad magic number
2308   39	common/cmd_doc.c	Image header has correct magic number
2309  -40	common/cmd_doc.c	Error reading Image from DOC device
2310   40	common/cmd_doc.c	Image header has correct magic number
2311   41	common/cmd_ide.c	before loading a Image from a IDE device
2312  -42	common/cmd_ide.c	Bad usage of "ide" command
2313   42	common/cmd_ide.c	correct usage of "ide" command
2314  -43	common/cmd_ide.c	No boot device
2315   43	common/cmd_ide.c	boot device found
2316  -44	common/cmd_ide.c	Device not available
2317   44	common/cmd_ide.c	Device available
2318  -45	common/cmd_ide.c	wrong partition selected
2319   45	common/cmd_ide.c	partition selected
2320  -46	common/cmd_ide.c	Unknown partition table
2321   46	common/cmd_ide.c	valid partition table found
2322  -47	common/cmd_ide.c	Invalid partition type
2323   47	common/cmd_ide.c	correct partition type
2324  -48	common/cmd_ide.c	Error reading Image Header on boot device
2325   48	common/cmd_ide.c	reading Image Header from IDE device OK
2326  -49	common/cmd_ide.c	Image header has bad magic number
2327   49	common/cmd_ide.c	Image header has correct magic number
2328  -50	common/cmd_ide.c	Image header has bad	 checksum
2329   50	common/cmd_ide.c	Image header has correct checksum
2330  -51	common/cmd_ide.c	Error reading Image from IDE device
2331   51	common/cmd_ide.c	reading Image from IDE device OK
2332   52	common/cmd_nand.c	before loading a Image from a NAND device
2333  -53	common/cmd_nand.c	Bad usage of "nand" command
2334   53	common/cmd_nand.c	correct usage of "nand" command
2335  -54	common/cmd_nand.c	No boot device
2336   54	common/cmd_nand.c	boot device found
2337  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2338   55	common/cmd_nand.c	correct chip ID found, device available
2339  -56	common/cmd_nand.c	Error reading Image Header on boot device
2340   56	common/cmd_nand.c	reading Image Header from NAND device OK
2341  -57	common/cmd_nand.c	Image header has bad magic number
2342   57	common/cmd_nand.c	Image header has correct magic number
2343  -58	common/cmd_nand.c	Error reading Image from NAND device
2344   58	common/cmd_nand.c	reading Image from NAND device OK
2345
2346  -60	common/env_common.c	Environment has a bad CRC, using default
2347
2348   64	net/eth.c		starting with Ethernet configuration.
2349  -64	net/eth.c		no Ethernet found.
2350   65	net/eth.c		Ethernet found.
2351
2352  -80	common/cmd_net.c	usage wrong
2353   80	common/cmd_net.c	before calling net_loop()
2354  -81	common/cmd_net.c	some error in net_loop() occurred
2355   81	common/cmd_net.c	net_loop() back without error
2356  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2357   82	common/cmd_net.c	trying automatic boot
2358   83	common/cmd_net.c	running "source" command
2359  -83	common/cmd_net.c	some error in automatic boot or "source" command
2360   84	common/cmd_net.c	end without errors
2361
2362FIT uImage format:
2363
2364  Arg	Where			When
2365  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2366 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2367  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2368 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2369  102	common/cmd_bootm.c	Kernel unit name specified
2370 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2371  103	common/cmd_bootm.c	Found configuration node
2372  104	common/cmd_bootm.c	Got kernel subimage node offset
2373 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2374  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2375 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2376  106	common/cmd_bootm.c	Architecture check OK
2377 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2378  107	common/cmd_bootm.c	Kernel subimage type OK
2379 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2380  108	common/cmd_bootm.c	Got kernel subimage data/size
2381 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2382 -109	common/cmd_bootm.c	Can't get kernel subimage type
2383 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2384 -111	common/cmd_bootm.c	Can't get kernel subimage os
2385 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2386 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2387
2388  120	common/image.c		Start initial ramdisk verification
2389 -120	common/image.c		Ramdisk FIT image has incorrect format
2390  121	common/image.c		Ramdisk FIT image has correct format
2391  122	common/image.c		No ramdisk subimage unit name, using configuration
2392 -122	common/image.c		Can't get configuration for ramdisk subimage
2393  123	common/image.c		Ramdisk unit name specified
2394 -124	common/image.c		Can't get ramdisk subimage node offset
2395  125	common/image.c		Got ramdisk subimage node offset
2396 -125	common/image.c		Ramdisk subimage hash verification failed
2397  126	common/image.c		Ramdisk subimage hash verification OK
2398 -126	common/image.c		Ramdisk subimage for unsupported architecture
2399  127	common/image.c		Architecture check OK
2400 -127	common/image.c		Can't get ramdisk subimage data/size
2401  128	common/image.c		Got ramdisk subimage data/size
2402  129	common/image.c		Can't get ramdisk load address
2403 -129	common/image.c		Got ramdisk load address
2404
2405 -130	common/cmd_doc.c	Incorrect FIT image format
2406  131	common/cmd_doc.c	FIT image format OK
2407
2408 -140	common/cmd_ide.c	Incorrect FIT image format
2409  141	common/cmd_ide.c	FIT image format OK
2410
2411 -150	common/cmd_nand.c	Incorrect FIT image format
2412  151	common/cmd_nand.c	FIT image format OK
2413
2414- Standalone program support:
2415		CONFIG_STANDALONE_LOAD_ADDR
2416
2417		This option defines a board specific value for the
2418		address where standalone program gets loaded, thus
2419		overwriting the architecture dependent default
2420		settings.
2421
2422- Frame Buffer Address:
2423		CONFIG_FB_ADDR
2424
2425		Define CONFIG_FB_ADDR if you want to use specific
2426		address for frame buffer.  This is typically the case
2427		when using a graphics controller has separate video
2428		memory.  U-Boot will then place the frame buffer at
2429		the given address instead of dynamically reserving it
2430		in system RAM by calling lcd_setmem(), which grabs
2431		the memory for the frame buffer depending on the
2432		configured panel size.
2433
2434		Please see board_init_f function.
2435
2436- Automatic software updates via TFTP server
2437		CONFIG_UPDATE_TFTP
2438		CONFIG_UPDATE_TFTP_CNT_MAX
2439		CONFIG_UPDATE_TFTP_MSEC_MAX
2440
2441		These options enable and control the auto-update feature;
2442		for a more detailed description refer to doc/README.update.
2443
2444- MTD Support (mtdparts command, UBI support)
2445		CONFIG_MTD_DEVICE
2446
2447		Adds the MTD device infrastructure from the Linux kernel.
2448		Needed for mtdparts command support.
2449
2450		CONFIG_MTD_PARTITIONS
2451
2452		Adds the MTD partitioning infrastructure from the Linux
2453		kernel. Needed for UBI support.
2454
2455- UBI support
2456		CONFIG_MTD_UBI_WL_THRESHOLD
2457		This parameter defines the maximum difference between the highest
2458		erase counter value and the lowest erase counter value of eraseblocks
2459		of UBI devices. When this threshold is exceeded, UBI starts performing
2460		wear leveling by means of moving data from eraseblock with low erase
2461		counter to eraseblocks with high erase counter.
2462
2463		The default value should be OK for SLC NAND flashes, NOR flashes and
2464		other flashes which have eraseblock life-cycle 100000 or more.
2465		However, in case of MLC NAND flashes which typically have eraseblock
2466		life-cycle less than 10000, the threshold should be lessened (e.g.,
2467		to 128 or 256, although it does not have to be power of 2).
2468
2469		default: 4096
2470
2471		CONFIG_MTD_UBI_BEB_LIMIT
2472		This option specifies the maximum bad physical eraseblocks UBI
2473		expects on the MTD device (per 1024 eraseblocks). If the
2474		underlying flash does not admit of bad eraseblocks (e.g. NOR
2475		flash), this value is ignored.
2476
2477		NAND datasheets often specify the minimum and maximum NVM
2478		(Number of Valid Blocks) for the flashes' endurance lifetime.
2479		The maximum expected bad eraseblocks per 1024 eraseblocks
2480		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2481		which gives 20 for most NANDs (MaxNVB is basically the total
2482		count of eraseblocks on the chip).
2483
2484		To put it differently, if this value is 20, UBI will try to
2485		reserve about 1.9% of physical eraseblocks for bad blocks
2486		handling. And that will be 1.9% of eraseblocks on the entire
2487		NAND chip, not just the MTD partition UBI attaches. This means
2488		that if you have, say, a NAND flash chip admits maximum 40 bad
2489		eraseblocks, and it is split on two MTD partitions of the same
2490		size, UBI will reserve 40 eraseblocks when attaching a
2491		partition.
2492
2493		default: 20
2494
2495		CONFIG_MTD_UBI_FASTMAP
2496		Fastmap is a mechanism which allows attaching an UBI device
2497		in nearly constant time. Instead of scanning the whole MTD device it
2498		only has to locate a checkpoint (called fastmap) on the device.
2499		The on-flash fastmap contains all information needed to attach
2500		the device. Using fastmap makes only sense on large devices where
2501		attaching by scanning takes long. UBI will not automatically install
2502		a fastmap on old images, but you can set the UBI parameter
2503		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2504		that fastmap-enabled images are still usable with UBI implementations
2505		without	fastmap support. On typical flash devices the whole fastmap
2506		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2507
2508		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2509		Set this parameter to enable fastmap automatically on images
2510		without a fastmap.
2511		default: 0
2512
2513		CONFIG_MTD_UBI_FM_DEBUG
2514		Enable UBI fastmap debug
2515		default: 0
2516
2517- SPL framework
2518		CONFIG_SPL
2519		Enable building of SPL globally.
2520
2521		CONFIG_SPL_LDSCRIPT
2522		LDSCRIPT for linking the SPL binary.
2523
2524		CONFIG_SPL_MAX_FOOTPRINT
2525		Maximum size in memory allocated to the SPL, BSS included.
2526		When defined, the linker checks that the actual memory
2527		used by SPL from _start to __bss_end does not exceed it.
2528		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2529		must not be both defined at the same time.
2530
2531		CONFIG_SPL_MAX_SIZE
2532		Maximum size of the SPL image (text, data, rodata, and
2533		linker lists sections), BSS excluded.
2534		When defined, the linker checks that the actual size does
2535		not exceed it.
2536
2537		CONFIG_SPL_TEXT_BASE
2538		TEXT_BASE for linking the SPL binary.
2539
2540		CONFIG_SPL_RELOC_TEXT_BASE
2541		Address to relocate to.  If unspecified, this is equal to
2542		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2543
2544		CONFIG_SPL_BSS_START_ADDR
2545		Link address for the BSS within the SPL binary.
2546
2547		CONFIG_SPL_BSS_MAX_SIZE
2548		Maximum size in memory allocated to the SPL BSS.
2549		When defined, the linker checks that the actual memory used
2550		by SPL from __bss_start to __bss_end does not exceed it.
2551		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2552		must not be both defined at the same time.
2553
2554		CONFIG_SPL_STACK
2555		Adress of the start of the stack SPL will use
2556
2557		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2558		When defined, SPL will panic() if the image it has
2559		loaded does not have a signature.
2560		Defining this is useful when code which loads images
2561		in SPL cannot guarantee that absolutely all read errors
2562		will be caught.
2563		An example is the LPC32XX MLC NAND driver, which will
2564		consider that a completely unreadable NAND block is bad,
2565		and thus should be skipped silently.
2566
2567		CONFIG_SPL_RELOC_STACK
2568		Adress of the start of the stack SPL will use after
2569		relocation.  If unspecified, this is equal to
2570		CONFIG_SPL_STACK.
2571
2572		CONFIG_SYS_SPL_MALLOC_START
2573		Starting address of the malloc pool used in SPL.
2574		When this option is set the full malloc is used in SPL and
2575		it is set up by spl_init() and before that, the simple malloc()
2576		can be used if CONFIG_SYS_MALLOC_F is defined.
2577
2578		CONFIG_SYS_SPL_MALLOC_SIZE
2579		The size of the malloc pool used in SPL.
2580
2581		CONFIG_SPL_OS_BOOT
2582		Enable booting directly to an OS from SPL.
2583		See also: doc/README.falcon
2584
2585		CONFIG_SPL_DISPLAY_PRINT
2586		For ARM, enable an optional function to print more information
2587		about the running system.
2588
2589		CONFIG_SPL_INIT_MINIMAL
2590		Arch init code should be built for a very small image
2591
2592		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2593		Partition on the MMC to load U-Boot from when the MMC is being
2594		used in raw mode
2595
2596		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2597		Sector to load kernel uImage from when MMC is being
2598		used in raw mode (for Falcon mode)
2599
2600		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2601		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2602		Sector and number of sectors to load kernel argument
2603		parameters from when MMC is being used in raw mode
2604		(for falcon mode)
2605
2606		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2607		Partition on the MMC to load U-Boot from when the MMC is being
2608		used in fs mode
2609
2610		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2611		Filename to read to load U-Boot when reading from filesystem
2612
2613		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2614		Filename to read to load kernel uImage when reading
2615		from filesystem (for Falcon mode)
2616
2617		CONFIG_SPL_FS_LOAD_ARGS_NAME
2618		Filename to read to load kernel argument parameters
2619		when reading from filesystem (for Falcon mode)
2620
2621		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2622		Set this for NAND SPL on PPC mpc83xx targets, so that
2623		start.S waits for the rest of the SPL to load before
2624		continuing (the hardware starts execution after just
2625		loading the first page rather than the full 4K).
2626
2627		CONFIG_SPL_SKIP_RELOCATE
2628		Avoid SPL relocation
2629
2630		CONFIG_SPL_NAND_BASE
2631		Include nand_base.c in the SPL.  Requires
2632		CONFIG_SPL_NAND_DRIVERS.
2633
2634		CONFIG_SPL_NAND_DRIVERS
2635		SPL uses normal NAND drivers, not minimal drivers.
2636
2637		CONFIG_SPL_NAND_ECC
2638		Include standard software ECC in the SPL
2639
2640		CONFIG_SPL_NAND_SIMPLE
2641		Support for NAND boot using simple NAND drivers that
2642		expose the cmd_ctrl() interface.
2643
2644		CONFIG_SPL_UBI
2645		Support for a lightweight UBI (fastmap) scanner and
2646		loader
2647
2648		CONFIG_SPL_NAND_RAW_ONLY
2649		Support to boot only raw u-boot.bin images. Use this only
2650		if you need to save space.
2651
2652		CONFIG_SPL_COMMON_INIT_DDR
2653		Set for common ddr init with serial presence detect in
2654		SPL binary.
2655
2656		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2657		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2658		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2659		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2660		CONFIG_SYS_NAND_ECCBYTES
2661		Defines the size and behavior of the NAND that SPL uses
2662		to read U-Boot
2663
2664		CONFIG_SPL_NAND_BOOT
2665		Add support NAND boot
2666
2667		CONFIG_SYS_NAND_U_BOOT_OFFS
2668		Location in NAND to read U-Boot from
2669
2670		CONFIG_SYS_NAND_U_BOOT_DST
2671		Location in memory to load U-Boot to
2672
2673		CONFIG_SYS_NAND_U_BOOT_SIZE
2674		Size of image to load
2675
2676		CONFIG_SYS_NAND_U_BOOT_START
2677		Entry point in loaded image to jump to
2678
2679		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2680		Define this if you need to first read the OOB and then the
2681		data. This is used, for example, on davinci platforms.
2682
2683		CONFIG_SPL_RAM_DEVICE
2684		Support for running image already present in ram, in SPL binary
2685
2686		CONFIG_SPL_PAD_TO
2687		Image offset to which the SPL should be padded before appending
2688		the SPL payload. By default, this is defined as
2689		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2690		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2691		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2692
2693		CONFIG_SPL_TARGET
2694		Final target image containing SPL and payload.  Some SPLs
2695		use an arch-specific makefile fragment instead, for
2696		example if more than one image needs to be produced.
2697
2698		CONFIG_FIT_SPL_PRINT
2699		Printing information about a FIT image adds quite a bit of
2700		code to SPL. So this is normally disabled in SPL. Use this
2701		option to re-enable it. This will affect the output of the
2702		bootm command when booting a FIT image.
2703
2704- TPL framework
2705		CONFIG_TPL
2706		Enable building of TPL globally.
2707
2708		CONFIG_TPL_PAD_TO
2709		Image offset to which the TPL should be padded before appending
2710		the TPL payload. By default, this is defined as
2711		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2712		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2713		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2714
2715- Interrupt support (PPC):
2716
2717		There are common interrupt_init() and timer_interrupt()
2718		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2719		for CPU specific initialization. interrupt_init_cpu()
2720		should set decrementer_count to appropriate value. If
2721		CPU resets decrementer automatically after interrupt
2722		(ppc4xx) it should set decrementer_count to zero.
2723		timer_interrupt() calls timer_interrupt_cpu() for CPU
2724		specific handling. If board has watchdog / status_led
2725		/ other_activity_monitor it works automatically from
2726		general timer_interrupt().
2727
2728
2729Board initialization settings:
2730------------------------------
2731
2732During Initialization u-boot calls a number of board specific functions
2733to allow the preparation of board specific prerequisites, e.g. pin setup
2734before drivers are initialized. To enable these callbacks the
2735following configuration macros have to be defined. Currently this is
2736architecture specific, so please check arch/your_architecture/lib/board.c
2737typically in board_init_f() and board_init_r().
2738
2739- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2740- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2741- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2742- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2743
2744Configuration Settings:
2745-----------------------
2746
2747- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2748		Optionally it can be defined to support 64-bit memory commands.
2749
2750- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2751		undefine this when you're short of memory.
2752
2753- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2754		width of the commands listed in the 'help' command output.
2755
2756- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2757		prompt for user input.
2758
2759- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2760
2761- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2762
2763- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2764
2765- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2766		the application (usually a Linux kernel) when it is
2767		booted
2768
2769- CONFIG_SYS_BAUDRATE_TABLE:
2770		List of legal baudrate settings for this board.
2771
2772- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2773		Begin and End addresses of the area used by the
2774		simple memory test.
2775
2776- CONFIG_SYS_MEMTEST_SCRATCH:
2777		Scratch address used by the alternate memory test
2778		You only need to set this if address zero isn't writeable
2779
2780- CONFIG_SYS_MEM_RESERVE_SECURE
2781		Only implemented for ARMv8 for now.
2782		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2783		is substracted from total RAM and won't be reported to OS.
2784		This memory can be used as secure memory. A variable
2785		gd->arch.secure_ram is used to track the location. In systems
2786		the RAM base is not zero, or RAM is divided into banks,
2787		this variable needs to be recalcuated to get the address.
2788
2789- CONFIG_SYS_MEM_TOP_HIDE:
2790		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2791		this specified memory area will get subtracted from the top
2792		(end) of RAM and won't get "touched" at all by U-Boot. By
2793		fixing up gd->ram_size the Linux kernel should gets passed
2794		the now "corrected" memory size and won't touch it either.
2795		This should work for arch/ppc and arch/powerpc. Only Linux
2796		board ports in arch/powerpc with bootwrapper support that
2797		recalculate the memory size from the SDRAM controller setup
2798		will have to get fixed in Linux additionally.
2799
2800		This option can be used as a workaround for the 440EPx/GRx
2801		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2802		be touched.
2803
2804		WARNING: Please make sure that this value is a multiple of
2805		the Linux page size (normally 4k). If this is not the case,
2806		then the end address of the Linux memory will be located at a
2807		non page size aligned address and this could cause major
2808		problems.
2809
2810- CONFIG_SYS_LOADS_BAUD_CHANGE:
2811		Enable temporary baudrate change while serial download
2812
2813- CONFIG_SYS_SDRAM_BASE:
2814		Physical start address of SDRAM. _Must_ be 0 here.
2815
2816- CONFIG_SYS_FLASH_BASE:
2817		Physical start address of Flash memory.
2818
2819- CONFIG_SYS_MONITOR_BASE:
2820		Physical start address of boot monitor code (set by
2821		make config files to be same as the text base address
2822		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2823		CONFIG_SYS_FLASH_BASE when booting from flash.
2824
2825- CONFIG_SYS_MONITOR_LEN:
2826		Size of memory reserved for monitor code, used to
2827		determine _at_compile_time_ (!) if the environment is
2828		embedded within the U-Boot image, or in a separate
2829		flash sector.
2830
2831- CONFIG_SYS_MALLOC_LEN:
2832		Size of DRAM reserved for malloc() use.
2833
2834- CONFIG_SYS_MALLOC_F_LEN
2835		Size of the malloc() pool for use before relocation. If
2836		this is defined, then a very simple malloc() implementation
2837		will become available before relocation. The address is just
2838		below the global data, and the stack is moved down to make
2839		space.
2840
2841		This feature allocates regions with increasing addresses
2842		within the region. calloc() is supported, but realloc()
2843		is not available. free() is supported but does nothing.
2844		The memory will be freed (or in fact just forgotten) when
2845		U-Boot relocates itself.
2846
2847- CONFIG_SYS_MALLOC_SIMPLE
2848		Provides a simple and small malloc() and calloc() for those
2849		boards which do not use the full malloc in SPL (which is
2850		enabled with CONFIG_SYS_SPL_MALLOC_START).
2851
2852- CONFIG_SYS_NONCACHED_MEMORY:
2853		Size of non-cached memory area. This area of memory will be
2854		typically located right below the malloc() area and mapped
2855		uncached in the MMU. This is useful for drivers that would
2856		otherwise require a lot of explicit cache maintenance. For
2857		some drivers it's also impossible to properly maintain the
2858		cache. For example if the regions that need to be flushed
2859		are not a multiple of the cache-line size, *and* padding
2860		cannot be allocated between the regions to align them (i.e.
2861		if the HW requires a contiguous array of regions, and the
2862		size of each region is not cache-aligned), then a flush of
2863		one region may result in overwriting data that hardware has
2864		written to another region in the same cache-line. This can
2865		happen for example in network drivers where descriptors for
2866		buffers are typically smaller than the CPU cache-line (e.g.
2867		16 bytes vs. 32 or 64 bytes).
2868
2869		Non-cached memory is only supported on 32-bit ARM at present.
2870
2871- CONFIG_SYS_BOOTM_LEN:
2872		Normally compressed uImages are limited to an
2873		uncompressed size of 8 MBytes. If this is not enough,
2874		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2875		to adjust this setting to your needs.
2876
2877- CONFIG_SYS_BOOTMAPSZ:
2878		Maximum size of memory mapped by the startup code of
2879		the Linux kernel; all data that must be processed by
2880		the Linux kernel (bd_info, boot arguments, FDT blob if
2881		used) must be put below this limit, unless "bootm_low"
2882		environment variable is defined and non-zero. In such case
2883		all data for the Linux kernel must be between "bootm_low"
2884		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2885		variable "bootm_mapsize" will override the value of
2886		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2887		then the value in "bootm_size" will be used instead.
2888
2889- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2890		Enable initrd_high functionality.  If defined then the
2891		initrd_high feature is enabled and the bootm ramdisk subcommand
2892		is enabled.
2893
2894- CONFIG_SYS_BOOT_GET_CMDLINE:
2895		Enables allocating and saving kernel cmdline in space between
2896		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2897
2898- CONFIG_SYS_BOOT_GET_KBD:
2899		Enables allocating and saving a kernel copy of the bd_info in
2900		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2901
2902- CONFIG_SYS_MAX_FLASH_BANKS:
2903		Max number of Flash memory banks
2904
2905- CONFIG_SYS_MAX_FLASH_SECT:
2906		Max number of sectors on a Flash chip
2907
2908- CONFIG_SYS_FLASH_ERASE_TOUT:
2909		Timeout for Flash erase operations (in ms)
2910
2911- CONFIG_SYS_FLASH_WRITE_TOUT:
2912		Timeout for Flash write operations (in ms)
2913
2914- CONFIG_SYS_FLASH_LOCK_TOUT
2915		Timeout for Flash set sector lock bit operation (in ms)
2916
2917- CONFIG_SYS_FLASH_UNLOCK_TOUT
2918		Timeout for Flash clear lock bits operation (in ms)
2919
2920- CONFIG_SYS_FLASH_PROTECTION
2921		If defined, hardware flash sectors protection is used
2922		instead of U-Boot software protection.
2923
2924- CONFIG_SYS_DIRECT_FLASH_TFTP:
2925
2926		Enable TFTP transfers directly to flash memory;
2927		without this option such a download has to be
2928		performed in two steps: (1) download to RAM, and (2)
2929		copy from RAM to flash.
2930
2931		The two-step approach is usually more reliable, since
2932		you can check if the download worked before you erase
2933		the flash, but in some situations (when system RAM is
2934		too limited to allow for a temporary copy of the
2935		downloaded image) this option may be very useful.
2936
2937- CONFIG_SYS_FLASH_CFI:
2938		Define if the flash driver uses extra elements in the
2939		common flash structure for storing flash geometry.
2940
2941- CONFIG_FLASH_CFI_DRIVER
2942		This option also enables the building of the cfi_flash driver
2943		in the drivers directory
2944
2945- CONFIG_FLASH_CFI_MTD
2946		This option enables the building of the cfi_mtd driver
2947		in the drivers directory. The driver exports CFI flash
2948		to the MTD layer.
2949
2950- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2951		Use buffered writes to flash.
2952
2953- CONFIG_FLASH_SPANSION_S29WS_N
2954		s29ws-n MirrorBit flash has non-standard addresses for buffered
2955		write commands.
2956
2957- CONFIG_SYS_FLASH_QUIET_TEST
2958		If this option is defined, the common CFI flash doesn't
2959		print it's warning upon not recognized FLASH banks. This
2960		is useful, if some of the configured banks are only
2961		optionally available.
2962
2963- CONFIG_FLASH_SHOW_PROGRESS
2964		If defined (must be an integer), print out countdown
2965		digits and dots.  Recommended value: 45 (9..1) for 80
2966		column displays, 15 (3..1) for 40 column displays.
2967
2968- CONFIG_FLASH_VERIFY
2969		If defined, the content of the flash (destination) is compared
2970		against the source after the write operation. An error message
2971		will be printed when the contents are not identical.
2972		Please note that this option is useless in nearly all cases,
2973		since such flash programming errors usually are detected earlier
2974		while unprotecting/erasing/programming. Please only enable
2975		this option if you really know what you are doing.
2976
2977- CONFIG_SYS_RX_ETH_BUFFER:
2978		Defines the number of Ethernet receive buffers. On some
2979		Ethernet controllers it is recommended to set this value
2980		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2981		buffers can be full shortly after enabling the interface
2982		on high Ethernet traffic.
2983		Defaults to 4 if not defined.
2984
2985- CONFIG_ENV_MAX_ENTRIES
2986
2987	Maximum number of entries in the hash table that is used
2988	internally to store the environment settings. The default
2989	setting is supposed to be generous and should work in most
2990	cases. This setting can be used to tune behaviour; see
2991	lib/hashtable.c for details.
2992
2993- CONFIG_ENV_FLAGS_LIST_DEFAULT
2994- CONFIG_ENV_FLAGS_LIST_STATIC
2995	Enable validation of the values given to environment variables when
2996	calling env set.  Variables can be restricted to only decimal,
2997	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2998	the variables can also be restricted to IP address or MAC address.
2999
3000	The format of the list is:
3001		type_attribute = [s|d|x|b|i|m]
3002		access_attribute = [a|r|o|c]
3003		attributes = type_attribute[access_attribute]
3004		entry = variable_name[:attributes]
3005		list = entry[,list]
3006
3007	The type attributes are:
3008		s - String (default)
3009		d - Decimal
3010		x - Hexadecimal
3011		b - Boolean ([1yYtT|0nNfF])
3012		i - IP address
3013		m - MAC address
3014
3015	The access attributes are:
3016		a - Any (default)
3017		r - Read-only
3018		o - Write-once
3019		c - Change-default
3020
3021	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3022		Define this to a list (string) to define the ".flags"
3023		environment variable in the default or embedded environment.
3024
3025	- CONFIG_ENV_FLAGS_LIST_STATIC
3026		Define this to a list (string) to define validation that
3027		should be done if an entry is not found in the ".flags"
3028		environment variable.  To override a setting in the static
3029		list, simply add an entry for the same variable name to the
3030		".flags" variable.
3031
3032	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3033	regular expression. This allows multiple variables to define the same
3034	flags without explicitly listing them for each variable.
3035
3036- CONFIG_ENV_ACCESS_IGNORE_FORCE
3037	If defined, don't allow the -f switch to env set override variable
3038	access flags.
3039
3040- CONFIG_USE_STDINT
3041	If stdint.h is available with your toolchain you can define this
3042	option to enable it. You can provide option 'USE_STDINT=1' when
3043	building U-Boot to enable this.
3044
3045The following definitions that deal with the placement and management
3046of environment data (variable area); in general, we support the
3047following configurations:
3048
3049- CONFIG_BUILD_ENVCRC:
3050
3051	Builds up envcrc with the target environment so that external utils
3052	may easily extract it and embed it in final U-Boot images.
3053
3054BE CAREFUL! The first access to the environment happens quite early
3055in U-Boot initialization (when we try to get the setting of for the
3056console baudrate). You *MUST* have mapped your NVRAM area then, or
3057U-Boot will hang.
3058
3059Please note that even with NVRAM we still use a copy of the
3060environment in RAM: we could work on NVRAM directly, but we want to
3061keep settings there always unmodified except somebody uses "saveenv"
3062to save the current settings.
3063
3064BE CAREFUL! For some special cases, the local device can not use
3065"saveenv" command. For example, the local device will get the
3066environment stored in a remote NOR flash by SRIO or PCIE link,
3067but it can not erase, write this NOR flash by SRIO or PCIE interface.
3068
3069- CONFIG_NAND_ENV_DST
3070
3071	Defines address in RAM to which the nand_spl code should copy the
3072	environment. If redundant environment is used, it will be copied to
3073	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3074
3075Please note that the environment is read-only until the monitor
3076has been relocated to RAM and a RAM copy of the environment has been
3077created; also, when using EEPROM you will have to use env_get_f()
3078until then to read environment variables.
3079
3080The environment is protected by a CRC32 checksum. Before the monitor
3081is relocated into RAM, as a result of a bad CRC you will be working
3082with the compiled-in default environment - *silently*!!! [This is
3083necessary, because the first environment variable we need is the
3084"baudrate" setting for the console - if we have a bad CRC, we don't
3085have any device yet where we could complain.]
3086
3087Note: once the monitor has been relocated, then it will complain if
3088the default environment is used; a new CRC is computed as soon as you
3089use the "saveenv" command to store a valid environment.
3090
3091- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3092		Echo the inverted Ethernet link state to the fault LED.
3093
3094		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3095		      also needs to be defined.
3096
3097- CONFIG_SYS_FAULT_MII_ADDR:
3098		MII address of the PHY to check for the Ethernet link state.
3099
3100- CONFIG_NS16550_MIN_FUNCTIONS:
3101		Define this if you desire to only have use of the NS16550_init
3102		and NS16550_putc functions for the serial driver located at
3103		drivers/serial/ns16550.c.  This option is useful for saving
3104		space for already greatly restricted images, including but not
3105		limited to NAND_SPL configurations.
3106
3107- CONFIG_DISPLAY_BOARDINFO
3108		Display information about the board that U-Boot is running on
3109		when U-Boot starts up. The board function checkboard() is called
3110		to do this.
3111
3112- CONFIG_DISPLAY_BOARDINFO_LATE
3113		Similar to the previous option, but display this information
3114		later, once stdio is running and output goes to the LCD, if
3115		present.
3116
3117- CONFIG_BOARD_SIZE_LIMIT:
3118		Maximum size of the U-Boot image. When defined, the
3119		build system checks that the actual size does not
3120		exceed it.
3121
3122Low Level (hardware related) configuration options:
3123---------------------------------------------------
3124
3125- CONFIG_SYS_CACHELINE_SIZE:
3126		Cache Line Size of the CPU.
3127
3128- CONFIG_SYS_CCSRBAR_DEFAULT:
3129		Default (power-on reset) physical address of CCSR on Freescale
3130		PowerPC SOCs.
3131
3132- CONFIG_SYS_CCSRBAR:
3133		Virtual address of CCSR.  On a 32-bit build, this is typically
3134		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3135
3136- CONFIG_SYS_CCSRBAR_PHYS:
3137		Physical address of CCSR.  CCSR can be relocated to a new
3138		physical address, if desired.  In this case, this macro should
3139		be set to that address.	 Otherwise, it should be set to the
3140		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3141		is typically relocated on 36-bit builds.  It is recommended
3142		that this macro be defined via the _HIGH and _LOW macros:
3143
3144		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3145			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3146
3147- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3148		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3149		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3150		used in assembly code, so it must not contain typecasts or
3151		integer size suffixes (e.g. "ULL").
3152
3153- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3154		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3155		used in assembly code, so it must not contain typecasts or
3156		integer size suffixes (e.g. "ULL").
3157
3158- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3159		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3160		forced to a value that ensures that CCSR is not relocated.
3161
3162- Floppy Disk Support:
3163		CONFIG_SYS_FDC_DRIVE_NUMBER
3164
3165		the default drive number (default value 0)
3166
3167		CONFIG_SYS_ISA_IO_STRIDE
3168
3169		defines the spacing between FDC chipset registers
3170		(default value 1)
3171
3172		CONFIG_SYS_ISA_IO_OFFSET
3173
3174		defines the offset of register from address. It
3175		depends on which part of the data bus is connected to
3176		the FDC chipset. (default value 0)
3177
3178		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3179		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3180		default value.
3181
3182		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3183		fdc_hw_init() is called at the beginning of the FDC
3184		setup. fdc_hw_init() must be provided by the board
3185		source code. It is used to make hardware-dependent
3186		initializations.
3187
3188- CONFIG_IDE_AHB:
3189		Most IDE controllers were designed to be connected with PCI
3190		interface. Only few of them were designed for AHB interface.
3191		When software is doing ATA command and data transfer to
3192		IDE devices through IDE-AHB controller, some additional
3193		registers accessing to these kind of IDE-AHB controller
3194		is required.
3195
3196- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3197		DO NOT CHANGE unless you know exactly what you're
3198		doing! (11-4) [MPC8xx systems only]
3199
3200- CONFIG_SYS_INIT_RAM_ADDR:
3201
3202		Start address of memory area that can be used for
3203		initial data and stack; please note that this must be
3204		writable memory that is working WITHOUT special
3205		initialization, i. e. you CANNOT use normal RAM which
3206		will become available only after programming the
3207		memory controller and running certain initialization
3208		sequences.
3209
3210		U-Boot uses the following memory types:
3211		- MPC8xx: IMMR (internal memory of the CPU)
3212
3213- CONFIG_SYS_GBL_DATA_OFFSET:
3214
3215		Offset of the initial data structure in the memory
3216		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3217		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3218		data is located at the end of the available space
3219		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3220		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3221		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3222		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3223
3224	Note:
3225		On the MPC824X (or other systems that use the data
3226		cache for initial memory) the address chosen for
3227		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3228		point to an otherwise UNUSED address space between
3229		the top of RAM and the start of the PCI space.
3230
3231- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3232
3233- CONFIG_SYS_OR_TIMING_SDRAM:
3234		SDRAM timing
3235
3236- CONFIG_SYS_MAMR_PTA:
3237		periodic timer for refresh
3238
3239- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3240  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3241  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3242  CONFIG_SYS_BR1_PRELIM:
3243		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3244
3245- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3246  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3247  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3248		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3249
3250- CONFIG_PCI_ENUM_ONLY
3251		Only scan through and get the devices on the buses.
3252		Don't do any setup work, presumably because someone or
3253		something has already done it, and we don't need to do it
3254		a second time.	Useful for platforms that are pre-booted
3255		by coreboot or similar.
3256
3257- CONFIG_PCI_INDIRECT_BRIDGE:
3258		Enable support for indirect PCI bridges.
3259
3260- CONFIG_SYS_SRIO:
3261		Chip has SRIO or not
3262
3263- CONFIG_SRIO1:
3264		Board has SRIO 1 port available
3265
3266- CONFIG_SRIO2:
3267		Board has SRIO 2 port available
3268
3269- CONFIG_SRIO_PCIE_BOOT_MASTER
3270		Board can support master function for Boot from SRIO and PCIE
3271
3272- CONFIG_SYS_SRIOn_MEM_VIRT:
3273		Virtual Address of SRIO port 'n' memory region
3274
3275- CONFIG_SYS_SRIOn_MEM_PHYS:
3276		Physical Address of SRIO port 'n' memory region
3277
3278- CONFIG_SYS_SRIOn_MEM_SIZE:
3279		Size of SRIO port 'n' memory region
3280
3281- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3282		Defined to tell the NAND controller that the NAND chip is using
3283		a 16 bit bus.
3284		Not all NAND drivers use this symbol.
3285		Example of drivers that use it:
3286		- drivers/mtd/nand/ndfc.c
3287		- drivers/mtd/nand/mxc_nand.c
3288
3289- CONFIG_SYS_NDFC_EBC0_CFG
3290		Sets the EBC0_CFG register for the NDFC. If not defined
3291		a default value will be used.
3292
3293- CONFIG_SPD_EEPROM
3294		Get DDR timing information from an I2C EEPROM. Common
3295		with pluggable memory modules such as SODIMMs
3296
3297  SPD_EEPROM_ADDRESS
3298		I2C address of the SPD EEPROM
3299
3300- CONFIG_SYS_SPD_BUS_NUM
3301		If SPD EEPROM is on an I2C bus other than the first
3302		one, specify here. Note that the value must resolve
3303		to something your driver can deal with.
3304
3305- CONFIG_SYS_DDR_RAW_TIMING
3306		Get DDR timing information from other than SPD. Common with
3307		soldered DDR chips onboard without SPD. DDR raw timing
3308		parameters are extracted from datasheet and hard-coded into
3309		header files or board specific files.
3310
3311- CONFIG_FSL_DDR_INTERACTIVE
3312		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3313
3314- CONFIG_FSL_DDR_SYNC_REFRESH
3315		Enable sync of refresh for multiple controllers.
3316
3317- CONFIG_FSL_DDR_BIST
3318		Enable built-in memory test for Freescale DDR controllers.
3319
3320- CONFIG_SYS_83XX_DDR_USES_CS0
3321		Only for 83xx systems. If specified, then DDR should
3322		be configured using CS0 and CS1 instead of CS2 and CS3.
3323
3324- CONFIG_RMII
3325		Enable RMII mode for all FECs.
3326		Note that this is a global option, we can't
3327		have one FEC in standard MII mode and another in RMII mode.
3328
3329- CONFIG_CRC32_VERIFY
3330		Add a verify option to the crc32 command.
3331		The syntax is:
3332
3333		=> crc32 -v <address> <count> <crc32>
3334
3335		Where address/count indicate a memory area
3336		and crc32 is the correct crc32 which the
3337		area should have.
3338
3339- CONFIG_LOOPW
3340		Add the "loopw" memory command. This only takes effect if
3341		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3342
3343- CONFIG_MX_CYCLIC
3344		Add the "mdc" and "mwc" memory commands. These are cyclic
3345		"md/mw" commands.
3346		Examples:
3347
3348		=> mdc.b 10 4 500
3349		This command will print 4 bytes (10,11,12,13) each 500 ms.
3350
3351		=> mwc.l 100 12345678 10
3352		This command will write 12345678 to address 100 all 10 ms.
3353
3354		This only takes effect if the memory commands are activated
3355		globally (CONFIG_CMD_MEMORY).
3356
3357- CONFIG_SKIP_LOWLEVEL_INIT
3358		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3359		low level initializations (like setting up the memory
3360		controller) are omitted and/or U-Boot does not
3361		relocate itself into RAM.
3362
3363		Normally this variable MUST NOT be defined. The only
3364		exception is when U-Boot is loaded (to RAM) by some
3365		other boot loader or by a debugger which performs
3366		these initializations itself.
3367
3368- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3369		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3370		to be skipped. The normal CP15 init (such as enabling the
3371		instruction cache) is still performed.
3372
3373- CONFIG_SPL_BUILD
3374		Modifies the behaviour of start.S when compiling a loader
3375		that is executed before the actual U-Boot. E.g. when
3376		compiling a NAND SPL.
3377
3378- CONFIG_TPL_BUILD
3379		Modifies the behaviour of start.S  when compiling a loader
3380		that is executed after the SPL and before the actual U-Boot.
3381		It is loaded by the SPL.
3382
3383- CONFIG_SYS_MPC85XX_NO_RESETVEC
3384		Only for 85xx systems. If this variable is specified, the section
3385		.resetvec is not kept and the section .bootpg is placed in the
3386		previous 4k of the .text section.
3387
3388- CONFIG_ARCH_MAP_SYSMEM
3389		Generally U-Boot (and in particular the md command) uses
3390		effective address. It is therefore not necessary to regard
3391		U-Boot address as virtual addresses that need to be translated
3392		to physical addresses. However, sandbox requires this, since
3393		it maintains its own little RAM buffer which contains all
3394		addressable memory. This option causes some memory accesses
3395		to be mapped through map_sysmem() / unmap_sysmem().
3396
3397- CONFIG_X86_RESET_VECTOR
3398		If defined, the x86 reset vector code is included. This is not
3399		needed when U-Boot is running from Coreboot.
3400
3401- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3402		Option to disable subpage write in NAND driver
3403		driver that uses this:
3404		drivers/mtd/nand/davinci_nand.c
3405
3406Freescale QE/FMAN Firmware Support:
3407-----------------------------------
3408
3409The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3410loading of "firmware", which is encoded in the QE firmware binary format.
3411This firmware often needs to be loaded during U-Boot booting, so macros
3412are used to identify the storage device (NOR flash, SPI, etc) and the address
3413within that device.
3414
3415- CONFIG_SYS_FMAN_FW_ADDR
3416	The address in the storage device where the FMAN microcode is located.  The
3417	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3418	is also specified.
3419
3420- CONFIG_SYS_QE_FW_ADDR
3421	The address in the storage device where the QE microcode is located.  The
3422	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3423	is also specified.
3424
3425- CONFIG_SYS_QE_FMAN_FW_LENGTH
3426	The maximum possible size of the firmware.  The firmware binary format
3427	has a field that specifies the actual size of the firmware, but it
3428	might not be possible to read any part of the firmware unless some
3429	local storage is allocated to hold the entire firmware first.
3430
3431- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3432	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3433	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3434	virtual address in NOR flash.
3435
3436- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3437	Specifies that QE/FMAN firmware is located in NAND flash.
3438	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3439
3440- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3441	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3442	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3443
3444- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3445	Specifies that QE/FMAN firmware is located in the remote (master)
3446	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3447	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3448	window->master inbound window->master LAW->the ucode address in
3449	master's memory space.
3450
3451Freescale Layerscape Management Complex Firmware Support:
3452---------------------------------------------------------
3453The Freescale Layerscape Management Complex (MC) supports the loading of
3454"firmware".
3455This firmware often needs to be loaded during U-Boot booting, so macros
3456are used to identify the storage device (NOR flash, SPI, etc) and the address
3457within that device.
3458
3459- CONFIG_FSL_MC_ENET
3460	Enable the MC driver for Layerscape SoCs.
3461
3462Freescale Layerscape Debug Server Support:
3463-------------------------------------------
3464The Freescale Layerscape Debug Server Support supports the loading of
3465"Debug Server firmware" and triggering SP boot-rom.
3466This firmware often needs to be loaded during U-Boot booting.
3467
3468- CONFIG_SYS_MC_RSV_MEM_ALIGN
3469	Define alignment of reserved memory MC requires
3470
3471Reproducible builds
3472-------------------
3473
3474In order to achieve reproducible builds, timestamps used in the U-Boot build
3475process have to be set to a fixed value.
3476
3477This is done using the SOURCE_DATE_EPOCH environment variable.
3478SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3479option for U-Boot or an environment variable in U-Boot.
3480
3481SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3482
3483Building the Software:
3484======================
3485
3486Building U-Boot has been tested in several native build environments
3487and in many different cross environments. Of course we cannot support
3488all possibly existing versions of cross development tools in all
3489(potentially obsolete) versions. In case of tool chain problems we
3490recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3491which is extensively used to build and test U-Boot.
3492
3493If you are not using a native environment, it is assumed that you
3494have GNU cross compiling tools available in your path. In this case,
3495you must set the environment variable CROSS_COMPILE in your shell.
3496Note that no changes to the Makefile or any other source files are
3497necessary. For example using the ELDK on a 4xx CPU, please enter:
3498
3499	$ CROSS_COMPILE=ppc_4xx-
3500	$ export CROSS_COMPILE
3501
3502Note: If you wish to generate Windows versions of the utilities in
3503      the tools directory you can use the MinGW toolchain
3504      (http://www.mingw.org).  Set your HOST tools to the MinGW
3505      toolchain and execute 'make tools'.  For example:
3506
3507       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3508
3509      Binaries such as tools/mkimage.exe will be created which can
3510      be executed on computers running Windows.
3511
3512U-Boot is intended to be simple to build. After installing the
3513sources you must configure U-Boot for one specific board type. This
3514is done by typing:
3515
3516	make NAME_defconfig
3517
3518where "NAME_defconfig" is the name of one of the existing configu-
3519rations; see boards.cfg for supported names.
3520
3521Note: for some board special configuration names may exist; check if
3522      additional information is available from the board vendor; for
3523      instance, the TQM823L systems are available without (standard)
3524      or with LCD support. You can select such additional "features"
3525      when choosing the configuration, i. e.
3526
3527      make TQM823L_defconfig
3528	- will configure for a plain TQM823L, i. e. no LCD support
3529
3530      make TQM823L_LCD_defconfig
3531	- will configure for a TQM823L with U-Boot console on LCD
3532
3533      etc.
3534
3535
3536Finally, type "make all", and you should get some working U-Boot
3537images ready for download to / installation on your system:
3538
3539- "u-boot.bin" is a raw binary image
3540- "u-boot" is an image in ELF binary format
3541- "u-boot.srec" is in Motorola S-Record format
3542
3543By default the build is performed locally and the objects are saved
3544in the source directory. One of the two methods can be used to change
3545this behavior and build U-Boot to some external directory:
3546
35471. Add O= to the make command line invocations:
3548
3549	make O=/tmp/build distclean
3550	make O=/tmp/build NAME_defconfig
3551	make O=/tmp/build all
3552
35532. Set environment variable KBUILD_OUTPUT to point to the desired location:
3554
3555	export KBUILD_OUTPUT=/tmp/build
3556	make distclean
3557	make NAME_defconfig
3558	make all
3559
3560Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3561variable.
3562
3563User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3564setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3565For example to treat all compiler warnings as errors:
3566
3567	make KCFLAGS=-Werror
3568
3569Please be aware that the Makefiles assume you are using GNU make, so
3570for instance on NetBSD you might need to use "gmake" instead of
3571native "make".
3572
3573
3574If the system board that you have is not listed, then you will need
3575to port U-Boot to your hardware platform. To do this, follow these
3576steps:
3577
35781.  Create a new directory to hold your board specific code. Add any
3579    files you need. In your board directory, you will need at least
3580    the "Makefile" and a "<board>.c".
35812.  Create a new configuration file "include/configs/<board>.h" for
3582    your board.
35833.  If you're porting U-Boot to a new CPU, then also create a new
3584    directory to hold your CPU specific code. Add any files you need.
35854.  Run "make <board>_defconfig" with your new name.
35865.  Type "make", and you should get a working "u-boot.srec" file
3587    to be installed on your target system.
35886.  Debug and solve any problems that might arise.
3589    [Of course, this last step is much harder than it sounds.]
3590
3591
3592Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3593==============================================================
3594
3595If you have modified U-Boot sources (for instance added a new board
3596or support for new devices, a new CPU, etc.) you are expected to
3597provide feedback to the other developers. The feedback normally takes
3598the form of a "patch", i. e. a context diff against a certain (latest
3599official or latest in the git repository) version of U-Boot sources.
3600
3601But before you submit such a patch, please verify that your modifi-
3602cation did not break existing code. At least make sure that *ALL* of
3603the supported boards compile WITHOUT ANY compiler warnings. To do so,
3604just run the buildman script (tools/buildman/buildman), which will
3605configure and build U-Boot for ALL supported system. Be warned, this
3606will take a while. Please see the buildman README, or run 'buildman -H'
3607for documentation.
3608
3609
3610See also "U-Boot Porting Guide" below.
3611
3612
3613Monitor Commands - Overview:
3614============================
3615
3616go	- start application at address 'addr'
3617run	- run commands in an environment variable
3618bootm	- boot application image from memory
3619bootp	- boot image via network using BootP/TFTP protocol
3620bootz   - boot zImage from memory
3621tftpboot- boot image via network using TFTP protocol
3622	       and env variables "ipaddr" and "serverip"
3623	       (and eventually "gatewayip")
3624tftpput - upload a file via network using TFTP protocol
3625rarpboot- boot image via network using RARP/TFTP protocol
3626diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3627loads	- load S-Record file over serial line
3628loadb	- load binary file over serial line (kermit mode)
3629md	- memory display
3630mm	- memory modify (auto-incrementing)
3631nm	- memory modify (constant address)
3632mw	- memory write (fill)
3633cp	- memory copy
3634cmp	- memory compare
3635crc32	- checksum calculation
3636i2c	- I2C sub-system
3637sspi	- SPI utility commands
3638base	- print or set address offset
3639printenv- print environment variables
3640setenv	- set environment variables
3641saveenv - save environment variables to persistent storage
3642protect - enable or disable FLASH write protection
3643erase	- erase FLASH memory
3644flinfo	- print FLASH memory information
3645nand	- NAND memory operations (see doc/README.nand)
3646bdinfo	- print Board Info structure
3647iminfo	- print header information for application image
3648coninfo - print console devices and informations
3649ide	- IDE sub-system
3650loop	- infinite loop on address range
3651loopw	- infinite write loop on address range
3652mtest	- simple RAM test
3653icache	- enable or disable instruction cache
3654dcache	- enable or disable data cache
3655reset	- Perform RESET of the CPU
3656echo	- echo args to console
3657version - print monitor version
3658help	- print online help
3659?	- alias for 'help'
3660
3661
3662Monitor Commands - Detailed Description:
3663========================================
3664
3665TODO.
3666
3667For now: just type "help <command>".
3668
3669
3670Environment Variables:
3671======================
3672
3673U-Boot supports user configuration using Environment Variables which
3674can be made persistent by saving to Flash memory.
3675
3676Environment Variables are set using "setenv", printed using
3677"printenv", and saved to Flash using "saveenv". Using "setenv"
3678without a value can be used to delete a variable from the
3679environment. As long as you don't save the environment you are
3680working with an in-memory copy. In case the Flash area containing the
3681environment is erased by accident, a default environment is provided.
3682
3683Some configuration options can be set using Environment Variables.
3684
3685List of environment variables (most likely not complete):
3686
3687  baudrate	- see CONFIG_BAUDRATE
3688
3689  bootdelay	- see CONFIG_BOOTDELAY
3690
3691  bootcmd	- see CONFIG_BOOTCOMMAND
3692
3693  bootargs	- Boot arguments when booting an RTOS image
3694
3695  bootfile	- Name of the image to load with TFTP
3696
3697  bootm_low	- Memory range available for image processing in the bootm
3698		  command can be restricted. This variable is given as
3699		  a hexadecimal number and defines lowest address allowed
3700		  for use by the bootm command. See also "bootm_size"
3701		  environment variable. Address defined by "bootm_low" is
3702		  also the base of the initial memory mapping for the Linux
3703		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3704		  bootm_mapsize.
3705
3706  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3707		  This variable is given as a hexadecimal number and it
3708		  defines the size of the memory region starting at base
3709		  address bootm_low that is accessible by the Linux kernel
3710		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3711		  as the default value if it is defined, and bootm_size is
3712		  used otherwise.
3713
3714  bootm_size	- Memory range available for image processing in the bootm
3715		  command can be restricted. This variable is given as
3716		  a hexadecimal number and defines the size of the region
3717		  allowed for use by the bootm command. See also "bootm_low"
3718		  environment variable.
3719
3720  updatefile	- Location of the software update file on a TFTP server, used
3721		  by the automatic software update feature. Please refer to
3722		  documentation in doc/README.update for more details.
3723
3724  autoload	- if set to "no" (any string beginning with 'n'),
3725		  "bootp" will just load perform a lookup of the
3726		  configuration from the BOOTP server, but not try to
3727		  load any image using TFTP
3728
3729  autostart	- if set to "yes", an image loaded using the "bootp",
3730		  "rarpboot", "tftpboot" or "diskboot" commands will
3731		  be automatically started (by internally calling
3732		  "bootm")
3733
3734		  If set to "no", a standalone image passed to the
3735		  "bootm" command will be copied to the load address
3736		  (and eventually uncompressed), but NOT be started.
3737		  This can be used to load and uncompress arbitrary
3738		  data.
3739
3740  fdt_high	- if set this restricts the maximum address that the
3741		  flattened device tree will be copied into upon boot.
3742		  For example, if you have a system with 1 GB memory
3743		  at physical address 0x10000000, while Linux kernel
3744		  only recognizes the first 704 MB as low memory, you
3745		  may need to set fdt_high as 0x3C000000 to have the
3746		  device tree blob be copied to the maximum address
3747		  of the 704 MB low memory, so that Linux kernel can
3748		  access it during the boot procedure.
3749
3750		  If this is set to the special value 0xFFFFFFFF then
3751		  the fdt will not be copied at all on boot.  For this
3752		  to work it must reside in writable memory, have
3753		  sufficient padding on the end of it for u-boot to
3754		  add the information it needs into it, and the memory
3755		  must be accessible by the kernel.
3756
3757  fdtcontroladdr- if set this is the address of the control flattened
3758		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3759		  defined.
3760
3761  i2cfast	- (PPC405GP|PPC405EP only)
3762		  if set to 'y' configures Linux I2C driver for fast
3763		  mode (400kHZ). This environment variable is used in
3764		  initialization code. So, for changes to be effective
3765		  it must be saved and board must be reset.
3766
3767  initrd_high	- restrict positioning of initrd images:
3768		  If this variable is not set, initrd images will be
3769		  copied to the highest possible address in RAM; this
3770		  is usually what you want since it allows for
3771		  maximum initrd size. If for some reason you want to
3772		  make sure that the initrd image is loaded below the
3773		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3774		  variable to a value of "no" or "off" or "0".
3775		  Alternatively, you can set it to a maximum upper
3776		  address to use (U-Boot will still check that it
3777		  does not overwrite the U-Boot stack and data).
3778
3779		  For instance, when you have a system with 16 MB
3780		  RAM, and want to reserve 4 MB from use by Linux,
3781		  you can do this by adding "mem=12M" to the value of
3782		  the "bootargs" variable. However, now you must make
3783		  sure that the initrd image is placed in the first
3784		  12 MB as well - this can be done with
3785
3786		  setenv initrd_high 00c00000
3787
3788		  If you set initrd_high to 0xFFFFFFFF, this is an
3789		  indication to U-Boot that all addresses are legal
3790		  for the Linux kernel, including addresses in flash
3791		  memory. In this case U-Boot will NOT COPY the
3792		  ramdisk at all. This may be useful to reduce the
3793		  boot time on your system, but requires that this
3794		  feature is supported by your Linux kernel.
3795
3796  ipaddr	- IP address; needed for tftpboot command
3797
3798  loadaddr	- Default load address for commands like "bootp",
3799		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3800
3801  loads_echo	- see CONFIG_LOADS_ECHO
3802
3803  serverip	- TFTP server IP address; needed for tftpboot command
3804
3805  bootretry	- see CONFIG_BOOT_RETRY_TIME
3806
3807  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3808
3809  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3810
3811  ethprime	- controls which interface is used first.
3812
3813  ethact	- controls which interface is currently active.
3814		  For example you can do the following
3815
3816		  => setenv ethact FEC
3817		  => ping 192.168.0.1 # traffic sent on FEC
3818		  => setenv ethact SCC
3819		  => ping 10.0.0.1 # traffic sent on SCC
3820
3821  ethrotate	- When set to "no" U-Boot does not go through all
3822		  available network interfaces.
3823		  It just stays at the currently selected interface.
3824
3825  netretry	- When set to "no" each network operation will
3826		  either succeed or fail without retrying.
3827		  When set to "once" the network operation will
3828		  fail when all the available network interfaces
3829		  are tried once without success.
3830		  Useful on scripts which control the retry operation
3831		  themselves.
3832
3833  npe_ucode	- set load address for the NPE microcode
3834
3835  silent_linux  - If set then Linux will be told to boot silently, by
3836		  changing the console to be empty. If "yes" it will be
3837		  made silent. If "no" it will not be made silent. If
3838		  unset, then it will be made silent if the U-Boot console
3839		  is silent.
3840
3841  tftpsrcp	- If this is set, the value is used for TFTP's
3842		  UDP source port.
3843
3844  tftpdstp	- If this is set, the value is used for TFTP's UDP
3845		  destination port instead of the Well Know Port 69.
3846
3847  tftpblocksize - Block size to use for TFTP transfers; if not set,
3848		  we use the TFTP server's default block size
3849
3850  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3851		  seconds, minimum value is 1000 = 1 second). Defines
3852		  when a packet is considered to be lost so it has to
3853		  be retransmitted. The default is 5000 = 5 seconds.
3854		  Lowering this value may make downloads succeed
3855		  faster in networks with high packet loss rates or
3856		  with unreliable TFTP servers.
3857
3858  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3859		  unit, minimum value = 0). Defines how many timeouts
3860		  can happen during a single file transfer before that
3861		  transfer is aborted. The default is 10, and 0 means
3862		  'no timeouts allowed'. Increasing this value may help
3863		  downloads succeed with high packet loss rates, or with
3864		  unreliable TFTP servers or client hardware.
3865
3866  vlan		- When set to a value < 4095 the traffic over
3867		  Ethernet is encapsulated/received over 802.1q
3868		  VLAN tagged frames.
3869
3870  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3871		  Unsigned value, in milliseconds. If not set, the period will
3872		  be either the default (28000), or a value based on
3873		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3874		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3875
3876The following image location variables contain the location of images
3877used in booting. The "Image" column gives the role of the image and is
3878not an environment variable name. The other columns are environment
3879variable names. "File Name" gives the name of the file on a TFTP
3880server, "RAM Address" gives the location in RAM the image will be
3881loaded to, and "Flash Location" gives the image's address in NOR
3882flash or offset in NAND flash.
3883
3884*Note* - these variables don't have to be defined for all boards, some
3885boards currently use other variables for these purposes, and some
3886boards use these variables for other purposes.
3887
3888Image		    File Name	     RAM Address       Flash Location
3889-----		    ---------	     -----------       --------------
3890u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3891Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3892device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3893ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3894
3895The following environment variables may be used and automatically
3896updated by the network boot commands ("bootp" and "rarpboot"),
3897depending the information provided by your boot server:
3898
3899  bootfile	- see above
3900  dnsip		- IP address of your Domain Name Server
3901  dnsip2	- IP address of your secondary Domain Name Server
3902  gatewayip	- IP address of the Gateway (Router) to use
3903  hostname	- Target hostname
3904  ipaddr	- see above
3905  netmask	- Subnet Mask
3906  rootpath	- Pathname of the root filesystem on the NFS server
3907  serverip	- see above
3908
3909
3910There are two special Environment Variables:
3911
3912  serial#	- contains hardware identification information such
3913		  as type string and/or serial number
3914  ethaddr	- Ethernet address
3915
3916These variables can be set only once (usually during manufacturing of
3917the board). U-Boot refuses to delete or overwrite these variables
3918once they have been set once.
3919
3920
3921Further special Environment Variables:
3922
3923  ver		- Contains the U-Boot version string as printed
3924		  with the "version" command. This variable is
3925		  readonly (see CONFIG_VERSION_VARIABLE).
3926
3927
3928Please note that changes to some configuration parameters may take
3929only effect after the next boot (yes, that's just like Windoze :-).
3930
3931
3932Callback functions for environment variables:
3933---------------------------------------------
3934
3935For some environment variables, the behavior of u-boot needs to change
3936when their values are changed.  This functionality allows functions to
3937be associated with arbitrary variables.  On creation, overwrite, or
3938deletion, the callback will provide the opportunity for some side
3939effect to happen or for the change to be rejected.
3940
3941The callbacks are named and associated with a function using the
3942U_BOOT_ENV_CALLBACK macro in your board or driver code.
3943
3944These callbacks are associated with variables in one of two ways.  The
3945static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3946in the board configuration to a string that defines a list of
3947associations.  The list must be in the following format:
3948
3949	entry = variable_name[:callback_name]
3950	list = entry[,list]
3951
3952If the callback name is not specified, then the callback is deleted.
3953Spaces are also allowed anywhere in the list.
3954
3955Callbacks can also be associated by defining the ".callbacks" variable
3956with the same list format above.  Any association in ".callbacks" will
3957override any association in the static list. You can define
3958CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3959".callbacks" environment variable in the default or embedded environment.
3960
3961If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3962regular expression. This allows multiple variables to be connected to
3963the same callback without explicitly listing them all out.
3964
3965
3966Command Line Parsing:
3967=====================
3968
3969There are two different command line parsers available with U-Boot:
3970the old "simple" one, and the much more powerful "hush" shell:
3971
3972Old, simple command line parser:
3973--------------------------------
3974
3975- supports environment variables (through setenv / saveenv commands)
3976- several commands on one line, separated by ';'
3977- variable substitution using "... ${name} ..." syntax
3978- special characters ('$', ';') can be escaped by prefixing with '\',
3979  for example:
3980	setenv bootcmd bootm \${address}
3981- You can also escape text by enclosing in single apostrophes, for example:
3982	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3983
3984Hush shell:
3985-----------
3986
3987- similar to Bourne shell, with control structures like
3988  if...then...else...fi, for...do...done; while...do...done,
3989  until...do...done, ...
3990- supports environment ("global") variables (through setenv / saveenv
3991  commands) and local shell variables (through standard shell syntax
3992  "name=value"); only environment variables can be used with "run"
3993  command
3994
3995General rules:
3996--------------
3997
3998(1) If a command line (or an environment variable executed by a "run"
3999    command) contains several commands separated by semicolon, and
4000    one of these commands fails, then the remaining commands will be
4001    executed anyway.
4002
4003(2) If you execute several variables with one call to run (i. e.
4004    calling run with a list of variables as arguments), any failing
4005    command will cause "run" to terminate, i. e. the remaining
4006    variables are not executed.
4007
4008Note for Redundant Ethernet Interfaces:
4009=======================================
4010
4011Some boards come with redundant Ethernet interfaces; U-Boot supports
4012such configurations and is capable of automatic selection of a
4013"working" interface when needed. MAC assignment works as follows:
4014
4015Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4016MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4017"eth1addr" (=>eth1), "eth2addr", ...
4018
4019If the network interface stores some valid MAC address (for instance
4020in SROM), this is used as default address if there is NO correspon-
4021ding setting in the environment; if the corresponding environment
4022variable is set, this overrides the settings in the card; that means:
4023
4024o If the SROM has a valid MAC address, and there is no address in the
4025  environment, the SROM's address is used.
4026
4027o If there is no valid address in the SROM, and a definition in the
4028  environment exists, then the value from the environment variable is
4029  used.
4030
4031o If both the SROM and the environment contain a MAC address, and
4032  both addresses are the same, this MAC address is used.
4033
4034o If both the SROM and the environment contain a MAC address, and the
4035  addresses differ, the value from the environment is used and a
4036  warning is printed.
4037
4038o If neither SROM nor the environment contain a MAC address, an error
4039  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4040  a random, locally-assigned MAC is used.
4041
4042If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4043will be programmed into hardware as part of the initialization process.	 This
4044may be skipped by setting the appropriate 'ethmacskip' environment variable.
4045The naming convention is as follows:
4046"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4047
4048Image Formats:
4049==============
4050
4051U-Boot is capable of booting (and performing other auxiliary operations on)
4052images in two formats:
4053
4054New uImage format (FIT)
4055-----------------------
4056
4057Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4058to Flattened Device Tree). It allows the use of images with multiple
4059components (several kernels, ramdisks, etc.), with contents protected by
4060SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4061
4062
4063Old uImage format
4064-----------------
4065
4066Old image format is based on binary files which can be basically anything,
4067preceded by a special header; see the definitions in include/image.h for
4068details; basically, the header defines the following image properties:
4069
4070* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4071  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4072  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4073  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4074  INTEGRITY).
4075* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4076  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4077  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4078* Compression Type (uncompressed, gzip, bzip2)
4079* Load Address
4080* Entry Point
4081* Image Name
4082* Image Timestamp
4083
4084The header is marked by a special Magic Number, and both the header
4085and the data portions of the image are secured against corruption by
4086CRC32 checksums.
4087
4088
4089Linux Support:
4090==============
4091
4092Although U-Boot should support any OS or standalone application
4093easily, the main focus has always been on Linux during the design of
4094U-Boot.
4095
4096U-Boot includes many features that so far have been part of some
4097special "boot loader" code within the Linux kernel. Also, any
4098"initrd" images to be used are no longer part of one big Linux image;
4099instead, kernel and "initrd" are separate images. This implementation
4100serves several purposes:
4101
4102- the same features can be used for other OS or standalone
4103  applications (for instance: using compressed images to reduce the
4104  Flash memory footprint)
4105
4106- it becomes much easier to port new Linux kernel versions because
4107  lots of low-level, hardware dependent stuff are done by U-Boot
4108
4109- the same Linux kernel image can now be used with different "initrd"
4110  images; of course this also means that different kernel images can
4111  be run with the same "initrd". This makes testing easier (you don't
4112  have to build a new "zImage.initrd" Linux image when you just
4113  change a file in your "initrd"). Also, a field-upgrade of the
4114  software is easier now.
4115
4116
4117Linux HOWTO:
4118============
4119
4120Porting Linux to U-Boot based systems:
4121---------------------------------------
4122
4123U-Boot cannot save you from doing all the necessary modifications to
4124configure the Linux device drivers for use with your target hardware
4125(no, we don't intend to provide a full virtual machine interface to
4126Linux :-).
4127
4128But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4129
4130Just make sure your machine specific header file (for instance
4131include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4132Information structure as we define in include/asm-<arch>/u-boot.h,
4133and make sure that your definition of IMAP_ADDR uses the same value
4134as your U-Boot configuration in CONFIG_SYS_IMMR.
4135
4136Note that U-Boot now has a driver model, a unified model for drivers.
4137If you are adding a new driver, plumb it into driver model. If there
4138is no uclass available, you are encouraged to create one. See
4139doc/driver-model.
4140
4141
4142Configuring the Linux kernel:
4143-----------------------------
4144
4145No specific requirements for U-Boot. Make sure you have some root
4146device (initial ramdisk, NFS) for your target system.
4147
4148
4149Building a Linux Image:
4150-----------------------
4151
4152With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4153not used. If you use recent kernel source, a new build target
4154"uImage" will exist which automatically builds an image usable by
4155U-Boot. Most older kernels also have support for a "pImage" target,
4156which was introduced for our predecessor project PPCBoot and uses a
4157100% compatible format.
4158
4159Example:
4160
4161	make TQM850L_defconfig
4162	make oldconfig
4163	make dep
4164	make uImage
4165
4166The "uImage" build target uses a special tool (in 'tools/mkimage') to
4167encapsulate a compressed Linux kernel image with header	 information,
4168CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4169
4170* build a standard "vmlinux" kernel image (in ELF binary format):
4171
4172* convert the kernel into a raw binary image:
4173
4174	${CROSS_COMPILE}-objcopy -O binary \
4175				 -R .note -R .comment \
4176				 -S vmlinux linux.bin
4177
4178* compress the binary image:
4179
4180	gzip -9 linux.bin
4181
4182* package compressed binary image for U-Boot:
4183
4184	mkimage -A ppc -O linux -T kernel -C gzip \
4185		-a 0 -e 0 -n "Linux Kernel Image" \
4186		-d linux.bin.gz uImage
4187
4188
4189The "mkimage" tool can also be used to create ramdisk images for use
4190with U-Boot, either separated from the Linux kernel image, or
4191combined into one file. "mkimage" encapsulates the images with a 64
4192byte header containing information about target architecture,
4193operating system, image type, compression method, entry points, time
4194stamp, CRC32 checksums, etc.
4195
4196"mkimage" can be called in two ways: to verify existing images and
4197print the header information, or to build new images.
4198
4199In the first form (with "-l" option) mkimage lists the information
4200contained in the header of an existing U-Boot image; this includes
4201checksum verification:
4202
4203	tools/mkimage -l image
4204	  -l ==> list image header information
4205
4206The second form (with "-d" option) is used to build a U-Boot image
4207from a "data file" which is used as image payload:
4208
4209	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4210		      -n name -d data_file image
4211	  -A ==> set architecture to 'arch'
4212	  -O ==> set operating system to 'os'
4213	  -T ==> set image type to 'type'
4214	  -C ==> set compression type 'comp'
4215	  -a ==> set load address to 'addr' (hex)
4216	  -e ==> set entry point to 'ep' (hex)
4217	  -n ==> set image name to 'name'
4218	  -d ==> use image data from 'datafile'
4219
4220Right now, all Linux kernels for PowerPC systems use the same load
4221address (0x00000000), but the entry point address depends on the
4222kernel version:
4223
4224- 2.2.x kernels have the entry point at 0x0000000C,
4225- 2.3.x and later kernels have the entry point at 0x00000000.
4226
4227So a typical call to build a U-Boot image would read:
4228
4229	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4230	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4231	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4232	> examples/uImage.TQM850L
4233	Image Name:   2.4.4 kernel for TQM850L
4234	Created:      Wed Jul 19 02:34:59 2000
4235	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4236	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4237	Load Address: 0x00000000
4238	Entry Point:  0x00000000
4239
4240To verify the contents of the image (or check for corruption):
4241
4242	-> tools/mkimage -l examples/uImage.TQM850L
4243	Image Name:   2.4.4 kernel for TQM850L
4244	Created:      Wed Jul 19 02:34:59 2000
4245	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4246	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4247	Load Address: 0x00000000
4248	Entry Point:  0x00000000
4249
4250NOTE: for embedded systems where boot time is critical you can trade
4251speed for memory and install an UNCOMPRESSED image instead: this
4252needs more space in Flash, but boots much faster since it does not
4253need to be uncompressed:
4254
4255	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4256	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4257	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4258	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4259	> examples/uImage.TQM850L-uncompressed
4260	Image Name:   2.4.4 kernel for TQM850L
4261	Created:      Wed Jul 19 02:34:59 2000
4262	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4263	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4264	Load Address: 0x00000000
4265	Entry Point:  0x00000000
4266
4267
4268Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4269when your kernel is intended to use an initial ramdisk:
4270
4271	-> tools/mkimage -n 'Simple Ramdisk Image' \
4272	> -A ppc -O linux -T ramdisk -C gzip \
4273	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4274	Image Name:   Simple Ramdisk Image
4275	Created:      Wed Jan 12 14:01:50 2000
4276	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4277	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4278	Load Address: 0x00000000
4279	Entry Point:  0x00000000
4280
4281The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4282option performs the converse operation of the mkimage's second form (the "-d"
4283option). Given an image built by mkimage, the dumpimage extracts a "data file"
4284from the image:
4285
4286	tools/dumpimage -i image -T type -p position data_file
4287	  -i ==> extract from the 'image' a specific 'data_file'
4288	  -T ==> set image type to 'type'
4289	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4290
4291
4292Installing a Linux Image:
4293-------------------------
4294
4295To downloading a U-Boot image over the serial (console) interface,
4296you must convert the image to S-Record format:
4297
4298	objcopy -I binary -O srec examples/image examples/image.srec
4299
4300The 'objcopy' does not understand the information in the U-Boot
4301image header, so the resulting S-Record file will be relative to
4302address 0x00000000. To load it to a given address, you need to
4303specify the target address as 'offset' parameter with the 'loads'
4304command.
4305
4306Example: install the image to address 0x40100000 (which on the
4307TQM8xxL is in the first Flash bank):
4308
4309	=> erase 40100000 401FFFFF
4310
4311	.......... done
4312	Erased 8 sectors
4313
4314	=> loads 40100000
4315	## Ready for S-Record download ...
4316	~>examples/image.srec
4317	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4318	...
4319	15989 15990 15991 15992
4320	[file transfer complete]
4321	[connected]
4322	## Start Addr = 0x00000000
4323
4324
4325You can check the success of the download using the 'iminfo' command;
4326this includes a checksum verification so you can be sure no data
4327corruption happened:
4328
4329	=> imi 40100000
4330
4331	## Checking Image at 40100000 ...
4332	   Image Name:	 2.2.13 for initrd on TQM850L
4333	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4334	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4335	   Load Address: 00000000
4336	   Entry Point:	 0000000c
4337	   Verifying Checksum ... OK
4338
4339
4340Boot Linux:
4341-----------
4342
4343The "bootm" command is used to boot an application that is stored in
4344memory (RAM or Flash). In case of a Linux kernel image, the contents
4345of the "bootargs" environment variable is passed to the kernel as
4346parameters. You can check and modify this variable using the
4347"printenv" and "setenv" commands:
4348
4349
4350	=> printenv bootargs
4351	bootargs=root=/dev/ram
4352
4353	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4354
4355	=> printenv bootargs
4356	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4357
4358	=> bootm 40020000
4359	## Booting Linux kernel at 40020000 ...
4360	   Image Name:	 2.2.13 for NFS on TQM850L
4361	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4362	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4363	   Load Address: 00000000
4364	   Entry Point:	 0000000c
4365	   Verifying Checksum ... OK
4366	   Uncompressing Kernel Image ... OK
4367	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
4368	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4369	time_init: decrementer frequency = 187500000/60
4370	Calibrating delay loop... 49.77 BogoMIPS
4371	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4372	...
4373
4374If you want to boot a Linux kernel with initial RAM disk, you pass
4375the memory addresses of both the kernel and the initrd image (PPBCOOT
4376format!) to the "bootm" command:
4377
4378	=> imi 40100000 40200000
4379
4380	## Checking Image at 40100000 ...
4381	   Image Name:	 2.2.13 for initrd on TQM850L
4382	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4383	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4384	   Load Address: 00000000
4385	   Entry Point:	 0000000c
4386	   Verifying Checksum ... OK
4387
4388	## Checking Image at 40200000 ...
4389	   Image Name:	 Simple Ramdisk Image
4390	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4391	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4392	   Load Address: 00000000
4393	   Entry Point:	 00000000
4394	   Verifying Checksum ... OK
4395
4396	=> bootm 40100000 40200000
4397	## Booting Linux kernel at 40100000 ...
4398	   Image Name:	 2.2.13 for initrd on TQM850L
4399	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4400	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4401	   Load Address: 00000000
4402	   Entry Point:	 0000000c
4403	   Verifying Checksum ... OK
4404	   Uncompressing Kernel Image ... OK
4405	## Loading RAMDisk Image at 40200000 ...
4406	   Image Name:	 Simple Ramdisk Image
4407	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4408	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4409	   Load Address: 00000000
4410	   Entry Point:	 00000000
4411	   Verifying Checksum ... OK
4412	   Loading Ramdisk ... OK
4413	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
4414	Boot arguments: root=/dev/ram
4415	time_init: decrementer frequency = 187500000/60
4416	Calibrating delay loop... 49.77 BogoMIPS
4417	...
4418	RAMDISK: Compressed image found at block 0
4419	VFS: Mounted root (ext2 filesystem).
4420
4421	bash#
4422
4423Boot Linux and pass a flat device tree:
4424-----------
4425
4426First, U-Boot must be compiled with the appropriate defines. See the section
4427titled "Linux Kernel Interface" above for a more in depth explanation. The
4428following is an example of how to start a kernel and pass an updated
4429flat device tree:
4430
4431=> print oftaddr
4432oftaddr=0x300000
4433=> print oft
4434oft=oftrees/mpc8540ads.dtb
4435=> tftp $oftaddr $oft
4436Speed: 1000, full duplex
4437Using TSEC0 device
4438TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4439Filename 'oftrees/mpc8540ads.dtb'.
4440Load address: 0x300000
4441Loading: #
4442done
4443Bytes transferred = 4106 (100a hex)
4444=> tftp $loadaddr $bootfile
4445Speed: 1000, full duplex
4446Using TSEC0 device
4447TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4448Filename 'uImage'.
4449Load address: 0x200000
4450Loading:############
4451done
4452Bytes transferred = 1029407 (fb51f hex)
4453=> print loadaddr
4454loadaddr=200000
4455=> print oftaddr
4456oftaddr=0x300000
4457=> bootm $loadaddr - $oftaddr
4458## Booting image at 00200000 ...
4459   Image Name:	 Linux-2.6.17-dirty
4460   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4461   Data Size:	 1029343 Bytes = 1005.2 kB
4462   Load Address: 00000000
4463   Entry Point:	 00000000
4464   Verifying Checksum ... OK
4465   Uncompressing Kernel Image ... OK
4466Booting using flat device tree at 0x300000
4467Using MPC85xx ADS machine description
4468Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4469[snip]
4470
4471
4472More About U-Boot Image Types:
4473------------------------------
4474
4475U-Boot supports the following image types:
4476
4477   "Standalone Programs" are directly runnable in the environment
4478	provided by U-Boot; it is expected that (if they behave
4479	well) you can continue to work in U-Boot after return from
4480	the Standalone Program.
4481   "OS Kernel Images" are usually images of some Embedded OS which
4482	will take over control completely. Usually these programs
4483	will install their own set of exception handlers, device
4484	drivers, set up the MMU, etc. - this means, that you cannot
4485	expect to re-enter U-Boot except by resetting the CPU.
4486   "RAMDisk Images" are more or less just data blocks, and their
4487	parameters (address, size) are passed to an OS kernel that is
4488	being started.
4489   "Multi-File Images" contain several images, typically an OS
4490	(Linux) kernel image and one or more data images like
4491	RAMDisks. This construct is useful for instance when you want
4492	to boot over the network using BOOTP etc., where the boot
4493	server provides just a single image file, but you want to get
4494	for instance an OS kernel and a RAMDisk image.
4495
4496	"Multi-File Images" start with a list of image sizes, each
4497	image size (in bytes) specified by an "uint32_t" in network
4498	byte order. This list is terminated by an "(uint32_t)0".
4499	Immediately after the terminating 0 follow the images, one by
4500	one, all aligned on "uint32_t" boundaries (size rounded up to
4501	a multiple of 4 bytes).
4502
4503   "Firmware Images" are binary images containing firmware (like
4504	U-Boot or FPGA images) which usually will be programmed to
4505	flash memory.
4506
4507   "Script files" are command sequences that will be executed by
4508	U-Boot's command interpreter; this feature is especially
4509	useful when you configure U-Boot to use a real shell (hush)
4510	as command interpreter.
4511
4512Booting the Linux zImage:
4513-------------------------
4514
4515On some platforms, it's possible to boot Linux zImage. This is done
4516using the "bootz" command. The syntax of "bootz" command is the same
4517as the syntax of "bootm" command.
4518
4519Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4520kernel with raw initrd images. The syntax is slightly different, the
4521address of the initrd must be augmented by it's size, in the following
4522format: "<initrd addres>:<initrd size>".
4523
4524
4525Standalone HOWTO:
4526=================
4527
4528One of the features of U-Boot is that you can dynamically load and
4529run "standalone" applications, which can use some resources of
4530U-Boot like console I/O functions or interrupt services.
4531
4532Two simple examples are included with the sources:
4533
4534"Hello World" Demo:
4535-------------------
4536
4537'examples/hello_world.c' contains a small "Hello World" Demo
4538application; it is automatically compiled when you build U-Boot.
4539It's configured to run at address 0x00040004, so you can play with it
4540like that:
4541
4542	=> loads
4543	## Ready for S-Record download ...
4544	~>examples/hello_world.srec
4545	1 2 3 4 5 6 7 8 9 10 11 ...
4546	[file transfer complete]
4547	[connected]
4548	## Start Addr = 0x00040004
4549
4550	=> go 40004 Hello World! This is a test.
4551	## Starting application at 0x00040004 ...
4552	Hello World
4553	argc = 7
4554	argv[0] = "40004"
4555	argv[1] = "Hello"
4556	argv[2] = "World!"
4557	argv[3] = "This"
4558	argv[4] = "is"
4559	argv[5] = "a"
4560	argv[6] = "test."
4561	argv[7] = "<NULL>"
4562	Hit any key to exit ...
4563
4564	## Application terminated, rc = 0x0
4565
4566Another example, which demonstrates how to register a CPM interrupt
4567handler with the U-Boot code, can be found in 'examples/timer.c'.
4568Here, a CPM timer is set up to generate an interrupt every second.
4569The interrupt service routine is trivial, just printing a '.'
4570character, but this is just a demo program. The application can be
4571controlled by the following keys:
4572
4573	? - print current values og the CPM Timer registers
4574	b - enable interrupts and start timer
4575	e - stop timer and disable interrupts
4576	q - quit application
4577
4578	=> loads
4579	## Ready for S-Record download ...
4580	~>examples/timer.srec
4581	1 2 3 4 5 6 7 8 9 10 11 ...
4582	[file transfer complete]
4583	[connected]
4584	## Start Addr = 0x00040004
4585
4586	=> go 40004
4587	## Starting application at 0x00040004 ...
4588	TIMERS=0xfff00980
4589	Using timer 1
4590	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4591
4592Hit 'b':
4593	[q, b, e, ?] Set interval 1000000 us
4594	Enabling timer
4595Hit '?':
4596	[q, b, e, ?] ........
4597	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4598Hit '?':
4599	[q, b, e, ?] .
4600	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4601Hit '?':
4602	[q, b, e, ?] .
4603	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4604Hit '?':
4605	[q, b, e, ?] .
4606	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4607Hit 'e':
4608	[q, b, e, ?] ...Stopping timer
4609Hit 'q':
4610	[q, b, e, ?] ## Application terminated, rc = 0x0
4611
4612
4613Minicom warning:
4614================
4615
4616Over time, many people have reported problems when trying to use the
4617"minicom" terminal emulation program for serial download. I (wd)
4618consider minicom to be broken, and recommend not to use it. Under
4619Unix, I recommend to use C-Kermit for general purpose use (and
4620especially for kermit binary protocol download ("loadb" command), and
4621use "cu" for S-Record download ("loads" command).  See
4622http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4623for help with kermit.
4624
4625
4626Nevertheless, if you absolutely want to use it try adding this
4627configuration to your "File transfer protocols" section:
4628
4629	   Name	   Program			Name U/D FullScr IO-Red. Multi
4630	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4631	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4632
4633
4634NetBSD Notes:
4635=============
4636
4637Starting at version 0.9.2, U-Boot supports NetBSD both as host
4638(build U-Boot) and target system (boots NetBSD/mpc8xx).
4639
4640Building requires a cross environment; it is known to work on
4641NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4642need gmake since the Makefiles are not compatible with BSD make).
4643Note that the cross-powerpc package does not install include files;
4644attempting to build U-Boot will fail because <machine/ansi.h> is
4645missing.  This file has to be installed and patched manually:
4646
4647	# cd /usr/pkg/cross/powerpc-netbsd/include
4648	# mkdir powerpc
4649	# ln -s powerpc machine
4650	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4651	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4652
4653Native builds *don't* work due to incompatibilities between native
4654and U-Boot include files.
4655
4656Booting assumes that (the first part of) the image booted is a
4657stage-2 loader which in turn loads and then invokes the kernel
4658proper. Loader sources will eventually appear in the NetBSD source
4659tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4660meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4661
4662
4663Implementation Internals:
4664=========================
4665
4666The following is not intended to be a complete description of every
4667implementation detail. However, it should help to understand the
4668inner workings of U-Boot and make it easier to port it to custom
4669hardware.
4670
4671
4672Initial Stack, Global Data:
4673---------------------------
4674
4675The implementation of U-Boot is complicated by the fact that U-Boot
4676starts running out of ROM (flash memory), usually without access to
4677system RAM (because the memory controller is not initialized yet).
4678This means that we don't have writable Data or BSS segments, and BSS
4679is not initialized as zero. To be able to get a C environment working
4680at all, we have to allocate at least a minimal stack. Implementation
4681options for this are defined and restricted by the CPU used: Some CPU
4682models provide on-chip memory (like the IMMR area on MPC8xx and
4683MPC826x processors), on others (parts of) the data cache can be
4684locked as (mis-) used as memory, etc.
4685
4686	Chris Hallinan posted a good summary of these issues to the
4687	U-Boot mailing list:
4688
4689	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4690	From: "Chris Hallinan" <clh@net1plus.com>
4691	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4692	...
4693
4694	Correct me if I'm wrong, folks, but the way I understand it
4695	is this: Using DCACHE as initial RAM for Stack, etc, does not
4696	require any physical RAM backing up the cache. The cleverness
4697	is that the cache is being used as a temporary supply of
4698	necessary storage before the SDRAM controller is setup. It's
4699	beyond the scope of this list to explain the details, but you
4700	can see how this works by studying the cache architecture and
4701	operation in the architecture and processor-specific manuals.
4702
4703	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4704	is another option for the system designer to use as an
4705	initial stack/RAM area prior to SDRAM being available. Either
4706	option should work for you. Using CS 4 should be fine if your
4707	board designers haven't used it for something that would
4708	cause you grief during the initial boot! It is frequently not
4709	used.
4710
4711	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4712	with your processor/board/system design. The default value
4713	you will find in any recent u-boot distribution in
4714	walnut.h should work for you. I'd set it to a value larger
4715	than your SDRAM module. If you have a 64MB SDRAM module, set
4716	it above 400_0000. Just make sure your board has no resources
4717	that are supposed to respond to that address! That code in
4718	start.S has been around a while and should work as is when
4719	you get the config right.
4720
4721	-Chris Hallinan
4722	DS4.COM, Inc.
4723
4724It is essential to remember this, since it has some impact on the C
4725code for the initialization procedures:
4726
4727* Initialized global data (data segment) is read-only. Do not attempt
4728  to write it.
4729
4730* Do not use any uninitialized global data (or implicitly initialized
4731  as zero data - BSS segment) at all - this is undefined, initiali-
4732  zation is performed later (when relocating to RAM).
4733
4734* Stack space is very limited. Avoid big data buffers or things like
4735  that.
4736
4737Having only the stack as writable memory limits means we cannot use
4738normal global data to share information between the code. But it
4739turned out that the implementation of U-Boot can be greatly
4740simplified by making a global data structure (gd_t) available to all
4741functions. We could pass a pointer to this data as argument to _all_
4742functions, but this would bloat the code. Instead we use a feature of
4743the GCC compiler (Global Register Variables) to share the data: we
4744place a pointer (gd) to the global data into a register which we
4745reserve for this purpose.
4746
4747When choosing a register for such a purpose we are restricted by the
4748relevant  (E)ABI  specifications for the current architecture, and by
4749GCC's implementation.
4750
4751For PowerPC, the following registers have specific use:
4752	R1:	stack pointer
4753	R2:	reserved for system use
4754	R3-R4:	parameter passing and return values
4755	R5-R10: parameter passing
4756	R13:	small data area pointer
4757	R30:	GOT pointer
4758	R31:	frame pointer
4759
4760	(U-Boot also uses R12 as internal GOT pointer. r12
4761	is a volatile register so r12 needs to be reset when
4762	going back and forth between asm and C)
4763
4764    ==> U-Boot will use R2 to hold a pointer to the global data
4765
4766    Note: on PPC, we could use a static initializer (since the
4767    address of the global data structure is known at compile time),
4768    but it turned out that reserving a register results in somewhat
4769    smaller code - although the code savings are not that big (on
4770    average for all boards 752 bytes for the whole U-Boot image,
4771    624 text + 127 data).
4772
4773On ARM, the following registers are used:
4774
4775	R0:	function argument word/integer result
4776	R1-R3:	function argument word
4777	R9:	platform specific
4778	R10:	stack limit (used only if stack checking is enabled)
4779	R11:	argument (frame) pointer
4780	R12:	temporary workspace
4781	R13:	stack pointer
4782	R14:	link register
4783	R15:	program counter
4784
4785    ==> U-Boot will use R9 to hold a pointer to the global data
4786
4787    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4788
4789On Nios II, the ABI is documented here:
4790	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4791
4792    ==> U-Boot will use gp to hold a pointer to the global data
4793
4794    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4795    to access small data sections, so gp is free.
4796
4797On NDS32, the following registers are used:
4798
4799	R0-R1:	argument/return
4800	R2-R5:	argument
4801	R15:	temporary register for assembler
4802	R16:	trampoline register
4803	R28:	frame pointer (FP)
4804	R29:	global pointer (GP)
4805	R30:	link register (LP)
4806	R31:	stack pointer (SP)
4807	PC:	program counter (PC)
4808
4809    ==> U-Boot will use R10 to hold a pointer to the global data
4810
4811NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4812or current versions of GCC may "optimize" the code too much.
4813
4814On RISC-V, the following registers are used:
4815
4816	x0: hard-wired zero (zero)
4817	x1: return address (ra)
4818	x2:	stack pointer (sp)
4819	x3:	global pointer (gp)
4820	x4:	thread pointer (tp)
4821	x5:	link register (t0)
4822	x8:	frame pointer (fp)
4823	x10-x11:	arguments/return values (a0-1)
4824	x12-x17:	arguments (a2-7)
4825	x28-31:	 temporaries (t3-6)
4826	pc:	program counter (pc)
4827
4828    ==> U-Boot will use gp to hold a pointer to the global data
4829
4830Memory Management:
4831------------------
4832
4833U-Boot runs in system state and uses physical addresses, i.e. the
4834MMU is not used either for address mapping nor for memory protection.
4835
4836The available memory is mapped to fixed addresses using the memory
4837controller. In this process, a contiguous block is formed for each
4838memory type (Flash, SDRAM, SRAM), even when it consists of several
4839physical memory banks.
4840
4841U-Boot is installed in the first 128 kB of the first Flash bank (on
4842TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4843booting and sizing and initializing DRAM, the code relocates itself
4844to the upper end of DRAM. Immediately below the U-Boot code some
4845memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4846configuration setting]. Below that, a structure with global Board
4847Info data is placed, followed by the stack (growing downward).
4848
4849Additionally, some exception handler code is copied to the low 8 kB
4850of DRAM (0x00000000 ... 0x00001FFF).
4851
4852So a typical memory configuration with 16 MB of DRAM could look like
4853this:
4854
4855	0x0000 0000	Exception Vector code
4856	      :
4857	0x0000 1FFF
4858	0x0000 2000	Free for Application Use
4859	      :
4860	      :
4861
4862	      :
4863	      :
4864	0x00FB FF20	Monitor Stack (Growing downward)
4865	0x00FB FFAC	Board Info Data and permanent copy of global data
4866	0x00FC 0000	Malloc Arena
4867	      :
4868	0x00FD FFFF
4869	0x00FE 0000	RAM Copy of Monitor Code
4870	...		eventually: LCD or video framebuffer
4871	...		eventually: pRAM (Protected RAM - unchanged by reset)
4872	0x00FF FFFF	[End of RAM]
4873
4874
4875System Initialization:
4876----------------------
4877
4878In the reset configuration, U-Boot starts at the reset entry point
4879(on most PowerPC systems at address 0x00000100). Because of the reset
4880configuration for CS0# this is a mirror of the on board Flash memory.
4881To be able to re-map memory U-Boot then jumps to its link address.
4882To be able to implement the initialization code in C, a (small!)
4883initial stack is set up in the internal Dual Ported RAM (in case CPUs
4884which provide such a feature like), or in a locked part of the data
4885cache. After that, U-Boot initializes the CPU core, the caches and
4886the SIU.
4887
4888Next, all (potentially) available memory banks are mapped using a
4889preliminary mapping. For example, we put them on 512 MB boundaries
4890(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4891on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4892programmed for SDRAM access. Using the temporary configuration, a
4893simple memory test is run that determines the size of the SDRAM
4894banks.
4895
4896When there is more than one SDRAM bank, and the banks are of
4897different size, the largest is mapped first. For equal size, the first
4898bank (CS2#) is mapped first. The first mapping is always for address
48990x00000000, with any additional banks following immediately to create
4900contiguous memory starting from 0.
4901
4902Then, the monitor installs itself at the upper end of the SDRAM area
4903and allocates memory for use by malloc() and for the global Board
4904Info data; also, the exception vector code is copied to the low RAM
4905pages, and the final stack is set up.
4906
4907Only after this relocation will you have a "normal" C environment;
4908until that you are restricted in several ways, mostly because you are
4909running from ROM, and because the code will have to be relocated to a
4910new address in RAM.
4911
4912
4913U-Boot Porting Guide:
4914----------------------
4915
4916[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4917list, October 2002]
4918
4919
4920int main(int argc, char *argv[])
4921{
4922	sighandler_t no_more_time;
4923
4924	signal(SIGALRM, no_more_time);
4925	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4926
4927	if (available_money > available_manpower) {
4928		Pay consultant to port U-Boot;
4929		return 0;
4930	}
4931
4932	Download latest U-Boot source;
4933
4934	Subscribe to u-boot mailing list;
4935
4936	if (clueless)
4937		email("Hi, I am new to U-Boot, how do I get started?");
4938
4939	while (learning) {
4940		Read the README file in the top level directory;
4941		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4942		Read applicable doc/*.README;
4943		Read the source, Luke;
4944		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4945	}
4946
4947	if (available_money > toLocalCurrency ($2500))
4948		Buy a BDI3000;
4949	else
4950		Add a lot of aggravation and time;
4951
4952	if (a similar board exists) {	/* hopefully... */
4953		cp -a board/<similar> board/<myboard>
4954		cp include/configs/<similar>.h include/configs/<myboard>.h
4955	} else {
4956		Create your own board support subdirectory;
4957		Create your own board include/configs/<myboard>.h file;
4958	}
4959	Edit new board/<myboard> files
4960	Edit new include/configs/<myboard>.h
4961
4962	while (!accepted) {
4963		while (!running) {
4964			do {
4965				Add / modify source code;
4966			} until (compiles);
4967			Debug;
4968			if (clueless)
4969				email("Hi, I am having problems...");
4970		}
4971		Send patch file to the U-Boot email list;
4972		if (reasonable critiques)
4973			Incorporate improvements from email list code review;
4974		else
4975			Defend code as written;
4976	}
4977
4978	return 0;
4979}
4980
4981void no_more_time (int sig)
4982{
4983      hire_a_guru();
4984}
4985
4986
4987Coding Standards:
4988-----------------
4989
4990All contributions to U-Boot should conform to the Linux kernel
4991coding style; see the kernel coding style guide at
4992https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4993script "scripts/Lindent" in your Linux kernel source directory.
4994
4995Source files originating from a different project (for example the
4996MTD subsystem) are generally exempt from these guidelines and are not
4997reformatted to ease subsequent migration to newer versions of those
4998sources.
4999
5000Please note that U-Boot is implemented in C (and to some small parts in
5001Assembler); no C++ is used, so please do not use C++ style comments (//)
5002in your code.
5003
5004Please also stick to the following formatting rules:
5005- remove any trailing white space
5006- use TAB characters for indentation and vertical alignment, not spaces
5007- make sure NOT to use DOS '\r\n' line feeds
5008- do not add more than 2 consecutive empty lines to source files
5009- do not add trailing empty lines to source files
5010
5011Submissions which do not conform to the standards may be returned
5012with a request to reformat the changes.
5013
5014
5015Submitting Patches:
5016-------------------
5017
5018Since the number of patches for U-Boot is growing, we need to
5019establish some rules. Submissions which do not conform to these rules
5020may be rejected, even when they contain important and valuable stuff.
5021
5022Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5023
5024Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5025see https://lists.denx.de/listinfo/u-boot
5026
5027When you send a patch, please include the following information with
5028it:
5029
5030* For bug fixes: a description of the bug and how your patch fixes
5031  this bug. Please try to include a way of demonstrating that the
5032  patch actually fixes something.
5033
5034* For new features: a description of the feature and your
5035  implementation.
5036
5037* A CHANGELOG entry as plaintext (separate from the patch)
5038
5039* For major contributions, add a MAINTAINERS file with your
5040  information and associated file and directory references.
5041
5042* When you add support for a new board, don't forget to add a
5043  maintainer e-mail address to the boards.cfg file, too.
5044
5045* If your patch adds new configuration options, don't forget to
5046  document these in the README file.
5047
5048* The patch itself. If you are using git (which is *strongly*
5049  recommended) you can easily generate the patch using the
5050  "git format-patch". If you then use "git send-email" to send it to
5051  the U-Boot mailing list, you will avoid most of the common problems
5052  with some other mail clients.
5053
5054  If you cannot use git, use "diff -purN OLD NEW". If your version of
5055  diff does not support these options, then get the latest version of
5056  GNU diff.
5057
5058  The current directory when running this command shall be the parent
5059  directory of the U-Boot source tree (i. e. please make sure that
5060  your patch includes sufficient directory information for the
5061  affected files).
5062
5063  We prefer patches as plain text. MIME attachments are discouraged,
5064  and compressed attachments must not be used.
5065
5066* If one logical set of modifications affects or creates several
5067  files, all these changes shall be submitted in a SINGLE patch file.
5068
5069* Changesets that contain different, unrelated modifications shall be
5070  submitted as SEPARATE patches, one patch per changeset.
5071
5072
5073Notes:
5074
5075* Before sending the patch, run the buildman script on your patched
5076  source tree and make sure that no errors or warnings are reported
5077  for any of the boards.
5078
5079* Keep your modifications to the necessary minimum: A patch
5080  containing several unrelated changes or arbitrary reformats will be
5081  returned with a request to re-formatting / split it.
5082
5083* If you modify existing code, make sure that your new code does not
5084  add to the memory footprint of the code ;-) Small is beautiful!
5085  When adding new features, these should compile conditionally only
5086  (using #ifdef), and the resulting code with the new feature
5087  disabled must not need more memory than the old code without your
5088  modification.
5089
5090* Remember that there is a size limit of 100 kB per message on the
5091  u-boot mailing list. Bigger patches will be moderated. If they are
5092  reasonable and not too big, they will be acknowledged. But patches
5093  bigger than the size limit should be avoided.
5094