xref: /openbmc/u-boot/README (revision fbe502e9)
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- USB Device Firmware Update (DFU) class support:
1176		CONFIG_DFU_OVER_USB
1177		This enables the USB portion of the DFU USB class
1178
1179		CONFIG_DFU_MMC
1180		This enables support for exposing (e)MMC devices via DFU.
1181
1182		CONFIG_DFU_NAND
1183		This enables support for exposing NAND devices via DFU.
1184
1185		CONFIG_DFU_RAM
1186		This enables support for exposing RAM via DFU.
1187		Note: DFU spec refer to non-volatile memory usage, but
1188		allow usages beyond the scope of spec - here RAM usage,
1189		one that would help mostly the developer.
1190
1191		CONFIG_SYS_DFU_DATA_BUF_SIZE
1192		Dfu transfer uses a buffer before writing data to the
1193		raw storage device. Make the size (in bytes) of this buffer
1194		configurable. The size of this buffer is also configurable
1195		through the "dfu_bufsiz" environment variable.
1196
1197		CONFIG_SYS_DFU_MAX_FILE_SIZE
1198		When updating files rather than the raw storage device,
1199		we use a static buffer to copy the file into and then write
1200		the buffer once we've been given the whole file.  Define
1201		this to the maximum filesize (in bytes) for the buffer.
1202		Default is 4 MiB if undefined.
1203
1204		DFU_DEFAULT_POLL_TIMEOUT
1205		Poll timeout [ms], is the timeout a device can send to the
1206		host. The host must wait for this timeout before sending
1207		a subsequent DFU_GET_STATUS request to the device.
1208
1209		DFU_MANIFEST_POLL_TIMEOUT
1210		Poll timeout [ms], which the device sends to the host when
1211		entering dfuMANIFEST state. Host waits this timeout, before
1212		sending again an USB request to the device.
1213
1214- Journaling Flash filesystem support:
1215		CONFIG_JFFS2_NAND
1216		Define these for a default partition on a NAND device
1217
1218		CONFIG_SYS_JFFS2_FIRST_SECTOR,
1219		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
1220		Define these for a default partition on a NOR device
1221
1222- Keyboard Support:
1223		See Kconfig help for available keyboard drivers.
1224
1225		CONFIG_KEYBOARD
1226
1227		Define this to enable a custom keyboard support.
1228		This simply calls drv_keyboard_init() which must be
1229		defined in your board-specific files. This option is deprecated
1230		and is only used by novena. For new boards, use driver model
1231		instead.
1232
1233- Video support:
1234		CONFIG_FSL_DIU_FB
1235		Enable the Freescale DIU video driver.	Reference boards for
1236		SOCs that have a DIU should define this macro to enable DIU
1237		support, and should also define these other macros:
1238
1239			CONFIG_SYS_DIU_ADDR
1240			CONFIG_VIDEO
1241			CONFIG_CFB_CONSOLE
1242			CONFIG_VIDEO_SW_CURSOR
1243			CONFIG_VGA_AS_SINGLE_DEVICE
1244			CONFIG_VIDEO_LOGO
1245			CONFIG_VIDEO_BMP_LOGO
1246
1247		The DIU driver will look for the 'video-mode' environment
1248		variable, and if defined, enable the DIU as a console during
1249		boot.  See the documentation file doc/README.video for a
1250		description of this variable.
1251
1252- LCD Support:	CONFIG_LCD
1253
1254		Define this to enable LCD support (for output to LCD
1255		display); also select one of the supported displays
1256		by defining one of these:
1257
1258		CONFIG_ATMEL_LCD:
1259
1260			HITACHI TX09D70VM1CCA, 3.5", 240x320.
1261
1262		CONFIG_NEC_NL6448AC33:
1263
1264			NEC NL6448AC33-18. Active, color, single scan.
1265
1266		CONFIG_NEC_NL6448BC20
1267
1268			NEC NL6448BC20-08. 6.5", 640x480.
1269			Active, color, single scan.
1270
1271		CONFIG_NEC_NL6448BC33_54
1272
1273			NEC NL6448BC33-54. 10.4", 640x480.
1274			Active, color, single scan.
1275
1276		CONFIG_SHARP_16x9
1277
1278			Sharp 320x240. Active, color, single scan.
1279			It isn't 16x9, and I am not sure what it is.
1280
1281		CONFIG_SHARP_LQ64D341
1282
1283			Sharp LQ64D341 display, 640x480.
1284			Active, color, single scan.
1285
1286		CONFIG_HLD1045
1287
1288			HLD1045 display, 640x480.
1289			Active, color, single scan.
1290
1291		CONFIG_OPTREX_BW
1292
1293			Optrex	 CBL50840-2 NF-FW 99 22 M5
1294			or
1295			Hitachi	 LMG6912RPFC-00T
1296			or
1297			Hitachi	 SP14Q002
1298
1299			320x240. Black & white.
1300
1301		CONFIG_LCD_ALIGNMENT
1302
1303		Normally the LCD is page-aligned (typically 4KB). If this is
1304		defined then the LCD will be aligned to this value instead.
1305		For ARM it is sometimes useful to use MMU_SECTION_SIZE
1306		here, since it is cheaper to change data cache settings on
1307		a per-section basis.
1308
1309
1310		CONFIG_LCD_ROTATION
1311
1312		Sometimes, for example if the display is mounted in portrait
1313		mode or even if it's mounted landscape but rotated by 180degree,
1314		we need to rotate our content of the display relative to the
1315		framebuffer, so that user can read the messages which are
1316		printed out.
1317		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
1318		initialized with a given rotation from "vl_rot" out of
1319		"vidinfo_t" which is provided by the board specific code.
1320		The value for vl_rot is coded as following (matching to
1321		fbcon=rotate:<n> linux-kernel commandline):
1322		0 = no rotation respectively 0 degree
1323		1 = 90 degree rotation
1324		2 = 180 degree rotation
1325		3 = 270 degree rotation
1326
1327		If CONFIG_LCD_ROTATION is not defined, the console will be
1328		initialized with 0degree rotation.
1329
1330		CONFIG_LCD_BMP_RLE8
1331
1332		Support drawing of RLE8-compressed bitmaps on the LCD.
1333
1334		CONFIG_I2C_EDID
1335
1336		Enables an 'i2c edid' command which can read EDID
1337		information over I2C from an attached LCD display.
1338
1339- Splash Screen Support: CONFIG_SPLASH_SCREEN
1340
1341		If this option is set, the environment is checked for
1342		a variable "splashimage". If found, the usual display
1343		of logo, copyright and system information on the LCD
1344		is suppressed and the BMP image at the address
1345		specified in "splashimage" is loaded instead. The
1346		console is redirected to the "nulldev", too. This
1347		allows for a "silent" boot where a splash screen is
1348		loaded very quickly after power-on.
1349
1350		CONFIG_SPLASHIMAGE_GUARD
1351
1352		If this option is set, then U-Boot will prevent the environment
1353		variable "splashimage" from being set to a problematic address
1354		(see doc/README.displaying-bmps).
1355		This option is useful for targets where, due to alignment
1356		restrictions, an improperly aligned BMP image will cause a data
1357		abort. If you think you will not have problems with unaligned
1358		accesses (for example because your toolchain prevents them)
1359		there is no need to set this option.
1360
1361		CONFIG_SPLASH_SCREEN_ALIGN
1362
1363		If this option is set the splash image can be freely positioned
1364		on the screen. Environment variable "splashpos" specifies the
1365		position as "x,y". If a positive number is given it is used as
1366		number of pixel from left/top. If a negative number is given it
1367		is used as number of pixel from right/bottom. You can also
1368		specify 'm' for centering the image.
1369
1370		Example:
1371		setenv splashpos m,m
1372			=> image at center of screen
1373
1374		setenv splashpos 30,20
1375			=> image at x = 30 and y = 20
1376
1377		setenv splashpos -10,m
1378			=> vertically centered image
1379			   at x = dspWidth - bmpWidth - 9
1380
1381- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
1382
1383		If this option is set, additionally to standard BMP
1384		images, gzipped BMP images can be displayed via the
1385		splashscreen support or the bmp command.
1386
1387- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
1388
1389		If this option is set, 8-bit RLE compressed BMP images
1390		can be displayed via the splashscreen support or the
1391		bmp command.
1392
1393- Compression support:
1394		CONFIG_GZIP
1395
1396		Enabled by default to support gzip compressed images.
1397
1398		CONFIG_BZIP2
1399
1400		If this option is set, support for bzip2 compressed
1401		images is included. If not, only uncompressed and gzip
1402		compressed images are supported.
1403
1404		NOTE: the bzip2 algorithm requires a lot of RAM, so
1405		the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
1406		be at least 4MB.
1407
1408- MII/PHY support:
1409		CONFIG_PHY_CLOCK_FREQ (ppc4xx)
1410
1411		The clock frequency of the MII bus
1412
1413		CONFIG_PHY_RESET_DELAY
1414
1415		Some PHY like Intel LXT971A need extra delay after
1416		reset before any MII register access is possible.
1417		For such PHY, set this option to the usec delay
1418		required. (minimum 300usec for LXT971A)
1419
1420		CONFIG_PHY_CMD_DELAY (ppc4xx)
1421
1422		Some PHY like Intel LXT971A need extra delay after
1423		command issued before MII status register can be read
1424
1425- IP address:
1426		CONFIG_IPADDR
1427
1428		Define a default value for the IP address to use for
1429		the default Ethernet interface, in case this is not
1430		determined through e.g. bootp.
1431		(Environment variable "ipaddr")
1432
1433- Server IP address:
1434		CONFIG_SERVERIP
1435
1436		Defines a default value for the IP address of a TFTP
1437		server to contact when using the "tftboot" command.
1438		(Environment variable "serverip")
1439
1440		CONFIG_KEEP_SERVERADDR
1441
1442		Keeps the server's MAC address, in the env 'serveraddr'
1443		for passing to bootargs (like Linux's netconsole option)
1444
1445- Gateway IP address:
1446		CONFIG_GATEWAYIP
1447
1448		Defines a default value for the IP address of the
1449		default router where packets to other networks are
1450		sent to.
1451		(Environment variable "gatewayip")
1452
1453- Subnet mask:
1454		CONFIG_NETMASK
1455
1456		Defines a default value for the subnet mask (or
1457		routing prefix) which is used to determine if an IP
1458		address belongs to the local subnet or needs to be
1459		forwarded through a router.
1460		(Environment variable "netmask")
1461
1462- Multicast TFTP Mode:
1463		CONFIG_MCAST_TFTP
1464
1465		Defines whether you want to support multicast TFTP as per
1466		rfc-2090; for example to work with atftp.  Lets lots of targets
1467		tftp down the same boot image concurrently.  Note: the Ethernet
1468		driver in use must provide a function: mcast() to join/leave a
1469		multicast group.
1470
1471- BOOTP Recovery Mode:
1472		CONFIG_BOOTP_RANDOM_DELAY
1473
1474		If you have many targets in a network that try to
1475		boot using BOOTP, you may want to avoid that all
1476		systems send out BOOTP requests at precisely the same
1477		moment (which would happen for instance at recovery
1478		from a power failure, when all systems will try to
1479		boot, thus flooding the BOOTP server. Defining
1480		CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
1481		inserted before sending out BOOTP requests. The
1482		following delays are inserted then:
1483
1484		1st BOOTP request:	delay 0 ... 1 sec
1485		2nd BOOTP request:	delay 0 ... 2 sec
1486		3rd BOOTP request:	delay 0 ... 4 sec
1487		4th and following
1488		BOOTP requests:		delay 0 ... 8 sec
1489
1490		CONFIG_BOOTP_ID_CACHE_SIZE
1491
1492		BOOTP packets are uniquely identified using a 32-bit ID. The
1493		server will copy the ID from client requests to responses and
1494		U-Boot will use this to determine if it is the destination of
1495		an incoming response. Some servers will check that addresses
1496		aren't in use before handing them out (usually using an ARP
1497		ping) and therefore take up to a few hundred milliseconds to
1498		respond. Network congestion may also influence the time it
1499		takes for a response to make it back to the client. If that
1500		time is too long, U-Boot will retransmit requests. In order
1501		to allow earlier responses to still be accepted after these
1502		retransmissions, U-Boot's BOOTP client keeps a small cache of
1503		IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
1504		cache. The default is to keep IDs for up to four outstanding
1505		requests. Increasing this will allow U-Boot to accept offers
1506		from a BOOTP client in networks with unusually high latency.
1507
1508- DHCP Advanced Options:
1509		You can fine tune the DHCP functionality by defining
1510		CONFIG_BOOTP_* symbols:
1511
1512		CONFIG_BOOTP_NISDOMAIN
1513		CONFIG_BOOTP_BOOTFILESIZE
1514		CONFIG_BOOTP_SEND_HOSTNAME
1515		CONFIG_BOOTP_NTPSERVER
1516		CONFIG_BOOTP_TIMEOFFSET
1517		CONFIG_BOOTP_VENDOREX
1518		CONFIG_BOOTP_MAY_FAIL
1519
1520		CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
1521		environment variable, not the BOOTP server.
1522
1523		CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
1524		after the configured retry count, the call will fail
1525		instead of starting over.  This can be used to fail over
1526		to Link-local IP address configuration if the DHCP server
1527		is not available.
1528
1529		CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
1530		to do a dynamic update of a DNS server. To do this, they
1531		need the hostname of the DHCP requester.
1532		If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
1533		of the "hostname" environment variable is passed as
1534		option 12 to the DHCP server.
1535
1536		CONFIG_BOOTP_DHCP_REQUEST_DELAY
1537
1538		A 32bit value in microseconds for a delay between
1539		receiving a "DHCP Offer" and sending the "DHCP Request".
1540		This fixes a problem with certain DHCP servers that don't
1541		respond 100% of the time to a "DHCP request". E.g. On an
1542		AT91RM9200 processor running at 180MHz, this delay needed
1543		to be *at least* 15,000 usec before a Windows Server 2003
1544		DHCP server would reply 100% of the time. I recommend at
1545		least 50,000 usec to be safe. The alternative is to hope
1546		that one of the retries will be successful but note that
1547		the DHCP timeout and retry process takes a longer than
1548		this delay.
1549
1550 - Link-local IP address negotiation:
1551		Negotiate with other link-local clients on the local network
1552		for an address that doesn't require explicit configuration.
1553		This is especially useful if a DHCP server cannot be guaranteed
1554		to exist in all environments that the device must operate.
1555
1556		See doc/README.link-local for more information.
1557
1558 - MAC address from environment variables
1559
1560		FDT_SEQ_MACADDR_FROM_ENV
1561
1562		Fix-up device tree with MAC addresses fetched sequentially from
1563		environment variables. This config work on assumption that
1564		non-usable ethernet node of device-tree are either not present
1565		or their status has been marked as "disabled".
1566
1567 - CDP Options:
1568		CONFIG_CDP_DEVICE_ID
1569
1570		The device id used in CDP trigger frames.
1571
1572		CONFIG_CDP_DEVICE_ID_PREFIX
1573
1574		A two character string which is prefixed to the MAC address
1575		of the device.
1576
1577		CONFIG_CDP_PORT_ID
1578
1579		A printf format string which contains the ascii name of
1580		the port. Normally is set to "eth%d" which sets
1581		eth0 for the first Ethernet, eth1 for the second etc.
1582
1583		CONFIG_CDP_CAPABILITIES
1584
1585		A 32bit integer which indicates the device capabilities;
1586		0x00000010 for a normal host which does not forwards.
1587
1588		CONFIG_CDP_VERSION
1589
1590		An ascii string containing the version of the software.
1591
1592		CONFIG_CDP_PLATFORM
1593
1594		An ascii string containing the name of the platform.
1595
1596		CONFIG_CDP_TRIGGER
1597
1598		A 32bit integer sent on the trigger.
1599
1600		CONFIG_CDP_POWER_CONSUMPTION
1601
1602		A 16bit integer containing the power consumption of the
1603		device in .1 of milliwatts.
1604
1605		CONFIG_CDP_APPLIANCE_VLAN_TYPE
1606
1607		A byte containing the id of the VLAN.
1608
1609- Status LED:	CONFIG_LED_STATUS
1610
1611		Several configurations allow to display the current
1612		status using a LED. For instance, the LED will blink
1613		fast while running U-Boot code, stop blinking as
1614		soon as a reply to a BOOTP request was received, and
1615		start blinking slow once the Linux kernel is running
1616		(supported by a status LED driver in the Linux
1617		kernel). Defining CONFIG_LED_STATUS enables this
1618		feature in U-Boot.
1619
1620		Additional options:
1621
1622		CONFIG_LED_STATUS_GPIO
1623		The status LED can be connected to a GPIO pin.
1624		In such cases, the gpio_led driver can be used as a
1625		status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
1626		to include the gpio_led driver in the U-Boot binary.
1627
1628		CONFIG_GPIO_LED_INVERTED_TABLE
1629		Some GPIO connected LEDs may have inverted polarity in which
1630		case the GPIO high value corresponds to LED off state and
1631		GPIO low value corresponds to LED on state.
1632		In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
1633		with a list of GPIO LEDs that have inverted polarity.
1634
1635- I2C Support:	CONFIG_SYS_I2C
1636
1637		This enable the NEW i2c subsystem, and will allow you to use
1638		i2c commands at the u-boot command line (as long as you set
1639		CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
1640		based realtime clock chips or other i2c devices. See
1641		common/cmd_i2c.c for a description of the command line
1642		interface.
1643
1644		ported i2c driver to the new framework:
1645		- drivers/i2c/soft_i2c.c:
1646		  - activate first bus with CONFIG_SYS_I2C_SOFT define
1647		    CONFIG_SYS_I2C_SOFT_SPEED and CONFIG_SYS_I2C_SOFT_SLAVE
1648		    for defining speed and slave address
1649		  - activate second bus with I2C_SOFT_DECLARATIONS2 define
1650		    CONFIG_SYS_I2C_SOFT_SPEED_2 and CONFIG_SYS_I2C_SOFT_SLAVE_2
1651		    for defining speed and slave address
1652		  - activate third bus with I2C_SOFT_DECLARATIONS3 define
1653		    CONFIG_SYS_I2C_SOFT_SPEED_3 and CONFIG_SYS_I2C_SOFT_SLAVE_3
1654		    for defining speed and slave address
1655		  - activate fourth bus with I2C_SOFT_DECLARATIONS4 define
1656		    CONFIG_SYS_I2C_SOFT_SPEED_4 and CONFIG_SYS_I2C_SOFT_SLAVE_4
1657		    for defining speed and slave address
1658
1659		- drivers/i2c/fsl_i2c.c:
1660		  - activate i2c driver with CONFIG_SYS_I2C_FSL
1661		    define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
1662		    offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
1663		    CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
1664		    bus.
1665		  - If your board supports a second fsl i2c bus, define
1666		    CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
1667		    CONFIG_SYS_FSL_I2C2_SPEED for the speed and
1668		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
1669		    second bus.
1670
1671		- drivers/i2c/tegra_i2c.c:
1672		  - activate this driver with CONFIG_SYS_I2C_TEGRA
1673		  - This driver adds 4 i2c buses with a fix speed from
1674		    100000 and the slave addr 0!
1675
1676		- drivers/i2c/ppc4xx_i2c.c
1677		  - activate this driver with CONFIG_SYS_I2C_PPC4XX
1678		  - CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
1679		  - CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
1680
1681		- drivers/i2c/i2c_mxc.c
1682		  - activate this driver with CONFIG_SYS_I2C_MXC
1683		  - enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
1684		  - enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
1685		  - enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
1686		  - enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
1687		  - define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
1688		  - define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
1689		  - define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
1690		  - define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
1691		  - define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
1692		  - define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
1693		  - define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
1694		  - define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
1695		If those defines are not set, default value is 100000
1696		for speed, and 0 for slave.
1697
1698		- drivers/i2c/rcar_i2c.c:
1699		  - activate this driver with CONFIG_SYS_I2C_RCAR
1700		  - This driver adds 4 i2c buses
1701
1702		  - CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
1703		  - CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
1704		  - CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
1705		  - CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
1706		  - CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
1707		  - CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
1708		  - CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
1709		  - CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
1710		  - CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
1711
1712		- drivers/i2c/sh_i2c.c:
1713		  - activate this driver with CONFIG_SYS_I2C_SH
1714		  - This driver adds from 2 to 5 i2c buses
1715
1716		  - CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
1717		  - CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
1718		  - CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
1719		  - CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
1720		  - CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
1721		  - CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
1722		  - CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
1723		  - CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
1724		  - CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
1725		  - CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
1726		  - CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
1727
1728		- drivers/i2c/omap24xx_i2c.c
1729		  - activate this driver with CONFIG_SYS_I2C_OMAP24XX
1730		  - CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
1731		  - CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
1732		  - CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
1733		  - CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
1734		  - CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
1735		  - CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
1736		  - CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
1737		  - CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
1738		  - CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
1739		  - CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
1740
1741		- drivers/i2c/zynq_i2c.c
1742		  - activate this driver with CONFIG_SYS_I2C_ZYNQ
1743		  - set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
1744		  - set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
1745
1746		- drivers/i2c/s3c24x0_i2c.c:
1747		  - activate this driver with CONFIG_SYS_I2C_S3C24X0
1748		  - This driver adds i2c buses (11 for Exynos5250, Exynos5420
1749		    9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
1750		    with a fix speed from 100000 and the slave addr 0!
1751
1752		- drivers/i2c/ihs_i2c.c
1753		  - activate this driver with CONFIG_SYS_I2C_IHS
1754		  - CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
1755		  - CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
1756		  - CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
1757		  - CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
1758		  - CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
1759		  - CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
1760		  - CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
1761		  - CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
1762		  - CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
1763		  - CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
1764		  - CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
1765		  - CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
1766		  - activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
1767		  - CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
1768		  - CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
1769		  - CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
1770		  - CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
1771		  - CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
1772		  - CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
1773		  - CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
1774		  - CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
1775
1776		additional defines:
1777
1778		CONFIG_SYS_NUM_I2C_BUSES
1779		Hold the number of i2c buses you want to use.
1780
1781		CONFIG_SYS_I2C_DIRECT_BUS
1782		define this, if you don't use i2c muxes on your hardware.
1783		if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
1784		omit this define.
1785
1786		CONFIG_SYS_I2C_MAX_HOPS
1787		define how many muxes are maximal consecutively connected
1788		on one i2c bus. If you not use i2c muxes, omit this
1789		define.
1790
1791		CONFIG_SYS_I2C_BUSES
1792		hold a list of buses you want to use, only used if
1793		CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
1794		a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
1795		CONFIG_SYS_NUM_I2C_BUSES = 9:
1796
1797		 CONFIG_SYS_I2C_BUSES	{{0, {I2C_NULL_HOP}}, \
1798					{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
1799					{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
1800					{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
1801					{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
1802					{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
1803					{1, {I2C_NULL_HOP}}, \
1804					{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
1805					{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
1806					}
1807
1808		which defines
1809			bus 0 on adapter 0 without a mux
1810			bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
1811			bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
1812			bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
1813			bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
1814			bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
1815			bus 6 on adapter 1 without a mux
1816			bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
1817			bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
1818
1819		If you do not have i2c muxes on your board, omit this define.
1820
1821- Legacy I2C Support:
1822		If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
1823		then the following macros need to be defined (examples are
1824		from include/configs/lwmon.h):
1825
1826		I2C_INIT
1827
1828		(Optional). Any commands necessary to enable the I2C
1829		controller or configure ports.
1830
1831		eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |=	PB_SCL)
1832
1833		I2C_ACTIVE
1834
1835		The code necessary to make the I2C data line active
1836		(driven).  If the data line is open collector, this
1837		define can be null.
1838
1839		eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |=  PB_SDA)
1840
1841		I2C_TRISTATE
1842
1843		The code necessary to make the I2C data line tri-stated
1844		(inactive).  If the data line is open collector, this
1845		define can be null.
1846
1847		eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
1848
1849		I2C_READ
1850
1851		Code that returns true if the I2C data line is high,
1852		false if it is low.
1853
1854		eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
1855
1856		I2C_SDA(bit)
1857
1858		If <bit> is true, sets the I2C data line high. If it
1859		is false, it clears it (low).
1860
1861		eg: #define I2C_SDA(bit) \
1862			if(bit) immr->im_cpm.cp_pbdat |=  PB_SDA; \
1863			else	immr->im_cpm.cp_pbdat &= ~PB_SDA
1864
1865		I2C_SCL(bit)
1866
1867		If <bit> is true, sets the I2C clock line high. If it
1868		is false, it clears it (low).
1869
1870		eg: #define I2C_SCL(bit) \
1871			if(bit) immr->im_cpm.cp_pbdat |=  PB_SCL; \
1872			else	immr->im_cpm.cp_pbdat &= ~PB_SCL
1873
1874		I2C_DELAY
1875
1876		This delay is invoked four times per clock cycle so this
1877		controls the rate of data transfer.  The data rate thus
1878		is 1 / (I2C_DELAY * 4). Often defined to be something
1879		like:
1880
1881		#define I2C_DELAY  udelay(2)
1882
1883		CONFIG_SOFT_I2C_GPIO_SCL / CONFIG_SOFT_I2C_GPIO_SDA
1884
1885		If your arch supports the generic GPIO framework (asm/gpio.h),
1886		then you may alternatively define the two GPIOs that are to be
1887		used as SCL / SDA.  Any of the previous I2C_xxx macros will
1888		have GPIO-based defaults assigned to them as appropriate.
1889
1890		You should define these to the GPIO value as given directly to
1891		the generic GPIO functions.
1892
1893		CONFIG_SYS_I2C_INIT_BOARD
1894
1895		When a board is reset during an i2c bus transfer
1896		chips might think that the current transfer is still
1897		in progress. On some boards it is possible to access
1898		the i2c SCLK line directly, either by using the
1899		processor pin as a GPIO or by having a second pin
1900		connected to the bus. If this option is defined a
1901		custom i2c_init_board() routine in boards/xxx/board.c
1902		is run early in the boot sequence.
1903
1904		CONFIG_I2C_MULTI_BUS
1905
1906		This option allows the use of multiple I2C buses, each of which
1907		must have a controller.	 At any point in time, only one bus is
1908		active.	 To switch to a different bus, use the 'i2c dev' command.
1909		Note that bus numbering is zero-based.
1910
1911		CONFIG_SYS_I2C_NOPROBES
1912
1913		This option specifies a list of I2C devices that will be skipped
1914		when the 'i2c probe' command is issued.	 If CONFIG_I2C_MULTI_BUS
1915		is set, specify a list of bus-device pairs.  Otherwise, specify
1916		a 1D array of device addresses
1917
1918		e.g.
1919			#undef	CONFIG_I2C_MULTI_BUS
1920			#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
1921
1922		will skip addresses 0x50 and 0x68 on a board with one I2C bus
1923
1924			#define CONFIG_I2C_MULTI_BUS
1925			#define CONFIG_SYS_I2C_NOPROBES	{{0,0x50},{0,0x68},{1,0x54}}
1926
1927		will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
1928
1929		CONFIG_SYS_SPD_BUS_NUM
1930
1931		If defined, then this indicates the I2C bus number for DDR SPD.
1932		If not defined, then U-Boot assumes that SPD is on I2C bus 0.
1933
1934		CONFIG_SYS_RTC_BUS_NUM
1935
1936		If defined, then this indicates the I2C bus number for the RTC.
1937		If not defined, then U-Boot assumes that RTC is on I2C bus 0.
1938
1939		CONFIG_SOFT_I2C_READ_REPEATED_START
1940
1941		defining this will force the i2c_read() function in
1942		the soft_i2c driver to perform an I2C repeated start
1943		between writing the address pointer and reading the
1944		data.  If this define is omitted the default behaviour
1945		of doing a stop-start sequence will be used.  Most I2C
1946		devices can use either method, but some require one or
1947		the other.
1948
1949- SPI Support:	CONFIG_SPI
1950
1951		Enables SPI driver (so far only tested with
1952		SPI EEPROM, also an instance works with Crystal A/D and
1953		D/As on the SACSng board)
1954
1955		CONFIG_SOFT_SPI
1956
1957		Enables a software (bit-bang) SPI driver rather than
1958		using hardware support. This is a general purpose
1959		driver that only requires three general I/O port pins
1960		(two outputs, one input) to function. If this is
1961		defined, the board configuration must define several
1962		SPI configuration items (port pins to use, etc). For
1963		an example, see include/configs/sacsng.h.
1964
1965		CONFIG_HARD_SPI
1966
1967		Enables a hardware SPI driver for general-purpose reads
1968		and writes.  As with CONFIG_SOFT_SPI, the board configuration
1969		must define a list of chip-select function pointers.
1970		Currently supported on some MPC8xxx processors.	 For an
1971		example, see include/configs/mpc8349emds.h.
1972
1973		CONFIG_SYS_SPI_MXC_WAIT
1974		Timeout for waiting until spi transfer completed.
1975		default: (CONFIG_SYS_HZ/100)     /* 10 ms */
1976
1977- FPGA Support: CONFIG_FPGA
1978
1979		Enables FPGA subsystem.
1980
1981		CONFIG_FPGA_<vendor>
1982
1983		Enables support for specific chip vendors.
1984		(ALTERA, XILINX)
1985
1986		CONFIG_FPGA_<family>
1987
1988		Enables support for FPGA family.
1989		(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)
1990
1991		CONFIG_FPGA_COUNT
1992
1993		Specify the number of FPGA devices to support.
1994
1995		CONFIG_SYS_FPGA_PROG_FEEDBACK
1996
1997		Enable printing of hash marks during FPGA configuration.
1998
1999		CONFIG_SYS_FPGA_CHECK_BUSY
2000
2001		Enable checks on FPGA configuration interface busy
2002		status by the configuration function. This option
2003		will require a board or device specific function to
2004		be written.
2005
2006		CONFIG_FPGA_DELAY
2007
2008		If defined, a function that provides delays in the FPGA
2009		configuration driver.
2010
2011		CONFIG_SYS_FPGA_CHECK_CTRLC
2012		Allow Control-C to interrupt FPGA configuration
2013
2014		CONFIG_SYS_FPGA_CHECK_ERROR
2015
2016		Check for configuration errors during FPGA bitfile
2017		loading. For example, abort during Virtex II
2018		configuration if the INIT_B line goes low (which
2019		indicated a CRC error).
2020
2021		CONFIG_SYS_FPGA_WAIT_INIT
2022
2023		Maximum time to wait for the INIT_B line to de-assert
2024		after PROB_B has been de-asserted during a Virtex II
2025		FPGA configuration sequence. The default time is 500
2026		ms.
2027
2028		CONFIG_SYS_FPGA_WAIT_BUSY
2029
2030		Maximum time to wait for BUSY to de-assert during
2031		Virtex II FPGA configuration. The default is 5 ms.
2032
2033		CONFIG_SYS_FPGA_WAIT_CONFIG
2034
2035		Time to wait after FPGA configuration. The default is
2036		200 ms.
2037
2038- Configuration Management:
2039		CONFIG_BUILD_TARGET
2040
2041		Some SoCs need special image types (e.g. U-Boot binary
2042		with a special header) as build targets. By defining
2043		CONFIG_BUILD_TARGET in the SoC / board header, this
2044		special image will be automatically built upon calling
2045		make / buildman.
2046
2047		CONFIG_IDENT_STRING
2048
2049		If defined, this string will be added to the U-Boot
2050		version information (U_BOOT_VERSION)
2051
2052- Vendor Parameter Protection:
2053
2054		U-Boot considers the values of the environment
2055		variables "serial#" (Board Serial Number) and
2056		"ethaddr" (Ethernet Address) to be parameters that
2057		are set once by the board vendor / manufacturer, and
2058		protects these variables from casual modification by
2059		the user. Once set, these variables are read-only,
2060		and write or delete attempts are rejected. You can
2061		change this behaviour:
2062
2063		If CONFIG_ENV_OVERWRITE is #defined in your config
2064		file, the write protection for vendor parameters is
2065		completely disabled. Anybody can change or delete
2066		these parameters.
2067
2068		Alternatively, if you define _both_ an ethaddr in the
2069		default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
2070		Ethernet address is installed in the environment,
2071		which can be changed exactly ONCE by the user. [The
2072		serial# is unaffected by this, i. e. it remains
2073		read-only.]
2074
2075		The same can be accomplished in a more flexible way
2076		for any variable by configuring the type of access
2077		to allow for those variables in the ".flags" variable
2078		or define CONFIG_ENV_FLAGS_LIST_STATIC.
2079
2080- Protected RAM:
2081		CONFIG_PRAM
2082
2083		Define this variable to enable the reservation of
2084		"protected RAM", i. e. RAM which is not overwritten
2085		by U-Boot. Define CONFIG_PRAM to hold the number of
2086		kB you want to reserve for pRAM. You can overwrite
2087		this default value by defining an environment
2088		variable "pram" to the number of kB you want to
2089		reserve. Note that the board info structure will
2090		still show the full amount of RAM. If pRAM is
2091		reserved, a new environment variable "mem" will
2092		automatically be defined to hold the amount of
2093		remaining RAM in a form that can be passed as boot
2094		argument to Linux, for instance like that:
2095
2096			setenv bootargs ... mem=\${mem}
2097			saveenv
2098
2099		This way you can tell Linux not to use this memory,
2100		either, which results in a memory region that will
2101		not be affected by reboots.
2102
2103		*WARNING* If your board configuration uses automatic
2104		detection of the RAM size, you must make sure that
2105		this memory test is non-destructive. So far, the
2106		following board configurations are known to be
2107		"pRAM-clean":
2108
2109			IVMS8, IVML24, SPD8xx,
2110			HERMES, IP860, RPXlite, LWMON,
2111			FLAGADM
2112
2113- Access to physical memory region (> 4GB)
2114		Some basic support is provided for operations on memory not
2115		normally accessible to U-Boot - e.g. some architectures
2116		support access to more than 4GB of memory on 32-bit
2117		machines using physical address extension or similar.
2118		Define CONFIG_PHYSMEM to access this basic support, which
2119		currently only supports clearing the memory.
2120
2121- Error Recovery:
2122		CONFIG_NET_RETRY_COUNT
2123
2124		This variable defines the number of retries for
2125		network operations like ARP, RARP, TFTP, or BOOTP
2126		before giving up the operation. If not defined, a
2127		default value of 5 is used.
2128
2129		CONFIG_ARP_TIMEOUT
2130
2131		Timeout waiting for an ARP reply in milliseconds.
2132
2133		CONFIG_NFS_TIMEOUT
2134
2135		Timeout in milliseconds used in NFS protocol.
2136		If you encounter "ERROR: Cannot umount" in nfs command,
2137		try longer timeout such as
2138		#define CONFIG_NFS_TIMEOUT 10000UL
2139
2140- Command Interpreter:
2141		CONFIG_SYS_PROMPT_HUSH_PS2
2142
2143		This defines the secondary prompt string, which is
2144		printed when the command interpreter needs more input
2145		to complete a command. Usually "> ".
2146
2147	Note:
2148
2149		In the current implementation, the local variables
2150		space and global environment variables space are
2151		separated. Local variables are those you define by
2152		simply typing `name=value'. To access a local
2153		variable later on, you have write `$name' or
2154		`${name}'; to execute the contents of a variable
2155		directly type `$name' at the command prompt.
2156
2157		Global environment variables are those you use
2158		setenv/printenv to work with. To run a command stored
2159		in such a variable, you need to use the run command,
2160		and you must not use the '$' sign to access them.
2161
2162		To store commands and special characters in a
2163		variable, please use double quotation marks
2164		surrounding the whole text of the variable, instead
2165		of the backslashes before semicolons and special
2166		symbols.
2167
2168- Command Line Editing and History:
2169		CONFIG_CMDLINE_PS_SUPPORT
2170
2171		Enable support for changing the command prompt string
2172		at run-time. Only static string is supported so far.
2173		The string is obtained from environment variables PS1
2174		and PS2.
2175
2176- Default Environment:
2177		CONFIG_EXTRA_ENV_SETTINGS
2178
2179		Define this to contain any number of null terminated
2180		strings (variable = value pairs) that will be part of
2181		the default environment compiled into the boot image.
2182
2183		For example, place something like this in your
2184		board's config file:
2185
2186		#define CONFIG_EXTRA_ENV_SETTINGS \
2187			"myvar1=value1\0" \
2188			"myvar2=value2\0"
2189
2190		Warning: This method is based on knowledge about the
2191		internal format how the environment is stored by the
2192		U-Boot code. This is NOT an official, exported
2193		interface! Although it is unlikely that this format
2194		will change soon, there is no guarantee either.
2195		You better know what you are doing here.
2196
2197		Note: overly (ab)use of the default environment is
2198		discouraged. Make sure to check other ways to preset
2199		the environment like the "source" command or the
2200		boot command first.
2201
2202		CONFIG_DELAY_ENVIRONMENT
2203
2204		Normally the environment is loaded when the board is
2205		initialised so that it is available to U-Boot. This inhibits
2206		that so that the environment is not available until
2207		explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
2208		this is instead controlled by the value of
2209		/config/load-environment.
2210
2211- Serial Flash support
2212		Usage requires an initial 'sf probe' to define the serial
2213		flash parameters, followed by read/write/erase/update
2214		commands.
2215
2216		The following defaults may be provided by the platform
2217		to handle the common case when only a single serial
2218		flash is present on the system.
2219
2220		CONFIG_SF_DEFAULT_BUS		Bus identifier
2221		CONFIG_SF_DEFAULT_CS		Chip-select
2222		CONFIG_SF_DEFAULT_MODE 		(see include/spi.h)
2223		CONFIG_SF_DEFAULT_SPEED		in Hz
2224
2225
2226- TFTP Fixed UDP Port:
2227		CONFIG_TFTP_PORT
2228
2229		If this is defined, the environment variable tftpsrcp
2230		is used to supply the TFTP UDP source port value.
2231		If tftpsrcp isn't defined, the normal pseudo-random port
2232		number generator is used.
2233
2234		Also, the environment variable tftpdstp is used to supply
2235		the TFTP UDP destination port value.  If tftpdstp isn't
2236		defined, the normal port 69 is used.
2237
2238		The purpose for tftpsrcp is to allow a TFTP server to
2239		blindly start the TFTP transfer using the pre-configured
2240		target IP address and UDP port. This has the effect of
2241		"punching through" the (Windows XP) firewall, allowing
2242		the remainder of the TFTP transfer to proceed normally.
2243		A better solution is to properly configure the firewall,
2244		but sometimes that is not allowed.
2245
2246- Show boot progress:
2247		CONFIG_SHOW_BOOT_PROGRESS
2248
2249		Defining this option allows to add some board-
2250		specific code (calling a user-provided function
2251		"show_boot_progress(int)") that enables you to show
2252		the system's boot progress on some display (for
2253		example, some LED's) on your board. At the moment,
2254		the following checkpoints are implemented:
2255
2256
2257Legacy uImage format:
2258
2259  Arg	Where			When
2260    1	common/cmd_bootm.c	before attempting to boot an image
2261   -1	common/cmd_bootm.c	Image header has bad	 magic number
2262    2	common/cmd_bootm.c	Image header has correct magic number
2263   -2	common/cmd_bootm.c	Image header has bad	 checksum
2264    3	common/cmd_bootm.c	Image header has correct checksum
2265   -3	common/cmd_bootm.c	Image data   has bad	 checksum
2266    4	common/cmd_bootm.c	Image data   has correct checksum
2267   -4	common/cmd_bootm.c	Image is for unsupported architecture
2268    5	common/cmd_bootm.c	Architecture check OK
2269   -5	common/cmd_bootm.c	Wrong Image Type (not kernel, multi)
2270    6	common/cmd_bootm.c	Image Type check OK
2271   -6	common/cmd_bootm.c	gunzip uncompression error
2272   -7	common/cmd_bootm.c	Unimplemented compression type
2273    7	common/cmd_bootm.c	Uncompression OK
2274    8	common/cmd_bootm.c	No uncompress/copy overwrite error
2275   -9	common/cmd_bootm.c	Unsupported OS (not Linux, BSD, VxWorks, QNX)
2276
2277    9	common/image.c		Start initial ramdisk verification
2278  -10	common/image.c		Ramdisk header has bad	   magic number
2279  -11	common/image.c		Ramdisk header has bad	   checksum
2280   10	common/image.c		Ramdisk header is OK
2281  -12	common/image.c		Ramdisk data   has bad	   checksum
2282   11	common/image.c		Ramdisk data   has correct checksum
2283   12	common/image.c		Ramdisk verification complete, start loading
2284  -13	common/image.c		Wrong Image Type (not PPC Linux ramdisk)
2285   13	common/image.c		Start multifile image verification
2286   14	common/image.c		No initial ramdisk, no multifile, continue.
2287
2288   15	arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
2289
2290  -30	arch/powerpc/lib/board.c	Fatal error, hang the system
2291  -31	post/post.c		POST test failed, detected by post_output_backlog()
2292  -32	post/post.c		POST test failed, detected by post_run_single()
2293
2294   34	common/cmd_doc.c	before loading a Image from a DOC device
2295  -35	common/cmd_doc.c	Bad usage of "doc" command
2296   35	common/cmd_doc.c	correct usage of "doc" command
2297  -36	common/cmd_doc.c	No boot device
2298   36	common/cmd_doc.c	correct boot device
2299  -37	common/cmd_doc.c	Unknown Chip ID on boot device
2300   37	common/cmd_doc.c	correct chip ID found, device available
2301  -38	common/cmd_doc.c	Read Error on boot device
2302   38	common/cmd_doc.c	reading Image header from DOC device OK
2303  -39	common/cmd_doc.c	Image header has bad magic number
2304   39	common/cmd_doc.c	Image header has correct magic number
2305  -40	common/cmd_doc.c	Error reading Image from DOC device
2306   40	common/cmd_doc.c	Image header has correct magic number
2307   41	common/cmd_ide.c	before loading a Image from a IDE device
2308  -42	common/cmd_ide.c	Bad usage of "ide" command
2309   42	common/cmd_ide.c	correct usage of "ide" command
2310  -43	common/cmd_ide.c	No boot device
2311   43	common/cmd_ide.c	boot device found
2312  -44	common/cmd_ide.c	Device not available
2313   44	common/cmd_ide.c	Device available
2314  -45	common/cmd_ide.c	wrong partition selected
2315   45	common/cmd_ide.c	partition selected
2316  -46	common/cmd_ide.c	Unknown partition table
2317   46	common/cmd_ide.c	valid partition table found
2318  -47	common/cmd_ide.c	Invalid partition type
2319   47	common/cmd_ide.c	correct partition type
2320  -48	common/cmd_ide.c	Error reading Image Header on boot device
2321   48	common/cmd_ide.c	reading Image Header from IDE device OK
2322  -49	common/cmd_ide.c	Image header has bad magic number
2323   49	common/cmd_ide.c	Image header has correct magic number
2324  -50	common/cmd_ide.c	Image header has bad	 checksum
2325   50	common/cmd_ide.c	Image header has correct checksum
2326  -51	common/cmd_ide.c	Error reading Image from IDE device
2327   51	common/cmd_ide.c	reading Image from IDE device OK
2328   52	common/cmd_nand.c	before loading a Image from a NAND device
2329  -53	common/cmd_nand.c	Bad usage of "nand" command
2330   53	common/cmd_nand.c	correct usage of "nand" command
2331  -54	common/cmd_nand.c	No boot device
2332   54	common/cmd_nand.c	boot device found
2333  -55	common/cmd_nand.c	Unknown Chip ID on boot device
2334   55	common/cmd_nand.c	correct chip ID found, device available
2335  -56	common/cmd_nand.c	Error reading Image Header on boot device
2336   56	common/cmd_nand.c	reading Image Header from NAND device OK
2337  -57	common/cmd_nand.c	Image header has bad magic number
2338   57	common/cmd_nand.c	Image header has correct magic number
2339  -58	common/cmd_nand.c	Error reading Image from NAND device
2340   58	common/cmd_nand.c	reading Image from NAND device OK
2341
2342  -60	common/env_common.c	Environment has a bad CRC, using default
2343
2344   64	net/eth.c		starting with Ethernet configuration.
2345  -64	net/eth.c		no Ethernet found.
2346   65	net/eth.c		Ethernet found.
2347
2348  -80	common/cmd_net.c	usage wrong
2349   80	common/cmd_net.c	before calling net_loop()
2350  -81	common/cmd_net.c	some error in net_loop() occurred
2351   81	common/cmd_net.c	net_loop() back without error
2352  -82	common/cmd_net.c	size == 0 (File with size 0 loaded)
2353   82	common/cmd_net.c	trying automatic boot
2354   83	common/cmd_net.c	running "source" command
2355  -83	common/cmd_net.c	some error in automatic boot or "source" command
2356   84	common/cmd_net.c	end without errors
2357
2358FIT uImage format:
2359
2360  Arg	Where			When
2361  100	common/cmd_bootm.c	Kernel FIT Image has correct format
2362 -100	common/cmd_bootm.c	Kernel FIT Image has incorrect format
2363  101	common/cmd_bootm.c	No Kernel subimage unit name, using configuration
2364 -101	common/cmd_bootm.c	Can't get configuration for kernel subimage
2365  102	common/cmd_bootm.c	Kernel unit name specified
2366 -103	common/cmd_bootm.c	Can't get kernel subimage node offset
2367  103	common/cmd_bootm.c	Found configuration node
2368  104	common/cmd_bootm.c	Got kernel subimage node offset
2369 -104	common/cmd_bootm.c	Kernel subimage hash verification failed
2370  105	common/cmd_bootm.c	Kernel subimage hash verification OK
2371 -105	common/cmd_bootm.c	Kernel subimage is for unsupported architecture
2372  106	common/cmd_bootm.c	Architecture check OK
2373 -106	common/cmd_bootm.c	Kernel subimage has wrong type
2374  107	common/cmd_bootm.c	Kernel subimage type OK
2375 -107	common/cmd_bootm.c	Can't get kernel subimage data/size
2376  108	common/cmd_bootm.c	Got kernel subimage data/size
2377 -108	common/cmd_bootm.c	Wrong image type (not legacy, FIT)
2378 -109	common/cmd_bootm.c	Can't get kernel subimage type
2379 -110	common/cmd_bootm.c	Can't get kernel subimage comp
2380 -111	common/cmd_bootm.c	Can't get kernel subimage os
2381 -112	common/cmd_bootm.c	Can't get kernel subimage load address
2382 -113	common/cmd_bootm.c	Image uncompress/copy overwrite error
2383
2384  120	common/image.c		Start initial ramdisk verification
2385 -120	common/image.c		Ramdisk FIT image has incorrect format
2386  121	common/image.c		Ramdisk FIT image has correct format
2387  122	common/image.c		No ramdisk subimage unit name, using configuration
2388 -122	common/image.c		Can't get configuration for ramdisk subimage
2389  123	common/image.c		Ramdisk unit name specified
2390 -124	common/image.c		Can't get ramdisk subimage node offset
2391  125	common/image.c		Got ramdisk subimage node offset
2392 -125	common/image.c		Ramdisk subimage hash verification failed
2393  126	common/image.c		Ramdisk subimage hash verification OK
2394 -126	common/image.c		Ramdisk subimage for unsupported architecture
2395  127	common/image.c		Architecture check OK
2396 -127	common/image.c		Can't get ramdisk subimage data/size
2397  128	common/image.c		Got ramdisk subimage data/size
2398  129	common/image.c		Can't get ramdisk load address
2399 -129	common/image.c		Got ramdisk load address
2400
2401 -130	common/cmd_doc.c	Incorrect FIT image format
2402  131	common/cmd_doc.c	FIT image format OK
2403
2404 -140	common/cmd_ide.c	Incorrect FIT image format
2405  141	common/cmd_ide.c	FIT image format OK
2406
2407 -150	common/cmd_nand.c	Incorrect FIT image format
2408  151	common/cmd_nand.c	FIT image format OK
2409
2410- Standalone program support:
2411		CONFIG_STANDALONE_LOAD_ADDR
2412
2413		This option defines a board specific value for the
2414		address where standalone program gets loaded, thus
2415		overwriting the architecture dependent default
2416		settings.
2417
2418- Frame Buffer Address:
2419		CONFIG_FB_ADDR
2420
2421		Define CONFIG_FB_ADDR if you want to use specific
2422		address for frame buffer.  This is typically the case
2423		when using a graphics controller has separate video
2424		memory.  U-Boot will then place the frame buffer at
2425		the given address instead of dynamically reserving it
2426		in system RAM by calling lcd_setmem(), which grabs
2427		the memory for the frame buffer depending on the
2428		configured panel size.
2429
2430		Please see board_init_f function.
2431
2432- Automatic software updates via TFTP server
2433		CONFIG_UPDATE_TFTP
2434		CONFIG_UPDATE_TFTP_CNT_MAX
2435		CONFIG_UPDATE_TFTP_MSEC_MAX
2436
2437		These options enable and control the auto-update feature;
2438		for a more detailed description refer to doc/README.update.
2439
2440- MTD Support (mtdparts command, UBI support)
2441		CONFIG_MTD_DEVICE
2442
2443		Adds the MTD device infrastructure from the Linux kernel.
2444		Needed for mtdparts command support.
2445
2446		CONFIG_MTD_PARTITIONS
2447
2448		Adds the MTD partitioning infrastructure from the Linux
2449		kernel. Needed for UBI support.
2450
2451- UBI support
2452		CONFIG_MTD_UBI_WL_THRESHOLD
2453		This parameter defines the maximum difference between the highest
2454		erase counter value and the lowest erase counter value of eraseblocks
2455		of UBI devices. When this threshold is exceeded, UBI starts performing
2456		wear leveling by means of moving data from eraseblock with low erase
2457		counter to eraseblocks with high erase counter.
2458
2459		The default value should be OK for SLC NAND flashes, NOR flashes and
2460		other flashes which have eraseblock life-cycle 100000 or more.
2461		However, in case of MLC NAND flashes which typically have eraseblock
2462		life-cycle less than 10000, the threshold should be lessened (e.g.,
2463		to 128 or 256, although it does not have to be power of 2).
2464
2465		default: 4096
2466
2467		CONFIG_MTD_UBI_BEB_LIMIT
2468		This option specifies the maximum bad physical eraseblocks UBI
2469		expects on the MTD device (per 1024 eraseblocks). If the
2470		underlying flash does not admit of bad eraseblocks (e.g. NOR
2471		flash), this value is ignored.
2472
2473		NAND datasheets often specify the minimum and maximum NVM
2474		(Number of Valid Blocks) for the flashes' endurance lifetime.
2475		The maximum expected bad eraseblocks per 1024 eraseblocks
2476		then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
2477		which gives 20 for most NANDs (MaxNVB is basically the total
2478		count of eraseblocks on the chip).
2479
2480		To put it differently, if this value is 20, UBI will try to
2481		reserve about 1.9% of physical eraseblocks for bad blocks
2482		handling. And that will be 1.9% of eraseblocks on the entire
2483		NAND chip, not just the MTD partition UBI attaches. This means
2484		that if you have, say, a NAND flash chip admits maximum 40 bad
2485		eraseblocks, and it is split on two MTD partitions of the same
2486		size, UBI will reserve 40 eraseblocks when attaching a
2487		partition.
2488
2489		default: 20
2490
2491		CONFIG_MTD_UBI_FASTMAP
2492		Fastmap is a mechanism which allows attaching an UBI device
2493		in nearly constant time. Instead of scanning the whole MTD device it
2494		only has to locate a checkpoint (called fastmap) on the device.
2495		The on-flash fastmap contains all information needed to attach
2496		the device. Using fastmap makes only sense on large devices where
2497		attaching by scanning takes long. UBI will not automatically install
2498		a fastmap on old images, but you can set the UBI parameter
2499		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
2500		that fastmap-enabled images are still usable with UBI implementations
2501		without	fastmap support. On typical flash devices the whole fastmap
2502		fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
2503
2504		CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT
2505		Set this parameter to enable fastmap automatically on images
2506		without a fastmap.
2507		default: 0
2508
2509		CONFIG_MTD_UBI_FM_DEBUG
2510		Enable UBI fastmap debug
2511		default: 0
2512
2513- SPL framework
2514		CONFIG_SPL
2515		Enable building of SPL globally.
2516
2517		CONFIG_SPL_LDSCRIPT
2518		LDSCRIPT for linking the SPL binary.
2519
2520		CONFIG_SPL_MAX_FOOTPRINT
2521		Maximum size in memory allocated to the SPL, BSS included.
2522		When defined, the linker checks that the actual memory
2523		used by SPL from _start to __bss_end does not exceed it.
2524		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2525		must not be both defined at the same time.
2526
2527		CONFIG_SPL_MAX_SIZE
2528		Maximum size of the SPL image (text, data, rodata, and
2529		linker lists sections), BSS excluded.
2530		When defined, the linker checks that the actual size does
2531		not exceed it.
2532
2533		CONFIG_SPL_TEXT_BASE
2534		TEXT_BASE for linking the SPL binary.
2535
2536		CONFIG_SPL_RELOC_TEXT_BASE
2537		Address to relocate to.  If unspecified, this is equal to
2538		CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
2539
2540		CONFIG_SPL_BSS_START_ADDR
2541		Link address for the BSS within the SPL binary.
2542
2543		CONFIG_SPL_BSS_MAX_SIZE
2544		Maximum size in memory allocated to the SPL BSS.
2545		When defined, the linker checks that the actual memory used
2546		by SPL from __bss_start to __bss_end does not exceed it.
2547		CONFIG_SPL_MAX_FOOTPRINT and CONFIG_SPL_BSS_MAX_SIZE
2548		must not be both defined at the same time.
2549
2550		CONFIG_SPL_STACK
2551		Adress of the start of the stack SPL will use
2552
2553		CONFIG_SPL_PANIC_ON_RAW_IMAGE
2554		When defined, SPL will panic() if the image it has
2555		loaded does not have a signature.
2556		Defining this is useful when code which loads images
2557		in SPL cannot guarantee that absolutely all read errors
2558		will be caught.
2559		An example is the LPC32XX MLC NAND driver, which will
2560		consider that a completely unreadable NAND block is bad,
2561		and thus should be skipped silently.
2562
2563		CONFIG_SPL_RELOC_STACK
2564		Adress of the start of the stack SPL will use after
2565		relocation.  If unspecified, this is equal to
2566		CONFIG_SPL_STACK.
2567
2568		CONFIG_SYS_SPL_MALLOC_START
2569		Starting address of the malloc pool used in SPL.
2570		When this option is set the full malloc is used in SPL and
2571		it is set up by spl_init() and before that, the simple malloc()
2572		can be used if CONFIG_SYS_MALLOC_F is defined.
2573
2574		CONFIG_SYS_SPL_MALLOC_SIZE
2575		The size of the malloc pool used in SPL.
2576
2577		CONFIG_SPL_OS_BOOT
2578		Enable booting directly to an OS from SPL.
2579		See also: doc/README.falcon
2580
2581		CONFIG_SPL_DISPLAY_PRINT
2582		For ARM, enable an optional function to print more information
2583		about the running system.
2584
2585		CONFIG_SPL_INIT_MINIMAL
2586		Arch init code should be built for a very small image
2587
2588		CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION
2589		Partition on the MMC to load U-Boot from when the MMC is being
2590		used in raw mode
2591
2592		CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR
2593		Sector to load kernel uImage from when MMC is being
2594		used in raw mode (for Falcon mode)
2595
2596		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTOR,
2597		CONFIG_SYS_MMCSD_RAW_MODE_ARGS_SECTORS
2598		Sector and number of sectors to load kernel argument
2599		parameters from when MMC is being used in raw mode
2600		(for falcon mode)
2601
2602		CONFIG_SYS_MMCSD_FS_BOOT_PARTITION
2603		Partition on the MMC to load U-Boot from when the MMC is being
2604		used in fs mode
2605
2606		CONFIG_SPL_FS_LOAD_PAYLOAD_NAME
2607		Filename to read to load U-Boot when reading from filesystem
2608
2609		CONFIG_SPL_FS_LOAD_KERNEL_NAME
2610		Filename to read to load kernel uImage when reading
2611		from filesystem (for Falcon mode)
2612
2613		CONFIG_SPL_FS_LOAD_ARGS_NAME
2614		Filename to read to load kernel argument parameters
2615		when reading from filesystem (for Falcon mode)
2616
2617		CONFIG_SPL_MPC83XX_WAIT_FOR_NAND
2618		Set this for NAND SPL on PPC mpc83xx targets, so that
2619		start.S waits for the rest of the SPL to load before
2620		continuing (the hardware starts execution after just
2621		loading the first page rather than the full 4K).
2622
2623		CONFIG_SPL_SKIP_RELOCATE
2624		Avoid SPL relocation
2625
2626		CONFIG_SPL_NAND_BASE
2627		Include nand_base.c in the SPL.  Requires
2628		CONFIG_SPL_NAND_DRIVERS.
2629
2630		CONFIG_SPL_NAND_DRIVERS
2631		SPL uses normal NAND drivers, not minimal drivers.
2632
2633		CONFIG_SPL_NAND_ECC
2634		Include standard software ECC in the SPL
2635
2636		CONFIG_SPL_NAND_SIMPLE
2637		Support for NAND boot using simple NAND drivers that
2638		expose the cmd_ctrl() interface.
2639
2640		CONFIG_SPL_UBI
2641		Support for a lightweight UBI (fastmap) scanner and
2642		loader
2643
2644		CONFIG_SPL_NAND_RAW_ONLY
2645		Support to boot only raw u-boot.bin images. Use this only
2646		if you need to save space.
2647
2648		CONFIG_SPL_COMMON_INIT_DDR
2649		Set for common ddr init with serial presence detect in
2650		SPL binary.
2651
2652		CONFIG_SYS_NAND_5_ADDR_CYCLE, CONFIG_SYS_NAND_PAGE_COUNT,
2653		CONFIG_SYS_NAND_PAGE_SIZE, CONFIG_SYS_NAND_OOBSIZE,
2654		CONFIG_SYS_NAND_BLOCK_SIZE, CONFIG_SYS_NAND_BAD_BLOCK_POS,
2655		CONFIG_SYS_NAND_ECCPOS, CONFIG_SYS_NAND_ECCSIZE,
2656		CONFIG_SYS_NAND_ECCBYTES
2657		Defines the size and behavior of the NAND that SPL uses
2658		to read U-Boot
2659
2660		CONFIG_SPL_NAND_BOOT
2661		Add support NAND boot
2662
2663		CONFIG_SYS_NAND_U_BOOT_OFFS
2664		Location in NAND to read U-Boot from
2665
2666		CONFIG_SYS_NAND_U_BOOT_DST
2667		Location in memory to load U-Boot to
2668
2669		CONFIG_SYS_NAND_U_BOOT_SIZE
2670		Size of image to load
2671
2672		CONFIG_SYS_NAND_U_BOOT_START
2673		Entry point in loaded image to jump to
2674
2675		CONFIG_SYS_NAND_HW_ECC_OOBFIRST
2676		Define this if you need to first read the OOB and then the
2677		data. This is used, for example, on davinci platforms.
2678
2679		CONFIG_SPL_RAM_DEVICE
2680		Support for running image already present in ram, in SPL binary
2681
2682		CONFIG_SPL_PAD_TO
2683		Image offset to which the SPL should be padded before appending
2684		the SPL payload. By default, this is defined as
2685		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2686		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2687		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2688
2689		CONFIG_SPL_TARGET
2690		Final target image containing SPL and payload.  Some SPLs
2691		use an arch-specific makefile fragment instead, for
2692		example if more than one image needs to be produced.
2693
2694		CONFIG_SPL_FIT_PRINT
2695		Printing information about a FIT image adds quite a bit of
2696		code to SPL. So this is normally disabled in SPL. Use this
2697		option to re-enable it. This will affect the output of the
2698		bootm command when booting a FIT image.
2699
2700- TPL framework
2701		CONFIG_TPL
2702		Enable building of TPL globally.
2703
2704		CONFIG_TPL_PAD_TO
2705		Image offset to which the TPL should be padded before appending
2706		the TPL payload. By default, this is defined as
2707		CONFIG_SPL_MAX_SIZE, or 0 if CONFIG_SPL_MAX_SIZE is undefined.
2708		CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
2709		payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
2710
2711- Interrupt support (PPC):
2712
2713		There are common interrupt_init() and timer_interrupt()
2714		for all PPC archs. interrupt_init() calls interrupt_init_cpu()
2715		for CPU specific initialization. interrupt_init_cpu()
2716		should set decrementer_count to appropriate value. If
2717		CPU resets decrementer automatically after interrupt
2718		(ppc4xx) it should set decrementer_count to zero.
2719		timer_interrupt() calls timer_interrupt_cpu() for CPU
2720		specific handling. If board has watchdog / status_led
2721		/ other_activity_monitor it works automatically from
2722		general timer_interrupt().
2723
2724
2725Board initialization settings:
2726------------------------------
2727
2728During Initialization u-boot calls a number of board specific functions
2729to allow the preparation of board specific prerequisites, e.g. pin setup
2730before drivers are initialized. To enable these callbacks the
2731following configuration macros have to be defined. Currently this is
2732architecture specific, so please check arch/your_architecture/lib/board.c
2733typically in board_init_f() and board_init_r().
2734
2735- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
2736- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
2737- CONFIG_BOARD_LATE_INIT: Call board_late_init()
2738- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
2739
2740Configuration Settings:
2741-----------------------
2742
2743- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
2744		Optionally it can be defined to support 64-bit memory commands.
2745
2746- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
2747		undefine this when you're short of memory.
2748
2749- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
2750		width of the commands listed in the 'help' command output.
2751
2752- CONFIG_SYS_PROMPT:	This is what U-Boot prints on the console to
2753		prompt for user input.
2754
2755- CONFIG_SYS_CBSIZE:	Buffer size for input from the Console
2756
2757- CONFIG_SYS_PBSIZE:	Buffer size for Console output
2758
2759- CONFIG_SYS_MAXARGS:	max. Number of arguments accepted for monitor commands
2760
2761- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
2762		the application (usually a Linux kernel) when it is
2763		booted
2764
2765- CONFIG_SYS_BAUDRATE_TABLE:
2766		List of legal baudrate settings for this board.
2767
2768- CONFIG_SYS_MEMTEST_START, CONFIG_SYS_MEMTEST_END:
2769		Begin and End addresses of the area used by the
2770		simple memory test.
2771
2772- CONFIG_SYS_MEMTEST_SCRATCH:
2773		Scratch address used by the alternate memory test
2774		You only need to set this if address zero isn't writeable
2775
2776- CONFIG_SYS_MEM_RESERVE_SECURE
2777		Only implemented for ARMv8 for now.
2778		If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
2779		is substracted from total RAM and won't be reported to OS.
2780		This memory can be used as secure memory. A variable
2781		gd->arch.secure_ram is used to track the location. In systems
2782		the RAM base is not zero, or RAM is divided into banks,
2783		this variable needs to be recalcuated to get the address.
2784
2785- CONFIG_SYS_MEM_TOP_HIDE:
2786		If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
2787		this specified memory area will get subtracted from the top
2788		(end) of RAM and won't get "touched" at all by U-Boot. By
2789		fixing up gd->ram_size the Linux kernel should gets passed
2790		the now "corrected" memory size and won't touch it either.
2791		This should work for arch/ppc and arch/powerpc. Only Linux
2792		board ports in arch/powerpc with bootwrapper support that
2793		recalculate the memory size from the SDRAM controller setup
2794		will have to get fixed in Linux additionally.
2795
2796		This option can be used as a workaround for the 440EPx/GRx
2797		CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
2798		be touched.
2799
2800		WARNING: Please make sure that this value is a multiple of
2801		the Linux page size (normally 4k). If this is not the case,
2802		then the end address of the Linux memory will be located at a
2803		non page size aligned address and this could cause major
2804		problems.
2805
2806- CONFIG_SYS_LOADS_BAUD_CHANGE:
2807		Enable temporary baudrate change while serial download
2808
2809- CONFIG_SYS_SDRAM_BASE:
2810		Physical start address of SDRAM. _Must_ be 0 here.
2811
2812- CONFIG_SYS_FLASH_BASE:
2813		Physical start address of Flash memory.
2814
2815- CONFIG_SYS_MONITOR_BASE:
2816		Physical start address of boot monitor code (set by
2817		make config files to be same as the text base address
2818		(CONFIG_SYS_TEXT_BASE) used when linking) - same as
2819		CONFIG_SYS_FLASH_BASE when booting from flash.
2820
2821- CONFIG_SYS_MONITOR_LEN:
2822		Size of memory reserved for monitor code, used to
2823		determine _at_compile_time_ (!) if the environment is
2824		embedded within the U-Boot image, or in a separate
2825		flash sector.
2826
2827- CONFIG_SYS_MALLOC_LEN:
2828		Size of DRAM reserved for malloc() use.
2829
2830- CONFIG_SYS_MALLOC_F_LEN
2831		Size of the malloc() pool for use before relocation. If
2832		this is defined, then a very simple malloc() implementation
2833		will become available before relocation. The address is just
2834		below the global data, and the stack is moved down to make
2835		space.
2836
2837		This feature allocates regions with increasing addresses
2838		within the region. calloc() is supported, but realloc()
2839		is not available. free() is supported but does nothing.
2840		The memory will be freed (or in fact just forgotten) when
2841		U-Boot relocates itself.
2842
2843- CONFIG_SYS_MALLOC_SIMPLE
2844		Provides a simple and small malloc() and calloc() for those
2845		boards which do not use the full malloc in SPL (which is
2846		enabled with CONFIG_SYS_SPL_MALLOC_START).
2847
2848- CONFIG_SYS_NONCACHED_MEMORY:
2849		Size of non-cached memory area. This area of memory will be
2850		typically located right below the malloc() area and mapped
2851		uncached in the MMU. This is useful for drivers that would
2852		otherwise require a lot of explicit cache maintenance. For
2853		some drivers it's also impossible to properly maintain the
2854		cache. For example if the regions that need to be flushed
2855		are not a multiple of the cache-line size, *and* padding
2856		cannot be allocated between the regions to align them (i.e.
2857		if the HW requires a contiguous array of regions, and the
2858		size of each region is not cache-aligned), then a flush of
2859		one region may result in overwriting data that hardware has
2860		written to another region in the same cache-line. This can
2861		happen for example in network drivers where descriptors for
2862		buffers are typically smaller than the CPU cache-line (e.g.
2863		16 bytes vs. 32 or 64 bytes).
2864
2865		Non-cached memory is only supported on 32-bit ARM at present.
2866
2867- CONFIG_SYS_BOOTM_LEN:
2868		Normally compressed uImages are limited to an
2869		uncompressed size of 8 MBytes. If this is not enough,
2870		you can define CONFIG_SYS_BOOTM_LEN in your board config file
2871		to adjust this setting to your needs.
2872
2873- CONFIG_SYS_BOOTMAPSZ:
2874		Maximum size of memory mapped by the startup code of
2875		the Linux kernel; all data that must be processed by
2876		the Linux kernel (bd_info, boot arguments, FDT blob if
2877		used) must be put below this limit, unless "bootm_low"
2878		environment variable is defined and non-zero. In such case
2879		all data for the Linux kernel must be between "bootm_low"
2880		and "bootm_low" + CONFIG_SYS_BOOTMAPSZ.	 The environment
2881		variable "bootm_mapsize" will override the value of
2882		CONFIG_SYS_BOOTMAPSZ.  If CONFIG_SYS_BOOTMAPSZ is undefined,
2883		then the value in "bootm_size" will be used instead.
2884
2885- CONFIG_SYS_BOOT_RAMDISK_HIGH:
2886		Enable initrd_high functionality.  If defined then the
2887		initrd_high feature is enabled and the bootm ramdisk subcommand
2888		is enabled.
2889
2890- CONFIG_SYS_BOOT_GET_CMDLINE:
2891		Enables allocating and saving kernel cmdline in space between
2892		"bootm_low" and "bootm_low" + BOOTMAPSZ.
2893
2894- CONFIG_SYS_BOOT_GET_KBD:
2895		Enables allocating and saving a kernel copy of the bd_info in
2896		space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
2897
2898- CONFIG_SYS_MAX_FLASH_BANKS:
2899		Max number of Flash memory banks
2900
2901- CONFIG_SYS_MAX_FLASH_SECT:
2902		Max number of sectors on a Flash chip
2903
2904- CONFIG_SYS_FLASH_ERASE_TOUT:
2905		Timeout for Flash erase operations (in ms)
2906
2907- CONFIG_SYS_FLASH_WRITE_TOUT:
2908		Timeout for Flash write operations (in ms)
2909
2910- CONFIG_SYS_FLASH_LOCK_TOUT
2911		Timeout for Flash set sector lock bit operation (in ms)
2912
2913- CONFIG_SYS_FLASH_UNLOCK_TOUT
2914		Timeout for Flash clear lock bits operation (in ms)
2915
2916- CONFIG_SYS_FLASH_PROTECTION
2917		If defined, hardware flash sectors protection is used
2918		instead of U-Boot software protection.
2919
2920- CONFIG_SYS_DIRECT_FLASH_TFTP:
2921
2922		Enable TFTP transfers directly to flash memory;
2923		without this option such a download has to be
2924		performed in two steps: (1) download to RAM, and (2)
2925		copy from RAM to flash.
2926
2927		The two-step approach is usually more reliable, since
2928		you can check if the download worked before you erase
2929		the flash, but in some situations (when system RAM is
2930		too limited to allow for a temporary copy of the
2931		downloaded image) this option may be very useful.
2932
2933- CONFIG_SYS_FLASH_CFI:
2934		Define if the flash driver uses extra elements in the
2935		common flash structure for storing flash geometry.
2936
2937- CONFIG_FLASH_CFI_DRIVER
2938		This option also enables the building of the cfi_flash driver
2939		in the drivers directory
2940
2941- CONFIG_FLASH_CFI_MTD
2942		This option enables the building of the cfi_mtd driver
2943		in the drivers directory. The driver exports CFI flash
2944		to the MTD layer.
2945
2946- CONFIG_SYS_FLASH_USE_BUFFER_WRITE
2947		Use buffered writes to flash.
2948
2949- CONFIG_FLASH_SPANSION_S29WS_N
2950		s29ws-n MirrorBit flash has non-standard addresses for buffered
2951		write commands.
2952
2953- CONFIG_SYS_FLASH_QUIET_TEST
2954		If this option is defined, the common CFI flash doesn't
2955		print it's warning upon not recognized FLASH banks. This
2956		is useful, if some of the configured banks are only
2957		optionally available.
2958
2959- CONFIG_FLASH_SHOW_PROGRESS
2960		If defined (must be an integer), print out countdown
2961		digits and dots.  Recommended value: 45 (9..1) for 80
2962		column displays, 15 (3..1) for 40 column displays.
2963
2964- CONFIG_FLASH_VERIFY
2965		If defined, the content of the flash (destination) is compared
2966		against the source after the write operation. An error message
2967		will be printed when the contents are not identical.
2968		Please note that this option is useless in nearly all cases,
2969		since such flash programming errors usually are detected earlier
2970		while unprotecting/erasing/programming. Please only enable
2971		this option if you really know what you are doing.
2972
2973- CONFIG_SYS_RX_ETH_BUFFER:
2974		Defines the number of Ethernet receive buffers. On some
2975		Ethernet controllers it is recommended to set this value
2976		to 8 or even higher (EEPRO100 or 405 EMAC), since all
2977		buffers can be full shortly after enabling the interface
2978		on high Ethernet traffic.
2979		Defaults to 4 if not defined.
2980
2981- CONFIG_ENV_MAX_ENTRIES
2982
2983	Maximum number of entries in the hash table that is used
2984	internally to store the environment settings. The default
2985	setting is supposed to be generous and should work in most
2986	cases. This setting can be used to tune behaviour; see
2987	lib/hashtable.c for details.
2988
2989- CONFIG_ENV_FLAGS_LIST_DEFAULT
2990- CONFIG_ENV_FLAGS_LIST_STATIC
2991	Enable validation of the values given to environment variables when
2992	calling env set.  Variables can be restricted to only decimal,
2993	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
2994	the variables can also be restricted to IP address or MAC address.
2995
2996	The format of the list is:
2997		type_attribute = [s|d|x|b|i|m]
2998		access_attribute = [a|r|o|c]
2999		attributes = type_attribute[access_attribute]
3000		entry = variable_name[:attributes]
3001		list = entry[,list]
3002
3003	The type attributes are:
3004		s - String (default)
3005		d - Decimal
3006		x - Hexadecimal
3007		b - Boolean ([1yYtT|0nNfF])
3008		i - IP address
3009		m - MAC address
3010
3011	The access attributes are:
3012		a - Any (default)
3013		r - Read-only
3014		o - Write-once
3015		c - Change-default
3016
3017	- CONFIG_ENV_FLAGS_LIST_DEFAULT
3018		Define this to a list (string) to define the ".flags"
3019		environment variable in the default or embedded environment.
3020
3021	- CONFIG_ENV_FLAGS_LIST_STATIC
3022		Define this to a list (string) to define validation that
3023		should be done if an entry is not found in the ".flags"
3024		environment variable.  To override a setting in the static
3025		list, simply add an entry for the same variable name to the
3026		".flags" variable.
3027
3028	If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3029	regular expression. This allows multiple variables to define the same
3030	flags without explicitly listing them for each variable.
3031
3032- CONFIG_ENV_ACCESS_IGNORE_FORCE
3033	If defined, don't allow the -f switch to env set override variable
3034	access flags.
3035
3036- CONFIG_USE_STDINT
3037	If stdint.h is available with your toolchain you can define this
3038	option to enable it. You can provide option 'USE_STDINT=1' when
3039	building U-Boot to enable this.
3040
3041The following definitions that deal with the placement and management
3042of environment data (variable area); in general, we support the
3043following configurations:
3044
3045- CONFIG_BUILD_ENVCRC:
3046
3047	Builds up envcrc with the target environment so that external utils
3048	may easily extract it and embed it in final U-Boot images.
3049
3050BE CAREFUL! The first access to the environment happens quite early
3051in U-Boot initialization (when we try to get the setting of for the
3052console baudrate). You *MUST* have mapped your NVRAM area then, or
3053U-Boot will hang.
3054
3055Please note that even with NVRAM we still use a copy of the
3056environment in RAM: we could work on NVRAM directly, but we want to
3057keep settings there always unmodified except somebody uses "saveenv"
3058to save the current settings.
3059
3060BE CAREFUL! For some special cases, the local device can not use
3061"saveenv" command. For example, the local device will get the
3062environment stored in a remote NOR flash by SRIO or PCIE link,
3063but it can not erase, write this NOR flash by SRIO or PCIE interface.
3064
3065- CONFIG_NAND_ENV_DST
3066
3067	Defines address in RAM to which the nand_spl code should copy the
3068	environment. If redundant environment is used, it will be copied to
3069	CONFIG_NAND_ENV_DST + CONFIG_ENV_SIZE.
3070
3071Please note that the environment is read-only until the monitor
3072has been relocated to RAM and a RAM copy of the environment has been
3073created; also, when using EEPROM you will have to use env_get_f()
3074until then to read environment variables.
3075
3076The environment is protected by a CRC32 checksum. Before the monitor
3077is relocated into RAM, as a result of a bad CRC you will be working
3078with the compiled-in default environment - *silently*!!! [This is
3079necessary, because the first environment variable we need is the
3080"baudrate" setting for the console - if we have a bad CRC, we don't
3081have any device yet where we could complain.]
3082
3083Note: once the monitor has been relocated, then it will complain if
3084the default environment is used; a new CRC is computed as soon as you
3085use the "saveenv" command to store a valid environment.
3086
3087- CONFIG_SYS_FAULT_ECHO_LINK_DOWN:
3088		Echo the inverted Ethernet link state to the fault LED.
3089
3090		Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
3091		      also needs to be defined.
3092
3093- CONFIG_SYS_FAULT_MII_ADDR:
3094		MII address of the PHY to check for the Ethernet link state.
3095
3096- CONFIG_NS16550_MIN_FUNCTIONS:
3097		Define this if you desire to only have use of the NS16550_init
3098		and NS16550_putc functions for the serial driver located at
3099		drivers/serial/ns16550.c.  This option is useful for saving
3100		space for already greatly restricted images, including but not
3101		limited to NAND_SPL configurations.
3102
3103- CONFIG_DISPLAY_BOARDINFO
3104		Display information about the board that U-Boot is running on
3105		when U-Boot starts up. The board function checkboard() is called
3106		to do this.
3107
3108- CONFIG_DISPLAY_BOARDINFO_LATE
3109		Similar to the previous option, but display this information
3110		later, once stdio is running and output goes to the LCD, if
3111		present.
3112
3113- CONFIG_BOARD_SIZE_LIMIT:
3114		Maximum size of the U-Boot image. When defined, the
3115		build system checks that the actual size does not
3116		exceed it.
3117
3118Low Level (hardware related) configuration options:
3119---------------------------------------------------
3120
3121- CONFIG_SYS_CACHELINE_SIZE:
3122		Cache Line Size of the CPU.
3123
3124- CONFIG_SYS_CCSRBAR_DEFAULT:
3125		Default (power-on reset) physical address of CCSR on Freescale
3126		PowerPC SOCs.
3127
3128- CONFIG_SYS_CCSRBAR:
3129		Virtual address of CCSR.  On a 32-bit build, this is typically
3130		the same value as CONFIG_SYS_CCSRBAR_DEFAULT.
3131
3132- CONFIG_SYS_CCSRBAR_PHYS:
3133		Physical address of CCSR.  CCSR can be relocated to a new
3134		physical address, if desired.  In this case, this macro should
3135		be set to that address.	 Otherwise, it should be set to the
3136		same value as CONFIG_SYS_CCSRBAR_DEFAULT.  For example, CCSR
3137		is typically relocated on 36-bit builds.  It is recommended
3138		that this macro be defined via the _HIGH and _LOW macros:
3139
3140		#define CONFIG_SYS_CCSRBAR_PHYS ((CONFIG_SYS_CCSRBAR_PHYS_HIGH
3141			* 1ull) << 32 | CONFIG_SYS_CCSRBAR_PHYS_LOW)
3142
3143- CONFIG_SYS_CCSRBAR_PHYS_HIGH:
3144		Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS.	This value is typically
3145		either 0 (32-bit build) or 0xF (36-bit build).	This macro is
3146		used in assembly code, so it must not contain typecasts or
3147		integer size suffixes (e.g. "ULL").
3148
3149- CONFIG_SYS_CCSRBAR_PHYS_LOW:
3150		Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS.  This macro is
3151		used in assembly code, so it must not contain typecasts or
3152		integer size suffixes (e.g. "ULL").
3153
3154- CONFIG_SYS_CCSR_DO_NOT_RELOCATE:
3155		If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
3156		forced to a value that ensures that CCSR is not relocated.
3157
3158- Floppy Disk Support:
3159		CONFIG_SYS_FDC_DRIVE_NUMBER
3160
3161		the default drive number (default value 0)
3162
3163		CONFIG_SYS_ISA_IO_STRIDE
3164
3165		defines the spacing between FDC chipset registers
3166		(default value 1)
3167
3168		CONFIG_SYS_ISA_IO_OFFSET
3169
3170		defines the offset of register from address. It
3171		depends on which part of the data bus is connected to
3172		the FDC chipset. (default value 0)
3173
3174		If CONFIG_SYS_ISA_IO_STRIDE CONFIG_SYS_ISA_IO_OFFSET and
3175		CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
3176		default value.
3177
3178		if CONFIG_SYS_FDC_HW_INIT is defined, then the function
3179		fdc_hw_init() is called at the beginning of the FDC
3180		setup. fdc_hw_init() must be provided by the board
3181		source code. It is used to make hardware-dependent
3182		initializations.
3183
3184- CONFIG_IDE_AHB:
3185		Most IDE controllers were designed to be connected with PCI
3186		interface. Only few of them were designed for AHB interface.
3187		When software is doing ATA command and data transfer to
3188		IDE devices through IDE-AHB controller, some additional
3189		registers accessing to these kind of IDE-AHB controller
3190		is required.
3191
3192- CONFIG_SYS_IMMR:	Physical address of the Internal Memory.
3193		DO NOT CHANGE unless you know exactly what you're
3194		doing! (11-4) [MPC8xx systems only]
3195
3196- CONFIG_SYS_INIT_RAM_ADDR:
3197
3198		Start address of memory area that can be used for
3199		initial data and stack; please note that this must be
3200		writable memory that is working WITHOUT special
3201		initialization, i. e. you CANNOT use normal RAM which
3202		will become available only after programming the
3203		memory controller and running certain initialization
3204		sequences.
3205
3206		U-Boot uses the following memory types:
3207		- MPC8xx: IMMR (internal memory of the CPU)
3208
3209- CONFIG_SYS_GBL_DATA_OFFSET:
3210
3211		Offset of the initial data structure in the memory
3212		area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
3213		CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
3214		data is located at the end of the available space
3215		(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
3216		GENERATED_GBL_DATA_SIZE), and the initial stack is just
3217		below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
3218		CONFIG_SYS_GBL_DATA_OFFSET) downward.
3219
3220	Note:
3221		On the MPC824X (or other systems that use the data
3222		cache for initial memory) the address chosen for
3223		CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
3224		point to an otherwise UNUSED address space between
3225		the top of RAM and the start of the PCI space.
3226
3227- CONFIG_SYS_SCCR:	System Clock and reset Control Register (15-27)
3228
3229- CONFIG_SYS_OR_TIMING_SDRAM:
3230		SDRAM timing
3231
3232- CONFIG_SYS_MAMR_PTA:
3233		periodic timer for refresh
3234
3235- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CONFIG_SYS_REMAP_OR_AM,
3236  CONFIG_SYS_PRELIM_OR_AM, CONFIG_SYS_OR_TIMING_FLASH, CONFIG_SYS_OR0_REMAP,
3237  CONFIG_SYS_OR0_PRELIM, CONFIG_SYS_BR0_PRELIM, CONFIG_SYS_OR1_REMAP, CONFIG_SYS_OR1_PRELIM,
3238  CONFIG_SYS_BR1_PRELIM:
3239		Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)
3240
3241- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
3242  CONFIG_SYS_OR_TIMING_SDRAM, CONFIG_SYS_OR2_PRELIM, CONFIG_SYS_BR2_PRELIM,
3243  CONFIG_SYS_OR3_PRELIM, CONFIG_SYS_BR3_PRELIM:
3244		Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)
3245
3246- CONFIG_PCI_ENUM_ONLY
3247		Only scan through and get the devices on the buses.
3248		Don't do any setup work, presumably because someone or
3249		something has already done it, and we don't need to do it
3250		a second time.	Useful for platforms that are pre-booted
3251		by coreboot or similar.
3252
3253- CONFIG_PCI_INDIRECT_BRIDGE:
3254		Enable support for indirect PCI bridges.
3255
3256- CONFIG_SYS_SRIO:
3257		Chip has SRIO or not
3258
3259- CONFIG_SRIO1:
3260		Board has SRIO 1 port available
3261
3262- CONFIG_SRIO2:
3263		Board has SRIO 2 port available
3264
3265- CONFIG_SRIO_PCIE_BOOT_MASTER
3266		Board can support master function for Boot from SRIO and PCIE
3267
3268- CONFIG_SYS_SRIOn_MEM_VIRT:
3269		Virtual Address of SRIO port 'n' memory region
3270
3271- CONFIG_SYS_SRIOn_MEM_PHYS:
3272		Physical Address of SRIO port 'n' memory region
3273
3274- CONFIG_SYS_SRIOn_MEM_SIZE:
3275		Size of SRIO port 'n' memory region
3276
3277- CONFIG_SYS_NAND_BUSWIDTH_16BIT
3278		Defined to tell the NAND controller that the NAND chip is using
3279		a 16 bit bus.
3280		Not all NAND drivers use this symbol.
3281		Example of drivers that use it:
3282		- drivers/mtd/nand/ndfc.c
3283		- drivers/mtd/nand/mxc_nand.c
3284
3285- CONFIG_SYS_NDFC_EBC0_CFG
3286		Sets the EBC0_CFG register for the NDFC. If not defined
3287		a default value will be used.
3288
3289- CONFIG_SPD_EEPROM
3290		Get DDR timing information from an I2C EEPROM. Common
3291		with pluggable memory modules such as SODIMMs
3292
3293  SPD_EEPROM_ADDRESS
3294		I2C address of the SPD EEPROM
3295
3296- CONFIG_SYS_SPD_BUS_NUM
3297		If SPD EEPROM is on an I2C bus other than the first
3298		one, specify here. Note that the value must resolve
3299		to something your driver can deal with.
3300
3301- CONFIG_SYS_DDR_RAW_TIMING
3302		Get DDR timing information from other than SPD. Common with
3303		soldered DDR chips onboard without SPD. DDR raw timing
3304		parameters are extracted from datasheet and hard-coded into
3305		header files or board specific files.
3306
3307- CONFIG_FSL_DDR_INTERACTIVE
3308		Enable interactive DDR debugging. See doc/README.fsl-ddr.
3309
3310- CONFIG_FSL_DDR_SYNC_REFRESH
3311		Enable sync of refresh for multiple controllers.
3312
3313- CONFIG_FSL_DDR_BIST
3314		Enable built-in memory test for Freescale DDR controllers.
3315
3316- CONFIG_SYS_83XX_DDR_USES_CS0
3317		Only for 83xx systems. If specified, then DDR should
3318		be configured using CS0 and CS1 instead of CS2 and CS3.
3319
3320- CONFIG_RMII
3321		Enable RMII mode for all FECs.
3322		Note that this is a global option, we can't
3323		have one FEC in standard MII mode and another in RMII mode.
3324
3325- CONFIG_CRC32_VERIFY
3326		Add a verify option to the crc32 command.
3327		The syntax is:
3328
3329		=> crc32 -v <address> <count> <crc32>
3330
3331		Where address/count indicate a memory area
3332		and crc32 is the correct crc32 which the
3333		area should have.
3334
3335- CONFIG_LOOPW
3336		Add the "loopw" memory command. This only takes effect if
3337		the memory commands are activated globally (CONFIG_CMD_MEMORY).
3338
3339- CONFIG_MX_CYCLIC
3340		Add the "mdc" and "mwc" memory commands. These are cyclic
3341		"md/mw" commands.
3342		Examples:
3343
3344		=> mdc.b 10 4 500
3345		This command will print 4 bytes (10,11,12,13) each 500 ms.
3346
3347		=> mwc.l 100 12345678 10
3348		This command will write 12345678 to address 100 all 10 ms.
3349
3350		This only takes effect if the memory commands are activated
3351		globally (CONFIG_CMD_MEMORY).
3352
3353- CONFIG_SKIP_LOWLEVEL_INIT
3354		[ARM, NDS32, MIPS, RISC-V only] If this variable is defined, then certain
3355		low level initializations (like setting up the memory
3356		controller) are omitted and/or U-Boot does not
3357		relocate itself into RAM.
3358
3359		Normally this variable MUST NOT be defined. The only
3360		exception is when U-Boot is loaded (to RAM) by some
3361		other boot loader or by a debugger which performs
3362		these initializations itself.
3363
3364- CONFIG_SKIP_LOWLEVEL_INIT_ONLY
3365		[ARM926EJ-S only] This allows just the call to lowlevel_init()
3366		to be skipped. The normal CP15 init (such as enabling the
3367		instruction cache) is still performed.
3368
3369- CONFIG_SPL_BUILD
3370		Modifies the behaviour of start.S when compiling a loader
3371		that is executed before the actual U-Boot. E.g. when
3372		compiling a NAND SPL.
3373
3374- CONFIG_TPL_BUILD
3375		Modifies the behaviour of start.S  when compiling a loader
3376		that is executed after the SPL and before the actual U-Boot.
3377		It is loaded by the SPL.
3378
3379- CONFIG_SYS_MPC85XX_NO_RESETVEC
3380		Only for 85xx systems. If this variable is specified, the section
3381		.resetvec is not kept and the section .bootpg is placed in the
3382		previous 4k of the .text section.
3383
3384- CONFIG_ARCH_MAP_SYSMEM
3385		Generally U-Boot (and in particular the md command) uses
3386		effective address. It is therefore not necessary to regard
3387		U-Boot address as virtual addresses that need to be translated
3388		to physical addresses. However, sandbox requires this, since
3389		it maintains its own little RAM buffer which contains all
3390		addressable memory. This option causes some memory accesses
3391		to be mapped through map_sysmem() / unmap_sysmem().
3392
3393- CONFIG_X86_RESET_VECTOR
3394		If defined, the x86 reset vector code is included. This is not
3395		needed when U-Boot is running from Coreboot.
3396
3397- CONFIG_SYS_NAND_NO_SUBPAGE_WRITE
3398		Option to disable subpage write in NAND driver
3399		driver that uses this:
3400		drivers/mtd/nand/davinci_nand.c
3401
3402Freescale QE/FMAN Firmware Support:
3403-----------------------------------
3404
3405The Freescale QUICCEngine (QE) and Frame Manager (FMAN) both support the
3406loading of "firmware", which is encoded in the QE firmware binary format.
3407This firmware often needs to be loaded during U-Boot booting, so macros
3408are used to identify the storage device (NOR flash, SPI, etc) and the address
3409within that device.
3410
3411- CONFIG_SYS_FMAN_FW_ADDR
3412	The address in the storage device where the FMAN microcode is located.  The
3413	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3414	is also specified.
3415
3416- CONFIG_SYS_QE_FW_ADDR
3417	The address in the storage device where the QE microcode is located.  The
3418	meaning of this address depends on which CONFIG_SYS_QE_FW_IN_xxx macro
3419	is also specified.
3420
3421- CONFIG_SYS_QE_FMAN_FW_LENGTH
3422	The maximum possible size of the firmware.  The firmware binary format
3423	has a field that specifies the actual size of the firmware, but it
3424	might not be possible to read any part of the firmware unless some
3425	local storage is allocated to hold the entire firmware first.
3426
3427- CONFIG_SYS_QE_FMAN_FW_IN_NOR
3428	Specifies that QE/FMAN firmware is located in NOR flash, mapped as
3429	normal addressable memory via the LBC.  CONFIG_SYS_FMAN_FW_ADDR is the
3430	virtual address in NOR flash.
3431
3432- CONFIG_SYS_QE_FMAN_FW_IN_NAND
3433	Specifies that QE/FMAN firmware is located in NAND flash.
3434	CONFIG_SYS_FMAN_FW_ADDR is the offset within NAND flash.
3435
3436- CONFIG_SYS_QE_FMAN_FW_IN_MMC
3437	Specifies that QE/FMAN firmware is located on the primary SD/MMC
3438	device.  CONFIG_SYS_FMAN_FW_ADDR is the byte offset on that device.
3439
3440- CONFIG_SYS_QE_FMAN_FW_IN_REMOTE
3441	Specifies that QE/FMAN firmware is located in the remote (master)
3442	memory space.	CONFIG_SYS_FMAN_FW_ADDR is a virtual address which
3443	can be mapped from slave TLB->slave LAW->slave SRIO or PCIE outbound
3444	window->master inbound window->master LAW->the ucode address in
3445	master's memory space.
3446
3447Freescale Layerscape Management Complex Firmware Support:
3448---------------------------------------------------------
3449The Freescale Layerscape Management Complex (MC) supports the loading of
3450"firmware".
3451This firmware often needs to be loaded during U-Boot booting, so macros
3452are used to identify the storage device (NOR flash, SPI, etc) and the address
3453within that device.
3454
3455- CONFIG_FSL_MC_ENET
3456	Enable the MC driver for Layerscape SoCs.
3457
3458Freescale Layerscape Debug Server Support:
3459-------------------------------------------
3460The Freescale Layerscape Debug Server Support supports the loading of
3461"Debug Server firmware" and triggering SP boot-rom.
3462This firmware often needs to be loaded during U-Boot booting.
3463
3464- CONFIG_SYS_MC_RSV_MEM_ALIGN
3465	Define alignment of reserved memory MC requires
3466
3467Reproducible builds
3468-------------------
3469
3470In order to achieve reproducible builds, timestamps used in the U-Boot build
3471process have to be set to a fixed value.
3472
3473This is done using the SOURCE_DATE_EPOCH environment variable.
3474SOURCE_DATE_EPOCH is to be set on the build host's shell, not as a configuration
3475option for U-Boot or an environment variable in U-Boot.
3476
3477SOURCE_DATE_EPOCH should be set to a number of seconds since the epoch, in UTC.
3478
3479Building the Software:
3480======================
3481
3482Building U-Boot has been tested in several native build environments
3483and in many different cross environments. Of course we cannot support
3484all possibly existing versions of cross development tools in all
3485(potentially obsolete) versions. In case of tool chain problems we
3486recommend to use the ELDK (see http://www.denx.de/wiki/DULG/ELDK)
3487which is extensively used to build and test U-Boot.
3488
3489If you are not using a native environment, it is assumed that you
3490have GNU cross compiling tools available in your path. In this case,
3491you must set the environment variable CROSS_COMPILE in your shell.
3492Note that no changes to the Makefile or any other source files are
3493necessary. For example using the ELDK on a 4xx CPU, please enter:
3494
3495	$ CROSS_COMPILE=ppc_4xx-
3496	$ export CROSS_COMPILE
3497
3498Note: If you wish to generate Windows versions of the utilities in
3499      the tools directory you can use the MinGW toolchain
3500      (http://www.mingw.org).  Set your HOST tools to the MinGW
3501      toolchain and execute 'make tools'.  For example:
3502
3503       $ make HOSTCC=i586-mingw32msvc-gcc HOSTSTRIP=i586-mingw32msvc-strip tools
3504
3505      Binaries such as tools/mkimage.exe will be created which can
3506      be executed on computers running Windows.
3507
3508U-Boot is intended to be simple to build. After installing the
3509sources you must configure U-Boot for one specific board type. This
3510is done by typing:
3511
3512	make NAME_defconfig
3513
3514where "NAME_defconfig" is the name of one of the existing configu-
3515rations; see boards.cfg for supported names.
3516
3517Note: for some board special configuration names may exist; check if
3518      additional information is available from the board vendor; for
3519      instance, the TQM823L systems are available without (standard)
3520      or with LCD support. You can select such additional "features"
3521      when choosing the configuration, i. e.
3522
3523      make TQM823L_defconfig
3524	- will configure for a plain TQM823L, i. e. no LCD support
3525
3526      make TQM823L_LCD_defconfig
3527	- will configure for a TQM823L with U-Boot console on LCD
3528
3529      etc.
3530
3531
3532Finally, type "make all", and you should get some working U-Boot
3533images ready for download to / installation on your system:
3534
3535- "u-boot.bin" is a raw binary image
3536- "u-boot" is an image in ELF binary format
3537- "u-boot.srec" is in Motorola S-Record format
3538
3539By default the build is performed locally and the objects are saved
3540in the source directory. One of the two methods can be used to change
3541this behavior and build U-Boot to some external directory:
3542
35431. Add O= to the make command line invocations:
3544
3545	make O=/tmp/build distclean
3546	make O=/tmp/build NAME_defconfig
3547	make O=/tmp/build all
3548
35492. Set environment variable KBUILD_OUTPUT to point to the desired location:
3550
3551	export KBUILD_OUTPUT=/tmp/build
3552	make distclean
3553	make NAME_defconfig
3554	make all
3555
3556Note that the command line "O=" setting overrides the KBUILD_OUTPUT environment
3557variable.
3558
3559User specific CPPFLAGS, AFLAGS and CFLAGS can be passed to the compiler by
3560setting the according environment variables KCPPFLAGS, KAFLAGS and KCFLAGS.
3561For example to treat all compiler warnings as errors:
3562
3563	make KCFLAGS=-Werror
3564
3565Please be aware that the Makefiles assume you are using GNU make, so
3566for instance on NetBSD you might need to use "gmake" instead of
3567native "make".
3568
3569
3570If the system board that you have is not listed, then you will need
3571to port U-Boot to your hardware platform. To do this, follow these
3572steps:
3573
35741.  Create a new directory to hold your board specific code. Add any
3575    files you need. In your board directory, you will need at least
3576    the "Makefile" and a "<board>.c".
35772.  Create a new configuration file "include/configs/<board>.h" for
3578    your board.
35793.  If you're porting U-Boot to a new CPU, then also create a new
3580    directory to hold your CPU specific code. Add any files you need.
35814.  Run "make <board>_defconfig" with your new name.
35825.  Type "make", and you should get a working "u-boot.srec" file
3583    to be installed on your target system.
35846.  Debug and solve any problems that might arise.
3585    [Of course, this last step is much harder than it sounds.]
3586
3587
3588Testing of U-Boot Modifications, Ports to New Hardware, etc.:
3589==============================================================
3590
3591If you have modified U-Boot sources (for instance added a new board
3592or support for new devices, a new CPU, etc.) you are expected to
3593provide feedback to the other developers. The feedback normally takes
3594the form of a "patch", i. e. a context diff against a certain (latest
3595official or latest in the git repository) version of U-Boot sources.
3596
3597But before you submit such a patch, please verify that your modifi-
3598cation did not break existing code. At least make sure that *ALL* of
3599the supported boards compile WITHOUT ANY compiler warnings. To do so,
3600just run the buildman script (tools/buildman/buildman), which will
3601configure and build U-Boot for ALL supported system. Be warned, this
3602will take a while. Please see the buildman README, or run 'buildman -H'
3603for documentation.
3604
3605
3606See also "U-Boot Porting Guide" below.
3607
3608
3609Monitor Commands - Overview:
3610============================
3611
3612go	- start application at address 'addr'
3613run	- run commands in an environment variable
3614bootm	- boot application image from memory
3615bootp	- boot image via network using BootP/TFTP protocol
3616bootz   - boot zImage from memory
3617tftpboot- boot image via network using TFTP protocol
3618	       and env variables "ipaddr" and "serverip"
3619	       (and eventually "gatewayip")
3620tftpput - upload a file via network using TFTP protocol
3621rarpboot- boot image via network using RARP/TFTP protocol
3622diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
3623loads	- load S-Record file over serial line
3624loadb	- load binary file over serial line (kermit mode)
3625md	- memory display
3626mm	- memory modify (auto-incrementing)
3627nm	- memory modify (constant address)
3628mw	- memory write (fill)
3629cp	- memory copy
3630cmp	- memory compare
3631crc32	- checksum calculation
3632i2c	- I2C sub-system
3633sspi	- SPI utility commands
3634base	- print or set address offset
3635printenv- print environment variables
3636setenv	- set environment variables
3637saveenv - save environment variables to persistent storage
3638protect - enable or disable FLASH write protection
3639erase	- erase FLASH memory
3640flinfo	- print FLASH memory information
3641nand	- NAND memory operations (see doc/README.nand)
3642bdinfo	- print Board Info structure
3643iminfo	- print header information for application image
3644coninfo - print console devices and informations
3645ide	- IDE sub-system
3646loop	- infinite loop on address range
3647loopw	- infinite write loop on address range
3648mtest	- simple RAM test
3649icache	- enable or disable instruction cache
3650dcache	- enable or disable data cache
3651reset	- Perform RESET of the CPU
3652echo	- echo args to console
3653version - print monitor version
3654help	- print online help
3655?	- alias for 'help'
3656
3657
3658Monitor Commands - Detailed Description:
3659========================================
3660
3661TODO.
3662
3663For now: just type "help <command>".
3664
3665
3666Environment Variables:
3667======================
3668
3669U-Boot supports user configuration using Environment Variables which
3670can be made persistent by saving to Flash memory.
3671
3672Environment Variables are set using "setenv", printed using
3673"printenv", and saved to Flash using "saveenv". Using "setenv"
3674without a value can be used to delete a variable from the
3675environment. As long as you don't save the environment you are
3676working with an in-memory copy. In case the Flash area containing the
3677environment is erased by accident, a default environment is provided.
3678
3679Some configuration options can be set using Environment Variables.
3680
3681List of environment variables (most likely not complete):
3682
3683  baudrate	- see CONFIG_BAUDRATE
3684
3685  bootdelay	- see CONFIG_BOOTDELAY
3686
3687  bootcmd	- see CONFIG_BOOTCOMMAND
3688
3689  bootargs	- Boot arguments when booting an RTOS image
3690
3691  bootfile	- Name of the image to load with TFTP
3692
3693  bootm_low	- Memory range available for image processing in the bootm
3694		  command can be restricted. This variable is given as
3695		  a hexadecimal number and defines lowest address allowed
3696		  for use by the bootm command. See also "bootm_size"
3697		  environment variable. Address defined by "bootm_low" is
3698		  also the base of the initial memory mapping for the Linux
3699		  kernel -- see the description of CONFIG_SYS_BOOTMAPSZ and
3700		  bootm_mapsize.
3701
3702  bootm_mapsize - Size of the initial memory mapping for the Linux kernel.
3703		  This variable is given as a hexadecimal number and it
3704		  defines the size of the memory region starting at base
3705		  address bootm_low that is accessible by the Linux kernel
3706		  during early boot.  If unset, CONFIG_SYS_BOOTMAPSZ is used
3707		  as the default value if it is defined, and bootm_size is
3708		  used otherwise.
3709
3710  bootm_size	- Memory range available for image processing in the bootm
3711		  command can be restricted. This variable is given as
3712		  a hexadecimal number and defines the size of the region
3713		  allowed for use by the bootm command. See also "bootm_low"
3714		  environment variable.
3715
3716  updatefile	- Location of the software update file on a TFTP server, used
3717		  by the automatic software update feature. Please refer to
3718		  documentation in doc/README.update for more details.
3719
3720  autoload	- if set to "no" (any string beginning with 'n'),
3721		  "bootp" will just load perform a lookup of the
3722		  configuration from the BOOTP server, but not try to
3723		  load any image using TFTP
3724
3725  autostart	- if set to "yes", an image loaded using the "bootp",
3726		  "rarpboot", "tftpboot" or "diskboot" commands will
3727		  be automatically started (by internally calling
3728		  "bootm")
3729
3730		  If set to "no", a standalone image passed to the
3731		  "bootm" command will be copied to the load address
3732		  (and eventually uncompressed), but NOT be started.
3733		  This can be used to load and uncompress arbitrary
3734		  data.
3735
3736  fdt_high	- if set this restricts the maximum address that the
3737		  flattened device tree will be copied into upon boot.
3738		  For example, if you have a system with 1 GB memory
3739		  at physical address 0x10000000, while Linux kernel
3740		  only recognizes the first 704 MB as low memory, you
3741		  may need to set fdt_high as 0x3C000000 to have the
3742		  device tree blob be copied to the maximum address
3743		  of the 704 MB low memory, so that Linux kernel can
3744		  access it during the boot procedure.
3745
3746		  If this is set to the special value 0xFFFFFFFF then
3747		  the fdt will not be copied at all on boot.  For this
3748		  to work it must reside in writable memory, have
3749		  sufficient padding on the end of it for u-boot to
3750		  add the information it needs into it, and the memory
3751		  must be accessible by the kernel.
3752
3753  fdtcontroladdr- if set this is the address of the control flattened
3754		  device tree used by U-Boot when CONFIG_OF_CONTROL is
3755		  defined.
3756
3757  i2cfast	- (PPC405GP|PPC405EP only)
3758		  if set to 'y' configures Linux I2C driver for fast
3759		  mode (400kHZ). This environment variable is used in
3760		  initialization code. So, for changes to be effective
3761		  it must be saved and board must be reset.
3762
3763  initrd_high	- restrict positioning of initrd images:
3764		  If this variable is not set, initrd images will be
3765		  copied to the highest possible address in RAM; this
3766		  is usually what you want since it allows for
3767		  maximum initrd size. If for some reason you want to
3768		  make sure that the initrd image is loaded below the
3769		  CONFIG_SYS_BOOTMAPSZ limit, you can set this environment
3770		  variable to a value of "no" or "off" or "0".
3771		  Alternatively, you can set it to a maximum upper
3772		  address to use (U-Boot will still check that it
3773		  does not overwrite the U-Boot stack and data).
3774
3775		  For instance, when you have a system with 16 MB
3776		  RAM, and want to reserve 4 MB from use by Linux,
3777		  you can do this by adding "mem=12M" to the value of
3778		  the "bootargs" variable. However, now you must make
3779		  sure that the initrd image is placed in the first
3780		  12 MB as well - this can be done with
3781
3782		  setenv initrd_high 00c00000
3783
3784		  If you set initrd_high to 0xFFFFFFFF, this is an
3785		  indication to U-Boot that all addresses are legal
3786		  for the Linux kernel, including addresses in flash
3787		  memory. In this case U-Boot will NOT COPY the
3788		  ramdisk at all. This may be useful to reduce the
3789		  boot time on your system, but requires that this
3790		  feature is supported by your Linux kernel.
3791
3792  ipaddr	- IP address; needed for tftpboot command
3793
3794  loadaddr	- Default load address for commands like "bootp",
3795		  "rarpboot", "tftpboot", "loadb" or "diskboot"
3796
3797  loads_echo	- see CONFIG_LOADS_ECHO
3798
3799  serverip	- TFTP server IP address; needed for tftpboot command
3800
3801  bootretry	- see CONFIG_BOOT_RETRY_TIME
3802
3803  bootdelaykey	- see CONFIG_AUTOBOOT_DELAY_STR
3804
3805  bootstopkey	- see CONFIG_AUTOBOOT_STOP_STR
3806
3807  ethprime	- controls which interface is used first.
3808
3809  ethact	- controls which interface is currently active.
3810		  For example you can do the following
3811
3812		  => setenv ethact FEC
3813		  => ping 192.168.0.1 # traffic sent on FEC
3814		  => setenv ethact SCC
3815		  => ping 10.0.0.1 # traffic sent on SCC
3816
3817  ethrotate	- When set to "no" U-Boot does not go through all
3818		  available network interfaces.
3819		  It just stays at the currently selected interface.
3820
3821  netretry	- When set to "no" each network operation will
3822		  either succeed or fail without retrying.
3823		  When set to "once" the network operation will
3824		  fail when all the available network interfaces
3825		  are tried once without success.
3826		  Useful on scripts which control the retry operation
3827		  themselves.
3828
3829  npe_ucode	- set load address for the NPE microcode
3830
3831  silent_linux  - If set then Linux will be told to boot silently, by
3832		  changing the console to be empty. If "yes" it will be
3833		  made silent. If "no" it will not be made silent. If
3834		  unset, then it will be made silent if the U-Boot console
3835		  is silent.
3836
3837  tftpsrcp	- If this is set, the value is used for TFTP's
3838		  UDP source port.
3839
3840  tftpdstp	- If this is set, the value is used for TFTP's UDP
3841		  destination port instead of the Well Know Port 69.
3842
3843  tftpblocksize - Block size to use for TFTP transfers; if not set,
3844		  we use the TFTP server's default block size
3845
3846  tftptimeout	- Retransmission timeout for TFTP packets (in milli-
3847		  seconds, minimum value is 1000 = 1 second). Defines
3848		  when a packet is considered to be lost so it has to
3849		  be retransmitted. The default is 5000 = 5 seconds.
3850		  Lowering this value may make downloads succeed
3851		  faster in networks with high packet loss rates or
3852		  with unreliable TFTP servers.
3853
3854  tftptimeoutcountmax	- maximum count of TFTP timeouts (no
3855		  unit, minimum value = 0). Defines how many timeouts
3856		  can happen during a single file transfer before that
3857		  transfer is aborted. The default is 10, and 0 means
3858		  'no timeouts allowed'. Increasing this value may help
3859		  downloads succeed with high packet loss rates, or with
3860		  unreliable TFTP servers or client hardware.
3861
3862  vlan		- When set to a value < 4095 the traffic over
3863		  Ethernet is encapsulated/received over 802.1q
3864		  VLAN tagged frames.
3865
3866  bootpretryperiod	- Period during which BOOTP/DHCP sends retries.
3867		  Unsigned value, in milliseconds. If not set, the period will
3868		  be either the default (28000), or a value based on
3869		  CONFIG_NET_RETRY_COUNT, if defined. This value has
3870		  precedence over the valu based on CONFIG_NET_RETRY_COUNT.
3871
3872The following image location variables contain the location of images
3873used in booting. The "Image" column gives the role of the image and is
3874not an environment variable name. The other columns are environment
3875variable names. "File Name" gives the name of the file on a TFTP
3876server, "RAM Address" gives the location in RAM the image will be
3877loaded to, and "Flash Location" gives the image's address in NOR
3878flash or offset in NAND flash.
3879
3880*Note* - these variables don't have to be defined for all boards, some
3881boards currently use other variables for these purposes, and some
3882boards use these variables for other purposes.
3883
3884Image		    File Name	     RAM Address       Flash Location
3885-----		    ---------	     -----------       --------------
3886u-boot		    u-boot	     u-boot_addr_r     u-boot_addr
3887Linux kernel	    bootfile	     kernel_addr_r     kernel_addr
3888device tree blob    fdtfile	     fdt_addr_r	       fdt_addr
3889ramdisk		    ramdiskfile	     ramdisk_addr_r    ramdisk_addr
3890
3891The following environment variables may be used and automatically
3892updated by the network boot commands ("bootp" and "rarpboot"),
3893depending the information provided by your boot server:
3894
3895  bootfile	- see above
3896  dnsip		- IP address of your Domain Name Server
3897  dnsip2	- IP address of your secondary Domain Name Server
3898  gatewayip	- IP address of the Gateway (Router) to use
3899  hostname	- Target hostname
3900  ipaddr	- see above
3901  netmask	- Subnet Mask
3902  rootpath	- Pathname of the root filesystem on the NFS server
3903  serverip	- see above
3904
3905
3906There are two special Environment Variables:
3907
3908  serial#	- contains hardware identification information such
3909		  as type string and/or serial number
3910  ethaddr	- Ethernet address
3911
3912These variables can be set only once (usually during manufacturing of
3913the board). U-Boot refuses to delete or overwrite these variables
3914once they have been set once.
3915
3916
3917Further special Environment Variables:
3918
3919  ver		- Contains the U-Boot version string as printed
3920		  with the "version" command. This variable is
3921		  readonly (see CONFIG_VERSION_VARIABLE).
3922
3923
3924Please note that changes to some configuration parameters may take
3925only effect after the next boot (yes, that's just like Windoze :-).
3926
3927
3928Callback functions for environment variables:
3929---------------------------------------------
3930
3931For some environment variables, the behavior of u-boot needs to change
3932when their values are changed.  This functionality allows functions to
3933be associated with arbitrary variables.  On creation, overwrite, or
3934deletion, the callback will provide the opportunity for some side
3935effect to happen or for the change to be rejected.
3936
3937The callbacks are named and associated with a function using the
3938U_BOOT_ENV_CALLBACK macro in your board or driver code.
3939
3940These callbacks are associated with variables in one of two ways.  The
3941static list can be added to by defining CONFIG_ENV_CALLBACK_LIST_STATIC
3942in the board configuration to a string that defines a list of
3943associations.  The list must be in the following format:
3944
3945	entry = variable_name[:callback_name]
3946	list = entry[,list]
3947
3948If the callback name is not specified, then the callback is deleted.
3949Spaces are also allowed anywhere in the list.
3950
3951Callbacks can also be associated by defining the ".callbacks" variable
3952with the same list format above.  Any association in ".callbacks" will
3953override any association in the static list. You can define
3954CONFIG_ENV_CALLBACK_LIST_DEFAULT to a list (string) to define the
3955".callbacks" environment variable in the default or embedded environment.
3956
3957If CONFIG_REGEX is defined, the variable_name above is evaluated as a
3958regular expression. This allows multiple variables to be connected to
3959the same callback without explicitly listing them all out.
3960
3961
3962Command Line Parsing:
3963=====================
3964
3965There are two different command line parsers available with U-Boot:
3966the old "simple" one, and the much more powerful "hush" shell:
3967
3968Old, simple command line parser:
3969--------------------------------
3970
3971- supports environment variables (through setenv / saveenv commands)
3972- several commands on one line, separated by ';'
3973- variable substitution using "... ${name} ..." syntax
3974- special characters ('$', ';') can be escaped by prefixing with '\',
3975  for example:
3976	setenv bootcmd bootm \${address}
3977- You can also escape text by enclosing in single apostrophes, for example:
3978	setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'
3979
3980Hush shell:
3981-----------
3982
3983- similar to Bourne shell, with control structures like
3984  if...then...else...fi, for...do...done; while...do...done,
3985  until...do...done, ...
3986- supports environment ("global") variables (through setenv / saveenv
3987  commands) and local shell variables (through standard shell syntax
3988  "name=value"); only environment variables can be used with "run"
3989  command
3990
3991General rules:
3992--------------
3993
3994(1) If a command line (or an environment variable executed by a "run"
3995    command) contains several commands separated by semicolon, and
3996    one of these commands fails, then the remaining commands will be
3997    executed anyway.
3998
3999(2) If you execute several variables with one call to run (i. e.
4000    calling run with a list of variables as arguments), any failing
4001    command will cause "run" to terminate, i. e. the remaining
4002    variables are not executed.
4003
4004Note for Redundant Ethernet Interfaces:
4005=======================================
4006
4007Some boards come with redundant Ethernet interfaces; U-Boot supports
4008such configurations and is capable of automatic selection of a
4009"working" interface when needed. MAC assignment works as follows:
4010
4011Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
4012MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
4013"eth1addr" (=>eth1), "eth2addr", ...
4014
4015If the network interface stores some valid MAC address (for instance
4016in SROM), this is used as default address if there is NO correspon-
4017ding setting in the environment; if the corresponding environment
4018variable is set, this overrides the settings in the card; that means:
4019
4020o If the SROM has a valid MAC address, and there is no address in the
4021  environment, the SROM's address is used.
4022
4023o If there is no valid address in the SROM, and a definition in the
4024  environment exists, then the value from the environment variable is
4025  used.
4026
4027o If both the SROM and the environment contain a MAC address, and
4028  both addresses are the same, this MAC address is used.
4029
4030o If both the SROM and the environment contain a MAC address, and the
4031  addresses differ, the value from the environment is used and a
4032  warning is printed.
4033
4034o If neither SROM nor the environment contain a MAC address, an error
4035  is raised. If CONFIG_NET_RANDOM_ETHADDR is defined, then in this case
4036  a random, locally-assigned MAC is used.
4037
4038If Ethernet drivers implement the 'write_hwaddr' function, valid MAC addresses
4039will be programmed into hardware as part of the initialization process.	 This
4040may be skipped by setting the appropriate 'ethmacskip' environment variable.
4041The naming convention is as follows:
4042"ethmacskip" (=>eth0), "eth1macskip" (=>eth1) etc.
4043
4044Image Formats:
4045==============
4046
4047U-Boot is capable of booting (and performing other auxiliary operations on)
4048images in two formats:
4049
4050New uImage format (FIT)
4051-----------------------
4052
4053Flexible and powerful format based on Flattened Image Tree -- FIT (similar
4054to Flattened Device Tree). It allows the use of images with multiple
4055components (several kernels, ramdisks, etc.), with contents protected by
4056SHA1, MD5 or CRC32. More details are found in the doc/uImage.FIT directory.
4057
4058
4059Old uImage format
4060-----------------
4061
4062Old image format is based on binary files which can be basically anything,
4063preceded by a special header; see the definitions in include/image.h for
4064details; basically, the header defines the following image properties:
4065
4066* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4067  4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
4068  LynxOS, pSOS, QNX, RTEMS, INTEGRITY;
4069  Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
4070  INTEGRITY).
4071* Target CPU Architecture (Provisions for Alpha, ARM, Intel x86,
4072  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
4073  Currently supported: ARM, Intel x86, MIPS, NDS32, Nios II, PowerPC).
4074* Compression Type (uncompressed, gzip, bzip2)
4075* Load Address
4076* Entry Point
4077* Image Name
4078* Image Timestamp
4079
4080The header is marked by a special Magic Number, and both the header
4081and the data portions of the image are secured against corruption by
4082CRC32 checksums.
4083
4084
4085Linux Support:
4086==============
4087
4088Although U-Boot should support any OS or standalone application
4089easily, the main focus has always been on Linux during the design of
4090U-Boot.
4091
4092U-Boot includes many features that so far have been part of some
4093special "boot loader" code within the Linux kernel. Also, any
4094"initrd" images to be used are no longer part of one big Linux image;
4095instead, kernel and "initrd" are separate images. This implementation
4096serves several purposes:
4097
4098- the same features can be used for other OS or standalone
4099  applications (for instance: using compressed images to reduce the
4100  Flash memory footprint)
4101
4102- it becomes much easier to port new Linux kernel versions because
4103  lots of low-level, hardware dependent stuff are done by U-Boot
4104
4105- the same Linux kernel image can now be used with different "initrd"
4106  images; of course this also means that different kernel images can
4107  be run with the same "initrd". This makes testing easier (you don't
4108  have to build a new "zImage.initrd" Linux image when you just
4109  change a file in your "initrd"). Also, a field-upgrade of the
4110  software is easier now.
4111
4112
4113Linux HOWTO:
4114============
4115
4116Porting Linux to U-Boot based systems:
4117---------------------------------------
4118
4119U-Boot cannot save you from doing all the necessary modifications to
4120configure the Linux device drivers for use with your target hardware
4121(no, we don't intend to provide a full virtual machine interface to
4122Linux :-).
4123
4124But now you can ignore ALL boot loader code (in arch/powerpc/mbxboot).
4125
4126Just make sure your machine specific header file (for instance
4127include/asm-ppc/tqm8xx.h) includes the same definition of the Board
4128Information structure as we define in include/asm-<arch>/u-boot.h,
4129and make sure that your definition of IMAP_ADDR uses the same value
4130as your U-Boot configuration in CONFIG_SYS_IMMR.
4131
4132Note that U-Boot now has a driver model, a unified model for drivers.
4133If you are adding a new driver, plumb it into driver model. If there
4134is no uclass available, you are encouraged to create one. See
4135doc/driver-model.
4136
4137
4138Configuring the Linux kernel:
4139-----------------------------
4140
4141No specific requirements for U-Boot. Make sure you have some root
4142device (initial ramdisk, NFS) for your target system.
4143
4144
4145Building a Linux Image:
4146-----------------------
4147
4148With U-Boot, "normal" build targets like "zImage" or "bzImage" are
4149not used. If you use recent kernel source, a new build target
4150"uImage" will exist which automatically builds an image usable by
4151U-Boot. Most older kernels also have support for a "pImage" target,
4152which was introduced for our predecessor project PPCBoot and uses a
4153100% compatible format.
4154
4155Example:
4156
4157	make TQM850L_defconfig
4158	make oldconfig
4159	make dep
4160	make uImage
4161
4162The "uImage" build target uses a special tool (in 'tools/mkimage') to
4163encapsulate a compressed Linux kernel image with header	 information,
4164CRC32 checksum etc. for use with U-Boot. This is what we are doing:
4165
4166* build a standard "vmlinux" kernel image (in ELF binary format):
4167
4168* convert the kernel into a raw binary image:
4169
4170	${CROSS_COMPILE}-objcopy -O binary \
4171				 -R .note -R .comment \
4172				 -S vmlinux linux.bin
4173
4174* compress the binary image:
4175
4176	gzip -9 linux.bin
4177
4178* package compressed binary image for U-Boot:
4179
4180	mkimage -A ppc -O linux -T kernel -C gzip \
4181		-a 0 -e 0 -n "Linux Kernel Image" \
4182		-d linux.bin.gz uImage
4183
4184
4185The "mkimage" tool can also be used to create ramdisk images for use
4186with U-Boot, either separated from the Linux kernel image, or
4187combined into one file. "mkimage" encapsulates the images with a 64
4188byte header containing information about target architecture,
4189operating system, image type, compression method, entry points, time
4190stamp, CRC32 checksums, etc.
4191
4192"mkimage" can be called in two ways: to verify existing images and
4193print the header information, or to build new images.
4194
4195In the first form (with "-l" option) mkimage lists the information
4196contained in the header of an existing U-Boot image; this includes
4197checksum verification:
4198
4199	tools/mkimage -l image
4200	  -l ==> list image header information
4201
4202The second form (with "-d" option) is used to build a U-Boot image
4203from a "data file" which is used as image payload:
4204
4205	tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
4206		      -n name -d data_file image
4207	  -A ==> set architecture to 'arch'
4208	  -O ==> set operating system to 'os'
4209	  -T ==> set image type to 'type'
4210	  -C ==> set compression type 'comp'
4211	  -a ==> set load address to 'addr' (hex)
4212	  -e ==> set entry point to 'ep' (hex)
4213	  -n ==> set image name to 'name'
4214	  -d ==> use image data from 'datafile'
4215
4216Right now, all Linux kernels for PowerPC systems use the same load
4217address (0x00000000), but the entry point address depends on the
4218kernel version:
4219
4220- 2.2.x kernels have the entry point at 0x0000000C,
4221- 2.3.x and later kernels have the entry point at 0x00000000.
4222
4223So a typical call to build a U-Boot image would read:
4224
4225	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4226	> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
4227	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz \
4228	> examples/uImage.TQM850L
4229	Image Name:   2.4.4 kernel for TQM850L
4230	Created:      Wed Jul 19 02:34:59 2000
4231	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4232	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4233	Load Address: 0x00000000
4234	Entry Point:  0x00000000
4235
4236To verify the contents of the image (or check for corruption):
4237
4238	-> tools/mkimage -l examples/uImage.TQM850L
4239	Image Name:   2.4.4 kernel for TQM850L
4240	Created:      Wed Jul 19 02:34:59 2000
4241	Image Type:   PowerPC Linux Kernel Image (gzip compressed)
4242	Data Size:    335725 Bytes = 327.86 kB = 0.32 MB
4243	Load Address: 0x00000000
4244	Entry Point:  0x00000000
4245
4246NOTE: for embedded systems where boot time is critical you can trade
4247speed for memory and install an UNCOMPRESSED image instead: this
4248needs more space in Flash, but boots much faster since it does not
4249need to be uncompressed:
4250
4251	-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux.gz
4252	-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
4253	> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
4254	> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/powerpc/coffboot/vmlinux \
4255	> examples/uImage.TQM850L-uncompressed
4256	Image Name:   2.4.4 kernel for TQM850L
4257	Created:      Wed Jul 19 02:34:59 2000
4258	Image Type:   PowerPC Linux Kernel Image (uncompressed)
4259	Data Size:    792160 Bytes = 773.59 kB = 0.76 MB
4260	Load Address: 0x00000000
4261	Entry Point:  0x00000000
4262
4263
4264Similar you can build U-Boot images from a 'ramdisk.image.gz' file
4265when your kernel is intended to use an initial ramdisk:
4266
4267	-> tools/mkimage -n 'Simple Ramdisk Image' \
4268	> -A ppc -O linux -T ramdisk -C gzip \
4269	> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
4270	Image Name:   Simple Ramdisk Image
4271	Created:      Wed Jan 12 14:01:50 2000
4272	Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
4273	Data Size:    566530 Bytes = 553.25 kB = 0.54 MB
4274	Load Address: 0x00000000
4275	Entry Point:  0x00000000
4276
4277The "dumpimage" is a tool to disassemble images built by mkimage. Its "-i"
4278option performs the converse operation of the mkimage's second form (the "-d"
4279option). Given an image built by mkimage, the dumpimage extracts a "data file"
4280from the image:
4281
4282	tools/dumpimage -i image -T type -p position data_file
4283	  -i ==> extract from the 'image' a specific 'data_file'
4284	  -T ==> set image type to 'type'
4285	  -p ==> 'position' (starting at 0) of the 'data_file' inside the 'image'
4286
4287
4288Installing a Linux Image:
4289-------------------------
4290
4291To downloading a U-Boot image over the serial (console) interface,
4292you must convert the image to S-Record format:
4293
4294	objcopy -I binary -O srec examples/image examples/image.srec
4295
4296The 'objcopy' does not understand the information in the U-Boot
4297image header, so the resulting S-Record file will be relative to
4298address 0x00000000. To load it to a given address, you need to
4299specify the target address as 'offset' parameter with the 'loads'
4300command.
4301
4302Example: install the image to address 0x40100000 (which on the
4303TQM8xxL is in the first Flash bank):
4304
4305	=> erase 40100000 401FFFFF
4306
4307	.......... done
4308	Erased 8 sectors
4309
4310	=> loads 40100000
4311	## Ready for S-Record download ...
4312	~>examples/image.srec
4313	1 2 3 4 5 6 7 8 9 10 11 12 13 ...
4314	...
4315	15989 15990 15991 15992
4316	[file transfer complete]
4317	[connected]
4318	## Start Addr = 0x00000000
4319
4320
4321You can check the success of the download using the 'iminfo' command;
4322this includes a checksum verification so you can be sure no data
4323corruption happened:
4324
4325	=> imi 40100000
4326
4327	## Checking Image at 40100000 ...
4328	   Image Name:	 2.2.13 for initrd on TQM850L
4329	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4330	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4331	   Load Address: 00000000
4332	   Entry Point:	 0000000c
4333	   Verifying Checksum ... OK
4334
4335
4336Boot Linux:
4337-----------
4338
4339The "bootm" command is used to boot an application that is stored in
4340memory (RAM or Flash). In case of a Linux kernel image, the contents
4341of the "bootargs" environment variable is passed to the kernel as
4342parameters. You can check and modify this variable using the
4343"printenv" and "setenv" commands:
4344
4345
4346	=> printenv bootargs
4347	bootargs=root=/dev/ram
4348
4349	=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4350
4351	=> printenv bootargs
4352	bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4353
4354	=> bootm 40020000
4355	## Booting Linux kernel at 40020000 ...
4356	   Image Name:	 2.2.13 for NFS on TQM850L
4357	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4358	   Data Size:	 381681 Bytes = 372 kB = 0 MB
4359	   Load Address: 00000000
4360	   Entry Point:	 0000000c
4361	   Verifying Checksum ... OK
4362	   Uncompressing Kernel Image ... OK
4363	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
4364	Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
4365	time_init: decrementer frequency = 187500000/60
4366	Calibrating delay loop... 49.77 BogoMIPS
4367	Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
4368	...
4369
4370If you want to boot a Linux kernel with initial RAM disk, you pass
4371the memory addresses of both the kernel and the initrd image (PPBCOOT
4372format!) to the "bootm" command:
4373
4374	=> imi 40100000 40200000
4375
4376	## Checking Image at 40100000 ...
4377	   Image Name:	 2.2.13 for initrd on TQM850L
4378	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4379	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4380	   Load Address: 00000000
4381	   Entry Point:	 0000000c
4382	   Verifying Checksum ... OK
4383
4384	## Checking Image at 40200000 ...
4385	   Image Name:	 Simple Ramdisk Image
4386	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4387	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4388	   Load Address: 00000000
4389	   Entry Point:	 00000000
4390	   Verifying Checksum ... OK
4391
4392	=> bootm 40100000 40200000
4393	## Booting Linux kernel at 40100000 ...
4394	   Image Name:	 2.2.13 for initrd on TQM850L
4395	   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4396	   Data Size:	 335725 Bytes = 327 kB = 0 MB
4397	   Load Address: 00000000
4398	   Entry Point:	 0000000c
4399	   Verifying Checksum ... OK
4400	   Uncompressing Kernel Image ... OK
4401	## Loading RAMDisk Image at 40200000 ...
4402	   Image Name:	 Simple Ramdisk Image
4403	   Image Type:	 PowerPC Linux RAMDisk Image (gzip compressed)
4404	   Data Size:	 566530 Bytes = 553 kB = 0 MB
4405	   Load Address: 00000000
4406	   Entry Point:	 00000000
4407	   Verifying Checksum ... OK
4408	   Loading Ramdisk ... OK
4409	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
4410	Boot arguments: root=/dev/ram
4411	time_init: decrementer frequency = 187500000/60
4412	Calibrating delay loop... 49.77 BogoMIPS
4413	...
4414	RAMDISK: Compressed image found at block 0
4415	VFS: Mounted root (ext2 filesystem).
4416
4417	bash#
4418
4419Boot Linux and pass a flat device tree:
4420-----------
4421
4422First, U-Boot must be compiled with the appropriate defines. See the section
4423titled "Linux Kernel Interface" above for a more in depth explanation. The
4424following is an example of how to start a kernel and pass an updated
4425flat device tree:
4426
4427=> print oftaddr
4428oftaddr=0x300000
4429=> print oft
4430oft=oftrees/mpc8540ads.dtb
4431=> tftp $oftaddr $oft
4432Speed: 1000, full duplex
4433Using TSEC0 device
4434TFTP from server 192.168.1.1; our IP address is 192.168.1.101
4435Filename 'oftrees/mpc8540ads.dtb'.
4436Load address: 0x300000
4437Loading: #
4438done
4439Bytes transferred = 4106 (100a hex)
4440=> tftp $loadaddr $bootfile
4441Speed: 1000, full duplex
4442Using TSEC0 device
4443TFTP from server 192.168.1.1; our IP address is 192.168.1.2
4444Filename 'uImage'.
4445Load address: 0x200000
4446Loading:############
4447done
4448Bytes transferred = 1029407 (fb51f hex)
4449=> print loadaddr
4450loadaddr=200000
4451=> print oftaddr
4452oftaddr=0x300000
4453=> bootm $loadaddr - $oftaddr
4454## Booting image at 00200000 ...
4455   Image Name:	 Linux-2.6.17-dirty
4456   Image Type:	 PowerPC Linux Kernel Image (gzip compressed)
4457   Data Size:	 1029343 Bytes = 1005.2 kB
4458   Load Address: 00000000
4459   Entry Point:	 00000000
4460   Verifying Checksum ... OK
4461   Uncompressing Kernel Image ... OK
4462Booting using flat device tree at 0x300000
4463Using MPC85xx ADS machine description
4464Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
4465[snip]
4466
4467
4468More About U-Boot Image Types:
4469------------------------------
4470
4471U-Boot supports the following image types:
4472
4473   "Standalone Programs" are directly runnable in the environment
4474	provided by U-Boot; it is expected that (if they behave
4475	well) you can continue to work in U-Boot after return from
4476	the Standalone Program.
4477   "OS Kernel Images" are usually images of some Embedded OS which
4478	will take over control completely. Usually these programs
4479	will install their own set of exception handlers, device
4480	drivers, set up the MMU, etc. - this means, that you cannot
4481	expect to re-enter U-Boot except by resetting the CPU.
4482   "RAMDisk Images" are more or less just data blocks, and their
4483	parameters (address, size) are passed to an OS kernel that is
4484	being started.
4485   "Multi-File Images" contain several images, typically an OS
4486	(Linux) kernel image and one or more data images like
4487	RAMDisks. This construct is useful for instance when you want
4488	to boot over the network using BOOTP etc., where the boot
4489	server provides just a single image file, but you want to get
4490	for instance an OS kernel and a RAMDisk image.
4491
4492	"Multi-File Images" start with a list of image sizes, each
4493	image size (in bytes) specified by an "uint32_t" in network
4494	byte order. This list is terminated by an "(uint32_t)0".
4495	Immediately after the terminating 0 follow the images, one by
4496	one, all aligned on "uint32_t" boundaries (size rounded up to
4497	a multiple of 4 bytes).
4498
4499   "Firmware Images" are binary images containing firmware (like
4500	U-Boot or FPGA images) which usually will be programmed to
4501	flash memory.
4502
4503   "Script files" are command sequences that will be executed by
4504	U-Boot's command interpreter; this feature is especially
4505	useful when you configure U-Boot to use a real shell (hush)
4506	as command interpreter.
4507
4508Booting the Linux zImage:
4509-------------------------
4510
4511On some platforms, it's possible to boot Linux zImage. This is done
4512using the "bootz" command. The syntax of "bootz" command is the same
4513as the syntax of "bootm" command.
4514
4515Note, defining the CONFIG_SUPPORT_RAW_INITRD allows user to supply
4516kernel with raw initrd images. The syntax is slightly different, the
4517address of the initrd must be augmented by it's size, in the following
4518format: "<initrd addres>:<initrd size>".
4519
4520
4521Standalone HOWTO:
4522=================
4523
4524One of the features of U-Boot is that you can dynamically load and
4525run "standalone" applications, which can use some resources of
4526U-Boot like console I/O functions or interrupt services.
4527
4528Two simple examples are included with the sources:
4529
4530"Hello World" Demo:
4531-------------------
4532
4533'examples/hello_world.c' contains a small "Hello World" Demo
4534application; it is automatically compiled when you build U-Boot.
4535It's configured to run at address 0x00040004, so you can play with it
4536like that:
4537
4538	=> loads
4539	## Ready for S-Record download ...
4540	~>examples/hello_world.srec
4541	1 2 3 4 5 6 7 8 9 10 11 ...
4542	[file transfer complete]
4543	[connected]
4544	## Start Addr = 0x00040004
4545
4546	=> go 40004 Hello World! This is a test.
4547	## Starting application at 0x00040004 ...
4548	Hello World
4549	argc = 7
4550	argv[0] = "40004"
4551	argv[1] = "Hello"
4552	argv[2] = "World!"
4553	argv[3] = "This"
4554	argv[4] = "is"
4555	argv[5] = "a"
4556	argv[6] = "test."
4557	argv[7] = "<NULL>"
4558	Hit any key to exit ...
4559
4560	## Application terminated, rc = 0x0
4561
4562Another example, which demonstrates how to register a CPM interrupt
4563handler with the U-Boot code, can be found in 'examples/timer.c'.
4564Here, a CPM timer is set up to generate an interrupt every second.
4565The interrupt service routine is trivial, just printing a '.'
4566character, but this is just a demo program. The application can be
4567controlled by the following keys:
4568
4569	? - print current values og the CPM Timer registers
4570	b - enable interrupts and start timer
4571	e - stop timer and disable interrupts
4572	q - quit application
4573
4574	=> loads
4575	## Ready for S-Record download ...
4576	~>examples/timer.srec
4577	1 2 3 4 5 6 7 8 9 10 11 ...
4578	[file transfer complete]
4579	[connected]
4580	## Start Addr = 0x00040004
4581
4582	=> go 40004
4583	## Starting application at 0x00040004 ...
4584	TIMERS=0xfff00980
4585	Using timer 1
4586	  tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0
4587
4588Hit 'b':
4589	[q, b, e, ?] Set interval 1000000 us
4590	Enabling timer
4591Hit '?':
4592	[q, b, e, ?] ........
4593	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
4594Hit '?':
4595	[q, b, e, ?] .
4596	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
4597Hit '?':
4598	[q, b, e, ?] .
4599	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
4600Hit '?':
4601	[q, b, e, ?] .
4602	tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
4603Hit 'e':
4604	[q, b, e, ?] ...Stopping timer
4605Hit 'q':
4606	[q, b, e, ?] ## Application terminated, rc = 0x0
4607
4608
4609Minicom warning:
4610================
4611
4612Over time, many people have reported problems when trying to use the
4613"minicom" terminal emulation program for serial download. I (wd)
4614consider minicom to be broken, and recommend not to use it. Under
4615Unix, I recommend to use C-Kermit for general purpose use (and
4616especially for kermit binary protocol download ("loadb" command), and
4617use "cu" for S-Record download ("loads" command).  See
4618http://www.denx.de/wiki/view/DULG/SystemSetup#Section_4.3.
4619for help with kermit.
4620
4621
4622Nevertheless, if you absolutely want to use it try adding this
4623configuration to your "File transfer protocols" section:
4624
4625	   Name	   Program			Name U/D FullScr IO-Red. Multi
4626	X  kermit  /usr/bin/kermit -i -l %l -s	 Y    U	   Y	   N	  N
4627	Y  kermit  /usr/bin/kermit -i -l %l -r	 N    D	   Y	   N	  N
4628
4629
4630NetBSD Notes:
4631=============
4632
4633Starting at version 0.9.2, U-Boot supports NetBSD both as host
4634(build U-Boot) and target system (boots NetBSD/mpc8xx).
4635
4636Building requires a cross environment; it is known to work on
4637NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
4638need gmake since the Makefiles are not compatible with BSD make).
4639Note that the cross-powerpc package does not install include files;
4640attempting to build U-Boot will fail because <machine/ansi.h> is
4641missing.  This file has to be installed and patched manually:
4642
4643	# cd /usr/pkg/cross/powerpc-netbsd/include
4644	# mkdir powerpc
4645	# ln -s powerpc machine
4646	# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
4647	# ${EDIT} powerpc/ansi.h	## must remove __va_list, _BSD_VA_LIST
4648
4649Native builds *don't* work due to incompatibilities between native
4650and U-Boot include files.
4651
4652Booting assumes that (the first part of) the image booted is a
4653stage-2 loader which in turn loads and then invokes the kernel
4654proper. Loader sources will eventually appear in the NetBSD source
4655tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
4656meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz
4657
4658
4659Implementation Internals:
4660=========================
4661
4662The following is not intended to be a complete description of every
4663implementation detail. However, it should help to understand the
4664inner workings of U-Boot and make it easier to port it to custom
4665hardware.
4666
4667
4668Initial Stack, Global Data:
4669---------------------------
4670
4671The implementation of U-Boot is complicated by the fact that U-Boot
4672starts running out of ROM (flash memory), usually without access to
4673system RAM (because the memory controller is not initialized yet).
4674This means that we don't have writable Data or BSS segments, and BSS
4675is not initialized as zero. To be able to get a C environment working
4676at all, we have to allocate at least a minimal stack. Implementation
4677options for this are defined and restricted by the CPU used: Some CPU
4678models provide on-chip memory (like the IMMR area on MPC8xx and
4679MPC826x processors), on others (parts of) the data cache can be
4680locked as (mis-) used as memory, etc.
4681
4682	Chris Hallinan posted a good summary of these issues to the
4683	U-Boot mailing list:
4684
4685	Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
4686	From: "Chris Hallinan" <clh@net1plus.com>
4687	Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
4688	...
4689
4690	Correct me if I'm wrong, folks, but the way I understand it
4691	is this: Using DCACHE as initial RAM for Stack, etc, does not
4692	require any physical RAM backing up the cache. The cleverness
4693	is that the cache is being used as a temporary supply of
4694	necessary storage before the SDRAM controller is setup. It's
4695	beyond the scope of this list to explain the details, but you
4696	can see how this works by studying the cache architecture and
4697	operation in the architecture and processor-specific manuals.
4698
4699	OCM is On Chip Memory, which I believe the 405GP has 4K. It
4700	is another option for the system designer to use as an
4701	initial stack/RAM area prior to SDRAM being available. Either
4702	option should work for you. Using CS 4 should be fine if your
4703	board designers haven't used it for something that would
4704	cause you grief during the initial boot! It is frequently not
4705	used.
4706
4707	CONFIG_SYS_INIT_RAM_ADDR should be somewhere that won't interfere
4708	with your processor/board/system design. The default value
4709	you will find in any recent u-boot distribution in
4710	walnut.h should work for you. I'd set it to a value larger
4711	than your SDRAM module. If you have a 64MB SDRAM module, set
4712	it above 400_0000. Just make sure your board has no resources
4713	that are supposed to respond to that address! That code in
4714	start.S has been around a while and should work as is when
4715	you get the config right.
4716
4717	-Chris Hallinan
4718	DS4.COM, Inc.
4719
4720It is essential to remember this, since it has some impact on the C
4721code for the initialization procedures:
4722
4723* Initialized global data (data segment) is read-only. Do not attempt
4724  to write it.
4725
4726* Do not use any uninitialized global data (or implicitly initialized
4727  as zero data - BSS segment) at all - this is undefined, initiali-
4728  zation is performed later (when relocating to RAM).
4729
4730* Stack space is very limited. Avoid big data buffers or things like
4731  that.
4732
4733Having only the stack as writable memory limits means we cannot use
4734normal global data to share information between the code. But it
4735turned out that the implementation of U-Boot can be greatly
4736simplified by making a global data structure (gd_t) available to all
4737functions. We could pass a pointer to this data as argument to _all_
4738functions, but this would bloat the code. Instead we use a feature of
4739the GCC compiler (Global Register Variables) to share the data: we
4740place a pointer (gd) to the global data into a register which we
4741reserve for this purpose.
4742
4743When choosing a register for such a purpose we are restricted by the
4744relevant  (E)ABI  specifications for the current architecture, and by
4745GCC's implementation.
4746
4747For PowerPC, the following registers have specific use:
4748	R1:	stack pointer
4749	R2:	reserved for system use
4750	R3-R4:	parameter passing and return values
4751	R5-R10: parameter passing
4752	R13:	small data area pointer
4753	R30:	GOT pointer
4754	R31:	frame pointer
4755
4756	(U-Boot also uses R12 as internal GOT pointer. r12
4757	is a volatile register so r12 needs to be reset when
4758	going back and forth between asm and C)
4759
4760    ==> U-Boot will use R2 to hold a pointer to the global data
4761
4762    Note: on PPC, we could use a static initializer (since the
4763    address of the global data structure is known at compile time),
4764    but it turned out that reserving a register results in somewhat
4765    smaller code - although the code savings are not that big (on
4766    average for all boards 752 bytes for the whole U-Boot image,
4767    624 text + 127 data).
4768
4769On ARM, the following registers are used:
4770
4771	R0:	function argument word/integer result
4772	R1-R3:	function argument word
4773	R9:	platform specific
4774	R10:	stack limit (used only if stack checking is enabled)
4775	R11:	argument (frame) pointer
4776	R12:	temporary workspace
4777	R13:	stack pointer
4778	R14:	link register
4779	R15:	program counter
4780
4781    ==> U-Boot will use R9 to hold a pointer to the global data
4782
4783    Note: on ARM, only R_ARM_RELATIVE relocations are supported.
4784
4785On Nios II, the ABI is documented here:
4786	http://www.altera.com/literature/hb/nios2/n2cpu_nii51016.pdf
4787
4788    ==> U-Boot will use gp to hold a pointer to the global data
4789
4790    Note: on Nios II, we give "-G0" option to gcc and don't use gp
4791    to access small data sections, so gp is free.
4792
4793On NDS32, the following registers are used:
4794
4795	R0-R1:	argument/return
4796	R2-R5:	argument
4797	R15:	temporary register for assembler
4798	R16:	trampoline register
4799	R28:	frame pointer (FP)
4800	R29:	global pointer (GP)
4801	R30:	link register (LP)
4802	R31:	stack pointer (SP)
4803	PC:	program counter (PC)
4804
4805    ==> U-Boot will use R10 to hold a pointer to the global data
4806
4807NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
4808or current versions of GCC may "optimize" the code too much.
4809
4810On RISC-V, the following registers are used:
4811
4812	x0: hard-wired zero (zero)
4813	x1: return address (ra)
4814	x2:	stack pointer (sp)
4815	x3:	global pointer (gp)
4816	x4:	thread pointer (tp)
4817	x5:	link register (t0)
4818	x8:	frame pointer (fp)
4819	x10-x11:	arguments/return values (a0-1)
4820	x12-x17:	arguments (a2-7)
4821	x28-31:	 temporaries (t3-6)
4822	pc:	program counter (pc)
4823
4824    ==> U-Boot will use gp to hold a pointer to the global data
4825
4826Memory Management:
4827------------------
4828
4829U-Boot runs in system state and uses physical addresses, i.e. the
4830MMU is not used either for address mapping nor for memory protection.
4831
4832The available memory is mapped to fixed addresses using the memory
4833controller. In this process, a contiguous block is formed for each
4834memory type (Flash, SDRAM, SRAM), even when it consists of several
4835physical memory banks.
4836
4837U-Boot is installed in the first 128 kB of the first Flash bank (on
4838TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
4839booting and sizing and initializing DRAM, the code relocates itself
4840to the upper end of DRAM. Immediately below the U-Boot code some
4841memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
4842configuration setting]. Below that, a structure with global Board
4843Info data is placed, followed by the stack (growing downward).
4844
4845Additionally, some exception handler code is copied to the low 8 kB
4846of DRAM (0x00000000 ... 0x00001FFF).
4847
4848So a typical memory configuration with 16 MB of DRAM could look like
4849this:
4850
4851	0x0000 0000	Exception Vector code
4852	      :
4853	0x0000 1FFF
4854	0x0000 2000	Free for Application Use
4855	      :
4856	      :
4857
4858	      :
4859	      :
4860	0x00FB FF20	Monitor Stack (Growing downward)
4861	0x00FB FFAC	Board Info Data and permanent copy of global data
4862	0x00FC 0000	Malloc Arena
4863	      :
4864	0x00FD FFFF
4865	0x00FE 0000	RAM Copy of Monitor Code
4866	...		eventually: LCD or video framebuffer
4867	...		eventually: pRAM (Protected RAM - unchanged by reset)
4868	0x00FF FFFF	[End of RAM]
4869
4870
4871System Initialization:
4872----------------------
4873
4874In the reset configuration, U-Boot starts at the reset entry point
4875(on most PowerPC systems at address 0x00000100). Because of the reset
4876configuration for CS0# this is a mirror of the on board Flash memory.
4877To be able to re-map memory U-Boot then jumps to its link address.
4878To be able to implement the initialization code in C, a (small!)
4879initial stack is set up in the internal Dual Ported RAM (in case CPUs
4880which provide such a feature like), or in a locked part of the data
4881cache. After that, U-Boot initializes the CPU core, the caches and
4882the SIU.
4883
4884Next, all (potentially) available memory banks are mapped using a
4885preliminary mapping. For example, we put them on 512 MB boundaries
4886(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
4887on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
4888programmed for SDRAM access. Using the temporary configuration, a
4889simple memory test is run that determines the size of the SDRAM
4890banks.
4891
4892When there is more than one SDRAM bank, and the banks are of
4893different size, the largest is mapped first. For equal size, the first
4894bank (CS2#) is mapped first. The first mapping is always for address
48950x00000000, with any additional banks following immediately to create
4896contiguous memory starting from 0.
4897
4898Then, the monitor installs itself at the upper end of the SDRAM area
4899and allocates memory for use by malloc() and for the global Board
4900Info data; also, the exception vector code is copied to the low RAM
4901pages, and the final stack is set up.
4902
4903Only after this relocation will you have a "normal" C environment;
4904until that you are restricted in several ways, mostly because you are
4905running from ROM, and because the code will have to be relocated to a
4906new address in RAM.
4907
4908
4909U-Boot Porting Guide:
4910----------------------
4911
4912[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
4913list, October 2002]
4914
4915
4916int main(int argc, char *argv[])
4917{
4918	sighandler_t no_more_time;
4919
4920	signal(SIGALRM, no_more_time);
4921	alarm(PROJECT_DEADLINE - toSec (3 * WEEK));
4922
4923	if (available_money > available_manpower) {
4924		Pay consultant to port U-Boot;
4925		return 0;
4926	}
4927
4928	Download latest U-Boot source;
4929
4930	Subscribe to u-boot mailing list;
4931
4932	if (clueless)
4933		email("Hi, I am new to U-Boot, how do I get started?");
4934
4935	while (learning) {
4936		Read the README file in the top level directory;
4937		Read http://www.denx.de/twiki/bin/view/DULG/Manual;
4938		Read applicable doc/*.README;
4939		Read the source, Luke;
4940		/* find . -name "*.[chS]" | xargs grep -i <keyword> */
4941	}
4942
4943	if (available_money > toLocalCurrency ($2500))
4944		Buy a BDI3000;
4945	else
4946		Add a lot of aggravation and time;
4947
4948	if (a similar board exists) {	/* hopefully... */
4949		cp -a board/<similar> board/<myboard>
4950		cp include/configs/<similar>.h include/configs/<myboard>.h
4951	} else {
4952		Create your own board support subdirectory;
4953		Create your own board include/configs/<myboard>.h file;
4954	}
4955	Edit new board/<myboard> files
4956	Edit new include/configs/<myboard>.h
4957
4958	while (!accepted) {
4959		while (!running) {
4960			do {
4961				Add / modify source code;
4962			} until (compiles);
4963			Debug;
4964			if (clueless)
4965				email("Hi, I am having problems...");
4966		}
4967		Send patch file to the U-Boot email list;
4968		if (reasonable critiques)
4969			Incorporate improvements from email list code review;
4970		else
4971			Defend code as written;
4972	}
4973
4974	return 0;
4975}
4976
4977void no_more_time (int sig)
4978{
4979      hire_a_guru();
4980}
4981
4982
4983Coding Standards:
4984-----------------
4985
4986All contributions to U-Boot should conform to the Linux kernel
4987coding style; see the kernel coding style guide at
4988https://www.kernel.org/doc/html/latest/process/coding-style.html, and the
4989script "scripts/Lindent" in your Linux kernel source directory.
4990
4991Source files originating from a different project (for example the
4992MTD subsystem) are generally exempt from these guidelines and are not
4993reformatted to ease subsequent migration to newer versions of those
4994sources.
4995
4996Please note that U-Boot is implemented in C (and to some small parts in
4997Assembler); no C++ is used, so please do not use C++ style comments (//)
4998in your code.
4999
5000Please also stick to the following formatting rules:
5001- remove any trailing white space
5002- use TAB characters for indentation and vertical alignment, not spaces
5003- make sure NOT to use DOS '\r\n' line feeds
5004- do not add more than 2 consecutive empty lines to source files
5005- do not add trailing empty lines to source files
5006
5007Submissions which do not conform to the standards may be returned
5008with a request to reformat the changes.
5009
5010
5011Submitting Patches:
5012-------------------
5013
5014Since the number of patches for U-Boot is growing, we need to
5015establish some rules. Submissions which do not conform to these rules
5016may be rejected, even when they contain important and valuable stuff.
5017
5018Please see http://www.denx.de/wiki/U-Boot/Patches for details.
5019
5020Patches shall be sent to the u-boot mailing list <u-boot@lists.denx.de>;
5021see https://lists.denx.de/listinfo/u-boot
5022
5023When you send a patch, please include the following information with
5024it:
5025
5026* For bug fixes: a description of the bug and how your patch fixes
5027  this bug. Please try to include a way of demonstrating that the
5028  patch actually fixes something.
5029
5030* For new features: a description of the feature and your
5031  implementation.
5032
5033* A CHANGELOG entry as plaintext (separate from the patch)
5034
5035* For major contributions, add a MAINTAINERS file with your
5036  information and associated file and directory references.
5037
5038* When you add support for a new board, don't forget to add a
5039  maintainer e-mail address to the boards.cfg file, too.
5040
5041* If your patch adds new configuration options, don't forget to
5042  document these in the README file.
5043
5044* The patch itself. If you are using git (which is *strongly*
5045  recommended) you can easily generate the patch using the
5046  "git format-patch". If you then use "git send-email" to send it to
5047  the U-Boot mailing list, you will avoid most of the common problems
5048  with some other mail clients.
5049
5050  If you cannot use git, use "diff -purN OLD NEW". If your version of
5051  diff does not support these options, then get the latest version of
5052  GNU diff.
5053
5054  The current directory when running this command shall be the parent
5055  directory of the U-Boot source tree (i. e. please make sure that
5056  your patch includes sufficient directory information for the
5057  affected files).
5058
5059  We prefer patches as plain text. MIME attachments are discouraged,
5060  and compressed attachments must not be used.
5061
5062* If one logical set of modifications affects or creates several
5063  files, all these changes shall be submitted in a SINGLE patch file.
5064
5065* Changesets that contain different, unrelated modifications shall be
5066  submitted as SEPARATE patches, one patch per changeset.
5067
5068
5069Notes:
5070
5071* Before sending the patch, run the buildman script on your patched
5072  source tree and make sure that no errors or warnings are reported
5073  for any of the boards.
5074
5075* Keep your modifications to the necessary minimum: A patch
5076  containing several unrelated changes or arbitrary reformats will be
5077  returned with a request to re-formatting / split it.
5078
5079* If you modify existing code, make sure that your new code does not
5080  add to the memory footprint of the code ;-) Small is beautiful!
5081  When adding new features, these should compile conditionally only
5082  (using #ifdef), and the resulting code with the new feature
5083  disabled must not need more memory than the old code without your
5084  modification.
5085
5086* Remember that there is a size limit of 100 kB per message on the
5087  u-boot mailing list. Bigger patches will be moderated. If they are
5088  reasonable and not too big, they will be acknowledged. But patches
5089  bigger than the size limit should be avoided.
5090