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#
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# (C) Copyright 2000 - 2013
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# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
#
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# SPDX-License-Identifier:	GPL-2.0+
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#

Summary:
========

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This directory contains the source code for U-Boot, a boot loader for
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Embedded boards based on PowerPC, ARM, MIPS and several other
processors, which can be installed in a boot ROM and used to
initialize and test the hardware or to download and run application
code.
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The development of U-Boot is closely related to Linux: some parts of
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the source code originate in the Linux source tree, we have some
header files in common, and special provision has been made to
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support booting of Linux images.

Some attention has been paid to make this software easily
configurable and extendable. For instance, all monitor commands are
implemented with the same call interface, so that it's very easy to
add new commands. Also, instead of permanently adding rarely used
code (for instance hardware test utilities) to the monitor, you can
load and run it dynamically.


Status:
=======

In general, all boards for which a configuration option exists in the
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Makefile have been tested to some extent and can be considered
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"working". In fact, many of them are used in production systems.

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In case of problems see the CHANGELOG file to find out who contributed
the specific port. In addition, there are various MAINTAINERS files
scattered throughout the U-Boot source identifying the people or
companies responsible for various boards and subsystems.
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Note: As of August, 2010, there is no longer a CHANGELOG file in the
actual U-Boot source tree; however, it can be created dynamically
from the Git log using:
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	make CHANGELOG

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Where to get help:
==================

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In case you have questions about, problems with or contributions for
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U-Boot, you should send a message to the U-Boot mailing list at
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<u-boot@lists.denx.de>. There is also an archive of previous traffic
on the mailing list - please search the archive before asking FAQ's.
Please see http://lists.denx.de/pipermail/u-boot and
http://dir.gmane.org/gmane.comp.boot-loaders.u-boot
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Where to get source code:
=========================

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The U-Boot source code is maintained in the Git repository at
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git://www.denx.de/git/u-boot.git ; you can browse it online at
http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=summary

The "snapshot" links on this page allow you to download tarballs of
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any version you might be interested in. Official releases are also
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available for FTP download from the ftp://ftp.denx.de/pub/u-boot/
directory.

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Pre-built (and tested) images are available from
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ftp://ftp.denx.de/pub/u-boot/images/


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Where we come from:
===================

- start from 8xxrom sources
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- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
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- clean up code
- make it easier to add custom boards
- make it possible to add other [PowerPC] CPUs
- extend functions, especially:
  * Provide extended interface to Linux boot loader
  * S-Record download
  * network boot
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  * PCMCIA / CompactFlash / ATA disk / SCSI ... boot
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- create ARMBoot project (http://sourceforge.net/projects/armboot)
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- add other CPU families (starting with ARM)
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- create U-Boot project (http://sourceforge.net/projects/u-boot)
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- current project page: see http://www.denx.de/wiki/U-Boot
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Names and Spelling:
===================

The "official" name of this project is "Das U-Boot". The spelling
"U-Boot" shall be used in all written text (documentation, comments
in source files etc.). Example:

	This is the README file for the U-Boot project.

File names etc. shall be based on the string "u-boot". Examples:

	include/asm-ppc/u-boot.h

	#include <asm/u-boot.h>

Variable names, preprocessor constants etc. shall be either based on
the string "u_boot" or on "U_BOOT". Example:

	U_BOOT_VERSION		u_boot_logo
	IH_OS_U_BOOT		u_boot_hush_start
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Versioning:
===========

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Starting with the release in October 2008, the names of the releases
were changed from numerical release numbers without deeper meaning
into a time stamp based numbering. Regular releases are identified by
names consisting of the calendar year and month of the release date.
Additional fields (if present) indicate release candidates or bug fix
releases in "stable" maintenance trees.

Examples:
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	U-Boot v2009.11	    - Release November 2009
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	U-Boot v2009.11.1   - Release 1 in version November 2009 stable tree
	U-Boot v2010.09-rc1 - Release candiate 1 for September 2010 release
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Directory Hierarchy:
====================

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/arch			Architecture specific files
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  /arc			Files generic to ARC architecture
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  /arm			Files generic to ARM architecture
  /avr32		Files generic to AVR32 architecture
  /blackfin		Files generic to Analog Devices Blackfin architecture
  /m68k			Files generic to m68k architecture
  /microblaze		Files generic to microblaze architecture
  /mips			Files generic to MIPS architecture
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  /nds32		Files generic to NDS32 architecture
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  /nios2		Files generic to Altera NIOS2 architecture
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  /openrisc		Files generic to OpenRISC architecture
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  /powerpc		Files generic to PowerPC architecture
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  /sandbox		Files generic to HW-independent "sandbox"
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  /sh			Files generic to SH architecture
  /sparc		Files generic to SPARC architecture
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  /x86			Files generic to x86 architecture
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/api			Machine/arch independent API for external apps
/board			Board dependent files
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/cmd			U-Boot commands functions
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/common			Misc architecture independent functions
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/configs		Board default configuration files
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/disk			Code for disk drive partition handling
/doc			Documentation (don't expect too much)
/drivers		Commonly used device drivers
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/dts			Contains Makefile for building internal U-Boot fdt.
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/examples		Example code for standalone applications, etc.
/fs			Filesystem code (cramfs, ext2, jffs2, etc.)
/include		Header Files
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/lib			Library routines generic to all architectures
/Licenses		Various license files
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/net			Networking code
/post			Power On Self Test
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/scripts		Various build scripts and Makefiles
/test			Various unit test files
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/tools			Tools to build S-Record or U-Boot images, etc.
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Software Configuration:
=======================

Configuration is usually done using C preprocessor defines; the
rationale behind that is to avoid dead code whenever possible.

There are two classes of configuration variables:

* Configuration _OPTIONS_:
  These are selectable by the user and have names beginning with
  "CONFIG_".

* Configuration _SETTINGS_:
  These depend on the hardware etc. and should not be meddled with if
  you don't know what you're doing; they have names beginning with
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  "CONFIG_SYS_".
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Previously, all configuration was done by hand, which involved creating
symbolic links and editing configuration files manually. More recently,
U-Boot has added the Kbuild infrastructure used by the Linux kernel,
allowing you to use the "make menuconfig" command to configure your
build.
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Selection of Processor Architecture and Board Type:
---------------------------------------------------

For all supported boards there are ready-to-use default
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configurations available; just type "make <board_name>_defconfig".
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Example: For a TQM823L module type:

	cd u-boot
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	make TQM823L_defconfig
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Note: If you're looking for the default configuration file for a board
you're sure used to be there but is now missing, check the file
doc/README.scrapyard for a list of no longer supported boards.
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Sandbox Environment:
--------------------

U-Boot can be built natively to run on a Linux host using the 'sandbox'
board. This allows feature development which is not board- or architecture-
specific to be undertaken on a native platform. The sandbox is also used to
run some of U-Boot's tests.

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See board/sandbox/README.sandbox for more details.
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Board Initialisation Flow:
--------------------------

This is the intended start-up flow for boards. This should apply for both
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SPL and U-Boot proper (i.e. they both follow the same rules).

Note: "SPL" stands for "Secondary Program Loader," which is explained in
more detail later in this file.

At present, SPL mostly uses a separate code path, but the function names
and roles of each function are the same. Some boards or architectures
may not conform to this.  At least most ARM boards which use
CONFIG_SPL_FRAMEWORK conform to this.

Execution typically starts with an architecture-specific (and possibly
CPU-specific) start.S file, such as:

	- arch/arm/cpu/armv7/start.S
	- arch/powerpc/cpu/mpc83xx/start.S
	- arch/mips/cpu/start.S
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and so on. From there, three functions are called; the purpose and
limitations of each of these functions are described below.
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lowlevel_init():
	- purpose: essential init to permit execution to reach board_init_f()
	- no global_data or BSS
	- there is no stack (ARMv7 may have one but it will soon be removed)
	- must not set up SDRAM or use console
	- must only do the bare minimum to allow execution to continue to
		board_init_f()
	- this is almost never needed
	- return normally from this function

board_init_f():
	- purpose: set up the machine ready for running board_init_r():
		i.e. SDRAM and serial UART
	- global_data is available
	- stack is in SRAM
	- BSS is not available, so you cannot use global/static variables,
		only stack variables and global_data

	Non-SPL-specific notes:
	- dram_init() is called to set up DRAM. If already done in SPL this
		can do nothing

	SPL-specific notes:
	- you can override the entire board_init_f() function with your own
		version as needed.
	- preloader_console_init() can be called here in extremis
	- should set up SDRAM, and anything needed to make the UART work
	- these is no need to clear BSS, it will be done by crt0.S
	- must return normally from this function (don't call board_init_r()
		directly)

Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
this point the stack and global_data are relocated to below
CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
memory.

board_init_r():
	- purpose: main execution, common code
	- global_data is available
	- SDRAM is available
	- BSS is available, all static/global variables can be used
	- execution eventually continues to main_loop()

	Non-SPL-specific notes:
	- U-Boot is relocated to the top of memory and is now running from
		there.

	SPL-specific notes:
	- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
		CONFIG_SPL_STACK_R_ADDR points into SDRAM
	- preloader_console_init() can be called here - typically this is
		done by defining CONFIG_SPL_BOARD_INIT and then supplying a
		spl_board_init() function containing this call
	- loads U-Boot or (in falcon mode) Linux



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Configuration Options:
----------------------

Configuration depends on the combination of board and CPU type; all
such information is kept in a configuration file
"include/configs/<board_name>.h".

Example: For a TQM823L module, all configuration settings are in
"include/configs/TQM823L.h".


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Many of the options are named exactly as the corresponding Linux
kernel configuration options. The intention is to make it easier to
build a config tool - later.


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The following options need to be configured:

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- CPU Type:	Define exactly one, e.g. CONFIG_MPC85XX.

- Board Type:	Define exactly one, e.g. CONFIG_MPC8540ADS.
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- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
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		Define exactly one, e.g. CONFIG_ATSTK1002
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- Marvell Family Member
		CONFIG_SYS_MVFS		- define it if you want to enable
					  multiple fs option at one time
					  for marvell soc family

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- 8xx CPU Options: (if using an MPC8xx CPU)
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		CONFIG_8xx_GCLK_FREQ	- deprecated: CPU clock if
					  get_gclk_freq() cannot work
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					  e.g. if there is no 32KHz
					  reference PIT/RTC clock
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		CONFIG_8xx_OSCLK	- PLL input clock (either EXTCLK
					  or XTAL/EXTAL)
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- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
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		CONFIG_SYS_8xx_CPUCLK_MIN
		CONFIG_SYS_8xx_CPUCLK_MAX
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		CONFIG_8xx_CPUCLK_DEFAULT
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			See doc/README.MPC866

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		CONFIG_SYS_MEASURE_CPUCLK
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		Define this to measure the actual CPU clock instead
		of relying on the correctness of the configured
		values. Mostly useful for board bringup to make sure
		the PLL is locked at the intended frequency. Note
		that this requires a (stable) reference clock (32 kHz
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		RTC clock or CONFIG_SYS_8XX_XIN)
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		CONFIG_SYS_DELAYED_ICACHE

		Define this option if you want to enable the
		ICache only when Code runs from RAM.

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- 85xx CPU Options:
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		CONFIG_SYS_PPC64

		Specifies that the core is a 64-bit PowerPC implementation (implements
		the "64" category of the Power ISA). This is necessary for ePAPR
		compliance, among other possible reasons.

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		CONFIG_SYS_FSL_TBCLK_DIV

		Defines the core time base clock divider ratio compared to the
		system clock.  On most PQ3 devices this is 8, on newer QorIQ
		devices it can be 16 or 32.  The ratio varies from SoC to Soc.

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		CONFIG_SYS_FSL_PCIE_COMPAT

		Defines the string to utilize when trying to match PCIe device
		tree nodes for the given platform.

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		CONFIG_SYS_PPC_E500_DEBUG_TLB

		Enables a temporary TLB entry to be used during boot to work
		around limitations in e500v1 and e500v2 external debugger
		support. This reduces the portions of the boot code where
		breakpoints and single stepping do not work.  The value of this
		symbol should be set to the TLB1 entry to be used for this
		purpose.

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		CONFIG_SYS_FSL_ERRATUM_A004510

		Enables a workaround for erratum A004510.  If set,
		then CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV and
		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY must be set.

		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV
		CONFIG_SYS_FSL_ERRATUM_A004510_SVR_REV2 (optional)

		Defines one or two SoC revisions (low 8 bits of SVR)
		for which the A004510 workaround should be applied.

		The rest of SVR is either not relevant to the decision
		of whether the erratum is present (e.g. p2040 versus
		p2041) or is implied by the build target, which controls
		whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.

		See Freescale App Note 4493 for more information about
		this erratum.

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		CONFIG_A003399_NOR_WORKAROUND
		Enables a workaround for IFC erratum A003399. It is only
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		required during NOR boot.
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		CONFIG_A008044_WORKAROUND
		Enables a workaround for T1040/T1042 erratum A008044. It is only
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		required during NAND boot and valid for Rev 1.0 SoC revision
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		CONFIG_SYS_FSL_CORENET_SNOOPVEC_COREONLY

		This is the value to write into CCSR offset 0x18600
		according to the A004510 workaround.

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		CONFIG_SYS_FSL_DSP_DDR_ADDR
		This value denotes start offset of DDR memory which is
		connected exclusively to the DSP cores.

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		CONFIG_SYS_FSL_DSP_M2_RAM_ADDR
		This value denotes start offset of M2 memory
		which is directly connected to the DSP core.

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		CONFIG_SYS_FSL_DSP_M3_RAM_ADDR
		This value denotes start offset of M3 memory which is directly
		connected to the DSP core.

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		CONFIG_SYS_FSL_DSP_CCSRBAR_DEFAULT
		This value denotes start offset of DSP CCSR space.

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		CONFIG_SYS_FSL_SINGLE_SOURCE_CLK
		Single Source Clock is clocking mode present in some of FSL SoC's.
		In this mode, a single differential clock is used to supply
		clocks to the sysclock, ddrclock and usbclock.

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		CONFIG_SYS_CPC_REINIT_F
		This CONFIG is defined when the CPC is configured as SRAM at the
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		time of U-Boot entry and is required to be re-initialized.
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		CONFIG_DEEP_SLEEP
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		Indicates this SoC supports deep sleep feature. If deep sleep is
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		supported, core will start to execute uboot when wakes up.

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- Generic CPU options:
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		CONFIG_SYS_GENERIC_GLOBAL_DATA
		Defines global data is initialized in generic board board_init_f().
		If this macro is defined, global data is created and cleared in
		generic board board_init_f(). Without this macro, architecture/board
		should initialize global data before calling board_init_f().

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		CONFIG_SYS_BIG_ENDIAN, CONFIG_SYS_LITTLE_ENDIAN

		Defines the endianess of the CPU. Implementation of those
		values is arch specific.

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		CONFIG_SYS_FSL_DDR
		Freescale DDR driver in use. This type of DDR controller is
		found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
		SoCs.

		CONFIG_SYS_FSL_DDR_ADDR
		Freescale DDR memory-mapped register base.

		CONFIG_SYS_FSL_DDR_EMU
		Specify emulator support for DDR. Some DDR features such as
		deskew training are not available.

		CONFIG_SYS_FSL_DDRC_GEN1
		Freescale DDR1 controller.

		CONFIG_SYS_FSL_DDRC_GEN2
		Freescale DDR2 controller.

		CONFIG_SYS_FSL_DDRC_GEN3
		Freescale DDR3 controller.

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		CONFIG_SYS_FSL_DDRC_GEN4
		Freescale DDR4 controller.

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		CONFIG_SYS_FSL_DDRC_ARM_GEN3
		Freescale DDR3 controller for ARM-based SoCs.

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		CONFIG_SYS_FSL_DDR1
		Board config to use DDR1. It can be enabled for SoCs with
		Freescale DDR1 or DDR2 controllers, depending on the board
		implemetation.

		CONFIG_SYS_FSL_DDR2
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		Board config to use DDR2. It can be enabled for SoCs with
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		Freescale DDR2 or DDR3 controllers, depending on the board
		implementation.

		CONFIG_SYS_FSL_DDR3
		Board config to use DDR3. It can be enabled for SoCs with
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		Freescale DDR3 or DDR3L controllers.

		CONFIG_SYS_FSL_DDR3L
		Board config to use DDR3L. It can be enabled for SoCs with
		DDR3L controllers.

		CONFIG_SYS_FSL_DDR4
		Board config to use DDR4. It can be enabled for SoCs with
		DDR4 controllers.
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		CONFIG_SYS_FSL_IFC_BE
		Defines the IFC controller register space as Big Endian

		CONFIG_SYS_FSL_IFC_LE
		Defines the IFC controller register space as Little Endian

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		CONFIG_SYS_FSL_PBL_PBI
		It enables addition of RCW (Power on reset configuration) in built image.
		Please refer doc/README.pblimage for more details

		CONFIG_SYS_FSL_PBL_RCW
		It adds PBI(pre-boot instructions) commands in u-boot build image.
		PBI commands can be used to configure SoC before it starts the execution.
		Please refer doc/README.pblimage for more details

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		CONFIG_SPL_FSL_PBL
		It adds a target to create boot binary having SPL binary in PBI format
		concatenated with u-boot binary.

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		CONFIG_SYS_FSL_DDR_BE
		Defines the DDR controller register space as Big Endian

		CONFIG_SYS_FSL_DDR_LE
		Defines the DDR controller register space as Little Endian

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		CONFIG_SYS_FSL_DDR_SDRAM_BASE_PHY
		Physical address from the view of DDR controllers. It is the
		same as CONFIG_SYS_DDR_SDRAM_BASE for  all Power SoCs. But
		it could be different for ARM SoCs.

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		CONFIG_SYS_FSL_DDR_INTLV_256B
		DDR controller interleaving on 256-byte. This is a special
		interleaving mode, handled by Dickens for Freescale layerscape
		SoCs with ARM core.

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		CONFIG_SYS_FSL_DDR_MAIN_NUM_CTRLS
		Number of controllers used as main memory.

		CONFIG_SYS_FSL_OTHER_DDR_NUM_CTRLS
		Number of controllers used for other than main memory.

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		CONFIG_SYS_FSL_HAS_DP_DDR
		Defines the SoC has DP-DDR used for DPAA.

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		CONFIG_SYS_FSL_SEC_BE
		Defines the SEC controller register space as Big Endian

		CONFIG_SYS_FSL_SEC_LE
		Defines the SEC controller register space as Little Endian

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- MIPS CPU options:
		CONFIG_SYS_INIT_SP_OFFSET

		Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
		pointer. This is needed for the temporary stack before
		relocation.

		CONFIG_SYS_MIPS_CACHE_MODE

		Cache operation mode for the MIPS CPU.
		See also arch/mips/include/asm/mipsregs.h.
		Possible values are:
			CONF_CM_CACHABLE_NO_WA
			CONF_CM_CACHABLE_WA
			CONF_CM_UNCACHED
			CONF_CM_CACHABLE_NONCOHERENT
			CONF_CM_CACHABLE_CE
			CONF_CM_CACHABLE_COW
			CONF_CM_CACHABLE_CUW
			CONF_CM_CACHABLE_ACCELERATED

		CONFIG_SYS_XWAY_EBU_BOOTCFG

		Special option for Lantiq XWAY SoCs for booting from NOR flash.
		See also arch/mips/cpu/mips32/start.S.

		CONFIG_XWAY_SWAP_BYTES

		Enable compilation of tools/xway-swap-bytes needed for Lantiq
		XWAY SoCs for booting from NOR flash. The U-Boot image needs to
		be swapped if a flash programmer is used.

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- ARM options:
		CONFIG_SYS_EXCEPTION_VECTORS_HIGH

		Select high exception vectors of the ARM core, e.g., do not
		clear the V bit of the c1 register of CP15.

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		CONFIG_SYS_THUMB_BUILD

		Use this flag to build U-Boot using the Thumb instruction
		set for ARM architectures. Thumb instruction set provides
		better code density. For ARM architectures that support
		Thumb2 this flag will result in Thumb2 code generated by
		GCC.

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		CONFIG_ARM_ERRATA_716044
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		CONFIG_ARM_ERRATA_742230
		CONFIG_ARM_ERRATA_743622
		CONFIG_ARM_ERRATA_751472
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		CONFIG_ARM_ERRATA_761320
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		CONFIG_ARM_ERRATA_773022
		CONFIG_ARM_ERRATA_774769
		CONFIG_ARM_ERRATA_794072
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		If set, the workarounds for these ARM errata are applied early
		during U-Boot startup. Note that these options force the
		workarounds to be applied; no CPU-type/version detection
		exists, unlike the similar options in the Linux kernel. Do not
		set these options unless they apply!

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		COUNTER_FREQUENCY
		Generic timer clock source frequency.

		COUNTER_FREQUENCY_REAL
		Generic timer clock source frequency if the real clock is
		different from COUNTER_FREQUENCY, and can only be determined
		at run time.

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		NOTE: The following can be machine specific errata. These
		do have ability to provide rudimentary version and machine
		specific checks, but expect no product checks.
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		CONFIG_ARM_ERRATA_430973
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		CONFIG_ARM_ERRATA_454179
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		CONFIG_ARM_ERRATA_621766
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		CONFIG_ARM_ERRATA_798870
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		CONFIG_ARM_ERRATA_801819
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- Tegra SoC options:
		CONFIG_TEGRA_SUPPORT_NON_SECURE

		Support executing U-Boot in non-secure (NS) mode. Certain
		impossible actions will be skipped if the CPU is in NS mode,
		such as ARM architectural timer initialization.

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- Linux Kernel Interface:
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		CONFIG_CLOCKS_IN_MHZ

		U-Boot stores all clock information in Hz
		internally. For binary compatibility with older Linux
		kernels (which expect the clocks passed in the
		bd_info data to be in MHz) the environment variable
		"clocks_in_mhz" can be defined so that U-Boot
		converts clock data to MHZ before passing it to the
		Linux kernel.
		When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
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		"clocks_in_mhz=1" is automatically included in the
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		default environment.

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		CONFIG_MEMSIZE_IN_BYTES		[relevant for MIPS only]

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		When transferring memsize parameter to Linux, some versions
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		expect it to be in bytes, others in MB.
		Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.

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		CONFIG_OF_LIBFDT
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		New kernel versions are expecting firmware settings to be
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		passed using flattened device trees (based on open firmware
		concepts).

		CONFIG_OF_LIBFDT
		 * New libfdt-based support
		 * Adds the "fdt" command
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		 * The bootm command automatically updates the fdt
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		OF_CPU - The proper name of the cpus node (only required for
			MPC512X and MPC5xxx based boards).
		OF_SOC - The proper name of the soc node (only required for
			MPC512X and MPC5xxx based boards).
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		OF_TBCLK - The timebase frequency.
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		OF_STDOUT_PATH - The path to the console device
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		boards with QUICC Engines require OF_QE to set UCC MAC
		addresses
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		CONFIG_OF_BOARD_SETUP

		Board code has addition modification that it wants to make
		to the flat device tree before handing it off to the kernel
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		CONFIG_OF_SYSTEM_SETUP

		Other code has addition modification that it wants to make
		to the flat device tree before handing it off to the kernel.
		This causes ft_system_setup() to be called before booting
		the kernel.

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		CONFIG_OF_IDE_FIXUP

		U-Boot can detect if an IDE device is present or not.
		If not, and this new config option is activated, U-Boot
		removes the ATA node from the DTS before booting Linux,
		so the Linux IDE driver does not probe the device and
		crash. This is needed for buggy hardware (uc101) where
		no pull down resistor is connected to the signal IDE5V_DD7.

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		CONFIG_MACH_TYPE	[relevant for ARM only][mandatory]

		This setting is mandatory for all boards that have only one
		machine type and must be used to specify the machine type
		number as it appears in the ARM machine registry
		(see http://www.arm.linux.org.uk/developer/machines/).
		Only boards that have multiple machine types supported
		in a single configuration file and the machine type is
		runtime discoverable, do not have to use this setting.

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- vxWorks boot parameters:

		bootvx constructs a valid bootline using the following
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		environments variables: bootdev, bootfile, ipaddr, netmask,
		serverip, gatewayip, hostname, othbootargs.
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		It loads the vxWorks image pointed bootfile.

		Note: If a "bootargs" environment is defined, it will overwride
		the defaults discussed just above.

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- Cache Configuration:
		CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
		CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
		CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot

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- Cache Configuration for ARM:
		CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
				      controller
		CONFIG_SYS_PL310_BASE - Physical base address of PL310
					controller register space

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- Serial Ports:
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		CONFIG_PL010_SERIAL
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		Define this if you want support for Amba PrimeCell PL010 UARTs.

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		CONFIG_PL011_SERIAL
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		Define this if you want support for Amba PrimeCell PL011 UARTs.

		CONFIG_PL011_CLOCK

		If you have Amba PrimeCell PL011 UARTs, set this variable to
		the clock speed of the UARTs.

		CONFIG_PL01x_PORTS

		If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
		define this to a list of base addresses for each (supported)
		port. See e.g. include/configs/versatile.h

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		CONFIG_SERIAL_HW_FLOW_CONTROL

		Define this variable to enable hw flow control in serial driver.
		Current user of this option is drivers/serial/nsl16550.c driver
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- Console Interface:
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		Depending on board, define exactly one serial port
		(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
		CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
		console by defining CONFIG_8xx_CONS_NONE
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		Note: if CONFIG_8xx_CONS_NONE is defined, the serial
		port routines must be defined elsewhere
		(i.e. serial_init(), serial_getc(), ...)

- Console Baudrate:
		CONFIG_BAUDRATE - in bps
		Select one of the baudrates listed in
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		CONFIG_SYS_BAUDRATE_TABLE, see below.
		CONFIG_SYS_BRGCLK_PRESCALE, baudrate prescale
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- Console Rx buffer length
		With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
		the maximum receive buffer length for the SMC.
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		This option is actual only for 82xx and 8xx possible.
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		If using CONFIG_SYS_SMC_RXBUFLEN also CONFIG_SYS_MAXIDLE
		must be defined, to setup the maximum idle timeout for
		the SMC.

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- Autoboot Command:
		CONFIG_BOOTCOMMAND
		Only needed when CONFIG_BOOTDELAY is enabled;
		define a command string that is automatically executed
		when no character is read on the console interface
		within "Boot Delay" after reset.

		CONFIG_BOOTARGS
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		This can be used to pass arguments to the bootm
		command. The value of CONFIG_BOOTARGS goes into the
		environment value "bootargs".
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		CONFIG_RAMBOOT and CONFIG_NFSBOOT
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		The value of these goes into the environment as
		"ramboot" and "nfsboot" respectively, and can be used
		as a convenience, when switching between booting from
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		RAM and NFS.
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- Bootcount:
		CONFIG_BOOTCOUNT_LIMIT
		Implements a mechanism for detecting a repeating reboot
		cycle, see:
		http://www.denx.de/wiki/view/DULG/UBootBootCountLimit

		CONFIG_BOOTCOUNT_ENV
		If no softreset save registers are found on the hardware
		"bootcount" is stored in the environment. To prevent a
		saveenv on all reboots, the environment variable
		"upgrade_available" is used. If "upgrade_available" is
		0, "bootcount" is always 0, if "upgrade_available" is
		1 "bootcount" is incremented in the environment.
		So the Userspace Applikation must set the "upgrade_available"
		and "bootcount" variable to 0, if a boot was successfully.

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- Pre-Boot Commands:
		CONFIG_PREBOOT

		When this option is #defined, the existence of the
		environment variable "preboot" will be checked
		immediately before starting the CONFIG_BOOTDELAY
		countdown and/or running the auto-boot command resp.
		entering interactive mode.

		This feature is especially useful when "preboot" is
		automatically generated or modified. For an example
		see the LWMON board specific code: here "preboot" is
		modified when the user holds down a certain
		combination of keys on the (special) keyboard when
		booting the systems

- Serial Download Echo Mode:
		CONFIG_LOADS_ECHO
		If defined to 1, all characters received during a
		serial download (using the "loads" command) are
		echoed back. This might be needed by some terminal
		emulations (like "cu"), but may as well just take
		time on others. This setting #define's the initial
		value of the "loads_echo" environment variable.

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- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
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		CONFIG_KGDB_BAUDRATE
		Select one of the baudrates listed in
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		CONFIG_SYS_BAUDRATE_TABLE, see below.
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- Monitor Functions:
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		Monitor commands can be included or excluded
		from the build by using the #include files
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		<config_cmd_all.h> and #undef'ing unwanted
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		commands, or adding #define's for wanted commands.
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		The default command configuration includes all commands
		except those marked below with a "*".

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		CONFIG_CMD_AES		  AES 128 CBC encrypt/decrypt
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		CONFIG_CMD_ASKENV	* ask for env variable
		CONFIG_CMD_BDI		  bdinfo
		CONFIG_CMD_BEDBUG	* Include BedBug Debugger
		CONFIG_CMD_BMP		* BMP support
		CONFIG_CMD_BSP		* Board specific commands
		CONFIG_CMD_BOOTD	  bootd
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		CONFIG_CMD_BOOTI	* ARM64 Linux kernel Image support
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		CONFIG_CMD_CACHE	* icache, dcache
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		CONFIG_CMD_CLK   	* clock command support
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		CONFIG_CMD_CONSOLE	  coninfo
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		CONFIG_CMD_CRC32	* crc32
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		CONFIG_CMD_DATE		* support for RTC, date/time...
		CONFIG_CMD_DHCP		* DHCP support
		CONFIG_CMD_DIAG		* Diagnostics
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		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
		CONFIG_CMD_DS4510_INFO	* ds4510 I2C info command
		CONFIG_CMD_DS4510_MEM	* ds4510 I2C eeprom/sram commansd
		CONFIG_CMD_DS4510_RST	* ds4510 I2C rst command
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		CONFIG_CMD_DTT		* Digital Therm and Thermostat
		CONFIG_CMD_ECHO		  echo arguments
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		CONFIG_CMD_EDITENV	  edit env variable
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		CONFIG_CMD_EEPROM	* EEPROM read/write support
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		CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
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		CONFIG_CMD_ELF		* bootelf, bootvx
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		CONFIG_CMD_ENV_CALLBACK	* display details about env callbacks
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		CONFIG_CMD_ENV_FLAGS	* display details about env flags
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		CONFIG_CMD_ENV_EXISTS	* check existence of env variable
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		CONFIG_CMD_EXPORTENV	* export the environment
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		CONFIG_CMD_EXT2		* ext2 command support
		CONFIG_CMD_EXT4		* ext4 command support
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		CONFIG_CMD_FS_GENERIC	* filesystem commands (e.g. load, ls)
					  that work for multiple fs types
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		CONFIG_CMD_FS_UUID	* Look up a filesystem UUID
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		CONFIG_CMD_SAVEENV	  saveenv
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		CONFIG_CMD_FDC		* Floppy Disk Support
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		CONFIG_CMD_FAT		* FAT command support
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		CONFIG_CMD_FLASH	  flinfo, erase, protect
		CONFIG_CMD_FPGA		  FPGA device initialization support
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		CONFIG_CMD_FUSE		* Device fuse support
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		CONFIG_CMD_GETTIME	* Get time since boot
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		CONFIG_CMD_GO		* the 'go' command (exec code)
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		CONFIG_CMD_GREPENV	* search environment
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		CONFIG_CMD_HASH		* calculate hash / digest
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		CONFIG_CMD_I2C		* I2C serial bus support
		CONFIG_CMD_IDE		* IDE harddisk support
		CONFIG_CMD_IMI		  iminfo
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		CONFIG_CMD_IMLS		  List all images found in NOR flash
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		CONFIG_CMD_IMLS_NAND	* List all images found in NAND flash
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		CONFIG_CMD_IMMAP	* IMMR dump support
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		CONFIG_CMD_IOTRACE	* I/O tracing for debugging
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		CONFIG_CMD_IMPORTENV	* import an environment
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		CONFIG_CMD_INI		* import data from an ini file into the env
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		CONFIG_CMD_IRQ		* irqinfo
		CONFIG_CMD_ITEST	  Integer/string test of 2 values
		CONFIG_CMD_JFFS2	* JFFS2 Support
		CONFIG_CMD_KGDB		* kgdb
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		CONFIG_CMD_LDRINFO	* ldrinfo (display Blackfin loader)
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		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
					  (169.254.*.*)
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		CONFIG_CMD_LOADB	  loadb
		CONFIG_CMD_LOADS	  loads
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		CONFIG_CMD_MD5SUM	* print md5 message digest
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					  (requires CONFIG_CMD_MEMORY and CONFIG_MD5)
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		CONFIG_CMD_MEMINFO	* Display detailed memory information
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		CONFIG_CMD_MEMORY	  md, mm, nm, mw, cp, cmp, crc, base,
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					  loop, loopw
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		CONFIG_CMD_MEMTEST	* mtest
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		CONFIG_CMD_MISC		  Misc functions like sleep etc
		CONFIG_CMD_MMC		* MMC memory mapped support
		CONFIG_CMD_MII		* MII utility commands
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		CONFIG_CMD_MTDPARTS	* MTD partition support
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		CONFIG_CMD_NAND		* NAND support
		CONFIG_CMD_NET		  bootp, tftpboot, rarpboot
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		CONFIG_CMD_NFS		  NFS support
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		CONFIG_CMD_PCA953X	* PCA953x I2C gpio commands
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		CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
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		CONFIG_CMD_PCI		* pciinfo
		CONFIG_CMD_PCMCIA		* PCMCIA support
		CONFIG_CMD_PING		* send ICMP ECHO_REQUEST to network
					  host
		CONFIG_CMD_PORTIO	* Port I/O
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		CONFIG_CMD_READ		* Read raw data from partition
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		CONFIG_CMD_REGINFO	* Register dump
		CONFIG_CMD_RUN		  run command in env variable
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		CONFIG_CMD_SANDBOX	* sb command to access sandbox features
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		CONFIG_CMD_SAVES	* save S record dump
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		CONFIG_SCSI		* SCSI Support
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		CONFIG_CMD_SDRAM	* print SDRAM configuration information
					  (requires CONFIG_CMD_I2C)
		CONFIG_CMD_SETGETDCR	  Support for DCR Register access
					  (4xx only)
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		CONFIG_CMD_SF		* Read/write/erase SPI NOR flash
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		CONFIG_CMD_SHA1SUM	* print sha1 memory digest
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					  (requires CONFIG_CMD_MEMORY)
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		CONFIG_CMD_SOFTSWITCH	* Soft switch setting command for BF60x
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		CONFIG_CMD_SOURCE	  "source" command Support
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		CONFIG_CMD_SPI		* SPI serial bus support
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		CONFIG_CMD_TFTPSRV	* TFTP transfer in server mode
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		CONFIG_CMD_TFTPPUT	* TFTP put command (upload)
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		CONFIG_CMD_TIME		* run command and report execution time (ARM specific)
		CONFIG_CMD_TIMER	* access to the system tick timer
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		CONFIG_CMD_USB		* USB support
		CONFIG_CMD_CDP		* Cisco Discover Protocol support
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		CONFIG_CMD_MFSL		* Microblaze FSL support
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		CONFIG_CMD_XIMG		  Load part of Multi Image
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		CONFIG_CMD_UUID		* Generate random UUID or GUID string
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		EXAMPLE: If you want all functions except of network
		support you can write:

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		#include "config_cmd_all.h"
		#undef CONFIG_CMD_NET
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	Other Commands:
		fdt (flattened device tree) command: CONFIG_OF_LIBFDT
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	Note:	Don't enable the "icache" and "dcache" commands
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		(configuration option CONFIG_CMD_CACHE) unless you know
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		what you (and your U-Boot users) are doing. Data
		cache cannot be enabled on systems like the 8xx or
		8260 (where accesses to the IMMR region must be
		uncached), and it cannot be disabled on all other
		systems where we (mis-) use the data cache to hold an
		initial stack and some data.
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		XXX - this list needs to get updated!

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- Removal of commands
		If no commands are needed to boot, you can disable
		CONFIG_CMDLINE to remove them. In this case, the command line
		will not be available, and when U-Boot wants to execute the
		boot command (on start-up) it will call board_run_command()
		instead. This can reduce image size significantly for very
		simple boot procedures.

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- Regular expression support:
		CONFIG_REGEX
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		If this variable is defined, U-Boot is linked against
		the SLRE (Super Light Regular Expression) library,
		which adds regex support to some commands, as for
		example "env grep" and "setexpr".
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- Device tree:
		CONFIG_OF_CONTROL
		If this variable is defined, U-Boot will use a device tree
		to configure its devices, instead of relying on statically
		compiled #defines in the board file. This option is
		experimental and only available on a few boards. The device
		tree is available in the global data as gd->fdt_blob.

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		U-Boot needs to get its device tree from somewhere. This can
		be done using one of the two options below:
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		CONFIG_OF_EMBED
		If this variable is defined, U-Boot will embed a device tree
		binary in its image. This device tree file should be in the
		board directory and called <soc>-<board>.dts. The binary file
		is then picked up in board_init_f() and made available through
		the global data structure as gd->blob.
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		CONFIG_OF_SEPARATE
		If this variable is defined, U-Boot will build a device tree
		binary. It will be called u-boot.dtb. Architecture-specific
		code will locate it at run-time. Generally this works by:

			cat u-boot.bin u-boot.dtb >image.bin

		and in fact, U-Boot does this for you, creating a file called
		u-boot-dtb.bin which is useful in the common case. You can
		still use the individual files if you need something more
		exotic.

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- Watchdog:
		CONFIG_WATCHDOG
		If this variable is defined, it enables watchdog
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		support for the SoC. There must be support in the SoC
		specific code for a watchdog. For the 8xx and 8260
		CPUs, the SIU Watchdog feature is enabled in the SYPCR
		register.  When supported for a specific SoC is
		available, then no further board specific code should
		be needed to use it.

		CONFIG_HW_WATCHDOG
		When using a watchdog circuitry external to the used
		SoC, then define this variable and provide board
		specific code for the "hw_watchdog_reset" function.
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		CONFIG_AT91_HW_WDT_TIMEOUT
		specify the timeout in seconds. default 2 seconds.

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- U-Boot Version:
		CONFIG_VERSION_VARIABLE
		If this variable is defined, an environment variable
		named "ver" is created by U-Boot showing the U-Boot
		version as printed by the "version" command.
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		Any change to this variable will be reverted at the
		next reset.
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- Real-Time Clock:

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		When CONFIG_CMD_DATE is selected, the type of the RTC
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		has to be selected, too. Define exactly one of the
		following options:

		CONFIG_RTC_MPC8xx	- use internal RTC of MPC8xx
		CONFIG_RTC_PCF8563	- use Philips PCF8563 RTC
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		CONFIG_RTC_MC13XXX	- use MC13783 or MC13892 RTC
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		CONFIG_RTC_MC146818	- use MC146818 RTC
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		CONFIG_RTC_DS1307	- use Maxim, Inc. DS1307 RTC
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		CONFIG_RTC_DS1337	- use Maxim, Inc. DS1337 RTC
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		CONFIG_RTC_DS1338	- use Maxim, Inc. DS1338 RTC
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		CONFIG_RTC_DS1339	- use Maxim, Inc. DS1339 RTC
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		CONFIG_RTC_DS164x	- use Dallas DS164x RTC
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		CONFIG_RTC_ISL1208	- use Intersil ISL1208 RTC
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		CONFIG_RTC_MAX6900	- use Maxim, Inc. MAX6900 RTC
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		CONFIG_SYS_RTC_DS1337_NOOSC	- Turn off the OSC output for DS1337
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		CONFIG_SYS_RV3029_TCR	- enable trickle charger on
					  RV3029 RTC.
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		Note that if the RTC uses I2C, then the I2C interface
		must also be configured. See I2C Support, below.

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- GPIO Support:
		CONFIG_PCA953X		- use NXP's PCA953X series I2C GPIO

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		The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
		chip-ngpio pairs that tell the PCA953X driver the number of
		pins supported by a particular chip.

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		Note that if the GPIO device uses I2C, then the I2C interface
		must also be configured. See I2C Support, below.

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- I/O tracing:
		When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
		accesses and can checksum them or write a list of them out
		to memory. See the 'iotrace' command for details. This is
		useful for testing device drivers since it can confirm that
		the driver behaves the same way before and after a code
		change. Currently this is supported on sandbox and arm. To
		add support for your architecture, add '#include <iotrace.h>'
		to the bottom of arch/<arch>/include/asm/io.h and test.

		Example output from the 'iotrace stats' command is below.
		Note that if the trace buffer is exhausted, the checksum will
		still continue to operate.

			iotrace is enabled
			Start:  10000000	(buffer start address)
			Size:   00010000	(buffer size)
			Offset: 00000120	(current buffer offset)
			Output: 10000120	(start + offset)
			Count:  00000018	(number of trace records)
			CRC32:  9526fb66	(CRC32 of all trace records)

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- Timestamp Support:

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		When CONFIG_TIMESTAMP is selected, the timestamp
		(date and time) of an image is printed by image
		commands like bootm or iminfo. This option is
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		automatically enabled when you select CONFIG_CMD_DATE .
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- Partition Labels (disklabels) Supported:
		Zero or more of the following:
		CONFIG_MAC_PARTITION   Apple's MacOS partition table.
		CONFIG_DOS_PARTITION   MS Dos partition table, traditional on the
				       Intel architecture, USB sticks, etc.
		CONFIG_ISO_PARTITION   ISO partition table, used on CDROM etc.
		CONFIG_EFI_PARTITION   GPT partition table, common when EFI is the
				       bootloader.  Note 2TB partition limit; see
				       disk/part_efi.c
		CONFIG_MTD_PARTITIONS  Memory Technology Device partition table.
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		If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
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		CONFIG_SCSI) you must configure support for at
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		least one non-MTD partition type as well.
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- IDE Reset method:
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		CONFIG_IDE_RESET_ROUTINE - this is defined in several
		board configurations files but used nowhere!
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		CONFIG_IDE_RESET - is this is defined, IDE Reset will
		be performed by calling the function
			ide_set_reset(int reset)
		which has to be defined in a board specific file
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- ATAPI Support:
		CONFIG_ATAPI

		Set this to enable ATAPI support.

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- LBA48 Support
		CONFIG_LBA48

		Set this to enable support for disks larger than 137GB
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		Also look at CONFIG_SYS_64BIT_LBA.
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		Whithout these , LBA48 support uses 32bit variables and will 'only'
		support disks up to 2.1TB.

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		CONFIG_SYS_64BIT_LBA:
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			When enabled, makes the IDE subsystem use 64bit sector addresses.
			Default is 32bit.

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- SCSI Support:
		At the moment only there is only support for the
		SYM53C8XX SCSI controller; define
		CONFIG_SCSI_SYM53C8XX to enable it.

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		CONFIG_SYS_SCSI_MAX_LUN [8], CONFIG_SYS_SCSI_MAX_SCSI_ID [7] and
		CONFIG_SYS_SCSI_MAX_DEVICE [CONFIG_SYS_SCSI_MAX_SCSI_ID *
		CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
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		maximum numbers of LUNs, SCSI ID's and target
		devices.
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		CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
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		The environment variable 'scsidevs' is set to the number of
		SCSI devices found during the last scan.
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- NETWORK Support (PCI):
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		CONFIG_E1000
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		Support for Intel 8254x/8257x gigabit chips.

		CONFIG_E1000_SPI
		Utility code for direct access to the SPI bus on Intel 8257x.
		This does not do anything useful unless you set at least one
		of CONFIG_CMD_E1000 or CONFIG_E1000_SPI_GENERIC.

		CONFIG_E1000_SPI_GENERIC
		Allow generic access to the SPI bus on the Intel 8257x, for
		example with the "sspi" command.

		CONFIG_CMD_E1000
		Management command for E1000 devices.  When used on devices
		with SPI support you can reprogram the EEPROM from U-Boot.
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		CONFIG_EEPRO100
		Support for Intel 82557/82559/82559ER chips.
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		Optional CONFIG_EEPRO100_SROM_WRITE enables EEPROM
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		write routine for first time initialisation.

		CONFIG_TULIP
		Support for Digital 2114x chips.
		Optional CONFIG_TULIP_SELECT_MEDIA for board specific
		modem chip initialisation (KS8761/QS6611).

		CONFIG_NATSEMI
		Support for National dp83815 chips.

		CONFIG_NS8382X
		Support for National dp8382[01] gigabit chips.

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- NETWORK Support (other):

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		CONFIG_DRIVER_AT91EMAC
		Support for AT91RM9200 EMAC.

			CONFIG_RMII
			Define this to use reduced MII inteface

			CONFIG_DRIVER_AT91EMAC_QUIET
			If this defined, the driver is quiet.
			The driver doen't show link status messages.

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		CONFIG_CALXEDA_XGMAC
		Support for the Calxeda XGMAC device

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		CONFIG_LAN91C96
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		Support for SMSC's LAN91C96 chips.

			CONFIG_LAN91C96_USE_32_BIT
			Define this to enable 32 bit addressing

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		CONFIG_SMC91111
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		Support for SMSC's LAN91C111 chip

			CONFIG_SMC91111_BASE
			Define this to hold the physical address
			of the device (I/O space)

			CONFIG_SMC_USE_32_BIT
			Define this if data bus is 32 bits

			CONFIG_SMC_USE_IOFUNCS
			Define this to use i/o functions instead of macros
			(some hardware wont work with macros)

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		CONFIG_DRIVER_TI_EMAC
		Support for davinci emac

			CONFIG_SYS_DAVINCI_EMAC_PHY_COUNT
			Define this if you have more then 3 PHYs.

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		CONFIG_FTGMAC100
		Support for Faraday's FTGMAC100 Gigabit SoC Ethernet

			CONFIG_FTGMAC100_EGIGA
			Define this to use GE link update with gigabit PHY.
			Define this if FTGMAC100 is connected to gigabit PHY.
			If your system has 10/100 PHY only, it might not occur
			wrong behavior. Because PHY usually return timeout or
			useless data when polling gigabit status and gigabit
			control registers. This behavior won't affect the
			correctnessof 10/100 link speed update.

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		CONFIG_SMC911X
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		Support for SMSC's LAN911x and LAN921x chips

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			CONFIG_SMC911X_BASE
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			Define this to hold the physical address
			of the device (I/O space)

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			CONFIG_SMC911X_32_BIT
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			Define this if data bus is 32 bits

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			CONFIG_SMC911X_16_BIT
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			Define this if data bus is 16 bits. If your processor
			automatically converts one 32 bit word to two 16 bit
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			words you may also try CONFIG_SMC911X_32_BIT.
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		CONFIG_SH_ETHER
		Support for Renesas on-chip Ethernet controller

			CONFIG_SH_ETHER_USE_PORT
			Define the number of ports to be used

			CONFIG_SH_ETHER_PHY_ADDR
			Define the ETH PHY's address

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			CONFIG_SH_ETHER_CACHE_WRITEBACK
			If this option is set, the driver enables cache flush.

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- PWM Support:
		CONFIG_PWM_IMX
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		Support for PWM module on the imx6.
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- TPM Support:
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		CONFIG_TPM
		Support TPM devices.

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		CONFIG_TPM_TIS_INFINEON
		Support for Infineon i2c bus TPM devices. Only one device
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		per system is supported at this time.

			CONFIG_TPM_TIS_I2C_BURST_LIMITATION
			Define the burst count bytes upper limit

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		CONFIG_TPM_ST33ZP24
		Support for STMicroelectronics TPM devices. Requires DM_TPM support.

			CONFIG_TPM_ST33ZP24_I2C
			Support for STMicroelectronics ST33ZP24 I2C devices.
			Requires TPM_ST33ZP24 and I2C.

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			CONFIG_TPM_ST33ZP24_SPI
			Support for STMicroelectronics ST33ZP24 SPI devices.
			Requires TPM_ST33ZP24 and SPI.

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		CONFIG_TPM_ATMEL_TWI
		Support for Atmel TWI TPM device. Requires I2C support.

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		CONFIG_TPM_TIS_LPC
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		Support for generic parallel port TPM devices. Only one device
		per system is supported at this time.

			CONFIG_TPM_TIS_BASE_ADDRESS
			Base address where the generic TPM device is mapped
			to. Contemporary x86 systems usually map it at
			0xfed40000.

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		CONFIG_CMD_TPM
		Add tpm monitor functions.
		Requires CONFIG_TPM. If CONFIG_TPM_AUTH_SESSIONS is set, also
		provides monitor access to authorized functions.

		CONFIG_TPM
		Define this to enable the TPM support library which provides
		functional interfaces to some TPM commands.
		Requires support for a TPM device.

		CONFIG_TPM_AUTH_SESSIONS
		Define this to enable authorized functions in the TPM library.
		Requires CONFIG_TPM and CONFIG_SHA1.

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- USB Support:
		At the moment only the UHCI host controller is
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		supported (PIP405, MIP405, MPC5200); define
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		CONFIG_USB_UHCI to enable it.
		define CONFIG_USB_KEYBOARD to enable the USB Keyboard
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		and define CONFIG_USB_STORAGE to enable the USB
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		storage devices.
		Note:
		Supported are USB Keyboards and USB Floppy drives
		(TEAC FD-05PUB).
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		MPC5200 USB requires additional defines:
			CONFIG_USB_CLOCK
				for 528 MHz Clock: 0x0001bbbb
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			CONFIG_PSC3_USB
				for USB on PSC3
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			CONFIG_USB_CONFIG
				for differential drivers: 0x00001000
				for single ended drivers: 0x00005000
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				for differential drivers on PSC3: 0x00000100
				for single ended drivers on PSC3: 0x00004100
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			CONFIG_SYS_USB_EVENT_POLL
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				May be defined to allow interrupt polling
				instead of using asynchronous interrupts
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		CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
		txfilltuning field in the EHCI controller on reset.

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		CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
		HW module registers.

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- USB Device:
		Define the below if you wish to use the USB console.
		Once firmware is rebuilt from a serial console issue the
		command "setenv stdin usbtty; setenv stdout usbtty" and
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		attach your USB cable. The Unix command "dmesg" should print
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		it has found a new device. The environment variable usbtty
		can be set to gserial or cdc_acm to enable your device to
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		appear to a USB host as a Linux gserial device or a
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		Common Device Class Abstract Control Model serial device.
		If you select usbtty = gserial you should be able to enumerate
		a Linux host by
		# modprobe usbserial vendor=0xVendorID product=0xProductID
		else if using cdc_acm, simply setting the environment
		variable usbtty to be cdc_acm should suffice. The following
		might be defined in YourBoardName.h
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			CONFIG_USB_DEVICE
			Define this to build a UDC device

			CONFIG_USB_TTY
			Define this to have a tty type of device available to
			talk to the UDC device
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			CONFIG_USBD_HS
			Define this to enable the high speed support for usb
			device and usbtty. If this feature is enabled, a routine
			int is_usbd_high_speed(void)
			also needs to be defined by the driver to dynamically poll
			whether the enumeration has succeded at high speed or full
			speed.

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			CONFIG_SYS_CONSOLE_IS_IN_ENV
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			Define this if you want stdin, stdout &/or stderr to
			be set to usbtty.

			mpc8xx:
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				CONFIG_SYS_USB_EXTC_CLK 0xBLAH
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				Derive USB clock from external clock "blah"
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				- CONFIG_SYS_USB_EXTC_CLK 0x02
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		If you have a USB-IF assigned VendorID then you may wish to
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		define your own vendor specific values either in BoardName.h
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		or directly in usbd_vendor_info.h. If you don't define
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		CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
		CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
		should pretend to be a Linux device to it's target host.

			CONFIG_USBD_MANUFACTURER
			Define this string as the name of your company for
			- CONFIG_USBD_MANUFACTURER "my company"
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			CONFIG_USBD_PRODUCT_NAME
			Define this string as the name of your product
			- CONFIG_USBD_PRODUCT_NAME "acme usb device"

			CONFIG_USBD_VENDORID
			Define this as your assigned Vendor ID from the USB
			Implementors Forum. This *must* be a genuine Vendor ID
			to avoid polluting the USB namespace.
			- CONFIG_USBD_VENDORID 0xFFFF
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			CONFIG_USBD_PRODUCTID
			Define this as the unique Product ID
			for your device
			- CONFIG_USBD_PRODUCTID 0xFFFF
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- ULPI Layer Support:
		The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
		the generic ULPI layer. The generic layer accesses the ULPI PHY
		via the platform viewport, so you need both the genric layer and
		the viewport enabled. Currently only Chipidea/ARC based
		viewport is supported.
		To enable the ULPI layer support, define CONFIG_USB_ULPI and
		CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
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		If your ULPI phy needs a different reference clock than the
		standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
		the appropriate value in Hz.
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- MMC Support:
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		The MMC controller on the Intel PXA is supported. To
		enable this define CONFIG_MMC. The MMC can be
		accessed from the boot prompt by mapping the device
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		to physical memory similar to flash. Command line is
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		enabled with CONFIG_CMD_MMC. The MMC driver also works with
		the FAT fs. This is enabled with CONFIG_CMD_FAT.
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		CONFIG_SH_MMCIF
		Support for Renesas on-chip MMCIF controller

			CONFIG_SH_MMCIF_ADDR
			Define the base address of MMCIF registers

			CONFIG_SH_MMCIF_CLK
			Define the clock frequency for MMCIF

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		CONFIG_GENERIC_MMC
		Enable the generic MMC driver

		CONFIG_SUPPORT_EMMC_BOOT
		Enable some additional features of the eMMC boot partitions.

		CONFIG_SUPPORT_EMMC_RPMB
		Enable the commands for reading, writing and programming the
		key for the Replay Protection Memory Block partition in eMMC.

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- USB Device Firmware Update (DFU) class support:
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		CONFIG_USB_FUNCTION_DFU
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		This enables the USB portion of the DFU USB class

		CONFIG_CMD_DFU
		This enables the command "dfu" which is used to have
		U-Boot create a DFU class device via USB.  This command
		requires that the "dfu_alt_info" environment variable be
		set and define the alt settings to expose to the host.

		CONFIG_DFU_MMC
		This enables support for exposing (e)MMC devices via DFU.

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		CONFIG_DFU_NAND
		This enables support for exposing NAND devices via DFU.

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		CONFIG_DFU_RAM
		This enables support for exposing RAM via DFU.
		Note: DFU spec refer to non-volatile memory usage, but
		allow usages beyond the scope of spec - here RAM usage,
		one that would help mostly the developer.

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		CONFIG_SYS_DFU_DATA_BUF_SIZE
		Dfu transfer uses a buffer before writing data to the
		raw storage device. Make the size (in bytes) of this buffer
		configurable. The size of this buffer is also configurable
		through the "dfu_bufsiz" environment variable.

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		CONFIG_SYS_DFU_MAX_FILE_SIZE
		When updating files rather than the raw storage device,
		we use a static buffer to copy the file into and then write
		the buffer once we've been given the whole file.  Define
		this to the maximum filesize (in bytes) for the buffer.
		Default is 4 MiB if undefined.

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		DFU_DEFAULT_POLL_TIMEOUT
		Poll timeout [ms], is the timeout a device can send to the
		host. The host must wait for this timeout before sending
		a subsequent DFU_GET_STATUS request to the device.

		DFU_MANIFEST_POLL_TIMEOUT
		Poll timeout [ms], which the device sends to the host when
		entering dfuMANIFEST state. Host waits this timeout, before
		sending again an USB request to the device.

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- USB Device Android Fastboot support:
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		CONFIG_USB_FUNCTION_FASTBOOT
		This enables the USB part of the fastboot gadget

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		CONFIG_CMD_FASTBOOT
		This enables the command "fastboot" which enables the Android
		fastboot mode for the platform's USB device. Fastboot is a USB
		protocol for downloading images, flashing and device control
		used on Android devices.
		See doc/README.android-fastboot for more information.

		CONFIG_ANDROID_BOOT_IMAGE
		This enables support for booting images which use the Android
		image format header.

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		CONFIG_FASTBOOT_BUF_ADDR
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		The fastboot protocol requires a large memory buffer for
		downloads. Define this to the starting RAM address to use for
		downloaded images.

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		CONFIG_FASTBOOT_BUF_SIZE
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		The fastboot protocol requires a large memory buffer for
		downloads. This buffer should be as large as possible for a
		platform. Define this to the size available RAM for fastboot.
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		CONFIG_FASTBOOT_FLASH
		The fastboot protocol includes a "flash" command for writing
		the downloaded image to a non-volatile storage device. Define
		this to enable the "fastboot flash" command.

		CONFIG_FASTBOOT_FLASH_MMC_DEV
		The fastboot "flash" command requires additional information
		regarding the non-volatile storage device. Define this to
		the eMMC device that fastboot should use to store the image.
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		CONFIG_FASTBOOT_GPT_NAME
		The fastboot "flash" command supports writing the downloaded
		image to the Protective MBR and the Primary GUID Partition
		Table. (Additionally, this downloaded image is post-processed
		to generate and write the Backup GUID Partition Table.)
		This occurs when the specified "partition name" on the
		"fastboot flash" command line matches this value.
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		The default is "gpt" if undefined.
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		CONFIG_FASTBOOT_MBR_NAME
		The fastboot "flash" command supports writing the downloaded
		image to DOS MBR.
		This occurs when the "partition name" specified on the
		"fastboot flash" command line matches this value.
		If not defined the default value "mbr" is used.

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- Journaling Flash filesystem support:
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		CONFIG_JFFS2_NAND
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		Define these for a default partition on a NAND device

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		CONFIG_SYS_JFFS2_FIRST_SECTOR,
		CONFIG_SYS_JFFS2_FIRST_BANK, CONFIG_SYS_JFFS2_NUM_BANKS
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		Define these for a default partition on a NOR device

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- FAT(File Allocation Table) filesystem write function support:
		CONFIG_FAT_WRITE
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		Define this to enable support for saving memory data as a
		file in FAT formatted partition.

		This will also enable the command "fatwrite" enabling the
		user to write files to FAT.
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CBFS (Coreboot Filesystem) support
		CONFIG_CMD_CBFS

		Define this to enable support for reading from a Coreboot
		filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
		and cbfsload.

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- FAT(File Allocation Table) filesystem cluster size:
		CONFIG_FS_FAT_MAX_CLUSTSIZE

		Define the max cluster size for fat operations else
		a default value of 65536 will be defined.

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- Keyboard Support:
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		See Kconfig help for available keyboard drivers.

		CONFIG_KEYBOARD

		Define this to enable a custom keyboard support.
		This simply calls drv_keyboard_init() which must be
		defined in your board-specific files. This option is deprecated
		and is only used by novena. For new boards, use driver model
		instead.
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- Video support:
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		CONFIG_FSL_DIU_FB
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		Enable the Freescale DIU video driver.	Reference boards for
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		SOCs that have a DIU should define this macro to enable DIU
		support, and should also define these other macros:

			CONFIG_SYS_DIU_ADDR
			CONFIG_VIDEO
			CONFIG_CMD_BMP
			CONFIG_CFB_CONSOLE
			CONFIG_VIDEO_SW_CURSOR
			CONFIG_VGA_AS_SINGLE_DEVICE
			CONFIG_VIDEO_LOGO
			CONFIG_VIDEO_BMP_LOGO

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		The DIU driver will look for the 'video-mode' environment
		variable, and if defined, enable the DIU as a console during
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		boot.  See the documentation file doc/README.video for a
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		description of this variable.
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- LCD Support:	CONFIG_LCD

		Define this to enable LCD support (for output to LCD
		display); also select one of the supported displays
		by defining one of these:

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		CONFIG_ATMEL_LCD:

			HITACHI TX09D70VM1CCA, 3.5", 240x320.

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		CONFIG_NEC_NL6448AC33:
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			NEC NL6448AC33-18. Active, color, single scan.
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		CONFIG_NEC_NL6448BC20
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			NEC NL6448BC20-08. 6.5", 640x480.
			Active, color, single scan.

		CONFIG_NEC_NL6448BC33_54

			NEC NL6448BC33-54. 10.4", 640x480.
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			Active, color, single scan.

		CONFIG_SHARP_16x9

			Sharp 320x240. Active, color, single scan.
			It isn't 16x9, and I am not sure what it is.

		CONFIG_SHARP_LQ64D341

			Sharp LQ64D341 display, 640x480.
			Active, color, single scan.

		CONFIG_HLD1045

			HLD1045 display, 640x480.
			Active, color, single scan.

		CONFIG_OPTREX_BW

			Optrex	 CBL50840-2 NF-FW 99 22 M5
			or
			Hitachi	 LMG6912RPFC-00T
			or
			Hitachi	 SP14Q002

			320x240. Black & white.

		Normally display is black on white background; define
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		CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
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		CONFIG_LCD_ALIGNMENT

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		Normally the LCD is page-aligned (typically 4KB). If this is
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		defined then the LCD will be aligned to this value instead.
		For ARM it is sometimes useful to use MMU_SECTION_SIZE
		here, since it is cheaper to change data cache settings on
		a per-section basis.


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		CONFIG_LCD_ROTATION

		Sometimes, for example if the display is mounted in portrait
		mode or even if it's mounted landscape but rotated by 180degree,
		we need to rotate our content of the display relative to the
		framebuffer, so that user can read the messages which are
		printed out.
		Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
		initialized with a given rotation from "vl_rot" out of
		"vidinfo_t" which is provided by the board specific code.
		The value for vl_rot is coded as following (matching to
		fbcon=rotate:<n> linux-kernel commandline):
		0 = no rotation respectively 0 degree
		1 = 90 degree rotation
		2 = 180 degree rotation
		3 = 270 degree rotation

		If CONFIG_LCD_ROTATION is not defined, the console will be
		initialized with 0degree rotation.

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		CONFIG_LCD_BMP_RLE8

		Support drawing of RLE8-compressed bitmaps on the LCD.

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		CONFIG_I2C_EDID

		Enables an 'i2c edid' command which can read EDID
		information over I2C from an attached LCD display.

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- Splash Screen Support: CONFIG_SPLASH_SCREEN
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		If this option is set, the environment is checked for
		a variable "splashimage". If found, the usual display
		of logo, copyright and system information on the LCD
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		is suppressed and the BMP image at the address
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		specified in "splashimage" is loaded instead. The
		console is redirected to the "nulldev", too. This
		allows for a "silent" boot where a splash screen is
		loaded very quickly after power-on.
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		CONFIG_SPLASHIMAGE_GUARD

		If this option is set, then U-Boot will prevent the environment
		variable "splashimage" from being set to a problematic address
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		(see doc/README.displaying-bmps).
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		This option is useful for targets where, due to alignment
		restrictions, an improperly aligned BMP image will cause a data
		abort. If you think you will not have problems with unaligned
		accesses (for example because your toolchain prevents them)
		there is no need to set this option.