Uboot-2016.05-rcreadme资源-CSDN下载

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### U-Boot 2016.05-rc Readme关键知识点解析 #### 概述 U-Boot（Universal Boot Loader）是一个广泛应用于嵌入式系统的启动加载程序，支持多种处理器架构，如PowerPC、ARM、MIPS等。本读取文档（Readme）针对的是U-Boot 2016.05-rc版本，该版本包含了用于嵌入式板卡初始化和测试硬件以及下载和运行应用代码的功能。U-Boot的发展与Linux紧密相关，其部分源码来源于Linux源树，并且特别支持Linux镜像的引导。 #### 版权声明与许可证该文档明确指出，U-Boot遵循GPL-2.0+许可证。这意味着任何人都可以自由地查看、修改和分发U-Boot的源代码，只要遵守GPL协议的规定即可。此许可证确保了开源社区能够积极参与到项目的开发和改进中来。 #### 软件配置与扩展性 U-Boot在设计上注重易配置性和可扩展性。例如，所有监控命令都使用相同的调用接口实现，这使得添加新命令变得非常容易。此外，对于不常用的功能（如硬件测试工具），U-Boot支持动态加载运行，无需永久集成到主程序中。这种设计不仅简化了主程序，还提高了系统的灵活性。 #### 状态概述文档中提到，所有在Makefile中定义的配置选项所对应的板卡都已经经过了一定程度的测试，并被认为是“可用”的。实际上，很多配置已经被实际产品采用。如果遇到问题，可以通过查看`CHANGELOG`文件来了解特定端口的贡献者信息。自2010年8月起，U-Boot源代码中不再包含静态的`CHANGELOG`文件，但可以通过`make CHANGELOG`命令动态生成。 #### 获取帮助对于U-Boot的相关问题、遇到的问题或贡献建议，可以发送邮件至U-Boot的邮件列表`[email protected]`。此外，文档推荐在提问前先搜索邮件列表的历史记录，以避免重复提问常见问题。关于邮件列表的更多信息，可以访问以下链接： - <http://lists.denx.de/pipermail/u-boot> - <http://dir.gmane.org/gmane.comp.boot-loaders.u-boot> #### 获取源代码 U-Boot的源代码托管在Git仓库中，可通过以下方式获取： - Git仓库地址：`git://www.denx.de/git/u-boot.git` - 在线浏览地址：<http://www.denx.de/cgi> 通过上述Git仓库地址，开发者可以轻松克隆或拉取最新的U-Boot源代码，以便于学习、修改和贡献。 ### 总结 U-Boot 2016.05-rc是一个功能强大的启动加载程序，它为多种嵌入式系统提供了稳定的基础。通过对U-Boot的深入了解，可以更好地利用其强大的特性来优化和定制自己的嵌入式平台。同时，U-Boot的开源性质鼓励开发者们积极贡献，共同推动项目的发展和完善。

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File: /home/kart/u-boot/README Page 1 of 92

# Wolfgang Denk, DENX Software Engineering, [email protected].

# SPDX-License-Identifier: GPL-2.0+

Summary:

========

This directory contains the source code for U-Boot, a boot loader for

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.

The development of U-Boot is closely related to Linux: some parts of

the source code originate in the Linux source tree, we have some

header files in common, and special provision has been made to

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

Makefile have been tested to some extent and can be considered

"working". In fact, many of them are used in production systems.

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.

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:

make CHANGELOG

Where to get help:

==================

In case you have questions about, problems with or contributions for

U-Boot, you should send a message to the U-Boot mailing list at

<[email protected]>. 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

Where to get source code:

=========================

The U-Boot source code is maintained in the Git repository at

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

any version you might be interested in. Official releases are also

available for FTP download from the ftp://ftp.denx.de/pub/u-boot/

directory.

Pre-built (and tested) images are available from

File: /home/kart/u-boot/README Page 2 of 92

ftp://ftp.denx.de/pub/u-boot/images/

Where we come from:

===================

- start from 8xxrom sources

- create PPCBoot project (http://sourceforge.net/projects/ppcboot)

- 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

* PCMCIA / CompactFlash / ATA disk / SCSI ... boot

- create ARMBoot project (http://sourceforge.net/projects/armboot)

- add other CPU families (starting with ARM)

- create U-Boot project (http://sourceforge.net/projects/u-boot)

- current project page: see http://www.denx.de/wiki/U-Boot

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

Versioning:

===========

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:

U-Boot v2009.11 - Release November 2009

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

Directory Hierarchy:

====================

/arch Architecture specific files

/arc Files generic to ARC architecture

/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

/nds32 Files generic to NDS32 architecture

File: /home/kart/u-boot/README Page 3 of 92

/nios2 Files generic to Altera NIOS2 architecture

/openrisc Files generic to OpenRISC architecture

/powerpc Files generic to PowerPC architecture

/sandbox Files generic to HW-independent "sandbox"

/sh Files generic to SH architecture

/sparc Files generic to SPARC architecture

/x86 Files generic to x86 architecture

/api Machine/arch independent API for external apps

/board Board dependent files

/common Misc architecture independent functions

/configs Board default configuration files

/disk Code for disk drive partition handling

/doc Documentation (don't expect too much)

/drivers Commonly used device drivers

/dts Contains Makefile for building internal U-Boot fdt.

/examples Example code for standalone applications, etc.

/fs Filesystem code (cramfs, ext2, jffs2, etc.)

/include Header Files

/lib Library routines generic to all architectures

/Licenses Various license files

/net Networking code

/post Power On Self Test

/scripts Various build scripts and Makefiles

/test Various unit test files

/tools Tools to build S-Record or U-Boot images, etc.

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

"CONFIG_SYS_".

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.

Selection of Processor Architecture and Board Type:

---------------------------------------------------

For all supported boards there are ready-to-use default

configurations available; just type "make <board_name>_defconfig".

Example: For a TQM823L module type:

cd u-boot

make TQM823L_defconfig

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.

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.

File: /home/kart/u-boot/README Page 4 of 92

See board/sandbox/README.sandbox for more details.

Board Initialisation Flow:

--------------------------

This is the intended start-up flow for boards. This should apply for both

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

and so on. From there, three functions are called; the purpose and

limitations of each of these functions are described below.

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:

File: /home/kart/u-boot/README Page 5 of 92

- 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

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".

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.

The following options need to be configured:

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

- Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.

- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)

Define exactly one, e.g. CONFIG_ATSTK1002

- CPU Module Type: (if CONFIG_COGENT is defined)

Define exactly one of

CONFIG_CMA286_60_OLD

--- FIXME --- not tested yet:

CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,

CONFIG_CMA287_23, CONFIG_CMA287_50

- Motherboard Type: (if CONFIG_COGENT is defined)

Define exactly one of

CONFIG_CMA101, CONFIG_CMA102

- Motherboard I/O Modules: (if CONFIG_COGENT is defined)

Define one or more of

CONFIG_CMA302

- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)

Define one or more of

CONFIG_LCD_HEARTBEAT - update a character position on

the LCD display every second with

a "rotator" |\-/|\-/

- Marvell Family Member

CONFIG_SYS_MVFS - define it if you want to enable

multiple fs option at one time

for marvell soc family

- 8xx CPU Options: (if using an MPC8xx CPU)

CONFIG_8xx_GCLK_FREQ - deprecated: CPU clock if

get_gclk_freq() cannot work

e.g. if there is no 32KHz

reference PIT/RTC clock

CONFIG_8xx_OSCLK - PLL input clock (either EXTCLK

or XTAL/EXTAL)

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