Difference between revisions of "U-Boot overview"

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1 Das U-Boot[edit]

Das U-Boot ("the Universal Boot Loader" or just U-Boot) is an open-source boot loader, which bootloader that can be used on ST boards to initialize the platform and load the Linux® kernel.

 
PC $> git clone githttps://gitgitlab.denx.de/u-boot/u-boot.git

Reading Read the README file is recommendedbefore starting using U-Boot. It covers the following topics:

  • the source file tree structure
  • the meaning description of the CONFIG defines
  • instructions for building U-Boot
  • a brief description of the Hush shell
  • a list of common environment variables

2 U-Boot overview[edit]

Zoom out to STM32MPU Embedded Software

The same U-Boot source can generate 2 two pieces of firmware used in the SPL and U-Boot STM32 MPU boot chain: SPL and U-Boot

  • Trusted boot chain: TF-A as FSBL and U-Boot as SSBL
  • Basic boot chain: SPL as FSBL and U-Boot as SSBL


Warning.png The basic boot chain cannot be used for product development (see Boot chains overview for details).

It is provided only as an example of the simplest SSBL and to support upstream U-Boot development. However, several known limitations have been identified when SPL is used in conjunction with the minimal secure monitor provided within U-Boot for basic boot chain. They apply to:

  • power
  • secure access to registers
  • limited features (STM32CubeProgrammer / boot from NAND Flash memory).

No fix is planned for these limitations.

2.1 SPL: FSBL for basic boot[edit]

The U-Boot SPL or just SPL is the first stage boot loader bootloader (FSBL) for the basic boot chain.
It is a small binary (bootstrap utility) , generated from the U-Boot source , which fits and stored in the internal and limited-size embedded RAM. SPL main features are the following:

  • It is loaded by the ROM code.
  • it does It performs the initial CPU and board configuration : (clocks and DDR memory).
  • it It loads the SSBL (U-Boot) into the DDR memory.

2.2 U-Boot: SSBL[edit]

U-Boot is the default second-stage boot loader bootloader (SSBL) for the STM32 MPU platforms for the 2 boot chains, . It is used both for trusted and basic boot chains. SSBL main features are the following:

  • it It is configurable and expendable.
  • it has It features a simple command line interface (CLI), usually allowing users to interact over a serial console port for interaction with the userit port console.
  • It provides scripting capabilities
  • it It loads the kernel into RAM and passes gives control to the kernel
  • it It manages many several internal and external devices like such as NAND , and NOR Flash memories, Ethernet , and USBit has many supported .
  • It supports the following features and commands for :
    • file File systems: FAT, UBI/UBIFS, JFFS
    • IP stack: FTP
    • displayDisplay: LCD, HDMI, BMP for splashcreen
    • USB: host profile (mass storage) or device profile (DFU stack)

2.3 SPL phases[edit]

The SPL runs through executes the following main following phases in SYSRAM:

  • board_init_f(): init drivers up to DDR initialisation driver initialization including DDR initialization (mininimal stack and heap: CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN)
  • configure configuration of heap in DDR memory (CONFIG_SPL_SYS_MALLOC_F_LEN)
  • board_init_r(): init initialization of the other drivers activated in the SPL device tree
  • load loading and execution of U-Boot (or Kernel in Falcon mode[1]: README.falcon ) and execute it.

2.4 U-Boot phases[edit]

U-Boot runs through executes the following main phases in DDR memory:

  • Pre-relocation initialization (common/board_f.c): minimal init initialization (cpusuch as CPU, clock, reset, ddr, console,...DDR and console) running at the load address CONFIG_SYS_TEXT_BASE load address.
  • Relocation: copy of the code to the end of DDR memory.
  • Post-relocation initialization:(common/board_r.c): init initialization of all the driversExecution of commands: .
  • Command execution through autoboot (CONFIG_AUTOBOOT) or console shell
    • execute Execution of the boot command (by default bootcmd=CONFIG_BOOTCOMMAND by default):
      for example, execute execution of the command 'bootm' to:
      • load and check images (such as kernel, device tree , and ramdisk....)
      • fixup the kernel device tree
      • install the secure monitor (optional) or
      • pass the control to the Linux kernel (or other to another target application)

3 U-Boot configuration[edit]

The U-Boot binary configuration is based on

  • Kbuild infrastructure (as in Linux Kernel, you can use "make menuconfig" in U-Boot)
    The configurations are based on:
  • other compilation flags defines defined in include/configs/stm32mp*.h
    the (these flags are progressively migrated to Kconfig)
    The file name is configured by through CONFIG_SYS_CONFIG_NAME
    (these flags are progressively migrating to Kconfig)
    for stm32mp157: we use .
    For STM32MP15x lines More info.png, the include/configs/stm32mp1.h file is used.
  • DeviceTree = : U-Boot and SPL binaries include a device tree blob which that is parsed at run timeruntime

All the configuration flags (prefixed by CONFIG_) are described in the source code: , either in the README file or in the documentation directory .
For example: , CONFIG_SPL => activate activates the SPL compilation.
Hence to compile U-Boot, you need to select the <target> and the device tree for the board in order to select choose a predefined configuration.
See Refer to #U-Boot_build for examples.

3.1 Kbuild[edit]

The Like the kernel, the U-Boot build system is based on configuration symbols as the kernel (defined in Kconfig files), and . The selected values are stored in a .config file in the build directory, with the same makefile target.

select

.
Proceed as follows:

  • Select a pre-defined configuration (defconfig file , in configs directory ) and generate the first .config:
 
PC $> make <config>_defconfig.

  • change Change the U-Boot compile configuration (modify .config) by using one of the 5 following five make command commands:
 
PC $> make menuconfig --> menu based program
 PC $> make config  --> line-oriented configuration
 PC $> make xconfig --> QT program[2]
 PC $> make gconfig --> GTK program
 PC $> make nconfig --> ncurse menu based program

You can then compile U-Boot with the updated .config.

Warning: the modification is only done performed locally in the build directory, it is . It will be lost after a "make distclean" So if you want to use your configuration as defconfig.

Save your configuration to be able to use it as a defconfig file:

  
PC $> make savedefconfig

This target saves the current config as a defconfig file in the build directory, and . It can then be compared with the predefined configuration (configs/stm32mp*defconfig).

The other makefile targets are are the following:

 
 PC $> make help
 ....
 Configuration targets:
   config	  - Update current config utilising a line-oriented program
   nconfig         - Update current config utilising a ncurses menu based
                     program
   menuconfig	  - Update current config utilising a menu based program
   xconfig	  - Update current config utilising a Qt based front-end
   gconfig	  - Update current config utilising a GTK+ based front-end
   oldconfig	  - Update current config utilising a provided .config as base
   localmodconfig  - Update current config disabling modules not loaded
   localyesconfig  - Update current config converting local mods to core
   defconfig	  - New config with default from ARCH supplied defconfig
   savedefconfig   - Save current config as ./defconfig (minimal config)
   allnoconfig	  - New config where all options are answered with no
   allyesconfig	  - New config where all options are accepted with yes
   allmodconfig	  - New config selecting modules when possible
   alldefconfig    - New config with all symbols set to default
   randconfig	  - New config with random answer to all options
   listnewconfig   - List new options
   olddefconfig	  - Same as oldconfig but sets new symbols to their
                    default value without prompting

3.2 Device tree[edit]

See Refer to doc/README.fdt-control for details.

The board device tree , with has the same binding as the kernel, . It is integrated with within the SPL and U-Boot binaries:

  • By default, it is appended at the end of the code by default (CONFIG_OF_SEPARATE).
  • It is embedded in the U-Boot binary (CONFIG_OF_EMBED): . This is useful for debug, allows easy debugging since it enables easy .elf file loading.

A default device tree is defined available in the defconfig file (with by setting CONFIG_DEFAULT_DEVICE_TREE).

You can also either select another supported device tree with using the make flag DEVICE_TREE
for stm32mp32 boards the file aremake flag. For stm32mp boards, the corresponding file is: arch/arm/dts/stm32mp*.dts .

  
PC $> make DEVICE_TREE=<dts-file-name>

or you can provide a precompiled device tree blob (with using EXT_DTB option):

  
PC $> make EXT_DTB=boot/<dts-file-name>.dtb

The SPL device tree is also generated from this device tree; but . However to reduce its size, the U-Boot makefile uses the fdtgrep tool to parse the full U-Boot DTB and identify all the drivers needed required by SPL.

To do this, U-Boot uses some specific device-tree flags to specify define if the associated driver is initialized prior to U-Boot relocation and/or if the associated node is present in SPL :

  • u-boot,dm-pre-reloc => present in SPL, initialized before relocation in U-Boot
  • u-boot,dm-pre-proper => initialized before relocation in U-Boot
  • u-boot,dm-spl => present in SPL

In the device tree used by U-Boot, these flags need to be added in each node used in SPL or in U-Boot before relocation but also and for each used handle (clock, reset, pincontrol).

4 U-Boot command line interface (CLI)[edit]

see Refer to U-Boot Command Line Interface.

If CONFIG_AUTOBOOT is activated, to enter in this console, you have CONFIG_BOOTDELAY seconds (2s by default) before bootcmd execution (CONFIG_BOOTCOMMAND) to enter the console by pressing any key when , after the line below is displayed . and bootcmd is executed (CONFIG_BOOTCOMMAND):

 Hit any key to stop autoboot:  2

4.1 Commands[edit]

The commands are defined in cmd/*.c , they . They are activated under associated configuration flag through the corresponding CONFIG_CMD_* configuration flag.

Use the help command help in the U-Boot shell to list the commands available commands on your device. List of :

 Board $> help

Below the list of all commands extracted from U-Boot Manual (not-exhaustive):

  • Information Commands
    • bdinfo - print prints Board Info structure
    • coninfo - print prints console devices and informationsinformation
    • flinfo - print FLASH prints Flash memory information
    • iminfo - print prints header information for application image
    • help - print prints online help
  • Memory Commands
    • base - print prints or set sets the address offset
    • crc32 - checksum calculation
    • cmp - memory compare
    • cp - memory copy
    • md - memory display
    • mm - memory modify (auto-incrementing)
    • mtest - simple RAM test
    • mw - memory write (fill)
    • nm - memory modify (constant address)
    • loop - infinite loop on address range
  • Flash Memory Commands
    • cp - memory copy
    • flinfo - print FLASH prints Flash memory information
    • erase - erase FLASH erases Flash memory
    • protect - enable or disable FLASH enables or disables Flash memory write protection
    • mtdparts - define defines a Linux compatible MTD partition scheme
  • Execution Control Commands
    • source - run runs a script from memory
    • bootm - boot boots application image from memory
    • go - start starts application at address 'addr'
  • Download Commands
    • bootp - boot boots image via network using BOOTP/TFTP protocol
    • dhcp - invoke invokes DHCP client to obtain IP/boot params
    • loadb - load loads binary file over serial line (kermit mode)
    • loads - load loads S-Record file over serial line
    • rarpboot- boot boots image via network using RARP/TFTP protocol
    • tftpboot- boot boots image via network using TFTP protocol
  • Environment Variables Commands
    • printenv- print prints environment variables
    • saveenv - save saves environment variables to persistent storage
    • setenv - set sets environment variables
    • run - run runs commands in an environment variable
    • bootd - boot boots default, i.e., run 'bootcmd'
  • Flattened Device Tree support
    • fdt addr - select selects the FDT to work on
    • fdt list - print prints one level
    • fdt print - recursive printprinting
    • fdt mknode - create creates new nodes
    • fdt set - set sets node properties
    • fdt rm - remove removes nodes or properties
    • fdt move - move moves FDT blob to new address
    • fdt chosen - fixup dynamic infoinformation
  • Special Commands
    • i2c - I2C sub-system
  • Storage devices
  • Miscellaneous Commands
    • echo - echo echoes args to console
    • reset - Perform RESET of the CPUPerforms a CPU reset
    • sleep - delay delays the execution for some a predefined time
    • version - print prints the monitor version

To add a new command, see refer to doc/README.commands .

4.2 U-Boot environment variables[edit]

The U-Boot behavior is configured with through environment variables.

see Refer to Manual and README / Environment Variables.

By default the env is NOT saved (CONFIG_ENV_IS_NOWHERE), only the default environment is used (saveenv command is not working)

You can modify this default environment On the first boot, U-Boot uses a default environment embedded in the U-Boot binary. You can modify it by changing the content of CONFIG_EXTRA_ENV_SETTINGS in your configuration file (for example ./include/configs/stm32mp1.h) (see README / - Default Environment).

You can also choose one location with configuration flags:

This environment can be modified and saved in the boot device. When it is present, it is loaded during U-Boot initialization:

  • for e•MMC/SD card boot (CONFIG_ENV_IS_IN_MMCEXT4), in the bootable ext4 partition "bootfs" in
    in file CONFIG_ENV_IS_IN_FLASHEXT4_FILE="uboot.env".
  • for NAND boot (CONFIG_ENV_IS_IN_SPIUBI), in the two UBI volumes "config" (CONFIG_ENV_IS_IN_FATUBI_VOLUME) and "config_r" (CONFIG_ENV_ISUBI_INVOLUME_NANDREDUND).
  • for NOR boot (CONFIG_ENV_IS_IN_UBISPI_FLASH), in the u-boot_env mtd parttion (at offset CONFIG_ENV_IS_IN_EEPROMOFFSET).

4.2.1 env command[edit]

The env command allows displaying, modifying and saving the environment in U-Boot console.

 Board $> help env
 env - environment handling commands
 
 Usage:
 env default [-f] -a - [forcibly] reset default environment
 env default [-f] var [...] - [forcibly] reset variable(s) to their default values
 env delete [-f] var [...] - [forcibly] delete variable(s)
 env edit name - edit environment variable
 env exists name - tests for existence of variable
 env print [-a | name ...] - print environment
 env print -e [name ...] - print UEFI environment
 env run var [...] - run commands in an environment variable
 env save - save environment
 env set -e name [arg ...] - set UEFI variable; unset if 'arg' not specified
 env set [-f] name [arg ...]

Example: proceed as follows to restore the default environment and save it. This is useful after a U-Boot upgrade:

 Board $> env default -a
 Board $> env save

4.2.2 bootcmd[edit]

Autoboot command: "bootcmd" variable is the autoboot command. It defines the command executed when U-Boot starts (CONFIG_BOOTCOMMAND).

But you can change this variable in CONFIG_EXTRA_ENV_SETTINGS (after BOOTENV macro needed for #Generic Distro configuration).


#define CONFIG_EXTRA_ENV_SETTINGS \
	"stdin=serial\0" \
	"stdout=serial\0" \
	"stderr=serial\0" \
	"kernel_addr_r=0xc2000000\0" \
	"fdt_addr_r=0xc4000000\0" \
	"scriptaddr=0xc4100000\0" \
	"pxefile_addr_r=0xc4200000\0" \
	"splashimage=0xc4300000\0"  \
	"ramdisk_addr_r=0xc4400000\0" \
	"fdt_high=0xffffffff\0" \
	"initrd_high=0xffffffff\0" \
	BOOTENV \
	"bootcmd=run bootcmd_mmc0\0"

For stm32mp, CONFIG_BOOTCOMMAND="run bootcmd_stm32mp":

 Board $> env print bootcmd    
  bootcmd=run bootcmd_stm32mp

"bootcmd_stm32mp" is a script that selects the command to be executed for each boot device (see ./include/configs/stm32mp1.h), based on generic distro scripts:

  • for serial/usb: execute the stm32prog command.
  • for mmc boot (e•MMC, SD card), boot only on the same device (bootcmd_mmc...).
  • for nand boot, boot with on ubifs partition on nand (bootcmd_ubi0).
  • for nor boot, use the default order e•MMC (SDMMC 1)/ NAND / SD card (SDMMC 0) / SDMMC2 (the default bootcmd: distro_bootcmd).
 Board $> env print bootcmd_stm32mp

You can then change this configuration:

  • either permanently in your board file (default environment by CONFIG_EXTRA_ENV_SETTINGS or change CONFIG_BOOTCOMMAND value) or
  • temporarily in the saved environment:
 Board $> env set bootcmd run bootcmd_mmc0 
 Board $> env save

Note: To reset the environment to its default value:

 Board $> env default bootcmd
 Board $> env save

4.3 Generic Distro configuration[edit]

see Refer to doc/README.distro for details.

This feature is activated for by default on ST boards (CONFIG_DISTRO_DEFAULTS):

  • one boot command (bootmcd_xxx) exists for each bootable device.
  • U-Boot is independent of the Linux distribution used.
  • bootcmd is defined in ./include/config_distro_bootcmd.h

With When DISTRO is enabled, the default command that is executed : by default is include/config_distro_bootcmd.h :

 bootcmd=run distro_bootcmd

This script will try tries any device found in the variable 'boot_targets' variable and execute executes the associated bootcmd.

Example for device mmc0, mmc1, mmc2, pxe and ubifs devices:

 bootcmd_mmc0=setenv devnum 0; run mmc_boot
 bootcmd_mmc1=setenv devnum 1; run mmc_boot
 bootcmd_mmc2=setenv devnum 2; run mmc_boot
 bootcmd_pxe=run boot_net_usb_start; dhcp; if pxe get; then pxe boot; fi
 bootcmd_ubifs0=setenv devnum 0; run ubifs_boot

U-Boot searchs searches for a configuration file extlinux.conf in a configuration file for each bootable device, this . This file defines the kernel configuration to usebe used:

  • bootargs
  • kernel + device tree + ramdisk files (optional)
  • FIT image

4.4 U-Boot scripting capabilities[edit]

"Script files" are command sequences that will be are executed by the U-Boot 's command interpreter; this . This feature is especially particularly useful when you to configure U-Boot to use a real shell (hush) as command interpreter.

See U-Boot script manual for an example.

5 U-Boot build[edit]

5.1 Prerequisites[edit]

You need:

  • a PC with Linux and tools:
  • U-Boot source code
    • the latest STMicroelectonics STMicroelectronics U-Boot version
      • tar.xz file from Developer Package (for example STM32MP1)
      • from GITHUB[3], with git command
 
PC $> git clone https://github.com/STMicroelectronics/u-boot

  • from the Mainline U-Boot in official GIT repository [4]
 
PC $> git clone httphttps://gitgitlab.denx.de/u-boot/u-boot.git


5.1.1 ARM cross compiler[edit]

You need to have a A cross compiler [5]must be installed on your Host (X86_64, i686, ...) for the ARM targeted Device architecture = ARM. In addition, the environment variables ( $PATH and $CROSS_COMPILE ) need to environment variables must be configured in your shell.

You can use gcc for ARM, available in:

  • the SDK toolchain

See ,
  • )
    PATH and CROSS_COMPILE are automatically updated.
  • an existing package
(for

  • For example, install gcc-arm-linux-gnueabihf on Ubuntu/Debian: (PC $> sudo apt-get
install gcc-arm-linux-gnueabihf)

for For example: , to use gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi.tar.xz
from https://releases.linaro.org/components/toolchain/binaries/7.2-2017.11/arm-linux-gnueabi/ unzip it
Unzip the toolchain in $HOME ,
and you need to update your environment with:

 
PC $> export PATH=$HOME/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi/bin:$PATH
 PC $> export CROSS_COMPILE=arm-linux-gnueabi-

5.2 Compilation[edit]

In the U-Boot source directory, you need to select the <target> and the <device tree> for your configuration and then execute the "make all" command. :

 
PC $> make <target>_defconfig
 PC $> make DEVICE_TREE=<device-tree> all

Optionally KBUILD_OUTPUT can be used optionally to change the output directory if you want to compile several targets or don't not to compile in the source directory, for . For example:

 
PC $> export KBUILD_OUTPUT=../build/basic

DEVICE_TREE can also be also exported to your environment when you support only one board , for is supported. For example:

 
PC $> export DEVICE_TREE=stm32mp157c-ev1

For all the stm32mp15 family, we manage 3 configurationsExamples from STM32MP15 U-Boot:

Three configurations are supported for STM32MP15x lines More info.png:

  • stm32mp15_trusted_defconfig: trusted boot chain, U-Boot (without SPL) is unsecure and uses Secure monitor from TF-A
  • stm32mp15_optee_defconfig: trusted boot chain, U-Boot (without SPL) is unsecure and uses Secure monitor from SecureOS = OP-TEE
  • stm32mp15_basic_defconfig: basic boot chain, with an SPL as FSBL, U-BOOT is secure and installs monitor with PSCI

The board diversity is only managed with the device tree.

Examples from STM32MP15 U-Boot:

 
PC $> export KBUILD_OUTPUT=../build/basictrusted
 PC $> make stm32mp15_basictrusted_defconfig
 PC $> make DEVICE_TREE=stm32mp157c-<board> all
 
PC $> export KBUILD_OUTPUT=../build/trustedoptee
 PC $> make stm32mp15_trusted_defconfig
 PC $> make export DEVICE_TREE=stm32mp157c-<board>
all  PC $> exportmake KBUILD_OUTPUT=../build/trustedstm32mp15_optee_defconfig
 PC $> export DEVICE_TREE=stm32mp157c-ev1
make all

 
PC $> make stm32mp15_trustedbasic_defconfig
 PC $> make DEVICE_TREE=stm32mp157c-<board>  all

Use help to list other targets:

 
PC $> make help

5.3 Output files[edit]

The resulting U-Boot files are present located in your build directory (U-Boot or KBUILD_OUTPUT) and SPL Images are in the spl subdirectory.

Two binary formats are used for stm32mp devices:

  • STM32 image format (*.stm32)
is
  • , managed by mkimage U-Boot tools and Signing_tool. It is requested by
boot
  • ROM code and TF-A (
for basic boot chain) or by TF-A (for trusted boot chain).
  • see STM32 header for binary files for details).
  • uImage (*.img) format, file including a U-Boot header, managed by SPL and U-Boot (for kernel load)

The U-Boot generated files are the following

  • For Trusted boot chain (TF-A is used as FSBL, with or without OP-TEE)
    • u-boot.stm32 : U-Boot binary with STM32 image header
    => SSBL for Trusted boot chain
    • , loaded by TF-A
  • For Basic boot chain (SPL is used as FSBL)
    • u-boot-spl.stm32 : SPL binary with STM32 image header, loaded by ROM code
    • u-boot.img : U-Boot binary with uImage header
    => SSBL for Basic boot chainu-boot : elf file,
    • , loaded by SPL

The files used to debug with gdb are

  • spl/u-boot-spl.stm32 : SPL binary with STM32 image header => FSBL for Basic boot chainboot : elf file for U-Boot
  • spl/u-boot-spl : elf file , used to debug with gdbfor SPL

6 References[edit]


<noinclude>

{{ArticleMainWriter|PatrickD}}

{{   ArticleApprovedVersion|PatrickD|GeraldB(Passed 13Nov'18), PatriceC(Done 13Nov'18), LionelD(Done 12Nov'18),NicolasLB(Done 13Nov'18), YannG(Passed 15Nov'18), NathalieS/Jean-ChristopheT(NotDone) |27 Nov'18 | Philip S. - 19 Feb '18 | 31 Jan'19 }} 

[[Category:U-Boot]]</noinclude>

== Das U-Boot ==
[https://en.wikipedia.org/wiki/Das_U-Boot Das U-Boot] ("the Universal Boot Loader" or just U-Boot) is an open-source boot loader, which bootloader that can be used on ST boards to initialize the platform and load the Linux<sup>&reg;</sup> kernel.
* Official website: [https://www.denx.de/wiki/U-Boot https://www.denx.de/wiki/U-Boot]
* Official manual: [http://www.denx.de/wiki/U-Boot/Documentation|U-Boot project documentation] and [https://www.denx.de/wiki/DULG/Manual https://www.denx.de/wiki/DULG/Manual]
* The official Official [https://www.denx.de/wiki/U-Boot/SourceCode '''source code'''] is available withunder [https://git-scm.com/ git] repository at [http://githttps://gitlab.denx.de/?p=u-boot.git;a=summary git.denx.de]
  {{PC$}} git clone git://git/u-boot]
  {{PC$}} git clone https://gitlab.denx.de/u-boot/u-boot.git
ReadingRead the {{CodeSource | U-Boot | README | README file}} is recommendedbefore starting using U-Boot. It covers the following topics:
* the source file tree structure
* the meaning description of the CONFIG defines
* instructions for building U-Boot
* a brief description of the Hush shell
* a list of common environment variables

== U-Boot overview ==
[[File: STM32MPU Embedded Software architecture overview.png|link=STM32MPU Embedded Software architecture overview|thumb|Zoom out to STM32MPU Embedded Software]]
The same U-Boot source can generate 2two pieces of firmware used in the SPL and U-Boot [[Boot_chains_overview#STM32MP boot chains|STM32 MPU boot chain]]:SPL and U-Boot* Trusted boot chain: TF-A as FSBL and U-Boot as SSBL
* Basic boot chain: SPL as FSBL and U-Boot as SSBL
<br clear=all>

{{Warning | The basic boot chain cannot be used for product development (see [[Boot_chains_overview#Boot_chains_features_set|Boot chains 
overview]] for details).}} 
It is provided only as an example of the simplest SSBL and to support upstream U-Boot development. However, several known limitations have been identified when SPL is used in conjunction with the minimal secure monitor provided within U-Boot for basic boot chain. They apply to:
* power
* secure access to registers
* limited features (STM32CubeProgrammer / boot from NAND Flash memory). 
No fix is planned for these limitations. 
=== SPL: FSBL for basic boot===
The '''U-Boot SPL''' or just '''SPL''' is the first stage boot loader bootloader (FSBL) for [[Boot_chains_overview#STM32MP boot chains|the basic boot chain]].<br/>It is a small binary (bootstrap utility), generated from the U-Boot source, which fits and stored in the internal and limited-size embedded RAM:. SPL main features are the following: * It is loaded by the ROM code

* it does.
* It performs the initial CPU and board configuration:  (clocks and DDR * itmemory).
* It loads the SSBL (U-Boot) into the DDR memory.


=== U-Boot: SSBL ===
'''U-Boot''' is the default second -stage boot loader bootloader (SSBL) for the STM32 MPU platforms for the 2 boot chains,. It is used both for [[Boot_chains_overview#STM32MP boot chains|trusted and basic]]:
* it boot chains. 
SSBL main features are the following: 
* It is configurable and expendable

* it has.
* It features a simple command line interface (CLI), usually allowing users to interact over a serial console port for interaction with the user
* it provides scripting capabilities
* itconsole. 
* It provides scripting capabilities
* It loads the kernel into RAM and passesgives control to the kernel
* itIt manages manyseveral internal and external devices like such as NAND,  and NOR Flash memories, Ethernet,  and USB

* it has many supported features and commands for
** file.
* It supports the following features and commands:
** File systems: FAT, UBI/UBIFS, JFFS
** IP stack: FTP
** displayDisplay: LCD, HDMI, BMP for splashcreen
** USB: host profile (mass storage) or device profile (DFU stack)

=== SPL phases ===The '''SPL''' runs through executes the following main following phases in SYSRAM:
* '''board_init_f()''': init drivers up to DDR initialisationdriver initialization including DDR initialization (mininimal stack and heap: CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN)
* configure configuration of heap in DDR memory (CONFIG_SPL_SYS_MALLOC_F_LEN)
* '''board_init_r()''': init initialization of the other drivers activated in the SPL device tree
* load loading and execution of U-Boot (or Kernel in Falcon mode<ref>https://www.denx.de/wiki/pub/U-Boot/MiniSummitELCE2013/2013-ELCE-U-Boot-Falcon-Boot.pdf</ref>: {{CodeSource | U-Boot | doc/README.falcon | README.falcon }}) and execute it
.
=== U-Boot phases ===
'''U-Boot''' runs through executes the following main  phases in DDR memory:
* '''Pre-relocation''' initialization (common/board_f.c): minimal init (cpu, clock, reset, ddr, console,...) running at the load address initialization (such as CPU, clock, reset, DDR and console) running at the CONFIG_SYS_TEXT_BASE load address.* '''Relocation''': copy of the code to the end of DDR memory.* '''Post-relocation initialization''':(common/board_r.c): init initialization of all the drivers

* '''Execution of commands''':.
* '''Command execution''' through autoboot (CONFIG_AUTOBOOT) or console shell
** execute Execution of the boot command (by default [[#bootcmd|bootcmd=CONFIG_BOOTCOMMAND]] by default): <br/>for example, execute execution of the command '<code>bootm'</code> to: 
*** load and check images (such as kernel, device tree,  and ramdisk....)
*** fixup the kernel device tree
*** install the secure monitor (optional) or *** pass the control to the Linux kernel (or other to another target application)

== U-Boot configuration ==
The U-Boot binary configuration is based on 
* '''Kbuild infrastructure''' (as in [[Menuconfig_or_how_to_configure_kernel|Linux Kernel]], you can use "<code>make menuconfig"</code> in U-Boot)<br/>The configurations are based on:
** options defined in Kconfig files (CONFIG_ compilation flags)
** the selected configuration file = : {{CodeSource | U-Boot | configs/ | configs/stm32mp*_defconfig}}<br/>

* '''other compilation flags''' definesdefined in {{CodeSource | U-Boot | include/configs/ | include/configs/stm32mp*.h}}<br/>the  (these flags are progressively migrated to Kconfig)<br/>The file name is configured bythrough CONFIG_SYS_CONFIG_NAME.<br/>(these flags are progressively migrating to Kconfig)<br/>for stm32mp157: we use For  {{MicroprocessorDevice | device=15}}, the {{CodeSource | U-Boot | include/configs/stm32mp1.h | include/configs/stm32mp1.h}} file 
is used.
* '''[[Device_tree|DeviceTree]]''' = : U-Boot and SPL binaries include a device tree blob whichthat is parsed at run timeruntimeAll the configuration flags (prefixed by CONFIG_) are described in the source code: , either in the {{CodeSource | U-Boot | README | README}} file or in the {{CodeSource | U-Boot | doc/ | documentation directory}}.<br/>For example:, CONFIG_SPL => activate activates the SPL compilation.<br />

Hence to compile U-Boot, you need to [[#Kbuild|select the <target>]] and [[#Device_tree|the device tree]] for the board in order to selectchoose a predefined configuration.<br/>
See Refer to [[#U-Boot_build]] for examples.

=== Kbuild ===
The Like the kernel, the U-Boot build system is based on [[Menuconfig_or_how_to_configure_kernel|configuration symbols as the kernel]] (defined in Kconfig files), and. The selected values are stored in a '''.config''' file in the build directory, with the same makefile target. 

* select .<br/>

Proceed as follows:
* Select a pre-defined configuration (defconfig file, in {{CodeSource | U-Boot | configs/ | configs directory }}) and generate the first '''.config''':

  {{PC$}} make <config>_defconfig


* change .

* Change the U-Boot compile configuration (modify .config) by using one of the 5 make commandfollowing  five <code>make</code> commands:

  {{PC$}} '''make menuconfig''' {{Highlight|--> menu based program}}
  {{PC$}} make config  {{Highlight|--> line-oriented configuration}}
  {{PC$}} make xconfig {{Highlight|--> QT program<ref>https://en.wikipedia.org/wiki/Xconfig</ref>}}
  {{PC$}} make gconfig {{Highlight|--> GTK program}}
  {{PC$}} make nconfig {{Highlight|--> ncurse menu based program}}
You can then compile U-Boot with the updated .config.

Warning: the modification is only done performed locally in the build directory, it is . It will be lost after a "<code>make distclean"

So if you want to use your configuration as defconfig:
   {{PC$}} make savedefconfig
</code>.

Save your configuration to be able to use it as a defconfig file:
   {{PC$}} make savedefconfigThis target saves the current config as a defconfig file in the build directory, and. It can then be compared with the predefined configuration (configs/stm32mp*defconfig).

The other makefile targets are :
the following:
{{PC$}} make help
  ....
  Configuration targets:
    config	  - Update current config utilising a line-oriented program
    nconfig         - Update current config utilising a ncurses menu based
                      program
    menuconfig	  - Update current config utilising a menu based program
    xconfig	  - Update current config utilising a Qt based front-end
    gconfig	  - Update current config utilising a GTK+ based front-end
    oldconfig	  - Update current config utilising a provided .config as base
    localmodconfig  - Update current config disabling modules not loaded
    localyesconfig  - Update current config converting local mods to core
    defconfig	  - New config with default from ARCH supplied defconfig
    savedefconfig   - Save current config as ./defconfig (minimal config)
    allnoconfig	  - New config where all options are answered with no
    allyesconfig	  - New config where all options are accepted with yes
    allmodconfig	  - New config selecting modules when possible
    alldefconfig    - New config with all symbols set to default
    randconfig	  - New config with random answer to all options
    listnewconfig   - List new options
    olddefconfig	  - Same as oldconfig but sets new symbols to their
                     default value without prompting

=== Device tree ===See Refer to {{CodeSource | U-Boot | doc/README.fdt-control | doc/README.fdt-control}} 
for details.
The board device tree, with has the same binding as the kernel, . It is integrated withwithin the SPL and U-Boot binaries:
* By default, it is appended at the end of the code by default  (CONFIG_OF_SEPARATE)

* embedded in .
* It is embedded in the U-Boot binary (CONFIG_OF_EMBED): useful for debug, allows easy elf file loading. This is useful for debugging since it enables easy .elf file loading.


A default device tree is definedavailable in the defconfig file (with by setting CONFIG_DEFAULT_DEVICE_TREE).

You can alsoeither select another supported device tree withusing the make flag DEVICE_TREE <br/> for stm32mp32 boards the file aremake flag. For stm32mp boards, the corresponding file is: {{CodeSource | U-Boot | arch/arm/dts/ | arch/arm/dts/stm32mp*.dts}}.

   {{PC$}} make DEVICE_TREE=<dts-file-name>


or you can provide a precompiled device tree blob (withusing EXT_DTB option):

   {{PC$}} make EXT_DTB=boot/<dts-file-name>.dtb

The SPL device tree is also generated from this device tree; but. However to reduce its size,  the U-Boot makefile uses the fdtgrep tool to parse the full U-Boot DTB and identify all the drivers neededrequired by SPL.

To do this, U-Boot uses some specific device-tree flags to specifydefine if the associated driver is initialized prior to U-Boot relocation and/or if the associated node is present in SPL :
* '''u-boot,dm-pre-reloc''' => present in SPL, initialized before relocation in U-Boot
* '''u-boot,dm-pre-proper''' => initialized before relocation in U-Boot
* '''u-boot,dm-spl''' => present in SPL

In the device tree used by U-Boot, these flags '''need to be added in each node''' used in SPL or in U-Boot before relocation but also and for each used handle (clock, reset, pincontrol).

== U-Boot command line interface (CLI) ==see Refer to [http://www.denx.de/wiki/view/DULG/UBootCommandLineInterface U-Boot Command Line Interface].


If CONFIG_AUTOBOOT is activated, to enter in this console, you have CONFIG_BOOTDELAY seconds (2s by default) before [[#bootcmd|bootcmd]] execution (CONFIG_BOOTCOMMAND)to enter the console by pressing any key when, after the line below is displayed. and [[#bootcmd|bootcmd]] is executed (CONFIG_BOOTCOMMAND):Hit any key to stop autoboot:  2

=== Commands ===
The commands are defined in {{CodeSource | U-Boot | cmd/ | cmd/*.c}}, they. They are activated under associated configuration flag '''CONFIG_CMD_*'''.

Use the command '''help''' through the corresponding '''CONFIG_CMD_*''' configuration flag.

Use the <code>help</code> command in the U-Boot shell to list the commands available commands on your device.

List of :
  {{Board$}} help

Below the list of all commands extracted from [http://www.denx.de/wiki/view/DULG/Manual U-Boot Manual] ('''not-exhaustive'''):
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupInfo Information Commands]
** bdinfo - printprints Board Info structure
** coninfo - printprints console devices and informationsinformation

** flinfo - print FLASHprints Flash memory information
** iminfo - printprints header information for application image
** help - printprints online help
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupMemory Memory Commands]
** base - printprints or set sets the address offset
** crc32 - checksum calculation
** cmp - memory compare
** cp - memory copy
** md - memory display
** mm - memory modify (auto-incrementing)
** mtest - simple RAM test
** mw - memory write (fill)
** nm - memory modify (constant address)
** loop - infinite loop on address range
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupFlash Flash Memory Commands]
** cp - memory copy
** flinfo - print FLASHprints Flash memory information
** erase - erase FLASHerases Flash memory
** protect - enableenables or disable FLASH disables Flash memory write protection
** mtdparts - definedefines a Linux compatible MTD partition scheme
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupExec Execution Control Commands]
** source - run runs a script from memory
** bootm - bootboots application image from memory
** go - startstarts application at address 'addr'
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupDownload Download Commands]
** bootp - bootboots image via network using BOOTP/TFTP protocol
** dhcp - invokeinvokes DHCP client to obtain IP/boot params
** loadb - loadloads binary file over serial line (kermit mode)
** loads - loadloads S-Record file over serial line
** rarpboot- bootboots image via network using RARP/TFTP protocol
** tftpboot- bootboots image via network using TFTP protocol
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupEnvironment Environment Variables Commands]
** printenv- printprints environment variables
** saveenv - savesaves environment variables to persistent storage
** setenv - setsets environment variables
** run - runruns commands in an environment variable
** bootd - bootboots default, i.e., run 'bootcmd'
* [http://www.denx.de/wiki/view/DULG/UBootCmdFDT Flattened Device Tree support]
** fdt addr - select selects the FDT to work on
** fdt list - printprints one level
** fdt print - recursive printprinting

** fdt mknode - createcreates new nodes
** fdt set - setsets node properties
** fdt rm - removeremoves nodes or properties
** fdt move - movemoves FDT blob to new address
** fdt chosen - fixup dynamic infoinformation

* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupSpecial Special Commands]
** i2c - I2C sub-system
* [http://www.denx.de/wiki/view/DULG/UBootStorageDevices Storage devices]
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupMisc Miscellaneous Commands]
** echo - echoechoes args to console
** reset - Perform RESET of the CPU
** sleep - delay execution for some time
** version - print Performs a CPU reset  
** sleep - delays the execution for a predefined time 
** version - prints the monitor version

To add a new command, see refer to {{CodeSource | U-Boot | doc/README.commands }}.


=== U-Boot environment variables ===

The U-Boot behavior is configured withthrough environment variables.
see Refer to [http://www.denx.de/wiki/view/DULG/UBootEnvVariables Manual] and {{CodeSource | U-Boot | README | README}} / Environment Variables


By default the env is NOT saved (CONFIG_ENV_IS_NOWHERE), only the default environment is used (saveenv command is not working)

You can modify this default environment .

On the first boot, U-Boot uses a default environment embedded in the U-Boot binary. You can modify it by changing the content of CONFIG_EXTRA_ENV_SETTINGS in your configuration file (for example ./include/configs/stm32mp1.h) (see {{CodeSource | U-Boot | README | README}} / - Default Environment).
You This environment can also choose one location with configuration flags:
* be modified and saved in the boot device. When it is present, it is loaded during U-Boot initialization:
* for ''e''•MMC/SD card boot (CONFIG_ENV_IS_IN_MMC
* CONFIG_ENV_IS_IN_FLASH
* EXT4), in the bootable ext4 partition "bootfs" in <br/>in file CONFIG_ENV_EXT4_FILE="uboot.env".
* for NAND boot (CONFIG_ENV_IS_IN_SPI
* CONFIG_ENV_IS_IN_FAT
* CONFIG_ ENV_IS_IN_NAND
* UBI), in the two UBI volumes "config" (CONFIG_ENV_UBI_VOLUME) and "config_r"  (CONFIG_ENV_UBI_VOLUME_REDUND).
* for NOR boot (CONFIG_ENV_IS_IN_UBI
* CONFIG_ENV_IS_IN_EEPROM

==== bootcmd ====
Autoboot command: SPI_FLASH), in the u-boot_env mtd parttion (at offset CONFIG_ENV_OFFSET).

==== env command ====

The <code>env</code> command allows displaying, modifying and saving the environment in U-Boot console.

  {{Board$}} help env
  env - environment handling commands

  Usage:
  env default [-f] -a - [forcibly] reset default environment
  env default [-f] var [...] - [forcibly] reset variable(s) to their default values
  env delete [-f] var [...] - [forcibly] delete variable(s)
  env edit name - edit environment variable
  env exists name - tests for existence of variable
  env print [-a | name ...] - print environment
  env print -e [name ...] - print UEFI environment
  env run var [...] - run commands in an environment variable
  env save - save environment
  env set -e name [arg ...] - set UEFI variable; unset if 'arg' not specified
  env set [-f] name [arg ...]

Example: proceed as follows to restore the default environment and save it. This is useful after a U-Boot upgrade:

  {{Board$}} env default -a
  {{Board$}} env save

==== bootcmd ====
"bootcmd" variable is the autoboot command. It defines the command executed when U-Boot starts (CONFIG_BOOTCOMMAND).
But you can change this variable in CONFIG_EXTRA_ENV_SETTINGS (after BOOTENV macro needed for [[#Generic Distro configuration]]).
<pre>

#define CONFIG_EXTRA_ENV_SETTINGS \
	"stdin=serial\0" \
	"stdout=serial\0" \
	"stderr=serial\0" \
	"kernel_addr_r=0xc2000000\0" \
	"fdt_addr_r=0xc4000000\0" \
	"scriptaddr=0xc4100000\0" \
	"pxefile_addr_r=0xc4200000\0" \
	"splashimage=0xc4300000\0"  \
	"ramdisk_addr_r=0xc4400000\0" \
	"fdt_high=0xffffffff\0" \
	"initrd_high=0xffffffff\0" \
	BOOTENV \
	"bootcmd=run bootcmd_mmc0\0"</pre>


=== Generic Distro configuration ===

see For stm32mp,  CONFIG_BOOTCOMMAND="run bootcmd_stm32mp":

  {{Board$}} env print bootcmd    
   bootcmd=run bootcmd_stm32mp

"bootcmd_stm32mp" is a script that selects the command to be executed for each boot device (see ./include/configs/stm32mp1.h), based on [[#Generic Distro configuration|generic distro scripts]]:
* for serial/usb: execute the <code>stm32prog</code> command.
* for mmc boot (''e''•MMC, SD card), boot only on the same device (bootcmd_mmc...).
* for nand boot, boot with on ubifs partition on nand (bootcmd_ubi0).
* for nor boot, use the default order ''e''•MMC (SDMMC 1)/ NAND / SD card (SDMMC 0) / SDMMC2 (the default bootcmd: distro_bootcmd).

  {{Board$}} env print bootcmd_stm32mp

You can then change this configuration:
* either permanently in your board file (default environment by CONFIG_EXTRA_ENV_SETTINGS or change CONFIG_BOOTCOMMAND value) or
* temporarily in the saved environment:

  {{Board$}} env set bootcmd run bootcmd_mmc0 
  {{Board$}} env save

Note: To reset the environment to its default value: 

  {{Board$}} env default bootcmd
  {{Board$}} env save

=== Generic Distro configuration ===

Refer to {{CodeSource | U-Boot | doc/README.distro | doc/README.distro}} 
for details.
This feature is activated for by default on ST boards (CONFIG_DISTRO_DEFAULTS):
* one boot command (bootmcd_xxx) exists for each bootable device.

* U-Boot is independent of the Linux distribution used.
* bootcmd is defined in {{CodeSource | U-Boot | ./include/config_distro_bootcmd.h }}
WithWhen DISTRO is enabled, the default command that is executed:  by default is {{CodeSource | U-Boot | include/config_distro_bootcmd.h}}:

  bootcmd=run distro_bootcmd

This script will try tries any device found in the variable 'boot_targets' variable and executeexecutes the associated bootcmd.

Example for device mmc0, mmc1, mmc2, pxe and ubifs devices:
  bootcmd_mmc0=setenv devnum 0; run mmc_boot
  bootcmd_mmc1=setenv devnum 1; run mmc_boot
  bootcmd_mmc2=setenv devnum 2; run mmc_boot
  bootcmd_pxe=run boot_net_usb_start; dhcp; if pxe get; then pxe boot; fi
  bootcmd_ubifs0=setenv devnum 0; run ubifs_boot

U-Boot searchssearches for a configuration file '''extlinux.conf''' in a bootable device, thisconfiguration file for each bootable device. This file defines the kernel configuration to usebe used: 
* bootargs
* kernel + device tree + ramdisk files (optional)
* FIT image

=== U-Boot scripting capabilities ===

"Script files" are command sequences that will be are executed by the U-Boot's command interpreter; this. This feature is especiallyparticularly useful when you to configure U-Boot to use a real shell (hush) as command interpreter.

See [http://www.denx.de/wiki/view/DULG/UBootScripts| U-Boot script manual] for an example.

== U-Boot build ==
=== Prerequisites ===
You need:* a PC with Linux and tools: 
** see [[PC_prerequisites]]
** [[#ARM cross compiler]]
* U-Boot source code
** the latest STMicroelectonicsSTMicroelectronics U-Boot version
*** tar.xz file from Developer Package (for example [[STM32MP1_Developer_Package#Installing_the_U-Boot|STM32MP1]])
*** from GITHUB<ref>https://github.com/STMicroelectronics/u-boot</ref>, with <code>git</code> command
  {{PC$}} git clone https://github.com/STMicroelectronics/u-boot
:* from the Mainline U-Boot in official GIT repository <ref>http://githttps://gitlab.denx.de/u-boot/u-boot.git or https://github.com/u-boot/u-boot</ref>

  {{PC$}} git clone http://githttps://gitlab.denx.de/u-boot/u-boot.git

==== ARM cross compiler ====
You need to have a A cross compiler <ref>https://en.wikipedia.org/wiki/Cross_compiler</ref> must be installed on your Host (X86_64, i686, ...) for the ARM targeted Device architecture = ARM. In addition, the environment variables ($PATH and $CROSS_COMPILE) need to  environment variables must be configured in your shell.

You can use gcc for ARM, available in:#* the SDK toolchain<br/>See  (see [[Cross-compile with OpenSTLinux SDK]], )<br/>PATH and CROSS_COMPILE are automatically updated.#* an existing package (for <br/>For example, install gcc-arm-linux-gnueabihf on Ubuntu/Debian: ({{PC$}} sudo apt-get install gcc-arm-linux-gnueabihf)
# an existing toolchain:
#*.
* an existing toolchain:
** gcc v8 toolchain provided by arm (https://developer.arm.com/open-source/gnu-toolchain/gnu-a/downloads/)#*** gcc v7 toolchain provided by linaro: (https://www.linaro.org/downloads/)
forFor example:, to use '''gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi.tar.xz'''<br/>from https://releases.linaro.org/components/toolchain/binaries/7.2-2017.11/arm-linux-gnueabi/

unzip it in $HOME,<br/>and you need to update your environment<br/>

Unzip the toolchain in $HOME and update your environment with:
  {{PC$}} export PATH=$HOME/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi/bin:$PATH
  {{PC$}} export CROSS_COMPILE=arm-linux-gnueabi-

=== Compilation  ===
In the U-Boot source directory, you need to select the <target> and the <device tree> for your configuration and then execute the "<code>make all"</code> command.:


  {{PC$}} make <target>_defconfig
  {{PC$}} make DEVICE_TREE=<device-tree> all
Optionally '''KBUILD_OUTPUT''' can be used optionally to change the output directory if you want to compile several targets or don't not to compile in the source directory, for. For example:
  {{PC$}} export KBUILD_OUTPUT=../build/basic

'''DEVICE_TREE''' can also be also exported to your environment when you support only one board, for  is supported. For example:
  {{PC$}} export DEVICE_TREE=stm32mp157c-ev1
For all the stm32mp15 family, we manage 3 configurations:
* stm32mp15_trusted_defconfigExamples from [[STM32MP15 U-Boot]]:

Three configurations are supported for  {{MicroprocessorDevice | device=15}}:
* {{Highlight|stm32mp15_trusted_defconfig}}: [[Boot_chains_overview#STM32MP boot chains|trusted boot chain]], U-Boot (without SPL) is unsecure and uses Secure monitor from TF-A
* {{Highlight|stm32mp15_optee_defconfig}}: [[Boot_chains_overview#STM32MP boot chains|trusted boot chain]], U-Boot (without SPL) is unsecure and uses Secure monitor from SecureOS = [[OP-TEE overview|OP-TEE]]
* stm32mp15_basic_defconfig: [[Boot_chains_overview#STM32MP boot chains|basic boot chain]], with an SPL as FSBL, U-BOOT is secure and installs monitor with PSCI

The board diversity is only managed with the device tree.
Examples from [[STM32MP15 U-Boot]]:  {{PC$}} export KBUILD_OUTPUT=../build/basictrusted

  {{PC$}} make stm32mp15_basictrusted_defconfig
  {{PC$}} make DEVICE_TREE=stm32mp157c-<board> all

  {{PC$}} export KBUILD_OUTPUT=../build/trustedoptee

  {{PC$}} make stm32mp15_trusted_defconfig
  {{PC$}} make export DEVICE_TREE=stm32mp157c-<board>
all
  {{PC$}} export KBUILD_OUTPUT=../build/trusted
  {{PC$}} export DEVICE_TREE=stm32mp157c-ev1
  {{PC$}} make stm32mp15_trusted_defconfig
  {{PC$}} make make stm32mp15_optee_defconfig
  {{PC$}} make all

  {{PC$}} make stm32mp15_basic_defconfig
  {{PC$}} make DEVICE_TREE=stm32mp157c-<board>  all

Use help to list other targets:
  {{PC$}} make help

=== Output files ===
The resulting U-Boot files are presentlocated in your build directory (U-Boot or KBUILD_OUTPUT) and SPL Images are in the spl subdirectory..

Two binary formats are used for stm32mp devices:
* STM32 image format (*.stm32) is,  managed by mkimage U-Boot tools and is requested by boot ROM (for basic boot chain) or by TF-A (for trusted boot chain).

* '''u-boot.stm32'''[[Signing_tool]]. It is requested by ROM code and TF-A (see [[STM32 header for binary files]] for details).
* uImage (*.img) format, file including a U-Boot header, managed by SPL and U-Boot (for kernel load)

The U-Boot generated files are the following
* For {{Highlight|'''Trusted boot chain'''}} (TF-A is used as FSBL, with or without OP-TEE)
** {{Highlight|'''u-boot.stm32'''}} : U-Boot binary with STM32 image header => SSBL for Trusted boot chain
* '''u-boot.img''' : U-Boot binary with uImage header => SSBL for Basic boot chain

* u-boot : elf file, , loaded by TF-A

* For '''Basic boot chain''' (SPL is used as FSBL)
** '''u-boot-spl.stm32''' : SPL binary with STM32 image header, loaded by ROM code
** '''u-boot.img''' : U-Boot binary with uImage header, loaded by SPL

The files used to debug with gdb * '''spl/u-boot-spl.stm32''' : SPL binary with STM32 image header => FSBL for Basic boot chainare
* u-boot : elf file for U-Boot* spl/u-boot-spl : elf file, used to debug with gdb

== References ==<references/> for SPL

== References ==<references/>

<noinclude>

[[Category:U-Boot]]
{{PublicationRequestId | 12893 | 2019-08-01}}</noinclude>
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<noinclude>
+
== Das U-Boot ==
{{ArticleMainWriter|PatrickD}}
+
[https://en.wikipedia.org/wiki/Das_U-Boot Das U-Boot] ("the Universal Boot Loader" or U-Boot) is an open-source bootloader that can be used on ST boards to initialize the platform and load the Linux<sup>&reg;</sup> kernel.
 
 
{{  ArticleApprovedVersion|PatrickD|GeraldB(Passed 13Nov'18), PatriceC(Done 13Nov'18), LionelD(Done 12Nov'18),NicolasLB(Done 13Nov'18), YannG(Passed 15Nov'18), NathalieS/Jean-ChristopheT(NotDone) |27 Nov'18 | Philip S. - 19 Feb '18 | 31 Jan'19 }}
 
 
 
[[Category:U-Boot]]
 
</noinclude>
 
   
== Das U-Boot ==
 
[https://en.wikipedia.org/wiki/Das_U-Boot Das U-Boot] ("the Universal Boot Loader" or just U-Boot) is an open-source boot loader, which can be used on ST boards to initialize the platform and load the Linux<sup>&reg;</sup> kernel.
 
 
* Official website: [https://www.denx.de/wiki/U-Boot https://www.denx.de/wiki/U-Boot]
 
* Official website: [https://www.denx.de/wiki/U-Boot https://www.denx.de/wiki/U-Boot]
 
* Official manual: [http://www.denx.de/wiki/U-Boot/Documentation|U-Boot project documentation] and [https://www.denx.de/wiki/DULG/Manual https://www.denx.de/wiki/DULG/Manual]
 
* Official manual: [http://www.denx.de/wiki/U-Boot/Documentation|U-Boot project documentation] and [https://www.denx.de/wiki/DULG/Manual https://www.denx.de/wiki/DULG/Manual]
* The official [https://www.denx.de/wiki/U-Boot/SourceCode '''source code'''] is available with [https://git-scm.com/ git] repository at [http://git.denx.de/?p=u-boot.git;a=summary git.denx.de]
+
* Official [https://www.denx.de/wiki/U-Boot/SourceCode '''source code'''] is available under [https://git-scm.com/ git] repository at [https://gitlab.denx.de/u-boot/u-boot]
   {{PC$}} git clone git://git.denx.de/u-boot.git
+
   {{PC$}} git clone https://gitlab.denx.de/u-boot/u-boot.git
   
Reading the {{CodeSource | U-Boot | README | README file}} is recommended. It covers the following topics:
+
Read the {{CodeSource | U-Boot | README | README file}} before starting using U-Boot. It covers the following topics:
* the source file tree structure
+
* source file tree structure
* the meaning of the CONFIG defines
+
* description of CONFIG defines
 
* instructions for building U-Boot
 
* instructions for building U-Boot
* a brief description of the Hush shell
+
* brief description of the Hush shell
* a list of common environment variables
+
* list of common environment variables
   
 
== U-Boot overview ==
 
== U-Boot overview ==
 
[[File: STM32MPU Embedded Software architecture overview.png|link=STM32MPU Embedded Software architecture overview|thumb|Zoom out to STM32MPU Embedded Software]]
 
[[File: STM32MPU Embedded Software architecture overview.png|link=STM32MPU Embedded Software architecture overview|thumb|Zoom out to STM32MPU Embedded Software]]
The same U-Boot source can generate 2 pieces of firmware used in the [[Boot_chains_overview#STM32MP boot chains|STM32 MPU boot chain]]: SPL and U-Boot
+
The same U-Boot source can generate two pieces of firmware used in SPL and U-Boot [[Boot_chains_overview#STM32MP boot chains|STM32 MPU boot chain]]:
* Trusted boot chain: U-Boot as SSBL
+
* Trusted boot chain: TF-A as FSBL and U-Boot as SSBL
 
* Basic boot chain: SPL as FSBL and U-Boot as SSBL
 
* Basic boot chain: SPL as FSBL and U-Boot as SSBL
  +
 
<br clear=all>
 
<br clear=all>
  +
  +
{{Warning | The basic boot chain cannot be used for product development (see [[Boot_chains_overview#Boot_chains_features_set|Boot chains
  +
overview]] for details).}}
  +
It is provided only as an example of the simplest SSBL and to support upstream U-Boot development. However, several known limitations have been identified when SPL is used in conjunction with the minimal secure monitor provided within U-Boot for basic boot chain. They apply to:
  +
* power
  +
* secure access to registers
  +
* limited features (STM32CubeProgrammer / boot from NAND Flash memory).
  +
No fix is planned for these limitations.
   
 
=== SPL: FSBL for basic boot===
 
=== SPL: FSBL for basic boot===
The '''U-Boot SPL''' or just '''SPL''' is the first stage boot loader (FSBL) for [[Boot_chains_overview#STM32MP boot chains|the basic boot chain]].<br/>It is a small binary (bootstrap utility), generated from the U-Boot source, which fits in the internal and limited embedded RAM:
+
The '''U-Boot SPL''' or '''SPL''' is the first stage bootloader (FSBL) for [[Boot_chains_overview#STM32MP boot chains|the basic boot chain]].<br/>It is a small binary (bootstrap utility) generated from the U-Boot source and stored in the internal limited-size embedded RAM. SPL main features are the following:  
* It is loaded by the ROM code
+
* It is loaded by the ROM code.
* it does the initial CPU and board configuration: clocks and DDR
+
* It performs the initial CPU and board configuration (clocks and DDR memory).
* it loads the SSBL (U-Boot) into DDR memory
+
* It loads the SSBL (U-Boot) into the DDR memory.
   
 
=== U-Boot: SSBL ===
 
=== U-Boot: SSBL ===
'''U-Boot''' is the default second stage boot loader (SSBL) for the STM32 MPU platforms for the 2 boot chains, [[Boot_chains_overview#STM32MP boot chains|trusted and basic]]:
+
'''U-Boot''' is the default second-stage bootloader (SSBL) for STM32 MPU platforms. It is used both for [[Boot_chains_overview#STM32MP boot chains|trusted and basic]] boot chains.
* it is configurable and expendable
+
SSBL main features are the following:  
* it has a simple command line interface (CLI), usually over a serial console port for interaction with the user
+
* It is configurable and expendable.
* it provides scripting capabilities
+
* It features a simple command line interface (CLI), allowing users to interact over a serial port console.
* it loads the kernel into RAM and passes control to the kernel
+
* It provides scripting capabilities
* it manages many internal and external devices like NAND, NOR, Ethernet, USB
+
* It loads the kernel into RAM and gives control to the kernel
* it has many supported features and commands for
+
* It manages several internal and external devices such as NAND and NOR Flash memories, Ethernet and USB.
** file systems: FAT, UBI/UBIFS, JFFS
+
* It supports the following features and commands:
  +
** File systems: FAT, UBI/UBIFS, JFFS
 
** IP stack: FTP
 
** IP stack: FTP
** display: LCD, HDMI, BMP for splashcreen
+
** Display: LCD, HDMI, BMP for splashcreen
** USB: host profile (mass storage) or device profile (DFU stack)
+
** USB: host (mass storage) or device (DFU stack)
   
 
=== SPL phases ===
 
=== SPL phases ===
The '''SPL''' runs through the main following phases in SYSRAM:
+
'''SPL''' executes the following main phases in SYSRAM:
* '''board_init_f()''': init drivers up to DDR initialisation (mininimal stack and heap: CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN)
+
* '''board_init_f()''': driver initialization including DDR initialization (mininimal stack and heap: CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN)
* configure heap in DDR (CONFIG_SPL_SYS_MALLOC_F_LEN)
+
* configuration of heap in DDR memory (CONFIG_SPL_SYS_MALLOC_F_LEN)
* '''board_init_r()''': init other drivers activated in the SPL device tree
+
* '''board_init_r()''': initialization of the other drivers activated in the SPL device tree
* load U-Boot (or Kernel in Falcon mode<ref>https://www.denx.de/wiki/pub/U-Boot/MiniSummitELCE2013/2013-ELCE-U-Boot-Falcon-Boot.pdf</ref>: {{CodeSource | U-Boot | doc/README.falcon | README.falcon }}) and execute it
+
* loading and execution of U-Boot (or Kernel in Falcon mode<ref>https://www.denx.de/wiki/pub/U-Boot/MiniSummitELCE2013/2013-ELCE-U-Boot-Falcon-Boot.pdf</ref>: {{CodeSource | U-Boot | doc/README.falcon | README.falcon }}).
   
 
=== U-Boot phases ===
 
=== U-Boot phases ===
'''U-Boot''' runs through the following main phases in DDR:
+
'''U-Boot''' executes the following main phases in DDR memory:
* '''Pre-relocation''' initialization (common/board_f.c): minimal init (cpu, clock, reset, ddr, console,...) running at the load address CONFIG_SYS_TEXT_BASE
+
* '''Pre-relocation''' initialization (common/board_f.c): minimal initialization (such as CPU, clock, reset, DDR and console) running at the CONFIG_SYS_TEXT_BASE load address.
* '''Relocation''': copy the code to the end of DDR
+
* '''Relocation''': copy of the code to the end of DDR memory.
* '''Post-relocation initialization''':(common/board_r.c): init all the drivers
+
* '''Post-relocation initialization''':(common/board_r.c): initialization of all the drivers.
* '''Execution of commands''': through autoboot (CONFIG_AUTOBOOT) or console shell
+
* '''Command execution''' through autoboot (CONFIG_AUTOBOOT) or console shell
** execute the boot command ([[#bootcmd|bootcmd=CONFIG_BOOTCOMMAND]] by default): <br/>for example, execute the command 'bootm' to:  
+
** Execution of the boot command (by default [[#bootcmd|bootcmd=CONFIG_BOOTCOMMAND]]): <br/>for example, execution of the command <code>bootm</code> to:  
*** load and check images (kernel, device tree, ramdisk....)
+
*** load and check images (such as kernel, device tree and ramdisk)
*** fixup kernel device tree
+
*** fixup the kernel device tree
*** install secure monitor (optional)
+
*** install the secure monitor (optional) or
*** pass control to the Linux kernel (or other target application)
+
*** pass the control to the Linux kernel (or to another target application)
   
 
== U-Boot configuration ==
 
== U-Boot configuration ==
 
The U-Boot binary configuration is based on  
 
The U-Boot binary configuration is based on  
* '''Kbuild infrastructure''' (as in [[Menuconfig_or_how_to_configure_kernel|Linux Kernel]], you can use "make menuconfig" in U-Boot)<br/>The configurations are based on:
+
* '''Kbuild infrastructure''' (as in [[Menuconfig_or_how_to_configure_kernel|Linux Kernel]], you can use <code>make menuconfig</code> in U-Boot)<br/>The configurations are based on:
 
** options defined in Kconfig files (CONFIG_ compilation flags)
 
** options defined in Kconfig files (CONFIG_ compilation flags)
** the selected configuration file = {{CodeSource | U-Boot | configs/ | configs/stm32mp*_defconfig}}<br/>
+
** the selected configuration file: {{CodeSource | U-Boot | configs/ | configs/stm32mp*_defconfig}}<br/>
* '''other compilation flags''' defines in {{CodeSource | U-Boot | include/configs/ | include/configs/stm32mp*.h}}<br/>the file name is configured by CONFIG_SYS_CONFIG_NAME<br/>(these flags are progressively migrating to Kconfig)<br/>for stm32mp157: we use {{CodeSource | U-Boot | include/configs/stm32mp1.h | include/configs/stm32mp1.h}} file
+
* '''other compilation flags''' defined in {{CodeSource | U-Boot | include/configs/ | include/configs/stm32mp*.h}} (these flags are progressively migrated to Kconfig)<br/>The file name is configured through CONFIG_SYS_CONFIG_NAME.<br/>For  {{MicroprocessorDevice | device=15}}, the {{CodeSource | U-Boot | include/configs/stm32mp1.h | include/configs/stm32mp1.h}} file is used.
   
* '''[[Device_tree|DeviceTree]]''' = U-Boot and SPL binaries include a device tree blob which is parsed at run time
+
* '''[[Device_tree|DeviceTree]]''': U-Boot and SPL binaries include a device tree blob that is parsed at runtime
All the configuration flags (CONFIG_) are described in the source code: the {{CodeSource | U-Boot | README | README}} file or {{CodeSource | U-Boot | doc/ | documentation directory}}<br/>example: CONFIG_SPL => activate the SPL compilation.<br />
+
All the configuration flags (prefixed by CONFIG_) are described in the source code, either in the {{CodeSource | U-Boot | README | README}} file or in the {{CodeSource | U-Boot | doc/ | documentation directory}}.<br/>For example, CONFIG_SPL activates the SPL compilation.<br />
Hence to compile U-Boot, you need to [[#Kbuild|select the <target>]] and [[#Device_tree|the device tree]] for the board to select a predefined configuration.<br/>
+
Hence to compile U-Boot, [[#Kbuild|select the <target>]] and [[#Device_tree|the device tree]] for the board in order to choose a predefined configuration.<br/>
See [[#U-Boot_build]] for examples.
+
Refer to [[#U-Boot_build]] for examples.
   
 
=== Kbuild ===
 
=== Kbuild ===
   
The U-Boot build system is based on [[Menuconfig_or_how_to_configure_kernel|configuration symbols as the kernel]] (defined in Kconfig files), and selected values are stored in a '''.config''' file in the build directory, with the same makefile target.
+
Like the kernel, the U-Boot build system is based on [[Menuconfig_or_how_to_configure_kernel|configuration symbols]] (defined in Kconfig files). The selected values are stored in a '''.config''' file in the build directory, with the same makefile target. .<br/>
 
+
Proceed as follows:
* select pre-defined configuration (defconfig file, in {{CodeSource | U-Boot | configs/ | configs directory }}) and generate the first '''.config'''
+
* Select a pre-defined configuration (defconfig file in {{CodeSource | U-Boot | configs/ | configs directory }}) and generate the first '''.config''':
   {{PC$}} make <config>_defconfig
+
   {{PC$}} make <config>_defconfig.
   
* change U-Boot compile configuration (modify .config) using one of the 5 make command
+
* Change the U-Boot compile configuration (modify .config) by using one of the following  five <code>make</code> commands:
 
   {{PC$}} '''make menuconfig''' {{Highlight|--> menu based program}}
 
   {{PC$}} '''make menuconfig''' {{Highlight|--> menu based program}}
 
   {{PC$}} make config  {{Highlight|--> line-oriented configuration}}
 
   {{PC$}} make config  {{Highlight|--> line-oriented configuration}}
Line 93: Line 96:
 
You can then compile U-Boot with the updated .config.
 
You can then compile U-Boot with the updated .config.
   
Warning: modification is only done locally in the build directory, it is lost after a "make distclean"
+
Warning: the modification is performed locally in the build directory. It will be lost after a <code>make distclean</code>.
   
So if you want to use your configuration as defconfig:
+
Save your configuration to be able to use it as a defconfig file:
 
   {{PC$}} make savedefconfig
 
   {{PC$}} make savedefconfig
  +
This target saves the current config as a defconfig file in the build directory. It can then be compared with the predefined configuration (configs/stm32mp*defconfig).
   
This target saves the current config as a defconfig file in the build directory, and can be compared with the predefined configuration (configs/stm32mp*defconfig).
+
The other makefile targets are the following:
 
 
The other makefile targets are :
 
   
  {{PC$}} make help
+
  {{PC$}} make help
 
   ....
 
   ....
 
   Configuration targets:
 
   Configuration targets:
Line 126: Line 128:
   
 
=== Device tree ===
 
=== Device tree ===
See {{CodeSource | U-Boot | doc/README.fdt-control | doc/README.fdt-control}}
+
Refer to {{CodeSource | U-Boot | doc/README.fdt-control | doc/README.fdt-control}} for details.
   
The board device tree, with the same binding as the kernel, is integrated with the SPL and U-Boot binaries:
+
The board device tree has the same binding as the kernel. It is integrated within the SPL and U-Boot binaries:
* appended at the end of the code by default (CONFIG_OF_SEPARATE)
+
* By default, it is appended at the end of the code (CONFIG_OF_SEPARATE).
* embedded in binary (CONFIG_OF_EMBED): useful for debug, allows easy elf file loading
+
* It is embedded in the U-Boot binary (CONFIG_OF_EMBED). This is useful for debugging since it enables easy .elf file loading.
   
A default device tree is defined in the defconfig file (with CONFIG_DEFAULT_DEVICE_TREE).
+
A default device tree is available in the defconfig file (by setting CONFIG_DEFAULT_DEVICE_TREE).
   
You can also select another supported device tree with the make flag DEVICE_TREE
+
You can either select another supported device tree using the DEVICE_TREE make flag. For stm32mp boards, the corresponding file is: {{CodeSource | U-Boot | arch/arm/dts/ | arch/arm/dts/stm32mp*.dts}}.
<br/> for stm32mp32 boards the file are: {{CodeSource | U-Boot | arch/arm/dts/ | arch/arm/dts/stm32mp*.dts}}
 
 
   {{PC$}} make DEVICE_TREE=<dts-file-name>
 
   {{PC$}} make DEVICE_TREE=<dts-file-name>
   
or you can provide a precompiled device tree blob (with EXT_DTB option)
+
or provide a precompiled device tree blob (using EXT_DTB option):
 
   {{PC$}} make EXT_DTB=boot/<dts-file-name>.dtb
 
   {{PC$}} make EXT_DTB=boot/<dts-file-name>.dtb
   
The SPL device tree is also generated from this device tree; but to reduce its size, the U-Boot makefile uses the fdtgrep tool to parse the full U-Boot DTB and identify all the drivers needed by SPL.
+
The SPL device tree is also generated from this device tree. However to reduce its size, the U-Boot makefile uses the fdtgrep tool to parse the full U-Boot DTB and identify all the drivers required by SPL.
   
To do this, U-Boot uses some specific device-tree flags to specify if the associated driver is initialized prior to U-Boot relocation and/or if the associated node is present in SPL :
+
To do this, U-Boot uses specific device-tree flags to define if the associated driver is initialized prior to U-Boot relocation and/or if the associated node is present in SPL :
 
* '''u-boot,dm-pre-reloc''' => present in SPL, initialized before relocation in U-Boot
 
* '''u-boot,dm-pre-reloc''' => present in SPL, initialized before relocation in U-Boot
  +
* '''u-boot,dm-pre-proper''' => initialized before relocation in U-Boot
 
* '''u-boot,dm-spl''' => present in SPL
 
* '''u-boot,dm-spl''' => present in SPL
   
In the device tree used by U-Boot, these flags '''need to be added in each node''' used in SPL or in U-Boot before relocation but also for each used handle (clock, reset, pincontrol).
+
In the device tree used by U-Boot, these flags '''need to be added in each node''' used in SPL or in U-Boot before relocation and for each used handle (clock, reset, pincontrol).
   
 
== U-Boot command line interface (CLI) ==
 
== U-Boot command line interface (CLI) ==
see [http://www.denx.de/wiki/view/DULG/UBootCommandLineInterface U-Boot Command Line Interface]
+
Refer to [http://www.denx.de/wiki/view/DULG/UBootCommandLineInterface U-Boot Command Line Interface].
   
If CONFIG_AUTOBOOT is activated, to enter in this console, you have CONFIG_BOOTDELAY seconds (2s by default) before [[#bootcmd|bootcmd]] execution (CONFIG_BOOTCOMMAND) by pressing any key when the line below is displayed.
+
If CONFIG_AUTOBOOT is activated, you have CONFIG_BOOTDELAY seconds (2s by default) to enter the console by pressing any key, after the line below is displayed and [[#bootcmd|bootcmd]] is executed (CONFIG_BOOTCOMMAND):
 
   Hit any key to stop autoboot:  2
 
   Hit any key to stop autoboot:  2
   
 
=== Commands ===
 
=== Commands ===
The commands are defined {{CodeSource | U-Boot | cmd/ | cmd/*.c}}, they are activated under associated configuration flag '''CONFIG_CMD_*'''.
+
The commands are defined in {{CodeSource | U-Boot | cmd/ | cmd/*.c}}. They are activated through the corresponding '''CONFIG_CMD_*''' configuration flag.
   
Use the command '''help''' in the U-Boot shell to list the available commands on your device.
+
Use the <code>help</code> command in the U-Boot shell to list the commands available on your device:
  +
  {{Board$}} help
   
List of commands extracted from [http://www.denx.de/wiki/view/DULG/Manual U-Boot Manual] ('''not-exhaustive'''):
+
Below the list of all commands extracted from [http://www.denx.de/wiki/view/DULG/Manual U-Boot Manual] ('''not-exhaustive'''):
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupInfo Information Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupInfo Information Commands]
** bdinfo - print Board Info structure
+
** bdinfo - prints Board Info structure
** coninfo - print console devices and informations
+
** coninfo - prints console devices and information
** flinfo - print FLASH memory information
+
** flinfo - prints Flash memory information
** iminfo - print header information for application image
+
** iminfo - prints header information for application image
** help - print online help
+
** help - prints online help
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupMemory Memory Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupMemory Memory Commands]
** base - print or set address offset
+
** base - prints or sets the address offset
 
** crc32 - checksum calculation
 
** crc32 - checksum calculation
 
** cmp - memory compare
 
** cmp - memory compare
Line 180: Line 183:
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupFlash Flash Memory Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupFlash Flash Memory Commands]
 
** cp - memory copy
 
** cp - memory copy
** flinfo - print FLASH memory information
+
** flinfo - prints Flash memory information
** erase - erase FLASH memory
+
** erase - erases Flash memory
** protect - enable or disable FLASH write protection
+
** protect - enables or disables Flash memory write protection
** mtdparts - define a Linux compatible MTD partition scheme
+
** mtdparts - defines a Linux compatible MTD partition scheme
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupExec Execution Control Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupExec Execution Control Commands]
** source - run script from memory
+
** source - runs a script from memory
** bootm - boot application image from memory
+
** bootm - boots application image from memory
** go - start application at address 'addr'
+
** go - starts application at address 'addr'
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupDownload Download Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupDownload Download Commands]
** bootp - boot image via network using BOOTP/TFTP protocol
+
** bootp - boots image via network using BOOTP/TFTP protocol
** dhcp - invoke DHCP client to obtain IP/boot params
+
** dhcp - invokes DHCP client to obtain IP/boot params
** loadb - load binary file over serial line (kermit mode)
+
** loadb - loads binary file over serial line (kermit mode)
** loads - load S-Record file over serial line
+
** loads - loads S-Record file over serial line
** rarpboot- boot image via network using RARP/TFTP protocol
+
** rarpboot- boots image via network using RARP/TFTP protocol
** tftpboot- boot image via network using TFTP protocol
+
** tftpboot- boots image via network using TFTP protocol
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupEnvironment Environment Variables Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupEnvironment Environment Variables Commands]
** printenv- print environment variables
+
** printenv- prints environment variables
** saveenv - save environment variables to persistent storage
+
** saveenv - saves environment variables to persistent storage
** setenv - set environment variables
+
** setenv - sets environment variables
** run - run commands in an environment variable
+
** run - runs commands in an environment variable
** bootd - boot default, i.e., run 'bootcmd'
+
** bootd - boots default, i.e., run 'bootcmd'
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdFDT Flattened Device Tree support]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdFDT Flattened Device Tree support]
** fdt addr - select FDT to work on
+
** fdt addr - selects the FDT to work on
** fdt list - print one level
+
** fdt list - prints one level
** fdt print - recursive print
+
** fdt print - recursive printing
** fdt mknode - create new nodes
+
** fdt mknode - creates new nodes
** fdt set - set node properties
+
** fdt set - sets node properties
** fdt rm - remove nodes or properties
+
** fdt rm - removes nodes or properties
** fdt move - move FDT blob to new address
+
** fdt move - moves FDT blob to new address
** fdt chosen - fixup dynamic info
+
** fdt chosen - fixup dynamic information
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupSpecial Special Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupSpecial Special Commands]
 
** i2c - I2C sub-system
 
** i2c - I2C sub-system
 
* [http://www.denx.de/wiki/view/DULG/UBootStorageDevices Storage devices]
 
* [http://www.denx.de/wiki/view/DULG/UBootStorageDevices Storage devices]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupMisc Miscellaneous Commands]
 
* [http://www.denx.de/wiki/view/DULG/UBootCmdGroupMisc Miscellaneous Commands]
** echo - echo args to console
+
** echo - echoes args to console
** reset - Perform RESET of the CPU
+
** reset - Performs a CPU reset 
** sleep - delay execution for some time
+
** sleep - delays the execution for a predefined time  
** version - print monitor version
+
** version - prints the monitor version
   
To add a new command, see {{CodeSource | U-Boot | doc/README.commands }}
+
To add a new command, refer to {{CodeSource | U-Boot | doc/README.commands }}.
   
 
=== U-Boot environment variables ===
 
=== U-Boot environment variables ===
   
The U-Boot behavior is configured with environment variables.
+
The U-Boot behavior is configured through environment variables.
  +
 
  +
Refer to [http://www.denx.de/wiki/view/DULG/UBootEnvVariables Manual] and {{CodeSource | U-Boot | README | README}} / Environment Variables.
  +
 
  +
On the first boot, U-Boot uses a default environment embedded in the U-Boot binary. You can modify it by changing the content of CONFIG_EXTRA_ENV_SETTINGS in your configuration file (for example ./include/configs/stm32mp1.h) (see {{CodeSource | U-Boot | README | README}} / - Default Environment).
  +
 
  +
This environment can be modified and saved in the boot device. When it is present, it is loaded during U-Boot initialization:
  +
* for ''e''•MMC/SD card boot (CONFIG_ENV_IS_IN_EXT4), in the bootable ext4 partition "bootfs" in <br/>in file CONFIG_ENV_EXT4_FILE="uboot.env".
  +
* for NAND boot (CONFIG_ENV_IS_IN_UBI), in the two UBI volumes "config" (CONFIG_ENV_UBI_VOLUME) and "config_r"  (CONFIG_ENV_UBI_VOLUME_REDUND).
  +
* for NOR boot (CONFIG_ENV_IS_IN_SPI_FLASH), in the u-boot_env mtd parttion (at offset CONFIG_ENV_OFFSET).
  +
 
  +
==== env command ====
   
see [http://www.denx.de/wiki/view/DULG/UBootEnvVariables Manual] and {{CodeSource | U-Boot | README | README}} / Environment Variables
+
The <code>env</code> command allows displaying, modifying and saving the environment in U-Boot console.
   
By default the env is NOT saved (CONFIG_ENV_IS_NOWHERE), only the default environment is used (saveenv command is not working)
+
  {{Board$}} help env
  +
  env - environment handling commands
  +
 
  +
  Usage:
  +
  env default [-f] -a - [forcibly] reset default environment
  +
  env default [-f] var [...] - [forcibly] reset variable(s) to their default values
  +
  env delete [-f] var [...] - [forcibly] delete variable(s)
  +
  env edit name - edit environment variable
  +
  env exists name - tests for existence of variable
  +
  env print [-a | name ...] - print environment
  +
  env print -e [name ...] - print UEFI environment
  +
  env run var [...] - run commands in an environment variable
  +
  env save - save environment
  +
  env set -e name [arg ...] - set UEFI variable; unset if 'arg' not specified
  +
  env set [-f] name [arg ...]
   
You can modify this default environment by changing the content of CONFIG_EXTRA_ENV_SETTINGS in your configuration file (for example ./include/configs/stm32mp1.h) (see {{CodeSource | U-Boot | README | README}} / - Default Environment).
+
Example: proceed as follows to restore the default environment and save it. This is useful after a U-Boot upgrade:
   
You can also choose one location with configuration flags:
+
  {{Board$}} env default -a
* CONFIG_ENV_IS_IN_MMC
+
  {{Board$}} env save
* CONFIG_ENV_IS_IN_FLASH
 
* CONFIG_ENV_IS_IN_SPI
 
* CONFIG_ENV_IS_IN_FAT
 
* CONFIG_ ENV_IS_IN_NAND
 
* CONFIG_ENV_IS_IN_UBI
 
* CONFIG_ENV_IS_IN_EEPROM
 
   
 
==== bootcmd ====
 
==== bootcmd ====
Autoboot command: defines the command executed when U-Boot starts (CONFIG_BOOTCOMMAND).
+
"bootcmd" variable is the autoboot command. It defines the command executed when U-Boot starts (CONFIG_BOOTCOMMAND).
   
But you can change this variable in CONFIG_EXTRA_ENV_SETTINGS (after BOOTENV macro needed for [[#Generic Distro configuration]]).
+
For stm32mp,  CONFIG_BOOTCOMMAND="run bootcmd_stm32mp":
   
<pre>
+
  {{Board$}} env print bootcmd   
#define CONFIG_EXTRA_ENV_SETTINGS \
+
  bootcmd=run bootcmd_stm32mp
"stdin=serial\0" \
+
 
"stdout=serial\0" \
+
"bootcmd_stm32mp" is a script that selects the command to be executed for each boot device (see ./include/configs/stm32mp1.h), based on [[#Generic Distro configuration|generic distro scripts]]:
"stderr=serial\0" \
+
* for serial/usb: execute the <code>stm32prog</code> command.
"kernel_addr_r=0xc2000000\0" \
+
* for mmc boot (''e''•MMC, SD card), boot only on the same device (bootcmd_mmc...).
"fdt_addr_r=0xc4000000\0" \
+
* for nand boot, boot with on ubifs partition on nand (bootcmd_ubi0).
"scriptaddr=0xc4100000\0" \
+
* for nor boot, use the default order ''e''•MMC (SDMMC 1)/ NAND / SD card (SDMMC 0) / SDMMC2 (the default bootcmd: distro_bootcmd).
"pxefile_addr_r=0xc4200000\0" \
+
 
"splashimage=0xc4300000\0"  \
+
  {{Board$}} env print bootcmd_stm32mp
"ramdisk_addr_r=0xc4400000\0" \
+
 
"fdt_high=0xffffffff\0" \
+
You can then change this configuration:
"initrd_high=0xffffffff\0" \
+
* either permanently in your board file (default environment by CONFIG_EXTRA_ENV_SETTINGS or change CONFIG_BOOTCOMMAND value) or
BOOTENV \
+
* temporarily in the saved environment:
"bootcmd=run bootcmd_mmc0\0"
+
 
</pre>
+
  {{Board$}} env set bootcmd run bootcmd_mmc0  
  +
  {{Board$}} env save
  +
 
  +
Note: To reset the environment to its default value:
  +
 
  +
  {{Board$}} env default bootcmd
  +
  {{Board$}} env save
   
 
=== Generic Distro configuration ===
 
=== Generic Distro configuration ===
   
see {{CodeSource | U-Boot | doc/README.distro | doc/README.distro}}
+
Refer to {{CodeSource | U-Boot | doc/README.distro | doc/README.distro}} for details.
   
This feature is activated for ST boards (CONFIG_DISTRO_DEFAULTS):
+
This feature is activated by default on ST boards (CONFIG_DISTRO_DEFAULTS):
* one boot command (bootmcd_xxx) exists for each bootable device
+
* one boot command (bootmcd_xxx) exists for each bootable device.
 
* U-Boot is independent of the Linux distribution used.
 
* U-Boot is independent of the Linux distribution used.
 
* bootcmd is defined in {{CodeSource | U-Boot | ./include/config_distro_bootcmd.h }}
 
* bootcmd is defined in {{CodeSource | U-Boot | ./include/config_distro_bootcmd.h }}
   
With DISTRO the default command executed: {{CodeSource | U-Boot | include/config_distro_bootcmd.h}}
+
When DISTRO is enabled, the command that is executed by default is {{CodeSource | U-Boot | include/config_distro_bootcmd.h}}:
 
   bootcmd=run distro_bootcmd
 
   bootcmd=run distro_bootcmd
   
This script will try any device found in the variable 'boot_targets' and execute the associated bootcmd.
+
This script tries any device found in the 'boot_targets' variable and executes the associated bootcmd.
   
Example for device mmc0, mmc1, mmc2, pxe and ubifs:
+
Example for mmc0, mmc1, mmc2, pxe and ubifs devices:
 
   bootcmd_mmc0=setenv devnum 0; run mmc_boot
 
   bootcmd_mmc0=setenv devnum 0; run mmc_boot
 
   bootcmd_mmc1=setenv devnum 1; run mmc_boot
 
   bootcmd_mmc1=setenv devnum 1; run mmc_boot
Line 283: Line 311:
 
   bootcmd_ubifs0=setenv devnum 0; run ubifs_boot
 
   bootcmd_ubifs0=setenv devnum 0; run ubifs_boot
   
U-Boot searchs for a configuration file '''extlinux.conf''' in a bootable device, this file defines the kernel configuration to use:  
+
U-Boot searches for a '''extlinux.conf''' configuration file for each bootable device. This file defines the kernel configuration to be used:  
 
* bootargs
 
* bootargs
 
* kernel + device tree + ramdisk files (optional)
 
* kernel + device tree + ramdisk files (optional)
Line 290: Line 318:
 
=== U-Boot scripting capabilities ===
 
=== U-Boot scripting capabilities ===
   
"Script files" are command sequences that will be executed by U-Boot's command interpreter; this feature is especially useful when you configure U-Boot to use a real shell (hush) as command interpreter.
+
"Script files" are command sequences that are executed by the U-Boot command interpreter. This feature is particularly useful to configure U-Boot to use a real shell (hush) as command interpreter.
   
See [http://www.denx.de/wiki/view/DULG/UBootScripts| U-Boot script manual] for example.
+
See [http://www.denx.de/wiki/view/DULG/UBootScripts| U-Boot script manual] for an example.
   
 
== U-Boot build ==
 
== U-Boot build ==
 
=== Prerequisites ===
 
=== Prerequisites ===
   
You need:
 
 
* a PC with Linux and tools:  
 
* a PC with Linux and tools:  
 
** see [[PC_prerequisites]]
 
** see [[PC_prerequisites]]
 
** [[#ARM cross compiler]]
 
** [[#ARM cross compiler]]
 
* U-Boot source code
 
* U-Boot source code
** the latest STMicroelectonics U-Boot version
+
** the latest STMicroelectronics U-Boot version
 
*** tar.xz file from Developer Package (for example [[STM32MP1_Developer_Package#Installing_the_U-Boot|STM32MP1]])
 
*** tar.xz file from Developer Package (for example [[STM32MP1_Developer_Package#Installing_the_U-Boot|STM32MP1]])
*** from GITHUB<ref>https://github.com/STMicroelectronics/u-boot</ref>, with git command
+
*** from GITHUB<ref>https://github.com/STMicroelectronics/u-boot</ref>, with <code>git</code> command
 
   {{PC$}} git clone https://github.com/STMicroelectronics/u-boot
 
   {{PC$}} git clone https://github.com/STMicroelectronics/u-boot
:* from the Mainline U-Boot in official GIT repository <ref>http://git.denx.de/u-boot.git or https://github.com/u-boot/u-boot</ref>
+
:* from the Mainline U-Boot in official GIT repository <ref>https://gitlab.denx.de/u-boot/u-boot.git or https://github.com/u-boot/u-boot</ref>
   {{PC$}} git clone http://git.denx.de/u-boot.git  
+
   {{PC$}} git clone https://gitlab.denx.de/u-boot/u-boot.git
   
 
==== ARM cross compiler ====
 
==== ARM cross compiler ====
   
You need to have a cross compiler <ref>https://en.wikipedia.org/wiki/Cross_compiler</ref> installed on your Host (X86_64, i686, ...) for the targeted Device architecture = ARM, the environment variables ($PATH and $CROSS_COMPILE) need to be configured in your shell.
+
A cross compiler <ref>https://en.wikipedia.org/wiki/Cross_compiler</ref> must be installed on your Host (X86_64, i686, ...) for the ARM targeted Device architecture. In addition, the $PATH and $CROSS_COMPILE environment variables must be configured in your shell.
   
 
You can use gcc for ARM, available in:
 
You can use gcc for ARM, available in:
# the SDK toolchain<br/>See [[Cross-compile with OpenSTLinux SDK]], PATH and CROSS_COMPILE are automatically updated.
+
* the SDK toolchain (see [[Cross-compile with OpenSTLinux SDK]])<br/>PATH and CROSS_COMPILE are automatically updated.
# an existing package (for example, on Ubuntu/Debian: ({{PC$}} sudo apt-get install gcc-arm-linux-gnueabihf)
+
* an existing package<br/>For example, install gcc-arm-linux-gnueabihf on Ubuntu/Debian: ({{PC$}} sudo apt-get.
# an existing toolchain:
+
* an existing toolchain:
#* gcc v8 toolchain provided by arm (https://developer.arm.com/open-source/gnu-toolchain/gnu-a/downloads/)
+
** gcc v8 toolchain provided by arm (https://developer.arm.com/open-source/gnu-toolchain/gnu-a/downloads/)
#* gcc v7 toolchain provided by linaro: (https://www.linaro.org/downloads/)
+
** gcc v7 toolchain provided by linaro: (https://www.linaro.org/downloads/)
   
for example:
+
For example, to use '''gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi.tar.xz'''<br/>from https://releases.linaro.org/components/toolchain/binaries/7.2-2017.11/arm-linux-gnueabi/<br/>
'''gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi.tar.xz'''<br/>from https://releases.linaro.org/components/toolchain/binaries/7.2-2017.11/arm-linux-gnueabi/
+
Unzip the toolchain in $HOME and update your environment with:
unzip it in $HOME,<br/>and you need to update your environment:
 
 
   {{PC$}} export PATH=$HOME/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi/bin:$PATH
 
   {{PC$}} export PATH=$HOME/gcc-linaro-7.2.1-2017.11-x86_64_arm-linux-gnueabi/bin:$PATH
 
   {{PC$}} export CROSS_COMPILE=arm-linux-gnueabi-
 
   {{PC$}} export CROSS_COMPILE=arm-linux-gnueabi-
   
 
=== Compilation  ===
 
=== Compilation  ===
In the U-Boot source directory, you need to select the <target> and the <device tree> for your configuration and then execute the "make all" command.
+
In the U-Boot source directory, select the <target> and the <device tree> for your configuration and then execute the <code>make all</code> command:
   
 
   {{PC$}} make <target>_defconfig
 
   {{PC$}} make <target>_defconfig
 
   {{PC$}} make DEVICE_TREE=<device-tree> all
 
   {{PC$}} make DEVICE_TREE=<device-tree> all
   
'''KBUILD_OUTPUT''' can be used optionally to change the output directory if you want to compile several targets or don't compile in the source directory, for example:
+
Optionally '''KBUILD_OUTPUT''' can be used to change the output directory to compile several targets or not to compile in the source directory. For example:
 
   {{PC$}} export KBUILD_OUTPUT=../build/basic
 
   {{PC$}} export KBUILD_OUTPUT=../build/basic
   
'''DEVICE_TREE''' can be also exported to your environment when you support only one board, for example:
+
'''DEVICE_TREE''' can also be exported to your environment when only one board is supported. For example:
 
   {{PC$}} export DEVICE_TREE=stm32mp157c-ev1
 
   {{PC$}} export DEVICE_TREE=stm32mp157c-ev1
   
For all the stm32mp15 family, we manage 3 configurations:
+
Examples from [[STM32MP15 U-Boot]]:
* stm32mp15_trusted_defconfig: [[Boot_chains_overview#STM32MP boot chains|trusted boot chain]], U-Boot (without SPL) is unsecure and uses Secure monitor from TF-A
+
 
* stm32mp15_optee_defconfig: [[Boot_chains_overview#STM32MP boot chains|trusted boot chain]], U-Boot (without SPL) is unsecure and uses Secure monitor from SecureOS = [[OP-TEE overview|OP-TEE]]
+
Three configurations are supported for  {{MicroprocessorDevice | device=15}}:
  +
* {{Highlight|stm32mp15_trusted_defconfig}}: [[Boot_chains_overview#STM32MP boot chains|trusted boot chain]], U-Boot (without SPL) is unsecure and uses Secure monitor from TF-A
  +
* {{Highlight|stm32mp15_optee_defconfig}}: [[Boot_chains_overview#STM32MP boot chains|trusted boot chain]], U-Boot (without SPL) is unsecure and uses Secure monitor from SecureOS = [[OP-TEE overview|OP-TEE]]
 
* stm32mp15_basic_defconfig: [[Boot_chains_overview#STM32MP boot chains|basic boot chain]], with an SPL as FSBL, U-BOOT is secure and installs monitor with PSCI
 
* stm32mp15_basic_defconfig: [[Boot_chains_overview#STM32MP boot chains|basic boot chain]], with an SPL as FSBL, U-BOOT is secure and installs monitor with PSCI
   
 
The board diversity is only managed with the device tree.
 
The board diversity is only managed with the device tree.
 
Examples from [[STM32MP15 U-Boot]]:
 
  {{PC$}} export KBUILD_OUTPUT=../build/basic
 
  {{PC$}} make stm32mp15_basic_defconfig
 
  {{PC$}} make DEVICE_TREE=stm32mp157c-<board> all
 
   
 
   {{PC$}} export KBUILD_OUTPUT=../build/trusted
 
   {{PC$}} export KBUILD_OUTPUT=../build/trusted
Line 354: Line 377:
 
   {{PC$}} make DEVICE_TREE=stm32mp157c-<board> all
 
   {{PC$}} make DEVICE_TREE=stm32mp157c-<board> all
   
   {{PC$}} export KBUILD_OUTPUT=../build/trusted
+
   {{PC$}} export KBUILD_OUTPUT=../build/optee
   {{PC$}} export DEVICE_TREE=stm32mp157c-ev1
+
   {{PC$}} export DEVICE_TREE=stm32mp157c-<board>
   {{PC$}} make stm32mp15_trusted_defconfig
+
   {{PC$}} make stm32mp15_optee_defconfig
 
   {{PC$}} make all
 
   {{PC$}} make all
  +
  +
  {{PC$}} make stm32mp15_basic_defconfig
  +
  {{PC$}} make DEVICE_TREE=stm32mp157c-<board>  all
   
 
Use help to list other targets:
 
Use help to list other targets:
Line 363: Line 389:
   
 
=== Output files ===
 
=== Output files ===
The resulting U-Boot files are present in your build directory (U-Boot or KBUILD_OUTPUT) and SPL Images are in the spl subdirectory.
+
The resulting U-Boot files are located in your build directory (U-Boot or KBUILD_OUTPUT).
   
STM32 image format (*.stm32) is managed by mkimage U-Boot tools and is requested by boot ROM (for basic boot chain) or by TF-A (for trusted boot chain).
+
Two binary formats are used for stm32mp devices:
  +
* STM32 image format (*.stm32)managed by mkimage U-Boot tools and [[Signing_tool]]. It is requested by ROM code and TF-A (see [[STM32 header for binary files]] for details).
  +
* uImage (*.img) format, file including a U-Boot header, managed by SPL and U-Boot (for kernel load)
   
* '''u-boot.stm32''' : U-Boot binary with STM32 image header => SSBL for Trusted boot chain
+
The U-Boot generated files are the following
* '''u-boot.img''' : U-Boot binary with uImage header => SSBL for Basic boot chain
+
* For {{Highlight|'''Trusted boot chain'''}} (TF-A is used as FSBL, with or without OP-TEE)
  +
** {{Highlight|'''u-boot.stm32'''}} : U-Boot binary with STM32 image header, loaded by TF-A
   
* u-boot : elf file, used to debug with gdb
+
* For '''Basic boot chain''' (SPL is used as FSBL)
* '''spl/u-boot-spl.stm32''' : SPL binary with STM32 image header => FSBL for Basic boot chain
+
** '''u-boot-spl.stm32''' : SPL binary with STM32 image header, loaded by ROM code
* spl/u-boot-spl : elf file, used to debug with gdb
+
** '''u-boot.img''' : U-Boot binary with uImage header, loaded by SPL
  +
 
  +
The files used to debug with gdb are
  +
* u-boot : elf file for U-Boot
  +
* spl/u-boot-spl : elf file for SPL
   
 
== References ==
 
== References ==
 
<references/>
 
<references/>
  +
  +
<noinclude>
  +
[[Category:U-Boot]]
  +
{{PublicationRequestId | 12893 | 2019-08-01}}
  +
</noinclude>

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