U-Boot 命令

在U-Boot提示符下可以访问U-Boot命令列表。键入“帮助”或“？”有关可用命令的完整列表。下面给出一个例子：

?       - alias for 'help'
base    - print or set address offset
bdinfo  - print Board Info structure
boot    - boot default, i.e., run 'bootcmd'
bootd   - boot default, i.e., run 'bootcmd'
bootm   - boot application image from memory
bootp   - boot image via network using BOOTP/TFTP protocol
cmp     - memory compare
coninfo - print console devices and information
cp      - memory copy
crc32   - checksum calculation
date    - get/set/reset date && time
echo    - echo args to console
editenv - edit environment variable
erase   - erase FLASH memory
ext2load- load binary file from a Ext2 filesystem
ext2ls  - list files in a directory (default /)
fatinfo - print information about filesystem
fatload - load binary file from a dos filesystem
fatls   - list files in a directory (default /)
fdt     - flattened device tree utility commands
flinfo  - print FLASH memory information
go      - start application at address 'addr'
help    - print command description/usage
iminfo  - print header information for application image
imls    - list all images found in flash
imxtract- extract a part of a multi-image
itest   - return true/false on integer compare
loadb   - load binary file over serial line (kermit mode)
loads   - load S-Record file over serial line
loady   - load binary file over serial line (ymodem mode)
loop    - infinite loop on address range
md      - memory display
mm      - memory modify (auto-incrementing address)
mmc     - MMC sub system
mmcinfo - display MMC info
mtest   - simple RAM read/write test
mw      - memory write (fill)
nfs     - boot image via network using NFS protocol
nm      - memory modify (constant address)
ping    - send ICMP ECHO_REQUEST to network host
printenv- print environment variables
protect - enable or disable FLASH write protection
rarpboot- boot image via network using RARP/TFTP protocol
reset   - Perform RESET of the CPU
run     - run commands in an environment variable
setenv  - set environment variables
sf      - SPI flash sub-system
sleep   - delay execution for some time
source  - run script from memory
sspi    - SPI utility commands
tftpboot- boot image via network using TFTP protocol
version - print monitor version

 

烧写QSPI Flash

U-Boot提供SF命令来对串行闪存设备进行编程。在所有通过u-boot进行的Xilinx平台上，您都可以使用SF命令对QSPI设备进行编程。这是将图像文件加载到QSPI设备的示例。

uboot> sf
Usage:
sf probe [[bus:]cs] [hz] [mode] - init flash device on given SPI bus and chip select
sf read addr offset len         - read 'len' bytes starting at 'offset' to memory at 'addr'
sf write addr offset len        - write 'len' bytes from memory at 'addr' to flash at 'offset'
sf erase offset [+]len          - erase 'len' bytes from 'offset'; '+len' round up 'len' to block size
sf update addr offset len       - erase and write 'len'bytes from memory at 'addr' to flash at 'offset
  
uboot> sf probe 0 0 0
SF: Detected N25Q128 with page size 256, total 16 MiB
16384 KiB N25Q128 at 0:0 is now current device

引导应用程序映像

U-Boot提供了bootm命令来引导应用程序映像（即Linux），该映像希望这些映像可以使用mkimage用U-Boot特定的标头包装。该命令可用于引导旧的U-Boot映像或新的多组件映像（FIT），如U-Boot中所述。

标准的Linux构建过程将构建包装器uImage，而Petalinux项目默认也会生成多组件FIT图像。

以下U-Boot命令说明了使用bootm命令使用单个映像和FIT映像从SD卡加载Linux映像。

 

u-boot> fatload mmc 0 0x3000000 uImage
u-boot> fatload mmc 0 0x2A00000 devicetree.dtb
u-boot> fatload mmc 0 0x2000000 uramdisk.image.gz
u-boot> bootm 0x3000000 0x2000000 0x2A00000
u-boot> fatload mmc 0 0x1000000 image.ub
u-boot> bootm 0x1000000

使用bootm命令，U-Boot会在引导Linux之前重新定位映像，以使上面的地址可能不是内核看到的地址。

U-Boot还会更改设备树，以告知内核ramdisk映像在内存中的位置（initrd-start和initrd-end）。bootm命令将r2寄存器设置为内存中设备树的地址，而go命令无法完成该操作。

使用booti命令和bootm命令的差异和用例也不断发展。

从U-Boot 2020.01开始，主要区别在于处理U-Boot帮助中所述的未压缩Linux映像文件（在64位Arm平台上常见）与压缩Linux zImage文件（在32位Arm平台上常见）。通常，仅根据Linux映像类型来区分用法，

不是仅基于体系结构来区分。booti-从内存中启动Linux内核“映像”格式。bootm-从内存启动应用程序映像

booti和bootm的完整帮助分别详细说明了用法上的差异。