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我有Am-1808板(evm zoom kit),现在我在 spi flash 中有 ubl 和 uboot,在 SD 卡中有文件系统和内核(uImage),我按照在 am-1808 板上运行 linux 的步骤从这里

我没有找到任何可以解释从 USB 启动 linux 的官方参考/文档,是否有可能我可以将文件系统 + 内核放在 USB 中,然后告诉 uboot 查找 USB 以从 USB 而不是 sd 查找 uImage-卡片。如果是,那么你能解释一下如何吗?

从 sd 卡中查找 uImage 的 u-boot 代码部分是:

#define CONFIG_BOOTARGS     "mem=32M console=ttyS2,115200n8 root=/dev/mmcblk0p2     rw rootwait ip=off"
#define CONFIG_BOOTCOMMAND  "if mmc rescan 0; then if fatload mmc 0 0xc0600000 boot.scr; then source 0xc0600000; else fatload mmc 0 0xc0700000 uImage; bootm c0700000; fi; else sf probe 0; sf read 0xc0700000 0x80000 0x220000; bootm 0xc0700000; fi"

我需要使用 usb 而不是 sd 卡来放置文件系统 + uImage,因为我必须将 sd 卡引脚 (mmc0) 用于其他目的。

更新:

解释了从 USB 启动 linux,但问题是 u-boot 无法识别“usb”命令,当我输入:usb reset 时,它给了我这个错误:

U-Boot > usb reset
Unknown command 'usb' - try 'help'

“usb”命令也不会出现在“help”命令显示的可用命令列表中。

U-Boot > help
?       - alias for 'help'
askenv  - get environment variables from stdin
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
dhcp    - boot image via network using DHCP/TFTP protocol
echo    - echo args to console
editenv - edit environment variable
env     - environment handling commands
exit    - exit script
ext2load- load binary file from a Ext2 filesystem
ext2ls  - list files in a directory (default /)
false   - do nothing, unsuccessfully
fatinfo - print information about filesystem
fatload - load binary file from a dos filesystem
fatls   - list files in a directory (default /)
go      - start application at address 'addr'
help    - print command description/usage
iminfo  - print header information for application image
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
mdc     - memory display cyclic
mii     - MII utility commands
mm      - memory modify (auto-incrementing address)
mmc     - MMC sub system
mmcinfo - display MMC info
mtest   - simple RAM read/write test
mw      - memory write (fill)
mwc     - memory write cyclic
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
reset   - Perform RESET of the CPU
run     - run commands in an environment variable
saveenv - save environment variables to persistent storage
saves   - save S-Record file over serial line
setenv  - set environment variables
sf      - SPI flash sub-system
showvar - print local hushshell variables
sleep   - delay execution for some time    
source  - run script from memory
sspi    - SPI utility command
test    - minimal test like /bin/sh
tftpboot- boot image via network using TFTP protocol
true    - do nothing, successfully
version - print monitor version

知道如何在 u-boot 中指定“usb”命令吗?我需要将uboot升级到更新版本吗?

问候

乌萨马

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