NXP Semiconductors ASUG, Руководство пользователя

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Table 13. Boot device switch settings
i.MX 8QuadXPlus boot switch Download mode (UUU mode) SD boot eMMC boot
SW2 Boot_Mode (1-4 bit) 1000 1100 0100
To test booting from SD, change the board Boot_Mode switch to 1100 (1-4 bit).
To test booting from eMMC, change the board Boot_Mode switch to 0100 (1-4 bit).
The default environment in boot.img is booting from eMMC. To use the default environment in boot.img, do not set bootargs
environment in U-Boot.
To clear the bootargs environment being set and saved before, use the following command:
U-Boot > setenv bootargs
U-Boot > saveenv # Save the environments
bootargs environment is an optional setting for boota. The boot.img includes a default bootargs, which is used if
if there is no bootargs defined in U-Boot.
NOTE
6.2 Boot-up configurations
This section explains some common boot-up configurations such as U-Boot environments, kernel command line, and DM-
verity configuartions.
6.2.1 U-Boot environment
• bootcmd: the first variable to run after U-Boot boot.
• bootargs: the kernel command line, which the bootloader passes to the kernel. As described in
Kernel command line
(bootargs) , bootargs environment is optional for booti. boot.img already has bootargs. If you do not define the bootargs
environment, it uses the default bootargs inside the image. If you have the environment, it is then used.
To use the default environment in boot.img, use the following command to clear the bootargs environment.
> setenv bootargs
• boota:
boota command parses the boot.img header to get the Image and ramdisk. It also passes the bootargs as needed (it only
passes bootargs in boot.img when it cannot find "bootargs" var in your U-Boot environment). To boot the system, do the
following:
> boota
To boot into recovery mode, execute the following command:
> boota recovery
NXP Semiconductors
Booting
Android
™
User's Guide, Rev. P9.0.0_2.3.2, 6 March 2020
User's Guide 14 / 31