修改第2级bootloader的include/configs/sama5d2_xplained.h文件
#define FAT_ENV_DEVICE_AND_PART "0"
#define CONFIG_BOOTCOMMAND "fatload mmc 0:1 0x21000000 at91-sama5d2_xplained.dtb; " \
"fatload mmc 0:1 0x22000000 zImage; " \
"bootz 0x22000000 - 0x21000000"
#define CONFIG_BOOTARGS \
"console=ttyS0,57600 earlyprintk " \
"root=/dev/mmcblk0p2 rw rootwait"
#define CONFIG_SYS_MMCSD_FS_BOOT_PARTITION 0
修改以上宏定义为emmc编号即可
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