summary: we wrote invalid data under the Uboot of the LS1021ATSN board, causing Uboot to fail to boot.
Our LS1021ATSN is the board that the SD card boot. After I loaded the sdcard.img in the card, I debug it via USB. Enter the following command under Uboot: mmc write 0x81000000 8 0x500, then I can't enter Uboot. Finally, I formatted the SD card to re-copy the sdcard.img or not enter.