Uboot run mmc dev 1: no sdcard present

my device is jetson-nano emmc 4G version with a sdcard slot, and i purpose to change default boot device to sdcard.

i have flashed my sdcard refer to
https://docs.nvidia.com/jetson/archives/l4t-archived/l4t-3231/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide%2Fflashing.html%23wwpID0E0PG0HA
and then plug into my device, but the bootloader still automatically boot from mmcblk0.
my first question is how to set mmcblk1 as default boot device?

i have tried to run bootcmd_mmc1 at uboot prompt, but prompt shown “no sdcard present”.
my second question is how to fix this error?

thanks

(sry for my bad english)

There is no such support yet.

One user gives out a patch but seems still has some bug.

thanks for reply.

may i keep this topic until be resolved?