hello ShayWang,
please refer to https://devtalk.nvidia.com/default/topic/1020778/jetson-tx1/jetpack-3-1-falsh-sh-k-ebt-jetson-tx1-mmcblk0p1-/post/5197337/#5197337
there’s erroneous in the R28.1 documentation.
we should use below commands to update u-boot partition for R28.1/TX1,
$ sudo ./flash.sh –k LNX jetson-tx1 mmcblk0p1