on the bottom of this page, there is info about using command line.

One thing important, this is for GL.iNet6416 only!!!

For AR150, pls change the command to:

tftp 0x81000000 openwrt.bin
erase 0x9f050000 +0x7c0000
cp.b 0x81000000 0x9f050000 0x7c0000
reset

the 0x7c0000 is the size of your firmware, or it must be bigger than the size. You can use $filesize to replace this value, if you don’t see there is an error.