Hi,
Automatic upgrade by tftp can be turned on by setting uboot env:
By openwrt command:
fw_setenv tftp_upgrade 1
or uboot command
setenv tftp_upgrade 1
saveenv
And the filename should be renamed:
s1300-factory-to-openwrt.img → qsdk-gl-s1300.bin
openwrt.bin → openwrt-gl-s1300.bin
and it should be put on two tftp server as you think.
Better flash openwrt-gl-s1300.bin firstly, when finished it will still boot to factory firmware, then power off and switch to tftp server with qsdk-gl-s1300.bin file.
Here’s the latest uboot source and s1300-factory-to-openwrt.img