Here's u-boot cpe210v3 u-boot-cp210v3
you can update through uart console.
Use hex editor to change the mac address with your mac, mac adress offset start at 0x30000.
To stop u-boot use ctrl-B at command prompt type following command
- tftpboot 0x80060000 u-boot210v3.bin
- erase 0x9f000000 +0x40000
- cp.b 0x80060000 0x9f000000 0x40000
- reset
after u-boot was updated, type "tp" to stop u-boot and tftp openwrt initrams or use standard recovery from tp-link.