The linksys firmwares can be too large for the tftp server to handle at boot_wait; it’s eaiser to log into openwrt, wget the binary into /tmp, remove the first 32 bytes of the bin to make a trx file.

dd if=firmware.bin of=firmware.trx bs=32 skip=1

and then write that directly to flash

mtd -r write firmware.trx linux .