and do you know for sure iwrt bl31 is any different than dito from openwrt ?
should be, a bit or less. and to avoid further crashes thats why I wanted to take precautions.
Problem is, you don't know if uboot writes the bl31 same way as openwrt would have.
I'd go for option 0, and boot the initramfs, see what uboot parameters are set, and if something needs to be changed.
garbled code, maybe input not being sent/received properly
or a speed change between uboot and linux
what do you mean by speed change cpu freq?
no, of serial port, on router.
is that normal or something wrong?
not normal, but your installation is kind of screwed up, so who knows ... 
@frollic i got my cp2102 delivered, but there are some settings in the control panel, i dont know anything except 115200 8N1, are these default settings correct? Thanks
leave them, they're irrelevant, and default's OK.
okay thanks
@frollic seems like its fully dead now, the ethernet or the ttl or the pi, none of it works, maybe the NAND got flushed due to too many connects and disconnnects or something else. So for NAND, Do I have to desolder it ? and how would I reprogram it?
tried reversing the Tx and Rx pins?
yes, and the ethernet isnt working when connected to pc, so I assume its flushed or fully dead
it sometimes shows ethernet active and goes offline for the rest of the time which didnt happen before. So something bad happened anyway
Managed to get into same situation.
Deployed tftp server with required .itb in tftproot, even downloaded it from another machine via tftp client, but router seems blind, tried to connect every of 4 ports during boot but with same result, it just loops message
ARP Retry count exceeded; starting again
Wrong Image Format for bootm command
ERROR: can't get kernel image!
If you skip the TFTPd, turn it off completely, is the uboot output any different?
No, everything the same. I also made firewall rule on tftp server to count incoming connections, but there aren't any connections detected by rule, the only attempt I see is from test tftp client from same network. Seems like router isn't even try to assign an ip address on any interface, at least i cannot ping 192.168.1.1 or detect it in arp table with ip neigh
upd: I tried to tcpdump interface where router should apperar, but nothing
I gave up on tftp way, and it seems to me the situation requires different approach. Long ago I successfully re-soldered spi flash chip on nexx wt1520 board from 8M to 16M one, and re-flashed it with ch341 programmer. Datasheet of AX6000's spi chip seems have same pinouts and operating voltage, like those chips that i previously re-flashed with ch341. The dumb question is, can i do the same trick with this router? And what exactly should i flash to it? I'm a bit stupid with spi layouts.