johnth:

Updated an old TP-LINK CPE510 v1.1
Booted existing historic OpenWrt in failsafe:
Linux version 4.9.184 (buildbot@2ccc8102e0c3) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r7808-ef686b7292) ) #0 Thu Jun 27 12:18:52 2019

sysupgrade -n to current snapshot
Linux version 5.4.138 (builder@buildhost) (gcc version 8.4.0 (OpenWrt GCC 8.4.0 r17311-7057e05485)) #0 Sun Aug 8 23:17:06 2021

Device bootloops:

[ 1.883394] Call Trace:
[ 1.885885] [<8057473c>] strcmp+0xc/0x40
[ 1.889876] [<803ab348>] __of_add_property+0x4c/0x84
[ 1.894912] [<803ab3c8>] of_add_property+0x48/0xc8
[ 1.899788] [<803b1730>] of_get_mac_address+0x120/0x3ac
[ 1.905107] [<8038c5c8>] ag71xx_probe+0x5cc/0xb74
[ 1.909901] [<80337168>] platform_drv_probe+0x40/0x94
[ 1.915029] [<8033527c>] really_probe+0x104/0x358
[ 1.919798] [<803332f0>] bus_for_each_drv+0x70/0xb0
[ 1.924743] [<80335134>] __device_attach+0x114/0x150
[ 1.929777] [<80334228>] bus_probe_device+0x9c/0xb8
[ 1.934723] [<803347ec>] deferred_probe_work_func+0x7c/0xbc
[ 1.940401] [<80099c28>] process_one_work+0x220/0x480
[ 1.945531] [<8009a1b4>] worker_thread+0x32c/0x5c8
[ 1.950405] [<8009ed2c>] kthread+0x138/0x140
[ 1.954739] [<80064cb8>] ret_from_kernel_thread+0x14/0x1c


TP-LINK SafeLoader TFTP recovery using OEM firmware, or OpenWrt factory image; fails with Incorrect File.

TP-LINK SafeLoader (Build time: Jun 12 2015 - 09:49:53)
CPU: 560MHz AHB: 225MHz DDR: 64MB
Performing LED check.. PASS
Press CTRL+B to enter SafeLoader: 1
Flash Manufacturer: Unknown(0xc8)
Flash Device ID: Unknown(0x4017)
Data flash init failed.
open user-config failed.
open user-config failed.
enet0 port4 up
TFTP server address is 192.168.0.100; our address is 192.168.0.254
Get filename 'recovery.bin'.
#################################################################
######################
Done.
Bytes transferred = 4453887, 1030 Kbytes/sec
Incorrect File.
Writting error.


Manually writing (SOIC8 clip) 21.02 snapshot 94efa1c to MTD succeeds, and provides bootable device.

sysupgrade -n snapshot from 21.02 snapshot results in same bootloop.
sysupgrade file matches Downloads checksum.