Bricked TPLink Archer C7v5 now stuck with kernel panic

Hi all,
today i bricked my Archer C7 v5. How? I flashed the wrong image (I used the Image for the A7 instead of C7 openwrt-19.07.7-ath79-generic-tplink_archer-a7-v5-squashfs-factory.bin) with sysupgrade -F image.bin
This was the installed image:

DISTRIB_ID='OpenWrt'
DISTRIB_RELEASE='19.07.1'
DISTRIB_REVISION='r10911-c155900f66'
DISTRIB_TARGET='ath79/generic'
DISTRIB_ARCH='mips_24kc'
DISTRIB_DESCRIPTION='OpenWrt 19.07.1 r10911-c155900f66'
DISTRIB_TAINTS=''

After that, I tried now for over 8h to get the router back to life. As for now, I have an Openwrt System installed on it again, but I get a Kernel Panic on boot. However, via failsafe boot (via JTAG which I soldered on the PCB) I can boot it up and do some things. The last thing I did, before this writing here, is a sysupgrade -n image.bin - the image used was the openwrt-19.07.7-ath79-generic-tplink_archer-c7-v5-squashfs-sysupgrade.bin.
Unfortunately the router is still not booting in "normal" mode.
One thing, which is unusual, that the first output on the command line is unreadable (just symbols and signs). Here you can see this:

But I was ignoring this, because the router is booting, it "just" gets a kernel panic during boot.
Here is the output of the console:

root@(none):/# sysupgrade -n /tmp/openwrt-19.07.7-ath79-generic-tplink_archer-c7
-v5-squashfs-sysupgrade.bin
Commencing upgrade. Closing all shell sessions.
Watchdog handover: fd=3
- watchdog -
root@(none):/# killall: telnetd: no process killed
Killed
Sending TERM to remaining processes ... sh sleep
Sending KILL to remaining processes ...
Switching to ramdisk...
Performing system upgrade...
Unlocking firmware ...

Writing from <stdin> to firmware ...
Upgrade completed
Rebooting system...
umount: can't unmount /tmp: Resource busy
umount: can't unmount /dev: Resource busy
[  782.257488] reboot: Restarting system
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[    0.360920] console [ttyS0] enabled
[    0.360920] console [ttyS0] enabled
[    0.368484] bootconsole [early0] disabled
[    0.368484] bootconsole [early0] disabled
[    0.393434] m25p80 spi0.0: w25q128 (16384 Kbytes)
[    0.398345] 8 fixed-partitions partitions found on MTD device spi0.0
[    0.404930] Creating 8 MTD partitions on "spi0.0":
[    0.409881] 0x000000000000-0x000000020000 : "factory-uboot"
[    0.416327] 0x000000020000-0x000000040000 : "u-boot"
[    0.422075] 0x000000040000-0x000000050000 : "partition-table"
[    0.428710] 0x000000050000-0x000000060000 : "art"
[    0.434269] 0x000000060000-0x000000080000 : "info"
[    0.439860] 0x000000080000-0x0000000c0000 : "user-config"
[    0.446124] 0x0000000c0000-0x000000fc0000 : "firmware"
[    0.455963] 2 uimage-fw partitions found on MTD device firmware
[    0.462083] Creating 2 MTD partitions on "firmware":
[    0.467257] 0x000000000000-0x0000001867e4 : "kernel"
[    0.473012] 0x0000001867e4-0x000000f00000 : "rootfs"
[    0.478770] mtd: device 8 (rootfs) set to be root filesystem
[    0.484695] 1 squashfs-split partitions found on MTD device rootfs
[    0.491087] 0x000000440000-0x000000f00000 : "rootfs_data"
[    0.497296] 0x000000ff0000-0x000001000000 : "default-config"
[    0.504807] libphy: Fixed MDIO Bus: probed
[    0.511215] ag71xx 19000000.eth: invalid MAC address, using random address
[    1.193468] libphy: ag71xx_mdio: probed
[    1.200419] switch0: Atheros AR8337 rev. 2 switch registered on mdio-bus.0
[    1.854580] ag71xx 19000000.eth: connected to PHY at mdio-bus.0:00 [uid=004dd036, driver=Atheros AR8216/AR8236/AR8316]
[    1.866161] eth0: Atheros AG71xx at 0xb9000000, irq 4, mode: sgmii
[    1.875248] NET: Registered protocol family 10
[    1.885003] Segment Routing with IPv6
[    1.888870] NET: Registered protocol family 17
[    1.893552] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[    1.906942] 8021q: 802.1Q VLAN Support v1.8
[    1.913263] hctosys: unable to open rtc device (rtc0)
[    1.924022] VFS: Mounted root (squashfs filesystem) readonly on device 31:8.
[    1.937895] Freeing unused kernel memory: 1212K
[    1.942578] This architecture does not have kernel memory protection.
[    2.557374] init: Console is alive
[    2.561096] init: - watchdog -
[    2.564302] random: fast init done
[    3.603441] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[    3.832812] usbcore: registered new interface driver usbfs
[    3.838600] usbcore: registered new interface driver hub
[    3.844189] usbcore: registered new device driver usb
[    3.854748] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[    3.862953] ehci-platform: EHCI generic platform driver
[    3.868624] ehci-platform 1b000000.usb: EHCI Host Controller
[    3.874541] ehci-platform 1b000000.usb: new USB bus registered, assigned bus number 1
[    3.882711] ehci-platform 1b000000.usb: irq 13, io mem 0x1b000000
[    3.913159] ehci-platform 1b000000.usb: USB 2.0 started, EHCI 1.00
[    3.920241] hub 1-0:1.0: USB hub found
[    3.924461] hub 1-0:1.0: 1 port detected
[    3.929584] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[    3.947478] init: - preinit -
[    4.895403] random: jshn: uninitialized urandom read (4 bytes read)
[    5.077392] random: jshn: uninitialized urandom read (4 bytes read)
[    5.330192] random: jshn: uninitialized urandom read (4 bytes read)
[    6.727704] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[    6.733847] IPv6: ADDRCONF(NETDEV_UP): eth0.1: link is not ready
[    6.777880] urandom_read: 4 callbacks suppressed
[    6.777887] random: procd: uninitialized urandom read (4 bytes read)
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
[    7.794440] eth0: link up (1000Mbps/Full duplex)
[    7.799301] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[    7.806103] IPv6: ADDRCONF(NETDEV_CHANGE): eth0.1: link becomes ready
[    9.918247] mount_root: jffs2 not ready yet, using temporary tmpfs overlay
[    9.947802] urandom-seed: Seed file not found (/etc/urandom.seed)
[   10.038573] eth0: link down
[   10.057963] procd: - early -
[   10.061033] procd: - watchdog -
[   10.732395] procd: - watchdog -
[   10.735970] procd: - ubus -
[   10.794714] random: ubusd: uninitialized urandom read (4 bytes read)
[   10.915278] random: ubusd: uninitialized urandom read (4 bytes read)
[   10.923066] procd: - init -
Please press Enter to activate this console.
[   11.738889] kmodloader: loading kernel modules from /etc/modules.d/*
[   11.767043] ip6_tables: (C) 2000-2006 Netfilter Core Team
[   11.791588] Loading modules backported from Linux version v4.19.161-0-gdaefdc9eb24b
[   11.799549] Backport generated by backports.git v4.19.161-1-0-g4bb568fe
[   11.825091] ip_tables: (C) 2000-2006 Netfilter Core Team
[   11.849888] nf_conntrack version 0.5.0 (2048 buckets, 8192 max)
[   11.953878] xt_time: kernel timezone is -0000
[   11.965012] urngd: v1.0.2 started.
[   12.057519] PPP generic driver version 2.4.2
[   12.073897] NET: Registered protocol family 24
[   12.126009] ath10k 4.19 driver, optimized for CT firmware, probing pci device: 0x3c.
[   12.153950] PCI: Enabling device 0000:00:00.0 (0000 -> 0002)
[   12.159973] ath10k_pci 0000:00:00.0: pci irq legacy oper_irq_mode 1 irq_mode 0 reset_mode 0
[   12.196917] random: crng init done
[   12.473272] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/fwcfg-pci-0000:00:00.0.txt failed with error -2
[   12.484171] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.768227] firmware ath10k!fwcfg-pci-0000:00:00.0.txt: firmware_loading_store: map pages failed
[   12.777601] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/pre-cal-pci-0000:00:00.0.bin failed with error -2
[   12.788682] ath10k_pci 0000:00:00.0: Falling back to user helper
[   13.158344] firmware ath10k!pre-cal-pci-0000:00:00.0.bin: firmware_loading_store: map pages failed
[   13.167897] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/cal-pci-0000:00:00.0.bin failed with error -2
[   13.178620] ath10k_pci 0000:00:00.0: Falling back to user helper
[   13.637595] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/ct-firmware-5.bin failed with error -2
[   13.648956] ath10k_pci 0000:00:00.0: Falling back to user helper
[   13.783956] firmware ath10k!QCA988X!hw2.0!ct-firmware-5.bin: firmware_loading_store: map pages failed
[   13.793777] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/ct-firmware-2.bin failed with error -2
[   13.805132] ath10k_pci 0000:00:00.0: Falling back to user helper
[   13.981575] firmware ath10k!QCA988X!hw2.0!ct-firmware-2.bin: firmware_loading_store: map pages failed
[   13.991395] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-6.bin failed with error -2
[   14.002476] ath10k_pci 0000:00:00.0: Falling back to user helper
[   14.184182] firmware ath10k!QCA988X!hw2.0!firmware-6.bin: firmware_loading_store: map pages failed
[   14.193735] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-5.bin failed with error -2
[   14.204819] ath10k_pci 0000:00:00.0: Falling back to user helper
[   14.382783] firmware ath10k!QCA988X!hw2.0!firmware-5.bin: firmware_loading_store: map pages failed
[   14.392333] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-4.bin failed with error -2
[   14.403420] ath10k_pci 0000:00:00.0: Falling back to user helper
[   14.586774] firmware ath10k!QCA988X!hw2.0!firmware-4.bin: firmware_loading_store: map pages failed
[   14.596323] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-3.bin failed with error -2
[   14.607409] ath10k_pci 0000:00:00.0: Falling back to user helper
[   14.785701] firmware ath10k!QCA988X!hw2.0!firmware-3.bin: firmware_loading_store: map pages failed
[   14.990134] ath10k_pci 0000:00:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043202ff sub 0000:0000
[   14.999710] ath10k_pci 0000:00:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[   15.012132] ath10k_pci 0000:00:00.0: firmware ver 10.1-ct-8x-__fW-022-538f0906 api 2 features wmi-10.x,has-wmi-mgmt-tx,mfp,txstatus-noack,wmi-10.x-CT,ratemask-CT,txrate-CT,get-temp-CT,tx-rc-CT,cust-stats-CT,retry-gt2-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT crc32 e1c91a74
[   15.068601] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/board-2.bin failed with error -2
[   15.079414] ath10k_pci 0000:00:00.0: Falling back to user helper
[   15.169744] firmware ath10k!QCA988X!hw2.0!board-2.bin: firmware_loading_store: map pages failed
[   15.179202] ath10k_pci 0000:00:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[   16.129095] ath10k_pci 0000:00:00.0: 10.1 wmi init: vdevs: 16  peers: 127  tid: 256
[   16.137928] ath10k_pci 0000:00:00.0: firmware crashed! (guid 079dae33-cc42-4680-9253-c22aaf83584a)
[   16.147232] ath10k_pci 0000:00:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043202ff sub 0000:0000
[   16.156766] ath10k_pci 0000:00:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[   16.169183] ath10k_pci 0000:00:00.0: firmware ver 10.1-ct-8x-__fW-022-538f0906 api 2 features wmi-10.x,has-wmi-mgmt-tx,mfp,txstatus-noack,wmi-10.x-CT,ratemask-CT,regdump-CT,txrate-CT,flush-all-CT,pingpong-CT,ch-regs-CT,nop-CT,set-special-CT,get-temp-CT,tx-rc-CT,cust-stats-CT,retry-gt2-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT crc32 e1c91a74
[   16.200538] ath10k_pci 0000:00:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[   16.208097] ath10k_pci 0000:00:00.0: htt-ver 0.0 wmi-op 2 htt-op 2 cal file max-sta 128 raw 0 hwcrypto 1
[   16.219928] ath10k_pci 0000:00:00.0: firmware register dump:
[   16.225788] ath10k_pci 0000:00:00.0: [00]: 0x4100016C 0x000015B3 0x009B2AA5 0x00955B31
[   16.233973] ath10k_pci 0000:00:00.0: [04]: 0x009B2AA5 0x00060130 0x0000001D 0x214B78B0
[   16.242143] ath10k_pci 0000:00:00.0: [08]: 0xFFFFFFFF 0x00401F6A 0x0000096C 0xFFFFFFFF
[   16.250326] ath10k_pci 0000:00:00.0: [12]: 0x00000009 0x00000000 0x009B2F41 0x009B2F99
[   16.258514] ath10k_pci 0000:00:00.0: [16]: 0x00958080 0x0094085D 0x00000000 0x00000000
[   16.266695] ath10k_pci 0000:00:00.0: [20]: 0x409B2AA5 0x0040AA14 0x0040AAC4 0x00000001
[   16.274875] ath10k_pci 0000:00:00.0: [24]: 0x809B366A 0x0040AA74 0x0040E0FC 0xC09B2AA5
[   16.283046] ath10k_pci 0000:00:00.0: [28]: 0x809B3B1E 0x0040AAA4 0x00401CC0 0x000000E2
[   16.291228] ath10k_pci 0000:00:00.0: [32]: 0x80984957 0x0040ABB4 0x0040E12C 0x0000003F
[   16.299414] ath10k_pci 0000:00:00.0: [36]: 0x8098F363 0x0040ABF4 0x0040E18C 0x004062DC
[   16.307597] ath10k_pci 0000:00:00.0: [40]: 0x80989459 0x0040AC54 0x0040ACB4 0x0040ACC4
[   16.315778] ath10k_pci 0000:00:00.0: [44]: 0x80988829 0x0040ACA4 0x0040F898 0x00400000
[   16.323968] ath10k_pci 0000:00:00.0: [48]: 0x8098996B 0x0040AD44 0x0040F898 0x00000001
[   16.332146] ath10k_pci 0000:00:00.0: [52]: 0x809AE88C 0x0040AD84 0x0040F898 0x004104DC
[   16.340329] ath10k_pci 0000:00:00.0: [56]: 0x809AB61E 0x0040ADA4 0x00400000 0x004150F4
[   16.348515] ath10k_pci 0000:00:00.0: Copy Engine register dump:
[   16.354643] ath10k_pci 0000:00:00.0: [00]: 0x00057400   7   7   3   3
[   16.361298] ath10k_pci 0000:00:00.0: [01]: 0x00057800   3   3   7   8
[   16.367968] ath10k_pci 0000:00:00.0: [02]: 0x00057c00   1   1   0   1
[   16.374633] ath10k_pci 0000:00:00.0: [03]: 0x00058000   1   1   4   1
[   16.381288] ath10k_pci 0000:00:00.0: [04]: 0x00058400   0   0  40   0
[   16.387957] ath10k_pci 0000:00:00.0: [05]: 0x00058800   0   0   0   0
[   16.394622] ath10k_pci 0000:00:00.0: [06]: 0x00058c00   0   0   0   0
[   16.401278] ath10k_pci 0000:00:00.0: [07]: 0x00059000   0   0   0   0
[   16.409953] ath10k_pci 0000:00:00.0: debug log header, dbuf: 0x412708  dropped: 0
[   16.418701] ath10k_pci 0000:00:00.0: [0] next: 0x412720 buf: 0x41056c sz: 1500 len: 56 count: 2 free: 0
[   16.429423] ath10k_pci 0000:00:00.0: ath10k_pci ATH10K_DBG_BUFFER:
[   16.435817] ath10k: [0000]: 74570000 0500FC17 70201031 08000000 80000000 98F84000 01005EC0 75570000
[   16.445180] ath10k: [0008]: 0100FC17 B3150000 B3150000 04A94000 6C010041 6241DCE6
[   16.452907] ath10k_pci 0000:00:00.0: ATH10K_END
[   16.458611] ath10k_pci 0000:00:00.0: [1] next: 0x412708 buf: 0x410b5c sz: 1500 len: 0 count: 0 free: 0
[   21.153136] ath10k_pci 0000:00:00.0: wmi unified ready event not received
[   21.286397] ath10k_pci 0000:00:00.0: could not init core (-145)
[   21.292668] ath10k_pci 0000:00:00.0: could not probe fw (-145)
[   21.298767] ath10k_pci 0000:00:00.0: cannot restart a device that hasn't been started
[   21.349413] Data bus error, epc == 8022f888, ra == 87221d48
[   21.355174] Oops[#1]:
[   21.357524] CPU: 0 PID: 623 Comm: kmodloader Not tainted 4.14.221 #0
[   21.364079] task: 87da4000 task.stack: 8747e000
[   21.368753] $ 0   : 00000000 00000061 deadc0de 87261b44
[   21.374154] $ 4   : b81143fc 000143fc 8747fa84 00000004
[   21.379557] $ 8   : 00000001 7c7c3c7c 7c7c7c7c 7c7c7c7c
[   21.384961] $12   : 7c7c3c7c 00000000 fffffffe 7c7c7c3c
[   21.390364] $16   : 00000018 87462080 00000000 8747fa84
[   21.395767] $20   : 80000003 00000004 000003ff 00014000
[   21.401169] $24   : 00000000 ffff0000
[   21.406572] $28   : 8747e000 8747fa10 00010000 87221d48
[   21.411975] Hi    : 0000005c
[   21.414941] Lo    : 4e910000
[   21.417911] epc   : 8022f888 0x8022f888
[   21.421876] ra    : 87221d48 0x87221d48 [ath9k_hw@87200000+0x53dc0]
[   21.428336] Status: 1100dc03 KERNEL EXL IE
[   21.432656] Cause : 0080001c (ExcCode 07)
[   21.436796] PrId  : 00019750 (MIPS 74Kc)
[   21.440844] Modules linked in: ath9k(+) ath9k_common pppoe ppp_async ath9k_hw ath10k_pci ath10k_core ath pppox ppp_generic nf_conntrack_ipv6 mac80211 iptable_nat ipt_REJECT ipt_MASQUERADE cfg80211 xt_time xt_tcpudp xt_state xt_nat xt_multiport xt_mark xt_mac xt_limit xt_conntrack xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_FLOWOFFLOAD xt_CT slhc nf_reject_ipv4 nf_nat_redirect nf_nat_masquerade_ipv4 nf_conntrack_ipv4 nf_nat_ipv4 nf_nat nf_log_ipv4 nf_flow_table_hw nf_flow_table nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache nf_conntrack iptable_mangle iptable_filter ip_tables crc_ccitt compat ledtrig_usbport nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT x_tables nf_reject_ipv6 ehci_platform ehci_hcd gpio_button_hotplug usbcore nls_base usb_common
[   21.512529] Process kmodloader (pid: 623, threadinfo=8747e000, task=87da4000, tls=77f57efc)
[   21.521143] Stack : fffffffe 00000114 00000111 87462080 00002710 00007044 00000220 87439000
[   21.529781]         000003ff 87462080 00000100 874620a8 00000001 87220000 00000000 87222acc
[   21.538417]         81000f5c 87462080 00007000 00007000 00000600 874624bc 874620a8 87250000
[   21.547047]         87462080 87609500 810055ec 804e0000 000186a0 ffffffff 87462080 8724f520
[   21.555683]         99999999 00008000 00000100 874620a8 00000001 87250000 00000000 87214ab0
[   21.564313]         ...
[   21.566839] Call Trace:
[   21.566886] [<87220000>] 0x87220000 [ath9k_hw@87200000+0x53dc0]
[   21.575510] [<87222acc>] 0x87222acc [ath9k_hw@87200000+0x53dc0]
[   21.581652] [<87214ab0>] 0x87214ab0 [ath9k_hw@87200000+0x53dc0]
[   21.587770] [<8009959c>] 0x8009959c
[   21.591377] [<87206af0>] 0x87206af0 [ath9k_hw@87200000+0x53dc0]
[   21.597486] [<800b8a54>] 0x800b8a54
[   21.601111] [<8009959c>] 0x8009959c
[   21.604715] [<87262760>] 0x87262760 [ath9k@87260000+0x18290]
[   21.610548] [<800b7030>] 0x800b7030
[   21.614178] [<8726f4e8>] 0x8726f4e8 [ath9k@87260000+0x18290]
[   21.620032] [<801a4be0>] 0x801a4be0
[   21.623664] [<802933c0>] 0x802933c0
[   21.627273] [<80291a30>] 0x80291a30
[   21.630870] [<8010ef08>] 0x8010ef08
[   21.634478] [<80293718>] 0x80293718
[   21.638089] [<80291c4c>] 0x80291c4c
[   21.641691] [<80291ba8>] 0x80291ba8
[   21.645287] [<8028fc54>] 0x8028fc54
[   21.648894] [<804382bc>] 0x804382bc
[   21.652513] [<80290f8c>] 0x80290f8c
[   21.656120] [<8727f000>] 0x8727f000 [ath9k@87260000+0x18290]
[   21.661961] [<802924d0>] 0x802924d0
[   21.665563] [<80437a34>] 0x80437a34
[   21.669175] [<8727f018>] 0x8727f018 [ath9k@87260000+0x18290]
[   21.675015] [<801a4e84>] 0x801a4e84
[   21.678614] [<80060960>] 0x80060960
[   21.682256] [<800d7c68>] 0x800d7c68
[   21.685864] [<8012ac18>] 0x8012ac18
[   21.689470] [<800d74e4>] 0x800d74e4
[   21.693081] [<800d5584>] 0x800d5584
[   21.696687] [<800797cc>] 0x800797cc
[   21.700284] [<800d794c>] 0x800d794c
[   21.703895] [<8006f7ec>] 0x8006f7ec
[   21.707501]
[   21.709034] Code: 00000000  8c820000  0000000f <03e00008> 00000000  0808be20  00000000  aca40000  03e00008
[   21.719106]
[   21.720689] ---[ end trace 3c367a059717ff06 ]---
[   21.727012] Kernel panic - not syncing: Fatal exception
[   21.733230] Rebooting in 1 seconds..

One last thing to mention, if I try to mount with "mount_root", this error is printed:

root@(none):/rom/root# mount_root
jffs2 not ready yet, using temporary tmpfs overlay
mount failed: lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work, options No such device

I'm now out of ideas how to get this thing back to life (if it's even possible)...
Any help appreciated

you appear to have serial console - the garbage during the reboot is the boot loader.
but with wrong speed configured.

should be fairly easy to get it back, using that.
Or TFTP.

Ok, this tftp method you mention, was actually what I did to get it in this state -> rename image to ArcherC7v5_tp_recovery.bin and Press reset when turned off, then turn on.
But it was not 100% successfull as you can see. Is there another tftp method I'm not aware of?

It was the sysupgrade that got you into this state, according to your C&P...?

I tried the sysupgrade -n after I recovered the Router with the tftp method. Before, it would not even start. When it came back after tftp recovery, it was in this state above, and then i tried the sysupgrade -n in failsafe Mode, but the resullt is the same as after tftp recovery.

The guide at https://openwrt.org/toh/tp-link/archer-c7-1750 is somewhat cryptic.

But what state was it exactly ?

And why did you apply the sysupgrade image once you recovered ?

You could try the images with the old wifi driver, instead of the ath79 -
https://downloads.openwrt.org/releases/19.07.7/targets/ar71xx/generic/
Since the crash looks like it's caused by the wifi driver.
Ath79 is to prefer thought, the other/old one is dropped in the next release.

Do another TFTP recovery using the factory image for the correct device, and you should be OK after the reboot.

It was in a state, in which only the Power led was on, nothing else. No lan connection or wifi.
I applied the sysupgrade because after the tftp recovery i got the same Kernel Panic as you can see in my first post. So i went to failsafe and tried a sysupgrade.
Regarding uboot output: you mentioned it could be the wrong speed, but I tried every baudrate from 2400 up to 250000. The output is always unreadable.
Could there be something wrong with uboot?
I willt try another tftp recovery with the openwrt 19.07.7 factory image. If that don't work, I try the ar71xx.

u-boot seems to do what it's supposed to, just not in a readable state :wink:

There's actually no speed specified in the wiki, although it's usually 115200 N81, no flow control.

That's what I'm using....

Ok, now I tried to flash openwrt-19.07.7-ar71xx-generic-archer-c7-v5-squashfs-factory.bin - same result, a kernel panic:

                                                 ▒  ▒▒0.4▒845▒] C▒▒sh▒▒g ▒▒lo▒▒te▒▒RA▒▒at▒▒ddr▒ss ▒▒3f▒▒00▒▒
                                                                                                            [▒   ▒.49▒▒89▒▒wo▒▒in▒▒et▒▒ti▒▒st▒▒p_b▒ts=▒0 m▒▒_o▒▒er▒▒5 ▒▒ck▒▒_o▒▒er▒▒
[ ▒  0▒▒06▒▒6]▒▒qu▒▒hf▒▒ v▒▒si▒▒ 4.▒ (2▒09/▒▒/3▒▒ P▒▒ll▒▒ L▒▒gh▒▒
[▒▒  ▒▒51▒▒87▒▒jff▒2: ▒ers▒▒n ▒▒2 ▒▒AN▒▒ (▒▒MM▒▒Y)▒▒LZM▒) (▒TIM▒▒ (▒▒OD▒▒PR▒▒RI▒▒) ▒▒) ▒▒01-▒006▒Red▒▒at▒▒In▒▒
▒▒  ▒▒0.▒▒518▒] i▒ sc▒▒du▒▒r ▒▒ad▒▒ne▒▒eg▒▒te▒▒d (▒efa▒lt)▒▒▒  ▒▒0.▒▒10▒▒] ▒▒ria▒: 8▒50/▒▒55▒▒dr▒▒er▒▒16▒▒or▒▒, ▒▒Q s▒ari▒g e▒▒bl▒▒
[▒▒  0▒549▒79]▒▒on▒▒le▒▒tt▒▒0]▒▒is▒▒le▒▒
                                        ▒  ▒▒0.▒▒333▒] s▒▒ia▒▒25▒▒0:▒▒ty▒▒ a▒▒MM▒▒ 0▒▒802▒000▒▒ir▒▒= ▒▒, ▒▒se▒▒au▒▒= ▒▒625▒0) ▒▒[    0.582444] console [ttyS0] enabled
[    0.582444] console [ttyS0] enabled
[    0.590003] bootconsole [early0] disabled
[    0.590003] bootconsole [early0] disabled
[    0.604547] m25p80 spi0.0: found w25q128, expected m25p80
[    0.619098] m25p80 spi0.0: w25q128 (16384 Kbytes)
[    0.623988] 5 cmdlinepart partitions found on MTD device spi0.0
[    0.630128] Creating 5 MTD partitions on "spi0.0":
[    0.635083] 0x000000000000-0x000000020000 : "factory-uboot"
[    0.642319] 0x000000020000-0x000000040000 : "u-boot"
[    0.648608] 0x000000050000-0x000000060000 : "art"
[    0.655164] 0x000000060000-0x000000080000 : "info"
[    0.661280] 0x0000000c0000-0x000000fc0000 : "firmware"
[    0.692411] 2 uimage-fw partitions found on MTD device firmware
[    0.698562] 0x0000000c0000-0x000000250000 : "kernel"
[    0.704282] 0x000000250000-0x000000fc0000 : "rootfs"
[    0.710024] mtd: device 6 (rootfs) set to be root filesystem
[    0.715953] 1 squashfs-split partitions found on MTD device rootfs
[    0.722344] 0x000000510000-0x000000fc0000 : "rootfs_data"
[    0.731161] libphy: Fixed MDIO Bus: probed
[    0.752910] switch0: Atheros AR8337 rev. 2 switch registered on ag71xx-mdio.0
[    1.475820] libphy: ag71xx_mdio: probed
[    2.107329] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd036, driver=Atheros AR8216/AR8236/AR8316]
[    2.118783] eth0: Atheros AG71xx at 0xb9000000, irq 4, mode: sgmii
[    2.127343] NET: Registered protocol family 10
[    2.136899] Segment Routing with IPv6
[    2.140770] NET: Registered protocol family 17
[    2.145395] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[    2.159283] 8021q: 802.1Q VLAN Support v1.8
[    2.165004] hctosys: unable to open rtc device (rtc0)
[    2.176006] VFS: Mounted root (squashfs filesystem) readonly on device 31:6.
[    2.185021] Freeing unused kernel memory: 320K
[    2.189647] This architecture does not have kernel memory protection.
[    2.585709] random: fast init done
[    2.776825] init: Console is alive
[    2.780542] init: - watchdog -
[    3.791626] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[    3.846165] usbcore: registered new interface driver usbfs
[    3.851921] usbcore: registered new interface driver hub
[    3.857517] usbcore: registered new device driver usb
[    3.867447] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[    3.875599] ehci-platform: EHCI generic platform driver
[    3.881122] ehci-platform ehci-platform.0: EHCI Host Controller
[    3.887295] ehci-platform ehci-platform.0: new USB bus registered, assigned bus number 1
[    3.897750] ehci-platform ehci-platform.0: irq 48, io mem 0x1b000000
[    3.925724] ehci-platform ehci-platform.0: USB 2.0 started, EHCI 1.00
[    3.933003] hub 1-0:1.0: USB hub found
[    3.937260] hub 1-0:1.0: 1 port detected
[    3.941715] ehci-platform ehci-platform.1: EHCI Host Controller
[    3.947904] ehci-platform ehci-platform.1: new USB bus registered, assigned bus number 2
[    3.958374] ehci-platform ehci-platform.1: irq 49, io mem 0x1b400000
[    3.985741] ehci-platform ehci-platform.1: USB 2.0 started, EHCI 1.00
[    3.993030] hub 2-0:1.0: USB hub found
[    3.997292] hub 2-0:1.0: 1 port detected
[    4.002395] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[    4.020286] init: - preinit -
[    5.098563] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[    5.124373] random: procd: uninitialized urandom read (4 bytes read)
Press the [f] key and hit [enter] to enter failsafe mode
Press the [1], [2], [3] or [4] key and hit [enter] to select the debug level
[    6.117364] eth0: link up (1000Mbps/Full duplex)
[    6.122347] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[    8.354988] mount_root: jffs2 not ready yet, using temporary tmpfs overlay
[    8.384574] urandom-seed: Seed file not found (/etc/urandom.seed)
[    8.490404] eth0: link down
[    8.503268] procd: - early -
[    8.506939] procd: - watchdog -
[    9.123462] procd: - watchdog -
[    9.127061] procd: - ubus -
[    9.227737] random: ubusd: uninitialized urandom read (4 bytes read)
[    9.256157] random: ubusd: uninitialized urandom read (4 bytes read)
[    9.263127] random: ubusd: uninitialized urandom read (4 bytes read)
[    9.270628] procd: - init -
Please press Enter to activate this console.
[    9.972793] kmodloader: loading kernel modules from /etc/modules.d/*
[   10.040541] ip6_tables: (C) 2000-2006 Netfilter Core Team
[   10.068399] Loading modules backported from Linux version v4.19.161-0-gdaefdc9eb24b
[   10.076373] Backport generated by backports.git v4.19.161-1-0-g4bb568fe
[   10.107696] ip_tables: (C) 2000-2006 Netfilter Core Team
[   10.130558] nf_conntrack version 0.5.0 (2048 buckets, 8192 max)
[   10.228566] xt_time: kernel timezone is -0000
[   10.375155] urngd: v1.0.2 started.
[   10.437790] PPP generic driver version 2.4.2
[   10.444329] NET: Registered protocol family 24
[   10.508146] pci 0000:00:00.0: using irq 40 for pin 1
[   10.513282] ath10k 4.19 driver, optimized for CT firmware, probing pci device: 0x3c.
[   10.536601] PCI: Enabling device 0000:00:00.0 (0000 -> 0002)
[   10.542625] ath10k_pci 0000:00:00.0: pci irq legacy oper_irq_mode 1 irq_mode 0 reset_mode 0
[   10.597073] random: crng init done
[   10.600592] random: 6 urandom warning(s) missed due to ratelimiting
[   10.855861] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/fwcfg-pci-0000:00:00.0.txt failed with error -2
[   10.866767] ath10k_pci 0000:00:00.0: Falling back to user helper
[   11.195077] firmware ath10k!fwcfg-pci-0000:00:00.0.txt: firmware_loading_store: map pages failed
[   11.204450] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/pre-cal-pci-0000:00:00.0.bin failed with error -2
[   11.215529] ath10k_pci 0000:00:00.0: Falling back to user helper
[   11.500833] firmware ath10k!pre-cal-pci-0000:00:00.0.bin: firmware_loading_store: map pages failed
[   11.510382] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/cal-pci-0000:00:00.0.bin failed with error -2
[   11.521111] ath10k_pci 0000:00:00.0: Falling back to user helper
[   11.856220] firmware ath10k!cal-pci-0000:00:00.0.bin: firmware_loading_store: map pages failed
[   11.865419] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/ct-firmware-5.bin failed with error -2
[   11.876779] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.128438] firmware ath10k!QCA988X!hw2.0!ct-firmware-5.bin: firmware_loading_store: map pages failed
[   12.138254] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/ct-firmware-2.bin failed with error -2
[   12.149609] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.288580] firmware ath10k!QCA988X!hw2.0!ct-firmware-2.bin: firmware_loading_store: map pages failed
[   12.298393] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-6.bin failed with error -2
[   12.309472] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.449073] firmware ath10k!QCA988X!hw2.0!firmware-6.bin: firmware_loading_store: map pages failed
[   12.458650] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-5.bin failed with error -2
[   12.469732] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.608555] firmware ath10k!QCA988X!hw2.0!firmware-5.bin: firmware_loading_store: map pages failed
[   12.618096] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-4.bin failed with error -2
[   12.629174] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.769743] firmware ath10k!QCA988X!hw2.0!firmware-4.bin: firmware_loading_store: map pages failed
[   12.779289] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-3.bin failed with error -2
[   12.790374] ath10k_pci 0000:00:00.0: Falling back to user helper
[   12.929865] firmware ath10k!QCA988X!hw2.0!firmware-3.bin: firmware_loading_store: map pages failed
[   12.943592] ath10k_pci 0000:00:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043202ff sub 0000:0000
[   12.953164] ath10k_pci 0000:00:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 0
[   12.965571] ath10k_pci 0000:00:00.0: firmware ver 10.1-ct-8x-__fW-022-538f0906 api 2 features wmi-10.x,has-wmi-mgmt-tx,mfp,txstatus-noack,wmi-10.x-CT,ratemask-CT,txrate-CT,get-temp-CT,tx-rc-CT,cust-stats-CT,retry-gt2-CT,txrate2-CT,beacon-cb-CT,wmi-block-ack-CT crc32 e1c91a74
[   13.078690] ath10k_pci 0000:00:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/board-2.bin failed with error -2
[   13.089509] ath10k_pci 0000:00:00.0: Falling back to user helper
[   13.162615] firmware ath10k!QCA988X!hw2.0!board-2.bin: firmware_loading_store: map pages failed
[   13.192730] ath10k_pci 0000:00:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[   13.279462] ath10k_pci 0000:00:00.0: otp calibration failed: 2
[   13.285496] ath10k_pci 0000:00:00.0: failed to run otp: -22 (download-cal-data)
[   13.293071] ath10k_pci 0000:00:00.0: could not init core (-22)
[   13.299198] ath10k_pci 0000:00:00.0: could not probe fw (-22)
[   13.355218] Data bus error, epc == 80231348, ra == 87721d48
[   13.360983] Oops[#1]:
[   13.363332] CPU: 0 PID: 579 Comm: kmodloader Not tainted 4.14.221 #0
[   13.369887] task: 87c810e0 task.stack: 874a8000
[   13.374560] $ 0   : 00000000 00000001 deadc0de 87761ac4
[   13.379962] $ 4   : b81143fc 000143fc 874a9a7c 00000004
[   13.385365] $ 8   : 00000001 7c7c3c7c 7c7c7c7c 7c7c7c7c
[   13.390769] $12   : 7c7c3c7c 87778128 87778b68 7c7c7c3c
[   13.396172] $16   : 00000018 87cde080 00000000 874a9a7c
[   13.401574] $20   : 80000003 00000004 000003ff 00014000
[   13.406977] $24   : 00000000 00000000
[   13.412381] $28   : 874a8000 874a9a08 00010000 87721d48
[   13.417784] Hi    : 0000005c
[   13.420750] Lo    : 4e910000
[   13.423719] epc   : 80231348 0x80231348
[   13.427683] ra    : 87721d48 0x87721d48 [ath9k_hw@87700000+0x53dc0]
[   13.434144] Status: 1100dc03 KERNEL EXL IE
[   13.438465] Cause : 0080001c (ExcCode 07)
[   13.442603] PrId  : 00019750 (MIPS 74Kc)
[   13.446643] Modules linked in: ath9k(+) ath9k_common pppoe ppp_async ath9k_hw ath10k_pci ath10k_core ath pppox ppp_generic nf_conntrack_ipv6 mac80211 iptable_nat ipt_REJECT ipt_MASQUERADE cfg80211 xt_time xt_tcpudp xt_state xt_nat xt_multiport xt_mark xt_mac xt_limit xt_conntrack xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_FLOWOFFLOAD xt_CT slhc nf_reject_ipv4 nf_nat_redirect nf_nat_masquerade_ipv4 nf_conntrack_ipv4 nf_nat_ipv4 nf_nat nf_log_ipv4 nf_flow_table_hw nf_flow_table nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache nf_conntrack iptable_mangle iptable_filter ip_tables crc_ccitt compat ledtrig_usbport nf_log_ipv6 nf_log_common ip6table_mangle ip6table_filter ip6_tables ip6t_REJECT x_tables nf_reject_ipv6 ehci_platform ehci_hcd gpio_button_hotplug usbcore nls_base usb_common
[   13.518328] Process kmodloader (pid: 579, threadinfo=874a8000, task=87c810e0, tls=77f63efc)
[   13.526943] Stack : 00000001 80478984 87f58034 804c0000 00000000 31000048 00000220 87578000
[   13.535579]         000003ff 87cde080 00000100 87cde0a8 00000001 87720000 00000000 87722acc
[   13.544207]         00000002 87cde080 00007000 00007000 00000600 87cde4bc 87cde0a8 87750000
[   13.552836]         00000001 00200041 00000001 00000000 000186a0 ffffffff 87cde080 8774f520
[   13.561464]         99999999 00008000 00000100 87cde0a8 00000001 87750000 00000000 87714ab0
[   13.570093]         ...
[   13.572621] Call Trace:
[   13.572663] [<87720000>] 0x87720000 [ath9k_hw@87700000+0x53dc0]
[   13.581291] [<87722acc>] 0x87722acc [ath9k_hw@87700000+0x53dc0]
[   13.587416] [<87714ab0>] 0x87714ab0 [ath9k_hw@87700000+0x53dc0]
[   13.593528] [<8009b25c>] 0x8009b25c
[   13.597135] [<87706af0>] 0x87706af0 [ath9k_hw@87700000+0x53dc0]
[   13.603242] [<80213cb0>] 0x80213cb0
[   13.606850] [<8009b25c>] 0x8009b25c
[   13.610460] [<877624fc>] 0x877624fc [ath9k@87760000+0x17590]
[   13.616294] [<80423aa4>] 0x80423aa4
[   13.619901] [<87764314>] 0x87764314 [ath9k@87760000+0x17590]
[   13.625748] [<87600564>] 0x87600564 [mac80211@87600000+0x6c6c0]
[   13.631866] [<8776eee8>] 0x8776eee8 [ath9k@87760000+0x17590]
[   13.637711] [<801a66a0>] 0x801a66a0
[   13.641329] [<80281ae4>] 0x80281ae4
[   13.644937] [<801a9538>] 0x801a9538
[   13.648533] [<80280010>] 0x80280010
[   13.652134] [<801109c8>] 0x801109c8
[   13.655744] [<80280224>] 0x80280224
[   13.659342] [<80280180>] 0x80280180
[   13.662939] [<8027e244>] 0x8027e244
[   13.666535] [<8042432c>] 0x8042432c
[   13.670146] [<8027f57c>] 0x8027f57c
[   13.673752] [<8777f000>] 0x8777f000 [ath9k@87760000+0x17590]
[   13.679587] [<80280aa0>] 0x80280aa0
[   13.683189] [<80423aa4>] 0x80423aa4
[   13.686798] [<8777f018>] 0x8777f018 [ath9k@87760000+0x17590]
[   13.692634] [<801a6944>] 0x801a6944
[   13.696237] [<80060960>] 0x80060960
[   13.699861] [<800d9728>] 0x800d9728
[   13.703459] [<8012c6d8>] 0x8012c6d8
[   13.707063] [<800d8fa4>] 0x800d8fa4
[   13.710665] [<800d7044>] 0x800d7044
[   13.714268] [<8012d064>] 0x8012d064
[   13.717866] [<8012d158>] 0x8012d158
[   13.721468] [<800d940c>] 0x800d940c
[   13.725076] [<800714ac>] 0x800714ac
[   13.728676]
[   13.730208] Code: 00000000  8c820000  0000000f <03e00008> 00000000  0808c4d0  00000000  aca40000  03e00008
[   13.740280]
[   13.741889] ---[ end trace 5ab76402a7430423 ]---
[   13.748132] Kernel panic - not syncing: Fatal exception
[   13.754245] Rebooting in 1 seconds..

I also tried the openwrt-19.07.7-ath79-generic-archer-c7-v5-squashfs-factory.bin - also the same

ath79 factory image gave me a different error output (I've shortened the middle part):

          [    0.361302] console [ttyS0] enabled
[    0.361302] console [ttyS0] enabled
[    0.368866] bootconsole [early0] disabled
[    0.368866] bootconsole [early0] disabled
[    0.393781] m25p80 spi0.0: w25q128 (16384 Kbytes)
[    0.398693] 8 fixed-partitions partitions found on MTD device spi0.0
[    0.405276] Creating 8 MTD partitions on "spi0.0":
[    0.410229] 0x000000000000-0x000000020000 : "factory-uboot"
[    0.416674] 0x000000020000-0x000000040000 : "u-boot"
[    0.422419] 0x000000040000-0x000000050000 : "partition-table"
[    0.429072] 0x000000050000-0x000000060000 : "art"
[    0.434602] 0x000000060000-0x000000080000 : "info"
[    0.440193] 0x000000080000-0x0000000c0000 : "user-config"
[    0.446460] 0x0000000c0000-0x000000fc0000 : "firmware"
[    0.456103] 2 uimage-fw partitions found on MTD device firmware
[    0.462224] Creating 2 MTD partitions on "firmware":
[    0.467396] 0x000000000000-0x0000001867e4 : "kernel"
[    0.473182] 0x0000001867e4-0x000000f00000 : "rootfs"
[    0.478896] mtd: device 8 (rootfs) set to be root filesystem
[    0.484819] 1 squashfs-split partitions found on MTD device rootfs
[    0.491209] 0x000000440000-0x000000f00000 : "rootfs_data"
[    0.497418] 0x000000ff0000-0x000001000000 : "default-config"
[    0.504949] libphy: Fixed MDIO Bus: probed
[    0.511336] ag71xx 19000000.eth: invalid MAC address, using random address
[    1.193452] libphy: ag71xx_mdio: probed
[    1.200404] switch0: Atheros AR8337 rev. 2 switch registered on mdio-bus.0
[    1.854565] ag71xx 19000000.eth: connected to PHY at mdio-bus.0:00 [uid=004dd036, driver=Atheros AR8216/AR8236/AR8316]
[    1.866154] eth0: Atheros AG71xx at 0xb9000000, irq 4, mode: sgmii
[    1.875243] NET: Registered protocol family 10
[    1.885020] Segment Routing with IPv6
[    1.888885] NET: Registered protocol family 17
[    1.893558] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[    1.906949] 8021q: 802.1Q VLAN Support v1.8
[    1.913234] hctosys: unable to open rtc device (rtc0)
[    1.920891] squashfs: SQUASHFS error: unable to read id index table
[    1.927687] jffs2: Flash size not aligned to erasesize, reducing to 13760KiB
[    1.935255] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000000: 0x6873 instead
[    1.945069] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000004: 0x8f04 instead
[    1.954870] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000008: 0xbd91 instead
[    1.964673] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000010: 0x1500 instead
[    1.974475] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000014: 0x0400 instead
[    1.984277] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000018: 0xc006 instead
[    1.994079] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0000001c: 0x0400 instead
[    2.003881] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000020: 0x6a16 instead
[    2.013684] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000028: 0x1655 instead
[    2.023486] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00000030: 0x0e55 instead
[    2.033286] jffs2: Further such events for this erase block will not be printed
[    2.042953] jffs2: Empty flash at 0x00000038 ends at 0x00000040
[    2.072004] jffs2: Empty flash at 0x00009854 ends at 0x0000985c
[    2.091188] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010000: 0x3171 instead
[    2.100992] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010004: 0xd7b7 instead
[    2.110791] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010008: 0x1cc9 instead
[    2.120593] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0001000c: 0x9140 instead
[    2.130395] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010010: 0x8792 instead
[    2.140198] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010014: 0xbaf4 instead
[    2.150000] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010018: 0x5ac9 instead
[    2.159801] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0001001c: 0x5102 instead
[    2.169604] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010020: 0x0ae2 instead
[    2.179406] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00010024: 0x640b instead
[    2.189204] jffs2: Further such events for this erase block will not be printed
[    2.233821] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020000: 0xd4e7 instead
[    2.243625] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020004: 0x0f13 instead
[    2.253426] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020008: 0x590a instead
[    2.263227] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0002000c: 0xcf95 instead
[    2.273013] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020010: 0xa285 instead
[    2.282814] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020014: 0xa42c instead
[    2.292616] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020018: 0x308b instead
[    2.302419] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0002001c: 0xdc60 instead
[    2.312220] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020020: 0x248a instead
[    2.322023] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00020024: 0x1dfd instead
[    2.331822] jffs2: Further such events for this erase block will not be printed
[    2.381377] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030000: 0xa75a instead
[    2.391193] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030004: 0xe5ae instead
[    2.400998] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030008: 0x8167 instead
[    2.410799] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0003000c: 0x5cc4 instead
[    2.420600] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030010: 0x1fe2 instead
[    2.430403] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030014: 0xb9b4 instead
[    2.440205] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030018: 0xe7a6 instead
[    2.450007] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0003001c: 0xe363 instead
[    2.459810] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030020: 0x4697 instead
[    2.469611] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00030024: 0x8bcd instead
[    2.479410] jffs2: Further such events for this erase block will not be printed
[    2.521580] jffs2: Old JFFS2 bitmask found at 0x0003ef34
[    2.527078] jffs2: You cannot use older JFFS2 filesystems with newer kernels
[    2.536797] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040000: 0xd424 instead
[    2.546599] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040004: 0xdb6e instead
[    2.556399] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040008: 0xd784 instead
[    2.566195] random: fast init done
[    2.569707] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0004000c: 0xd638 instead
[    2.579507] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040010: 0xc325 instead
[    2.589309] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040014: 0x98ad instead
[    2.599110] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040018: 0x1211 instead
[    2.608913] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0004001c: 0xcd63 instead
[    2.618715] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040020: 0x04b7 instead
[    2.628517] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00040024: 0x4c70 instead
[    2.638316] jffs2: Further such events for this erase block will not be printed
[    2.682917] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050000: 0x9c18 instead
[    2.692718] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050004: 0xefdb instead
[    2.702517] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050008: 0x3eb7 instead
[    2.712320] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0005000c: 0x8242 instead
[    2.722122] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050010: 0xab9b instead
[    2.731925] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050014: 0xe0b3 instead
[    2.741727] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050018: 0x316b instead
[    2.751528] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0005001c: 0x3753 instead
[    2.761331] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050020: 0x266f instead
[    2.771133] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00050024: 0xd372 instead
[    2.780933] jffs2: Further such events for this erase block will not be printed
[    2.825546] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060000: 0x7010 instead
[    2.835352] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060004: 0x35b0 instead
[    2.845152] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060008: 0x16c1 instead
[    2.854954] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0006000c: 0x07e2 instead
[    2.864757] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060010: 0x1d2e instead
[    2.879430] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060014: 0x7b22 instead
[    2.889243] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060018: 0xd544 instead
[    2.899048] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0006001c: 0x2d9e instead
[    2.908850] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060020: 0x564c instead
[    2.918668] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00060024: 0x392b instead
[    2.928472] jffs2: Further such events for this erase block will not be printed
[    2.973083] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070000: 0x7b27 instead
[    2.982888] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070004: 0x95cb instead
[    2.992689] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070008: 0x4718 instead
[    3.002490] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0007000c: 0x297f instead
[    3.012292] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070010: 0xe052 instead
[    3.022095] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070014: 0x55ee instead
[    3.031897] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070018: 0x048e instead
[    3.041701] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0007001c: 0x427b instead
[    3.051501] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070020: 0x8b20 instead
[    3.061304] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00070024: 0x2567 instead
[    3.071102] jffs2: Further such events for this erase block will not be printed
[    3.115716] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080000: 0x8487 instead
[    3.125522] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080004: 0x3bee instead
[    3.135323] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080008: 0x6356 instead
[    3.145125] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0008000c: 0x84a5 instead
[    3.154926] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080010: 0xc977 instead
[    3.164729] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080014: 0xd9a6 instead
[    3.174531] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080018: 0xb701 instead
[    3.184333] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x0008001c: 0x470f instead
[    3.194135] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080020: 0x9200 instead
[    3.203942] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x00080024: 0x52d5 instead
[    3.213735] jffs2: Further such events for this erase block will not be printed
[    3.239626] jffs2: Old JFFS2 bitmask found at 0x00087638
.
.
.
[    8.205528] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0000: 0xc7b4 instead
[    8.215330] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0004: 0xe836 instead
[    8.225130] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0008: 0xea1a instead
[    8.234933] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a000c: 0x94df instead
[    8.244735] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0010: 0xf377 instead
[    8.254538] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0014: 0xe04b instead
[    8.264339] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0018: 0x9c89 instead
[    8.274141] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a001c: 0x1ad4 instead
[    8.283944] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0020: 0x866a instead
[    8.293746] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002a0024: 0xb834 instead
[    8.303545] jffs2: Further such events for this erase block will not be printed
[    8.348152] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0000: 0x1b4e instead
[    8.357956] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0004: 0x0356 instead
[    8.367756] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0008: 0x1a96 instead
[    8.377559] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b000c: 0x740a instead
[    8.387360] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0010: 0x437a instead
[    8.397163] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0014: 0x585e instead
[    8.406964] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0018: 0x4d3d instead
[    8.416766] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b001c: 0xceec instead
[    8.426568] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0020: 0x93e7 instead
[    8.436371] jffs2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x002b0024: 0xb746 instead
[    8.446170] jffs2: Further such events for this erase block will not be printed
[    8.521969] jffs2: Cowardly refusing to erase blocks on filesystem with no valid JFFS2 nodes
[    8.530694] jffs2: empty_blocks 171, bad_blocks 0, c->nr_blocks 215
[    8.537251] VFS: Cannot open root device "(null)" or unknown-block(31,8): error -5
[    8.545083] Please append a correct "root=" boot option; here are the available partitions:
[    8.553726] 1f00             128 mtdblock0
[    8.553730]  (driver?)
[    8.560481] 1f01             128 mtdblock1
[    8.560484]  (driver?)
[    8.567245] 1f02              64 mtdblock2
[    8.567248]  (driver?)
[    8.574017] 1f03              64 mtdblock3
[    8.574021]  (driver?)
[    8.580765] 1f04             128 mtdblock4
[    8.580768]  (driver?)
[    8.587531] 1f05             256 mtdblock5
[    8.587534]  (driver?)
[    8.594294] 1f06           15360 mtdblock6
[    8.594298]  (driver?)
[    8.601041] 1f07            1561 mtdblock7
[    8.601044]  (driver?)
[    8.607807] 1f08           13798 mtdblock8
[    8.607811]  (driver?)
[    8.614571] 1f09           11008 mtdblock9
[    8.614575]  (driver?)
[    8.621318] 1f0a              64 mtdblock10
[    8.621321]  (driver?)
[    8.628172] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(31,8)
[    8.639731] Rebooting in 1 seconds..

I'm no expert in radio, but perhaps you managed to do something with your ART data, when you applied the wrong image, since it's the wifi driver that's causing the crash.

You might want to try to go back to stock (again, using TFTP), and see if it get it up and running, and if the radio works there.

Depending on what state the openwrt is in, you should be able to write the ART data using it, if not, u-boot would be required. JTAG might work too, but I have no experience with that.

Ok, I want to reflash my art partition. I found an art image on github which should fit, but i need uboot to write it, and I cannot read the output. So how should i write the image to the right position in the flash?

dmesg tells you where the art partition resides.
cat /proc/mtd should confirm this.

Check if the mtd command is available in openwrt recovery mode.

yep, the cat out put shows me the art partition. But unfortunately I cannot write to it, cause it is read-only.

root@(none):/# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00020000 00010000 "factory-uboot"
mtd1: 00020000 00010000 "u-boot"
mtd2: 00010000 00010000 "partition-table"
mtd3: 00010000 00010000 "art"
mtd4: 00020000 00010000 "info"
mtd5: 00040000 00010000 "user-config"
mtd6: 00f00000 00010000 "firmware"
mtd7: 00190000 00010000 "kernel"
mtd8: 00d70000 00010000 "rootfs"
mtd9: 00ab0000 00010000 "rootfs_data"
mtd10: 00010000 00010000 "default-config"

root@(none):/# mtd -r write /tmp/art.bin mtd3
Could not open mtd device: mtd3
Can't open device for writing!

I followed this guide:

it mentions to install kmod-mtd-rw, but how should i do this in failsafe mode?

This is the flash layout of your C7

image

This is the one of my A7

[    0.409835] 0x000000000000-0x000000020000 : "factory-uboot"
[    0.416285] 0x000000020000-0x000000040000 : "u-boot"
[    0.422031] 0x000000040000-0x000000f00000 : "firmware"
[    0.429758] 2 uimage-fw partitions found on MTD device firmware
[    0.435917] Creating 2 MTD partitions on "firmware":
[    0.441049] 0x000000000000-0x0000001867ec : "kernel"
[    0.446835] 0x0000001867ec-0x000000ec0000 : "rootfs"
[    0.452557] mtd: device 4 (rootfs) set to be root filesystem
[    0.458486] 1 squashfs-split partitions found on MTD device rootfs
[    0.464896] 0x000000440000-0x000000ec0000 : "rootfs_data"
[    0.471091] 0x000000f40000-0x000000f60000 : "info"
[    0.476712] 0x000000f60000-0x000000fb0000 : "config"
[    0.482491] 0x000000fc0000-0x000000fd0000 : "partition-table"
[    0.489101] 0x000000ff0000-0x000001000000 : "art"

The firmware partition of the A7 starts at 0x4000.
I think that when you flashed your C7 with the image for A7 you have overwritten everything, starting from 0x4000, including partition-table, art, info and user-config. The missing MAC should prove that:

[ 0.511215] ag71xx 19000000.eth: invalid MAC address, using random address

Ask some owner of C7 to dump those partitions for you and try to recover your device using mtd. If you bring the device back to life, you could change the MAC addresses later.
As @frollic mentioned, check the mtd command availability in failsafe mode, especially the possibility to unlock the mtd partitions.

Hi,
ok, at least I got the art partition already, but I cannot copy it using mtd, because it is read-only.
Don't know how to unlock it in failsafe mode

What is the result of

mtd unlock /dev/mtd3

Hi, it looks like this:

root@(none):/# mtd unlock /dev/mtd3
Could not open mtd device: /dev/mtd3
Could not open mtd device: /dev/mtd3
root@(none):/# ls /dev/
console             mtd7                random
cpu_dma_latency     mtd7ro              shm
full                mtd8                tty
gpiochip0           mtd8ro              ttyS0
hw_random           mtd9                ttyS1
kmsg                mtd9ro              ttyS10
memory_bandwidth    mtdblock0           ttyS11
mtd0                mtdblock1           ttyS12
mtd0ro              mtdblock10          ttyS13
mtd1                mtdblock2           ttyS14
mtd10               mtdblock3           ttyS15
mtd10ro             mtdblock4           ttyS2
mtd1ro              mtdblock5           ttyS3
mtd2                mtdblock6           ttyS4
mtd2ro              mtdblock7           ttyS5
mtd3                mtdblock8           ttyS6
mtd3ro              mtdblock9           ttyS7
mtd4                network_latency     ttyS8
mtd4ro              network_throughput  ttyS9
mtd5                null                urandom
mtd5ro              port                watchdog
mtd6                ptmx                zero
mtd6ro              pts

you could try dd instead

dd if=/tmp/art.bin of=/dev/mtd3

Unfortunately this does not work:

root@(none):/# dd if=/tmp/art.bin of=/dev/mtd3
dd: can't open '/dev/mtd3': Permission denied