Ok, so I installed the official 18.06.2 image now without preserving settings, but the firmware still crashes... Ouch!
Here's the full dmesg:
[ 0.000000] Linux version 4.9.152 (buildbot@builds-03.infra.lede-project.org) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r7549-217219e) ) #0 Mon Jan 28 08:54:32 2019
[ 0.000000] MyLoader: sysp=2008a593, boardp=004f2f0d, parts=e80ee408
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU0 revision is: 00019750 (MIPS 74Kc)
[ 0.000000] SoC: Qualcomm Atheros QCA9558 ver 1 rev 0
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 08000000 @ 00000000 (usable)
[ 0.000000] Initrd not found or empty - disabling initrd
[ 0.000000] Primary instruction cache 64kB, VIPT, 4-way, linesize 32 bytes.
[ 0.000000] Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000000000000-0x0000000007ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x0000000007ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000007ffffff]
[ 0.000000] On node 0 totalpages: 32768
[ 0.000000] free_area_init_node: node 0, pgdat 8044a204, node_mem_map 81000020
[ 0.000000] Normal zone: 256 pages used for memmap
[ 0.000000] Normal zone: 0 pages reserved
[ 0.000000] Normal zone: 32768 pages, LIFO batch:7
[ 0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[ 0.000000] pcpu-alloc: [0] 0
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 32512
[ 0.000000] Kernel command line: board=ARCHER-C7-V2 console=ttyS0,115200 rootfstype=squashfs noinitrd
[ 0.000000] PID hash table entries: 512 (order: -1, 2048 bytes)
[ 0.000000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
[ 0.000000] Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Writing ErrCtl register=00000000
[ 0.000000] Readback ErrCtl register=00000000
[ 0.000000] Memory: 125004K/131072K available (3388K kernel code, 175K rwdata, 448K rodata, 268K init, 211K bss, 6068K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS:51
[ 0.000000] Clocks: CPU:720.000MHz, DDR:600.000MHz, AHB:200.000MHz, Ref:40.000MHz
[ 0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 5309056796 ns
[ 0.000008] sched_clock: 32 bits at 360MHz, resolution 2ns, wraps every 5965232126ns
[ 0.008295] Calibrating delay loop... 358.80 BogoMIPS (lpj=1794048)
[ 0.071187] pid_max: default: 32768 minimum: 301
[ 0.076186] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.083231] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.092881] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[ 0.103376] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.110856] NET: Registered protocol family 16
[ 0.116775] MIPS: machine is TP-LINK Archer C7
[ 0.124592] ar724x-pci ar724x-pci.0: PCIe link is down
[ 0.130093] registering PCI controller with io_map_base unset
[ 0.136305] registering PCI controller with io_map_base unset
[ 0.623001] Can't analyze schedule() prologue at 803ab684
[ 0.637864] PCI host bridge to bus 0000:00
[ 0.642230] pci_bus 0000:00: root bus resource [mem 0x10000000-0x11ffffff]
[ 0.649576] pci_bus 0000:00: root bus resource [io 0x0000]
[ 0.655504] pci_bus 0000:00: root bus resource [??? 0x00000000 flags 0x0]
[ 0.662727] pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
[ 0.671164] pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to 00
[ 0.671265] PCI host bridge to bus 0000:01
[ 0.675644] pci_bus 0000:01: root bus resource [mem 0x12000000-0x13ffffff]
[ 0.682954] pci_bus 0000:01: root bus resource [io 0x0001]
[ 0.688884] pci_bus 0000:01: root bus resource [??? 0x00000000 flags 0x0]
[ 0.696100] pci_bus 0000:01: No busn resource found for root bus, will use [bus 01-ff]
[ 0.704554] pci 0000:01:00.0: [168c:003c] type 00 class 0x028000
[ 0.704592] pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x001fffff 64bit]
[ 0.704641] pci 0000:01:00.0: reg 0x30: [mem 0x00000000-0x0000ffff pref]
[ 0.704708] pci 0000:01:00.0: supports D1 D2
[ 0.704875] pci_bus 0000:01: busn_res: [bus 01-ff] end is updated to 01
[ 0.704897] pci 0000:01:00.0: BAR 0: assigned [mem 0x12000000-0x121fffff 64bit]
[ 0.712692] pci 0000:01:00.0: BAR 6: assigned [mem 0x12200000-0x1220ffff pref]
[ 0.720398] pci 0000:01:00.0: using irq 41 for pin 1
[ 0.728374] clocksource: Switched to clocksource MIPS
[ 0.734636] NET: Registered protocol family 2
[ 0.740043] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.747464] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.754270] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.761112] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 0.767336] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 0.774239] NET: Registered protocol family 1
[ 0.778939] PCI: CLS 0 bytes, default 32
[ 0.781161] Crashlog allocated RAM at address 0x3f00000
[ 0.787598] workingset: timestamp_bits=30 max_order=15 bucket_order=0
[ 0.800206] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.806406] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[ 0.824341] io scheduler noop registered
[ 0.828551] io scheduler deadline registered (default)
[ 0.834363] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[ 0.843333] console [ttyS0] disabled
[ 0.867202] serial8250.0: ttyS0 at MMIO 0x18020000 (irq = 11, base_baud = 2500000) is a 16550A
[ 0.876388] console [ttyS0] enabled
[ 0.883806] bootconsole [early0] disabled
[ 0.897153] m25p80 spi0.0: found w25q128, expected m25p80
[ 0.913286] m25p80 spi0.0: w25q128 (16384 Kbytes)
[ 0.918549] 5 tp-link partitions found on MTD device spi0.0
[ 0.924197] Creating 5 MTD partitions on "spi0.0":
[ 0.929085] 0x000000000000-0x000000020000 : "u-boot"
[ 0.935626] 0x000000020000-0x0000001703cc : "kernel"
[ 0.942308] 0x0000001703cc-0x000000ff0000 : "rootfs"
[ 0.948647] mtd: device 2 (rootfs) set to be root filesystem
[ 0.954426] 1 squashfs-split partitions found on MTD device rootfs
[ 0.960724] 0x000000400000-0x000000ff0000 : "rootfs_data"
[ 0.967914] 0x000000ff0000-0x000001000000 : "art"
[ 0.974367] 0x000000020000-0x000000ff0000 : "firmware"
[ 0.982047] libphy: Fixed MDIO Bus: probed
[ 0.999208] switch0: Atheros AR8327 rev. 4 switch registered on ag71xx-mdio.0
[ 1.697329] libphy: ag71xx_mdio: probed
[ 2.329879] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd034, driver=Atheros AR8216/AR8236/AR8316]
[ 2.341232] eth0: Atheros AG71xx at 0xb9000000, irq 4, mode:RGMII
[ 2.608369] random: fast init done
[ 2.969999] eth1: Atheros AG71xx at 0xba000000, irq 5, mode:SGMII
[ 2.977939] NET: Registered protocol family 10
[ 2.985877] NET: Registered protocol family 17
[ 2.990475] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 3.003720] 8021q: 802.1Q VLAN Support v1.8
[ 3.009357] hctosys: unable to open rtc device (rtc0)
[ 3.020422] VFS: Mounted root (squashfs filesystem) readonly on device 31:2.
[ 3.028581] Freeing unused kernel memory: 268K
[ 3.033089] This architecture does not have kernel memory protection.
[ 3.726442] init: Console is alive
[ 3.730113] init: - watchdog -
[ 4.778452] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[ 4.836591] usbcore: registered new interface driver usbfs
[ 4.842284] usbcore: registered new interface driver hub
[ 4.847738] usbcore: registered new device driver usb
[ 4.857182] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[ 4.865080] ehci-platform: EHCI generic platform driver
[ 4.870494] ehci-platform ehci-platform.0: EHCI Host Controller
[ 4.876532] ehci-platform ehci-platform.0: new USB bus registered, assigned bus number 1
[ 4.886814] ehci-platform ehci-platform.0: TX-TX IDP fix enabled
[ 4.892951] ehci-platform ehci-platform.0: irq 48, io mem 0x1b000000
[ 4.928406] ehci-platform ehci-platform.0: USB 2.0 started, EHCI 1.00
[ 4.935653] hub 1-0:1.0: USB hub found
[ 4.939763] hub 1-0:1.0: 1 port detected
[ 4.944043] ehci-platform ehci-platform.1: EHCI Host Controller
[ 4.950117] ehci-platform ehci-platform.1: new USB bus registered, assigned bus number 2
[ 4.960409] ehci-platform ehci-platform.1: TX-TX IDP fix enabled
[ 4.966518] ehci-platform ehci-platform.1: irq 49, io mem 0x1b400000
[ 4.998395] ehci-platform ehci-platform.1: USB 2.0 started, EHCI 1.00
[ 5.005648] hub 2-0:1.0: USB hub found
[ 5.009749] hub 2-0:1.0: 1 port detected
[ 5.014374] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[ 5.032087] init: - preinit -
[ 6.161163] eth1: link up (1000Mbps/Full duplex)
[ 6.184722] random: procd: uninitialized urandom read (4 bytes read)
[ 9.415009] mount_root: jffs2 not ready yet, using temporary tmpfs overlay
[ 9.442346] urandom-seed: Seed file not found (/etc/urandom.seed)
[ 9.579237] eth1: link down
[ 9.591773] procd: - early -
[ 9.594775] procd: - watchdog -
[ 10.199801] procd: - watchdog -
[ 10.203207] procd: - ubus -
[ 10.328624] random: ubusd: uninitialized urandom read (4 bytes read)
[ 10.358222] random: ubusd: uninitialized urandom read (4 bytes read)
[ 10.365070] random: ubusd: uninitialized urandom read (4 bytes read)
[ 10.372312] procd: - init -
[ 10.699961] kmodloader: loading kernel modules from /etc/modules.d/*
[ 10.731509] ip6_tables: (C) 2000-2006 Netfilter Core Team
[ 10.746889] Loading modules backported from Linux version wt-2017-11-01-0-gfe248fc2c180
[ 10.755049] Backport generated by backports.git v4.14-rc2-1-31-g86cf0e5d
[ 10.764306] ip_tables: (C) 2000-2006 Netfilter Core Team
[ 10.776548] nf_conntrack version 0.5.0 (2048 buckets, 8192 max)
[ 10.824860] xt_time: kernel timezone is -0000
[ 10.993248] PPP generic driver version 2.4.2
[ 10.999588] NET: Registered protocol family 24
[ 11.022325] PCI: Enabling device 0000:01:00.0 (0000 -> 0002)
[ 11.028241] ath10k_pci 0000:01:00.0: pci irq legacy oper_irq_mode 1 irq_mode 0 reset_mode 0
[ 11.301673] ath10k_pci 0000:01:00.0: Direct firmware load for ath10k/pre-cal-pci-0000:01:00.0.bin failed with error -2
[ 11.312558] ath10k_pci 0000:01:00.0: Falling back to user helper
[ 11.488972] firmware ath10k!pre-cal-pci-0000:01:00.0.bin: firmware_loading_store: map pages failed
[ 11.498272] ath10k_pci 0000:01:00.0: Direct firmware load for ath10k/cal-pci-0000:01:00.0.bin failed with error -2
[ 11.508805] ath10k_pci 0000:01:00.0: Falling back to user helper
[ 11.704569] ath10k_pci 0000:01:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/firmware-6.bin failed with error -2
[ 11.715456] ath10k_pci 0000:01:00.0: Falling back to user helper
[ 11.808547] firmware ath10k!QCA988X!hw2.0!firmware-6.bin: firmware_loading_store: map pages failed
[ 11.821954] ath10k_pci 0000:01:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043202ff sub 0000:0000
[ 11.831337] ath10k_pci 0000:01:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 1
[ 11.844384] ath10k_pci 0000:01:00.0: firmware ver 10.2.4-1.0-00037 api 5 features no-p2p,raw-mode,mfp,allows-mesh-bcast crc32 a4a52adb
[ 11.938805] ath10k_pci 0000:01:00.0: Direct firmware load for ath10k/QCA988X/hw2.0/board-2.bin failed with error -2
[ 11.949424] ath10k_pci 0000:01:00.0: Falling back to user helper
[ 12.023257] firmware ath10k!QCA988X!hw2.0!board-2.bin: firmware_loading_store: map pages failed
[ 12.053838] ath10k_pci 0000:01:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[ 13.144513] ath10k_pci 0000:01:00.0: firmware crashed! (guid 41f831c6-9670-4f1b-9ca7-106c960d2ff6)
[ 13.153639] ath10k_pci 0000:01:00.0: qca988x hw2.0 target 0x4100016c chip_id 0x043202ff sub 0000:0000
[ 13.162995] ath10k_pci 0000:01:00.0: kconfig debug 0 debugfs 1 tracing 0 dfs 1 testmode 1
[ 13.176046] ath10k_pci 0000:01:00.0: firmware ver 10.2.4-1.0-00037 api 5 features no-p2p,raw-mode,mfp,allows-mesh-bcast crc32 a4a52adb
[ 13.188360] ath10k_pci 0000:01:00.0: board_file api 1 bmi_id N/A crc32 bebc7c08
[ 13.195780] ath10k_pci 0000:01:00.0: htt-ver 0.0 wmi-op 5 htt-op 2 cal file max-sta 128 raw 0 hwcrypto 1
[ 13.207420] ath10k_pci 0000:01:00.0: firmware register dump:
[ 13.213178] ath10k_pci 0000:01:00.0: [00]: 0x4100016C 0x00000000 0x00988490 0x00000000
[ 13.221216] ath10k_pci 0000:01:00.0: [04]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.229258] ath10k_pci 0000:01:00.0: [08]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.237285] ath10k_pci 0000:01:00.0: [12]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.245319] ath10k_pci 0000:01:00.0: [16]: 0x00000000 0x00000000 0x00000000 0x00988490
[ 13.253353] ath10k_pci 0000:01:00.0: [20]: 0x00000000 0x00401930 0x00000000 0x00000000
[ 13.261387] ath10k_pci 0000:01:00.0: [24]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.269421] ath10k_pci 0000:01:00.0: [28]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.277449] ath10k_pci 0000:01:00.0: [32]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.285491] ath10k_pci 0000:01:00.0: [36]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.293525] ath10k_pci 0000:01:00.0: [40]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.301559] ath10k_pci 0000:01:00.0: [44]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.309593] ath10k_pci 0000:01:00.0: [48]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.317621] ath10k_pci 0000:01:00.0: [52]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.325653] ath10k_pci 0000:01:00.0: [56]: 0x00000000 0x00000000 0x00000000 0x00000000
[ 13.333685] ath10k_pci 0000:01:00.0: Copy Engine register dump:
[ 13.339704] ath10k_pci 0000:01:00.0: [00]: 0x00057400 5 5 6 5
[ 13.346243] ath10k_pci 0000:01:00.0: [01]: 0x00057800 5 5 4 5
[ 13.352790] ath10k_pci 0000:01:00.0: [02]: 0x00057c00 0 0 63 0
[ 13.359341] ath10k_pci 0000:01:00.0: [03]: 0x00058000 0 0 0 0
[ 13.365876] ath10k_pci 0000:01:00.0: [04]: 0x00058400 0 0 0 0
[ 13.372423] ath10k_pci 0000:01:00.0: [05]: 0x00058800 0 0 0 0
[ 13.378967] ath10k_pci 0000:01:00.0: [06]: 0x00058c00 0 0 0 0
[ 13.385509] ath10k_pci 0000:01:00.0: [07]: 0x00059000 0 0 0 0
[ 14.218385] ath10k_pci 0000:01:00.0: failed to receive control response completion, polling..
[ 15.258383] ath10k_pci 0000:01:00.0: ctl_resp never came in (-145)
[ 15.264655] ath10k_pci 0000:01:00.0: failed to connect to HTC: -145
[ 15.399608] ath10k_pci 0000:01:00.0: could not init core (-145)
[ 15.405746] ath10k_pci 0000:01:00.0: could not probe fw (-145)
[ 15.411729] ath10k_pci 0000:01:00.0: cannot restart a device that hasn't been started
[ 15.453140] ath: EEPROM regdomain: 0x0
[ 15.453147] ath: EEPROM indicates default country code should be used
[ 15.453150] ath: doing EEPROM country->regdmn map search
[ 15.453162] ath: country maps to regdmn code: 0x3a
[ 15.453167] ath: Country alpha2 being used: US
[ 15.453170] ath: Regpair used: 0x3a
[ 15.469157] ieee80211 phy1: Selected rate control algorithm 'minstrel_ht'
[ 15.472280] ieee80211 phy1: Atheros AR9550 Rev:0 mem=0xb8100000, irq=47
[ 15.557047] kmodloader: done loading kernel modules from /etc/modules.d/*
[ 16.817644] urandom_read: 5 callbacks suppressed
[ 16.817650] random: jshn: uninitialized urandom read (4 bytes read)
[ 29.369526] jffs2_scan_eraseblock(): End of filesystem marker found at 0x0
[ 29.376527] jffs2_build_filesystem(): unlocking the mtd device...
[ 29.416365] done.
[ 29.418332] jffs2_build_filesystem(): erasing all blocks after the end marker...
[ 29.812770] eth1: link up (1000Mbps/Full duplex)
[ 29.817531] IPv6: ADDRCONF(NETDEV_UP): eth1: link is not ready
[ 29.870589] br-lan: port 1(eth1.1) entered blocking state
[ 29.876078] br-lan: port 1(eth1.1) entered disabled state
[ 29.881931] device eth1.1 entered promiscuous mode
[ 29.886807] device eth1 entered promiscuous mode
[ 29.988495] br-lan: port 1(eth1.1) entered blocking state
[ 29.993980] br-lan: port 1(eth1.1) entered forwarding state
[ 29.999797] IPv6: ADDRCONF(NETDEV_UP): br-lan: link is not ready
[ 30.087717] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[ 30.133954] IPv6: ADDRCONF(NETDEV_UP): eth0.2: link is not ready
[ 30.858414] IPv6: ADDRCONF(NETDEV_CHANGE): eth1: link becomes ready
[ 30.865153] IPv6: ADDRCONF(NETDEV_CHANGE): br-lan: link becomes ready
[ 31.099816] eth0: link up (1000Mbps/Full duplex)
[ 31.181782] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[ 31.216598] IPv6: ADDRCONF(NETDEV_CHANGE): eth0.2: link becomes ready
[ 74.472658] done.
[ 74.474643] jffs2: notice: (1292) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[ 129.638409] random: crng init done
Since you also own the Archer C7 v2, maybe you know this: Is it safe to go back to the TP-Link vendor firmware and can I flash OpenWrt again after doing so? I think I read once that newer TP-Link firmwares check the signatures of firmware images and may not allow you to install OpenWrt. Obviously, I don't like to lock myself out and be stuck with the vendor firmware if I flash that just for testing...
Next on my list is to open up the device to see if the miniPCIe module has somehow loosened...