OK - finally found time to get a solder sucker - cleared the holes, bit of a mess on RX hole. Anyway fixed on a 3 pin header.
Now on the UART I can see the boot messages - but I havn't been able to interrupt it. What I've been doing in gnu screen is hammering t, but it has no effect. The output I'm getting is:
ROM VER: 1.1.4
CFG 05
DDR autotuning Rev 0.3ff
DDR size from 0xa0000000 - 0xa3ffffff
DDR check ok... start booting...
U-Boot 2010.06-LANTIQ-v-2.0.40-svn4806 (Jun 12 2014 - 10:34:17)
CLOCK CPU 500M RAM 250M
DRAM: 64 MiB
Using default environment
In: serial
Out: serial
Err: serial
Net: Internal phy(GE) firmware version: 0x8434
vr9 Switch8192 KiB W25Q64 at 0:3 is now current device
Type "run flash_nfs" to mount root filesystem over NFS
Hit any key to stop autoboot: 1 0
8192 KiB W25Q64 at 0:3 is now current device
8192 KiB W25Q64 at 0:3 is now current device
Uncompressing ...
Starting kernel ...
[ 0.000000] Linux version 4.9.111 (buildbot@builds-03.infra.lede-project.org) (gcc version 7.3.0 (OpenWrt GCC 7.3.0 r7102-3f3a2c9) ) #0 SMP Sat Jul 14 13:48:14 2018
[ 0.000000] SoC: xRX200 rev 1.2
[ 0.000000] bootconsole [early0] enabled
[ 0.000000] CPU0 revision is: 00019556 (MIPS 34Kc)
[ 0.000000] MIPS: machine is TP-LINK TD-W8970
[ 0.000000] Determined physical RAM map:
[ 0.000000] memory: 04000000 @ 00000000 (usable)
[ 0.000000] Initrd not found or empty - disabling initrd
[ 0.000000] Detected 1 available secondary CPU(s)
[ 0.000000] Primary instruction cache 32kB, 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 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000003ffffff]
[ 0.000000] percpu: Embedded 12 pages/cpu @8108c000 s17488 r8192 d23472 u49152
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256
[ 0.000000] Kernel command line: console=ttyLTQ0,115200
[ 0.000000] PID hash table entries: 256 (order: -2, 1024 bytes)
[ 0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
[ 0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] Writing ErrCtl register=00025080
[ 0.000000] Readback ErrCtl register=00025080
[ 0.000000] Memory: 57884K/65536K available (4302K kernel code, 177K rwdata, 900K rodata, 1260K init, 244K bss, 7652K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
[ 0.000000] Hierarchical RCU implementation.
[ 0.000000] NR_IRQS:256
[ 0.000000] Setting up vectored interrupts
[ 0.000000] Setting up IPI vectored interrupts
[ 0.000000] CPU Clock: 500MHz
[ 0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041786 ns
[ 0.000011] sched_clock: 32 bits at 250MHz, resolution 4ns, wraps every 8589934590ns
[ 0.007886] Calibrating delay loop... 332.54 BogoMIPS (lpj=665088)
[ 0.042390] pid_max: default: 32768 minimum: 301
[ 0.047271] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.053810] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.065459] Primary instruction cache 32kB, VIPT, 4-way, linesize 32 bytes.
[ 0.065472] Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
[ 0.065681] CPU1 revision is: 00019556 (MIPS 34Kc)
[ 0.116548] Synchronize counters for CPU 1:
[ 0.116550] done.
[ 0.123043] Brought up 2 CPUs
[ 0.130663] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[ 0.140335] futex hash table entries: 512 (order: 2, 16384 bytes)
[ 0.146575] pinctrl core: initialized pinctrl subsystem
[ 0.153092] NET: Registered protocol family 16
[ 0.166327] pinctrl-xway 1e100b10.pinmux: Init done
[ 0.172320] dma-xway 1e104100.dma: Init done - hw rev: 7, ports: 7, channels: 28
[ 0.285526] dcdc-xrx200 1f106a00.dcdc: Core Voltage : 1016 mV
[ 0.291346] Can't analyze schedule() prologue at 8043081c
[ 0.429372] PCI host bridge /fpi@10000000/pcie@d900000 ranges:
[ 0.463252] usbcore: registered new interface driver usbfs
[ 0.468885] usbcore: registered new interface driver hub
[ 0.474289] usbcore: registered new device driver usb
[ 0.480005] PCI host bridge to bus 0000:00
[ 0.484038] pci_bus 0000:00: root bus resource [mem 0x1c000000-0x1cffffff]
[ 0.490940] pci_bus 0000:00: root bus resource [io 0x1d800000-0x1d8fffff]
[ 0.497887] pci_bus 0000:00: root bus resource [??? 0x00000000 flags 0x0]
[ 0.504750] pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
[ 0.512819] ifx_pcie_rc_class_early_fixup: fixed pcie host bridge to pci-pci bridge
[ 0.532425] pci 0000:00:00.0: BAR 8: assigned [mem 0x1c000000-0x1c0fffff]
[ 0.539130] pci 0000:00:00.0: BAR 9: assigned [mem 0x1c100000-0x1c1fffff pref]
[ 0.546437] pci 0000:01:00.0: BAR 0: assigned [mem 0x1c000000-0x1c01ffff 64bit]
[ 0.553751] random: fast init done
[ 0.557239] pci 0000:01:00.0: BAR 6: assigned [mem 0x1c100000-0x1c10ffff pref]
[ 0.564558] pci 0000:00:00.0: PCI bridge to [bus 01]
[ 0.569580] pci 0000:00:00.0: bridge window [mem 0x1c000000-0x1c0fffff]
[ 0.576455] pci 0000:00:00.0: bridge window [mem 0x1c100000-0x1c1fffff pref]
[ 0.583749] ifx_pcie_bios_map_irq port 0 dev 0000:00:00.0 slot 0 pin 1
[ 0.590409] ifx_pcie_bios_map_irq dev 0000:00:00.0 irq 144 assigned
[ 0.596750] ifx_pcie_bios_map_irq port 0 dev 0000:01:00.0 slot 0 pin 1
[ 0.603415] ifx_pcie_bios_map_irq dev 0000:01:00.0 irq 144 assigned
[ 0.612065] clocksource: Switched to clocksource MIPS
[ 0.619585] NET: Registered protocol family 2
[ 0.625223] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.632129] TCP bind hash table entries: 1024 (order: 1, 8192 bytes)
[ 0.638553] TCP: Hash tables configured (established 1024 bind 1024)
[ 0.645058] UDP hash table entries: 256 (order: 1, 8192 bytes)
[ 0.650915] UDP-Lite hash table entries: 256 (order: 1, 8192 bytes)
[ 0.657514] NET: Registered protocol family 1
[ 0.662682] gptu: totally 6 16-bit timers/counters
[ 0.667566] gptu: misc_register on minor 63
[ 0.671777] gptu: succeeded to request irq 126
[ 0.676218] gptu: succeeded to request irq 127
[ 0.680703] gptu: succeeded to request irq 128
[ 0.685247] gptu: succeeded to request irq 129
[ 0.689734] gptu: succeeded to request irq 130
[ 0.694266] gptu: succeeded to request irq 131
[ 0.699147] phy-xrx200 gphy-xrx200: requesting lantiq/xrx200_phy11g_a22.bin
[ 0.706735] phy-xrx200 gphy-xrx200: booting GPHY0 firmware at 3A60000
[ 0.713092] phy-xrx200 gphy-xrx200: booting GPHY1 firmware at 3A60000
[ 0.821023] No VPEs reserved for AP/SP, not initialize VPE loader
[ 0.821023] Pass maxvpes=<n> argument as kernel argument
[ 0.832391] No TCs reserved for AP/SP, not initializing RTLX.
[ 0.832391] Pass maxtcs=<n> argument as kernel argument
[ 0.845279] Crashlog allocated RAM at address 0x3f00000
[ 0.851063] workingset: timestamp_bits=30 max_order=14 bucket_order=0
[ 0.873968] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[ 0.879721] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[ 0.895055] io scheduler noop registered
[ 0.899005] io scheduler deadline registered (default)
[ 0.905352] 1e100c00.serial: ttyLTQ0 at MMIO 0x1e100c00 (irq = 112, base_baud = 0) is a lantiq,asc
[ 0.914279] console [ttyLTQ0] enabled
[ 0.914279] console [ttyLTQ0] enabled
[ 0.921600] bootconsole [early0] disabled
[ 0.921600] bootconsole [early0] disabled
[ 0.933090] spi-lantiq-ssc 1e100800.spi: Lantiq SSC SPI controller (Rev 8, TXFS 8, RXFS 8, DMA 1)
[ 0.954310] m25p80 spi32766.4: s25fl064k (8192 Kbytes)
[ 0.958153] 4 fixed-partitions partitions found on MTD device spi32766.4
[ 0.964733] Creating 4 MTD partitions on "spi32766.4":
[ 0.969895] 0x000000000000-0x000000020000 : "u-boot"
[ 0.977214] 0x000000020000-0x0000007c0000 : "firmware"
[ 1.291075] random: crng init done
[ 2.062545] 2 tplink-fw partitions found on MTD device firmware
[ 2.067066] 0x000000020000-0x0000001c8963 : "kernel"
[ 2.074254] 0x0000001c8964-0x0000007c0000 : "rootfs"
[ 2.079975] mtd: device 3 (rootfs) set to be root filesystem
[ 2.084539] 1 squashfs-split partitions found on MTD device rootfs
[ 2.090549] 0x0000004f0000-0x0000007c0000 : "rootfs_data"
[ 2.098284] 0x0000007c0000-0x0000007d0000 : "config"
[ 2.104210] 0x0000007d0000-0x000000800000 : "boardconfig"
[ 2.113790] libphy: Fixed MDIO Bus: probed
[ 2.221449] libphy: lantiq,xrx200-mdio: probed
[ 2.300670] Intel XWAY PHY11G (PEF 7071/PEF 7072) v1.4 0:00: attached PHY driver [Intel XWAY PHY11G (PEF 7071/PEF 7072) v1.4] (mii_bus:phy_addr=0:00, irq=-1)
[ 2.384648] Intel XWAY PHY11G (PEF 7071/PEF 7072) v1.4 0:05: attached PHY driver [Intel XWAY PHY11G (PEF 7071/PEF 7072) v1.4] (mii_bus:phy_addr=0:05, irq=-1)
[ 2.468632] Intel XWAY PHY11G (xRX v1.2 integrated) 0:11: attached PHY driver [Intel XWAY PHY11G (xRX v1.2 integrated)] (mii_bus:phy_addr=0:11, irq=-1)
[ 2.552631] Intel XWAY PHY11G (xRX v1.2 integrated) 0:13: attached PHY driver [Intel XWAY PHY11G (xRX v1.2 integrated)] (mii_bus:phy_addr=0:13, irq=-1)
[ 2.668558] ltq-cputemp cputemp@0: Current CPU die temperature: 28.5 °C
[ 2.674240] wdt 1f8803f0.watchdog: Init done
[ 2.682902] NET: Registered protocol family 10
[ 2.688302] NET: Registered protocol family 17
[ 2.691402] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[ 2.704342] 8021q: 802.1Q VLAN Support v1.8
[ 2.716500] squashfs: SQUASHFS error: unable to read id index table
[ 2.721886] List of all partitions:
[ 2.724892] 1f00 128 mtdblock0 [ 2.728847] (driver?)
[ 2.731162] 1f01 7808 mtdblock1 [ 2.735179] (driver?)
[ 2.737568] 1f02 1698 mtdblock2 [ 2.741533] (driver?)
[ 2.743869] 1f03 6109 mtdblock3 [ 2.747908] (driver?)
[ 2.750253] 1f04 2880 mtdblock4 [ 2.754263] (driver?)
[ 2.756607] 1f05 64 mtdblock5 [ 2.760616] (driver?)
[ 2.762931] 1f06 192 mtdblock6 [ 2.766949] (driver?)
[ 2.769326] No filesystem could mount root, tried: [ 2.774002] squashfs
[ 2.776283]
[ 2.777724] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(31,3)
[ 2.789074] Rebooting in 1 seconds..
Any idea - try redoing the pins? Or ask an expert at work?