hailfinger:

Device:
VGV7510KW22 / o2 Box 6431

Software versions:
OpenWrt SNAPSHOT r5944-ad4232e
Linux version 4.9.77 (buildbot@slashdirt-03) (gcc version 5.5.0 (OpenWrt GCC 5.5.0 r5944-ad4232e) ) #0 SMP Thu Jan 25 10:00:48 2018
SoC: xRX200 rev 1.2
The same problem also happens with LEDE 17.04

Steps to reproduce:
Sometimes, the box spuriously reboots. Time between spurious reboots varies between 12 hours and 2 weeks. After such a spurious reboot, some ethernet ports no longer work. Remote syslog via UDP does not log any error messages before a spurious reboot. Sometimes, ethernet ports stop working without a previous spurious reboot, but that's pretty rare (once a month).

Workaround:
Perform a manual reboot after the spurious reboot. This fixes the ethernet link malfunctioning. It does not help with the spurious reboots, though.

Possibly relevant diff between a clean reboot dmesg and a spurious reboot dmesg:
--- dmesg-normal-reboot.txt.notimestamps 2018-02-05 11:42:10.656203272 +0100
+++ dmesg-spurious-reboot.txt.notimestamps 2018-02-05 11:40:47.264201277 +0100
@@ -30,8 +30,8 @@
PID hash table entries: 256 (order: -2, 1024 bytes)
Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
-Writing ErrCtl register=00014098
-Readback ErrCtl register=00014098
+Writing ErrCtl register=00014090
+Readback ErrCtl register=00014090
Memory: 55392K/63488K available (4334K kernel code, 178K rwdata, 1324K rodata, 1252K init, 244K bss, 8096K reserved, 0K cma-reserved)
SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
Hierarchical RCU implementation.
@@ -123,12 +123,14 @@
libphy: Fixed MDIO Bus: probed
libphy: lantiq,xrx200-mdio: probed
ICPlus IP101A/G 0:01: attached PHY driver [ICPlus IP101A/G] (mii_bus:phy_addr=0:01, irq=-1)
-Intel XWAY PHY22F (xRX integrated) 0:11: attached PHY driver [Intel XWAY PHY22F (xRX integrated)] (mii_bus:phy_addr=0:11, irq=-1)
-Intel XWAY PHY22F (xRX integrated) 0:12: attached PHY driver [Intel XWAY PHY22F (xRX integrated)] (mii_bus:phy_addr=0:12, irq=-1)
-random: fast init done
+lantiq,xrx200-net 1e108000.eth eth0 (uninitialized): no PHY found
+xrx200-mdio: probing phy of port 2 failed
+lantiq,xrx200-net 1e108000.eth eth0 (uninitialized): no PHY found
+xrx200-mdio: probing phy of port 3 failed
Intel XWAY PHY22F (xRX integrated) 0:13: attached PHY driver [Intel XWAY PHY22F (xRX integrated)] (mii_bus:phy_addr=0:13, irq=-1)
+random: fast init done
Intel XWAY PHY22F (xRX integrated) 0:14: attached PHY driver [Intel XWAY PHY22F (xRX integrated)] (mii_bus:phy_addr=0:14, irq=-1)
-ltq-cputemp cputemp@0: Current CPU die temperature: 54.0 °C
+ltq-cputemp cputemp@0: Current CPU die temperature: 52.5 °C
wdt 1f8803f0.watchdog: Init done
NET: Registered protocol family 10
NET: Registered protocol family 17
@@ -139,7 +141,6 @@
This architecture does not have kernel memory protection.
init: Console is alive
init: - watchdog -
-lantiq,xrx200-net 1e108000.eth eth0: port 2 got link
kmodloader: loading kernel modules from /etc/modules-boot.d/*
dwc2 1e101000.ifxhcd: requested GPIO 509
dwc2 1e101000.ifxhcd: DWC OTG Controller
@@ -151,12 +152,12 @@
hub 1-0:1.0: 1 port detected
kmodloader: done loading kernel modules from /etc/modules-boot.d/*
init: - preinit -
-jffs2: notice: (440) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
+IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
+jffs2: notice: (436) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
mount_root: switching to jffs2 overlay
urandom-seed: Seeding with /etc/urandom.seed
procd: - early -
procd: - watchdog -
-lantiq,xrx200-net 1e108000.eth eth0: port 2 lost link
procd: - watchdog -
procd: - ubus -
procd: - init -
@@ -207,19 +208,19 @@
device eth0 entered promiscuous mode
IPv6: ADDRCONF(NETDEV_UP): br-lan: link is not ready
IPv6: ADDRCONF(NETDEV_UP): eth0.13: link is not ready
-lantiq,xrx200-net 1e108000.eth eth0: port 2 got link
-IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
-br-lan: port 1(eth0.1) entered blocking state
-br-lan: port 1(eth0.1) entered forwarding state
-IPv6: ADDRCONF(NETDEV_CHANGE): eth0.13: link becomes ready
-IPv6: ADDRCONF(NETDEV_CHANGE): br-lan: link becomes ready
+random: crng init done
PTM 1.0.27 PTM (E1) firmware version 0.30
ifxmips_ptm: PTM init succeed
IPv6: ADDRCONF(NETDEV_UP): dsl0: link is not ready
IPv6: ADDRCONF(NETDEV_UP): dsl0.7: link is not ready
-random: crng init done
enter showtime
IPv6: ADDRCONF(NETDEV_CHANGE): dsl0: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): dsl0.7: link becomes ready
enter showtime
pppoe-wan: renamed from ppp0