[OpenWrt-Devel] Link detection - TP-Link Archer C7 v2

[Richard Clark]

I am having some problems with link detection on eth0 / WAN on the
TP-Link Archer C7 V2 router.

Removing the network cable from the WAN port does not change the link
status, so when it is added back in, various scripts never kick off to
get new DHCP, restart the firewall, etc.

This was on a self compiled 14.07 with various mods, but then reflashed
with the stock 14.07, same effect.  Pulled down and flashed with
15.05rc1 (OpenWrt Chaos Calmer 15.05-rc1 / LuCI Master
(git-15.126.50380-7a54785) and still same effect.

The MDIO code seems to notice the change (on 15.05, nothing on 14.07):

Tue May 26 19:45:04 2015 kern.info kernel: [  139.980000] Atheros
AR8216/AR8236/AR8316 ag71xx-mdio.0:00: Port 1 is down
Tue May 26 19:45:28 2015 kern.info kernel: [  163.990000] Atheros
AR8216/AR8236/AR8316 ag71xx-mdio.0:00: Port 1 is up

This does not translate down to the link state on the device - ethtool,
ifconfig, ip all continue to show the link as up.

Loading up the mii module and using mii-tool works though (BB + CC):
root at OpenWrt:~# mii-tool -w eth0
20:15:31 eth0: no link
20:15:37 eth0: negotiated 1000baseT-FD flow-control, link ok
20:15:50 eth0: no link
20:15:58 eth0: negotiated 1000baseT-FD flow-control, link ok

Also, swconfig tracks the status proper as well (BB + CC)
swconfig dev ag71xx-mdio.0 port 1 get link

Looking for 'link' issues on a 'TP-Link' router is a bit challenging and
have not been able to find existing bug reports other than:

https://dev.openwrt.org/ticket/17674 (set to closed / duplicate) but no
reference

Any thoughts, suggestions, or can someone give me some pointers on where
I can be digging in the openwrt kernel code for where that Ethernet
driver 'link status' get filled in ?

ps.. This all works on a different Atheros generic device (GL-Inet), so
it is TP-Link specific.

Thanks,

-- 
Richard C
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