[FS#631] AR8327 switch link state change check not working on TL-WR1043ND v3 (QCA9558)

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Vittorio Gambaletta (VittGam) (VittGam) 

Attached to Project - LEDE Project
Summary - AR8327 switch link state change check not working on TL-WR1043ND v3 (QCA9558)
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Hello,

On my TP-LINK TL-WR1043ND v3 (ar71xx QCA9558) with today's LEDE snapshot, the AR8327 switch isn't sending port change interrupt events to the CPU.

The `ar8xxx_check_link_states` function in `target/linux/generic/files/drivers/net/phy/ar8216.c` is not being called at all, since not only the messages about port link status change aren't printed to the dmesg, but the ARL table isn't getting cleaned either. I don't understand why this is happening...

This regression is not present in other routers with the same AR8327 switch chip (but rev. 2 instead of rev. 4), such as TP-LINK TL-WDR4300 v1 (ar71xx) and TP-LINK TL-WDR4900 v1 (mpc85xx).

(Latest LEDE stable release also does exibit the regression.)

Below you can see a session with LEDE; and a session with OpenWrt CC 15.05.1 release, which does not exibit the problem.

(The CC image is for the TL-WR1043ND v2, since v3 images weren't built yet at that time; v2 and v3 are the same hardware, as it can be seen from the FCC docs, where TP-LINK requested an ID change from v2 to v3.)

Please let me know if there's anything I can try to help debug this problem!

```
BusyBox v1.26.2 () built-in shell (ash)

     _________
    /        /\      _    ___ ___  ___
   /  LE    /  \    | |  | __|   \| __|
  /    DE  /    \   | |__| _|| |) | _|
 /________/  LE  \  |____|___|___/|___|                      lede-project.org
 \        \   DE /
  \    LE  \    /  -----------------------------------------------------------
   \  DE    \  /    Reboot (SNAPSHOT, r1-2f09a1e)
    \________\/    -----------------------------------------------------------

=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root at LEDE:~# dmesg | grep 8327
[    0.815273] switch0: Atheros AR8327 rev. 4 switch registered on ag71xx-mdio.0
root at LEDE:~# dmesg | grep 8216
[    2.046658] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd034, driver=Atheros AR8216/AR8236/AR8316]
root at LEDE:~# swconfig dev switch0 get arl_table
address resolution table
Port 0: MAC 
Port 4: MAC 
Port 4: MAC 
Port 6: MAC 

root at LEDE:~# dmesg | grep 8216
[    2.046658] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd034, driver=Atheros AR8216/AR8236/AR8316]
root at LEDE:~# swconfig dev switch0 get arl_table
address resolution table
Port 0: MAC 
Port 3: MAC 
Port 4: MAC 
Port 6: MAC 

root at LEDE:~# 
```

```
BusyBox v1.23.2 (2016-01-02 18:01:44 CET) built-in shell (ash)

  _______                     ________        __
 |       |.-----.-----.-----.|  |  |  |.----.|  |_
 |   -   ||  _  |  -__|     ||  |  |  ||   _||   _|
 |_______||   __|_____|__|__||________||__|  |____|
          |__| W I R E L E S S   F R E E D O M
 -----------------------------------------------------
 CHAOS CALMER (15.05.1, r48532)
 -----------------------------------------------------
  * 1 1/2 oz Gin            Shake with a glassful
  * 1/4 oz Triple Sec       of broken ice and pour
  * 3/4 oz Lime Juice       unstrained into a goblet.
  * 1 1/2 oz Orange Juice
  * 1 tsp. Grenadine Syrup
 -----------------------------------------------------
root at OpenWrt:/# dmesg | grep 8327
[    0.750000] switch0: Atheros AR8327 rev. 4 switch registered on ag71xx-mdio.0
root at OpenWrt:/# dmesg | grep 8216
[    1.440000] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd034, driver=Atheros AR8216/AR8236/AR8316]
[   24.680000] Atheros AR8216/AR8236/AR8316 ag71xx-mdio.0:00: Port 4 is up

root at OpenWrt:/# swconfig dev switch0 get arl_table
address resolution table
Port 0: MAC 
Port 4: MAC 
Port 4: MAC 
Port 6: MAC 

root at OpenWrt:/# dmesg | grep 8216
[    1.440000] ag71xx ag71xx.0: connected to PHY at ag71xx-mdio.0:00 [uid=004dd034, driver=Atheros AR8216/AR8236/AR8316]
[   24.680000] Atheros AR8216/AR8236/AR8316 ag71xx-mdio.0:00: Port 4 is up
[ 1306.510000] Atheros AR8216/AR8236/AR8316 ag71xx-mdio.0:00: Port 4 is down
[ 1310.530000] Atheros AR8216/AR8236/AR8316 ag71xx-mdio.0:00: Port 3 is up
root at OpenWrt:/# swconfig dev switch0 get arl_table
address resolution table
Port 0: MAC 
Port 3: MAC 
Port 6: MAC 

root at OpenWrt:/# uname -a
Linux OpenWrt 3.18.23 #1 Sun Jan 31 18:39:35 CET 2016 mips GNU/Linux
root at OpenWrt:/# 
```

Cheers,
Vittorio

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=631