[PATCH v2 3/3] ucc_geth: Fix hangs after switching from full to half duplex

[Scott Wood]

Anton Vorontsov wrote:
> MPC8360 QE UCC ethernet controllers hang when changing link duplex
> under a load (a bit of NFS activity is enough).
> 
>   PHY: mdio at e0102120:00 - Link is Up - 1000/Full
>   sh-3.00# ethtool -s eth0 speed 100 duplex half autoneg off
>   PHY: mdio at e0102120:00 - Link is Down
>   PHY: mdio at e0102120:00 - Link is Up - 100/Half
>   NETDEV WATCHDOG: eth0 (ucc_geth): transmit queue 0 timed out
>   ------------[ cut here ]------------
>   Badness at c01fcbd0 [verbose debug info unavailable]
>   NIP: c01fcbd0 LR: c01fcbd0 CTR: c0194e44
>   ...
> 
> The cure is to disable the controller before changing speed/duplex
> and enable it afterwards.
> 
> Since ugeth_graceful_stop_{tx,rx} now may be called from an atomic
> context, switch the two functions from msleep() to mdelay().

Ouch.  Can we put this in a workqueue or something?

-Scott