wm MDIC write error

[Mark Davies <mark%ecs.vuw.ac.nz@localhost>]

Hi,
   I have a 6.0_STABLE/i386 (almost 6.1) box with an onboard PCH2 LAN 
82579LM (wm0) and an Intel i82574L on a PCIe card (wm1)

When I first boot the machine both network ports work fine but after a 
while wm1 stops and I get lots of the following logged:

          [...]
wm1: MDIC write error: phy 1 reg 0
wm1: MDIC write error: phy 1 reg 4
wm1: MDIC write error: phy 1 reg 9
wm1: MDIC write error: phy 1 reg 0
          [...]

Need to powercycle the machine to get it working again.

Anybody know whats broken here?  Have a fix? (in current?)

cheers
mark