Hi Mike,

[...]
> An EMAC soft-reset clobbering the MDIO controller state is a
> possibility.  I will poll TI designers to see if this could be the case.

To test this theory out, I hacked up a crude
beat-it-to-death-and-see-if-it-breaks kinda patch (attached).  This
tests 10000 mdio read cycles while constantly doing an emac soft-reset.

I ran this on a dm365 evm, and the test didn't raise a single failed read:
> davinci_mdio davinci_mdio.0: davinci mdio revision 1.4
> davinci_mdio davinci_mdio.0: detected phy mask fffffffc
> 10000 test loops completed, 10000 reads ok

The failure in question seems to be limited to the da8xx family (tested
da830 evm), where:
> davinci_mdio davinci_mdio.0: davinci mdio revision 1.5
> davinci_mdio davinci_mdio.0: detected phy mask fffffff1
> idle triggered!!

The MDIO module upgrade (rev 1.4 -> 1.5) could have something to do with
this behavior.  Even so, I can't explain why this issue wasn't seen on
da8xx prior to this series.  The original code should (at least in
theory) have sporadically locked up on emac open.

Regards
Cyril.