fxp hangs reseting to a stable state

This is the first time I've tried to run -current on this little board.
Up-to-date RELENG_4 kernels run fine. The probe message (port & memory) values
are the same.

On -current, the kernel gets up to the point in the fxp code where it is
supposedly doing a "reset to a stable state" and then it hangs. I have set
the kernel option BREAK_TO_DEBUGGER, but I can't get it to drop to DDB.

The fxp driver reports that it is using memory space register mapping, so I
guess that there is something different about the memory access in -current
compared to RELENG_4. The question is what?

I assume it's not a bios setup problem since RELENG_4 works fine. The kernels
are net booted (using etherboot) over the very device that -current hangs
on. Weird.

Any hints on what is going on?

-- 
John Birrell