Fix flags a bad PHY register read by looking at the second bit time of the turnaround. If this bit floats high, it is bad; if the PHY drives it low, it is good. If no PHY is at this PHY address, the read will fail as desired.
This problem is fixed in the latest 6.2 EDK Service Pack, available at:
The first service pack containing the fix is EDK 6.2 Service Pack 2.