On Rev. B silicon, we disabled the enhanced busfree detection logic to

On Rev. B silicon, we disabled the enhanced busfree detection logic to
close holes in detecting busfrees that occur after a packetized target
transitions to a non-packetized phase.  The most common case where this
occurs is when a target is externally reset so the controller believes
a packetzied negotiation agreement is still in effect.  Unfortunately,
disabling this feature seems to cause problems for the 7901B.  Re-enable
ehanced busfree detection for this part.

Obtained-from: FreeBSD