the
  port while TF or HBUS_DATA don't.

* Only CONNECT (reflects SErr.X) interrupt is taken into account not
  PHYRDY (SErr.N), as CONNECT is better cue for starting EH.

* AHCI may be invoked without any active command.  e.g. CONNECT irq
  occuring while no qc in progress still triggers EH and will reset
  the port and revalidate attached device.

Signed-off-by: Tejun Heo <htejun@gmail.com>
M„<‰œ-x