The modified driver on initio site has enough clue on how to use IDMA.
Use IDMA for ATA_PROT_DMA.

* LBA48 now works as long as it uses DMA (LBA48 devices still aren't
  allowed as it can destroy data if PIO is used for any reason).

* No need to mask IRQs for read DMAs as IDMA_DONE is properly raised
  after transfer to memory is actually completed.  There will be some
  spurious interrupts but host_intr will handle it correctly and
  manipulating port IRQ mask interacts badly with the other port for
  some reason, so command type dependent port IRQ masking is not used
  anymore.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>