Jeff,

Patch 3/3: Fix pdc2027x ATAPI DMA lost irq problem

Description:
   Sometimes pdc2027x will lost irq after ATAPI DMA data transfer.
   With the previous rule (cmd->request_bufflen % 256), the ATAPI DMA irq lost
problem still occurs during the test.

   Root cause for the irq lost is unknown. I've tried your ATAPI DMA alignment
patch, but the problem still occurs, even the buffer is aligned. I guess it is pdc2027x hardware problem.

   The following workarounds are adapted from the Promise pdc618 GPL driver.
They seems know about the problem and has the workaround.

Changes:
   - Only turn on ATAPI DMA for READ, WRITE, READ_CD and READ_DVD_STRUCTURE commands.
   - For WRITE_10, if LBA -45150 (FFFF4FA2h) to  -1 (FFFFFFFFh) then use PIO mode.

For your review, thanks.

Albert

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>