Apple ATA DMA problems with ATAPI

[Justin Hibbits]

Well, it seems I was bitten by the ATA DMA problems from a few months back.
When trying to mount a DVD, I got the folling messages:

Mar 22 13:34:29 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:34:29 narn kernel: acd0: TIMEOUT - READ_BIG retrying (1 retry left)
Mar 22 13:35:19 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:35:19 narn kernel: acd0: TIMEOUT - READ_BIG retrying (0 retries left)
Mar 22 13:36:09 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:36:09 narn kernel: acd0: FAILURE - READ_BIG timed out
Mar 22 13:36:59 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:36:59 narn kernel: acd0: TIMEOUT - READ_BIG retrying (1 retry left)
Mar 22 13:37:49 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:37:49 narn kernel: acd0: TIMEOUT - READ_BIG retrying (0 retries left)
Mar 22 13:38:39 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:38:39 narn kernel: acd0: FAILURE - READ_BIG timed out
Mar 22 13:39:30 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:39:30 narn kernel: acd0: TIMEOUT - READ_BIG retrying (1 retry left)
Mar 22 13:39:44 narn kernel: acd0: WARNING - TEST_UNIT_READY taskqueue timeout - completing request directly
Mar 22 13:39:44 narn kernel: acd0: FAILURE - TEST_UNIT_READY timed out
Mar 22 13:39:55 narn kernel: acd0: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly
Mar 22 13:41:44 narn kernel: acd0: WARNING - PREVENT_ALLOW taskqueue timeout - completing request directly
Mar 22 13:42:04 narn kernel: acd0: WARNING - TEST_UNIT_READY taskqueue timeout - completing request directly

Using -CURRENT powerpc trunk from a couple weeks ago:  r189096:189865M
(multi-version because of network problems, shouldn't affect ATA).

Hardware is MDD single 1.25GHz (2003), chipset info from dmesg:

ata1: <Apple MacIO ATA Controller> mem 0x20000-0x20fff,0x8b00-0x8bff irq 20,12 on macio0
acd0: DVDR <HL-DT-ST RW/DVD GCC-4480B/1.03> at ata1-master WDMA2

- Justin