libata: Fix a large collection of DMA mode mismatches

Dave Müller sent a diff for the pata_oldpiix that highlighted a problem
where a lot of the ATA drivers assume dma_mode == 0 means "no DMA" while
the core code uses 0xFF.

This turns out to have other consequences such as code doing >= XFER_UDMA_0
also catching 0xFF as UDMAlots. Fortunately it doesn't generally affect
set_dma_mode, although some drivers call back into their own set mode code
from other points.

Having been through the drivers I've added helpers for using_udma/using_mwdma
dma_enabled so that people don't open code ranges that may change (eg if UDMA8
appears somewhere)

Thanks to David for the initial bits
[and added fix for pata_oldpiix from and signed-off-by Dave Mueller
 <dave.mueller@gmx.ch>  -jg]

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/ata/pata_sc1200.c b/drivers/ata/pata_sc1200.c
index cbab397..0278fd2 100644
--- a/drivers/ata/pata_sc1200.c
+++ b/drivers/ata/pata_sc1200.c
@@ -167,10 +167,10 @@ static unsigned int sc1200_qc_issue(struct ata_queued_cmd *qc)
 	struct ata_device *prev = ap->private_data;
 
 	/* See if the DMA settings could be wrong */
-	if (adev->dma_mode != 0 && adev != prev && prev != NULL) {
+	if (ata_dma_enabled(adev) && adev != prev && prev != NULL) {
 		/* Maybe, but do the channels match MWDMA/UDMA ? */
-		if ((adev->dma_mode >= XFER_UDMA_0 && prev->dma_mode < XFER_UDMA_0) ||
-		    (adev->dma_mode < XFER_UDMA_0 && prev->dma_mode >= XFER_UDMA_0))
+		if ((ata_using_udma(adev) && !ata_using_udma(prev)) ||
+		    (ata_using_udma(prev) && !ata_using_udma(adev)))
 		    	/* Switch the mode bits */
 		    	sc1200_set_dmamode(ap, adev);
 	}