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>

drivers/ata/libata-core.c

@@ -3288,7 +3288,7 @@ int ata_do_set_mode(struct ata_link *link, struct ata_device **r_failed_dev)
 		dev->dma_mode = ata_xfer_mask2mode(dma_mask);
 
 		found = 1;
-		if (dev->dma_mode != 0xff)
+		if (ata_dma_enabled(dev))
 			used_dma = 1;
 	}
 	if (!found)
@@ -3313,7 +3313,7 @@ int ata_do_set_mode(struct ata_link *link, struct ata_device **r_failed_dev)
 
 	/* step 3: set host DMA timings */
 	ata_link_for_each_dev(dev, link) {
-		if (!ata_dev_enabled(dev) || dev->dma_mode == 0xff)
+		if (!ata_dev_enabled(dev) || !ata_dma_enabled(dev))
 			continue;
 
 		dev->xfer_mode = dev->dma_mode;

drivers/ata/pata_acpi.c

@@ -181,7 +181,7 @@ static unsigned int pacpi_qc_issue(struct ata_queued_cmd *qc)
 
 	if (adev != acpi->last) {
 		pacpi_set_piomode(ap, adev);
-		if (adev->dma_mode)
+		if (ata_dma_enabled(adev))
 			pacpi_set_dmamode(ap, adev);
 		acpi->last = adev;
 	}

drivers/ata/pata_atiixp.c

@@ -183,7 +183,7 @@ static void atiixp_bmdma_start(struct ata_queued_cmd *qc)
 	u16 tmp16;
 
 	pci_read_config_word(pdev, ATIIXP_IDE_UDMA_CONTROL, &tmp16);
-	if (adev->dma_mode >= XFER_UDMA_0)
+	if (ata_using_udma(adev))
 		tmp16 |= (1 << dn);
 	else
 		tmp16 &= ~(1 << dn);

drivers/ata/pata_cs5530.c

@@ -149,10 +149,10 @@ static unsigned int cs5530_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 */
 		    	cs5530_set_dmamode(ap, adev);
 	}

drivers/ata/pata_oldpiix.c

@@ -198,7 +198,7 @@ static unsigned int oldpiix_qc_issue(struct ata_queued_cmd *qc)
 
 	if (adev != ap->private_data) {
 		oldpiix_set_piomode(ap, adev);
-		if (adev->dma_mode)
+		if (ata_dma_enabled(adev))
 			oldpiix_set_dmamode(ap, adev);
 	}
 	return ata_sff_qc_issue(qc);

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);
 	}

include/linux/libata.h

@@ -1429,6 +1429,28 @@ static inline unsigned long ata_deadline(unsigned long from_jiffies,
 	return from_jiffies + msecs_to_jiffies(timeout_msecs);
 }
 
+/* Don't open code these in drivers as there are traps. Firstly the range may
+   change in future hardware and specs, secondly 0xFF means 'no DMA' but is
+   > UDMA_0. Dyma ddreigiau */
+
+static inline int ata_using_mwdma(struct ata_device *adev)
+{
+	if (adev->dma_mode >= XFER_MW_DMA_0 && adev->dma_mode <= XFER_MW_DMA_4)
+		return 1;
+	return 0;
+}
+
+static inline int ata_using_udma(struct ata_device *adev)
+{
+	if (adev->dma_mode >= XFER_UDMA_0 && adev->dma_mode <= XFER_UDMA_7)
+		return 1;
+	return 0;
+}
+
+static inline int ata_dma_enabled(struct ata_device *adev)
+{
+	return (adev->dma_mode == 0xFF ? 0 : 1);
+}
 
 /**************************************************************************
  * PMP - drivers/ata/libata-pmp.c