7 files changed, 33 insertions, 11 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 5f8f57a818fb..79e3a8e7a84a 100644
--- a/drivers/ata/libata-core.c
+++ b/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;
diff --git a/drivers/ata/pata_acpi.c b/drivers/ata/pata_acpi.c
index fbe605711554..eb919c16a03e 100644
--- a/drivers/ata/pata_acpi.c
+++ b/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;
         }
diff --git a/drivers/ata/pata_atiixp.c b/drivers/ata/pata_atiixp.c
index d7de7baf58a8..e8a0d99d7356 100644
--- a/drivers/ata/pata_atiixp.c
+++ b/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);
diff --git a/drivers/ata/pata_cs5530.c b/drivers/ata/pata_cs5530.c
index 744beebaaf49..0c4b271a9d5a 100644
--- a/drivers/ata/pata_cs5530.c
+++ b/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);
         }
diff --git a/drivers/ata/pata_oldpiix.c b/drivers/ata/pata_oldpiix.c
index e678af383d13..df64f2443001 100644
--- a/drivers/ata/pata_oldpiix.c
+++ b/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);
diff --git a/drivers/ata/pata_sc1200.c b/drivers/ata/pata_sc1200.c
index cbab397e3db7..0278fd2b8fb1 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);
         }
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 80233fdc159f..225bfc5bd9ec 100644
--- a/include/linux/libata.h
+++ b/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