pata_cmd64x: fix overclocking of UDMA0-2 modes

adev->dma_mode stores the transfer mode value not UDMA mode number
so the condition in cmd64x_set_dmamode() is always true and the higher
UDMA clock is always selected.  This can potentially result in data
corruption when UDMA33 device is used, when 40-wire cable is used or
when the error recovery code decides to lower the device speed down.

The issue was introduced in the commit 6a40da0 ("libata cmd64x: whack
into a shape that looks like the documentation") which goes back to
kernel 2.6.20.

Cc: stable@kernel.org
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/pata_cmd64x.c b/drivers/ata/pata_cmd64x.c
index 58c09e2..0efb1f5 100644 (file)
--- a/drivers/ata/pata_cmd64x.c
+++ b/drivers/ata/pata_cmd64x.c
@@ -219,7 +219,7 @@ static void cmd64x_set_dmamode(struct ata_port *ap, struct ata_device *adev)
                regU |= udma_data[adev->dma_mode - XFER_UDMA_0] << shift;
                /* Merge the control bits */
                regU |= 1 << adev->devno; /* UDMA on */
-               if (adev->dma_mode > 2) /* 15nS timing */
+               if (adev->dma_mode > XFER_UDMA_2) /* 15nS timing */
                        regU |= 4 << adev->devno;
        } else {
                regU &= ~ (1 << adev->devno);   /* UDMA off */