Fix broken pata_via cable detection

via_do_set_mode overwrites 80-wire cable detection bits. Let's
preserve them.

Signed-off-by: Laurent Riffard <laurent.riffard@free.fr>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/ata/pata_via.c b/drivers/ata/pata_via.c
index ea18e33f50ef..1b0acafad1a6 100644
--- a/drivers/ata/pata_via.c
+++ b/drivers/ata/pata_via.c
@@ -243,7 +243,6 @@ static void via_do_set_mode(struct ata_port *ap, struct ata_device *adev, int mo
         int ut;
         int offset = 3 - (2*ap->port_no) - adev->devno;
 
-
         /* Calculate the timing values we require */
         ata_timing_compute(adev, mode, &t, T, UT);
 
@@ -290,9 +289,17 @@ static void via_do_set_mode(struct ata_port *ap, struct ata_device *adev, int mo
                         ut = t.udma ? (0xe0 | (FIT(t.udma, 2, 9) - 2)) : 0x07;
                         break;
         }
+
         /* Set UDMA unless device is not UDMA capable */
-        if (udma_type)
-                pci_write_config_byte(pdev, 0x50 + offset, ut);
+        if (udma_type) {
+                u8 cable80_status;
+
+                /* Get 80-wire cable detection bit */
+                pci_read_config_byte(pdev, 0x50 + offset, &cable80_status);
+                cable80_status &= 0x10;
+
+                pci_write_config_byte(pdev, 0x50 + offset, ut | cable80_status);
+        }
 }
 
 static void via_set_piomode(struct ata_port *ap, struct ata_device *adev)