via82cxxx: fix UDMA settings programming

* preserve 80-wire cable detection bit
* don't clear UDMA settings when programming PIO/MWDMA modes

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 2 deletions

diff --git a/drivers/ide/via82cxxx.c b/drivers/ide/via82cxxx.c
index 3db35b0142dc..fbecf8ea8207 100644
--- a/drivers/ide/via82cxxx.c
+++ b/drivers/ide/via82cxxx.c
@@ -146,10 +146,25 @@ static void via_set_speed(ide_hwif_t *hwif, u8 dn, struct ide_timing *timing)
         case ATA_UDMA4: t = timing->udma ? (0xe8 | (clamp_val(timing->udma, 2, 9) - 2)) : 0x0f; break;
         case ATA_UDMA5: t = timing->udma ? (0xe0 | (clamp_val(timing->udma, 2, 9) - 2)) : 0x07; break;
         case ATA_UDMA6: t = timing->udma ? (0xe0 | (clamp_val(timing->udma, 2, 9) - 2)) : 0x07; break;
-        default: return;
         }
 
-        pci_write_config_byte(dev, VIA_UDMA_TIMING + (3 - dn), t);
+        /* Set UDMA unless device is not UDMA capable */
+        if (vdev->via_config->udma_mask) {
+                u8 udma_etc;
+
+                pci_read_config_byte(dev, VIA_UDMA_TIMING + 3 - dn, &udma_etc);
+
+                /* clear transfer mode bit */
+                udma_etc &= ~0x20;
+
+                if (timing->udma) {
+                        /* preserve 80-wire cable detection bit */
+                        udma_etc &= 0x10;
+                        udma_etc |= t;
+                }
+
+                pci_write_config_byte(dev, VIA_UDMA_TIMING + 3 - dn, udma_etc);
+        }
 }
 
 /**