1 files changed, 17 insertions, 6 deletions

diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index 9c07b88631be..924e4474068d 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -685,8 +685,14 @@ static void piix_set_piomode (struct ata_port *ap, struct ata_device *adev)
         if (adev->class == ATA_DEV_ATA)
                 control |= 4;   /* PPE enable */
 
+        /* PIO configuration clears DTE unconditionally.  It will be
+         * programmed in set_dmamode which is guaranteed to be called
+         * after set_piomode if any DMA mode is available.
+         */
         pci_read_config_word(dev, master_port, &master_data);
         if (is_slave) {
+                /* clear TIME1|IE1|PPE1|DTE1 */
+                master_data &= 0xff0f;
                 /* Enable SITRE (seperate slave timing register) */
                 master_data |= 0x4000;
                 /* enable PPE1, IE1 and TIME1 as needed */
@@ -694,12 +700,14 @@ static void piix_set_piomode (struct ata_port *ap, struct ata_device *adev)
                 pci_read_config_byte(dev, slave_port, &slave_data);
                 slave_data &= (ap->port_no ? 0x0f : 0xf0);
                 /* Load the timing nibble for this slave */
-                slave_data |= ((timings[pio][0] << 2) | timings[pio][1]) << (ap->port_no ? 4 : 0);
+                slave_data |= ((timings[pio][0] << 2) | timings[pio][1])
+                                                << (ap->port_no ? 4 : 0);
         } else {
-                /* Master keeps the bits in a different format */
-                master_data &= 0xccf8;
+                /* clear ISP|RCT|TIME0|IE0|PPE0|DTE0 */
+                master_data &= 0xccf0;
                 /* Enable PPE, IE and TIME as appropriate */
                 master_data |= control;
+                /* load ISP and RCT */
                 master_data |=
                         (timings[pio][0] << 12) |
                         (timings[pio][1] << 8);
@@ -816,7 +824,7 @@ static void do_pata_set_dmamode (struct ata_port *ap, struct ata_device *adev, i
                         master_data &= 0xFF4F;  /* Mask out IORDY|TIME1|DMAONLY */
                         master_data |= control << 4;
                         pci_read_config_byte(dev, 0x44, &slave_data);
-                        slave_data &= (0x0F + 0xE1 * ap->port_no);
+                        slave_data &= (ap->port_no ? 0x0f : 0xf0);
                         /* Load the matching timing */
                         slave_data |= ((timings[pio][0] << 2) | timings[pio][1]) << (ap->port_no ? 4 : 0);
                         pci_write_config_byte(dev, 0x44, slave_data);
@@ -828,8 +836,11 @@ static void do_pata_set_dmamode (struct ata_port *ap, struct ata_device *adev, i
                                 (timings[pio][0] << 12) |
                                 (timings[pio][1] << 8);
                 }
-                udma_enable &= ~(1 << devid);
-                pci_write_config_word(dev, master_port, master_data);
+
+                if (ap->udma_mask) {
+                        udma_enable &= ~(1 << devid);
+                        pci_write_config_word(dev, master_port, master_data);
+                }
         }
         /* Don't scribble on 0x48 if the controller does not support UDMA */
         if (ap->udma_mask)