[PATCH] ata_piix: fix pio/mwdma programming (for testing, don't apply)

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Hello, Art Haas, Alan.

Okay, here's another try at fixing the detection bug.  I went through
intel ich docs and compared with the ide piix driver.  This patch
fixes the following problems.

* Control bits in the timing register wasn't cleared properly while
  programming PIO mode.

* MWDMA mode programming cleared the wrong part of control bits.  I
  think this can fix your problem.

* MWDMA mode programming cleared udma_mask even when the controller
  doesn't support UDMA.  This doesn't matter for your case.

Please test and report the result.  Thanks.

FOR TESTING. DO NOT APPLY.

diff --git a/drivers/ata/ata_piix.c b/drivers/ata/ata_piix.c
index c6bf1a3..51f55a0 100644
--- a/drivers/ata/ata_piix.c
+++ b/drivers/ata/ata_piix.c
@@ -728,8 +728,14 @@ 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 */
@@ -737,12 +743,14 @@ 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);
@@ -859,7 +867,7 @@ 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);
@@ -871,8 +879,11 @@ 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)
-
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