ahci: disable 64bit DMA by default on SB600s

index acd1162..c950159 100644
@@ -447,7 +447,8 @@ static const struct ata_port_info ahci_port_info[] = {
 	[board_ahci_sb600] =
 	{
 		AHCI_HFLAGS	(AHCI_HFLAG_IGN_SERR_INTERNAL |
-				 AHCI_HFLAG_NO_MSI | AHCI_HFLAG_SECT255),
+				 AHCI_HFLAG_NO_MSI | AHCI_HFLAG_SECT255 |
+				 AHCI_HFLAG_32BIT_ONLY),
 		.flags		= AHCI_FLAG_COMMON,
 		.pio_mask	= ATA_PIO4,
 		.udma_mask	= ATA_UDMA6,

@@ -2650,17 +2651,15 @@ static void ahci_p5wdh_workaround(struct ata_host *host)
 	}
 }
 
-/*
- * SB600 ahci controller on certain boards can't do 64bit DMA with
- * older BIOS.
- */
-static bool ahci_sb600_32bit_only(struct pci_dev *pdev)
+/* only some SB600 ahci controllers can do 64bit DMA */
+static bool ahci_sb600_enable_64bit(struct pci_dev *pdev)
 {
 	static const struct dmi_system_id sysids[] = {
 		/*
 		 * The oldest version known to be broken is 0901 and
 		 * working is 1501 which was released on 2007-10-26.
-		 * Force 32bit DMA on anything older than 1501.
+		 * Enable 64bit DMA on 1501 and anything newer.
+		 *
 		 * Please read bko#9412 for more info.
 		 */
 		{

@@ -2672,48 +2671,29 @@ static bool ahci_sb600_32bit_only(struct pci_dev *pdev)
 			},
 			.driver_data = "20071026",	/* yyyymmdd */
 		},
-		/*
-		 * It's yet unknown whether more recent BIOS fixes the
-		 * problem.  Blacklist the whole board for the time
-		 * being.  Please read the following thread for more
-		 * info.
-		 *
-		 * http://thread.gmane.org/gmane.linux.ide/42326
-		 */
-		{
-			.ident = "Gigabyte GA-MA69VM-S2",
-			.matches = {
-				DMI_MATCH(DMI_BOARD_VENDOR,
-					  "Gigabyte Technology Co., Ltd."),
-				DMI_MATCH(DMI_BOARD_NAME, "GA-MA69VM-S2"),
-			},
-		},
 		{ }
 	};
 	const struct dmi_system_id *match;
+	int year, month, date;
+	char buf[9];
 
 	match = dmi_first_match(sysids);
 	if (pdev->bus->number != 0 || pdev->devfn != PCI_DEVFN(0x12, 0) ||
 	    !match)
 		return false;
 
-	if (match->driver_data) {
-		int year, month, date;
-		char buf[9];
-
-		dmi_get_date(DMI_BIOS_DATE, &year, &month, &date);
-		snprintf(buf, sizeof(buf), "%04d%02d%02d", year, month, date);
-
-		if (strcmp(buf, match->driver_data) >= 0)
-			return false;
+	dmi_get_date(DMI_BIOS_DATE, &year, &month, &date);
+	snprintf(buf, sizeof(buf), "%04d%02d%02d", year, month, date);
 
+	if (strcmp(buf, match->driver_data) >= 0) {
+		dev_printk(KERN_WARNING, &pdev->dev, "%s: enabling 64bit DMA\n",
+			   match->ident);
+		return true;
+	} else {
 		dev_printk(KERN_WARNING, &pdev->dev, "%s: BIOS too old, "
 			   "forcing 32bit DMA, update BIOS\n", match->ident);
-	} else
-		dev_printk(KERN_WARNING, &pdev->dev, "%s: this board can't "
-			   "do 64bit DMA, forcing 32bit\n", match->ident);
-
-	return true;
+		return false;
+	}
 }
 
 static bool ahci_broken_system_poweroff(struct pci_dev *pdev)

@@ -2926,9 +2906,9 @@ static int ahci_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (board_id == board_ahci_sb700 && pdev->revision >= 0x40)
 		hpriv->flags &= ~AHCI_HFLAG_IGN_SERR_INTERNAL;
 
-	/* apply sb600 32bit only quirk */
-	if (ahci_sb600_32bit_only(pdev))
-		hpriv->flags |= AHCI_HFLAG_32BIT_ONLY;
+	/* only some SB600s can do 64bit DMA */
+	if (ahci_sb600_enable_64bit(pdev))
+		hpriv->flags &= ~AHCI_HFLAG_32BIT_ONLY;
 
 	if ((hpriv->flags & AHCI_HFLAG_NO_MSI) || pci_enable_msi(pdev))
 		pci_intx(pdev, 1);

Index: tree0/drivers/ata/ahci.c
===================================================================
@@ -433,7 +433,8 @@ static const struct ata_port_info ahci_p
 	[board_ahci_sb600] =
 	{
 		AHCI_HFLAGS	(AHCI_HFLAG_IGN_SERR_INTERNAL |
-				 AHCI_HFLAG_NO_MSI | AHCI_HFLAG_SECT255),
+				 AHCI_HFLAG_NO_MSI | AHCI_HFLAG_SECT255 |
+				 AHCI_HFLAG_32BIT_ONLY),
 		.flags		= AHCI_FLAG_COMMON,
 		.pio_mask	= ATA_PIO4,
 		.udma_mask	= ATA_UDMA6,

@@ -2608,7 +2609,7 @@ static void ahci_p5wdh_workaround(struct
  * 1501 which was released on 2007-10-26.  Force 32bit DMA on anything
  * older than 1501.  Please read bko#9412 for more info.
  */
-static bool ahci_asus_m2a_vm_32bit_only(struct pci_dev *pdev)
+static bool ahci_asus_m2a_vm_enable_64bit(struct pci_dev *pdev)
 {
 	static const struct dmi_system_id sysids[] = {
 		{

@@ -2639,12 +2640,12 @@ static bool ahci_asus_m2a_vm_32bit_only(
 	if (date && strlen(date) >= 10 && date[2] == '/' && date[5] == '/' &&
 	    (year > 2007 ||
 	     (year == 2007 && strncmp(date, cutoff_mmdd, 5) >= 0)))
-		return false;
+		return true;
 
 	dev_printk(KERN_WARNING, &pdev->dev, "ASUS M2A-VM: BIOS too old, "
 		   "forcing 32bit DMA, update BIOS\n");
 
-	return true;
+	return false;
 }
 
 static bool ahci_broken_system_poweroff(struct pci_dev *pdev)

@@ -2858,8 +2859,8 @@ static int ahci_init_one(struct pci_dev
 		hpriv->flags &= ~AHCI_HFLAG_IGN_SERR_INTERNAL;
 
 	/* apply ASUS M2A_VM quirk */
-	if (ahci_asus_m2a_vm_32bit_only(pdev))
-		hpriv->flags |= AHCI_HFLAG_32BIT_ONLY;
+	if (ahci_asus_m2a_vm_enable_64bit(pdev))
+		hpriv->flags &= ~AHCI_HFLAG_32BIT_ONLY;
 
 	if ((hpriv->flags & AHCI_HFLAG_NO_MSI) || pci_enable_msi(pdev))
 		pci_intx(pdev, 1);