[PATCH] ahci: disable 64bit dma on sb600

SB600 claims it can do 64bit DMA but it can't.  Disable it.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/ata/ahci.c

@@ -170,6 +170,7 @@ enum {
 	AHCI_FLAG_IGN_IRQ_IF_ERR	= (1 << 25), /* ignore IRQ_IF_ERR */
 	AHCI_FLAG_HONOR_PI		= (1 << 26), /* honor PORTS_IMPL */
 	AHCI_FLAG_IGN_SERR_INTERNAL	= (1 << 27), /* ignore SERR_INTERNAL */
+	AHCI_FLAG_32BIT_ONLY		= (1 << 28), /* force 32bit */
 };
 
 struct ahci_cmd_hdr {
@@ -370,7 +371,8 @@ static const struct ata_port_info ahci_port_info[] = {
 		.flags		= ATA_FLAG_SATA | ATA_FLAG_NO_LEGACY |
 				  ATA_FLAG_MMIO | ATA_FLAG_PIO_DMA |
 				  ATA_FLAG_SKIP_D2H_BSY |
-				  AHCI_FLAG_IGN_SERR_INTERNAL,
+				  AHCI_FLAG_IGN_SERR_INTERNAL |
+				  AHCI_FLAG_32BIT_ONLY,
 		.pio_mask	= 0x1f, /* pio0-4 */
 		.udma_mask	= 0x7f, /* udma0-6 ; FIXME */
 		.port_ops	= &ahci_ops,
@@ -1579,6 +1581,12 @@ static int ahci_host_init(struct ata_probe_ent *probe_ent)
 		probe_ent->n_ports = cap_n_ports;
 
 	using_dac = hpriv->cap & HOST_CAP_64;
+	if (using_dac && (probe_ent->port_flags & AHCI_FLAG_32BIT_ONLY)) {
+		dev_printk(KERN_INFO, &pdev->dev,
+			   "controller can't do 64bit DMA, forcing 32bit\n");
+		using_dac = 0;
+	}
+
 	if (using_dac &&
 	    !pci_set_dma_mask(pdev, DMA_64BIT_MASK)) {
 		rc = pci_set_consistent_dma_mask(pdev, DMA_64BIT_MASK);