[PATCH] ahci: disable NCQ support on vt8251

vt8251 chokes on NCQ commands.  Two different disks from different
vendors are showing the same symptom and it seems that the windows
driver from via doesn't support NCQ either.  Disable NCQ support on
this controller for the time being.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Aalderd Bouwman <boac@wanadoo.nl>
Cc: Bastiaan Jacques <b.jacques@planet.nl>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/scsi/ahci.c

@@ -164,6 +164,7 @@ enum {
 
 	/* ap->flags bits */
 	AHCI_FLAG_RESET_NEEDS_CLO	= (1 << 24),
+	AHCI_FLAG_NO_NCQ		= (1 << 25),
 };
 
 struct ahci_cmd_hdr {
@@ -277,7 +278,7 @@ static const struct ata_port_info ahci_port_info[] = {
 		.host_flags	= ATA_FLAG_SATA | ATA_FLAG_NO_LEGACY |
 				  ATA_FLAG_MMIO | ATA_FLAG_PIO_DMA |
 				  ATA_FLAG_SKIP_D2H_BSY |
-				  AHCI_FLAG_RESET_NEEDS_CLO,
+				  AHCI_FLAG_RESET_NEEDS_CLO | AHCI_FLAG_NO_NCQ,
 		.pio_mask	= 0x1f, /* pio0-4 */
 		.udma_mask	= 0x7f, /* udma0-6 ; FIXME */
 		.port_ops	= &ahci_ops,
@@ -1386,7 +1387,8 @@ static int ahci_init_one (struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (rc)
 		goto err_out_hpriv;
 
-	if (hpriv->cap & HOST_CAP_NCQ)
+	if (!(probe_ent->host_flags & AHCI_FLAG_NO_NCQ) &&
+	    (hpriv->cap & HOST_CAP_NCQ))
 		probe_ent->host_flags |= ATA_FLAG_NCQ;
 
 	ahci_print_info(probe_ent);