[PATCH] ahci: disable NCQ support on vt8251

[Tejun Heo <htejun@gmail.com>]

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>
---

diff --git a/drivers/scsi/ahci.c b/drivers/scsi/ahci.c
index e261b37..8208546 100644
--- a/drivers/scsi/ahci.c
+++ b/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_p
 		.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,
@@ -1362,7 +1363,8 @@ static int ahci_init_one (struct pci_dev
 	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);