libata: add support for NCQ commands for SG interface

This patch is needed to make NCQ commands with FPDMA protocol value
(eg READ/WRITE FPDMA) work over SCSI Generic (SG) interface.
Signed-off-by: Vinayak Kale <vinayak.kale@seagate.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/libata-scsi.c

@@ -2912,12 +2912,14 @@ ata_scsi_map_proto(u8 byte1)
 	case 5:		/* PIO Data-out */
 		return ATA_PROT_PIO;
 
+	case 12:	/* FPDMA */
+		return ATA_PROT_NCQ;
+
 	case 0:		/* Hard Reset */
 	case 1:		/* SRST */
 	case 8:		/* Device Diagnostic */
 	case 9:		/* Device Reset */
 	case 7:		/* DMA Queued */
-	case 12:	/* FPDMA */
 	case 15:	/* Return Response Info */
 	default:	/* Reserved */
 		break;
@@ -2990,6 +2992,10 @@ static unsigned int ata_scsi_pass_thru(struct ata_queued_cmd *qc)
 		tf->command = cdb[9];
 	}
 
+	/* For NCQ commands with FPDMA protocol, copy the tag value */
+	if (tf->protocol == ATA_PROT_NCQ)
+		tf->nsect = qc->tag << 3;
+
 	/* enforce correct master/slave bit */
 	tf->device = dev->devno ?
 		tf->device | ATA_DEV1 : tf->device & ~ATA_DEV1;