[libata] sata_mv: off-by-1 fix

This patch addresses a number of weird behaviours observed
for the sata_mv driver, by fixing an "off by one" bug in processing
of the EDMA response queue.

Basically, sata_mv was looking in the wrong place for
command results, and this produced a lot of unpredictable behaviour.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/scsi/sata_mv.c

@@ -1263,6 +1263,7 @@ static u8 mv_get_crpb_status(struct ata_port *ap)
 	void __iomem *port_mmio = mv_ap_base(ap);
 	struct mv_port_priv *pp = ap->private_data;
 	u32 out_ptr;
+	u8 ata_status;
 
 	out_ptr = readl(port_mmio + EDMA_RSP_Q_OUT_PTR_OFS);
 
@@ -1270,6 +1271,8 @@ static u8 mv_get_crpb_status(struct ata_port *ap)
 	WARN_ON(((out_ptr >> EDMA_RSP_Q_PTR_SHIFT) & MV_MAX_Q_DEPTH_MASK) !=
 		pp->rsp_consumer);
 
+	ata_status = pp->crpb[pp->rsp_consumer].flags >> CRPB_FLAG_STATUS_SHIFT;
+
 	/* increment our consumer index... */
 	pp->rsp_consumer = mv_inc_q_index(&pp->rsp_consumer);
 
@@ -1284,7 +1287,7 @@ static u8 mv_get_crpb_status(struct ata_port *ap)
 	writelfl(out_ptr, port_mmio + EDMA_RSP_Q_OUT_PTR_OFS);
 
 	/* Return ATA status register for completed CRPB */
-	return (pp->crpb[pp->rsp_consumer].flags >> CRPB_FLAG_STATUS_SHIFT);
+	return ata_status;
 }
 
 /**