sata_mv ncq Restrict max sectors to 8-bits on GenII NCQ

The GenII chips have only 8-bits for the sector_count field when performing NCQ.
Add a dev_config method to restrict this when necessary, taking care not to
override any other restriction already in place (likely none, but someday.. ?).

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

drivers/ata/sata_mv.c

@@ -449,6 +449,7 @@ static void mv_error_handler(struct ata_port *ap);
 static void mv_post_int_cmd(struct ata_queued_cmd *qc);
 static void mv_eh_freeze(struct ata_port *ap);
 static void mv_eh_thaw(struct ata_port *ap);
+static void mv6_dev_config(struct ata_device *dev);
 static int mv_init_one(struct pci_dev *pdev, const struct pci_device_id *ent);
 
 static void mv5_phy_errata(struct mv_host_priv *hpriv, void __iomem *mmio,
@@ -541,6 +542,7 @@ static const struct ata_port_operations mv5_ops = {
 };
 
 static const struct ata_port_operations mv6_ops = {
+	.dev_config             = mv6_dev_config,
 	.tf_load		= ata_tf_load,
 	.tf_read		= ata_tf_read,
 	.check_status		= ata_check_status,
@@ -1054,6 +1056,17 @@ static int mv_scr_write(struct ata_port *ap, unsigned int sc_reg_in, u32 val)
 		return -EINVAL;
 }
 
+static void mv6_dev_config(struct ata_device *adev)
+{
+	/*
+	 * We don't have hob_nsect when doing NCQ commands on Gen-II.
+	 * See mv_qc_prep() for more info.
+	 */
+	if (adev->flags & ATA_DFLAG_NCQ)
+		if (adev->max_sectors > ATA_MAX_SECTORS)
+			adev->max_sectors = ATA_MAX_SECTORS;
+}
+
 static void mv_edma_cfg(struct mv_port_priv *pp, struct mv_host_priv *hpriv,
 			void __iomem *port_mmio, int want_ncq)
 {