sata_mv: Prevent PIO commands to be defered too long if traffic in progress.

Use excl_link when non NCQ commands are defered, to be sure they are processed
as soon as outstanding commands are completed. It prevents some commands to be
defered indifinitely when using a port multiplier.

Signed-off-by: Gwendal Grignou <gwendal@google.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 17f9ff9..6f5093b 100644 (file)
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -1382,6 +1382,25 @@ static int mv_qc_defer(struct ata_queued_cmd *qc)
         */
        if (pp->pp_flags & MV_PP_FLAG_DELAYED_EH)
                return ATA_DEFER_PORT;
+
+       /* PIO commands need exclusive link: no other commands [DMA or PIO]
+        * can run concurrently.
+        * set excl_link when we want to send a PIO command in DMA mode
+        * or a non-NCQ command in NCQ mode.
+        * When we receive a command from that link, and there are no
+        * outstanding commands, mark a flag to clear excl_link and let
+        * the command go through.
+        */
+       if (unlikely(ap->excl_link)) {
+               if (link == ap->excl_link) {
+                       if (ap->nr_active_links)
+                               return ATA_DEFER_PORT;
+                       qc->flags |= ATA_QCFLAG_CLEAR_EXCL;
+                       return 0;
+               } else
+                       return ATA_DEFER_PORT;
+       }
+
        /*
         * If the port is completely idle, then allow the new qc.
         */
@@ -1395,8 +1414,14 @@ static int mv_qc_defer(struct ata_queued_cmd *qc)
         * doesn't allow it.
         */
        if ((pp->pp_flags & MV_PP_FLAG_EDMA_EN) &&
-           (pp->pp_flags & MV_PP_FLAG_NCQ_EN) && ata_is_ncq(qc->tf.protocol))
-               return 0;
+           (pp->pp_flags & MV_PP_FLAG_NCQ_EN)) {
+               if (ata_is_ncq(qc->tf.protocol))
+                       return 0;
+               else {
+                       ap->excl_link = link;
+                       return ATA_DEFER_PORT;
+               }
+       }
 
        return ATA_DEFER_PORT;
 }