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>

1 files changed, 27 insertions, 2 deletions

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 17f9ff9067a2..6f5093b7c8c5 100644
--- 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;
 }