libata: implement ATA_DFLAG_DUBIOUS_XFER

ATA_DFLAG_DUBIOUS_XFER is set whenever data transfer speed or method
changes and gets cleared when data transfer command succeeds in the
newly configured transfer mode.

This will be used to improve speed down logic.

Signed-off-by: Tejun Heo <htejun@gmail.com<
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 86c10cc751e9..124b6f111cc3 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -5797,6 +5797,22 @@ static void fill_result_tf(struct ata_queued_cmd *qc)
         ap->ops->tf_read(ap, &qc->result_tf);
 }
 
+static void ata_verify_xfer(struct ata_queued_cmd *qc)
+{
+        struct ata_device *dev = qc->dev;
+
+        if (ata_tag_internal(qc->tag))
+                return;
+
+        if (ata_is_nodata(qc->tf.protocol))
+                return;
+
+        if ((dev->mwdma_mask || dev->udma_mask) && ata_is_pio(qc->tf.protocol))
+                return;
+
+        dev->flags &= ~ATA_DFLAG_DUBIOUS_XFER;
+}
+
 /**
  *      ata_qc_complete - Complete an active ATA command
  *      @qc: Command to complete
@@ -5868,6 +5884,9 @@ void ata_qc_complete(struct ata_queued_cmd *qc)
                         break;
                 }
 
+                if (unlikely(dev->flags & ATA_DFLAG_DUBIOUS_XFER))
+                        ata_verify_xfer(qc);
+
                 __ata_qc_complete(qc);
         } else {
                 if (qc->flags & ATA_QCFLAG_EH_SCHEDULED)