libata: improve probe failure handling

* Move forcing device to PIO0 on device disable into
  ata_dev_disable().  This makes both old and new EHs act the same
  way.

* Speed down only PIO mode on probe failure.  All commands used during
  probing are PIO commands.  There's no point in speeding down DMA.

* Retry at least once after -ENODEV.  Some devices report garbled
  IDENTIFY data after certain events.  This shouldn't cause device
  detach and re-attach.

* Rearrange EH failure path for simplicity.

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

1 files changed, 18 insertions, 17 deletions

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 7b61562cdd40..1abfdba8d99b 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -1964,8 +1964,7 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 {
         struct ata_eh_context *ehc = &ap->eh_context;
         struct ata_device *dev;
-        int down_xfermask, i, rc;
-        int dnxfer_sel;
+        int i, rc;
 
         DPRINTK("ENTER\n");
 
@@ -1994,7 +1993,6 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
         }
 
  retry:
-        down_xfermask = 0;
         rc = 0;
 
         /* if UNLOADING, finish immediately */
@@ -2039,10 +2037,8 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
         /* configure transfer mode if necessary */
         if (ehc->i.flags & ATA_EHI_SETMODE) {
                 rc = ata_set_mode(ap, &dev);
-                if (rc) {
-                        down_xfermask = 1;
+                if (rc)
                         goto dev_fail;
-                }
                 ehc->i.flags &= ~ATA_EHI_SETMODE;
         }
 
@@ -2054,22 +2050,27 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
         goto out;
 
  dev_fail:
+        ehc->tries[dev->devno]--;
+
         switch (rc) {
-        case -ENODEV:
-                /* device missing, schedule probing */
-                ehc->i.probe_mask |= (1 << dev->devno);
         case -EINVAL:
+                /* eeek, something went very wrong, give up */
                 ehc->tries[dev->devno] = 0;
                 break;
+
+        case -ENODEV:
+                /* device missing or wrong IDENTIFY data, schedule probing */
+                ehc->i.probe_mask |= (1 << dev->devno);
+                /* give it just one more chance */
+                ehc->tries[dev->devno] = min(ehc->tries[dev->devno], 1);
         case -EIO:
-                sata_down_spd_limit(ap);
-        default:
-                ehc->tries[dev->devno]--;
-                dnxfer_sel = ATA_DNXFER_ANY;
-                if (ehc->tries[dev->devno] == 1)
-                        dnxfer_sel = ATA_DNXFER_FORCE_PIO0;
-                if (down_xfermask && ata_down_xfermask_limit(dev, dnxfer_sel))
-                        ehc->tries[dev->devno] = 0;
+                if (ehc->tries[dev->devno] == 1) {
+                        /* This is the last chance, better to slow
+                         * down than lose it.
+                         */
+                        sata_down_spd_limit(ap);
+                        ata_down_xfermask_limit(dev, ATA_DNXFER_PIO);
+                }
         }
 
         if (ata_dev_enabled(dev) && !ehc->tries[dev->devno]) {