libata: retry link resume if necessary

Interestingly, when SIDPR is used in ata_piix, writes to DET in
SControl sometimes get ignored leading to detection failure.  Update
sata_link_resume() such that it reads back SControl after clearing DET
and retry if it's not clear.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: fengxiangjun <fengxiangjun@neusoft.com>
Reported-by: Jim Faulkner <jfaulkne@ccs.neu.edu>
Cc: stable@kernel.org
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 22ff51b..6728328 100644 (file)
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3790,21 +3790,45 @@ int sata_link_debounce(struct ata_link *link, const unsigned long *params,
 int sata_link_resume(struct ata_link *link, const unsigned long *params,
                     unsigned long deadline)
 {
+       int tries = ATA_LINK_RESUME_TRIES;
        u32 scontrol, serror;
        int rc;
 
        if ((rc = sata_scr_read(link, SCR_CONTROL, &scontrol)))
                return rc;
 
-       scontrol = (scontrol & 0x0f0) | 0x300;
+       /*
+        * Writes to SControl sometimes get ignored under certain
+        * controllers (ata_piix SIDPR).  Make sure DET actually is
+        * cleared.
+        */
+       do {
+               scontrol = (scontrol & 0x0f0) | 0x300;
+               if ((rc = sata_scr_write(link, SCR_CONTROL, scontrol)))
+                       return rc;
+               /*
+                * Some PHYs react badly if SStatus is pounded
+                * immediately after resuming.  Delay 200ms before
+                * debouncing.
+                */
+               msleep(200);
 
-       if ((rc = sata_scr_write(link, SCR_CONTROL, scontrol)))
-               return rc;
+               /* is SControl restored correctly? */
+               if ((rc = sata_scr_read(link, SCR_CONTROL, &scontrol)))
+                       return rc;
+       } while ((scontrol & 0xf0f) != 0x300 && --tries);
 
-       /* Some PHYs react badly if SStatus is pounded immediately
-        * after resuming.  Delay 200ms before debouncing.
-        */
-       msleep(200);
+       if ((scontrol & 0xf0f) != 0x300) {
+               ata_link_printk(link, KERN_ERR,
+                               "failed to resume link (SControl %X)\n",
+                               scontrol);
+               return 0;
+       }
+
+       if (tries < ATA_LINK_RESUME_TRIES)
+               ata_link_printk(link, KERN_WARNING,
+                               "link resume succeeded after %d retries\n",
+                               ATA_LINK_RESUME_TRIES - tries);
 
        if ((rc = sata_link_debounce(link, params, deadline)))
                return rc;

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6a9c4dd..7311225 100644 (file)
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -354,6 +354,9 @@ enum {
        /* max tries if error condition is still set after ->error_handler */
        ATA_EH_MAX_TRIES        = 5,
 
+       /* sometimes resuming a link requires several retries */
+       ATA_LINK_RESUME_TRIES   = 5,
+
        /* how hard are we gonna try to probe/recover devices */
        ATA_PROBE_MAX_TRIES     = 3,
        ATA_EH_DEV_TRIES        = 3,