libata: Ignore spurious PHY event on LPM policy change

When the LPM policy is set to ATA_LPM_MAX_POWER, the device might
generate a spurious PHY event that cuases errors on the link.
Ignore this event if it occured within 10s after the policy change.

The timeout was chosen observing that on a Dell XPS13 9333 these
spurious events can occur up to roughly 6s after the policy change.

Link: http://lkml.kernel.org/g/3352987.ugV1Ipy7Z5@xps13
Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org

3 files changed, 26 insertions, 1 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 12adcf78f94b..85e659945c12 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6766,8 +6766,21 @@ u32 ata_wait_register(struct ata_port *ap, void __iomem *reg, u32 mask, u32 val,
  */
 bool sata_lpm_ignore_phy_events(struct ata_link *link)
 {
+        unsigned long lpm_timeout = link->last_lpm_change +
+                                    msecs_to_jiffies(ATA_TMOUT_SPURIOUS_PHY);
+
         /* if LPM is enabled, PHYRDY doesn't mean anything */
-        return !!(link->lpm_policy > ATA_LPM_MAX_POWER);
+        if (link->lpm_policy > ATA_LPM_MAX_POWER)
+                return true;
+
+        /* ignore the first PHY event after the LPM policy changed
+         * as it is might be spurious
+         */
+        if ((link->flags & ATA_LFLAG_CHANGED) &&
+            time_before(jiffies, lpm_timeout))
+                return true;
+
+        return false;
 }
 EXPORT_SYMBOL_GPL(sata_lpm_ignore_phy_events);
 
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 07f41be38fbe..cf0022ec07f2 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -3597,6 +3597,9 @@ static int ata_eh_set_lpm(struct ata_link *link, enum ata_lpm_policy policy,
                 }
         }
 
+        link->last_lpm_change = jiffies;
+        link->flags |= ATA_LFLAG_CHANGED;
+
         return 0;
 
 fail:
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 6138d87277af..28aeae46f355 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -205,6 +205,7 @@ enum {
         ATA_LFLAG_SW_ACTIVITY   = (1 << 7), /* keep activity stats */
         ATA_LFLAG_NO_LPM        = (1 << 8), /* disable LPM on this link */
         ATA_LFLAG_RST_ONCE      = (1 << 9), /* limit recovery to one reset */
+        ATA_LFLAG_CHANGED       = (1 << 10), /* LPM state changed on this link */
 
         /* struct ata_port flags */
         ATA_FLAG_SLAVE_POSS     = (1 << 0), /* host supports slave dev */
@@ -309,6 +310,12 @@ enum {
          */
         ATA_TMOUT_PMP_SRST_WAIT = 5000,
 
+        /* When the LPM policy is set to ATA_LPM_MAX_POWER, there might
+         * be a spurious PHY event, so ignore the first PHY event that
+         * occurs within 10s after the policy change.
+         */
+        ATA_TMOUT_SPURIOUS_PHY  = 10000,
+
         /* ATA bus states */
         BUS_UNKNOWN             = 0,
         BUS_DMA                 = 1,
@@ -788,6 +795,8 @@ struct ata_link {
         struct ata_eh_context   eh_context;
 
         struct ata_device       device[ATA_MAX_DEVICES];
+
+        unsigned long           last_lpm_change; /* when last LPM change happened */
 };
 #define ATA_LINK_CLEAR_BEGIN            offsetof(struct ata_link, active_tag)
 #define ATA_LINK_CLEAR_END              offsetof(struct ata_link, device[0])