2 files changed, 50 insertions, 23 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index c6c316fc8379..ffc689d9e972 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3490,22 +3490,11 @@ int sata_link_resume(struct ata_link *link, const unsigned long *params,
         if ((rc = sata_link_debounce(link, params, deadline)))
                 return rc;
 
-        /* Clear SError.  PMP and some host PHYs require this to
-         * operate and clearing should be done before checking PHY
-         * online status to avoid race condition (hotplugging between
-         * link resume and status check).
-         */
+        /* clear SError, some PHYs require this even for SRST to work */
         if (!(rc = sata_scr_read(link, SCR_ERROR, &serror)))
                 rc = sata_scr_write(link, SCR_ERROR, serror);
-        if (rc == 0 || rc == -EINVAL) {
-                unsigned long flags;
 
-                spin_lock_irqsave(link->ap->lock, flags);
-                link->eh_info.serror = 0;
-                spin_unlock_irqrestore(link->ap->lock, flags);
-                rc = 0;
-        }
-        return rc;
+        return rc != -EINVAL ? rc : 0;
 }
 
 /**
@@ -3704,8 +3693,14 @@ int sata_std_hardreset(struct ata_link *link, unsigned int *class,
  */
 void ata_std_postreset(struct ata_link *link, unsigned int *classes)
 {
+        u32 serror;
+
         DPRINTK("ENTER\n");
 
+        /* reset complete, clear SError */
+        if (!sata_scr_read(link, SCR_ERROR, &serror))
+                sata_scr_write(link, SCR_ERROR, serror);
+
         /* print link status */
         sata_print_link_status(link);
 
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index 06a92c58a49d..751dad0138ae 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -2047,19 +2047,11 @@ static int ata_do_reset(struct ata_link *link, ata_reset_fn_t reset,
                         unsigned int *classes, unsigned long deadline)
 {
         struct ata_device *dev;
-        int rc;
 
         ata_link_for_each_dev(dev, link)
                 classes[dev->devno] = ATA_DEV_UNKNOWN;
 
-        rc = reset(link, classes, deadline);
-
-        /* convert all ATA_DEV_UNKNOWN to ATA_DEV_NONE */
-        ata_link_for_each_dev(dev, link)
-                if (classes[dev->devno] == ATA_DEV_UNKNOWN)
-                        classes[dev->devno] = ATA_DEV_NONE;
-
-        return rc;
+        return reset(link, classes, deadline);
 }
 
 static int ata_eh_followup_srst_needed(struct ata_link *link,
@@ -2096,7 +2088,7 @@ int ata_eh_reset(struct ata_link *link, int classify,
         ata_reset_fn_t reset;
         unsigned long flags;
         u32 sstatus;
-        int rc;
+        int nr_known, rc;
 
         /*
          * Prepare to reset
@@ -2245,9 +2237,49 @@ int ata_eh_reset(struct ata_link *link, int classify,
         if (ata_is_host_link(link))
                 ata_eh_thaw_port(ap);
 
+        /* postreset() should clear hardware SError.  Although SError
+         * is cleared during link resume, clearing SError here is
+         * necessary as some PHYs raise hotplug events after SRST.
+         * This introduces race condition where hotplug occurs between
+         * reset and here.  This race is mediated by cross checking
+         * link onlineness and classification result later.
+         */
         if (postreset)
                 postreset(link, classes);
 
+        /* clear cached SError */
+        spin_lock_irqsave(link->ap->lock, flags);
+        link->eh_info.serror = 0;
+        spin_unlock_irqrestore(link->ap->lock, flags);
+
+        /* Make sure onlineness and classification result correspond.
+         * Hotplug could have happened during reset and some
+         * controllers fail to wait while a drive is spinning up after
+         * being hotplugged causing misdetection.  By cross checking
+         * link onlineness and classification result, those conditions
+         * can be reliably detected and retried.
+         */
+        nr_known = 0;
+        ata_link_for_each_dev(dev, link) {
+                /* convert all ATA_DEV_UNKNOWN to ATA_DEV_NONE */
+                if (classes[dev->devno] == ATA_DEV_UNKNOWN)
+                        classes[dev->devno] = ATA_DEV_NONE;
+                else
+                        nr_known++;
+        }
+
+        if (classify && !nr_known && ata_link_online(link)) {
+                if (try < max_tries) {
+                        ata_link_printk(link, KERN_WARNING, "link online but "
+                                       "device misclassified, retrying\n");
+                        rc = -EAGAIN;
+                        goto fail;
+                }
+                ata_link_printk(link, KERN_WARNING,
+                               "link online but device misclassified, "
+                               "device detection might fail\n");
+        }
+
         /* reset successful, schedule revalidation */
         ata_eh_done(link, NULL, ATA_EH_RESET);
         ehc->i.action |= ATA_EH_REVALIDATE;