libata: clear SError after link resume

SError used to be cleared in ->postreset.  This has small hotplug race
condition.  If a device is plugged in after reset is complete but
postreset hasn't run yet, its hotplug event gets lost when SError is
cleared.  This patch makes sata_link_resume() clear SError.  This
kills the race condition and makes a lot of sense as some PMP and host
PHYs don't work properly without SError cleared.

This change makes sata_pmp_std_{pre|post}_reset()'s unnecessary as
they become identical to ata_std counterparts.  It also simplifies
sata_pmp_hardreset() and ahci_vt8251_hardreset().

Signed-off-by: Tejun Heo <htejun@gmail.com>

1 files changed, 22 insertions, 13 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index c4fd4afbf34..e00b620f161 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -90,9 +90,9 @@ const struct ata_port_operations sata_port_ops = {
 const struct ata_port_operations sata_pmp_port_ops = {
         .inherits               = &sata_port_ops,
 
-        .pmp_prereset           = sata_pmp_std_prereset,
+        .pmp_prereset           = ata_std_prereset,
         .pmp_hardreset          = sata_pmp_std_hardreset,
-        .pmp_postreset          = sata_pmp_std_postreset,
+        .pmp_postreset          = ata_std_postreset,
         .error_handler          = sata_pmp_error_handler,
 };
 
@@ -3493,7 +3493,7 @@ 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)
 {
-        u32 scontrol;
+        u32 scontrol, serror;
         int rc;
 
         if ((rc = sata_scr_read(link, SCR_CONTROL, &scontrol)))
@@ -3509,7 +3509,25 @@ int sata_link_resume(struct ata_link *link, const unsigned long *params,
          */
         msleep(200);
 
-        return sata_link_debounce(link, params, deadline);
+        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).
+         */
+        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;
 }
 
 /**
@@ -3701,18 +3719,11 @@ 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");
 
         /* print link status */
         sata_print_link_status(link);
 
-        /* clear SError */
-        if (sata_scr_read(link, SCR_ERROR, &serror) == 0)
-                sata_scr_write(link, SCR_ERROR, serror);
-        link->eh_info.serror = 0;
-
         DPRINTK("EXIT\n");
 }
 
@@ -6296,9 +6307,7 @@ EXPORT_SYMBOL_GPL(ata_pci_device_resume);
 #endif /* CONFIG_PCI */
 
 EXPORT_SYMBOL_GPL(sata_pmp_qc_defer_cmd_switch);
-EXPORT_SYMBOL_GPL(sata_pmp_std_prereset);
 EXPORT_SYMBOL_GPL(sata_pmp_std_hardreset);
-EXPORT_SYMBOL_GPL(sata_pmp_std_postreset);
 EXPORT_SYMBOL_GPL(sata_pmp_error_handler);
 
 EXPORT_SYMBOL_GPL(__ata_ehi_push_desc);