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>

4 files changed, 23 insertions, 112 deletions

diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 0f553aaa6f79..a69bcca4eb1b 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -1377,7 +1377,6 @@ static int ahci_vt8251_hardreset(struct ata_link *link, unsigned int *class,
                                  unsigned long deadline)
 {
         struct ata_port *ap = link->ap;
-        u32 serror;
         bool online;
         int rc;
 
@@ -1388,10 +1387,6 @@ static int ahci_vt8251_hardreset(struct ata_link *link, unsigned int *class,
         rc = sata_link_hardreset(link, sata_ehc_deb_timing(&link->eh_context),
                                  deadline, &online, NULL);
 
-        /* vt8251 needs SError cleared for the port to operate */
-        ahci_scr_read(ap, SCR_ERROR, &serror);
-        ahci_scr_write(ap, SCR_ERROR, serror);
-
         ahci_start_engine(ap);
 
         DPRINTK("EXIT, rc=%d, class=%u\n", rc, *class);
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index c4fd4afbf349..e00b620f161a 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);
diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
index 7f1a87f01ab2..2f8a9577c26d 100644
--- a/drivers/ata/libata-pmp.c
+++ b/drivers/ata/libata-pmp.c
@@ -176,49 +176,6 @@ int sata_pmp_scr_write(struct ata_link *link, int reg, u32 val)
 }
 
 /**
- *      sata_pmp_std_prereset - prepare PMP link for reset
- *      @link: link to be reset
- *      @deadline: deadline jiffies for the operation
- *
- *      @link is about to be reset.  Initialize it.
- *
- *      LOCKING:
- *      Kernel thread context (may sleep)
- *
- *      RETURNS:
- *      0 on success, -errno otherwise.
- */
-int sata_pmp_std_prereset(struct ata_link *link, unsigned long deadline)
-{
-        struct ata_eh_context *ehc = &link->eh_context;
-        const unsigned long *timing = sata_ehc_deb_timing(ehc);
-        int rc;
-
-        /* if we're about to do hardreset, nothing more to do */
-        if (ehc->i.action & ATA_EH_HARDRESET)
-                return 0;
-
-        /* resume link */
-        rc = sata_link_resume(link, timing, deadline);
-        if (rc) {
-                /* phy resume failed */
-                ata_link_printk(link, KERN_WARNING, "failed to resume link "
-                                "for reset (errno=%d)\n", rc);
-                return rc;
-        }
-
-        /* clear SError bits including .X which blocks the port when set */
-        rc = sata_scr_write(link, SCR_ERROR, 0xffffffff);
-        if (rc) {
-                ata_link_printk(link, KERN_ERR,
-                                "failed to clear SError (errno=%d)\n", rc);
-                return rc;
-        }
-
-        return 0;
-}
-
-/**
  *      sata_pmp_std_hardreset - standard hardreset method for PMP link
  *      @link: link to be reset
  *      @class: resulting class of attached device
@@ -238,33 +195,13 @@ int sata_pmp_std_prereset(struct ata_link *link, unsigned long deadline)
 int sata_pmp_std_hardreset(struct ata_link *link, unsigned int *class,
                            unsigned long deadline)
 {
-        const unsigned long *timing = sata_ehc_deb_timing(&link->eh_context);
-        bool online;
         u32 tmp;
         int rc;
 
         DPRINTK("ENTER\n");
 
-        /* do hardreset */
-        rc = sata_link_hardreset(link, timing, deadline, &online, NULL);
-        if (rc) {
-                ata_link_printk(link, KERN_ERR,
-                                "COMRESET failed (errno=%d)\n", rc);
-                goto out;
-        }
-
-        /* clear SError bits including .X which blocks the port when set */
-        rc = sata_scr_write(link, SCR_ERROR, 0xffffffff);
-        if (rc) {
-                ata_link_printk(link, KERN_ERR, "failed to clear SError "
-                                "during hardreset (errno=%d)\n", rc);
-                goto out;
-        }
+        rc = sata_std_hardreset(link, class, deadline);
 
-        /* if device is present, follow up with srst to wait for !BSY */
-        if (online)
-                rc = -EAGAIN;
- out:
         /* if SCR isn't accessible, we need to reset the PMP */
         if (rc && rc != -EAGAIN && sata_scr_read(link, SCR_STATUS, &tmp))
                 rc = -ERESTART;
@@ -274,34 +211,6 @@ int sata_pmp_std_hardreset(struct ata_link *link, unsigned int *class,
 }
 
 /**
- *      ata_std_postreset - standard postreset method for PMP link
- *      @link: the target ata_link
- *      @classes: classes of attached devices
- *
- *      This function is invoked after a successful reset.  Note that
- *      the device might have been reset more than once using
- *      different reset methods before postreset is invoked.
- *
- *      LOCKING:
- *      Kernel thread context (may sleep)
- */
-void sata_pmp_std_postreset(struct ata_link *link, unsigned int *class)
-{
-        u32 serror;
-
-        DPRINTK("ENTER\n");
-
-        /* clear SError */
-        if (sata_scr_read(link, SCR_ERROR, &serror) == 0)
-                sata_scr_write(link, SCR_ERROR, serror);
-
-        /* print link status */
-        sata_print_link_status(link);
-
-        DPRINTK("EXIT\n");
-}
-
-/**
  *      sata_pmp_read_gscr - read GSCR block of SATA PMP
  *      @dev: PMP device
  *      @gscr: buffer to read GSCR block into
diff --git a/include/linux/libata.h b/include/linux/libata.h
index c060cd3cba66..b9188371b12a 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -1025,10 +1025,8 @@ static inline int ata_acpi_cbl_80wire(struct ata_port *ap,
  * PMP - drivers/ata/libata-pmp.c
  */
 extern int sata_pmp_qc_defer_cmd_switch(struct ata_queued_cmd *qc);
-extern int sata_pmp_std_prereset(struct ata_link *link, unsigned long deadline);
 extern int sata_pmp_std_hardreset(struct ata_link *link, unsigned int *class,
                                   unsigned long deadline);
-extern void sata_pmp_std_postreset(struct ata_link *link, unsigned int *class);
 extern void sata_pmp_error_handler(struct ata_port *ap);
 
 /*