[PATCH] libata-eh-fw: implement freeze/thaw

Freezing is performed atomic w.r.t. host_set->lock and once frozen
LLDD is not allowed to access the port or any qc on it.  Also, libata
makes sure that no new qc gets issued to a frozen port.

A frozen port is thawed after a reset operation completes
successfully, so reset methods must do its job while the port is
frozen.  During initialization all ports get frozen before requesting
IRQ, so reset methods are always invoked on a frozen port.

Optional ->freeze and ->thaw operations notify LLDD that the port is
being frozen and thawed, respectively.  LLDD can disable/enable
hardware interrupt in these callbacks if the controller's IRQ mask can
be changed dynamically.  If the controller doesn't allow such
operation, LLDD can check for frozen state in the interrupt handler
and ack/clear interrupts unconditionally while frozen.

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

1 files changed, 24 insertions, 2 deletions

diff --git a/drivers/scsi/libata-core.c b/drivers/scsi/libata-core.c
index 9c97783462d6..63857a90ac28 100644
--- a/drivers/scsi/libata-core.c
+++ b/drivers/scsi/libata-core.c
@@ -987,6 +987,12 @@ unsigned ata_exec_internal(struct ata_device *dev,
 
         spin_lock_irqsave(&ap->host_set->lock, flags);
 
+        /* no internal command while frozen */
+        if (ap->flags & ATA_FLAG_FROZEN) {
+                spin_unlock_irqrestore(&ap->host_set->lock, flags);
+                return AC_ERR_SYSTEM;
+        }
+
         /* initialize internal qc */
 
         /* XXX: Tag 0 is used for drivers with legacy EH as some
@@ -2565,8 +2571,11 @@ void ata_std_postreset(struct ata_port *ap, unsigned int *classes)
                 sata_scr_write(ap, SCR_ERROR, serror);
 
         /* re-enable interrupts */
-        if (ap->ioaddr.ctl_addr)        /* FIXME: hack. create a hook instead */
-                ata_irq_on(ap);
+        if (!ap->ops->error_handler) {
+                /* FIXME: hack. create a hook instead */
+                if (ap->ioaddr.ctl_addr)
+                        ata_irq_on(ap);
+        }
 
         /* is double-select really necessary? */
         if (classes[0] != ATA_DEV_NONE)
@@ -2681,6 +2690,8 @@ int ata_drive_probe_reset(struct ata_port *ap, ata_probeinit_fn_t probeinit,
 {
         int rc = -EINVAL;
 
+        ata_eh_freeze_port(ap);
+
         if (probeinit)
                 probeinit(ap);
 
@@ -2725,6 +2736,9 @@ int ata_drive_probe_reset(struct ata_port *ap, ata_probeinit_fn_t probeinit,
         if (rc == 0) {
                 if (postreset)
                         postreset(ap, classes);
+
+                ata_eh_thaw_port(ap);
+
                 if (classes[0] == ATA_DEV_UNKNOWN)
                         rc = -ENODEV;
         }
@@ -4039,6 +4053,10 @@ static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
         struct ata_queued_cmd *qc = NULL;
         unsigned int i;
 
+        /* no command while frozen */
+        if (unlikely(ap->flags & ATA_FLAG_FROZEN))
+                return NULL;
+
         /* the last tag is reserved for internal command. */
         for (i = 0; i < ATA_MAX_QUEUE - 1; i++)
                 if (!test_and_set_bit(i, &ap->qactive)) {
@@ -4953,6 +4971,7 @@ int ata_device_add(const struct ata_probe_ent *ent)
 
                 ata_chk_status(ap);
                 host_set->ops->irq_clear(ap);
+                ata_eh_freeze_port(ap); /* freeze port before requesting IRQ */
                 count++;
         }
 
@@ -5385,5 +5404,8 @@ EXPORT_SYMBOL_GPL(ata_scsi_device_resume);
 EXPORT_SYMBOL_GPL(ata_eng_timeout);
 EXPORT_SYMBOL_GPL(ata_port_schedule_eh);
 EXPORT_SYMBOL_GPL(ata_port_abort);
+EXPORT_SYMBOL_GPL(ata_port_freeze);
+EXPORT_SYMBOL_GPL(ata_eh_freeze_port);
+EXPORT_SYMBOL_GPL(ata_eh_thaw_port);
 EXPORT_SYMBOL_GPL(ata_eh_qc_complete);
 EXPORT_SYMBOL_GPL(ata_eh_qc_retry);