ide: use lock bitops for ports serialization (v2)

* Add ->host_busy field to struct ide_host and use it's first bit
  together with lock bitops to provide new ports serialization method.

* Convert core IDE code to use new ide_[un]lock_host() helpers.

  This removes the need for taking hwgroup->lock if host is already
  busy on serialized hosts and makes it possible to merge ide_hwgroup_t
  into ide_hwif_t (done in the later patch).

* Remove no longer needed ide_hwgroup_t.busy and ide_[un]lock_hwgroup().

* Update do_ide_request() documentation.

v2:
* ide_release_lock() should be called inside IDE_HFLAG_SERIALIZE check.

* Add ide_hwif_t.busy flag and ide_[un]lock_port() for serializing
  devices on a port.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

1 files changed, 63 insertions, 42 deletions

diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
index 4ce793c05629..8f371821c614 100644
--- a/drivers/ide/ide-io.c
+++ b/drivers/ide/ide-io.c
@@ -666,45 +666,54 @@ void ide_stall_queue (ide_drive_t *drive, unsigned long timeout)
 }
 EXPORT_SYMBOL(ide_stall_queue);
 
+static inline int ide_lock_port(ide_hwif_t *hwif)
+{
+        if (hwif->busy)
+                return 1;
+
+        hwif->busy = 1;
+
+        return 0;
+}
+
+static inline void ide_unlock_port(ide_hwif_t *hwif)
+{
+        hwif->busy = 0;
+}
+
+static inline int ide_lock_host(struct ide_host *host, ide_hwif_t *hwif)
+{
+        int rc = 0;
+
+        if (host->host_flags & IDE_HFLAG_SERIALIZE) {
+                rc = test_and_set_bit_lock(IDE_HOST_BUSY, &host->host_busy);
+                if (rc == 0) {
+                        /* for atari only */
+                        ide_get_lock(ide_intr, hwif);
+                }
+        }
+        return rc;
+}
+
+static inline void ide_unlock_host(struct ide_host *host)
+{
+        if (host->host_flags & IDE_HFLAG_SERIALIZE) {
+                /* for atari only */
+                ide_release_lock();
+                clear_bit_unlock(IDE_HOST_BUSY, &host->host_busy);
+        }
+}
+
 /*
  * Issue a new request to a drive from hwgroup
- *
- * A hwgroup is a serialized group of IDE interfaces.  Usually there is
- * exactly one hwif (interface) per hwgroup, but buggy controllers (eg. CMD640)
- * may have both interfaces in a single hwgroup to "serialize" access.
- * Or possibly multiple ISA interfaces can share a common IRQ by being grouped
- * together into one hwgroup for serialized access.
- *
- * Note also that several hwgroups can end up sharing a single IRQ,
- * possibly along with many other devices.  This is especially common in
- * PCI-based systems with off-board IDE controller cards.
- *
- * The IDE driver uses a per-hwgroup lock to protect the hwgroup->busy flag.
- *
- * The first thread into the driver for a particular hwgroup sets the
- * hwgroup->busy flag to indicate that this hwgroup is now active,
- * and then initiates processing of the top request from the request queue.
- *
- * Other threads attempting entry notice the busy setting, and will simply
- * queue their new requests and exit immediately.  Note that hwgroup->busy
- * remains set even when the driver is merely awaiting the next interrupt.
- * Thus, the meaning is "this hwgroup is busy processing a request".
- *
- * When processing of a request completes, the completing thread or IRQ-handler
- * will start the next request from the queue.  If no more work remains,
- * the driver will clear the hwgroup->busy flag and exit.
- *
- * The per-hwgroup spinlock is used to protect all access to the
- * hwgroup->busy flag, but is otherwise not needed for most processing in
- * the driver.  This makes the driver much more friendlier to shared IRQs
- * than previous designs, while remaining 100% (?) SMP safe and capable.
  */
 void do_ide_request(struct request_queue *q)
 {
         ide_drive_t     *drive = q->queuedata;
         ide_hwif_t      *hwif = drive->hwif;
+        struct ide_host *host = hwif->host;
         ide_hwgroup_t   *hwgroup = hwif->hwgroup;
-        struct request  *rq;
+        struct request  *rq = NULL;
         ide_startstop_t startstop;
 
         /*
@@ -721,9 +730,13 @@ void do_ide_request(struct request_queue *q)
                 blk_remove_plug(q);
 
         spin_unlock_irq(q->queue_lock);
+
+        if (ide_lock_host(host, hwif))
+                goto plug_device_2;
+
         spin_lock_irq(&hwgroup->lock);
 
-        if (!ide_lock_hwgroup(hwgroup, hwif)) {
+        if (!ide_lock_port(hwif)) {
                 ide_hwif_t *prev_port;
 repeat:
                 prev_port = hwif->host->cur_port;
@@ -731,7 +744,7 @@ repeat:
 
                 if (drive->dev_flags & IDE_DFLAG_SLEEPING) {
                         if (time_before(drive->sleep, jiffies)) {
-                                ide_unlock_hwgroup(hwgroup);
+                                ide_unlock_port(hwif);
                                 goto plug_device;
                         }
                 }
@@ -761,7 +774,7 @@ repeat:
                 spin_lock_irq(&hwgroup->lock);
 
                 if (!rq) {
-                        ide_unlock_hwgroup(hwgroup);
+                        ide_unlock_port(hwif);
                         goto out;
                 }
 
@@ -782,7 +795,7 @@ repeat:
                     blk_pm_request(rq) == 0 &&
                     (rq->cmd_flags & REQ_PREEMPT) == 0) {
                         /* there should be no pending command at this point */
-                        ide_unlock_hwgroup(hwgroup);
+                        ide_unlock_port(hwif);
                         goto plug_device;
                 }
 
@@ -798,11 +811,15 @@ repeat:
                 goto plug_device;
 out:
         spin_unlock_irq(&hwgroup->lock);
+        if (rq == NULL)
+                ide_unlock_host(host);
         spin_lock_irq(q->queue_lock);
         return;
 
 plug_device:
         spin_unlock_irq(&hwgroup->lock);
+        ide_unlock_host(host);
+plug_device_2:
         spin_lock_irq(q->queue_lock);
 
         if (!elv_queue_empty(q))
@@ -844,9 +861,9 @@ static ide_startstop_t ide_dma_timeout_retry(ide_drive_t *drive, int error)
         ide_dma_off_quietly(drive);
 
         /*
-         * un-busy drive etc (hwgroup->busy is cleared on return) and
-         * make sure request is sane
+         * un-busy drive etc and make sure request is sane
          */
+
         rq = HWGROUP(drive)->rq;
 
         if (!rq)
@@ -895,6 +912,7 @@ static void ide_plug_device(ide_drive_t *drive)
 void ide_timer_expiry (unsigned long data)
 {
         ide_hwgroup_t   *hwgroup = (ide_hwgroup_t *) data;
+        ide_hwif_t      *uninitialized_var(hwif);
         ide_drive_t     *uninitialized_var(drive);
         ide_handler_t   *handler;
         ide_expiry_t    *expiry;
@@ -918,7 +936,6 @@ void ide_timer_expiry (unsigned long data)
                         printk(KERN_ERR "%s: ->cur_dev was NULL\n", __func__);
                         hwgroup->handler = NULL;
                 } else {
-                        ide_hwif_t *hwif;
                         ide_startstop_t startstop = ide_stopped;
 
                         if ((expiry = hwgroup->expiry) != NULL) {
@@ -964,15 +981,17 @@ void ide_timer_expiry (unsigned long data)
                         spin_lock_irq(&hwgroup->lock);
                         enable_irq(hwif->irq);
                         if (startstop == ide_stopped) {
-                                ide_unlock_hwgroup(hwgroup);
+                                ide_unlock_port(hwif);
                                 plug_device = 1;
                         }
                 }
         }
         spin_unlock_irqrestore(&hwgroup->lock, flags);
 
-        if (plug_device)
+        if (plug_device) {
+                ide_unlock_host(hwif->host);
                 ide_plug_device(drive);
+        }
 }
 
 /**
@@ -1150,7 +1169,7 @@ irqreturn_t ide_intr (int irq, void *dev_id)
          */
         if (startstop == ide_stopped) {
                 if (hwgroup->handler == NULL) { /* paranoia */
-                        ide_unlock_hwgroup(hwgroup);
+                        ide_unlock_port(hwif);
                         plug_device = 1;
                 } else
                         printk(KERN_ERR "%s: %s: huh? expected NULL handler "
@@ -1161,8 +1180,10 @@ out_handled:
 out:
         spin_unlock_irqrestore(&hwgroup->lock, flags);
 out_early:
-        if (plug_device)
+        if (plug_device) {
+                ide_unlock_host(hwif->host);
                 ide_plug_device(drive);
+        }
 
         return irq_ret;
 }