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>

diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
index 4ce793c..8f37182 100644 (file)
--- 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;
 }

diff --git a/include/linux/ide.h b/include/linux/ide.h
index 8b74ccd..00df155 100644 (file)
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -828,6 +828,7 @@ typedef struct hwif_s {
 
        unsigned        present    : 1; /* this interface exists */
        unsigned        sg_mapped  : 1; /* sg_table and sg_nents are ready */
+       unsigned        busy       : 1; /* serializes devices on a port */
 
        struct device           gendev;
        struct device           *portdev;
@@ -851,8 +852,13 @@ struct ide_host {
        unsigned long   host_flags;
        void            *host_priv;
        ide_hwif_t      *cur_port;      /* for hosts requiring serialization */
+
+       /* used for hosts requiring serialization */
+       volatile long   host_busy;
 };
 
+#define IDE_HOST_BUSY 0
+
 /*
  *  internal ide interrupt handler type
  */
@@ -866,8 +872,6 @@ typedef struct hwgroup_s {
                /* irq handler, if active */
        ide_startstop_t (*handler)(ide_drive_t *);
 
-               /* BOOL: protects all fields below */
-       volatile int busy;
                /* BOOL: polling active & poll_timeout field valid */
        unsigned int polling    : 1;
 
@@ -1271,26 +1275,6 @@ extern void ide_stall_queue(ide_drive_t *drive, unsigned long timeout);
 
 extern void ide_timer_expiry(unsigned long);
 extern irqreturn_t ide_intr(int irq, void *dev_id);
-
-static inline int ide_lock_hwgroup(ide_hwgroup_t *hwgroup, ide_hwif_t *hwif)
-{
-       if (hwgroup->busy)
-               return 1;
-
-       hwgroup->busy = 1;
-       /* for atari only */
-       ide_get_lock(ide_intr, hwif);
-
-       return 0;
-}
-
-static inline void ide_unlock_hwgroup(ide_hwgroup_t *hwgroup)
-{
-       /* for atari only */
-       ide_release_lock();
-       hwgroup->busy = 0;
-}
-
 extern void do_ide_request(struct request_queue *);
 
 void ide_init_disk(struct gendisk *, ide_drive_t *);
@@ -1617,13 +1601,6 @@ static inline void ide_set_max_pio(ide_drive_t *drive)
 
 extern spinlock_t ide_lock;
 extern struct mutex ide_cfg_mtx;
-/*
- * Structure locking:
- *
- * ide_hwgroup_t->busy: hwgroup->lock
- * ide_hwif_t->{hwgroup,mate}: constant, no locking
- * ide_drive_t->hwif: constant, no locking
- */
 
 #define local_irq_set(flags)   do { local_save_flags((flags)); local_irq_enable_in_hardirq(); } while (0)