1 files changed, 112 insertions, 156 deletions

diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index 30b6921f094f..bbae30ceb8fb 100644
--- a/drivers/dma/amba-pl08x.c
+++ b/drivers/dma/amba-pl08x.c
@@ -210,8 +210,6 @@ enum pl08x_dma_chan_state {
  * struct pl08x_dma_chan - this structure wraps a DMA ENGINE channel
  * @chan: wrappped abstract channel
  * @phychan: the physical channel utilized by this channel, if there is one
- * @phychan_hold: if non-zero, hold on to the physical channel even if we
- * have no pending entries
  * @tasklet: tasklet scheduled by the IRQ to handle actual work etc
  * @name: name of channel
  * @cd: channel platform data
@@ -230,7 +228,6 @@ enum pl08x_dma_chan_state {
 struct pl08x_dma_chan {
         struct dma_chan chan;
         struct pl08x_phy_chan *phychan;
-        int phychan_hold;
         struct tasklet_struct tasklet;
         const char *name;
         const struct pl08x_channel_data *cd;
@@ -587,19 +584,111 @@ pl08x_get_phy_channel(struct pl08x_driver_data *pl08x,
         return ch;
 }
 
+/* Mark the physical channel as free.  Note, this write is atomic. */
 static inline void pl08x_put_phy_channel(struct pl08x_driver_data *pl08x,
                                          struct pl08x_phy_chan *ch)
 {
-        unsigned long flags;
+        ch->serving = NULL;
+}
 
-        spin_lock_irqsave(&ch->lock, flags);
+/*
+ * Try to allocate a physical channel.  When successful, assign it to
+ * this virtual channel, and initiate the next descriptor.  The
+ * virtual channel lock must be held at this point.
+ */
+static void pl08x_phy_alloc_and_start(struct pl08x_dma_chan *plchan)
+{
+        struct pl08x_driver_data *pl08x = plchan->host;
+        struct pl08x_phy_chan *ch;
 
-        /* Stop the channel and clear its interrupts */
-        pl08x_terminate_phy_chan(pl08x, ch);
+        ch = pl08x_get_phy_channel(pl08x, plchan);
+        if (!ch) {
+                dev_dbg(&pl08x->adev->dev, "no physical channel available for xfer on %s\n", plchan->name);
+                plchan->state = PL08X_CHAN_WAITING;
+                return;
+        }
 
-        /* Mark it as free */
-        ch->serving = NULL;
-        spin_unlock_irqrestore(&ch->lock, flags);
+        dev_dbg(&pl08x->adev->dev, "allocated physical channel %d for xfer on %s\n",
+                ch->id, plchan->name);
+
+        plchan->phychan = ch;
+        plchan->state = PL08X_CHAN_RUNNING;
+        pl08x_start_next_txd(plchan);
+}
+
+static void pl08x_phy_reassign_start(struct pl08x_phy_chan *ch,
+        struct pl08x_dma_chan *plchan)
+{
+        struct pl08x_driver_data *pl08x = plchan->host;
+
+        dev_dbg(&pl08x->adev->dev, "reassigned physical channel %d for xfer on %s\n",
+                ch->id, plchan->name);
+
+        /*
+         * We do this without taking the lock; we're really only concerned
+         * about whether this pointer is NULL or not, and we're guaranteed
+         * that this will only be called when it _already_ is non-NULL.
+         */
+        ch->serving = plchan;
+        plchan->phychan = ch;
+        plchan->state = PL08X_CHAN_RUNNING;
+        pl08x_start_next_txd(plchan);
+}
+
+/*
+ * Free a physical DMA channel, potentially reallocating it to another
+ * virtual channel if we have any pending.
+ */
+static void pl08x_phy_free(struct pl08x_dma_chan *plchan)
+{
+        struct pl08x_driver_data *pl08x = plchan->host;
+        struct pl08x_dma_chan *p, *next;
+
+ retry:
+        next = NULL;
+
+        /* Find a waiting virtual channel for the next transfer. */
+        list_for_each_entry(p, &pl08x->memcpy.channels, chan.device_node)
+                if (p->state == PL08X_CHAN_WAITING) {
+                        next = p;
+                        break;
+                }
+
+        if (!next) {
+                list_for_each_entry(p, &pl08x->slave.channels, chan.device_node)
+                        if (p->state == PL08X_CHAN_WAITING) {
+                                next = p;
+                                break;
+                        }
+        }
+
+        /* Ensure that the physical channel is stopped */
+        pl08x_terminate_phy_chan(pl08x, plchan->phychan);
+
+        if (next) {
+                bool success;
+
+                /*
+                 * Eww.  We know this isn't going to deadlock
+                 * but lockdep probably doesn't.
+                 */
+                spin_lock(&next->lock);
+                /* Re-check the state now that we have the lock */
+                success = next->state == PL08X_CHAN_WAITING;
+                if (success)
+                        pl08x_phy_reassign_start(plchan->phychan, next);
+                spin_unlock(&next->lock);
+
+                /* If the state changed, try to find another channel */
+                if (!success)
+                        goto retry;
+        } else {
+                /* No more jobs, so free up the physical channel */
+                pl08x_put_phy_channel(pl08x, plchan->phychan);
+        }
+
+        plchan->phychan = NULL;
+        plchan->state = PL08X_CHAN_IDLE;
 }
 
 /*
@@ -1028,45 +1117,6 @@ static void pl08x_free_chan_resources(struct dma_chan *chan)
 {
 }
 
-/*
- * This should be called with the channel plchan->lock held
- */
-static int prep_phy_channel(struct pl08x_dma_chan *plchan)
-{
-        struct pl08x_driver_data *pl08x = plchan->host;
-        struct pl08x_phy_chan *ch;
-
-        /* Check if we already have a channel */
-        if (plchan->phychan) {
-                ch = plchan->phychan;
-                goto got_channel;
-        }
-
-        ch = pl08x_get_phy_channel(pl08x, plchan);
-        if (!ch) {
-                /* No physical channel available, cope with it */
-                dev_dbg(&pl08x->adev->dev, "no physical channel available for xfer on %s\n", plchan->name);
-                return -EBUSY;
-        }
-
-        plchan->phychan = ch;
-        dev_dbg(&pl08x->adev->dev, "allocated physical channel %d for xfer on %s\n",
-                 ch->id, plchan->name);
-
-got_channel:
-        plchan->phychan_hold++;
-
-        return 0;
-}
-
-static void release_phy_channel(struct pl08x_dma_chan *plchan)
-{
-        struct pl08x_driver_data *pl08x = plchan->host;
-
-        pl08x_put_phy_channel(pl08x, plchan->phychan);
-        plchan->phychan = NULL;
-}
-
 static dma_cookie_t pl08x_tx_submit(struct dma_async_tx_descriptor *tx)
 {
         struct pl08x_dma_chan *plchan = to_pl08x_chan(tx->chan);
@@ -1079,19 +1129,6 @@ static dma_cookie_t pl08x_tx_submit(struct dma_async_tx_descriptor *tx)
 
         /* Put this onto the pending list */
         list_add_tail(&txd->node, &plchan->pend_list);
-
-        /*
-         * If there was no physical channel available for this memcpy,
-         * stack the request up and indicate that the channel is waiting
-         * for a free physical channel.
-         */
-        if (!plchan->slave && !plchan->phychan) {
-                /* Do this memcpy whenever there is a channel ready */
-                plchan->state = PL08X_CHAN_WAITING;
-        } else {
-                plchan->phychan_hold--;
-        }
-
         spin_unlock_irqrestore(&plchan->lock, flags);
 
         return cookie;
@@ -1282,19 +1319,10 @@ static void pl08x_issue_pending(struct dma_chan *chan)
 
         spin_lock_irqsave(&plchan->lock, flags);
         list_splice_tail_init(&plchan->pend_list, &plchan->issued_list);
-
-        /* Something is already active, or we're waiting for a channel... */
-        if (plchan->at || plchan->state == PL08X_CHAN_WAITING) {
-                spin_unlock_irqrestore(&plchan->lock, flags);
-                return;
-        }
-
-        /* Take the first element in the queue and execute it */
         if (!list_empty(&plchan->issued_list)) {
-                plchan->state = PL08X_CHAN_RUNNING;
-                pl08x_start_next_txd(plchan);
+                if (!plchan->phychan && plchan->state != PL08X_CHAN_WAITING)
+                        pl08x_phy_alloc_and_start(plchan);
         }
-
         spin_unlock_irqrestore(&plchan->lock, flags);
 }
 
@@ -1302,48 +1330,18 @@ static int pl08x_prep_channel_resources(struct pl08x_dma_chan *plchan,
                                         struct pl08x_txd *txd)
 {
         struct pl08x_driver_data *pl08x = plchan->host;
-        unsigned long flags;
-        int num_llis, ret;
+        int num_llis;
 
         num_llis = pl08x_fill_llis_for_desc(pl08x, txd);
         if (!num_llis) {
+                unsigned long flags;
+
                 spin_lock_irqsave(&plchan->lock, flags);
                 pl08x_free_txd(pl08x, txd);
                 spin_unlock_irqrestore(&plchan->lock, flags);
+
                 return -EINVAL;
         }
-
-        spin_lock_irqsave(&plchan->lock, flags);
-
-        /*
-         * See if we already have a physical channel allocated,
-         * else this is the time to try to get one.
-         */
-        ret = prep_phy_channel(plchan);
-        if (ret) {
-                /*
-                 * No physical channel was available.
-                 *
-                 * memcpy transfers can be sorted out at submission time.
-                 */
-                if (plchan->slave) {
-                        pl08x_free_txd_list(pl08x, plchan);
-                        pl08x_free_txd(pl08x, txd);
-                        spin_unlock_irqrestore(&plchan->lock, flags);
-                        return -EBUSY;
-                }
-        } else
-                /*
-                 * Else we're all set, paused and ready to roll, status
-                 * will switch to PL08X_CHAN_RUNNING when we call
-                 * issue_pending(). If there is something running on the
-                 * channel already we don't change its state.
-                 */
-                if (plchan->state == PL08X_CHAN_IDLE)
-                        plchan->state = PL08X_CHAN_PAUSED;
-
-        spin_unlock_irqrestore(&plchan->lock, flags);
-
         return 0;
 }
 
@@ -1563,14 +1561,11 @@ static int pl08x_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
                 plchan->state = PL08X_CHAN_IDLE;
 
                 if (plchan->phychan) {
-                        pl08x_terminate_phy_chan(pl08x, plchan->phychan);
-
                         /*
                          * Mark physical channel as free and free any slave
                          * signal
                          */
-                        release_phy_channel(plchan);
-                        plchan->phychan_hold = 0;
+                        pl08x_phy_free(plchan);
                 }
                 /* Dequeue jobs and free LLIs */
                 if (plchan->at) {
@@ -1670,50 +1665,6 @@ static void pl08x_tasklet(unsigned long data)
 
         spin_lock_irqsave(&plchan->lock, flags);
         list_splice_tail_init(&plchan->done_list, &head);
-
-        if (plchan->at || !list_empty(&plchan->pend_list) || plchan->phychan_hold) {
-                /*
-                 * This channel is still in use - we have a new txd being
-                 * prepared and will soon be queued.  Don't give up the
-                 * physical channel.
-                 */
-        } else {
-                struct pl08x_dma_chan *waiting = NULL;
-
-                /*
-                 * No more jobs, so free up the physical channel
-                 */
-                release_phy_channel(plchan);
-                plchan->state = PL08X_CHAN_IDLE;
-
-                /*
-                 * And NOW before anyone else can grab that free:d up
-                 * physical channel, see if there is some memcpy pending
-                 * that seriously needs to start because of being stacked
-                 * up while we were choking the physical channels with data.
-                 */
-                list_for_each_entry(waiting, &pl08x->memcpy.channels,
-                                    chan.device_node) {
-                        if (waiting->state == PL08X_CHAN_WAITING) {
-                                int ret;
-
-                                /* This should REALLY not fail now */
-                                ret = prep_phy_channel(waiting);
-                                BUG_ON(ret);
-                                waiting->phychan_hold--;
-                                waiting->state = PL08X_CHAN_RUNNING;
-                                /*
-                                 * Eww.  We know this isn't going to deadlock
-                                 * but lockdep probably doens't.
-                                 */
-                                spin_lock(&waiting->lock);
-                                pl08x_start_next_txd(waiting);
-                                spin_unlock(&waiting->lock);
-                                break;
-                        }
-                }
-        }
-
         spin_unlock_irqrestore(&plchan->lock, flags);
 
         while (!list_empty(&head)) {
@@ -1784,9 +1735,14 @@ static irqreturn_t pl08x_irq(int irq, void *dev)
                                 dma_cookie_complete(&tx->tx);
                                 list_add_tail(&tx->node, &plchan->done_list);
 
-                                /* And start the next descriptor */
+                                /*
+                                 * And start the next descriptor (if any),
+                                 * otherwise free this channel.
+                                 */
                                 if (!list_empty(&plchan->issued_list))
                                         pl08x_start_next_txd(plchan);
+                                else
+                                        pl08x_phy_free(plchan);
                         }
                         spin_unlock(&plchan->lock);