1 files changed, 112 insertions, 156 deletions

diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index 30b6921..bbae30c 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);