[PATCH] dma: shdma: transfer based runtime PM

[Guennadi Liakhovetski]

Currently the shdma dmaengine driver uses runtime PM to save power, when
no channel on the specific controller is requested by a user. This patch
switches the driver to count individual DMA transfers. That way the
controller can be powered down between transfers, even if some of its
channels are in use.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
---

tested on mackerel (sh7372) with dmatest, sh_mobile_sdhi and sh_mmcif with 
runtime PM and STR.

 drivers/dma/shdma.c |   94 +++++++++++++++++++++++++++++++++++++--------------
 drivers/dma/shdma.h |    7 ++++
 2 files changed, 75 insertions(+), 26 deletions(-)

diff --git a/drivers/dma/shdma.c b/drivers/dma/shdma.c
index e7bb747..81809c2 100644
--- a/drivers/dma/shdma.c
+++ b/drivers/dma/shdma.c
@@ -259,15 +259,23 @@ static int dmae_set_dmars(struct sh_dmae_chan *sh_chan, u16 val)
 	return 0;
 }
 
+static void sh_chan_xfer_ld_queue(struct sh_dmae_chan *sh_chan);
+
 static dma_cookie_t sh_dmae_tx_submit(struct dma_async_tx_descriptor *tx)
 {
 	struct sh_desc *desc = tx_to_sh_desc(tx), *chunk, *last = desc, *c;
 	struct sh_dmae_chan *sh_chan = to_sh_chan(tx->chan);
+	struct sh_dmae_slave *param = tx->chan->private;
 	dma_async_tx_callback callback = tx->callback;
 	dma_cookie_t cookie;
-	unsigned long flags;
+	bool power_up;
 
-	spin_lock_irqsave(&sh_chan->desc_lock, flags);
+	spin_lock_irq(&sh_chan->desc_lock);
+
+	if (list_empty(&sh_chan->ld_queue))
+		power_up = true;
+	else
+		power_up = false;
 
 	cookie = sh_chan->common.cookie;
 	cookie++;
@@ -303,7 +311,38 @@ static dma_cookie_t sh_dmae_tx_submit(struct dma_async_tx_descriptor *tx)
 		tx->cookie, &last->async_tx, sh_chan->id,
 		desc->hw.sar, desc->hw.tcr, desc->hw.dar);
 
-	spin_unlock_irqrestore(&sh_chan->desc_lock, flags);
+	if (power_up) {
+		sh_chan->pm_state = DMAE_PM_BUSY;
+
+		pm_runtime_get(sh_chan->dev);
+
+		spin_unlock_irq(&sh_chan->desc_lock);
+
+		pm_runtime_barrier(sh_chan->dev);
+
+		spin_lock_irq(&sh_chan->desc_lock);
+
+		/* Have we been reset, while waiting? */
+		if (sh_chan->pm_state != DMAE_PM_ESTABLISHED) {
+			dev_dbg(sh_chan->dev, "Bring up channel %d\n",
+				sh_chan->id);
+			if (param) {
+				const struct sh_dmae_slave_config *cfg =
+					param->config;
+
+				dmae_set_dmars(sh_chan, cfg->mid_rid);
+				dmae_set_chcr(sh_chan, cfg->chcr);
+			} else {
+				dmae_init(sh_chan);
+			}
+
+			if (sh_chan->pm_state == DMAE_PM_PENDING)
+				sh_chan_xfer_ld_queue(sh_chan);
+			sh_chan->pm_state = DMAE_PM_ESTABLISHED;
+		}
+	}
+
+	spin_unlock_irq(&sh_chan->desc_lock);
 
 	return cookie;
 }
@@ -347,8 +386,6 @@ static int sh_dmae_alloc_chan_resources(struct dma_chan *chan)
 	struct sh_dmae_slave *param = chan->private;
 	int ret;
 
-	pm_runtime_get_sync(sh_chan->dev);
-
 	/*
 	 * This relies on the guarantee from dmaengine that alloc_chan_resources
 	 * never runs concurrently with itself or free_chan_resources.
@@ -368,11 +405,6 @@ static int sh_dmae_alloc_chan_resources(struct dma_chan *chan)
 		}
 
 		param->config = cfg;
-
-		dmae_set_dmars(sh_chan, cfg->mid_rid);
-		dmae_set_chcr(sh_chan, cfg->chcr);
-	} else {
-		dmae_init(sh_chan);
 	}
 
 	while (sh_chan->descs_allocated < NR_DESCS_PER_CHANNEL) {
@@ -401,7 +433,6 @@ edescalloc:
 etestused:
 efindslave:
 	chan->private = NULL;
-	pm_runtime_put(sh_chan->dev);
 	return ret;
 }
 
@@ -413,7 +444,6 @@ static void sh_dmae_free_chan_resources(struct dma_chan *chan)
 	struct sh_dmae_chan *sh_chan = to_sh_chan(chan);
 	struct sh_desc *desc, *_desc;
 	LIST_HEAD(list);
-	int descs = sh_chan->descs_allocated;
 
 	/* Protect against ISR */
 	spin_lock_irq(&sh_chan->desc_lock);
@@ -440,9 +470,6 @@ static void sh_dmae_free_chan_resources(struct dma_chan *chan)
 
 	spin_unlock_irq(&sh_chan->desc_lock);
 
-	if (descs > 0)
-		pm_runtime_put(sh_chan->dev);
-
 	list_for_each_entry_safe(desc, _desc, &list, node)
 		kfree(desc);
 }
@@ -676,7 +703,6 @@ static int sh_dmae_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
 						  struct sh_desc, node);
 		desc->partial = (desc->hw.tcr - sh_dmae_readl(sh_chan, TCR)) <<
 			sh_chan->xmit_shift;
-
 	}
 	spin_unlock_irqrestore(&sh_chan->desc_lock, flags);
 
@@ -761,7 +787,13 @@ static dma_async_tx_callback __ld_cleanup(struct sh_dmae_chan *sh_chan, bool all
 		     async_tx_test_ack(&desc->async_tx)) || all) {
 			/* Remove from ld_queue list */
 			desc->mark = DESC_IDLE;
+
 			list_move(&desc->node, &sh_chan->ld_free);
+
+			if (list_empty(&sh_chan->ld_queue)) {
+				dev_dbg(sh_chan->dev, "Bring down channel %d\n", sh_chan->id);
+				pm_runtime_put(sh_chan->dev);
+			}
 		}
 	}
 
@@ -791,16 +823,14 @@ static void sh_dmae_chan_ld_cleanup(struct sh_dmae_chan *sh_chan, bool all)
 		;
 }
 
+/* Called under spin_lock_irq(&sh_chan->desc_lock) */
 static void sh_chan_xfer_ld_queue(struct sh_dmae_chan *sh_chan)
 {
 	struct sh_desc *desc;
 
-	spin_lock_irq(&sh_chan->desc_lock);
 	/* DMA work check */
-	if (dmae_is_busy(sh_chan)) {
-		spin_unlock_irq(&sh_chan->desc_lock);
+	if (dmae_is_busy(sh_chan))
 		return;
-	}
 
 	/* Find the first not transferred descriptor */
 	list_for_each_entry(desc, &sh_chan->ld_queue, node)
@@ -813,14 +843,18 @@ static void sh_chan_xfer_ld_queue(struct sh_dmae_chan *sh_chan)
 			dmae_start(sh_chan);
 			break;
 		}
-
-	spin_unlock_irq(&sh_chan->desc_lock);
 }
 
 static void sh_dmae_memcpy_issue_pending(struct dma_chan *chan)
 {
 	struct sh_dmae_chan *sh_chan = to_sh_chan(chan);
-	sh_chan_xfer_ld_queue(sh_chan);
+
+	spin_lock_irq(&sh_chan->desc_lock);
+	if (sh_chan->pm_state == DMAE_PM_ESTABLISHED)
+		sh_chan_xfer_ld_queue(sh_chan);
+	else
+		sh_chan->pm_state = DMAE_PM_PENDING;
+	spin_unlock_irq(&sh_chan->desc_lock);
 }
 
 static enum dma_status sh_dmae_tx_status(struct dma_chan *chan,
@@ -913,6 +947,12 @@ static bool sh_dmae_reset(struct sh_dmae_device *shdev)
 
 		list_splice_init(&sh_chan->ld_queue, &dl);
 
+		if (!list_empty(&dl)) {
+			dev_dbg(sh_chan->dev, "Bring down channel %d\n", sh_chan->id);
+			pm_runtime_put(sh_chan->dev);
+		}
+		sh_chan->pm_state = DMAE_PM_ESTABLISHED;
+
 		spin_unlock(&sh_chan->desc_lock);
 
 		/* Complete all  */
@@ -966,10 +1006,10 @@ static void dmae_do_tasklet(unsigned long data)
 			break;
 		}
 	}
-	spin_unlock_irq(&sh_chan->desc_lock);
-
 	/* Next desc */
 	sh_chan_xfer_ld_queue(sh_chan);
+	spin_unlock_irq(&sh_chan->desc_lock);
+
 	sh_dmae_chan_ld_cleanup(sh_chan, false);
 }
 
@@ -1037,7 +1077,9 @@ static int __devinit sh_dmae_chan_probe(struct sh_dmae_device *shdev, int id,
 		return -ENOMEM;
 	}
 
-	/* copy struct dma_device */
+	new_sh_chan->pm_state = DMAE_PM_ESTABLISHED;
+
+	/* reference struct dma_device */
 	new_sh_chan->common.device = &shdev->common;
 
 	new_sh_chan->dev = shdev->common.dev;
diff --git a/drivers/dma/shdma.h b/drivers/dma/shdma.h
index dc56576..2b55a27 100644
--- a/drivers/dma/shdma.h
+++ b/drivers/dma/shdma.h
@@ -23,6 +23,12 @@
 
 struct device;
 
+enum dmae_pm_state {
+	DMAE_PM_ESTABLISHED,
+	DMAE_PM_BUSY,
+	DMAE_PM_PENDING,
+};
+
 struct sh_dmae_chan {
 	dma_cookie_t completed_cookie;	/* The maximum cookie completed */
 	spinlock_t desc_lock;		/* Descriptor operation lock */
@@ -38,6 +44,7 @@ struct sh_dmae_chan {
 	u32 __iomem *base;
 	char dev_id[16];		/* unique name per DMAC of channel */
 	int pm_error;
+	enum dmae_pm_state pm_state;
 };
 
 struct sh_dmae_device {
-- 
1.7.2.5

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