1 files changed, 25 insertions, 45 deletions

diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
index 1a44c8086d77..ae10f5614f95 100644
--- a/drivers/dma/bcm2835-dma.c
+++ b/drivers/dma/bcm2835-dma.c
@@ -406,38 +406,32 @@ static void bcm2835_dma_fill_cb_chain_with_sg(
 	}
 }
 
-static int bcm2835_dma_abort(void __iomem *chan_base)
+static int bcm2835_dma_abort(struct bcm2835_chan *c)
 {
-	unsigned long cs;
+	void __iomem *chan_base = c->chan_base;
 	long int timeout = 10000;
 
-	cs = readl(chan_base + BCM2835_DMA_CS);
-	if (!(cs & BCM2835_DMA_ACTIVE))
+	/*
+	 * A zero control block address means the channel is idle.
+	 * (The ACTIVE flag in the CS register is not a reliable indicator.)
+	 */
+	if (!readl(chan_base + BCM2835_DMA_ADDR))
 		return 0;
 
 	/* Write 0 to the active bit - Pause the DMA */
 	writel(0, chan_base + BCM2835_DMA_CS);
 
 	/* Wait for any current AXI transfer to complete */
-	while ((cs & BCM2835_DMA_ISPAUSED) && --timeout) {
+	while ((readl(chan_base + BCM2835_DMA_CS) &
+		BCM2835_DMA_WAITING_FOR_WRITES) && --timeout)
 		cpu_relax();
-		cs = readl(chan_base + BCM2835_DMA_CS);
-	}
 
-	/* We'll un-pause when we set of our next DMA */
+	/* Peripheral might be stuck and fail to signal AXI write responses */
 	if (!timeout)
-		return -ETIMEDOUT;
-
-	if (!(cs & BCM2835_DMA_ACTIVE))
-		return 0;
-
-	/* Terminate the control block chain */
-	writel(0, chan_base + BCM2835_DMA_NEXTCB);
-
-	/* Abort the whole DMA */
-	writel(BCM2835_DMA_ABORT | BCM2835_DMA_ACTIVE,
-	       chan_base + BCM2835_DMA_CS);
+		dev_err(c->vc.chan.device->dev,
+			"failed to complete outstanding writes\n");
 
+	writel(BCM2835_DMA_RESET, chan_base + BCM2835_DMA_CS);
 	return 0;
 }
 
@@ -476,8 +470,15 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data)
 
 	spin_lock_irqsave(&c->vc.lock, flags);
 
-	/* Acknowledge interrupt */
-	writel(BCM2835_DMA_INT, c->chan_base + BCM2835_DMA_CS);
+	/*
+	 * Clear the INT flag to receive further interrupts. Keep the channel
+	 * active in case the descriptor is cyclic or in case the client has
+	 * already terminated the descriptor and issued a new one. (May happen
+	 * if this IRQ handler is threaded.) If the channel is finished, it
+	 * will remain idle despite the ACTIVE flag being set.
+	 */
+	writel(BCM2835_DMA_INT | BCM2835_DMA_ACTIVE,
+	       c->chan_base + BCM2835_DMA_CS);
 
 	d = c->desc;
 
@@ -485,11 +486,7 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data)
 		if (d->cyclic) {
 			/* call the cyclic callback */
 			vchan_cyclic_callback(&d->vd);
-
-			/* Keep the DMA engine running */
-			writel(BCM2835_DMA_ACTIVE,
-			       c->chan_base + BCM2835_DMA_CS);
-		} else {
+		} else if (!readl(c->chan_base + BCM2835_DMA_ADDR)) {
 			vchan_cookie_complete(&c->desc->vd);
 			bcm2835_dma_start_desc(c);
 		}
@@ -779,7 +776,6 @@ static int bcm2835_dma_terminate_all(struct dma_chan *chan)
 	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
 	struct bcm2835_dmadev *d = to_bcm2835_dma_dev(c->vc.chan.device);
 	unsigned long flags;
-	int timeout = 10000;
 	LIST_HEAD(head);
 
 	spin_lock_irqsave(&c->vc.lock, flags);
@@ -789,27 +785,11 @@ static int bcm2835_dma_terminate_all(struct dma_chan *chan)
 	list_del_init(&c->node);
 	spin_unlock(&d->lock);
 
-	/*
-	 * Stop DMA activity: we assume the callback will not be called
-	 * after bcm_dma_abort() returns (even if it does, it will see
-	 * c->desc is NULL and exit.)
-	 */
+	/* stop DMA activity */
 	if (c->desc) {
 		vchan_terminate_vdesc(&c->desc->vd);
 		c->desc = NULL;
-		bcm2835_dma_abort(c->chan_base);
-
-		/* Wait for stopping */
-		while (--timeout) {
-			if (!(readl(c->chan_base + BCM2835_DMA_CS) &
-						BCM2835_DMA_ACTIVE))
-				break;
-
-			cpu_relax();
-		}
-
-		if (!timeout)
-			dev_err(d->ddev.dev, "DMA transfer could not be terminated\n");
+		bcm2835_dma_abort(c);
 	}
 
 	vchan_get_all_descriptors(&c->vc, &head);