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path: root/drivers/dma/bcm2835-dma.c
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Diffstat (limited to 'drivers/dma/bcm2835-dma.c')
-rw-r--r--drivers/dma/bcm2835-dma.c70
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);