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[v2,4/6] dmaengine: sun6i: track paused virtual channels

Message ID 20261023-submit-sun6i-dma-lifetime-next-v1-v2-4-c9e07cc44bf8@gmail.com (mailing list archive)
State New
Headers
Series dmaengine: sun6i: fix interrupt routing and channel lifetime |

Commit Message

James Hilliard Oct. 23, 2026, 6:42 p.m. UTC 
sun6i_dma_tx_status() only returns the cookie state, so a paused but
incomplete transfer is reported as DMA_IN_PROGRESS. The 8250 RX flush
path pauses the channel and calls its completion helper before terminating
it. That helper ignores an in-progress transfer to avoid consuming a new
RX operation. With sun6i it consequently drops the partial buffer and
leaves rx_running set, preventing another receive from being submitted.

Track pause state under the channel-assignment lock and report DMA_PAUSED
for incomplete cookies, including status queries without a residue output.
Flush the hardware pause request before returning. Completed cookies
remain DMA_COMPLETE.

Keep paused channels out of the pending queue and do not start a queued
descriptor when a paused channel's previous descriptor completes. Release
the completed physical channel so other virtual channels can use it, and
clear its hardware pause request before reassignment. The paused virtual
channel retains its queued descriptors until resume.

Resume requeues an unassigned channel only once and schedules the
allocator, so an idle controller does not require an unrelated completion
to resume it. Clear the pause state when terminating the channel.

Fixes: 555859308723 ("dmaengine: sun6i: Add driver for the Allwinner A31 DMA controller")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/dma/sun6i-dma.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
index a21acb9ecc27..157746c9423d 100644
--- a/drivers/dma/sun6i-dma.c
+++ b/drivers/dma/sun6i-dma.c
@@ -208,6 +208,7 @@  struct sun6i_vchan {
 	u8			port;
 	u8			irq_type;
 	bool			cyclic;
+	bool			paused;
 };
 
 struct sun6i_dma_dev {
@@ -534,13 +535,17 @@  static void sun6i_dma_tasklet(struct tasklet_struct *t)
 		pchan = vchan->phy;
 
 		if (pchan && !pchan->desc) {
-			if (sun6i_dma_start_desc(vchan)) {
+			if (vchan->paused || sun6i_dma_start_desc(vchan)) {
 				/*
 				 * No current txd associated with this channel
 				 */
 				dev_dbg(sdev->slave.dev, "pchan %u: free\n",
 					pchan->idx);
 
+				/* The next owner must not inherit the pause request. */
+				writel(DMA_CHAN_PAUSE_RESUME,
+				       pchan->base + DMA_CHAN_PAUSE);
+
 				/* Mark this channel free */
 				vchan->phy = NULL;
 				pchan->vchan = NULL;
@@ -932,10 +937,12 @@  static int sun6i_dma_pause(struct dma_chan *chan)
 	dev_dbg(dmaengine_chan_dev(chan), "vchan %p: pause\n", &vchan->vc);
 
 	spin_lock_irqsave(&sdev->lock, flags);
+	vchan->paused = true;
 	pchan = vchan->phy;
 	if (pchan) {
 		writel(DMA_CHAN_PAUSE_PAUSE,
 		       pchan->base + DMA_CHAN_PAUSE);
+		readl(pchan->base + DMA_CHAN_PAUSE);
 	} else {
 		list_del_init(&vchan->node);
 	}
@@ -957,12 +964,14 @@  static int sun6i_dma_resume(struct dma_chan *chan)
 	spin_lock(&vchan->vc.lock);
 	pchan = vchan->phy;
 
+	vchan->paused = false;
 	if (pchan) {
 		writel(DMA_CHAN_PAUSE_RESUME,
 		       pchan->base + DMA_CHAN_PAUSE);
-	} else if (!list_empty(&vchan->vc.desc_issued)) {
+	} else if (!list_empty(&vchan->vc.desc_issued) && list_empty(&vchan->node)) {
 		list_add_tail(&vchan->node, &sdev->pending);
 	}
+	tasklet_schedule(&sdev->task);
 
 	spin_unlock(&vchan->vc.lock);
 	spin_unlock_irqrestore(&sdev->lock, flags);
@@ -991,6 +1000,7 @@  static int sun6i_dma_terminate_all(struct dma_chan *chan)
 	}
 
 	vchan->cyclic = false;
+	vchan->paused = false;
 	vchan_get_all_descriptors(&vchan->vc, &head);
 
 	if (pchan) {
@@ -1037,6 +1047,8 @@  static enum dma_status sun6i_dma_tx_status(struct dma_chan *chan,
 	spin_lock_irqsave(&sdev->lock, flags);
 	spin_lock(&vchan->vc.lock);
 	ret = dma_cookie_status(chan, cookie, state);
+	if (ret == DMA_IN_PROGRESS && vchan->paused)
+		ret = DMA_PAUSED;
 	if (ret == DMA_COMPLETE || !state)
 		goto out;
 	pchan = vchan->phy;
@@ -1071,7 +1083,7 @@  static void sun6i_dma_issue_pending(struct dma_chan *chan)
 	spin_lock(&vchan->vc.lock);
 
 	if (vchan_issue_pending(&vchan->vc)) {
-		if (!vchan->phy && list_empty(&vchan->node)) {
+		if (!vchan->paused && !vchan->phy && list_empty(&vchan->node)) {
 			list_add_tail(&vchan->node, &sdev->pending);
 			tasklet_schedule(&sdev->task);
 			dev_dbg(dmaengine_chan_dev(chan), "vchan %p: issued\n",