dmaengine: andes: atcdmac300: Fix the descriptor timeout issue (torvalds#167)

In v5_advance_work, v5_complete_all() moves the descriptors from the queue
to the active_list. If active_list is empty, the operation of this DMA
channel is stopped and the DMA channel is set to idle (chan_used = 0).
However, if a new descriptor is added to the queue between the calls
to v5_complete_all() and the check for list_empty(&v5chan->active_list),
this descriptor will not be executed.

	if (list_is_singular(&v5chan->active_list)) {
		v5_complete_all(v5chan);
	} ...

	if (list_empty(&v5chan->active_list))
		v5chan->chan_used = 0;
	else
		v5_dostart(v5chan, v5_first_active(v5chan));

The solution is to process the new descriptor in the queue before
stopping the DMA channel if there is a new descriptor in the queue.

	if (list_is_singular(&v5chan->active_list)) {
		v5_complete_all(v5chan);
	} ...

	spin_lock(&v5chan->lock);
	if (list_empty(&v5chan->active_list)) {
		if (!list_empty(&v5chan->queue)) {
		list_move(v5chan->queue.next, &v5chan->active_list);
	...

Signed-off-by: CL Wang <[email protected]>
Reviewed-on: https://gitea.andestech.com/RD-SW/linux/pulls/167
Reviewed-by: Tim Shih-Ting OuYang <[email protected]>
Reviewed-by: randolph <[email protected]>
Co-authored-by: CL Wang <[email protected]>
Co-committed-by: CL Wang <[email protected]>

Author: CL Wang

drivers/dma/atcdmac300.c

@@ -315,10 +315,23 @@ static void v5_advance_work(struct v5_dma_chan *v5chan)
 				DMA_TRANS_NOERROR);
 		}
 
-		if (list_empty(&v5chan->active_list))
-			v5chan->chan_used = 0;
-		else
+		spin_lock(&v5chan->lock);
+		if (list_empty(&v5chan->active_list)) {
+			if (!list_empty(&v5chan->queue)) {
+				list_move(v5chan->queue.next,
+					  &v5chan->active_list);
+				spin_unlock(&v5chan->lock);
+				v5_dostart(v5chan,
+					   v5_first_active(v5chan));
+
+			} else {
+				v5chan->chan_used = 0;
+				spin_unlock(&v5chan->lock);
+			}
+		} else {
+			spin_unlock(&v5chan->lock);
 			v5_dostart(v5chan, v5_first_active(v5chan));
+		}
 	} else {
 		/* For cyclic mode */
 		struct dmaengine_result res;