[PATCH v2 1/2] dmaengine: dw-edma: Fix to change for continuous transfer

[Shunsuke Mie <mie@igel.co.jp>]

The dw-edma driver stops after processing a DMA request even if a request
remains in the issued queue, which is not the expected behavior. The DMA
engine API requires continuous processing.

Add a trigger to start after one processing finished if there are requests
remain.

Fixes: e63d79d1ffcd ("dmaengine: Add Synopsys eDMA IP core driver")
Signed-off-by: Shunsuke Mie <mie@igel.co.jp>
---
Changes

v2:
- Refactor code
- Rebase to next-20230411

v1: https://lore.kernel.org/dmaengine/20221223022608.550697-1-mie@igel.co.jp/
- Initial patch

 drivers/dma/dw-edma/dw-edma-core.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 1906a836f0aa..26a395d02f5d 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -181,7 +181,7 @@ static void vchan_free_desc(struct virt_dma_desc *vdesc)
 	dw_edma_free_desc(vd2dw_edma_desc(vdesc));
 }
 
-static void dw_edma_start_transfer(struct dw_edma_chan *chan)
+static int dw_edma_start_transfer(struct dw_edma_chan *chan)
 {
 	struct dw_edma_chunk *child;
 	struct dw_edma_desc *desc;
@@ -189,16 +189,16 @@ static void dw_edma_start_transfer(struct dw_edma_chan *chan)
 
 	vd = vchan_next_desc(&chan->vc);
 	if (!vd)
-		return;
+		return 0;
 
 	desc = vd2dw_edma_desc(vd);
 	if (!desc)
-		return;
+		return 0;
 
 	child = list_first_entry_or_null(&desc->chunk->list,
 					 struct dw_edma_chunk, list);
 	if (!child)
-		return;
+		return 0;
 
 	dw_edma_v0_core_start(child, !desc->xfer_sz);
 	desc->xfer_sz += child->ll_region.sz;
@@ -206,6 +206,8 @@ static void dw_edma_start_transfer(struct dw_edma_chan *chan)
 	list_del(&child->list);
 	kfree(child);
 	desc->chunks_alloc--;
+
+	return 1;
 }
 
 static void dw_edma_device_caps(struct dma_chan *dchan,
@@ -602,14 +604,14 @@ static void dw_edma_done_interrupt(struct dw_edma_chan *chan)
 		switch (chan->request) {
 		case EDMA_REQ_NONE:
 			desc = vd2dw_edma_desc(vd);
-			if (desc->chunks_alloc) {
-				chan->status = EDMA_ST_BUSY;
-				dw_edma_start_transfer(chan);
-			} else {
+			if (!desc->chunks_alloc) {
 				list_del(&vd->node);
 				vchan_cookie_complete(vd);
-				chan->status = EDMA_ST_IDLE;
 			}
+
+			/* Continue transferring if there are remaining chunks or issued requests.
+			 */
+			chan->status = dw_edma_start_transfer(chan) ? EDMA_ST_BUSY : EDMA_ST_IDLE;
 			break;
 
 		case EDMA_REQ_STOP:
-- 
2.25.1