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

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Date:   Fri, 23 Dec 2022 11:26:07 +0900
From:   Shunsuke Mie <mie@...l.co.jp>
To:     Gustavo Pimentel <gustavo.pimentel@...opsys.com>
Cc:     Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, Shunsuke Mie <mie@...l.co.jp>
Subject: [PATCH 1/2] dmaengine: dw-edma: Fix to change for continuous transfer

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.

Fix it to 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@...l.co.jp>
---
 drivers/dma/dw-edma/dw-edma-core.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index c54b24ff5206..669b97313911 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -170,7 +170,7 @@ 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;
@@ -178,16 +178,16 @@ 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;
@@ -195,6 +195,8 @@ static void dw_edma_start_transfer(struct dw_edma_chan *chan)
 	list_del(&child->list);
 	kfree(child);
 	desc->chunks_alloc--;
+
+	return 1;
 }
 
 static int dw_edma_device_config(struct dma_chan *dchan,
@@ -568,14 +570,17 @@ 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 to transfer in case of there are rest chunks, or issued
+			 * requests remain.
+			 */
+			chan->status = EDMA_ST_BUSY;
+			if (!dw_edma_start_transfer(chan))
+				chan->status = EDMA_ST_IDLE;
 			break;
 
 		case EDMA_REQ_STOP:
-- 
2.25.1