[PATCH v15 12/12] dmaengine: imx-sdma: add terminated list for freed descriptor in worker

[Robin Gong]

Add terminated list for keeping descriptor so that it could be freed in
worker without any potential involving next descriptor raised up before
this descriptor freed, because vchan_get_all_descriptors get all
descriptors including the last terminated descriptor and the next
descriptor, hence, the next descriptor maybe freed unexpectly when it's
done in worker without this patch.
https://www.spinics.net/lists/dmaengine/msg23367.html

Signed-off-by: Robin Gong <yibin.gong at nxp.com>
Reported-by: Richard Leitner <richard.leitner at skidata.com>
Reviewed-by: Lucas Stach <l.stach at pengutronix.de>
---
 drivers/dma/imx-sdma.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index c449755..6e0490d 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -439,6 +439,7 @@ struct sdma_channel {
 	enum dma_status			status;
 	struct imx_dma_data		data;
 	struct work_struct		terminate_worker;
+	struct list_head                terminated;
 	bool				is_ram_script;
 };
 
@@ -1107,9 +1108,6 @@ static void sdma_channel_terminate_work(struct work_struct *work)
 {
 	struct sdma_channel *sdmac = container_of(work, struct sdma_channel,
 						  terminate_worker);
-	unsigned long flags;
-	LIST_HEAD(head);
-
 	/*
 	 * According to NXP R&D team a delay of one BD SDMA cost time
 	 * (maximum is 1ms) should be added after disable of the channel
@@ -1118,10 +1116,7 @@ static void sdma_channel_terminate_work(struct work_struct *work)
 	 */
 	usleep_range(1000, 2000);
 
-	spin_lock_irqsave(&sdmac->vc.lock, flags);
-	vchan_get_all_descriptors(&sdmac->vc, &head);
-	spin_unlock_irqrestore(&sdmac->vc.lock, flags);
-	vchan_dma_desc_free_list(&sdmac->vc, &head);
+	vchan_dma_desc_free_list(&sdmac->vc, &sdmac->terminated);
 }
 
 static int sdma_terminate_all(struct dma_chan *chan)
@@ -1135,6 +1130,13 @@ static int sdma_terminate_all(struct dma_chan *chan)
 
 	if (sdmac->desc) {
 		vchan_terminate_vdesc(&sdmac->desc->vd);
+		/*
+		 * move out current descriptor into terminated list so that
+		 * it could be free in sdma_channel_terminate_work alone
+		 * later without potential involving next descriptor raised
+		 * up before the last descriptor terminated.
+		 */
+		vchan_get_all_descriptors(&sdmac->vc, &sdmac->terminated);
 		sdmac->desc = NULL;
 		schedule_work(&sdmac->terminate_worker);
 	}
@@ -2132,6 +2134,7 @@ static int sdma_probe(struct platform_device *pdev)
 
 		sdmac->channel = i;
 		sdmac->vc.desc_free = sdma_desc_free;
+		INIT_LIST_HEAD(&sdmac->terminated);
 		INIT_WORK(&sdmac->terminate_worker,
 				sdma_channel_terminate_work);
 		/*
-- 
2.7.4