[PATCH 4.14 200/209] media: stm32-dcmi: fix DMA corruption when stopping streaming

[Greg Kroah-Hartman]

From: Hugues Fruchet <hugues.fruchet@xxxxxx>

commit b3ce6f6ff3c260ee53b0f2236e5fd950d46957da upstream.

Avoid call of dmaengine_terminate_all() between
dmaengine_prep_slave_single() and dmaengine_submit() by locking
the whole DMA submission sequence.

Signed-off-by: Hugues Fruchet <hugues.fruchet@xxxxxx>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
Signed-off-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/media/platform/stm32/stm32-dcmi.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

--- a/drivers/media/platform/stm32/stm32-dcmi.c
+++ b/drivers/media/platform/stm32/stm32-dcmi.c
@@ -161,6 +161,9 @@ struct stm32_dcmi {
 	u32				misr;
 	int				errors_count;
 	int				buffers_count;
+
+	/* Ensure DMA operations atomicity */
+	struct mutex			dma_lock;
 };
 
 static inline struct stm32_dcmi *notifier_to_dcmi(struct v4l2_async_notifier *n)
@@ -291,6 +294,13 @@ static int dcmi_start_dma(struct stm32_d
 		return ret;
 	}
 
+	/*
+	 * Avoid call of dmaengine_terminate_all() between
+	 * dmaengine_prep_slave_single() and dmaengine_submit()
+	 * by locking the whole DMA submission sequence
+	 */
+	mutex_lock(&dcmi->dma_lock);
+
 	/* Prepare a DMA transaction */
 	desc = dmaengine_prep_slave_single(dcmi->dma_chan, buf->paddr,
 					   buf->size,
@@ -298,6 +308,7 @@ static int dcmi_start_dma(struct stm32_d
 	if (!desc) {
 		dev_err(dcmi->dev, "%s: DMA dmaengine_prep_slave_single failed for buffer size %zu\n",
 			__func__, buf->size);
+		mutex_unlock(&dcmi->dma_lock);
 		return -EINVAL;
 	}
 
@@ -309,9 +320,12 @@ static int dcmi_start_dma(struct stm32_d
 	dcmi->dma_cookie = dmaengine_submit(desc);
 	if (dma_submit_error(dcmi->dma_cookie)) {
 		dev_err(dcmi->dev, "%s: DMA submission failed\n", __func__);
+		mutex_unlock(&dcmi->dma_lock);
 		return -ENXIO;
 	}
 
+	mutex_unlock(&dcmi->dma_lock);
+
 	dma_async_issue_pending(dcmi->dma_chan);
 
 	return 0;
@@ -690,7 +704,9 @@ static void dcmi_stop_streaming(struct v
 	spin_unlock_irq(&dcmi->irqlock);
 
 	/* Stop all pending DMA operations */
+	mutex_lock(&dcmi->dma_lock);
 	dmaengine_terminate_all(dcmi->dma_chan);
+	mutex_unlock(&dcmi->dma_lock);
 
 	clk_disable(dcmi->mclk);
 
@@ -1662,6 +1678,7 @@ static int dcmi_probe(struct platform_de
 
 	spin_lock_init(&dcmi->irqlock);
 	mutex_init(&dcmi->lock);
+	mutex_init(&dcmi->dma_lock);
 	init_completion(&dcmi->complete);
 	INIT_LIST_HEAD(&dcmi->buffers);