dmaengine: edma: Fetch echan->edesc while holding lock in edma_comletion_handler

In order to avoid possible race condition when client drivers are using
dmaengine_terminate_sync() call to disable the channel.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Suggested-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/edma.c

@@ -1369,12 +1369,11 @@ static struct dma_async_tx_descriptor *edma_prep_dma_cyclic(
 static void edma_completion_handler(struct edma_chan *echan)
 {
 	struct device *dev = echan->vchan.chan.device->dev;
-	struct edma_desc *edesc = echan->edesc;
-
-	if (!edesc)
-		return;
+	struct edma_desc *edesc;
 
 	spin_lock(&echan->vchan.lock);
+	edesc = echan->edesc;
+	if (edesc) {
 		if (edesc->cyclic) {
 			vchan_cyclic_callback(&edesc->vdesc);
 			spin_unlock(&echan->vchan.lock);
@@ -1399,6 +1398,7 @@ static void edma_completion_handler(struct edma_chan *echan)
 			edesc->processed_stat = edesc->processed;
 		}
 		edma_execute(echan);
+	}
 
 	spin_unlock(&echan->vchan.lock);
 }