[media] rcar_vin: helper function for streaming stop

The code that tests that capture from a stream has stopped is
presently insufficient and the potential for a race condition
exists where frame capture may generate an interrupt between
requesting the capture process halt and freeing buffers.

This patch refactors code out of rcar_vin_videobuf_release() and
into rcar_vin_wait_stop_streaming(), and ensures there are calls
in places where we need to know that capturing has finished.

Signed-off-by: Ian Molton <ian.molton@codethink.co.uk>
Signed-off-by: William Towle <william.towle@codethink.co.uk>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/platform/soc_camera/rcar_vin.c

@@ -804,6 +804,28 @@ error:
 	vb2_buffer_done(vb, VB2_BUF_STATE_ERROR);
 }
 
+/*
+ * Wait for capture to stop and all in-flight buffers to be finished with by
+ * the video hardware. This must be called under &priv->lock
+ *
+ */
+static void rcar_vin_wait_stop_streaming(struct rcar_vin_priv *priv)
+{
+	while (priv->state != STOPPED) {
+		/* issue stop if running */
+		if (priv->state == RUNNING)
+			rcar_vin_request_capture_stop(priv);
+
+		/* wait until capturing has been stopped */
+		if (priv->state == STOPPING) {
+			priv->request_to_stop = true;
+			spin_unlock_irq(&priv->lock);
+			wait_for_completion(&priv->capture_stop);
+			spin_lock_irq(&priv->lock);
+		}
+	}
+}
+
 static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
 {
 	struct soc_camera_device *icd = soc_camera_from_vb2q(vb->vb2_queue);
@@ -823,20 +845,8 @@ static void rcar_vin_videobuf_release(struct vb2_buffer *vb)
 	}
 
 	if (buf_in_use) {
-		while (priv->state != STOPPED) {
-
-			/* issue stop if running */
-			if (priv->state == RUNNING)
-				rcar_vin_request_capture_stop(priv);
-
-			/* wait until capturing has been stopped */
-			if (priv->state == STOPPING) {
-				priv->request_to_stop = true;
-				spin_unlock_irq(&priv->lock);
-				wait_for_completion(&priv->capture_stop);
-				spin_lock_irq(&priv->lock);
-			}
-		}
+		rcar_vin_wait_stop_streaming(priv);
+
 		/*
 		 * Capturing has now stopped. The buffer we have been asked
 		 * to release could be any of the current buffers in use, so
@@ -870,8 +880,11 @@ static void rcar_vin_stop_streaming(struct vb2_queue *vq)
 	struct list_head *buf_head, *tmp;
 
 	spin_lock_irq(&priv->lock);
+
+	rcar_vin_wait_stop_streaming(priv);
 	list_for_each_safe(buf_head, tmp, &priv->capture)
 		list_del_init(buf_head);
+
 	spin_unlock_irq(&priv->lock);
 }