[media] v4l: vsp1: Prevent multiple streamon race commencing pipeline early

With multiple inputs through the BRU it is feasible for the streams to
race each other at stream-on.

Multiple VIDIOC_STREAMON calls racing each other could have process
N-1 skipping over the pipeline setup section and then start the pipeline
early, if videobuf2 has already enqueued buffers to the driver for
process N but not called the .start_streaming() operation yet

In the case of the video pipelines, this
can present two serious issues.

 1) A null-dereference if the pipe->dl is committed at the same time as
    the vsp1_video_setup_pipeline() is processing

 2) A hardware hang, where a display list is committed without having
    called vsp1_video_setup_pipeline() first

Repair this issue, by ensuring that only the stream which configures the
pipeline is able to start it.

Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/media/platform/vsp1/vsp1_video.c b/drivers/media/platform/vsp1/vsp1_video.c
index 317fba485cd736f70650cd053eaaf247415c69c3..6c1b79f7aea5fcc6060a2828bbb53b2bab1c2e2c 100644 (file)
--- a/drivers/media/platform/vsp1/vsp1_video.c
+++ b/drivers/media/platform/vsp1/vsp1_video.c
@@ -797,6 +797,7 @@ static int vsp1_video_start_streaming(struct vb2_queue *vq, unsigned int count)
 {
        struct vsp1_video *video = vb2_get_drv_priv(vq);
        struct vsp1_pipeline *pipe = video->rwpf->pipe;
+       bool start_pipeline = false;
        unsigned long flags;
        int ret;
 
@@ -807,11 +808,23 @@ static int vsp1_video_start_streaming(struct vb2_queue *vq, unsigned int count)
                        mutex_unlock(&pipe->lock);
                        return ret;
                }
+
+               start_pipeline = true;
        }
 
        pipe->stream_count++;
        mutex_unlock(&pipe->lock);
 
+       /*
+        * vsp1_pipeline_ready() is not sufficient to establish that all streams
+        * are prepared and the pipeline is configured, as multiple streams
+        * can race through streamon with buffers already queued; Therefore we
+        * don't even attempt to start the pipeline until the last stream has
+        * called through here.
+        */
+       if (!start_pipeline)
+               return 0;
+
        spin_lock_irqsave(&pipe->irqlock, flags);
        if (vsp1_pipeline_ready(pipe))
                vsp1_video_pipeline_run(pipe);