Re: [PATCH 3/3] rcar-vin: handle transfer errors from subdevices and stop streaming if required

[Niklas Söderlund]

Hi Michael,

Thanks for your work.

I like this patch, I think it captures the issue discussed in the 
previous thread quiet nicely. One small nit below.

On 2022-05-19 20:00:09 +0200, Michael Rodin wrote:
> When a subdevice sends a transfer error event during streaming and we can
> not capture new frames, then we know for sure that this is an unrecoverable
> failure and not just a temporary glitch. In this case we can not ignore the
> transfer error any more and have to notify userspace. In response to the
> transfer error event userspace can try to restart streaming and hope that
> it works again.
> 
> This patch is based on the patch [1] from Niklas Söderlund, however it adds
> more logic to check whether the VIN hardware module is actually affected by
> the transfer errors reported by the usptream device. For this it takes some
> ideas from the imx driver where EOF interrupts are monitored by the
> eof_timeout_timer added by commit 4a34ec8e470c ("[media] media: imx: Add
> CSI subdev driver").
> 
> [1] https://lore.kernel.org/linux-renesas-soc/20211108160220.767586-4-niklas.soderlund+renesas@xxxxxxxxxxxx/
> 
> Signed-off-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> ---
>  drivers/media/platform/renesas/rcar-vin/rcar-dma.c | 34 ++++++++++++++++++++++
>  .../media/platform/renesas/rcar-vin/rcar-v4l2.c    | 18 +++++++++++-
>  drivers/media/platform/renesas/rcar-vin/rcar-vin.h |  7 +++++
>  3 files changed, 58 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/renesas/rcar-vin/rcar-dma.c b/drivers/media/platform/renesas/rcar-vin/rcar-dma.c
> index 2272f1c..596a367 100644
> --- a/drivers/media/platform/renesas/rcar-vin/rcar-dma.c
> +++ b/drivers/media/platform/renesas/rcar-vin/rcar-dma.c
> @@ -13,6 +13,7 @@
>  #include <linux/delay.h>
>  #include <linux/interrupt.h>
>  #include <linux/pm_runtime.h>
> +#include <media/v4l2-event.h>
>  
>  #include <media/videobuf2-dma-contig.h>
>  
> @@ -1060,6 +1061,9 @@ static irqreturn_t rvin_irq(int irq, void *data)
>  		vin_dbg(vin, "Dropping frame %u\n", vin->sequence);
>  	}
>  
> +	cancel_delayed_work(&vin->frame_timeout);
> +	schedule_delayed_work(&vin->frame_timeout, msecs_to_jiffies(FRAME_TIMEOUT_MS));
> +
>  	vin->sequence++;
>  
>  	/* Prepare for next frame */
> @@ -1283,6 +1287,7 @@ int rvin_start_streaming(struct rvin_dev *vin)
>  	spin_lock_irqsave(&vin->qlock, flags);
>  
>  	vin->sequence = 0;
> +	vin->xfer_error = false;
>  
>  	ret = rvin_capture_start(vin);
>  	if (ret)
> @@ -1290,6 +1295,10 @@ int rvin_start_streaming(struct rvin_dev *vin)
>  
>  	spin_unlock_irqrestore(&vin->qlock, flags);
>  
> +	/* We start the frame watchdog only after we have successfully started streaming */
> +	if (!ret)
> +		schedule_delayed_work(&vin->frame_timeout, msecs_to_jiffies(FRAME_TIMEOUT_MS));
> +
>  	return ret;
>  }
>  
> @@ -1332,6 +1341,12 @@ void rvin_stop_streaming(struct rvin_dev *vin)
>  	}
>  
>  	vin->state = STOPPING;
> +	/*
> +	 * Since we are now stopping and don't expect more frames to be captured, make sure that
> +	 * there is no pending work for error handling.
> +	 */
> +	cancel_delayed_work_sync(&vin->frame_timeout);
> +	vin->xfer_error = false;

Do we need to set xfer_error to false here? The delayed work is canceled 
and we reset the xfer_error when we start in rvin_start_streaming().

>  
>  	/* Wait until only scratch buffer is used, max 3 interrupts. */
>  	retries = 0;
> @@ -1424,6 +1439,23 @@ void rvin_dma_unregister(struct rvin_dev *vin)
>  	v4l2_device_unregister(&vin->v4l2_dev);
>  }
>  
> +static void rvin_frame_timeout(struct work_struct *work)
> +{
> +	struct delayed_work *dwork = to_delayed_work(work);
> +	struct rvin_dev *vin = container_of(dwork, struct rvin_dev, frame_timeout);
> +	struct v4l2_event event = {
> +		.type = V4L2_EVENT_XFER_ERROR,
> +	};
> +
> +	vin_dbg(vin, "Frame timeout!\n");
> +
> +	if (!vin->xfer_error)
> +		return;
> +	vin_err(vin, "Unrecoverable transfer error detected, stopping streaming\n");
> +	vb2_queue_error(&vin->queue);
> +	v4l2_event_queue(&vin->vdev, &event);
> +}
> +
>  int rvin_dma_register(struct rvin_dev *vin, int irq)
>  {
>  	struct vb2_queue *q = &vin->queue;
> @@ -1470,6 +1502,8 @@ int rvin_dma_register(struct rvin_dev *vin, int irq)
>  		goto error;
>  	}
>  
> +	INIT_DELAYED_WORK(&vin->frame_timeout, rvin_frame_timeout);
> +
>  	return 0;
>  error:
>  	rvin_dma_unregister(vin);
> diff --git a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c b/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
> index 2e2aa9d..bd7f6fe2 100644
> --- a/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
> +++ b/drivers/media/platform/renesas/rcar-vin/rcar-v4l2.c
> @@ -648,6 +648,8 @@ static int rvin_subscribe_event(struct v4l2_fh *fh,
>  	switch (sub->type) {
>  	case V4L2_EVENT_SOURCE_CHANGE:
>  		return v4l2_event_subscribe(fh, sub, 4, NULL);
> +	case V4L2_EVENT_XFER_ERROR:
> +		return v4l2_event_subscribe(fh, sub, 1, NULL);
>  	}
>  	return v4l2_ctrl_subscribe_event(fh, sub);
>  }
> @@ -1000,9 +1002,23 @@ void rvin_v4l2_unregister(struct rvin_dev *vin)
>  static void rvin_notify_video_device(struct rvin_dev *vin,
>  				     unsigned int notification, void *arg)
>  {
> +	const struct v4l2_event *event;
> +
>  	switch (notification) {
>  	case V4L2_DEVICE_NOTIFY_EVENT:
> -		v4l2_event_queue(&vin->vdev, arg);
> +		event = arg;
> +
> +		switch (event->type) {
> +		case V4L2_EVENT_XFER_ERROR:
> +			if (vin->state != STOPPED && vin->state != STOPPING) {
> +				vin_dbg(vin, "Subdevice signaled transfer error.\n");
> +				vin->xfer_error = true;
> +			}
> +			break;
> +		default:
> +			break;
> +		}
> +
>  		break;
>  	default:
>  		break;
> diff --git a/drivers/media/platform/renesas/rcar-vin/rcar-vin.h b/drivers/media/platform/renesas/rcar-vin/rcar-vin.h
> index 1f94589..4726a69 100644
> --- a/drivers/media/platform/renesas/rcar-vin/rcar-vin.h
> +++ b/drivers/media/platform/renesas/rcar-vin/rcar-vin.h
> @@ -31,6 +31,9 @@
>  /* Max number on VIN instances that can be in a system */
>  #define RCAR_VIN_NUM 32
>  
> +/* maximum time we wait before signalling an error to userspace */
> +#define FRAME_TIMEOUT_MS 1000
> +
>  struct rvin_group;
>  
>  enum model_id {
> @@ -207,6 +210,8 @@ struct rvin_info {
>   * @std:		active video standard of the video source
>   *
>   * @alpha:		Alpha component to fill in for supported pixel formats
> + * @xfer_error:		Indicates if any transfer errors occurred in the current streaming session.
> + * @frame_timeout:	Watchdog for monitoring regular capturing of frames in rvin_irq.
>   */
>  struct rvin_dev {
>  	struct device *dev;
> @@ -251,6 +256,8 @@ struct rvin_dev {
>  	v4l2_std_id std;
>  
>  	unsigned int alpha;
> +	bool xfer_error;
> +	struct delayed_work frame_timeout;
>  };
>  
>  #define vin_to_source(vin)		((vin)->parallel.subdev)
> -- 
> 2.7.4
> 

-- 
Kind Regards,
Niklas Söderlund