linux-kernel - Re: [PATCH v1 3/3] staging: media: ipu3: Stop streaming in inverse order of starting

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Message-ID: <e6ff8ad5-933d-fbbb-0c4b-ae19c65e8439@linux.intel.com>
Date: Thu, 4 Jul 2024 15:03:07 +0800
From: Bingbu Cao <bingbu.cao@...ux.intel.com>
To: Max Staudt <mstaudt@...omium.org>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Bingbu Cao <bingbu.cao@...el.com>, Tianshu Qiu <tian.shu.qiu@...el.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 Ricardo Ribalda <ribalda@...omium.org>
Subject: Re: [PATCH v1 3/3] staging: media: ipu3: Stop streaming in inverse
 order of starting

Max,

Thanks for your patch.

On 6/20/24 10:45 PM, Max Staudt wrote:
> imgu_vb2_stop_streaming() did not order shutdown items in the inverse
> order and count of what imgu_vb2_start_streaming() does. Consequently,
> v6.7's new WARN_ON in call_s_stream() started screaming because it was
> called multiple times on the entire pipe, yet it should only be called
> when the pipe is interrupted by any first node being taken offline.
> 
> This reorders streamoff to be the inverse of streamon, and uses
> analogous conditions to decide when and how often to call additional
> teardown functions.
> 
> v4l2_subdev_call(s_stream, 0) remains outside the streaming_lock,
> analogously to imgu_vb2_start_streaming().
> 
> Signed-off-by: Max Staudt <mstaudt@...omium.org>
> ---
>  drivers/staging/media/ipu3/ipu3-v4l2.c | 36 +++++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/media/ipu3/ipu3-v4l2.c b/drivers/staging/media/ipu3/ipu3-v4l2.c
> index 3ff390b04e1a..e7aee7e3db5b 100644
> --- a/drivers/staging/media/ipu3/ipu3-v4l2.c
> +++ b/drivers/staging/media/ipu3/ipu3-v4l2.c
> @@ -535,29 +535,51 @@ static void imgu_vb2_stop_streaming(struct vb2_queue *vq)
>  		container_of(vq, struct imgu_video_device, vbq);
>  	int r;
>  	unsigned int pipe;
> +	bool stop_streaming = false;
>  
> +	/* Verify that the node had been setup with imgu_v4l2_node_setup() */
>  	WARN_ON(!node->enabled);
>  
>  	pipe = node->pipe;
>  	dev_dbg(dev, "Try to stream off node [%u][%u]", pipe, node->id);
> -	imgu_pipe = &imgu->imgu_pipe[pipe];
> -	r = v4l2_subdev_call(&imgu_pipe->imgu_sd.subdev, video, s_stream, 0);
> -	if (r)
> -		dev_err(&imgu->pci_dev->dev,
> -			"failed to stop subdev streaming\n");

I guess the subdev streams API can help us on this, but current fix
looks fine for me.

>  
> +	/*
> +	 * When the first node of a streaming setup is stopped, the entire
> +	 * pipeline needs to stop before individual nodes are disabled.
> +	 * Perform the inverse of the initial setup.
> +	 *
> +	 * Part 1 - s_stream on the entire pipeline

stream on or off? it is a little confusing.

> +	 */
>  	mutex_lock(&imgu->streaming_lock);
> -	/* Was this the first node with streaming disabled? */
>  	if (imgu->streaming) {
>  		/* Yes, really stop streaming now */
>  		dev_dbg(dev, "IMGU streaming is ready to stop");
>  		r = imgu_s_stream(imgu, false);
>  		if (!r)
>  			imgu->streaming = false;
> +		stop_streaming = true;
>  	}
> -
>  	mutex_unlock(&imgu->streaming_lock);
>  
> +	/* Part 2 - s_stream on subdevs
> +	 *
> +	 * If we call s_stream multiple times, Linux v6.7's call_s_stream()
> +	 * WARNs and aborts. Thus, disable all pipes at once, and only once.
> +	 */
> +	if (stop_streaming) {

> +		for_each_set_bit(pipe, imgu->css.enabled_pipes,
> +				 IMGU_MAX_PIPE_NUM) {
> +			imgu_pipe = &imgu->imgu_pipe[pipe];
> +
> +			r = v4l2_subdev_call(&imgu_pipe->imgu_sd.subdev,
> +					     video, s_stream, 0);
> +			if (r)
> +				dev_err(&imgu->pci_dev->dev,
> +					"failed to stop subdev streaming\n");
> +		}

Is it possible to move this loop into 'if (imgu->streaming)' above?

> +	}
> +
> +	/* Part 3 - individual node teardown */
>  	video_device_pipeline_stop(&node->vdev);
>  	imgu_return_all_buffers(imgu, node, VB2_BUF_STATE_ERROR);
>  }
> 

-- 
Best regards,
Bingbu Cao