linux-kernel - Re: [PATCH] media: imx: imx7-mipi-csis: Fix runtime PM imbalance in mipi_csis_s

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Date:   Thu, 8 Apr 2021 14:57:02 +0100
From:   Rui Miguel Silva <rmfrfs@...il.com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
Cc:     kjlu@....edu, Steve Longerbeam <slongerbeam@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: imx: imx7-mipi-csis: Fix runtime PM imbalance in
 mipi_csis_s_stream

Hi Liu,
Thanks for your patch.

On Thu, Apr 08, 2021 at 05:08:27PM +0800, Dinghao Liu wrote:
> When v4l2_subdev_call() fails, a pairing PM usage counter
> decrement is needed to keep the counter balanced. It's the
> same for the following error paths in case 'enable' is on.
> 
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>  drivers/staging/media/imx/imx7-mipi-csis.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/imx/imx7-mipi-csis.c b/drivers/staging/media/imx/imx7-mipi-csis.c
> index a01a7364b4b9..2a3fff231a40 100644
> --- a/drivers/staging/media/imx/imx7-mipi-csis.c
> +++ b/drivers/staging/media/imx/imx7-mipi-csis.c
> @@ -627,21 +627,26 @@ static int mipi_csis_s_stream(struct v4l2_subdev *mipi_sd, int enable)
>  			return ret;
>  		}
>  		ret = v4l2_subdev_call(state->src_sd, core, s_power, 1);
> -		if (ret < 0)
> +		if (ret < 0) {
> +			pm_runtime_put_noidle(&state->pdev->dev);

I think here we should go completely pm_runtime_put to call the
mipi_csis_pm_suspend down the line, right?

>  			return ret;
> +		}
>  	}
>  
>  	mutex_lock(&state->lock);
>  	if (enable) {
>  		if (state->flags & ST_SUSPENDED) {
>  			ret = -EBUSY;
> +			pm_runtime_put_noidle(&state->pdev->dev);

since we are in ST_SUSPENDED state, for sure the pm counter was
already 0.

>  			goto unlock;
>  		}
>  
>  		mipi_csis_start_stream(state);
>  		ret = v4l2_subdev_call(state->src_sd, video, s_stream, 1);
> -		if (ret < 0)
> +		if (ret < 0) {
> +			pm_runtime_put_noidle(&state->pdev->dev);

here also we need the pm_runtime_put, maybe just changing the unlock
tag bellow from:
    if (!enable)
        pm_runtime_put(&state->pdev->dev);

to 
    if (!enable || (ret < 0))
        pm_runtime_put(&state->pdev->dev);

will not hurt the first case and will complete the suspend routine
afterward in the second case.

------
Cheers,
     Rui
>  			goto unlock;
> +		}
>  
>  		mipi_csis_log_counters(state, true);
>  
> -- 
> 2.17.1
> 
>