linux-kernel - Re: [PATCH] media: vsp1: Fix runtime PM imbalance in vsp1

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Date:   Mon, 8 Jun 2020 04:54:56 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
Cc:     kjlu@....edu,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: vsp1: Fix runtime PM imbalance in vsp1_probe

Hi Dinghao,

Thank you for the patch.

On Sat, May 23, 2020 at 07:54:26PM +0800, Dinghao Liu wrote:
> pm_runtime_get_sync() increments the runtime PM usage counter even
> when it returns an error code. Thus a pairing decrement is needed on
> the error handling path to keep the counter balanced.

I wonder how many bugs we have today, and how many bugs will keep
appearing in the future, due to this historical design mistake :-( 

> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>  drivers/media/platform/vsp1/vsp1_drv.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/vsp1/vsp1_drv.c b/drivers/media/platform/vsp1/vsp1_drv.c
> index c650e45bb0ad..017a54f2fdd8 100644
> --- a/drivers/media/platform/vsp1/vsp1_drv.c
> +++ b/drivers/media/platform/vsp1/vsp1_drv.c
> @@ -846,8 +846,10 @@ static int vsp1_probe(struct platform_device *pdev)
>  	pm_runtime_enable(&pdev->dev);
>  
>  	ret = pm_runtime_get_sync(&pdev->dev);
> -	if (ret < 0)
> +	if (ret < 0) {
> +		pm_runtime_put_sync(&pdev->dev);
>  		goto done;
> +	}

This change looks good to me, but we also need a similar change in the
vsp1_device_get() function if I'm not mistaken. Could you combine both
in the same patch ?

>  
>  	vsp1->version = vsp1_read(vsp1, VI6_IP_VERSION);
>  	pm_runtime_put_sync(&pdev->dev);

-- 
Regards,

Laurent Pinchart