linux-kernel - Re: [PATCH v4 06/79] media: i2c: imx334: fix the pm runtime get logic

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Message-ID: <20210430165439.0000712c@Huawei.com>
Date:   Fri, 30 Apr 2021 16:54:39 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
CC:     <linuxarm@...wei.com>, <mauro.chehab@...wei.com>,
        "Paul J. Murphy" <paul.j.murphy@...el.com>,
        Daniele Alessandrelli <daniele.alessandrelli@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH v4 06/79] media: i2c: imx334: fix the pm runtime get
 logic

On Wed, 28 Apr 2021 16:51:27 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> wrote:

> The PM runtime get logic is currently broken, as it checks if
> ret is zero instead of checking if it is an error code,
> as reported by Dan Carpenter.
> 
> While here, use the pm_runtime_resume_and_get() as added by:
> commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> added pm_runtime_resume_and_get() in order to automatically handle
> dev->power.usage_count decrement on errors.

Perhaps also call out that a fail of pm_runtime_get_sync in current
code would potentially result in a spurious runtime_suspend() call
whereas using pm_runtime_resume_and_get() will call
pm_runtime_put_noidle()

> 
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Reviewed-by: Daniele Alessandrelli <daniele.alessandrelli@...el.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> ---
>  drivers/media/i2c/imx334.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/i2c/imx334.c b/drivers/media/i2c/imx334.c
> index 047aa7658d21..23f28606e570 100644
> --- a/drivers/media/i2c/imx334.c
> +++ b/drivers/media/i2c/imx334.c
> @@ -717,9 +717,9 @@ static int imx334_set_stream(struct v4l2_subdev *sd, int enable)
>  	}
>  
>  	if (enable) {
> -		ret = pm_runtime_get_sync(imx334->dev);
> -		if (ret)
> -			goto error_power_off;
> +		ret = pm_runtime_resume_and_get(imx334->dev);
> +		if (ret < 0)
> +			goto error_unlock;
>  
>  		ret = imx334_start_streaming(imx334);
>  		if (ret)
> @@ -737,6 +737,7 @@ static int imx334_set_stream(struct v4l2_subdev *sd, int enable)
>  
>  error_power_off:
>  	pm_runtime_put(imx334->dev);
> +error_unlock:
>  	mutex_unlock(&imx334->mutex);
>  
>  	return ret;