Re: [PATCH 06/25] media: i2c: imx334: fix the pm runtime get logic

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed, 5 May 2021 11:41:56 +0200
Mauro Carvalho Chehab <mchehab+huawei@kernel.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. As a bonus, such function
> always return zero on success.
> 
> It should also be noticed that a fail of pm_runtime_get_sync() would
> potentially result in a spurious runtime_suspend(), instead of
> using pm_runtime_put_noidle().

Irony here is that pm_runtime_resume_and_get() returns <= 0 so with that
function change, you can stick with if (ret) and still be correct.

So only one of the two changes is needed to fix the bug.

J
> 
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Reviewed-by: Daniele Alessandrelli <daniele.alessandrelli@intel.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.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;