linux-kernel - Re: [PATCH v4 12/79] media: renesas-ceu: Properly check for PM errors

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Message-ID: <20210430172815.00007111@Huawei.com>
Date:   Fri, 30 Apr 2021 17:28:15 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
CC:     <linuxarm@...wei.com>, <mauro.chehab@...wei.com>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v4 12/79] media: renesas-ceu: Properly check for PM
 errors

On Wed, 28 Apr 2021 16:51:33 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> wrote:

> Right now, the driver just assumes that PM runtime resume
> worked, but it may fail.
> 
> Well, the pm_runtime_get_sync() internally increments the
> dev->power.usage_count without decrementing it, even on errors.
> 
> So, using it is tricky. Let's replace it by the new
> pm_runtime_resume_and_get(), introduced by:
> commit dd8088d5a896 ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
> and return an error if something bad happens.
> 
> This should ensure that the PM runtime usage_count will be
> properly decremented if an error happens at open time.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
LGTM
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/media/platform/renesas-ceu.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/renesas-ceu.c b/drivers/media/platform/renesas-ceu.c
> index cd137101d41e..17f01b6e3fe0 100644
> --- a/drivers/media/platform/renesas-ceu.c
> +++ b/drivers/media/platform/renesas-ceu.c
> @@ -1099,10 +1099,10 @@ static int ceu_open(struct file *file)
>  
>  	mutex_lock(&ceudev->mlock);
>  	/* Causes soft-reset and sensor power on on first open */
> -	pm_runtime_get_sync(ceudev->dev);
> +	ret = pm_runtime_resume_and_get(ceudev->dev);
>  	mutex_unlock(&ceudev->mlock);
>  
> -	return 0;
> +	return ret;
>  }
>  
>  static int ceu_release(struct file *file)