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Date:   Wed, 5 May 2021 13:32:15 +0100
From:   Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
CC:     <linuxarm@huawei.com>, <mauro.chehab@huawei.com>,
        "Lad, Prabhakar" <prabhakar.csengg@gmail.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-media@vger.kernel.org>
Subject: Re: [PATCH 16/25] media: am437x: fix pm_runtime_get_sync() usage
 count
Message-ID: <20210505133215.00005f4e@Huawei.com>
In-Reply-To: <8688555079cf30f5848bb020b5ecf0b0132b2c7e.1620207353.git.mchehab+huawei@kernel.org>
References: <cover.1620207353.git.mchehab+huawei@kernel.org>
        <8688555079cf30f5848bb020b5ecf0b0132b2c7e.1620207353.git.mchehab+huawei@kernel.org>
Organization: Huawei Technologies Research and Development (UK) Ltd.
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On Wed, 5 May 2021 11:42:06 +0200
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> wrote:

> The pm_runtime_get_sync() internally increments the
> dev->power.usage_count without decrementing it, even on errors.
> 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")
> in order to properly decrement the usage counter, avoiding
> a potential PM usage counter leak.
> 
> While here, ensure that the driver will check if PM runtime
> resumed at vpfe_initialize_device().
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/media/platform/am437x/am437x-vpfe.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/am437x/am437x-vpfe.c b/drivers/media/platform/am437x/am437x-vpfe.c
> index 6cdc77dda0e4..1c9cb9e05fdf 100644
> --- a/drivers/media/platform/am437x/am437x-vpfe.c
> +++ b/drivers/media/platform/am437x/am437x-vpfe.c
> @@ -1021,7 +1021,9 @@ static int vpfe_initialize_device(struct vpfe_device *vpfe)
>  	if (ret)
>  		return ret;
>  
> -	pm_runtime_get_sync(vpfe->pdev);
> +	ret = pm_runtime_resume_and_get(vpfe->pdev);
> +	if (ret < 0)
> +		return ret;
>  
>  	vpfe_config_enable(&vpfe->ccdc, 1);
>  
> @@ -2443,7 +2445,11 @@ static int vpfe_probe(struct platform_device *pdev)
>  	pm_runtime_enable(&pdev->dev);
>  
>  	/* for now just enable it here instead of waiting for the open */
> -	pm_runtime_get_sync(&pdev->dev);
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret < 0) {
> +		vpfe_err(vpfe, "Unable to resume device.\n");
> +		goto probe_out_v4l2_unregister;
> +	}
>  
>  	vpfe_ccdc_config_defaults(ccdc);
>  
> @@ -2530,6 +2536,11 @@ static int vpfe_suspend(struct device *dev)
>  
>  	/* only do full suspend if streaming has started */
>  	if (vb2_start_streaming_called(&vpfe->buffer_queue)) {
> +		/*
> +		 * ignore RPM resume errors here, as it is already too late.
> +		 * A check like that should happen earlier, either at
> +		 * open() or just before start streaming.
> +		 */
>  		pm_runtime_get_sync(dev);
>  		vpfe_config_enable(ccdc, 1);
>