linux-kernel - Re: [PATCH v4 14/79] media: am437x: fix pm_runtime_get

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Date:   Fri, 30 Apr 2021 17:36:46 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
CC:     <linuxarm@...wei.com>, <mauro.chehab@...wei.com>,
        "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>
Subject: Re: [PATCH v4 14/79] media: am437x: fix pm_runtime_get_sync() usage
 count

On Wed, 28 Apr 2021 16:51:35 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.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 and avoid memory
> leaks.
> 
> While here, ensure that the driver will check if PM runtime
> resumed at vpfe_initialize_device().
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>

resume and suspend carrying regardless needs a comment I think.
(see below)
> ---
>  drivers/media/platform/am437x/am437x-vpfe.c | 22 +++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/platform/am437x/am437x-vpfe.c b/drivers/media/platform/am437x/am437x-vpfe.c
> index 6cdc77dda0e4..bced526f30f2 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);
>  
> @@ -2527,10 +2533,11 @@ static int vpfe_suspend(struct device *dev)
>  {
>  	struct vpfe_device *vpfe = dev_get_drvdata(dev);
>  	struct vpfe_ccdc *ccdc = &vpfe->ccdc;
> +	int ret;
>  
>  	/* only do full suspend if streaming has started */
>  	if (vb2_start_streaming_called(&vpfe->buffer_queue)) {
> -		pm_runtime_get_sync(dev);
> +		ret = pm_runtime_resume_and_get(dev);

Carrying on when you know the resume failed, seems interesting enough to
deserve a comment in the code.  Not sure you can usefully do anything
but it seems likely a lot of the calls that follow will fail.


>  		vpfe_config_enable(ccdc, 1);
>  
>  		/* Save VPFE context */
> @@ -2541,7 +2548,8 @@ static int vpfe_suspend(struct device *dev)
>  		vpfe_config_enable(ccdc, 0);
>  
>  		/* Disable both master and slave clock */
> -		pm_runtime_put_sync(dev);
> +		if (ret >= 0)
> +			pm_runtime_put_sync(dev);
>  	}
>  
>  	/* Select sleep pin state */
> @@ -2583,18 +2591,20 @@ static int vpfe_resume(struct device *dev)
>  {
>  	struct vpfe_device *vpfe = dev_get_drvdata(dev);
>  	struct vpfe_ccdc *ccdc = &vpfe->ccdc;
> +	int ret;
>  
>  	/* only do full resume if streaming has started */
>  	if (vb2_start_streaming_called(&vpfe->buffer_queue)) {
>  		/* Enable both master and slave clock */
> -		pm_runtime_get_sync(dev);
> +		ret = pm_runtime_resume_and_get(dev);
>  		vpfe_config_enable(ccdc, 1);
>  
>  		/* Restore VPFE context */
>  		vpfe_restore_context(ccdc);
>  
>  		vpfe_config_enable(ccdc, 0);
> -		pm_runtime_put_sync(dev);
> +		if (ret >= 0)
> +			pm_runtime_put_sync(dev);
>  	}
>  
>  	/* Select default pin state */