linux-kernel - Re: [PATCH] dmaengine: ti: Fix runtime PM imbalance on error

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Message-ID: <6169df3d-3d04-644c-fc70-a184ecfa97c8@gmail.com>
Date:   Sat, 22 Jan 2022 10:09:53 +0200
From:   Péter Ujfalusi <peter.ujfalusi@...il.com>
To:     Yongzhi Liu <lyz_cs@....edu.cn>, vkoul@...nel.org
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: ti: Fix runtime PM imbalance on error



On 1/16/22 13:31, Yongzhi Liu wrote:
> pm_runtime_get_sync() increments the runtime PM usage counter even
> when it returns an error code, thus a matching decrement is needed on
> the error handling path to keep the counter balanced.

The patch is correct, however the commit message is a bit incorrect.

We are not adding any visible matching decrement, we are switching to
pm_runtime_resume_and_get() which only increments the usage counter if
pm_runtime_resume() is successful.
Granted internally it does a pm_runtime_put_noidle() if resume call fails.

Switch to pm_runtime_resume_and_get() to keep the device's use caunt
balanced?

> 
> Signed-off-by: Yongzhi Liu <lyz_cs@....edu.cn>
> ---
>  drivers/dma/ti/edma.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/ti/edma.c b/drivers/dma/ti/edma.c
> index 08e47f4..a73f779 100644
> --- a/drivers/dma/ti/edma.c
> +++ b/drivers/dma/ti/edma.c
> @@ -2398,9 +2398,9 @@ static int edma_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, ecc);
>  
>  	pm_runtime_enable(dev);
> -	ret = pm_runtime_get_sync(dev);
> +	ret = pm_runtime_resume_and_get(dev);
>  	if (ret < 0) {
> -		dev_err(dev, "pm_runtime_get_sync() failed\n");
> +		dev_err(dev, "pm_runtime_resume_and_get() failed\n");
>  		pm_runtime_disable(dev);
>  		return ret;
>  	}

-- 
Péter