linux-kernel - Re: [PATCH v4 09/14] dmaengine: tegra-apb: Clean up runtime PM teardown

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Message-ID: <9a5c4f82-5653-8d81-e304-76675aff5d8f@nvidia.com>
Date:   Wed, 15 Jan 2020 09:57:44 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
CC:     <dmaengine@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 09/14] dmaengine: tegra-apb: Clean up runtime PM
 teardown


On 12/01/2020 17:30, Dmitry Osipenko wrote:
> It's cleaner to teardown RPM by revering the enable sequence, which makes
> code much easier to follow.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/dma/tegra20-apb-dma.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 7158bd3145c4..cc4a9ca20780 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -1429,13 +1429,15 @@ static int tegra_dma_probe(struct platform_device *pdev)
>  	spin_lock_init(&tdma->global_lock);
>  
>  	pm_runtime_enable(&pdev->dev);
> -	if (!pm_runtime_enabled(&pdev->dev))
> +	if (!pm_runtime_enabled(&pdev->dev)) {
>  		ret = tegra_dma_runtime_resume(&pdev->dev);
> -	else
> +		if (ret)
> +			return ret;
> +	} else {
>  		ret = pm_runtime_get_sync(&pdev->dev);
> -
> -	if (ret < 0)
> -		goto err_pm_disable;
> +		if (ret < 0)
> +			goto err_pm_disable;
> +	}
>  
>  	/* Reset DMA controller */
>  	reset_control_assert(tdma->rst);
> @@ -1545,9 +1547,10 @@ static int tegra_dma_probe(struct platform_device *pdev)
>  	dma_async_device_unregister(&tdma->dma_dev);
>  
>  err_pm_disable:
> -	pm_runtime_disable(&pdev->dev);
> -	if (!pm_runtime_status_suspended(&pdev->dev))
> +	if (!pm_runtime_enabled(&pdev->dev))
>  		tegra_dma_runtime_suspend(&pdev->dev);
> +	else
> +		pm_runtime_disable(&pdev->dev);
>  
>  	return ret;
>  }
> @@ -1558,9 +1561,10 @@ static int tegra_dma_remove(struct platform_device *pdev)
>  
>  	dma_async_device_unregister(&tdma->dma_dev);
>  
> -	pm_runtime_disable(&pdev->dev);
> -	if (!pm_runtime_status_suspended(&pdev->dev))
> +	if (!pm_runtime_enabled(&pdev->dev))
>  		tegra_dma_runtime_suspend(&pdev->dev);
> +	else
> +		pm_runtime_disable(&pdev->dev);

Looks like dma_async_device_unregister() will warn if a client still has
a channel requested but does not prevent the unregister from completing.
So it could be possible that we could be leaving the controller active now.

Jon

-- 
nvpublic