linux-kernel - Re: [PATCH v2 5/7] dmaengine: dw: platform: power on device on shutdown

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Date:	Thu, 26 Nov 2015 22:31:05 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org, dmaengine@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v2 5/7] dmaengine: dw: platform: power on device on
 shutdown

On Thu, Nov 26, 2015 at 05:19:11PM +0200, Andy Shevchenko wrote:
> We have to call dw_dma_disable() to stop any ongoing transfer.

Ok

> On some platforms we can't do that since DMA device is powered off.

Umm, you said we have ongoing transfer which means DMA should be on..!!

> Moreover we have no
> possibility at that point to check if the platform is affected or not. That's
> why we call pm_runtime_get_sync() / pm_runtime_put() unconditionally. On the
> other hand we can't use pm_runtime_suspended() because runtime PM framework is
> not fully used by the driver.

Shouldn't that be fixed?

> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/dma/dw/platform.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index 68a4815..d0734e9 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -239,7 +239,19 @@ static void dw_shutdown(struct platform_device *pdev)
>  {
>  	struct dw_dma_chip *chip = platform_get_drvdata(pdev);
>  
> +	/*
> +	 * We have to call dw_dma_disable() to stop any ongoing transfer. On
> +	 * some platforms we can't do that since DMA device is powered off.
> +	 * Moreover we have no possibility to check if the platform is affected
> +	 * or not. That's why we call pm_runtime_get_sync() / pm_runtime_put()
> +	 * unconditionally. On the other hand we can't use
> +	 * pm_runtime_suspended() because runtime PM framework is not fully
> +	 * used by the driver.
> +	 */
> +	pm_runtime_get_sync(chip->dev);
>  	dw_dma_disable(chip);
> +	pm_runtime_put_sync_suspend(chip->dev);
> +
>  	clk_disable_unprepare(chip->clk);
>  }
>  
> -- 
> 2.6.2
> 

-- 
~Vinod
--
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