linux-kernel - Re: [PATCH v2 2/4] dmaengine: Add STM32 DMA driver

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Date:	Wed, 14 Oct 2015 15:17:14 +0200
From:	"M'boumba Cedric Madianga" <cedric.madianga@...il.com>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	Maxime Coquelin <mcoquelin.stm32@...il.com>, robh+dt@...nel.org,
	pawel.moll@....com, Mark Rutland <mark.rutland@....com>,
	ijc+devicetree@...lion.org.uk, Kumar Gala <galak@...eaurora.org>,
	linux@....linux.org.uk, Vinod Koul <vinod.koul@...el.com>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmaengine@...r.kernel.org
Subject: Re: [PATCH v2 2/4] dmaengine: Add STM32 DMA driver

Hi Daniel,

>>> +
>>> +static int stm32_dma_remove(struct platform_device *pdev)
>>> +{
>>> +       struct stm32_dma_device *dmadev = platform_get_drvdata(pdev);
>>> +
>>> +       of_dma_controller_free(pdev->dev.of_node);
>>> +
>>> +       dma_async_device_unregister(&dmadev->ddev);
>>> +
>>> +       clk_disable_unprepare(dmadev->clk);
>>
>>
>> What is the purpose of disabling/unpreparing the clock here?
>> stm32_dma_alloc_chan_resources() and stm32_dma_free_chan_resources() should
>> pair up and the clock should already be stopped.

stm32_dma_remove() could be called during an on-going transfer during
module unload.
So in that case, it seems that disabling/unpreparing the clock is needed.

BR,
Cedric
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