linux-kernel - Re: [PATCH] dmaengine: pxa_dma: implement device

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Message-ID: <20160712043516.GP9681@localhost>
Date:	Tue, 12 Jul 2016 10:05:16 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:	Daniel Mack <daniel@...que.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pxa_dma: implement device_synchronize

On Sun, Jul 10, 2016 at 11:50:49PM +0200, Robert Jarzmik wrote:
> Implement the function which wait until a dma channel is stopped to have
> a synchronization point.
> 
> This also protects the pxad_remove() from races, such as spurious
> interrupts while removing the driver, because :
>  - as long as there is one dma channel requested, ie. dma_chan_get() but
>    no dma_chan_put(), the try_module_get() of dma_chan_get() prevents
>    the remove() routine from running
>  - when the last channel is released, ie. the last dma_chan_put() is
>    called, if there is a running DMA, pxad_synchronize() is called
>  - pxad_synchronize() waits for the channel to stop, which in turn
>    ensures on pxa architecture that the interrupt cannot be fired anymore

Applied, thanks

-- 
~Vinod