linux-kernel - Re: [PATCH V7 3/3] dma: add Qualcomm Technologies HIDMA channel driver

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Date:	Sat, 5 Dec 2015 13:30:30 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Sinan Kaya <okaya@...eaurora.org>
Cc:	dmaengine@...r.kernel.org, timur@...eaurora.org,
	cov@...eaurora.org, jcm@...hat.com, agross@...eaurora.org,
	arnd@...db.de, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V7 3/3] dma: add Qualcomm Technologies HIDMA channel
 driver

On Wed, Dec 02, 2015 at 02:04:05PM -0500, Sinan Kaya wrote:
> >> > You are missing the point. Channel can be paused, yes but the descriptor
> >> > is in queue and is not paused. The descriptor running is paused, yes.
> >> > There is subtle difference between these
> > I'll follow your recommendation. PAUSE for the currently active
> > descriptor and DMA_IN_PROGRESS for the rest.
> > 
> 
> I'm now confused.
> 
> I looked at several DMA driver implementations.
> 
> 1. They call dma_cookie_status function to see if the job is done.
> 2. If done, they return right ahead.
> 3. Otherwise, dma_cookie_status returns DMA_IN_PROGRESS.
> 4. Next the code checks if the channel is paused and return value is
> DMA_IN_PROGRESS. The code changes return code to DMA_PAUSED.
> 
> Whereas, I was returning paused first before even checking if the
> descriptor is done. Are you OK with the sequence 1..4 above?

Yes am okay with this with slight change in 4.

You should set to PAUSED only for current descriptor and not for the ones in
queue

-- 
~Vinod
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