From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH] dma: mv_xor_v2: new driver
Date: Fri, 17 Jun 2016 08:09:20 +0530
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To: Thomas Petazzoni <thomas.petazzoni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
Cc: dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Ian Campbell <ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>, Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>, Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>, Jason Cooper <jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org>, Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>, Sebastian Hesselbarth <sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Gregory Clement <gregory.clement-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>, Nadav Haklai <nadavh-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>, Lior Amsalem <alior-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
List-Id: devicetree@vger.kernel.org

On Thu, Jun 16, 2016 at 02:42:24PM +0200, Thomas Petazzoni wrote:
> Hello,
> 
> On Wed, 15 Jun 2016 22:11:31 +0530, Vinod Koul wrote:
> 
> > > This is probably the only thing that I have not changed. The mv_xor
> > > driver is already using the same strategy, and enqueuing in
> > > issue_pending() would force us to add the request to a temporary linked
> > > list, which would be dequeued in issue_pending(). This is quite a bit
> > > of additional processing, while pushing the new requests directly to
> > > the engine works fine.  
> > 
> > Well that is wrong! And patch is welcome for mv_xor as well :)
> > 
> > The DMAengine API mandates that we should submit a descriptor to a queue and
> > then push them by invoking issue_pending.
> > 
> > The users are also expected to follow this
> 
> I have just sent a v4 that fixes this for the mv_xor_v2 driver. Now, in
> ->tx_submit() we only fill in the HW descriptors, but do not tell the
> engine to process them. It's only at ->issue_pending() time that we
> tell the engine that there N new descriptors to process.

Okay that sounds good to me, I will take a look at it..
> 
> I'll have a look at mv_xor a bit later.

Sounds fair enough

-- 
~Vinod
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