linux-kernel - Re: [PATCH 7/8] dmaengine/dw_dmac: Unmap all memory buffers after completion of slave transfers

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Message-ID: <20120118093559.GB1068@n2100.arm.linux.org.uk>
Date:	Wed, 18 Jan 2012 09:35:59 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Viresh Kumar <viresh.kumar@...com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	Pratyush ANAND <pratyush.anand@...com>,
	Rajeev KUMAR <rajeev-dlh.kumar@...com>,
	Bhupesh SHARMA <bhupesh.sharma@...com>,
	Armando VISCONTI <armando.visconti@...com>,
	Mirko GARDI <mirko.gardi@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Vipin KUMAR <vipin.kumar@...com>,
	Shiraz HASHIM <shiraz.hashim@...com>,
	Amit VIRDI <Amit.VIRDI@...com>,
	Vipul Kumar SAMAR <vipulkumar.samar@...com>,
	"viresh.linux@...il.com" <viresh.linux@...il.com>,
	Deepak SIKRI <deepak.sikri@...com>,
	Bhavna YADAV <bhavna.yadav@...com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Vincenzo FRASCINO <Vincenzo.FRASCINO@...com>
Subject: Re: [PATCH 7/8] dmaengine/dw_dmac: Unmap all memory buffers after
	completion of slave transfers

On Tue, Jan 17, 2012 at 02:37:10PM +0530, Viresh Kumar wrote:
> On 1/17/2012 2:22 PM, Linus Walleij wrote:
> > Basically the driver using the dmaengine shall map/unmap buffers
> > used for slave transfers, not the driver.
> > 
> > I usually map them before setting up a transfer and unmaps them
> > when egtting the callback from the DMA engine that the transfer is
> > complete.
> > 
> 
> You implemented similar stuff in amba-pl08x :) .
> 
> if (!plchan->slave)
> 	pl08x_unmap_buffers(txd);

Take a look at that.  "If *NOT* slave, unmap the buffers".  That is in
keeping with what I've been saying.  Slave transfers *do* *not* get
automatic buffer unmapping.
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