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Date: Sun, 8 Dec 2002 16:28:43 +1100
From: David Gibson <david@gibson.dropbear.id.au>
To: "Adam J. Richter" <adam@yggdrasil.com>, James.Bottomley@steeleye.com,
       jgarzik@pobox.com, linux-kernel@vger.kernel.org, miles@gnu.org
Subject: Re: [RFC] generic device DMA implementation
Message-ID: <20021208052843.GA30968@zax.zax>
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References: <200212060714.XAA06006@adam.yggdrasil.com> <20021207094530.GB22230@zax.zax> <20021207112657.A18207@flint.arm.linux.org.uk>
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On Sat, Dec 07, 2002 at 11:26:57AM +0000, Russell King wrote:
> On Sat, Dec 07, 2002 at 08:45:30PM +1100, David Gibson wrote:
> > Actually, no, since my idea was to remove the "consistent_alloc()"
> > path from the driver entirely - leaving only the map/sync approach.
> > That gives a result which is correct everywhere (afaict) but (as
> > you've since pointed out) will perform poorly on platforms where the
> > map/sync operations are expensive.
> 
> As I've also pointed out in the past couple of days, doing this will
> mean that you then need to teach the drivers to align structures to
> cache line boundaries.  Otherwise, you _will_ get into a situation
> where you _will_ loose data.

Sure, but that's already an issue with the current streaming DMA API.

-- 
David Gibson			| For every complex problem there is a
david@gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson
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