linux-kernel - Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added

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Message-Id: <201106151320.42182.arnd@arndb.de>
Date:	Wed, 15 Jun 2011 13:20:42 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Michal Nazarewicz" <mina86@...a86.com>
Cc:	"Zach Pfeffer" <zach.pfeffer@...aro.org>,
	"Daniel Stone" <daniels@...labora.com>,
	"Ankita Garg" <ankita@...ibm.com>,
	"Daniel Walker" <dwalker@...eaurora.org>,
	"Jesse Barker" <jesse.barker@...aro.org>,
	"Mel Gorman" <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	"Kyungmin Park" <kyungmin.park@...sung.com>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added

On Wednesday 15 June 2011, Michal Nazarewicz wrote:
> On Tue, 14 Jun 2011 22:42:24 +0200, Arnd Bergmann <arnd@...db.de> wrote:
> > * We still need to solve the same problem in case of IOMMU mappings
> >   at some point, even if today's hardware doesn't have this combination.
> >   It would be good to use the same solution for both.
> 
> I don't think I follow.  What does IOMMU has to do with CMA?

The point is that on the higher level device drivers, we want to
hide the presence of CMA and/or IOMMU behind the dma mapping API,
but the device drivers do need to know about the bank properties.

If we want to solve the problem of allocating per-bank memory inside
of CMA, we also need to solve it inside of the IOMMU code, using
the same device driver interface.

	Arnd
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