From: Arnd Bergmann <arnd@arndb.de>
To: "Michal Nazarewicz" <mina86@mina86.com>
Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added
Date: Wed, 15 Jun 2011 13:20:42 +0200
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Cc: "Zach Pfeffer" <zach.pfeffer@linaro.org>,
        "Daniel Stone" <daniels@collabora.com>,
        "Ankita Garg" <ankita@in.ibm.com>,
        "Daniel Walker" <dwalker@codeaurora.org>,
        "Jesse Barker" <jesse.barker@linaro.org>, "Mel Gorman" <mel@csn.ul.ie>,
        linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org,
        linux-mm@kvack.org, "Kyungmin Park" <kyungmin.park@samsung.com>,
        "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org
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On Wednesday 15 June 2011, Michal Nazarewicz wrote:
> On Tue, 14 Jun 2011 22:42:24 +0200, Arnd Bergmann <arnd@arndb.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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