From: Arnd Bergmann <arnd@arndb.de>
To: David Sin <davidsin@ti.com>
Subject: Re: [PATCH 0/9] TI DMM-TILER driver
Date: Thu, 16 Dec 2010 18:43:48 +0100
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Cc: linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org,
        Greg KH <greg@kroah.com>, Russell King <rmk@arm.linux.org.uk>,
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On Thursday 16 December 2010 18:37:38 David Sin wrote:
> I'm not sure exactly how DRM/GEM works..  What functionality do you think is 
> overlapping?  The main feature, aside from reduced page accesses, of the DMM 
> hw block is to provide physically contiguous 2 dimensional memory blocks for 
> image and video processing.  This hw sits between the interconnect and the 
> ext memory interface in the OMAP, and contains an MMU-like address traslator 
> for "virtually" physically contiguous memory and sdram pages.

As far as I can tell, both DMM and GEM at a high level manage objects
in video memory. The IOMMU that you have on the Omap hardware seems
to resemble the GART that sits between PC-style video cards and main
memory.

I don't know any details, but google quickly finds
http://lwn.net/Articles/283798/ with a description of the
initial GEM design. My main thought when looking over the
DMM code was that this should not be tied too closely to a
specific hardware, and GEM seems to be an existing abstraction
that may fit what you need.

	Arnd
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