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List:       freedesktop-xorg
Subject:    Re: EXA for radeon experimental patch
From:       Benjamin Herrenschmidt <benh () kernel ! crashing ! org>
Date:       2005-09-01 11:11:50
Message-ID: 1125573111.8735.54.camel () gaston
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On Thu, 2005-09-01 at 11:44 +0100, Alan Cox wrote:
> On Iau, 2005-09-01 at 09:16 +0200, Lars Knoll wrote:
> > What about writes from GPU to PCI? Maybe these exist.
> 
> Quite a few cards can do this. It is one reason things like VIA drivers
> have command filters for DRI - to stop people blitting patches into the
> kernel memory.
> 
> In addition almost any AGP card can copy from video memory to AGP. You
> then pull the pages out of the GART (fast), cache them (fast), use them
> (fast), flush them to ram (not too slow), and put them uncached back
> into the GART.

Yup, except that quite a bit of AGP chipsets don't support writes from
the card to AGP memory :(

It would be useful to have the AGP backend to expose that info

Ben.


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