EXA pixmap alignments.

Michel Dänzer michel at daenzer.net
Wed Sep 28 14:03:13 PDT 2005

On Wed, 2005-09-28 at 09:18 -0400, Felix Kühling wrote:
> Am Mittwoch, den 28.09.2005, 18:59 +1000 schrieb Benjamin Herrenschmidt:
> > On Wed, 2005-09-28 at 08:32 +0200, Lars Knoll wrote:
> > 
> > > Btw, is there any way to know if an AGP chipset supports writes 
> > > from card to AGP?
> > 
> > Not really afaik. The radeon DRI does a sneaky test at startup, it
> > "tries" to do a writeback to a scratch location and verifies if it
> > actually worked. If not, it uses MMIO reads to read the scratch value
> > (used for register aging afaik), if yes, it reads the one that was
> > written to AGP. That's the only thing that info is used for though at
> > the moment.
> That test used to be unreliable on my old Radeon 7500. The test would
> pass and the AGP writeback would fail later on after a few seconds of
> 3D. I had to work around that problem by reducing AGP speed from 4x to
> 2x.

Yeah, we should really use PCI transfers for scratch register and ring
read pointer writeback.

Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer

More information about the xorg mailing list