Vertical sync and KMS

[Sven Arvidsson]

On Sat, 2010-11-20 at 13:34 +0100, Sylvain Beucler wrote:
> Hi,
> 
> Since the switch to KMS (Kernel Mode Setting) in the current Debian, I
> cannot get vertical sync to work with free 3D drivers.
> 
> (Vertical syncs caps the game framerate to the physical screen's
> refresh rate, typically 60Hz, avoiding tearing and unnecessary display
> updates, and permitting smooth scrolling.)
> 
> The only way to get vsync back is either use a proprietary driver or
> switch back to UMS (in either case: when that's actually possible).  I
> tried with 2 ATI Radeon cards and an Intel one, using a simple
> scrolling demo with bare OpenGL, SDL 1.3 and Pyglet.
> 
> Do you get this issue in other distros, and do you know what's the
> cause?

It should work, for both radeon and intel, but I'm not sure if it's
supported in Mesa 7.8. You might need 7.9 from experimental.

Then either setting "vblank_mode=2" as an environment variable or or a
drirc configuration like the one below should give you vertical sync:

        <driconf>
           <device screen="0" driver="dri2">
              <application name="Default">
                  <option name="vblank_mode" value="2" />
              </application>
            </device>
        </driconf>


-- 
Cheers,
Sven Arvidsson
http://www.whiz.se
PGP Key ID 760BDD22

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