[Bug 42035] no way to turn off vsync

[Michel Dänzer]

On Mon, 2011-10-24 at 23:23 +0200, Michal Suchanek wrote:
> 2011/10/24 Michel Dänzer <michel at daenzer.net>:
> > On Mon, 2011-10-24 at 16:25 +0200, Michal Suchanek wrote:
> >> 2011/10/24 Michel Dänzer <michel at daenzer.net>:
> >> > On Mon, 2011-10-24 at 14:00 +0200, Michal Suchanek wrote:
> 
> >> I am asking this because my experiments with glxgears  without the
> >> patch show vrefresh limited fps, fps unlimited by vrefresh, and 0 fps
> >> depending on some variables like what screen the window is on, if the
> >> window is mapped or not,
> >
> > Sounds like issues with determining which CRTC to synchronize to.
> >
> >> if the screen is blanked or not,
> >
> > As you discovered recently, the hardware CRTCs only generate vertical
> > blank interrupts while they're enabled.
> >
> >> and current phase of the Moon or some other variable I can't figure out.
> >
> > It's certainly nothing to do with the phase of the moon. :)
> 
> I wonder what is it what determines if the application runs uncapped
> or gets stuck in some GL call when the crtc is turned off.
> 
> One week it would consistently stop applications on turning the crtcs
> off, another it would consistently run them uncapped.

It's hard to say without tracking down at least where they get stuck.

> Without restarting the X server, no less.

That could indicate it's related to some counter wrapping around or
something like that. 


> > Not sure what any of that has to do with this patch though.
> 
> With this patch it should be at least possible to turn off all this
> when it does not work.

Exactly. So, have you had a chance to try it? Does it address your bug
report? 


-- 
Earthling Michel Dänzer           |                   http://www.amd.com
Libre software enthusiast         |          Debian, X and DRI developer