[Bug 42035] no way to turn off vsync

[Michel Dänzer]

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:
> >> 2011/10/24 Michel Dänzer <michel at daenzer.net>:
> >> > On Don, 2011-10-20 at 12:16 +0200, Michal Suchanek wrote:
> >> >>
> >> >> On 20 October 2011 11:38,  <bugzilla-daemon at freedesktop.org> wrote:
> >> >> > https://bugs.freedesktop.org/show_bug.cgi?id=42035
> >> >> >
> >> >> > --- Comment #1 from Michel Dänzer <michel at daenzer.net> 2011-10-20 02:38:29 PDT ---
> >> >> >> This should be runtime configurable, preferably per-application like dri.
> >> >> >
> >> >> > That would require some xserver dri2 changes first, to allow the driver to tell
> >> >> > the different cases apart. There's been some discussion about this on the
> >> >> > xorg-devel list, started by Chris Wilson.
> >> >>
> >> >> Anyone can point at the discussion or say what the problem is with this?
> >> >
> >> > Actually, the radeon driver patch below might be good enough, at least
> >> > for now. It disables Option "SwapBuffersWait" by default when the real
> >> > sync-to-vblank functionality is working. There should be no need for the
> >> > vline waits for DRI2 in that case.
> >> >
> >> > Thoughts
> >>
> >> Is it possible to determine if the option is on or off?
> >>
> >> Or does it produce some log messages saying what it enables based on what?
> >
> > You're welcome to try it yourself. ;) Anyway, the updated patch below shows
> 
> 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. :)

Not sure what any of that has to do with this patch though.


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