Vblanks, CRTCs and GLX, oh my!

Michel Dänzer michel at tungstengraphics.com
Fri Sep 21 08:04:14 PDT 2007

On Fri, 2007-09-21 at 07:59 -0700, Jesse Barnes wrote:
> On Friday, September 21, 2007 2:51:02 am Michel Dänzer wrote:
> > > So:
> > >   - use the vblank-rework tree to make per-CRTC vblank counters (as
> > > you
> > >     say, this breaks some setups but will fix others)
> >
> > Out of curiosity, what setups are you thinking of that this will fix on
> > its own? Can't think of any offhand.
> It should fix the case where a client is waiting on pipe B when vblank 
> interrupts on pipe A go from off to on.  Currently, that'll cause the client 
> to switch to the wrong vblank counter after pipe A's interrupts become 
> active.  In the vblank rework tree, it'll either not work in the first place 
> (because it's using the wrong counter) or it'll work and keep working due to 
> passing in DRM_VBLANK_SECONDARY.  I think this is the correct
> behavior.

Unless I'm missing something, this would only be true if
xf86-video-intel ever enabled vblank interrupts for pipe B only, which
it doesn't (with a DRM that supports vblank interrupts on both pipes
independently). It always leaves them enabled for pipe A, even when pipe
A is actually disabled.

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

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