Waiting for vertical refresh on Intel 965 and 945 chips in recent git

[Michel Dänzer]

On Fri, 2007-06-08 at 21:18 +1000, Hamish Moffatt wrote:
> On Fri, Jun 08, 2007 at 08:23:05AM +0200, Michel Dänzer wrote:
> > On Thu, 2007-06-07 at 18:00 +0100, Simon Farnsworth wrote:
> > > 
> > > In the 7.2 release, I could use the DRM directly to wait for vertical
> > > blanking, using the DRM_IOCTL_WAIT_VBLANK ioctl. The intel driver has
> > > been changed to only enable the interrupt if 3D is in use, so I reworked
> > > my code to use the GLX_SGI_video_sync extension to wait for VBlank.
> > > 
> > > I am now finding that the OpenGL based wait for VBlank also fails if the
> > > window I create to get an OpenGL context is fully obscured;
> > > glXWaitVideoSyncSGI returns 5 (GLX_BAD_CONTEXT). My code automatically
> > > falls back to trying the DRM method, but DRM_IOCTL_WAIT_VBLANK returns
> > > 16 (EBUSY).
> > 
> > Yes, this is because the X server DRI layer now counts DRI windows
> > according to visibility, to allow e.g. page flipping to work with
> > multiple windows as long as only one of them is visible. So the intel
> > driver can't tell the difference between a window being invisible and it
> > not existing at all and disables the vblank interrupts.
> 
> How is "3D in use" defined?

With current xserver master: One or more DRI windows is visible.

With xserver 1.3 or older: One or more DRI windows exists.

> MythTV uses DRM vertical blanking sync with Xv output; I wouldn't say it
> uses 3D by any stretch of the imagination.

Doesn't it use GL for the menus? If so, the above conditions are
probably satisfied with direct rendering or AIGLX.


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