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

[Torgeir Veimo]

On 8 Jun 2007, at 12:18, 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?
>
> MythTV uses DRM vertical blanking sync with Xv output; I wouldn't  
> say it
> uses 3D by any stretch of the imagination.

If the screensaver is disabled, as is often the case when a media  
player runs full screen, can't that be a toggle to always turn on  
vblank irqs?


-- 
Torgeir Veimo
torgeir at pobox.com