[Bug 39696] dual head: different vert refresh freq, applications sync to the wrong one

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Aug 9 03:54:58 PDT 2011


--- Comment #1 from Michel Dänzer <michel at daenzer.net> 2011-08-09 03:54:57 PDT ---
(In reply to comment #1)
> KMS always sets sligthly different vertical refresh frequencies: 
> The internal display runs at 60 Hz, the external monitor runs at 59.9 Hz.

Please attach the Xorg.0.log file, but most likely the external monitor's
timing is what it specifies as preferred in its EDID.

> However, although I only look at the external monitor,

Then you could switch off the internal display?

> 1.) Is there a way to run both displays at exactly the same vert frequency

You could try manually setting the internal display's mode on the external
monitor (or the other way around, but internal panels are typically pickier).

> and with synchronized vertical retrace?

There's no mechanism for that yet in general. However, if you manage to use the
same mode for both displays, you might be able to source both of them off the
same CRTC, in which case they should be perfectly synchronized.

> 2.) Is there a way to switch 3D and video application sync
> from the internal to the external vsync rate?

For video, you can use the XV_CRTC attribute to choose which CRTC to sync to
(see the radeon manpage).

There's no such mechanism for 3D yet.

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