On Wed, 2011-04-27 at 10:32 +0200, Michel Dänzer wrote:
On Mit, 2011-04-27 at 16:10 +1000, christopher.halse.rogers@canonical.com wrote:
From: Christopher James Halse Rogers christopher.halse.rogers@canonical.com
This is the least-bad behaviour. It means that we signal the vblank event before it actually happens, but since we're disabling vblanks there's no guarantee that it will *ever* happen otherwise.
This may indeed be the best we can do for events that are pending when the CRTC is disabled[0], but I can't see anything that would prevent new events from getting scheduled (or synchronous vblank waits from timing out) while the CRTC is disabled?
[0] Though it might unnecessarily send events prematurely when the CRTC is just disabled temporarily, e.g. as part of a modeset.
Also, this patch won't seem to help at all for other drivers which don't call drm_vblank_off() directly when disabling a CRTC.
This is true. On the other hand, the other drivers don't wedge the vblank code into a state where vblanks cannot be re-enabled. So it's only a problem when disabling one of 2+ monitors on those drivers, whereas it's easily triggerable on single monitor systems on intel.
Maybe it would be possible to move those calls to core code, and/or only force sending out events when the CRTC isn't just getting disabled temporarily.
As in: have the core modesetting code call drm_vblank_off before making the driver-specific calls when disabling a crtc? I'll look into it - that would appear to be a more general solution.
It would be nice if the OML_sync_control had been written with a less than laser-like focus on the single monitor case, too. :/