[PATCH 1/3] drm: Send pending vblank events before disabling vblank.

Michel Dänzer michel at daenzer.net
Wed Apr 27 01:32:36 PDT 2011

On Mit, 2011-04-27 at 16:10 +1000, christopher.halse.rogers at canonical.com wrote:
> From: Christopher James Halse Rogers <christopher.halse.rogers at 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.

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

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

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