Re: [PATCH 09/12] drm/i915: rip our vblank reset hacks for runtime PM

Thierry Reding
2014-05-21T12:49:05Z

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On Tue, May 20, 2014 at 03:03:41PM +0300, Ville Syrjälä wrote:
> On Wed, May 14, 2014 at 08:51:11PM +0200, Daniel Vetter wrote:
> > Now that we unconditionally dtrt when disabling/enabling crtcs we
> > don't need any hacks any longer to keep the vblank logic sane when
> > all the registers go poof. So let's rip it all out.
>
> Hmm. drm_update_vblank_count() will now see some kind of diff between
> the last and current value when the registers got cloberred. So the
> vblank counter reported to userspace will jump. But I guess that's fine
> as long as userspace realizes that the counter is not at all reliable
> across modesets.

I think that's a fair assumption. Modeset is kind of a heavy operation
and I wouldn't expect applications to perform one all that often. That
should be even more true of applications that rely on the counters. At
least that would be my expectation.

Thierry

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