[Intel-gfx] [PATCH 2/8] drm/i915: skip redundant operations whilst enabling pipes and planes

[Chris Wilson]

On Fri, 18 Mar 2011 09:25:22 -0700, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> On Fri, 18 Mar 2011 08:02:04 +0000
> Chris Wilson <chris at chris-wilson.co.uk> wrote:
> 
> > If the pipe or plane is already enabled, then we do not need to enable
> > it again and can skip the delay.
> > 
> > References: https://bugs.freedesktop.org/show_bug.cgi?id=34601
> > Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> 
> Does this one actually fix the issue?  Unless we're trying to get
> suspend, resume, or mode setting down under 100ms it's probably not
> worth it to try to avoid the vblank waits (this is me being paranoid
> about our mode setting code).

This is the one QA identified as fixing the regression from b24e717988,
which worries me.

I admit to not knowing what the root cause is, but it was a change
introduced by b24e71798 and had unfortunate side-effects.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre