From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>
Subject: Re: [PATCH 3/4] drm/i915: Drop the excessive vblank
 waits from modeset codepaths
Date: Wed, 16 Apr 2014 16:27:12 +0300
Message-ID: <20140416132712.GI18465@intel.com>
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To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
List-Id: intel-gfx@lists.freedesktop.org

On Wed, Mar 12, 2014 at 09:25:42AM +0000, Chris Wilson wrote:
> On Wed, Mar 12, 2014 at 11:16:59AM +0200, Ville Syrj=E4l=E4 wrote:
> > On Wed, Mar 12, 2014 at 08:35:39AM +0000, Chris Wilson wrote:
> > > On Tue, Mar 11, 2014 at 07:37:35PM +0200, ville.syrjala@linux.intel.c=
om wrote:
> > > > From: Ville Syrj=E4l=E4 <ville.syrjala@linux.intel.com>
> > > > =

> > > > Now that we've plugged the mmio vs. ring flip race, we shouldn't ne=
ed
> > > > these vblank waits in the modeset codepaths anymore. So get rid of
> > > > them.
> > > =

> > > Hmm, could we not add an assert(DSPSURFLIVE =3D=3D
> > > intel_crtc->dspsurf)?
> > =

> > Where would you want the assert?
> =

> assert_plane_is_bound(new_fb) in crtc_enable() and
> assert_plane_is_bound(old_fb) in crt_disable(). i.e. add them to our set
> of plane/pipe checks through modeset.

We can't really add live base address checks to such places w/o adding
extra vblank waits. For example if we first do a set_base w/o waiting for
vblank and then disable the crtc. By the time we get to crtc_disable()
there's no guarantee that the mmio flip from set_base has completed, and
hence the live surface address may still have the old value.

For the atomic page flip stuff the live address can serve as a decent
debug tool to make sure the flip has really completed or not completed
when we expect. IIRC I had such a debug patch in my atomic branch.

-- =

Ville Syrj=E4l=E4
Intel OTC