Re: [Intel-gfx] [PATCH] drm/i915: Fix display problems after resume

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Sep 12, 2022 at 02:48:54PM +0200, Thomas Hellström wrote:
> On Mon, 2022-09-12 at 15:43 +0300, Ville Syrjälä wrote:
> > On Mon, Sep 12, 2022 at 02:19:57PM +0200, Thomas Hellström wrote:
> > > Commit 39a2bd34c933 ("drm/i915: Use the vma resource as argument
> > > for gtt
> > > binding / unbinding") introduced a regression that due to the vma
> > > resource
> > > tracking of the binding state, dpt ptes were not correctly
> > > repopulated.
> > 
> > Doesn't this mean all ggtt ptes weren't repopulated? So I'm
> > wondering how anything at all has been working?
> 
> ggtt ptes had a different check that was copy-pasted from the pre-vma-
> resource code and that wasn't that strict. Hence why it worked.

The ggtt one seems to want to skip if the vma is already bound 
with the other flag than what we're using this time, but doesn't
skip if it's already bound with the same flag(s). I have no idea
what it's trying to achieve there.

The dpt case skips if it's a bound at all, which seems much more
obvious but the fact that ggtt code never did that makes me
suspect it's not that clear cut.

So seems to me that the two checks are trying to do achieve
different goals, but at least I can't tell why that is.

-- 
Ville Syrjälä
Intel