[Intel-gfx] [PATCH 3/3] drm/i915: don't rewrite the GTT on resume v2

[Jesse Barnes]

On Tue, 30 Oct 2012 21:32:17 +0000
Chris Wilson <chris at chris-wilson.co.uk> wrote:

> On Tue, 30 Oct 2012 18:59:31 +0100, Daniel Vetter <daniel at ffwll.ch> wrote:
> > On Fri, Oct 26, 2012 at 10:08:38AM -0700, Jesse Barnes wrote:
> > > The BIOS shouldn't be touching this memory across suspend/resume, so
> > > just leave it alone.  This saves us ~50ms on resume on my T420.
> > > 
> > > v2: change gtt restore default on pre-gen4 (Chris)
> > >     move needs_gtt_restore flag into dev_priv
> > > 
> > > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> > 
> > I've just realized: GGTT PTEs are stored in stolen mem, and hence not
> > restored accross S4.
> 
> How to ruin the day. So we may as just evict everything upon suspend and
> rebuild as needed?

Yeah Daniel is a party pooper.

So I need to measure this again anyway now that we write combine
things, it may not be worth it anymore (though 2M of writes is still a
fairly large amount).  If it's still a long delay, I'll just apply it
to the S3 paths instead of S4.

-- 
Jesse Barnes, Intel Open Source Technology Center