[Intel-gfx] [PATCH 2/4] drm/i915: Remove WaFbcDisableDpfcClockGating on HSW

[Ben Widawsky]

On Mon, Oct 28, 2013 at 03:05:12PM +0200, Ville Syrjälä wrote:
> On Mon, Oct 28, 2013 at 10:22:31AM -0200, Paulo Zanoni wrote:
> > 2013/10/27 Daniel Vetter <daniel at ffwll.ch>:
> > > On Fri, Oct 25, 2013 at 03:27:50PM -0200, Paulo Zanoni wrote:
> > >> 2013/10/24 Ben Widawsky <benjamin.widawsky at intel.com>:
> > >> > Production HSW does not need it. I confirmed this with Art.
> > >> >
> > >> > Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> > >>
> > >> I just hope these things don't start uncovering bugs :)
> > >>
> > >> Reviewed-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> > >
> > > Merged the first 2 patches of this series. Not sure what to do with the
> > > other two, since fbc is essentially disabled on pre-hsw. And no one seems
> > > to really work on it :( So I only see minimal reasons to frob with it ...
> > 
> > IMHO what you said is another reason to actually merge the other two
> > patches, since they make FBC-only WAs be applied only on FBC (e.g.,
> > probably never).
> 
> Another reason would be keeping the codepaths at least somewhat similar.
> Could make it a bit easier to fix things later. If it would be me who
> gets to fix the FBC mess at some point, I'd try to fix it for all gens
> for sure.
> 
> At some point I posted a patch to attempt a quick FBC fix for SNB:
> "[PATCH] drm/i915: Attempt to fix FBC render tracking with hardware contexts"
> 
> In theory that could make FBC work equally well for SNB as it works for
> IVB+. And I must confess that I have FBC enabled on my IVB ultrabook
> currently since it appears to save a rather significant amount of power.
> 
> -- 
> Ville Syrjälä
> Intel OTC


I just looked at your patch, and I should probably comment there, but
it's 5 months old :D. Did you actually observe a fix of something with
that patch? I feel like the way in which we enable/disable tracking, it
shouldn't make a difference.

FWIW: I have two other patches I didn't post yet for SNB. Unfortunately,
I only know one person with failing fbc on SNB, and given his
description, I am not certain it will fix anything.

http://cgit.freedesktop.org/~bwidawsk/drm-intel/log/?h=fbc_fixes

-- 
Ben Widawsky, Intel Open Source Technology Center