[Mesa-dev] [PATCH 08/64] i965/blorp: Only set src_z for gen8+ 3D textures

[Chad Versace]

On Tue 21 Jun 2016, Pohjolainen, Topi wrote:
> On Mon, Jun 20, 2016 at 08:52:50PM -0700, Kenneth Graunke wrote:
> > On Friday, June 17, 2016 4:55:41 PM PDT Jason Ekstrand wrote:
> > > On Thu, Jun 16, 2016 at 10:08 AM, Chad Versace <chad.versace at intel.com>
> > > wrote:
> > > 
> > > > On Sat 11 Jun 2016, Jason Ekstrand wrote:

> > > > Enlighten me. Why does blorp use 3D surfaces on gen >= 8 but not
> > > > earlier?


> > > History?  TBH, I'm not really sure.  Probably because SKL 3-D is different
> > > but you'd have to ask topi to be sure.
> > 
> > Historically, we did everything via tile x/y offsets, and so BLORP
> > worked that way too.  However, we never applied any offsets to the
> > auxiliary surfaces (i.e. CMS).  This seems fairly sketchy, and got
> > us into trouble when we ported it to Gen8.  As a hack, falling back
> > from CMS to UMS made things work out.
> > 
> > Rather than try and figure out proper offset calculations for CCS_D,
> > CCS_E, and HiZ, Topi decided to just access everything using level/layer
> > like we do for normal GL.  It seemed a lot safer, and worked out well.
> > 
> > Gen6 never uses CMS, so it works out.  Topi seemed to think that Gen7
> > can't do CMS for array textures (though I can't seem to find that code
> > to confirm), so it might work out.  I'm still not sure why Gen7 works.
> 
> I need to dig some more for this, I can't remember either.
> 
> > 
> > Honestly, I think it'd be better to convert Gen6-7 to be like Gen8+.

Yes, I agree. We should XOffset/YOffset when possible.