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

[Pohjolainen, Topi]

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:
> > > > Otherwise, we end up with a bogus value in the third component.  On
> > > gen6-7
> > > > where we always use 2D textures, this can cause problems if the
> > > > SurfaceArray bit is set in the SURFACE_STATE.
> > >
> > > Enlighten me. Why does blorp use 3D surfaces on gen >= 8 but not
> > > earlier?

Related (but not answering the question):
on 9e4d19372b1d7f6ab12ddab1929a53335d9cce06:

diff --git a/src/mesa/drivers/dri/i965/brw_blorp.h b/src/mesa/drivers/dri/i965/brw_blorp.h
index 7ebcee2..a1aaa20 100644
--- a/src/mesa/drivers/dri/i965/brw_blorp.h
+++ b/src/mesa/drivers/dri/i965/brw_blorp.h
@@ -196,8 +196,14 @@ struct brw_blorp_wm_push_constants
    float rect_grid_y1;
    brw_blorp_coord_transform_params x_transform;
    brw_blorp_coord_transform_params y_transform;
+
+   /* Minimum layer setting works for all the textures types but texture_3d
+    * for which the setting has no effect. Use the z-coordinate instead.
+    */
+   uint32_t src_z;
+

The setting actually works on SKL+ if I remember correctly but as I needed
something for gen8 I thought using the mechanism for both instead of adding
yet another path.

> > >
> > 
> > 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+.



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