[Nouveau] [Bug 92306] GL Excess demo renders incorrectly on nv43

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=92306

--- Comment #17 from Ben Skeggs <skeggsb at gmail.com> ---
(In reply to Ilia Mirkin from comment #14)
> (In reply to Andrew Randrianasulu from comment #13)
> > (In reply to Ilia Mirkin from comment #12)
> > > (In reply to Andrew Randrianasulu from comment #11)
> > > > "Mismatched color and zeta formats, ignoring zeta."
> > > 
> > > Yeah, as I suspected... unfortunately there's not a ton you can do besides
> > > fixing the issue. The problem is that you can't render to a 32-bit color
> > > format (e.g. RGBA8) while using a 16-bit zeta (Z16), and conversely you
> > > can't render to a 16-bit color format (e.g. RGB565) while using a 32-bit
> > > zeta (Z24S8).
> > > 
> > > My current solution to this problem is to just not set the zeta buffer and
> > > move on with life. This leads to incorrect rendering, but at least no hangs.
> > > 
> > > The proper solution is to have 2 depth textures that you copy to and fro and
> > > set the "right" one for the given color format. Ideally while minimizing the
> > > number of copies.
> > 
> > Hm, but in my case it apparently worked fine... so, may be check is
> > overrestrictive?
> > 
> > I also tried to apply this path on top of mesa version indicated above
> > ((git-93161be)
> > 
> > ----patch---
> > diff --git a/src/gallium/drivers/nouveau/nv30/nv30_state.c
> > b/src/gallium/drivers/nouveau/nv30/nv30_state.c
> > index fd604c2..cceedfd 100644
> > --- a/src/gallium/drivers/nouveau/nv30/nv30_state.c
> > +++ b/src/gallium/drivers/nouveau/nv30/nv30_state.c
> > @@ -382,7 +382,7 @@ nv30_set_framebuffer_state(struct pipe_context *pipe,
> >             (util_format_get_blocksize(fb->zsbuf->format) > 2) !=
> >             (util_format_get_blocksize(fb->cbufs[0]->format) > 2)) {
> >            nv30->framebuffer.zsbuf = NULL;
> > -          debug_printf("Mismatched color and zeta formats, ignoring
> > zeta.\n");
> > +          debug_printf("Mismatched color %d and zeta %d formats, ignoring
> > zeta.\n", fb->cbufs[0]->format, fb->zsbuf->format);
> >         }
> >      }
> >  }
> > --------end-----
> > 
> > and got this in terminal:
> > "Mismatched color 1 and zeta 16 formats, ignoring zeta."
> > 
> > This is a bit strange, this demo from ~2002 era, and apparently was  working
> > fine on older nvidia hardware. And on nouveau, until this  commit.  I will
> > retest just for making sure it doesn't flood my dmesg with errors ....
> 
> You should be seeing errors about invalid values in dmesg for 0208 or some
> similar method. I'm guessing that the zeta buffer is used in such a way that
> things happen to work out, but the card doesn't really support it.
> 
> src/gallium/include/pipe/p_format.h:   PIPE_FORMAT_B8G8R8A8_UNORM          =
> 1,
> src/gallium/include/pipe/p_format.h:   PIPE_FORMAT_Z16_UNORM               =
> 16,
> 
> Not a valid combo, AFAIK.

I believe that restriction might only apply to swizzled surfaces.

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