[Mesa-dev] [PATCH 2/2] radeonsi: work around an MSAA fast stencil clear problem

[Marek Olšák]

For the series:

Reviewed-by: Marek Olšák <marek.olsak at amd.com>

Marek

On Sat, Apr 23, 2016 at 12:31 AM, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>
> A piglit test (arb_texture_multisample-stencil-clear) has been sent.
> This problem was discovered analyzing
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93767
> ---
>  src/gallium/drivers/radeonsi/si_state.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
> index 7ae6e8a..eb733f4 100644
> --- a/src/gallium/drivers/radeonsi/si_state.c
> +++ b/src/gallium/drivers/radeonsi/si_state.c
> @@ -2383,9 +2383,21 @@ static void si_init_depth_surface(struct si_context *sctx,
>                 z_info |= S_028040_TILE_SURFACE_ENABLE(1) |
>                           S_028040_ALLOW_EXPCLEAR(1);
>
> -               if (rtex->surface.flags & RADEON_SURF_SBUFFER)
> -                       s_info |= S_028044_ALLOW_EXPCLEAR(1);
> -               else
> +               if (rtex->surface.flags & RADEON_SURF_SBUFFER) {
> +                       /* Workaround: For a not yet understood reason, the
> +                        * combination of MSAA, fast stencil clear and stencil
> +                        * decompress messes with subsequent stencil buffer
> +                        * uses. Problem was reproduced on Verde, Bonaire,
> +                        * Tonga, and Carrizo.
> +                        *
> +                        * Disabling EXPCLEAR works around the problem.
> +                        *
> +                        * Check piglit's arb_texture_multisample-stencil-clear
> +                        * test if you want to try changing this.
> +                        */
> +                       if (rtex->resource.b.b.nr_samples <= 1)
> +                               s_info |= S_028044_ALLOW_EXPCLEAR(1);
> +               } else
>                         /* Use all of the htile_buffer for depth if there's no stencil. */
>                         s_info |= S_028044_TILE_STENCIL_DISABLE(1);
>
> --
> 2.5.0
>
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