[Mesa-dev] [PATCH] nvc0: Disable BGRA8 images on Fermi

[Ilia Mirkin]

Actually, for unknown reasons, storing to BGRA8 images doesn't work on
Fermi. This breaks PBO downloads.

Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>

On Fri, Jun 2, 2017 at 8:45 PM, Lyude <lyude at redhat.com> wrote:
> For unknown reasons, using BGRA8 images on Fermi results in breaking
> reads from PBOs, such that they always return 0x0. Discovered this
> through a glamor bug, and confirmed it does indeed break a good number
> of piglit tests such as spec/arb_pixel_buffer_object/pbo-read-argb8888
>
> Until we have a proper fix, just disable this functionality on Fermi.
>
> Signed-off-by: Lyude <lyude at redhat.com>
> ---
>  src/gallium/drivers/nouveau/nvc0/nvc0_screen.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/src/gallium/drivers/nouveau/nvc0/nvc0_screen.c b/src/gallium/drivers/nouveau/nvc0/nvc0_screen.c
> index c636926..f6c5c72 100644
> --- a/src/gallium/drivers/nouveau/nvc0/nvc0_screen.c
> +++ b/src/gallium/drivers/nouveau/nvc0/nvc0_screen.c
> @@ -87,11 +87,20 @@ nvc0_screen_is_format_supported(struct pipe_screen *pscreen,
>     bindings &= ~(PIPE_BIND_LINEAR |
>                   PIPE_BIND_SHARED);
>
> -   if (bindings & PIPE_BIND_SHADER_IMAGE && sample_count > 1 &&
> -       nouveau_screen(pscreen)->class_3d >= GM107_3D_CLASS) {
> -      /* MS images are currently unsupported on Maxwell because they have to
> -       * be handled explicitly. */
> -      return false;
> +   if (bindings & PIPE_BIND_SHADER_IMAGE) {
> +      if (sample_count > 1 &&
> +          nouveau_screen(pscreen)->class_3d >= GM107_3D_CLASS) {
> +         /* MS images are currently unsupported on Maxwell because they have to
> +          * be handled explicitly. */
> +         return false;
> +      }
> +
> +      if (format == PIPE_FORMAT_B8G8R8A8_UNORM &&
> +          nouveau_screen(pscreen)->class_3d < NVE4_3D_CLASS) {
> +         /* This should work on Fermi, but for currently unknown reasons it
> +          * does not and results in breaking reads from pbos. */
> +         return false;
> +      }
>     }
>
>     return (( nvc0_format_table[format].usage |
> --
> 2.9.4
>
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