[Mesa-dev] [PATCH] isl: Add assertions for render target swizzle restrictions

[Nanley Chery]

On Tue, Jan 31, 2017 at 06:51:12PM -0800, Jason Ekstrand wrote:
> ---
>  src/intel/isl/isl_surface_state.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/src/intel/isl/isl_surface_state.c b/src/intel/isl/isl_surface_state.c
> index b735478..c7b220b 100644
> --- a/src/intel/isl/isl_surface_state.c
> +++ b/src/intel/isl/isl_surface_state.c
> @@ -453,6 +453,38 @@ isl_genX(surf_fill_state_s)(const struct isl_device *dev, void *state,
>  #endif
>  
>  #if (GEN_GEN >= 8 || GEN_IS_HASWELL)
> +   if (info->view->usage & ISL_SURF_USAGE_RENDER_TARGET_BIT) {

It seems that haswell actually allows this, though I don't know if it's
a feature we'd ever want to use.

>From the Haswell PRM, RENDER_SURFACE_STATE::Shader Channel Select R

   If more than one shader channel select is set to the same
   surface channel only the first shader channel in RGBA order will
   be written.

-Nanley

> +      /* From the Sky Lake PRM Vol. 2d,
> +       * RENDER_SURFACE_STATE::Shader Channel Select Red
> +       *
> +       *    "For Render Target, Red, Green and Blue Shader Channel Selects
> +       *    MUST be such that only valid components can be swapped i.e. only
> +       *    change the order of components in the pixel. Any other values for
> +       *    these Shader Channel Select fields are not valid for Render
> +       *    Targets. This also means that there MUST not be multiple shader
> +       *    channels mapped to the same RT channel."
> +       */
> +      assert(info->view->swizzle.r == ISL_CHANNEL_SELECT_RED ||
> +             info->view->swizzle.r == ISL_CHANNEL_SELECT_GREEN ||
> +             info->view->swizzle.r == ISL_CHANNEL_SELECT_BLUE);
> +      assert(info->view->swizzle.g == ISL_CHANNEL_SELECT_RED ||
> +             info->view->swizzle.g == ISL_CHANNEL_SELECT_GREEN ||
> +             info->view->swizzle.g == ISL_CHANNEL_SELECT_BLUE);
> +      assert(info->view->swizzle.b == ISL_CHANNEL_SELECT_RED ||
> +             info->view->swizzle.b == ISL_CHANNEL_SELECT_GREEN ||
> +             info->view->swizzle.b == ISL_CHANNEL_SELECT_BLUE);
> +      assert(info->view->swizzle.r != info->view->swizzle.g);
> +      assert(info->view->swizzle.r != info->view->swizzle.b);
> +      assert(info->view->swizzle.g != info->view->swizzle.b);
> +
> +      /* From the Sky Lake PRM Vol. 2d,
> +       * RENDER_SURFACE_STATE::Shader Channel Select Alpha
> +       *
> +       *    "For Render Target, this field MUST be programmed to
> +       *    value = SCS_ALPHA."
> +       */
> +      assert(info->view->swizzle.a == ISL_CHANNEL_SELECT_ALPHA);
> +   }
>     s.ShaderChannelSelectRed = info->view->swizzle.r;
>     s.ShaderChannelSelectGreen = info->view->swizzle.g;
>     s.ShaderChannelSelectBlue = info->view->swizzle.b;
> -- 
> 2.5.0.400.gff86faf
> 
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