[Mesa-dev] [PATCH 5/5] i965/gen9: Don't allow the RGBX formats for texturing/rendering

[Anuj Phogat]

On Mon, Nov 23, 2015 at 3:00 AM, Neil Roberts <neil at linux.intel.com> wrote:
> Ben Widawsky <ben at bwidawsk.net> writes:
>
>>> +   /* The RGBX formats are not renderable. Normally these get mapped
>>> +    * internally to RGBA formats when rendering. However on Gen9+ when this
>>> +    * internal override is used fast clears don't work so they are disabled in
>>> +    * brw_meta_fast_clear. To avoid this problem we can just pretend not to
>>> +    * support RGBX formats at all. This will cause the upper layers of Mesa to
>>> +    * pick the RGBA formats instead. This works fine because when it is used
>>
>> A lot of these formats are already unsupported for fast clears. In fact, I
>> believe only MESA_FORMAT_R8G8B8X8_UNORM is a problem. Are you trying to
>> accomplish something else here as well?
>
> I tested all of the formats with the fast-clear Piglit test and I think
> all of them are supported for fast clears on MSRTs. Don't forget that
> the ccs_e field in the surface_format_info isn't used for MSRTs. The
> first three do actually cause failures but for some reason
> MESA_FORMAT_RGBX_FLOAT16 does actually work. MESA_FORMAT_RGBX_FLOAT32
> isn't used because there is no override to make it use
> MESA_FORMAT_RGBA_FLOAT32 as a render target anyway. Presumably that
> means it will end up using RGBA for sampling as well and there are
> probably going to be some bugs with this format on platforms without
> texture swizzle or that the use the blorp so it probably should have
> this override. However I think that is a separate patch. If we did fix
> that then it would make sense to leave this format in this patch.
>
> Regards,
> - Neil
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Looks like the right thing to do.

Reviewed-by: Anuj Phogat <anuj.phogat at gmail.com>