[Mesa-dev] [PATCH] i965: Enable EWA anisotropic filtering algorithm for isotropic case

[Popov, Pavel E]

I agree. I just sent this patch to focus attention on this issue (Bug 82463).
- Pavel 

-----Original Message-----
From: Kenneth Graunke [mailto:kenneth at whitecape.org] 
Sent: Monday, August 11, 2014 11:32 PM
To: mesa-dev at lists.freedesktop.org
Cc: Popov, Pavel E
Subject: Re: [Mesa-dev] [PATCH] i965: Enable EWA anisotropic filtering algorithm for isotropic case

On Monday, August 11, 2014 07:05:36 PM Pavel Popov wrote:
> See the reasons in Bug 82463:
> https://bugs.freedesktop.org/show_bug.cgi?id=82463
> 
> Signed-off-by: Pavel Popov <pavel.e.popov at intel.com>
> ---
>  src/mesa/drivers/dri/i965/brw_sampler_state.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_sampler_state.c b/src/mesa/drivers/dri/i965/brw_sampler_state.c
> index d03047b..2b3f676 100644
> --- a/src/mesa/drivers/dri/i965/brw_sampler_state.c
> +++ b/src/mesa/drivers/dri/i965/brw_sampler_state.c
> @@ -114,8 +114,8 @@ brw_emit_sampler_state(struct brw_context *brw,
>     if (brw->gen >= 7) {
>        ss[0] |= SET_FIELD(lod_bias & 0x1fff, GEN7_SAMPLER_LOD_BIAS);
>  
> -      if (min_filter == BRW_MAPFILTER_ANISOTROPIC)
> -         ss[0] |= GEN7_SAMPLER_EWA_ANISOTROPIC_ALGORIHTM;
> +      /* Use EWA algorithm for anisotropic and isotropic cases */
> +      ss[0] |= GEN7_SAMPLER_EWA_ANISOTROPIC_ALGORIHTM;
>  
>        ss[1] = SET_FIELD(min_lod, GEN7_SAMPLER_MIN_LOD) |
>                SET_FIELD(max_lod, GEN7_SAMPLER_MAX_LOD) |
> 

Doing this fixes various Piglit miplevel tests - mostly 3D I think - but it breaks quite a few other ones, at least on Haswell.

I think we need to understand what's going on there before we can commit something like this.