Re: [PATCH] drm/i915/cnl: WaSendPushConstantsFromMMIO / WaDisableGatherAtSetShaderCommonSlice

[Rafael Antognolli <rafael.antognolli@intel.com>]

I can confirm this fixes my CNL issues, and it's what we could
understand from the sparse documentation.

Tested-by: Rafael Antognolli <rafael.antognolli@intel.com>

On Thu, Oct 05, 2017 at 03:26:40PM -0700, Rodrigo Vivi wrote:
> WaSendPushConstantsFromMMIO: "If not using RS, we must send two
> MMIO registers at context create to trigger push constants at
> 3D primitive"
> 
> There is almost no documentation on Spec or wa_database about
> this WaSendPushConstantsFromMMIO. So we also found out in another
> place that WaSendPushConstantsFromMMIO was only adding
> COMMON_SLICE_CHICKEN2 in a white list.
> 
> So we looked to the programming notes of COMMON_SLICE_CHICKEN2
> and we notice that this bit 12 is marked in association with
> 2 other MMIO registers for SKL+. Apparently for SKL+ we should
> check few MMIOs to decide for set or reset of this bit 12.
> 
> Also "gather" is related to gather and packing of constants elements
> into "push constants".
> 
> Mesa has no plans of using RS so there is no need to whitelist
> and we only need to initialize the context image with that bit clear.
> 
> v2: Move to cnl_init_workarounds as Chris suggested.
>     Add both Wa names and improve commit message as Rafael suggested.
> 
> Cc: Rafael Antognolli <rafael.antognolli@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_engine_cs.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 807a7aafc089..3beb7d327785 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -1296,6 +1296,11 @@ static int cnl_init_workarounds(struct intel_engine_cs *engine)
>  		WA_SET_BIT_MASKED(COMMON_SLICE_CHICKEN2,
>  				  GEN8_CSC2_SBE_VUE_CACHE_CONSERVATIVE);
>  
> +	/* WaDisableGatherAtSetShaderCommonSlice:cnl */
> +	/* WaSendPushConstantsFromMMIO:cnl */
> +	WA_CLR_BIT_MASKED(COMMON_SLICE_CHICKEN2,
> +			  GEN9_DISABLE_GATHER_AT_SET_SHADER_COMMON_SLICE);
> +
>  	/* WaInPlaceDecompressionHang:cnl */
>  	I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA,
>  		   (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> -- 
> 2.13.5
> 
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