[Intel-gfx] [PATCH] drm/i915: Transform WaInPlaceDecompressionHang to a simple reg write

[Oscar Mateo]

Hey Mika,

Regarding this patch: is there a consensus on where is the most 
appropriate place to apply workarounds? My understanding is that 
per-context workarounds (WAS_SET_BIT, etc...) go in 
xxx_init_workarounds, while those that are needed only during 
initialization (I915_WRITE) go in xxx_init_clock_gating. But it doesn't 
look like this general rule is being followed (probably because 
xxx_init_clock_gating is a very misleading name?).

This has probably been discussed before, so it would be good if we could 
document the answer somewhere (maybe it already is?).

Thanks,

Oscar



On 09/06/2017 02:12 PM, Oscar Mateo wrote:
> Afaict, GEN9_GAMT_ECO_REG_RW_IA does not live in the context, so writing
> it on every context creation is overkill (and wrong).
>
> Cc: Mika Kuoppala <mika.kuoppala at intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
> ---
>   drivers/gpu/drm/i915/intel_engine_cs.c | 25 +++++++++++++++----------
>   1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 23812ec..9f01a5c 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -985,8 +985,9 @@ static int skl_init_workarounds(struct intel_engine_cs *engine)
>   
>   	/* WaInPlaceDecompressionHang:skl */
>   	if (IS_SKL_REVID(dev_priv, SKL_REVID_H0, REVID_FOREVER))
> -		WA_SET_BIT(GEN9_GAMT_ECO_REG_RW_IA,
> -			   GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
> +		I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA,
> +			   (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> +			    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
>   
>   	/* WaDisableLSQCROPERFforOCL:skl */
>   	ret = wa_ring_whitelist_reg(engine, GEN8_L3SQCREG4);
> @@ -1059,8 +1060,9 @@ static int bxt_init_workarounds(struct intel_engine_cs *engine)
>   
>   	/* WaInPlaceDecompressionHang:bxt */
>   	if (IS_BXT_REVID(dev_priv, BXT_REVID_C0, REVID_FOREVER))
> -		WA_SET_BIT(GEN9_GAMT_ECO_REG_RW_IA,
> -			   GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
> +		I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA,
> +			   (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> +			    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
>   
>   	return 0;
>   }
> @@ -1089,8 +1091,9 @@ static int cnl_init_workarounds(struct intel_engine_cs *engine)
>   				  GEN8_CSC2_SBE_VUE_CACHE_CONSERVATIVE);
>   
>   	/* WaInPlaceDecompressionHang:cnl */
> -	WA_SET_BIT(GEN9_GAMT_ECO_REG_RW_IA,
> -		   GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
> +	I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA,
> +		   (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> +		    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
>   
>   	/* WaPushConstantDereferenceHoldDisable:cnl */
>   	WA_SET_BIT(GEN7_ROW_CHICKEN2, PUSH_CONSTANT_DEREF_DISABLE);
> @@ -1143,8 +1146,9 @@ static int kbl_init_workarounds(struct intel_engine_cs *engine)
>   		GEN7_SBE_SS_CACHE_DISPATCH_PORT_SHARING_DISABLE);
>   
>   	/* WaInPlaceDecompressionHang:kbl */
> -	WA_SET_BIT(GEN9_GAMT_ECO_REG_RW_IA,
> -		   GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
> +	I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA,
> +		   (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> +		    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
>   
>   	/* WaDisableLSQCROPERFforOCL:kbl */
>   	ret = wa_ring_whitelist_reg(engine, GEN8_L3SQCREG4);
> @@ -1196,8 +1200,9 @@ static int cfl_init_workarounds(struct intel_engine_cs *engine)
>   		GEN7_SBE_SS_CACHE_DISPATCH_PORT_SHARING_DISABLE);
>   
>   	/* WaInPlaceDecompressionHang:cfl */
> -	WA_SET_BIT(GEN9_GAMT_ECO_REG_RW_IA,
> -		   GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
> +	I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA,
> +		   (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
> +		    GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
>   
>   	return 0;
>   }