Re: [PATCH 02/22] drm/i915/icl: Enable Sampler DFR

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Apr 20, 2018 at 01:33:46PM -0700, Oscar Mateo wrote:
> Sampler Dynamic Frequency Rebalancing (DFR) aims to reduce Sampler
> power by dynamically changing its clock frequency in low-throughput
> conditions. This patches enables it by default on Gen11.
> 
> v2: Wrong operation to clear the bit (Praveen)
> v3: Rebased on top of the WA refactoring
> 
> Cc: Praveen Paneri <praveen.paneri@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
> Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h          | 3 +++
>  drivers/gpu/drm/i915/intel_workarounds.c | 4 ++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index f2ee225..4b7e6bc 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -8218,6 +8218,9 @@ enum {
>  #define GEN8_GARBCNTL                   _MMIO(0xB004)
>  #define   GEN9_GAPS_TSV_CREDIT_DISABLE  (1<<7)
>  
> +#define GEN10_DFR_RATIO_EN_AND_CHICKEN	_MMIO(0x9550)
> +#define   DFR_DISABLE			(1 << 9)
> +
>  /* IVYBRIDGE DPF */
>  #define GEN7_L3CDERRST1(slice)		_MMIO(0xB008 + (slice) * 0x200) /* L3CD Error Status 1 */
>  #define   GEN7_L3CDERRST1_ROW_MASK	(0x7ff<<14)
> diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
> index 3f00623..60a5b1d 100644
> --- a/drivers/gpu/drm/i915/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/intel_workarounds.c
> @@ -692,6 +692,10 @@ static void icl_gt_workarounds_apply(struct drm_i915_private *dev_priv)
>  	I915_WRITE(_3D_CHICKEN3,
>  		   _MASKED_BIT_ENABLE(_3D_CHICKEN3_AA_LINE_QUALITY_FIX_ENABLE));
>  
> +	/* This is not an Wa. Enable to reduce Sampler power */

First of all it is strange that a feature is under a chicken bit,
but if it is not an wa, but a PM feature, shouldn't we add it to some sort of
init clock gating function, or a new specific function called when it makes sense?

> +	I915_WRITE(GEN10_DFR_RATIO_EN_AND_CHICKEN,
> +		   (I915_READ(GEN10_DFR_RATIO_EN_AND_CHICKEN) & ~DFR_DISABLE));
> +
>  	/* WaInPlaceDecompressionHang:icl */
>  	I915_WRITE(GEN9_GAMT_ECO_REG_RW_IA, (I915_READ(GEN9_GAMT_ECO_REG_RW_IA) |
>  					     GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS));
> -- 
> 1.9.1
> 
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