[PATCH v4 09/17] drm/i915/vrr: Add compute config for DC Balance params

[Nautiyal, Ankit K]

On 5/6/2025 8:25 PM, Mitul Golani wrote:
> Compute DC Balance parameters and tunable params based on
> experiments.
>
> --v2:
> - Document tunable params. (Ankit)
>
> --v3:
> - Add line spaces to compute config. (Ankit)
> - Remove redundancy checks.
>
> Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani at intel.com>

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>


> ---
>   drivers/gpu/drm/i915/display/intel_vrr.c | 25 ++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index 726fa49558d1..dcaae7631b0a 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -16,6 +16,13 @@
>   
>   #define FIXED_POINT_PRECISION		100
>   #define CMRR_PRECISION_TOLERANCE	10
> +/*
> + * Tunable parameters for DC Balance correction.
> + * These are captured based on experimentations.
> + */
> +#define DCB_CORRECTION_SENSITIVITY	30
> +#define DCB_CORRECTION_AGGRESSIVENESS	1000
> +#define DCB_BLANK_TARGET		50
>   
>   bool intel_vrr_is_capable(struct intel_connector *connector)
>   {
> @@ -409,6 +416,24 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
>   			(crtc_state->hw.adjusted_mode.crtc_vtotal -
>   			 crtc_state->hw.adjusted_mode.vsync_end);
>   	}
> +
> +	if (crtc_state->vrr.dc_balance.enable) {
> +		crtc_state->vrr.dc_balance.vmax = crtc_state->vrr.vmax;
> +		crtc_state->vrr.dc_balance.vmin = crtc_state->vrr.vmin;
> +		crtc_state->vrr.dc_balance.max_increase =
> +			crtc_state->vrr.vmax - crtc_state->vrr.vmin;
> +		crtc_state->vrr.dc_balance.max_decrease =
> +			crtc_state->vrr.vmax - crtc_state->vrr.vmin;
> +		crtc_state->vrr.dc_balance.guardband =
> +			DIV_ROUND_UP(crtc_state->vrr.dc_balance.vmax *
> +				     DCB_CORRECTION_SENSITIVITY, 100);
> +		crtc_state->vrr.dc_balance.slope =
> +			DIV_ROUND_UP(DCB_CORRECTION_AGGRESSIVENESS * 10,
> +				     crtc_state->vrr.dc_balance.guardband);
> +		crtc_state->vrr.dc_balance.vblank_target =
> +			DIV_ROUND_UP((crtc_state->vrr.vmax - crtc_state->vrr.vmin) *
> +				     DCB_BLANK_TARGET, 100);
> +	}
>   }
>   
>   void intel_vrr_compute_config_late(struct intel_crtc_state *crtc_state)