[PATCH v3 08/15] drm/i915/vrr: Add compute config for DC balance params

[Nautiyal, Ankit K]

On 4/28/2025 11:50 AM, Mitul Golani wrote:
> Compute DC Balance parameters and tunable params based on
> experiments.
>
> --v2:
> - Document tunable params. (Ankit)
>
> Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani 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 55923eadc3c1..bc99701be2b5 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 (HAS_VRR_DC_BALANCE(display) && 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);

We can make the longer lines more readable with a bit of formatting by 
breaking the line after multiplication or at comma:

                 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);

Regards,

Ankit


> +	}
>   }
>   
>   void intel_vrr_compute_config_late(struct intel_crtc_state *crtc_state)