Re: [PATCH 06/19] drm/i915/vrr: Use crtc_vtotal for vmin

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Feb 14, 2025 at 05:41:16PM +0530, Ankit Nautiyal wrote:
> To have fixed refresh rate with VRR timing generator the
> guardband/pipeline full can't be programmed on the fly. So we need to
> ensure that the values satisfy both the fixed and variable refresh
> rates.
> 
> Since we compute these value based on vmin, lets set the vmin to
> crtc_vtotal for both fixed and variable timings instead of using the
> current refresh rate based approach. This way the guardband remains
> sufficient for both cases.
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_vrr.c | 34 +++++++++++++++++-------
>  1 file changed, 25 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index efa2aa284285..3bcf2a026ad3 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -246,18 +246,34 @@ void intel_vrr_compute_vrr_timings(struct intel_crtc_state *crtc_state)
>  	crtc_state->mode_flags |= I915_MODE_FLAG_VRR;
>  }
>  
> +/*
> + * For fixed refresh rate mode Vmin, Vmax and Flipline all are set to
> + * Vtotal value.
> + */
>  static
> -int intel_vrr_compute_vmin(struct intel_connector *connector,
> -			   struct drm_display_mode *adjusted_mode)
> +int intel_vrr_fixed_rr_vtotal(const struct intel_crtc_state *crtc_state)
>  {
> -	int vmin;
> -	const struct drm_display_info *info = &connector->base.display_info;
> +	struct intel_display *display = to_intel_display(crtc_state);
> +	int crtc_vtotal = crtc_state->hw.adjusted_mode.crtc_vtotal;
>  
> -	vmin = DIV_ROUND_UP(adjusted_mode->crtc_clock * 1000,
> -			    adjusted_mode->crtc_htotal * info->monitor_range.max_vfreq);
> -	vmin = max_t(int, vmin, adjusted_mode->crtc_vtotal);
> +	if (DISPLAY_VER(display) >= 13)
> +		return crtc_vtotal;
> +	else
> +		return crtc_vtotal -
> +			intel_vrr_real_vblank_delay(crtc_state);
> +}
>  
> -	return vmin;
> +static
> +int intel_vrr_compute_vmin(struct intel_crtc_state *crtc_state)
> +{
> +	/*
> +	 * To make fixed rr and vrr work seamless the guardband/pipeline full
> +	 * should be set such that it satisfies both the fixed and variable
> +	 * timings.
> +	 * For this set the vmin as crtc_vtotal. With this we never need to
> +	 * change anything to do with the guardband.
> +	 */
> +	return intel_vrr_fixed_rr_vtotal(crtc_state);

We don't have the vblank delay dialed in at this point. So this
needs to be just the normal vtotal wihtout any adjustments.

>  }
>  
>  static
> @@ -305,7 +321,7 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
>  	if (HAS_LRR(display))
>  		crtc_state->update_lrr = true;
>  
> -	vmin = intel_vrr_compute_vmin(connector, adjusted_mode);
> +	vmin = intel_vrr_compute_vmin(crtc_state);
>  	vmax = intel_vrr_compute_vmax(connector, adjusted_mode);
>  
>  	if (vmin >= vmax)
> -- 
> 2.45.2

-- 
Ville Syrjälä
Intel