Re: [PATCH 1/5] drm/i915/vrr: Extract helpers to convert between guardband and pipeline_full values

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 9/18/2025 2:04 AM, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> I'd like to move towards a world where we can't more or less
> pretend that the ICl/TGL VRR hardware works the same way as
> ADL+. To that end extract some helpers to convert between
> the guardband and pipeline_full representations.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Thanks for this, it will really help to just work with guardband instead 
of pipeline_full and all.

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


> ---
>   drivers/gpu/drm/i915/display/intel_vrr.c | 28 ++++++++++++++++++------
>   1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index 3eed37f271b0..5fee85b0bc99 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -119,6 +119,20 @@ static int intel_vrr_vmin_flipline(const struct intel_crtc_state *crtc_state)
>   	return crtc_state->vrr.vmin + intel_vrr_flipline_offset(display);
>   }
>   
> +static int intel_vrr_guardband_to_pipeline_full(const struct intel_crtc_state *crtc_state,
> +						int guardband)
> +{
> +	/* hardware imposes one extra scanline somewhere */
> +	return guardband - crtc_state->framestart_delay - 1;
> +}
> +
> +static int intel_vrr_pipeline_full_to_guardband(const struct intel_crtc_state *crtc_state,
> +						int pipeline_full)
> +{
> +	/* hardware imposes one extra scanline somewhere */
> +	return pipeline_full + crtc_state->framestart_delay + 1;
> +}
> +
>   /*
>    * Without VRR registers get latched at:
>    *  vblank_start
> @@ -142,8 +156,8 @@ static int intel_vrr_vblank_exit_length(const struct intel_crtc_state *crtc_stat
>   	if (DISPLAY_VER(display) >= 13)
>   		return crtc_state->vrr.guardband;
>   	else
> -		/* hardware imposes one extra scanline somewhere */
> -		return crtc_state->vrr.pipeline_full + crtc_state->framestart_delay + 1;
> +		return intel_vrr_pipeline_full_to_guardband(crtc_state,
> +							    crtc_state->vrr.pipeline_full);
>   }
>   
>   int intel_vrr_vmin_vtotal(const struct intel_crtc_state *crtc_state)
> @@ -417,18 +431,18 @@ void intel_vrr_compute_config_late(struct intel_crtc_state *crtc_state)
>   {
>   	struct intel_display *display = to_intel_display(crtc_state);
>   	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
> +	int guardband;
>   
>   	if (!intel_vrr_possible(crtc_state))
>   		return;
>   
> +	guardband = crtc_state->vrr.vmin - adjusted_mode->crtc_vblank_start;
> +
>   	if (DISPLAY_VER(display) >= 13) {
> -		crtc_state->vrr.guardband =
> -			crtc_state->vrr.vmin - adjusted_mode->crtc_vblank_start;
> +		crtc_state->vrr.guardband = guardband;
>   	} else {
> -		/* hardware imposes one extra scanline somewhere */
>   		crtc_state->vrr.pipeline_full =
> -			min(255, crtc_state->vrr.vmin - adjusted_mode->crtc_vblank_start -
> -			    crtc_state->framestart_delay - 1);
> +			min(255, intel_vrr_guardband_to_pipeline_full(crtc_state, guardband));
>   
>   		/*
>   		 * vmin/vmax/flipline also need to be adjusted by