Re: [PATCH 13/18] drm/i915/vrr: Drop the extra vmin adjustment for ADL+

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

On 12/11/2024 2:40 AM, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Apparently on ICL/TGL need the annoying vmin adjustemnt. On
typo: adjustement
> ADL+ we can program flipling==vmin and the hardware actually
typo: flipline
> respects that properly.

I had tried to remove this earlier for ADL+, but was lost with +1 and -1 
(handling this offset) in different places, and failed miserably.

Thanks for this patch, its now quite clear.

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


>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_vrr.c | 39 ++++++++++++++++--------
>   1 file changed, 27 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index a0ddc288c1a3..15017254d250 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -82,6 +82,19 @@ int intel_vrr_vblank_delay(const struct intel_crtc_state *crtc_state)
>   		crtc_state->hw.adjusted_mode.crtc_vdisplay;
>   }
>   
> +static int intel_vrr_flipline_offset(struct intel_display *display)
> +{
> +	/* ICL/TGL hardware imposes flipline>=vmin+1 */
> +	return DISPLAY_VER(display) < 13 ? 1 : 0;
> +}
> +
> +static int intel_vrr_vmin_flipline(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +
> +	return crtc_state->vrr.vmin + intel_vrr_flipline_offset(display);
> +}
> +
>   /*
>    * Without VRR registers get latched at:
>    *  vblank_start
> @@ -111,8 +124,8 @@ static int intel_vrr_vblank_exit_length(const struct intel_crtc_state *crtc_stat
>   
>   int intel_vrr_vmin_vtotal(const struct intel_crtc_state *crtc_state)
>   {
> -	/* Min vblank actually determined by flipline that is always >=vmin+1 */
> -	return crtc_state->vrr.vmin + 1;
> +	/* Min vblank actually determined by flipline */
> +	return intel_vrr_vmin_flipline(crtc_state);
>   }
>   
>   int intel_vrr_vmax_vtotal(const struct intel_crtc_state *crtc_state)
> @@ -122,8 +135,8 @@ int intel_vrr_vmax_vtotal(const struct intel_crtc_state *crtc_state)
>   
>   int intel_vrr_vmin_vblank_start(const struct intel_crtc_state *crtc_state)
>   {
> -	/* Min vblank actually determined by flipline that is always >=vmin+1 */
> -	return crtc_state->vrr.vmin + 1 - intel_vrr_vblank_exit_length(crtc_state);
> +	/* Min vblank actually determined by flipline */
> +	return intel_vrr_vmin_flipline(crtc_state) - intel_vrr_vblank_exit_length(crtc_state);
>   }
>   
>   int intel_vrr_vmax_vblank_start(const struct intel_crtc_state *crtc_state)
> @@ -220,15 +233,17 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
>   	if (vmin >= vmax)
>   		return;
>   
> -	/*
> -	 * flipline determines the min vblank length the hardware will
> -	 * generate, and flipline>=vmin+1, hence we reduce vmin by one
> -	 * to make sure we can get the actual min vblank length.
> -	 */
> -	crtc_state->vrr.vmin = vmin - 1;
> +	crtc_state->vrr.vmin = vmin;
>   	crtc_state->vrr.vmax = vmax;
>   
> -	crtc_state->vrr.flipline = crtc_state->vrr.vmin + 1;
> +	crtc_state->vrr.flipline = crtc_state->vrr.vmin;
> +
> +	/*
> +	 * flipline determines the min vblank length the hardware will
> +	 * generate, and on ICL/TGL flipline>=vmin+1, hence we reduce
> +	 * vmin by one to make sure we can get the actual min vblank length.
> +	 */
> +	crtc_state->vrr.vmin -= intel_vrr_flipline_offset(display);
>   
>   	/*
>   	 * When panel is VRR capable and userspace has
> @@ -273,7 +288,7 @@ void intel_vrr_compute_config_late(struct intel_crtc_state *crtc_state)
>   
>   	if (DISPLAY_VER(display) >= 13) {
>   		crtc_state->vrr.guardband =
> -			crtc_state->vrr.vmin + 1 - adjusted_mode->crtc_vblank_start;
> +			crtc_state->vrr.vmin - adjusted_mode->crtc_vblank_start;
>   	} else {
>   		crtc_state->vrr.pipeline_full =
>   			min(255, crtc_state->vrr.vmin - adjusted_mode->crtc_vblank_start -