Re: [PATCH 07/22] drm/i915/vrr: Prepare for fixed refresh rate timings

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

On Tue, Mar 04, 2025 at 01:49:33PM +0530, Ankit Nautiyal wrote:
> Currently we always compute the timings as if vrr is enabled.
> With this approach the state checker becomes complicated when we
> introduce fixed refresh rate mode with vrr timing generator.
> 
> To avoid the complications, instead of always computing vrr timings, we
> compute vrr timings based on uapi.vrr_enable knob.
> So when the knob is disabled we always compute vmin=flipline=vmax.
> 
> v2: Use actual timings without any adjustments while preparing for
> fixed timings in compute_config. (Ville)
> v3: Avoid setting fixed timings if !vrr_possible().
> 
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (#v2)
> ---
>  drivers/gpu/drm/i915/display/intel_vrr.c | 73 ++++++++++++++++++++++++
>  1 file changed, 73 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index e0573e28014b..0e606dfe4a56 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -246,6 +246,68 @@ 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_fixed_rr_vtotal(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +	int crtc_vtotal = crtc_state->hw.adjusted_mode.crtc_vtotal;
> +
> +	if (DISPLAY_VER(display) >= 13)
> +		return crtc_vtotal;
> +	else
> +		return crtc_vtotal -
> +			intel_vrr_real_vblank_delay(crtc_state);
> +}
> +
> +static
> +int intel_vrr_fixed_rr_vmax(const struct intel_crtc_state *crtc_state)
> +{
> +	return intel_vrr_fixed_rr_vtotal(crtc_state);
> +}
> +
> +static
> +int intel_vrr_fixed_rr_vmin(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +
> +	return intel_vrr_fixed_rr_vtotal(crtc_state) -
> +		intel_vrr_flipline_offset(display);
> +}
> +
> +static
> +int intel_vrr_fixed_rr_flipline(const struct intel_crtc_state *crtc_state)
> +{
> +	return intel_vrr_fixed_rr_vtotal(crtc_state);
> +}
> +
> +static
> +void intel_vrr_set_fixed_rr_timings(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_display *display = to_intel_display(crtc_state);
> +	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
> +
> +	if (!intel_vrr_possible(crtc_state))
> +		return;
> +
> +	intel_de_write(display, TRANS_VRR_VMIN(display, cpu_transcoder),
> +		       intel_vrr_fixed_rr_vmin(crtc_state) - 1);
> +	intel_de_write(display, TRANS_VRR_VMAX(display, cpu_transcoder),
> +		       intel_vrr_fixed_rr_vmax(crtc_state) - 1);
> +	intel_de_write(display, TRANS_VRR_FLIPLINE(display, cpu_transcoder),
> +		       intel_vrr_fixed_rr_flipline(crtc_state) - 1);
> +}
> +
> +static
> +void intel_vrr_prepare_fixed_timings(struct intel_crtc_state *crtc_state)
> +{
> +	crtc_state->vrr.vmax = intel_vrr_vmin_flipline(crtc_state);
> +	crtc_state->vrr.flipline = intel_vrr_vmin_flipline(crtc_state);

I think it would be cleaner to just use crtc_vtotal during
all this timing compute stuff, and move the magic vmin
adjustment to be done after it's all done.

> +}
> +
>  static
>  int intel_vrr_compute_vmin(struct intel_crtc_state *crtc_state)
>  {
> @@ -325,6 +387,8 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
>  		intel_vrr_compute_vrr_timings(crtc_state);
>  	else if (is_cmrr_frac_required(crtc_state) && is_edp)
>  		intel_vrr_compute_cmrr_timings(crtc_state);
> +	else
> +		intel_vrr_prepare_fixed_timings(crtc_state);

The "compute" vs. "prepare" difference in terminology is a bit 
confusing.

>  
>  	if (HAS_AS_SDP(display)) {
>  		crtc_state->vrr.vsync_start =
> @@ -496,6 +560,13 @@ void intel_vrr_enable(const struct intel_crtc_state *crtc_state)
>  	if (!crtc_state->vrr.enable)
>  		return;
>  
> +	intel_de_write(display, TRANS_VRR_VMIN(display, cpu_transcoder),
> +		       crtc_state->vrr.vmin - 1);
> +	intel_de_write(display, TRANS_VRR_VMAX(display, cpu_transcoder),
> +		       crtc_state->vrr.vmax - 1);
> +	intel_de_write(display, TRANS_VRR_FLIPLINE(display, cpu_transcoder),
> +		       crtc_state->vrr.flipline - 1);
> +
>  	intel_de_write(display, TRANS_PUSH(display, cpu_transcoder),
>  		       TRANS_PUSH_EN);
>  
> @@ -523,6 +594,8 @@ void intel_vrr_disable(const struct intel_crtc_state *old_crtc_state)
>  				TRANS_VRR_STATUS(display, cpu_transcoder),
>  				VRR_STATUS_VRR_EN_LIVE, 1000);
>  	intel_de_write(display, TRANS_PUSH(display, cpu_transcoder), 0);
> +
> +	intel_vrr_set_fixed_rr_timings(old_crtc_state);
>  }
>  
>  static
> -- 
> 2.45.2

-- 
Ville Syrjälä
Intel