Re: [Intel-gfx] [PATCH v4 15/18] drm/i915/display: Helpers for VRR vblank min and max start

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

On Wed, Jan 13, 2021 at 02:09:32PM -0800, Manasi Navare wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> With VRR the earliest the registers can get latched are at
> flipline decision boundary, calculate that as vrr_vmin_vblank_start()
> and the latest the regsiters can get latched are vmax decision boundary
> calculate that as vrr_vmax_vblank_start()
> 
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_vrr.c | 36 ++++++++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_vrr.h |  2 ++
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index 5dc6d578760a..9a18c36e4a9a 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -45,6 +45,42 @@ intel_vrr_check_modeset(struct intel_atomic_state *state)
>  	}
>  }
>  
> +/*
> + * Without VRR registers get latched at:
> + *  vblank_start
> + *
> + * With VRR the earliest registers can get latched is:
> + *  intel_vrr_vmin_vblank_start(), which if we want to maintain
> + *  the correct min vtotal is >=vblank_start+1
> + *
> + * The latest point registers can get latched is the vmax decision boundary:
> + *  intel_vrr_vmax_vblank_start()
> + *
> + * Between those two points the vblank exit starts (and hence registers get
> + * latched) ASAP after a push is sent.
> + *
> + * framestart_delay is programmable 0-3.
> + */
> +static int intel_vrr_vblank_exit_length(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> +	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
> +
> +	/* TODO: Not sure why the hw imposes the extra scanline?, also check on TGL */

We can now drop the TGL TODO(s) since I tested it and confirmed it
follows the same rules.

> +	return crtc_state->vrr.pipeline_full + i915->framestart_delay + 2;
> +}
> +
> +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);
> +}
> +
> +int intel_vrr_vmax_vblank_start(const struct intel_crtc_state *crtc_state)
> +{
> +	return crtc_state->vrr.vmax - intel_vrr_vblank_exit_length(crtc_state);
> +}
> +
>  void
>  intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
>  			 struct drm_connector_state *conn_state)
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.h b/drivers/gpu/drm/i915/display/intel_vrr.h
> index 7610051edad2..d8b6b45557ca 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.h
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.h
> @@ -27,5 +27,7 @@ void intel_vrr_send_push(const struct intel_crtc_state *crtc_state);
>  void intel_vrr_disable(const struct intel_crtc_state *old_crtc_state);
>  void intel_vrr_get_config(struct intel_crtc *crtc,
>  			  struct intel_crtc_state *crtc_state);
> +int intel_vrr_vmax_vblank_start(const struct intel_crtc_state *crtc_state);
> +int intel_vrr_vmin_vblank_start(const struct intel_crtc_state *crtc_state);
>  
>  #endif /* __INTEL_VRR_H__ */
> -- 
> 2.19.1

-- 
Ville Syrjälä
Intel
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