[PATCH] drm/i915/vrr: Set vrr.vmin to min Vtotal to re-enable LRR for PTL
Ville Syrjälä
ville.syrjala at linux.intel.com
Wed May 28 11:47:25 UTC 2025
On Fri, May 09, 2025 at 08:41:07AM +0530, Ankit Nautiyal wrote:
> Currently in intel_vrr_compute_config, we set vrr.vmin to crtc_vtotal for
> all cases to avoid having vrr.vmin changed when we switch from
> fixed refresh rate timings to variable refresh rate timings. This works for
> all cases, except for LRR case where user can change the clock so as to
> seamlessly switch to a lower refresh rate only for a VRR supporting panel.
>
> In LRR case the crtc_vtotal changes for the mode, and due to which vrr.vmin
> changes and therefore the guardband also changes. Since we cannot change
> the guardband on the fly when VRR Timing Generator is on, this gets
> rejected.
>
> To overcome this, for panels that support VRR, instead of setting the
> vrr.vmin to crtc_vtotal, we set that to the lowest Vtotal (for highest
> Refresh rate supported by the panel). For non-vrr panels, the vrr.vmin
> stays the same i.e. crtc_vtotal.
The guardband must match the actual vblank length or else we'll end
up completely changing where the double buffered registers get
latched/vblank interrupts are generated. And nothing is prepared
for that.
>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> ---
> drivers/gpu/drm/i915/display/intel_vrr.c | 64 ++++++++++++++++--------
> 1 file changed, 42 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c
> index c6565baf815a..f0949a598f53 100644
> --- a/drivers/gpu/drm/i915/display/intel_vrr.c
> +++ b/drivers/gpu/drm/i915/display/intel_vrr.c
> @@ -278,6 +278,9 @@ int intel_vrr_fixed_rr_vmin(const struct intel_crtc_state *crtc_state)
> {
> struct intel_display *display = to_intel_display(crtc_state);
>
> + if (crtc_state->vrr.in_range)
> + return crtc_state->vrr.vmin;
> +
> return intel_vrr_fixed_rr_vtotal(crtc_state) -
> intel_vrr_flipline_offset(display);
> }
> @@ -308,26 +311,37 @@ static
> void intel_vrr_compute_fixed_rr_timings(struct intel_crtc_state *crtc_state)
> {
> /*
> - * For fixed rr, vmin = vmax = flipline.
> - * vmin is already set to crtc_vtotal set vmax and flipline the same.
> + * For fixed rr vmax = flipline.
> + * set vmax and flipline same as vtotal.
> */
> crtc_state->vrr.vmax = crtc_state->hw.adjusted_mode.crtc_vtotal;
> crtc_state->vrr.flipline = crtc_state->hw.adjusted_mode.crtc_vtotal;
> }
>
> static
> -int intel_vrr_compute_vmin(struct intel_crtc_state *crtc_state)
> +int intel_vrr_compute_fixed_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.
> + * For non VRR supporting panels/config, set the vmin to crtc_vtotal.
> + * This will help the case where VRR TG is used even for non-vrr panels/config.
> */
> return crtc_state->hw.adjusted_mode.crtc_vtotal;
> }
>
> +static
> +int intel_vrr_compute_vmin(struct intel_connector *connector,
> + const struct drm_display_mode *adjusted_mode)
> +{
> + const struct drm_display_info *info = &connector->base.display_info;
> + int vmin;
> +
> + vmin = adjusted_mode->crtc_clock * 1000 /
> + (adjusted_mode->crtc_htotal * info->monitor_range.max_vfreq);
> + vmin = min_t(int, vmin, adjusted_mode->crtc_vtotal);
> +
> + return vmin;
> +}
> +
> static
> int intel_vrr_compute_vmax(struct intel_connector *connector,
> const struct drm_display_mode *adjusted_mode)
> @@ -374,13 +388,13 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state,
> if (crtc_state->joiner_pipes)
> crtc_state->vrr.in_range = false;
>
> - vmin = intel_vrr_compute_vmin(crtc_state);
> -
> if (crtc_state->vrr.in_range) {
> if (HAS_LRR(display))
> crtc_state->update_lrr = true;
> vmax = intel_vrr_compute_vmax(connector, adjusted_mode);
> + vmin = intel_vrr_compute_vmin(connector, adjusted_mode);
> } else {
> + vmin = intel_vrr_compute_fixed_vmin(crtc_state);
> vmax = vmin;
> }
>
> @@ -671,8 +685,7 @@ void intel_vrr_transcoder_disable(const struct intel_crtc_state *crtc_state)
> bool intel_vrr_is_fixed_rr(const struct intel_crtc_state *crtc_state)
> {
> return crtc_state->vrr.flipline &&
> - crtc_state->vrr.flipline == crtc_state->vrr.vmax &&
> - crtc_state->vrr.flipline == intel_vrr_vmin_flipline(crtc_state);
> + crtc_state->vrr.flipline == crtc_state->vrr.vmax;
> }
>
> void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
> @@ -713,16 +726,6 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
> crtc_state->vrr.vmin = intel_de_read(display,
> TRANS_VRR_VMIN(display, cpu_transcoder)) + 1;
>
> - /*
> - * For platforms that always use VRR Timing Generator, the VTOTAL.Vtotal
> - * bits are not filled. Since for these platforms TRAN_VMIN is always
> - * filled with crtc_vtotal, use TRAN_VRR_VMIN to get the vtotal for
> - * adjusted_mode.
> - */
> - if (intel_vrr_always_use_vrr_tg(display))
> - crtc_state->hw.adjusted_mode.crtc_vtotal =
> - intel_vrr_vmin_vtotal(crtc_state);
> -
> if (HAS_AS_SDP(display)) {
> trans_vrr_vsync =
> intel_de_read(display,
> @@ -732,6 +735,23 @@ void intel_vrr_get_config(struct intel_crtc_state *crtc_state)
> crtc_state->vrr.vsync_end =
> REG_FIELD_GET(VRR_VSYNC_END_MASK, trans_vrr_vsync);
> }
> + /*
> + * For platforms that always use VRR Timing Generator, the VTOTAL.Vtotal
> + * bits are not filled. For fixed timings the vmax vtotal can be used to
> + * fill the VTOTAL. For variable timings, we need to compute the vtotal.
> + */
> + if (intel_vrr_always_use_vrr_tg(display)) {
> + u32 crtc_vtotal;
> +
> + if (intel_vrr_is_fixed_rr(crtc_state))
> + crtc_vtotal = intel_vrr_vmax_vtotal(crtc_state);
> + else
> + crtc_vtotal = intel_vrr_vmin_vtotal(crtc_state) +
> + crtc_state->vrr.guardband +
> + crtc_state->vrr.vsync_start +
> + crtc_state->vrr.vsync_end + 1;
This looks like nonsense to me. No idea what you're trying to do here.
> + crtc_state->hw.adjusted_mode.crtc_vtotal = crtc_vtotal;
> + }
> }
>
> vrr_enable = trans_vrr_ctl & VRR_CTL_VRR_ENABLE;
> --
> 2.45.2
--
Ville Syrjälä
Intel
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