On Fri, Dec 02, 2022 at 03:44:10PM +0200, Ville Syrjala wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > We are miscalculating both the guardband value, and the resulting > vblank exit length on adl+. This means that our start of vblank > (double buffered register latch point) is incorrect, and we also > think that it's not where it actually is (hence vblank evasion/etc. > may not work properly). Fix up the calculations to match the real > hardware behaviour (as reverse engineered by intel_display_poller). > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/display/intel_vrr.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_vrr.c b/drivers/gpu/drm/i915/display/intel_vrr.c > index 6655dd2c1684..753e7b211708 100644 > --- a/drivers/gpu/drm/i915/display/intel_vrr.c > +++ b/drivers/gpu/drm/i915/display/intel_vrr.c > @@ -78,10 +78,10 @@ static int intel_vrr_vblank_exit_length(const struct intel_crtc_state *crtc_stat > struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc); > struct drm_i915_private *i915 = to_i915(crtc->base.dev); > > - /* The hw imposes the extra scanline before frame start */ > if (DISPLAY_VER(i915) >= 13) > - return crtc_state->vrr.guardband + crtc_state->framestart_delay + 1; > + return crtc_state->vrr.guardband; This makes sense since with guardband, there is no framestart delay > else > + /* The hw imposes the extra scanline before frame start */ > return crtc_state->vrr.pipeline_full + crtc_state->framestart_delay + 1; > } > > @@ -151,7 +151,7 @@ intel_vrr_compute_config(struct intel_crtc_state *crtc_state, > * number of scan lines. Assuming 0 for no DSB. > */ > crtc_state->vrr.guardband = > - crtc_state->vrr.vmin - adjusted_mode->crtc_vdisplay; > + crtc_state->vrr.vmin + 1 - adjusted_mode->crtc_vdisplay; Why are we adding + 1 here? The bspec says guardband should be : Guardband = Vmin - Vactive - Window2 where in our case Window2 = 0 If we need that + 1 to get this working, then perhaps we need to update Bspec? I kind of want to see if this is still breaking if we dont have that + 1? Manasi > } else { > crtc_state->vrr.pipeline_full = > min(255, crtc_state->vrr.vmin - adjusted_mode->crtc_vdisplay - > -- > 2.37.4 >