On Mon, Dec 05, 2022 at 12:34:25PM -0800, Navare, Manasi wrote: > 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 framestart delay is still a thing. But it's not something that affects how the hardware interprets the guardband value. > > > 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? flipline is what actaully determines the start of vblank, and 'flipline>=vmin+1' always. > > I kind of want to see if this is still breaking if we dont have that + > 1? Without it start of vblank happens one line later than where we want it to happen. > > Manasi > > > } else { > > crtc_state->vrr.pipeline_full = > > min(255, crtc_state->vrr.vmin - adjusted_mode->crtc_vdisplay - > > -- > > 2.37.4 > > -- Ville Syrjälä Intel