On Wed, Dec 07, 2022 at 01:05:15PM -0800, Navare, Manasi wrote: > On Wed, Dec 07, 2022 at 05:10:54PM +0200, Ville Syrjälä wrote: > > 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 <[email protected]> > > > > > > > > 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 <[email protected]> > > > > --- > > > > 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. > > Flipline would be always >=vmin as per the bspec,
Not sure where in bspec you see that. All I see is >vmin, and it even says you et an extra line if you try to set them equal. Pretty sure I verified that behaviour on the hw on icl/tgl since I put the extra -1 to the vmin calculation. Though I haven't actually tested it on adl+. > have we tried with > that or if that definitely doesnt work then we need to have this changed > in the bspec. > > Either way if this is the only value that works then with this change > added to bspec: > > Reviewed-by: Manasi Navare <[email protected]> > > Manasi > > > > > > > > > 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 -- Ville Syrjälä Intel
