On Wed, 2025-01-22 at 20:13 +0200, Ville Syrjälä wrote:
> On Wed, Jan 22, 2025 at 11:30:01AM +0200, Vinod Govindapillai wrote:
> > If FBC is already active, we don't need to call FBC activate
> > routine again during the post plane update. As this will
> > explicitly call the nuke and also rewrite the FBC ctl registers.
> > Xe doesn't support legacy fences. Hence fence programming also
> > not required as part of this fbc_haw_activate.
> >
> > "intel_atomic_commit_tail-> intel_post_plane_update->
> > intel_fbc_post_update-> _intel_fbc_post_update" path will be
> > executed during the normal flip cases. FBC HW will nuke on sync
> > flip event and driver do not need to call the nuke explicitly.
> >
> > This is much more relevant in case of dirty rectangle support
> > in FBC with the follow-up patches. Nuke on flip in that case will
> > remove all the benefits of fetching only the modified region.
> > Also any FBC related register updates with dirty rectangle
> > support enabled will trigger nuke by FBC HW.
> >
> > The front buffer rendering sequence will call intel_fbc_flush()
> > and which will call intel_fbc_nuke() or intel_fbc_activate()
> > based on FBC status explicitly and won't get impacted by this
> > change.
> >
> > Signed-off-by: Vinod Govindapillai <vinod.govindapillai@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_fbc.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> > index df05904bac8a..ab9649dd606c 100644
> > --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> > +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> > @@ -1556,11 +1556,22 @@ static void __intel_fbc_disable(struct intel_fbc *fbc)
> >
> > static void __intel_fbc_post_update(struct intel_fbc *fbc)
> > {
> > + struct intel_display *display = fbc->display;
> > +
> > lockdep_assert_held(&fbc->lock);
> >
> > fbc->flip_pending = false;
> > fbc->busy_bits = 0;
> >
> > + /*
> > + * When dirty rectangle is enabled, any updates to FBC registers will
> > + * trigger nuke. So avoid calling intel_fbc_activate if fbc is already
> > + * active and for XE3 cases. Xe doesn't support legacy fences. So
> > + * no need to update the fences as well.
> > + */
> > + if (DISPLAY_VER(display) >= 30 && fbc->active)
> > + return;
>
> Don't like platform checks in generic code. Either we should
> skip the stride programming inside the hw specific function,
> or we pull the strie programming into a separate hook which
> we can then skip completely when FBC was already active.
What I understood from Hw team is that any FBC register touch will trigger nuke not just the stride.
So in this case we need to skip the entire hw_activate if the fbc is already active.
BR
Vinod
>
> > +
> > intel_fbc_activate(fbc);
> > }
> >
> > --
> > 2.43.0
>
