On Mon, Aug 24, 2020 at 07:46:30PM +0000, Shankar, Uma wrote:
> 
> > -----Original Message-----
> > From: Ville Syrjälä <[email protected]>
> > Sent: Monday, August 24, 2020 11:46 PM
> > To: Shankar, Uma <[email protected]>
> > Cc: [email protected]
> > Subject: Re: [Intel-gfx] [PATCH] drm/i915/display: Add an extra vblank wait
> > before fbc activation
> > 
> > On Mon, Aug 17, 2020 at 01:14:18PM +0530, Uma Shankar wrote:
> > > Add an extra vblank before fbc is activated.
> > > WA: 1409689360
> > > Corruption with FBC around plane 1A enabling. In the Frame Buffer
> > > Compression programming sequence "Display Plane Enabling with FBC"
> > > add a wait for vblank between plane enabling step 1 and FBC enabling
> > > step 2.
> > 
> > Already there due to drm_atomic_helper_wait_for_flip_done().
> 
> Hi Ville,
> __intel_fbc_post_update is also called through intel_fbc_flush. The extra 
> wait at that point seem
> to be taking care of this case as well.
> 
> We can add it in vblank worker as suggested by Maarten or do you feel this 
> should be handled differently.

There's already supposed to be something that prevents the frontbuffer
stuff from racing with plane updates.

> 
> Regards,
> Uma Shankar
> 
> > >
> > > Signed-off-by: Uma Shankar <[email protected]>
> > > Signed-off-by: Stanislav Lisovskiy <[email protected]>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_fbc.c | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c
> > > b/drivers/gpu/drm/i915/display/intel_fbc.c
> > > index 2ab32e6532ff..0ed252ff2c53 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> > > @@ -1085,10 +1085,12 @@ static void __intel_fbc_post_update(struct
> > intel_crtc *crtc)
> > >   if (!intel_fbc_can_activate(crtc))
> > >           return;
> > >
> > > - if (!fbc->busy_bits)
> > > + if (!fbc->busy_bits) {
> > > +         intel_wait_for_vblank(dev_priv, crtc->pipe);
> > >           intel_fbc_hw_activate(dev_priv);
> > > - else
> > > + } else {
> > >           intel_fbc_deactivate(dev_priv, "frontbuffer write");
> > > + }
> > >  }
> > >
> > >  void intel_fbc_post_update(struct intel_atomic_state *state,
> > > --
> > > 2.22.0
> > >
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > [email protected]
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > 
> > --
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel
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