[Intel-gfx] [PATCH] drm/i915/display: Add an extra vblank wait before fbc activation

[Shankar, Uma]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Sent: Monday, August 24, 2020 11:46 PM
> To: Shankar, Uma <uma.shankar at intel.com>
> Cc: intel-gfx at lists.freedesktop.org
> 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.

Regards,
Uma Shankar

> >
> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
> > ---
> >  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
> >
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> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> --
> Ville Syrjälä
> Intel