[Intel-gfx] [v2 1/2] drm/i915/display/tgl: Disable FBC with PSR2

[Shankar, Uma]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Sent: Thursday, November 19, 2020 9:12 PM
> To: Shankar, Uma <uma.shankar at intel.com>
> Cc: intel-gfx at lists.freedesktop.org
> Subject: Re: [v2 1/2] drm/i915/display/tgl: Disable FBC with PSR2
> 
> On Thu, Nov 19, 2020 at 09:20:49PM +0530, Uma Shankar wrote:
> > There are some corner cases wrt underrun when we enable FBC with PSR2
> > on TGL. Recommendation from hardware is to keep this combination
> > disabled.
> >
> > Bspec: 50422 HSD: 14010260002
> >
> > v2: Added psr2 enabled check from crtc_state (Anshuman) Added Bspec
> > link and HSD referneces (Jose)
> >
> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> > ---
> >  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 a5b072816a7b..c64ed1cd29b1 100644
> > --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> > +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> > @@ -799,6 +799,17 @@ static bool intel_fbc_can_activate(struct intel_crtc
> *crtc)
> >  	struct intel_fbc *fbc = &dev_priv->fbc;
> >  	struct intel_fbc_state_cache *cache = &fbc->state_cache;
> >
> > +	/*
> > +	 * Tigerlake is not supporting FBC with PSR2.
> > +	 * Recommendation is to keep this combination disabled
> > +	 * Bspec: 50422 HSD: 14010260002
> > +	 */
> > +	if (crtc->config && crtc->config->has_psr2 &&
> 
> Please don't add more crtc->config usages. After several years we've almost
> reached the point where we can finally remove it.
> I should porbably take a look at how much work would be required to at least
> make it always NULL on g4x+.
> 
> The fbc state tracking is a total mess atm, but I think you can stuff this into
> intel_fbc_update_state_cache() and either just set cache->plane.visible=false
> (which is a bit of a lie but would work), or add a new thing into the
> params/cache.

Ok sure, so I hope below logic will keep this disabled:
  if (crtc_state->has_psr2 && IS_TIGERLAKE(dev_priv))
                cache->plane.visible = false;

        if (!cache->plane.visible)
                return;

Will update and re-send the patch.

Thanks & Regards,
Uma Shankar

> My plan is to eliminate most of the this params/cache mess and just cache the
> things fbc really needs for hw activate/deactivate. I do have a wip branch but
> haven't had time recently to continue the work.
> 
> > +	    IS_TIGERLAKE(dev_priv)) {
> > +		fbc->no_fbc_reason = "not supported with PSR2";
> > +		return false;
> > +	}
> > +
> >  	if (!intel_fbc_can_enable(dev_priv))
> >  		return false;
> >
> > --
> > 2.26.2
> 
> --
> Ville Syrjälä
> Intel