Re: [Intel-gfx] [PATCH v2 6/8] drm/i915: Fix PSF GV point mask when SAGV is not possible

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Wed, Mar 09, 2022 at 09:34:58PM +0200, Lisovskiy, Stanislav wrote:
> On Wed, Mar 09, 2022 at 09:08:12PM +0200, Ville Syrjälä wrote:
> > On Wed, Mar 09, 2022 at 08:59:59PM +0200, Lisovskiy, Stanislav wrote:
> > > On Wed, Mar 09, 2022 at 06:49:46PM +0200, Ville Syrjala wrote:
> > > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > > 
> > > > Don't just mask off all the PSF GV points when SAGV gets disabled.
> > > > This should in fact cause the Pcode to reject the request since
> > > > at least one PSF point must remain enabled at all times.
> > > 
> > > Good point, however I think this is not the full fix:
> > > 
> > > BSpec says:
> > > 
> > > "At least one GV point of each type must always remain unmasked."
> > > 
> > > and
> > > 
> > > "The GV point of each type providing the highest bandwidth 
> > >  for display must always remain unmasked."
> > > 
> > > So I guess we should then also choose thr PSF GV point with
> > > the highest bandwidth as well.
> > 
> > The spec says PSF GV is fast enough to now stall the display data
> > fetch so we don't need to restrict the PSF points here.
> 
> But why it asks to ensure that we have the PSF GV of highest bandwidth to
> stay always unmasked then?
> 
> Stan

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

> 
> > 
> > -- 
> > Ville Syrjälä
> > Intel