Re: [Intel-gfx] [PATCH 2/2] drm/i915: Stop adding planes to the commit needlessly

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Mar 25, 2021 at 11:35:53AM +0200, Lisovskiy, Stanislav wrote:
> On Thu, Mar 25, 2021 at 02:44:15AM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > The dbuf bandwidth calculations don't need the planes to be
> > added to the state. Each plane's data rate has already been
> > precalculated and stored in the crtc state, and that with
> > the dbuf slice usage for each plane is all the dbuf bandwidth
> > code needs to figure out what the minimum cdclk is.
> > 
> > What we're trying to do here is make sure each plane recalculates
> > its minimum cdclk (ie. plane->min_cdclk()) on those platforms where
> > the number of active planes affects the result of said calculation.
> > Nothing to do with any dbuf cdclk requirements.
> 
> So does it mean that if we lets say had active plane mask as
> 011(planes 0, 1 were active) and new active planes are 101(planes 0, 2
> are active) - we should not add plane 2 to the state?
> Because hamming weight will be obviously same, however I think it would
> be wrong not have plane 2 in the state at all then..
> 
> Or will it be added somewhere else?

If someone is asking to disable plane 2 then it will be added to
the state already during the atomic/setplance ioctl handling.

> 
> 
> Stan
> 
> > 
> > Not sure if we had stuff in slightly different order or what,
> > but at least in the current scheme this is not necessary.
> > 
> > Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display.c | 10 ++--------
> >  1 file changed, 2 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > index 17490d29dc13..2300d58ba47f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -9811,7 +9811,7 @@ static bool active_planes_affects_min_cdclk(struct drm_i915_private *dev_priv)
> >  	/* See {hsw,vlv,ivb}_plane_ratio() */
> >  	return IS_BROADWELL(dev_priv) || IS_HASWELL(dev_priv) ||
> >  		IS_CHERRYVIEW(dev_priv) || IS_VALLEYVIEW(dev_priv) ||
> > -		IS_IVYBRIDGE(dev_priv) || (DISPLAY_VER(dev_priv) >= 11);
> > +		IS_IVYBRIDGE(dev_priv);
> >  }
> >  
> >  static int intel_crtc_add_bigjoiner_planes(struct intel_atomic_state *state,
> > @@ -9898,13 +9898,7 @@ static int intel_atomic_check_planes(struct intel_atomic_state *state)
> >  		old_active_planes = old_crtc_state->active_planes & ~BIT(PLANE_CURSOR);
> >  		new_active_planes = new_crtc_state->active_planes & ~BIT(PLANE_CURSOR);
> >  
> > -		/*
> > -		 * Not only the number of planes, but if the plane configuration had
> > -		 * changed might already mean we need to recompute min CDCLK,
> > -		 * because different planes might consume different amount of Dbuf bandwidth
> > -		 * according to formula: Bw per plane = Pixel rate * bpp * pipe/plane scale factor
> > -		 */
> > -		if (old_active_planes == new_active_planes)
> > +		if (hweight8(old_active_planes) == hweight8(new_active_planes))
> >  			continue;
> >  
> >  		ret = intel_crtc_add_planes_to_state(state, crtc, new_active_planes);
> > -- 
> > 2.26.2
> > 

-- 
Ville Syrjälä
Intel
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