Re: [PATCH v10 5/6] drm/i915/display: handle systems with duplicate psf gv points

["Govindapillai, Vinod" <vinod.govindapillai@intel.com>]

On Mon, 2024-04-08 at 11:29 +0300, Lisovskiy, Stanislav wrote:
> On Fri, Apr 05, 2024 at 02:35:32PM +0300, Vinod Govindapillai wrote:
> > From: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > 
> > There could be multiple qgv and psf gv points with similar values.
> > Apparently pcode's handling og psf and qgv points are different. For
> > qgv case, pcode sets whatever is asked by the driver. But in case
> > of psf gv points, it compares the bw from points before setting the
> > mask. This can cause problems in scenarios where we have to disable
> > sagv by setting the highest bw point and there could be multiple
> > points with highest bw. So to set the maximum psf gv point, find
> > out all the points with the highest bw and set all together.
> > 
> > v1: - use the same treatment to qgv points as well (Vinod)
> > 
> > v2: - pcode confirms that for qgv points, it sets whatever the
> >       driver sets (Vinod)
> > 
> > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_bw.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> > index 5f4f93524bef..6fb228a1a28f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bw.c
> > +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> > @@ -874,6 +874,8 @@ static unsigned int icl_max_bw_psf_gv_point_mask(struct drm_i915_private
> > *i915)
> >                 if (max_data_rate > max_bw) {
> >                         max_bw_point_mask = BIT(i);
> >                         max_bw = max_data_rate;
> > +               } else if (max_data_rate == max_bw) {
> > +                       max_bw_point_mask |= BIT(i);
> 
> So we just came back to where we started. Wondering still, why it even bothers to expose
> two equal PSF GV points. Not only having duplicate points doesn't make much sense for 
> the driver(since the BW they provide is the same), but also requires some additional
> logic on top to handle those.

Yes. Unfortunately this is what pcode expects for psf gv points. (Please have a look at the email
thread with the pcode team/Art etc.)

For qgv, it sets whatever the driver sets!

BR
Vinod
> 
> Stan
> 
> >                 }
> >         }
> >  
> > -- 
> > 2.34.1
> >