Re: [PATCH v10 2/6] drm/i915/display: Extract code required to calculate max qgv/psf gv point

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

On Mon, 2024-04-08 at 11:32 +0300, Lisovskiy, Stanislav wrote:
> On Fri, Apr 05, 2024 at 02:35:29PM +0300, Vinod Govindapillai wrote:
> > From: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > 
> > We need that in order to force disable SAGV in next patch.
> > Also it is beneficial to separate that code, as in majority cases,
> > when SAGV is enabled, we don't even need those calculations.
> > Also we probably need to determine max PSF GV point as well, however
> > currently we don't do that when we disable SAGV, which might be
> > actually causing some issues in that case.
> > 
> > v2: - Introduce helper adl_qgv_bw(counterpart to adl_psf_bw)
> >       (Ville Syrjälä)
> >     - Don't restrict psf gv points for SAGV disable case
> >       (Ville Syrjälä)
> > v3: - Update icl_max_bw_qgv_point_mask to return max qgv point
> >       mask (Vinod)
> > v4: - Minor changes in icl_find_qgv_points (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 | 80 +++++++++++++++----------
> >  1 file changed, 50 insertions(+), 30 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> > index 77886cc21211..c00094e5f11c 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bw.c
> > +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> > @@ -661,6 +661,22 @@ static unsigned int adl_psf_bw(struct drm_i915_private *dev_priv,
> >         return bi->psf_bw[psf_gv_point];
> >  }
> >  
> > +static unsigned int icl_qgv_bw(struct drm_i915_private *i915,
> > +                              int num_active_planes, int qgv_point)
> > +{
> > +       unsigned int idx;
> > +
> > +       if (DISPLAY_VER(i915) >= 12)
> > +               idx = tgl_max_bw_index(i915, num_active_planes, qgv_point);
> > +       else
> > +               idx = icl_max_bw_index(i915, num_active_planes, qgv_point);
> > +
> > +       if (idx >= ARRAY_SIZE(i915->display.bw.max))
> > +               return 0;
> > +
> > +       return i915->display.bw.max[idx].deratedbw[qgv_point];
> > +}
> > +
> >  void intel_bw_init_hw(struct drm_i915_private *dev_priv)
> >  {
> >         if (!HAS_DISPLAY(dev_priv))
> > @@ -806,6 +822,35 @@ intel_atomic_get_bw_state(struct intel_atomic_state *state)
> >         return to_intel_bw_state(bw_state);
> >  }
> >  
> > +static unsigned int icl_max_bw_qgv_point_mask(struct drm_i915_private *i915,
> > +                                             int num_active_planes)
> > +{
> > +       unsigned int num_qgv_points = i915->display.bw.max[0].num_qgv_points;
> > +       unsigned int max_bw_point_mask = 0;
> > +       unsigned int max_bw = 0;
> > +       int i;
> > +
> > +       for (i = 0; i < num_qgv_points; i++) {
> > +               unsigned int max_data_rate =
> > +                       icl_qgv_bw(i915, num_active_planes, i);
> > +
> > +               /*
> > +                * We need to know which qgv point gives us
> > +                * maximum bandwidth in order to disable SAGV
> > +                * if we find that we exceed SAGV block time
> > +                * with watermarks. By that moment we already
> > +                * have those, as it is calculated earlier in
> > +                * intel_atomic_check,
> > +                */
> > +               if (max_data_rate > max_bw) {
> > +                       max_bw_point_mask = BIT(i);
> > +                       max_bw = max_data_rate;
> > +               }
> > +       }
> > +
> > +       return max_bw_point_mask;
> > +}
> > +
> 
> Wondering, why we just don't call it "max_bw_point", of course "mask"
> could be applied to single point as well, however in most cases it still
> kind of implies that there are few of those, however we always find
> a single one here.

Okay.. For QGV max point, indeed we are finding point with max bw. So the name can be changed. I
think it can be changed before merging instead of floating another version - well if we these
patches can be RB-ed 

Vinod

> 
> Stan
> 
> >  static int mtl_find_qgv_points(struct drm_i915_private *i915,
> >                                unsigned int data_rate,
> >                                unsigned int num_active_planes,
> > @@ -883,8 +928,6 @@ static int icl_find_qgv_points(struct drm_i915_private *i915,
> >                                const struct intel_bw_state *old_bw_state,
> >                                struct intel_bw_state *new_bw_state)
> >  {
> > -       unsigned int max_bw_point = 0;
> > -       unsigned int max_bw = 0;
> >         unsigned int num_psf_gv_points = i915->display.bw.max[0].num_psf_gv_points;
> >         unsigned int num_qgv_points = i915->display.bw.max[0].num_qgv_points;
> >         u16 psf_points = 0;
> > @@ -897,31 +940,8 @@ static int icl_find_qgv_points(struct drm_i915_private *i915,
> >                 return ret;
> >  
> >         for (i = 0; i < num_qgv_points; i++) {
> > -               unsigned int idx;
> > -               unsigned int max_data_rate;
> > -
> > -               if (DISPLAY_VER(i915) >= 12)
> > -                       idx = tgl_max_bw_index(i915, num_active_planes, i);
> > -               else
> > -                       idx = icl_max_bw_index(i915, num_active_planes, i);
> > -
> > -               if (idx >= ARRAY_SIZE(i915->display.bw.max))
> > -                       continue;
> > -
> > -               max_data_rate = i915->display.bw.max[idx].deratedbw[i];
> > -
> > -               /*
> > -                * We need to know which qgv point gives us
> > -                * maximum bandwidth in order to disable SAGV
> > -                * if we find that we exceed SAGV block time
> > -                * with watermarks. By that moment we already
> > -                * have those, as it is calculated earlier in
> > -                * intel_atomic_check,
> > -                */
> > -               if (max_data_rate > max_bw) {
> > -                       max_bw_point = i;
> > -                       max_bw = max_data_rate;
> > -               }
> > +               unsigned int max_data_rate = icl_qgv_bw(i915,
> > +                                                       num_active_planes, i);
> >                 if (max_data_rate >= data_rate)
> >                         qgv_points |= BIT(i);
> >  
> > @@ -965,9 +985,9 @@ static int icl_find_qgv_points(struct drm_i915_private *i915,
> >          * cause.
> >          */
> >         if (!intel_can_enable_sagv(i915, new_bw_state)) {
> > -               qgv_points = BIT(max_bw_point);
> > -               drm_dbg_kms(&i915->drm, "No SAGV, using single QGV point %d\n",
> > -                           max_bw_point);
> > +               qgv_points = icl_max_bw_qgv_point_mask(i915, num_active_planes);
> > +               drm_dbg_kms(&i915->drm, "No SAGV, using single QGV point mask 0x%x\n",
> > +                           qgv_points);
> >         }
> >  
> >         /*
> > -- 
> > 2.34.1
> >