[PATCH 6/6] drm/i915/watermark: Modify latency programmed into PKG_C_LATENCY

[Kandpal, Suraj]

> -----Original Message-----
> From: Govindapillai, Vinod <vinod.govindapillai at intel.com>
> Sent: Wednesday, November 13, 2024 3:50 PM
> To: Kandpal, Suraj <suraj.kandpal at intel.com>; intel-xe at lists.freedesktop.org;
> intel-gfx at lists.freedesktop.org
> Cc: Syrjala, Ville <ville.syrjala at intel.com>
> Subject: Re: [PATCH 6/6] drm/i915/watermark: Modify latency programmed
> into PKG_C_LATENCY
> 
> On Tue, 2024-11-12 at 14:15 +0530, Suraj Kandpal wrote:
> > Increase the latency programmed into PKG_C_LATENCY latency to be a
> > multiple of line time which is written into WM_LINETIME.
> >
> > --v2
> > -Fix commit subject line [Sai Teja]
> > -Use individual DISPLAY_VER checks instead of range [Sai Teja]
> > -Initialize max_linetime [Sai Teja]
> >
> > --v3
> > -take into account the scenario when adjusted_latency is 0 [Vinod]
> >
> > --v4
> > -rename adjusted_latency to latency [Mitul] -fix the condition in
> > which dpkgc is disabled [Vinod]
> >
> > WA: 22020299601
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_wm.c | 21 ++++++++++++++++-----
> >  1 file changed, 16 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_wm.c
> > b/drivers/gpu/drm/i915/display/intel_wm.c
> > index ffc7dde86629..47c82aa2adf9 100644
> > --- a/drivers/gpu/drm/i915/display/intel_wm.c
> > +++ b/drivers/gpu/drm/i915/display/intel_wm.c
> > @@ -157,8 +157,9 @@ intel_wm_compute_dpkgc_latency(struct
> > intel_atomic_state *state,
> >         struct intel_display *display = to_intel_display(state);
> >         struct intel_crtc *crtc;
> >         struct intel_crtc_state *new_crtc_state;
> > -       u32 max_latency = LNL_PKG_C_LATENCY_MASK;
> > +       u32 latency = LNL_PKG_C_LATENCY_MASK;
> >         u32 added_waketime = 0;
> > +       u32 max_linetime = 0;
> >         int i;
> >         bool fixed_refresh_rate = false;
> >
> > @@ -170,17 +171,27 @@ intel_wm_compute_dpkgc_latency(struct
> > intel_atomic_state *state,
> >                      new_crtc_state->vrr.vmin ==
> > new_crtc_state->vrr.flipline) ||
> >                     !new_crtc_state->vrr.enable)
> >                         fixed_refresh_rate = true;
> > +
> > +               max_linetime = max(new_crtc_state->linetime,
> > +max_linetime);
> >         }
> >
> >         if (fixed_refresh_rate) {
> > -               max_latency = skl_watermark_max_latency(i915, 1);
> > -               if (max_latency == 0)
> > -                       max_latency = LNL_PKG_C_LATENCY_MASK;
> > +               latency = skl_watermark_max_latency(i915, 1);
> > +
> > +               /* Wa_22020299601 */
> > +               if (latency) {
> > +                       if (DISPLAY_VER(display) == 20 ||
> > +DISPLAY_VER(display) == 30)
> > +                               latency = max_linetime *
> > +                                       DIV_ROUND_UP(latency,
> > +max_linetime);
> 
> new_crtc_state->linetime could be 0. So you need to protect division by 0
> here?

Sure will do that here.

Regards,
Suraj Kandpal

> 
> BR
> Vinod
> 
> > +               } else {
> > +                       latency = LNL_PKG_C_LATENCY_MASK;
> > +               }
> > +
> >                 added_waketime = DSB_EXE_TIME +
> >                         display->sagv.block_time_us;
> >         }
> >
> > -       display->wm.dpkgc_latency = max_latency;
> > +       display->wm.dpkgc_latency = latency;
> >         display->wm.dpkgc_added_waketime = added_waketime;
> >
> >         return 0;