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

[Govindapillai, Vinod]

Hi Suraj,

Some comments, please have a look..

On Fri, 2024-11-08 at 14:20 +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]
> > 
> > WA: 22020299601
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/skl_watermark.c | 26 ++++++++++++++------
> >  1 file changed, 18 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c >
> > b/drivers/gpu/drm/i915/display/skl_watermark.c
> > index d3bbf335c749..9e208db55abb 100644
> > --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> > +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> > @@ -2848,9 +2848,11 @@ static int skl_wm_add_affected_planes(struct intel_atomic_state *state,
> >   * Program PKG_C_LATENCY Added Wake Time = 0
> >   */
> >  static void
> > -skl_program_dpkgc_latency(struct drm_i915_private *i915, bool enable_dpkgc)
> > +skl_program_dpkgc_latency(struct drm_i915_private *i915,
> > +                         bool enable_dpkgc,
> > +                         u32 max_linetime)
> >  {
> > -       u32 max_latency = 0;
> > +       u32 adjusted_latency = 0;
I guess, if you initialize adjusted_latency to LNL_PKG_C_LATENCY_MASK, you could get rid of the else
branch below. May be you could have a preparatory patch which get rid of this else branch?

> >         u32 clear = 0, val = 0;
> >         u32 added_wake_time = 0;
> >  
> > @@ -2858,18 +2860,23 @@ skl_program_dpkgc_latency(struct drm_i915_private *i915, bool >
> > enable_dpkgc)
> >                 return;
> >  
> >         if (enable_dpkgc) {
> > -               max_latency = skl_watermark_max_latency(i915, 1);
> > -               if (max_latency == 0)
> > -                       max_latency = LNL_PKG_C_LATENCY_MASK;
> > +               adjusted_latency = skl_watermark_max_latency(i915, 1);
> > +               if (adjusted_latency == 0)
> > +                       adjusted_latency = LNL_PKG_C_LATENCY_MASK;
> > +
Also, here I guess you need to avoid this WA if adjusted_latency is 0 ie. invalid level 1 latency.

Also use intel_display instead of i915 wherever possible related to this change. 

> > +               /* Wa_22020299601 */
> > +               if (DISPLAY_VER(i915) == 20 || DISPLAY_VER(i915) == 30)
> > +                       adjusted_latency = max_linetime *
> > +                               DIV_ROUND_UP(adjusted_latency, max_linetime);
> >                 added_wake_time = DSB_EXE_TIME +
> >                         i915->display.sagv.block_time_us;
> >         } else {
> > -               max_latency = LNL_PKG_C_LATENCY_MASK;
> > +               adjusted_latency = LNL_PKG_C_LATENCY_MASK;
> >                 added_wake_time = 0;
> >         }
> >  
> >         clear |= LNL_ADDED_WAKE_TIME_MASK | LNL_PKG_C_LATENCY_MASK;
> > -       val |= REG_FIELD_PREP(LNL_PKG_C_LATENCY_MASK, max_latency);
> > +       val |= REG_FIELD_PREP(LNL_PKG_C_LATENCY_MASK, adjusted_latency);
> >         val |= REG_FIELD_PREP(LNL_ADDED_WAKE_TIME_MASK, added_wake_time);
> >  
> >         intel_uncore_rmw(&i915->uncore, LNL_PKG_C_LATENCY, clear, val);
> > @@ -2882,6 +2889,7 @@ skl_compute_wm(struct intel_atomic_state *state)
> >         struct intel_crtc_state __maybe_unused *new_crtc_state;
> >         int ret, i;
> >         bool enable_dpkgc = false;
> > +       u32 max_linetime = 0;
> >  
> >         for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> >                 ret = skl_build_pipe_wm(state, crtc);
> > @@ -2911,9 +2919,11 @@ skl_compute_wm(struct intel_atomic_state *state)
> >                      new_crtc_state->vrr.vmin == new_crtc_state->vrr.flipline) ||
> >                     !new_crtc_state->vrr.enable)
> >                         enable_dpkgc = true;
> > +
> > +               max_linetime = max(new_crtc_state->linetime, max_linetime);
> >         }
> >  
> > -       skl_program_dpkgc_latency(to_i915(state->base.dev), enable_dpkgc);
> > +       skl_program_dpkgc_latency(to_i915(state->base.dev), enable_dpkgc, max_linetime);
> >  
> >         skl_print_wm_changes(state);
> >