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

[Govindapillai, Vinod]

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?

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;