On Thu, Sep 11, 2025 at 08:15:42AM +0530, Ankit Nautiyal wrote:
> Refactor dsc_prefill_latency and scaler_prefill_latency to take
> linetime as an explicit parameter instead of computing it internally.
>
> This avoids redundant calculations and simplifies scanline conversion
> logic in skl_is_vblank_too_short().
>
> This change also facilitates future extraction of these helpers for use
> cases where latencies are computed for an optimized guardband, based on the
> highest resolution mode, rather than the current mode.
>
> Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
> Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.gol...@intel.com>
> ---
> drivers/gpu/drm/i915/display/skl_watermark.c | 18 ++++++++----------
> 1 file changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c
> b/drivers/gpu/drm/i915/display/skl_watermark.c
> index 51548447f4aa..49d424f5b305 100644
> --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> @@ -2176,13 +2176,11 @@ cdclk_prefill_adjustment(const struct
> intel_crtc_state *crtc_state)
> }
>
> static int
> -dsc_prefill_latency(const struct intel_crtc_state *crtc_state)
> +dsc_prefill_latency(const struct intel_crtc_state *crtc_state, int linetime)
> {
> struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> const struct intel_crtc_scaler_state *scaler_state =
> &crtc_state->scaler_state;
> - int linetime = DIV_ROUND_UP(1000 * crtc_state->hw.adjusted_mode.htotal,
> - crtc_state->hw.adjusted_mode.clock);
> int num_scaler_users = hweight32(scaler_state->scaler_users);
> int chroma_downscaling_factor =
> crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420 ? 4 :
> 1;
> @@ -2206,18 +2204,16 @@ dsc_prefill_latency(const struct intel_crtc_state
> *crtc_state)
>
> dsc_prefill_latency *= cdclk_prefill_adjustment(crtc_state);
>
> - return intel_usecs_to_scanlines(&crtc_state->hw.adjusted_mode,
> dsc_prefill_latency);
> + return dsc_prefill_latency;
> }
>
> static int
> -scaler_prefill_latency(const struct intel_crtc_state *crtc_state)
> +scaler_prefill_latency(const struct intel_crtc_state *crtc_state, int
> linetime)
> {
> const struct intel_crtc_scaler_state *scaler_state =
> &crtc_state->scaler_state;
> int num_scaler_users = hweight32(scaler_state->scaler_users);
> int scaler_prefill_latency = 0;
> - int linetime = DIV_ROUND_UP(1000 * crtc_state->hw.adjusted_mode.htotal,
> - crtc_state->hw.adjusted_mode.clock);
>
> if (!num_scaler_users)
> return scaler_prefill_latency;
> @@ -2238,7 +2234,7 @@ scaler_prefill_latency(const struct intel_crtc_state
> *crtc_state)
>
> scaler_prefill_latency *= cdclk_prefill_adjustment(crtc_state);
>
> - return intel_usecs_to_scanlines(&crtc_state->hw.adjusted_mode,
> scaler_prefill_latency);
> + return scaler_prefill_latency;
> }
>
> static bool
> @@ -2247,11 +2243,13 @@ skl_is_vblank_too_short(const struct intel_crtc_state
> *crtc_state,
> {
> const struct drm_display_mode *adjusted_mode =
> &crtc_state->hw.adjusted_mode;
> + int linetime = DIV_ROUND_UP(1000 * adjusted_mode->htotal,
> + adjusted_mode->clock);
>
> return crtc_state->framestart_delay +
> intel_usecs_to_scanlines(adjusted_mode, latency) +
> - scaler_prefill_latency(crtc_state) +
> - dsc_prefill_latency(crtc_state) +
> + DIV_ROUND_UP(scaler_prefill_latency(crtc_state, linetime),
> linetime) +
> + DIV_ROUND_UP(dsc_prefill_latency(crtc_state, linetime),
> linetime) +
Looks like you could just add up all the usec latency numbers and
convert the whole thing with a single intel_usecs_to_scanlines() call
instead of this mismash of hand rolled and non-hand rolled stuff.
> wm0_lines >
> adjusted_mode->crtc_vtotal - adjusted_mode->crtc_vblank_start;
> }
> --
> 2.45.2
--
Ville Syrjälä
Intel
