On Thu, Jul 13, 2023 at 04:03:34PM +0530, Ankit Nautiyal wrote:
> As per Bsepc:49259, Bigjoiner BW check puts restriction on the
> compressed bpp for a given CDCLK, pixelclock in cases where
> Bigjoiner + DSC are used.
>
> Currently compressed bpp is computed first, and it is ensured that
> the bpp will work at least with the max CDCLK freq.
>
> Since the CDCLK is computed later, lets account for Bigjoiner BW
> check while calculating Min CDCLK.
>
> v2: Use pixel clock in the bw calculations. (Ville)
>
> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_cdclk.c | 61 +++++++++++++++++-----
> 1 file changed, 47 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> index 701909966545..788dba576294 100644
> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> @@ -2533,6 +2533,51 @@ static int intel_planes_min_cdclk(const struct intel_crtc_state *crtc_state)
> return min_cdclk;
> }
>
> +static int intel_vdsc_min_cdclk(const struct intel_crtc_state *crtc_state)
> +{
> + struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> + struct drm_i915_private *i915 = to_i915(crtc->base.dev);
> + int num_vdsc_instances = intel_dsc_get_num_vdsc_instances(crtc_state);
> + int min_cdclk = 0;
> +
> + /*
> + * When we decide to use only one VDSC engine, since
> + * each VDSC operates with 1 ppc throughput, pixel clock
> + * cannot be higher than the VDSC clock (cdclk)
> + * If there 2 VDSC engines, then pixel clock can't be higher than
> + * VDSC clock(cdclk) * 2 and so on.
> + */
> + min_cdclk = max_t(int, min_cdclk,
> + DIV_ROUND_UP(crtc_state->pixel_rate, num_vdsc_instances));
> +
> + if (crtc_state->bigjoiner_pipes) {
> + int pixel_clock = crtc_state->hw.adjusted_mode.clock;
> +
> + /*
> + * According to Bigjoiner bw check:
> + * compressed_bpp <= PPC * CDCLK * Big joiner Interface bits / Pixel clock
> + *
> + * We have already computed compressed_bpp, so now compute the min CDCLK that
> + * is required to support this compressed_bpp.
> + *
> + * => CDCLK >= compressed_bpp * Pixel clock / (PPC * Bigjoiner Interface bits)
> + *
> + * Since PPC = 2 with bigjoiner
> + * => CDCLK >= compressed_bpp * Pixel clock / 2 * Bigjoiner Interface bits
> + *
> + * #TODO Bspec mentions to account for FEC overhead while using pixel clock.
> + * Check if we need to use FEC overhead in the above calculations.
There is already some function used in intel_dp.c:
intel_dp_mode_to_fec_clock(mode_clock) => Should you may be just use that one, to account FEC
overhead?
> + */
> + int bigjoiner_interface_bits = DISPLAY_VER(i915) > 13 ? 36 : 24;
> + int min_cdclk_bj = (crtc_state->dsc.compressed_bpp * pixel_clock) /
> + (2 * bigjoiner_interface_bits);
I would use "num_vdsc_instances" instead of 2, since we even get those explicitly.
> +
> + min_cdclk = max(min_cdclk, min_cdclk_bj);
> + }
> +
> + return min_cdclk;
> +}
> +
> int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
> {
> struct drm_i915_private *dev_priv =
> @@ -2604,20 +2649,8 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
> /* Account for additional needs from the planes */
> min_cdclk = max(intel_planes_min_cdclk(crtc_state), min_cdclk);
>
> - /*
> - * When we decide to use only one VDSC engine, since
> - * each VDSC operates with 1 ppc throughput, pixel clock
> - * cannot be higher than the VDSC clock (cdclk)
> - * If there 2 VDSC engines, then pixel clock can't be higher than
> - * VDSC clock(cdclk) * 2 and so on.
> - */
> - if (crtc_state->dsc.compression_enable) {
> - int num_vdsc_instances = intel_dsc_get_num_vdsc_instances(crtc_state);
> -
> - min_cdclk = max_t(int, min_cdclk,
> - DIV_ROUND_UP(crtc_state->pixel_rate,
> - num_vdsc_instances));
> - }
> + if (crtc_state->dsc.compression_enable)
> + min_cdclk = max(min_cdclk, intel_vdsc_min_cdclk(crtc_state));
With notes above taken care of:
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
>
> /*
> * HACK. Currently for TGL/DG2 platforms we calculate
> --
> 2.40.1
>
