Re: [Intel-gfx] [PATCH 5/5] drm/i915: Get proper min cdclk if vDSC enabled

["Kulkarni, Vandita" <vandita.kulkarni@intel.com>]

> -----Original Message-----
> From: Lee, Shawn C <shawn.c.lee@intel.com>
> Sent: Tuesday, July 20, 2021 8:01 PM
> To: Kulkarni, Vandita <vandita.kulkarni@intel.com>; intel-
> gfx@lists.freedesktop.org
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>; Jani Nikula
> <jani.nikula@linux.intel.com>; Chiou, Cooper <cooper.chiou@intel.com>;
> Tseng, William <william.tseng@intel.com>
> Subject: RE: [PATCH 5/5] drm/i915: Get proper min cdclk if vDSC enabled
> 
> 
> On Tue, July 19, 2021, Vandita Kulkarni <vandita.kulkarni@intel.com> wrote:
> >>
> >> VDSC engine can process only 1 pixel per Cd clock. In case VDSC is
> >> used and max slice count == 1, max supported pixel clock should be 100%
> of CD clock.
> >> Then do min_cdclk and pixel clock comparison to get proper min cdclk.
> >>
> >> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> >> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> >> Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
> >> Cc: Cooper Chiou <cooper.chiou@intel.com>
> >> Cc: William Tseng <william.tseng@intel.com>
> >> Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/display/intel_cdclk.c | 12 ++++++++++++
> >>  1 file changed, 12 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c
> >> b/drivers/gpu/drm/i915/display/intel_cdclk.c
> >> index 71067a62264d..c33d574eb991 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> >> @@ -2159,6 +2159,18 @@ 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);
> >>
> >> +/*
> >> + * VDSC engine can process only 1 pixel per Cd clock.
> >> + * In case VDSC is used and max slice count == 1,
> >> + * max supported pixel clock should be 100% of CD clock.
> >> + * Then do min_cdclk and pixel clock comparison to get cdclk.
> >> + */
> >> +if (DISPLAY_VER(dev_priv) >= 11 &&
> >
> >I think you could just check for dsc enable and slice count ==1.
> >
> 
> DP and eDP would apply the same thing if dsc enabled and sink's dsc slice
> count ==1.
> Is that right?
Yes.
> 
> >Also better to have a check if crtc_clock exceeds dev_priv->max_cdclk_freq
> in dsi_dsc compute_config as well.
> >and return -EINVAL .
> >
> >-Vandita
Since we do not have bigjoiner support on dsi yet and the check wrt max_cdclk_freq
is taken care in intel_crtc_compute_config. I think you can leave this for now.
You do not need this clock check again in dsi_compute_config

-Vandita
> >
> 
> We should have this checking in dsi_dsc_compute_config() just like DP driver
> did. What do you think?
> 
> 	if (adjusted_mode->crtc_clock > dev_priv->max_cdclk_freq ||
> 	    pipe_config->bigjoiner) {
> 		if (pipe_config->dsc.slice_count < 2) {
> 			drm_dbg_kms(&dev_priv->drm,
> 				    "Cannot split stream to use 2 VDSC
> instances\n");
> 			return -EINVAL;
> 		}
> 
> 		pipe_config->dsc.dsc_split = true;
> 	}
> 
> Best regards,
> Shawn
> 
> >> +    intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DSI) &&
> >> +    crtc_state->dsc.compression_enable &&
> >> +    crtc_state->dsc.slice_count == 1)
> >
> >> +min_cdclk = max(min_cdclk, (int)crtc_state->pixel_rate);
> >> +
> >>  /*
> >>   * HACK. Currently for TGL platforms we calculate
> >>   * min_cdclk initially based on pixel_rate divided
> >> --
> >> 2.17.1
> >
> >

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