[PATCH] drm/i915/display: Fix RGB limited range handling for DP

[Shankar, Uma]

> -----Original Message-----
> From: Jani Nikula <jani.nikula at linux.intel.com>
> Sent: Wednesday, July 2, 2025 2:13 PM
> To: Shankar, Uma <uma.shankar at intel.com>; intel-gfx at lists.freedesktop.org;
> intel-xe at lists.freedesktop.org
> Cc: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>;
> ville.syrjala at linux.intel.com; Almahallawy, Khaled
> <khaled.almahallawy at intel.com>; Shankar, Uma <uma.shankar at intel.com>
> Subject: Re: [PATCH] drm/i915/display: Fix RGB limited range handling for DP
> 
> On Tue, 01 Jul 2025, Uma Shankar <uma.shankar at intel.com> wrote:
> > RGB limited range should be selected only if explicitly asked by
> > userspace by the broadcast RGB property with LIMITED_RANGE. This is
> > mostly enabled in case of CEA modes.
> >
> > Display port by default uses Full Range, fixed the same. This will
> > help set correct MSA information for colorimetry. Fixes a CTS issue
> > wrt colorimetry.
> 
> If we decide to go this way, the commit message *must* capture the history
> precisely, and not pretend this is the only way and everything that was before was
> wrong. And that we're primarily doing it to pass CTS.

Yes Sure Jani, will include the history and the spec changes in commit message

> 
> > Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 21 +++++++--------------
> >  1 file changed, 7 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index f48912f308df..8758b9d60d5e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -2708,8 +2708,6 @@ bool intel_dp_limited_color_range(const struct
> > intel_crtc_state *crtc_state,  {
> >  	const struct intel_digital_connector_state *intel_conn_state =
> >  		to_intel_digital_connector_state(conn_state);
> > -	const struct drm_display_mode *adjusted_mode =
> > -		&crtc_state->hw.adjusted_mode;
> >
> >  	/*
> >  	 * Our YCbCr output is always limited range.
> > @@ -2721,18 +2719,13 @@ bool intel_dp_limited_color_range(const struct
> intel_crtc_state *crtc_state,
> >  	if (crtc_state->output_format != INTEL_OUTPUT_FORMAT_RGB)
> >  		return false;
> >
> > -	if (intel_conn_state->broadcast_rgb ==
> INTEL_BROADCAST_RGB_AUTO) {
> > -		/*
> > -		 * See:
> > -		 * CEA-861-E - 5.1 Default Encoding Parameters
> > -		 * VESA DisplayPort Ver.1.2a - 5.1.1.1 Video Colorimetry
> > -		 */
> > -		return crtc_state->pipe_bpp != 18 &&
> > -			drm_default_rgb_quant_range(adjusted_mode) ==
> > -			HDMI_QUANTIZATION_RANGE_LIMITED;
> > -	} else {
> > -		return intel_conn_state->broadcast_rgb ==
> > -			INTEL_BROADCAST_RGB_LIMITED;
> > +	switch (intel_conn_state->broadcast_rgb) {
> > +	case INTEL_BROADCAST_RGB_LIMITED:
> > +		return true;
> > +	case INTEL_BROADCAST_RGB_FULL:
> > +	case INTEL_BROADCAST_RGB_AUTO:
> > +	default:
> > +		return false;
> >  	}
> 
> That's just:
> 
> 	return intel_conn_state->broadcast_rgb ==
> INTEL_BROADCAST_RGB_LIMITED;
> 
> 
> >  }
> 
> --
> Jani Nikula, Intel