[Intel-gfx] [PATCH v7] drm/i915/icl: Set GCP_COLOR_INDICATION only for 10/12 bit deep color

[Aditya Swarup]

On Wed, Apr 17, 2019 at 12:57:44PM +0300, Jani Nikula wrote:
> On Fri, 05 Apr 2019, Aditya Swarup <aditya.swarup at intel.com> wrote:
> > From: Clinton Taylor <Clinton.A.Taylor at intel.com>
> >
> > v2: Fix commit msg to reflect why issue occurs(Jani)
> > Set GCP_COLOR_INDICATION only when we set 10/12 bit deep color.
> >
> > Changing settings from 10/12 bit deep color to 8 bit(& vice versa)
> > doesn't work correctly using xrandr max bpc property. When we
> > connect a monitor which supports deep color, the highest deep color
> > setting is selected; which sets GCP_COLOR_INDICATION. When we change
> > the setting to 8 bit color, we still set GCP_COLOR_INDICATION which
> > doesn't allow the switch back to 8 bit color.
> >
> > v3,4: Add comments & drop changes in intel_hdmi_compute_config(Ville)
> > Since HSW+, GCP_COLOR_INDICATION is not required for 8bpc.
> >
> > Drop the changes in intel_hdmi_compute_config as desired_bpp
> > is needed to change values for pipe_bpp based on bw_constrained flag.
> >
> > v5: Fix missing logical && in condition for setting GCP_COLOR_INDICATION.
> >
> > v6: Fix comment formatting (Ville)
> >
> > v7: Add reviewed by Ville
> >
> > Signed-off-by: Clinton Taylor <Clinton.A.Taylor at intel.com>
> > Signed-off-by: Aditya Swarup <aditya.swarup at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Cc: Jani Nikula <jani.nikula at intel.com>
> > Cc: Manasi Navare <manasi.d.navare at intel.com>
> > Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_hdmi.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> > index 5ccb305a6e1c..f2c0aba4371b 100644
> > --- a/drivers/gpu/drm/i915/intel_hdmi.c
> > +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> > @@ -962,8 +962,11 @@ static void intel_hdmi_compute_gcp_infoframe(struct intel_encoder *encoder,
> >  	crtc_state->infoframes.enable |=
> >  		intel_hdmi_infoframe_enable(HDMI_PACKET_TYPE_GENERAL_CONTROL);
> >  
> > -	/* Indicate color depth whenever the sink supports deep color */
> > -	if (hdmi_sink_is_deep_color(conn_state))
> > +	/* Indicate color depth whenever the sink supports deep color
> > +	 * Also, 8bpc + color depth indication is no longer supported
> > +	 * for HSW+ platforms.
> > +	 */
> 
> Frankly the comment confuses me as the condition has nothing to do with
> HSW+ and applies for pre-HSW as well. And the "whenever" in the first
> line is no longer true.

You are correct, Clint and me spent time investigating this Spec/HW
monstrosity for the correct conditions required for sending
GCP_COLOR_INDICATION.

> 
> I do understand the point here, we don't need to use color indication
> when we're not using deep color anyway, and moreover this combo isn't
> supported on HSW+.
> 
> The final question is, under what circumstances would we use pipe_bpp >
> 24 when the sink does *not* support bpc > 8?
> 
> IOW, could we simply use
> 
> 	if (crtc_state->pipe_bpp > 24)
> 
> here?
No we do need the check for sink, as that is the real check for
determining whether sink supports deep color or not. For some platforms,
we do send GCP_COLOR_INDICATION even for 8 bpc when the sink supports
deep color. This will be clear with the next version of the patch.

> 
> 
> BR,
> Jani.
> 
> 
> > +	if (hdmi_sink_is_deep_color(conn_state) && crtc_state->pipe_bpp > 24)
> >  		crtc_state->infoframes.gcp |= GCP_COLOR_INDICATION;
> >  
> >  	/* Enable default_phase whenever the display mode is suitably aligned */
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center