Re: [Intel-gfx] [PATCH 15/15] drm/i915: replace drm_detect_hdmi_monitor() with drm_display_info.is_hdmi

[Claudio Suarez <cssk@net-c.es>]

On Fri, Oct 15, 2021 at 03:30:49PM +0300, Ville Syrjälä wrote:
> On Fri, Oct 15, 2021 at 01:37:13PM +0200, Claudio Suarez wrote:
> > Once EDID is parsed, the monitor HDMI support information is available
> > through drm_display_info.is_hdmi. Retriving the same information with
> > drm_detect_hdmi_monitor() is less efficient. Change to
> > drm_display_info.is_hdmi where possible.
> > 
> > This is a TODO task in Documentation/gpu/todo.rst
> > 
> > Signed-off-by: Claudio Suarez <cssk@net-c.es>
> > ---
> >  drivers/gpu/drm/i915/display/intel_connector.c | 5 +++++
> >  drivers/gpu/drm/i915/display/intel_connector.h | 1 +
> >  drivers/gpu/drm/i915/display/intel_hdmi.c      | 2 +-
> >  drivers/gpu/drm/i915/display/intel_sdvo.c      | 3 ++-
> >  4 files changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_connector.c b/drivers/gpu/drm/i915/display/intel_connector.c
> > index 9bed1ccecea0..3346b55df6e1 100644
> > --- a/drivers/gpu/drm/i915/display/intel_connector.c
> > +++ b/drivers/gpu/drm/i915/display/intel_connector.c
> > @@ -213,6 +213,11 @@ int intel_ddc_get_modes(struct drm_connector *connector,
> >  	return ret;
> >  }
> >  
> > +bool intel_connector_is_hdmi_monitor(struct drm_connector *connector)
> > +{
> > +	return connector->display_info.is_hdmi;
> > +}
> > +
> >  static const struct drm_prop_enum_list force_audio_names[] = {
> >  	{ HDMI_AUDIO_OFF_DVI, "force-dvi" },
> >  	{ HDMI_AUDIO_OFF, "off" },
> > diff --git a/drivers/gpu/drm/i915/display/intel_connector.h b/drivers/gpu/drm/i915/display/intel_connector.h
> > index 661a37a3c6d8..ceda6e72ece6 100644
> > --- a/drivers/gpu/drm/i915/display/intel_connector.h
> > +++ b/drivers/gpu/drm/i915/display/intel_connector.h
> > @@ -27,6 +27,7 @@ enum pipe intel_connector_get_pipe(struct intel_connector *connector);
> >  int intel_connector_update_modes(struct drm_connector *connector,
> >  				 struct edid *edid);
> >  int intel_ddc_get_modes(struct drm_connector *c, struct i2c_adapter *adapter);
> > +bool intel_connector_is_hdmi_monitor(struct drm_connector *connector);
> >  void intel_attach_force_audio_property(struct drm_connector *connector);
> >  void intel_attach_broadcast_rgb_property(struct drm_connector *connector);
> >  void intel_attach_aspect_ratio_property(struct drm_connector *connector);
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > index b04685bb6439..2b1d7c5bebdd 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > @@ -2355,7 +2355,7 @@ intel_hdmi_set_edid(struct drm_connector *connector)
> >  	to_intel_connector(connector)->detect_edid = edid;
> >  	if (edid && edid->input & DRM_EDID_INPUT_DIGITAL) {
> >  		intel_hdmi->has_audio = drm_detect_monitor_audio(edid);
> > -		intel_hdmi->has_hdmi_sink = drm_detect_hdmi_monitor(edid);
> > +		intel_hdmi->has_hdmi_sink = intel_connector_is_hdmi_monitor(connector);
> 
> Hmm. Have we parse the EDID by this point actually? I don't think that
> was the case in the past but maybe it changed at some point.

Yes, I think so. The complete code is:

----
        edid = drm_get_edid(connector, i2c);

        if (!edid && !intel_gmbus_is_forced_bit(i2c)) {
                drm_dbg_kms(&dev_priv->drm,
                            "HDMI GMBUS EDID read failed, retry using GPIO bit-banging\n");
                intel_gmbus_force_bit(i2c, true);
                edid = drm_get_edid(connector, i2c);
                intel_gmbus_force_bit(i2c, false);
        }

        intel_hdmi_dp_dual_mode_detect(connector, edid != NULL);

        intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS, wakeref);

        to_intel_connector(connector)->detect_edid = edid;
        if (edid && edid->input & DRM_EDID_INPUT_DIGITAL) {
                intel_hdmi->has_audio = drm_detect_monitor_audio(edid);
                intel_hdmi->has_hdmi_sink = intel_connector_is_hdmi_monitor(connector);
----
The edid value comes from drm_get_edid(), first or second.
drm_get_edid() internally calls drm_connector_update_edid_property()
drm_connector_update_edid_property() calls drm_add_display_info() and parses the edid.
So, the edid is parsed.
I checked this and I read the docs many times because at the first time I felt something
was wrong. But that is the sequence of calls.

> 
> >  
> >  		connected = true;
> >  	}
> > diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c b/drivers/gpu/drm/i915/display/intel_sdvo.c
> > index 6cb27599ea03..a32279e4fee8 100644
> > --- a/drivers/gpu/drm/i915/display/intel_sdvo.c
> > +++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
> > @@ -2060,8 +2060,9 @@ intel_sdvo_tmds_sink_detect(struct drm_connector *connector)
> >  		if (edid->input & DRM_EDID_INPUT_DIGITAL) {
> >  			status = connector_status_connected;
> >  			if (intel_sdvo_connector->is_hdmi) {
> > -				intel_sdvo->has_hdmi_monitor = drm_detect_hdmi_monitor(edid);
> >  				intel_sdvo->has_hdmi_audio = drm_detect_monitor_audio(edid);
> > +				intel_sdvo->has_hdmi_monitor =
> > +					intel_connector_is_hdmi_monitor(connector);
> 
> FYI there's a third copy of this in intel_dp.c

Yes. But in this case the edid comes from intel_dp_get_edid().
In intel_dp_get_edid(), there is a if. One of the branches calls drm_get_edid(),
so no problem here. But the other branch gets the edid from drm_edid_duplicate().
I haven't seen any guarantee that display_info is updated in this case.

I didn't change this file for that reason.

Thank you for your comments :)

BR
Claudio Suarez.