[PATCH 01/15] drm/i915/hdmi: do dual mode detect only if connected

[Jani Nikula]

On Thu, 13 Oct 2022, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> On Thu, Oct 13, 2022 at 09:41:21PM +0300, Ville Syrjälä wrote:
>> On Tue, Oct 11, 2022 at 04:49:35PM +0300, Jani Nikula wrote:
>> > For normal connector detect, there's really no point in trying dual mode
>> > detect if the connector is disconnected. We can simplify the detect
>> > sequence by skipping it. Since intel_hdmi_dp_dual_mode_detect() is only
>> > called when EDID is present, we can drop the has_edid parameter.
>> > 
>> > The functional effect is speeding up disconnected connector detection
>> > ever so slightly, and, combined with firmware EDID, also stop logging
>> > about assuming dual mode adaptor.
>> > 
>> > It's a bit subtle, but this will also skip dual mode detect if the
>> > connector is force connected and a) there's no EDID of any kind, normal
>> > or override/firmare or b) there's EDID but it does not indicate
>> > digital. These are corner cases no matter what, and arguably forcing
>> > should not be limited by dual mode detect.
>> > 
>> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> > Signed-off-by: Jani Nikula <jani.nikula at intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_hdmi.c | 17 +++++++----------
>> >  1 file changed, 7 insertions(+), 10 deletions(-)
>> > 
>> > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
>> > index 93519fb23d9d..a332eaac86cd 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_unset_edid(struct drm_connector *connector)
>> >  }
>> >  
>> >  static void
>> > -intel_hdmi_dp_dual_mode_detect(struct drm_connector *connector, bool has_edid)
>> > +intel_hdmi_dp_dual_mode_detect(struct drm_connector *connector)
>> >  {
>> >  	struct drm_i915_private *dev_priv = to_i915(connector->dev);
>> >  	struct intel_hdmi *hdmi = intel_attached_hdmi(to_intel_connector(connector));
>> > @@ -2371,16 +2371,13 @@ intel_hdmi_dp_dual_mode_detect(struct drm_connector *connector, bool has_edid)
>> >  	 * CONFIG1 pin, but no such luck on our hardware.
>> >  	 *
>> >  	 * The only method left to us is to check the VBT to see
>> > -	 * if the port is a dual mode capable DP port. But let's
>> > -	 * only do that when we sucesfully read the EDID, to avoid
>> > -	 * confusing log messages about DP dual mode adaptors when
>> > -	 * there's nothing connected to the port.
>> > +	 * if the port is a dual mode capable DP port.
>> >  	 */
>> >  	if (type == DRM_DP_DUAL_MODE_UNKNOWN) {
>> >  		/* An overridden EDID imply that we want this port for testing.
>> >  		 * Make sure not to set limits for that port.
>> >  		 */
>> > -		if (has_edid && !connector->override_edid &&
>> > +		if (!connector->override_edid &&
>> >  		    intel_bios_is_port_dp_dual_mode(dev_priv, port)) {
>> >  			drm_dbg_kms(&dev_priv->drm,
>> >  				    "Assuming DP dual mode adaptor presence based on VBT\n");
>> > @@ -2435,18 +2432,18 @@ intel_hdmi_set_edid(struct drm_connector *connector)
>> >  		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) {
>> 
>> We didn't have this digital input thing before. What happens with
>> HDMI->VGA dongles for example?
>> 
>> Hmm. This whole thing might already be broken on those. I suspect
>> I've only used my HDMI->VGA dongle on LSPCON machines, so never
>> noticed this. Need to go plug that thing into a native HDMI port...
>
> Except I must have left it elsewhere since I can't find it here.
> So can't test right now unfortunately.
>
> I first thought this digital check thing might be due to
> the DVI-I shenanigans in intel_crt_detect_ddc(), but that
> was added for am unspecified gen2 machine in commit f5afcd3dd0dc
> ("drm/i915/crt: Check for a analog monitor in case of DVI-I")
> so not even relevant here. And I don't think I've ever seen
> a g4x+ machine with an actual DVI-I port.
>
> commit aa93d632c496 ("drm/i915: Require digital monitor
> on HDMI ports for detect") is where this check was added,
> but there is no actual justification for checking the
> digital thing vs. just making sure the edid read succeeded.
>
> So looks to me like this check can just be removed. And
> if we do come across some real DVI-I use cases we should
> probably check the VBT DDC pin assignments before we go
> assuming anything about the wiring.

Are you saying remove the "edid->input & DRM_EDID_INPUT_DIGITAL"
altogether? Or turn this into:

	if (edid) {
		if (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);
		}
		connected = true;
	}

Since e.g. DP wraps the audio/hdmi detect calls in digital check.

OTOH I really want to get rid of the detect audio/hdmi calls [1]. Just a
lot of old cruft and the rabbit hole gets deeper. :(


BR,
Jani.



[1] https://patchwork.freedesktop.org/series/108024/


-- 
Jani Nikula, Intel Open Source Graphics Center