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

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

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@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@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...

>  		intel_hdmi->has_audio = drm_detect_monitor_audio(edid);
>  		intel_hdmi->has_hdmi_sink = drm_detect_hdmi_monitor(edid);
>  
> +		intel_hdmi_dp_dual_mode_detect(connector);
> +
>  		connected = true;
>  	}
>  
> +	intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS, wakeref);
> +
>  	cec_notifier_set_phys_addr_from_edid(intel_hdmi->cec_notifier, edid);
>  
>  	return connected;
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel