Hello, Testing a new monitor with speakers connection by a DisplayPort adapter to HDMI.. I came to realize the real problem related to these messages appearing at boot time and dmesg:
drm:pid38311:drm_dp_dual_mode_detect *ERROR* [drm] *ERROR* Unexpected DP dual mode adaptor ID 20 drm:pid26205:drm_dp_dual_mode_detect *ERROR* [drm] *ERROR* Unexpected DP dual mode adaptor ID 20 ..in few words the DP adapter that should pass audio and video channels together let pass the video flow only (and indeed I'm able to use my new screen) but without the audio channel (HDMI cable and connection tested). Hope this is helpful, thanks == Daniele Bonini
