HD-Audio DP-MST Support

To support DP MST audio, HD Audio hdmi codec driver introduces virtual pin and dynamic pcm assignment.

Virtual pin is an extension of per_pin. The most difference of DP MST from legacy is that DP MST introduces device entry. Each pin can contain several device entries. Each device entry behaves as a pin.

As each pin may contain several device entries and each codec may contain several pins, if we use one pcm per per_pin, there will be many PCMs. The new solution is to create a few PCMs and to dynamically bind pcm to per_pin. Driver uses spec->dyn_pcm_assign flag to indicate whether to use the new solution.

PCM

To be added

Jack

Presume:
  • MST must be dyn_pcm_assign, and it is acomp (for Intel scenario);
  • NON-MST may or may not be dyn_pcm_assign, it can be acomp or !acomp;
So there are the following scenarios:
  1. MST (&& dyn_pcm_assign && acomp)
  2. NON-MST && dyn_pcm_assign && acomp
  3. NON-MST && !dyn_pcm_assign && !acomp

Below discussion will ignore MST and NON-MST difference as it doesn’t impact on jack handling too much.

Driver uses struct hdmi_pcm pcm[] array in hdmi_spec and snd_jack is a member of hdmi_pcm. Each pin has one struct hdmi_pcm * pcm pointer.

For !dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] statically.

For dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] when monitor is hotplugged.

Build Jack

  • dyn_pcm_assign

    Will not use hda_jack but use snd_jack in spec->pcm_rec[pcm_idx].jack directly.

  • !dyn_pcm_assign

    Use hda_jack and assign spec->pcm_rec[pcm_idx].jack = jack->jack statically.

Unsolicited Event Enabling

Enable unsolicited event if !acomp.

Monitor Hotplug Event Handling

  • acomp

    pin_eld_notify() -> check_presence_and_report() -> hdmi_present_sense() -> sync_eld_via_acomp().

    Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for both dyn_pcm_assign and !dyn_pcm_assign

  • !acomp

    hdmi_unsol_event() -> hdmi_intrinsic_event() -> check_presence_and_report() -> hdmi_present_sense() -> hdmi_prepsent_sense_via_verbs()

    Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for dyn_pcm_assign. Use hda_jack mechanism to handle jack events.

Others to be added later