| rjw | 1f88458 | 2022-01-06 17:20:42 +0800 | [diff] [blame^] | 1 | ======================= |
| 2 | HD-Audio DP-MST Support |
| 3 | ======================= |
| 4 | |
| 5 | To support DP MST audio, HD Audio hdmi codec driver introduces virtual pin |
| 6 | and dynamic pcm assignment. |
| 7 | |
| 8 | Virtual pin is an extension of per_pin. The most difference of DP MST |
| 9 | from legacy is that DP MST introduces device entry. Each pin can contain |
| 10 | several device entries. Each device entry behaves as a pin. |
| 11 | |
| 12 | As each pin may contain several device entries and each codec may contain |
| 13 | several pins, if we use one pcm per per_pin, there will be many PCMs. |
| 14 | The new solution is to create a few PCMs and to dynamically bind pcm to |
| 15 | per_pin. Driver uses spec->dyn_pcm_assign flag to indicate whether to use |
| 16 | the new solution. |
| 17 | |
| 18 | PCM |
| 19 | === |
| 20 | To be added |
| 21 | |
| 22 | Pin Initialization |
| 23 | ================== |
| 24 | Each pin may have several device entries (virtual pins). On Intel platform, |
| 25 | the device entries number is dynamically changed. If DP MST hub is connected, |
| 26 | it is in DP MST mode, and the device entries number is 3. Otherwise, the |
| 27 | device entries number is 1. |
| 28 | |
| 29 | To simplify the implementation, all the device entries will be initialized |
| 30 | when bootup no matter whether it is in DP MST mode or not. |
| 31 | |
| 32 | Connection list |
| 33 | =============== |
| 34 | DP MST reuses connection list code. The code can be reused because |
| 35 | device entries on the same pin have the same connection list. |
| 36 | |
| 37 | This means DP MST gets the device entry connection list without the |
| 38 | device entry setting. |
| 39 | |
| 40 | Jack |
| 41 | ==== |
| 42 | |
| 43 | Presume: |
| 44 | - MST must be dyn_pcm_assign, and it is acomp (for Intel scenario); |
| 45 | - NON-MST may or may not be dyn_pcm_assign, it can be acomp or !acomp; |
| 46 | |
| 47 | So there are the following scenarios: |
| 48 | a. MST (&& dyn_pcm_assign && acomp) |
| 49 | b. NON-MST && dyn_pcm_assign && acomp |
| 50 | c. NON-MST && !dyn_pcm_assign && !acomp |
| 51 | |
| 52 | Below discussion will ignore MST and NON-MST difference as it doesn't |
| 53 | impact on jack handling too much. |
| 54 | |
| 55 | Driver uses struct hdmi_pcm pcm[] array in hdmi_spec and snd_jack is |
| 56 | a member of hdmi_pcm. Each pin has one struct hdmi_pcm * pcm pointer. |
| 57 | |
| 58 | For !dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] statically. |
| 59 | |
| 60 | For dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] |
| 61 | when monitor is hotplugged. |
| 62 | |
| 63 | |
| 64 | Build Jack |
| 65 | ---------- |
| 66 | |
| 67 | - dyn_pcm_assign |
| 68 | |
| 69 | Will not use hda_jack but use snd_jack in spec->pcm_rec[pcm_idx].jack directly. |
| 70 | |
| 71 | - !dyn_pcm_assign |
| 72 | |
| 73 | Use hda_jack and assign spec->pcm_rec[pcm_idx].jack = jack->jack statically. |
| 74 | |
| 75 | |
| 76 | Unsolicited Event Enabling |
| 77 | -------------------------- |
| 78 | Enable unsolicited event if !acomp. |
| 79 | |
| 80 | |
| 81 | Monitor Hotplug Event Handling |
| 82 | ------------------------------ |
| 83 | - acomp |
| 84 | |
| 85 | pin_eld_notify() -> check_presence_and_report() -> hdmi_present_sense() -> |
| 86 | sync_eld_via_acomp(). |
| 87 | |
| 88 | Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for |
| 89 | both dyn_pcm_assign and !dyn_pcm_assign |
| 90 | |
| 91 | - !acomp |
| 92 | |
| 93 | hdmi_unsol_event() -> hdmi_intrinsic_event() -> check_presence_and_report() -> |
| 94 | hdmi_present_sense() -> hdmi_prepsent_sense_via_verbs() |
| 95 | |
| 96 | Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for dyn_pcm_assign. |
| 97 | Use hda_jack mechanism to handle jack events. |
| 98 | |
| 99 | |
| 100 | Others to be added later |
| 101 | ======================== |