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 ========================
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