From 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 12:05:51 +0200 Subject: Adding upstream version 5.10.209. Signed-off-by: Daniel Baumann --- Documentation/sound/hd-audio/dp-mst.rst | 101 ++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 Documentation/sound/hd-audio/dp-mst.rst (limited to 'Documentation/sound/hd-audio/dp-mst.rst') diff --git a/Documentation/sound/hd-audio/dp-mst.rst b/Documentation/sound/hd-audio/dp-mst.rst new file mode 100644 index 000000000..1617459e3 --- /dev/null +++ b/Documentation/sound/hd-audio/dp-mst.rst @@ -0,0 +1,101 @@ +======================= +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 + +Pin Initialization +================== +Each pin may have several device entries (virtual pins). On Intel platform, +the device entries number is dynamically changed. If DP MST hub is connected, +it is in DP MST mode, and the device entries number is 3. Otherwise, the +device entries number is 1. + +To simplify the implementation, all the device entries will be initialized +when bootup no matter whether it is in DP MST mode or not. + +Connection list +=============== +DP MST reuses connection list code. The code can be reused because +device entries on the same pin have the same connection list. + +This means DP MST gets the device entry connection list without the +device entry setting. + +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: + a. MST (&& dyn_pcm_assign && acomp) + b. NON-MST && dyn_pcm_assign && acomp + c. 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 +======================== -- cgit v1.2.3