102 lines
3 KiB
ReStructuredText
102 lines
3 KiB
ReStructuredText
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=======================
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HD-Audio DP-MST Support
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=======================
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To support DP MST audio, HD Audio hdmi codec driver introduces virtual pin
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and dynamic pcm assignment.
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Virtual pin is an extension of per_pin. The most difference of DP MST
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from legacy is that DP MST introduces device entry. Each pin can contain
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several device entries. Each device entry behaves as a pin.
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As each pin may contain several device entries and each codec may contain
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several pins, if we use one pcm per per_pin, there will be many PCMs.
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The new solution is to create a few PCMs and to dynamically bind pcm to
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per_pin. Driver uses spec->dyn_pcm_assign flag to indicate whether to use
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the new solution.
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PCM
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===
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To be added
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Pin Initialization
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==================
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Each pin may have several device entries (virtual pins). On Intel platform,
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the device entries number is dynamically changed. If DP MST hub is connected,
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it is in DP MST mode, and the device entries number is 3. Otherwise, the
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device entries number is 1.
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To simplify the implementation, all the device entries will be initialized
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when bootup no matter whether it is in DP MST mode or not.
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Connection list
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===============
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DP MST reuses connection list code. The code can be reused because
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device entries on the same pin have the same connection list.
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This means DP MST gets the device entry connection list without the
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device entry setting.
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Jack
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====
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Presume:
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- MST must be dyn_pcm_assign, and it is acomp (for Intel scenario);
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- NON-MST may or may not be dyn_pcm_assign, it can be acomp or !acomp;
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So there are the following scenarios:
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a. MST (&& dyn_pcm_assign && acomp)
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b. NON-MST && dyn_pcm_assign && acomp
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c. NON-MST && !dyn_pcm_assign && !acomp
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Below discussion will ignore MST and NON-MST difference as it doesn't
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impact on jack handling too much.
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Driver uses struct hdmi_pcm pcm[] array in hdmi_spec and snd_jack is
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a member of hdmi_pcm. Each pin has one struct hdmi_pcm * pcm pointer.
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For !dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n] statically.
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For dyn_pcm_assign, per_pin->pcm will assigned to spec->pcm[n]
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when monitor is hotplugged.
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Build Jack
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----------
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- dyn_pcm_assign
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Will not use hda_jack but use snd_jack in spec->pcm_rec[pcm_idx].jack directly.
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- !dyn_pcm_assign
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Use hda_jack and assign spec->pcm_rec[pcm_idx].jack = jack->jack statically.
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Unsolicited Event Enabling
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--------------------------
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Enable unsolicited event if !acomp.
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Monitor Hotplug Event Handling
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------------------------------
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- acomp
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pin_eld_notify() -> check_presence_and_report() -> hdmi_present_sense() ->
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sync_eld_via_acomp().
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Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for
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both dyn_pcm_assign and !dyn_pcm_assign
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- !acomp
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hdmi_unsol_event() -> hdmi_intrinsic_event() -> check_presence_and_report() ->
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hdmi_present_sense() -> hdmi_prepsent_sense_via_verbs()
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Use directly snd_jack_report() on spec->pcm_rec[pcm_idx].jack for dyn_pcm_assign.
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Use hda_jack mechanism to handle jack events.
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Others to be added later
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========================
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