ASoC: doc: ReSTize dapm.txt

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Dynamic Audio Power Management for Portable Devices

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

1. Description

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

Description

===========

Dynamic Audio Power Management (DAPM) is designed to allow portable

Linux devices to use the minimum amount of power within the audio

There are 4 power domains within DAPM

   1. Codec bias domain - VREF, VMID (core codec and audio power)

Codec bias domain

      VREF, VMID (core codec and audio power)

      Usually controlled at codec probe/remove and suspend/resume, although

      can be set at stream time if power is not needed for sidetone, etc.

   2. Platform/Machine domain - physically connected inputs and outputs

Platform/Machine domain

      physically connected inputs and outputs

      Is platform/machine and user action specific, is configured by the

      machine driver and responds to asynchronous events e.g when HP

      are inserted

   3. Path domain - audio subsystem signal paths

Path domain

      audio subsystem signal paths

      Automatically set when mixer and mux settings are changed by the user.

      e.g. alsamixer, amixer.

   4. Stream domain - DACs and ADCs.

Stream domain

      DACs and ADCs.

      Enabled and disabled when stream playback/capture is started and

      stopped respectively. e.g. aplay, arecord.

widgets hereafter.

2. DAPM Widgets

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

DAPM Widgets

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

Audio DAPM widgets fall into a number of types:-

 o Mixer      - Mixes several analog signals into a single analog signal.

 o Mux        - An analog switch that outputs only one of many inputs.

 o PGA        - A programmable gain amplifier or attenuation widget.

 o ADC        - Analog to Digital Converter

 o DAC        - Digital to Analog Converter

 o Switch     - An analog switch

 o Input      - A codec input pin

 o Output     - A codec output pin

 o Headphone  - Headphone (and optional Jack)

 o Mic        - Mic (and optional Jack)

 o Line       - Line Input/Output (and optional Jack)

 o Speaker    - Speaker

 o Supply     - Power or clock supply widget used by other widgets.

 o Regulator  - External regulator that supplies power to audio components.

 o Clock      -	External clock that supplies clock to audio components.

 o AIF IN     - Audio Interface Input (with TDM slot mask).

 o AIF OUT    - Audio Interface Output (with TDM slot mask).

 o Siggen     - Signal Generator.

 o DAI IN     - Digital Audio Interface Input.

 o DAI OUT    - Digital Audio Interface Output.

 o DAI Link   - DAI Link between two DAI structures */

 o Pre        - Special PRE widget (exec before all others)

 o Post       - Special POST widget (exec after all others)

Mixer

	Mixes several analog signals into a single analog signal.

Mux

	An analog switch that outputs only one of many inputs.

PGA

	A programmable gain amplifier or attenuation widget.

ADC

	Analog to Digital Converter

DAC

	Digital to Analog Converter

Switch

	An analog switch

Input

	A codec input pin

Output

	A codec output pin

Headphone

	Headphone (and optional Jack)

Mic

	Mic (and optional Jack)

Line

	Line Input/Output (and optional Jack)

Speaker

	Speaker

Supply

	Power or clock supply widget used by other widgets.

Regulator

	External regulator that supplies power to audio components.

Clock

	External clock that supplies clock to audio components.

AIF IN

	Audio Interface Input (with TDM slot mask).

AIF OUT

	Audio Interface Output (with TDM slot mask).

Siggen

	Signal Generator.

DAI IN

	Digital Audio Interface Input.

DAI OUT

	Digital Audio Interface Output.

DAI Link

	DAI Link between two DAI structures

Pre

	Special PRE widget (exec before all others)

Post

	Special POST widget (exec after all others)

(Widgets are defined in include/sound/soc-dapm.h)

parameters for stream name and kcontrols.

2.1 Stream Domain Widgets

-------------------------

Stream Domain Widgets

---------------------

Stream Widgets relate to the stream power domain and only consist of ADCs

(analog to digital converters), DACs (digital to analog converters),

AIF IN and AIF OUT.

Stream widgets have the following format:-

::

  SND_SOC_DAPM_DAC(name, stream name, reg, shift, invert),

  SND_SOC_DAPM_AIF_IN(name, stream, slot, reg, shift, invert)

snd_soc_codec_dai.

e.g. stream widgets for HiFi playback and capture

::

  SND_SOC_DAPM_DAC("HiFi DAC", "HiFi Playback", REG, 3, 1),

  SND_SOC_DAPM_ADC("HiFi ADC", "HiFi Capture", REG, 2, 1),

e.g. stream widgets for AIF

::

  SND_SOC_DAPM_AIF_IN("AIF1RX", "AIF1 Playback", 0, SND_SOC_NOPM, 0, 0),

  SND_SOC_DAPM_AIF_OUT("AIF1TX", "AIF1 Capture", 0, SND_SOC_NOPM, 0, 0),

2.2 Path Domain Widgets

-----------------------

Path Domain Widgets

-------------------

Path domain widgets have a ability to control or affect the audio signal or

audio paths within the audio subsystem. They have the following form:-

::

  SND_SOC_DAPM_PGA(name, reg, shift, invert, controls, num_controls)

Any widget kcontrols can be set using the controls and num_controls members.

e.g. Mixer widget (the kcontrols are declared first)

::

  /* Output Mixer */

  static const snd_kcontrol_new_t wm8731_output_mixer_controls[] = {

as for SND_SOC_DAPM_MIXER.

2.3 Machine domain Widgets

--------------------------

Machine domain Widgets

----------------------

Machine widgets are different from codec widgets in that they don't have a

codec register bit associated with them. A machine widget is assigned to each

machine audio component (non codec or DSP) that can be independently

powered. e.g.

 o Speaker Amp

 o Microphone Bias

 o Jack connectors

* Speaker Amp

* Microphone Bias

* Jack connectors

A machine widget can have an optional call back.

e.g. Jack connector widget for an external Mic that enables Mic Bias

when the Mic is inserted:-

when the Mic is inserted:-::

  static int spitz_mic_bias(struct snd_soc_dapm_widget* w, int event)

  {

  SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias),

2.4 Codec (BIAS) Domain

-----------------------

Codec (BIAS) Domain

-------------------

The codec bias power domain has no widgets and is handled by the codecs DAPM

event handler. This handler is called when the codec powerstate is changed wrt

to any stream event or by kernel PM events.

2.5 Virtual Widgets

-------------------

Virtual Widgets

---------------

Sometimes widgets exist in the codec or machine audio map that don't have any

corresponding soft power control. In this case it is necessary to create

a virtual widget - a widget with no control bits e.g.

::

  SND_SOC_DAPM_MIXER("AC97 Mixer", SND_SOC_DAPM_NOPM, 0, 0, NULL, 0),

subsystem individually with a call to snd_soc_dapm_new_control().

3. Codec/DSP Widget Interconnections

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Codec/DSP Widget Interconnections

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

Widgets are connected to each other within the codec, platform and machine by

audio paths (called interconnections). Each interconnection must be defined in

Each input in this example has a kcontrol associated with it (defined in example

above) and is connected to the output mixer via its kcontrol name. We can now

connect the destination widget (wrt audio signal) with its source widgets.

::

	/* output mixer */

	{"Output Mixer", "Line Bypass Switch", "Line Input"},

So we have :-

	Destination Widget  <=== Path Name <=== Source Widget

Or:-

	Sink, Path, Source

Or :-

	"Output Mixer" is connected to the "DAC" via the "HiFi Playback Switch".

* Destination Widget  <=== Path Name <=== Source Widget, or

* Sink, Path, Source, or

* ``Output Mixer`` is connected to the ``DAC`` via the ``HiFi Playback Switch``.

When there is no path name connecting widgets (e.g. a direct connection) we

pass NULL for the path name.

Interconnections are created with a call to:-

::

  snd_soc_dapm_connect_input(codec, sink, path, source);

physical state of the machine.

3.1 Machine Widget Interconnections

-----------------------------------

Machine Widget Interconnections

-------------------------------

Machine widget interconnections are created in the same way as codec ones and

directly connect the codec pins to machine level widgets.

e.g. connects the speaker out codec pins to the internal speaker.

::

	/* ext speaker connected to codec pins LOUT2, ROUT2  */

	{"Ext Spk", NULL , "ROUT2"},

and pins that are NC respectively.

4 Endpoint Widgets

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

Endpoint Widgets

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

An endpoint is a start or end point (widget) of an audio signal within the

machine and includes the codec. e.g.

 o Headphone Jack

 o Internal Speaker

 o Internal Mic

 o Mic Jack

 o Codec Pins

* Headphone Jack

* Internal Speaker

* Internal Mic

* Mic Jack

* Codec Pins

Endpoints are added to the DAPM graph so that their usage can be determined in

order to save power. e.g. NC codecs pins will be switched OFF, unconnected

jacks can also be switched OFF.

5 DAPM Widget Events

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

DAPM Widget Events

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

Some widgets can register their interest with the DAPM core in PM events.

e.g. A Speaker with an amplifier registers a widget so the amplifier can be

powered only when the spk is in use.

::

  /* turn speaker amplifier on/off depending on use */

  static int corgi_amp_event(struct snd_soc_dapm_widget *w, int event)

Please see soc-dapm.h for all other widgets that support events.

5.1 Event types

---------------

Event types

-----------

The following event types are supported by event widgets.

::

  /* dapm event types */

  #define SND_SOC_DAPM_PRE_PMU	0x1 	/* before widget power up */

   overview

   codec

   dai

   dapm