Documentation/sound/soc/dapm.rst - arm/linux - Git at Google

 ===================================================
 Dynamic Audio Power Management for Portable Devices
 ===================================================

 Description
 ===========

 Dynamic Audio Power Management (DAPM) is designed to allow portable
 Linux devices to use the minimum amount of power within the audio
 subsystem at all times. It is independent of other kernel PM and as
 such, can easily co-exist with the other PM systems.

 DAPM is also completely transparent to all user space applications as
 all power switching is done within the ASoC core. No code changes or
 recompiling are required for user space applications. DAPM makes power
 switching decisions based upon any audio stream (capture/playback)
 activity and audio mixer settings within the device.

 DAPM spans the whole machine. It covers power control within the entire
 audio subsystem, this includes internal codec power blocks and machine
 level power systems.

 There are 4 power domains within DAPM

 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.

 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

 Path domain
       audio subsystem signal paths

       Automatically set when mixer and mux settings are changed by the user.
       e.g. alsamixer, amixer.

 Stream domain
       DACs and ADCs.

       Enabled and disabled when stream playback/capture is started and
       stopped respectively. e.g. aplay, arecord.

 All DAPM power switching decisions are made automatically by consulting an audio
 routing map of the whole machine. This map is specific to each machine and
 consists of the interconnections between every audio component (including
 internal codec components). All audio components that effect power are called
 widgets hereafter.


 DAPM Widgets
 ============

 Audio DAPM widgets fall into a number of types:-

 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)

 Widgets can be added to the sound card by any of the component driver types.
 There are convenience macros defined in soc-dapm.h that can be used to quickly
 build a list of widgets of the codecs and machines DAPM widgets.

 Most widgets have a name, register, shift and invert. Some widgets have extra
 parameters for stream name and kcontrols.


 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)

 NOTE: the stream name must match the corresponding stream name in your codec
 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),


 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[] = {
   SOC_DAPM_SINGLE("Line Bypass Switch", WM8731_APANA, 3, 1, 0),
   SOC_DAPM_SINGLE("Mic Sidetone Switch", WM8731_APANA, 5, 1, 0),
   SOC_DAPM_SINGLE("HiFi Playback Switch", WM8731_APANA, 4, 1, 0),
   };

   SND_SOC_DAPM_MIXER("Output Mixer", WM8731_PWR, 4, 1, wm8731_output_mixer_controls,
 	ARRAY_SIZE(wm8731_output_mixer_controls)),

 If you don't want the mixer elements prefixed with the name of the mixer widget,
 you can use SND_SOC_DAPM_MIXER_NAMED_CTL instead. the parameters are the same
 as for SND_SOC_DAPM_MIXER.


 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.

 * 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:-::

   static int spitz_mic_bias(struct snd_soc_dapm_widget* w, int event)
   {
 	gpio_set_value(SPITZ_GPIO_MIC_BIAS, SND_SOC_DAPM_EVENT_ON(event));
 	return 0;
   }

   SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias),


 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.


 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),

 This can be used to merge to signal paths together in software.

 After all the widgets have been defined, they can then be added to the DAPM
 subsystem individually with a call to snd_soc_dapm_new_control().


 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
 order to create a map of all audio paths between widgets.

 This is easiest with a diagram of the codec or DSP (and schematic of the machine
 audio system), as it requires joining widgets together via their audio signal
 paths.

 e.g., from the WM8731 output mixer (wm8731.c)

 The WM8731 output mixer has 3 inputs (sources)

 1. Line Bypass Input
 2. DAC (HiFi playback)
 3. Mic Sidetone Input

 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"},
 	{"Output Mixer", "HiFi Playback Switch", "DAC"},
 	{"Output Mixer", "Mic Sidetone Switch", "Mic Bias"},

 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``.

 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);

 Finally, snd_soc_dapm_new_widgets(codec) must be called after all widgets and
 interconnections have been registered with the core. This causes the core to
 scan the codec and machine so that the internal DAPM state matches the
 physical state of the machine.


 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"},
 	{"Ext Spk", NULL , "LOUT2"},

 This allows the DAPM to power on and off pins that are connected (and in use)
 and pins that are NC respectively.


 Endpoint Widgets
 ================
 An endpoint is a start or end point (widget) of an audio signal within the
 machine and includes the codec. e.g.

 * 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.


 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)
   {
 	gpio_set_value(CORGI_GPIO_APM_ON, SND_SOC_DAPM_EVENT_ON(event));
 	return 0;
   }

   /* corgi machine dapm widgets */
   static const struct snd_soc_dapm_widget wm8731_dapm_widgets =
 	SND_SOC_DAPM_SPK("Ext Spk", corgi_amp_event);

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


 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 */
   #define SND_SOC_DAPM_POST_PMU	0x2		/* after widget power up */
   #define SND_SOC_DAPM_PRE_PMD	0x4 	/* before widget power down */
   #define SND_SOC_DAPM_POST_PMD	0x8		/* after widget power down */
   #define SND_SOC_DAPM_PRE_REG	0x10	/* before audio path setup */
   #define SND_SOC_DAPM_POST_REG	0x20	/* after audio path setup */
	===================================================
	Dynamic Audio Power Management for Portable Devices
	===================================================

	Description
	===========

	Dynamic Audio Power Management (DAPM) is designed to allow portable
	Linux devices to use the minimum amount of power within the audio
	subsystem at all times. It is independent of other kernel PM and as
	such, can easily co-exist with the other PM systems.

	DAPM is also completely transparent to all user space applications as
	all power switching is done within the ASoC core. No code changes or
	recompiling are required for user space applications. DAPM makes power
	switching decisions based upon any audio stream (capture/playback)
	activity and audio mixer settings within the device.

	DAPM spans the whole machine. It covers power control within the entire
	audio subsystem, this includes internal codec power blocks and machine
	level power systems.

	There are 4 power domains within DAPM

	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.

	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

	Path domain
	audio subsystem signal paths

	Automatically set when mixer and mux settings are changed by the user.
	e.g. alsamixer, amixer.

	Stream domain
	DACs and ADCs.

	Enabled and disabled when stream playback/capture is started and
	stopped respectively. e.g. aplay, arecord.

	All DAPM power switching decisions are made automatically by consulting an audio
	routing map of the whole machine. This map is specific to each machine and
	consists of the interconnections between every audio component (including
	internal codec components). All audio components that effect power are called
	widgets hereafter.


	DAPM Widgets
	============

	Audio DAPM widgets fall into a number of types:-

	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)

	Widgets can be added to the sound card by any of the component driver types.
	There are convenience macros defined in soc-dapm.h that can be used to quickly
	build a list of widgets of the codecs and machines DAPM widgets.

	Most widgets have a name, register, shift and invert. Some widgets have extra
	parameters for stream name and kcontrols.


	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)

	NOTE: the stream name must match the corresponding stream name in your codec
	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),


	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[] = {
	SOC_DAPM_SINGLE("Line Bypass Switch", WM8731_APANA, 3, 1, 0),
	SOC_DAPM_SINGLE("Mic Sidetone Switch", WM8731_APANA, 5, 1, 0),
	SOC_DAPM_SINGLE("HiFi Playback Switch", WM8731_APANA, 4, 1, 0),
	};

	SND_SOC_DAPM_MIXER("Output Mixer", WM8731_PWR, 4, 1, wm8731_output_mixer_controls,
	ARRAY_SIZE(wm8731_output_mixer_controls)),

	If you don't want the mixer elements prefixed with the name of the mixer widget,
	you can use SND_SOC_DAPM_MIXER_NAMED_CTL instead. the parameters are the same
	as for SND_SOC_DAPM_MIXER.


	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.

	* 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:-::

	static int spitz_mic_bias(struct snd_soc_dapm_widget* w, int event)
	{
	gpio_set_value(SPITZ_GPIO_MIC_BIAS, SND_SOC_DAPM_EVENT_ON(event));
	return 0;
	}

	SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias),


	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.


	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),

	This can be used to merge to signal paths together in software.

	After all the widgets have been defined, they can then be added to the DAPM
	subsystem individually with a call to snd_soc_dapm_new_control().


	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
	order to create a map of all audio paths between widgets.

	This is easiest with a diagram of the codec or DSP (and schematic of the machine
	audio system), as it requires joining widgets together via their audio signal
	paths.

	e.g., from the WM8731 output mixer (wm8731.c)

	The WM8731 output mixer has 3 inputs (sources)

	1. Line Bypass Input
	2. DAC (HiFi playback)
	3. Mic Sidetone Input

	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"},
	{"Output Mixer", "HiFi Playback Switch", "DAC"},
	{"Output Mixer", "Mic Sidetone Switch", "Mic Bias"},

	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``.

	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);

	Finally, snd_soc_dapm_new_widgets(codec) must be called after all widgets and
	interconnections have been registered with the core. This causes the core to
	scan the codec and machine so that the internal DAPM state matches the
	physical state of the machine.


	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"},
	{"Ext Spk", NULL , "LOUT2"},

	This allows the DAPM to power on and off pins that are connected (and in use)
	and pins that are NC respectively.


	Endpoint Widgets
	================
	An endpoint is a start or end point (widget) of an audio signal within the
	machine and includes the codec. e.g.

	* 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.


	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)
	{
	gpio_set_value(CORGI_GPIO_APM_ON, SND_SOC_DAPM_EVENT_ON(event));
	return 0;
	}

	/* corgi machine dapm widgets */
	static const struct snd_soc_dapm_widget wm8731_dapm_widgets =
	SND_SOC_DAPM_SPK("Ext Spk", corgi_amp_event);

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


	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 */
	#define SND_SOC_DAPM_POST_PMU 0x2 /* after widget power up */
	#define SND_SOC_DAPM_PRE_PMD 0x4 /* before widget power down */
	#define SND_SOC_DAPM_POST_PMD 0x8 /* after widget power down */
	#define SND_SOC_DAPM_PRE_REG 0x10 /* before audio path setup */
	#define SND_SOC_DAPM_POST_REG 0x20 /* after audio path setup */