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diff --git a/Documentation/sound/soc/dapm.rst b/Documentation/sound/soc/dapm.rst new file mode 100644 index 000000000..8e4410793 --- /dev/null +++ b/Documentation/sound/soc/dapm.rst @@ -0,0 +1,360 @@ +=================================================== +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) +Buffer + Inter widget audio data buffer within a DSP. +Scheduler + DSP internal scheduler that schedules component/pipeline processing + work. +Effect + Widget that performs an audio processing effect. +SRC + Sample Rate Converter within DSP or CODEC +ASRC + Asynchronous Sample Rate Converter within DSP or CODEC +Encoder + Widget that encodes audio data from one format (usually PCM) to another + usually more compressed format. +Decoder + Widget that decodes audio data from a compressed format to an + uncompressed format like PCM. + + +(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 */ |