1Dynamic Audio Power Management for Portable Devices 2=================================================== 3 41. Description 5============== 6 7Dynamic Audio Power Management (DAPM) is designed to allow portable 8Linux devices to use the minimum amount of power within the audio 9subsystem at all times. It is independent of other kernel PM and as 10such, can easily co-exist with the other PM systems. 11 12DAPM is also completely transparent to all user space applications as 13all power switching is done within the ASoC core. No code changes or 14recompiling are required for user space applications. DAPM makes power 15switching decisions based upon any audio stream (capture/playback) 16activity and audio mixer settings within the device. 17 18DAPM spans the whole machine. It covers power control within the entire 19audio subsystem, this includes internal codec power blocks and machine 20level power systems. 21 22There are 4 power domains within DAPM 23 24 1. Codec bias domain - VREF, VMID (core codec and audio power) 25 Usually controlled at codec probe/remove and suspend/resume, although 26 can be set at stream time if power is not needed for sidetone, etc. 27 28 2. Platform/Machine domain - physically connected inputs and outputs 29 Is platform/machine and user action specific, is configured by the 30 machine driver and responds to asynchronous events e.g when HP 31 are inserted 32 33 3. Path domain - audio subsystem signal paths 34 Automatically set when mixer and mux settings are changed by the user. 35 e.g. alsamixer, amixer. 36 37 4. Stream domain - DACs and ADCs. 38 Enabled and disabled when stream playback/capture is started and 39 stopped respectively. e.g. aplay, arecord. 40 41All DAPM power switching decisions are made automatically by consulting an audio 42routing map of the whole machine. This map is specific to each machine and 43consists of the interconnections between every audio component (including 44internal codec components). All audio components that effect power are called 45widgets hereafter. 46 47 482. DAPM Widgets 49=============== 50 51Audio DAPM widgets fall into a number of types:- 52 53 o Mixer - Mixes several analog signals into a single analog signal. 54 o Mux - An analog switch that outputs only one of many inputs. 55 o PGA - A programmable gain amplifier or attenuation widget. 56 o ADC - Analog to Digital Converter 57 o DAC - Digital to Analog Converter 58 o Switch - An analog switch 59 o Input - A codec input pin 60 o Output - A codec output pin 61 o Headphone - Headphone (and optional Jack) 62 o Mic - Mic (and optional Jack) 63 o Line - Line Input/Output (and optional Jack) 64 o Speaker - Speaker 65 o Supply - Power or clock supply widget used by other widgets. 66 o Regulator - External regulator that supplies power to audio components. 67 o Clock - External clock that supplies clock to audio components. 68 o AIF IN - Audio Interface Input (with TDM slot mask). 69 o AIF OUT - Audio Interface Output (with TDM slot mask). 70 o Siggen - Signal Generator. 71 o DAI IN - Digital Audio Interface Input. 72 o DAI OUT - Digital Audio Interface Output. 73 o DAI Link - DAI Link between two DAI structures */ 74 o Pre - Special PRE widget (exec before all others) 75 o Post - Special POST widget (exec after all others) 76 77(Widgets are defined in include/sound/soc-dapm.h) 78 79Widgets can be added to the sound card by any of the component driver types. 80There are convenience macros defined in soc-dapm.h that can be used to quickly 81build a list of widgets of the codecs and machines DAPM widgets. 82 83Most widgets have a name, register, shift and invert. Some widgets have extra 84parameters for stream name and kcontrols. 85 86 872.1 Stream Domain Widgets 88------------------------- 89 90Stream Widgets relate to the stream power domain and only consist of ADCs 91(analog to digital converters), DACs (digital to analog converters), 92AIF IN and AIF OUT. 93 94Stream widgets have the following format:- 95 96SND_SOC_DAPM_DAC(name, stream name, reg, shift, invert), 97SND_SOC_DAPM_AIF_IN(name, stream, slot, reg, shift, invert) 98 99NOTE: the stream name must match the corresponding stream name in your codec 100snd_soc_codec_dai. 101 102e.g. stream widgets for HiFi playback and capture 103 104SND_SOC_DAPM_DAC("HiFi DAC", "HiFi Playback", REG, 3, 1), 105SND_SOC_DAPM_ADC("HiFi ADC", "HiFi Capture", REG, 2, 1), 106 107e.g. stream widgets for AIF 108 109SND_SOC_DAPM_AIF_IN("AIF1RX", "AIF1 Playback", 0, SND_SOC_NOPM, 0, 0), 110SND_SOC_DAPM_AIF_OUT("AIF1TX", "AIF1 Capture", 0, SND_SOC_NOPM, 0, 0), 111 112 1132.2 Path Domain Widgets 114----------------------- 115 116Path domain widgets have a ability to control or affect the audio signal or 117audio paths within the audio subsystem. They have the following form:- 118 119SND_SOC_DAPM_PGA(name, reg, shift, invert, controls, num_controls) 120 121Any widget kcontrols can be set using the controls and num_controls members. 122 123e.g. Mixer widget (the kcontrols are declared first) 124 125/* Output Mixer */ 126static const snd_kcontrol_new_t wm8731_output_mixer_controls[] = { 127SOC_DAPM_SINGLE("Line Bypass Switch", WM8731_APANA, 3, 1, 0), 128SOC_DAPM_SINGLE("Mic Sidetone Switch", WM8731_APANA, 5, 1, 0), 129SOC_DAPM_SINGLE("HiFi Playback Switch", WM8731_APANA, 4, 1, 0), 130}; 131 132SND_SOC_DAPM_MIXER("Output Mixer", WM8731_PWR, 4, 1, wm8731_output_mixer_controls, 133 ARRAY_SIZE(wm8731_output_mixer_controls)), 134 135If you dont want the mixer elements prefixed with the name of the mixer widget, 136you can use SND_SOC_DAPM_MIXER_NAMED_CTL instead. the parameters are the same 137as for SND_SOC_DAPM_MIXER. 138 139 1402.3 Machine domain Widgets 141-------------------------- 142 143Machine widgets are different from codec widgets in that they don't have a 144codec register bit associated with them. A machine widget is assigned to each 145machine audio component (non codec or DSP) that can be independently 146powered. e.g. 147 148 o Speaker Amp 149 o Microphone Bias 150 o Jack connectors 151 152A machine widget can have an optional call back. 153 154e.g. Jack connector widget for an external Mic that enables Mic Bias 155when the Mic is inserted:- 156 157static int spitz_mic_bias(struct snd_soc_dapm_widget* w, int event) 158{ 159 gpio_set_value(SPITZ_GPIO_MIC_BIAS, SND_SOC_DAPM_EVENT_ON(event)); 160 return 0; 161} 162 163SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias), 164 165 1662.4 Codec (BIAS) Domain 167----------------------- 168 169The codec bias power domain has no widgets and is handled by the codecs DAPM 170event handler. This handler is called when the codec powerstate is changed wrt 171to any stream event or by kernel PM events. 172 173 1742.5 Virtual Widgets 175------------------- 176 177Sometimes widgets exist in the codec or machine audio map that don't have any 178corresponding soft power control. In this case it is necessary to create 179a virtual widget - a widget with no control bits e.g. 180 181SND_SOC_DAPM_MIXER("AC97 Mixer", SND_SOC_DAPM_NOPM, 0, 0, NULL, 0), 182 183This can be used to merge to signal paths together in software. 184 185After all the widgets have been defined, they can then be added to the DAPM 186subsystem individually with a call to snd_soc_dapm_new_control(). 187 188 1893. Codec/DSP Widget Interconnections 190==================================== 191 192Widgets are connected to each other within the codec, platform and machine by 193audio paths (called interconnections). Each interconnection must be defined in 194order to create a map of all audio paths between widgets. 195 196This is easiest with a diagram of the codec or DSP (and schematic of the machine 197audio system), as it requires joining widgets together via their audio signal 198paths. 199 200e.g., from the WM8731 output mixer (wm8731.c) 201 202The WM8731 output mixer has 3 inputs (sources) 203 204 1. Line Bypass Input 205 2. DAC (HiFi playback) 206 3. Mic Sidetone Input 207 208Each input in this example has a kcontrol associated with it (defined in example 209above) and is connected to the output mixer via its kcontrol name. We can now 210connect the destination widget (wrt audio signal) with its source widgets. 211 212 /* output mixer */ 213 {"Output Mixer", "Line Bypass Switch", "Line Input"}, 214 {"Output Mixer", "HiFi Playback Switch", "DAC"}, 215 {"Output Mixer", "Mic Sidetone Switch", "Mic Bias"}, 216 217So we have :- 218 219 Destination Widget <=== Path Name <=== Source Widget 220 221Or:- 222 223 Sink, Path, Source 224 225Or :- 226 227 "Output Mixer" is connected to the "DAC" via the "HiFi Playback Switch". 228 229When there is no path name connecting widgets (e.g. a direct connection) we 230pass NULL for the path name. 231 232Interconnections are created with a call to:- 233 234snd_soc_dapm_connect_input(codec, sink, path, source); 235 236Finally, snd_soc_dapm_new_widgets(codec) must be called after all widgets and 237interconnections have been registered with the core. This causes the core to 238scan the codec and machine so that the internal DAPM state matches the 239physical state of the machine. 240 241 2423.1 Machine Widget Interconnections 243----------------------------------- 244Machine widget interconnections are created in the same way as codec ones and 245directly connect the codec pins to machine level widgets. 246 247e.g. connects the speaker out codec pins to the internal speaker. 248 249 /* ext speaker connected to codec pins LOUT2, ROUT2 */ 250 {"Ext Spk", NULL , "ROUT2"}, 251 {"Ext Spk", NULL , "LOUT2"}, 252 253This allows the DAPM to power on and off pins that are connected (and in use) 254and pins that are NC respectively. 255 256 2574 Endpoint Widgets 258=================== 259An endpoint is a start or end point (widget) of an audio signal within the 260machine and includes the codec. e.g. 261 262 o Headphone Jack 263 o Internal Speaker 264 o Internal Mic 265 o Mic Jack 266 o Codec Pins 267 268Endpoints are added to the DAPM graph so that their usage can be determined in 269order to save power. e.g. NC codecs pins will be switched OFF, unconnected 270jacks can also be switched OFF. 271 272 2735 DAPM Widget Events 274==================== 275 276Some widgets can register their interest with the DAPM core in PM events. 277e.g. A Speaker with an amplifier registers a widget so the amplifier can be 278powered only when the spk is in use. 279 280/* turn speaker amplifier on/off depending on use */ 281static int corgi_amp_event(struct snd_soc_dapm_widget *w, int event) 282{ 283 gpio_set_value(CORGI_GPIO_APM_ON, SND_SOC_DAPM_EVENT_ON(event)); 284 return 0; 285} 286 287/* corgi machine dapm widgets */ 288static const struct snd_soc_dapm_widget wm8731_dapm_widgets = 289 SND_SOC_DAPM_SPK("Ext Spk", corgi_amp_event); 290 291Please see soc-dapm.h for all other widgets that support events. 292 293 2945.1 Event types 295--------------- 296 297The following event types are supported by event widgets. 298 299/* dapm event types */ 300#define SND_SOC_DAPM_PRE_PMU 0x1 /* before widget power up */ 301#define SND_SOC_DAPM_POST_PMU 0x2 /* after widget power up */ 302#define SND_SOC_DAPM_PRE_PMD 0x4 /* before widget power down */ 303#define SND_SOC_DAPM_POST_PMD 0x8 /* after widget power down */ 304#define SND_SOC_DAPM_PRE_REG 0x10 /* before audio path setup */ 305#define SND_SOC_DAPM_POST_REG 0x20 /* after audio path setup */ 306