1=================================================== 2Dynamic Audio Power Management for Portable Devices 3=================================================== 4 5Description 6=========== 7 8Dynamic Audio Power Management (DAPM) is designed to allow portable 9Linux devices to use the minimum amount of power within the audio 10subsystem at all times. It is independent of other kernel power 11management frameworks and, as such, can easily co-exist with them. 12 13DAPM is also completely transparent to all user space applications as 14all power switching is done within the ASoC core. No code changes or 15recompiling are required for user space applications. DAPM makes power 16switching decisions based upon any audio stream (capture/playback) 17activity and audio mixer settings within the device. 18 19DAPM is based on two basic elements, called widgets and routes: 20 21 * a **widget** is every part of the audio hardware that can be enabled by 22 software when in use and disabled to save power when not in use 23 * a **route** is an interconnection between widgets that exists when sound 24 can flow from one widget to the other 25 26All DAPM power switching decisions are made automatically by consulting an 27audio routing graph. This graph is specific to each sound card and spans 28the whole sound card, so some DAPM routes connect two widgets belonging to 29different components (e.g. the LINE OUT pin of a CODEC and the input pin of 30an amplifier). 31 32The graph for the STM32MP1-DK1 sound card is shown in picture: 33 34.. kernel-figure:: dapm-graph.svg 35 :alt: Example DAPM graph 36 :align: center 37 38You can also generate compatible graph for your sound card using 39`tools/sound/dapm-graph` utility. 40 41DAPM power domains 42================== 43 44There are 4 power domains within DAPM: 45 46Codec bias domain 47 VREF, VMID (core codec and audio power) 48 49 Usually controlled at codec probe/remove and suspend/resume, although 50 can be set at stream time if power is not needed for sidetone, etc. 51 52Platform/Machine domain 53 physically connected inputs and outputs 54 55 Is platform/machine and user action specific, is configured by the 56 machine driver and responds to asynchronous events e.g when HP 57 are inserted 58 59Path domain 60 audio subsystem signal paths 61 62 Automatically set when mixer and mux settings are changed by the user. 63 e.g. alsamixer, amixer. 64 65Stream domain 66 DACs and ADCs. 67 68 Enabled and disabled when stream playback/capture is started and 69 stopped respectively. e.g. aplay, arecord. 70 71 72DAPM Widgets 73============ 74 75Audio DAPM widgets fall into a number of types: 76 77Mixer 78 Mixes several analog signals into a single analog signal. 79Mux 80 An analog switch that outputs only one of many inputs. 81PGA 82 A programmable gain amplifier or attenuation widget. 83ADC 84 Analog to Digital Converter 85DAC 86 Digital to Analog Converter 87Switch 88 An analog switch 89Input 90 A codec input pin 91Output 92 A codec output pin 93Headphone 94 Headphone (and optional Jack) 95Mic 96 Mic (and optional Jack) 97Line 98 Line Input/Output (and optional Jack) 99Speaker 100 Speaker 101Supply 102 Power or clock supply widget used by other widgets. 103Regulator 104 External regulator that supplies power to audio components. 105Clock 106 External clock that supplies clock to audio components. 107AIF IN 108 Audio Interface Input (with TDM slot mask). 109AIF OUT 110 Audio Interface Output (with TDM slot mask). 111Siggen 112 Signal Generator. 113DAI IN 114 Digital Audio Interface Input. 115DAI OUT 116 Digital Audio Interface Output. 117DAI Link 118 DAI Link between two DAI structures 119Pre 120 Special PRE widget (exec before all others) 121Post 122 Special POST widget (exec after all others) 123Buffer 124 Inter widget audio data buffer within a DSP. 125Scheduler 126 DSP internal scheduler that schedules component/pipeline processing 127 work. 128Effect 129 Widget that performs an audio processing effect. 130SRC 131 Sample Rate Converter within DSP or CODEC 132ASRC 133 Asynchronous Sample Rate Converter within DSP or CODEC 134Encoder 135 Widget that encodes audio data from one format (usually PCM) to another 136 usually more compressed format. 137Decoder 138 Widget that decodes audio data from a compressed format to an 139 uncompressed format like PCM. 140 141 142(Widgets are defined in include/sound/soc-dapm.h) 143 144Widgets can be added to the sound card by any of the component driver types. 145There are convenience macros defined in soc-dapm.h that can be used to quickly 146build a list of widgets of the codecs and machines DAPM widgets. 147 148Most widgets have a name, register, shift and invert. Some widgets have extra 149parameters for stream name and kcontrols. 150 151 152Stream Domain Widgets 153--------------------- 154 155Stream Widgets relate to the stream power domain and only consist of ADCs 156(analog to digital converters), DACs (digital to analog converters), 157AIF IN and AIF OUT. 158 159Stream widgets have the following format: 160:: 161 162 SND_SOC_DAPM_DAC(name, stream name, reg, shift, invert), 163 SND_SOC_DAPM_AIF_IN(name, stream, slot, reg, shift, invert) 164 165NOTE: the stream name must match the corresponding stream name in your codec 166snd_soc_dai_driver. 167 168e.g. stream widgets for HiFi playback and capture 169:: 170 171 SND_SOC_DAPM_DAC("HiFi DAC", "HiFi Playback", REG, 3, 1), 172 SND_SOC_DAPM_ADC("HiFi ADC", "HiFi Capture", REG, 2, 1), 173 174e.g. stream widgets for AIF 175:: 176 177 SND_SOC_DAPM_AIF_IN("AIF1RX", "AIF1 Playback", 0, SND_SOC_NOPM, 0, 0), 178 SND_SOC_DAPM_AIF_OUT("AIF1TX", "AIF1 Capture", 0, SND_SOC_NOPM, 0, 0), 179 180 181Path Domain Widgets 182------------------- 183 184Path domain widgets have a ability to control or affect the audio signal or 185audio paths within the audio subsystem. They have the following form: 186:: 187 188 SND_SOC_DAPM_PGA(name, reg, shift, invert, controls, num_controls) 189 190Any widget kcontrols can be set using the controls and num_controls members. 191 192e.g. Mixer widget (the kcontrols are declared first) 193:: 194 195 /* Output Mixer */ 196 static const snd_kcontrol_new_t wm8731_output_mixer_controls[] = { 197 SOC_DAPM_SINGLE("Line Bypass Switch", WM8731_APANA, 3, 1, 0), 198 SOC_DAPM_SINGLE("Mic Sidetone Switch", WM8731_APANA, 5, 1, 0), 199 SOC_DAPM_SINGLE("HiFi Playback Switch", WM8731_APANA, 4, 1, 0), 200 }; 201 202 SND_SOC_DAPM_MIXER("Output Mixer", WM8731_PWR, 4, 1, wm8731_output_mixer_controls, 203 ARRAY_SIZE(wm8731_output_mixer_controls)), 204 205If you don't want the mixer elements prefixed with the name of the mixer widget, 206you can use SND_SOC_DAPM_MIXER_NAMED_CTL instead. the parameters are the same 207as for SND_SOC_DAPM_MIXER. 208 209 210Machine domain Widgets 211---------------------- 212 213Machine widgets are different from codec widgets in that they don't have a 214codec register bit associated with them. A machine widget is assigned to each 215machine audio component (non codec or DSP) that can be independently 216powered. e.g. 217 218* Speaker Amp 219* Microphone Bias 220* Jack connectors 221 222A machine widget can have an optional call back. 223 224e.g. Jack connector widget for an external Mic that enables Mic Bias 225when the Mic is inserted:: 226 227 static int spitz_mic_bias(struct snd_soc_dapm_widget* w, int event) 228 { 229 gpio_set_value(SPITZ_GPIO_MIC_BIAS, SND_SOC_DAPM_EVENT_ON(event)); 230 return 0; 231 } 232 233 SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias), 234 235 236Codec (BIAS) Domain 237------------------- 238 239The codec bias power domain has no widgets and is handled by the codec DAPM 240event handler. This handler is called when the codec powerstate is changed wrt 241to any stream event or by kernel PM events. 242 243 244Virtual Widgets 245--------------- 246 247Sometimes widgets exist in the codec or machine audio graph that don't have any 248corresponding soft power control. In this case it is necessary to create 249a virtual widget - a widget with no control bits e.g. 250:: 251 252 SND_SOC_DAPM_MIXER("AC97 Mixer", SND_SOC_NOPM, 0, 0, NULL, 0), 253 254This can be used to merge two signal paths together in software. 255 256Registering DAPM controls 257========================= 258 259In many cases the DAPM widgets are implemented statically in a ``static 260const struct snd_soc_dapm_widget`` array in a codec driver, and simply 261declared via the ``dapm_widgets`` and ``num_dapm_widgets`` fields of the 262``struct snd_soc_component_driver``. 263 264Similarly, routes connecting them are implemented statically in a ``static 265const struct snd_soc_dapm_route`` array and declared via the 266``dapm_routes`` and ``num_dapm_routes`` fields of the same struct. 267 268With the above declared, the driver registration will take care of 269populating them:: 270 271 static const struct snd_soc_dapm_widget wm2000_dapm_widgets[] = { 272 SND_SOC_DAPM_OUTPUT("SPKN"), 273 SND_SOC_DAPM_OUTPUT("SPKP"), 274 ... 275 }; 276 277 /* Target, Path, Source */ 278 static const struct snd_soc_dapm_route wm2000_audio_map[] = { 279 { "SPKN", NULL, "ANC Engine" }, 280 { "SPKP", NULL, "ANC Engine" }, 281 ... 282 }; 283 284 static const struct snd_soc_component_driver soc_component_dev_wm2000 = { 285 ... 286 .dapm_widgets = wm2000_dapm_widgets, 287 .num_dapm_widgets = ARRAY_SIZE(wm2000_dapm_widgets), 288 .dapm_routes = wm2000_audio_map, 289 .num_dapm_routes = ARRAY_SIZE(wm2000_audio_map), 290 ... 291 }; 292 293In more complex cases the list of DAPM widgets and/or routes can be only 294known at probe time. This happens for example when a driver supports 295different models having a different set of features. In those cases 296separate widgets and routes arrays implementing the case-specific features 297can be registered programmatically by calling snd_soc_dapm_new_controls() 298and snd_soc_dapm_add_routes(). 299 300 301Codec/DSP Widget Interconnections 302================================= 303 304Widgets are connected to each other within the codec, platform and machine by 305audio paths (called interconnections). Each interconnection must be defined in 306order to create a graph of all audio paths between widgets. 307 308This is easiest with a diagram of the codec or DSP (and schematic of the machine 309audio system), as it requires joining widgets together via their audio signal 310paths. 311 312For example the WM8731 output mixer (wm8731.c) has 3 inputs (sources): 313 3141. Line Bypass Input 3152. DAC (HiFi playback) 3163. Mic Sidetone Input 317 318Each input in this example has a kcontrol associated with it (defined in 319the example above) and is connected to the output mixer via its kcontrol 320name. We can now connect the destination widget (wrt audio signal) with its 321source widgets. :: 322 323 /* output mixer */ 324 {"Output Mixer", "Line Bypass Switch", "Line Input"}, 325 {"Output Mixer", "HiFi Playback Switch", "DAC"}, 326 {"Output Mixer", "Mic Sidetone Switch", "Mic Bias"}, 327 328So we have: 329 330* Destination Widget <=== Path Name <=== Source Widget, or 331* Sink, Path, Source, or 332* ``Output Mixer`` is connected to the ``DAC`` via the ``HiFi Playback Switch``. 333 334When there is no path name connecting widgets (e.g. a direct connection) we 335pass NULL for the path name. 336 337Interconnections are created with a call to:: 338 339 snd_soc_dapm_connect_input(codec, sink, path, source); 340 341Finally, snd_soc_dapm_new_widgets() must be called after all widgets and 342interconnections have been registered with the core. This causes the core to 343scan the codec and machine so that the internal DAPM state matches the 344physical state of the machine. 345 346 347Machine Widget Interconnections 348------------------------------- 349Machine widget interconnections are created in the same way as codec ones and 350directly connect the codec pins to machine level widgets. 351 352e.g. connects the speaker out codec pins to the internal speaker. 353:: 354 355 /* ext speaker connected to codec pins LOUT2, ROUT2 */ 356 {"Ext Spk", NULL , "ROUT2"}, 357 {"Ext Spk", NULL , "LOUT2"}, 358 359This allows the DAPM to power on and off pins that are connected (and in use) 360and pins that are NC respectively. 361 362 363Endpoint Widgets 364================ 365An endpoint is a start or end point (widget) of an audio signal within the 366machine and includes the codec. e.g. 367 368* Headphone Jack 369* Internal Speaker 370* Internal Mic 371* Mic Jack 372* Codec Pins 373 374Endpoints are added to the DAPM graph so that their usage can be determined in 375order to save power. e.g. NC codecs pins will be switched OFF, unconnected 376jacks can also be switched OFF. 377 378 379DAPM Widget Events 380================== 381 382Widgets needing to implement a more complex behaviour than what DAPM can do 383can set a custom "event handler" by setting a function pointer. An example 384is a power supply needing to enable a GPIO:: 385 386 static int sof_es8316_speaker_power_event(struct snd_soc_dapm_widget *w, 387 struct snd_kcontrol *kcontrol, int event) 388 { 389 if (SND_SOC_DAPM_EVENT_ON(event)) 390 gpiod_set_value_cansleep(gpio_pa, true); 391 else 392 gpiod_set_value_cansleep(gpio_pa, false); 393 394 return 0; 395 } 396 397 static const struct snd_soc_dapm_widget st_widgets[] = { 398 ... 399 SND_SOC_DAPM_SUPPLY("Speaker Power", SND_SOC_NOPM, 0, 0, 400 sof_es8316_speaker_power_event, 401 SND_SOC_DAPM_PRE_PMD | SND_SOC_DAPM_POST_PMU), 402 }; 403 404See soc-dapm.h for all other widgets that support events. 405 406 407Event types 408----------- 409 410The following event types are supported by event widgets:: 411 412 /* dapm event types */ 413 #define SND_SOC_DAPM_PRE_PMU 0x1 /* before widget power up */ 414 #define SND_SOC_DAPM_POST_PMU 0x2 /* after widget power up */ 415 #define SND_SOC_DAPM_PRE_PMD 0x4 /* before widget power down */ 416 #define SND_SOC_DAPM_POST_PMD 0x8 /* after widget power down */ 417 #define SND_SOC_DAPM_PRE_REG 0x10 /* before audio path setup */ 418 #define SND_SOC_DAPM_POST_REG 0x20 /* after audio path setup */ 419 #define SND_SOC_DAPM_WILL_PMU 0x40 /* called at start of sequence */ 420 #define SND_SOC_DAPM_WILL_PMD 0x80 /* called at start of sequence */ 421 #define SND_SOC_DAPM_PRE_POST_PMD (SND_SOC_DAPM_PRE_PMD | SND_SOC_DAPM_POST_PMD) 422 #define SND_SOC_DAPM_PRE_POST_PMU (SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_POST_PMU) 423
