Based on kernel version 6.11
. Page generated on 2024-09-24 08:21 EST
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 | =================================================== 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 power management frameworks and, as such, can easily co-exist with them. 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 is based on two basic elements, called widgets and routes: * a **widget** is every part of the audio hardware that can be enabled by software when in use and disabled to save power when not in use * a **route** is an interconnection between widgets that exists when sound can flow from one widget to the other All DAPM power switching decisions are made automatically by consulting an audio routing graph. This graph is specific to each sound card and spans the whole sound card, so some DAPM routes connect two widgets belonging to different components (e.g. the LINE OUT pin of a CODEC and the input pin of an amplifier). The graph for the STM32MP1-DK1 sound card is shown in picture: .. kernel-figure:: dapm-graph.svg :alt: Example DAPM graph :align: center DAPM power domains ================== 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. 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_dai_driver. 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 codec 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 graph 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_NOPM, 0, 0, NULL, 0), This can be used to merge two signal paths together in software. Registering DAPM controls ========================= In many cases the DAPM widgets are implemented statically in a ``static const struct snd_soc_dapm_widget`` array in a codec driver, and simply declared via the ``dapm_widgets`` and ``num_dapm_widgets`` fields of the ``struct snd_soc_component_driver``. Similarly, routes connecting them are implemented statically in a ``static const struct snd_soc_dapm_route`` array and declared via the ``dapm_routes`` and ``num_dapm_routes`` fields of the same struct. With the above declared, the driver registration will take care of populating them:: static const struct snd_soc_dapm_widget wm2000_dapm_widgets[] = { SND_SOC_DAPM_OUTPUT("SPKN"), SND_SOC_DAPM_OUTPUT("SPKP"), ... }; /* Target, Path, Source */ static const struct snd_soc_dapm_route wm2000_audio_map[] = { { "SPKN", NULL, "ANC Engine" }, { "SPKP", NULL, "ANC Engine" }, ... }; static const struct snd_soc_component_driver soc_component_dev_wm2000 = { ... .dapm_widgets = wm2000_dapm_widgets, .num_dapm_widgets = ARRAY_SIZE(wm2000_dapm_widgets), .dapm_routes = wm2000_audio_map, .num_dapm_routes = ARRAY_SIZE(wm2000_audio_map), ... }; In more complex cases the list of DAPM widgets and/or routes can be only known at probe time. This happens for example when a driver supports different models having a different set of features. In those cases separate widgets and routes arrays implementing the case-specific features can be registered programmatically by calling snd_soc_dapm_new_controls() and snd_soc_dapm_add_routes(). 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 graph 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. For example the WM8731 output mixer (wm8731.c) 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 the 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() 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 ================== Widgets needing to implement a more complex behaviour than what DAPM can do can set a custom "event handler" by setting a function pointer. An example is a power supply needing to enable a GPIO:: static int sof_es8316_speaker_power_event(struct snd_soc_dapm_widget *w, struct snd_kcontrol *kcontrol, int event) { if (SND_SOC_DAPM_EVENT_ON(event)) gpiod_set_value_cansleep(gpio_pa, true); else gpiod_set_value_cansleep(gpio_pa, false); return 0; } static const struct snd_soc_dapm_widget st_widgets[] = { ... SND_SOC_DAPM_SUPPLY("Speaker Power", SND_SOC_NOPM, 0, 0, sof_es8316_speaker_power_event, SND_SOC_DAPM_PRE_PMD | SND_SOC_DAPM_POST_PMU), }; 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 */ #define SND_SOC_DAPM_WILL_PMU 0x40 /* called at start of sequence */ #define SND_SOC_DAPM_WILL_PMD 0x80 /* called at start of sequence */ #define SND_SOC_DAPM_PRE_POST_PMD (SND_SOC_DAPM_PRE_PMD | SND_SOC_DAPM_POST_PMD) #define SND_SOC_DAPM_PRE_POST_PMU (SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_POST_PMU) |