1 ==============================================
2 Dynamic Audio Power Management for Portable De
3 ==============================================
4
5 Description
6 ===========
7
8 Dynamic Audio Power Management (DAPM) is desig
9 Linux devices to use the minimum amount of pow
10 subsystem at all times. It is independent of o
11 management frameworks and, as such, can easily
12
13 DAPM is also completely transparent to all use
14 all power switching is done within the ASoC co
15 recompiling are required for user space applic
16 switching decisions based upon any audio strea
17 activity and audio mixer settings within the d
18
19 DAPM is based on two basic elements, called wi
20
21 * a **widget** is every part of the audio har
22 software when in use and disabled to save p
23 * a **route** is an interconnection between w
24 can flow from one widget to the other
25
26 All DAPM power switching decisions are made au
27 audio routing graph. This graph is specific to
28 the whole sound card, so some DAPM routes conn
29 different components (e.g. the LINE OUT pin of
30 an amplifier).
31
32 The graph for the STM32MP1-DK1 sound card is s
33
34 .. kernel-figure:: dapm-graph.svg
35 :alt: Example DAPM graph
36 :align: center
37
38 DAPM power domains
39 ==================
40
41 There are 4 power domains within DAPM:
42
43 Codec bias domain
44 VREF, VMID (core codec and audio power)
45
46 Usually controlled at codec probe/remove
47 can be set at stream time if power is no
48
49 Platform/Machine domain
50 physically connected inputs and outputs
51
52 Is platform/machine and user action spec
53 machine driver and responds to asynchron
54 are inserted
55
56 Path domain
57 audio subsystem signal paths
58
59 Automatically set when mixer and mux set
60 e.g. alsamixer, amixer.
61
62 Stream domain
63 DACs and ADCs.
64
65 Enabled and disabled when stream playbac
66 stopped respectively. e.g. aplay, arecor
67
68
69 DAPM Widgets
70 ============
71
72 Audio DAPM widgets fall into a number of types
73
74 Mixer
75 Mixes several analog signals into a si
76 Mux
77 An analog switch that outputs only one
78 PGA
79 A programmable gain amplifier or atten
80 ADC
81 Analog to Digital Converter
82 DAC
83 Digital to Analog Converter
84 Switch
85 An analog switch
86 Input
87 A codec input pin
88 Output
89 A codec output pin
90 Headphone
91 Headphone (and optional Jack)
92 Mic
93 Mic (and optional Jack)
94 Line
95 Line Input/Output (and optional Jack)
96 Speaker
97 Speaker
98 Supply
99 Power or clock supply widget used by o
100 Regulator
101 External regulator that supplies power
102 Clock
103 External clock that supplies clock to
104 AIF IN
105 Audio Interface Input (with TDM slot m
106 AIF OUT
107 Audio Interface Output (with TDM slot
108 Siggen
109 Signal Generator.
110 DAI IN
111 Digital Audio Interface Input.
112 DAI OUT
113 Digital Audio Interface Output.
114 DAI Link
115 DAI Link between two DAI structures
116 Pre
117 Special PRE widget (exec before all ot
118 Post
119 Special POST widget (exec after all ot
120 Buffer
121 Inter widget audio data buffer within
122 Scheduler
123 DSP internal scheduler that schedules
124 work.
125 Effect
126 Widget that performs an audio processi
127 SRC
128 Sample Rate Converter within DSP or CO
129 ASRC
130 Asynchronous Sample Rate Converter wit
131 Encoder
132 Widget that encodes audio data from on
133 usually more compressed format.
134 Decoder
135 Widget that decodes audio data from a
136 uncompressed format like PCM.
137
138
139 (Widgets are defined in include/sound/soc-dapm
140
141 Widgets can be added to the sound card by any
142 There are convenience macros defined in soc-da
143 build a list of widgets of the codecs and mach
144
145 Most widgets have a name, register, shift and
146 parameters for stream name and kcontrols.
147
148
149 Stream Domain Widgets
150 ---------------------
151
152 Stream Widgets relate to the stream power doma
153 (analog to digital converters), DACs (digital
154 AIF IN and AIF OUT.
155
156 Stream widgets have the following format:
157 ::
158
159 SND_SOC_DAPM_DAC(name, stream name, reg, shi
160 SND_SOC_DAPM_AIF_IN(name, stream, slot, reg,
161
162 NOTE: the stream name must match the correspon
163 snd_soc_dai_driver.
164
165 e.g. stream widgets for HiFi playback and capt
166 ::
167
168 SND_SOC_DAPM_DAC("HiFi DAC", "HiFi Playback"
169 SND_SOC_DAPM_ADC("HiFi ADC", "HiFi Capture",
170
171 e.g. stream widgets for AIF
172 ::
173
174 SND_SOC_DAPM_AIF_IN("AIF1RX", "AIF1 Playback
175 SND_SOC_DAPM_AIF_OUT("AIF1TX", "AIF1 Capture
176
177
178 Path Domain Widgets
179 -------------------
180
181 Path domain widgets have a ability to control
182 audio paths within the audio subsystem. They h
183 ::
184
185 SND_SOC_DAPM_PGA(name, reg, shift, invert, c
186
187 Any widget kcontrols can be set using the cont
188
189 e.g. Mixer widget (the kcontrols are declared
190 ::
191
192 /* Output Mixer */
193 static const snd_kcontrol_new_t wm8731_outpu
194 SOC_DAPM_SINGLE("Line Bypass Switch", WM8731
195 SOC_DAPM_SINGLE("Mic Sidetone Switch", WM873
196 SOC_DAPM_SINGLE("HiFi Playback Switch", WM87
197 };
198
199 SND_SOC_DAPM_MIXER("Output Mixer", WM8731_PW
200 ARRAY_SIZE(wm8731_output_mixer_control
201
202 If you don't want the mixer elements prefixed
203 you can use SND_SOC_DAPM_MIXER_NAMED_CTL inste
204 as for SND_SOC_DAPM_MIXER.
205
206
207 Machine domain Widgets
208 ----------------------
209
210 Machine widgets are different from codec widge
211 codec register bit associated with them. A mac
212 machine audio component (non codec or DSP) tha
213 powered. e.g.
214
215 * Speaker Amp
216 * Microphone Bias
217 * Jack connectors
218
219 A machine widget can have an optional call bac
220
221 e.g. Jack connector widget for an external Mic
222 when the Mic is inserted::
223
224 static int spitz_mic_bias(struct snd_soc_dap
225 {
226 gpio_set_value(SPITZ_GPIO_MIC_BIAS, SN
227 return 0;
228 }
229
230 SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias)
231
232
233 Codec (BIAS) Domain
234 -------------------
235
236 The codec bias power domain has no widgets and
237 event handler. This handler is called when the
238 to any stream event or by kernel PM events.
239
240
241 Virtual Widgets
242 ---------------
243
244 Sometimes widgets exist in the codec or machin
245 corresponding soft power control. In this case
246 a virtual widget - a widget with no control bi
247 ::
248
249 SND_SOC_DAPM_MIXER("AC97 Mixer", SND_SOC_NOP
250
251 This can be used to merge two signal paths tog
252
253 Registering DAPM controls
254 =========================
255
256 In many cases the DAPM widgets are implemented
257 const struct snd_soc_dapm_widget`` array in a
258 declared via the ``dapm_widgets`` and ``num_da
259 ``struct snd_soc_component_driver``.
260
261 Similarly, routes connecting them are implemen
262 const struct snd_soc_dapm_route`` array and de
263 ``dapm_routes`` and ``num_dapm_routes`` fields
264
265 With the above declared, the driver registrati
266 populating them::
267
268 static const struct snd_soc_dapm_widget wm20
269 SND_SOC_DAPM_OUTPUT("SPKN"),
270 SND_SOC_DAPM_OUTPUT("SPKP"),
271 ...
272 };
273
274 /* Target, Path, Source */
275 static const struct snd_soc_dapm_route wm200
276 { "SPKN", NULL, "ANC Engine" },
277 { "SPKP", NULL, "ANC Engine" },
278 ...
279 };
280
281 static const struct snd_soc_component_driver
282 ...
283 .dapm_widgets = wm2000_dapm_
284 .num_dapm_widgets = ARRAY_SIZE(w
285 .dapm_routes = wm2000_audio
286 .num_dapm_routes = ARRAY_SIZE(w
287 ...
288 };
289
290 In more complex cases the list of DAPM widgets
291 known at probe time. This happens for example
292 different models having a different set of fea
293 separate widgets and routes arrays implementin
294 can be registered programmatically by calling
295 and snd_soc_dapm_add_routes().
296
297
298 Codec/DSP Widget Interconnections
299 =================================
300
301 Widgets are connected to each other within the
302 audio paths (called interconnections). Each in
303 order to create a graph of all audio paths bet
304
305 This is easiest with a diagram of the codec or
306 audio system), as it requires joining widgets
307 paths.
308
309 For example the WM8731 output mixer (wm8731.c)
310
311 1. Line Bypass Input
312 2. DAC (HiFi playback)
313 3. Mic Sidetone Input
314
315 Each input in this example has a kcontrol asso
316 the example above) and is connected to the out
317 name. We can now connect the destination widge
318 source widgets. ::
319
320 /* output mixer */
321 {"Output Mixer", "Line Bypass Switch",
322 {"Output Mixer", "HiFi Playback Switch
323 {"Output Mixer", "Mic Sidetone Switch"
324
325 So we have:
326
327 * Destination Widget <=== Path Name <=== Sour
328 * Sink, Path, Source, or
329 * ``Output Mixer`` is connected to the ``DAC``
330
331 When there is no path name connecting widgets
332 pass NULL for the path name.
333
334 Interconnections are created with a call to::
335
336 snd_soc_dapm_connect_input(codec, sink, path
337
338 Finally, snd_soc_dapm_new_widgets() must be ca
339 interconnections have been registered with the
340 scan the codec and machine so that the interna
341 physical state of the machine.
342
343
344 Machine Widget Interconnections
345 -------------------------------
346 Machine widget interconnections are created in
347 directly connect the codec pins to machine lev
348
349 e.g. connects the speaker out codec pins to th
350 ::
351
352 /* ext speaker connected to codec pins
353 {"Ext Spk", NULL , "ROUT2"},
354 {"Ext Spk", NULL , "LOUT2"},
355
356 This allows the DAPM to power on and off pins
357 and pins that are NC respectively.
358
359
360 Endpoint Widgets
361 ================
362 An endpoint is a start or end point (widget) o
363 machine and includes the codec. e.g.
364
365 * Headphone Jack
366 * Internal Speaker
367 * Internal Mic
368 * Mic Jack
369 * Codec Pins
370
371 Endpoints are added to the DAPM graph so that
372 order to save power. e.g. NC codecs pins will
373 jacks can also be switched OFF.
374
375
376 DAPM Widget Events
377 ==================
378
379 Widgets needing to implement a more complex be
380 can set a custom "event handler" by setting a
381 is a power supply needing to enable a GPIO::
382
383 static int sof_es8316_speaker_power_event(st
384 stru
385 {
386 if (SND_SOC_DAPM_EVENT_ON(event))
387 gpiod_set_value_cansleep(gpio_
388 else
389 gpiod_set_value_cansleep(gpio_
390
391 return 0;
392 }
393
394 static const struct snd_soc_dapm_widget st_w
395 ...
396 SND_SOC_DAPM_SUPPLY("Speaker Power", S
397 sof_es8316_speaker
398 SND_SOC_DAPM_PRE_P
399 };
400
401 See soc-dapm.h for all other widgets that supp
402
403
404 Event types
405 -----------
406
407 The following event types are supported by eve
408
409 /* dapm event types */
410 #define SND_SOC_DAPM_PRE_PMU 0x1
411 #define SND_SOC_DAPM_POST_PMU 0x2
412 #define SND_SOC_DAPM_PRE_PMD 0x4
413 #define SND_SOC_DAPM_POST_PMD 0x8
414 #define SND_SOC_DAPM_PRE_REG 0x10
415 #define SND_SOC_DAPM_POST_REG 0x20
416 #define SND_SOC_DAPM_WILL_PMU 0x40
417 #define SND_SOC_DAPM_WILL_PMD 0x80
418 #define SND_SOC_DAPM_PRE_POST_PMD (SND_S
419 #define SND_SOC_DAPM_PRE_POST_PMU (SND_S
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