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 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 susbsystem 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 Pre - Special PRE widget (exec before all others) 67 o Post - Special POST widget (exec after all others) 68 69(Widgets are defined in include/sound/soc-dapm.h) 70 71Widgets are usually added in the codec driver and the machine driver. There are 72convenience macros defined in soc-dapm.h that can be used to quickly build a 73list of widgets of the codecs and machines DAPM widgets. 74 75Most widgets have a name, register, shift and invert. Some widgets have extra 76parameters for stream name and kcontrols. 77 78 792.1 Stream Domain Widgets 80------------------------- 81 82Stream Widgets relate to the stream power domain and only consist of ADCs 83(analog to digital converters) and DACs (digital to analog converters). 84 85Stream widgets have the following format:- 86 87SND_SOC_DAPM_DAC(name, stream name, reg, shift, invert), 88 89NOTE: the stream name must match the corresponding stream name in your codec 90snd_soc_codec_dai. 91 92e.g. stream widgets for HiFi playback and capture 93 94SND_SOC_DAPM_DAC("HiFi DAC", "HiFi Playback", REG, 3, 1), 95SND_SOC_DAPM_ADC("HiFi ADC", "HiFi Capture", REG, 2, 1), 96 97 982.2 Path Domain Widgets 99----------------------- 100 101Path domain widgets have a ability to control or affect the audio signal or 102audio paths within the audio subsystem. They have the following form:- 103 104SND_SOC_DAPM_PGA(name, reg, shift, invert, controls, num_controls) 105 106Any widget kcontrols can be set using the controls and num_controls members. 107 108e.g. Mixer widget (the kcontrols are declared first) 109 110/* Output Mixer */ 111static const snd_kcontrol_new_t wm8731_output_mixer_controls[] = { 112SOC_DAPM_SINGLE("Line Bypass Switch", WM8731_APANA, 3, 1, 0), 113SOC_DAPM_SINGLE("Mic Sidetone Switch", WM8731_APANA, 5, 1, 0), 114SOC_DAPM_SINGLE("HiFi Playback Switch", WM8731_APANA, 4, 1, 0), 115}; 116 117SND_SOC_DAPM_MIXER("Output Mixer", WM8731_PWR, 4, 1, wm8731_output_mixer_controls, 118 ARRAY_SIZE(wm8731_output_mixer_controls)), 119 120If you dont want the mixer elements prefixed with the name of the mixer widget, 121you can use SND_SOC_DAPM_MIXER_NAMED_CTL instead. the parameters are the same 122as for SND_SOC_DAPM_MIXER. 123 1242.3 Platform/Machine domain Widgets 125----------------------------------- 126 127Machine widgets are different from codec widgets in that they don't have a 128codec register bit associated with them. A machine widget is assigned to each 129machine audio component (non codec) that can be independently powered. e.g. 130 131 o Speaker Amp 132 o Microphone Bias 133 o Jack connectors 134 135A machine widget can have an optional call back. 136 137e.g. Jack connector widget for an external Mic that enables Mic Bias 138when the Mic is inserted:- 139 140static int spitz_mic_bias(struct snd_soc_dapm_widget* w, int event) 141{ 142 gpio_set_value(SPITZ_GPIO_MIC_BIAS, SND_SOC_DAPM_EVENT_ON(event)); 143 return 0; 144} 145 146SND_SOC_DAPM_MIC("Mic Jack", spitz_mic_bias), 147 148 1492.4 Codec Domain 150---------------- 151 152The codec power domain has no widgets and is handled by the codecs DAPM event 153handler. This handler is called when the codec powerstate is changed wrt to any 154stream event or by kernel PM events. 155 156 1572.5 Virtual Widgets 158------------------- 159 160Sometimes widgets exist in the codec or machine audio map that don't have any 161corresponding soft power control. In this case it is necessary to create 162a virtual widget - a widget with no control bits e.g. 163 164SND_SOC_DAPM_MIXER("AC97 Mixer", SND_SOC_DAPM_NOPM, 0, 0, NULL, 0), 165 166This can be used to merge to signal paths together in software. 167 168After all the widgets have been defined, they can then be added to the DAPM 169subsystem individually with a call to snd_soc_dapm_new_control(). 170 171 1723. Codec Widget Interconnections 173================================ 174 175Widgets are connected to each other within the codec and machine by audio paths 176(called interconnections). Each interconnection must be defined in order to 177create a map of all audio paths between widgets. 178 179This is easiest with a diagram of the codec (and schematic of the machine audio 180system), as it requires joining widgets together via their audio signal paths. 181 182e.g., from the WM8731 output mixer (wm8731.c) 183 184The WM8731 output mixer has 3 inputs (sources) 185 186 1. Line Bypass Input 187 2. DAC (HiFi playback) 188 3. Mic Sidetone Input 189 190Each input in this example has a kcontrol associated with it (defined in example 191above) and is connected to the output mixer via its kcontrol name. We can now 192connect the destination widget (wrt audio signal) with its source widgets. 193 194 /* output mixer */ 195 {"Output Mixer", "Line Bypass Switch", "Line Input"}, 196 {"Output Mixer", "HiFi Playback Switch", "DAC"}, 197 {"Output Mixer", "Mic Sidetone Switch", "Mic Bias"}, 198 199So we have :- 200 201 Destination Widget <=== Path Name <=== Source Widget 202 203Or:- 204 205 Sink, Path, Source 206 207Or :- 208 209 "Output Mixer" is connected to the "DAC" via the "HiFi Playback Switch". 210 211When there is no path name connecting widgets (e.g. a direct connection) we 212pass NULL for the path name. 213 214Interconnections are created with a call to:- 215 216snd_soc_dapm_connect_input(codec, sink, path, source); 217 218Finally, snd_soc_dapm_new_widgets(codec) must be called after all widgets and 219interconnections have been registered with the core. This causes the core to 220scan the codec and machine so that the internal DAPM state matches the 221physical state of the machine. 222 223 2243.1 Machine Widget Interconnections 225----------------------------------- 226Machine widget interconnections are created in the same way as codec ones and 227directly connect the codec pins to machine level widgets. 228 229e.g. connects the speaker out codec pins to the internal speaker. 230 231 /* ext speaker connected to codec pins LOUT2, ROUT2 */ 232 {"Ext Spk", NULL , "ROUT2"}, 233 {"Ext Spk", NULL , "LOUT2"}, 234 235This allows the DAPM to power on and off pins that are connected (and in use) 236and pins that are NC respectively. 237 238 2394 Endpoint Widgets 240=================== 241An endpoint is a start or end point (widget) of an audio signal within the 242machine and includes the codec. e.g. 243 244 o Headphone Jack 245 o Internal Speaker 246 o Internal Mic 247 o Mic Jack 248 o Codec Pins 249 250When a codec pin is NC it can be marked as not used with a call to 251 252snd_soc_dapm_set_endpoint(codec, "Widget Name", 0); 253 254The last argument is 0 for inactive and 1 for active. This way the pin and its 255input widget will never be powered up and consume power. 256 257This also applies to machine widgets. e.g. if a headphone is connected to a 258jack then the jack can be marked active. If the headphone is removed, then 259the headphone jack can be marked inactive. 260 261 2625 DAPM Widget Events 263==================== 264 265Some widgets can register their interest with the DAPM core in PM events. 266e.g. A Speaker with an amplifier registers a widget so the amplifier can be 267powered only when the spk is in use. 268 269/* turn speaker amplifier on/off depending on use */ 270static int corgi_amp_event(struct snd_soc_dapm_widget *w, int event) 271{ 272 gpio_set_value(CORGI_GPIO_APM_ON, SND_SOC_DAPM_EVENT_ON(event)); 273 return 0; 274} 275 276/* corgi machine dapm widgets */ 277static const struct snd_soc_dapm_widget wm8731_dapm_widgets = 278 SND_SOC_DAPM_SPK("Ext Spk", corgi_amp_event); 279 280Please see soc-dapm.h for all other widgets that support events. 281 282 2835.1 Event types 284--------------- 285 286The following event types are supported by event widgets. 287 288/* dapm event types */ 289#define SND_SOC_DAPM_PRE_PMU 0x1 /* before widget power up */ 290#define SND_SOC_DAPM_POST_PMU 0x2 /* after widget power up */ 291#define SND_SOC_DAPM_PRE_PMD 0x4 /* before widget power down */ 292#define SND_SOC_DAPM_POST_PMD 0x8 /* after widget power down */ 293#define SND_SOC_DAPM_PRE_REG 0x10 /* before audio path setup */ 294#define SND_SOC_DAPM_POST_REG 0x20 /* after audio path setup */ 295