mirror of https://gitee.com/openkylin/linux.git
295 lines
10 KiB
Plaintext
295 lines
10 KiB
Plaintext
Dynamic Audio Power Management for Portable Devices
|
|
===================================================
|
|
|
|
1. 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 PM and as
|
|
such, can easily co-exist with the other PM systems.
|
|
|
|
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 spans the whole machine. It covers power control within the entire
|
|
audio subsystem, this includes internal codec power blocks and machine
|
|
level power systems.
|
|
|
|
There are 4 power domains within DAPM
|
|
|
|
1. Codec 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.
|
|
|
|
2. 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
|
|
|
|
3. Path domain - audio susbsystem signal paths
|
|
Automatically set when mixer and mux settings are changed by the user.
|
|
e.g. alsamixer, amixer.
|
|
|
|
4. Stream domain - DACs and ADCs.
|
|
Enabled and disabled when stream playback/capture is started and
|
|
stopped respectively. e.g. aplay, arecord.
|
|
|
|
All DAPM power switching decisions are made automatically by consulting an audio
|
|
routing map of the whole machine. This map is specific to each machine and
|
|
consists of the interconnections between every audio component (including
|
|
internal codec components). All audio components that effect power are called
|
|
widgets hereafter.
|
|
|
|
|
|
2. DAPM Widgets
|
|
===============
|
|
|
|
Audio DAPM widgets fall into a number of types:-
|
|
|
|
o Mixer - Mixes several analog signals into a single analog signal.
|
|
o Mux - An analog switch that outputs only one of many inputs.
|
|
o PGA - A programmable gain amplifier or attenuation widget.
|
|
o ADC - Analog to Digital Converter
|
|
o DAC - Digital to Analog Converter
|
|
o Switch - An analog switch
|
|
o Input - A codec input pin
|
|
o Output - A codec output pin
|
|
o Headphone - Headphone (and optional Jack)
|
|
o Mic - Mic (and optional Jack)
|
|
o Line - Line Input/Output (and optional Jack)
|
|
o Speaker - Speaker
|
|
o Supply - Power or clock supply widget used by other widgets.
|
|
o Pre - Special PRE widget (exec before all others)
|
|
o Post - Special POST widget (exec after all others)
|
|
|
|
(Widgets are defined in include/sound/soc-dapm.h)
|
|
|
|
Widgets are usually added in the codec driver and the machine driver. 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.
|
|
|
|
|
|
2.1 Stream Domain Widgets
|
|
-------------------------
|
|
|
|
Stream Widgets relate to the stream power domain and only consist of ADCs
|
|
(analog to digital converters) and DACs (digital to analog converters).
|
|
|
|
Stream widgets have the following format:-
|
|
|
|
SND_SOC_DAPM_DAC(name, stream name, reg, shift, invert),
|
|
|
|
NOTE: the stream name must match the corresponding stream name in your codec
|
|
snd_soc_codec_dai.
|
|
|
|
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),
|
|
|
|
|
|
2.2 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 dont 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.
|
|
|
|
2.3 Platform/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) that can be independently powered. e.g.
|
|
|
|
o Speaker Amp
|
|
o Microphone Bias
|
|
o 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),
|
|
|
|
|
|
2.4 Codec Domain
|
|
----------------
|
|
|
|
The codec power domain has no widgets and is handled by the codecs DAPM event
|
|
handler. This handler is called when the codec powerstate is changed wrt to any
|
|
stream event or by kernel PM events.
|
|
|
|
|
|
2.5 Virtual Widgets
|
|
-------------------
|
|
|
|
Sometimes widgets exist in the codec or machine audio map 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_DAPM_NOPM, 0, 0, NULL, 0),
|
|
|
|
This can be used to merge to signal paths together in software.
|
|
|
|
After all the widgets have been defined, they can then be added to the DAPM
|
|
subsystem individually with a call to snd_soc_dapm_new_control().
|
|
|
|
|
|
3. Codec Widget Interconnections
|
|
================================
|
|
|
|
Widgets are connected to each other within the codec and machine by audio paths
|
|
(called interconnections). Each interconnection must be defined in order to
|
|
create a map of all audio paths between widgets.
|
|
|
|
This is easiest with a diagram of the codec (and schematic of the machine audio
|
|
system), as it requires joining widgets together via their audio signal paths.
|
|
|
|
e.g., from the WM8731 output mixer (wm8731.c)
|
|
|
|
The WM8731 output mixer 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 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(codec) 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.
|
|
|
|
|
|
3.1 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.
|
|
|
|
|
|
4 Endpoint Widgets
|
|
===================
|
|
An endpoint is a start or end point (widget) of an audio signal within the
|
|
machine and includes the codec. e.g.
|
|
|
|
o Headphone Jack
|
|
o Internal Speaker
|
|
o Internal Mic
|
|
o Mic Jack
|
|
o Codec Pins
|
|
|
|
When a codec pin is NC it can be marked as not used with a call to
|
|
|
|
snd_soc_dapm_set_endpoint(codec, "Widget Name", 0);
|
|
|
|
The last argument is 0 for inactive and 1 for active. This way the pin and its
|
|
input widget will never be powered up and consume power.
|
|
|
|
This also applies to machine widgets. e.g. if a headphone is connected to a
|
|
jack then the jack can be marked active. If the headphone is removed, then
|
|
the headphone jack can be marked inactive.
|
|
|
|
|
|
5 DAPM Widget Events
|
|
====================
|
|
|
|
Some widgets can register their interest with the DAPM core in PM events.
|
|
e.g. A Speaker with an amplifier registers a widget so the amplifier can be
|
|
powered only when the spk is in use.
|
|
|
|
/* turn speaker amplifier on/off depending on use */
|
|
static int corgi_amp_event(struct snd_soc_dapm_widget *w, int event)
|
|
{
|
|
gpio_set_value(CORGI_GPIO_APM_ON, SND_SOC_DAPM_EVENT_ON(event));
|
|
return 0;
|
|
}
|
|
|
|
/* corgi machine dapm widgets */
|
|
static const struct snd_soc_dapm_widget wm8731_dapm_widgets =
|
|
SND_SOC_DAPM_SPK("Ext Spk", corgi_amp_event);
|
|
|
|
Please see soc-dapm.h for all other widgets that support events.
|
|
|
|
|
|
5.1 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 */
|