Commit 9e549244 authored by David Lechner's avatar David Lechner Committed by Dmitry Torokhov
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Input: pwm-beeper - add optional amplifier regulator

This adds an optional regulator to the pwm-beeper device. This regulator
acts as an amplifier. The amplifier is only enabled while beeping in order
to reduce power consumption.

Tested on LEGO MINDSTORMS EV3, which has a speaker connected to PWM through
an amplifier.
Signed-off-by: default avatarDavid Lechner <>
Acked-by: default avatarRob Herring <>
Signed-off-by: default avatarDmitry Torokhov <>
parent 62481881
......@@ -5,3 +5,19 @@ Registers a PWM device as beeper.
Required properties:
- compatible: should be "pwm-beeper"
- pwms: phandle to the physical PWM device
Optional properties:
- amp-supply: phandle to a regulator that acts as an amplifier for the beeper
beeper_amp: amplifier {
compatible = "fixed-regulator";
gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
beeper {
compatible = "pwm-beeper";
pwms = <&pwm0>;
amp-supply = <&beeper_amp>;
......@@ -14,6 +14,7 @@
#include <linux/input.h>
#include <linux/regulator/consumer.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/of.h>
......@@ -25,30 +26,59 @@
struct pwm_beeper {
struct input_dev *input;
struct pwm_device *pwm;
struct regulator *amplifier;
struct work_struct work;
unsigned long period;
bool suspended;
bool amplifier_on;
#define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))
static void __pwm_beeper_set(struct pwm_beeper *beeper)
static int pwm_beeper_on(struct pwm_beeper *beeper, unsigned long period)
unsigned long period = beeper->period;
int error;
error = pwm_config(beeper->pwm, period / 2, period);
if (error)
return error;
error = pwm_enable(beeper->pwm);
if (error)
return error;
if (!beeper->amplifier_on) {
error = regulator_enable(beeper->amplifier);
if (error) {
return error;
if (period) {
pwm_config(beeper->pwm, period / 2, period);
} else
beeper->amplifier_on = true;
return 0;
static void pwm_beeper_off(struct pwm_beeper *beeper)
if (beeper->amplifier_on) {
beeper->amplifier_on = false;
static void pwm_beeper_work(struct work_struct *work)
struct pwm_beeper *beeper =
container_of(work, struct pwm_beeper, work);
struct pwm_beeper *beeper = container_of(work, struct pwm_beeper, work);
unsigned long period = READ_ONCE(beeper->period);
if (period)
pwm_beeper_on(beeper, period);
static int pwm_beeper_event(struct input_dev *input,
......@@ -83,9 +113,7 @@ static int pwm_beeper_event(struct input_dev *input,
static void pwm_beeper_stop(struct pwm_beeper *beeper)
if (beeper->period)
static void pwm_beeper_close(struct input_dev *input)
......@@ -120,6 +148,15 @@ static int pwm_beeper_probe(struct platform_device *pdev)
beeper->amplifier = devm_regulator_get(dev, "amp");
if (IS_ERR(beeper->amplifier)) {
error = PTR_ERR(beeper->amplifier);
if (error != -EPROBE_DEFER)
dev_err(dev, "Failed to get 'amp' regulator: %d\n",
return error;
INIT_WORK(&beeper->work, pwm_beeper_work);
beeper->input = devm_input_allocate_device(dev);
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