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: David Lechner <david@lechnology.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

diff --git a/Documentation/devicetree/bindings/input/pwm-beeper.txt b/Documentation/devicetree/bindings/input/pwm-beeper.txt
index be332ae..529408b 100644 (file)
--- a/Documentation/devicetree/bindings/input/pwm-beeper.txt
+++ b/Documentation/devicetree/bindings/input/pwm-beeper.txt
@@ -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
+
+Example:
+
+beeper_amp: amplifier {
+       compatible = "fixed-regulator";
+       gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
+};
+
+beeper {
+       compatible = "pwm-beeper";
+       pwms = <&pwm0>;
+       amp-supply = <&beeper_amp>;
+};

diff --git a/drivers/input/misc/pwm-beeper.c b/drivers/input/misc/pwm-beeper.c
index 069d594..ad9b231 100644 (file)
--- a/drivers/input/misc/pwm-beeper.c
+++ b/drivers/input/misc/pwm-beeper.c
@@ -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) {
+                       pwm_disable(beeper->pwm);
+                       return error;
+               }
 
-       if (period) {
-               pwm_config(beeper->pwm, period / 2, period);
-               pwm_enable(beeper->pwm);
-       } else
-               pwm_disable(beeper->pwm);
+               beeper->amplifier_on = true;
+       }
+
+       return 0;
+}
+
+static void pwm_beeper_off(struct pwm_beeper *beeper)
+{
+       if (beeper->amplifier_on) {
+               regulator_disable(beeper->amplifier);
+               beeper->amplifier_on = false;
+       }
+
+       pwm_disable(beeper->pwm);
 }
 
 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);
 
-       __pwm_beeper_set(beeper);
+       if (period)
+               pwm_beeper_on(beeper, period);
+       else
+               pwm_beeper_off(beeper);
 }
 
 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)
 {
        cancel_work_sync(&beeper->work);
-
-       if (beeper->period)
-               pwm_disable(beeper->pwm);
+       pwm_beeper_off(beeper);
 }
 
 static void pwm_beeper_close(struct input_dev *input)
@@ -120,6 +148,15 @@ static int pwm_beeper_probe(struct platform_device *pdev)
         */
        pwm_apply_args(beeper->pwm);
 
+       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",
+                               error);
+               return error;
+       }
+
        INIT_WORK(&beeper->work, pwm_beeper_work);
 
        beeper->input = devm_input_allocate_device(dev);