[PATCH v2 3/3] Input: pwm-beeper: add optional amplifier regulator

[David Lechner]

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 <da...@lechnology.com>
---
 drivers/input/misc/pwm-beeper.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/input/misc/pwm-beeper.c b/drivers/input/misc/pwm-beeper.c
index 30ac227..708e88e 100644
--- 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>
@@ -25,8 +26,10 @@
 struct pwm_beeper {
        struct input_dev *input;
        struct pwm_device *pwm;
+       struct regulator *reg;
        struct work_struct work;
        unsigned long period;
+       bool reg_enabled;
 };
 
 #define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))
@@ -38,8 +41,20 @@ static void __pwm_beeper_set(struct pwm_beeper *beeper)
        if (period) {
                pwm_config(beeper->pwm, period / 2, period);
                pwm_enable(beeper->pwm);
-       } else
+               if (beeper->reg) {
+                       int error;
+
+                       error = regulator_enable(beeper->reg);
+                       if (!error)
+                               beeper->reg_enabled = true;
+               }
+       } else {
+               if (beeper->reg_enabled) {
+                       regulator_disable(beeper->reg);
+                       beeper->reg_enabled = false;
+               }
                pwm_disable(beeper->pwm);
+       }
 }
 
 static void pwm_beeper_work(struct work_struct *work)
@@ -82,6 +97,10 @@ static void pwm_beeper_stop(struct pwm_beeper *beeper)
 {
        cancel_work_sync(&beeper->work);
 
+       if (beeper->reg_enabled) {
+               regulator_disable(beeper->reg);
+               beeper->reg_enabled = false;
+       }
        if (beeper->period)
                pwm_disable(beeper->pwm);
 }
@@ -111,6 +130,14 @@ static int pwm_beeper_probe(struct platform_device *pdev)
                return error;
        }
 
+       beeper->reg = devm_regulator_get_optional(&pdev->dev, "amp");
+       error = PTR_ERR_OR_ZERO(beeper->reg);
+       if (error) {
+               if (error != -EPROBE_DEFER)
+                       dev_err(dev, "Failed to get amp regulator\n");
+               return error;
+       }
+
        /*
         * FIXME: pwm_apply_args() should be removed when switching to
         * the atomic PWM API.
-- 
2.7.4