On 01/14/2017 01:19 PM, Dmitry Torokhov wrote:
On Wed, Jan 11, 2017 at 02:02:01PM -0600, David Lechner wrote: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@xxxxxxxxxxxxxx> --- 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");If you do not use optional regulator then you will not have to check if you have it or not everywhere: regulator core will give you a dummy that you can toggle to your heart's content.
Some months ago, I learned that if you are not using device tree and you do not call regulator_has_full_constraints(), then you do not get a dummy regulator. And here, we are only checking if the regulator exists in one place. We will still need the checks for beeper->reg_enabled to keep calls to regulator_enable() and regulator_disable() balanced.
On the other hand, it is recommended that you always call regulator_has_full_constraints(), so I don't mind changing it if that is what you think we should do. But, I don't really see much of an advantage to changing it compared to the current implementation.
+ 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. -- 2.7.4Thanks.
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