Messages in this thread | | | Subject | Re: [PATCH v2 3/3] Input: pwm-beeper: add optional amplifier regulator | From | David Lechner <> | Date | Sun, 15 Jan 2017 19:04:09 -0600 |
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On 01/15/2017 06:34 PM, Dmitry Torokhov wrote: > On Sun, Jan 15, 2017 at 06:12:29PM -0600, David Lechner wrote: >> 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@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"); >>> >>> 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. > > Why? You do not have checks for calls to pwm_enable() and pwm_disable(), > (or rather beeper->period is used as such flag) why regulator would be > any different?
regulator_enable() has a __must_check attribute on it, so we get compiler warnings if we do not check the return value. Also, if enabling the regulator fails and returns an error, then calling regulator_disable() later would cause an imbalance.
pwm_enable() and pwm_disable() work differently because they don't count how many times they have been called. regulator_enable() and regulator_disable(), on the other hand, work like reference counting.
> >> >> 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. > > It greatly simplifies control flow in the driver (since I believe you > can get rid of the flags you introduced). > > As far as arch not having full constraints - I am not sure if this makes > sense anymore. I am not quite sure what the original intent here was, we > should probably ask Mark Brown. But a lot of drivers do expect the dummy > substitution to imply work.
I am OK with using the dummy regulator, but I don't see how I can get rid of the beeper->reg_enabled flag.
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