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Subject: Re: [PATCH 1/2] leds: Add control of the voltage/current regulator to
 the LED core
To:     Dan Murphy <dmurphy@ti.com>, <jacek.anaszewski@gmail.com>,
        <pavel@ucw.cz>, <robh+dt@kernel.org>, <mark.rutland@arm.com>,
        <daniel.thompson@linaro.org>
CC:     <linux-leds@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <devicetree@vger.kernel.org>
References: <20190708103547.23528-1-jjhiblot@ti.com>
 <20190708103547.23528-2-jjhiblot@ti.com>
 <56d16260-ff82-3439-4c1f-2a3a1552bc7d@ti.com>
From:   Jean-Jacques Hiblot <jjhiblot@ti.com>
Message-ID: <ab4818c0-bc7a-13e1-c6ce-e977b0234de0@ti.com>
Date:   Mon, 15 Jul 2019 11:01:29 +0200
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Hi Dan,

On 12/07/2019 20:49, Dan Murphy wrote:
> JJ
>
> On 7/8/19 5:35 AM, Jean-Jacques Hiblot wrote:
>> A LED is usually powered by a voltage/current regulator. Let the LED 
>> core
> Let the LED core know
>> about it. This allows the LED core to turn on or off the power supply
>> as needed.
>
>>
>> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
>> ---
>>   drivers/leds/led-class.c | 10 ++++++++
>>   drivers/leds/led-core.c  | 53 +++++++++++++++++++++++++++++++++++++---
>>   include/linux/leds.h     |  4 +++
>>   3 files changed, 64 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
>> index 4793e77808e2..e01b2d982564 100644
>> --- a/drivers/leds/led-class.c
>> +++ b/drivers/leds/led-class.c
>> @@ -17,6 +17,7 @@
>>   #include <linux/slab.h>
>>   #include <linux/spinlock.h>
>>   #include <linux/timer.h>
>> +#include <linux/regulator/consumer.h>
>
> What if you move this to leds.h so core and class can both include it.
>
>
>>   #include <uapi/linux/uleds.h>
>>   #include "leds.h"
>>   @@ -272,6 +273,15 @@ int of_led_classdev_register(struct device 
>> *parent, struct device_node *np,
>>           dev_warn(parent, "Led %s renamed to %s due to name collision",
>>                   led_cdev->name, dev_name(led_cdev->dev));
>>   +    led_cdev->regulator = devm_regulator_get(led_cdev->dev, "power");
>
> Is the regulator always going to be called power?

Actually in the dts, that will be "power-supply". I lacked the 
imagination to come up with a better name.


>
>> +    if (IS_ERR(led_cdev->regulator)) {
>> +        dev_err(led_cdev->dev, "Cannot get the power supply for %s\n",
>> +            led_cdev->name);
>> +        device_unregister(led_cdev->dev);
>> +        mutex_unlock(&led_cdev->led_access);
>> +        return PTR_ERR(led_cdev->regulator);
>
> This is listed as optional in the DT doc.  This appears to be required.

The regulator core will provide a dummy regulator if none is given in 
the device tree. I would rather have an error in that case, but that is 
not how it works.


>
> I prefer to keep it optional.  Many LED drivers are connected to fixed 
> non-managed supplies.
>
>> +    }
>> +
>>       if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
>>           ret = led_add_brightness_hw_changed(led_cdev);
>>           if (ret) {
>> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
>> index 7107cd7e87cf..139de6b08cad 100644
>> --- a/drivers/leds/led-core.c
>> +++ b/drivers/leds/led-core.c
>> @@ -16,6 +16,7 @@
>>   #include <linux/rwsem.h>
>>   #include <linux/slab.h>
>>   #include "leds.h"
>> +#include <linux/regulator/consumer.h>
>>     DECLARE_RWSEM(leds_list_lock);
>>   EXPORT_SYMBOL_GPL(leds_list_lock);
>> @@ -23,6 +24,31 @@ EXPORT_SYMBOL_GPL(leds_list_lock);
>>   LIST_HEAD(leds_list);
>>   EXPORT_SYMBOL_GPL(leds_list);
>>   +static bool __led_need_regulator_update(struct led_classdev 
>> *led_cdev,
>> +                    int brightness)
>> +{
>> +    bool new_regulator_state = (brightness != LED_OFF);
>> +
>> +    return led_cdev->regulator_state != new_regulator_state;
>> +}
>> +
>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>> +                int brightness)
>> +{
>> +    if (__led_need_regulator_update(led_cdev, brightness)) {
>> +        int ret;
>
> Prefer to this to be moved up.
ok
>
>> +
>> +        if (brightness != LED_OFF)
>> +            ret = regulator_enable(led_cdev->regulator);
>> +        else
>> +            ret = regulator_disable(led_cdev->regulator);
>> +        if (ret)
>> +            return ret;
> new line
>> +        led_cdev->regulator_state = (brightness != LED_OFF);
>> +    }
>> +    return 0;
>> +}
>> +
>>   static int __led_set_brightness(struct led_classdev *led_cdev,
>>                   enum led_brightness value)
>>   {
>> @@ -80,6 +106,7 @@ static void led_timer_function(struct timer_list *t)
>>       }
>>         led_set_brightness_nosleep(led_cdev, brightness);
>> +    __led_handle_regulator(led_cdev, brightness);
>
> Again this seems to indicate that the regulator is a required property 
> for the LEDs
>
> This needs to be made optional.  And the same comment through out for 
> every call.
>
>
>>         /* Return in next iteration if led is in one-shot mode and we 
>> are in
>>        * the final blink state so that the led is toggled each 
>> delay_on +
>> @@ -115,6 +142,8 @@ static void set_brightness_delayed(struct 
>> work_struct *ws)
>>       if (ret == -ENOTSUPP)
>>           ret = __led_set_brightness_blocking(led_cdev,
>>                       led_cdev->delayed_set_value);
>> +    __led_handle_regulator(led_cdev, led_cdev->delayed_set_value);
>> +
>>       if (ret < 0 &&
>>           /* LED HW might have been unplugged, therefore don't warn */
>>           !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
>> @@ -141,6 +170,7 @@ static void led_set_software_blink(struct 
>> led_classdev *led_cdev,
>>       /* never on - just set to off */
>>       if (!delay_on) {
>>           led_set_brightness_nosleep(led_cdev, LED_OFF);
>> +        __led_handle_regulator(led_cdev, LED_OFF);
>>           return;
>>       }
>>   @@ -148,6 +178,7 @@ static void led_set_software_blink(struct 
>> led_classdev *led_cdev,
>>       if (!delay_off) {
>>           led_set_brightness_nosleep(led_cdev,
>>                          led_cdev->blink_brightness);
>> +        __led_handle_regulator(led_cdev, led_cdev->blink_brightness);
>>           return;
>>       }
>>   @@ -256,8 +287,14 @@ void led_set_brightness_nopm(struct 
>> led_classdev *led_cdev,
>>                     enum led_brightness value)
>>   {
>>       /* Use brightness_set op if available, it is guaranteed not to 
>> sleep */
>> -    if (!__led_set_brightness(led_cdev, value))
>> -        return;
>> +    if (!__led_set_brightness(led_cdev, value)) {
>> +        /*
>> +         * if regulator state doesn't need to be changed, that is all/
>> +         * Otherwise delegate the change to a work queue
>> +         */
>> +        if (!__led_need_regulator_update(led_cdev, value))
>> +            return;
>> +    }
>>         /* If brightness setting can sleep, delegate it to a work 
>> queue task */
>>       led_cdev->delayed_set_value = value;
>> @@ -280,6 +317,8 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nosleep);
>>   int led_set_brightness_sync(struct led_classdev *led_cdev,
>>                   enum led_brightness value)
>>   {
>> +    int ret;
>> +
>>       if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
>>           return -EBUSY;
>>   @@ -288,7 +327,15 @@ int led_set_brightness_sync(struct 
>> led_classdev *led_cdev,
>>       if (led_cdev->flags & LED_SUSPENDED)
>>           return 0;
>>   -    return __led_set_brightness_blocking(led_cdev, 
>> led_cdev->brightness);
>> +    ret = __led_set_brightness_blocking(led_cdev, 
>> led_cdev->brightness);
>> +    if (ret)
>> +        return ret;
>> +
>> +    ret = __led_handle_regulator(led_cdev, led_cdev->brightness);
>
> Can't you just return here?

ok


thanks for the review

JJ

>
> Dan
>
>> +    if (ret)
>> +        return ret;
>> +
>> +    return 0;
>>   }
>>   EXPORT_SYMBOL_GPL(led_set_brightness_sync);
>>   diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index 9b2bf574a17a..bee8e3f8dddd 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -123,6 +123,10 @@ struct led_classdev {
>>         /* Ensures consistent access to the LED Flash Class device */
>>       struct mutex        led_access;
>> +
>> +    /* regulator */
>> +    struct regulator    *regulator;
>> +    bool            regulator_state;
>>   };
>>     extern int of_led_classdev_register(struct device *parent,