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Subject: Re: [PATCH 1/2] leds: Add control of the voltage/current regulator to
 the LED core
To:     Jean-Jacques Hiblot <jjhiblot@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>
From:   Dan Murphy <dmurphy@ti.com>
Message-ID: <56d16260-ff82-3439-4c1f-2a3a1552bc7d@ti.com>
Date:   Fri, 12 Jul 2019 13:49:21 -0500
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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?

> +	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.

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.

> +
> +		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?

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,