[PATCH v3 0/3] leds: Add control of the voltage/current regulator to the LED core

[PATCH v3 0/3] leds: Add control of the voltage/current regulator to the LED core

[Jean-Jacques Hiblot]

This series makes it possible for the LED core to manage the power supply
of a LED. It uses the regulator API to disable/enable the power if when the
LED is turned on/off.
This is especially useful in situations where the LED driver/controller is
not supplying the power.

While at it, throw in a fix for led_set_brightness_sync() so that it can
work with drivers that don't provide brightness_set_blocking()

changes in v3:
- reword device-tree description
- reword commit log
- remove regulator updates from functions used in atomic context. If the
  regulator must be updated, it is defered to a workqueue.
- Fix led_set_brightness_sync() to work with the non-blocking function
  __led_set_brightness()

changes in v2:
- use devm_regulator_get_optional() to avoid using the dummy regulator and
  do some unnecessary work

Jean-Jacques Hiblot (3):
  dt-bindings: leds: document the "power-supply" property
  leds: Add control of the voltage/current regulator to the LED core
  leds: Make led_set_brightness_sync() also use __led_set_brightness()

 .../devicetree/bindings/leds/common.txt       |  4 ++
 drivers/leds/led-class.c                      | 15 ++++++
 drivers/leds/led-core.c                       | 53 +++++++++++++++++--
 drivers/leds/leds.h                           |  1 +
 include/linux/leds.h                          |  4 ++
 5 files changed, 73 insertions(+), 4 deletions(-)

-- 
2.17.1

[PATCH v3 1/3] dt-bindings: leds: document the "power-supply" property

[Jean-Jacques Hiblot]

Sometimes LEDs are powered by a voltage/current regulator. Describing it
in the device-tree makes it possible for the LED core to enable/disable it
when needed.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Dan Murphy <dmurphy@ti.com>
---
 Documentation/devicetree/bindings/leds/common.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/leds/common.txt b/Documentation/devicetree/bindings/leds/common.txt
index 70876ac11367..f496ec1c1542 100644
--- a/Documentation/devicetree/bindings/leds/common.txt
+++ b/Documentation/devicetree/bindings/leds/common.txt
@@ -61,6 +61,9 @@ Optional properties for child nodes:
 - panic-indicator : This property specifies that the LED should be used,
 		    if at all possible, as a panic indicator.
 
+- power-supply : Is a phandle to a voltage/current regulator used to to power
+		 the LED.
+
 - trigger-sources : List of devices which should be used as a source triggering
 		    this LED activity. Some LEDs can be related to a specific
 		    device and should somehow indicate its state. E.g. USB 2.0
@@ -106,6 +109,7 @@ gpio-leds {
 		label = "Status";
 		linux,default-trigger = "heartbeat";
 		gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+		power-supply = <&led_regulator>;
 	};
 
 	usb {
-- 
2.17.1

[PATCH v3 2/3] leds: Add control of the voltage/current regulator to the LED core

[Jean-Jacques Hiblot]

Sometimes LEDs are powered by an external voltage/current regulator. Let
the LED core know about it. This allows the LED core to turn on or off
managed power supplies.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Dan Murphy <dmurphy@ti.com>
---
 drivers/leds/led-class.c | 15 +++++++++++++
 drivers/leds/led-core.c  | 47 +++++++++++++++++++++++++++++++++++++---
 drivers/leds/leds.h      |  1 +
 include/linux/leds.h     |  4 ++++
 4 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 4793e77808e2..cadd43c30d50 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -253,6 +253,7 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
 {
 	char name[LED_MAX_NAME_SIZE];
 	int ret;
+	struct regulator *regulator;
 
 	ret = led_classdev_next_name(led_cdev->name, name, sizeof(name));
 	if (ret < 0)
@@ -272,6 +273,20 @@ 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));
 
+	regulator = devm_regulator_get_optional(led_cdev->dev, "power");
+	if (IS_ERR(regulator)) {
+		if (PTR_ERR(regulator) != -ENODEV) {
+			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(regulator);
+		}
+		led_cdev->regulator = NULL;
+	} else {
+		led_cdev->regulator = regulator;
+	}
+
 	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..dab32cf778f2 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -23,6 +23,33 @@ 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_state = (brightness != LED_OFF);
+
+	return led_cdev->regulator && led_cdev->regulator_state != new_state;
+}
+
+static int __led_handle_regulator(struct led_classdev *led_cdev,
+				int brightness)
+{
+	int rc;
+
+	if (__led_need_regulator_update(led_cdev, brightness)) {
+
+		if (brightness != LED_OFF)
+			rc = regulator_enable(led_cdev->regulator);
+		else
+			rc = regulator_disable(led_cdev->regulator);
+		if (rc)
+			return rc;
+
+		led_cdev->regulator_state = (brightness != LED_OFF);
+	}
+	return 0;
+}
+
 static int __led_set_brightness(struct led_classdev *led_cdev,
 				enum led_brightness value)
 {
@@ -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) &&
@@ -256,8 +285,14 @@ 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 +315,8 @@ 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 +325,11 @@ 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;
+
+	return __led_handle_regulator(led_cdev, led_cdev->brightness);
 }
 EXPORT_SYMBOL_GPL(led_set_brightness_sync);
 
diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
index 47b229469069..5aa5c038bd38 100644
--- a/drivers/leds/leds.h
+++ b/drivers/leds/leds.h
@@ -11,6 +11,7 @@
 
 #include <linux/rwsem.h>
 #include <linux/leds.h>
+#include <linux/regulator/consumer.h>
 
 static inline int led_get_brightness(struct led_classdev *led_cdev)
 {
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,
-- 
2.17.1

Re: [PATCH v3 2/3] leds: Add control of the voltage/current regulator to the LED core

[Jacek Anaszewski]

Hi Jean,

Thank you for the updated patch set.

I have some more comments below.

On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
> Sometimes LEDs are powered by an external voltage/current regulator. Let
> the LED core know about it. This allows the LED core to turn on or off
> managed power supplies.
> 
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> Reviewed-by: Dan Murphy <dmurphy@ti.com>
> ---
>  drivers/leds/led-class.c | 15 +++++++++++++
>  drivers/leds/led-core.c  | 47 +++++++++++++++++++++++++++++++++++++---
>  drivers/leds/leds.h      |  1 +
>  include/linux/leds.h     |  4 ++++
>  4 files changed, 64 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 4793e77808e2..cadd43c30d50 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -253,6 +253,7 @@ int of_led_classdev_register(struct device *parent, struct device_node *np,
>  {
>  	char name[LED_MAX_NAME_SIZE];
>  	int ret;
> +	struct regulator *regulator;
>  
>  	ret = led_classdev_next_name(led_cdev->name, name, sizeof(name));
>  	if (ret < 0)
> @@ -272,6 +273,20 @@ 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));
>  
> +	regulator = devm_regulator_get_optional(led_cdev->dev, "power");
> +	if (IS_ERR(regulator)) {
> +		if (PTR_ERR(regulator) != -ENODEV) {
> +			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(regulator);
> +		}
> +		led_cdev->regulator = NULL;
> +	} else {
> +		led_cdev->regulator = regulator;
> +	}
> +
>  	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..dab32cf778f2 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -23,6 +23,33 @@ 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_state = (brightness != LED_OFF);

How about:

bool new_state = !!brightness;

> +
> +	return led_cdev->regulator && led_cdev->regulator_state != new_state;
> +}
> +static int __led_handle_regulator(struct led_classdev *led_cdev,
> +				int brightness)
> +{
> +	int rc;
> +
> +	if (__led_need_regulator_update(led_cdev, brightness)) {
> +
> +		if (brightness != LED_OFF)
> +			rc = regulator_enable(led_cdev->regulator);
> +		else
> +			rc = regulator_disable(led_cdev->regulator);
> +		if (rc)
> +			return rc;
> +
> +		led_cdev->regulator_state = (brightness != LED_OFF);
> +	}
> +	return 0;
> +}

Let's have these function names without leading underscores.

>  static int __led_set_brightness(struct led_classdev *led_cdev,
>  				enum led_brightness value)
>  {
> @@ -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 you called it from __led_set_brightness() and
from __led_set_brightness_blocking() you wouldn't need this change here.

> +
>  	if (ret < 0 &&
>  	    /* LED HW might have been unplugged, therefore don't warn */
>  	    !(ret == -ENODEV && (led_cdev->flags & LED_UNREGISTERING) &&
> @@ -256,8 +285,14 @@ 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;
> +	}

This change should be also not needed then.

>  
>  	/* If brightness setting can sleep, delegate it to a work queue task */
>  	led_cdev->delayed_set_value = value;
> @@ -280,6 +315,8 @@ 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 +325,11 @@ 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;
> +
> +	return __led_handle_regulator(led_cdev, led_cdev->brightness);

As well as this one.

>  }
>  EXPORT_SYMBOL_GPL(led_set_brightness_sync);
>  
> diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
> index 47b229469069..5aa5c038bd38 100644
> --- a/drivers/leds/leds.h
> +++ b/drivers/leds/leds.h
> @@ -11,6 +11,7 @@
>  
>  #include <linux/rwsem.h>
>  #include <linux/leds.h>
> +#include <linux/regulator/consumer.h>
>  
>  static inline int led_get_brightness(struct led_classdev *led_cdev)
>  {
> 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,
> 

-- 
Best regards,
Jacek Anaszewski

Re: [PATCH v3 2/3] leds: Add control of the voltage/current regulator to the LED core

[Jean-Jacques Hiblot]

On 18/07/2019 14:24, Jacek Anaszewski wrote:
> Hi Jean,
>
> Thank you for the updated patch set.
>
> I have some more comments below.
>
> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
>>   
>> +static bool __led_need_regulator_update(struct led_classdev *led_cdev,
>> +					int brightness)
>> +{
>> +	bool new_state = (brightness != LED_OFF);
> How about:
>
> bool new_state = !!brightness;

Throughout the code LED_OFF is used when the LED is turned off. I think 
it would be more consistent to use it there too.

>
>> +
>> +	return led_cdev->regulator && led_cdev->regulator_state != new_state;
>> +}
>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>> +				int brightness)
>> +{
>> +	int rc;
>> +
>> +	if (__led_need_regulator_update(led_cdev, brightness)) {
>> +
>> +		if (brightness != LED_OFF)
>> +			rc = regulator_enable(led_cdev->regulator);
>> +		else
>> +			rc = regulator_disable(led_cdev->regulator);
>> +		if (rc)
>> +			return rc;
>> +
>> +		led_cdev->regulator_state = (brightness != LED_OFF);
>> +	}
>> +	return 0;
>> +}
> Let's have these function names without leading underscores.
OK.
>
>>   static int __led_set_brightness(struct led_classdev *led_cdev,
>>   				enum led_brightness value)
>>   {
>> @@ -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 you called it from __led_set_brightness() and

We cannot call it from __led_set_brightness() because it is supposed not 
to block.

JJ

Re: [PATCH v3 2/3] leds: Add control of the voltage/current regulator to the LED core

[Jacek Anaszewski]

On 7/18/19 3:31 PM, Jean-Jacques Hiblot wrote:
> 
> On 18/07/2019 14:24, Jacek Anaszewski wrote:
>> Hi Jean,
>>
>> Thank you for the updated patch set.
>>
>> I have some more comments below.
>>
>> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
>>>   +static bool __led_need_regulator_update(struct led_classdev
>>> *led_cdev,
>>> +                    int brightness)
>>> +{
>>> +    bool new_state = (brightness != LED_OFF);
>> How about:
>>
>> bool new_state = !!brightness;
> 
> Throughout the code LED_OFF is used when the LED is turned off. I think
> it would be more consistent to use it there too.

Basically brightness is a scalar and 0 always means off.
We treat enum led_brightness as a legacy type - it is no
longer valid on the whole its span since LED_FULL = 255
was depreciated with addition of max_brightness property.

IMHO use of reverse logic here only hinders code analysis.

>>> +
>>> +    return led_cdev->regulator && led_cdev->regulator_state !=
>>> new_state;
>>> +}
>>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>>> +                int brightness)
>>> +{
>>> +    int rc;
>>> +
>>> +    if (__led_need_regulator_update(led_cdev, brightness)) {
>>> +
>>> +        if (brightness != LED_OFF)
>>> +            rc = regulator_enable(led_cdev->regulator);
>>> +        else
>>> +            rc = regulator_disable(led_cdev->regulator);
>>> +        if (rc)
>>> +            return rc;
>>> +
>>> +        led_cdev->regulator_state = (brightness != LED_OFF);
>>> +    }
>>> +    return 0;
>>> +}
>> Let's have these function names without leading underscores.
> OK.
>>
>>>   static int __led_set_brightness(struct led_classdev *led_cdev,
>>>                   enum led_brightness value)
>>>   {
>>> @@ -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 you called it from __led_set_brightness() and
> 
> We cannot call it from __led_set_brightness() because it is supposed not
> to block.

You're right. The problematic part is that with regulator handling
we cannot treat the whole brightness setting operation uniformly
for brightness_set op case, i.e. without mediation of a workqueue.

Now you have to fire workqueue in led_set_brightness_nopm()
even for brightness_set() op path, if regulator state needs update.
This is ugly and can be misleading. Can be also error prone and
have non-obvious implications for software blink state transitions.

I think we would first need to improve locking between the workqueue
and led_timer_function(). I proposed a patch [0] over a year
ago.

Only then we could think of adding another asynchronous dependency
to the brightness setting chain.

[0] https://lkml.org/lkml/2018/1/17/1144

-- 
Best regards,
Jacek Anaszewski

Re: [PATCH v3 2/3] leds: Add control of the voltage/current regulator to the LED core

[Jean-Jacques Hiblot]

Hi Jacek,

On 18/07/2019 19:49, Jacek Anaszewski wrote:
> On 7/18/19 3:31 PM, Jean-Jacques Hiblot wrote:
>> On 18/07/2019 14:24, Jacek Anaszewski wrote:
>>> Hi Jean,
>>>
>>> Thank you for the updated patch set.
>>>
>>> I have some more comments below.
>>>
>>> On 7/17/19 3:59 PM, Jean-Jacques Hiblot wrote:
>>>>    +static bool __led_need_regulator_update(struct led_classdev
>>>> *led_cdev,
>>>> +                    int brightness)
>>>> +{
>>>> +    bool new_state = (brightness != LED_OFF);
>>> How about:
>>>
>>> bool new_state = !!brightness;
>> Throughout the code LED_OFF is used when the LED is turned off. I think
>> it would be more consistent to use it there too.
> Basically brightness is a scalar and 0 always means off.
> We treat enum led_brightness as a legacy type - it is no
> longer valid on the whole its span since LED_FULL = 255
> was depreciated with addition of max_brightness property.
>
> IMHO use of reverse logic here only hinders code analysis.
>
>>>> +
>>>> +    return led_cdev->regulator && led_cdev->regulator_state !=
>>>> new_state;
>>>> +}
>>>> +static int __led_handle_regulator(struct led_classdev *led_cdev,
>>>> +                int brightness)
>>>> +{
>>>> +    int rc;
>>>> +
>>>> +    if (__led_need_regulator_update(led_cdev, brightness)) {
>>>> +
>>>> +        if (brightness != LED_OFF)
>>>> +            rc = regulator_enable(led_cdev->regulator);
>>>> +        else
>>>> +            rc = regulator_disable(led_cdev->regulator);
>>>> +        if (rc)
>>>> +            return rc;
>>>> +
>>>> +        led_cdev->regulator_state = (brightness != LED_OFF);
>>>> +    }
>>>> +    return 0;
>>>> +}
>>> Let's have these function names without leading underscores.
>> OK.
>>>>    static int __led_set_brightness(struct led_classdev *led_cdev,
>>>>                    enum led_brightness value)
>>>>    {
>>>> @@ -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 you called it from __led_set_brightness() and
>> We cannot call it from __led_set_brightness() because it is supposed not
>> to block.
> You're right. The problematic part is that with regulator handling
> we cannot treat the whole brightness setting operation uniformly
> for brightness_set op case, i.e. without mediation of a workqueue.
>
> Now you have to fire workqueue in led_set_brightness_nopm()
> even for brightness_set() op path, if regulator state needs update.
> This is ugly and can be misleading. Can be also error prone and
> have non-obvious implications for software blink state transitions.

Taking your queue I reworked the series to take better care of the 
concurrency issues.

I believe it's in better shape right now.

>
> I think we would first need to improve locking between the workqueue
> and led_timer_function(). I proposed a patch [0] over a year
> ago.

I tried the patch and get a lot of warning because of triggers on 
storage devices.

Making led_set_brightness() not callable from a IRQ context, is probably 
not the right approach anymore.


JJ

>
> Only then we could think of adding another asynchronous dependency
> to the brightness setting chain.
>
> [0] https://lkml.org/lkml/2018/1/17/1144
>

[PATCH v3 3/3] leds: Make led_set_brightness_sync() also use __led_set_brightness()

[Jean-Jacques Hiblot]

There are some LED drivers that do not implement brightness_set_blocking(),
for those drivers led_set_brightness_sync() cannot work.
Fixing it by calling first __led_set_brightness() and falling back to
__led_set_brightness_blocking() if it failed.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
---
 drivers/leds/led-core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index dab32cf778f2..4a0506081c0e 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -320,15 +320,19 @@ int led_set_brightness_sync(struct led_classdev *led_cdev,
 	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
 		return -EBUSY;
 
-	led_cdev->brightness = min(value, led_cdev->max_brightness);
+	value = min(value, led_cdev->max_brightness);
 
 	if (led_cdev->flags & LED_SUSPENDED)
 		return 0;
 
-	ret = __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
+	ret = __led_set_brightness(led_cdev, value);
+	if (ret == -ENOTSUPP)
+		ret = __led_set_brightness_blocking(led_cdev, value);
 	if (ret)
 		return ret;
 
+	led_cdev->brightness = value;
+
 	return __led_handle_regulator(led_cdev, led_cdev->brightness);
 }
 EXPORT_SYMBOL_GPL(led_set_brightness_sync);
-- 
2.17.1