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Subject[PATCH v6 2/2] leds: Add control of the voltage/current regulator to the LED core
Date
A LED is usually powered by a voltage/current regulator. Let the LED core
know about it. This allows the LED core to turn on or off the power supply
as needed.

Because turning ON/OFF a regulator might block, it is not done
synchronously but done in a workqueue. Turning ON the regulator is always
done as soon as possible, turning it off can be delayed by setting the
"power-off-delays-ms" property. The intent is to keep the regulator
powered on when the blink rate of the LED is high.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
---
drivers/leds/led-class.c | 21 +++++++
drivers/leds/led-core.c | 122 ++++++++++++++++++++++++++++++++++++++-
drivers/leds/leds.h | 18 ++++++
include/linux/leds.h | 8 +++
4 files changed, 167 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 80c96dd96afc..47d9f920091c 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -344,6 +344,7 @@ int led_classdev_register_ext(struct device *parent,
char final_name[LED_MAX_NAME_SIZE];
const char *proposed_name = composed_name;
int ret;
+ struct regulator *regulator;

if (init_data) {
if (init_data->devname_mandatory && !init_data->devicename) {
@@ -379,6 +380,24 @@ int led_classdev_register_ext(struct device *parent,
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 (regulator != ERR_PTR(-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 {
+ mutex_init(&led_cdev->regulator_access);
+ led_cdev->regulator = regulator;
+ atomic_set(&led_cdev->regulator_state, REG_R_OFF_U_OFF);
+ fwnode_property_read_u32(init_data->fwnode, "off-delay-ms",
+ &led_cdev->reg_off_delay);
+ }
+
if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
ret = led_add_brightness_hw_changed(led_cdev);
if (ret) {
@@ -458,6 +477,8 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
up_write(&leds_list_lock);

mutex_destroy(&led_cdev->led_access);
+ if (led_cdev->regulator)
+ mutex_destroy(&led_cdev->regulator_access);
}
EXPORT_SYMBOL_GPL(led_classdev_unregister);

diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index f1f718dbe0f8..81105c1ee907 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -37,6 +37,73 @@ const char * const led_colors[LED_COLOR_ID_MAX] = {
};
EXPORT_SYMBOL_GPL(led_colors);

+static void turn_off_regulator_if_needed(struct led_classdev *led_cdev)
+{
+ int old = atomic_cmpxchg(&led_cdev->regulator_state, REG_R_ON_U_OFF,
+ REG_R_OFF_U_OFF);
+ if (old == REG_R_ON_U_OFF) {
+ int rc = regulator_disable(led_cdev->regulator);
+
+ if (rc) {
+ dev_err(led_cdev->dev,
+ "Failed to disable the regulator (%d)\n", rc);
+ atomic_or(REG_R_ON, &led_cdev->regulator_state);
+ }
+ }
+}
+
+static void try_turn_on_regulator_if_needed(struct led_classdev *led_cdev)
+{
+ int old = atomic_cmpxchg(&led_cdev->regulator_state, REG_R_OFF_U_ON,
+ REG_R_ON_U_ON);
+ if (old == REG_R_OFF_U_ON) {
+ int rc = regulator_enable(led_cdev->regulator);
+
+ if (rc) {
+ dev_err(led_cdev->dev,
+ "Failed to enable the regulator (%d)\n", rc);
+ atomic_and(~REG_R_ON, &led_cdev->regulator_state);
+ }
+ }
+}
+
+static void turn_off_regulator_delayed(struct work_struct *ws)
+{
+ struct led_classdev *led_cdev =
+ container_of(ws, struct led_classdev, reg_off_work.work);
+
+ /*
+ * Take the lock to prevent very unlikely updates due to
+ * led_handle_regulator() being executed at the same time
+ */
+ mutex_lock(&led_cdev->regulator_access);
+
+ turn_off_regulator_if_needed(led_cdev);
+
+ mutex_unlock(&led_cdev->regulator_access);
+}
+
+static void led_handle_regulator(struct led_classdev *led_cdev)
+{
+ int delay = (led_cdev->flags & LED_SUSPENDED) ? 0 :
+ led_cdev->reg_off_delay;
+
+ if (!led_cdev->regulator)
+ return;
+
+ /*
+ * Take the lock to prevent very unlikely updates due to
+ * turn_off_regulator_delayed() being executed at the same time
+ */
+ mutex_lock(&led_cdev->regulator_access);
+
+ try_turn_on_regulator_if_needed(led_cdev);
+ if (!delay)
+ turn_off_regulator_if_needed(led_cdev);
+
+ mutex_unlock(&led_cdev->regulator_access);
+}
+
static int __led_set_brightness(struct led_classdev *led_cdev,
enum led_brightness value)
{
@@ -135,6 +202,8 @@ static void set_brightness_delayed(struct work_struct *ws)
(led_cdev->flags & LED_HW_PLUGGABLE)))
dev_err(led_cdev->dev,
"Setting an LED's brightness failed (%d)\n", ret);
+
+ led_handle_regulator(led_cdev);
}

static void led_set_software_blink(struct led_classdev *led_cdev,
@@ -189,6 +258,7 @@ static void led_blink_setup(struct led_classdev *led_cdev,
void led_init_core(struct led_classdev *led_cdev)
{
INIT_WORK(&led_cdev->set_brightness_work, set_brightness_delayed);
+ INIT_DELAYED_WORK(&led_cdev->reg_off_work, turn_off_regulator_delayed);

timer_setup(&led_cdev->blink_timer, led_timer_function, 0);
}
@@ -269,8 +339,56 @@ EXPORT_SYMBOL_GPL(led_set_brightness);
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))
+ bool defer_work = false;
+ bool regulator_on = !!value;
+
+
+ if (led_cdev->regulator) {
+ int old;
+
+ if (regulator_on)
+ old = atomic_fetch_or(REG_U_ON,
+ &led_cdev->regulator_state);
+ else
+ old = atomic_fetch_and(~REG_U_ON,
+ &led_cdev->regulator_state);
+
+ if (!regulator_on && old == REG_R_ON_U_ON) {
+ int delay = (led_cdev->flags & LED_SUSPENDED) ? 0 :
+ led_cdev->reg_off_delay;
+
+ /*
+ * the regulator must be turned off. This cannot be
+ * here because we can't sleep. Defer the job or, if a
+ * delay is asked for, schedule a delayed work
+ */
+ if (delay)
+ schedule_delayed_work(
+ &led_cdev->reg_off_work,
+ msecs_to_jiffies(delay));
+ else
+ defer_work = true;
+ } else if (regulator_on && old == REG_R_OFF_U_OFF) {
+ /*
+ * the regulator must be enabled. This cannot be here
+ * because we can't sleep. Defer the job
+ */
+ defer_work = true;
+ }
+ /*
+ * small optimization. Cancel the work that had been started
+ * to turn OFF the regulator. It wouldn't have been turned off
+ * anyway because regulator_state has changed to REG_R_x_U_ON
+ */
+ if (regulator_on && old == REG_R_ON_U_OFF)
+ cancel_delayed_work(&led_cdev->reg_off_work);
+ }
+
+ /*
+ * If defered work is not asked for, use brightness_set
+ * op now if available, it is guaranteed not to sleep
+ */
+ if (!defer_work && !__led_set_brightness(led_cdev, value))
return;

/* If brightness setting can sleep, delegate it to a work queue task */
diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
index 0b577cece8f7..5cb76e547b7d 100644
--- a/drivers/leds/leds.h
+++ b/drivers/leds/leds.h
@@ -11,6 +11,24 @@

#include <linux/rwsem.h>
#include <linux/leds.h>
+#include <linux/regulator/consumer.h>
+
+/*
+ * The regulator state tracks 2 boolean variables:
+ * - the state of regulator (or more precisely the state required by
+ * led core layer, as many users can interact with the same regulator).
+ * It is tracked by bit 0.
+ * - the state last asked-for by the LED user. It is tracked by bit 1.
+ */
+#define REG_R_ON BIT(0)
+#define REG_U_ON BIT(1)
+
+enum { REG_R_OFF_U_OFF = 0,
+ REG_R_ON_U_OFF = REG_R_ON,
+ REG_R_OFF_U_ON = REG_U_ON,
+ REG_R_ON_U_ON = REG_R_ON | REG_U_ON
+};
+

static inline int led_get_brightness(struct led_classdev *led_cdev)
{
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 9b94cf752012..90afbbc67bb0 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -149,6 +149,14 @@ struct led_classdev {

/* Ensures consistent access to the LED Flash Class device */
struct mutex led_access;
+
+ /* regulator */
+ struct regulator *regulator;
+ struct mutex regulator_access;
+ atomic_t regulator_state;
+ int reg_off_delay;
+ struct delayed_work reg_off_work;
+
};

/**
--
2.17.1
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