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. A sysfs interface is made available to dynamically enable/disable this feature and tune the off-delay. Signed-off-by: Jean-Jacques Hiblot <[email protected]> --- drivers/leds/led-class.c | 156 +++++++++++++++++++++++++++++++++++++-- drivers/leds/led-core.c | 129 +++++++++++++++++++++++++++++++- drivers/leds/leds.h | 18 +++++ include/linux/leds.h | 9 +++ 4 files changed, 304 insertions(+), 8 deletions(-) diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c index c5ff1d3d00a3..c1ad89d56129 100644 --- a/drivers/leds/led-class.c +++ b/drivers/leds/led-class.c @@ -25,6 +25,112 @@ static struct class *leds_class; +static ssize_t regulator_auto_off_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct led_classdev *led_cdev = dev_get_drvdata(dev); + + return sprintf(buf, "%s\n", + led_cdev->reg_auto_off ? "enabled" : "disabled"); +} + +static ssize_t regulator_auto_off_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t size) +{ + struct led_classdev *led_cdev = dev_get_drvdata(dev); + ssize_t ret = size; + bool auto_off; + + if (strncmp(buf, "enable\n", size) == 0) + auto_off = true; + else if (strncmp(buf, "disable\n", size) == 0) + auto_off = false; + else + return -EINVAL; + + mutex_lock(&led_cdev->led_access); + + if (led_sysfs_is_disabled(led_cdev)) { + ret = -EBUSY; + goto unlock; + } + + /* no changes ? */ + if (led_cdev->reg_auto_off == auto_off) + goto unlock; + led_cdev->reg_auto_off = auto_off; + + /* cancel a possibly pending auto-off operation */ + if (!auto_off) + cancel_delayed_work(&led_cdev->reg_off_work); + + /* + * call led_set_brightness_nopm() to trigger an update of the + * regulator's state. + */ + led_set_brightness_nopm(led_cdev, led_cdev->brightness); + flush_work(&led_cdev->set_brightness_work); + +unlock: + mutex_unlock(&led_cdev->led_access); + return ret; +} +static DEVICE_ATTR_RW(regulator_auto_off); + +static ssize_t regulator_auto_off_delay_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct led_classdev *led_cdev = dev_get_drvdata(dev); + + return sprintf(buf, "%u ms\n", led_cdev->reg_off_delay); +} + +static ssize_t regulator_auto_off_delay_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t size) +{ + struct led_classdev *led_cdev = dev_get_drvdata(dev); + unsigned long delay; + ssize_t ret; + + mutex_lock(&led_cdev->led_access); + + if (led_sysfs_is_disabled(led_cdev)) { + ret = -EBUSY; + goto unlock; + } + + ret = kstrtoul(buf, 10, &delay); + if (ret) + goto unlock; + ret = size; + + if (led_cdev->reg_off_delay == delay) + goto unlock; + led_cdev->reg_off_delay = delay; + + if (!led_cdev->reg_auto_off) + goto unlock; + + /* + * If a auto-off operation is in progress cancel it, + * and re-trigger it with the new delay + */ + if (cancel_delayed_work(&led_cdev->reg_off_work)) + schedule_delayed_work(&led_cdev->reg_off_work, + msecs_to_jiffies(led_cdev->reg_off_delay)); +unlock: + mutex_unlock(&led_cdev->led_access); + return ret; +} +static DEVICE_ATTR_RW(regulator_auto_off_delay); + +static struct attribute *auto_off_attrs[] = { + &dev_attr_regulator_auto_off.attr, + &dev_attr_regulator_auto_off_delay.attr, + NULL +}; +ATTRIBUTE_GROUPS(auto_off); + static ssize_t brightness_show(struct device *dev, struct device_attribute *attr, char *buf) { @@ -351,6 +457,7 @@ 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) { @@ -385,14 +492,38 @@ 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); + ret = PTR_ERR(regulator); + goto error; + } + led_cdev->regulator = NULL; + } else { + mutex_init(&led_cdev->regulator_access); + led_cdev->regulator = regulator; + if (fwnode_property_read_u32(init_data->fwnode, "off-delay-ms", + &led_cdev->reg_off_delay)) { + led_cdev->reg_auto_off = false; + atomic_set(&led_cdev->regulator_state, REG_R_ON_U_OFF); + ret = regulator_enable(led_cdev->regulator); + if (ret) + goto error; + } else { + led_cdev->reg_auto_off = true; + atomic_set(&led_cdev->regulator_state, REG_R_OFF_U_OFF); + } + ret = device_add_groups(led_cdev->dev, auto_off_groups); + if (ret) + goto error; + } + if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) { ret = led_add_brightness_hw_changed(led_cdev); - if (ret) { - device_unregister(led_cdev->dev); - led_cdev->dev = NULL; - mutex_unlock(&led_cdev->led_access); - return ret; - } + if (ret) + goto error; } led_cdev->work_flags = 0; @@ -424,7 +555,14 @@ int led_classdev_register_ext(struct device *parent, led_cdev->name); return 0; + +error: + device_unregister(led_cdev->dev); + led_cdev->dev = NULL; + mutex_unlock(&led_cdev->led_access); + return ret; } + EXPORT_SYMBOL_GPL(led_classdev_register_ext); /** @@ -450,6 +588,7 @@ void led_classdev_unregister(struct led_classdev *led_cdev) /* Stop blinking */ led_stop_software_blink(led_cdev); + led_cdev->reg_off_delay = 0; led_set_brightness(led_cdev, LED_OFF); flush_work(&led_cdev->set_brightness_work); @@ -464,6 +603,11 @@ void led_classdev_unregister(struct led_classdev *led_cdev) up_write(&leds_list_lock); mutex_destroy(&led_cdev->led_access); + if (led_cdev->regulator) { + if (!led_cdev->reg_auto_off) + regulator_disable(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..d2253524670d 100644 --- a/drivers/leds/led-core.c +++ b/drivers/leds/led-core.c @@ -37,6 +37,74 @@ 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 +203,8 @@ 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 +259,7 @@ 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 +340,62 @@ 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 the regulator must not be turned OFF automatically, + * make sure it is turned ON. + */ + if (!led_cdev->reg_auto_off) + regulator_on = true; + + 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..b0a4d1f56825 100644 --- a/include/linux/leds.h +++ b/include/linux/leds.h @@ -149,6 +149,15 @@ 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; + bool reg_auto_off; + int reg_off_delay; + struct delayed_work reg_off_work; + }; /** -- 2.17.1
