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Subject[PATCH v4 4/5] leds: pwm: add support for default-state device property
Date
This patch adds support for "default-state" devicetree property, which
allows to defer pwm init to first use of led.

This allows to configure the PWM early in bootloader to let the LED
blink until an application in Linux userspace sets something different.

Signed-off-by: Denis Osterland-Heim <Denis.Osterland@diehl.com>
---
drivers/leds/leds-pwm.c | 54 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
index 07eab2d8b7c7..73d36d5fb427 100644
--- a/drivers/leds/leds-pwm.c
+++ b/drivers/leds/leds-pwm.c
@@ -18,10 +18,15 @@
#include <linux/pwm.h>
#include <linux/slab.h>

+#define LEDS_PWM_DEFSTATE_OFF 0
+#define LEDS_PWM_DEFSTATE_ON 1
+#define LEDS_PWM_DEFSTATE_KEEP 2
+
struct led_pwm {
const char *name;
const char *default_trigger;
u8 active_low;
+ u8 default_state;
unsigned int max_brightness;
};

@@ -88,7 +93,30 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,

led_data->cdev.brightness_set_blocking = led_pwm_set;

- pwm_init_state(led_data->pwm, &led_data->pwmstate);
+ /* init PWM state */
+ if (led->default_state == LEDS_PWM_DEFSTATE_KEEP) {
+ pwm_get_state(led_data->pwm, &led_data->pwmstate);
+ if (!led_data->pwmstate.period) {
+ led->default_state = LEDS_PWM_DEFSTATE_OFF;
+ dev_warn(dev,
+ "failed to read period for %s, default to off",
+ led->name);
+ }
+ }
+ if (led->default_state != LEDS_PWM_DEFSTATE_KEEP)
+ pwm_init_state(led_data->pwm, &led_data->pwmstate);
+
+ /* set brightness */
+ if (led->default_state == LEDS_PWM_DEFSTATE_ON)
+ led_data->cdev.brightness = led->max_brightness;
+ else if (led->default_state == LEDS_PWM_DEFSTATE_KEEP) {
+ uint64_t brightness;
+
+ brightness = led->max_brightness;
+ brightness *= led_data->pwmstate.duty_cycle;
+ do_div(brightness, led_data->pwmstate.period);
+ led_data->cdev.brightness = brightness;
+ }

ret = devm_led_classdev_register(dev, &led_data->cdev);
if (ret) {
@@ -97,11 +125,13 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
return ret;
}

- ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
- if (ret) {
- dev_err(dev, "failed to set led PWM value for %s: %d",
- led->name, ret);
- return ret;
+ if (led->default_state != LEDS_PWM_DEFSTATE_KEEP) {
+ ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
+ if (ret) {
+ dev_err(dev, "failed to set led PWM value for %s: %d",
+ led->name, ret);
+ return ret;
+ }
}

priv->num_leds++;
@@ -117,6 +147,8 @@ static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
memset(&led, 0, sizeof(led));

device_for_each_child_node(dev, fwnode) {
+ const char *state = NULL;
+
ret = fwnode_property_read_string(fwnode, "label", &led.name);
if (ret && is_of_node(fwnode))
led.name = to_of_node(fwnode)->name;
@@ -134,6 +166,16 @@ static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
fwnode_property_read_u32(fwnode, "max-brightness",
&led.max_brightness);

+ if (!fwnode_property_read_string(fwnode, "default-state",
+ &state)) {
+ if (!strcmp(state, "keep"))
+ led.default_state = LEDS_PWM_DEFSTATE_KEEP;
+ else if (!strcmp(state, "on"))
+ led.default_state = LEDS_PWM_DEFSTATE_ON;
+ else
+ led.default_state = LEDS_PWM_DEFSTATE_OFF;
+ }
+
ret = led_pwm_add(dev, priv, &led, fwnode);
if (ret) {
fwnode_handle_put(fwnode);
--
2.25.1


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