LEDs provide status about the following:
LEDs can be configured as simple GPIOs, with on/off control only, or as PWM with adjustment brightness and color.
The CONFIG_PLATFORM_EC_LED_DT option, found in the Kconfig.led_dt file, enables devicetree based configuration of LED policies and colors.
Enabling the devicetree LED implementation requires that you disable the legacy EC implementation.
Example:
# LED CONFIG_PLATFORM_EC_LED_COMMON=n
The animation tick interval can be configured via CONFIG_PLATFORM_EC_LED_ANIMATION_TICK_MS (default 30ms). Lower values result in smoother animations but increase CPU usage.
Enable other config options supported in the legacy code.
LEDs are configured in two steps.
The LED colors are configured using either GPIO based LEDs or PWM based LEDs.
Configure GPIO based LEDs using cros-ec,gpio-led-pins compatible node described by cros-ec,gpio_led_pins.yaml.
Example:
For this example, the board contains dual-channel LED, one channel turns on the blue color, and one channel turns on the amber color. To set the LED color to amber, the yellow channel is enabled and the blue channel is disabled.
led_pins: gpio-led-pins {
compatible = "cros-ec,gpio-led-pins";
/* Amber - turn on yellow LED */
color_amber: color-amber {
led-pins = <&gpio_ec_chg_led_y_c1 &gpio_ec_chg_led_b_c1>;
led-values = <1 0>;
};
/* Blue - turn on blue LED */
color_blue: color-blue {
led-pins = <&gpio_ec_chg_led_y_c1 &gpio_ec_chg_led_b_c1>;
led-values = <0 1>;
};
/* White - turn on both LEDs */
color_white: color-white {
led-pins = <&gpio_ec_chg_led_y_c1 &gpio_ec_chg_led_b_c1>;
led-values = <1 1>;
};
/* Off - turn off both LEDs */
color_off: color-off {
led-pins = <&gpio_ec_chg_led_y_c1 &gpio_ec_chg_led_b_c1>;
led-values = <0 0>;
};
};
GPIO LED Pins dts file example: led_pins_herobrine.dts
Configure PWM based LEDs with two separate nodes. The pwm-leds node, described in pwm-leds.yaml, configures the PWM channel and frequency. The cros-ec,pwm-led-pins node, described in cros-ec,pwm_led_pins.yaml, configures the LED colors. PWM LEDs can vary duty-cycle percentage, providing finer color control over GPIO LEDs.
Example:
For this example, the board contains dual-channel LED, one channel controls white color intensity, and one channel controls the amber color intensity. To set the LED color to amber, the yellow channel duty-cycle is set to 100 percentage and white channel duty-cycle is set to 0.
pwmleds {
compatible = "pwm-leds";
pwm_y: pwm_y {
pwms = <&pwm2 0 PWM_HZ(100) PWM_POLARITY_INVERTED>;
};
pwm_w: pwm_w {
pwms = <&pwm3 0 PWM_HZ(100) PWM_POLARITY_INVERTED>;
};
};
led_pins: pwm-led-pins {
compatible = "cros-ec,pwm-led-pins";
pwm-frequency = <100>;
/* Amber - turn on yellow LED */
color_amber: color-amber {
led-pwms = <&pwm_y &pwm_w>;
pwm-values = <100 0>;
};
/* White - turn on white LED */
color_white: color-white {
led-pwms = <&pwm_y &pwm_w>;
pwm-values = <0 100>;
};
/* Off - turn off both LEDs */
color_off: color-off {
led-pwms = <&pwm_y &pwm_w>;
pwm-values = <0 0>;
};
};
PWM LED Pins dts file example: led_pins_skyrim.dts
cros-ec,led-policy nodes describe the LED policy and set the LED behavior by referencing cros-ec,gpio-led-pins or cros-ec,pwm-led-pins nodes. These are described in cros-ec,led_policy.yaml
Example:
Color policies to configure physical behavior of an LED
e.g. If you want an LED to blink, create 2 color policies, one to turn on the LED and one to turn off the LED.
color-0 {
led-color = <&color_amber>;
period-ms = <1000>;
};
color-1 {
led-color = <&color-off>;
period-ms = <1000>;
};
To tie this behavior with a system state, properties defining system state and color policies are added to cros-ec,led-policy node.
e.g. To add a blinking behavior for a system state where charge-state is “LED_PWR_STATE_DISCHARGE” and chipset-state is “POWER_S3”, a policy node is defined as below.
led-policy {
compatible = "cros-ec,led-policy";
led-pins = <&led_pins>;
...
...
power-state-discharge-s3 {
charge-state = "LED_PWR_STATE_DISCHARGE";
chipset-state = "POWER_S3";
/* Amber 1 sec, off 3 sec */
color-0 {
led-color = <&color_amber>;
period-ms = <1000>;
};
color-1 {
led-color = <&color_off>;
period-ms = <3000>;
};
};
...
...
}
Note: It is recommended to split the policy specification and the pins specification into two devicetree files. e.g. led_policy_skyrim.dts, led_pins_skyrim.dts
LED policy dts file examples led_policy_skyrim.dts, led_policy_herobrine.dts
None
The LEDs are controlled by hook task in the file led_driver/led.c.
TODO: Enable support for ledtest
color-amberExample CL enabling single port pwm based LEDs