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pwm-backlight bindings
Required properties:
- compatible: "pwm-backlight"
- pwms: OF device-tree PWM specification (see PWM binding[0])
- power-supply: regulator for supply voltage
Optional properties:
- pwm-names: a list of names for the PWM devices specified in the
"pwms" property (see PWM binding[0])
- enable-gpios: contains a single GPIO specifier for the GPIO which enables
and disables the backlight (see GPIO binding[1])
- post-pwm-on-delay-ms: Delay in ms between setting an initial (non-zero) PWM
and enabling the backlight using GPIO.
- pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
and setting PWM value to 0.
- brightness-levels: Array of distinct brightness levels. Typically these
are in the range from 0 to 255, but any range starting at
0 will do. The actual brightness level (PWM duty cycle)
will be interpolated from these values. 0 means a 0% duty
cycle (darkest/off), while the last value in the array
represents a 100% duty cycle (brightest).
- default-brightness-level: The default brightness level (index into the
array defined by the "brightness-levels" property).
- num-interpolated-steps: Number of interpolated steps between each value
of brightness-levels table. This way a high
resolution pwm duty cycle can be used without
having to list out every possible value in the
brightness-level array.
[0]: Documentation/devicetree/bindings/pwm/pwm.txt
[1]: Documentation/devicetree/bindings/gpio/gpio.txt
Example:
backlight {
compatible = "pwm-backlight";
pwms = <&pwm 0 5000000>;
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
power-supply = <&vdd_bl_reg>;
enable-gpios = <&gpio 58 0>;
post-pwm-on-delay-ms = <10>;
pwm-off-delay-ms = <10>;
};
Example using num-interpolation-steps:
backlight {
compatible = "pwm-backlight";
pwms = <&pwm 0 5000000>;
brightness-levels = <0 2048 4096 8192 16384 65535>;
num-interpolated-steps = <2048>;
default-brightness-level = <4096>;
power-supply = <&vdd_bl_reg>;
enable-gpios = <&gpio 58 0>;
};
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