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