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| -rw-r--r-- | Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt new file mode 100644 index 000000000..64fa2fbd9 --- /dev/null +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt @@ -0,0 +1,61 @@ +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>; + }; |