Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

   1 pwm-backlight bindings
   2
   3 Required properties:
   4   - compatible: "pwm-backlight"
   5   - pwms: OF device-tree PWM specification (see PWM binding[0])
   6   - power-supply: regulator for supply voltage
   7
   8 Optional properties:
   9   - pwm-names: a list of names for the PWM devices specified in the
  10                "pwms" property (see PWM binding[0])
  11   - enable-gpios: contains a single GPIO specifier for the GPIO which enables
  12                   and disables the backlight (see GPIO binding[1])
  13   - post-pwm-on-delay-ms: Delay in ms between setting an initial (non-zero) PWM
  14                           and enabling the backlight using GPIO.
  15   - pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
  16                       and setting PWM value to 0.
  17   - brightness-levels: Array of distinct brightness levels. Typically these
  18                        are in the range from 0 to 255, but any range starting at
  19                        0 will do. The actual brightness level (PWM duty cycle)
  20                        will be interpolated from these values. 0 means a 0% duty
  21                        cycle (darkest/off), while the last value in the array
  22                        represents a 100% duty cycle (brightest).
  23   - default-brightness-level: The default brightness level (index into the
  24                               array defined by the "brightness-levels" property).
  25   - num-interpolated-steps: Number of interpolated steps between each value
  26                             of brightness-levels table. This way a high
  27                             resolution pwm duty cycle can be used without
  28                             having to list out every possible value in the
  29                             brightness-level array.
  30
  31 [0]: Documentation/devicetree/bindings/pwm/pwm.txt
  32 [1]: Documentation/devicetree/bindings/gpio/gpio.txt
  33
  34 Example:
  35
  36         backlight {
  37                 compatible = "pwm-backlight";
  38                 pwms = <&pwm 0 5000000>;
  39
  40                 brightness-levels = <0 4 8 16 32 64 128 255>;
  41                 default-brightness-level = <6>;
  42
  43                 power-supply = <&vdd_bl_reg>;
  44                 enable-gpios = <&gpio 58 0>;
  45                 post-pwm-on-delay-ms = <10>;
  46                 pwm-off-delay-ms = <10>;
  47         };
  48
  49 Example using num-interpolation-steps:
  50
  51         backlight {
  52                 compatible = "pwm-backlight";
  53                 pwms = <&pwm 0 5000000>;
  54
  55                 brightness-levels = <0 2048 4096 8192 16384 65535>;
  56                 num-interpolated-steps = <2048>;
  57                 default-brightness-level = <4096>;
  58
  59                 power-supply = <&vdd_bl_reg>;
  60                 enable-gpios = <&gpio 58 0>;
  61         };