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

   1 # SPDX-License-Identifier: GPL-2.0-only
   2 %YAML 1.2
   3 ---
   4 $id: http://devicetree.org/schemas/leds/backlight/pwm-backlight.yaml#
   5 $schema: http://devicetree.org/meta-schemas/core.yaml#
   6
   7 title: pwm-backlight bindings
   8
   9 maintainers:
  10   - Lee Jones <lee.jones@linaro.org>
  11   - Daniel Thompson <daniel.thompson@linaro.org>
  12   - Jingoo Han <jingoohan1@gmail.com>
  13
  14 properties:
  15   compatible:
  16     const: pwm-backlight
  17
  18   pwms:
  19     maxItems: 1
  20
  21   pwm-names: true
  22
  23   power-supply:
  24     description: regulator for supply voltage
  25
  26   enable-gpios:
  27     description:
  28       Contains a single GPIO specifier for the GPIO which enables and disables
  29       the backlight.
  30     maxItems: 1
  31
  32   post-pwm-on-delay-ms:
  33     description:
  34       Delay in ms between setting an initial (non-zero) PWM and enabling the
  35       backlight using GPIO.
  36
  37   pwm-off-delay-ms:
  38     description:
  39       Delay in ms between disabling the backlight using GPIO and setting PWM
  40       value to 0.
  41
  42   brightness-levels:
  43     description:
  44       Array of distinct brightness levels. Typically these are in the range
  45       from 0 to 255, but any range starting at 0 will do. The actual brightness
  46       level (PWM duty cycle) will be interpolated from these values. 0 means a
  47       0% duty cycle (darkest/off), while the last value in the array represents
  48       a 100% duty cycle (brightest).
  49     $ref: /schemas/types.yaml#/definitions/uint32-array
  50
  51   default-brightness-level:
  52     description:
  53       The default brightness level (index into the array defined by the
  54       "brightness-levels" property).
  55     $ref: /schemas/types.yaml#/definitions/uint32
  56
  57   num-interpolated-steps:
  58     description:
  59       Number of interpolated steps between each value of brightness-levels
  60       table. This way a high resolution pwm duty cycle can be used without
  61       having to list out every possible value in the brightness-level array.
  62     $ref: /schemas/types.yaml#/definitions/uint32
  63
  64 dependencies:
  65   default-brightness-level: [brightness-levels]
  66   num-interpolated-steps: [brightness-levels]
  67
  68 required:
  69   - compatible
  70   - pwms
  71   - power-supply
  72
  73 additionalProperties: false
  74
  75 examples:
  76   - |
  77     backlight {
  78         compatible = "pwm-backlight";
  79         pwms = <&pwm 0 5000000>;
  80
  81         brightness-levels = <0 4 8 16 32 64 128 255>;
  82         default-brightness-level = <6>;
  83
  84         power-supply = <&vdd_bl_reg>;
  85         enable-gpios = <&gpio 58 0>;
  86         post-pwm-on-delay-ms = <10>;
  87         pwm-off-delay-ms = <10>;
  88     };
  89
  90   - |
  91     // Example using num-interpolation-steps:
  92     backlight {
  93         compatible = "pwm-backlight";
  94         pwms = <&pwm 0 5000000>;
  95
  96         brightness-levels = <0 2048 4096 8192 16384 65535>;
  97         num-interpolated-steps = <2048>;
  98         default-brightness-level = <4096>;
  99
 100         power-supply = <&vdd_bl_reg>;
 101         enable-gpios = <&gpio 58 0>;
 102     };
 103
 104 ...