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-rw-r--r--dts/Bindings/leds/backlight/pwm-backlight.txt34
1 files changed, 27 insertions, 7 deletions
diff --git a/dts/Bindings/leds/backlight/pwm-backlight.txt b/dts/Bindings/leds/backlight/pwm-backlight.txt
index 3108109..64fa2fb 100644
--- a/dts/Bindings/leds/backlight/pwm-backlight.txt
+++ b/dts/Bindings/leds/backlight/pwm-backlight.txt
@@ -3,13 +3,6 @@ pwm-backlight bindings
Required properties:
- compatible: "pwm-backlight"
- pwms: OF device-tree PWM specification (see PWM binding[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)
- power-supply: regulator for supply voltage
Optional properties:
@@ -21,6 +14,19 @@ Optional properties:
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
@@ -39,3 +45,17 @@ Example:
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>;
+ };