On Wed, Feb 07, 2018 at 03:13:35PM +0100, Enric Balletbo i Serra wrote:
> The num-interpolated-steps property specifies the number of
> interpolated steps between each value of brightness-level table. This is
> useful for high resolution PWMs to not have to list out every possible
> value in the brightness-level array.
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
Acked-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> ---
> Changes since v1:
> - Add an example with a small but realistic curve. Suggested by Rob and
> Daniel
>
> .../bindings/leds/backlight/pwm-backlight.txt | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> index 310810906613..ce9b5746b774 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> @@ -21,6 +21,11 @@ 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.
> + - 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 +44,17 @@ 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>;
> + };
> --
> 2.15.1
>
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