| Message ID | 20180208113032.27810-3-enric.balletbo@collabora.com |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | backlight: pwm_bl: support linear interpolation and brightness to human eye | expand |
On Thu, Feb 08, 2018 at 12:30:30PM +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@collabora.com> > Acked-by: Daniel Thompson <daniel.thompson@linaro.org> > --- > Changes since v2: > - Add Acked-by: Daniel Thompson <daniel.thompson@linaro.org> > 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(+) Reviewed-by: Rob Herring <robh@kernel.org> -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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>; + };