On Fri, Jun 19, 2020 at 11:53:41PM +0200, Sam Ravnborg wrote: > > diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml > > new file mode 100644 > > index 000000000000..7e1f109a38a4 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml > > @@ -0,0 +1,98 @@ > > +# SPDX-License-Identifier: GPL-2.0-only > > +%YAML 1.2 > > +--- > > +$id: http://devicetree.org/schemas/leds/backlight/pwm-backlight.yaml# > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > + > > +title: pwm-backlight bindings > > + > > +maintainers: > > + - Lee Jones <lee.jones@xxxxxxxxxx> > > + - Daniel Thompson <daniel.thompson@xxxxxxxxxx> > > + - Jingoo Han <jingoohan1@xxxxxxxxx> > > + > > +properties: > > + compatible: > > + const: pwm-backlight > > + > > + pwms: > > + maxItems: 1 > > + > > + pwm-names: true > > + > > + power-supply: > > + description: regulator for supply voltage > > + > > + enable-gpios: > > + description: Contains a single GPIO specifier for the GPIO which enables > > + and disables the backlight > > + maxItems: 1 > > + > > + post-pwm-on-delay-ms: > > + description: Delay in ms between setting an initial (non-zero) PWM and > > + enabling the backlight using GPIO. > > + > > + pwm-off-delay-ms: > > + description: Delay in ms between disabling the backlight using GPIO > > + and setting PWM value to 0. > > + > > + brightness-levels: > > + description: 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). > > + $ref: /schemas/types.yaml#/definitions/uint32-array > > + > > + default-brightness-level: > > + description: The default brightness level (index into the array defined > > + by the "brightness-levels" property). > > + $ref: /schemas/types.yaml#/definitions/uint32 > Same comment as before... Sorry the "ditto" meant I didn't thing about PWM as much as I should have. The situation for PWM is a little different to LED. That's mostly because we decided not to clutter the LED code with "num-interpolated-steps". The PWM code implements the default-brightness-level as an index into the brightness array *after* it has been expanded using interpolation. In other words today Linux treats the default-brightness-level more like[1]. description: The default brightness level. When num-interpolated-steps is not set this is simply an index into the array defined by the "brightness-levels" property. If num-interpolated-steps is set the brightness array will be expanded by interpolation before we index to get a default level. This is the best I have come up with so far... but I concede it still lacks elegance. Daniel. [1] I don't know my way round the BSD code bases to be sure what they do... I did a couple of web searches but didn't pull up anything definitive. > > > + > > + num-interpolated-steps: > > + description: 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. > > + $ref: /schemas/types.yaml#/definitions/uint32 > > + > > +dependencies: > > + default-brightness-level: [brightness-levels] > > + num-interpolated-steps: [brightness-levels] > > + > > +required: > > + - compatible > > + - pwms > > + - power-supply > > + > > +additionalProperties: false > > + > > +examples: > > + - | > > + backlight { > > + compatible = "pwm-backlight"; > > + pwms = <&pwm 0 5000000>; > > + > > + brightness-levels = <0 4 8 16 32 64 128 255>; > > + default-brightness-level = <6>; > > + > > + power-supply = <&vdd_bl_reg>; > > + enable-gpios = <&gpio 58 0>; > > + 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>; > > + }; > > + > > +... > > -- > > 2.25.1 > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
