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SubjectRe: [PATCH v2 04/10] dt-bindings: pwm: Add bindings for PWM function in Netronix EC
Hi,

On Mon, 14 Sep 2020 18:54:43 -0600
Rob Herring <robh@kernel.org> wrote:

> On Sat, Sep 05, 2020 at 03:32:24PM +0200, Jonathan Neuschäfer wrote:
> > The Netronix embedded controller as found in Kobo Aura and Tolino Shine
> > supports one PWM channel, which is used to control the frontlight
> > brightness on these devices.
> >
> > Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> > ---
> >
> > v2:
> > - Add plaintext binding to patch description, for comparison
> > - Fix pwm-cells property (should be 2, not 1)
> > - Add dummy regulator to example, because the pwm-backlight binding requires a
> > power supply
> >
> >
> > For reference, here is the binding in text form:
> >
> >
> > PWM functionality in Netronix Embedded Controller
> >
> > Required properties:
> > - compatible: should be "netronix,ntxec-pwm"
> > - #pwm-cells: should be 2.
> >
> > Available PWM channels:
> > - 0: The PWM channel controlled by registers 0xa1-0xa7
> >
> > Example:
> >
> > embedded-controller@43 {
> > compatible = "netronix,ntxec";
> > ...
> >
> > ec_pwm: pwm {
> > compatible = "netronix,ntxec-pwm";
> > #pwm-cells = <1>;
> > };
> > };
> >
> > ...
> >
> > backlight {
> > compatible = "pwm-backlight";
> > pwms = <&ec_pwm 0 50000>;
> > };
> > ---
> > .../bindings/mfd/netronix,ntxec.yaml | 19 +++++++++++
> > .../bindings/pwm/netronix,ntxec-pwm.yaml | 33 +++++++++++++++++++
> > 2 files changed, 52 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> > index 596df460f98eb..73c873dda3e70 100644
> > --- a/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> > +++ b/Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> > @@ -31,6 +31,9 @@ properties:
> > description:
> > The EC can signal interrupts via a GPIO line
> >
> > + pwm:
> > + $ref: ../pwm/netronix,ntxec-pwm.yaml
> > +
> > required:
> > - compatible
> > - reg
> > @@ -53,5 +56,21 @@ examples:
> > interrupts = <11 IRQ_TYPE_EDGE_FALLING>;
> > interrupt-controller;
> > #interrupt-cells = <1>;
> > +
> > + ec_pwm: pwm {
> > + compatible = "netronix,ntxec-pwm";
> > + #pwm-cells = <2>;
> > + };
> > };
> > };
> > +
> > + backlight {
> > + compatible = "pwm-backlight";
> > + pwms = <&ec_pwm 0 50000>;
> > + power-supply = <&backlight_regulator>;
> > + };
> > +
> > + backlight_regulator: regulator-dummy {
> > + compatible = "regulator-fixed";
> > + regulator-name = "backlight";
> > + };
> > diff --git a/Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml b/Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml
> > new file mode 100644
> > index 0000000000000..0c9d2801b8de1
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pwm/netronix,ntxec-pwm.yaml
> > @@ -0,0 +1,33 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/pwm/netronix,ntxec-pwm.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: PWM functionality in Netronix embedded controller
> > +
> > +maintainers:
> > + - Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> > +
> > +description: |
> > + See also Documentation/devicetree/bindings/mfd/netronix,ntxec.yaml
> > +
> > + The Netronix EC contains PWM functionality, which is usually used to drive
> > + the backlight LED.
> > +
> > + The following PWM channels are supported:
> > + - 0: The PWM channel controlled by registers 0xa1-0xa7
> > +
> > +allOf:
> > + - $ref: pwm.yaml#
> > +
> > +properties:
> > + compatible:
> > + const: netronix,ntxec-pwm
> > +
> > + "#pwm-cells":
> > + const: 2
>
> Just move this to the parent and make the parent a pwm provider. There's
> no need for child nodes for this or the rtc.
>
hmm, there are apparently devices without rtc. If there is a child node
for the rtc, the corresponding devicetrees could disable rtc by not
having that node.
But maybe using the controller version is also feasible for that task.

Regards,
Andreas

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