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Date: Tue, 15 Sep 2020 08:31:55 -0600
From: Rob Herring <robh@...nel.org>
To: Andreas Kemnade <andreas@...nade.info>
Cc: Jonathan Neuschäfer <j.neuschaefer@....net>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Lee Jones <lee.jones@...aro.org>,
Thierry Reding <thierry.reding@...il.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>,
Alessandro Zummo <a.zummo@...ertech.it>,
Alexandre Belloni <alexandre.belloni@...tlin.com>,
Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
NXP Linux Team <linux-imx@....com>,
Sam Ravnborg <sam@...nborg.org>,
Linus Walleij <linus.walleij@...aro.org>,
Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
Stephan Gerhold <stephan@...hold.net>,
Lubomir Rintel <lkundrak@...sk>,
Mark Brown <broonie@...nel.org>, allen <allen.chen@....com.tw>,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
devicetree@...r.kernel.org,
Linux PWM List <linux-pwm@...r.kernel.org>,
"open list:REAL TIME CLOCK (RTC) SUBSYSTEM"
<linux-rtc@...r.kernel.org>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Heiko Stuebner <heiko@...ech.de>,
Josua Mayer <josua.mayer@....eu>,
Arnd Bergmann <arnd@...db.de>, Daniel Palmer <daniel@...f.com>
Subject: Re: [PATCH v2 04/10] dt-bindings: pwm: Add bindings for PWM function
in Netronix EC
On Tue, Sep 15, 2020 at 12:24 AM Andreas Kemnade <andreas@...nade.info> wrote:
>
> Hi,
>
> On Mon, 14 Sep 2020 18:54:43 -0600
> Rob Herring <robh@...nel.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@....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@....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.
If not probeable, then the compatible string should distinguish that.
Rob
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