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Date:   Tue, 13 Oct 2020 14:08:23 +0200
From:   Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
To:     Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc:     f.fainelli@gmail.com, linux@roeck-us.net, jdelvare@suse.com,
        wahrenst@gmx.net, Eric Anholt <eric@anholt.net>,
        bcm-kernel-feedback-list@broadcom.com,
        linux-rpi-kernel@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-pwm@vger.kernel.org, Ray Jui <rjui@broadcom.com>,
        Scott Branden <sbranden@broadcom.com>,
        linux-hwmon@vger.kernel.org, robh+dt@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: pwm: Add binding for RPi firmware PWM
 bus
Message-ID: <20201013120823.hhy7wyqsb3f3ufnx@pengutronix.de>
References: <20201009153031.986-1-nsaenzjulienne@suse.de>
 <20201009153031.986-2-nsaenzjulienne@suse.de>
 <20201012070132.it23vl6f3ytavqgj@pengutronix.de>
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On Tue, Oct 13, 2020 at 12:35:38PM +0200, Nicolas Saenz Julienne wrote:
> Hi Uwe, thanks for having a look at this.
>=20
> On Mon, 2020-10-12 at 09:01 +0200, Uwe Kleine-K=F6nig wrote:
> > On Fri, Oct 09, 2020 at 05:30:28PM +0200, Nicolas Saenz Julienne wrote:
> > > The PWM bus controlling the fan in RPi's official PoE hat can only be
> > > controlled by the board's co-processor.
> > >=20
> > > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> > > ---
> > >  .../arm/bcm/raspberrypi,bcm2835-firmware.yaml | 21 +++++++++++++++++=
++
> > >  .../pwm/raspberrypi,firmware-pwm.h            | 13 ++++++++++++
> > >  2 files changed, 34 insertions(+)
> > >  create mode 100644 include/dt-bindings/pwm/raspberrypi,firmware-pwm.h
> > >=20
> > > diff --git a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bc=
m2835-firmware.yaml b/Documentation/devicetree/bindings/arm/bcm/raspberrypi=
,bcm2835-firmware.yaml
> > > index a2c63c8b1d10..dcaf00e8602e 100644
> > > --- a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-f=
irmware.yaml
> > > +++ b/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-f=
irmware.yaml
> > > @@ -64,6 +64,22 @@ properties:
> > >        - compatible
> > >        - "#reset-cells"
> > > =20
> > > +  pwm:
> > > +    type: object
> > > +
> > > +    properties:
> > > +      compatible:
> > > +        const: raspberrypi,firmware-pwm
> > > +
> > > +      "#pwm-cells":
> > > +        const: 1
> > > +        description: >
> > > +          The argument is the PWM bus number.
> >=20
> > This is wrong. #pwm-cells specifies the number of "arguments" for
> > phandles pointing to this node. And I would prefer this being 2 to match
> > the stuff described in the generic pwm binding.
>=20
> I saw buses out there with the same limitation as this one (unable to cha=
nge
> frequency) that used a single cell, so I whent with it. That said I'll be=
 happy
> to change it and drop the custom *_xlate() function in benefit of the def=
ault
> one.

As the first cell after the phandle is for the period and only the
second if for flags, this is a poor argument. So yes, use #pwm-cells =3D
<2> and drop the custom xlate() function please.

Best regards
Uwe

--=20
Pengutronix e.K.                           | Uwe Kleine-K=F6nig            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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