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Message-ID: <ed008eeec841448fb597b144a8f706a3ae1a513e.camel@gmail.com>
Date: Tue, 11 Feb 2025 10:01:51 +0000
From: Nuno Sá <noname.nuno@...il.com>
To: Jonathan Cameron <jic23@...nel.org>, Conor Dooley <conor@...nel.org>
Cc: Robert Budai <robert.budai@...log.com>, Lars-Peter Clausen
<lars@...afoo.de>, Michael Hennerich <Michael.Hennerich@...log.com>,
Alexandru Ardelean <alexandru.ardelean@...log.com>, Rob Herring
<robh+dt@...nel.org>, Krzysztof Kozlowski
<krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
Jonathan Corbet <corbet@....net>, Nuno Sa <nuno.sa@...log.com>, Ramona
Gradinariu <ramona.gradinariu@...log.com>, Trevor Gamblin
<tgamblin@...libre.com>, Marcelo Schmitt <marcelo.schmitt@...log.com>,
Paul Cercueil <paul@...pouillou.net>, David Lechner
<dlechner@...libre.com>, Antoniu Miclaus <antoniu.miclaus@...log.com>,
linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v6 4/6] dt-bindings: iio: Add adis16550 bindings
On Sat, 2025-02-08 at 15:38 +0000, Jonathan Cameron wrote:
> On Wed, 5 Feb 2025 19:52:37 +0000
> Conor Dooley <conor@...nel.org> wrote:
>
> > On Wed, Feb 05, 2025 at 04:11:51PM +0000, Nuno Sá wrote:
> > > On Tue, 2025-02-04 at 19:25 +0000, Conor Dooley wrote:
> > > > On Tue, Feb 04, 2025 at 04:36:08PM +0200, Robert Budai wrote:
> > > > > Document the ADIS16550 device devicetree bindings.
> > > > >
> > > > > Co-developed-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> > > > > Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> > > > > Signed-off-by: Ramona Gradinariu <ramona.gradinariu@...log.com>
> > > > > Signed-off-by: Robert Budai <robert.budai@...log.com>
> > > > > ---
> > > > >
> > > > > v6:
> > > > > - applied blank line suggestions
> > > > > - added clock-frequency dependency change suggestions
> > > > > - yamllint corrections
> > > > >
> > > > > .../bindings/iio/imu/adi,adis16550.yaml | 83
> > > > > +++++++++++++++++++
> > > > > MAINTAINERS | 9 ++
> > > > > 2 files changed, 92 insertions(+)
> > > > > create mode 100644
> > > > > Documentation/devicetree/bindings/iio/imu/adi,adis16550.yaml
> > > > >
> > > > > diff --git
> > > > > a/Documentation/devicetree/bindings/iio/imu/adi,adis16550.yaml
> > > > > b/Documentation/devicetree/bindings/iio/imu/adi,adis16550.yaml
> > > > > new file mode 100644
> > > > > index 000000000000..8750bb937979
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/iio/imu/adi,adis16550.yaml
> > > > > @@ -0,0 +1,83 @@
> > > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > > +%YAML 1.2
> > > > > +---
> > > > > +$id: http://devicetree.org/schemas/iio/imu/adi,adis16550.yaml#
> > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > > +
> > > > > +title: Analog Devices ADIS16550 and similar IMUs
> > > > > +
> > > > > +maintainers:
> > > > > + - Nuno Sa <nuno.sa@...log.com>
> > > > > + - Ramona Gradinariu <ramona.gradinariu@...log.com>
> > > > > + - Antoniu Miclaus <antoniu.miclaus@...log.com>
> > > > > +
> > > > > +properties:
> > > > > + compatible:
> > > > > + enum:
> > > > > + - adi,adis16550
> > > > > +
> > > > > + reg:
> > > > > + maxItems: 1
> > > > > +
> > > > > + spi-cpha: true
> > > > > + spi-cpol: true
> > > > > +
> > > > > + spi-max-frequency:
> > > > > + maximum: 15000000
> > > > > +
> > > > > + vdd-supply: true
> > > > > +
> > > > > + interrupts:
> > > > > + maxItems: 1
> > > > > +
> > > > > + reset-gpios:
> > > > > + description:
> > > > > + Must be the device tree identifier of the RESET pin. If
> > > > > specified,
> > > > > + it will be asserted during driver probe. As the line is active
> > > > > low,
> > > > > + it should be marked GPIO_ACTIVE_LOW.
> > > > > + maxItems: 1
> > > > > +
> > > > > + clocks:
> > > > > + description: If not provided, then the internal clock is used.
> > > > > + maxItems: 1
> > > > > +
> > > > > + clock-frequency:
> > > > > + description: Clock frequency in Hz when an external clock is
> > > > > used.
> > > > > + oneOf:
> > > > > + - minimum: 1
> > > > > + maximum: 128
> > > > > + - minimum: 3000
> > > > > + maximum: 4500
> > > >
> > > > I don't get why this is a property, to be honest. When you've got an
> > > > external clock, why isn't the frequency obtained from the clock provider
> > > > node?
> > > >
> > >
> > > The main purpose of this property is actually to show/document the
> > > constrains of
> > > the external clock. We can very well just error out in the driver (and we
> > > do
> > > that) and not have this property. I mentioned this property to Robert some
> > > revisions ago and I also pointed out that I wasn't really sure if it
> > > should be
> > > used or not (I guess this is more for fixed clock providers...). IIRC, I
> > > did
> > > asked for some advice/comments but we got none so I assume Robert just
> > > decided
> > > to use it and see what you guys had to say about it.
> >
> > NGL, this is one of the kinda of things where if you're relying on
> > dt-bindings to avoid cocking up your board design, things have already
> > gotten pretty badly wrong! That said, "clock-frequency" is a
> > property for cpus, fixed-frequency clock providers and i2c buses, you'd
> > need a vendor prefix and a unit suffix here IMO. Also, I don't really
> > think that it actually does anything at all, given it does not constrain the
> > clock you're linking to with the clocks property. This may as well just be
> > a comment in the description of the clocks property, for all that it does.
>
> I'd just drop it.
>
Agreed...
- Nuno Sá
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