linux-kernel - Re: [PATCH v4 2/3] dt-bindings: clock: add TI CDCE6214 binding

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Message-ID: <aBxbr8CyKmdZQobS@pengutronix.de>
Date: Thu, 8 May 2025 09:22:23 +0200
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Stephen Boyd <sboyd@...nel.org>
Cc: Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Michael Turquette <mturquette@...libre.com>,
	Rob Herring <robh@...nel.org>, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	kernel@...gutronix.de,
	Alvin Šipraga <alsi@...g-olufsen.dk>
Subject: Re: [PATCH v4 2/3] dt-bindings: clock: add TI CDCE6214 binding

On Wed, May 07, 2025 at 01:11:31PM -0700, Stephen Boyd wrote:
> Quoting Sascha Hauer (2025-05-07 01:05:13)
> > On Mon, May 05, 2025 at 10:50:49AM -0700, Stephen Boyd wrote:
> > > Quoting Sascha Hauer (2025-04-30 02:01:35)
> > > > diff --git a/Documentation/devicetree/bindings/clock/ti,cdce6214.yaml b/Documentation/devicetree/bindings/clock/ti,cdce6214.yaml
> > > > new file mode 100644
> > > > index 0000000000000..d4a3a3df9ceb9
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/clock/ti,cdce6214.yaml
> > > > @@ -0,0 +1,155 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > +
> > > > +patternProperties:
> > > > +  '^clk@[0-1]$':
> > > > +    type: object
> > > > +    description:
> > > > +      optional child node that can be used to specify input pin parameters. The reg
> > > > +      properties match the CDCE6214_CLK_* defines.
> > > 
> > > Presumably the EEPROM is typically used to configure all this stuff? Do
> > > you actually need to program this from the kernel, or are you
> > > implementing all this for development purposes?
> > 
> > The EEPROM could be used to configure this. I don't know if the final
> > product will have the EEPROM programmed, but even if it is, should we
> > make this mandatory?
> 
> No I'm not asking about making the property/node required. I'm wondering
> if you're actually using these bindings. If they're not used then I
> worry we're putting a bunch of configuration in here that we'll never
> use.

At the moment we are using the device tree binding. I asked our customer if
they plan to use it in production as well.

> 
> > 
> > Speaking of the EEPROM I think we should make sure that the pin
> > configuration in the device tree is optional so that we do not overwrite
> > settings from the EEPROM if it contains valid values.
> 
> Ok. Aren't the pinctrl settings already optional?

Yes, they are, but when the pin setup is missing I haven't explicitly taken
care to not overwrite any settings made by the EEPROM. Likely the driver
just does it right. Without pin setup the registers are just not
touched.

Sascha

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