linux-kernel - Re: [PATCH v4 2/5] dt-bindings: iio: adc: ad7192: Update clock config

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Date: Sat, 15 Jun 2024 12:05:38 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Conor Dooley <conor@...nel.org>
Cc: Alisa-Dariana Roman <alisadariana@...il.com>, Alisa-Dariana Roman
 <alisa.roman@...log.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Michael Hennerich <michael.hennerich@...log.com>,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, Alexandru Tachici
 <alexandru.tachici@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, Rob
 Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor
 Dooley <conor+dt@...nel.org>, Liam Girdwood <lgirdwood@...il.com>, Mark
 Brown <broonie@...nel.org>
Subject: Re: [PATCH v4 2/5] dt-bindings: iio: adc: ad7192: Update clock
 config

On Thu, 13 Jun 2024 17:41:52 +0100
Conor Dooley <conor@...nel.org> wrote:

> On Thu, Jun 13, 2024 at 02:39:58PM +0300, Alisa-Dariana Roman wrote:
> > There are actually 4 configuration modes of clock source for AD719X
> > devices. Either a crystal can be attached externally between MCLK1 and
> > MCLK2 pins, or an external CMOS-compatible clock can drive the MCLK2
> > pin. The other 2 modes make use of the 4.92MHz internal clock.
> > 
> > Add clock name xtal alongside mclk. When an external crystal is
> > attached, xtal should be chosen. When an external clock is used, mclk
> > should be chosen.  
> 
> This is still missing an explanation of why a new name is needed.
> Hint: do you need to change register settings to use one versus the
> other?

Absolutely - dt reviewer shouldn't need to look at the code to find this
out as it wastes their over subscribed time!

> 
> > 
> > The presence of an external clock source is optional, not required. When
> > absent, internal clock is used. Modify required property accordingly and
> > modify second example to showcase this.
> > 
> > Signed-off-by: Alisa-Dariana Roman <alisa.roman@...log.com>
> > ---
> >  .../devicetree/bindings/iio/adc/adi,ad7192.yaml    | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7192.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7192.yaml
> > index a03da9489ed9..3ae2f860d24c 100644
> > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad7192.yaml
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7192.yaml
> > @@ -39,11 +39,15 @@ properties:
> >  
> >    clocks:
> >      maxItems: 1
> > -    description: phandle to the master clock (mclk)
> > +    description: |
> > +      Optionally, either a crystal can be attached externally between MCLK1 and
> > +      MCLK2 pins, or an external CMOS-compatible clock can drive the MCLK2
> > +      pin. If absent, internal 4.92MHz clock is used.

Trivial but doesn't need to be formatted, so don't think the | matters.

> >  
> >    clock-names:
> > -    items:
> > -      - const: mclk
> > +    enum:
> > +      - xtal
> > +      - mclk
> >  
> >    interrupts:
> >      maxItems: 1
> > @@ -135,8 +139,6 @@ patternProperties:
> >  required:
> >    - compatible
> >    - reg
> > -  - clocks
> > -  - clock-names
> >    - interrupts
> >    - dvdd-supply
> >    - avdd-supply
> > @@ -202,8 +204,6 @@ examples:
> >              spi-max-frequency = <1000000>;
> >              spi-cpol;
> >              spi-cpha;
> > -            clocks = <&ad7192_mclk>;
> > -            clock-names = "mclk";

Why drop it from the example?  It's a valid setting to have one after all.

> >              interrupts = <25 0x2>;
> >              interrupt-parent = <&gpio>;
> >              aincom-supply = <&aincom>;
> > -- 
> > 2.34.1
> >