linux-kernel - Re: [PATCH v2 1/3] dt-bindings: iio: adc: sophgo,cv18xx-saradc.yaml: Add Sophgo SARADC binding documentation

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Message-ID: <20240706-remote-undergo-3b9dfe44d16f@spud>
Date: Sat, 6 Jul 2024 13:42:30 +0100
From: Conor Dooley <conor@...nel.org>
To: Thomas Bonnefille <thomas.bonnefille@...tlin.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Chen Wang <unicorn_wang@...look.com>,
	Inochi Amaoto <inochiama@...look.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Miquèl Raynal <miquel.raynal@...tlin.com>,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 1/3] dt-bindings: iio: adc: sophgo,cv18xx-saradc.yaml:
 Add Sophgo SARADC binding documentation

On Fri, Jul 05, 2024 at 05:24:19PM +0200, Thomas Bonnefille wrote:
> 
> 
> On 7/5/24 5:01 PM, Conor Dooley wrote:
> > On Fri, Jul 05, 2024 at 03:42:23PM +0200, Thomas Bonnefille wrote:
> > > The Sophgo SARADC is a Successive Approximation ADC that can be found in
> > > the Sophgo SoC.
> > > 
> > > Signed-off-by: Thomas Bonnefille <thomas.bonnefille@...tlin.com>
> > > ---
> > >   .../bindings/iio/adc/sophgo,cv18xx-saradc.yaml     | 63 ++++++++++++++++++++++
> > >   1 file changed, 63 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/sophgo,cv18xx-saradc.yaml b/Documentation/devicetree/bindings/iio/adc/sophgo,cv18xx-saradc.yaml
> > > new file mode 100644
> > > index 000000000000..31bd8ac6dfa5
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/adc/sophgo,cv18xx-saradc.yaml
> > > @@ -0,0 +1,63 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/iio/adc/sophgo,cv18xx-saradc.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title:
> > > +  Sophgo CV18XX SoC series 3 channels Successive Approximation Analog to
> > > +  Digital Converters
> > > +
> > > +maintainers:
> > > +  - Thomas Bonnefille <thomas.bonnefille@...tlin.com>
> > > +
> > > +description:
> > > +  Datasheet at https://github.com/sophgo/sophgo-doc/releases
> > > +
> > > +properties:
> > > +  compatible:
> > > +    oneOf:
> > > +      - items:
> > > +          - enum:
> > > +              - sophgo,cv1800b-saradc
> > > +          - const: sophgo,cv18xx-saradc
> > 
> > I don't think the fallback here makes sense. If there's other devices
> > with a compatible programming model added later, we can fall back to the
> > cv1800b.
> > 
> 
> Ok I'll do that, I wasn't sure if it was a good practice to fallback on
> another SoC specific compatible.
> 
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  interrupts:
> > > +    maxItems: 1
> > > +
> > > +  clocks:
> > > +    description:
> > > +      SARADC will use the presence of this clock to determine if the controller
> > > +      needs to be explicitly clocked by it (Active domain) or if it is part of
> > > +      the No-Die Domain, along with the RTC, which does not require explicit
> > > +      clocking.
> > 
> > What does "explicit clocking" mean? Is it clocked directly (or via
> > dividers) by a clock on the board or another source?
> > 
> 
> It means that, if a clock is provided, the driver will work in "Active
> Domain" and will use the clock generator of the SoC to get the right clock
> signal.
> 
> However if no clock is provided, the controller will work in "No-Die" domain
> (Always On) and use the RTCSYS subsystem to get its clock signal.

So it does have a clock, but provided by a different provider. I don't
really understand why that would "excuse" it from having a clocks
property, with the RTCSYS as the provider.

> 
> Indeed "explicitly clocked" may not be the right word to describe that,
> maybe some thing like that is better :
> 
> "SARADC will use the presence of this clock to determine if the controller
> needs to use the clock generator to get its clock signal (Active domain) or
> if it is part of the No-Die Domain, along with the RTC, and does not require
> the clock generator."



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