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: <6b5459fd-2873-4c26-b986-882413b8d95b@bootlin.com>
Date: Fri, 5 Jul 2024 17:24:19 +0200
From: Thomas Bonnefille <thomas.bonnefille@...tlin.com>
To: Conor Dooley <conor@...nel.org>
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 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.

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."

Regards,
Thomas