linux-kernel - Re: [PATCH 3/3] dt-bindings: hwmon: max31790: Add pwmout-pin-as-tach-input property

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Message-ID: <e7ae980c-8408-46e3-909d-29b3d7e1e050@amperemail.onmicrosoft.com>
Date: Mon, 18 Mar 2024 23:50:37 +0700
From: Chanh Nguyen <chanh@...eremail.onmicrosoft.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Chanh Nguyen <chanh@...amperecomputing.com>, Jean Delvare
 <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Justin Ledford
 <justinledford@...gle.com>, devicetree@...r.kernel.org,
 linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
 OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
 Open Source Submission <patches@...erecomputing.com>
Cc: Phong Vo <phong@...amperecomputing.com>,
 Thang Nguyen <thang@...amperecomputing.com>,
 Quan Nguyen <quan@...amperecomputing.com>
Subject: Re: [PATCH 3/3] dt-bindings: hwmon: max31790: Add
 pwmout-pin-as-tach-input property



On 18/03/2024 17:02, Krzysztof Kozlowski wrote:
> On 18/03/2024 10:48, Chanh Nguyen wrote:
>>
>>
>> On 11/03/2024 23:56, Krzysztof Kozlowski wrote:
>>> On 11/03/2024 12:13, Chanh Nguyen wrote:
>>>> Add pwmout-pin-as-tach-input property.
>>>
>>> Why is this split from original binding? This does not make much
>>> sense... Add complete hardware description.
>>>
>>
>> Ok Krzysztof, I will merg the "[PATCH 1/3] dt-bindings: hwmon: Add maxim
>> max31790 driver bindings" commit and "[PATCH 3/3] dt-bindings: hwmon:
>> max31790: Add pwmout-pin-as-tach-input property" commit.
> 
> Later I checked your driver code and this explains a bit. However first
> patch should explain that instead. The split is fine, but just lack of
> rationale is confusing.
> 

Thank Krzysztof. I'll try to explain in detail each patch in v2.

> 
>>
>>>>
>>>> Signed-off-by: Chanh Nguyen <chanh@...amperecomputing.com>
>>>> ---
>>>>    Documentation/devicetree/bindings/hwmon/max31790.yaml | 11 +++++++++++
>>>>    1 file changed, 11 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/hwmon/max31790.yaml b/Documentation/devicetree/bindings/hwmon/max31790.yaml
>>>> index 5a93e6bdebda..447cac17053a 100644
>>>> --- a/Documentation/devicetree/bindings/hwmon/max31790.yaml
>>>> +++ b/Documentation/devicetree/bindings/hwmon/max31790.yaml
>>>> @@ -25,6 +25,16 @@ properties:
>>>>      reg:
>>>>        maxItems: 1
>>>>    
>>>> +  pwmout-pin-as-tach-input:
>>>> +    description: |
>>>> +      An array of six integers responds to six PWM channels for
>>>> +      configuring the pwm to tach mode.
>>>> +      When set to 0, the associated PWMOUT produces a PWM waveform for
>>>> +      control of fan speed. When set to 1, PWMOUT becomes a TACH input
>>>
>>> No vendor prefix, so generic property... but where is it defined?
>>>
>>
>> Thank Krzysztof! It is not generic property, I'll add the vendor prefix.
>>
>> I'll update the "pwmout-pin-as-tach-input" to
>> "maxim,pwmout-pin-as-tach-input" at v2.
> 
> Except that you should really look into common properties and use them.
> Or explain why do you need new property?
> 
> Best regards,
> Krzysztof
> 

I'm also discussing with Rob Herring that on patch 3/3, I checked in the 
Documentation/devicetree/bindings/hwmon/fan-common.yaml. I found the 
tach-ch property, but it seems to define the tach channel used for the 
fan. It does not match my purpose. I want to configure the PWM-OUT pin 
to become a TACH-IN pin. I wonder if I can use the tach-ch property for 
my purpose.