linux-kernel - Re: [PATCH 2/2] dt-bindings: mfd: cros-ec: add properties for thermal cooling cells

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Message-ID: <d31298f5-718f-45cc-9387-7412b68b5b0f@kernel.org>
Date: Mon, 25 Nov 2024 09:48:27 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: "Sung-Chi, Li" <lschyi@...omium.org>
Cc: Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>,
 Sebastian Reichel <sre@...nel.org>, Lee Jones <lee@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, chrome-platform@...ts.linux.dev,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] dt-bindings: mfd: cros-ec: add properties for thermal
 cooling cells

On 25/11/2024 09:43, Sung-Chi, Li wrote:
> On Mon, Nov 25, 2024 at 08:32:19AM +0100, Krzysztof Kozlowski wrote:
>> On 25/11/2024 03:50, Sung-Chi, Li wrote:
>>> On Fri, Nov 22, 2024 at 08:49:14AM +0100, Krzysztof Kozlowski wrote:
>>>> On Fri, Nov 22, 2024 at 11:47:22AM +0800, Sung-Chi Li wrote:
>>>>> The cros_ec supports limiting the input current to act as a passive
>>>>> thermal cooling device. Add the property '#cooling-cells' bindings, such
>>>>> that thermal framework can recognize cros_ec as a valid thermal cooling
>>>>> device.
>>>>>
>>>>> Signed-off-by: Sung-Chi Li <lschyi@...omium.org>
>>>>> ---
>>>>>  Documentation/devicetree/bindings/mfd/google,cros-ec.yaml | 3 +++
>>>>>  1 file changed, 3 insertions(+)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>>>>> index aac8819bd00b..2b6f098057af 100644
>>>>> --- a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>>>>> +++ b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
>>>>> @@ -96,6 +96,9 @@ properties:
>>>>>    '#gpio-cells':
>>>>>      const: 2
>>>>>  
>>>>> +  '#cooling-cells':
>>>>> +    const: 2
>>>>
>>>> This is not a cooling device. BTW, your commit msg is somehow circular.
>>>> "Add cooling to make it a cooling device because it will be then cooling
>>>> device."
>>>>
>>>> Power supply already provides necessary framework for managing charging
>>>> current and temperatures. If this is to stay, you need to explain why
>>>> this is suitable to be considered a thermal zone or system cooling
>>>> device (not power supply or input power cooling).
>>>>
>>>> Best regards,
>>>> Krzysztof
>>>>
>>>
>>> Thank you, I will rephrase the commit message. The reason to not to use the
>>> managing charging current and temperatures in the power supply framework is
>>> that:
>>>
>>> - The EC may not have the thermal sensor value for the charger, and there is no
>>>   protocol for getting the thermal sensor value for the charger (there is
>>>   command for reading thermal sensor values, but there is no specification for
>>>   what sensor index is for the charger, if the charger provides thermal value).
>>> - The managing mechanism only take the charger thermal value into account, and
>>>   I would like to control the current based on the thermal condition of the
>>>   whole device.
>>>
>>> I will include these explanation in the following changes.
>>
>>
>> This does not explain me why this is supposed to be thermal zone. I
>> already said it, but let's repeat: This is not a thermal zone. This
>> isn't thermal zone sensor, either.
> 
> Hi, I added the explanation in the commit message in v2, in short, I need to use
> different thermal sensors, and need finer thermal controls, so I have to use
> thermal zone. This is included in the v2 commit message.
You resolved nothing there. I don't care that "you need to use thermal
sensors". That's not a valid reason. If next time you say "I need to
make it a current regulator", shall we accept incorrect description? No.

I repeat multiple times: this is not a SoC cooling device, this is not a
thermal zone and not a thermal sensor.

This is a power supply or charger or battery. Eventually it might be
hardware monitoring sensor. Use appropriate properties for this category
of device.

Best regards,
Krzysztof