linux-kernel - Re: [PATCH v2 1/2] dt-bindings: hwmon: Add support for ST TSC1641 power monitor

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Message-ID: <ea00a07b-d0d6-49a2-a9d6-ef6c1ecf57dd@kernel.org>
Date: Mon, 27 Oct 2025 19:01:47 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>,
 Igor Reznichenko <igor@...nichenko.net>
Cc: conor+dt@...nel.org, corbet@....net, david.hunter.linux@...il.com,
 devicetree@...r.kernel.org, krzk+dt@...nel.org, linux-doc@...r.kernel.org,
 linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org, robh@...nel.org,
 skhan@...uxfoundation.org
Subject: Re: [PATCH v2 1/2] dt-bindings: hwmon: Add support for ST TSC1641
 power monitor

On 27/10/2025 17:53, Guenter Roeck wrote:
> On 10/27/25 01:40, Krzysztof Kozlowski wrote:
>> On 26/10/2025 20:58, Guenter Roeck wrote:
>>>>>>> +  reg:
>>>>>>> +    maxItems: 1
>>>>>>> +
>>>>>>> +  shunt-resistor-micro-ohms:
>>>>>>> +    description: Shunt resistor value in micro-ohms. Since device has internal
>>>>>>> +      16-bit RSHUNT register with 10 uOhm LSB, the maximum value is capped at
>>>>>>> +      655.35 mOhm.
>>>>>>> +    minimum: 100
>>>>>>> +    default: 1000
>>>>>>> +    maximum: 655350
>>>>>>> +
>>>>>>> +  st,alert-polarity-active-high:
>>>>>>
>>>>>> Isn't this just interrupt? You need proper interrupts property and then
>>>>>> its flag define the type of interrupt.
>>>>>
>>>>> This controls a bit written into device register.
>>>>> I omitted interrupt property after looking at existing power monitor bindings,
>>>>> especially hwmon/ti,ina2xx.yaml. INA226 has very similar bit controlling alert
>>>>> pin polarity and binding doesn't define alert pin as interrupt. Overall, I didn't
>>>>> find many power monitor bindings defining alert pins as interrupts.
>>>>
>>>>
>>>> On INA2xx that's SMBUS Alert. Is this the case here as well?
>>>>
>>>
>>> It could be wired to SMBus alert, or it could be wired to a CPU interrupt pin.
>>
>> So please explain me why CPU interrupt pin, which in every really every
>> device called "interrupts", would not be "interrupts" here? How CPU can
>> even guess the number of the interrupt in such case, without
>> "interrupts" property?
>>
> 
> I thought we were discussing the need for the st,alert-polarity-active-high
> property, sorry.


Yes, we kind of do, I am just trying to understand what is expressed
here. If this is a CPU interrupt, its flags should mark the proper
signal level, including inverter.

If this is something else (or both), then this property might make
sense, I just don't know what is this.

Best regards,
Krzysztof