linux-kernel - Re: [PATCH v6 7/7] arm64: dts: qcom: ipq5424: Add thermal zone nodes

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Message-ID: <6565a4ec-6db6-4442-a07f-ace467c47395@oss.qualcomm.com>
Date: Tue, 12 Nov 2024 12:02:49 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Manikanta Mylavarapu <quic_mmanikan@...cinc.com>,
        Konrad Dybcio <konradybcio@...il.com>, srinivas.kandagatla@...aro.org,
        robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
        amitk@...nel.org, thara.gopinath@...il.com, rafael@...nel.org,
        daniel.lezcano@...aro.org, rui.zhang@...el.com, lukasz.luba@....com,
        andersson@...nel.org, konradybcio@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc: quic_srichara@...cinc.com, quic_varada@...cinc.com
Subject: Re: [PATCH v6 7/7] arm64: dts: qcom: ipq5424: Add thermal zone nodes



On 11-Nov-24 12:51, Manikanta Mylavarapu wrote:
> 
> 
> On 11/7/2024 8:17 PM, Konrad Dybcio wrote:
>> On 6.11.2024 11:25 AM, Manikanta Mylavarapu wrote:
>>>
>>>
>>> On 11/6/2024 2:42 PM, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 11/6/24 09:47, Manikanta Mylavarapu wrote:
>>>>>
>>>>>
>>>>> On 11/4/2024 7:21 PM, Konrad Dybcio wrote:
>>>>>> On 4.11.2024 1:44 PM, Manikanta Mylavarapu wrote:
>>>>>>> Add thermal zone nodes for sensors present in IPQ5424.
>>>>>>>
>>>>>>> Signed-off-by: Manikanta Mylavarapu <quic_mmanikan@...cinc.com>
>>>>>>> ---
>>>>>> [...]
>>>>>>
>>>>>>> +
>>>>>>> +        cpu3-thermal {
>>>>>>> +            polling-delay-passive = <0>;
>>>>>>> +            polling-delay = <0>;
>>>>>>> +            thermal-sensors = <&tsens 13>;
>>>>>>> +
>>>>>>> +            trips {
>>>>>>> +                cpu-critical {
>>>>>>> +                    temperature = <120000>;
>>>>>>> +                    hysteresis = <9000>;
>>>>>>> +                    type = "critical";
>>>>>>> +                };
>>>>>>> +
>>>>>>> +                cpu-passive {
>>>>>>> +                    temperature = <110000>;
>>>>>>> +                    hysteresis = <9000>;
>>>>>>> +                    type = "passive";
>>>>>>
>>>>>> You have a passive trip point without passive polling
>>>>>>
>>>>>
>>>>> Okay, will remove this.
>>>>
>>>> You most likely want to preserve it, while keeping a sensible
>>>> polling frequency, so that userspace will be aware of the current
>>>> CPU temperature. <100> sounds like a sensible value here.
>>>>
>>>> Konrad
>>>
>>> Temperature sensor's present in IPQ5424 supports interrupts.
>>
>> Correct.
>>
>>> Hence no need to configure polling frequency.
>>
>> No, that interrupt firing signifies crossing the temp threshold (meaning
>> no updates beyond that) or the tsens watchdog barking.
>>
>> Konrad
> 
> An interrupt fires when the temperature crosses a threshold.

Which means you can't monitor the temperature at runtime
without polling..

Konrad