Re: [PATCH 2/2] thermal: qcom: Add support for Qualcomm MBG thermal monitoring

[Konrad Dybcio]

On 6/19/26 8:45 AM, Sachin Gupta wrote:
> 
> 
> On 6/16/2026 3:40 PM, Konrad Dybcio wrote:
>> On 6/1/26 1:01 PM, Sachin Gupta wrote:
>>> From: Satya Priya Kakitapalli <quic_skakitap@xxxxxxxxxxx>
>>>
>>> Add driver for the Qualcomm MBG thermal monitoring device. It monitors
>>> the die temperature, and when there is a level 1 upper threshold
>>> violation, it receives an interrupt over spmi. The driver reads
>>> the fault status register and notifies thermal accordingly.
>>>
>>> Signed-off-by: Satya Priya Kakitapalli <quic_skakitap@xxxxxxxxxxx>
>>> Co-developed-by: Sachin Gupta <sachin.gupta@xxxxxxxxxxxxxxxx>
>>> Signed-off-by: Sachin Gupta <sachin.gupta@xxxxxxxxxxxxxxxx>
>>> ---

[...]

>>> +    /*
>>> +     * Configure the last_temp one degree higher, to ensure the
>>> +     * violated temp is returned to thermal framework when it reads
>>> +     * temperature for the first time after the violation happens.
>>> +     * This is needed to account for the inaccuracy in the conversion
>>> +     * formula used which leads to the thermal framework setting back
>>> +     * the same thresholds in case the temperature it reads does not
>>> +     * show violation.
>>> +     */
>>> +    chip->last_temp = temp + MBG_TEMP_CONSTANT;
>>
>> Will this work fine if the user tries to set the max temp supported
>> by the hardware (i.e. is there headroom for max+1)?
>>
> 
> In the current implementation, temp == MBG_MAX_SUPPORTED_TEMP is not accepted (temp < MBG_MAX_SUPPORTED_TEMP), so the last_temp = temp + MBG_TEMP_CONSTANT path is never taken at absolute max. For accepted trips (strictly below max), there is headroom for the +1C adjustment.

You check for `temp < MBG_MAX_SUPPORTED_TEMP` and there's:

#define MBG_MAX_SUPPORTED_TEMP 160000,

so passing temp=159999 is "valid" and after the addition it becomes 160999,
which in my understanding is outside the range

Konrad