Re: [PATCH] arm64: dts: qcom: shikra: Drop CPU critical trips

[Gaurav Kohli <gaurav.kohli@oss.qualcomm.com>]

On 10/20/2026 6:26 PM, Abel Vesa wrote:
> On 26-10-19 20:03:47, Gaurav Kohli wrote:
>>
>>
>> On 10/15/2026 4:43 PM, Konrad Dybcio wrote:
>>> On 9/25/26 12:24 PM, Gaurav Kohli wrote:
>>>>
>>>>
>>>> On 9/25/2026 3:13 PM, Abel Vesa wrote:
>>>>> On 26-09-24 19:52:32, Gaurav Kohli wrote:
>>>>>> Shikra firmware handles CPU thermal mitigation up to 117 C, while
>>>>>> Linux CPU critical trips trigger at 115 C. This can shut the system
>>>>>> down before firmware reaches the end of its mitigation range.
>>>>>>
>>>>>> Drop the critical trips from the CPU thermal zones and leave the hot
>>>>>> trips, non-CPU critical trips and GPUSS passive cooling map unchanged.
>>>>>
>>>>> I thought that was the whole point of having the critical trips set to
>>>>> 115 C, so that the kernel can gracefully shut down before firmware cuts
>>>>> it off.
>>>>>
>>>>> What happens if CPU gets to 117 C and the critical trips are removed?
>>>>> How will firmware thermal mitigation handle it?
>>>>
>>>> Thanks Abel for review.
>>>>
>>>> For the CPU thermal zones on this SoC, hardware-side mitigation is already available at 115 C and 117 C, and hardware shutdown is at 120 C. Because of that, a Linux critical trip at 115 C is not very useful. It overlaps with the hardware mitigation range and can trigger shutdown before the firmware thermal sequence has completed.
>>>
>>> Does the hardware mitigation just pull the plug, or does it signal
>>> to the OS that it's about to? We absolutely need the OS to be aware,
>>> so that e.g. the filesystem will be synced.
>>
>> Thanks Konrad for the review.
>>
>> The OS is not notified before the final HW shutdown at 120 C. There is also
>> no useful margin for a Linux critical trip here, firmware/HW mitigation
>> starts at 115/117 C and hw shutdown is at 120.
>>
>> So 115 C overlaps with firmware mitigation, while placing it higher is
>> too close to HW shutdown to be useful.
> 
> But having the 115 C one will allow the kernel to take all the necessary
> steps to bring the system down gracefully, while relying solely on the
> firmware will just kill the system before kernel can do anything.

Thanks Abel for the review.

On this target, 115/117 C firmware mitigation is throttling/prevention, 
not shutdown. The final HW shutdown threshold is 120 C.

The 115 C Linux critical trip therefore starts shutdown exactly when 
firmware mitigation begins. Moving it higher also leaves too little 
margin before 120 C.

So this patch drops only the CPU critical trips. Would you prefer 
keeping a Linux critical trip at 118 C ?

> 
> I don't understand why you want to reach firmware/HW mitigation anyway.