linux-kernel - Re: [PATCH V3] thermal/core/power_allocator: avoid thermal cdev can not be reset

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Date:   Fri, 14 Apr 2023 17:06:59 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     Di Shen <di.shen@...soc.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, xuewen.yan@...soc.com,
        jeson.gao@...soc.com, zhanglyra@...il.com, orsonzhai@...il.com,
        rui.zhang@...el.com, amitk@...nel.org, rafael@...nel.org,
        Di Shen <cindygm567@...il.com>
Subject: Re: [PATCH V3] thermal/core/power_allocator: avoid thermal cdev can
 not be reset

On 14/04/2023 16:18, Lukasz Luba wrote:
> 
> 
> On 4/14/23 12:12, Daniel Lezcano wrote:
>> On 13/04/2023 10:40, Di Shen wrote:
>>> We have discussed this question in patch-v1:
>>> https://lore.kernel.org/all/f6aaa5f1-495d-a158-14d8-ddb2bffbd9c2@arm.com/
>>>
>>> Simply put, we use the trip_temp in the Android System; set different
>>> trip_temp for thermal control of different scenarios.
>>
>> The changes are dealing with the trip points and trying to detect the 
>> threshold. That part should be handled in the thermal core or thermal 
>> trip side, not in the governor.
>>
>> AFAICT, if a trip point is changed, then the power allocator should be 
>> reset, including the cdev state.
>>
>> It would be more convenient to add an ops to the governor ops 
>> structure to reset the governor and then call it when a trip point is 
>> changed in thermal_zone_set_trip()
>>
>>
> 
> Sounds reasonable to have a proper API and fwk handling this corner
> case scenario.
> Although, if there is a need for a 'easy-to-backport' fix for IPA only,
> I agree with this patch, since it's straight forward to put in some
> Android kernel. We can later fix the framework to handle this properly.
> Anyway, both ways are OK to me.

Unfortunately, we can not do the maintenance of the Linux kernel based 
on an 'easy-to-backport' policy to Android.

This patch could be applied from-list to Android as a hotfix. But for 
Linux the fix should be more elaborated. One solution is to add a 
'reset' ops and call it from the trip point update function.

Did you double check the issue is not impacting the other governors too ?


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