linux-kernel - Re: [PATCH v1 07/16] thermal: gov_power_allocator: Eliminate a redundant variable

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Date: Tue, 23 Apr 2024 20:00:32 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
 Lukasz Luba <lukasz.luba@....com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v1 07/16] thermal: gov_power_allocator: Eliminate a
 redundant variable

On 23/04/2024 19:54, Rafael J. Wysocki wrote:
> On Tue, Apr 23, 2024 at 7:35 PM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>> On 10/04/2024 18:12, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>
>>> Notice that the passive field in struct thermal_zone_device is not
>>> used by the Power Allocator governor itself and so the ordering of
>>> its updates with respect to allow_maximum_power() or allocate_power()
>>> does not matter.
>>>
>>> Accordingly, make power_allocator_manage() update that field right
>>> before returning, which allows the current value of it to be passed
>>> directly to allow_maximum_power() without using the additional update
>>> variable that can be dropped.
>>>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>> ---
>>
>> The step_wise and the power allocator are changing the tz->passive
>> values, so telling the core to start and stop the passive mitigation timer.
>>
>> It looks strange that a plugin controls the core internal and not the
>> opposite.
>>
>> I'm wondering if it would not make sense to have the following ops:
>>
>>          .start
>>          .stop
>>
>> .start is called when the first trip point is crossed the way up
>> .stop is called when the first trip point is crossed the way down
>>
>>    - The core is responsible to start and stop the passive mitigation timer.
>>
>>    - the governors do no longer us tz->passive
>>
>> The reset of the governor can happen at start or stop, as well as the
>> device cooling states.
> 
> I have a patch that simply increments tz->passive when a passive trip
> point is passed on the way up and decrements it when a passive trip
> point is crossed on the way down.  It appears to work reasonably well.

Does it make the governors getting ride of it ? Or at least not changing 
its value ?

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