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

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Date: Tue, 23 Apr 2024 20:09:41 +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 20:05, Rafael J. Wysocki wrote:
> On Tue, Apr 23, 2024 at 8:00 PM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>> 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 ?
> 
> Not yet, but I'm going to update it this way.  The governors should
> not mess up with tz->passive IMV.

+1

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