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

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Date: Tue, 23 Apr 2024 19:35:19 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: 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 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.


>   drivers/thermal/gov_power_allocator.c |    9 +++------
>   1 file changed, 3 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/thermal/gov_power_allocator.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/gov_power_allocator.c
> +++ linux-pm/drivers/thermal/gov_power_allocator.c
> @@ -747,21 +747,18 @@ static void power_allocator_manage(struc
>   {
>   	struct power_allocator_params *params = tz->governor_data;
>   	const struct thermal_trip *trip = params->trip_switch_on;
> -	bool update;
>   
>   	lockdep_assert_held(&tz->lock);
>   
>   	if (trip && tz->temperature < trip->temperature) {
> -		update = tz->passive;
> -		tz->passive = 0;
>   		reset_pid_controller(params);
> -		allow_maximum_power(tz, update);
> +		allow_maximum_power(tz, tz->passive);
> +		tz->passive = 0;
>   		return;
>   	}
>   
> -	tz->passive = 1;
> -
>   	allocate_power(tz, params->trip_max->temperature);
> +	tz->passive = 1;
>   }
>   
>   static struct thermal_governor thermal_gov_power_allocator = {
> 
> 
> 

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