linux-kernel - Re: [RESEND][PATCH V2] thermal: power_allocator: Avoid overwriting PID coefficients from setup time

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Date: Mon, 12 Feb 2024 14:14:25 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Di Shen <di.shen@...soc.com>
Cc: lukasz.luba@....com, rafael@...nel.org, daniel.lezcano@...aro.org, 
	rui.zhang@...el.com, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	xuewen.yan@...soc.com, zhanglyra@...il.com, orsonzhai@...il.com, 
	cindygm567@...il.com
Subject: Re: [RESEND][PATCH V2] thermal: power_allocator: Avoid overwriting
 PID coefficients from setup time

On Wed, Feb 7, 2024 at 3:09 AM Di Shen <di.shen@...soc.com> wrote:
>
> When the PID coefficients k_* are set via sysfs before the IPA
> algorithm is triggered then the coefficients would be overwritten after
> IPA throttle() is called. The old configuration values might be
> different than the new values estimated by the IPA internal algorithm.
>
> There might be a time delay when this overwriting happens. It
> depends on the thermal zone temperature value. The temperature value
> needs to cross the first trip point value then IPA algorithms start
> operating. Although, the PID coefficients setup time should not be
> affected or linked to any later operating phase and values must not be
> overwritten.
>
> This patch initializes params->sustainable_power when the governor
> binds to thermal zone to avoid overwriting k_*. The basic function won't
> be affected, as the k_* still can be estimated if the sustainable_power
> is modified.
>
> Signed-off-by: Di Shen <di.shen@...soc.com>
> Reviewed-by: Lukasz Luba <lukasz.luba@....com>
> ---
>  drivers/thermal/gov_power_allocator.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
> index 81e061f183ad..1b17dc4c219c 100644
> --- a/drivers/thermal/gov_power_allocator.c
> +++ b/drivers/thermal/gov_power_allocator.c
> @@ -711,6 +711,8 @@ static int power_allocator_bind(struct thermal_zone_device *tz)
>
>         if (!tz->tzp->sustainable_power)
>                 dev_warn(&tz->device, "power_allocator: sustainable_power will be estimated\n");
> +       else
> +               params->sustainable_power = tz->tzp->sustainable_power;
>
>         estimate_pid_constants(tz, tz->tzp->sustainable_power,
>                                params->trip_switch_on,
> --

Applied as 6.9 material, thanks!