linux-kernel - Re: [PATCH V2] thermal/core/power_allocator: avoid thermal cdev can not be reset

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Date:   Thu, 16 Mar 2023 10:21:35 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Di Shen <di.shen@...soc.com>
Cc:     lukasz.luba@....com, rafael@...nel.org, daniel.lezcano@...aro.org,
        amitk@...nel.org, rui.zhang@...el.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, xuewen.yan@...soc.com,
        jeson.gao@...soc.com, orsonzhai@...il.com
Subject: Re: [PATCH V2] thermal/core/power_allocator: avoid thermal cdev can
 not be reset

On Wed, 15 Mar 2023 at 17:30, Di Shen <di.shen@...soc.com> wrote:
>
> Commit <0952177f2a1f>(thermal/core/power_allocator: Update once
> cooling devices when temp is low) adds a update flag to avoid
> the thermal event is triggered when there is no need, and
> thermal cdev would be update once when temperature is low.
>
> But when the trips are writable, and switch_on_temp is set
> to be a higher value, the cooling device state may not be
> reset to 0, because last_temperature is smaller than the
> switch_on_temp.
>
> For example:
> First:
> swicth_on_temp=70 control_temp=85;
>
> Then userspace change the trip_temp:
> swicth_on_temp=45 control_temp=55 cur_temp=54
>
> Then userspace reset the trip_temp:
> swicth_on_temp=70 control_temp=85 cur_temp=57 last_temp=54
>
> At this time, the cooling device state should be reset to 0.
> However, because cur_temp(57) < switch_on_temp(70)
> last_temp(54) < swicth_on_temp(70)  ---->  update = false,
> update is false, the cooling device state can not be reset.
>
> This patch adds a function thermal_cdev_needs_update() to
> renew the update flag value only when the trips are writable,
> so that thermal cdev->state can be reset after switch_on_temp
> changed from low to high.
>
> Signed-off-by: Di Shen <di.shen@...soc.com>
> ---

A change log should be provided under '---' to describe changes since
the last version, and add '---' at the end of the change log, that
will not be shown in the commit history after being applied.

Thanks,
Chunyan

>  drivers/thermal/gov_power_allocator.c | 39 ++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
> index 0eaf1527d3e3..c9e1f3b15f15 100644
> --- a/drivers/thermal/gov_power_allocator.c
> +++ b/drivers/thermal/gov_power_allocator.c
> @@ -59,6 +59,8 @@ static inline s64 div_frac(s64 x, s64 y)
>   *                     governor switches on when this trip point is crossed.
>   *                     If the thermal zone only has one passive trip point,
>   *                     @trip_switch_on should be INVALID_TRIP.
> + * @last_switch_on_temp:Record the last switch_on_temp only when trips
> +                       are writable.
>   * @trip_max_desired_temperature:      last passive trip point of the thermal
>   *                                     zone.  The temperature we are
>   *                                     controlling for.
> @@ -70,6 +72,9 @@ struct power_allocator_params {
>         s64 err_integral;
>         s32 prev_err;
>         int trip_switch_on;
> +#ifdef CONFIG_THERMAL_WRITABLE_TRIPS
> +       int last_switch_on_temp;
> +#endif
>         int trip_max_desired_temperature;
>         u32 sustainable_power;
>  };
> @@ -554,6 +559,25 @@ static void get_governor_trips(struct thermal_zone_device *tz,
>         }
>  }
>
> +#ifdef CONFIG_THERMAL_WRITABLE_TRIPS
> +static bool thermal_cdev_needs_update(struct thermal_zone_device *tz, int switch_on_temp)
> +{
> +       bool update;
> +       struct power_allocator_params *params = tz->governor_data;
> +       int last_switch_on_temp = params->last_switch_on_temp;
> +
> +       update = (tz->last_temperature >= last_switch_on_temp);
> +       params->last_switch_on_temp = switch_on_temp;
> +
> +       return update;
> +}
> +#else
> +static inline bool thermal_cdev_needs_update(struct thermal_zone_device *tz, int switch_on_temp)
> +{
> +       return false;
> +}
> +#endif
> +
>  static void reset_pid_controller(struct power_allocator_params *params)
>  {
>         params->err_integral = 0;
> @@ -709,12 +733,15 @@ static int power_allocator_throttle(struct thermal_zone_device *tz, int trip_id)
>                 return 0;
>
>         ret = __thermal_zone_get_trip(tz, params->trip_switch_on, &trip);
> -       if (!ret && (tz->temperature < trip.temperature)) {
> -               update = (tz->last_temperature >= trip.temperature);
> -               tz->passive = 0;
> -               reset_pid_controller(params);
> -               allow_maximum_power(tz, update);
> -               return 0;
> +       if (!ret) {
> +               update = thermal_cdev_needs_update(tz, trip.temperature);
> +               if (tz->temperature < trip.temperature) {
> +                       update |= (tz->last_temperature >= trip.temperature);
> +                       tz->passive = 0;
> +                       reset_pid_controller(params);
> +                       allow_maximum_power(tz, update);
> +                       return 0;
> +               }
>         }
>
>         tz->passive = 1;
> --
> 2.17.1
>