linux-kernel - Re: [PATCH v2 2/5] thermal: trip: Make thermal_zone_set

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Date: Mon, 10 Jun 2024 20:01:32 +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>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Lukasz Luba <lukasz.luba@....com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v2 2/5] thermal: trip: Make thermal_zone_set_trips() use
 trip thresholds

On 28/05/2024 18:51, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Modify thermal_zone_set_trips() to use trip thresholds instead of
> computing the low temperature for each trip to avoid deriving both
> the high and low temperature levels from the same trip (which may
> happen if the zone temperature falls into the hysteresis range of
> one trip).
> 
> Accordingly, make __thermal_zone_device_update() call
> thermal_zone_set_trips() later, when threshold values have been
> updated for all trips.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> v1 -> v2: Rebase.
> 
> ---
>   drivers/thermal/thermal_core.c |    4 ++--
>   drivers/thermal/thermal_trip.c |   14 ++++----------
>   2 files changed, 6 insertions(+), 12 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -513,13 +513,13 @@ void __thermal_zone_device_update(struct
>   	if (tz->temperature == THERMAL_TEMP_INVALID)
>   		return;
>   
> -	thermal_zone_set_trips(tz);
> -
>   	tz->notify_event = event;
>   
>   	for_each_trip_desc(tz, td)
>   		handle_thermal_trip(tz, td, &way_up_list, &way_down_list);

Would it make sense to use the for_each_trip_desc() loop here and update
low and high on the fly in this loop ?

If a trip point is crossed the way up or down, then 
handle_thermal_trip() returns a value which in turn results in updating 
low and high. If low and high are changed then the we call 
thermal_zone_set_trips() after the loop.

The results for the thermal_zone_set_trips() will be the loop, the low, 
high, prev_low_trip and prev_high_trip variables going away.

The resulting function should be:

void thermal_zone_set_trips(struct thermal_zone_device *tz, int low, int 
high)
{
         int ret;

         lockdep_assert_held(&tz->lock);

         if (!tz->ops.set_trips)
                 return;

         /* 
 

          * Set a temperature window. When this window is left the 
driver 

          * must inform the thermal core via thermal_zone_device_update. 
 

          */
         ret = tz->ops.set_trips(tz, low, high);
         if (ret)
                 dev_err(&tz->device, "Failed to set trips: %d\n", ret);
}

But if you consider that is an additional change, then:

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>


> +	thermal_zone_set_trips(tz);
> +
>   	list_sort(&way_up_list, &way_up_list, thermal_trip_notify_cmp);
>   	list_for_each_entry(td, &way_up_list, notify_list_node)
>   		thermal_trip_crossed(tz, &td->trip, governor, true);
> Index: linux-pm/drivers/thermal/thermal_trip.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_trip.c
> +++ linux-pm/drivers/thermal/thermal_trip.c
> @@ -88,17 +88,11 @@ void thermal_zone_set_trips(struct therm
>   		return;
>   
>   	for_each_trip_desc(tz, td) {
> -		const struct thermal_trip *trip = &td->trip;
> -		int trip_low;
> +		if (td->threshold < tz->temperature && td->threshold > low)
> +			low = td->threshold;
>   
> -		trip_low = trip->temperature - trip->hysteresis;
> -
> -		if (trip_low < tz->temperature && trip_low > low)
> -			low = trip_low;
> -
> -		if (trip->temperature > tz->temperature &&
> -		    trip->temperature < high)
> -			high = trip->temperature;
> +		if (td->threshold > tz->temperature && td->threshold < high)
> +			high = td->threshold;
>   	}
>   
>   	/* No need to change trip points */
> 
> 
> 

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