Re: [PATCH v1] thermal: trip: Avoid skipping trips in thermal_zone_set_trips()

[Daniel Lezcano]

On 30/07/2024 16:41, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Say there are 3 trip points A, B, C sorted in ascending temperature
> order with no hysteresis.  If the zone temerature is exactly equal to
> B, thermal_zone_set_trips() will set the boundaries to A and C and the
> hardware will not catch any crossing of B (either way) until either A
> or C is crossed and the boundaries are changed.

When the temperature is B, an interrupt fired which led to the 
thermal_zone_update() and in turn it calls thermal_zone_set_trips()

As the current temperature is equal to trip B, it makes sense to set A 
and C, as B has been processes when handling the thermal trips right 
before calling thermal_zone_set_trips()

I'm failing to understand the issue you describe

Were you able to reproduce the issue with emul_temp ?


> To avoid that, use non-strict inequalities when comparing the trip
> threshold to the zone temperature in thermal_zone_set_trips().
>
> In the example above, it will cause both boundaries to be set to B,
> which is desirable because an interrupt will trigger when the zone
> temperature becomes different from B regardless of which way it goes.
> That will allow a new interval to be set depending on the direction of
> the zone temperature change.
>
> Fixes: 893bae92237d ("thermal: trip: Make thermal_zone_set_trips() use trip thresholds")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
>
> 6.11-rc material.
>
> ---
>   drivers/thermal/thermal_trip.c |    4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> Index: linux-pm/drivers/thermal/thermal_trip.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_trip.c
> +++ linux-pm/drivers/thermal/thermal_trip.c
> @@ -82,10 +82,10 @@ void thermal_zone_set_trips(struct therm
>   		return;
>   
>   	for_each_trip_desc(tz, td) {
> -		if (td->threshold < tz->temperature && td->threshold > low)
> +		if (td->threshold <= tz->temperature && td->threshold > low)
>   			low = td->threshold;
>   
> -		if (td->threshold > tz->temperature && td->threshold < high)
> +		if (td->threshold >= tz->temperature && td->threshold < high)
>   			high = td->threshold;
>   	}
>   

--
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog