linux-kernel - Re: [PATCH v1 3/6] thermal: gov_fair_share: Rearrange get_trip

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Date:   Thu, 12 Oct 2023 17:04:24 +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>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Lukasz Luba <lukasz.luba@....com>
Subject: Re: [PATCH v1 3/6] thermal: gov_fair_share: Rearrange
 get_trip_level()

On 06/10/2023 19:42, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Make get_trip_level() use for_each_trip() to iterate over trip points
> and make it call thermal_zone_trip_id() to obtain the integer ID of a
> given trip point so as to avoid relying on the knowledge of struct
> thermal_zone_device internals.
> 
> The general functionality is not expected to be changed.
> 
> This change causes the governor to use trip pointers instead of trip
> indices everywhere except for the fair_share_throttle() second argument
> that will be modified subsequently along with the definition of the
> governor .throttle() callback.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>   drivers/thermal/gov_fair_share.c |   30 ++++++++++++++----------------
>   1 file changed, 14 insertions(+), 16 deletions(-)
> 
> Index: linux-pm/drivers/thermal/gov_fair_share.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/gov_fair_share.c
> +++ linux-pm/drivers/thermal/gov_fair_share.c
> @@ -15,29 +15,27 @@
>   
>   #include "thermal_core.h"
>   
> -/**
> - * get_trip_level: - obtains the current trip level for a zone
> - * @tz:		thermal zone device
> - */
>   static int get_trip_level(struct thermal_zone_device *tz)
>   {
> -	struct thermal_trip trip;
> -	int count;
> +	const struct thermal_trip *trip, *level_trip = NULL;
> +	int trip_level;
>   
> -	for (count = 0; count < tz->num_trips; count++) {
> -		__thermal_zone_get_trip(tz, count, &trip);
> -		if (tz->temperature < trip.temperature)
> +	for_each_trip(tz, trip) {
> +		if (level_trip && trip->temperature >= tz->temperature)
>   			break;

Even if very likely the trip points are ordered by the hardware 
enumeration, strictly we don't have yet the guarantee the trips are 
ordered (as that is the final goal to correctly detect thresholds 
crossing with the generic trip). We should go through all the trip 
points, no?

> +		level_trip = trip;
>   	}
>   
> -	/*
> -	 * count > 0 only if temperature is greater than first trip
> -	 * point, in which case, trip_point = count - 1
> -	 */
> -	if (count > 0)
> -		trace_thermal_zone_trip(tz, count - 1, trip.type);
> +	/*  Bail out if the temperature is not greater than any trips. */
> +	if (level_trip->temperature >= tz->temperature)
> +		return 0;

Isn't simpler to remove the test level_trip != NULL in the loop and then 
check here if it is NULL and then return 0.

> +	trip_level = thermal_zone_trip_id(tz, level_trip);
> +
> +	trace_thermal_zone_trip(tz, trip_level, level_trip->type);
>   
> -	return count;
> +	return trip_level;
>   }
>   
>   static long get_target_state(struct thermal_zone_device *tz,
> 
> 
> 

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