linux-kernel - Re: [PATCH] drivers: thermal: Reset previous low and high trip during thermal zone init

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Date:   Fri, 05 Nov 2021 23:16:49 +0530
From:   manafm@...eaurora.org
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers: thermal: Reset previous low and high trip during
 thermal zone init

On 2021-11-05 20:52, Rafael J. Wysocki wrote:
> On Tue, Nov 2, 2021 at 9:01 PM Manaf Meethalavalappu Pallikunhi
> <manafm@...eaurora.org> wrote:
>> 
>> During the suspend is in process, thermal_zone_device_update bails out
>> thermal zone re-evaluation for any sensor trip violation without
>> setting next valid trip to that sensor. It assumes during resume
>> it will re-evaluate same thermal zone and update trip. But when it is
>> in suspend temperature goes down and on resume path while updating
>> thermal zone if temperature is less than previously violated trip,
>> thermal zone set trip function evaluates the same previous high and
>> previous low trip as new high and low trip. Since there is no change
>> in high/low trip, it bails out from thermal zone set trip API without
>> setting any trip. It leads to a case where sensor high trip or low
>> trip is disabled forever even though thermal zone has a valid high
>> or low trip.
>> 
>> During thermal zone device init, reset thermal zone previous high
>> and low trip. It resolves above mentioned scenario.
> 
> Makes sense to me.
> 
> Daniel?
> 
>> Signed-off-by: Manaf Meethalavalappu Pallikunhi 
>> <manafm@...eaurora.org>
>> ---
>>  drivers/thermal/thermal_core.c | 2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/drivers/thermal/thermal_core.c 
>> b/drivers/thermal/thermal_core.c
>> index 21db445..2b7a0b4 100644
>> --- a/drivers/thermal/thermal_core.c
>> +++ b/drivers/thermal/thermal_core.c
>> @@ -477,6 +477,8 @@ static void thermal_zone_device_init(struct 
>> thermal_zone_device *tz)
>>  {
>>         struct thermal_instance *pos;
>>         tz->temperature = THERMAL_TEMP_INVALID;
>> +       tz->prev_low_trip = -INT_MAX;
> 
> Why not use INT_MIN instead?
> 
The thermal_zone_set_trips API uses -INT_MAX as default low trip to 
start trip aggregation. I used the same default values here as well.

>> +       tz->prev_high_trip = INT_MAX;
>>         list_for_each_entry(pos, &tz->thermal_instances, tz_node)
>>                 pos->initialized = false;
>>  }
>> --