linux-kernel - Re: [PATCH v3] thermal/core: Clear all mitigation when thermal zone is disabled

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Date:   Wed, 19 Jan 2022 20:12:10 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Manaf Meethalavalappu Pallikunhi <quic_manafm@...cinc.com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Matthias Kaehlcke <mka@...omium.org>, thara.gopinath@...il.com
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] thermal/core: Clear all mitigation when thermal zone
 is disabled


Hi Manaf,

On 19/01/2022 20:05, Manaf Meethalavalappu Pallikunhi wrote:
> Hi Rafael/Daniel,
> 
> Could you please check and comment  ?

It is in my todo list, I'll review it before the end of the week.

Regards

  -- Daniel

> On 1/11/2022 2:15 AM, Manaf Meethalavalappu Pallikunhi wrote:
>> Hi Thara,
>>
>> On 1/10/2022 11:25 PM, Thara Gopinath wrote:
>>> Hi Manaf,
>>>
>>> On 1/7/22 1:56 PM, Manaf Meethalavalappu Pallikunhi wrote:
>>>> Whenever a thermal zone is in trip violated state, there is a chance
>>>> that the same thermal zone mode can be disabled either via thermal
>>>> core API or via thermal zone sysfs. Once it is disabled, the framework
>>>> bails out any re-evaluation of thermal zone. It leads to a case where
>>>> if it is already in mitigation state, it will stay the same state
>>>> until it is re-enabled.
>>>>
>>>> To avoid above mentioned issue, on thermal zone disable request
>>>> reset thermal zone and clear mitigation for each trip explicitly.
>>>>
>>>> Signed-off-by: Manaf Meethalavalappu Pallikunhi
>>>> <quic_manafm@...cinc.com>
>>>> ---
>>>>   drivers/thermal/thermal_core.c | 12 ++++++++++--
>>>>   1 file changed, 10 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/thermal/thermal_core.c
>>>> b/drivers/thermal/thermal_core.c
>>>> index 51374f4..e288c82 100644
>>>> --- a/drivers/thermal/thermal_core.c
>>>> +++ b/drivers/thermal/thermal_core.c
>>>> @@ -447,10 +447,18 @@ static int thermal_zone_device_set_mode(struct
>>>> thermal_zone_device *tz,
>>>>         thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
>>>>   -    if (mode == THERMAL_DEVICE_ENABLED)
>>>> +    if (mode == THERMAL_DEVICE_ENABLED) {
>>>>           thermal_notify_tz_enable(tz->id);
>>>> -    else
>>>> +    } else {
>>>> +        int trip;
>>>> +
>>>> +        /* make sure all previous throttlings are cleared */
>>>> +        thermal_zone_device_init(tz);
>>>
>>> It looks weird to do a init when you are actually disabling the
>>> thermal zone.
>>>
>>>
>>>> +        for (trip = 0; trip < tz->trips; trip++)
>>>> +            handle_thermal_trip(tz, trip);
>>>
>>> So this is exactly what thermal_zone_device_update does except that
>>> thermal_zone_device_update checks for the mode and bails out if the
>>> zone is disabled.
>>> This will work because as you explained in v2, the temperature is
>>> reset in thermal_zone_device_init and handle_thermal_trip will remove
>>> the mitigation if any.
>>>
>>> My two cents here (Rafael and Daniel can comment more on this).
>>>
>>> I think it will be cleaner if we can have a third mode
>>> THERMAL_DEVICE_DISABLING and have thermal_zone_device_update handle
>>> clearing the mitigation. So this will look like
>>> if (mode == THERMAL_DEVICE_DISABLED)
>>>     tz->mode = THERMAL_DEVICE_DISABLING;
>>> else
>>>     tz->mode = mode;
>>>
>>> thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
>>>
>>> if (mode == THERMAL_DEVICE_DISABLED)
>>>     tz->mode = mode;
>>>
>>> You will have to update update_temperature to set tz->temperature =
>>> THERMAL_TEMP_INVALID and thermal_zone_set_trips to set
>>> tz->prev_low_trip = -INT_MAX and tz->prev_high_trip = INT_MAX for
>>> THERMAL_DEVICE_DISABLING mode.
>>
>> I think just updating above fields doesn't guarantee complete clearing
>> of mitigation for all governors. For  step_wise governor, to make sure
>> mitigation removed completely, we have to set each
>> thermal-instance->initialized = false as well.
>>
>> If we add that to above list of variables in update_temperature()
>> under if (mode == THERMAL_DEVICE_DISABLING) , it is same as
>> thermal_zone_device_init function does in current patch. We are just
>> resetting same fields in different place under a new mode, right ?
>>
>> Thanks,
>>
>> Manaf
>>


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