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

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Date:   Mon, 10 Jan 2022 12:55:27 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Manaf Meethalavalappu Pallikunhi <quic_manafm@...cinc.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.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 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.

-- 
Warm Regards
Thara (She/Her/Hers)
> +
>   		thermal_notify_tz_disable(tz->id);
> +	}
>   
>   	return ret;
>   }
>