linux-kernel - Re: [PATCH 1/3] thermal: core: Add indication for userspace usage

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Message-Id: <860126B8-1152-4EE3-B15E-B4E45EFE879F@canonical.com>
Date:   Mon, 30 Nov 2020 16:23:59 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Zhang Rui <rui.zhang@...el.com>, amitk@...nel.org,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH 1/3] thermal: core: Add indication for userspace usage



> On Nov 30, 2020, at 15:57, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
> 
> 
> [Added Srinivas]
> 
> On 28/11/2020 18:54, Kai-Heng Feng wrote:
>> We are seeing thermal shutdown on Intel based mobile workstations, the
>> shutdown happens during the first trip handle in
>> thermal_zone_device_register():
>> kernel: thermal thermal_zone15: critical temperature reached (101 C), shutting down
>> 
>> However, we shouldn't do a thermal shutdown here, since
>> 1) We may want to use a dedicated daemon, Intel's thermald in this case,
>> to handle thermal shutdown.
>> 
>> 2) For ACPI based system, _CRT doesn't mean shutdown unless it's inside
>> ThermalZone. ACPI Spec, 11.4.4 _CRT (Critical Temperature):
>> "... If this object it present under a device, the device’s driver
>> evaluates this object to determine the device’s critical cooling
>> temperature trip point. This value may then be used by the device’s
>> driver to program an internal device temperature sensor trip point."
>> 
>> So a "critical trip" here merely means we should take a more aggressive
>> cooling method.
> 
> Well, actually it is stated before:
> 
> "This object, when defined under a thermal zone, returns the critical
> temperature at which OSPM must shutdown the system".

This means specifically for the ACPI ThermalZone in AML, e.g.:

ThermalZone (TZ0) {
....
    Method(_CRT) { ... }
 } // end of TZ0

However the device is not under any ACPI ThermalZone.

> 
> That is what does the thermal subsystem, no ?
> 
>> So add an indication to let thermal core know it should leave thermal
>> device to userspace to handle.
> 
> You may want to check the 'HOT' trip point and then use the notification
> mechanism to get notified in userspace and take action from there (eg.
> offline some CPUs).

For this particular issue we are facing, the thermal shutdown happens in thermal_zone_device_register() and userspace isn't up yet.

Kai-Heng

> 
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>> ---
>> drivers/thermal/thermal_core.c | 3 +++
>> include/linux/thermal.h        | 2 ++
>> 2 files changed, 5 insertions(+)
>> 
>> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
>> index c6d74bc1c90b..6561e3767529 100644
>> --- a/drivers/thermal/thermal_core.c
>> +++ b/drivers/thermal/thermal_core.c
>> @@ -1477,6 +1477,9 @@ thermal_zone_device_register(const char *type, int trips, int mask,
>> 			goto unregister;
>> 	}
>> 
>> +	if (tz->tzp && tz->tzp->userspace)
>> +		thermal_zone_device_disable(tz);
>> +
>> 	mutex_lock(&thermal_list_lock);
>> 	list_add_tail(&tz->node, &thermal_tz_list);
>> 	mutex_unlock(&thermal_list_lock);
>> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
>> index d07ea27e72a9..e8e8fac78fc8 100644
>> --- a/include/linux/thermal.h
>> +++ b/include/linux/thermal.h
>> @@ -247,6 +247,8 @@ struct thermal_zone_params {
>> 	 */
>> 	bool no_hwmon;
>> 
>> +	bool userspace;
>> +
>> 	int num_tbps;	/* Number of tbp entries */
>> 	struct thermal_bind_params *tbp;
>> 
>> 
> 
> 
> -- 
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