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Subject: Re: [PATCH 1/3] thermal: core: Add indication for userspace usage
From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
In-Reply-To: <f863f2e1e322a8819c660f5eefbbc4acf7522990.camel@linux.intel.com>
Date:   Mon, 7 Dec 2020 13:36:35 +0800
Cc:     Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Zhang Rui <rui.zhang@intel.com>, amitk@kernel.org,
        "open list:THERMAL" <linux-pm@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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References: <20201128175450.12456-1-kai.heng.feng@canonical.com>
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 <860126B8-1152-4EE3-B15E-B4E45EFE879F@canonical.com>
 <fc67ad02826fb3adfd8457e1a0baf234a8fa3fce.camel@linux.intel.com>
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 <f863f2e1e322a8819c660f5eefbbc4acf7522990.camel@linux.intel.com>
To:     Daniel Lezcano <daniel.lezcano@linaro.org>
Precedence: bulk


> On Dec 1, 2020, at 02:39, Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> wrote:
> 
> On Tue, 2020-12-01 at 02:22 +0800, Kai-Heng Feng wrote:
>>> On Dec 1, 2020, at 02:13, Srinivas Pandruvada <
>>> srinivas.pandruvada@linux.intel.com> wrote:
>> 
>> [snipped] 
>> 
>>>>> What about creating an new callback
>>>>> 
>>>>> enum thermal_trip_status {
>>>>> 	THERMAL_TRIP_DISABLED = 0,
>>>>> 	THERMAL_TRIP_ENABLED,
>>>>> };
>>>>> 
>>>>> int get_trip_status(struct thermal_zone_device *, int trip,
>>>>> enum
>>>>> thermal_trip_status *state);
>>>>> 
>>>>> Then in 
>>>>> static void handle_thermal_trip(struct thermal_zone_device *tz,
>>>>> int
>>>>> trip)
>>>>> {
>>>>> 
>>>>> /* before tz->ops->get_trip_temp(tz, trip, &trip_temp); */
>>>>> if (tz->ops->get_trip_status) {
>>>>> 	enum thermal_trip_status *status;
>>>>> 
>>>>> 	if (!tz->ops->get_trip_status(tz, trip, &status)) {
>>>>> 		if (status == THERMAL_TRIP_DISABLED)
>>>>> 			return;	
>>>>> 	}
>>>>> }
>>>>> ...
>>>>> ...
>>>>> 
>>>>> }
>>>>> 
>>>>> 
>>>>> This callback will help the cases:
>>>>> - Allows drivers to selectively disable certain trips during
>>>>> init
>>>>> state
>>>>> or system resume where there can be spikes or always. int340x
>>>>> drivers
>>>>> can disable always.
>>>> 
>>>> This sounds really great. This is indeed can happen on system
>>>> resume,
>>>> before userspace process thaw.
>>>> 
>>>>> - Still give options for drivers to handle critical trip even
>>>>> if
>>>>> they
>>>>> are bound to user space governors. User space process may be
>>>>> dead,
>>>>> so
>>>>> still allow kernel to process graceful shutdown
>>>> 
>>>> To make the scenario happen, do we need a new sysfs to let
>>>> usespace
>>>> enable it with THERMAL_TRIP_ENABLED?
>>> This should be drivers call not user space.
>> 
>> Understood. So after thermal_zone_device_register(), the driver can
>> decide to what to return on get_trip_temp().
> get_trip_status()
> 
>> Let me work on a new patch if there's no other concern.
> Better to wait for confirmation from Daniel and others.

Daniel,

Do you like Srinivas' proposed solution?

I hope we can find a solution in upstream kernel soon.

Kai-Heng

> 
> Thanks,
> Srinivas
> 
>> 
>> Kai-Heng
>> 
>>> Thanks,
>>> Srinivas