Re: Thermal notifications without setting thermal governor to userspace?

[Daniel Lezcano <daniel.lezcano@linaro.org>]

On 04/04/2022 19:17, Chris Down wrote:
> Daniel Lezcano writes:
>> Well on regular desktop, the thermal is managed under the hood by the 
>> firmware/hardware, few sensors are exported AFAICT. I don't think a 
>> thermal daemon would have a benefit on these platforms.
> 
> Maybe we have different expectations? On my laptop, a Thinkpad T14s, 
> things seem not too bad:

That is not a desktop but a laptop, it is different :)

Can you give the content of:

cat /sys/class/thermal/thermal_zone*/type
cat /sys/class/thermal/thermal_zone*/trip_*type

and

cat /sys/class/thermal/cooling_device*/type

?


>      % printf '%s\n' /sys/class/hwmon/hwmon*/temp*_input
>      /sys/class/hwmon/hwmon1/temp1_input
>      /sys/class/hwmon/hwmon2/temp1_input
>      /sys/class/hwmon/hwmon2/temp2_input
>      /sys/class/hwmon/hwmon2/temp3_input
>      /sys/class/hwmon/hwmon4/temp1_input
>      /sys/class/hwmon/hwmon4/temp2_input
>      /sys/class/hwmon/hwmon4/temp3_input
>      /sys/class/hwmon/hwmon4/temp4_input
>      /sys/class/hwmon/hwmon4/temp5_input
>      /sys/class/hwmon/hwmon4/temp6_input
>      /sys/class/hwmon/hwmon4/temp7_input
>      /sys/class/hwmon/hwmon4/temp8_input
>      /sys/class/hwmon/hwmon6/temp1_input
>      /sys/class/hwmon/hwmon8/temp1_input
>      /sys/class/hwmon/hwmon8/temp2_input
>      /sys/class/hwmon/hwmon8/temp3_input
>      /sys/class/hwmon/hwmon8/temp4_input
>      /sys/class/hwmon/hwmon8/temp5_input
> 
> There are working temperature sensors out of the box for the CPU, wifi 
> card, ACPI thermal zone, and extended sensors from thinkpad_acpi.
> 
> In my case, I'd like to get notifications in userspace when certain 
> temperatures are reached.
> 
> So if I understood correctly, there's no way to dynamically configure 
> temperature thresholds and get breach events even as root, even with the 
> new netlink solution?

There is a way but you need:

1. A programmable trip point

 
https://uefi.org/specs/ACPI/6.4/11_Thermal_Management/thermal-control.html#dynamically-changing-cooling-temperature-trip-points

1.1 A passive trip point dedicated for userspace (no cooling device 
associated)

1.2 Writable kernel config option

The trip point will be writable in sysfs

2. Get trip point crossed

Use the netlink

But you don't need to monitor all these thermal zones, it is up to the 
in-kernel thermal framework to deal with the trip point individually and 
protect the system.

The userspace should monitor what is considered as the 'case' sensor or 
'skin' sensor. The temperature on those sensor moves very slowly, so 
monitoring them by getting the temperature every second should be enough.



-- 
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog