Re: [PATCH] arm64: dts: qcom: x1e78100-thinkpad-t14s: Add thermal zones for PMICs

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 9/22/26 8:18 PM, Daniel Lezcano wrote:
> Add the thermal zones for the ThinkPad T14s and describe the board
> temperature sensors exposed through the PMK8550 VADC.
> 
> The keyboard area is the main thermal constraint under sustained CPU
> load. Add a passive thermal zone for it and progressively throttle the
> three CPU groups as the temperature approaches the 53°C limit. The
> groups are activated at 49°C, 51°C and 53°C respectively, with a
> 1000 m°C hysteresis and a 500 ms passive polling interval.
> 
> The cooling maps limit each CPU cooling device to state 6, which
> corresponds to approximately 1.9 GHz. Testing showed that the system can
> sustain the workload with all three CPU clusters capped at this
> frequency while maintaining the expected performance, making it a
> suitable upper cooling state for thermal regulation.
> 
> Several configurations were evaluated while tuning the keyboard zone.
> Using a single 53°C trip for all CPUs allowed the temperature to rise
> quickly but resulted in a stable operating point around 54.3°C, about
> 1.3°C above the intended limit. Introducing staged cooling before the
> target significantly reduced the thermal overshoot. A 49/51/53°C
> configuration kept the steady-state temperature close to 53°C, while a
> later 49.5/51.5/53°C configuration improved the heating response but
> shifted the equilibrium slightly above the target. Based on these
> results, keep the earlier 49/51/53°C staging.
> 
> Also add a passive back-cover thermal zone which uses the GPU as a
> cooling device at 64°C, together with a 73°C critical shutdown trip.

The GPU contributes much less to the thermal situation. 64C sounds
like a lot for backcover - what is the threshold on Windows?

Konrad