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Fri, 16 Oct 2026 02:56:06 -0700 (PDT) Date: Fri, 16 Oct 2026 11:56:00 +0200 From: Stephan Gerhold To: Daniel Lezcano Cc: andersson@kernel.org, konradybcio@kernel.org, robh@kernel.org, krzk+dt@kernel.org, johannes.goede@oss.qualcomm.com, conor+dt@kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Mark Pearson Subject: Re: [PATCH v3] arm64: dts: qcom: x1e78100-thinkpad-t14s: Add thermal zones for PMICs Message-ID: References: <20261014193524.5590-1-daniel.lezcano@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20261014193524.5590-1-daniel.lezcano@oss.qualcomm.com> On Wed, Oct 14, 2026 at 09:35:24PM +0200, Daniel Lezcano wrote: > Add thermal zones for the ThinkPad T14s and describe the board > temperature sensors exposed through the PMK8550 VADC. > > Add a passive thermal zone for the keyboard area, which is the main > thermal constraint under sustained load. The EC reports a thermal alert > at 57.85°C, so use this value as the passive trip point and allow the > thermal framework to throttle all CPUs and the GPU when the threshold is > reached. Use a 1000 m°C hysteresis and a 500 ms passive polling interval. > > An earlier approach used staged CPU cluster throttling in an attempt to > start thermal mitigation before reaching the target temperature. Testing > did not show a significant improvement compared to throttling all CPUs at > the EC thermal alert threshold. It also introduced a latency imbalance > between the different CPU clusters, which could negatively affect > workloads depending on where tasks are scheduled. > > A more optimal solution would require a significantly more complex, > system-wide approach, accounting for the workload distribution and the > available power and thermal headroom across the CPU clusters and other > devices. Such an approach would also require kernel mechanisms which are > not currently available. Keep the thermal policy simple here and use a > single passive trip, which at least ensures that the system is actively > mitigated before reaching temperatures that could ultimately lead to a > thermal shutdown. > > The mitigation temperature is derived from the platform behaviour when > using the balanced power profile available under Windows. A separate > change will adjust this trip point dynamically according to events > reported by the embedded controller. Name the trip > "keyboard-ec-alert" so that the EC driver can identify the corresponding > trip point in the device tree. > > Also add a 73°C critical trip to shut the system down if the keyboard > temperature reaches an unsafe level. > > Add a thermal zone for the back cover with a 73°C critical shutdown > trip. > > Describe the SoC, SMB, SDX, east and west board temperature sensors as > monitoring-only thermal zones. > > Thermal camera measurements were also used to compare the reported > temperatures with the physical temperature of the chassis. The measured > values appear to primarily represent temperatures inside the enclosure > rather than the user-contact surface temperature. No unsafe external > surface temperature was observed during these tests, although this should > not be considered a substitute for formal platform thermal qualification. > Thanks to Mark, I was able to get some info on the location/purpose of the thermal sensors in the T14s. As you noted already here, the sensors are primarily focused on specific components inside the enclosure rather than user-contact surface temperatures. Below I added some suggestions for more accurate names for the thermal zones. Perhaps that helps to optimize the thermal control further. > Finally, enable ADC thermal monitoring on the corresponding PMK8550 VADC > channels used by these thermal zones. > > Signed-off-by: Daniel Lezcano > --- > .../qcom/x1e78100-lenovo-thinkpad-t14s.dtsi | 105 ++++++++++++++++++ > 1 file changed, 105 insertions(+) > > diff --git a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi > index 75ad74bcb042..2d0a434d2248 100644 > --- a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi > +++ b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi > @@ -502,6 +502,81 @@ platform { > }; > }; > }; > + > + thermal-zones { > + backcover-thermal { > + critical-action = "shutdown"; > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_THM_100K_PU(1)>; dram-thermal or memory-thermal (or maybe keyboard-thermal if you want to give it a user-surface name, although that purpose seems to be secondary). Next to DRAM memory, on the top part of the mainboard, facing upwards to the keyboard. Unrelated to the backcover. > + > + trips { > + backcover-critical { > + temperature = <73000>; > + hysteresis = <1000>; > + type = "critical"; > + }; Is this critical temperature is appropriate for the DRAM temperature? Windows seems to have 115°C here as critical trip point which is maybe a bit too high. > + }; > + }; > + > + east-thermal { > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX4_THM_100K_PU(1)>; gpu-pmic-thermal (next to GPU-related PMICs close to the SoC) > + }; > + > + keyboard-thermal { > + critical-action = "shutdown"; > + polling-delay-passive = <500>; > + > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_GPIO_100K_PU(1)>; fan-thermal or heatpipe-thermal (or maybe backcover-thermal if you want to give it a user-surface name, although that purpose seems to be secondary). Next to fan/heat pipe, on the bottom part of the mainboard, facing downwards to the back cover. Unrelated to the keyboard. > + > + trips { > + keyboard_ec_alert: keyboard-ec-alert { > + temperature = <57850>; > + hysteresis = <1000>; > + type = "passive"; > + }; > + > + keyboard-critical { > + temperature = <73000>; > + hysteresis = <1000>; > + type = "critical"; > + }; > + }; > + > + cooling-maps { > + map0 { > + trip = <&keyboard_ec_alert>; > + cooling-device = <&cpu0 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu1 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu2 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu3 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu4 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu5 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu6 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu7 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu8 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu9 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu10 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&cpu11 THERMAL_NO_LIMIT THERMAL_NO_LIMIT>, > + <&gpu THERMAL_NO_LIMIT THERMAL_NO_LIMIT>; > + }; > + }; > + }; > + > + sdx-thermal { > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX3_THM_100K_PU(1)>; wwan-thermal > + }; > + > + smb-thermal { > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_THM_100K_PU(1)>; charger-thermal > + }; > + > + soc-thermal { > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_GPIO_100K_PU(1)>; cpu-pmic-thermal (next to CPU-related PMICs close to SoC) > + }; > + > + west-thermal { > + thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX5_THM_100K_PU(1)>; typec-thermal or usbc-thermal Next to USB-C ports, bottom part of mainboard, facing towards the back cover. > + }; > + }; There is also ssd-thermal @ SYS_THERM7 thermal-sensors = <&pmk8550_adc_tm ADC5_GEN3_AMUX6_THM_100K_PU(1)>; as I mentioned before. Windows uses the EC sensors for throttling, although given that we don't have interrupt support for the EC yet, I think it is fine to initially use the PMIC sensors. Thanks, Stephan