Re: [PATCH v4] arm64: dts: qcom: x1e78100-thinkpad-t14s: Add thermal zones for PMICs

[Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>]

On 10/23/26 11:17, Stephan Gerhold wrote:
> On Fri, Oct 23, 2026 at 10:38:27AM +0200, Daniel Lezcano wrote:
>> The ThinkPad T14s needs thermal mitigation under sustained workloads to
>> limit temperature rise before thermal shutdown. EC interrupt-driven thermal
>> monitoring is not yet supported, so use the board temperature sensors
>> exposed through the PMK8550 VADC to provide mitigation now.
>>
>> Describe the sensors near DRAM, the fan/heatpipe, the GPU and CPU PMICs,
>> the charger, the WWAN area and the USB-C ports. The DRAM-area sensor faces
>> the keyboard, while the fan/heatpipe-area sensor faces the back cover.
>> These are internal board measurements rather than direct measurements of
>> the user-contact surfaces.
>>
>> Use the heatpipe-area sensor for passive mitigation at 57.85 degrees
>> Celsius, derived from observed platform behaviour with the Windows
>> balanced power profile. Map the passive trip to all CPUs and the GPU,
>> with 1 degree Celsius hysteresis and a 500 ms passive polling interval.
>> Name the trip "backcover-ec-alert" so that the planned EC support can
>> locate and adjust it.
>>
>> An earlier approach using staged CPU-cluster throttling did not show a
>> significant improvement and introduced a latency imbalance between CPU
>> clusters. Keep a single passive trip to provide timely mitigation.
>>
>> Add 73 degree Celsius critical shutdown trips for the DRAM-area and
>> heatpipe-area sensors. Retain these baseline thresholds pending
>> sensor-specific hardware validation. The reported Windows DRAM threshold
>> of 115 degrees Celsius has not been established to apply to these VADC
>> measurements and does not justify changing the shutdown thresholds.
>>
>> Thermal camera measurements indicate that the readings primarily reflect
>> internal temperatures rather than chassis surface temperatures. No unsafe
>> external surface temperature was observed during those tests, but they do
>> not establish qualified critical limits for the internal sensors.
>>
>> Expose the remaining sensors as monitoring-only zones and enable ADC
>> threshold monitoring on the corresponding PMK8550 VADC channels.
>>
>> Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
>> Link: https://patch.msgid.link/20261014193524.5590-1-daniel.lezcano@oss.qualcomm.com
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
>> ---
>>   .../qcom/x1e78100-lenovo-thinkpad-t14s.dtsi   | 112 ++++++++++++++++++
>>   1 file changed, 112 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..21f4569068e1 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 +502,88 @@ platform {
>>   			};
>>   		};
>>   	};
>> +
>> +	thermal-zones {
>> +		/* Sensor near DRAM, facing the keyboard. */
>> +		dram-thermal {
>> +			critical-action = "shutdown";
>> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_THM_100K_PU(1)>;
>> +
>> +			trips {
>> +				dram-critical {
>> +					temperature = <73000>;
>> +					hysteresis = <1000>;
>> +					type = "critical";
>> +				};
>> +			};
>> +		};
>> +
>> +		/* Sensor near the GPU PMICs. */
>> +		gpu-pmic-thermal {
>> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX4_THM_100K_PU(1)>;
>> +		};
>> +
>> +		/* Sensor near the fan/heatpipe, facing the back cover. */
>> +		heatpipe-thermal {
>> +			critical-action = "shutdown";
>> +			polling-delay-passive = <500>;
>> +
>> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_GPIO_100K_PU(1)>;
>> +
>> +			trips {
>> +				backcover_ec_alert: backcover-ec-alert {
>> +					temperature = <57850>;
>> +					hysteresis = <1000>;
>> +					type = "passive";
>> +				};
>> +
>> +				heatpipe-critical {
>> +					temperature = <73000>;
>> +					hysteresis = <1000>;
>> +					type = "critical";
>> +				};
>> +			};
>> +
>> +			cooling-maps {
>> +				map0 {
>> +					trip = <&backcover_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>;
>> +				};
>> +			};
>> +		};
>> +
>> +		/* Sensor in the WWAN area. */
>> +		wwan-thermal {
>> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX3_THM_100K_PU(1)>;
>> +		};
>> +
>> +		/* Sensor in the charger area. */
>> +		charger-thermal {
>> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_THM_100K_PU(1)>;
>> +		};
>> +
>> +		/* Sensor near the CPU PMICs. */
>> +		cpu-pmic-thermal {
> 
> I'm a bit confused by the node order here. It's not ordered by the
> thermal sensor (SYS_THERMx) like in x1e80100-crd.dts, but it's not
> ordered alphabetically either. Or is it still the old order from the
> previous revision?
> 
> I think I'd personally prefer ordering by SYS_THERMx, but alphabetical
> order would be our typical rule.

Oh, yes I changed the name but forgot to reorder alphabetically :(

> 
> Anyway, for the changes itself:
> 
> Reviewed-by: Stephan Gerhold <stephan.gerhold@linaro.org>
> 
> Thanks for fixing the names!
> Stephan