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

[Stephan Gerhold]

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@xxxxxxxxxxxxxxxx>
> Link: https://patch.msgid.link/20261014193524.5590-1-daniel.lezcano@xxxxxxxxxxxxxxxx
> Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxxxxxxxx>
> ---
>  .../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.

> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_GPIO_100K_PU(1)>;
> +		};
> +
> +		/* Sensor near the USB-C ports. */
> +		typec-thermal {
> +			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX5_THM_100K_PU(1)>;
> +		};
> +	};
>  };

Anyway, for the changes itself:

Reviewed-by: Stephan Gerhold <stephan.gerhold@xxxxxxxxxx>

Thanks for fixing the names!
Stephan