[PATCH v2 3/3] arm64: dts: qcom: x1e78100-t14s: Add thermal zones for keyboard skin and charging sensors

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

The Lenovo ThinkPad T14s embedded controller exposes several platform
temperature sensors that are already used by the firmware for thermal
management.

Expose the EC as a thermal sensor provider and describe the keyboard
skin and charging circuitry sensors as thermal zones in the device
tree.

The keyboard thermal zone defines passive and hot trip points, while
the charging thermal zone also associates a cooling map with the CPU
clusters, allowing the generic thermal framework to apply CPU
throttling when the charging circuitry temperature exceeds the passive
threshold.

This integrates the EC temperature sensors with the Linux thermal
framework and enables platform thermal management using standard
thermal zone definitions.

The EC protocol currently does not provide a mechanism to program trip
points from Linux. Consequently, the thermal zones rely on periodic
polling to detect threshold crossings.

Using the charging circuitry temperature for thermal mitigation provides
a conservative approximation of the platform thermal state and prevents
the platform from reaching critical temperatures under sustained heavy
CPU load.

Without this change the platform reaches a critical thermal condition
and resets under heavy load.

Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
---
 .../qcom/x1e78100-lenovo-thinkpad-t14s.dtsi   | 68 ++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

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 5d49df41be02..a19a363da9ed 100644
--- a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
+++ b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
@@ -979,7 +979,7 @@ &i2c6 {
 
 	status = "okay";
 
-	embedded-controller@28 {
+	ec: embedded-controller@28 {
 		compatible = "lenovo,thinkpad-t14s-ec";
 		reg = <0x28>;
 
@@ -988,6 +988,8 @@ embedded-controller@28 {
 		pinctrl-0 = <&ec_int_n_default>;
 		pinctrl-names = "default";
 
+		#thermal-sensor-cells = <1>;
+
 		wakeup-source;
 	};
 };
@@ -1729,3 +1731,67 @@ &usb_mp_qmpphy1 {
 
 	status = "okay";
 };
+
+&thermal_zones {
+	ec-keyboard-thermal {
+		polling-delay = <5000>;
+		polling-delay-passive = <1000>;
+
+		thermal-sensors = <&ec 1>;
+
+		trips {
+			trip-point0 {
+				temperature = <55000>;
+				hysteresis = <2000>;
+				type = "passive";
+			};
+
+			trip-point1 {
+				temperature = <62000>;
+				hysteresis = <0>;
+				type = "hot";
+			};
+		};
+	};
+
+	ec-charging-thermal {
+		/* EC trip points cannot yet be programmed. */
+		polling-delay = <5000>;
+		polling-delay-passive = <2000>;
+
+		thermal-sensors = <&ec 3>;
+
+		trips {
+			ec_charging_psv0: trip-point0 {
+				temperature = <55000>;
+				hysteresis = <0>;
+				type = "passive";
+			};
+
+			ec_charging_alrt0: trip-point1 {
+				temperature = <63000>;
+				hysteresis = <0>;
+				type = "hot";
+			};
+		};
+
+		cooling-maps {
+			map0 {
+				trip = <&ec_charging_psv0>;
+				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>;
+			};
+		};
+
+	};
+};
-- 
2.53.0