[PATCH v2] arm64: dts: qcom: x1e78100-thinkpad-t14s: Add thermal zones for PMICs

[PATCH v2] arm64: dts: qcom: x1e78100-thinkpad-t14s: Add thermal zones for PMICs

[Daniel Lezcano]

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.

Finally, enable ADC thermal monitoring on the corresponding PMK8550 VADC
channels used by these thermal zones.

Signed-off-by: Daniel Lezcano <daniel.lezcano@oss.qualcomm.com>
---
 .../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..5d3a0a5ead68 100644
--- a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
+++ b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
@@ -20,6 +20,81 @@ / {
 	compatible = "lenovo,thinkpad-t14s", "qcom,x1e78100", "qcom,x1e80100";
 	chassis-type = "laptop";
 
+	thermal-zones {
+		soc-thermal {
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_GPIO_100K_PU(1)>;
+		};
+
+		keyboard-thermal {
+			critical-action = "shutdown";
+			polling-delay-passive = <500>;
+
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_GPIO_100K_PU(1)>;
+
+			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>;
+				};
+			};
+		};
+
+		backcover-thermal {
+			critical-action = "shutdown";
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX1_THM_100K_PU(1)>;
+
+			trips {
+				backcover-critical {
+					temperature = <73000>;
+					hysteresis = <1000>;
+					type = "critical";
+				};
+			};
+		};
+
+		smb-thermal {
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX2_THM_100K_PU(1)>;
+		};
+
+		sdx-thermal {
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX3_THM_100K_PU(1)>;
+		};
+
+		east-thermal {
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX4_THM_100K_PU(1)>;
+		};
+
+		west-thermal {
+			thermal-sensors = <&pmk8550_vadc ADC5_GEN3_AMUX5_THM_100K_PU(1)>;
+		};
+	};
+
 	wcd938x: audio-codec {
 		compatible = "qcom,wcd9385-codec";
 
@@ -1612,6 +1687,36 @@ wwan_sw_en: wwan-sw-en-state {
 	};
 };
 
+&pmk8550_vadc {
+	channel@144 {
+		qcom,adc-tm;
+	};
+
+	channel@145 {
+		qcom,adc-tm;
+	};
+
+	channel@146 {
+		qcom,adc-tm;
+	};
+
+	channel@147 {
+		qcom,adc-tm;
+	};
+
+	channel@148 {
+		qcom,adc-tm;
+	};
+
+	channel@14a {
+		qcom,adc-tm;
+	};
+
+	channel@14b {
+		qcom,adc-tm;
+	};
+};
+
 &usb_1_ss0_hsphy {
 	vdd-supply = <&vreg_l3j_0p8>;
 	vdda12-supply = <&vreg_l2j_1p2>;
-- 
2.53.0