linux-kernel - [PATCH 3/3] arm64: zynqmp: Add thermal zones

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Message-Id: <20240812215129.3599832-4-sean.anderson@linux.dev>
Date: Mon, 12 Aug 2024 17:51:28 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Michal Simek <michal.simek@....com>,
	linux-arm-kernel@...ts.infradead.org
Cc: Rob Herring <robh@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: [PATCH 3/3] arm64: zynqmp: Add thermal zones

Add some thermal trip points. We can't undervolt the CPUs to save power
when we underclock them, so there isn't really a point in throttling
them until we are about to overheat. As such, the passive trip point is
right below the critical trip point.

The critical trip point is the extended/industrial-grade maximum
junction temperature of 100C minus the maximum temperature sensor error
of 3.5C (in the range -55C to 110C). Automotive- and military-grade
parts can go up to 125C, but as far as I can tell there is no way to
detect them at runtime. Userspace can adjust the trip points at runtime,
but this may not be viable when booting above 100C. I think it's
reasonable to ask automotive/military users to edit their device trees
to bump the trip points, but if that proves to be an issue we can
always go with no default temperatures. However, that wouldn't be too
nice for the majority of extended/industrial users.

Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---

 arch/arm64/boot/dts/xilinx/zynqmp.dtsi | 86 ++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)

diff --git a/arch/arm64/boot/dts/xilinx/zynqmp.dtsi b/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
index 21c1adbaf35f..467f084c6469 100644
--- a/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
+++ b/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
@@ -18,6 +18,7 @@
 #include <dt-bindings/interrupt-controller/irq.h>
 #include <dt-bindings/power/xlnx-zynqmp-power.h>
 #include <dt-bindings/reset/xlnx-zynqmp-resets.h>
+#include <dt-bindings/thermal/thermal.h>
 
 / {
 	compatible = "xlnx,zynqmp";
@@ -36,6 +37,7 @@ cpus {
 		#size-cells = <0>;
 
 		cpu0: cpu@0 {
+			#cooling-cells = <2>;
 			compatible = "arm,cortex-a53";
 			device_type = "cpu";
 			enable-method = "psci";
@@ -46,6 +48,7 @@ cpu0: cpu@0 {
 		};
 
 		cpu1: cpu@1 {
+			#cooling-cells = <2>;
 			compatible = "arm,cortex-a53";
 			device_type = "cpu";
 			enable-method = "psci";
@@ -56,6 +59,7 @@ cpu1: cpu@1 {
 		};
 
 		cpu2: cpu@2 {
+			#cooling-cells = <2>;
 			compatible = "arm,cortex-a53";
 			device_type = "cpu";
 			enable-method = "psci";
@@ -66,6 +70,7 @@ cpu2: cpu@2 {
 		};
 
 		cpu3: cpu@3 {
+			#cooling-cells = <2>;
 			compatible = "arm,cortex-a53";
 			device_type = "cpu";
 			enable-method = "psci";
@@ -406,6 +411,87 @@ ams {
 			<&xilinx_ams 27>, <&xilinx_ams 28>, <&xilinx_ams 29>;
 	};
 
+
+	tsens_apu: thermal-sensor-apu {
+		compatible = "generic-adc-thermal";
+		#thermal-sensor-cells = <0>;
+		io-channels = <&xilinx_ams 7>;
+		io-channel-names = "sensor-channel";
+	};
+
+	tsens_rpu: thermal-sensor-rpu {
+		compatible = "generic-adc-thermal";
+		#thermal-sensor-cells = <0>;
+		io-channels = <&xilinx_ams 8>;
+		io-channel-names = "sensor-channel";
+	};
+
+	tsens_pl: thermal-sensor-pl {
+		compatible = "generic-adc-thermal";
+		#thermal-sensor-cells = <0>;
+		io-channels = <&xilinx_ams 20>;
+		io-channel-names = "sensor-channel";
+	};
+
+	thermal-zones {
+		apu-thermal {
+			polling-delay-passive = <1000>;
+			polling-delay = <5000>;
+			thermal-sensors = <&tsens_apu>;
+
+			trips {
+				apu_passive: passive {
+					temperature = <93000>;
+					hysteresis = <3500>;
+					type = "passive";
+				};
+
+				apu_critical: critical {
+					temperature = <96500>;
+					hysteresis = <3500>;
+					type = "critical";
+				};
+			};
+
+			cooling-maps {
+				map {
+					trip = <&apu_passive>;
+					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>;
+				};
+			};
+		};
+
+		rpu-thermal {
+			polling-delay = <10000>;
+			thermal-sensors = <&tsens_rpu>;
+
+			trips {
+				critical {
+					temperature = <96500>;
+					hysteresis = <3500>;
+					type = "critical";
+				};
+			};
+		};
+
+		pl-thermal {
+			polling-delay = <10000>;
+			thermal-sensors = <&tsens_pl>;
+
+			trips {
+				critical {
+					temperature = <96500>;
+					hysteresis = <3500>;
+					type = "critical";
+				};
+			};
+		};
+	};
+
 	amba: axi {
 		compatible = "simple-bus";
 		bootph-all;
-- 
2.35.1.1320.gc452695387.dirty