linux-kernel - [PATCH v2] ARM: dts: sun8i-h3: Add thermal trip points/cooling maps

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Date:   Mon, 24 Feb 2020 17:54:46 +0100
From:   Ondrej Jirman <megous@...ous.com>
To:     linux-sunxi@...glegroups.com
Cc:     Ondrej Jirman <megous@...ous.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED
        DEVICE TREE BINDINGS),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Allwinner
        sunXi SoC support), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] ARM: dts: sun8i-h3: Add thermal trip points/cooling maps

This enables passive cooling by down-regulating CPU voltage
and frequency.

For trip points, I used a slightly lowered values from the BSP
code. The critical temperature of 110°C from BSP code seemed
like a lot, so I rounded it off to 100°C.

The critical trip point value is 30°C above the maximum recommended
ambient temperature (70°C) for the SoC from the datasheet, so there's
some headroom even at such a high ambient temperature.

Signed-off-by: Ondrej Jirman <megous@...ous.com>
---
 arch/arm/boot/dts/sun8i-h3.dtsi | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

v2:
- added more detail to the commit description

diff --git a/arch/arm/boot/dts/sun8i-h3.dtsi b/arch/arm/boot/dts/sun8i-h3.dtsi
index 20217e2ca4d3a..e83aa6866e7ea 100644
--- a/arch/arm/boot/dts/sun8i-h3.dtsi
+++ b/arch/arm/boot/dts/sun8i-h3.dtsi
@@ -41,6 +41,7 @@
  */
 
 #include "sunxi-h3-h5.dtsi"
+#include <dt-bindings/thermal/thermal.h>
 
 / {
 	cpu0_opp_table: opp_table0 {
@@ -227,6 +228,30 @@ cpu_thermal: cpu-thermal {
 			polling-delay-passive = <0>;
 			polling-delay = <0>;
 			thermal-sensors = <&ths 0>;
+
+			trips {
+				cpu_hot_trip: cpu-hot {
+					temperature = <80000>;
+					hysteresis = <2000>;
+					type = "passive";
+				};
+
+				cpu_very_hot_trip: cpu-very-hot {
+					temperature = <100000>;
+					hysteresis = <0>;
+					type = "critical";
+				};
+			};
+
+			cooling-maps {
+				cpu-hot-limit {
+					trip = <&cpu_hot_trip>;
+					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>;
+				};
+			};
 		};
 	};
 };
-- 
2.25.1