[PATCH v2 3/3] ARM: dts: rockchip: Configure the GPU thermal zone for mickey

[Matthias Kaehlcke <mka@chromium.org>]

mickey crams a lot of hardware into a tiny package, which requires
more aggressive thermal throttling than for devices with a larger
footprint. Configure the GPU thermal zone to throttle the GPU
progressively at temperatures >= 60°C. Heat dissipated by the
CPUs also affects the GPU temperature, hence we cap the CPU
frequency to 1.4 GHz for temperatures above 65°C. Further throttling
of the CPUs may be performed by the CPU thermal zone.

The configuration matches that of the downstream Chrome OS 3.14
kernel, the 'official' kernel for mickey.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
Changes in v2:
- specify all CPUs as cooling devices
- s/downstram/downstream/ in commit message

Note: this patch depends on "ARM: dts: rockchip: Add #cooling-cells
entry for rk3288 GPU" (https://lore.kernel.org/patchwork/patch/1075005/)
---
 arch/arm/boot/dts/rk3288-veyron-mickey.dts | 67 ++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/arch/arm/boot/dts/rk3288-veyron-mickey.dts b/arch/arm/boot/dts/rk3288-veyron-mickey.dts
index 34797abe3403..945e80801292 100644
--- a/arch/arm/boot/dts/rk3288-veyron-mickey.dts
+++ b/arch/arm/boot/dts/rk3288-veyron-mickey.dts
@@ -136,6 +136,73 @@
 	};
 };
 
+&gpu_thermal {
+	/delete-node/ trips;
+	/delete-node/ cooling-maps;
+
+	trips {
+		gpu_alert_warmish: gpu_alert_warmish {
+			temperature = <60000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "passive";
+		};
+		gpu_alert_warm: gpu_alert_warm {
+			temperature = <65000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "passive";
+		};
+		gpu_alert_hotter: gpu_alert_hotter {
+			temperature = <84000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "passive";
+		};
+		gpu_alert_very_very_hot: gpu_alert_very_very_hot {
+			temperature = <86000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "passive";
+		};
+		gpu_crit: gpu_crit {
+			temperature = <90000>; /* millicelsius */
+			hysteresis = <2000>; /* millicelsius */
+			type = "critical";
+		};
+	};
+
+	cooling-maps {
+		/* After 1st level throttle the GPU down to as low as 400 MHz */
+		gpu_warmish_limit_gpu {
+			trip = <&gpu_alert_warmish>;
+			cooling-device = <&gpu THERMAL_NO_LIMIT 1>;
+		};
+
+		/*
+		 * Slightly after we throttle the GPU, we'll also make sure that
+		 * the CPU can't go faster than 1.4 GHz.  Note that we won't
+		 * throttle the CPU lower than 1.4 GHz due to GPU heat--we'll
+		 * let the CPU do the rest itself.
+		 */
+		gpu_warm_limit_cpu {
+			trip = <&gpu_alert_warm>;
+			cooling-device = <&cpu0 4 4>,
+					 <&cpu1 4 4>,
+					 <&cpu2 4 4>,
+					 <&cpu3 4 4>;
+		};
+
+		/* When hot, GPU goes down to 300 MHz */
+		gpu_hotter_limit_gpu {
+			trip = <&gpu_alert_hotter>;
+			cooling-device = <&gpu 2 2>;
+		};
+
+		/* When really hot, don't let GPU go _above_ 300 MHz */
+		gpu_very_very_hot_limit_gpu {
+			trip = <&gpu_alert_very_very_hot>;
+			cooling-device = <&gpu 2 THERMAL_NO_LIMIT>;
+		};
+	};
+};
+
 &i2c2 {
 	status = "disabled";
 };
-- 
2.21.0.1020.gf2820cf01a-goog