linux-kernel - [PATCH v2 2/3] ARM: dts: rockchip: Use the GPU to cool CPU thermal zone of veyron mickey

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Message-Id: <20190520220051.54847-2-mka@chromium.org>
Date:   Mon, 20 May 2019 15:00:50 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Heiko Stuebner <heiko@...ech.de>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH v2 2/3] ARM: dts: rockchip: Use the GPU to cool CPU thermal zone of veyron mickey

On rk3288 the CPU and GPU temperatures are correlated. Limit the GPU
frequency on veyron mickey to 400 MHz for CPU temperatures >= 65°C
and to 300 MHz for CPU temperatures >= 85°C.

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

Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
Changes in v2:
- added 'cpu_warm_limit_gpu' to throttle GPU for T.cpu >= 65°C
- removed comment saying that GPU isn't throttled beyond 400 MHz
  based on CPU temperature
- updated 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 | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/arm/boot/dts/rk3288-veyron-mickey.dts b/arch/arm/boot/dts/rk3288-veyron-mickey.dts
index 52f6abc22291..34797abe3403 100644
--- a/arch/arm/boot/dts/rk3288-veyron-mickey.dts
+++ b/arch/arm/boot/dts/rk3288-veyron-mickey.dts
@@ -75,9 +75,7 @@
 	cooling-maps {
 		/*
 		 * After 1st level, throttle the CPU down to as low as 1.4 GHz
-		 * and don't let the GPU go faster than 400 MHz.  Note that we
-		 * won't throttle the GPU lower than 400 MHz due to CPU
-		 * heat--we'll let the GPU do the rest itself.
+		 * and don't let the GPU go faster than 400 MHz.
 		 */
 		cpu_warm_limit_cpu {
 			trip = <&cpu_alert_warm>;
@@ -86,6 +84,10 @@
 					 <&cpu2 THERMAL_NO_LIMIT 4>,
 					 <&cpu3 THERMAL_NO_LIMIT 4>;
 		};
+		cpu_warm_limit_gpu {
+			trip = <&cpu_alert_warm>;
+			cooling-device = <&gpu 1 1>;
+		};
 
 		/*
 		 * Add some discrete steps to help throttling system deal
@@ -125,6 +127,12 @@
 					 <&cpu2 8 THERMAL_NO_LIMIT>,
 					 <&cpu3 8 THERMAL_NO_LIMIT>;
 		};
+
+		/* At very hot, don't let GPU go over 300 MHz */
+		cpu_very_hot_limit_gpu {
+			trip = <&cpu_alert_very_hot>;
+			cooling-device = <&gpu 2 2>;
+		};
 	};
 };
 
-- 
2.21.0.1020.gf2820cf01a-goog