linux-kernel - [PATCH 01/11] ARM: dts: exynos: enable polling in Exynos 4210

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Date:   Tue, 29 Aug 2023 11:18:39 +0200
From:   Mateusz Majewski <m.majewski2@...sung.com>
To:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Cc:     Mateusz Majewski <m.majewski2@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: [PATCH 01/11] ARM: dts: exynos: enable polling in Exynos 4210

It seems that thermal in Exynos 4210 is broken without this, as it will
never decrease cooling after increasing it.

Signed-off-by: Mateusz Majewski <m.majewski2@...sung.com>
---
 arch/arm/boot/dts/samsung/exynos4210.dtsi | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/samsung/exynos4210.dtsi b/arch/arm/boot/dts/samsung/exynos4210.dtsi
index 0e27c3375e2e..aae185b7f91c 100644
--- a/arch/arm/boot/dts/samsung/exynos4210.dtsi
+++ b/arch/arm/boot/dts/samsung/exynos4210.dtsi
@@ -391,8 +391,14 @@ &cpu_alert2 {
 };
 
 &cpu_thermal {
-	polling-delay-passive = <0>;
-	polling-delay = <0>;
+	/* Exynos 4210 supports thermal interrupts, but only for the rising threshold.
+	 * This means that polling is not needed for preventing overheating, but only
+	 * for decreasing cooling when possible. Hence we poll with a high delay.
+	 * Ideally, we would disable polling for the first trip point, but this isn't
+	 * really possible without outrageous hacks.
+	 */
+	polling-delay-passive = <5000>;
+	polling-delay = <5000>;
 };
 
 &gic {
-- 
2.41.0