linux-kernel - [PATCH v2] ARM: dts: exynos: enable polling in Exynos 4210

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Date:   Mon, 11 Sep 2023 15:34:14 +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
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>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: [PATCH v2] 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>
---
v1 -> v2: Just uploaded separately from all the thermal: exynos:
  patches with a shorter recipient list, no change otherwise.

 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