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From:   Chen-Yu Tsai <wenst@chromium.org>
To:     Matthias Brugger <matthias.bgg@gmail.com>
Cc:     Chen-Yu Tsai <wenst@chromium.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        =?UTF-8?q?N=C3=ADcolas=20F=20=2E=20R=20=2E=20A=20=2E=20Prado?= 
        <nfraprado@collabora.com>
Subject: [PATCH 1/4] arm64: dts: mediatek: mt8183: Fix systimer 13 MHz clock description
Date:   Thu,  1 Dec 2022 16:42:26 +0800
Message-Id: <20221201084229.3464449-2-wenst@chromium.org>
In-Reply-To: <20221201084229.3464449-1-wenst@chromium.org>
References: <20221201084229.3464449-1-wenst@chromium.org>
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The systimer block derives its 13 MHz clock by dividing the main 26 MHz
oscillator clock by 2 internally, not through the TOPCKGEN clock
controller.

On the MT8183 this divider is set either by power-on-reset or by the
bootloader. The bootloader may then make the divider unconfigurable to,
but can be read out by, the operating system.

Making the systimer block take the 26 MHz clock directly requires
changing the implementations. As an ABI compatible fix, change the
input clock of the systimer block a fixed factor divide-by-2 clock
that takes the 26 MHz oscillator as its input.

Fixes: 5bc8e2875ffb ("arm64: dts: mt8183: add systimer0 device node")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
---
 arch/arm64/boot/dts/mediatek/mt8183.dtsi | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/mediatek/mt8183.dtsi b/arch/arm64/boot/dts/mediatek/mt8183.dtsi
index 19ff1babc359..0cbbaebe1213 100644
--- a/arch/arm64/boot/dts/mediatek/mt8183.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt8183.dtsi
@@ -585,6 +585,15 @@ psci {
 		method = "smc";
 	};
 
+	clk13m: fixed-factor-clock-13m {
+		compatible = "fixed-factor-clock";
+		#clock-cells = <0>;
+		clocks = <&clk26m>;
+		clock-div = <2>;
+		clock-mult = <1>;
+		clock-output-names = "clk13m";
+	};
+
 	clk26m: oscillator {
 		compatible = "fixed-clock";
 		#clock-cells = <0>;
@@ -968,8 +977,7 @@ systimer: timer@10017000 {
 				     "mediatek,mt6765-timer";
 			reg = <0 0x10017000 0 0x1000>;
 			interrupts = <GIC_SPI 200 IRQ_TYPE_LEVEL_HIGH>;
-			clocks = <&topckgen CLK_TOP_CLK13M>;
-			clock-names = "clk13m";
+			clocks = <&clk13m>;
 		};
 
 		iommu: iommu@10205000 {
-- 
2.38.1.584.g0f3c55d4c2-goog