linux-kernel - [PATCH 2/2] arm64: dts: mediatek: mt8195: Make sure MSDCPLL's rate is 400MHz

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Message-Id: <20230522093002.75137-3-angelogioacchino.delregno@collabora.com>
Date:   Mon, 22 May 2023 11:30:02 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     matthias.bgg@...il.com
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, weiyi.lu@...iatek.com, ikjn@...omium.org,
        chun-jie.chen@...iatek.com, tinghan.shen@...iatek.com,
        seiya.wang@...iatek.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, kernel@...labora.com,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Subject: [PATCH 2/2] arm64: dts: mediatek: mt8195: Make sure MSDCPLL's rate is 400MHz

Some bootloaders will set MSDCPLL's rate lower than 400MHz: what I have
seen is this clock being set at around 384MHz.
This is a performance concern (and possibly a stability one, for picky
eMMC/SD cards) as the MSDC controller's internal divier will choose a
frequency that is lower than expected, in the end causing a difference
in the expected mmc/sd device's timings.

Make sure that the MSDCPLL frequency is always set to 400MHz to both
improve performance and reliability of the sd/mmc storage.

Fixes: 37f2582883be ("arm64: dts: Add mediatek SoC mt8195 and evaluation board")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 arch/arm64/boot/dts/mediatek/mt8195.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
index a44aae4ab953..daac8e050ce7 100644
--- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
@@ -852,6 +852,8 @@ apmixedsys: syscon@...0c000 {
 			compatible = "mediatek,mt8195-apmixedsys", "syscon";
 			reg = <0 0x1000c000 0 0x1000>;
 			#clock-cells = <1>;
+			assigned-clocks = <&apmixedsys CLK_APMIXED_MSDCPLL>;
+			assigned-clock-rates = <400000000>;
 		};
 
 		systimer: timer@...17000 {
-- 
2.40.1