linux-kernel - [PATCH] arm64: dts: allwinner: t527: orangepi-4a: Limit eMMC clock to 75 MHz

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Message-Id: <20250821132935.2070398-1-wens@kernel.org>
Date: Thu, 21 Aug 2025 21:29:35 +0800
From: Chen-Yu Tsai <wens@...nel.org>
To: Chen-Yu Tsai <wens@...e.org>,
	Jernej Skrabec <jernej@...nel.org>,
	Samuel Holland <samuel@...lland.org>
Cc: linux-sunxi@...ts.linux.dev,
	Andre Przywara <andre.przywara@....com>,
	linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: dts: allwinner: t527: orangepi-4a: Limit eMMC clock to 75 MHz

From: Chen-Yu Tsai <wens@...e.org>

The eMMC on the Orange Pi 4A doesn't function correctly at full speed
of 150 MHz under HS200 mode. Either the traces on the board or module
aren't great, or the SoC's internal delays are incorrect. Tuning the
pin drive strength did not help.

After some experimenting, 75 MHz was found to be stable enough. Use this
as the maximum frequency for now.

Fixes: de713ccb9934 ("arm64: dts: allwinner: t527: Add OrangePi 4A board")
Signed-off-by: Chen-Yu Tsai <wens@...e.org>
---
 arch/arm64/boot/dts/allwinner/sun55i-t527-orangepi-4a.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/allwinner/sun55i-t527-orangepi-4a.dts b/arch/arm64/boot/dts/allwinner/sun55i-t527-orangepi-4a.dts
index c52d09cf0888..fb5311a46c2e 100644
--- a/arch/arm64/boot/dts/allwinner/sun55i-t527-orangepi-4a.dts
+++ b/arch/arm64/boot/dts/allwinner/sun55i-t527-orangepi-4a.dts
@@ -160,6 +160,7 @@ &mmc2 {
 	mmc-ddr-1_8v;
 	mmc-hs200-1_8v;
 	non-removable;
+	max-frequency = <75000000>;
 	vmmc-supply = <&reg_cldo3>;
 	vqmmc-supply = <&reg_cldo1>;
 	status = "okay";
-- 
2.39.5