From f7f062919f4101505ff7ce2efccc9dcec5c334cd Mon Sep 17 00:00:00 2001
From: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Date: Wed, 19 Jan 2022 14:49:48 +0100
Subject: [PATCH] arm64: dts: rockchip: fix rk3399-puma eMMC HS400 signal
integrity
[ Upstream commit 62966cbdda8a92f82d966a45aa671e788b2006f7 ]
There are signal integrity issues running the eMMC at 200MHz on Puma
RK3399-Q7.
Similar to the work-around found for RK3399 Gru boards, lowering the
frequency to 100MHz made the eMMC much more stable, so let's lower the
frequency to 100MHz.
It might be possible to run at 150MHz as on RK3399 Gru boards but only
100MHz was extensively tested.
Cc: Quentin Schulz <foss+kernel@0leil.net>
Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Link: https://lore.kernel.org/r/20220119134948.1444965-1-quentin.schulz@theobroma-systems.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
index 4660416c8f38..544110aaffc5 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
@@ -472,6 +472,12 @@
};
&sdhci {
+ /*
+ * Signal integrity isn't great at 200MHz but 100MHz has proven stable
+ * enough.
+ */
+ max-frequency = <100000000>;
+
bus-width = <8>;
mmc-hs400-1_8v;
mmc-hs400-enhanced-strobe;