diff mbox series

[5.4,27/43] arm64: dts: rockchip: fix rk3399-puma eMMC HS400 signal integrity

Message ID 20220317124528.428426719@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH March 17, 2022, 12:45 p.m. UTC 
From: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>

[ 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 mbox series

Patch

diff --git a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
index 45b86933c6ea..390b86ec6538 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
@@ -467,6 +467,12 @@ 
 };
 
 &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;