current/SOURCES/arm64-dts-rockchip-fix-rk3399-puma-emmc-hs400-signal.patch

From 0ab4d9e31514c39e5ae6d61d93547aa4a459fbc9 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Wed, 19 Jan 2022 14:49:48 +0100
Subject: arm64: dts: rockchip: fix rk3399-puma eMMC HS400 signal integrity

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 --git a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
index 002ece51c3ba..08fa00364b42 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
@@ -439,6 +439,12 @@
 };
 
 &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;
-- 
2.34.1

1	From 0ab4d9e31514c39e5ae6d61d93547aa4a459fbc9 Mon Sep 17 00:00:00 2001
2	From: Sasha Levin <sashal@kernel.org>
3	Date: Wed, 19 Jan 2022 14:49:48 +0100
4	Subject: arm64: dts: rockchip: fix rk3399-puma eMMC HS400 signal integrity
5
6	From: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
7
8	[ Upstream commit 62966cbdda8a92f82d966a45aa671e788b2006f7 ]
9
10	There are signal integrity issues running the eMMC at 200MHz on Puma
11	RK3399-Q7.
12
13	Similar to the work-around found for RK3399 Gru boards, lowering the
14	frequency to 100MHz made the eMMC much more stable, so let's lower the
15	frequency to 100MHz.
16
17	It might be possible to run at 150MHz as on RK3399 Gru boards but only
18	100MHz was extensively tested.
19
20	Cc: Quentin Schulz <foss+kernel@0leil.net>
21	Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
22	Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
23	Link: https://lore.kernel.org/r/20220119134948.1444965-1-quentin.schulz@theobroma-systems.com
24	Signed-off-by: Heiko Stuebner <heiko@sntech.de>
25	Signed-off-by: Sasha Levin <sashal@kernel.org>
26	---
27	arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi \| 6 ++++++
28	1 file changed, 6 insertions(+)
29
30	diff --git a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
31	index 002ece51c3ba..08fa00364b42 100644
32	--- a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
33	+++ b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
34	@@ -439,6 +439,12 @@
35	};
36
37	&sdhci {
38	+ /*
39	+ * Signal integrity isn't great at 200MHz but 100MHz has proven stable
40	+ * enough.
41	+ */
42	+ max-frequency = <100000000>;
43	+
44	bus-width = <8>;
45	mmc-hs400-1_8v;
46	mmc-hs400-enhanced-strobe;
47	--
48	2.34.1
49