arm64: dts: rockchip: fix rk3399-puma eMMC HS400 signal integrity

stable inclusion
from stable-v5.10.107
commit f7f062919f4101505ff7ce2efccc9dcec5c334cd
bugzilla: https://gitee.com/openeuler/kernel/issues/I574A2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f7f062919f4101505ff7ce2efccc9dcec5c334cd

--------------------------------

[ Upstream commit 62966cbd ]

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: NJakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Signed-off-by: NQuentin Schulz <quentin.schulz@theobroma-systems.com>
Link: https://lore.kernel.org/r/20220119134948.1444965-1-quentin.schulz@theobroma-systems.comSigned-off-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

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;