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    Subject[PATCH 4.19 06/57] arm64: dts: rockchip: fix rk3399-puma eMMC HS400 signal integrity
    Date
    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 b155f657292b..ce1320e4c106 100644
    --- a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
    +++ b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
    @@ -468,6 +468,12 @@
    };

    &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


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