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    Subject[PATCH 4.19 633/639] arm64: dts: juno: Fix UART frequency
    Date
    From: Andre Przywara <andre.przywara@arm.com>

    [ Upstream commit 39a1a8941b27c37f79508426e27a2ec29829d66c ]

    Older versions of the Juno *SoC* TRM [1] recommended that the UART clock
    source should be 7.2738 MHz, whereas the *system* TRM [2] stated a more
    correct value of 7.3728 MHz. Somehow the wrong value managed to end up in
    our DT.

    Doing a prime factorisation, a modulo divide by 115200 and trying
    to buy a 7.2738 MHz crystal at your favourite electronics dealer suggest
    that the old value was actually a typo. The actual UART clock is driven
    by a PLL, configured via a parameter in some board.txt file in the
    firmware, which reads 7.37 MHz (sic!).

    Fix this to correct the baud rate divisor calculation on the Juno board.

    [1] http://infocenter.arm.com/help/topic/com.arm.doc.ddi0515b.b/DDI0515B_b_juno_arm_development_platform_soc_trm.pdf
    [2] http://infocenter.arm.com/help/topic/com.arm.doc.100113_0000_07_en/arm_versatile_express_juno_development_platform_(v2m_juno)_technical_reference_manual_100113_0000_07_en.pdf

    Fixes: 71f867ec130e ("arm64: Add Juno board device tree.")
    Signed-off-by: Andre Przywara <andre.przywara@arm.com>
    Acked-by: Liviu Dudau <liviu.dudau@arm.com>
    Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/arm64/boot/dts/arm/juno-clocks.dtsi | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/arm64/boot/dts/arm/juno-clocks.dtsi b/arch/arm64/boot/dts/arm/juno-clocks.dtsi
    index e5e265dfa9025..2870b5eeb1984 100644
    --- a/arch/arm64/boot/dts/arm/juno-clocks.dtsi
    +++ b/arch/arm64/boot/dts/arm/juno-clocks.dtsi
    @@ -8,10 +8,10 @@
    */
    / {
    /* SoC fixed clocks */
    - soc_uartclk: refclk7273800hz {
    + soc_uartclk: refclk7372800hz {
    compatible = "fixed-clock";
    #clock-cells = <0>;
    - clock-frequency = <7273800>;
    + clock-frequency = <7372800>;
    clock-output-names = "juno:uartclk";
    };

    --
    2.20.1


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