linux-kernel - Re: [PATCH v2] arm64: dts: ti: k3-am64-mcu: remove incorrect UART base clock rates

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Date:   Fri, 22 Apr 2022 14:18:43 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Matthias Schiffer <matthias.schiffer@...tq-group.com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>
CC:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] arm64: dts: ti: k3-am64-mcu: remove incorrect UART
 base clock rates

Hi,

On 19/04/22 1:21 pm, Matthias Schiffer wrote:
> We found that (at least some versions of) the sci-fw set the base clock
> rate for UARTs in the MCU domain to 96 MHz instead of the expected 48 MHz,
> leading to incorrect baud rates when used from Linux.
> 
> As the 8250_omap driver will query the actual clock rate from the clk
> driver when clock-frequency is unset, removing the incorrect property is
> sufficient to fix the baud rate.
> 
> Fixes: 8abae9389bdb ("arm64: dts: ti: Add support for AM642 SoC")
> Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
> ---

Reviewed-by: Vignesh Raghavendra <vigneshr@...com>


> 
> v2: remove incorrect clock-frequency instead of using
>     assigned-clock-rates to modify the base clock
> 
>  arch/arm64/boot/dts/ti/k3-am64-mcu.dtsi | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-am64-mcu.dtsi b/arch/arm64/boot/dts/ti/k3-am64-mcu.dtsi
> index 2bb5c9ff172c..02d4285acbb8 100644
> --- a/arch/arm64/boot/dts/ti/k3-am64-mcu.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-am64-mcu.dtsi
> @@ -10,7 +10,6 @@ mcu_uart0: serial@...0000 {
>  		compatible = "ti,am64-uart", "ti,am654-uart";
>  		reg = <0x00 0x04a00000 0x00 0x100>;
>  		interrupts = <GIC_SPI 185 IRQ_TYPE_LEVEL_HIGH>;
> -		clock-frequency = <48000000>;
>  		current-speed = <115200>;
>  		power-domains = <&k3_pds 149 TI_SCI_PD_EXCLUSIVE>;
>  		clocks = <&k3_clks 149 0>;
> @@ -21,7 +20,6 @@ mcu_uart1: serial@...0000 {
>  		compatible = "ti,am64-uart", "ti,am654-uart";
>  		reg = <0x00 0x04a10000 0x00 0x100>;
>  		interrupts = <GIC_SPI 186 IRQ_TYPE_LEVEL_HIGH>;
> -		clock-frequency = <48000000>;
>  		current-speed = <115200>;
>  		power-domains = <&k3_pds 160 TI_SCI_PD_EXCLUSIVE>;
>  		clocks = <&k3_clks 160 0>;