[PATCH 13/13] arm64: dts: ti: k3-j784s4-j742s2-evm-common: fix USB clocking for compliance

[Francesco Dolcini]

On Tue, May 05, 2026 at 04:36:14PM +0530, Siddharth Vadapalli wrote:
> According to section "6.5.3 Normative Spread Spectrum Clocking (SSC)" of
> the USB 3.2 Specification, SSC should be enabled by default. This protects
> against EMI violations. Hence, enable internal SSC for USB SuperSpeed.
> 
> Fixes: 39b623c05c46 ("arm64: dts: ti: Refactor J784s4-evm to a common file")
> Fixes: bed97e94ee2d ("arm64: dts: ti: k3-j784s4-evm: Enable USB3 support")
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Siddharth Vadapalli <s-vadapalli at ti.com>
> ---
>  arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi
> index ff3a85cbc524..0884773ad230 100644
> --- a/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-j784s4-j742s2-evm-common.dtsi
> @@ -1010,12 +1010,18 @@ serdes0_usb_link: phy at 3 {
>  		cdns,num-lanes = <1>;
>  		#phy-cells = <0>;
>  		cdns,phy-type = <PHY_TYPE_USB3>;
> +		cdns,ssc-mode = <2>; /* 2 for internal SSC */
>  		resets = <&serdes_wiz0 4>;
>  	};
>  };
>  
>  &serdes_wiz0 {
>  	status = "okay";
> +	ti,core-clk-sel = <1>;  /* Select internal reference clock */
> +	ti,ssc-enable; /* Enable SSC */
> +	ti,ssc-type = <1>; /* 1 for Downspread */
> +	ti,ssc-frequency-hz = <33000>; /* 33 KHz */
> +	ti,ssc-depth-per-mil = <5>; /* 0.5% depth */

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