Re: [PATCH v2 01/13] arm64: dts: ti: k3-am642-hummingboard-t: fix USB clocking for compliance

Josua Mayer
2026-05-06T14:18:19Z

Am 06.05.26 um 16:09 schrieb Siddharth Vadapalli:
> 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: e2b691804319 ("arm64: dts: ti: k3-am642-hummingboard-t: Convert overlay to board dts")
> Fixes: bbef42084cc1 ("arm64: dts: ti: hummingboard-t: add overlays for m.2 pci-e and usb-3")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
> Acked-by: Josua Mayer <josua@solid-run.com>

Your (submitter) Signed-off should always be last.

> ---
>
> v1:
> https://lore.kernel.org/r/20260505110631.1144200-2-s-vadapalli@ti.com/
> Changes since v1:
> - Collected Acked-by tag.
>
> arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dts | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dts b/arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dts
> index ee9bd618f370..90a158531f60 100644
> --- a/arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dts
> +++ b/arch/arm64/boot/dts/ti/k3-am642-hummingboard-t-usb3.dts
> @@ -15,6 +15,14 @@ / {
> model = "SolidRun AM642 HummingBoard-T with USB-3.1 Gen 1";
> };
>
> +&serdes_wiz0 {
> + 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 */
> +};
> +
> &serdes0 {
> #address-cells = <1>;
> #size-cells = <0>;
> @@ -23,6 +31,7 @@ serdes0_link: phy@0 {
> reg = <0>;
> cdns,num-lanes = <1>;
> cdns,phy-type = <PHY_TYPE_USB3>;
> + cdns,ssc-mode = <2>; /* 2 for internal SSC */
> #phy-cells = <0>;
> resets = <&serdes_wiz0 1>;
> };