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

[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 at vger.kernel.org>
Signed-off-by: Siddharth Vadapalli <s-vadapalli at ti.com>
---
 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 at 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>;
 	};
-- 
2.51.1