We followed the product design guide and connected the USBSS lanes to our connector (we are using a USB C connector so they go through a mux) and are using USB0 instead of USB2 for USB2.0 (so we can do recovery over the type C connector).
We already got the USB3.0 device mode to work well and measured a bandwidth over the CDC ECM device of about 2.6Gbps but it would be great to know if it is possible to reach Gen2 speeds.
As a reference this is the output on the host machine (to show that Gen1 is working):
[ 2965.454848] usb 2-5: new SuperSpeed Gen 1 USB device number 2 using xhci_hcd
[ 2965.479411] usb 2-5: New USB device found, idVendor=0955, idProduct=7020, bcdDevice= 0.02
[ 2965.479413] usb 2-5: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2965.479415] usb 2-5: Product: Linux for Tegra
[ 2965.479416] usb 2-5: Manufacturer: NVIDIA
[ 2965.479417] usb 2-5: SerialNumber: 1421920020933
[ 2965.519524] usbcore: registered new interface driver cdc_acm
[ 2965.534850] cdc_ether 2-5:1.2 usb0: register 'cdc_ether' at usb-0000:02:00.0-5, CDC Ethernet Device, 46:be:68:4f:d9:5e
[ 2965.534893] usbcore: registered new interface driver cdc_ether
[ 2965.541169] cdc_ether 2-5:1.2 enp2s0f0u5i2: renamed from usb0