Hi, On Tue, May 23, 2023 at 10:53:17AM +0200, Tomasz Moń wrote: > Hello, > > Dell Latitude 5330 with 12th Gen Intel(R) Core(TM) i7-1265U contains > following PCI devices: > * 8086:461e - Alder Lake-P Thunderbolt 4 USB Controller > * 8086:51ed - Alder Lake PCH USB 3.2 xHCI Host Controller > > Thunderbolt 4 USB Controller initializes first and therefore following > usb host controllers are registered: > * usb1 - USB 2.0 High-Speed > * usb2 - USB 3.2 Enhanced SuperSpeed > * usb3 - USB 2.0 High-Speed > * usb4 - USB 3.1 Enhanced SuperSpeed > > When I connect SuperSpeed device directly to the Dell Latitude, it ends > up on usb4. Low/Full/High-Speed devices end up on usb3 as expected. > > When I connect Thunderbolt 3 dock, two new host controllers show up: > * usb5 - USB 2.0 High-Speed > * usb6 - USB 3.0 SuperSpeed > > Devices connected through Thunderbolt 3 dock end up on expected host > controllers, i.e. Low/Full/High-Speed devices connect to usb5 and > SuperSpeed devices end up on usb6. > > Is Thunderbolt 3 essentially tunnelling the USB 2.0 traffic (by > tunnelling PCIe xHCI host controller traffic) on the superspeed > differential pairs (operating in alternate TBT3 mode)? It is not. The USB 2.x wires are separate on type-C cables. > When I connect Thunderbolt 4 dock, the SuperSpeed devices connected to > dock ports end up on usb2 host controller. However, Low/Full/High-Speed > devices do end up on usb3 (USB 3.2 xHCI) and not on usb1 (Alder Lake-P > Thunderbolt 4 USB Controller). Yes, that's expected the TBT USB controller (on the host) does not support USB 2.x so it is routed to the PCH one. > Is there any condition under which the Low/Full/High-Speed devices > would end up on usb1 (USB 2.0 High-Speed host controller interface > created for Thunderbolt 4 USB Controller)? If I understood this right, then no. > Does the Alder Lake-P Thunderbolt 4 USB Controller even feature USB 2.0 > interface? If not, should the (effectively dummy) usb1 host controller > even be registered? Is the USB 2.0 functionality provided entirely by > the Alder Lake PCH USB 3.2 xHCI Host Controller (i.e. when there is no > TBT3 dock connected)? It does not.
