On Tue, 2023-05-23 at 12:01 +0300, Mika Westerberg wrote: > On Tue, May 23, 2023 at 10:53:17AM +0200, Tomasz Moń wrote: > > 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. Yes, the USB 2.x wires are separate on type-C cables. But this does not answer the question why there is new USB 2.0 High-Speed controller showing up that the devices do connect to. Wouldn't the Low/Full/High-Speed devices traffic appear on usb3 (PCH controller) if the USB 2.x wires in type-C cable were really used in this case (instead of the usb5 which appeared only after Thunderbolt 3 was connected)? I forgot to mention that the Thunderbolt 3 docking station in question has Intel Corporation DSL6540 Thunderbolt 3 Bridge [Alpine Ridge 4C 2015] and ASMedia Technology Inc. ASM1042A USB 3.0 Host Controller. The way I understand it, that the usb5 and usb6 come from ASM1042A (which implements xHCI). The communication would then be: * Dell Latitude <-> Thunderbolt 3 dock (TBT3 tunnelling PCIe xHCI) * ASM1042 (in Thunderbolt 3 dock) <-> USB 2.x devices connected to the dock (data never makes it to type-C D+/D- wires, because it is ASM1042 that generates the tokens) Is there a flaw in my understanding? > > 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. Should the driver be changed to not even register the dummy USB 2.0 interface in such case? -- Tomasz Moń | Senior Firmware Engineer P +48 882 826 111 | Wrocław, Poland nordicsemi.com | devzone.nordicsemi.com
