Re: Possible problem with thunderbolt 4

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Fri, Dec 30, 2022 at 12:38:27PM +0100, Christian Schaubschläger wrote:
> Ok, setting CONFIG_USB4=n makes everything work as expected! Even
> hotplugging the dock works fine.

Yes but things like power management does not.

> Now I've tried this: CONFIG_USB4=m and blacklist the thunderbolt
> module (because disabling CONFIG_USB4 in general is not an option for
> me (I guess?) There's probably hardware out there where the firmware
> doesn't set up the PCIe tunnels. Then I need the linux thunderbolt
> driver to do this I suppose).

You must have CONFIG_USB4=n because that makes the Linux ACPI core not
to negotiate software connection manager support. Blaclisting the
Thunderbolt driver does not do that as that code is always built-in.

> So with CONFIG_USB=m and blacklisting the thunderbolt module this
> happens: the tunnel is there before and after linux (PXE works), but
> in linux none of the devices that sit behind the PCIe tunnel (network,
> external display) are there... that's strange, because I would have
> expected that CONFIG_USB4=m + blacklist thunderbolt would be the same
> as CONFIG_USB4=n. Which obviously isn't the case. I've attached lspci
> output from either case.

See above.

> Is there any other option to decide at boottime whether or not to use
> the USB4 driver (besides using two different kernels)?

No but this is not the "final" solution - just an experiment.

Okay so we have this:

- When both Linux and Windows uses the same firmware connection manager
  all work.

- If you install Windows 11 (or whatever the fresh one is that actually
  supports USB4 and software connection manager) you end up in the
  exact same situation.

Can you try following:

1. Go back to CONFIG_USB4=m
2. Boot the system up
3. Check that the PCIe tunneling is up and things work as expected
4. Unplug the dock
5. Unload the Thunderbolt driver

  # rmmod thunderbolt

6. Plug the dock back
7. Soft reboot the system

Does this make the PXE boot see the connected device?