On Thu, Oct 24, 2024 at 04:13:55PM +0300, Mathias Nyman wrote:
> Fix a boot hang issue triggered when a USB3 device is incorrectly assumed
> to be tunneled over USB4, thus attempting to create a device link between
> the USB3 "consumer" device and the USB4 "supplier" Host Interface before
> the USB4 side is properly bound to a driver.
>
> This could happen if xhci isn't capable of detecting tunneled devices,
> but ACPI tables contain all info needed to assume device is tunneled.
> i.e. udev->tunnel_mode == USB_LINK_UNKNOWN.
>
> It turns out that even for actual tunneled USB3 devices it can't be
> assumed that the thunderbolt driver providing the tunnel is loaded
> before the tunneled USB3 device is created.
> The tunnel can be created by BIOS and remain in use by thunderbolt/USB4
> host driver once it loads.
>
> Solve this by making the device link "stateless", which doesn't create
> a driver presence order dependency between the supplier and consumer
> drivers.
> It still guarantees correct suspend/resume and shutdown ordering.
>
> cc: Mario Limonciello <mario.limonciello@xxxxxxx>
> Fixes: f1bfb4a6fed6 ("usb: acpi: add device link between tunneled USB3 device and USB4 Host Interface")
> Tested-by: Harry Wentland <harry.wentland@xxxxxxx>
> Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
