New: Thunderbolt: "failed to calculate available bandwidth" causes DisplayPort tunnel drop with Apple Studio Display

https://bugzilla.kernel.org/show_bug.cgi?id=221293

Bug ID: 221293
Summary: Thunderbolt: "failed to calculate available bandwidth"
causes DisplayPort tunnel drop with Apple Studio Display
Product: Drivers
Version: 2.5
Hardware: All
OS: Linux
Status: NEW
Severity: normal
Priority: P3
Component: USB
Assignee: [email protected]
Reporter: [email protected]
Regression: No

Created attachment 309779
--> https://bugzilla.kernel.org/attachment.cgi?id=309779&action=edit
dmesg thunderbolt log and hardware details

Apple Studio Display connected via Thunderbolt to ThinkPad X1 Carbon intermittently loses DisplayPort tunnel. The kernel logs:

thunderbolt 0000:00:0d.3: 0:12 <-> 1:20 (USB3): failed to calculate available
bandwidth

followed by "failed to reach state TB_PORT_UP" and device disconnect.

USB3 hub (05ac:8014) and DP contend for bandwidth. Manually unbinding the USB3 hub restores DP, confirming contention. Suspend/resume recovers correctly but DPMS wake does not.

Hardware: ThinkPad X1 Carbon, Intel Gen12 TB controller, kernel 6.8.0-106-generic, Ubuntu 24.x Wayland.

Full dmesg and hardware details attached.

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