[Bug 221293] New: Thunderbolt: "failed to calculate available bandwidth" causes DisplayPort tunnel drop with Apple Studio Display

[Bug 221293] New: Thunderbolt: "failed to calculate available bandwidth" causes DisplayPort tunnel drop with Apple Studio Display

[bugzilla-daemon]

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: drivers_usb@kernel-bugs.kernel.org
          Reporter: aylin.ahmed@jetbot.co.uk
        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.

-- 
You may reply to this email to add a comment.

You are receiving this mail because:
You are watching the assignee of the bug.