From: bugzilla-daemon@kernel.org
To: linux-usb@vger.kernel.org
Subject: [Bug 221293] New: Thunderbolt: "failed to calculate available bandwidth" causes DisplayPort tunnel drop with Apple Studio Display
Date: Sat, 28 Mar 2026 22:26:40 +0000 [thread overview]
Message-ID: <bug-221293-208809@https.bugzilla.kernel.org/> (raw)
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.
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