1
Diagnostic step 1
Collect kernel USB traces: enable dynamic USB tracing (echo '1' > /sys/kernel/debug/tracing/events/usb/enable) or use usbmon during reproduction to capture reset sequences and record timestamps relative to dropout events
FULL AI ANALYSIS
USB audio interface dropouts only when laptop charger is plugged into Thunderbolt dock
Generated Oct 3, 2026, 12:35:03 AM
Analysis summary
USB resets logged when charger is connected and disappearance of issue when connecting device directly indicate the dock's power delivery or bus power switching is causing USB device resets. Possible causes include ground/power noise induced by PD negotiation, USB hub power sequencing bug in dock firmware, or host controller driver entering a different power state when AC power is present. Reproducing across OSes strengthens case for dock‑side root cause.
Possible causes
Dock firmware handling of USB power rail changes during PD negotiation causes momentary USB hub reset
80%Grounding or power noise introduced via the dock's power supply under load triggers hub protection reset
60%Host controller driver reacts to external power by changing USB power state or interrupt coalescing, exposing a timing bug that resets devices
30%Suggested fixes
2
Diagnostic step 2
Capture dmesg with timestamps while toggling charger and reproducing the issue; save logs and usbmon output for vendor analysis
3
Diagnostic step 3
As a reversible workaround, plug the audio interface into the laptop's built-in port or use an isolated powered USB hub connected to the dock bypassing the dock's internal hub; test whether this prevents resets
4
Diagnostic step 4
Try a different dock power brick known to be well‑filtered; test with charger connected to laptop rather than via dock (if possible) to confirm PD negotiation path is the culprit
5
Diagnostic step 5
If traces show hub reset events initiated by the dock (hub port power off), collect vendor‑requested logs and escalate to dock manufacturer for firmware analysis and replacement recommendation