Loosing connection to all ports on USB-hub when only disconnecting a few

Question

I have an issue with disconnects using a Basler USB-hub. https://www.baslerweb.com/en/products/vision-components/additional-accessories/usb-3-0-hub-4-ports-side-by-side/

The USB-hub is connected to a motherboard port. The USB-hub has four slots that are all connected. When I disconnect one cable at a time from the USB-hub, I sometimes lose connection to all others as well.

I found the following logs from /var/log/syslog

// Physically disconnect one cable

Oct 18 08:41:22 COMPUTER kernel: [56581.663187] usb 2-6.2: USB disconnect, device number 101
Oct 18 08:41:22 COMPUTER upowerd[1440]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6.2/2-6.2:1.1
Oct 18 08:41:22 COMPUTER upowerd[1440]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6.2

// Physically disconnect second cable (I now loose connection to all four ports)

Oct 18 08:41:31 COMPUTER kernel: [56589.887127] usb 2-6.4: USB disconnect, device number 105
Oct 18 08:41:31 COMPUTER upowerd[1440]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6.4/2-6.4:1.0
Oct 18 08:41:31 COMPUTER upowerd[1440]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6.4/2-6.4:1.1
Oct 18 08:41:31 COMPUTER upowerd[1440]: unhandled action 'unbind' on /sys/devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6.4

Does anyone recognize this issue?

Answer 1

You should be more specific about your "a hub". It could be power delivery issues, or it could be more complicated. Some older USB 2.0 hubs are sensitive to "surprise disconnect". Before a DS port senses a disconnect (which occurs only at SOF), double-amplitude reflections from incoming broadcasted traffic may cause spurious upstream traffic, which will be considered as "babbling", and the host will reset the root port. Get a better, USB-IF certified self-powered hub, and use shorter cables if possible.