At some moment, my USB WLAN stick stopped working, and the log was polluted by messages like:
usb 6-1: new high speed USB device using ehci_hcd and address 62 hub 6-0:1.0: unable to enumerate USB device on port 1 hub 6-0:1.0: unable to enumerate USB device on port 1
At first, I decided that the stick had broken after years of work, but out of curiousity tried to connect it to every USB port I found. It worked. The stick worked again when plugged into the keyboard, which in term was connected to the KVM.
What is funny, I did nothing, but after a few days the stick worked again correctly in its original port. I forgot about the problem. But after yet another vacations, the problem appeared again, and again disappeared in a few days.
I have no idea why.
But I finally found a solution here: [Solved] Unable to enumerate USB device (Disabling ehci_hcd). I need to disable ehci_hcd. In my case, the commands is:
# cd /sys/bus/pci/drivers/ehci_hcd # echo -n "0000:00:1a.7" > unbind
As a side effect, I do not have USB 2.0 on this bus anymore, but it is not a problem.
To issue the command automatically on boot, one could edit/etc/rc.local, but in my case I need to have network loaded before. The best solution (I hope) is based on advice here:
You can disable this on boot by creating a /etc/udev/rules.d/disable-ehci.rules file containing:
ACTION=="add", SUBSYSTEM=="pci", DRIVER=="ehci_hcd", \ RUN+="/bin/sh -c 'echo -n %k > %S%p/driver/unbind'"