Repita o comando "dmesg | grep usb | tail".
falstaff@ubuntu:~$ dmesg | grep usb | tail
[ 2802.508451] usb usb5: root hub lost power or was reset
[ 2802.508510] usb usb6: root hub lost power or was reset
[ 2802.744061] PM: resume of drv:usb dev:usb2 complete after 131.978 msecs
[ 2802.860066] usb 2-5: reset high speed USB device using ehci_hcd and address 2
[ 2803.044551] PM: resume of drv:usb dev:2-5 complete after 294.548 msecs
[ 2804.740064] usb 2-2: reset high speed USB device using ehci_hcd and address 3
[ 2804.875087] PM: resume of drv:usb dev:2-2 complete after 246.186 msecs
[ 4477.117270] usbcore: registered new interface driver usbserial
[ 4477.119382] usbcore: registered new interface driver usbserial_generic
[ 4477.119387] usbserial: USB Serial Driver core
falstaff@ubuntu:~$