Use for occasional crashing of Renesas USB 3.0 ports on the Dell Precision
M4600 (and also not arsed to take out the better USB 3.0 ExpressCard):

[RUN THIS AS SUPERUSER!]
echo 0000:0a:00.0 > /sys/bus/pci/drivers/xhci_hcd/unbind
echo 0000:0a:00.0 > /sys/bus/pci/drivers/xhci_hcd/bind