From Technologic Systems Manuals

This board features USB OTG which is wired to support a second USB host port (that's the top one). The Marvell OTG driver has a known issue where it does not properly support hotplugged USB devices. If a device is plugged in during boot it will work, but if it is plugged in after kernel initialization the following command must be used in order to set the port in to host mode.:

echo 1 > /proc/driver/otg