There is a sys entry for this in Linux. From Documentation/usb/power-management.txt:
power/level
This file contains one of three words: "on", "auto", or "suspend". You can write those words to the file to change the device's setting. "on" means that the device should be resumed and autosuspend is not allowed. (Of course, system suspends are still allowed.) "auto" is the normal state in which the kernel is allowed to autosuspend and autoresume the device. "suspend" means that the device should remain suspended, and autoresume is not allowed. (But remote wakeup may still be allowed, since it is controlled separately by the power/wakeup attribute.)
Something like: echo on > /sys/bus/usb/devices/usb5/power/level
You may need to play with the autosuspend setting as well. Without telling the kernel to stop trying, it may suspend the port automatically.
Good luck!