This should be possible with HS host controller of FX3. Why do you use GX3 here? Is it due to the USB cable length limitation?
Yes. We wish to overcome the USB cable limitation.
If you just want to extend the cable, we can suggest active cable and optical cable, please refer below link for detail:
Optical cable extenders - http://investors.cypress.com/releasedetail.cfm?releaseid=855041