mambasoft/2.6.38.3-hannspad — comment on commit a11cd3a0554c8685ea7c875c1b2ea684a2e9df42
File:  line 0
By mambasoft:

I think you refer to USB0_VBUS which is currently managed by the tegra-otg driver. When in peripheral mode it is set to out:
gpio-8 (USB0 VBUS ) out lo

and in host mode to in:
gpio-8 (USB0 VBUS ) in lo

When in host mode (which can be manually set via /sys/usbbus/host_mode) it also detects the presence of a USB device through OTG cable because it switches from HOST to SUSPEND mode when cable is removed and back from SUSPEND to HOST when connected. I think everything is quite working, only output power in host mode is missing...