if I understood the reference manual (chapter 8.12.38) correctly, the K1 has the ability to enable a pull-up or pull-down resistor on the gpio pins.
Unfortunately, it seems that this cannot be done via the sysfs interface. Is there another way?
The Jetson tk1 schematic shows that some of the GPIO have pull up resistors on the circuit board itself (leading to the 1.8V rails). These are not programmable without a soldering iron.
If you are looking for the control of tri-state logic, each GPIO has a register associated with this. GPIO/SFIO controllers have a register associated with it to control this functionality at a base physical controller address plus offset from that base (offset depending on which GPIO within the controller you are looking at). You can go into the kernel and locate which virtual address corresponds to the necessary physical address and simply write to the proper location to toggle tri-state.
If you simply want something other than 1.8V you might just pick up level converters, e.g., to 3.3V. It might be better to mention what it is you want to accomplish.