Fathom S powering Rpi?

I have a raspberry pi hooked up to the ROV side interface of the fathom s board via the gpio serial port. When I supplied the board with 12v (for the camera) it powered up the raspberry pi while the raspberry pi wasn’t plugged in.
Can I run the raspberry pi off this (2.5amps)? Or is it a problem that this is happening?
Im asking bc i have a bulky voltage converter that I would like to get rid of to free up space.