Qualcomm says it's fine to fast-charge your phone over USB-C
 

Technically, USB-C and fast-charging methods like Qualcomm's Quick Charge 3.0 aren't supposed to mix. As Google's Benson Leung (a frequent crusader for good USB implementations) noted last fall, the USB-C spec explicitly forbids the variable voltage...

http://www.engadget.com/2016/04/24/q...ge-over-usb-c/