UP2 SPI on Linux Mint 18
For what it's worth I have been able to install Linux Mint 18 onto a SATA drive and get the SPI working at 25 MHz, which is the maximum SCLK frequency according to the Intel documentation. I followed the UP2 instructions for installing Ubuntu including replacing the kernel. I also cloned the mraa library from GIT and built it after installing all of the dependencies. After changing the example spi.c frequency to 25000000 and running the executable pin 23 showed the expected 25 MHz SCLK.