28335 McBSP I/O Pins in SPI Mode

I want to use 28335's McBSP peripheral as SPI Master for three different slaves (three different CS with GPIOs).

I am planning to use only the CLKX, DX and RX pins of the McBSPI.

Can i use the other unused pins MFSX, MFSR, MCLKR as GPIO or they have to be kept in some specific pull up or pull down state for SPI master mode to work.

Thanks