TMS320F28069M: Low clock SPI

I have a display with as low clock as 18KHz

To fulfill the clock requirements can I use the following solution (to prescale the clock (90MHz))?

I did not experienced yet the solution below. To use the SPI interface of the TMS320F28069M (90MHz) I call the function downclock(), do the SPI communication and then call the function upclock(). I do for each time I want to do SPI communication. Will this work? SPI Prescaller is 127

Thanks

Luis Gonçalves

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void downclock(void)
{
SysCtrlRegs.LOSPCP.all = 0x0007;
InitPll(6,2);
while (SysCtrlRegs.PLLSTS.bit.PLLLOCKS != 1);
}

Communication SPI and display information function

void upclock(void)
{
SysCtrlRegs.LOSPCP.all = 0x0002;
InitPll(18,2);
while (SysCtrlRegs.PLLSTS.bit.PLLLOCKS != 1);
}