BIOS_setCpuFreq(&cpuFreq) doesnot change the clock frequency on EK_TM4C123

Hi

I am using SYS/BIOS6 with CCS 6.1 and am trying to change CPU clock frequency from 80Mhz to 40Mhz. However it does not seem to be working.

The code snippet is reproduced below:

  cpuFreq.hi=0;

    cpuFreq.lo=40000000;

    BIOS_setCpuFreq(&cpuFreq);

BIOS_getCpuFreq(&cpuFreq1);

      System_printf("%d   %d",cpuFreq1.hi,cpuFreq1.lo);

    System_flush();

   while (1)

      {

     GPIO_toggle(LCD_DATA0_SCAN0);

       }

The frequency observed on  the GPIO above doesnot change. Even though cpuFreq1.lo  being printed on the console by System_printf does.

Any Suggetions.

Regards