Variables defined in U-boot source code:
FREQ integer part = 0x0B
FREQ float part = 0x851EB7 (the maximum if 0xFFFFFF), so 0x851EB7 is around 0.52
fvco=(N/P)*fr=64*27MHz = 1728MHz
fs=(fvco*k)/FREQ, where k=8 (always)
You can tweak FREQ (integer and float part) to adjust CPU frequency.
For example, setting it to 15 (FREQ.integer=0x0E, FREQ.float=0) will change the CPU speed to 987Mhz.
The theoretic maximum is around 1500Mhz, but the TI tested max speed is 1200MHz.