VCO
VCO(3, 250000000, 500000000),
VCO(2, 500000000, 750000000),
VCO(1, 750000000, 1000000000),
VCO(0, 1000000000, 2150400000),
u32 multiplier, prediv, VCO, sysdiv, pll_rdiv;
VCO = xvclk * multiplier / prediv;
sysclk = VCO / sysdiv / pll_rdiv * 2 / bit_div2x / sclk_rdiv;