AC100_CLKOUT_PRE_DIV_SHIFT
div = (reg >> AC100_CLKOUT_PRE_DIV_SHIFT) &
((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1) << AC100_CLKOUT_PRE_DIV_SHIFT,
(pre_div - 1) << AC100_CLKOUT_PRE_DIV_SHIFT);