muldiv32
symb = muldiv32(p->symbol_rate, 65536, state->base->mclk);
frac = muldiv32(frac, 0x40000, state->ref_freq);
cutoff = 5000000 + muldiv32(p->symbol_rate, 135, 200);
c->min = muldiv32(a->min, b->min, k, &r);
c->max = muldiv32(a->max, b->max, k, &r);
c->min = muldiv32(a->min, k, b->max, &r);
c->max = muldiv32(a->max, k, b->min, &r);