round_closest
sc->sda_hold_time = round_closest(freq * sda_hold, 1000000000);
sc->ss_hcnt = round_closest(freq * (4000 + sda_fall), 1000000000) - 3;
sc->ss_lcnt = round_closest(freq * (4700 + scl_fall), 1000000000) - 1;
sc->fs_hcnt = round_closest(freq * (600 + sda_fall), 1000000000) - 3;
sc->fs_lcnt = round_closest(freq * (1300 + scl_fall), 1000000000) - 1;