__clk_notify
__clk_notify(core, msg, old_rate, core->rate);
ret = __clk_notify(core, PRE_RATE_CHANGE, core->rate, new_rate);
ret = __clk_notify(core, event, core->rate, core->new_rate);
__clk_notify(core, POST_RATE_CHANGE, old_rate, core->rate);