In reply to dave_59:
If i understand correctly what Raj is pointing out is a way to check if clock gets gated after some event.
In general, we use concurrent assertion to check if clock(gated_clk) gets gated when clk_en goes low in which ref_clk is used in assertion. The same is also indicated in this thread,(link)
How should a check be implemented for gated_clk in absence of ref_clk. i.e. i just have gated_clk and clk_en and i want to check that my clock(gated_clk) is not gated when clk_en is high and i do not have ref_clk to be used in concurrent assertion.