PM / EM: Micro optimization in em_cpu_energy

When the sum of the utilization of CPUs in a power domain is zero,
return the energy as 0 without doing any computations.

Acked-by: Quentin Perret <[email protected]>
Reviewed-by: Dietmar Eggemann <[email protected]>
Signed-off-by: Pavankumar Kondeti <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: Pavankumar Kondeti

include/linux/energy_model.h

@@ -106,6 +106,9 @@ static inline unsigned long em_cpu_energy(struct em_perf_domain *pd,
 	struct em_perf_state *ps;
 	int i, cpu;
 
+	if (!sum_util)
+		return 0;
+
 	/*
 	 * In order to predict the performance state, map the utilization of
 	 * the most utilized CPU of the performance domain to a requested