ANDROID: sched: Compute cpu capacity available at current frequency

capacity_orig_of() returns the max available compute capacity of a cpu.
For scale-invariant utilization tracking and energy-aware scheduling
decisions it is useful to know the compute capacity available at the
current OPP of a cpu.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Andres Oportus <andresoportus@google.com>

kernel/sched/fair.c

@@ -5104,6 +5104,17 @@ static void record_wakee(struct task_struct *p)
 	}
 }
 
+/*
+ * Returns the current capacity of cpu after applying both
+ * cpu and freq scaling.
+ */
+static unsigned long capacity_curr_of(int cpu)
+{
+	return cpu_rq(cpu)->cpu_capacity_orig *
+	       arch_scale_freq_capacity(NULL, cpu)
+	       >> SCHED_CAPACITY_SHIFT;
+}
+
 static inline bool energy_aware(void)
 {
 	return sched_feat(ENERGY_AWARE);