perf/arm_dsu: Allow standard cycles events

Since we do not use the divide-by-64 option, there should be no
significant difference between the dedicated cycle counter and the
standard cycles event. Since using the latter on DSU-120 now has
the side-effect of allowing multiple cycles events to be scheduled
simultaneously (beneficial for multiple cycle-based metrics), there
seems little reason not to allow the same on older DSUs as well.

Signed-off-by: Robin Murphy <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>

drivers/perf/arm_dsu_pmu.c

···
 	unsigned long *used_mask = hw_events->used_mask;
 
 	if (evtype == DSU_PMU_EVT_CYCLES && dsu_pmu->has_pmccntr) {
-		if (test_and_set_bit(DSU_PMU_IDX_CYCLE_COUNTER, used_mask))
-			return -EAGAIN;
-		return DSU_PMU_IDX_CYCLE_COUNTER;
+		if (!test_and_set_bit(DSU_PMU_IDX_CYCLE_COUNTER, used_mask))
+			return DSU_PMU_IDX_CYCLE_COUNTER;
 	}
 
 	idx = find_first_zero_bit(used_mask, dsu_pmu->num_counters);