arm64: Utilize for_each_cpu_wrap for reference lookup

JIRA: https://issues.redhat.com/browse/RHEL-80968

commit 20711ef
Author: Beata Michalska <beata.michalska@arm.com>
Date:   Thu Feb 20 09:10:15 2025 +0000

    arm64: Utilize for_each_cpu_wrap for reference lookup

    While searching for a reference CPU within a given policy,
    arch_freq_get_on_cpu relies on cpumask_next_wrap to iterate over
    all available CPUs and to ensure each is verified only once.
    Recent changes to cpumask_next_wrap will handle the latter no more,
    so switching to for_each_cpu_wrap, which  preserves expected behavior
    while ensuring compatibility with the updates.
    Not to mention that when iterating over each CPU, using a dedicated
    iterator is preferable to an open-coded loop.

    Fixes: 16d1e27 ("arm64: Provide an AMU-based version of arch_freq_get_on_cpu")
    Signed-off-by: Beata Michalska <beata.michalska@arm.com>
    Link: https://lore.kernel.org/r/20250220091015.2319901-1-beata.michalska@arm.com
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Signed-off-by: Jennifer Berringer <jberring@redhat.com>

Author: Jennifer Berringer

arch/arm64/kernel/topology.c

@@ -254,7 +254,7 @@ int arch_freq_get_on_cpu(int cpu)
 		if (!housekeeping_cpu(cpu, HK_TYPE_TICK) ||
 		    time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
 			struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-			int ref_cpu = cpu;
+			int ref_cpu;
 
 			if (!policy)
 				return -EINVAL;
@@ -265,11 +265,15 @@ int arch_freq_get_on_cpu(int cpu)
 				return -EOPNOTSUPP;
 			}
 
-			do {
-				ref_cpu = cpumask_next_wrap(ref_cpu, policy->cpus,
-							    start_cpu, true);
-
-			} while (ref_cpu < nr_cpu_ids && idle_cpu(ref_cpu));
+			for_each_cpu_wrap(ref_cpu, policy->cpus, cpu + 1) {
+				if (ref_cpu == start_cpu) {
+					/* Prevent verifying same CPU twice */
+					ref_cpu = nr_cpu_ids;
+					break;
+				}
+				if (!idle_cpu(ref_cpu))
+					break;
+			}
 
 			cpufreq_cpu_put(policy);