arch_topology: init capacity_freq_ref to 0

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

commit 004b500
Author: Ionela Voinescu <ionela.voinescu@arm.com>
Date:   Tue Aug 27 16:48:18 2024 +0100

    arch_topology: init capacity_freq_ref to 0

    It's useful to have capacity_freq_ref initialized to 0 for users of
    arch_scale_freq_ref() to detect when capacity_freq_ref was not
    yet set.

    The only scenario affected by this change in the init value is when a
    cpufreq driver is never loaded. As a result, the only setter of a
    cpu scale factor remains the call of topology_normalize_cpu_scale()
    from parse_dt_topology(). There we cannot use the value 0 of
    capacity_freq_ref so we have to compensate for its uninitialized state.

    Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
    Signed-off-by: Beata Michalska <beata.michalska@arm.com>
    Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
    Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
    Link: https://lore.kernel.org/r/20240827154818.1195849-1-ionela.voinescu@arm.com
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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

Author: Jennifer Berringer

drivers/base/arch_topology.c

@@ -28,7 +28,7 @@
 static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data);
 static struct cpumask scale_freq_counters_mask;
 static bool scale_freq_invariant;
-DEFINE_PER_CPU(unsigned long, capacity_freq_ref) = 1;
+DEFINE_PER_CPU(unsigned long, capacity_freq_ref) = 0;
 EXPORT_PER_CPU_SYMBOL_GPL(capacity_freq_ref);
 
 static bool supports_scale_freq_counters(const struct cpumask *cpus)
@@ -293,13 +293,15 @@ void topology_normalize_cpu_scale(void)
 
 	capacity_scale = 1;
 	for_each_possible_cpu(cpu) {
-		capacity = raw_capacity[cpu] * per_cpu(capacity_freq_ref, cpu);
+		capacity = raw_capacity[cpu] *
+			   (per_cpu(capacity_freq_ref, cpu) ?: 1);
 		capacity_scale = max(capacity, capacity_scale);
 	}
 
 	pr_debug("cpu_capacity: capacity_scale=%llu\n", capacity_scale);
 	for_each_possible_cpu(cpu) {
-		capacity = raw_capacity[cpu] * per_cpu(capacity_freq_ref, cpu);
+		capacity = raw_capacity[cpu] *
+			   (per_cpu(capacity_freq_ref, cpu) ?: 1);
 		capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
 			capacity_scale);
 		topology_set_cpu_scale(cpu, capacity);