cpufreq: Process remote callbacks from any CPU if the platform permits

On many platforms, CPUs can do DVFS across cpufreq policies. i.e CPU
from policy-A can change frequency of CPUs belonging to policy-B.

This is quite common in case of ARM platforms where we don't
configure any per-cpu register.

Add a flag to identify such platforms and update
cpufreq_can_do_remote_dvfs() to allow remote callbacks if this flag is
set.

Also enable the flag for cpufreq-dt driver which is used only on ARM
platforms currently.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 17 insertions, 2 deletions

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index fef3c2160691..d83ab94d041a 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -274,6 +274,7 @@ static int cpufreq_init(struct cpufreq_policy *policy)
                 transition_latency = CPUFREQ_ETERNAL;
 
         policy->cpuinfo.transition_latency = transition_latency;
+        policy->dvfs_possible_from_any_cpu = true;
 
         return 0;
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index c4035964e6b3..1981a4a167ce 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -127,6 +127,15 @@ struct cpufreq_policy {
          */
         unsigned int            transition_delay_us;
 
+        /*
+         * Remote DVFS flag (Not added to the driver structure as we don't want
+         * to access another structure from scheduler hotpath).
+         *
+         * Should be set if CPUs can do DVFS on behalf of other CPUs from
+         * different cpufreq policies.
+         */
+        bool                    dvfs_possible_from_any_cpu;
+
          /* Cached frequency lookup from cpufreq_driver_resolve_freq. */
         unsigned int cached_target_freq;
         int cached_resolved_idx;
@@ -564,8 +573,13 @@ struct governor_attr {
 
 static inline bool cpufreq_can_do_remote_dvfs(struct cpufreq_policy *policy)
 {
-        /* Allow remote callbacks only on the CPUs sharing cpufreq policy */
-        if (cpumask_test_cpu(smp_processor_id(), policy->cpus))
+        /*
+         * Allow remote callbacks if:
+         * - dvfs_possible_from_any_cpu flag is set
+         * - the local and remote CPUs share cpufreq policy
+         */
+        if (policy->dvfs_possible_from_any_cpu ||
+            cpumask_test_cpu(smp_processor_id(), policy->cpus))
                 return true;
 
         return false;