2 files changed, 47 insertions, 0 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d8d6bc9d1815..d57806a85def 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -353,6 +353,41 @@ void cpufreq_notify_post_transition(struct cpufreq_policy *policy,
 }
 EXPORT_SYMBOL_GPL(cpufreq_notify_post_transition);
 
+void cpufreq_freq_transition_begin(struct cpufreq_policy *policy,
+                struct cpufreq_freqs *freqs)
+{
+wait:
+        wait_event(policy->transition_wait, !policy->transition_ongoing);
+
+        spin_lock(&policy->transition_lock);
+
+        if (unlikely(policy->transition_ongoing)) {
+                spin_unlock(&policy->transition_lock);
+                goto wait;
+        }
+
+        policy->transition_ongoing = true;
+
+        spin_unlock(&policy->transition_lock);
+
+        cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE);
+}
+EXPORT_SYMBOL_GPL(cpufreq_freq_transition_begin);
+
+void cpufreq_freq_transition_end(struct cpufreq_policy *policy,
+                struct cpufreq_freqs *freqs, int transition_failed)
+{
+        if (unlikely(WARN_ON(!policy->transition_ongoing)))
+                return;
+
+        cpufreq_notify_post_transition(policy, freqs, transition_failed);
+
+        policy->transition_ongoing = false;
+
+        wake_up(&policy->transition_wait);
+}
+EXPORT_SYMBOL_GPL(cpufreq_freq_transition_end);
+
 
 /*********************************************************************
  *                          SYSFS INTERFACE                          *
@@ -985,6 +1020,8 @@ static struct cpufreq_policy *cpufreq_policy_alloc(void)
 
         INIT_LIST_HEAD(&policy->policy_list);
         init_rwsem(&policy->rwsem);
+        spin_lock_init(&policy->transition_lock);
+        init_waitqueue_head(&policy->transition_wait);
 
         return policy;
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 2d2e62c8666a..e33760268a86 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -16,6 +16,7 @@
 #include <linux/completion.h>
 #include <linux/kobject.h>
 #include <linux/notifier.h>
+#include <linux/spinlock.h>
 #include <linux/sysfs.h>
 
 /*********************************************************************
@@ -104,6 +105,11 @@ struct cpufreq_policy {
          *     __cpufreq_governor(data, CPUFREQ_GOV_POLICY_EXIT);
          */
         struct rw_semaphore     rwsem;
+
+        /* Synchronization for frequency transitions */
+        bool                    transition_ongoing; /* Tracks transition status */
+        spinlock_t              transition_lock;
+        wait_queue_head_t       transition_wait;
 };
 
 /* Only for ACPI */
@@ -337,6 +343,10 @@ void cpufreq_notify_transition(struct cpufreq_policy *policy,
                 struct cpufreq_freqs *freqs, unsigned int state);
 void cpufreq_notify_post_transition(struct cpufreq_policy *policy,
                 struct cpufreq_freqs *freqs, int transition_failed);
+void cpufreq_freq_transition_begin(struct cpufreq_policy *policy,
+                struct cpufreq_freqs *freqs);
+void cpufreq_freq_transition_end(struct cpufreq_policy *policy,
+                struct cpufreq_freqs *freqs, int transition_failed);
 
 #else /* CONFIG_CPU_FREQ */
 static inline int cpufreq_register_notifier(struct notifier_block *nb,