cpufreq: Add policy create/remove notifiers back

This effectively reverts some changes made by commit f9f41e3
("cpufreq: Remove policy create/remove notifiers").

We have a new use case for policy create/remove notifiers (for
allocating/freeing QoS requests per policy), so add them back.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -1266,7 +1266,17 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
 				   DEV_PM_QOS_MAX_FREQUENCY);
 	dev_pm_qos_remove_notifier(dev, &policy->nb_min,
 				   DEV_PM_QOS_MIN_FREQUENCY);
-	dev_pm_qos_remove_request(policy->max_freq_req);
+
+	if (policy->max_freq_req) {
+		/*
+		 * CPUFREQ_CREATE_POLICY notification is sent only after
+		 * successfully adding max_freq_req request.
+		 */
+		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
+					     CPUFREQ_REMOVE_POLICY, policy);
+		dev_pm_qos_remove_request(policy->max_freq_req);
+	}
+
 	dev_pm_qos_remove_request(policy->min_freq_req);
 	kfree(policy->min_freq_req);
 
@@ -1391,6 +1401,9 @@ static int cpufreq_online(unsigned int cpu)
 				ret);
 			goto out_destroy_policy;
 		}
+
+		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
+				CPUFREQ_CREATE_POLICY, policy);
 	}
 
 	if (cpufreq_driver->get && has_target()) {

include/linux/cpufreq.h

@@ -458,6 +458,8 @@ static inline void cpufreq_resume(void) {}
 /* Policy Notifiers  */
 #define CPUFREQ_ADJUST			(0)
 #define CPUFREQ_NOTIFY			(1)
+#define CPUFREQ_CREATE_POLICY		(2)
+#define CPUFREQ_REMOVE_POLICY		(3)
 
 #ifdef CONFIG_CPU_FREQ
 int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list);