cpufreq: handle cpufreq being disabled for all exported function.

When disable_cpufreq() is called some exported functions are still
being used that do not have a check for cpufreq being disabled.

Add a disabled check into cpufreq_cpu_get() to return NULL if
cpufreq is disabled this covers most of the exported functions. For
the exported functions that do not call cpufreq_cpu_get() add an
explicit check.
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -183,6 +183,9 @@ static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
 
 struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
 {
+	if (cpufreq_disabled())
+		return NULL;
+
 	return __cpufreq_cpu_get(cpu, false);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_get);
@@ -201,6 +204,9 @@ static void __cpufreq_cpu_put(struct cpufreq_policy *data, bool sysfs)
 
 void cpufreq_cpu_put(struct cpufreq_policy *data)
 {
+	if (cpufreq_disabled())
+		return;
+
 	__cpufreq_cpu_put(data, false);
 }
 EXPORT_SYMBOL_GPL(cpufreq_cpu_put);
@@ -267,6 +273,9 @@ void cpufreq_notify_transition(struct cpufreq_freqs *freqs, unsigned int state)
 
 	BUG_ON(irqs_disabled());
 
+	if (cpufreq_disabled())
+		return;
+
 	freqs->flags = cpufreq_driver->flags;
 	pr_debug("notification %u of frequency transition to %u kHz\n",
 		state, freqs->new);
@@ -1408,6 +1417,9 @@ int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list)
 {
 	int ret;
 
+	if (cpufreq_disabled())
+		return -EINVAL;
+
 	WARN_ON(!init_cpufreq_transition_notifier_list_called);
 
 	switch (list) {
@@ -1442,6 +1454,9 @@ int cpufreq_unregister_notifier(struct notifier_block *nb, unsigned int list)
 {
 	int ret;
 
+	if (cpufreq_disabled())
+		return -EINVAL;
+
 	switch (list) {
 	case CPUFREQ_TRANSITION_NOTIFIER:
 		ret = srcu_notifier_chain_unregister(
@@ -1522,6 +1537,9 @@ int __cpufreq_driver_getavg(struct cpufreq_policy *policy, unsigned int cpu)
 {
 	int ret = 0;
 
+	if (cpufreq_disabled())
+		return ret;
+
 	if (!(cpu_online(cpu) && cpufreq_driver->getavg))
 		return 0;