cpufreq: distinguish drivers that do asynchronous notifications

There are few special cases like exynos5440 which doesn't send POSTCHANGE
notification from their ->target() routine and call some kind of bottom halves
for doing this work, work/tasklet/etc.. From which they finally send POSTCHANGE
notification.

Its better if we distinguish them from other cpufreq drivers in some way so that
core can handle them specially. So this patch introduces another flag:
CPUFREQ_ASYNC_NOTIFICATION, which will be set by such drivers.

This also changes exynos5440-cpufreq.c and powernow-k8 in order to set this
flag.
Acked-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/exynos5440-cpufreq.c

@@ -312,7 +312,7 @@ static int exynos_cpufreq_cpu_init(struct cpufreq_policy *policy)
 }
 
 static struct cpufreq_driver exynos_driver = {
-	.flags		= CPUFREQ_STICKY,
+	.flags		= CPUFREQ_STICKY | CPUFREQ_ASYNC_NOTIFICATION,
 	.verify		= cpufreq_generic_frequency_table_verify,
 	.target_index	= exynos_target,
 	.get		= exynos_getspeed,

drivers/cpufreq/powernow-k8.c

@@ -1204,6 +1204,7 @@ static unsigned int powernowk8_get(unsigned int cpu)
 }
 
 static struct cpufreq_driver cpufreq_amd64_driver = {
+	.flags		= CPUFREQ_ASYNC_NOTIFICATION,
 	.verify		= cpufreq_generic_frequency_table_verify,
 	.target_index	= powernowk8_target,
 	.bios_limit	= acpi_processor_get_bios_limit,

include/linux/cpufreq.h

@@ -237,6 +237,13 @@ struct cpufreq_driver {
  */
 #define CPUFREQ_HAVE_GOVERNOR_PER_POLICY (1 << 3)
 
+/*
+ * Driver will do POSTCHANGE notifications from outside of their ->target()
+ * routine and so must set cpufreq_driver->flags with this flag, so that core
+ * can handle them specially.
+ */
+#define CPUFREQ_ASYNC_NOTIFICATION  (1 << 4)
+
 int cpufreq_register_driver(struct cpufreq_driver *driver_data);
 int cpufreq_unregister_driver(struct cpufreq_driver *driver_data);