PM: domains: Improve runtime PM performance state handling

GENPD core doesn't support handling performance state changes while
consumer device is runtime-suspended or when runtime PM is disabled.
GENPD core may override performance state that was configured by device
driver while RPM of the device was disabled or device was RPM-suspended.

Let's close that gap by allowing drivers to control performance state
while RPM of a consumer device is disabled and to set up performance
state of RPM-suspended device that will be applied by GENPD core on
RPM-resume of the device.

Fixes: 5937c3ce ("PM: domains: Drop/restore performance state votes for devices at runtime PM")
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/domain.c

@@ -435,7 +435,7 @@ static void genpd_restore_performance_state(struct device *dev,
 int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state)
 {
 	struct generic_pm_domain *genpd;
-	int ret;
+	int ret = 0;
 
 	genpd = dev_to_genpd_safe(dev);
 	if (!genpd)
@@ -446,7 +446,13 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state)
 		return -EINVAL;
 
 	genpd_lock(genpd);
-	ret = genpd_set_performance_state(dev, state);
+	if (pm_runtime_suspended(dev)) {
+		dev_gpd_data(dev)->rpm_pstate = state;
+	} else {
+		ret = genpd_set_performance_state(dev, state);
+		if (!ret)
+			dev_gpd_data(dev)->rpm_pstate = 0;
+	}
 	genpd_unlock(genpd);
 
 	return ret;