PM / Domains: Don't power on at attach for the multi PM domain case

There are no legacy behavior in drivers to consider while attaching a
device to genpd - for the multiple PM domain case.

For that reason, let's instead require the driver to runtime resume the
device, via calling pm_runtime_get_sync() for example, when it needs to
power on the corresponding PM domain.

This allows us to improve the situation during attach. Instead of always
power on the PM domain, which may be unnecessary, let's leave it in its
current state. Additionally, to avoid the PM domain to stay powered on,
let's schedule a power off work.

Fixes: 3c095f3 (PM / Domains: Add support for multi PM domains ...)
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/domain.c

@@ -2235,7 +2235,7 @@ static void genpd_dev_pm_sync(struct device *dev)
 }
 
 static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
-				 unsigned int index)
+				 unsigned int index, bool power_on)
 {
 	struct of_phandle_args pd_args;
 	struct generic_pm_domain *pd;
@@ -2271,9 +2271,11 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
 	dev->pm_domain->detach = genpd_dev_pm_detach;
 	dev->pm_domain->sync = genpd_dev_pm_sync;
 
-	genpd_lock(pd);
-	ret = genpd_power_on(pd, 0);
-	genpd_unlock(pd);
+	if (power_on) {
+		genpd_lock(pd);
+		ret = genpd_power_on(pd, 0);
+		genpd_unlock(pd);
+	}
 
 	if (ret)
 		genpd_remove_device(pd, dev);
@@ -2307,7 +2309,7 @@ int genpd_dev_pm_attach(struct device *dev)
 				       "#power-domain-cells") != 1)
 		return 0;
 
-	return __genpd_dev_pm_attach(dev, dev->of_node, 0);
+	return __genpd_dev_pm_attach(dev, dev->of_node, 0, true);
 }
 EXPORT_SYMBOL_GPL(genpd_dev_pm_attach);
 
@@ -2359,14 +2361,14 @@ struct device *genpd_dev_pm_attach_by_id(struct device *dev,
 	}
 
 	/* Try to attach the device to the PM domain at the specified index. */
-	ret = __genpd_dev_pm_attach(genpd_dev, dev->of_node, index);
+	ret = __genpd_dev_pm_attach(genpd_dev, dev->of_node, index, false);
 	if (ret < 1) {
 		device_unregister(genpd_dev);
 		return ret ? ERR_PTR(ret) : NULL;
 	}
 
-	pm_runtime_set_active(genpd_dev);
 	pm_runtime_enable(genpd_dev);
+	genpd_queue_power_off_work(dev_to_genpd(genpd_dev));
 
 	return genpd_dev;
 }