pmdomain: core: Set the required dev for a required OPP during genpd attach

In the single PM domain case there is no need for platform code to specify
the index of the corresponding required OPP in DT, as the index must be
zero. This allows us to assign a required dev for the required OPP from
genpd, while attaching a device to its PM domain.

In this way, we can remove some of the genpd specific code in the OPP core
for the single PM domain case. Although, this cleanup is made from a
subsequent change.

Signed-off-by: Ulf Hansson <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/pmdomain/core.c

···
 
 	spin_unlock_irq(&dev->power.lock);
 
+	dev_pm_opp_clear_config(gpd_data->opp_token);
 	kfree(gpd_data->td);
 	kfree(gpd_data);
 	dev_pm_put_subsys_data(dev);
···
 	genpd_queue_power_off_work(pd);
 }
 
+static int genpd_set_required_opp_dev(struct device *dev,
+				      struct device *base_dev)
+{
+	struct dev_pm_opp_config config = {
+		.required_dev = dev,
+	};
+	int ret;
+
+	/* Limit support to non-providers for now. */
+	if (of_property_present(base_dev->of_node, "#power-domain-cells"))
+		return 0;
+
+	if (!dev_pm_opp_of_has_required_opp(base_dev))
+		return 0;
+
+	ret = dev_pm_opp_set_config(base_dev, &config);
+	if (ret < 0)
+		return ret;
+
+	dev_gpd_data(dev)->opp_token = ret;
+	return 0;
+}
+
 static int genpd_set_required_opp(struct device *dev, unsigned int index)
 {
 	int ret, pstate;
···
 }
 
 static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
-				 unsigned int index, bool power_on)
+				 unsigned int index, unsigned int num_domains,
+				 bool power_on)
 {
 	struct of_phandle_args pd_args;
 	struct generic_pm_domain *pd;
···
 
 	dev->pm_domain->detach = genpd_dev_pm_detach;
 	dev->pm_domain->sync = genpd_dev_pm_sync;
+
+	/*
+	 * For a single PM domain the index of the required OPP must be zero, so
+	 * let's try to assign a required dev in that case. In the multiple PM
+	 * domains case, we need platform code to specify the index.
+	 */
+	if (num_domains == 1) {
+		ret = genpd_set_required_opp_dev(dev, base_dev);
+		if (ret)
+			goto err;
+	}
 
 	ret = genpd_set_required_opp(dev, index);
 	if (ret)
···
 				       "#power-domain-cells") != 1)
 		return 0;
 
-	return __genpd_dev_pm_attach(dev, dev, 0, true);
+	return __genpd_dev_pm_attach(dev, dev, 0, 1, true);
 }
 EXPORT_SYMBOL_GPL(genpd_dev_pm_attach);
 
···
 	}
 
 	/* Try to attach the device to the PM domain at the specified index. */
-	ret = __genpd_dev_pm_attach(virt_dev, dev, index, false);
+	ret = __genpd_dev_pm_attach(virt_dev, dev, index, num_domains, false);
 	if (ret < 1) {
 		device_unregister(virt_dev);
 		return ret ? ERR_PTR(ret) : NULL;

include/linux/pm_domain.h

···
 	unsigned int performance_state;
 	unsigned int default_pstate;
 	unsigned int rpm_pstate;
+	unsigned int opp_token;
 	bool hw_mode;
 	void *data;
 };