OPP: Fix required_opp_tables for multiple genpds using same table

The required_opp_tables parsing is not perfect, as the OPP core does the
parsing solely based on the DT node pointers.

The core sets the required_opp_tables entry to the first OPP table in
the "opp_tables" list, that matches with the node pointer.

If the target DT OPP table is used by multiple devices and they all
create separate instances of 'struct opp_table' from it, then it is
possible that the required_opp_tables entry may be set to the incorrect
sibling device.

Unfortunately, there is no clear way to initialize the right values
during the initial parsing and we need to do this at a later point of
time.

Cross check the OPP table again while the genpds are attached and fix
them if required.

Also add a new API for the genpd core to fetch the device pointer for
the genpd.

Cc: Thorsten Leemhuis <[e-mail]>
Reported-by: Vladimir Lypak <[e-mail]>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218682
Co-developed-by: Vladimir Lypak <[e-mail]>
Signed-off-by: Viresh Kumar <[e-mail]>
Reviewed-by: Ulf Hansson <[e-mail]>

drivers/opp/core.c

···
 static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
 			const char * const *names, struct device ***virt_devs)
 {
-	struct device *virt_dev;
+	struct device *virt_dev, *gdev;
+	struct opp_table *genpd_table;
 	int index = 0, ret = -EINVAL;
 	const char * const *name = names;
 
···
 			ret = virt_dev ? PTR_ERR(virt_dev) : -ENODEV;
 			dev_err(dev, "Couldn't attach to pm_domain: %d\n", ret);
 			goto err;
+		}
+
+		/*
+		 * The required_opp_tables parsing is not perfect, as the OPP
+		 * core does the parsing solely based on the DT node pointers.
+		 * The core sets the required_opp_tables entry to the first OPP
+		 * table in the "opp_tables" list, that matches with the node
+		 * pointer.
+		 *
+		 * If the target DT OPP table is used by multiple devices and
+		 * they all create separate instances of 'struct opp_table' from
+		 * it, then it is possible that the required_opp_tables entry
+		 * may be set to the incorrect sibling device.
+		 *
+		 * Cross check it again and fix if required.
+		 */
+		gdev = dev_to_genpd_dev(virt_dev);
+		if (IS_ERR(gdev))
+			return PTR_ERR(gdev);
+
+		genpd_table = _find_opp_table(gdev);
+		if (!IS_ERR(genpd_table)) {
+			if (genpd_table != opp_table->required_opp_tables[index]) {
+				dev_pm_opp_put_opp_table(opp_table->required_opp_tables[index]);
+				opp_table->required_opp_tables[index] = genpd_table;
+			} else {
+				dev_pm_opp_put_opp_table(genpd_table);
+			}
 		}
 
 		/*

drivers/pmdomain/core.c

···
 	return pd_to_genpd(dev->pm_domain);
 }
 
+struct device *dev_to_genpd_dev(struct device *dev)
+{
+	struct generic_pm_domain *genpd = dev_to_genpd(dev);
+
+	if (IS_ERR(genpd))
+		return ERR_CAST(genpd);
+
+	return &genpd->dev;
+}
+
 static int genpd_stop_dev(const struct generic_pm_domain *genpd,
 			  struct device *dev)
 {

include/linux/pm_domain.h

···
 int pm_genpd_init(struct generic_pm_domain *genpd,
 		  struct dev_power_governor *gov, bool is_off);
 int pm_genpd_remove(struct generic_pm_domain *genpd);
+struct device *dev_to_genpd_dev(struct device *dev);
 int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state);
 int dev_pm_genpd_add_notifier(struct device *dev, struct notifier_block *nb);
 int dev_pm_genpd_remove_notifier(struct device *dev);
···
 static inline int pm_genpd_remove(struct generic_pm_domain *genpd)
 {
 	return -EOPNOTSUPP;
+}
+
+static inline struct device *dev_to_genpd_dev(struct device *dev)
+{
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 static inline int dev_pm_genpd_set_performance_state(struct device *dev,