OPP: Introduce an OF helper function to inform if required-opps is used

As being shown from a subsequent change to genpd, it's useful to understand
if a device's OF node has an OPP-table described and whether it contains
OPP nodes that makes use of the required-opps DT property.

For this reason, let's introduce an OPP OF helper function called
dev_pm_opp_of_has_required_opp().

Signed-off-by: Ulf Hansson <[email protected]>
Signed-off-by: Viresh Kumar <[email protected]>

Author: storulf

drivers/opp/of.c

@@ -1443,6 +1443,38 @@ int of_get_required_opp_performance_state(struct device_node *np, int index)
 }
 EXPORT_SYMBOL_GPL(of_get_required_opp_performance_state);
 
+/**
+ * dev_pm_opp_of_has_required_opp - Find out if a required-opps exists.
+ * @dev: The device to investigate.
+ *
+ * Returns true if the device's node has a "operating-points-v2" property and if
+ * the corresponding node for the opp-table describes opp nodes that uses the
+ * "required-opps" property.
+ *
+ * Return: True if a required-opps is present, else false.
+ */
+bool dev_pm_opp_of_has_required_opp(struct device *dev)
+{
+	struct device_node *opp_np, *np;
+	int count;
+
+	opp_np = _opp_of_get_opp_desc_node(dev->of_node, 0);
+	if (!opp_np)
+		return false;
+
+	np = of_get_next_available_child(opp_np, NULL);
+	of_node_put(opp_np);
+	if (!np) {
+		dev_warn(dev, "Empty OPP table\n");
+		return false;
+	}
+
+	count = of_count_phandle_with_args(np, "required-opps", NULL);
+	of_node_put(np);
+
+	return count > 0;
+}
+
 /**
  * dev_pm_opp_get_of_node() - Gets the DT node corresponding to an opp
  * @opp:	opp for which DT node has to be returned for

include/linux/pm_opp.h

@@ -474,6 +474,7 @@ int dev_pm_opp_of_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpuma
 struct device_node *dev_pm_opp_of_get_opp_desc_node(struct device *dev);
 struct device_node *dev_pm_opp_get_of_node(struct dev_pm_opp *opp);
 int of_get_required_opp_performance_state(struct device_node *np, int index);
+bool dev_pm_opp_of_has_required_opp(struct device *dev);
 int dev_pm_opp_of_find_icc_paths(struct device *dev, struct opp_table *opp_table);
 int dev_pm_opp_of_register_em(struct device *dev, struct cpumask *cpus);
 int dev_pm_opp_calc_power(struct device *dev, unsigned long *uW,
@@ -552,6 +553,11 @@ static inline int of_get_required_opp_performance_state(struct device_node *np,
 	return -EOPNOTSUPP;
 }
 
+static inline bool dev_pm_opp_of_has_required_opp(struct device *dev)
+{
+	return false;
+}
+
 static inline int dev_pm_opp_of_find_icc_paths(struct device *dev, struct opp_table *opp_table)
 {
 	return -EOPNOTSUPP;