[PATCH v4 2/5] OPP: Add function to look up required OPP's for a given OPP

[Saravana Kannan <saravanak@google.com>]

Add a function that allows looking up required OPPs given a source OPP
table, destination OPP table and the source OPP.

Signed-off-by: Saravana Kannan <saravanak@google.com>
---
 drivers/opp/core.c     | 53 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm_opp.h | 11 +++++++++
 2 files changed, 64 insertions(+)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 438fcd134d93..5460b7da110e 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1883,6 +1883,59 @@ void dev_pm_opp_detach_genpd(struct opp_table *opp_table)
 }
 EXPORT_SYMBOL_GPL(dev_pm_opp_detach_genpd);
 
+/**
+ * dev_pm_opp_xlate_required_opp() - Find required OPP for @src_table OPP.
+ * @src_table: OPP table which has @dst_table as one of its required OPP table.
+ * @dst_table: Required OPP table of the @src_table.
+ *
+ * This function returns the OPP (present in @dst_table) pointed out by the
+ * "required-opps" property of the OPP (present in @src_table).
+ *
+ * The callers are required to call dev_pm_opp_put() for the returned OPP after
+ * use.
+ *
+ * Return: destination table OPP on success, otherwise NULL on errors.
+ */
+struct dev_pm_opp *dev_pm_opp_xlate_required_opp(struct opp_table *src_table,
+						 struct opp_table *dst_table,
+						 struct dev_pm_opp *src_opp)
+{
+	struct dev_pm_opp *opp, *dest_opp = NULL;
+	int i;
+
+	if (!src_table || !dst_table || !src_opp)
+		return NULL;
+
+	for (i = 0; i < src_table->required_opp_count; i++) {
+		if (src_table->required_opp_tables[i]->np == dst_table->np)
+			break;
+	}
+
+	if (unlikely(i == src_table->required_opp_count)) {
+		pr_err("%s: Couldn't find matching OPP table (%p: %p)\n",
+		       __func__, src_table, dst_table);
+		return NULL;
+	}
+
+	mutex_lock(&src_table->lock);
+
+	list_for_each_entry(opp, &src_table->opp_list, node) {
+		if (opp == src_opp) {
+			dest_opp = opp->required_opps[i];
+			dev_pm_opp_get(dest_opp);
+			goto unlock;
+		}
+	}
+
+	pr_err("%s: Couldn't find matching OPP (%p: %p)\n", __func__, src_table,
+	       dst_table);
+
+unlock:
+	mutex_unlock(&src_table->lock);
+
+	return dest_opp;
+}
+
 /**
  * dev_pm_opp_xlate_performance_state() - Find required OPP's pstate for src_table.
  * @src_table: OPP table which has dst_table as one of its required OPP table.
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index af5021f27cb7..21d331de98b9 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -130,6 +130,9 @@ struct opp_table *dev_pm_opp_register_set_opp_helper(struct device *dev, int (*s
 void dev_pm_opp_unregister_set_opp_helper(struct opp_table *opp_table);
 struct opp_table *dev_pm_opp_attach_genpd(struct device *dev, const char **names);
 void dev_pm_opp_detach_genpd(struct opp_table *opp_table);
+struct dev_pm_opp *dev_pm_opp_xlate_required_opp(struct opp_table *src_table,
+						 struct opp_table *dst_table,
+						 struct dev_pm_opp *src_opp);
 int dev_pm_opp_xlate_performance_state(struct opp_table *src_table, struct opp_table *dst_table, unsigned int pstate);
 int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq);
 int dev_pm_opp_set_sharing_cpus(struct device *cpu_dev, const struct cpumask *cpumask);
@@ -299,6 +302,14 @@ static inline struct opp_table *dev_pm_opp_attach_genpd(struct device *dev, cons
 
 static inline void dev_pm_opp_detach_genpd(struct opp_table *opp_table) {}
 
+static inline struct dev_pm_opp *dev_pm_opp_xlate_required_opp(
+						struct opp_table *src_table,
+						struct opp_table *dst_table,
+						struct dev_pm_opp *src_opp)
+{
+	return NULL;
+}
+
 static inline int dev_pm_opp_xlate_performance_state(struct opp_table *src_table, struct opp_table *dst_table, unsigned int pstate)
 {
 	return -ENOTSUPP;
-- 
2.22.0.709.g102302147b-goog