[PATCH] PM / OPP: Implement free_opp_table function

[Inderpal Singh]

At the driver unloading time the associated opp table may need
to be deleted. Otherwise it amounts to memory leak. The existing
OPP library does not have provison to do so.

Hence this patch implements the function to free the opp table.

Signed-off-by: Inderpal Singh <inderpal.s@xxxxxxxxxxx>
---
 drivers/base/power/opp.c | 41 +++++++++++++++++++++++++++++++++++++++++
 include/linux/pm_opp.h   |  6 ++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
index d9e376a..d45ffd5 100644
--- a/drivers/base/power/opp.c
+++ b/drivers/base/power/opp.c
@@ -654,4 +654,45 @@ int of_init_opp_table(struct device *dev)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_init_opp_table);
+
+/**
+ * dev_pm_opp_free_opp_table() - free the opp table
+ * @dev:	device for which we do this operation
+ *
+ * Free up the allocated opp table
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * Hence this function internally uses RCU updater strategy with mutex locks to
+ * keep the integrity of the internal data structures. Callers should ensure
+ * that this function is *NOT* called under RCU protection or in contexts where
+ * mutex locking or synchronize_rcu() blocking calls cannot be used.
+ */
+void dev_pm_opp_free_opp_table(struct device *dev)
+{
+	struct device_opp *dev_opp = NULL;
+	struct dev_pm_opp *opp;
+
+	/* Hold our list modification lock here */
+	mutex_lock(&dev_opp_list_lock);
+
+	/* Check for existing list for 'dev' */
+	dev_opp = find_device_opp(dev);
+	if (IS_ERR(dev_opp)) {
+		mutex_unlock(&dev_opp_list_lock);
+		return;
+	}
+
+	while (!list_empty(&dev_opp->opp_list)) {
+		opp = list_entry_rcu(dev_opp->opp_list.next,
+					struct dev_pm_opp, node);
+		list_del_rcu(&opp->node);
+		kfree_rcu(opp, head);
+	}
+
+	list_del_rcu(&dev_opp->node);
+	mutex_unlock(&dev_opp_list_lock);
+	synchronize_rcu();
+	kfree(dev_opp);
+}
+EXPORT_SYMBOL_GPL(dev_pm_opp_free_opp_table);
 #endif
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index 0330217..3c29620 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -50,6 +50,8 @@ int dev_pm_opp_enable(struct device *dev, unsigned long freq);
 int dev_pm_opp_disable(struct device *dev, unsigned long freq);
 
 struct srcu_notifier_head *dev_pm_opp_get_notifier(struct device *dev);
+
+void dev_pm_opp_free_opp_table(struct device *dev);
 #else
 static inline unsigned long dev_pm_opp_get_voltage(struct dev_pm_opp *opp)
 {
@@ -105,6 +107,10 @@ static inline struct srcu_notifier_head *dev_pm_opp_get_notifier(
 {
 	return ERR_PTR(-EINVAL);
 }
+
+void dev_pm_opp_free_opp_table(struct device *dev)
+{
+}
 #endif		/* CONFIG_PM_OPP */
 
 #if defined(CONFIG_PM_OPP) && defined(CONFIG_OF)
-- 
1.8.3.2

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