PM / OPP: Don't expose srcu_head to register notifiers

Let the OPP core provide helpers to register notifiers for any device,
instead of exposing srcu_head outside of the core.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 52 insertions, 40 deletions

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index 614d779ab6a2..f35effad60d1 100644
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -1860,29 +1860,63 @@ int dev_pm_opp_disable(struct device *dev, unsigned long freq)
 EXPORT_SYMBOL_GPL(dev_pm_opp_disable);
 
 /**
- * dev_pm_opp_get_notifier() - find notifier_head of the device with opp
- * @dev:        device pointer used to lookup OPP table.
+ * dev_pm_opp_register_notifier() - Register OPP notifier for the device
+ * @dev:        Device for which notifier needs to be registered
+ * @nb:         Notifier block to be registered
  *
- * Return: pointer to  notifier head if found, otherwise -ENODEV or
- * -EINVAL based on type of error casted as pointer. value must be checked
- *  with IS_ERR to determine valid pointer or error result.
+ * Return: 0 on success or a negative error value.
+ */
+int dev_pm_opp_register_notifier(struct device *dev, struct notifier_block *nb)
+{
+        struct opp_table *opp_table;
+        int ret;
+
+        rcu_read_lock();
+
+        opp_table = _find_opp_table(dev);
+        if (IS_ERR(opp_table)) {
+                ret = PTR_ERR(opp_table);
+                goto unlock;
+        }
+
+        ret = srcu_notifier_chain_register(&opp_table->srcu_head, nb);
+
+unlock:
+        rcu_read_unlock();
+
+        return ret;
+}
+EXPORT_SYMBOL(dev_pm_opp_register_notifier);
+
+/**
+ * dev_pm_opp_unregister_notifier() - Unregister OPP notifier for the device
+ * @dev:        Device for which notifier needs to be unregistered
+ * @nb:         Notifier block to be unregistered
  *
- * Locking: This function must be called under rcu_read_lock(). opp_table is a
- * RCU protected pointer. The reason for the same is that the opp pointer which
- * is returned will remain valid for use with opp_get_{voltage, freq} only while
- * under the locked area. The pointer returned must be used prior to unlocking
- * with rcu_read_unlock() to maintain the integrity of the pointer.
+ * Return: 0 on success or a negative error value.
  */
-struct srcu_notifier_head *dev_pm_opp_get_notifier(struct device *dev)
+int dev_pm_opp_unregister_notifier(struct device *dev,
+                                   struct notifier_block *nb)
 {
-        struct opp_table *opp_table = _find_opp_table(dev);
+        struct opp_table *opp_table;
+        int ret;
 
-        if (IS_ERR(opp_table))
-                return ERR_CAST(opp_table); /* matching type */
+        rcu_read_lock();
+
+        opp_table = _find_opp_table(dev);
+        if (IS_ERR(opp_table)) {
+                ret = PTR_ERR(opp_table);
+                goto unlock;
+        }
+
+        ret = srcu_notifier_chain_unregister(&opp_table->srcu_head, nb);
 
-        return &opp_table->srcu_head;
+unlock:
+        rcu_read_unlock();
+
+        return ret;
 }
-EXPORT_SYMBOL_GPL(dev_pm_opp_get_notifier);
+EXPORT_SYMBOL(dev_pm_opp_unregister_notifier);
 
 /*
  * Free OPPs either created using static entries present in DT or even the
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 47206a21bb90..a545c0fee6e1 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -1265,18 +1265,7 @@ EXPORT_SYMBOL(devfreq_recommended_opp);
  */
 int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
 {
-        struct srcu_notifier_head *nh;
-        int ret = 0;
-
-        rcu_read_lock();
-        nh = dev_pm_opp_get_notifier(dev);
-        if (IS_ERR(nh))
-                ret = PTR_ERR(nh);
-        rcu_read_unlock();
-        if (!ret)
-                ret = srcu_notifier_chain_register(nh, &devfreq->nb);
-
-        return ret;
+        return dev_pm_opp_register_notifier(dev, &devfreq->nb);
 }
 EXPORT_SYMBOL(devfreq_register_opp_notifier);
 
@@ -1292,18 +1281,7 @@ EXPORT_SYMBOL(devfreq_register_opp_notifier);
  */
 int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
 {
-        struct srcu_notifier_head *nh;
-        int ret = 0;
-
-        rcu_read_lock();
-        nh = dev_pm_opp_get_notifier(dev);
-        if (IS_ERR(nh))
-                ret = PTR_ERR(nh);
-        rcu_read_unlock();
-        if (!ret)
-                ret = srcu_notifier_chain_unregister(nh, &devfreq->nb);
-
-        return ret;
+        return dev_pm_opp_unregister_notifier(dev, &devfreq->nb);
 }
 EXPORT_SYMBOL(devfreq_unregister_opp_notifier);