PM / clk: Add support for adding a specific clock from device-tree

Some drivers using the PM clocks framework need to add specific clocks
from device-tree using a name by calling the functions
of_clk_get_by_name() and then pm_clk_add_clk(). Rather than having
drivers call both functions, add a helper function of_pm_clk_add_clk()
that will call these functions so drivers can call a single function
to add a specific clock from device-tree.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/power/clock_ops.c

@@ -140,6 +140,38 @@ int pm_clk_add_clk(struct device *dev, struct clk *clk)
 EXPORT_SYMBOL_GPL(pm_clk_add_clk);
 
 
+/**
+ * of_pm_clk_add_clk - Start using a device clock for power management.
+ * @dev: Device whose clock is going to be used for power management.
+ * @name: Name of clock that is going to be used for power management.
+ *
+ * Add the clock described in the 'clocks' device-tree node that matches
+ * with the 'name' provided, to the list of clocks used for the power
+ * management of @dev. On success, returns 0. Returns a negative error
+ * code if the clock is not found or cannot be added.
+ */
+int of_pm_clk_add_clk(struct device *dev, const char *name)
+{
+	struct clk *clk;
+	int ret;
+
+	if (!dev || !dev->of_node || !name)
+		return -EINVAL;
+
+	clk = of_clk_get_by_name(dev->of_node, name);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	ret = pm_clk_add_clk(dev, clk);
+	if (ret) {
+		clk_put(clk);
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_pm_clk_add_clk);
+
 /**
  * of_pm_clk_add_clks - Start using device clock(s) for power management.
  * @dev: Device whose clock(s) is going to be used for power management.

include/linux/pm_clock.h

@@ -42,6 +42,7 @@ extern int pm_clk_create(struct device *dev);
 extern void pm_clk_destroy(struct device *dev);
 extern int pm_clk_add(struct device *dev, const char *con_id);
 extern int pm_clk_add_clk(struct device *dev, struct clk *clk);
+extern int of_pm_clk_add_clk(struct device *dev, const char *name);
 extern int of_pm_clk_add_clks(struct device *dev);
 extern void pm_clk_remove(struct device *dev, const char *con_id);
 extern void pm_clk_remove_clk(struct device *dev, struct clk *clk);