clk: Add devm_clk_get()

Add a resource managed clk_get() to simplify clock usage in
drivers. This allows driver authors to "get and forget" about
their clocks by automatically calling clk_put() when the driver
is detached. This also encourages clock consumers to use the
clk_get() API correctly by passing in a struct device as an
argument.

Change-Id: I1ed53cd3c26c0390fa30cd3c3dca14bcdd59939f
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/clkdev.c

@@ -83,6 +83,31 @@ struct clk *clk_get(struct device *dev, const char *con_id)
 }
 EXPORT_SYMBOL(clk_get);
 
+static void devm_clk_release(struct device *dev, void *res)
+{
+	clk_put(*(struct clk **)res);
+}
+
+struct clk *devm_clk_get(struct device *dev, const char *id)
+{
+	struct clk **ptr, *clk;
+
+	ptr = devres_alloc(devm_clk_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	clk = clk_get(dev, id);
+	if (!IS_ERR(clk)) {
+		*ptr = clk;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return clk;
+}
+EXPORT_SYMBOL(devm_clk_get);
+
 void clk_put(struct clk *clk)
 {
 	__clk_put(clk);

include/linux/clk.h

@@ -100,6 +100,16 @@ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb);
  */
 struct clk *clk_get(struct device *dev, const char *id);
 
+/**
+ * devm_clk_get - Resource managed clk_get()
+ * @dev: device for clk "consumer"
+ * @id: clk ID.
+ *
+ * Managed clk_get(). Clocks returned from this function are
+ * automatically clk_put() on driver detach.
+ */
+struct clk *devm_clk_get(struct device *dev, const char *id);
+
 /**
  * clk_prepare - prepare a clock source
  * @clk: clock source