clk: add API to enable clock

The most basic thing for clock is to enable it, but it is missing
in this uclass.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NSimon Glass <sjg@chromium.org>

drivers/clk/clk-uclass.c

@@ -32,6 +32,16 @@ ulong clk_set_rate(struct udevice *dev, ulong rate)
 	return ops->set_rate(dev, rate);
 }
 
+int clk_enable(struct udevice *dev, int periph)
+{
+	struct clk_ops *ops = clk_get_ops(dev);
+
+	if (!ops->enable)
+		return -ENOSYS;
+
+	return ops->enable(dev, periph);
+}
+
 ulong clk_get_periph_rate(struct udevice *dev, int periph)
 {
 	struct clk_ops *ops = clk_get_ops(dev);

include/clk.h

@@ -32,6 +32,15 @@ struct clk_ops {
 	 */
 	ulong (*set_rate)(struct udevice *dev, ulong rate);
 
+	/**
+	 * enable() - Enable the clock for a peripheral
+	 *
+	 * @dev:	clock provider
+	 * @periph:	Peripheral ID to enable
+	 * @return zero on success, or -ve error code
+	 */
+	int (*enable)(struct udevice *dev, int periph);
+
 	/**
 	 * get_periph_rate() - Get clock rate for a peripheral
 	 *
@@ -70,6 +79,15 @@ ulong clk_get_rate(struct udevice *dev);
  */
 ulong clk_set_rate(struct udevice *dev, ulong rate);
 
+/**
+ * clk_enable() - Enable the clock for a peripheral
+ *
+ * @dev:	clock provider
+ * @periph:	Peripheral ID to enable
+ * @return zero on success, or -ve error code
+ */
+int clk_enable(struct udevice *dev, int periph);
+
 /**
  * clk_get_periph_rate() - Get current clock rate for a peripheral
  *