clk: add api to get clk consumer from clk_hw

clk_register() is deprecated. Using 'clk' member of struct clk_hw is
discouraged. With this constraint, it is difficult for driver to
register clocks using the clk_hw API and then use the clock with
the consumer API

This adds a simple helper, clk_hw_get_clk(), to get a struct clk from
a struct clk_hw. Like other clk_get() variant, each call to this helper
must be balanced with a call to clk_put(). To make life easier on the
consumers, a memory managed version is provided as well.

Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20201021162147.563655-3-jbrunet@baylibre.com
Tested-by: Kevin Hilman <khilman@baylibre.com>
[sboyd@kernel.org: Fix kernel-doc]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -3667,6 +3667,24 @@ struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
 	return clk;
 }
 
+/**
+ * clk_hw_get_clk - get clk consumer given an clk_hw
+ * @hw: clk_hw associated with the clk being consumed
+ * @con_id: connection ID string on device
+ *
+ * Returns: new clk consumer
+ * This is the function to be used by providers which need
+ * to get a consumer clk and act on the clock element
+ * Calls to this function must be balanced with calls clk_put()
+ */
+struct clk *clk_hw_get_clk(struct clk_hw *hw, const char *con_id)
+{
+	struct device *dev = hw->core->dev;
+
+	return clk_hw_create_clk(dev, hw, dev_name(dev), con_id);
+}
+EXPORT_SYMBOL(clk_hw_get_clk);
+
 static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
 {
 	const char *dst;
@@ -4187,6 +4205,49 @@ void devm_clk_hw_unregister(struct device *dev, struct clk_hw *hw)
 }
 EXPORT_SYMBOL_GPL(devm_clk_hw_unregister);
 
+static void devm_clk_release(struct device *dev, void *res)
+{
+	clk_put(*(struct clk **)res);
+}
+
+/**
+ * devm_clk_hw_get_clk - resource managed clk_hw_get_clk()
+ * @dev: device that is registering this clock
+ * @hw: clk_hw associated with the clk being consumed
+ * @con_id: connection ID string on device
+ *
+ * Managed clk_hw_get_clk(). Clocks got with this function are
+ * automatically clk_put() on driver detach. See clk_put()
+ * for more information.
+ */
+struct clk *devm_clk_hw_get_clk(struct device *dev, struct clk_hw *hw,
+				const char *con_id)
+{
+	struct clk *clk;
+	struct clk **clkp;
+
+	/* This should not happen because it would mean we have drivers
+	 * passing around clk_hw pointers instead of having the caller use
+	 * proper clk_get() style APIs
+	 */
+	WARN_ON_ONCE(dev != hw->core->dev);
+
+	clkp = devres_alloc(devm_clk_release, sizeof(*clkp), GFP_KERNEL);
+	if (!clkp)
+		return ERR_PTR(-ENOMEM);
+
+	clk = clk_hw_get_clk(hw, con_id);
+	if (!IS_ERR(clk)) {
+		*clkp = clk;
+		devres_add(dev, clkp);
+	} else {
+		devres_free(clkp);
+	}
+
+	return clk;
+}
+EXPORT_SYMBOL_GPL(devm_clk_hw_get_clk);
+
 /*
  * clkdev helpers
  */

include/linux/clk-provider.h

@@ -1088,6 +1088,11 @@ static inline struct clk_hw *__clk_get_hw(struct clk *clk)
 	return (struct clk_hw *)clk;
 }
 #endif
+
+struct clk *clk_hw_get_clk(struct clk_hw *hw, const char *con_id);
+struct clk *devm_clk_hw_get_clk(struct device *dev, struct clk_hw *hw,
+				const char *con_id);
+
 unsigned int clk_hw_get_num_parents(const struct clk_hw *hw);
 struct clk_hw *clk_hw_get_parent(const struct clk_hw *hw);
 struct clk_hw *clk_hw_get_parent_by_index(const struct clk_hw *hw,