clk: Add of_clk_hw_register() API for early clk drivers

In some circumstances drivers register clks early and don't have access
to a struct device because the device model isn't initialized yet. Add
an API to let drivers register clks associated with a struct device_node
so that these drivers can participate in getting parent clks through DT.

Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Rob Herring <robh@kernel.org>
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -45,6 +45,7 @@ struct clk_core {
 	struct clk_hw		*hw;
 	struct module		*owner;
 	struct device		*dev;
+	struct device_node	*of_node;
 	struct clk_core		*parent;
 	const char		**parent_names;
 	struct clk_core		**parents;
@@ -3313,7 +3314,8 @@ struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
 	return clk;
 }
 
-static struct clk *__clk_register(struct device *dev, struct clk_hw *hw)
+static struct clk *
+__clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 {
 	int i, ret;
 	struct clk_core *core;
@@ -3339,6 +3341,7 @@ static struct clk *__clk_register(struct device *dev, struct clk_hw *hw)
 	if (dev && pm_runtime_enabled(dev))
 		core->rpm_enabled = true;
 	core->dev = dev;
+	core->of_node = np;
 	if (dev && dev->driver)
 		core->owner = dev->driver->owner;
 	core->hw = hw;
@@ -3429,7 +3432,7 @@ static struct clk *__clk_register(struct device *dev, struct clk_hw *hw)
  */
 struct clk *clk_register(struct device *dev, struct clk_hw *hw)
 {
-	return __clk_register(dev, hw);
+	return __clk_register(dev, dev_of_node(dev), hw);
 }
 EXPORT_SYMBOL_GPL(clk_register);
 
@@ -3445,10 +3448,27 @@ EXPORT_SYMBOL_GPL(clk_register);
  */
 int clk_hw_register(struct device *dev, struct clk_hw *hw)
 {
-	return PTR_ERR_OR_ZERO(__clk_register(dev, hw));
+	return PTR_ERR_OR_ZERO(__clk_register(dev, dev_of_node(dev), hw));
 }
 EXPORT_SYMBOL_GPL(clk_hw_register);
 
+/*
+ * of_clk_hw_register - register a clk_hw and return an error code
+ * @node: device_node of device that is registering this clock
+ * @hw: link to hardware-specific clock data
+ *
+ * of_clk_hw_register() is the primary interface for populating the clock tree
+ * with new clock nodes when a struct device is not available, but a struct
+ * device_node is. It returns an integer equal to zero indicating success or
+ * less than zero indicating failure. Drivers must test for an error code after
+ * calling of_clk_hw_register().
+ */
+int of_clk_hw_register(struct device_node *node, struct clk_hw *hw)
+{
+	return PTR_ERR_OR_ZERO(__clk_register(NULL, node, hw));
+}
+EXPORT_SYMBOL_GPL(of_clk_hw_register);
+
 /* Free memory allocated for a clock. */
 static void __clk_release(struct kref *ref)
 {

include/linux/clk-provider.h

@@ -773,6 +773,7 @@ struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw);
 
 int __must_check clk_hw_register(struct device *dev, struct clk_hw *hw);
 int __must_check devm_clk_hw_register(struct device *dev, struct clk_hw *hw);
+int __must_check of_clk_hw_register(struct device_node *node, struct clk_hw *hw);
 
 void clk_unregister(struct clk *clk);
 void devm_clk_unregister(struct device *dev, struct clk *clk);