clk: Look for parents with clkdev based clk_lookups

In addition to looking for DT based parents, support clkdev based
clk_lookups. This should allow non-DT based clk drivers to participate
in the parent lookup process.

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>
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -324,14 +324,15 @@ static struct clk_core *clk_core_lookup(const char *name)
 }
 
 /**
- * clk_core_get - Find the parent of a clk using a clock specifier in DT
+ * clk_core_get - Find the clk_core parent of a clk
  * @core: clk to find parent of
- * @name: name to search for in 'clock-names' of device providing clk
+ * @name: name to search for
  *
  * This is the preferred method for clk providers to find the parent of a
  * clk when that parent is external to the clk controller. The parent_names
  * array is indexed and treated as a local name matching a string in the device
- * node's 'clock-names' property. This allows clk providers to use their own
+ * node's 'clock-names' property or as the 'con_id' matching the device's
+ * dev_name() in a clk_lookup. This allows clk providers to use their own
  * namespace instead of looking for a globally unique parent string.
  *
  * For example the following DT snippet would allow a clock registered by the
@@ -359,15 +360,23 @@ static struct clk_core *clk_core_lookup(const char *name)
  */
 static struct clk_core *clk_core_get(struct clk_core *core, const char *name)
 {
-	struct clk_hw *hw;
+	struct clk_hw *hw = ERR_PTR(-ENOENT);
+	struct device *dev = core->dev;
+	const char *dev_id = dev ? dev_name(dev) : NULL;
 	struct device_node *np = core->of_node;
 
-	if (!np)
-		return ERR_PTR(-ENOENT);
+	if (np)
+		hw = of_clk_get_hw(np, -1, name);
 
-	/* TODO: Support clkdev clk_lookups */
-	hw = of_clk_get_hw(np, -1, name);
-	if (IS_ERR_OR_NULL(hw))
+	/*
+	 * If the DT search above couldn't find the provider or the provider
+	 * didn't know about this clk, fallback to looking up via clkdev based
+	 * clk_lookups
+	 */
+	if (PTR_ERR(hw) == -ENOENT)
+		hw = clk_find_hw(dev_id, name);
+
+	if (IS_ERR(hw))
 		return ERR_CAST(hw);
 
 	return hw->core;

drivers/clk/clk.h

@@ -19,6 +19,8 @@ static inline struct clk_hw *of_clk_get_hw(struct device_node *np,
 }
 #endif
 
+struct clk_hw *clk_find_hw(const char *dev_id, const char *con_id);
+
 #ifdef CONFIG_COMMON_CLK
 struct clk *clk_hw_create_clk(struct device *dev, struct clk_hw *hw,
 			      const char *dev_id, const char *con_id);

drivers/clk/clkdev.c

@@ -72,7 +72,7 @@ static struct clk_lookup *clk_find(const char *dev_id, const char *con_id)
 	return cl;
 }
 
-static struct clk_hw *clk_find_hw(const char *dev_id, const char *con_id)
+struct clk_hw *clk_find_hw(const char *dev_id, const char *con_id)
 {
 	struct clk_lookup *cl;
 	struct clk_hw *hw = ERR_PTR(-ENOENT);