dm: clk: Define clk_get_by_id() for clk operations

This commit adds the clk_get_by_id() function, which is responsible
for getting the udevice with matching clk->id. Such approach allows
re-usage of inherit DM list relationship for the same class (UCLASS_CLK).
As a result - we don't need any other external list - it is just enough
to look for UCLASS_CLK related udevices.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Peng Fan <peng.fan@nxp.com>

drivers/clk/clk-uclass.c

@@ -491,6 +491,28 @@ int clk_disable_bulk(struct clk_bulk *bulk)
 	return 0;
 }
 
+int clk_get_by_id(ulong id, struct clk **clkp)
+{
+	struct udevice *dev;
+	struct uclass *uc;
+	int ret;
+
+	ret = uclass_get(UCLASS_CLK, &uc);
+	if (ret)
+		return ret;
+
+	uclass_foreach_dev(dev, uc) {
+		struct clk *clk = dev_get_clk_ptr(dev);
+
+		if (clk && clk->id == id) {
+			*clkp = clk;
+			return 0;
+		}
+	}
+
+	return -ENOENT;
+}
+
 UCLASS_DRIVER(clk) = {
 	.id		= UCLASS_CLK,
 	.name		= "clk",

include/clk.h

@@ -345,4 +345,15 @@ static inline bool clk_valid(struct clk *clk)
 {
 	return !!clk->dev;
 }
+
+/**
+ * clk_get_by_id() - Get the clock by its ID
+ *
+ * @id:	The clock ID to search for
+ *
+ * @clkp:	A pointer to clock struct that has been found among added clocks
+ *              to UCLASS_CLK
+ * @return zero on success, or -ENOENT on error
+ */
+int clk_get_by_id(ulong id, struct clk **clkp);
 #endif