clk: add DT fixed-clock binding support

Add support for DT "fixed-clock" binding to the common fixed rate clock
support.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
[Rob Herring] Rework and move into common clock infrastructure
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clk-fixed-rate.c

@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/err.h>
+#include <linux/of.h>
 
 /*
  * DOC: basic fixed-rate clock that cannot gate
@@ -79,3 +80,25 @@ struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
 
 	return clk;
 }
+
+#ifdef CONFIG_OF
+/**
+ * of_fixed_clk_setup() - Setup function for simple fixed rate clock
+ */
+void __init of_fixed_clk_setup(struct device_node *node)
+{
+	struct clk *clk;
+	const char *clk_name = node->name;
+	u32 rate;
+
+	if (of_property_read_u32(node, "clock-frequency", &rate))
+		return;
+
+	of_property_read_string(node, "clock-output-names", &clk_name);
+
+	clk = clk_register_fixed_rate(NULL, clk_name, NULL, CLK_IS_ROOT, rate);
+	if (clk)
+		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+}
+EXPORT_SYMBOL_GPL(of_fixed_clk_setup);
+#endif

include/linux/clk-provider.h

@@ -172,6 +172,8 @@ struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
 		const char *parent_name, unsigned long flags,
 		unsigned long fixed_rate);
 
+void of_fixed_clk_setup(struct device_node *np);
+
 /**
  * struct clk_gate - gating clock
  *