clk: add common of_clk_init() function

Modify of_clk_init function so that it will determine which
driver to initialize based on device tree instead of each driver
registering to it.

Based on a similar patch for drivers/irqchip by Thomas Petazzoni and
drivers/clocksource by Stephen Warren.
Signed-off-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Tested-by: Tony Prisk <linux@prisktech.co.nz>
Tested-by: Pawel Moll <pawel.moll@arm.com>
Tested-by: Rob Herring <rob.herring@calxeda.com>
Tested-by: Josh Cartwright <josh.cartwright@ni.com>
Reviewed-by: Josh Cartwright <josh.cartwright@ni.com>
Acked-by: Maxime Ripard <maxime.ripard@anandra.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: merge conflict from missing CLKSRC_OF_TABLES()]
Signed-off-by: Mike Turquette <mturquette@linaro.org>

drivers/clk/clk-fixed-rate.c

@@ -101,4 +101,5 @@ void of_fixed_clk_setup(struct device_node *node)
 		of_clk_add_provider(node, of_clk_src_simple_get, clk);
 }
 EXPORT_SYMBOL_GPL(of_fixed_clk_setup);
+CLK_OF_DECLARE(fixed_clk, "fixed-clock", of_fixed_clk_setup);
 #endif

drivers/clk/clk.c

@@ -18,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/device.h>
+#include <linux/init.h>
 
 static DEFINE_SPINLOCK(enable_lock);
 static DEFINE_MUTEX(prepare_lock);
@@ -1803,6 +1804,11 @@ struct of_clk_provider {
 	void *data;
 };
 
+extern struct of_device_id __clk_of_table[];
+
+static const struct of_device_id __clk_of_table_sentinel
+	__used __section(__clk_of_table_end);
+
 static LIST_HEAD(of_clk_providers);
 static DEFINE_MUTEX(of_clk_lock);
 
@@ -1931,6 +1937,9 @@ void __init of_clk_init(const struct of_device_id *matches)
 {
 	struct device_node *np;
 
+	if (!matches)
+		matches = __clk_of_table;
+
 	for_each_matching_node(np, matches) {
 		const struct of_device_id *match = of_match_node(matches, np);
 		of_clk_init_cb_t clk_init_cb = match->data;

include/asm-generic/vmlinux.lds.h

@@ -150,6 +150,15 @@
 #endif
 
 
+#ifdef CONFIG_COMMON_CLK
+#define CLK_OF_TABLES() . = ALIGN(8);				\
+			VMLINUX_SYMBOL(__clk_of_table) = .;	\
+			*(__clk_of_table)			\
+			*(__clk_of_table_end)
+#else
+#define CLK_OF_TABLES()
+#endif
+
 #define KERNEL_DTB()							\
 	STRUCT_ALIGN();							\
 	VMLINUX_SYMBOL(__dtb_start) = .;				\
@@ -493,6 +502,7 @@
 	DEV_DISCARD(init.rodata)					\
 	CPU_DISCARD(init.rodata)					\
 	MEM_DISCARD(init.rodata)					\
+	CLK_OF_TABLES()							\
 	KERNEL_DTB()
 
 #define INIT_TEXT							\

include/linux/clk-provider.h

@@ -379,7 +379,13 @@ struct clk_onecell_data {
 };
 struct clk *of_clk_src_onecell_get(struct of_phandle_args *clkspec, void *data);
 const char *of_clk_get_parent_name(struct device_node *np, int index);
+
 void of_clk_init(const struct of_device_id *matches);
 
+#define CLK_OF_DECLARE(name, compat, fn)			\
+	static const struct of_device_id __clk_of_table_##name	\
+		__used __section(__clk_of_table)		\
+		= { .compatible = compat, .data = fn };
+
 #endif /* CONFIG_COMMON_CLK */
 #endif /* CLK_PROVIDER_H */