[PATCH V3 1/2] clocksource: add common of_clksrc_init() function

[Stephen Warren]

From: Stephen Warren <swarren at nvidia.com>

It is desirable to move all clocksource drivers to drivers/clocksource,
yet each requires its own initialization function. We'd rather not
pollute <linux/> with a header for each function. Instead, create a
single of_clksrc_init() function which will determine which clocksource
driver to initialize based on device tree.

Inspired by a similar patch for drivers/irqchip by Thomas Petazzoni.

Signed-off-by: Stephen Warren <swarren at nvidia.com>
---
v3: Use a linker section to replace manually maintained table.
v2: New patch.

This series is based on the ARM sys_timer rework that I reposted today.

I hope that these patches can be taken through arm-soc tree for 3.9;
I will repost them based on 3.8-rc1 at the appropriate time.
---
 drivers/clocksource/Kconfig       |    3 +++
 drivers/clocksource/Makefile      |    1 +
 drivers/clocksource/clksrc-of.c   |   41 +++++++++++++++++++++++++++++++++++++
 include/asm-generic/vmlinux.lds.h |   10 +++++++++
 include/linux/clocksource.h       |   10 +++++++++
 5 files changed, 65 insertions(+)
 create mode 100644 drivers/clocksource/clksrc-of.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index c9f67de..4f300c5 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -1,3 +1,6 @@
+config CLKSRC_OF
+	bool
+
 config CLKSRC_I8253
 	bool
 
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 24fb888..29017a3 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -1,3 +1,4 @@
+obj-$(CONFIG_CLKSRC_OF)	+= clksrc-of.o
 obj-$(CONFIG_ATMEL_TCB_CLKSRC)	+= tcb_clksrc.o
 obj-$(CONFIG_X86_CYCLONE_TIMER)	+= cyclone.o
 obj-$(CONFIG_X86_PM_TIMER)	+= acpi_pm.o
diff --git a/drivers/clocksource/clksrc-of.c b/drivers/clocksource/clksrc-of.c
new file mode 100644
index 0000000..04c7820
--- /dev/null
+++ b/drivers/clocksource/clksrc-of.c
@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2012, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/init.h>
+#include <linux/of.h>
+
+extern struct of_device_id *__start_clksrc_of_match_tables[];
+extern struct of_device_id *__stop_clksrc_of_match_tables[];
+
+void __init clocksource_of_init(void)
+{
+	struct of_device_id **table;
+	struct of_device_id **stop;
+	struct device_node *np;
+	const struct of_device_id *match;
+	void (*init_func)(void);
+
+	table = __start_clksrc_of_match_tables;
+	stop = __stop_clksrc_of_match_tables;
+
+	for ( ; table < stop; table++) {
+		for_each_matching_node(np, *table) {
+			match = of_match_node(*table, np);
+			init_func = match->data;
+			init_func();
+		}
+	}
+}
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d1ea7ce..b17f793 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -149,6 +149,15 @@
 #define TRACE_SYSCALLS()
 #endif
 
+#ifdef CONFIG_CLKSRC_OF
+#define CLKSRC_OF_MATCH_TABLES() \
+		. = ALIGN(8);						\
+		VMLINUX_SYMBOL(__start_clksrc_of_match_tables) = .;	\
+		*(__clksrc_of_table)					\
+		VMLINUX_SYMBOL(__stop_clksrc_of_match_tables) = .;
+#else
+#define CLKSRC_OF_MATCH_TABLES()
+#endif
 
 #define KERNEL_DTB()							\
 	STRUCT_ALIGN();							\
@@ -490,6 +499,7 @@
 	*(.init.rodata)							\
 	FTRACE_EVENTS()							\
 	TRACE_SYSCALLS()						\
+	CLKSRC_OF_MATCH_TABLES()					\
 	DEV_DISCARD(init.rodata)					\
 	CPU_DISCARD(init.rodata)					\
 	MEM_DISCARD(init.rodata)					\
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 4dceaf8..3b0f30e 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -332,4 +332,14 @@ extern int clocksource_mmio_init(void __iomem *, const char *,
 
 extern int clocksource_i8253_init(void);
 
+#ifdef CONFIG_CLKSRC_OF
+extern void clocksource_of_init(void);
+
+#define CLKSRC_OF_MATCH_TABLE(name, table)			\
+	static const struct of_device_id __used			\
+		__attribute__((section("__clksrc_of_table")))	\
+		*__p_clksrc_of_match_table_##name = table;
+
+#endif
+
 #endif /* _LINUX_CLOCKSOURCE_H */
-- 
1.7.10.4