i386: prepare sharing the PIT code

PIT clock events work already and the PIT handling is the same for
i386 and x86_64. x86_64 does not support PIT as a clock source, so
disable the PIT clocksource for x86_64.

Use the i386 i8253.h include file for x86_64 as well to share the
exports and the PIT constants.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

arch/x86/kernel/time_64.c

@@ -32,7 +32,6 @@
 #include <acpi/achware.h>	/* for PM timer frequency */
 #include <acpi/acpi_bus.h>
 #endif
-#include <asm/8253pit.h>
 #include <asm/i8253.h>
 #include <asm/pgtable.h>
 #include <asm/vsyscall.h>
@@ -292,9 +291,6 @@ static unsigned int __init tsc_calibrate_cpu_khz(void)
 	return pmc_now * tsc_khz / (tsc_now - tsc_start);
 }
 
-#define PIT_MODE 0x43
-#define PIT_CH0  0x40
-
 static void __pit_init(int val, u8 mode)
 {
 	unsigned long flags;

include/asm-x86/i8253.h

@@ -1,5 +1,23 @@
-#ifdef CONFIG_X86_32
-# include "i8253_32.h"
-#else
-# include "i8253_64.h"
+#ifndef __ASM_I8253_H__
+#define __ASM_I8253_H__
+
+#ifdef CONFIG_X86_64
+# include <asm/8253pit.h>
 #endif
+
+/* i8253A PIT registers */
+#define PIT_MODE		0x43
+#define PIT_CH0			0x40
+#define PIT_CH2			0x42
+
+extern spinlock_t i8253_lock;
+
+#ifdef CONFIG_GENERIC_CLOCKEVENTS
+
+extern struct clock_event_device *global_clock_event;
+
+extern void setup_pit_timer(void);
+
+#endif
+
+#endif	/* __ASM_I8253_H__ */