clocksource: Replace vread with generic arch data

The vread field was bloating struct clocksource everywhere except
x86_64, and I want to change the way this works on x86_64, so let's
split it out into per-arch data.

Cc: [e-mail]
Cc: Clemens Ladisch <[e-mail]>
Cc: [e-mail]
Cc: Tony Luck <[e-mail]>
Cc: Fenghua Yu <[e-mail]>
Cc: John Stultz <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andy Lutomirski <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: H. Peter Anvin <[e-mail]>

arch/x86/include/asm/clocksource.h

···
+/* x86-specific clocksource additions */
+
+#ifndef _ASM_X86_CLOCKSOURCE_H
+#define _ASM_X86_CLOCKSOURCE_H
+
+#ifdef CONFIG_X86_64
+
+#define __ARCH_HAS_CLOCKSOURCE_DATA
+
+struct arch_clocksource_data {
+	cycle_t (*vread)(void);
+};
+
+#endif /* CONFIG_X86_64 */
+
+#endif /* _ASM_X86_CLOCKSOURCE_H */

arch/x86/kernel/hpet.c

···
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 	.resume		= hpet_resume_counter,
 #ifdef CONFIG_X86_64
-	.vread		= vread_hpet,
+	.archdata	= { .vread = vread_hpet },
 #endif
 };
 

arch/x86/kernel/tsc.c

···
 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
 				  CLOCK_SOURCE_MUST_VERIFY,
 #ifdef CONFIG_X86_64
-	.vread                  = vread_tsc,
+	.archdata               = { .vread = vread_tsc },
 #endif
 };
 

arch/x86/kernel/vsyscall_64.c

···
 	write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
 
 	/* copy vsyscall data */
-	vsyscall_gtod_data.clock.vread		= clock->vread;
+	vsyscall_gtod_data.clock.vread		= clock->archdata.vread;
 	vsyscall_gtod_data.clock.cycle_last	= clock->cycle_last;
 	vsyscall_gtod_data.clock.mask		= clock->mask;
 	vsyscall_gtod_data.clock.mult		= mult;

include/asm-generic/clocksource.h

···
+/*
+ * Architectures should override this file to add private userspace
+ * clock magic if needed.
+ */

include/linux/clocksource.h

···
 typedef u64 cycle_t;
 struct clocksource;
 
+#include <asm/clocksource.h>
+
 /**
  * struct cyclecounter - hardware abstraction for a free running counter
  *	Provides completely state-free accessors to the underlying hardware.
···
  * @shift:		cycle to nanosecond divisor (power of two)
  * @max_idle_ns:	max idle time permitted by the clocksource (nsecs)
  * @flags:		flags describing special properties
- * @vread:		vsyscall based read
+ * @archdata:		arch-specific data
  * @suspend:		suspend function for the clocksource, if necessary
  * @resume:		resume function for the clocksource, if necessary
  */
···
 #else
 #define CLKSRC_FSYS_MMIO_SET(mmio, addr)      do { } while (0)
 #endif
+
+#ifdef __ARCH_HAS_CLOCKSOURCE_DATA
+	struct arch_clocksource_data archdata;
+#endif
+
 	const char *name;
 	struct list_head list;
 	int rating;
-	cycle_t (*vread)(void);
 	int (*enable)(struct clocksource *cs);
 	void (*disable)(struct clocksource *cs);
 	unsigned long flags;