[PATCH 5/7] clocksource: add latch to clocksource

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Add latch for data used by clock read operations. This is in preparation
for the clock latch synchronization scheme. "cycle_last" rely on
timekeeper seqlock synchronization, and will therefore need to be
latched.

Add:
- cycle_last_latch (array of 2 elements),
- read_latch(),
- update_latch().

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 include/linux/clocksource.h |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index dbbf8aa..ef9c2e5 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -180,6 +180,10 @@ struct clocksource {
 #ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
 	struct arch_clocksource_data archdata;
 #endif
+	cycle_t (*read_latch)(struct clocksource *cs, int index);
+	void (*update_latch)(struct clocksource *cs, int oldindex,
+			int newindex);
+	cycle_t cycle_last_latch[2];
 
 	const char *name;
 	struct list_head list;
-- 
1.7.10.4