clocksource: add suspend callback

Add a clocksource suspend callback.  This callback can be used by the
clocksource driver to shutdown and perform any kind of late suspend
activities even though the clocksource driver itself is a non-sysdev
driver.

One example where this is useful is to fix the sh_cmt.c platform driver
that today suspends using the platform bus and shuts down the clocksource
too early.

With this callback in place the sh_cmt driver will suspend using the
clocksource and clockevent hooks and leave the platform device pm
callbacks unused.

Signed-off-by: Magnus Damm <damm@opensource.se>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 0de7e72c3995..4bca8b60cdf7 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -154,6 +154,7 @@ extern u64 timecounter_cyc2time(struct timecounter *tc,
  * @max_idle_ns:        max idle time permitted by the clocksource (nsecs)
  * @flags:              flags describing special properties
  * @vread:              vsyscall based read
+ * @suspend:            suspend function for the clocksource, if necessary
  * @resume:             resume function for the clocksource, if necessary
  */
 struct clocksource {
@@ -172,6 +173,7 @@ struct clocksource {
         u64 max_idle_ns;
         unsigned long flags;
         cycle_t (*vread)(void);
+        void (*suspend)(struct clocksource *cs);
         void (*resume)(struct clocksource *cs);
 #ifdef CONFIG_IA64
         void *fsys_mmio;        /* used by fsyscall asm code */
@@ -277,6 +279,7 @@ extern void clocksource_unregister(struct clocksource*);
 extern void clocksource_touch_watchdog(void);
 extern struct clocksource* clocksource_get_next(void);
 extern void clocksource_change_rating(struct clocksource *cs, int rating);
+extern void clocksource_suspend(void);
 extern void clocksource_resume(void);
 extern struct clocksource * __init __weak clocksource_default_clock(void);
 extern void clocksource_mark_unstable(struct clocksource *cs);
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 08adacb2a1ed..bd246660902c 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -441,6 +441,18 @@ static inline int clocksource_watchdog_kthread(void *data) { return 0; }
 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
 
 /**
+ * clocksource_suspend - suspend the clocksource(s)
+ */
+void clocksource_suspend(void)
+{
+        struct clocksource *cs;
+
+        list_for_each_entry_reverse(cs, &clocksource_list, list)
+                if (cs->suspend)
+                        cs->suspend(cs);
+}
+
+/**
  * clocksource_resume - resume the clocksource(s)
  */
 void clocksource_resume(void)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 7faaa32fbf4f..843d8a711b16 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -622,6 +622,7 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
         write_sequnlock_irqrestore(&xtime_lock, flags);
 
         clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
+        clocksource_suspend();
 
         return 0;
 }