timekeeping: Increase granularity of read_persistent_clock()

The persistent clock of some architectures (e.g. s390) have a
better granularity than seconds. To reduce the delta between the
host clock and the guest clock in a virtualized system change the 
read_persistent_clock function to return a struct timespec.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134811.013873340@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 5d465b207e72..bf67dcb4a44c 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -178,7 +178,7 @@ static int set_rtc_mmss(unsigned long nowtime)
 }
 
 /* not static: needed by APM */
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
         unsigned long retval, flags;
 
@@ -186,7 +186,8 @@ unsigned long read_persistent_clock(void)
         retval = get_wallclock();
         spin_unlock_irqrestore(&rtc_lock, flags);
 
-        return retval;
+        ts->tv_sec = retval;
+        ts->tv_nsec = 0;
 }
 
 int update_persistent_clock(struct timespec now)