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>

2 files changed, 9 insertions, 4 deletions

diff --git a/arch/mips/lasat/ds1603.c b/arch/mips/lasat/ds1603.c
index 52cb1436a12a..c6fd96ff118d 100644
--- a/arch/mips/lasat/ds1603.c
+++ b/arch/mips/lasat/ds1603.c
@@ -135,7 +135,7 @@ static void rtc_end_op(void)
         lasat_ndelay(1000);
 }
 
-unsigned long read_persistent_clock(void)
+void read_persistent_clock(struct timespec *ts)
 {
         unsigned long word;
         unsigned long flags;
@@ -147,7 +147,8 @@ unsigned long read_persistent_clock(void)
         rtc_end_op();
         spin_unlock_irqrestore(&rtc_lock, flags);
 
-        return word;
+        ts->tv_sec = word;
+        ts->tv_nsec = 0;
 }
 
 int rtc_mips_set_mmss(unsigned long time)
diff --git a/arch/mips/lasat/sysctl.c b/arch/mips/lasat/sysctl.c
index 8f88886feb12..3f04d4c406b7 100644
--- a/arch/mips/lasat/sysctl.c
+++ b/arch/mips/lasat/sysctl.c
@@ -92,10 +92,12 @@ static int rtctmp;
 int proc_dolasatrtc(ctl_table *table, int write, struct file *filp,
                        void *buffer, size_t *lenp, loff_t *ppos)
 {
+        struct timespec ts;
         int r;
 
         if (!write) {
-                rtctmp = read_persistent_clock();
+                read_persistent_clock(&ts);
+                rtctmp = ts.tv_sec;
                 /* check for time < 0 and set to 0 */
                 if (rtctmp < 0)
                         rtctmp = 0;
@@ -134,9 +136,11 @@ int sysctl_lasat_rtc(ctl_table *table,
                     void *oldval, size_t *oldlenp,
                     void *newval, size_t newlen)
 {
+        struct timespec ts;
         int r;
 
-        rtctmp = read_persistent_clock();
+        read_persistent_clock(&ts);
+        rtctmp = ts.tv_sec;
         if (rtctmp < 0)
                 rtctmp = 0;
         r = sysctl_intvec(table, oldval, oldlenp, newval, newlen);