1 files changed, 28 insertions, 8 deletions

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 369ff02c4ab2..6ded50dfa75a 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -253,32 +253,52 @@ void update_vsyscall_tz(void)
  */
 void __init time_init(void)
 {
+        struct timespec ts;
+        unsigned long flags;
+        cycle_t now;
+
         /* Reset time synchronization interfaces. */
         etr_reset();
         stp_reset();
 
-        /* set xtime */
-        tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &xtime);
-        set_normalized_timespec(&wall_to_monotonic,
-                                -xtime.tv_sec, -xtime.tv_nsec);
-
         /* request the clock comparator external interrupt */
         if (register_early_external_interrupt(0x1004,
                                               clock_comparator_interrupt,
                                               &ext_int_info_cc) != 0)
                 panic("Couldn't request external interrupt 0x1004");
 
-        if (clocksource_register(&clocksource_tod) != 0)
-                panic("Could not register TOD clock source");
-
         /* request the timing alert external interrupt */
         if (register_early_external_interrupt(0x1406,
                                               timing_alert_interrupt,
                                               &ext_int_etr_cc) != 0)
                 panic("Couldn't request external interrupt 0x1406");
 
+        if (clocksource_register(&clocksource_tod) != 0)
+                panic("Could not register TOD clock source");
+
+        /*
+         * The TOD clock is an accurate clock. The xtime should be
+         * initialized in a way that the difference between TOD and
+         * xtime is reasonably small. Too bad that timekeeping_init
+         * sets xtime.tv_nsec to zero. In addition the clock source
+         * change from the jiffies clock source to the TOD clock
+         * source add another error of up to 1/HZ second. The same
+         * function sets wall_to_monotonic to a value that is too
+         * small for /proc/uptime to be accurate.
+         * Reset xtime and wall_to_monotonic to sane values.
+         */
+        write_seqlock_irqsave(&xtime_lock, flags);
+        now = get_clock();
+        tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
+        clocksource_tod.cycle_last = now;
+        clocksource_tod.raw_time = xtime;
+        tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
+        set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
+        write_sequnlock_irqrestore(&xtime_lock, flags);
+
         /* Enable TOD clock interrupts on the boot cpu. */
         init_cpu_timer();
+
         /* Enable cpu timer interrupts on the boot cpu. */
         vtime_init();
 }