timekeeping: Introduce read_boot_clock
Add the new function read_boot_clock to get the exact time the system
has been started. For architectures without support for exact boot
time a new weak function is added that returns 0. Use the exact boot
time to initialize wall_to_monotonic, or xtime if the read_boot_clock
returned 0.
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: <20090814134811.296703241@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index a94ec48..6bff1a1 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -187,6 +187,11 @@
tod_to_timeval(get_clock() - TOD_UNIX_EPOCH, ts);
}
+void read_boot_clock(struct timespec *ts)
+{
+ tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, ts);
+}
+
static cycle_t read_tod_clock(struct clocksource *cs)
{
return get_clock();
@@ -243,9 +248,6 @@
*/
void __init time_init(void)
{
- struct timespec ts;
- unsigned long flags;
-
/* Reset time synchronization interfaces. */
etr_reset();
stp_reset();
@@ -261,15 +263,6 @@
if (clocksource_register(&clocksource_tod) != 0)
panic("Could not register TOD clock source");
- /*
- * Reset wall_to_monotonic to the initial timestamp created
- * in head.S to get a precise value in /proc/uptime.
- */
- write_seqlock_irqsave(&xtime_lock, flags);
- 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();
