x86_64: use generic cmos update

Use the generic cmos update function in kernel/time/ntp.c

Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86_64/Kconfig

@@ -32,6 +32,10 @@ config GENERIC_TIME_VSYSCALL
 	bool
 	default y
 
+config GENERIC_CMOS_UPDATE
+	bool
+	default y
+
 config ZONE_DMA32
 	bool
 	default y

arch/x86_64/kernel/time.c

@@ -80,8 +80,9 @@ EXPORT_SYMBOL(profile_pc);
  * sheet for details.
  */
 
-static void set_rtc_mmss(unsigned long nowtime)
+static int set_rtc_mmss(unsigned long nowtime)
 {
+	int retval = 0;
 	int real_seconds, real_minutes, cmos_minutes;
 	unsigned char control, freq_select;
 
@@ -121,6 +122,7 @@ static void set_rtc_mmss(unsigned long nowtime)
 	if (abs(real_minutes - cmos_minutes) >= 30) {
 		printk(KERN_WARNING "time.c: can't update CMOS clock "
 		       "from %d to %d\n", cmos_minutes, real_minutes);
+		retval = -1;
 	} else {
 		BIN_TO_BCD(real_seconds);
 		BIN_TO_BCD(real_minutes);
@@ -140,12 +142,17 @@ static void set_rtc_mmss(unsigned long nowtime)
 	CMOS_WRITE(freq_select, RTC_FREQ_SELECT);
 
 	spin_unlock(&rtc_lock);
+
+	return retval;
 }
 
+int update_persistent_clock(struct timespec now)
+{
+	return set_rtc_mmss(now.tv_sec);
+}
 
 void main_timer_handler(void)
 {
-	static unsigned long rtc_update = 0;
 /*
  * Here we are in the timer irq handler. We have irqs locally disabled (so we
  * don't need spin_lock_irqsave()) but we don't know if the timer_bh is running
@@ -173,20 +180,6 @@ void main_timer_handler(void)
 	if (!using_apic_timer)
 		smp_local_timer_interrupt();
 
-/*
- * If we have an externally synchronized Linux clock, then update CMOS clock
- * accordingly every ~11 minutes. set_rtc_mmss() will be called in the jiffy
- * closest to exactly 500 ms before the next second. If the update fails, we
- * don't care, as it'll be updated on the next turn, and the problem (time way
- * off) isn't likely to go away much sooner anyway.
- */
-
-	if (ntp_synced() && xtime.tv_sec > rtc_update &&
-		abs(xtime.tv_nsec - 500000000) <= tick_nsec / 2) {
-		set_rtc_mmss(xtime.tv_sec);
-		rtc_update = xtime.tv_sec + 660;
-	}
-
 	write_sequnlock(&xtime_lock);
 }