Revert "RTC: sa1100: remove redundant code of setting alarm"

This reverts commit 42874759.

This wasn't tested as a stand-alone patch, and it has build errors
without the following patches applied:

drivers/rtc/rtc-sa1100.c: In function 'sa1100_rtc_set_alarm':
drivers/rtc/rtc-sa1100.c:208: error: 'now' undeclared (first use in this function)
drivers/rtc/rtc-sa1100.c:208: error: (Each undeclared identifier is reported only once
drivers/rtc/rtc-sa1100.c:208: error: for each function it appears in.)
drivers/rtc/rtc-sa1100.c:210: error: incompatible type for argument 3 of 'rtc_next_alarm_time'
drivers/rtc/rtc-sa1100.c:211: error: 'time' undeclared (first use in this function)

So it too gets reverted to bring us back to a working point.

drivers/rtc/rtc-sa1100.c

@@ -45,6 +45,16 @@ static const unsigned long RTC_FREQ = 1024;
 static struct rtc_time rtc_alarm;
 static DEFINE_SPINLOCK(sa1100_rtc_lock);
 
+static inline int rtc_periodic_alarm(struct rtc_time *tm)
+{
+	return  (tm->tm_year == -1) ||
+		((unsigned)tm->tm_mon >= 12) ||
+		((unsigned)(tm->tm_mday - 1) >= 31) ||
+		((unsigned)tm->tm_hour > 23) ||
+		((unsigned)tm->tm_min > 59) ||
+		((unsigned)tm->tm_sec > 59);
+}
+
 /*
  * Calculate the next alarm time given the requested alarm time mask
  * and the current time.
@@ -72,6 +82,27 @@ static void rtc_next_alarm_time(struct rtc_time *next, struct rtc_time *now,
 	}
 }
 
+static int rtc_update_alarm(struct rtc_time *alrm)
+{
+	struct rtc_time alarm_tm, now_tm;
+	unsigned long now, time;
+	int ret;
+
+	do {
+		now = RCNR;
+		rtc_time_to_tm(now, &now_tm);
+		rtc_next_alarm_time(&alarm_tm, &now_tm, alrm);
+		ret = rtc_tm_to_time(&alarm_tm, &time);
+		if (ret != 0)
+			break;
+
+		RTSR = RTSR & (RTSR_HZE|RTSR_ALE|RTSR_AL);
+		RTAR = time;
+	} while (now != RCNR);
+
+	return ret;
+}
+
 static irqreturn_t sa1100_rtc_interrupt(int irq, void *dev_id)
 {
 	struct platform_device *pdev = to_platform_device(dev_id);
@@ -115,6 +146,9 @@ static irqreturn_t sa1100_rtc_interrupt(int irq, void *dev_id)
 
 	rtc_update_irq(rtc, 1, events);
 
+	if (rtsr & RTSR_AL && rtc_periodic_alarm(&rtc_alarm))
+		rtc_update_alarm(&rtc_alarm);
+
 	spin_unlock(&sa1100_rtc_lock);
 
 	return IRQ_HANDLED;
@@ -200,21 +234,16 @@ static int sa1100_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 
 static int sa1100_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
 {
-	struct rtc_time now_tm, alarm_tm;
 	int ret;
 
 	spin_lock_irq(&sa1100_rtc_lock);
-
-	now = RCNR;
-	rtc_time_to_tm(now, &now_tm);
-	rtc_next_alarm_time(&alarm_tm, &now_tm, alrm->time);
-	rtc_tm_to_time(&alarm_tm, &time);
-	RTAR = time;
-	if (alrm->enabled)
-		RTSR |= RTSR_ALE;
-	else
-		RTSR &= ~RTSR_ALE;
-
+	ret = rtc_update_alarm(&alrm->time);
+	if (ret == 0) {
+		if (alrm->enabled)
+			RTSR |= RTSR_ALE;
+		else
+			RTSR &= ~RTSR_ALE;
+	}
 	spin_unlock_irq(&sa1100_rtc_lock);
 
 	return ret;