rtc: fix alarm read and set offset

The offset needs to be added after reading the alarm value.

It also needs to be subtracted after the now < alarm test.

Tested-by: Jon Hunter <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/interface.c

···
 			return err;
 
 		/* full-function RTCs won't have such missing fields */
-		if (rtc_valid_tm(&alarm->time) == 0)
+		if (rtc_valid_tm(&alarm->time) == 0) {
+			rtc_add_offset(rtc, &alarm->time);
 			return 0;
+		}
 
 		/* get the "after" timestamp, to detect wrapped fields */
 		err = rtc_read_time(rtc, &now);
···
 	if (err)
 		return err;
 
-	rtc_subtract_offset(rtc, &alarm->time);
 	scheduled = rtc_tm_to_time64(&alarm->time);
 
 	/* Make sure we're not setting alarms in the past */
···
 	 * the is alarm set for the next second and the second ticks
 	 * over right here, before we set the alarm.
 	 */
+
+	rtc_subtract_offset(rtc, &alarm->time);
 
 	if (!rtc->ops)
 		err = -ENODEV;
···
 
 	mutex_unlock(&rtc->ops_lock);
 
-	rtc_add_offset(rtc, &alarm->time);
 	return err;
 }
 EXPORT_SYMBOL_GPL(rtc_set_alarm);