rtc: mc13xxx: make rtc_read_time() more readable

Remove unnecessary locks when reading the time and make the read
operation until the values of day matched between reading the seconds,
it will make the mc13xxx_rtc_read_time() procedure more readable.
Additionally, patch introduced a "seconds in a day" definition.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Sascha Hauer <kernel@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-mc13xxx.c

@@ -23,6 +23,8 @@
 #define MC13XXX_RTCDAY	22
 #define MC13XXX_RTCDAYA	23
 
+#define SEC_PER_DAY	(24 * 60 * 60)
+
 struct mc13xxx_rtc {
 	struct rtc_device *rtc;
 	struct mc13xxx *mc13xxx;
@@ -61,42 +63,27 @@ static int mc13xxx_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
 	unsigned int seconds, days1, days2;
-	unsigned long s1970;
-	int ret;
 
 	if (!priv->valid)
 		return -ENODATA;
 
-	mc13xxx_lock(priv->mc13xxx);
+	do {
+		int ret;
 
-	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days1);
-	if (unlikely(ret))
-		goto out;
-
-	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCTOD, &seconds);
-	if (unlikely(ret))
-		goto out;
-
-	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days2);
-out:
-	mc13xxx_unlock(priv->mc13xxx);
-
-	if (ret)
-		return ret;
-
-	if (days2 == days1 + 1) {
-		if (seconds >= 86400 / 2)
-			days2 = days1;
-		else
-			days1 = days2;
-	}
+		ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days1);
+		if (ret)
+			return ret;
 
-	if (days1 != days2)
-		return -EIO;
+		ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCTOD, &seconds);
+		if (ret)
+			return ret;
 
-	s1970 = days1 * 86400 + seconds;
+		ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days2);
+		if (ret)
+			return ret;
+	} while (days1 != days2);
 
-	rtc_time_to_tm(s1970, tm);
+	rtc_time_to_tm(days1 * SEC_PER_DAY + seconds, tm);
 
 	return rtc_valid_tm(tm);
 }
@@ -108,8 +95,8 @@ static int mc13xxx_rtc_set_mmss(struct device *dev, unsigned long secs)
 	unsigned int alarmseconds;
 	int ret;
 
-	seconds = secs % 86400;
-	days = secs / 86400;
+	seconds = secs % SEC_PER_DAY;
+	days = secs / SEC_PER_DAY;
 
 	mc13xxx_lock(priv->mc13xxx);
 
@@ -121,7 +108,7 @@ static int mc13xxx_rtc_set_mmss(struct device *dev, unsigned long secs)
 	if (unlikely(ret))
 		goto out;
 
-	if (alarmseconds < 86400) {
+	if (alarmseconds < SEC_PER_DAY) {
 		ret = mc13xxx_reg_write(priv->mc13xxx,
 				MC13XXX_RTCTODA, 0x1ffff);
 		if (unlikely(ret))
@@ -145,7 +132,7 @@ static int mc13xxx_rtc_set_mmss(struct device *dev, unsigned long secs)
 		goto out;
 
 	/* restore alarm */
-	if (alarmseconds < 86400) {
+	if (alarmseconds < SEC_PER_DAY) {
 		ret = mc13xxx_reg_write(priv->mc13xxx,
 				MC13XXX_RTCTODA, alarmseconds);
 		if (unlikely(ret))
@@ -181,7 +168,7 @@ static int mc13xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCTODA, &seconds);
 	if (unlikely(ret))
 		goto out;
-	if (seconds >= 86400) {
+	if (seconds >= SEC_PER_DAY) {
 		ret = -ENODATA;
 		goto out;
 	}
@@ -202,7 +189,7 @@ out:
 	alarm->enabled = enabled;
 	alarm->pending = pending;
 
-	s1970 = days * 86400 + seconds;
+	s1970 = days * SEC_PER_DAY + seconds;
 
 	rtc_time_to_tm(s1970, &alarm->time);
 	dev_dbg(dev, "%s: %lu\n", __func__, s1970);
@@ -240,8 +227,8 @@ static int mc13xxx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
 	if (unlikely(ret))
 		goto out;
 
-	seconds = s1970 % 86400;
-	days = s1970 / 86400;
+	seconds = s1970 % SEC_PER_DAY;
+	days = s1970 / SEC_PER_DAY;
 
 	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCDAYA, days);
 	if (unlikely(ret))