driver/rtc/class.c: check the error after rtc_read_time()

In rtc_suspend() and rtc_resume(), the error after rtc_read_time() is not
checked.  If rtc device fail to read time, we cannot guarantee the
following process.

Add the verification code for returned rtc_read_time() error.
Signed-off-by: Hyogi Gim <hyogi.gim@lge.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/class.c

@@ -53,6 +53,7 @@ static int rtc_suspend(struct device *dev)
 	struct rtc_device	*rtc = to_rtc_device(dev);
 	struct rtc_time		tm;
 	struct timespec		delta, delta_delta;
+	int err;
 
 	if (has_persistent_clock())
 		return 0;
@@ -61,7 +62,12 @@ static int rtc_suspend(struct device *dev)
 		return 0;
 
 	/* snapshot the current RTC and system time at suspend*/
-	rtc_read_time(rtc, &tm);
+	err = rtc_read_time(rtc, &tm);
+	if (err < 0) {
+		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
+		return 0;
+	}
+
 	getnstimeofday(&old_system);
 	rtc_tm_to_time(&tm, &old_rtc.tv_sec);
 
@@ -94,6 +100,7 @@ static int rtc_resume(struct device *dev)
 	struct rtc_time		tm;
 	struct timespec		new_system, new_rtc;
 	struct timespec		sleep_time;
+	int err;
 
 	if (has_persistent_clock())
 		return 0;
@@ -104,7 +111,12 @@ static int rtc_resume(struct device *dev)
 
 	/* snapshot the current rtc and system time at resume */
 	getnstimeofday(&new_system);
-	rtc_read_time(rtc, &tm);
+	err = rtc_read_time(rtc, &tm);
+	if (err < 0) {
+		pr_debug("%s:  fail to read rtc time\n", dev_name(&rtc->dev));
+		return 0;
+	}
+
 	if (rtc_valid_tm(&tm) != 0) {
 		pr_debug("%s:  bogus resume time\n", dev_name(&rtc->dev));
 		return 0;