rtc: use rtc_valid_tm() error code when reading date/time

There's a wrong comment in some RTC drivers that say it's better to ignore
rtc_valid_tm() when reading RTC timestamp. However this is wrong and is
better to return to the userspace the error if timestamp is not valid.
Signed-off-by: Andrea Scian <andrea.scian@dave.eu>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-isl12022.c

@@ -151,12 +151,7 @@ static int isl12022_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 		tm->tm_sec, tm->tm_min, tm->tm_hour,
 		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
 
-	/* The clock can give out invalid datetime, but we cannot return
-	 * -EINVAL otherwise hwclock will refuse to set the time on bootup. */
-	if (rtc_valid_tm(tm) < 0)
-		dev_err(&client->dev, "retrieved date and time is invalid.\n");
-
-	return 0;
+	return rtc_valid_tm(tm);
 }
 
 static int isl12022_set_datetime(struct i2c_client *client, struct rtc_time *tm)

drivers/rtc/rtc-pcf2123.c

@@ -165,13 +165,7 @@ static int pcf2123_rtc_read_time(struct device *dev, struct rtc_time *tm)
 			tm->tm_sec, tm->tm_min, tm->tm_hour,
 			tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
 
-	/* the clock can give out invalid datetime, but we cannot return
-	 * -EINVAL otherwise hwclock will refuse to set the time on bootup.
-	 */
-	if (rtc_valid_tm(tm) < 0)
-		dev_err(dev, "retrieved date/time is not valid.\n");
-
-	return 0;
+	return rtc_valid_tm(tm);
 }
 
 static int pcf2123_rtc_set_time(struct device *dev, struct rtc_time *tm)

drivers/rtc/rtc-pcf2127.c

@@ -88,13 +88,7 @@ static int pcf2127_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 		tm->tm_sec, tm->tm_min, tm->tm_hour,
 		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
 
-	/* the clock can give out invalid datetime, but we cannot return
-	 * -EINVAL otherwise hwclock will refuse to set the time on bootup.
-	 */
-	if (rtc_valid_tm(tm) < 0)
-		dev_err(&client->dev, "retrieved date/time is not valid.\n");
-
-	return 0;
+	return rtc_valid_tm(tm);
 }
 
 static int pcf2127_set_datetime(struct i2c_client *client, struct rtc_time *tm)