rtc: sh: Fix invalid alarm warning for non-enabled alarm

When no alarm has been programmed on RSK-RZA1, an error message is
printed during boot:

    rtc rtc0: invalid alarm value: 2019-03-14T255:255:255

sh_rtc_read_alarm_value() returns 0xff when querying a hardware alarm
field that is not enabled.  __rtc_read_alarm() validates the received
alarm values, and fills in missing fields when needed.
While 0xff is handled fine for the year, month, and day fields, and
corrected as considered being out-of-range, this is not the case for the
hour, minute, and second fields, where -1 is expected for missing
fields.

Fix this by returning -1 instead, as this value is handled fine for all
fields.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/rtc/rtc-sh.c b/drivers/rtc/rtc-sh.c
index d417b203cbc5..1d3de2a3d1a4 100644
--- a/drivers/rtc/rtc-sh.c
+++ b/drivers/rtc/rtc-sh.c
@@ -374,7 +374,7 @@ static int sh_rtc_set_time(struct device *dev, struct rtc_time *tm)
 static inline int sh_rtc_read_alarm_value(struct sh_rtc *rtc, int reg_off)
 {
         unsigned int byte;
-        int value = 0xff;       /* return 0xff for ignored values */
+        int value = -1;                 /* return -1 for ignored values */
 
         byte = readb(rtc->regbase + reg_off);
         if (byte & AR_ENB) {