rtc: cmos: ignore bogus century byte
[ Upstream commit 2a4daadd4d3e507138f8937926e6a4df49c6bfdc ]
Older versions of Libreboot and Coreboot had an invalid value
(`3' in my case) in the century byte affecting the GM45 in
the Thinkpad X200. Not everybody's updated their firmwares,
and Linux <= 4.2 was able to read the RTC without problems,
so workaround this by ignoring invalid values.
Fixes: 3c217e51d8a272b9 ("rtc: cmos: century support")
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Sylvain Chouleur <sylvain.chouleur@intel.com>
Cc: Patrick McDermott <patrick.mcdermott@libiquity.com>
Cc: linux-rtc@vger.kernel.org
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index 2f1772a..18a6f15 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -82,7 +82,7 @@
time->tm_year += real_year - 72;
#endif
- if (century)
+ if (century > 20)
time->tm_year += (century - 19) * 100;
/*