From: Riwen Lu <luriwen@kylinos.cn>
Date: Thu, 6 Jan 2022 08:46:09 +0000 (+0800)
Subject: rtc: cmos: Evaluate century appropriate
X-Git-Tag: v5.17-rc1~24^2~1
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=ff164ae39b82ee483b24579c8e22a13a8ce5bd04;p=linux-block.git

rtc: cmos: Evaluate century appropriate

There's limiting the year to 2069. When setting the rtc year to 2070,
reading it returns 1970. Evaluate century starting from 19 to count the
correct year.

$ sudo date -s 20700106
Mon 06 Jan 2070 12:00:00 AM CST
$ sudo hwclock -w
$ sudo hwclock -r
1970-01-06 12:00:49.604968+08:00

Fixes: 2a4daadd4d3e5071 ("rtc: cmos: ignore bogus century byte")

Signed-off-by: Riwen Lu <luriwen@kylinos.cn>
Acked-by: Eric Wong <e@80x24.org>
Reviewed-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220106084609.1223688-1-luriwen@kylinos.cn
---

diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index 7f689f1bafc5..ae9f131b43c0 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -159,7 +159,7 @@ int mc146818_get_time(struct rtc_time *time)
 #endif
 
 #ifdef CONFIG_ACPI
-	if (p.century > 20)
+	if (p.century > 19)
 		time->tm_year += (p.century - 19) * 100;
 #endif