Commit cce3ce89 authored by Huacai Chen's avatar Huacai Chen Committed by Linus Torvalds

rtc: fix CMOS time error after writing /proc/acpi/alarm

When writing /proc/acpi/alarm in adjust mode, e.g.
	echo "+0000-00-00 00:00:15" >/proc/acpi/alarm
The "century" field should be read and added to "year" field before
writing, otherwise the CMOS time will go back to 2000 years ago, e.g.
	# cat /proc/acpi/alarm
	0008-06-21 11:38:46
Then the system time may be reset to the date of manufacture after
rebooting. This patch fixed this issue.
Signed-off-by: default avatarHuacai Chen <>
Acked-by: default avatarPavel Machek <>
Acked-by: default avatarZhao Yakui <>
Acked-by: default avatarAlessandro Zummo <>
Acked-by: default avatarLen Brown <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 471d47e3
......@@ -315,8 +315,11 @@ acpi_system_write_alarm(struct file *file,
cmos_bcd_write(day, acpi_gbl_FADT.day_alarm, rtc_control);
if (acpi_gbl_FADT.month_alarm)
cmos_bcd_write(mo, acpi_gbl_FADT.month_alarm, rtc_control);
if (acpi_gbl_FADT.century)
if (acpi_gbl_FADT.century) {
if (adjust)
yr += cmos_bcd_read(acpi_gbl_FADT.century, rtc_control) * 100;
cmos_bcd_write(yr / 100, acpi_gbl_FADT.century, rtc_control);
/* enable the rtc alarm interrupt */
rtc_control |= RTC_AIE;
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