[PATCH] RTC: Fix CMOS time error after writing /proc/acpi/alarm

[Chen, Huacai]

From: Huacai Chen <huacai.chen@xxxxxxxxx>

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: Huacai Chen <huacai.chen@xxxxxxxxx>
Acked-by: Pavel Machek <pavel@xxxxxxx>
---
diff --git a/drivers/acpi/sleep/proc.c b/drivers/acpi/sleep/proc.c
index 224c57c..c9fdf7b 100644
--- a/drivers/acpi/sleep/proc.c
+++ b/drivers/acpi/sleep/proc.c
@@ -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;
 	CMOS_WRITE(rtc_control, RTC_CONTROL);
---
This is for Linux 2.6.26-rc7.
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