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

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

[Chen, Huacai]

From: Huacai Chen <huacai.chen@intel.com>

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@intel.com>
Acked-by: Pavel Machek <pavel@suse.cz>
---
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.

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

[Zhao Yakui]

On Mon, 2008-06-23 at 18:52 +0800, Chen, Huacai wrote:
> From: Huacai Chen <huacai.chen@intel.com>
> 
> 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@intel.com>
> Acked-by: Pavel Machek <pavel@suse.cz>
> ---
> 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);
> +	}
this is OK. 
>  	/* 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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Re: [PATCH] RTC: Fix CMOS time error after writing /proc/acpi/alarm

[Alessandro Zummo]

On Mon, 23 Jun 2008 18:52:21 +0800
"Chen, Huacai" <huacai.chen@intel.com> wrote:

> From: Huacai Chen <huacai.chen@intel.com>
> 
> 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@intel.com>
> Acked-by: Pavel Machek <pavel@suse.cz>

 Acked-by: Alessandro Zummo <a.zummo@towertech.it>

-- 

 Best regards,

 Alessandro Zummo,
  Tower Technologies - Torino, Italy

  http://www.towertech.it