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

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Date:	Tue, 24 Jun 2008 14:37:53 +0800
From:	Zhao Yakui <yakui.zhao@...el.com>
To:	"Chen, Huacai" <huacai.chen@...el.com>
Cc:	linux-acpi@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	rtc-linux@...glegroups.com, lenb@...nel.org, p_gortmaker@...oo.com,
	a.zummo@...ertech.it, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RTC: Fix CMOS time error after writing /proc/acpi/alarm

On Mon, 2008-06-23 at 18:52 +0800, Chen, Huacai wrote:
> From: Huacai Chen <huacai.chen@...el.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@...el.com>
> Acked-by: Pavel Machek <pavel@...e.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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