x86: Do full rtc synchronization with ntp

Every 11 minutes ntp attempts to update the x86 rtc with the current
system time.  Currently, the x86 code only updates the rtc if the system
time is within +/-15 minutes of the current value of the rtc. This
was done originally to avoid setting the RTC if the RTC was in localtime
mode (common with Windows dualbooting).  Other architectures do a full
synchronization and now that we have better infrastructure to detect
when the RTC is in localtime, there is no reason that x86 should be
software limited to a 30 minute window.

This patch changes the behavior of the kernel to do a full synchronization
(year, month, day, hour, minute, and second) of the rtc when ntp requests
a synchronization between the system time and the rtc.

I've used the RTC library functions in this patchset as they do all the
required bounds checking.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: x86@kernel.org
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: linux-efi@vger.kernel.org
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
[jstultz: Tweak commit message, fold in build fix found by fengguang
Also add select RTC_LIB to X86, per new dependency, as found by prarit]
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 26 insertions, 18 deletions

diff --git a/arch/x86/platform/mrst/vrtc.c b/arch/x86/platform/mrst/vrtc.c
index 225bd0f..d62b0a3 100644
--- a/arch/x86/platform/mrst/vrtc.c
+++ b/arch/x86/platform/mrst/vrtc.c
@@ -85,27 +85,35 @@ unsigned long vrtc_get_time(void)
 	return mktime(year, mon, mday, hour, min, sec);
 }
 
-/* Only care about the minutes and seconds */
 int vrtc_set_mmss(unsigned long nowtime)
 {
-	int real_sec, real_min;
 	unsigned long flags;
-	int vrtc_min;
-
-	spin_lock_irqsave(&rtc_lock, flags);
-	vrtc_min = vrtc_cmos_read(RTC_MINUTES);
-
-	real_sec = nowtime % 60;
-	real_min = nowtime / 60;
-	if (((abs(real_min - vrtc_min) + 15)/30) & 1)
-		real_min += 30;
-	real_min %= 60;
-
-	vrtc_cmos_write(real_sec, RTC_SECONDS);
-	vrtc_cmos_write(real_min, RTC_MINUTES);
-	spin_unlock_irqrestore(&rtc_lock, flags);
-
-	return 0;
+	struct rtc_time tm;
+	int year;
+	int retval = 0;
+
+	rtc_time_to_tm(nowtime, &tm);
+	if (!rtc_valid_tm(&tm) && tm.tm_year >= 72) {
+		/*
+		 * tm.year is the number of years since 1900, and the
+		 * vrtc need the years since 1972.
+		 */
+		year = tm.tm_year - 72;
+		spin_lock_irqsave(&rtc_lock, flags);
+		vrtc_cmos_write(year, RTC_YEAR);
+		vrtc_cmos_write(tm.tm_mon, RTC_MONTH);
+		vrtc_cmos_write(tm.tm_mday, RTC_DAY_OF_MONTH);
+		vrtc_cmos_write(tm.tm_hour, RTC_HOURS);
+		vrtc_cmos_write(tm.tm_min, RTC_MINUTES);
+		vrtc_cmos_write(tm.tm_sec, RTC_SECONDS);
+		spin_unlock_irqrestore(&rtc_lock, flags);
+	} else {
+		printk(KERN_ERR
+		       "%s: Invalid vRTC value: write of %lx to vRTC failed\n",
+			__FUNCTION__, nowtime);
+		retval = -EINVAL;
+	}
+	return retval;
 }
 
 void __init mrst_rtc_init(void)