vrtc: change its year offset from 1960 to 1972

Real world year equals the value in vrtc YEAR register plus an offset.  We
used 1960 for original developepment as the offset to make leap year
consistent, but for a device's first use, its YEAR register is 0 and the
system year will be parsed as 1960 which is not a valid UNIX time and will
cause many applications to fail mysteriously.  Devices use 1972 instead to
fix this issue.

Updated patch which adds a sanity check suggested by Mathias

Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/x86/platform/mrst/vrtc.c b/arch/x86/platform/mrst/vrtc.c
index a8ac6f1eb66d56c0b3aac1e65591a4b2f707b3ed..225bd0f0f675395643c47859e61e0e5b6354ecb1 100644 (file)
--- a/arch/x86/platform/mrst/vrtc.c
+++ b/arch/x86/platform/mrst/vrtc.c
@@ -76,8 +76,8 @@ unsigned long vrtc_get_time(void)
 
        spin_unlock_irqrestore(&rtc_lock, flags);
 
-       /* vRTC YEAR reg contains the offset to 1960 */
-       year += 1960;
+       /* vRTC YEAR reg contains the offset to 1972 */
+       year += 1972;
 
        printk(KERN_INFO "vRTC: sec: %d min: %d hour: %d day: %d "
                "mon: %d year: %d\n", sec, min, hour, mday, mon, year);

diff --git a/drivers/rtc/rtc-mrst.c b/drivers/rtc/rtc-mrst.c
index d33544802a2ea5fc023390a069bcbc1f9d147a41..bb21f443fb7038719458d03c97e4b4eb00a225a1 100644 (file)
--- a/drivers/rtc/rtc-mrst.c
+++ b/drivers/rtc/rtc-mrst.c
@@ -76,12 +76,15 @@ static inline unsigned char vrtc_is_updating(void)
 /*
  * rtc_time's year contains the increment over 1900, but vRTC's YEAR
  * register can't be programmed to value larger than 0x64, so vRTC
- * driver chose to use 1960 (1970 is UNIX time start point) as the base,
+ * driver chose to use 1972 (1970 is UNIX time start point) as the base,
  * and does the translation at read/write time.
  *
- * Why not just use 1970 as the offset? it's because using 1960 will
+ * Why not just use 1970 as the offset? it's because using 1972 will
  * make it consistent in leap year setting for both vrtc and low-level
- * physical rtc devices.
+ * physical rtc devices. Then why not use 1960 as the offset? If we use
+ * 1960, for a device's first use, its YEAR register is 0 and the system
+ * year will be parsed as 1960 which is not a valid UNIX time and will
+ * cause many applications to fail mysteriously.
  */
 static int mrst_read_time(struct device *dev, struct rtc_time *time)
 {
@@ -99,10 +102,10 @@ static int mrst_read_time(struct device *dev, struct rtc_time *time)
        time->tm_year = vrtc_cmos_read(RTC_YEAR);
        spin_unlock_irqrestore(&rtc_lock, flags);
 
-       /* Adjust for the 1960/1900 */
-       time->tm_year += 60;
+       /* Adjust for the 1972/1900 */
+       time->tm_year += 72;
        time->tm_mon--;
-       return RTC_24H;
+       return rtc_valid_tm(time);
 }
 
 static int mrst_set_time(struct device *dev, struct rtc_time *time)
@@ -119,9 +122,9 @@ static int mrst_set_time(struct device *dev, struct rtc_time *time)
        min = time->tm_min;
        sec = time->tm_sec;
 
-       if (yrs < 70 || yrs > 138)
+       if (yrs < 72 || yrs > 138)
                return -EINVAL;
-       yrs -= 60;
+       yrs -= 72;
 
        spin_lock_irqsave(&rtc_lock, flags);