[PATCH] x86_64: Handle years beyond 2100

ACPIv2 has an official but optional way to get a date >2100.  Use it.
But all the platforms I tested didn't seem to support it.  But anyways
the x86-64 kernel should be ready for the 22nd century now.  Actually i
shouldn't care about this because I will be dead by then @)

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 17 insertions, 5 deletions

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 86039baaaf18..2f7c21206574 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -517,6 +517,7 @@ static unsigned long get_cmos_time(void)
         unsigned int timeout = 1000000, year, mon, day, hour, min, sec;
         unsigned char uip = 0, this = 0;
         unsigned long flags;
+        unsigned extyear = 0;
 
 /*
  * The Linux interpretation of the CMOS clock register contents: When the
@@ -545,6 +546,11 @@ static unsigned long get_cmos_time(void)
         mon = CMOS_READ(RTC_MONTH);
         year = CMOS_READ(RTC_YEAR);
 
+#ifdef CONFIG_ACPI
+        if (acpi_fadt.revision >= FADT2_REVISION_ID && acpi_fadt.century)
+                extyear = CMOS_READ(acpi_fadt.century);
+#endif
+
         spin_unlock_irqrestore(&rtc_lock, flags);
 
         /*
@@ -559,11 +565,17 @@ static unsigned long get_cmos_time(void)
         BCD_TO_BIN(mon);
         BCD_TO_BIN(year);
 
-        /*
-         * x86-64 systems only exists since 2002.
-         * This will work up to Dec 31, 2100
-         */
-        year += 2000;
+        if (extyear) {
+                BCD_TO_BIN(extyear);
+                year += extyear;
+                printk(KERN_INFO "Extended CMOS year: %d\n", extyear);
+        } else { 
+                /*
+                 * x86-64 systems only exists since 2002.
+                 * This will work up to Dec 31, 2100
+                 */
+                year += 2000;
+        }
 
         return mktime(year, mon, day, hour, min, sec);
 }