[PATCH] RTC: Remove RTC UIP synchronization on x86_64

Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Andi Kleen <ak@muc.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 29 deletions

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 7f58fa682491..473b514b66e4 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -504,42 +504,25 @@ unsigned long long sched_clock(void)
 
 static unsigned long get_cmos_time(void)
 {
-        unsigned int timeout = 1000000, year, mon, day, hour, min, sec;
-        unsigned char uip = 0, this = 0;
+        unsigned int year, mon, day, hour, min, sec;
         unsigned long flags;
         unsigned extyear = 0;
 
-/*
- * The Linux interpretation of the CMOS clock register contents: When the
- * Update-In-Progress (UIP) flag goes from 1 to 0, the RTC registers show the
- * second which has precisely just started. Waiting for this can take up to 1
- * second, we timeout approximately after 2.4 seconds on a machine with
- * standard 8.3 MHz ISA bus.
- */
-
         spin_lock_irqsave(&rtc_lock, flags);
 
-        while (timeout && (!uip || this)) {
-                uip |= this;
-                this = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
-                timeout--;
-        }
-
-        /*
-         * Here we are safe to assume the registers won't change for a whole
-         * second, so we just go ahead and read them.
-         */
-        sec = CMOS_READ(RTC_SECONDS);
-        min = CMOS_READ(RTC_MINUTES);
-        hour = CMOS_READ(RTC_HOURS);
-        day = CMOS_READ(RTC_DAY_OF_MONTH);
-        mon = CMOS_READ(RTC_MONTH);
-        year = CMOS_READ(RTC_YEAR);
-
+        do {
+                sec = CMOS_READ(RTC_SECONDS);
+                min = CMOS_READ(RTC_MINUTES);
+                hour = CMOS_READ(RTC_HOURS);
+                day = CMOS_READ(RTC_DAY_OF_MONTH);
+                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);
+                if (acpi_fadt.revision >= FADT2_REVISION_ID &&
+                                        acpi_fadt.century)
+                        extyear = CMOS_READ(acpi_fadt.century);
 #endif
+        } while (sec != CMOS_READ(RTC_SECONDS));
 
         spin_unlock_irqrestore(&rtc_lock, flags);