linux 2.6.16.38 w/ vs2.0.3-rc1

[linux-2.6.git] / include / asm-mips / mc146818-time.h

diff --git a/include/asm-mips/mc146818-time.h b/include/asm-mips/mc146818-time.h
index 41ac8d3..4721486 100644 (file)
--- a/include/asm-mips/mc146818-time.h
+++ b/include/asm-mips/mc146818-time.h
@@ -86,14 +86,43 @@ static inline int mc146818_set_rtc_mmss(unsigned long nowtime)
        return retval;
 }
 
+/*
+ * Returns true if a clock update is in progress
+ */
+static inline unsigned char rtc_is_updating(void)
+{
+       unsigned char uip;
+       unsigned long flags;
+
+       spin_lock_irqsave(&rtc_lock, flags);
+       uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
+       spin_unlock_irqrestore(&rtc_lock, flags);
+       return uip;
+}
+
 static inline unsigned long mc146818_get_cmos_time(void)
 {
        unsigned int year, mon, day, hour, min, sec;
+       int i;
        unsigned long flags;
 
-       spin_lock_irqsave(&rtc_lock, flags);
+       /*
+        * 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.
+        * Let's hope other operating systems interpret the RTC the same way.
+        */
+
+       /* read RTC exactly on falling edge of update flag */
+       for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
+               if (rtc_is_updating())
+                       break;
+       for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
+               if (!rtc_is_updating())
+                       break;
 
-       do {
+       spin_lock_irqsave(&rtc_lock, flags);
+       do { /* Isn't this overkill ? UIP above should guarantee consistency */
                sec = CMOS_READ(RTC_SECONDS);
                min = CMOS_READ(RTC_MINUTES);
                hour = CMOS_READ(RTC_HOURS);