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);