/*
+ * arch/ppc/platforms/chrp_time.c
+ *
* Copyright (C) 1991, 1992, 1995 Linus Torvalds
*
* Adapted for PowerPC (PReP) by Gary Thomas
void chrp_get_rtc_time(struct rtc_time *tm)
{
unsigned int year, mon, day, hour, min, sec;
+ int uip, i;
+
+ /* 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.
+ */
- do {
+ /* Since the UIP flag is set for about 2.2 ms and the clock
+ * is typically written with a precision of 1 jiffy, trying
+ * to obtain a precision better than a few milliseconds is
+ * an illusion. Only consistency is interesting, this also
+ * allows to use the routine for /dev/rtc without a potential
+ * 1 second kernel busy loop triggered by any reader of /dev/rtc.
+ */
+
+ for ( i = 0; i<1000000; i++) {
+ uip = chrp_cmos_clock_read(RTC_FREQ_SELECT);
sec = chrp_cmos_clock_read(RTC_SECONDS);
min = chrp_cmos_clock_read(RTC_MINUTES);
hour = chrp_cmos_clock_read(RTC_HOURS);
day = chrp_cmos_clock_read(RTC_DAY_OF_MONTH);
mon = chrp_cmos_clock_read(RTC_MONTH);
year = chrp_cmos_clock_read(RTC_YEAR);
- } while (sec != chrp_cmos_clock_read(RTC_SECONDS));
+ uip |= chrp_cmos_clock_read(RTC_FREQ_SELECT);
+ if ((uip & RTC_UIP)==0) break;
+ }
if (!(chrp_cmos_clock_read(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
BCD_TO_BIN(sec);