[PATCH] RTC: Remove RTC UIP synchronization on PPC Maple

Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/powerpc/platforms/maple/time.c

@@ -60,34 +60,14 @@ static void maple_clock_write(unsigned long val, int addr)
 
 void maple_get_rtc_time(struct rtc_time *tm)
 {
-	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.
-	 */
-
-	/* 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 = maple_clock_read(RTC_FREQ_SELECT);
+	do {
 		tm->tm_sec = maple_clock_read(RTC_SECONDS);
 		tm->tm_min = maple_clock_read(RTC_MINUTES);
 		tm->tm_hour = maple_clock_read(RTC_HOURS);
 		tm->tm_mday = maple_clock_read(RTC_DAY_OF_MONTH);
 		tm->tm_mon = maple_clock_read(RTC_MONTH);
 		tm->tm_year = maple_clock_read(RTC_YEAR);
-		uip |= maple_clock_read(RTC_FREQ_SELECT);
-		if ((uip & RTC_UIP)==0)
-			break;
-	}
+	} while (tm->tm_sec != maple_clock_read(RTC_SECONDS));
 
 	if (!(maple_clock_read(RTC_CONTROL) & RTC_DM_BINARY)
 	    || RTC_ALWAYS_BCD) {