timekeeping: Increase granularity of read_persistent_clock(), build fix

Fix the following build problem on powerpc:

  arch/powerpc/kernel/time.c: In function 'read_persistent_clock':
  arch/powerpc/kernel/time.c:788: error: 'return' with a value, in function returning void
  arch/powerpc/kernel/time.c:791: error: 'return' with a value, in function returning void

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: dwalker@fifo99.com
Cc: johnstul@us.ibm.com
LKML-Reference: <20090822222313.74b9619c@skybase>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/powerpc/kernel/time.c

@@ -774,6 +774,7 @@ void read_persistent_clock(struct timespec *ts)
 	struct rtc_time tm;
 	static int first = 1;
 
+	ts->tv_nsec = 0;
 	/* XXX this is a litle fragile but will work okay in the short term */
 	if (first) {
 		first = 0;
@@ -781,15 +782,18 @@ void read_persistent_clock(struct timespec *ts)
 			timezone_offset = ppc_md.time_init();
 
 		/* get_boot_time() isn't guaranteed to be safe to call late */
-		if (ppc_md.get_boot_time)
-			return ppc_md.get_boot_time() -timezone_offset;
+		if (ppc_md.get_boot_time) {
+			ts->tv_sec = ppc_md.get_boot_time() - timezone_offset;
+			return;
+		}
+	}
+	if (!ppc_md.get_rtc_time) {
+		ts->tv_sec = 0;
+		return;
 	}
-	if (!ppc_md.get_rtc_time)
-		return 0;
 	ppc_md.get_rtc_time(&tm);
 	ts->tv_sec = mktime(tm.tm_year+1900, tm.tm_mon+1, tm.tm_mday,
 			    tm.tm_hour, tm.tm_min, tm.tm_sec);
-	ts->tv_nsec = 0;
 }
 
 /* clocksource code */