Fix timer overflow in DaVinci

Signed-off-by: Dirk Behme <dirk.behme@gmail.com>

cpu/arm926ejs/davinci/timer.c

@@ -61,6 +61,11 @@ davinci_timer		*timer = (davinci_timer *)CFG_TIMERBASE;
 #define TIMER_LOAD_VAL	(CFG_HZ_CLOCK / CFG_HZ)
 #define READ_TIMER	timer->tim34
 
+/* Timer runs with CFG_HZ_CLOCK, currently 27MHz. To avoid wrap 
+   around of timestamp already after min ~159s, divide it, e.g. by 16.
+   timestamp will then wrap around all min ~42min */
+#define DIV(x)          ((x) >> 4)
+
 static ulong timestamp;
 static ulong lastinc;
 
@@ -101,20 +106,20 @@ void udelay(unsigned long usec)
 
 void reset_timer_masked(void)
 {
-	lastinc = READ_TIMER;
+        lastinc = DIV(READ_TIMER);
 	timestamp = 0;
 }
 
 ulong get_timer_raw(void)
 {
-	ulong now = READ_TIMER;
+        ulong now = DIV(READ_TIMER);
 
 	if (now >= lastinc) {
 		/* normal mode */
 		timestamp += now - lastinc;
 	} else {
 		/* overflow ... */
-		timestamp += now + TIMER_LOAD_VAL - lastinc;
+	        timestamp += now + DIV(TIMER_LOAD_VAL) - lastinc;
 	}
 	lastinc = now;
 	return timestamp;
@@ -122,7 +127,7 @@ ulong get_timer_raw(void)
 
 ulong get_timer_masked(void)
 {
-	return(get_timer_raw() / TIMER_LOAD_VAL);
+        return(get_timer_raw() / DIV(TIMER_LOAD_VAL));
 }
 
 void udelay_masked(unsigned long usec)