renew the timer if it underflows

libprof.c

@@ -10,6 +10,11 @@ uint32_t volatile *prof_tcnt = NULL;
 /* Timer ID */
 static int prof_timer = -1;
 
+static int callback(void)
+{
+	return TIMER_CONTINUE;
+}
+
 /* prof_init(): Initialize the profiler's timer */
 int prof_init(void)
 {
@@ -17,7 +22,7 @@ int prof_init(void)
 	int timer = -1;
 	for(int t = 2; t >= 0 && timer == -1; t--)
 	{
-		timer = timer_setup(t | TIMER_Pphi_4, 0xffffffff, NULL);
+		timer = timer_setup(t | TIMER_Pphi_4, 0xffffffff, callback);
 	}
 	if(timer == -1)
 	{