Fix timer code for ARM systems: make sure that udelay() does not
reset timers so it's save to use udelay() in timeout code.

cpu/sa1100/interrupts.c

diff --git a/cpu/sa1100/interrupts.c b/cpu/sa1100/interrupts.c
index 93a78d7..b393e0d 100644
--- a/cpu/sa1100/interrupts.c
+++ b/cpu/sa1100/interrupts.c
@@ -206,15 +206,24 @@
 void udelay_masked (unsigned long usec)
 {
 	ulong tmo;
+	ulong endtime;
+	signed long diff;
 
-	tmo = usec / 1000;
-	tmo *= CFG_HZ;
-	tmo /= 1000;
+	if (usec >= 1000) {
+		tmo = usec / 1000;
+		tmo *= CFG_HZ;
+		tmo /= 1000;
+	} else {
+		tmo = usec * CFG_HZ;
+		tmo /= (1000*1000);
+	}
 
-	reset_timer_masked ();
+	endtime = get_timer_masked () + tmo;
 
-	while (tmo >= get_timer_masked ())
-		/*NOP*/;
+	do {
+		ulong now = get_timer_masked ();
+		diff = endtime - now;
+	} while (diff >= 0);
 }
 
 /*