ep93xx timer: Fix possible overflow in usecs_to_ticks()

ep93xx timer: Use 64-bit values in usecs_to_ticks() in order to avoid
overflows in intermediate values

Signed-off-by: Matthias Kaehlcke <matthias@kaehlcke.net>

diff --git a/cpu/arm920t/ep93xx/timer.c b/cpu/arm920t/ep93xx/timer.c
index b1a01a0..bc4ec8f 100644 (file)
--- a/cpu/arm920t/ep93xx/timer.c
+++ b/cpu/arm920t/ep93xx/timer.c
@@ -36,7 +36,7 @@
 #define TIMER_CLKSEL   (1 << 3)
 #define TIMER_ENABLE   (1 << 7)
 
-#define TIMER_FREQ                     508469
+#define TIMER_FREQ                     508469          /* ticks / second */
 #define TIMER_MAX_VAL                  0xFFFFFFFF
 
 static struct ep93xx_timer
@@ -53,18 +53,10 @@ static inline unsigned long clk_to_systicks(unsigned long long clk_ticks)
        return (unsigned long)sys_ticks;
 }
 
-static inline unsigned long usecs_to_ticks(unsigned long usecs)
+static inline unsigned long long usecs_to_ticks(unsigned long usecs)
 {
-       unsigned long ticks;
-
-       if (usecs >= 1000) {
-               ticks = usecs / 1000;
-               ticks *= TIMER_FREQ;
-               ticks /= 1000;
-       } else {
-               ticks = usecs * TIMER_FREQ;
-               ticks /= (1000 * 1000);
-       }
+       unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ;
+       do_div(ticks, 1000 * 1000);
 
        return ticks;
 }