diff --git a/drivers/watchdog/booke_wdt.c b/drivers/watchdog/booke_wdt.c
index 225398fd5049..e8380ef65c1c 100644
--- a/drivers/watchdog/booke_wdt.c
+++ b/drivers/watchdog/booke_wdt.c
@@ -22,6 +22,8 @@
 
 #include <asm/reg_booke.h>
 #include <asm/system.h>
+#include <asm/time.h>
+#include <asm/div64.h>
 
 /* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
  * Also, the wdt_period sets the watchdog timer period timeout.
@@ -32,7 +34,7 @@
  */
 
 #ifdef	CONFIG_FSL_BOOKE
-#define WDT_PERIOD_DEFAULT 63	/* Ex. wdt_period=28 bus=333Mhz,reset=~40sec */
+#define WDT_PERIOD_DEFAULT 38	/* Ex. wdt_period=28 bus=333Mhz,reset=~40sec */
 #else
 #define WDT_PERIOD_DEFAULT 3	/* Refer to the PPC40x and PPC4xx manuals */
 #endif				/* for timing information */
@@ -41,7 +43,7 @@ u32 booke_wdt_enabled;
 u32 booke_wdt_period = WDT_PERIOD_DEFAULT;
 
 #ifdef	CONFIG_FSL_BOOKE
-#define WDTP(x)		((((63-x)&0x3)<<30)|(((63-x)&0x3c)<<15))
+#define WDTP(x)		((((x)&0x3)<<30)|(((x)&0x3c)<<15))
 #define WDTP_MASK	(WDTP(0))
 #else
 #define WDTP(x)		(TCR_WP(x))
@@ -50,6 +52,45 @@ u32 booke_wdt_period = WDT_PERIOD_DEFAULT;
 
 static DEFINE_SPINLOCK(booke_wdt_lock);
 
+/* For the specified period, determine the number of seconds
+ * corresponding to the reset time.  There will be a watchdog
+ * exception at approximately 3/5 of this time.
+ *
+ * The formula to calculate this is given by:
+ * 2.5 * (2^(63-period+1)) / timebase_freq
+ *
+ * In order to simplify things, we assume that period is
+ * at least 1.  This will still result in a very long timeout.
+ */
+static unsigned long long period_to_sec(unsigned int period)
+{
+	unsigned long long tmp = 1ULL << (64 - period);
+	unsigned long tmp2 = ppc_tb_freq;
+
+	/* tmp may be a very large number and we don't want to overflow,
+	 * so divide the timebase freq instead of multiplying tmp
+	 */
+	tmp2 = tmp2 / 5 * 2;
+
+	do_div(tmp, tmp2);
+	return tmp;
+}
+
+/*
+ * This procedure will find the highest period which will give a timeout
+ * greater than the one required. e.g. for a bus speed of 66666666 and
+ * and a parameter of 2 secs, then this procedure will return a value of 38.
+ */
+static unsigned int sec_to_period(unsigned int secs)
+{
+	unsigned int period;
+	for (period = 63; period > 0; period--) {
+		if (period_to_sec(period) >= secs)
+			return period;
+	}
+	return 0;
+}
+
 static void __booke_wdt_ping(void *data)
 {
 	mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
@@ -93,7 +134,7 @@ static long booke_wdt_ioctl(struct file *file,
 
 	switch (cmd) {
 	case WDIOC_GETSUPPORT:
-		if (copy_to_user(arg, &ident, sizeof(struct watchdog_info)))
+		if (copy_to_user((void *)arg, &ident, sizeof(ident)))
 			return -EFAULT;
 	case WDIOC_GETSTATUS:
 		return put_user(ident.options, p);
@@ -115,8 +156,16 @@ static long booke_wdt_ioctl(struct file *file,
 		booke_wdt_ping();
 		return 0;
 	case WDIOC_SETTIMEOUT:
-		if (get_user(booke_wdt_period, p))
+		if (get_user(tmp, p))
 			return -EFAULT;
+#ifdef	CONFIG_FSL_BOOKE
+		/* period of 1 gives the largest possible timeout */
+		if (tmp > period_to_sec(1))
+			return -EINVAL;
+		booke_wdt_period = sec_to_period(tmp);
+#else
+		booke_wdt_period = tmp;
+#endif
 		mtspr(SPRN_TCR, (mfspr(SPRN_TCR) & ~WDTP_MASK) |
 						WDTP(booke_wdt_period));
 		return 0;