diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index ce44fe27f48fd3f17188fd2bdd5907dca2448d46..320136f5fe28a9ffea527bf1b337415b7bfe5317 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -337,6 +337,7 @@
 #define   LPCR_AIL_0	0x00000000	/* MMU off exception offset 0x0 */
 #define   LPCR_AIL_3	0x01800000	/* MMU on exception offset 0xc00...4xxx */
 #define   LPCR_ONL	0x00040000	/* online - PURR/SPURR count */
+#define   LPCR_LD	0x00020000	/* large decremeter */
 #define   LPCR_PECE	0x0001f000	/* powersave exit cause enable */
 #define     LPCR_PECEDP	0x00010000	/* directed priv dbells cause exit */
 #define     LPCR_PECEDH	0x00008000	/* directed hyp dbells cause exit */
diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index 1092fdd7e73728f88c38193800f19b5ae06a1679..09211640a0e0ab7009e29a1063745f2f93e29875 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h
@@ -146,7 +146,7 @@ static inline void set_tb(unsigned int upper, unsigned int lower)
  * in auto-reload mode.  The problem is PIT stops counting when it
  * hits zero.  If it would wrap, we could use it just like a decrementer.
  */
-static inline unsigned int get_dec(void)
+static inline u64 get_dec(void)
 {
 #if defined(CONFIG_40x)
 	return (mfspr(SPRN_PIT));
@@ -160,10 +160,10 @@ static inline unsigned int get_dec(void)
  * in when the decrementer generates its interrupt: on the 1 to 0
  * transition for Book E/4xx, but on the 0 to -1 transition for others.
  */
-static inline void set_dec(int val)
+static inline void set_dec(u64 val)
 {
 #if defined(CONFIG_40x)
-	mtspr(SPRN_PIT, val);
+	mtspr(SPRN_PIT, (u32) val);
 #else
 #ifndef CONFIG_BOOKE
 	--val;
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 3ed9a5a21d77997fa96f3cb39dde621701c30f52..6b4d01d1ccf03b630351eb46edb35e7b0ad1c50a 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -96,7 +96,8 @@ static struct clocksource clocksource_timebase = {
 	.read         = timebase_read,
 };
 
-#define DECREMENTER_MAX	0x7fffffff
+#define DECREMENTER_DEFAULT_MAX 0x7FFFFFFF
+u64 decrementer_max = DECREMENTER_DEFAULT_MAX;
 
 static int decrementer_set_next_event(unsigned long evt,
 				      struct clock_event_device *dev);
@@ -504,8 +505,8 @@ static void __timer_interrupt(void)
 		__this_cpu_inc(irq_stat.timer_irqs_event);
 	} else {
 		now = *next_tb - now;
-		if (now <= DECREMENTER_MAX)
-			set_dec((int)now);
+		if (now <= decrementer_max)
+			set_dec(now);
 		/* We may have raced with new irq work */
 		if (test_irq_work_pending())
 			set_dec(1);
@@ -535,7 +536,7 @@ void timer_interrupt(struct pt_regs * regs)
 	/* Ensure a positive value is written to the decrementer, or else
 	 * some CPUs will continue to take decrementer exceptions.
 	 */
-	set_dec(DECREMENTER_MAX);
+	set_dec(decrementer_max);
 
 	/* Some implementations of hotplug will get timer interrupts while
 	 * offline, just ignore these and we also need to set
@@ -583,9 +584,9 @@ static void generic_suspend_disable_irqs(void)
 	 * with suspending.
 	 */
 
-	set_dec(DECREMENTER_MAX);
+	set_dec(decrementer_max);
 	local_irq_disable();
-	set_dec(DECREMENTER_MAX);
+	set_dec(decrementer_max);
 }
 
 static void generic_suspend_enable_irqs(void)
@@ -866,7 +867,7 @@ static int decrementer_set_next_event(unsigned long evt,
 
 static int decrementer_shutdown(struct clock_event_device *dev)
 {
-	decrementer_set_next_event(DECREMENTER_MAX, dev);
+	decrementer_set_next_event(decrementer_max, dev);
 	return 0;
 }
 
@@ -892,6 +893,49 @@ static void register_decrementer_clockevent(int cpu)
 	clockevents_register_device(dec);
 }
 
+static void enable_large_decrementer(void)
+{
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		return;
+
+	if (decrementer_max <= DECREMENTER_DEFAULT_MAX)
+		return;
+
+	/*
+	 * If we're running as the hypervisor we need to enable the LD manually
+	 * otherwise firmware should have done it for us.
+	 */
+	if (cpu_has_feature(CPU_FTR_HVMODE))
+		mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_LD);
+}
+
+static void __init set_decrementer_max(void)
+{
+	struct device_node *cpu;
+	u32 bits = 32;
+
+	/* Prior to ISAv3 the decrementer is always 32 bit */
+	if (!cpu_has_feature(CPU_FTR_ARCH_300))
+		return;
+
+	cpu = of_find_node_by_type(NULL, "cpu");
+
+	if (of_property_read_u32(cpu, "ibm,dec-bits", &bits) == 0) {
+		if (bits > 64 || bits < 32) {
+			pr_warn("time_init: firmware supplied invalid ibm,dec-bits");
+			bits = 32;
+		}
+
+		/* calculate the signed maximum given this many bits */
+		decrementer_max = (1ul << (bits - 1)) - 1;
+	}
+
+	of_node_put(cpu);
+
+	pr_info("time_init: %u bit decrementer (max: %llx)\n",
+		bits, decrementer_max);
+}
+
 static void __init init_decrementer_clockevent(void)
 {
 	int cpu = smp_processor_id();
@@ -899,7 +943,7 @@ static void __init init_decrementer_clockevent(void)
 	clockevents_calc_mult_shift(&decrementer_clockevent, ppc_tb_freq, 4);
 
 	decrementer_clockevent.max_delta_ns =
-		clockevent_delta2ns(DECREMENTER_MAX, &decrementer_clockevent);
+		clockevent_delta2ns(decrementer_max, &decrementer_clockevent);
 	decrementer_clockevent.min_delta_ns =
 		clockevent_delta2ns(2, &decrementer_clockevent);
 
@@ -908,6 +952,9 @@ static void __init init_decrementer_clockevent(void)
 
 void secondary_cpu_time_init(void)
 {
+	/* Enable and test the large decrementer for this cpu */
+	enable_large_decrementer();
+
 	/* Start the decrementer on CPUs that have manual control
 	 * such as BookE
 	 */
@@ -973,6 +1020,10 @@ void __init time_init(void)
 	vdso_data->tb_update_count = 0;
 	vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
 
+	/* initialise and enable the large decrementer (if we have one) */
+	set_decrementer_max();
+	enable_large_decrementer();
+
 	/* Start the decrementer on CPUs that have manual control
 	 * such as BookE
 	 */