1 files changed, 48 insertions, 24 deletions

diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
index a42c80745325..ef62b07b2b48 100644
--- a/arch/x86/kernel/i8253.c
+++ b/arch/x86/kernel/i8253.c
@@ -13,10 +13,17 @@
 #include <asm/delay.h>
 #include <asm/i8253.h>
 #include <asm/io.h>
+#include <asm/hpet.h>
 
 DEFINE_SPINLOCK(i8253_lock);
 EXPORT_SYMBOL(i8253_lock);
 
+#ifdef CONFIG_X86_32
+static void pit_disable_clocksource(void);
+#else
+static inline void pit_disable_clocksource(void) { }
+#endif
+
 /*
  * HPET replaces the PIT, when enabled. So we need to know, which of
  * the two timers is used
@@ -31,38 +38,38 @@ struct clock_event_device *global_clock_event;
 static void init_pit_timer(enum clock_event_mode mode,
                            struct clock_event_device *evt)
 {
-        unsigned long flags;
-
-        spin_lock_irqsave(&i8253_lock, flags);
+        spin_lock(&i8253_lock);
 
         switch(mode) {
         case CLOCK_EVT_MODE_PERIODIC:
                 /* binary, mode 2, LSB/MSB, ch 0 */
-                outb_p(0x34, PIT_MODE);
-                outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
-                outb(LATCH >> 8 , PIT_CH0);     /* MSB */
+                outb_pit(0x34, PIT_MODE);
+                outb_pit(LATCH & 0xff , PIT_CH0);       /* LSB */
+                outb_pit(LATCH >> 8 , PIT_CH0);         /* MSB */
                 break;
 
         case CLOCK_EVT_MODE_SHUTDOWN:
         case CLOCK_EVT_MODE_UNUSED:
                 if (evt->mode == CLOCK_EVT_MODE_PERIODIC ||
                     evt->mode == CLOCK_EVT_MODE_ONESHOT) {
-                        outb_p(0x30, PIT_MODE);
-                        outb_p(0, PIT_CH0);
-                        outb_p(0, PIT_CH0);
+                        outb_pit(0x30, PIT_MODE);
+                        outb_pit(0, PIT_CH0);
+                        outb_pit(0, PIT_CH0);
                 }
+                pit_disable_clocksource();
                 break;
 
         case CLOCK_EVT_MODE_ONESHOT:
                 /* One shot setup */
-                outb_p(0x38, PIT_MODE);
+                pit_disable_clocksource();
+                outb_pit(0x38, PIT_MODE);
                 break;
 
         case CLOCK_EVT_MODE_RESUME:
                 /* Nothing to do here */
                 break;
         }
-        spin_unlock_irqrestore(&i8253_lock, flags);
+        spin_unlock(&i8253_lock);
 }
 
 /*
@@ -72,12 +79,10 @@ static void init_pit_timer(enum clock_event_mode mode,
  */
 static int pit_next_event(unsigned long delta, struct clock_event_device *evt)
 {
-        unsigned long flags;
-
-        spin_lock_irqsave(&i8253_lock, flags);
-        outb_p(delta & 0xff , PIT_CH0); /* LSB */
-        outb(delta >> 8 , PIT_CH0);     /* MSB */
-        spin_unlock_irqrestore(&i8253_lock, flags);
+        spin_lock(&i8253_lock);
+        outb_pit(delta & 0xff , PIT_CH0);       /* LSB */
+        outb_pit(delta >> 8 , PIT_CH0);         /* MSB */
+        spin_unlock(&i8253_lock);
 
         return 0;
 }
@@ -148,15 +153,15 @@ static cycle_t pit_read(void)
          * count), it cannot be newer.
          */
         jifs = jiffies;
-        outb_p(0x00, PIT_MODE); /* latch the count ASAP */
-        count = inb_p(PIT_CH0); /* read the latched count */
-        count |= inb_p(PIT_CH0) << 8;
+        outb_pit(0x00, PIT_MODE);       /* latch the count ASAP */
+        count = inb_pit(PIT_CH0);       /* read the latched count */
+        count |= inb_pit(PIT_CH0) << 8;
 
         /* VIA686a test code... reset the latch if count > max + 1 */
         if (count > LATCH) {
-                outb_p(0x34, PIT_MODE);
-                outb_p(LATCH & 0xff, PIT_CH0);
-                outb(LATCH >> 8, PIT_CH0);
+                outb_pit(0x34, PIT_MODE);
+                outb_pit(LATCH & 0xff, PIT_CH0);
+                outb_pit(LATCH >> 8, PIT_CH0);
                 count = LATCH - 1;
         }
 
@@ -195,9 +200,28 @@ static struct clocksource clocksource_pit = {
         .shift  = 20,
 };
 
+static void pit_disable_clocksource(void)
+{
+        /*
+         * Use mult to check whether it is registered or not
+         */
+        if (clocksource_pit.mult) {
+                clocksource_unregister(&clocksource_pit);
+                clocksource_pit.mult = 0;
+        }
+}
+
 static int __init init_pit_clocksource(void)
 {
-        if (num_possible_cpus() > 1) /* PIT does not scale! */
+         /*
+          * Several reasons not to register PIT as a clocksource:
+          *
+          * - On SMP PIT does not scale due to i8253_lock
+          * - when HPET is enabled
+          * - when local APIC timer is active (PIT is switched off)
+          */
+        if (num_possible_cpus() > 1 || is_hpet_enabled() ||
+            pit_clockevent.mode != CLOCK_EVT_MODE_PERIODIC)
                 return 0;
 
         clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20);