5 files changed, 37 insertions, 27 deletions

diff --git a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
index 4d75b373f90e..a0dcb7c87c30 100644
--- a/arch/i386/kernel/time.c
+++ b/arch/i386/kernel/time.c
@@ -441,7 +441,7 @@ static void __init hpet_time_init(void)
         set_normalized_timespec(&wall_to_monotonic,
                 -xtime.tv_sec, -xtime.tv_nsec);
 
-        if (hpet_enable() >= 0) {
+        if ((hpet_enable() >= 0) && hpet_use_timer) {
                 printk("Using HPET for base-timer\n");
         }
 
diff --git a/arch/i386/kernel/time_hpet.c b/arch/i386/kernel/time_hpet.c
index 244a31b04be7..10a0cbb88e75 100644
--- a/arch/i386/kernel/time_hpet.c
+++ b/arch/i386/kernel/time_hpet.c
@@ -26,6 +26,7 @@
 static unsigned long hpet_period;       /* fsecs / HPET clock */
 unsigned long hpet_tick;                /* hpet clks count per tick */
 unsigned long hpet_address;             /* hpet memory map physical address */
+int hpet_use_timer;
 
 static int use_hpet;            /* can be used for runtime check of hpet */
 static int boot_hpet_disable;   /* boottime override for HPET timer */
@@ -73,27 +74,30 @@ static int hpet_timer_stop_set_go(unsigned long tick)
         hpet_writel(0, HPET_COUNTER);
         hpet_writel(0, HPET_COUNTER + 4);
 
-        /*
-         * Set up timer 0, as periodic with first interrupt to happen at
-         * hpet_tick, and period also hpet_tick.
-         */
-        cfg = hpet_readl(HPET_T0_CFG);
-        cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
-               HPET_TN_SETVAL | HPET_TN_32BIT;
-        hpet_writel(cfg, HPET_T0_CFG);
-
-        /*
-         * The first write after writing TN_SETVAL to the config register sets
-         * the counter value, the second write sets the threshold.
-         */
-        hpet_writel(tick, HPET_T0_CMP);
-        hpet_writel(tick, HPET_T0_CMP);
+        if (hpet_use_timer) {
+                /*
+                 * Set up timer 0, as periodic with first interrupt to happen at
+                 * hpet_tick, and period also hpet_tick.
+                 */
+                cfg = hpet_readl(HPET_T0_CFG);
+                cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
+                       HPET_TN_SETVAL | HPET_TN_32BIT;
+                hpet_writel(cfg, HPET_T0_CFG);
 
+                /*
+                 * The first write after writing TN_SETVAL to the config register sets
+                 * the counter value, the second write sets the threshold.
+                 */
+                hpet_writel(tick, HPET_T0_CMP);
+                hpet_writel(tick, HPET_T0_CMP);
+        }
         /*
          * Go!
          */
         cfg = hpet_readl(HPET_CFG);
-        cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
+        if (hpet_use_timer)
+                cfg |= HPET_CFG_LEGACY;
+        cfg |= HPET_CFG_ENABLE;
         hpet_writel(cfg, HPET_CFG);
 
         return 0;
@@ -128,12 +132,11 @@ int __init hpet_enable(void)
          * However, we can do with one timer otherwise using the
          * the single HPET timer for system time.
          */
-        if (
 #ifdef CONFIG_HPET_EMULATE_RTC
-                !(id & HPET_ID_NUMBER) ||
-#endif
-            !(id & HPET_ID_LEGSUP))
+        if (!(id & HPET_ID_NUMBER))
                 return -1;
+#endif
+
 
         hpet_period = hpet_readl(HPET_PERIOD);
         if ((hpet_period < HPET_MIN_PERIOD) || (hpet_period > HPET_MAX_PERIOD))
@@ -152,6 +155,8 @@ int __init hpet_enable(void)
         if (hpet_tick_rem > (hpet_period >> 1))
                 hpet_tick++; /* rounding the result */
 
+        hpet_use_timer = id & HPET_ID_LEGSUP;
+
         if (hpet_timer_stop_set_go(hpet_tick))
                 return -1;
 
@@ -202,7 +207,8 @@ int __init hpet_enable(void)
 #endif
 
 #ifdef CONFIG_X86_LOCAL_APIC
-        wait_timer_tick = wait_hpet_tick;
+        if (hpet_use_timer)
+                wait_timer_tick = wait_hpet_tick;
 #endif
         return 0;
 }
diff --git a/arch/i386/kernel/timers/timer_hpet.c b/arch/i386/kernel/timers/timer_hpet.c
index 713134e71844..f778f471a09a 100644
--- a/arch/i386/kernel/timers/timer_hpet.c
+++ b/arch/i386/kernel/timers/timer_hpet.c
@@ -79,7 +79,7 @@ static unsigned long get_offset_hpet(void)
 
         eax = hpet_readl(HPET_COUNTER);
         eax -= hpet_last;       /* hpet delta */
-
+        eax = min(hpet_tick, eax);
         /*
          * Time offset = (hpet delta) * ( usecs per HPET clock )
          *             = (hpet delta) * ( usecs per tick / HPET clocks per tick)
@@ -105,9 +105,12 @@ static void mark_offset_hpet(void)
         last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low;
         rdtsc(last_tsc_low, last_tsc_high);
 
-        offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
-        if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))) {
-                int lost_ticks = (offset - hpet_last) / hpet_tick;
+        if (hpet_use_timer)
+                offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
+        else
+                offset = hpet_readl(HPET_COUNTER);
+        if (unlikely(((offset - hpet_last) >= (2*hpet_tick)) && (hpet_last != 0))) {
+                int lost_ticks = ((offset - hpet_last) / hpet_tick) - 1;
                 jiffies_64 += lost_ticks;
         }
         hpet_last = offset;
diff --git a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c
index a685994e5c8e..7926d967be00 100644
--- a/arch/i386/kernel/timers/timer_tsc.c
+++ b/arch/i386/kernel/timers/timer_tsc.c
@@ -477,7 +477,7 @@ static int __init init_tsc(char* override)
         if (cpu_has_tsc) {
                 unsigned long tsc_quotient;
 #ifdef CONFIG_HPET_TIMER
-                if (is_hpet_enabled()){
+                if (is_hpet_enabled() && hpet_use_timer) {
                         unsigned long result, remain;
                         printk("Using TSC for gettimeofday\n");
                         tsc_quotient = calibrate_tsc_hpet(NULL);
diff --git a/include/asm-i386/hpet.h b/include/asm-i386/hpet.h
index 6e20b079f1d3..16ef9f996e3f 100644
--- a/include/asm-i386/hpet.h
+++ b/include/asm-i386/hpet.h
@@ -92,6 +92,7 @@
 
 extern unsigned long hpet_tick;         /* hpet clks count per tick */
 extern unsigned long hpet_address;      /* hpet memory map physical address */
+extern int hpet_use_timer;
 
 extern int hpet_rtc_timer_init(void);
 extern int hpet_enable(void);