1 files changed, 13 insertions, 6 deletions

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 59fd3b6b1303..73deaffadd03 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -210,8 +210,8 @@ static void hpet_legacy_clockevent_register(void)
         /* Calculate the min / max delta */
         hpet_clockevent.max_delta_ns = clockevent_delta2ns(0x7FFFFFFF,
                                                            &hpet_clockevent);
-        hpet_clockevent.min_delta_ns = clockevent_delta2ns(0x30,
-                                                           &hpet_clockevent);
+        /* 5 usec minimum reprogramming delta. */
+        hpet_clockevent.min_delta_ns = 5000;
 
         /*
          * Start hpet with the boot cpu mask and make it
@@ -270,15 +270,22 @@ static void hpet_legacy_set_mode(enum clock_event_mode mode,
 }
 
 static int hpet_legacy_next_event(unsigned long delta,
-                           struct clock_event_device *evt)
+                                  struct clock_event_device *evt)
 {
-        unsigned long cnt;
+        u32 cnt;
 
         cnt = hpet_readl(HPET_COUNTER);
-        cnt += delta;
+        cnt += (u32) delta;
         hpet_writel(cnt, HPET_T0_CMP);
 
-        return ((long)(hpet_readl(HPET_COUNTER) - cnt ) > 0) ? -ETIME : 0;
+        /*
+         * We need to read back the CMP register to make sure that
+         * what we wrote hit the chip before we compare it to the
+         * counter.
+         */
+        WARN_ON((u32)hpet_readl(HPET_T0_CMP) != cnt);
+
+        return (s32)((u32)hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
 }
 
 /*