1 files changed, 9 insertions, 1 deletions

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ee4fa1bfcb33..23b4ecdffa9b 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -4,6 +4,7 @@
 #include <linux/sysdev.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
+#include <linux/slab.h>
 #include <linux/hpet.h>
 #include <linux/init.h>
 #include <linux/cpu.h>
@@ -399,9 +400,15 @@ static int hpet_next_event(unsigned long delta,
          * then we might have a real hardware problem. We can not do
          * much about it here, but at least alert the user/admin with
          * a prominent warning.
+         * An erratum on some chipsets (ICH9,..), results in comparator read
+         * immediately following a write returning old value. Workaround
+         * for this is to read this value second time, when first
+         * read returns old value.
          */
-        WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt,
+        if (unlikely((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt)) {
+                WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt,
                   KERN_WARNING "hpet: compare register read back failed.\n");
+        }
 
         return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
 }
@@ -1143,6 +1150,7 @@ int hpet_set_periodic_freq(unsigned long freq)
                 do_div(clc, freq);
                 clc >>= hpet_clockevent.shift;
                 hpet_pie_delta = clc;
+                hpet_pie_limit = 0;
         }
         return 1;
 }