Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

[linux-2.6-block.git] / drivers / char / hpet.c

diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index 53fdc7ff387051507ade9def9a75eb67ff1bfd13..50dfa3bc71cee00de3eeb20858416ce4a4941bfd 100644 (file)
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -46,7 +46,7 @@
 /*
  * The High Precision Event Timer driver.
  * This driver is closely modelled after the rtc.c driver.
- * http://www.intel.com/hardwaredesign/hpetspec.htm
+ * http://www.intel.com/hardwaredesign/hpetspec_1.pdf
  */
 #define        HPET_USER_FREQ  (64)
 #define        HPET_DRIFT      (500)
@@ -713,7 +713,7 @@ static struct ctl_table_header *sysctl_header;
  */
 #define        TICK_CALIBRATE  (1000UL)
 
-static unsigned long hpet_calibrate(struct hpets *hpetp)
+static unsigned long __hpet_calibrate(struct hpets *hpetp)
 {
        struct hpet_timer __iomem *timer = NULL;
        unsigned long t, m, count, i, flags, start;
@@ -750,6 +750,26 @@ static unsigned long hpet_calibrate(struct hpets *hpetp)
        return (m - start) / i;
 }
 
+static unsigned long hpet_calibrate(struct hpets *hpetp)
+{
+       unsigned long ret = -1;
+       unsigned long tmp;
+
+       /*
+        * Try to calibrate until return value becomes stable small value.
+        * If SMI interruption occurs in calibration loop, the return value
+        * will be big. This avoids its impact.
+        */
+       for ( ; ; ) {
+               tmp = __hpet_calibrate(hpetp);
+               if (ret <= tmp)
+                       break;
+               ret = tmp;
+       }
+
+       return ret;
+}
+
 int hpet_alloc(struct hpet_data *hdp)
 {
        u64 cap, mcfg;