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path: root/drivers/char/hpet.c
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Diffstat (limited to 'drivers/char/hpet.c')
-rw-r--r--drivers/char/hpet.c22
1 files changed, 21 insertions, 1 deletions
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c
index 32b8bbf5003..50dfa3bc71c 100644
--- a/drivers/char/hpet.c
+++ b/drivers/char/hpet.c
@@ -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;