diff options
| author | Yasunori Goto <y-goto@jp.fujitsu.com> | 2009-04-02 16:58:31 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-02 19:05:01 -0700 |
| commit | 303d379c54fc9ed553562e36c1cbd1791a3f5d17 (patch) | |
| tree | fa16886ba42f97af18eed3f2b791f54ce7ee2b09 /drivers/char | |
| parent | 1f80769ffd36e74357fe896dc43dddf1af1510f3 (diff) | |
hpet: fix the possibility of insane return value of hpet_calibrate() against SMI
hpet_calibrate() has a possibility of miss-calibration due to SMI. If SMI
interrupts in the while loop of calibration, then return value will be
big. This change calibrates until stabilizing by the return value with a
small value.
[akpm@linux-foundation.org: trivial style tweaks]
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Acked-by: Clemens Ladisch <clemens@ladisch.de>
Acked-by: Vojtech Pavlik <vojtech@suse.cz>
Cc: Robert Picco <Robert.Picco@hp.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/hpet.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/drivers/char/hpet.c b/drivers/char/hpet.c index 32b8bbf5003e..50dfa3bc71ce 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; |