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Subject[PATCH] [26/99] cpuidle: menu: fixed wrapping timers at 4.294 seconds
Date
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Tero Kristo <tero.kristo@nokia.com>

commit 7467571f4480b273007517b26297c07154c73924 upstream.

Cpuidle menu governor is using u32 as a temporary datatype for storing
nanosecond values which wrap around at 4.294 seconds. This causes errors
in predicted sleep times resulting in higher than should be C state
selection and increased power consumption. This also breaks cpuidle
state residency statistics.

Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
drivers/cpuidle/governors/menu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6.35.y/drivers/cpuidle/governors/menu.c
===================================================================
--- linux-2.6.35.y.orig/drivers/cpuidle/governors/menu.c
+++ linux-2.6.35.y/drivers/cpuidle/governors/menu.c
@@ -236,6 +236,7 @@ static int menu_select(struct cpuidle_de
int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
int i;
int multiplier;
+ struct timespec t;

if (data->needs_update) {
menu_update(dev);
@@ -250,8 +251,9 @@ static int menu_select(struct cpuidle_de
return 0;

/* determine the expected residency time, round up */
+ t = ktime_to_timespec(tick_nohz_get_sleep_length());
data->expected_us =
- DIV_ROUND_UP((u32)ktime_to_ns(tick_nohz_get_sleep_length()), 1000);
+ t.tv_sec * USEC_PER_SEC + t.tv_nsec / NSEC_PER_USEC;


data->bucket = which_bucket(data->expected_us);

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