cpuidle: menu: fixed wrapping timers at 4.294 seconds

BugLink: http://bugs.launchpad.net/bugs/774947

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.

cc: stable@kernel.org # .32.x through .39.x
Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
Signed-off-by: Len Brown <len.brown@intel.com>
(cherry picked from commit 7467571f4480b273007517b26297c07154c73924)
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index f508690..c47f3d0 100644 (file)
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -237,6 +237,7 @@ static int menu_select(struct cpuidle_device *dev)
        unsigned int power_usage = -1;
        int i;
        int multiplier;
+       struct timespec t;
 
        if (data->needs_update) {
                menu_update(dev);
@@ -251,8 +252,9 @@ static int menu_select(struct cpuidle_device *dev)
                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);