Below is a patch from android kernel that maintains a histogram of
suspend times. Please review and provide feedback.

Statistices on the time spent in suspend are kept in
/sys/kernel/debug/sleep_time.

Cc: Android Kernel Team
Cc: Colin Cross
Cc: Todd Poynor
Cc: San Mehat
Cc: Benoit Goby
Cc: John Stultz
Cc: Thomas Gleixner
Signed-off-by: Colin Cross
Signed-off-by: Todd Poynor
[zoran.markovic@linaro.org: Re-formatted suspend time table to better
fit expected values. Moved accounting of suspend time into timekeeping
core. Removed CONFIG_SUSPEND_TIME flag and made the feature conditional
on CONFIG_DEBUG_FS. Changed the file name to sleep_time to better fit
terminology in timekeeping core. Changed seq_printf to seq_puts. Tweaked
commit message]
Signed-off-by: Zoran Markovic
Signed-off-by: John Stultz