• Viresh Kumar's avatar
    thermal: Add cooling device's statistics in sysfs · 8ea22951
    Viresh Kumar authored
    This extends the sysfs interface for thermal cooling devices and exposes
    some pretty useful statistics. These statistics have proven to be quite
    useful specially while doing benchmarks related to the task scheduler,
    where we want to make sure that nothing has disrupted the test,
    specially the cooling device which may have put constraints on the CPUs.
    The information exposed here tells us to what extent the CPUs were
    constrained by the thermal framework.
    
    The write-only "reset" file is used to reset the statistics.
    
    The read-only "time_in_state_ms" file shows the time (in msec) spent by the
    device in the respective cooling states, and it prints one line per
    cooling state.
    
    The read-only "total_trans" file shows single positive integer value
    showing the total number of cooling state transitions the device has
    gone through since the time the cooling device is registered or the time
    when statistics were reset last.
    
    The read-only "trans_table" file shows a two dimensional matrix, where
    an entry <i,j> (row i, column j) represents the number of transitions
    from State_i to State_j.
    
    This is how the directory structure looks like for a single cooling
    device:
    
    $ ls -R /sys/class/thermal/cooling_device0/
    /sys/class/thermal/cooling_device0/:
    cur_state  max_state  power  stats  subsystem  type  uevent
    
    /sys/class/thermal/cooling_device0/power:
    autosuspend_delay_ms  runtime_active_time  runtime_suspended_time
    control               runtime_status
    
    /sys/class/thermal/cooling_device0/stats:
    reset  time_in_state_ms  total_trans  trans_table
    
    This is tested on ARM 64-bit Hisilicon hikey620 board running Ubuntu and
    ARM 64-bit Hisilicon hikey960 board running Android.
    Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
    Signed-off-by: default avatarZhang Rui <rui.zhang@intel.com>
    8ea22951
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