thermal: Add cooling device's statistics in sysfs
authorViresh Kumar <viresh.kumar@linaro.org>
Mon, 2 Apr 2018 10:56:25 +0000 (16:26 +0530)
committerZhang Rui <rui.zhang@intel.com>
Mon, 2 Apr 2018 13:49:01 +0000 (21:49 +0800)
commit8ea229511e06f9635ecc338dcbe0db41a73623f0
treea963ef526322117373498ff22950fffc942a5b14
parent0c8efd610b58cb23cefdfa12015799079aef94ae
thermal: Add cooling device's statistics in sysfs

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: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Documentation/thermal/sysfs-api.txt
drivers/thermal/Kconfig
drivers/thermal/thermal_core.c
drivers/thermal/thermal_core.h
drivers/thermal/thermal_helpers.c
drivers/thermal/thermal_sysfs.c
include/linux/thermal.h