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>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index 27e3b1df7360..5e4150261500 100644
--- a/drivers/thermal/thermal_core.h
+++ b/drivers/thermal/thermal_core.h
@@ -73,6 +73,7 @@ int thermal_build_list_of_policies(char *buf);
 int thermal_zone_create_device_groups(struct thermal_zone_device *, int);
 void thermal_zone_destroy_device_groups(struct thermal_zone_device *);
 void thermal_cooling_device_setup_sysfs(struct thermal_cooling_device *);
+void thermal_cooling_device_destroy_sysfs(struct thermal_cooling_device *cdev);
 /* used only at binding time */
 ssize_t
 thermal_cooling_device_trip_point_show(struct device *,
@@ -84,6 +85,15 @@ ssize_t thermal_cooling_device_weight_store(struct device *,
 					    struct device_attribute *,
 					    const char *, size_t);
 
+#ifdef CONFIG_THERMAL_STATISTICS
+void thermal_cooling_device_stats_update(struct thermal_cooling_device *cdev,
+					 unsigned long new_state);
+#else
+static inline void
+thermal_cooling_device_stats_update(struct thermal_cooling_device *cdev,
+				    unsigned long new_state) {}
+#endif /* CONFIG_THERMAL_STATISTICS */
+
 #ifdef CONFIG_THERMAL_GOV_STEP_WISE
 int thermal_gov_step_wise_register(void);
 void thermal_gov_step_wise_unregister(void);