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, 225 insertions, 0 deletions

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index ba81c9080f6e..23b5e0a709b0 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -20,6 +20,7 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/jiffies.h>
 
 #include "thermal_core.h"
 
@@ -721,6 +722,7 @@ thermal_cooling_device_cur_state_store(struct device *dev,
 	result = cdev->ops->set_cur_state(cdev, state);
 	if (result)
 		return result;
+	thermal_cooling_device_stats_update(cdev, state);
 	return count;
 }
 
@@ -745,14 +747,237 @@ static const struct attribute_group cooling_device_attr_group = {
 
 static const struct attribute_group *cooling_device_attr_groups[] = {
 	&cooling_device_attr_group,
+	NULL, /* Space allocated for cooling_device_stats_attr_group */
 	NULL,
 };
 
+#ifdef CONFIG_THERMAL_STATISTICS
+struct cooling_dev_stats {
+	spinlock_t lock;
+	unsigned int total_trans;
+	unsigned long state;
+	unsigned long max_states;
+	ktime_t last_time;
+	ktime_t *time_in_state;
+	unsigned int *trans_table;
+};
+
+static void update_time_in_state(struct cooling_dev_stats *stats)
+{
+	ktime_t now = ktime_get(), delta;
+
+	delta = ktime_sub(now, stats->last_time);
+	stats->time_in_state[stats->state] =
+		ktime_add(stats->time_in_state[stats->state], delta);
+	stats->last_time = now;
+}
+
+void thermal_cooling_device_stats_update(struct thermal_cooling_device *cdev,
+					 unsigned long new_state)
+{
+	struct cooling_dev_stats *stats = cdev->stats;
+
+	spin_lock(&stats->lock);
+
+	if (stats->state == new_state)
+		goto unlock;
+
+	update_time_in_state(stats);
+	stats->trans_table[stats->state * stats->max_states + new_state]++;
+	stats->state = new_state;
+	stats->total_trans++;
+
+unlock:
+	spin_unlock(&stats->lock);
+}
+
+static ssize_t
+thermal_cooling_device_total_trans_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct thermal_cooling_device *cdev = to_cooling_device(dev);
+	struct cooling_dev_stats *stats = cdev->stats;
+	int ret;
+
+	spin_lock(&stats->lock);
+	ret = sprintf(buf, "%u\n", stats->total_trans);
+	spin_unlock(&stats->lock);
+
+	return ret;
+}
+
+static ssize_t
+thermal_cooling_device_time_in_state_show(struct device *dev,
+					  struct device_attribute *attr,
+					  char *buf)
+{
+	struct thermal_cooling_device *cdev = to_cooling_device(dev);
+	struct cooling_dev_stats *stats = cdev->stats;
+	ssize_t len = 0;
+	int i;
+
+	spin_lock(&stats->lock);
+	update_time_in_state(stats);
+
+	for (i = 0; i < stats->max_states; i++) {
+		len += sprintf(buf + len, "state%u\t%llu\n", i,
+			       ktime_to_ms(stats->time_in_state[i]));
+	}
+	spin_unlock(&stats->lock);
+
+	return len;
+}
+
+static ssize_t
+thermal_cooling_device_reset_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct thermal_cooling_device *cdev = to_cooling_device(dev);
+	struct cooling_dev_stats *stats = cdev->stats;
+	int i, states = stats->max_states;
+
+	spin_lock(&stats->lock);
+
+	stats->total_trans = 0;
+	stats->last_time = ktime_get();
+	memset(stats->trans_table, 0,
+	       states * states * sizeof(*stats->trans_table));
+
+	for (i = 0; i < stats->max_states; i++)
+		stats->time_in_state[i] = ktime_set(0, 0);
+
+	spin_unlock(&stats->lock);
+
+	return count;
+}
+
+static ssize_t
+thermal_cooling_device_trans_table_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct thermal_cooling_device *cdev = to_cooling_device(dev);
+	struct cooling_dev_stats *stats = cdev->stats;
+	ssize_t len = 0;
+	int i, j;
+
+	len += snprintf(buf + len, PAGE_SIZE - len, " From  :    To\n");
+	len += snprintf(buf + len, PAGE_SIZE - len, "       : ");
+	for (i = 0; i < stats->max_states; i++) {
+		if (len >= PAGE_SIZE)
+			break;
+		len += snprintf(buf + len, PAGE_SIZE - len, "state%2u  ", i);
+	}
+	if (len >= PAGE_SIZE)
+		return PAGE_SIZE;
+
+	len += snprintf(buf + len, PAGE_SIZE - len, "\n");
+
+	for (i = 0; i < stats->max_states; i++) {
+		if (len >= PAGE_SIZE)
+			break;
+
+		len += snprintf(buf + len, PAGE_SIZE - len, "state%2u:", i);
+
+		for (j = 0; j < stats->max_states; j++) {
+			if (len >= PAGE_SIZE)
+				break;
+			len += snprintf(buf + len, PAGE_SIZE - len, "%8u ",
+				stats->trans_table[i * stats->max_states + j]);
+		}
+		if (len >= PAGE_SIZE)
+			break;
+		len += snprintf(buf + len, PAGE_SIZE - len, "\n");
+	}
+
+	if (len >= PAGE_SIZE) {
+		pr_warn_once("Thermal transition table exceeds PAGE_SIZE. Disabling\n");
+		return -EFBIG;
+	}
+	return len;
+}
+
+static DEVICE_ATTR(total_trans, 0444, thermal_cooling_device_total_trans_show,
+		   NULL);
+static DEVICE_ATTR(time_in_state_ms, 0444,
+		   thermal_cooling_device_time_in_state_show, NULL);
+static DEVICE_ATTR(reset, 0200, NULL, thermal_cooling_device_reset_store);
+static DEVICE_ATTR(trans_table, 0444,
+		   thermal_cooling_device_trans_table_show, NULL);
+
+static struct attribute *cooling_device_stats_attrs[] = {
+	&dev_attr_total_trans.attr,
+	&dev_attr_time_in_state_ms.attr,
+	&dev_attr_reset.attr,
+	&dev_attr_trans_table.attr,
+	NULL
+};
+
+static const struct attribute_group cooling_device_stats_attr_group = {
+	.attrs = cooling_device_stats_attrs,
+	.name = "stats"
+};
+
+static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
+{
+	struct cooling_dev_stats *stats;
+	unsigned long states;
+	int var;
+
+	if (cdev->ops->get_max_state(cdev, &states))
+		return;
+
+	states++; /* Total number of states is highest state + 1 */
+
+	var = sizeof(*stats);
+	var += sizeof(*stats->time_in_state) * states;
+	var += sizeof(*stats->trans_table) * states * states;
+
+	stats = kzalloc(var, GFP_KERNEL);
+	if (!stats)
+		return;
+
+	stats->time_in_state = (ktime_t *)(stats + 1);
+	stats->trans_table = (unsigned int *)(stats->time_in_state + states);
+	cdev->stats = stats;
+	stats->last_time = ktime_get();
+	stats->max_states = states;
+
+	spin_lock_init(&stats->lock);
+
+	/* Fill the empty slot left in cooling_device_attr_groups */
+	var = ARRAY_SIZE(cooling_device_attr_groups) - 2;
+	cooling_device_attr_groups[var] = &cooling_device_stats_attr_group;
+}
+
+static void cooling_device_stats_destroy(struct thermal_cooling_device *cdev)
+{
+	kfree(cdev->stats);
+	cdev->stats = NULL;
+}
+
+#else
+
+static inline void
+cooling_device_stats_setup(struct thermal_cooling_device *cdev) {}
+static inline void
+cooling_device_stats_destroy(struct thermal_cooling_device *cdev) {}
+
+#endif /* CONFIG_THERMAL_STATISTICS */
+
 void thermal_cooling_device_setup_sysfs(struct thermal_cooling_device *cdev)
 {
+	cooling_device_stats_setup(cdev);
 	cdev->device.groups = cooling_device_attr_groups;
 }
 
+void thermal_cooling_device_destroy_sysfs(struct thermal_cooling_device *cdev)
+{
+	cooling_device_stats_destroy(cdev);
+}
+
 /* these helper will be used only at the time of bindig */
 ssize_t
 thermal_cooling_device_trip_point_show(struct device *dev,