[PATCH 3/7] thermal: stats: introduce thermal zone stats/ directory

Eduardo Valentin
2023-05-19T03:28:05Z

From: Eduardo Valentin <eduval@amazon.com>

This patch adds a new sysfs interface to report
statistics of each thermal zone. This interface
follows the existing thermal statistics for cooling
devices design, in which it is provided a reset
mechanism. The patch adds a statistic to track
the maximum gradient (dT/dt) to the thermal zone
stats/ folder.

Sample, how gradient changes using emulation:

$ cat stats/max_gradient
0
$ echo 2000 > emul_temp
$ cat temp
2000
$ cat stats/max_gradient
2849
$ cat temp
2000

Cc: "Rafael J. Wysocki" <rafael@kernel.org> (supporter:THERMAL)
Cc: Daniel Lezcano <daniel.lezcano@linaro.org> (supporter:THERMAL)
Cc: Amit Kucheria <amitk@kernel.org> (reviewer:THERMAL)
Cc: Zhang Rui <rui.zhang@intel.com> (reviewer:THERMAL)
Cc: Jonathan Corbet <corbet@lwn.net> (maintainer:DOCUMENTATION)
Cc: linux-pm@vger.kernel.org (open list:THERMAL)
Cc: linux-doc@vger.kernel.org (open list:DOCUMENTATION)
Cc: linux-kernel@vger.kernel.org (open list)

Signed-off-by: Eduardo Valentin <eduval@amazon.com>
---
.../driver-api/thermal/sysfs-api.rst | 3 +
drivers/thermal/thermal_core.c | 1 +
drivers/thermal/thermal_core.h | 3 +
drivers/thermal/thermal_sysfs.c | 142 +++++++++++++++++-
include/linux/thermal.h | 2 +
5 files changed, 147 insertions(+), 4 deletions(-)

diff --git a/Documentation/driver-api/thermal/sysfs-api.rst b/Documentation/driver-api/thermal/sysfs-api.rst
index 75309a51d9b3..18140dbb1ce1 100644
--- a/Documentation/driver-api/thermal/sysfs-api.rst
+++ b/Documentation/driver-api/thermal/sysfs-api.rst
@@ -355,6 +355,9 @@ Thermal zone device sys I/F, created once it's registered::
|---integral_cutoff: Offset above which errors are accumulated
|---slope: Slope constant applied as linear extrapolation
|---offset: Offset constant applied as linear extrapolation
+ |---stats: Directory containing thermal zone device's stats
+ |---stats/reset_tz_stats: Writes to this file resets the statistics.
+ |---stats/max_gradient: The maximum recorded dT/dt in uC/ms.

Thermal cooling device sys I/F, created once it's registered::

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 4bb77af6a6f4..3ba970c0744f 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -385,6 +385,7 @@ static void update_temperature(struct thermal_zone_device *tz)

tz->last_temperature = tz->temperature;
tz->temperature = temp;
+ thermal_zone_device_stats_update(tz);

trace_thermal_temperature(tz);

diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index ed6511c3b794..ef37b92bbb7c 100644
--- a/drivers/thermal/thermal_core.h
+++ b/drivers/thermal/thermal_core.h
@@ -140,10 +140,13 @@ ssize_t weight_store(struct device *, struct device_attribute *, const char *,
size_t);

#ifdef CONFIG_THERMAL_STATISTICS
+void thermal_zone_device_stats_update(struct thermal_zone_device *tz);
void thermal_cooling_device_stats_update(struct thermal_cooling_device *cdev,
struct thermal_instance *instance,
unsigned long new_state);
#else
+static inline
+void thermal_zone_device_stats_update(struct thermal_zone_device *tz) {}
static inline void
thermal_cooling_device_stats_update(struct thermal_cooling_device *cdev,
struct thermal_instance *instance,
diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 0bce1415f7e8..aa28c1cae916 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -537,20 +537,147 @@ static void destroy_trip_attrs(struct thermal_zone_device *tz)
kfree(tz->trips_attribute_group.attrs);
}

+#ifdef CONFIG_THERMAL_STATISTICS
+/* thermal zone device statistics handling */
+struct thermal_zone_device_stats {
+ spinlock_t lock; /* protects this struct */
+ s64 max_gradient;
+ ktime_t last_time;
+};
+
+#define DELTA_MILLI_C_TO_MICRO_C(t0, t1) (((t0) - (t1)) * 1000)
+static void temperature_stats_update(struct thermal_zone_device *tz)
+{
+ struct thermal_zone_device_stats *stats = tz->stats;
+ ktime_t now = ktime_get(), delta;
+ s64 cur_gradient, delta_temp;
+
+ delta = ktime_sub(now, stats->last_time);
+ stats->last_time = now;
+
+ /* to see sub 1C/s, use uC/ms */
+ delta_temp = DELTA_MILLI_C_TO_MICRO_C(tz->temperature,
+ tz->last_temperature);
+ cur_gradient = ktime_to_ms(delta);
+ if (cur_gradient)
+ cur_gradient = div64_s64(delta_temp, cur_gradient);
+
+ /* Corner case of initialization, first temp read */
+ if (tz->last_temperature == 0)
+ cur_gradient = 0;
+
+ /* update fastest temperature rise from our perspective */
+ if (cur_gradient > stats->max_gradient)
+ stats->max_gradient = cur_gradient;
+}
+
+void thermal_zone_device_stats_update(struct thermal_zone_device *tz)
+{
+ struct thermal_zone_device_stats *stats = tz->stats;
+
+ spin_lock(&stats->lock);
+ temperature_stats_update(tz);
+ spin_unlock(&stats->lock);
+}
+
+static ssize_t max_gradient_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct thermal_zone_device *tz = to_thermal_zone(dev);
+ struct thermal_zone_device_stats *stats = tz->stats;
+ int ret;
+
+ spin_lock(&stats->lock);
+ temperature_stats_update(tz);
+ ret = snprintf(buf, PAGE_SIZE, "%lld\n", stats->max_gradient);
+ spin_unlock(&stats->lock);
+
+ return ret;
+}
+
+static ssize_t
+reset_tz_stats_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct thermal_zone_device *tz = to_thermal_zone(dev);
+ struct thermal_zone_device_stats *stats = tz->stats;
+
+ spin_lock(&stats->lock);
+
+ stats->max_gradient = 0;
+ stats->last_time = ktime_get();
+
+ spin_unlock(&stats->lock);
+
+ return count;
+}
+
+static DEVICE_ATTR_RO(max_gradient);
+static DEVICE_ATTR_WO(reset_tz_stats);
+
+static struct attribute *thermal_zone_device_stats_attrs[] = {
+ &dev_attr_max_gradient.attr,
+ &dev_attr_reset_tz_stats.attr,
+ NULL
+};
+
+static const struct attribute_group thermal_zone_device_stats_attr_group = {
+ .attrs = thermal_zone_device_stats_attrs,
+ .name = "stats"
+};
+
+static void
+thermal_zone_device_stats_setup(struct thermal_zone_device *tz,
+ const struct attribute_group **group)
+{
+ struct thermal_zone_device_stats *stats;
+ int var;
+
+ var = sizeof(*stats);
+
+ stats = kzalloc(var, GFP_KERNEL);
+ if (!stats)
+ return;
+
+ stats->last_time = ktime_get();
+ spin_lock_init(&stats->lock);
+ tz->stats = stats;
+
+ /* Fill the empty slot left in thermal_zone_device_attr_groups */
+ *group = &thermal_zone_device_stats_attr_group;
+}
+
+static void thermal_zone_device_stats_destroy(struct thermal_zone_device *tz)
+{
+ kfree(tz->stats);
+ tz->stats = NULL;
+}
+#else
+
+static inline void
+thermal_zone_device_stats_setup(struct thermal_zone_device *tz,
+ const struct attribute_group **group) {}
+static inline void
+thermal_zone_device_stats_destroy(struct thermal_zone_device *tz) {}
+
+#endif
+
int thermal_zone_create_device_groups(struct thermal_zone_device *tz,
int mask)
{
const struct attribute_group **groups;
- int i, size, result;
+ int i, size, result, extras = 2;

+ if (IS_ENABLED(CONFIG_THERMAL_STATISTIC))
+ extras++;
/* we need one extra for trips and the NULL to terminate the array */
- size = ARRAY_SIZE(thermal_zone_attribute_groups) + 2;
+ size = ARRAY_SIZE(thermal_zone_attribute_groups) + extras;
/* This also takes care of API requirement to be NULL terminated */
groups = kcalloc(size, sizeof(*groups), GFP_KERNEL);
if (!groups)
return -ENOMEM;

- for (i = 0; i < size - 2; i++)
+ for (i = 0; i < size - extras; i++)
groups[i] = thermal_zone_attribute_groups[i];

if (tz->num_trips) {
@@ -561,9 +688,15 @@ int thermal_zone_create_device_groups(struct thermal_zone_device *tz,
return result;
}

- groups[size - 2] = &tz->trips_attribute_group;
+ groups[size - extras] = &tz->trips_attribute_group;
}

+ /*
+ * This will be nop if CONFIG_THERMAL_STATISTICS is not defined,
+ * otherwise, it is always the last entry in the group prior to NULL
+ */
+ thermal_zone_device_stats_setup(tz, &groups[size - 2]);
+
tz->device.groups = groups;

return 0;
@@ -578,6 +711,7 @@ void thermal_zone_destroy_device_groups(struct thermal_zone_device *tz)
destroy_trip_attrs(tz);

kfree(tz->device.groups);
+ thermal_zone_device_stats_destroy(tz);
}

/* sys I/F for cooling device */
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 87837094d549..9dc8292f0314 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -121,6 +121,7 @@ struct thermal_cooling_device {
* @trip_type_attrs: attributes for trip points for sysfs: trip type
* @trip_hyst_attrs: attributes for trip points for sysfs: trip hysteresis
* @mode: current mode of this thermal zone
+ * @stats: private pointer to stats collected on this thermal zone
* @devdata: private pointer for device private data
* @trips: an array of struct thermal_trip
* @num_trips: number of trip points the thermal zone supports
@@ -162,6 +163,7 @@ struct thermal_zone_device {
struct thermal_attr *trip_type_attrs;
struct thermal_attr *trip_hyst_attrs;
enum thermal_device_mode mode;
+ void *stats;
void *devdata;
struct thermal_trip *trips;
int num_trips;
--
2.34.1