[4/7] thermal: stats: introduce thermal zone stats/min_gradient

From: Eduardo Valentin <eduval@amazon.com>

The patch adds a statistic to track
the minimum gradient (dT/dt) to the thermal zone
stats/ folder.

Samples:

$ echo 1000 > emul_temp
$ cat stats/min_gradient
0
$ echo 2000 > emul_temp
$ echo 1000 > emul_temp
$ cat stats/min_gradient
-3460

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          |  1 +
 drivers/thermal/thermal_sysfs.c               | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+)

On Fri, May 19, 2023 at 5:27 AM Eduardo Valentin <evalenti@kernel.org> wrote:
>
> From: Eduardo Valentin <eduval@amazon.com>
>
> The patch adds a statistic to track
> the minimum gradient (dT/dt) to the thermal zone
> stats/ folder.
>
> Samples:
>
> $ echo 1000 > emul_temp
> $ cat stats/min_gradient
> 0
> $ echo 2000 > emul_temp
> $ echo 1000 > emul_temp
> $ cat stats/min_gradient
> -3460
>
> 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>

This can be easily folded into the previous patch IMO.

> ---
>  .../driver-api/thermal/sysfs-api.rst          |  1 +
>  drivers/thermal/thermal_sysfs.c               | 23 +++++++++++++++++++
>  2 files changed, 24 insertions(+)
>
> diff --git a/Documentation/driver-api/thermal/sysfs-api.rst b/Documentation/driver-api/thermal/sysfs-api.rst
> index 18140dbb1ce1..ed5e6ba4e0d7 100644
> --- a/Documentation/driver-api/thermal/sysfs-api.rst
> +++ b/Documentation/driver-api/thermal/sysfs-api.rst
> @@ -358,6 +358,7 @@ Thermal zone device sys I/F, created once it's registered::
>      |---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.
> +    |---stats/min_gradient:    The minimum recorded dT/dt in uC/ms.
>
>  Thermal cooling device sys I/F, created once it's registered::
>
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index aa28c1cae916..f89ec9a7e8c8 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -542,6 +542,7 @@ static void destroy_trip_attrs(struct thermal_zone_device *tz)
>  struct thermal_zone_device_stats {
>         spinlock_t lock; /* protects this struct */
>         s64 max_gradient;
> +       s64 min_gradient;
>         ktime_t last_time;
>  };
>
> @@ -569,6 +570,10 @@ static void temperature_stats_update(struct thermal_zone_device *tz)
>         /* update fastest temperature rise from our perspective */
>         if (cur_gradient > stats->max_gradient)
>                 stats->max_gradient = cur_gradient;
> +
> +       /* update fastest temperature decay from our perspective */
> +       if (cur_gradient < stats->min_gradient)
> +               stats->min_gradient = cur_gradient;
>  }
>
>  void thermal_zone_device_stats_update(struct thermal_zone_device *tz)
> @@ -595,6 +600,21 @@ static ssize_t max_gradient_show(struct device *dev,
>         return ret;
>  }
>
> +static ssize_t min_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->min_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)
> @@ -604,6 +624,7 @@ reset_tz_stats_store(struct device *dev, struct device_attribute *attr,
>
>         spin_lock(&stats->lock);
>
> +       stats->min_gradient = 0;
>         stats->max_gradient = 0;
>         stats->last_time = ktime_get();
>
> @@ -612,10 +633,12 @@ reset_tz_stats_store(struct device *dev, struct device_attribute *attr,
>         return count;
>  }
>
> +static DEVICE_ATTR_RO(min_gradient);
>  static DEVICE_ATTR_RO(max_gradient);
>  static DEVICE_ATTR_WO(reset_tz_stats);
>
>  static struct attribute *thermal_zone_device_stats_attrs[] = {
> +       &dev_attr_min_gradient.attr,
>         &dev_attr_max_gradient.attr,
>         &dev_attr_reset_tz_stats.attr,
>         NULL
> --
> 2.34.1
>