Re: [PATCH v2 1/5] thermal: Add support for hardware-tracked trip points

Javi Merino
2016-05-24T12:57:42Z

On Tue, May 03, 2016 at 05:33:29PM +0800, Caesar Wang wrote:
> From: Sascha Hauer <s.hauer@pengutronix.de>
>
> This adds support for hardware-tracked trip points to the device tree
> thermal sensor framework.
>
> The framework supports an arbitrary number of trip points. Whenever
> the current temperature is updated, the trip points immediately
> below and above the current temperature are found. A .set_trips
> callback is then called with the temperatures. If there is no trip
> point above or below the current temperature, the passed trip
> temperature will be -INT_MAX or INT_MAX respectively. In this callback,
> the driver should program the hardware such that it is notified
> when either of these trip points are triggered. When a trip point
> is triggered, the driver should call `thermal_zone_device_update'
> for the respective thermal zone. This will cause the trip points
> to be updated again.
>
> If .set_trips is not implemented, the framework behaves as before.
>
> This patch is based on an earlier version from Mikko Perttunen
> <mikko.perttunen@kapsi.fi>
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Signed-off-by: Caesar Wang <wxt@rock-chips.com>
> Cc: Zhang Rui <rui.zhang@intel.com>
> Cc: Eduardo Valentin <edubezval@gmail.com>
> Cc: linux-pm@vger.kernel.org
>
> ---
>
> Changes in v2:
> - update the sysfs-api.txt for set_trips
>
> Documentation/thermal/sysfs-api.txt | 7 +++++
> drivers/thermal/thermal_core.c | 52 +++++++++++++++++++++++++++++++++++++
> include/linux/thermal.h | 3 +++
> 3 files changed, 62 insertions(+)
>
> diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt
> index efc3f3d..75d8838 100644
> --- a/Documentation/thermal/sysfs-api.txt
> +++ b/Documentation/thermal/sysfs-api.txt
> @@ -49,6 +49,9 @@ temperature) and throttle appropriate devices.
> .bind: bind the thermal zone device with a thermal cooling device.
> .unbind: unbind the thermal zone device with a thermal cooling device.
> .get_temp: get the current temperature of the thermal zone.
> + .set_trips: set the trip points window. Whenever the current temperature
> + is updated, the trip points immediately below and above the
> + current temperature are found.
> .get_mode: get the current mode (enabled/disabled) of the thermal zone.
> - "enabled" means the kernel thermal management is enabled.
> - "disabled" will prevent kernel thermal driver action upon trip points
> @@ -95,6 +98,10 @@ temperature) and throttle appropriate devices.
> get_temp: a pointer to a function that reads the
> sensor temperature. This is mandatory
> callback provided by sensor driver.
> + set_trips: a pointer to a function that sets a
> + temperature window. When this window is
> + left the driver must inform the thermal
> + core via thermal_zone_device_update.
> get_trend: a pointer to a function that reads the
> sensor temperature trend.
> set_emul_temp: a pointer to a function that sets
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 5133cd1..e5bfbd3 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -520,6 +520,51 @@ exit:
> }
> EXPORT_SYMBOL_GPL(thermal_zone_get_temp);
>
> +static void thermal_zone_set_trips(struct thermal_zone_device *tz)
> +{
> + int low = -INT_MAX;
> + int high = INT_MAX;
> + int trip_temp, hysteresis;
> + int temp = tz->temperature;
> + int i, ret;
> +
> + if (!tz->ops->set_trips)
> + return;
> +
> + for (i = 0; i < tz->trips; i++) {
> + int trip_low;
> +
> + tz->ops->get_trip_temp(tz, i, &trip_temp);
> + tz->ops->get_trip_hyst(tz, i, &hysteresis);
> +
> + trip_low = trip_temp - hysteresis;
> +
> + if (trip_low < temp && trip_low > low)
> + low = trip_low;
> +
> + if (trip_temp > temp && trip_temp < high)
> + high = trip_temp;
> + }
> +
> + /* No need to change trip points */
> + if (tz->prev_low_trip == low && tz->prev_high_trip == high)
> + return;
> +
> + tz->prev_low_trip = low;
> + tz->prev_high_trip = high;
> +
> + dev_dbg(&tz->device, "new temperature boundaries: %d < x < %d\n",
> + low, high);
> +
> + /*
> + * Set a temperature window. When this window is left the driver
> + * must inform the thermal core via thermal_zone_device_update.
> + */
> + ret = tz->ops->set_trips(tz, low, high);
> + if (ret)
> + dev_err(&tz->device, "Failed to set trips: %d\n", ret);

This function can be called at the same time from multiple places so
it should be reentrant. I think you should call mutex_lock(tz->lock)
before "if (tz->prev_low_trip == low && ..." and unlock it here.

> +}
> +
> static void update_temperature(struct thermal_zone_device *tz)
> {
> int temp, ret;
> @@ -569,6 +614,8 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
>
> update_temperature(tz);
>
> + thermal_zone_set_trips(tz);
> +
> for (count = 0; count < tz->trips; count++)
> handle_thermal_trip(tz, count);
> }
> @@ -754,6 +801,9 @@ trip_point_hyst_store(struct device *dev, struct device_attribute *attr,
> */
> ret = tz->ops->set_trip_hyst(tz, trip, temperature);
>
> + if (!ret)
> + thermal_zone_set_trips(tz);
> +

You should add a similar call to thermal_zone_set_trips() in trip_point_temp_store()

> return ret ? ret : count;
> }
>
> @@ -1843,6 +1893,8 @@ struct thermal_zone_device *thermal_zone_device_register(const char *type,
> tz->trips = trips;
> tz->passive_delay = passive_delay;
> tz->polling_delay = polling_delay;
> + tz->prev_low_trip = INT_MAX;
> + tz->prev_high_trip = -INT_MAX;
> /* A new thermal zone needs to be updated anyway. */
> atomic_set(&tz->need_update, 1);
>
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index e45abe7..e258359 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -98,6 +98,7 @@ struct thermal_zone_device_ops {
> int (*unbind) (struct thermal_zone_device *,
> struct thermal_cooling_device *);
> int (*get_temp) (struct thermal_zone_device *, int *);
> + int (*set_trips) (struct thermal_zone_device *, int, int);
> int (*get_mode) (struct thermal_zone_device *,
> enum thermal_device_mode *);
> int (*set_mode) (struct thermal_zone_device *,
> @@ -199,6 +200,8 @@ struct thermal_zone_device {
> int last_temperature;
> int emul_temperature;
> int passive;
> + int prev_low_trip;
> + int prev_high_trip;

Please document these fields in the kerneldoc comment before struct
thermal_zone_device.

> unsigned int forced_passive;
> atomic_t need_update;
> struct thermal_zone_device_ops *ops;

Cheers,
Javi