[PATCH 12/13] thermal: thermal: Add support for hardware-tracked trip points

[Sascha Hauer]

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 ULONG_MAX or 0 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 at kapsi.fi>

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 drivers/thermal/thermal_core.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/thermal.h        |  3 +++
 2 files changed, 45 insertions(+)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index 420c702..4e1aaab 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -453,6 +453,45 @@ int thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp)
 }
 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;
+
+	if (!tz->ops->set_trips)
+		return;
+
+	/* No need to change trip points */
+	if (temp > tz->prev_low_trip && temp < tz->prev_high_trip)
+		return;
+
+	for (i = 0; i < tz->trips; i++) {
+		unsigned long 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;
+	}
+
+	tz->prev_low_trip = low;
+	tz->prev_high_trip = high;
+
+	dev_dbg(&tz->device, "new temperature boundaries: %d < x < %d\n",
+			low, high);
+
+	tz->ops->set_trips(tz, low, high);
+}
+
 void thermal_zone_device_update(struct thermal_zone_device *tz)
 {
 	int temp, ret, count;
@@ -473,6 +512,7 @@ void thermal_zone_device_update(struct thermal_zone_device *tz)
 	mutex_lock(&tz->lock);
 	tz->last_temperature = tz->temperature;
 	tz->temperature = temp;
+	thermal_zone_set_trips(tz);
 	mutex_unlock(&tz->lock);
 
 	trace_thermal_temperature(tz);
@@ -1494,6 +1534,8 @@ 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;
 
 	dev_set_name(&tz->device, "thermal_zone%d", tz->id);
 	result = device_register(&tz->device);
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 07bd5e8..aef6e13 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -87,6 +87,7 @@ 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 *,
@@ -180,6 +181,8 @@ struct thermal_zone_device {
 	int last_temperature;
 	int emul_temperature;
 	int passive;
+	int prev_low_trip;
+	int prev_high_trip;
 	unsigned int forced_passive;
 	const struct thermal_zone_device_ops *ops;
 	const struct thermal_zone_params *tzp;
-- 
2.1.4