Thermal: Introduce .get_trend() callback.

According to ACPI spec, tc1 and tc2 are used by OSPM
to anticipate the temperature trends.
We introduced the same concept to the generic thermal layer
for passive cooling, but now it seems that these values
are hard to be used on other platforms.

So We introduce .get_trend() as a more general solution.

For the platform thermal drivers that have their own way to
anticipate the temperature trends, they should provide
their own .get_trend() callback.
Or else, we will calculate the temperature trends by simply
comparing the current temperature and the cached previous
temperature reading.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Valentin, Eduardo <eduardo.valentin@ti.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index d7ef69d835f2..bb95709a6be8 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -706,6 +706,38 @@ static int thermal_get_crit_temp(struct thermal_zone_device *thermal,
 		return -EINVAL;
 }
 
+static int thermal_get_trend(struct thermal_zone_device *thermal,
+				int trip, enum thermal_trend *trend)
+{
+	struct acpi_thermal *tz = thermal->devdata;
+	enum thermal_trip_type type;
+	int i;
+
+	if (thermal_get_trip_type(thermal, trip, &type))
+		return -EINVAL;
+
+	/* Only PASSIVE trip points need TREND */
+	if (type != THERMAL_TRIP_PASSIVE)
+		return -EINVAL;
+
+	/*
+	 * tz->temperature has already been updated by generic thermal layer,
+	 * before this callback being invoked
+	 */
+	i = (tz->trips.passive.tc1 * (tz->temperature - tz->last_temperature))
+		+ (tz->trips.passive.tc2
+		* (tz->temperature - tz->trips.passive.temperature));
+
+	if (i > 0)
+		*trend = THERMAL_TREND_RAISING;
+	else if (i < 0)
+		*trend = THERMAL_TREND_DROPPING;
+	else
+		*trend = THERMAL_TREND_STABLE;
+	return 0;
+}
+
+
 static int thermal_notify(struct thermal_zone_device *thermal, int trip,
 			   enum thermal_trip_type trip_type)
 {
@@ -838,6 +870,7 @@ static const struct thermal_zone_device_ops acpi_thermal_zone_ops = {
 	.get_trip_type = thermal_get_trip_type,
 	.get_trip_temp = thermal_get_trip_temp,
 	.get_crit_temp = thermal_get_crit_temp,
+	.get_trend = thermal_get_trend,
 	.notify = thermal_notify,
 };