mlxsw: core: Use different get_trend() callbacks for different thermal zones

The driver registers three different types of thermal zones: For the
ASIC itself, for port modules and for gearboxes.

Currently, all three types use the same get_trend() callback which does
not work correctly for the ASIC thermal zone. The callback assumes that
the device data is of type 'struct mlxsw_thermal_module', whereas for
the ASIC thermal zone 'struct mlxsw_thermal' is passed as device data.

Fix this by using one get_trend() callback for the ASIC thermal zone and
another for the other two types.

Fixes: 6f73862fabd9 ("mlxsw: core: Add the hottest thermal zone detection")
Signed-off-by: Vadim Pasternak <[e-mail]>
Reviewed-by: Jiri Pirko <[e-mail]>
Signed-off-by: Ido Schimmel <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mellanox/mlxsw/core_thermal.c

···
 static int mlxsw_thermal_trend_get(struct thermal_zone_device *tzdev,
 				   int trip, enum thermal_trend *trend)
 {
-	struct mlxsw_thermal_module *tz = tzdev->devdata;
-	struct mlxsw_thermal *thermal = tz->parent;
+	struct mlxsw_thermal *thermal = tzdev->devdata;
 
 	if (trip < 0 || trip >= MLXSW_THERMAL_NUM_TRIPS)
 		return -EINVAL;
···
 	return 0;
 }
 
+static int mlxsw_thermal_module_trend_get(struct thermal_zone_device *tzdev,
+					  int trip, enum thermal_trend *trend)
+{
+	struct mlxsw_thermal_module *tz = tzdev->devdata;
+	struct mlxsw_thermal *thermal = tz->parent;
+
+	if (trip < 0 || trip >= MLXSW_THERMAL_NUM_TRIPS)
+		return -EINVAL;
+
+	if (tzdev == thermal->tz_highest_dev)
+		return 1;
+
+	*trend = THERMAL_TREND_STABLE;
+	return 0;
+}
+
 static struct thermal_zone_device_ops mlxsw_thermal_module_ops = {
 	.bind		= mlxsw_thermal_module_bind,
 	.unbind		= mlxsw_thermal_module_unbind,
···
 	.set_trip_temp	= mlxsw_thermal_module_trip_temp_set,
 	.get_trip_hyst	= mlxsw_thermal_module_trip_hyst_get,
 	.set_trip_hyst	= mlxsw_thermal_module_trip_hyst_set,
-	.get_trend	= mlxsw_thermal_trend_get,
+	.get_trend	= mlxsw_thermal_module_trend_get,
 };
 
 static int mlxsw_thermal_gearbox_temp_get(struct thermal_zone_device *tzdev,
···
 	.set_trip_temp	= mlxsw_thermal_module_trip_temp_set,
 	.get_trip_hyst	= mlxsw_thermal_module_trip_hyst_get,
 	.set_trip_hyst	= mlxsw_thermal_module_trip_hyst_set,
-	.get_trend	= mlxsw_thermal_trend_get,
+	.get_trend	= mlxsw_thermal_module_trend_get,
 };
 
 static int mlxsw_thermal_get_max_state(struct thermal_cooling_device *cdev,