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General Purpose Analog To Digital Converter (ADC) based thermal sensor.
On some of platforms, thermal sensor like thermistors are connected to
one of ADC channel and sensor resistance is read via voltage across the
sensor resistor. The voltage read across the sensor is mapped to
temperature using voltage-temperature lookup table.
Required properties:
===================
- compatible: Must be "generic-adc-thermal".
- #thermal-sensor-cells: Should be 1. See ./thermal.txt for a description
of this property.
Optional properties:
===================
- temperature-lookup-table: Two dimensional array of Integer; lookup table
to map the relation between ADC value and
temperature. When ADC is read, the value is
looked up on the table to get the equivalent
temperature.
The first value of the each row of array is the
temperature in milliCelsius and second value of
the each row of array is the ADC read value.
If not specified, driver assumes the ADC channel
gives milliCelsius directly.
Example :
#include <dt-bindings/thermal/thermal.h>
i2c@7000c400 {
ads1015: ads1015@4a {
reg = <0x4a>;
compatible = "ads1015";
sampling-frequency = <3300>;
#io-channel-cells = <1>;
};
};
tboard_thermistor: thermal-sensor {
compatible = "generic-adc-thermal";
#thermal-sensor-cells = <0>;
io-channels = <&ads1015 1>;
io-channel-names = "sensor-channel";
temperature-lookup-table = < (-40000) 2578
(-39000) 2577
(-38000) 2576
(-37000) 2575
(-36000) 2574
(-35000) 2573
(-34000) 2572
(-33000) 2571
(-32000) 2569
(-31000) 2568
(-30000) 2567
::::::::::
118000 254
119000 247
120000 240
121000 233
122000 226
123000 220
124000 214
125000 208>;
};
dummy_cool_dev: dummy-cool-dev {
compatible = "dummy-cooling-dev";
#cooling-cells = <2>; /* min followed by max */
};
thermal-zones {
Tboard {
polling-delay = <15000>; /* milliseconds */
polling-delay-passive = <0>; /* milliseconds */
thermal-sensors = <&tboard_thermistor>;
trips {
therm_est_trip: therm_est_trip {
temperature = <40000>;
type = "active";
hysteresis = <1000>;
};
};
cooling-maps {
map0 {
trip = <&therm_est_trip>;
cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
contribution = <100>;
};
};
};
};
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