0001 General Purpose Analog To Digital Converter (ADC) based thermal sensor.
0002
0003 On some of platforms, thermal sensor like thermistors are connected to
0004 one of ADC channel and sensor resistance is read via voltage across the
0005 sensor resistor. The voltage read across the sensor is mapped to
0006 temperature using voltage-temperature lookup table.
0007
0008 Required properties:
0009 ===================
0010 - compatible: Must be "generic-adc-thermal".
0011 - #thermal-sensor-cells: Should be 1. See Documentation/devicetree/bindings/thermal/thermal-sensor.yaml for a description
0012 of this property.
0013 Optional properties:
0014 ===================
0015 - temperature-lookup-table: Two dimensional array of Integer; lookup table
0016 to map the relation between ADC value and
0017 temperature. When ADC is read, the value is
0018 looked up on the table to get the equivalent
0019 temperature.
0020
0021 The first value of the each row of array is the
0022 temperature in milliCelsius and second value of
0023 the each row of array is the ADC read value.
0024
0025 If not specified, driver assumes the ADC channel
0026 gives milliCelsius directly.
0027
0028 Example :
0029 #include <dt-bindings/thermal/thermal.h>
0030
0031 i2c@7000c400 {
0032 ads1015: ads1015@4a {
0033 reg = <0x4a>;
0034 compatible = "ads1015";
0035 sampling-frequency = <3300>;
0036 #io-channel-cells = <1>;
0037 };
0038 };
0039
0040 tboard_thermistor: thermal-sensor {
0041 compatible = "generic-adc-thermal";
0042 #thermal-sensor-cells = <0>;
0043 io-channels = <&ads1015 1>;
0044 io-channel-names = "sensor-channel";
0045 temperature-lookup-table = < (-40000) 2578
0046 (-39000) 2577
0047 (-38000) 2576
0048 (-37000) 2575
0049 (-36000) 2574
0050 (-35000) 2573
0051 (-34000) 2572
0052 (-33000) 2571
0053 (-32000) 2569
0054 (-31000) 2568
0055 (-30000) 2567
0056 ::::::::::
0057 118000 254
0058 119000 247
0059 120000 240
0060 121000 233
0061 122000 226
0062 123000 220
0063 124000 214
0064 125000 208>;
0065 };
0066
0067 dummy_cool_dev: dummy-cool-dev {
0068 compatible = "dummy-cooling-dev";
0069 #cooling-cells = <2>; /* min followed by max */
0070 };
0071
0072 thermal-zones {
0073 Tboard {
0074 polling-delay = <15000>; /* milliseconds */
0075 polling-delay-passive = <0>; /* milliseconds */
0076 thermal-sensors = <&tboard_thermistor>;
0077
0078 trips {
0079 therm_est_trip: therm_est_trip {
0080 temperature = <40000>;
0081 type = "active";
0082 hysteresis = <1000>;
0083 };
0084 };
0085
0086 cooling-maps {
0087 map0 {
0088 trip = <&therm_est_trip>;
0089 cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
0090 contribution = <100>;
0091 };
0092
0093 };
0094 };
0095 };
