Documentation/devicetree/bindings/thermal/thermal-generic-adc.txt

   1 General Purpose Analog To Digital Converter (ADC) based thermal sensor.
   2
   3 On some of platforms, thermal sensor like thermistors are connected to
   4 one of ADC channel and sensor resistance is read via voltage across the
   5 sensor resistor. The voltage read across the sensor is mapped to
   6 temperature using voltage-temperature lookup table.
   7
   8 Required properties:
   9 ===================
  10 - compatible:                Must be "generic-adc-thermal".
  11 - temperature-lookup-table:  Two dimensional array of Integer; lookup table
  12                              to map the relation between ADC value and
  13                              temperature. When ADC is read, the value is
  14                              looked up on the table to get the equivalent
  15                              temperature.
  16                              The first value of the each row of array is the
  17                              temperature in milliCelsius and second value of
  18                              the each row of array is the ADC read value.
  19 - #thermal-sensor-cells:     Should be 1. See ./thermal.txt for a description
  20                              of this property.
  21
  22 Example :
  23 #include <dt-bindings/thermal/thermal.h>
  24
  25 i2c@7000c400 {
  26         ads1015: ads1015@4a {
  27                 reg = <0x4a>;
  28                 compatible = "ads1015";
  29                 sampling-frequency = <3300>;
  30                 #io-channel-cells = <1>;
  31         };
  32 };
  33
  34 tboard_thermistor: thermal-sensor {
  35         compatible = "generic-adc-thermal";
  36         #thermal-sensor-cells = <0>;
  37         io-channels = <&ads1015 1>;
  38         io-channel-names = "sensor-channel";
  39         temperature-lookup-table = <    (-40000) 2578
  40                                         (-39000) 2577
  41                                         (-38000) 2576
  42                                         (-37000) 2575
  43                                         (-36000) 2574
  44                                         (-35000) 2573
  45                                         (-34000) 2572
  46                                         (-33000) 2571
  47                                         (-32000) 2569
  48                                         (-31000) 2568
  49                                         (-30000) 2567
  50                                         ::::::::::
  51                                         118000 254
  52                                         119000 247
  53                                         120000 240
  54                                         121000 233
  55                                         122000 226
  56                                         123000 220
  57                                         124000 214
  58                                         125000 208>;
  59 };
  60
  61 dummy_cool_dev: dummy-cool-dev {
  62         compatible = "dummy-cooling-dev";
  63         #cooling-cells = <2>; /* min followed by max */
  64 };
  65
  66 thermal-zones {
  67         Tboard {
  68                 polling-delay = <15000>; /* milliseconds */
  69                 polling-delay-passive = <0>; /* milliseconds */
  70                 thermal-sensors = <&tboard_thermistor>;
  71
  72                 trips {
  73                         therm_est_trip: therm_est_trip {
  74                                 temperature = <40000>;
  75                                 type = "active";
  76                                 hysteresis = <1000>;
  77                         };
  78                 };
  79
  80                 cooling-maps {
  81                         map0 {
  82                                 trip = <&therm_est_trip>;
  83                                 cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
  84                                 contribution = <100>;
  85                         };
  86
  87                 };
  88         };
  89 };