arch/arm/boot/dts/overlays/gpio-fan-overlay.dts

   1 /*
   2  * Overlay for the Raspberry Pi GPIO Fan @ BCM GPIO12.
   3  * References:
   4  *      - https://www.raspberrypi.org/forums/viewtopic.php?f=107&p=1367135#p1365084
   5  *
   6  * Optional parameters:
   7  *      - "gpiopin"     - BCM number of the pin driving the fan, default 12 (GPIO12);
   8  *      - "temp"        - CPU temperature at which fan is started in millicelsius, default 55000;
   9  *
  10  * Requires:
  11  *      - kernel configurations: CONFIG_SENSORS_GPIO_FAN=m;
  12  *      - kernel rebuild;
  13  *      - N-MOSFET connected to gpiopin, 2N7002-[https://en.wikipedia.org/wiki/2N7000];
  14  *      - DC Fan connected to N-MOSFET Drain terminal, a 12V fan is working fine and quite silently;
  15  *        [https://www.tme.eu/en/details/ee40101s1-999-a/dc12v-fans/sunon/ee40101s1-1000u-999/]
  16  *
  17  *                   ┌─────────────────────┐
  18  *                   │Fan negative terminal│
  19  *                   └┬────────────────────┘
  20  *                    │D
  21  *             G   │──┘
  22  * [GPIO12]──────┤ │<─┐  2N7002
  23  *                 │──┤
  24  *                    │S
  25  *                   ─┴─
  26  *                   GND
  27  *
  28  * Build:
  29  *      - `sudo dtc -W no-unit_address_vs_reg -@ -I dts -O dtb -o /boot/overlays/gpio-fan.dtbo gpio-fan-overlay.dts`
  30  * Activate:
  31  *      - sudo nano /boot/config.txt add "dtoverlay=gpio-fan" or "dtoverlay=gpio-fan,gpiopin=12,temp=45000"
  32  *       or
  33  *      - sudo sh -c 'printf "\n# Enable PI GPIO-Fan Default\ndtoverlay=gpio-fan\n" >> /boot/config.txt'
  34  *      - sudo sh -c 'printf "\n# Enable PI GPIO-Fan Custom\ndtoverlay=gpio-fan,gpiopin=12,temp=45000\n" >> /boot/config.txt'
  35  *
  36  */
  37 /dts-v1/;
  38 /plugin/;
  39
  40 / {
  41         compatible = "brcm,bcm2835";
  42
  43         fragment@0 {
  44                 target-path = "/";
  45                 __overlay__ {
  46                         fan0: gpio-fan@0 {
  47                                 compatible = "gpio-fan";
  48                                 gpios = <&gpio 12 0>;
  49                                 gpio-fan,speed-map = <0    0>,
  50                                                                          <5000 1>;
  51                                 #cooling-cells = <2>;
  52                         };
  53                 };
  54         };
  55
  56         fragment@1 {
  57                 target = <&cpu_thermal>;
  58                 polling-delay = <2000>; /* milliseconds */
  59                 __overlay__ {
  60                         trips {
  61                                 cpu_hot: trip-point@0 {
  62                                         temperature = <55000>;  /* (millicelsius) Fan started at 55°C */
  63                                         hysteresis = <10000>;   /* (millicelsius) Fan stopped at 45°C */
  64                                         type = "active";
  65                                 };
  66                         };
  67                         cooling-maps {
  68                                 map0 {
  69                                         trip = <&cpu_hot>;
  70                                         cooling-device = <&fan0 1 1>;
  71                                 };
  72                         };
  73                 };
  74         };
  75         __overrides__ {
  76                 gpiopin = <&fan0>,"gpios:4", <&fan0>,"brcm,pins:0";
  77                 temp = <&cpu_hot>,"temperature:0";
  78                 hyst = <&cpu_hot>,"hysteresis:0";
  79         };
  80 };