/*
 * Overlay for the Raspberry Pi GPIO Fan @ BCM GPIO12.
 * References: 
 *	- https://www.raspberrypi.org/forums/viewtopic.php?f=107&p=1367135#p1365084
 *
 * Optional parameters:
 *	- "gpiopin"	- BCM number of the pin driving the fan, default 12 (GPIO12);
 * 	- "temp"	- CPU temperature at which fan is started in millicelsius, default 55000;
 *
 * Requires:
 *	- kernel configurations: CONFIG_SENSORS_GPIO_FAN=m;
 *	- kernel rebuild;
 *	- N-MOSFET connected to gpiopin, 2N7002-[https://en.wikipedia.org/wiki/2N7000];
 *	- DC Fan connected to N-MOSFET Drain terminal, a 12V fan is working fine and quite silently;
 *	  [https://www.tme.eu/en/details/ee40101s1-999-a/dc12v-fans/sunon/ee40101s1-1000u-999/]
 *
 *                   ┌─────────────────────┐
 *                   │Fan negative terminal│
 *                   └┬────────────────────┘
 *                    │D
 *             G   │──┘
 * [GPIO12]──────┤ │<─┐  2N7002
 *                 │──┤
 *                    │S
 *                   ─┴─
 *                   GND
 *
 * Build:
 * 	- `sudo dtc -W no-unit_address_vs_reg -@ -I dts -O dtb -o /boot/overlays/gpio-fan.dtbo gpio-fan-overlay.dts`
 * Activate:
 *	- sudo nano /boot/config.txt add "dtoverlay=gpio-fan" or "dtoverlay=gpio-fan,gpiopin=12,temp=45000"
 *	 or
 *	- sudo sh -c 'printf "\n# Enable PI GPIO-Fan Default\ndtoverlay=gpio-fan\n" >> /boot/config.txt'
 *	- sudo sh -c 'printf "\n# Enable PI GPIO-Fan Custom\ndtoverlay=gpio-fan,gpiopin=12,temp=45000\n" >> /boot/config.txt'
 *
 */
/dts-v1/;
/plugin/;

/ {
	compatible = "brcm,bcm2835";

	fragment@0 {
		target-path = "/";
		__overlay__ {
			fan0: gpio-fan@0 {
				compatible = "gpio-fan";
				gpios = <&gpio 12 0>;
				gpio-fan,speed-map = <0    0>,
									 <5000 1>;
				#cooling-cells = <2>;
			};
		};
	};

	fragment@1 {
		target = <&cpu_thermal>;
		polling-delay = <2000>;	/* milliseconds */
		__overlay__ {
			trips {
				cpu_hot: trip-point@0 {
					temperature = <55000>;	/* (millicelsius) Fan started at 55°C */
					hysteresis = <10000>;	/* (millicelsius) Fan stopped at 45°C */
					type = "active";
				};
			};
			cooling-maps {
				map0 {
					trip = <&cpu_hot>;
					cooling-device = <&fan0 1 1>;
				};
			};
		};
	};
	__overrides__ {
		gpiopin = <&fan0>,"gpios:4", <&fan0>,"brcm,pins:0";
		temp = <&cpu_hot>,"temperature:0";
		hyst = <&cpu_hot>,"hysteresis:0";
	};
};