overlays: Add gpio-shutdown overlay

[matthijskooijman]

This overlay facilitates the addition of a powerbutton by converting
GPIO edges into KEY_POWER keypresses, which can be handled by
systemd-logind to shut down the system.

The overlay was separately tested on:

• Raspberry Pi Zero W running Linux telegraaf 4.9.28+ BCM270x: Make bcm2835-pm-wdt and bcm2835-rng available #998 Mon May 15 16:50:35 BST 2017 armv6l GNU/Linux
• Raspberry Pi B+ running Linux raspberrypi 4.4.50+ bcm2708_fb: Add ARCH_BCM2835 support #970 Mon Feb 20 19:12:50 GMT 2017 armv6l GNU/Linux
• Rasbperry Pi B running Linux raspberrypi 4.4.34+ SPI: merge upstream patches for spi-bcm2835 that went into mainline (for 4.1) #930 Wed Nov 23 15:12:30 GMT 2016 armv6l GNU/Linux

I tested manually using dtc -@ -I dts -O dtb -o gpio-shutdown.dtbo gpio-shutdown-overlay.dts. I did not test compilation inside the kernel tree, for I have not got the environment set up for that.

For some more background, see the comments in the overlay source file and this blogpost: http://www.stderr.nl/Blog/Hardware/RaspberryPi/PowerButton.html

[pelwell]

The kernel patches build the overlay as expected. Nice job, especially on the comments.

[matthijskooijman]

Thanks, great to have it merged so fast :-D

[pali]

Overlay in this pull request does not work for RPI 1 rev 1. RPI 1 rev 1 uses GPIO1 instead of GPIO3.

I modified original overlay for RPI 1 rev 1 by applying following diff and then it start working on RPI 1 rev 1 too:

--- gpio-shutdown-overlay.dts	2017-07-07 02:09:12.000000000 +0200
+++ gpio-shutdown-rpi1-overlay.dts	2018-12-25 14:58:42.000000000 +0100
@@ -1,13 +1,14 @@
 // Definitions for gpio-poweroff module
+// Modified for RPI 1 rev 1 (changed GPIO3 to gpio GPIO1)
 /dts-v1/;
 /plugin/;
 
 // This overlay sets up an input device that generates KEY_POWER events
-// when a given GPIO pin changes. It defaults to using GPIO3, which can
+// when a given GPIO pin changes. It defaults to using GPIO1, which can
 // also be used to wake up (start) the Rpi again after shutdown. Since
 // wakeup is active-low, this defaults to active-low with a pullup
 // enabled, but all of this can be changed using overlay parameters (but
-// note that GPIO3 has an external pullup on at least some boards).
+// note that GPIO1 has an external pullup on at least some boards).
 
 / {
 	compatible = "brcm,bcm2708";
@@ -22,8 +23,8 @@
 			// by a "pinctrl client", as is done below. See:
 			//   https://www.kernel.org/doc/Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
 			//   https://www.kernel.org/doc/Documentation/devicetree/bindings/pinctrl/brcm,bcm2835-gpio.txt
-			pin_state: shutdown_button_pins {
-				brcm,pins = <3>; // gpio number
+			pin_state: shutdown_button_rpi1_pins {
+				brcm,pins = <1>; // gpio number
 				brcm,function = <0>; // 0 = input, 1 = output
 				brcm,pull = <2>; // 0 = none, 1 = pull down, 2 = pull up
 			};
@@ -33,7 +34,7 @@
 		// Add a new device to the /soc devicetree node
 		target-path = "/soc";
 		__overlay__ {
-			shutdown_button {
+			shutdown_button_rpi1 {
 				// Let the gpio-keys driver handle this device. See:
 				// https://www.kernel.org/doc/Documentation/devicetree/bindings/input/gpio-keys.txt
 				compatible = "gpio-keys";
@@ -49,10 +50,10 @@
 				// Define a single key, called "shutdown" that monitors the gpio and sends KEY_POWER
 				// (keycode 116, see
 				// https://github.com/torvalds/linux/blob/v4.12/include/uapi/linux/input-event-codes.h#L190)
-				button: shutdown {
-					label = "shutdown";
+				button: shutdown_rpi1 {
+					label = "shutdown_rpi1";
 					linux,code = <116>; // KEY_POWER
-					gpios = <&gpio 3 1>;
+					gpios = <&gpio 1 1>;
 				};
 			};
 		};
@@ -69,7 +70,7 @@
 		           <&pin_state>,"brcm,pins:0";
 
 		// Allow changing the internal pullup/down state. 0 = none, 1 = pulldown, 2 = pullup
-		// Note that GPIO3 and GPIO2 are the I2c pins and have an external pullup (at least
+		// Note that GPIO1 and GPIO0 are the I2c pins and have an external pullup (at least
                 // on some boards).
 		gpio_pull = <&pin_state>,"brcm,pull:0";
 

[matthijskooijman]

Rather than modifying the overlay, you can just specify a different GPIO as an argument. E.g.

dtoverlay=gpio-shutdown,gpio_pin=1

Or did you try this and did it not work? It might be good to add this to the documentation somewhere (i.e. that this version needs gpio1 rather than 3).

[pelwell]

@matthijskooijman Thank you for saving me the typing!

[pali]

@matthijskooijman I have not know that it is possible to specify different GPIO... Where to write that line? Directly to config.txt, replacing my current dtoverlay=gpio-shutdown-rpi1 line? Or it is argument for kernel via cmdline?

[matthijskooijman]

The former. See also the docs

[pali]

@matthijskooijman Now I tested dtoverlay=gpio-shutdown,gpio_pin=1 and it is working fine without need to modification of gpio-shutdown-overlay.dts like I used to use it til now.

So thanks for simplification of setup for my RPI 1 rev 1.

What about updating that README file by adding a note that for RPI 1 rev 1 it is needed to change gpio_pin parameter from default value to 1?