1Driver a GPIO line that can be used to turn the power off.
2
3The driver supports both level triggered and edge triggered power off.
4At driver load time, the driver will request the given gpio line and
5install a handler to power off the system. If the optional properties
6'input' is not found, the GPIO line will be driven in the inactive
7state. Otherwise its configured as an input.
8
9When the power-off handler is called, the gpio is configured as an
10output, and drive active, so triggering a level triggered power off
11condition. This will also cause an inactive->active edge condition, so
12triggering positive edge triggered power off. After a delay of 100ms,
13the GPIO is set to inactive, thus causing an active->inactive edge,
14triggering negative edge triggered power off. After another 100ms
15delay the GPIO is driver active again. If the power is still on and
16the CPU still running after a 3000ms delay, a WARN_ON(1) is emitted.
17
18Required properties:
19- compatible : should be "gpio-poweroff".
20- gpios : The GPIO to set high/low, see "gpios property" in
21  Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be
22  low to power down the board set it to "Active Low", otherwise set
23  gpio to "Active High".
24
25Optional properties:
26- input : Initially configure the GPIO line as an input. Only reconfigure
27  it to an output when the power-off handler is called. If this optional
28  property is not specified, the GPIO is initialized as an output in its
29  inactive state.
30- active-delay-ms: Delay (default 100) to wait after driving gpio active
31- inactive-delay-ms: Delay (default 100) to wait after driving gpio inactive
32- timeout-ms: Time to wait before asserting a WARN_ON(1). If nothing is
33              specified, 3000 ms is used.
34
35Examples:
36
37gpio-poweroff {
38	compatible = "gpio-poweroff";
39	gpios = <&gpio 4 0>;
40	timeout-ms = <3000>;
41};
42