1# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
2%YAML 1.2
3---
4$id: http://devicetree.org/schemas/power/reset/gpio-restart.yaml#
5$schema: http://devicetree.org/meta-schemas/core.yaml#
6
7title: GPIO controlled reset
8
9maintainers:
10  - Sebastian Reichel <sre@kernel.org>
11
12description: >
13  Drive a GPIO line that can be used to restart the system from a restart handler.
14
15  This binding supports level and edge triggered reset.  At driver load time, the driver will
16  request the given gpio line and install a restart handler. If the optional properties
17  'open-source' is not found, the GPIO line will be driven in the inactive state.  Otherwise its
18  not driven until the restart is initiated.
19
20  When the system is restarted, the restart handler will be invoked in priority order.  The GPIO
21  is configured as an output, and driven active, triggering a level triggered reset condition.
22  This will also cause an inactive->active edge condition, triggering positive edge triggered
23  reset. After a delay specified by active-delay, the GPIO is set to inactive, thus causing an
24  active->inactive edge, triggering negative edge triggered reset. After a delay specified by
25  inactive-delay, the GPIO is driven active again.  After a delay specified by wait-delay, the
26  restart handler completes allowing other restart handlers to be attempted.
27
28properties:
29  compatible:
30    const: gpio-restart
31
32  gpios:
33    description: The GPIO to set high/low, see "gpios property" in
34      Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be low to reset the board
35      set it to "Active Low", otherwise set GPIO to "Active High".
36
37  open-source:
38    $ref: /schemas/types.yaml#/definitions/flag
39    description: Treat the GPIO as being open source and defer driving it to when the restart is
40      initiated.  If this optional property is not specified, the GPIO is initialized as an output
41      in its inactive state.
42
43  priority:
44    $ref: /schemas/types.yaml#/definitions/uint32
45    description: |
46      A priority ranging from 0 to 255 (default 129) according to the following guidelines:
47
48        0:   Restart handler of last resort, with limited restart capabilities.
49        128: Default restart handler; use if no other restart handler is expected to be available,
50             and/or if restart functionality is sufficient to restart the entire system.
51        255: Highest priority restart handler, will preempt all other restart handlers.
52    minimum: 0
53    maximum: 255
54    default: 129
55
56  active-delay:
57    $ref: /schemas/types.yaml#/definitions/uint32
58    description: Delay (default 100) to wait after driving gpio active [ms]
59    default: 100
60
61  inactive-delay:
62    $ref: /schemas/types.yaml#/definitions/uint32
63    description: Delay (default 100) to wait after driving gpio inactive [ms]
64    default: 100
65
66  wait-delay:
67    $ref: /schemas/types.yaml#/definitions/uint32
68    description: Delay (default 3000) to wait after completing restart sequence [ms]
69    default: 100
70
71additionalProperties: false
72
73required:
74  - compatible
75  - gpios
76
77examples:
78  - |
79    gpio-restart {
80      compatible = "gpio-restart";
81      gpios = <&gpio 4 0>;
82      priority = <128>;
83      active-delay = <100>;
84      inactive-delay = <100>;
85      wait-delay = <3000>;
86    };
87