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
7 title: GPIO controlled reset
8
9 maintainers:
10 - Sebastian Reichel <sre@kernel.org>
11
12 description: >
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
28 allOf:
29 - $ref: restart-handler.yaml#
30
31 properties:
32 compatible:
33 const: gpio-restart
34
35 gpios:
36 description: The GPIO to set high/low, see "gpios property" in
37 Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be low to reset the board
38 set it to "Active Low", otherwise set GPIO to "Active High".
39
40 open-source:
41 $ref: /schemas/types.yaml#/definitions/flag
42 description: Treat the GPIO as being open source and defer driving it to when the restart is
43 initiated. If this optional property is not specified, the GPIO is initialized as an output
44 in its inactive state.
45
46 priority:
47 default: 129
48
49 active-delay:
50 $ref: /schemas/types.yaml#/definitions/uint32
51 description: Delay (default 100) to wait after driving gpio active [ms]
52 default: 100
53
54 inactive-delay:
55 $ref: /schemas/types.yaml#/definitions/uint32
56 description: Delay (default 100) to wait after driving gpio inactive [ms]
57 default: 100
58
59 wait-delay:
60 $ref: /schemas/types.yaml#/definitions/uint32
61 description: Delay (default 3000) to wait after completing restart sequence [ms]
62 default: 100
63
64 additionalProperties: false
65
66 required:
67 - compatible
68 - gpios
69
70 examples:
71 - |
72 gpio-restart {
73 compatible = "gpio-restart";
74 gpios = <&gpio 4 0>;
75 priority = <128>;
76 active-delay = <100>;
77 inactive-delay = <100>;
78 wait-delay = <3000>;
79 };
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