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