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Diffstat (limited to 'Documentation/devicetree/bindings/gpio/gpio-restart.txt')
| -rw-r--r-- | Documentation/devicetree/bindings/gpio/gpio-restart.txt | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio-restart.txt b/Documentation/devicetree/bindings/gpio/gpio-restart.txt new file mode 100644 index 000000000000..af3701bc15c4 --- /dev/null +++ b/Documentation/devicetree/bindings/gpio/gpio-restart.txt @@ -0,0 +1,54 @@ +Drive a GPIO line that can be used to restart the system from a restart +handler. + +This binding supports level and edge triggered reset. At driver load +time, the driver will request the given gpio line and install a restart +handler. If the optional properties 'open-source' is not found, the GPIO line +will be driven in the inactive state. Otherwise its not driven until +the restart is initiated. + +When the system is restarted, the restart handler will be invoked in +priority order. The gpio is configured as an output, and driven active, +triggering a level triggered reset condition. This will also cause an +inactive->active edge condition, triggering positive edge triggered +reset. After a delay specified by active-delay, the GPIO is set to +inactive, thus causing an active->inactive edge, triggering negative edge +triggered reset. After a delay specified by inactive-delay, the GPIO +is driven active again. After a delay specified by wait-delay, the +restart handler completes allowing other restart handlers to be attempted. + +Required properties: +- compatible : should be "gpio-restart". +- gpios : The GPIO to set high/low, see "gpios property" in + Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be + low to reset the board set it to "Active Low", otherwise set + gpio to "Active High". + +Optional properties: +- open-source : Treat the GPIO as being open source and defer driving + it to when the restart is initiated. If this optional property is not + specified, the GPIO is initialized as an output in its inactive state. +- priority : A priority ranging from 0 to 255 (default 128) according to + the following guidelines: + 0: Restart handler of last resort, with limited restart + capabilities + 128: Default restart handler; use if no other restart handler is + expected to be available, and/or if restart functionality is + sufficient to restart the entire system + 255: Highest priority restart handler, will preempt all other + restart handlers +- active-delay: Delay (default 100) to wait after driving gpio active [ms] +- inactive-delay: Delay (default 100) to wait after driving gpio inactive [ms] +- wait-delay: Delay (default 3000) to wait after completing restart + sequence [ms] + +Examples: + +gpio-restart { + compatible = "gpio-restart"; + gpios = <&gpio 4 0>; + priority = <128>; + active-delay = <100>; + inactive-delay = <100>; + wait-delay = <3000>; +}; |