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