forked from Minki/linux
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
|
||
|
|
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>;
|
||
|
|
};
|