Commit | Line | Data |
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371bb20d DR |
1 | Drive a GPIO line that can be used to restart the system from a restart |
2 | handler. | |
3 | ||
4 | This binding supports level and edge triggered reset. At driver load | |
5 | time, the driver will request the given gpio line and install a restart | |
6 | handler. If the optional properties 'open-source' is not found, the GPIO line | |
7 | will be driven in the inactive state. Otherwise its not driven until | |
8 | the restart is initiated. | |
9 | ||
10 | When the system is restarted, the restart handler will be invoked in | |
11 | priority order. The gpio is configured as an output, and driven active, | |
12 | triggering a level triggered reset condition. This will also cause an | |
13 | inactive->active edge condition, triggering positive edge triggered | |
14 | reset. After a delay specified by active-delay, the GPIO is set to | |
15 | inactive, thus causing an active->inactive edge, triggering negative edge | |
16 | triggered reset. After a delay specified by inactive-delay, the GPIO | |
17 | is driven active again. After a delay specified by wait-delay, the | |
18 | restart handler completes allowing other restart handlers to be attempted. | |
19 | ||
20 | Required properties: | |
21 | - compatible : should be "gpio-restart". | |
22 | - gpios : The GPIO to set high/low, see "gpios property" in | |
23 | Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be | |
24 | low to reset the board set it to "Active Low", otherwise set | |
25 | gpio to "Active High". | |
26 | ||
27 | Optional properties: | |
28 | - open-source : Treat the GPIO as being open source and defer driving | |
29 | it to when the restart is initiated. If this optional property is not | |
30 | specified, the GPIO is initialized as an output in its inactive state. | |
31 | - priority : A priority ranging from 0 to 255 (default 128) according to | |
32 | the following guidelines: | |
33 | 0: Restart handler of last resort, with limited restart | |
34 | capabilities | |
35 | 128: Default restart handler; use if no other restart handler is | |
36 | expected to be available, and/or if restart functionality is | |
37 | sufficient to restart the entire system | |
38 | 255: Highest priority restart handler, will preempt all other | |
39 | restart handlers | |
40 | - active-delay: Delay (default 100) to wait after driving gpio active [ms] | |
41 | - inactive-delay: Delay (default 100) to wait after driving gpio inactive [ms] | |
42 | - wait-delay: Delay (default 3000) to wait after completing restart | |
43 | sequence [ms] | |
44 | ||
45 | Examples: | |
46 | ||
47 | gpio-restart { | |
48 | compatible = "gpio-restart"; | |
49 | gpios = <&gpio 4 0>; | |
50 | priority = <128>; | |
51 | active-delay = <100>; | |
52 | inactive-delay = <100>; | |
53 | wait-delay = <3000>; | |
54 | }; |