path: root/Documentation
diff options
authorAndrew Lunn <andrew@lunn.ch>2013-01-06 11:10:35 +0100
committerJason Cooper <jason@lakedaemon.net>2013-01-06 17:53:00 +0000
commit5343527bbfab3f71f64d8ba5d51ce12dec8d82d0 (patch)
tree42e197b8fb215663bbdd5023226acea16c0b55f5 /Documentation
parent53dfa8e4aa740cc7a19a39d6d4542f856c6b49ae (diff)
Power: gpio-poweroff: Fix documentation and gpio_is_valid
Improve the documentation to clarify level vs edge triggered power off. Improve the comments for level vs edge triggered power off. Make use of gpio_is_valid(). Reported-by: Stephen Warren <swarren@wwwdotorg.org> Signed-off-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: Jason Cooper <jason@lakedaemon.net>
Diffstat (limited to 'Documentation')
1 files changed, 17 insertions, 3 deletions
diff --git a/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt b/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
index 558cdf3c9ab..d4eab9227ea 100644
--- a/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio-poweroff.txt
@@ -1,4 +1,19 @@
-GPIO line that should be set high/low to power off a device
+Driver a GPIO line that can be used to turn the power off.
+The driver supports both level triggered and edge triggered power off.
+At driver load time, the driver will request the given gpio line and
+install a pm_power_off handler. If the optional properties 'input' is
+not found, the GPIO line will be driven in the inactive
+state. Otherwise its configured as an input.
+When the pm_power_off is called, the gpio is configured as an output,
+and drive active, so triggering a level triggered power off
+condition. This will also cause an inactive->active edge condition, so
+triggering positive edge triggered power off. After a delay of 100ms,
+the GPIO is set to inactive, thus causing an active->inactive edge,
+triggering negative edge triggered power off. After another 100ms
+delay the GPIO is driver active again. If the power is still on and
+the CPU still running after a 3000ms delay, a WARN_ON(1) is emitted.
Required properties:
- compatible : should be "gpio-poweroff".
@@ -13,10 +28,9 @@ Optional properties:
property is not specified, the GPIO is initialized as an output in its
inactive state.
gpio-poweroff {
compatible = "gpio-poweroff";
- gpios = <&gpio 4 0>; /* GPIO 4 Active Low */
+ gpios = <&gpio 4 0>;