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>

2 files changed, 32 insertions, 21 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.
 
-
 Examples:
 
 gpio-poweroff {
         compatible = "gpio-poweroff";
-        gpios = <&gpio 4 0>; /* GPIO 4 Active Low */
+        gpios = <&gpio 4 0>;
 };
diff --git a/drivers/power/reset/gpio-poweroff.c b/drivers/power/reset/gpio-poweroff.c
index 0491e5335d0..adc943b3fc3 100644
--- a/drivers/power/reset/gpio-poweroff.c
+++ b/drivers/power/reset/gpio-poweroff.c
@@ -29,15 +29,16 @@ static int gpio_active_low;
 
 static void gpio_poweroff_do_poweroff(void)
 {
-        BUG_ON(gpio_num == -1);
+        BUG_ON(!gpio_is_valid(gpio_num));
 
-        /* drive it active */
+        /* drive it active, also inactive->active edge */
         gpio_direction_output(gpio_num, !gpio_active_low);
         mdelay(100);
-        /* rising edge or drive inactive */
+        /* drive inactive, also active->inactive edge */
         gpio_set_value(gpio_num, gpio_active_low);
         mdelay(100);
-        /* falling edge */
+
+        /* drive it active, also inactive->active edge */
         gpio_set_value(gpio_num, !gpio_active_low);
 
         /* give it some time */
@@ -60,15 +61,12 @@ static int __devinit gpio_poweroff_probe(struct platform_device *pdev)
         }
 
         gpio_num = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
-        if (gpio_num < 0) {
-                pr_err("%s: Could not get GPIO configuration: %d",
-                       __func__, gpio_num);
-                return -ENODEV;
-        }
+        if (!gpio_is_valid(gpio_num))
+                return gpio_num;
+
         gpio_active_low = flags & OF_GPIO_ACTIVE_LOW;
 
-        if (of_get_property(pdev->dev.of_node, "input", NULL))
-                input = true;
+        input = of_property_read_bool(pdev->dev.of_node, "input");
 
         ret = gpio_request(gpio_num, "poweroff-gpio");
         if (ret) {
@@ -98,8 +96,7 @@ err:
 
 static int __devexit gpio_poweroff_remove(struct platform_device *pdev)
 {
-        if (gpio_num != -1)
-                gpio_free(gpio_num);
+        gpio_free(gpio_num);
         if (pm_power_off == &gpio_poweroff_do_poweroff)
                 pm_power_off = NULL;
 
@@ -115,15 +112,15 @@ static struct platform_driver gpio_poweroff_driver = {
         .probe = gpio_poweroff_probe,
         .remove = __devexit_p(gpio_poweroff_remove),
         .driver = {
-                   .name = "poweroff-gpio",
-                   .owner = THIS_MODULE,
-                   .of_match_table = of_gpio_poweroff_match,
-                   },
+                .name = "poweroff-gpio",
+                .owner = THIS_MODULE,
+                .of_match_table = of_gpio_poweroff_match,
+        },
 };
 
 module_platform_driver(gpio_poweroff_driver);
 
 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 MODULE_DESCRIPTION("GPIO poweroff driver");
-MODULE_LICENSE("GPL");
+MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("platform:poweroff-gpio");