drivers/power/reset/gpio-poweroff.c

   1 /*
   2  * Toggles a GPIO pin to power down a device
   3  *
   4  * Jamie Lentin <jm@lentin.co.uk>
   5  * Andrew Lunn <andrew@lunn.ch>
   6  *
   7  * Copyright (C) 2012 Jamie Lentin
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  */
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/delay.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/gpio.h>
  19 #include <linux/of_platform.h>
  20 #include <linux/of_gpio.h>
  21 #include <linux/module.h>
  22
  23 /*
  24  * Hold configuration here, cannot be more than one instance of the driver
  25  * since pm_power_off itself is global.
  26  */
  27 static int gpio_num = -1;
  28 static int gpio_active_low;
  29
  30 static void gpio_poweroff_do_poweroff(void)
  31 {
  32         BUG_ON(gpio_num == -1);
  33
  34         /* drive it active */
  35         gpio_direction_output(gpio_num, !gpio_active_low);
  36         mdelay(100);
  37         /* rising edge or drive inactive */
  38         gpio_set_value(gpio_num, gpio_active_low);
  39         mdelay(100);
  40         /* falling edge */
  41         gpio_set_value(gpio_num, !gpio_active_low);
  42
  43         /* give it some time */
  44         mdelay(3000);
  45
  46         WARN_ON(1);
  47 }
  48
  49 static int __devinit gpio_poweroff_probe(struct platform_device *pdev)
  50 {
  51         enum of_gpio_flags flags;
  52         bool input = false;
  53         int ret;
  54
  55         /* If a pm_power_off function has already been added, leave it alone */
  56         if (pm_power_off != NULL) {
  57                 pr_err("%s: pm_power_off function already registered",
  58                        __func__);
  59                 return -EBUSY;
  60         }
  61
  62         gpio_num = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
  63         if (gpio_num < 0) {
  64                 pr_err("%s: Could not get GPIO configuration: %d",
  65                        __func__, gpio_num);
  66                 return -ENODEV;
  67         }
  68         gpio_active_low = flags & OF_GPIO_ACTIVE_LOW;
  69
  70         if (of_get_property(pdev->dev.of_node, "input", NULL))
  71                 input = true;
  72
  73         ret = gpio_request(gpio_num, "poweroff-gpio");
  74         if (ret) {
  75                 pr_err("%s: Could not get GPIO %d", __func__, gpio_num);
  76                 return ret;
  77         }
  78         if (input) {
  79                 if (gpio_direction_input(gpio_num)) {
  80                         pr_err("Could not set direction of GPIO %d to input",
  81                                gpio_num);
  82                         goto err;
  83                 }
  84         } else {
  85                 if (gpio_direction_output(gpio_num, gpio_active_low)) {
  86                         pr_err("Could not set direction of GPIO %d", gpio_num);
  87                         goto err;
  88                 }
  89         }
  90
  91         pm_power_off = &gpio_poweroff_do_poweroff;
  92         return 0;
  93
  94 err:
  95         gpio_free(gpio_num);
  96         return -ENODEV;
  97 }
  98
  99 static int __devexit gpio_poweroff_remove(struct platform_device *pdev)
 100 {
 101         if (gpio_num != -1)
 102                 gpio_free(gpio_num);
 103         if (pm_power_off == &gpio_poweroff_do_poweroff)
 104                 pm_power_off = NULL;
 105
 106         return 0;
 107 }
 108
 109 static const struct of_device_id of_gpio_poweroff_match[] = {
 110         { .compatible = "gpio-poweroff", },
 111         {},
 112 };
 113
 114 static struct platform_driver gpio_poweroff_driver = {
 115         .probe = gpio_poweroff_probe,
 116         .remove = __devexit_p(gpio_poweroff_remove),
 117         .driver = {
 118                    .name = "poweroff-gpio",
 119                    .owner = THIS_MODULE,
 120                    .of_match_table = of_gpio_poweroff_match,
 121                    },
 122 };
 123
 124 module_platform_driver(gpio_poweroff_driver);
 125
 126 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 127 MODULE_DESCRIPTION("GPIO poweroff driver");
 128 MODULE_LICENSE("GPL");
 129 MODULE_ALIAS("platform:poweroff-gpio");