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_is_valid(gpio_num));
  33
  34         /* drive it active, also inactive->active edge */
  35         gpio_direction_output(gpio_num, !gpio_active_low);
  36         mdelay(100);
  37         /* drive inactive, also active->inactive edge */
  38         gpio_set_value(gpio_num, gpio_active_low);
  39         mdelay(100);
  40
  41         /* drive it active, also inactive->active edge */
  42         gpio_set_value(gpio_num, !gpio_active_low);
  43
  44         /* give it some time */
  45         mdelay(3000);
  46
  47         WARN_ON(1);
  48 }
  49
  50 static int gpio_poweroff_probe(struct platform_device *pdev)
  51 {
  52         enum of_gpio_flags flags;
  53         bool input = false;
  54         int ret;
  55
  56         /* If a pm_power_off function has already been added, leave it alone */
  57         if (pm_power_off != NULL) {
  58                 pr_err("%s: pm_power_off function already registered",
  59                        __func__);
  60                 return -EBUSY;
  61         }
  62
  63         gpio_num = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
  64         if (!gpio_is_valid(gpio_num))
  65                 return gpio_num;
  66
  67         gpio_active_low = flags & OF_GPIO_ACTIVE_LOW;
  68
  69         input = of_property_read_bool(pdev->dev.of_node, "input");
  70
  71         ret = gpio_request(gpio_num, "poweroff-gpio");
  72         if (ret) {
  73                 pr_err("%s: Could not get GPIO %d", __func__, gpio_num);
  74                 return ret;
  75         }
  76         if (input) {
  77                 if (gpio_direction_input(gpio_num)) {
  78                         pr_err("Could not set direction of GPIO %d to input",
  79                                gpio_num);
  80                         goto err;
  81                 }
  82         } else {
  83                 if (gpio_direction_output(gpio_num, gpio_active_low)) {
  84                         pr_err("Could not set direction of GPIO %d", gpio_num);
  85                         goto err;
  86                 }
  87         }
  88
  89         pm_power_off = &gpio_poweroff_do_poweroff;
  90         return 0;
  91
  92 err:
  93         gpio_free(gpio_num);
  94         return -ENODEV;
  95 }
  96
  97 static int gpio_poweroff_remove(struct platform_device *pdev)
  98 {
  99         gpio_free(gpio_num);
 100         if (pm_power_off == &gpio_poweroff_do_poweroff)
 101                 pm_power_off = NULL;
 102
 103         return 0;
 104 }
 105
 106 static const struct of_device_id of_gpio_poweroff_match[] = {
 107         { .compatible = "gpio-poweroff", },
 108         {},
 109 };
 110
 111 static struct platform_driver gpio_poweroff_driver = {
 112         .probe = gpio_poweroff_probe,
 113         .remove = gpio_poweroff_remove,
 114         .driver = {
 115                 .name = "poweroff-gpio",
 116                 .owner = THIS_MODULE,
 117                 .of_match_table = of_gpio_poweroff_match,
 118         },
 119 };
 120
 121 module_platform_driver(gpio_poweroff_driver);
 122
 123 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 124 MODULE_DESCRIPTION("GPIO poweroff driver");
 125 MODULE_LICENSE("GPL v2");
 126 MODULE_ALIAS("platform:poweroff-gpio");