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/consumer.h>
  19 #include <linux/of_platform.h>
  20 #include <linux/module.h>
  21
  22 /*
  23  * Hold configuration here, cannot be more than one instance of the driver
  24  * since pm_power_off itself is global.
  25  */
  26 static struct gpio_desc *reset_gpio;
  27
  28 static void gpio_poweroff_do_poweroff(void)
  29 {
  30         BUG_ON(!reset_gpio);
  31
  32         /* drive it active, also inactive->active edge */
  33         gpiod_direction_output(reset_gpio, 1);
  34         mdelay(100);
  35         /* drive inactive, also active->inactive edge */
  36         gpiod_set_value(reset_gpio, 0);
  37         mdelay(100);
  38
  39         /* drive it active, also inactive->active edge */
  40         gpiod_set_value(reset_gpio, 1);
  41
  42         /* give it some time */
  43         mdelay(3000);
  44
  45         WARN_ON(1);
  46 }
  47
  48 static int gpio_poweroff_probe(struct platform_device *pdev)
  49 {
  50         bool input = false;
  51         enum gpiod_flags flags;
  52
  53         /* If a pm_power_off function has already been added, leave it alone */
  54         if (pm_power_off != NULL) {
  55                 dev_err(&pdev->dev,
  56                         "%s: pm_power_off function already registered",
  57                        __func__);
  58                 return -EBUSY;
  59         }
  60
  61         input = of_property_read_bool(pdev->dev.of_node, "input");
  62         if (input)
  63                 flags = GPIOD_IN;
  64         else
  65                 flags = GPIOD_OUT_LOW;
  66
  67         reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
  68         if (IS_ERR(reset_gpio))
  69                 return PTR_ERR(reset_gpio);
  70
  71         pm_power_off = &gpio_poweroff_do_poweroff;
  72         return 0;
  73 }
  74
  75 static int gpio_poweroff_remove(struct platform_device *pdev)
  76 {
  77         if (pm_power_off == &gpio_poweroff_do_poweroff)
  78                 pm_power_off = NULL;
  79
  80         return 0;
  81 }
  82
  83 static const struct of_device_id of_gpio_poweroff_match[] = {
  84         { .compatible = "gpio-poweroff", },
  85         {},
  86 };
  87
  88 static struct platform_driver gpio_poweroff_driver = {
  89         .probe = gpio_poweroff_probe,
  90         .remove = gpio_poweroff_remove,
  91         .driver = {
  92                 .name = "poweroff-gpio",
  93                 .of_match_table = of_gpio_poweroff_match,
  94         },
  95 };
  96
  97 module_platform_driver(gpio_poweroff_driver);
  98
  99 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 100 MODULE_DESCRIPTION("GPIO poweroff driver");
 101 MODULE_LICENSE("GPL v2");
 102 MODULE_ALIAS("platform:poweroff-gpio");