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 #define DEFAULT_TIMEOUT_MS 3000
  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 struct gpio_desc *reset_gpio;
  28 static u32 timeout = DEFAULT_TIMEOUT_MS;
  29
  30 static void gpio_poweroff_do_poweroff(void)
  31 {
  32         BUG_ON(!reset_gpio);
  33
  34         /* drive it active, also inactive->active edge */
  35         gpiod_direction_output(reset_gpio, 1);
  36         mdelay(100);
  37         /* drive inactive, also active->inactive edge */
  38         gpiod_set_value_cansleep(reset_gpio, 0);
  39         mdelay(100);
  40
  41         /* drive it active, also inactive->active edge */
  42         gpiod_set_value_cansleep(reset_gpio, 1);
  43
  44         /* give it some time */
  45         mdelay(timeout);
  46
  47         WARN_ON(1);
  48 }
  49
  50 static int gpio_poweroff_probe(struct platform_device *pdev)
  51 {
  52         bool input = false;
  53         enum gpiod_flags flags;
  54
  55         /* If a pm_power_off function has already been added, leave it alone */
  56         if (pm_power_off != NULL) {
  57                 dev_err(&pdev->dev,
  58                         "%s: pm_power_off function already registered",
  59                        __func__);
  60                 return -EBUSY;
  61         }
  62
  63         input = device_property_read_bool(&pdev->dev, "input");
  64         if (input)
  65                 flags = GPIOD_IN;
  66         else
  67                 flags = GPIOD_OUT_LOW;
  68
  69         device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
  70
  71         reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
  72         if (IS_ERR(reset_gpio))
  73                 return PTR_ERR(reset_gpio);
  74
  75         pm_power_off = &gpio_poweroff_do_poweroff;
  76         return 0;
  77 }
  78
  79 static int gpio_poweroff_remove(struct platform_device *pdev)
  80 {
  81         if (pm_power_off == &gpio_poweroff_do_poweroff)
  82                 pm_power_off = NULL;
  83
  84         return 0;
  85 }
  86
  87 static const struct of_device_id of_gpio_poweroff_match[] = {
  88         { .compatible = "gpio-poweroff", },
  89         {},
  90 };
  91
  92 static struct platform_driver gpio_poweroff_driver = {
  93         .probe = gpio_poweroff_probe,
  94         .remove = gpio_poweroff_remove,
  95         .driver = {
  96                 .name = "poweroff-gpio",
  97                 .of_match_table = of_gpio_poweroff_match,
  98         },
  99 };
 100
 101 module_platform_driver(gpio_poweroff_driver);
 102
 103 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 104 MODULE_DESCRIPTION("GPIO poweroff driver");
 105 MODULE_LICENSE("GPL v2");
 106 MODULE_ALIAS("platform:poweroff-gpio");