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 static u32 active_delay = 100;
  30 static u32 inactive_delay = 100;
  31
  32 static void gpio_poweroff_do_poweroff(void)
  33 {
  34         BUG_ON(!reset_gpio);
  35
  36         /* drive it active, also inactive->active edge */
  37         gpiod_direction_output(reset_gpio, 1);
  38         mdelay(active_delay);
  39
  40         /* drive inactive, also active->inactive edge */
  41         gpiod_set_value_cansleep(reset_gpio, 0);
  42         mdelay(inactive_delay);
  43
  44         /* drive it active, also inactive->active edge */
  45         gpiod_set_value_cansleep(reset_gpio, 1);
  46
  47         /* give it some time */
  48         mdelay(timeout);
  49
  50         WARN_ON(1);
  51 }
  52
  53 static int gpio_poweroff_probe(struct platform_device *pdev)
  54 {
  55         bool input = false;
  56         enum gpiod_flags flags;
  57
  58         /* If a pm_power_off function has already been added, leave it alone */
  59         if (pm_power_off != NULL) {
  60                 dev_err(&pdev->dev,
  61                         "%s: pm_power_off function already registered",
  62                        __func__);
  63                 return -EBUSY;
  64         }
  65
  66         input = device_property_read_bool(&pdev->dev, "input");
  67         if (input)
  68                 flags = GPIOD_IN;
  69         else
  70                 flags = GPIOD_OUT_LOW;
  71
  72         device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);
  73         device_property_read_u32(&pdev->dev, "inactive-delay-ms",
  74                                  &inactive_delay);
  75         device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
  76
  77         reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
  78         if (IS_ERR(reset_gpio))
  79                 return PTR_ERR(reset_gpio);
  80
  81         pm_power_off = &gpio_poweroff_do_poweroff;
  82         return 0;
  83 }
  84
  85 static int gpio_poweroff_remove(struct platform_device *pdev)
  86 {
  87         if (pm_power_off == &gpio_poweroff_do_poweroff)
  88                 pm_power_off = NULL;
  89
  90         return 0;
  91 }
  92
  93 static const struct of_device_id of_gpio_poweroff_match[] = {
  94         { .compatible = "gpio-poweroff", },
  95         {},
  96 };
  97
  98 static struct platform_driver gpio_poweroff_driver = {
  99         .probe = gpio_poweroff_probe,
 100         .remove = gpio_poweroff_remove,
 101         .driver = {
 102                 .name = "poweroff-gpio",
 103                 .of_match_table = of_gpio_poweroff_match,
 104         },
 105 };
 106
 107 module_platform_driver(gpio_poweroff_driver);
 108
 109 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
 110 MODULE_DESCRIPTION("GPIO poweroff driver");
 111 MODULE_LICENSE("GPL v2");
 112 MODULE_ALIAS("platform:poweroff-gpio");