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Linux/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");
103 

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