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_num == -1); 33 34 /* drive it active */ 35 gpio_direction_output(gpio_num, !gpio_active_low); 36 mdelay(100); 37 /* rising edge or drive inactive */ 38 gpio_set_value(gpio_num, gpio_active_low); 39 mdelay(100); 40 /* falling edge */ 41 gpio_set_value(gpio_num, !gpio_active_low); 42 43 /* give it some time */ 44 mdelay(3000); 45 46 WARN_ON(1); 47 } 48 49 static int __devinit gpio_poweroff_probe(struct platform_device *pdev) 50 { 51 enum of_gpio_flags flags; 52 bool input = false; 53 int ret; 54 55 /* If a pm_power_off function has already been added, leave it alone */ 56 if (pm_power_off != NULL) { 57 pr_err("%s: pm_power_off function already registered", 58 __func__); 59 return -EBUSY; 60 } 61 62 gpio_num = of_get_gpio_flags(pdev->dev.of_node, 0, &flags); 63 if (gpio_num < 0) { 64 pr_err("%s: Could not get GPIO configuration: %d", 65 __func__, gpio_num); 66 return -ENODEV; 67 } 68 gpio_active_low = flags & OF_GPIO_ACTIVE_LOW; 69 70 if (of_get_property(pdev->dev.of_node, "input", NULL)) 71 input = true; 72 73 ret = gpio_request(gpio_num, "poweroff-gpio"); 74 if (ret) { 75 pr_err("%s: Could not get GPIO %d", __func__, gpio_num); 76 return ret; 77 } 78 if (input) { 79 if (gpio_direction_input(gpio_num)) { 80 pr_err("Could not set direction of GPIO %d to input", 81 gpio_num); 82 goto err; 83 } 84 } else { 85 if (gpio_direction_output(gpio_num, gpio_active_low)) { 86 pr_err("Could not set direction of GPIO %d", gpio_num); 87 goto err; 88 } 89 } 90 91 pm_power_off = &gpio_poweroff_do_poweroff; 92 return 0; 93 94 err: 95 gpio_free(gpio_num); 96 return -ENODEV; 97 } 98 99 static int __devexit gpio_poweroff_remove(struct platform_device *pdev) 100 { 101 if (gpio_num != -1) 102 gpio_free(gpio_num); 103 if (pm_power_off == &gpio_poweroff_do_poweroff) 104 pm_power_off = NULL; 105 106 return 0; 107 } 108 109 static const struct of_device_id of_gpio_poweroff_match[] = { 110 { .compatible = "gpio-poweroff", }, 111 {}, 112 }; 113 114 static struct platform_driver gpio_poweroff_driver = { 115 .probe = gpio_poweroff_probe, 116 .remove = __devexit_p(gpio_poweroff_remove), 117 .driver = { 118 .name = "poweroff-gpio", 119 .owner = THIS_MODULE, 120 .of_match_table = of_gpio_poweroff_match, 121 }, 122 }; 123 124 module_platform_driver(gpio_poweroff_driver); 125 126 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>"); 127 MODULE_DESCRIPTION("GPIO poweroff driver"); 128 MODULE_LICENSE("GPL"); 129 MODULE_ALIAS("platform:poweroff-gpio"); 130