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"); 107