1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Toggles a GPIO pin to power down a device 4 * 5 * Jamie Lentin <jm@lentin.co.uk> 6 * Andrew Lunn <andrew@lunn.ch> 7 * 8 * Copyright (C) 2012 Jamie Lentin 9 */ 10 #include <linux/kernel.h> 11 #include <linux/init.h> 12 #include <linux/delay.h> 13 #include <linux/platform_device.h> 14 #include <linux/gpio/consumer.h> 15 #include <linux/of_platform.h> 16 #include <linux/module.h> 17 18 #define DEFAULT_TIMEOUT_MS 3000 19 /* 20 * Hold configuration here, cannot be more than one instance of the driver 21 * since pm_power_off itself is global. 22 */ 23 static struct gpio_desc *reset_gpio; 24 static u32 timeout = DEFAULT_TIMEOUT_MS; 25 static u32 active_delay = 100; 26 static u32 inactive_delay = 100; 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(active_delay); 35 36 /* drive inactive, also active->inactive edge */ 37 gpiod_set_value_cansleep(reset_gpio, 0); 38 mdelay(inactive_delay); 39 40 /* drive it active, also inactive->active edge */ 41 gpiod_set_value_cansleep(reset_gpio, 1); 42 43 /* give it some time */ 44 mdelay(timeout); 45 46 WARN_ON(1); 47 } 48 49 static int gpio_poweroff_probe(struct platform_device *pdev) 50 { 51 bool input = false; 52 enum gpiod_flags flags; 53 54 /* If a pm_power_off function has already been added, leave it alone */ 55 if (pm_power_off != NULL) { 56 dev_err(&pdev->dev, 57 "%s: pm_power_off function already registered\n", 58 __func__); 59 return -EBUSY; 60 } 61 62 input = device_property_read_bool(&pdev->dev, "input"); 63 if (input) 64 flags = GPIOD_IN; 65 else 66 flags = GPIOD_OUT_LOW; 67 68 device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay); 69 device_property_read_u32(&pdev->dev, "inactive-delay-ms", 70 &inactive_delay); 71 device_property_read_u32(&pdev->dev, "timeout-ms", &timeout); 72 73 reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags); 74 if (IS_ERR(reset_gpio)) 75 return PTR_ERR(reset_gpio); 76 77 pm_power_off = &gpio_poweroff_do_poweroff; 78 return 0; 79 } 80 81 static int gpio_poweroff_remove(struct platform_device *pdev) 82 { 83 if (pm_power_off == &gpio_poweroff_do_poweroff) 84 pm_power_off = NULL; 85 86 return 0; 87 } 88 89 static const struct of_device_id of_gpio_poweroff_match[] = { 90 { .compatible = "gpio-poweroff", }, 91 {}, 92 }; 93 MODULE_DEVICE_TABLE(of, of_gpio_poweroff_match); 94 95 static struct platform_driver gpio_poweroff_driver = { 96 .probe = gpio_poweroff_probe, 97 .remove = gpio_poweroff_remove, 98 .driver = { 99 .name = "poweroff-gpio", 100 .of_match_table = of_gpio_poweroff_match, 101 }, 102 }; 103 104 module_platform_driver(gpio_poweroff_driver); 105 106 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>"); 107 MODULE_DESCRIPTION("GPIO poweroff driver"); 108 MODULE_ALIAS("platform:poweroff-gpio"); 109