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/* * Toggles a GPIO pin to power down a device * * Jamie Lentin <jm@lentin.co.uk> * Andrew Lunn <andrew@lunn.ch> * * Copyright (C) 2012 Jamie Lentin * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * */ #include <linux/kernel.h> #include <linux/init.h> #include <linux/delay.h> #include <linux/platform_device.h> #include <linux/gpio/consumer.h> #include <linux/of_platform.h> #include <linux/module.h> /* * Hold configuration here, cannot be more than one instance of the driver * since pm_power_off itself is global. */ static struct gpio_desc *reset_gpio; static void gpio_poweroff_do_poweroff(void) { BUG_ON(!reset_gpio); /* drive it active, also inactive->active edge */ gpiod_direction_output(reset_gpio, 1); mdelay(100); /* drive inactive, also active->inactive edge */ gpiod_set_value(reset_gpio, 0); mdelay(100); /* drive it active, also inactive->active edge */ gpiod_set_value(reset_gpio, 1); /* give it some time */ mdelay(3000); WARN_ON(1); } static int gpio_poweroff_probe(struct platform_device *pdev) { bool input = false; enum gpiod_flags flags; /* If a pm_power_off function has already been added, leave it alone */ if (pm_power_off != NULL) { dev_err(&pdev->dev, "%s: pm_power_off function already registered", __func__); return -EBUSY; } input = of_property_read_bool(pdev->dev.of_node, "input"); if (input) flags = GPIOD_IN; else flags = GPIOD_OUT_LOW; reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags); if (IS_ERR(reset_gpio)) return PTR_ERR(reset_gpio); pm_power_off = &gpio_poweroff_do_poweroff; return 0; } static int gpio_poweroff_remove(struct platform_device *pdev) { if (pm_power_off == &gpio_poweroff_do_poweroff) pm_power_off = NULL; return 0; } static const struct of_device_id of_gpio_poweroff_match[] = { { .compatible = "gpio-poweroff", }, {}, }; static struct platform_driver gpio_poweroff_driver = { .probe = gpio_poweroff_probe, .remove = gpio_poweroff_remove, .driver = { .name = "poweroff-gpio", .of_match_table = of_gpio_poweroff_match, }, }; module_platform_driver(gpio_poweroff_driver); MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>"); MODULE_DESCRIPTION("GPIO poweroff driver"); MODULE_LICENSE("GPL v2"); MODULE_ALIAS("platform:poweroff-gpio"); |