Eric Lee / smarc-fsl-linux-kernel

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drivers/power/reset/gpio-poweroff.c 2.37 KB
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81f7e3824   Eric Lee   Initial Release, ... 
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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");