/*
   * GPIO Reset Controller driver
   *
   * Copyright 2013 Philipp Zabel, Pengutronix
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  #include <linux/delay.h>
  #include <linux/err.h>
  #include <linux/gpio.h>
  #include <linux/module.h>
  #include <linux/of_gpio.h>
  #include <linux/platform_device.h>

  #include <linux/pinctrl/consumer.h>

  #include <linux/reset-controller.h>
  
  struct gpio_reset_data {
  	struct reset_controller_dev rcdev;
  	unsigned int gpio;
  	bool active_low;
  	s32 delay_us;

  	s32 post_delay_ms;

  };
  
  static void gpio_reset_set(struct reset_controller_dev *rcdev, int asserted)
  {
  	struct gpio_reset_data *drvdata = container_of(rcdev,
  			struct gpio_reset_data, rcdev);
  	int value = asserted;
  
  	if (drvdata->active_low)
  		value = !value;

  	gpio_set_value_cansleep(drvdata->gpio, value);

  }
  
  static int gpio_reset(struct reset_controller_dev *rcdev, unsigned long id)
  {
  	struct gpio_reset_data *drvdata = container_of(rcdev,
  			struct gpio_reset_data, rcdev);
  
  	if (drvdata->delay_us < 0)
  		return -ENOSYS;
  
  	gpio_reset_set(rcdev, 1);
  	udelay(drvdata->delay_us);
  	gpio_reset_set(rcdev, 0);

  	if (drvdata->post_delay_ms < 0)
  		return 0;
  
  	msleep(drvdata->post_delay_ms);

  	return 0;
  }
  
  static int gpio_reset_assert(struct reset_controller_dev *rcdev,
  		unsigned long id)
  {
  	gpio_reset_set(rcdev, 1);
  
  	return 0;
  }
  
  static int gpio_reset_deassert(struct reset_controller_dev *rcdev,
  		unsigned long id)
  {
  	gpio_reset_set(rcdev, 0);
  
  	return 0;
  }
  
  static struct reset_control_ops gpio_reset_ops = {
  	.reset = gpio_reset,
  	.assert = gpio_reset_assert,
  	.deassert = gpio_reset_deassert,
  };
  
  static int of_gpio_reset_xlate(struct reset_controller_dev *rcdev,
  			       const struct of_phandle_args *reset_spec)
  {
  	if (WARN_ON(reset_spec->args_count != 0))
  		return -EINVAL;
  
  	return 0;
  }
  
  static int gpio_reset_probe(struct platform_device *pdev)
  {
  	struct device_node *np = pdev->dev.of_node;
  	struct gpio_reset_data *drvdata;
  	enum of_gpio_flags flags;
  	unsigned long gpio_flags;
  	bool initially_in_reset;
  	int ret;
  
  	drvdata = devm_kzalloc(&pdev->dev, sizeof(*drvdata), GFP_KERNEL);
  	if (drvdata == NULL)
  		return -ENOMEM;
  
  	if (of_gpio_named_count(np, "reset-gpios") != 1) {
  		dev_err(&pdev->dev,
  			"reset-gpios property missing, or not a single gpio
  ");
  		return -EINVAL;
  	}
  
  	drvdata->gpio = of_get_named_gpio_flags(np, "reset-gpios", 0, &flags);
  	if (drvdata->gpio == -EPROBE_DEFER) {
  		return drvdata->gpio;
  	} else if (!gpio_is_valid(drvdata->gpio)) {
  		dev_err(&pdev->dev, "invalid reset gpio: %d
  ", drvdata->gpio);
  		return drvdata->gpio;
  	}
  
  	drvdata->active_low = flags & OF_GPIO_ACTIVE_LOW;
  
  	ret = of_property_read_u32(np, "reset-delay-us", &drvdata->delay_us);
  	if (ret < 0)
  		drvdata->delay_us = -1;
  	else if (drvdata->delay_us < 0)
  		dev_warn(&pdev->dev, "reset delay too high
  ");

  	/* It is optional.
  	 * Some devices need some milliseconds to wait after reset.
  	 */
  	ret = of_property_read_u32(np, "reset-post-delay-ms", &drvdata->post_delay_ms);
  	if (ret < 0)
  		drvdata->post_delay_ms = -1;

  	initially_in_reset = of_property_read_bool(np, "initially-in-reset");
  	if (drvdata->active_low ^ initially_in_reset)
  		gpio_flags = GPIOF_OUT_INIT_HIGH;
  	else
  		gpio_flags = GPIOF_OUT_INIT_LOW;
  
  	ret = devm_gpio_request_one(&pdev->dev, drvdata->gpio, gpio_flags, NULL);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "failed to request gpio %d: %d
  ",
  			drvdata->gpio, ret);
  		return ret;
  	}
  
  	platform_set_drvdata(pdev, drvdata);
  
  	drvdata->rcdev.of_node = np;
  	drvdata->rcdev.owner = THIS_MODULE;
  	drvdata->rcdev.nr_resets = 1;
  	drvdata->rcdev.ops = &gpio_reset_ops;
  	drvdata->rcdev.of_xlate = of_gpio_reset_xlate;
  	reset_controller_register(&drvdata->rcdev);
  
  	return 0;
  }
  
  static int gpio_reset_remove(struct platform_device *pdev)
  {
  	struct gpio_reset_data *drvdata = platform_get_drvdata(pdev);
  
  	reset_controller_unregister(&drvdata->rcdev);
  
  	return 0;
  }
  
  static struct of_device_id gpio_reset_dt_ids[] = {
  	{ .compatible = "gpio-reset" },
  	{ }
  };

  #ifdef CONFIG_PM_SLEEP
  static int gpio_reset_suspend(struct device *dev)
  {
  	pinctrl_pm_select_sleep_state(dev);
  
  	return 0;
  }
  static int gpio_reset_resume(struct device *dev)
  {
  	pinctrl_pm_select_default_state(dev);
  
  	return 0;
  }
  #endif
  
  static const struct dev_pm_ops gpio_reset_pm_ops = {
  	SET_LATE_SYSTEM_SLEEP_PM_OPS(gpio_reset_suspend, gpio_reset_resume)
  };

  static struct platform_driver gpio_reset_driver = {
  	.probe = gpio_reset_probe,
  	.remove = gpio_reset_remove,
  	.driver = {
  		.name = "gpio-reset",
  		.owner = THIS_MODULE,
  		.of_match_table = of_match_ptr(gpio_reset_dt_ids),

  		.pm = &gpio_reset_pm_ops,

  	},
  };

  static int __init gpio_reset_init(void)
  {
  	return platform_driver_register(&gpio_reset_driver);
  }
  arch_initcall(gpio_reset_init);
  
  static void __exit gpio_reset_exit(void)
  {
  	platform_driver_unregister(&gpio_reset_driver);
  }
  module_exit(gpio_reset_exit);

  
  MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
  MODULE_DESCRIPTION("gpio reset controller");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:gpio-reset");
  MODULE_DEVICE_TABLE(of, gpio_reset_dt_ids);