/*
   * Reset Controller framework
   *
   * 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/device.h>
  #include <linux/err.h>
  #include <linux/export.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/reset.h>
  #include <linux/reset-controller.h>
  #include <linux/slab.h>
  
  static DEFINE_MUTEX(reset_controller_list_mutex);
  static LIST_HEAD(reset_controller_list);
  
  /**
   * struct reset_control - a reset control
   * @rcdev: a pointer to the reset controller device
   *         this reset control belongs to
   * @id: ID of the reset controller in the reset
   *      controller device
   */
  struct reset_control {
  	struct reset_controller_dev *rcdev;
  	struct device *dev;
  	unsigned int id;
  };
  
  /**
   * of_reset_simple_xlate - translate reset_spec to the reset line number
   * @rcdev: a pointer to the reset controller device
   * @reset_spec: reset line specifier as found in the device tree
   * @flags: a flags pointer to fill in (optional)
   *
   * This simple translation function should be used for reset controllers
   * with 1:1 mapping, where reset lines can be indexed by number without gaps.
   */
  static int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
  			  const struct of_phandle_args *reset_spec)
  {
  	if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
  		return -EINVAL;
  
  	if (reset_spec->args[0] >= rcdev->nr_resets)
  		return -EINVAL;
  
  	return reset_spec->args[0];
  }
  
  /**
   * reset_controller_register - register a reset controller device
   * @rcdev: a pointer to the initialized reset controller device
   */
  int reset_controller_register(struct reset_controller_dev *rcdev)
  {
  	if (!rcdev->of_xlate) {
  		rcdev->of_reset_n_cells = 1;
  		rcdev->of_xlate = of_reset_simple_xlate;
  	}
  
  	mutex_lock(&reset_controller_list_mutex);
  	list_add(&rcdev->list, &reset_controller_list);
  	mutex_unlock(&reset_controller_list_mutex);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(reset_controller_register);
  
  /**
   * reset_controller_unregister - unregister a reset controller device
   * @rcdev: a pointer to the reset controller device
   */
  void reset_controller_unregister(struct reset_controller_dev *rcdev)
  {
  	mutex_lock(&reset_controller_list_mutex);
  	list_del(&rcdev->list);
  	mutex_unlock(&reset_controller_list_mutex);
  }
  EXPORT_SYMBOL_GPL(reset_controller_unregister);
  
  /**
   * reset_control_reset - reset the controlled device
   * @rstc: reset controller
   */
  int reset_control_reset(struct reset_control *rstc)
  {
  	if (rstc->rcdev->ops->reset)
  		return rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
  
  	return -ENOSYS;
  }
  EXPORT_SYMBOL_GPL(reset_control_reset);
  
  /**
   * reset_control_assert - asserts the reset line
   * @rstc: reset controller
   */
  int reset_control_assert(struct reset_control *rstc)
  {
  	if (rstc->rcdev->ops->assert)
  		return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
  
  	return -ENOSYS;
  }
  EXPORT_SYMBOL_GPL(reset_control_assert);
  
  /**
   * reset_control_deassert - deasserts the reset line
   * @rstc: reset controller
   */
  int reset_control_deassert(struct reset_control *rstc)
  {
  	if (rstc->rcdev->ops->deassert)
  		return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
  
  	return -ENOSYS;
  }
  EXPORT_SYMBOL_GPL(reset_control_deassert);
  
  /**
   * reset_control_status - returns a negative errno if not supported, a
   * positive value if the reset line is asserted, or zero if the reset
   * line is not asserted.
   * @rstc: reset controller
   */
  int reset_control_status(struct reset_control *rstc)
  {
  	if (rstc->rcdev->ops->status)
  		return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
  
  	return -ENOSYS;
  }
  EXPORT_SYMBOL_GPL(reset_control_status);
  
  /**
   * of_reset_control_get - Lookup and obtain a reference to a reset controller.
   * @node: device to be reset by the controller
   * @id: reset line name
   *
   * Returns a struct reset_control or IS_ERR() condition containing errno.
   *
   * Use of id names is optional.
   */
  struct reset_control *of_reset_control_get(struct device_node *node,
  					   const char *id)
  {
  	struct reset_control *rstc = ERR_PTR(-EPROBE_DEFER);
  	struct reset_controller_dev *r, *rcdev;
  	struct of_phandle_args args;
  	int index = 0;
  	int rstc_id;
  	int ret;
  
  	if (id)
  		index = of_property_match_string(node,
  						 "reset-names", id);
  	ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
  					 index, &args);
  	if (ret)
  		return ERR_PTR(ret);
  
  	mutex_lock(&reset_controller_list_mutex);
  	rcdev = NULL;
  	list_for_each_entry(r, &reset_controller_list, list) {
  		if (args.np == r->of_node) {
  			rcdev = r;
  			break;
  		}
  	}
  	of_node_put(args.np);
  
  	if (!rcdev) {
  		mutex_unlock(&reset_controller_list_mutex);
  		return ERR_PTR(-EPROBE_DEFER);
  	}
  
  	rstc_id = rcdev->of_xlate(rcdev, &args);
  	if (rstc_id < 0) {
  		mutex_unlock(&reset_controller_list_mutex);
  		return ERR_PTR(rstc_id);
  	}
  
  	try_module_get(rcdev->owner);
  	mutex_unlock(&reset_controller_list_mutex);
  
  	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
  	if (!rstc) {
  		module_put(rcdev->owner);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	rstc->rcdev = rcdev;
  	rstc->id = rstc_id;
  
  	return rstc;
  }
  EXPORT_SYMBOL_GPL(of_reset_control_get);
  
  /**
   * reset_control_get - Lookup and obtain a reference to a reset controller.
   * @dev: device to be reset by the controller
   * @id: reset line name
   *
   * Returns a struct reset_control or IS_ERR() condition containing errno.
   *
   * Use of id names is optional.
   */
  struct reset_control *reset_control_get(struct device *dev, const char *id)
  {
  	struct reset_control *rstc;
  
  	if (!dev)
  		return ERR_PTR(-EINVAL);
  
  	rstc = of_reset_control_get(dev->of_node, id);
  	if (!IS_ERR(rstc))
  		rstc->dev = dev;
  
  	return rstc;
  }
  EXPORT_SYMBOL_GPL(reset_control_get);
  
  /**
   * reset_control_put - free the reset controller
   * @rstc: reset controller
   */
  
  void reset_control_put(struct reset_control *rstc)
  {
  	if (IS_ERR(rstc))
  		return;
  
  	module_put(rstc->rcdev->owner);
  	kfree(rstc);
  }
  EXPORT_SYMBOL_GPL(reset_control_put);
  
  static void devm_reset_control_release(struct device *dev, void *res)
  {
  	reset_control_put(*(struct reset_control **)res);
  }
  
  /**
   * devm_reset_control_get - resource managed reset_control_get()
   * @dev: device to be reset by the controller
   * @id: reset line name
   *
   * Managed reset_control_get(). For reset controllers returned from this
   * function, reset_control_put() is called automatically on driver detach.
   * See reset_control_get() for more information.
   */
  struct reset_control *devm_reset_control_get(struct device *dev, const char *id)
  {
  	struct reset_control **ptr, *rstc;
  
  	ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
  			   GFP_KERNEL);
  	if (!ptr)
  		return ERR_PTR(-ENOMEM);
  
  	rstc = reset_control_get(dev, id);
  	if (!IS_ERR(rstc)) {
  		*ptr = rstc;
  		devres_add(dev, ptr);
  	} else {
  		devres_free(ptr);
  	}
  
  	return rstc;
  }
  EXPORT_SYMBOL_GPL(devm_reset_control_get);
  
  /**
   * device_reset - find reset controller associated with the device
   *                and perform reset
   * @dev: device to be reset by the controller
   *
   * Convenience wrapper for reset_control_get() and reset_control_reset().
   * This is useful for the common case of devices with single, dedicated reset
   * lines.
   */
  int device_reset(struct device *dev)
  {
  	struct reset_control *rstc;
  	int ret;
  
  	rstc = reset_control_get(dev, NULL);
  	if (IS_ERR(rstc))
  		return PTR_ERR(rstc);
  
  	ret = reset_control_reset(rstc);
  
  	reset_control_put(rstc);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(device_reset);