text: /*
   * 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/atomic.h>
  #include <linux/device.h>
  #include <linux/err.h>
  #include <linux/export.h>
  #include <linux/kernel.h>
  #include <linux/kref.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_list_mutex);
  static LIST_HEAD(reset_controller_list);
  
  static DEFINE_MUTEX(reset_lookup_mutex);
  static LIST_HEAD(reset_lookup_list);
  
  /**
   * struct reset_control - a reset control
   * @rcdev: a pointer to the reset controller device
   *         this reset control belongs to
   * @list: list entry for the rcdev's reset controller list
   * @id: ID of the reset controller in the reset
   *      controller device
   * @refcnt: Number of gets of this reset_control
   * @shared: Is this a shared (1), or an exclusive (0) reset_control?
   * @deassert_cnt: Number of times this reset line has been deasserted
   * @triggered_count: Number of times this reset line has been reset. Currently
   *                   only used for shared resets, which means that the value
   *                   will be either 0 or 1.
   */
  struct reset_control {
  	struct reset_controller_dev *rcdev;
  	struct list_head list;
  	unsigned int id;
  	struct kref refcnt;
  	bool shared;
  	bool array;
  	atomic_t deassert_count;
  	atomic_t triggered_count;
  };
  
  /**
   * struct reset_control_array - an array of reset controls
   * @base: reset control for compatibility with reset control API functions
   * @num_rstcs: number of reset controls
   * @rstc: array of reset controls
   */
  struct reset_control_array {
  	struct reset_control base;
  	unsigned int num_rstcs;
  	struct reset_control *rstc[];
  };
  
  /**
   * 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 (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;
  	}
  
  	INIT_LIST_HEAD(&rcdev->reset_control_head);
  
  	mutex_lock(&reset_list_mutex);
  	list_add(&rcdev->list, &reset_controller_list);
  	mutex_unlock(&reset_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_list_mutex);
  	list_del(&rcdev->list);
  	mutex_unlock(&reset_list_mutex);
  }
  EXPORT_SYMBOL_GPL(reset_controller_unregister);
  
  static void devm_reset_controller_release(struct device *dev, void *res)
  {
  	reset_controller_unregister(*(struct reset_controller_dev **)res);
  }
  
  /**
   * devm_reset_controller_register - resource managed reset_controller_register()
   * @dev: device that is registering this reset controller
   * @rcdev: a pointer to the initialized reset controller device
   *
   * Managed reset_controller_register(). For reset controllers registered by
   * this function, reset_controller_unregister() is automatically called on
   * driver detach. See reset_controller_register() for more information.
   */
  int devm_reset_controller_register(struct device *dev,
  				   struct reset_controller_dev *rcdev)
  {
  	struct reset_controller_dev **rcdevp;
  	int ret;
  
  	rcdevp = devres_alloc(devm_reset_controller_release, sizeof(*rcdevp),
  			      GFP_KERNEL);
  	if (!rcdevp)
  		return -ENOMEM;
  
  	ret = reset_controller_register(rcdev);
  	if (!ret) {
  		*rcdevp = rcdev;
  		devres_add(dev, rcdevp);
  	} else {
  		devres_free(rcdevp);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(devm_reset_controller_register);
  
  /**
   * reset_controller_add_lookup - register a set of lookup entries
   * @lookup: array of reset lookup entries
   * @num_entries: number of entries in the lookup array
   */
  void reset_controller_add_lookup(struct reset_control_lookup *lookup,
  				 unsigned int num_entries)
  {
  	struct reset_control_lookup *entry;
  	unsigned int i;
  
  	mutex_lock(&reset_lookup_mutex);
  	for (i = 0; i < num_entries; i++) {
  		entry = &lookup[i];
  
  		if (!entry->dev_id || !entry->provider) {
  			pr_warn("%s(): reset lookup entry badly specified, skipping\n",
  				__func__);
  			continue;
  		}
  
  		list_add_tail(&entry->list, &reset_lookup_list);
  	}
  	mutex_unlock(&reset_lookup_mutex);
  }
  EXPORT_SYMBOL_GPL(reset_controller_add_lookup);
  
  static inline struct reset_control_array *
  rstc_to_array(struct reset_control *rstc) {
  	return container_of(rstc, struct reset_control_array, base);
  }
  
  static int reset_control_array_reset(struct reset_control_array *resets)
  {
  	int ret, i;
  
  	for (i = 0; i < resets->num_rstcs; i++) {
  		ret = reset_control_reset(resets->rstc[i]);
  		if (ret)
  			return ret;
  	}
  
  	return 0;
  }
  
  static int reset_control_array_assert(struct reset_control_array *resets)
  {
  	int ret, i;
  
  	for (i = 0; i < resets->num_rstcs; i++) {
  		ret = reset_control_assert(resets->rstc[i]);
  		if (ret)
  			goto err;
  	}
  
  	return 0;
  
  err:
  	while (i--)
  		reset_control_deassert(resets->rstc[i]);
  	return ret;
  }
  
  static int reset_control_array_deassert(struct reset_control_array *resets)
  {
  	int ret, i;
  
  	for (i = 0; i < resets->num_rstcs; i++) {
  		ret = reset_control_deassert(resets->rstc[i]);
  		if (ret)
  			goto err;
  	}
  
  	return 0;
  
  err:
  	while (i--)
  		reset_control_assert(resets->rstc[i]);
  	return ret;
  }
  
  static inline bool reset_control_is_array(struct reset_control *rstc)
  {
  	return rstc->array;
  }
  
  /**
   * reset_control_reset - reset the controlled device
   * @rstc: reset controller
   *
   * On a shared reset line the actual reset pulse is only triggered once for the
   * lifetime of the reset_control instance: for all but the first caller this is
   * a no-op.
   * Consumers must not use reset_control_(de)assert on shared reset lines when
   * reset_control_reset has been used.
   *
   * If rstc is NULL it is an optional reset and the function will just
   * return 0.
   */
  int reset_control_reset(struct reset_control *rstc)
  {
  	int ret;
  
  	if (!rstc)
  		return 0;
  
  	if (WARN_ON(IS_ERR(rstc)))
  		return -EINVAL;
  
  	if (reset_control_is_array(rstc))
  		return reset_control_array_reset(rstc_to_array(rstc));
  
  	if (!rstc->rcdev->ops->reset)
  		return -ENOTSUPP;
  
  	if (rstc->shared) {
  		if (WARN_ON(atomic_read(&rstc->deassert_count) != 0))
  			return -EINVAL;
  
  		if (atomic_inc_return(&rstc->triggered_count) != 1)
  			return 0;
  	}
  
  	ret = rstc->rcdev->ops->reset(rstc->rcdev, rstc->id);
  	if (rstc->shared && ret)
  		atomic_dec(&rstc->triggered_count);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(reset_control_reset);
  
  /**
   * reset_control_assert - asserts the reset line
   * @rstc: reset controller
   *
   * Calling this on an exclusive reset controller guarantees that the reset
   * will be asserted. When called on a shared reset controller the line may
   * still be deasserted, as long as other users keep it so.
   *
   * For shared reset controls a driver cannot expect the hw's registers and
   * internal state to be reset, but must be prepared for this to happen.
   * Consumers must not use reset_control_reset on shared reset lines when
   * reset_control_(de)assert has been used.
   * return 0.
   *
   * If rstc is NULL it is an optional reset and the function will just
   * return 0.
   */
  int reset_control_assert(struct reset_control *rstc)
  {
  	if (!rstc)
  		return 0;
  
  	if (WARN_ON(IS_ERR(rstc)))
  		return -EINVAL;
  
  	if (reset_control_is_array(rstc))
  		return reset_control_array_assert(rstc_to_array(rstc));
  
  	if (rstc->shared) {
  		if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
  			return -EINVAL;
  
  		if (WARN_ON(atomic_read(&rstc->deassert_count) == 0))
  			return -EINVAL;
  
  		if (atomic_dec_return(&rstc->deassert_count) != 0)
  			return 0;
  
  		/*
  		 * Shared reset controls allow the reset line to be in any state
  		 * after this call, so doing nothing is a valid option.
  		 */
  		if (!rstc->rcdev->ops->assert)
  			return 0;
  	} else {
  		/*
  		 * If the reset controller does not implement .assert(), there
  		 * is no way to guarantee that the reset line is asserted after
  		 * this call.
  		 */
  		if (!rstc->rcdev->ops->assert)
  			return -ENOTSUPP;
  	}
  
  	return rstc->rcdev->ops->assert(rstc->rcdev, rstc->id);
  }
  EXPORT_SYMBOL_GPL(reset_control_assert);
  
  /**
   * reset_control_deassert - deasserts the reset line
   * @rstc: reset controller
   *
   * After calling this function, the reset is guaranteed to be deasserted.
   * Consumers must not use reset_control_reset on shared reset lines when
   * reset_control_(de)assert has been used.
   * return 0.
   *
   * If rstc is NULL it is an optional reset and the function will just
   * return 0.
   */
  int reset_control_deassert(struct reset_control *rstc)
  {
  	if (!rstc)
  		return 0;
  
  	if (WARN_ON(IS_ERR(rstc)))
  		return -EINVAL;
  
  	if (reset_control_is_array(rstc))
  		return reset_control_array_deassert(rstc_to_array(rstc));
  
  	if (rstc->shared) {
  		if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
  			return -EINVAL;
  
  		if (atomic_inc_return(&rstc->deassert_count) != 1)
  			return 0;
  	}
  
  	/*
  	 * If the reset controller does not implement .deassert(), we assume
  	 * that it handles self-deasserting reset lines via .reset(). In that
  	 * case, the reset lines are deasserted by default. If that is not the
  	 * case, the reset controller driver should implement .deassert() and
  	 * return -ENOTSUPP.
  	 */
  	if (!rstc->rcdev->ops->deassert)
  		return 0;
  
  	return rstc->rcdev->ops->deassert(rstc->rcdev, rstc->id);
  }
  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 or if the desc is NULL (optional reset).
   * @rstc: reset controller
   */
  int reset_control_status(struct reset_control *rstc)
  {
  	if (!rstc)
  		return 0;
  
  	if (WARN_ON(IS_ERR(rstc)) || reset_control_is_array(rstc))
  		return -EINVAL;
  
  	if (rstc->rcdev->ops->status)
  		return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);
  
  	return -ENOTSUPP;
  }
  EXPORT_SYMBOL_GPL(reset_control_status);
  
  static struct reset_control *__reset_control_get_internal(
  				struct reset_controller_dev *rcdev,
  				unsigned int index, bool shared)
  {
  	struct reset_control *rstc;
  
  	lockdep_assert_held(&reset_list_mutex);
  
  	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
  		if (rstc->id == index) {
  			if (WARN_ON(!rstc->shared || !shared))
  				return ERR_PTR(-EBUSY);
  
  			kref_get(&rstc->refcnt);
  			return rstc;
  		}
  	}
  
  	rstc = kzalloc(sizeof(*rstc), GFP_KERNEL);
  	if (!rstc)
  		return ERR_PTR(-ENOMEM);
  
  	try_module_get(rcdev->owner);
  
  	rstc->rcdev = rcdev;
  	list_add(&rstc->list, &rcdev->reset_control_head);
  	rstc->id = index;
  	kref_init(&rstc->refcnt);
  	rstc->shared = shared;
  
  	return rstc;
  }
  
  static void __reset_control_release(struct kref *kref)
  {
  	struct reset_control *rstc = container_of(kref, struct reset_control,
  						  refcnt);
  
  	lockdep_assert_held(&reset_list_mutex);
  
  	module_put(rstc->rcdev->owner);
  
  	list_del(&rstc->list);
  	kfree(rstc);
  }
  
  static void __reset_control_put_internal(struct reset_control *rstc)
  {
  	lockdep_assert_held(&reset_list_mutex);
  
  	kref_put(&rstc->refcnt, __reset_control_release);
  }
  
  struct reset_control *__of_reset_control_get(struct device_node *node,
  				     const char *id, int index, bool shared,
  				     bool optional)
  {
  	struct reset_control *rstc;
  	struct reset_controller_dev *r, *rcdev;
  	struct of_phandle_args args;
  	int rstc_id;
  	int ret;
  
  	if (!node)
  		return ERR_PTR(-EINVAL);
  
  	if (id) {
  		index = of_property_match_string(node,
  						 "reset-names", id);
  		if (index == -EILSEQ)
  			return ERR_PTR(index);
  		if (index < 0)
  			return optional ? NULL : ERR_PTR(-ENOENT);
  	}
  
  	ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
  					 index, &args);
  	if (ret == -EINVAL)
  		return ERR_PTR(ret);
  	if (ret)
  		return optional ? NULL : ERR_PTR(ret);
  
  	mutex_lock(&reset_list_mutex);
  	rcdev = NULL;
  	list_for_each_entry(r, &reset_controller_list, list) {
  		if (args.np == r->of_node) {
  			rcdev = r;
  			break;
  		}
  	}
  
  	if (!rcdev) {
  		rstc = ERR_PTR(-EPROBE_DEFER);
  		goto out;
  	}
  
  	if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
  		rstc = ERR_PTR(-EINVAL);
  		goto out;
  	}
  
  	rstc_id = rcdev->of_xlate(rcdev, &args);
  	if (rstc_id < 0) {
  		rstc = ERR_PTR(rstc_id);
  		goto out;
  	}
  
  	/* reset_list_mutex also protects the rcdev's reset_control list */
  	rstc = __reset_control_get_internal(rcdev, rstc_id, shared);
  
  out:
  	mutex_unlock(&reset_list_mutex);
  	of_node_put(args.np);
  
  	return rstc;
  }
  EXPORT_SYMBOL_GPL(__of_reset_control_get);
  
  static struct reset_controller_dev *
  __reset_controller_by_name(const char *name)
  {
  	struct reset_controller_dev *rcdev;
  
  	lockdep_assert_held(&reset_list_mutex);
  
  	list_for_each_entry(rcdev, &reset_controller_list, list) {
  		if (!rcdev->dev)
  			continue;
  
  		if (!strcmp(name, dev_name(rcdev->dev)))
  			return rcdev;
  	}
  
  	return NULL;
  }
  
  static struct reset_control *
  __reset_control_get_from_lookup(struct device *dev, const char *con_id,
  				bool shared, bool optional)
  {
  	const struct reset_control_lookup *lookup;
  	struct reset_controller_dev *rcdev;
  	const char *dev_id = dev_name(dev);
  	struct reset_control *rstc = NULL;
  
  	if (!dev)
  		return ERR_PTR(-EINVAL);
  
  	mutex_lock(&reset_lookup_mutex);
  
  	list_for_each_entry(lookup, &reset_lookup_list, list) {
  		if (strcmp(lookup->dev_id, dev_id))
  			continue;
  
  		if ((!con_id && !lookup->con_id) ||
  		    ((con_id && lookup->con_id) &&
  		     !strcmp(con_id, lookup->con_id))) {
  			mutex_lock(&reset_list_mutex);
  			rcdev = __reset_controller_by_name(lookup->provider);
  			if (!rcdev) {
  				mutex_unlock(&reset_list_mutex);
  				mutex_unlock(&reset_lookup_mutex);
  				/* Reset provider may not be ready yet. */
  				return ERR_PTR(-EPROBE_DEFER);
  			}
  
  			rstc = __reset_control_get_internal(rcdev,
  							    lookup->index,
  							    shared);
  			mutex_unlock(&reset_list_mutex);
  			break;
  		}
  	}
  
  	mutex_unlock(&reset_lookup_mutex);
  
  	if (!rstc)
  		return optional ? NULL : ERR_PTR(-ENOENT);
  
  	return rstc;
  }
  
  struct reset_control *__reset_control_get(struct device *dev, const char *id,
  					  int index, bool shared, bool optional)
  {
  	if (dev->of_node)
  		return __of_reset_control_get(dev->of_node, id, index, shared,
  					      optional);
  
  	return __reset_control_get_from_lookup(dev, id, shared, optional);
  }
  EXPORT_SYMBOL_GPL(__reset_control_get);
  
  static void reset_control_array_put(struct reset_control_array *resets)
  {
  	int i;
  
  	mutex_lock(&reset_list_mutex);
  	for (i = 0; i < resets->num_rstcs; i++)
  		__reset_control_put_internal(resets->rstc[i]);
  	mutex_unlock(&reset_list_mutex);
  }
  
  /**
   * reset_control_put - free the reset controller
   * @rstc: reset controller
   */
  void reset_control_put(struct reset_control *rstc)
  {
  	if (IS_ERR_OR_NULL(rstc))
  		return;
  
  	if (reset_control_is_array(rstc)) {
  		reset_control_array_put(rstc_to_array(rstc));
  		return;
  	}
  
  	mutex_lock(&reset_list_mutex);
  	__reset_control_put_internal(rstc);
  	mutex_unlock(&reset_list_mutex);
  }
  EXPORT_SYMBOL_GPL(reset_control_put);
  
  static void devm_reset_control_release(struct device *dev, void *res)
  {
  	reset_control_put(*(struct reset_control **)res);
  }
  
  struct reset_control *__devm_reset_control_get(struct device *dev,
  				     const char *id, int index, bool shared,
  				     bool optional)
  {
  	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, index, shared, optional);
  	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
   * @optional: whether it is optional to reset the device
   *
   * 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, bool optional)
  {
  	struct reset_control *rstc;
  	int ret;
  
  	rstc = __reset_control_get(dev, NULL, 0, 0, optional);
  	if (IS_ERR(rstc))
  		return PTR_ERR(rstc);
  
  	ret = reset_control_reset(rstc);
  
  	reset_control_put(rstc);
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(__device_reset);
  
  /**
   * APIs to manage an array of reset controls.
   */
  /**
   * of_reset_control_get_count - Count number of resets available with a device
   *
   * @node: device node that contains 'resets'.
   *
   * Returns positive reset count on success, or error number on failure and
   * on count being zero.
   */
  static int of_reset_control_get_count(struct device_node *node)
  {
  	int count;
  
  	if (!node)
  		return -EINVAL;
  
  	count = of_count_phandle_with_args(node, "resets", "#reset-cells");
  	if (count == 0)
  		count = -ENOENT;
  
  	return count;
  }
  
  /**
   * of_reset_control_array_get - Get a list of reset controls using
   *				device node.
   *
   * @np: device node for the device that requests the reset controls array
   * @shared: whether reset controls are shared or not
   * @optional: whether it is optional to get the reset controls
   *
   * Returns pointer to allocated reset_control_array on success or
   * error on failure
   */
  struct reset_control *
  of_reset_control_array_get(struct device_node *np, bool shared, bool optional)
  {
  	struct reset_control_array *resets;
  	struct reset_control *rstc;
  	int num, i;
  
  	num = of_reset_control_get_count(np);
  	if (num < 0)
  		return optional ? NULL : ERR_PTR(num);
  
  	resets = kzalloc(struct_size(resets, rstc, num), GFP_KERNEL);
  	if (!resets)
  		return ERR_PTR(-ENOMEM);
  
  	for (i = 0; i < num; i++) {
  		rstc = __of_reset_control_get(np, NULL, i, shared, optional);
  		if (IS_ERR(rstc))
  			goto err_rst;
  		resets->rstc[i] = rstc;
  	}
  	resets->num_rstcs = num;
  	resets->base.array = true;
  
  	return &resets->base;
  
  err_rst:
  	mutex_lock(&reset_list_mutex);
  	while (--i >= 0)
  		__reset_control_put_internal(resets->rstc[i]);
  	mutex_unlock(&reset_list_mutex);
  
  	kfree(resets);
  
  	return rstc;
  }
  EXPORT_SYMBOL_GPL(of_reset_control_array_get);
  
  /**
   * devm_reset_control_array_get - Resource managed reset control array get
   *
   * @dev: device that requests the list of reset controls
   * @shared: whether reset controls are shared or not
   * @optional: whether it is optional to get the reset controls
   *
   * The reset control array APIs are intended for a list of resets
   * that just have to be asserted or deasserted, without any
   * requirements on the order.
   *
   * Returns pointer to allocated reset_control_array on success or
   * error on failure
   */
  struct reset_control *
  devm_reset_control_array_get(struct device *dev, bool shared, bool optional)
  {
  	struct reset_control **devres;
  	struct reset_control *rstc;
  
  	devres = devres_alloc(devm_reset_control_release, sizeof(*devres),
  			      GFP_KERNEL);
  	if (!devres)
  		return ERR_PTR(-ENOMEM);
  
  	rstc = of_reset_control_array_get(dev->of_node, shared, optional);
  	if (IS_ERR(rstc)) {
  		devres_free(devres);
  		return rstc;
  	}
  
  	*devres = rstc;
  	devres_add(dev, devres);
  
  	return rstc;
  }
  EXPORT_SYMBOL_GPL(devm_reset_control_array_get);
  