xref: /linux/drivers/reset/core.c (revision ccef9ef0aa2b9a7814e4def6f18b25211b8ae530)

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Reset Controller framework
 *
 * Copyright 2013 Philipp Zabel, Pengutronix
 */

#include <linux/acpi.h>
#include <linux/atomic.h>
#include <linux/auxiliary_bus.h>
#include <linux/cleanup.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/fwnode.h>
#include <linux/gpio/driver.h>
#include <linux/gpio/machine.h>
#include <linux/gpio/property.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/property.h>
#include <linux/reset.h>
#include <linux/reset-controller.h>
#include <linux/slab.h>
#include <linux/srcu.h>

static DEFINE_MUTEX(reset_list_mutex);
static LIST_HEAD(reset_controller_list);

/* Protects reset_gpio_lookup_list */
static DEFINE_MUTEX(reset_gpio_lookup_mutex);
static LIST_HEAD(reset_gpio_lookup_list);
static DEFINE_IDA(reset_gpio_ida);

/**
 * struct reset_control - a reset control
 * @rcdev: a pointer to the reset controller device
 *         this reset control belongs to
 * @srcu: protects the rcdev pointer from removal during consumer access
 * @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
 * @acquired: Only one reset_control may be acquired for a given rcdev and id.
 * @shared: Is this a shared (1), or an exclusive (0) reset_control?
 * @array: Is this an array of reset controls (1)?
 * @deassert_count: 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.
 * @lock: serializes the internals of reset_control_acquire()
 */
struct reset_control {
	struct reset_controller_dev __rcu *rcdev;
	struct srcu_struct srcu;
	struct list_head list;
	unsigned int id;
	struct kref refcnt;
	bool acquired;
	bool shared;
	bool array;
	atomic_t deassert_count;
	atomic_t triggered_count;
	struct mutex lock;
};

/**
 * 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[] __counted_by(num_rstcs);
};

/**
 * struct reset_gpio_lookup - lookup key for ad-hoc created reset-gpio devices
 * @ref_args: Reference to the reset controller with all the args like GPIO number
 * @swnode: Software node containing the reference to the GPIO provider
 * @list: list entry for the reset_gpio_lookup_list
 * @adev: Auxiliary device representing the reset controller
 */
struct reset_gpio_lookup {
	struct fwnode_reference_args ref_args;
	struct fwnode_handle *swnode;
	struct list_head list;
	struct auxiliary_device adev;
};

static const char *rcdev_name(struct reset_controller_dev *rcdev)
{
	if (rcdev->dev)
		return dev_name(rcdev->dev);

	if (rcdev->fwnode)
		return fwnode_get_name(rcdev->fwnode);

	return NULL;
}

/**
 * fwnode_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 firmware
 *
 * This static translation function is used by default if neither fwnode_xlate
 * not of_xlate in :c:type:`reset_controller_dev` is not set. It is useful for
 * all reset controllers with 1:1 mapping, where reset lines can be indexed by
 * number without gaps.
 */
static int fwnode_reset_simple_xlate(struct reset_controller_dev *rcdev,
				     const struct fwnode_reference_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_node && rcdev->fwnode) || (rcdev->of_xlate && rcdev->fwnode_xlate))
		return -EINVAL;

	if (rcdev->of_node && !rcdev->fwnode)
		rcdev->fwnode = of_fwnode_handle(rcdev->of_node);

	if (!rcdev->fwnode) {
		rcdev->fwnode = dev_fwnode(rcdev->dev);
		if (!rcdev->fwnode)
			return -EINVAL;
	}

	if (rcdev->of_xlate)
		rcdev->fwnode_reset_n_cells = rcdev->of_reset_n_cells;

	if (!rcdev->fwnode_xlate && !rcdev->of_xlate) {
		rcdev->fwnode_xlate = fwnode_reset_simple_xlate;
		rcdev->fwnode_reset_n_cells = 1;
	}

	INIT_LIST_HEAD(&rcdev->reset_control_head);
	mutex_init(&rcdev->lock);

	guard(mutex)(&reset_list_mutex);

	list_add(&rcdev->list, &reset_controller_list);

	return 0;
}
EXPORT_SYMBOL_GPL(reset_controller_register);

static void reset_controller_remove(struct reset_controller_dev *rcdev,
				    struct reset_control *rstc)
{
	lockdep_assert_held(&rcdev->lock);

	list_del(&rstc->list);
	module_put(rcdev->owner);
	put_device(rcdev->dev);
}

/**
 * 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)
{
	struct reset_control *rstc, *pos;

	scoped_guard(mutex, &reset_list_mutex)
		list_del(&rcdev->list);

	scoped_guard(mutex, &rcdev->lock) {
		/*
		 * Numb but don't free the remaining reset control handles that are
		 * still held by consumers.
		 */
		list_for_each_entry_safe(rstc, pos, &rcdev->reset_control_head, list) {
			rcu_assign_pointer(rstc->rcdev, NULL);
			synchronize_srcu(&rstc->srcu);
			reset_controller_remove(rcdev, rstc);
		}
	}

	mutex_destroy(&rcdev->lock);
}
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) {
		devres_free(rcdevp);
		return ret;
	}

	*rcdevp = rcdev;
	devres_add(dev, rcdevp);

	return ret;
}
EXPORT_SYMBOL_GPL(devm_reset_controller_register);

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_rearm(struct reset_control_array *resets)
{
	struct reset_control *rstc;
	int i;

	for (i = 0; i < resets->num_rstcs; i++) {
		rstc = resets->rstc[i];

		if (!rstc)
			continue;

		if (WARN_ON(IS_ERR(rstc)))
			return -EINVAL;

		if (rstc->shared) {
			if (WARN_ON(atomic_read(&rstc->deassert_count) != 0))
				return -EINVAL;
		} else {
			if (!rstc->acquired)
				return -EPERM;
		}
	}

	for (i = 0; i < resets->num_rstcs; i++) {
		rstc = resets->rstc[i];

		if (rstc && rstc->shared)
			WARN_ON(atomic_dec_return(&rstc->triggered_count) < 0);
	}

	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 int reset_control_array_acquire(struct reset_control_array *resets)
{
	unsigned int i;
	int err;

	for (i = 0; i < resets->num_rstcs; i++) {
		err = reset_control_acquire(resets->rstc[i]);
		if (err < 0)
			goto release;
	}

	return 0;

release:
	while (i--)
		reset_control_release(resets->rstc[i]);

	return err;
}

static void reset_control_array_release(struct reset_control_array *resets)
{
	unsigned int i;

	for (i = 0; i < resets->num_rstcs; i++)
		reset_control_release(resets->rstc[i]);
}

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)
{
	struct reset_controller_dev *rcdev;
	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));

	guard(srcu)(&rstc->srcu);

	rcdev = srcu_dereference(rstc->rcdev, &rstc->srcu);
	if (!rcdev)
		return -ENODEV;

	if (!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;
	} else {
		if (!rstc->acquired)
			return -EPERM;
	}

	ret = rcdev->ops->reset(rcdev, rstc->id);
	if (rstc->shared && ret)
		atomic_dec(&rstc->triggered_count);

	return ret;
}
EXPORT_SYMBOL_GPL(reset_control_reset);

/**
 * reset_control_bulk_reset - reset the controlled devices in order
 * @num_rstcs: number of entries in rstcs array
 * @rstcs: array of struct reset_control_bulk_data with reset controls set
 *
 * Issue a reset on all provided reset controls, in order.
 *
 * See also: reset_control_reset()
 */
int reset_control_bulk_reset(int num_rstcs,
			     struct reset_control_bulk_data *rstcs)
{
	int ret, i;

	for (i = 0; i < num_rstcs; i++) {
		ret = reset_control_reset(rstcs[i].rstc);
		if (ret)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(reset_control_bulk_reset);

/**
 * reset_control_rearm - allow shared reset line to be re-triggered
 * @rstc: reset controller
 *
 * On a shared reset line the actual reset pulse is only triggered once for the
 * lifetime of the reset_control instance, except if this call is used.
 *
 * Calls to this function must be balanced with calls to reset_control_reset,
 * a warning is thrown in case triggered_count ever dips below 0.
 *
 * Consumers must not use reset_control_(de)assert on shared reset lines when
 * reset_control_reset or reset_control_rearm have been used.
 *
 * If rstc is NULL the function will just return 0.
 */
int reset_control_rearm(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_rearm(rstc_to_array(rstc));

	if (rstc->shared) {
		if (WARN_ON(atomic_read(&rstc->deassert_count) != 0))
			return -EINVAL;

		WARN_ON(atomic_dec_return(&rstc->triggered_count) < 0);
	} else {
		if (!rstc->acquired)
			return -EPERM;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(reset_control_rearm);

/**
 * 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.
 *
 * If rstc is NULL it is an optional reset and the function will just
 * return 0.
 */
int reset_control_assert(struct reset_control *rstc)
{
	struct reset_controller_dev *rcdev;

	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));

	guard(srcu)(&rstc->srcu);

	rcdev = srcu_dereference(rstc->rcdev, &rstc->srcu);
	if (!rcdev)
		return -ENODEV;

	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 (!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 (!rcdev->ops->assert)
			return -ENOTSUPP;

		if (!rstc->acquired) {
			WARN(1, "reset %s (ID: %u) is not acquired\n",
			     rcdev_name(rcdev), rstc->id);
			return -EPERM;
		}
	}

	return rcdev->ops->assert(rcdev, rstc->id);
}
EXPORT_SYMBOL_GPL(reset_control_assert);

/**
 * reset_control_bulk_assert - asserts the reset lines in order
 * @num_rstcs: number of entries in rstcs array
 * @rstcs: array of struct reset_control_bulk_data with reset controls set
 *
 * Assert the reset lines for all provided reset controls, in order.
 * If an assertion fails, already asserted resets are deasserted again.
 *
 * See also: reset_control_assert()
 */
int reset_control_bulk_assert(int num_rstcs,
			      struct reset_control_bulk_data *rstcs)
{
	int ret, i;

	for (i = 0; i < num_rstcs; i++) {
		ret = reset_control_assert(rstcs[i].rstc);
		if (ret)
			goto err;
	}

	return 0;

err:
	while (i--)
		reset_control_deassert(rstcs[i].rstc);
	return ret;
}
EXPORT_SYMBOL_GPL(reset_control_bulk_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.
 *
 * If rstc is NULL it is an optional reset and the function will just
 * return 0.
 */
int reset_control_deassert(struct reset_control *rstc)
{
	struct reset_controller_dev *rcdev;

	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));

	guard(srcu)(&rstc->srcu);

	rcdev = srcu_dereference(rstc->rcdev, &rstc->srcu);
	if (!rcdev)
		return -ENODEV;

	if (rstc->shared) {
		if (WARN_ON(atomic_read(&rstc->triggered_count) != 0))
			return -EINVAL;

		if (atomic_inc_return(&rstc->deassert_count) != 1)
			return 0;
	} else {
		if (!rstc->acquired) {
			WARN(1, "reset %s (ID: %u) is not acquired\n",
			     rcdev_name(rcdev), rstc->id);
			return -EPERM;
		}
	}

	/*
	 * 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 (!rcdev->ops->deassert)
		return 0;

	return rcdev->ops->deassert(rcdev, rstc->id);
}
EXPORT_SYMBOL_GPL(reset_control_deassert);

/**
 * reset_control_bulk_deassert - deasserts the reset lines in reverse order
 * @num_rstcs: number of entries in rstcs array
 * @rstcs: array of struct reset_control_bulk_data with reset controls set
 *
 * Deassert the reset lines for all provided reset controls, in reverse order.
 * If a deassertion fails, already deasserted resets are asserted again.
 *
 * See also: reset_control_deassert()
 */
int reset_control_bulk_deassert(int num_rstcs,
				struct reset_control_bulk_data *rstcs)
{
	int ret, i;

	for (i = num_rstcs - 1; i >= 0; i--) {
		ret = reset_control_deassert(rstcs[i].rstc);
		if (ret)
			goto err;
	}

	return 0;

err:
	while (i < num_rstcs)
		reset_control_assert(rstcs[i++].rstc);
	return ret;
}
EXPORT_SYMBOL_GPL(reset_control_bulk_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)
{
	struct reset_controller_dev *rcdev;

	if (!rstc)
		return 0;

	if (WARN_ON(IS_ERR(rstc)) || reset_control_is_array(rstc))
		return -EINVAL;

	guard(srcu)(&rstc->srcu);

	rcdev = srcu_dereference(rstc->rcdev, &rstc->srcu);
	if (!rcdev)
		return -ENODEV;

	if (rcdev->ops->status)
		return rcdev->ops->status(rcdev, rstc->id);

	return -ENOTSUPP;
}
EXPORT_SYMBOL_GPL(reset_control_status);

/**
 * reset_control_acquire() - acquires a reset control for exclusive use
 * @rstc: reset control
 *
 * This is used to explicitly acquire a reset control for exclusive use. Note
 * that exclusive resets are requested as acquired by default. In order for a
 * second consumer to be able to control the reset, the first consumer has to
 * release it first. Typically the easiest way to achieve this is to call the
 * reset_control_get_exclusive_released() to obtain an instance of the reset
 * control. Such reset controls are not acquired by default.
 *
 * Consumers implementing shared access to an exclusive reset need to follow
 * a specific protocol in order to work together. Before consumers can change
 * a reset they must acquire exclusive access using reset_control_acquire().
 * After they are done operating the reset, they must release exclusive access
 * with a call to reset_control_release(). Consumers are not granted exclusive
 * access to the reset as long as another consumer hasn't released a reset.
 *
 * See also: reset_control_release()
 */
int reset_control_acquire(struct reset_control *rstc)
{
	struct reset_controller_dev *rcdev;
	struct reset_control *rc;

	if (!rstc)
		return 0;

	if (WARN_ON(IS_ERR(rstc)))
		return -EINVAL;

	if (reset_control_is_array(rstc))
		return reset_control_array_acquire(rstc_to_array(rstc));

	guard(mutex)(&rstc->lock);

	if (rstc->acquired)
		return 0;

	guard(srcu)(&rstc->srcu);

	rcdev = srcu_dereference(rstc->rcdev, &rstc->srcu);
	if (!rcdev)
		return -ENODEV;

	scoped_guard(mutex, &rcdev->lock) {
		list_for_each_entry(rc, &rcdev->reset_control_head, list) {
			if (rstc != rc && rstc->id == rc->id) {
				if (rc->acquired)
					return -EBUSY;
			}
		}
	}

	rstc->acquired = true;

	return 0;
}
EXPORT_SYMBOL_GPL(reset_control_acquire);

/**
 * reset_control_bulk_acquire - acquires reset controls for exclusive use
 * @num_rstcs: number of entries in rstcs array
 * @rstcs: array of struct reset_control_bulk_data with reset controls set
 *
 * This is used to explicitly acquire reset controls requested with
 * reset_control_bulk_get_exclusive_release() for temporary exclusive use.
 *
 * See also: reset_control_acquire(), reset_control_bulk_release()
 */
int reset_control_bulk_acquire(int num_rstcs,
			       struct reset_control_bulk_data *rstcs)
{
	int ret, i;

	for (i = 0; i < num_rstcs; i++) {
		ret = reset_control_acquire(rstcs[i].rstc);
		if (ret)
			goto err;
	}

	return 0;

err:
	while (i--)
		reset_control_release(rstcs[i].rstc);
	return ret;
}
EXPORT_SYMBOL_GPL(reset_control_bulk_acquire);

/**
 * reset_control_release() - releases exclusive access to a reset control
 * @rstc: reset control
 *
 * Releases exclusive access right to a reset control previously obtained by a
 * call to reset_control_acquire(). Until a consumer calls this function, no
 * other consumers will be granted exclusive access.
 *
 * See also: reset_control_acquire()
 */
void reset_control_release(struct reset_control *rstc)
{
	if (!rstc || WARN_ON(IS_ERR(rstc)))
		return;

	if (reset_control_is_array(rstc))
		reset_control_array_release(rstc_to_array(rstc));
	else
		rstc->acquired = false;
}
EXPORT_SYMBOL_GPL(reset_control_release);

/**
 * reset_control_bulk_release() - releases exclusive access to reset controls
 * @num_rstcs: number of entries in rstcs array
 * @rstcs: array of struct reset_control_bulk_data with reset controls set
 *
 * Releases exclusive access right to reset controls previously obtained by a
 * call to reset_control_bulk_acquire().
 *
 * See also: reset_control_release(), reset_control_bulk_acquire()
 */
void reset_control_bulk_release(int num_rstcs,
				struct reset_control_bulk_data *rstcs)
{
	int i;

	for (i = 0; i < num_rstcs; i++)
		reset_control_release(rstcs[i].rstc);
}
EXPORT_SYMBOL_GPL(reset_control_bulk_release);

static struct reset_control *
__reset_control_get_internal(struct reset_controller_dev *rcdev,
			     unsigned int index, enum reset_control_flags flags)
{
	bool shared = flags & RESET_CONTROL_FLAGS_BIT_SHARED;
	bool acquired = flags & RESET_CONTROL_FLAGS_BIT_ACQUIRED;
	struct reset_control *rstc;
	int ret;

	lockdep_assert_held(&rcdev->lock);

	/* Expect callers to filter out OPTIONAL and DEASSERTED bits */
	if (WARN_ON(flags & ~(RESET_CONTROL_FLAGS_BIT_SHARED |
			      RESET_CONTROL_FLAGS_BIT_ACQUIRED)))
		return ERR_PTR(-EINVAL);

	list_for_each_entry(rstc, &rcdev->reset_control_head, list) {
		if (rstc->id == index) {
			/*
			 * Allow creating a secondary exclusive reset_control
			 * that is initially not acquired for an already
			 * controlled reset line.
			 */
			if (!rstc->shared && !shared && !acquired)
				break;

			if (WARN_ON(!rstc->shared || !shared))
				return ERR_PTR(-EBUSY);

			kref_get(&rstc->refcnt);
			return rstc;
		}
	}

	rstc = kzalloc_obj(*rstc);
	if (!rstc)
		return ERR_PTR(-ENOMEM);

	ret = init_srcu_struct(&rstc->srcu);
	if (ret) {
		kfree(rstc);
		return ERR_PTR(ret);
	}

	if (!try_module_get(rcdev->owner)) {
		cleanup_srcu_struct(&rstc->srcu);
		kfree(rstc);
		return ERR_PTR(-ENODEV);
	}

	rcu_assign_pointer(rstc->rcdev, rcdev);
	list_add(&rstc->list, &rcdev->reset_control_head);
	rstc->id = index;
	kref_init(&rstc->refcnt);
	mutex_init(&rstc->lock);
	rstc->acquired = acquired;
	rstc->shared = shared;
	get_device(rcdev->dev);

	return rstc;
}

static void __reset_control_release(struct kref *kref)
{
	struct reset_control *rstc = container_of(kref, struct reset_control,
						  refcnt);
	struct reset_controller_dev *rcdev;

	lockdep_assert_held(&rstc->srcu);

	rcdev = rcu_replace_pointer(rstc->rcdev, NULL, true);
	if (rcdev) {
		lockdep_assert_held(&rcdev->lock);
		reset_controller_remove(rcdev, rstc);
	}

	mutex_destroy(&rstc->lock);
}

static void reset_control_put_internal(struct reset_control *rstc)
{
	struct reset_controller_dev *rcdev;
	int ret = 0;

	if (IS_ERR_OR_NULL(rstc))
		return;

	scoped_guard(srcu, &rstc->srcu) {
		rcdev = srcu_dereference(rstc->rcdev, &rstc->srcu);
		if (!rcdev)
			/* Already released. */
			return;

		guard(mutex)(&rcdev->lock);
		ret = kref_put(&rstc->refcnt, __reset_control_release);
	}

	if (ret) {
		synchronize_srcu(&rstc->srcu);
		cleanup_srcu_struct(&rstc->srcu);
		kfree(rstc);
	}
}

static void reset_gpio_aux_device_release(struct device *dev)
{
	WARN(1, "reset-gpio device %s should never have been removed", dev_name(dev));
}

static int reset_create_gpio_aux_device(struct reset_gpio_lookup *rgpio_dev,
					struct device *parent)
{
	struct auxiliary_device *adev = &rgpio_dev->adev;
	int ret, id;

	id = ida_alloc(&reset_gpio_ida, GFP_KERNEL);
	if (id < 0)
		return -ENOMEM;

	adev->id = id;
	adev->name = "gpio";
	adev->dev.parent = parent;
	adev->dev.platform_data = &rgpio_dev->ref_args;
	adev->dev.release = reset_gpio_aux_device_release;
	device_set_node(&adev->dev, rgpio_dev->swnode);

	ret = auxiliary_device_init(adev);
	if (ret) {
		ida_free(&reset_gpio_ida, id);
		return ret;
	}

	ret = __auxiliary_device_add(adev, "reset");
	if (ret) {
		auxiliary_device_uninit(adev);
		ida_free(&reset_gpio_ida, id);
		return ret;
	}

	return 0;
}

static void reset_gpio_add_devlink(struct fwnode_handle *fwnode,
				   struct reset_gpio_lookup *rgpio_dev)
{
	struct device *consumer;

	/*
	 * We must use get_dev_from_fwnode() and not ref_find_device_by_node()
	 * because the latter only considers the platform bus while we want to
	 * get consumers of any kind that can be associated with firmware
	 * nodes: auxiliary, soundwire, etc.
	 */
	consumer = get_dev_from_fwnode(fwnode);
	if (consumer) {
		if (!device_link_add(consumer, &rgpio_dev->adev.dev,
				     DL_FLAG_AUTOREMOVE_CONSUMER))
			pr_warn("Failed to create a device link between reset-gpio and its consumer");

		put_device(consumer);
	}
	/*
	 * else { }
	 *
	 * TODO: If ever there's a case where we need to support shared
	 * reset-gpios retrieved from a device node for which there's no
	 * device present yet, this is where we'd set up a notifier waiting
	 * for the device to appear in the system. This would be a lot of code
	 * that would go unused for now so let's cross that bridge when and if
	 * we get there.
	 */
}

/* TODO: move it out into drivers/base/ */
static bool fwnode_reference_args_equal(const struct fwnode_reference_args *left,
					const struct fwnode_reference_args *right)
{
	return left->fwnode == right->fwnode && left->nargs == right->nargs &&
	       !memcmp(left->args, right->args, sizeof(left->args[0]) * left->nargs);
}

/*
 * @np: OF-node associated with the consumer
 * @args: Reference to the GPIO provider with all the args like GPIO number
 */
static int __reset_add_reset_gpio_device(struct fwnode_handle *fwnode,
					 const struct fwnode_reference_args *args)
{
	struct property_entry properties[3] = { };
	unsigned int offset, flags, lflags;
	struct reset_gpio_lookup *rgpio_dev;
	struct device *parent;
	int ret, prop = 0;

	/*
	 * Currently only #gpio-cells=2 is supported with the meaning of:
	 * args[0]: GPIO number
	 * args[1]: GPIO flags
	 * TODO: Handle other cases.
	 */
	if (args->nargs != 2)
		return -ENOENT;

	/*
	 * Registering reset-gpio device might cause immediate
	 * bind, resulting in its probe() registering new reset controller thus
	 * taking reset_list_mutex lock via reset_controller_register().
	 */
	lockdep_assert_not_held(&reset_list_mutex);

	offset = args->args[0];
	flags = args->args[1];

	/*
	 * Later we map GPIO flags between OF and Linux, however not all
	 * constants from include/dt-bindings/gpio/gpio.h and
	 * include/linux/gpio/machine.h match each other.
	 *
	 * FIXME: Find a better way of translating OF flags to GPIO lookup
	 * flags.
	 */
	if (flags > GPIO_ACTIVE_LOW) {
		pr_err("reset-gpio code does not support GPIO flags %u for GPIO %u\n",
		       flags, offset);
		return -EINVAL;
	}

	struct gpio_device *gdev __free(gpio_device_put) =
			gpio_device_find_by_fwnode(args->fwnode);
	if (!gdev)
		return -EPROBE_DEFER;

	guard(mutex)(&reset_gpio_lookup_mutex);

	list_for_each_entry(rgpio_dev, &reset_gpio_lookup_list, list) {
		if (fwnode_reference_args_equal(args, &rgpio_dev->ref_args)) {
			/*
			 * Already on the list, create the device link
			 * and stop here.
			 */
			reset_gpio_add_devlink(fwnode, rgpio_dev);
			return 0;
		}
	}

	lflags = GPIO_PERSISTENT | (flags & GPIO_ACTIVE_LOW);
	parent = gpio_device_to_device(gdev);
	properties[prop++] = PROPERTY_ENTRY_STRING("compatible", "reset-gpio");
	properties[prop++] = PROPERTY_ENTRY_GPIO("reset-gpios", parent->fwnode, offset, lflags);

	/* Not freed on success, because it is persisent subsystem data. */
	rgpio_dev = kzalloc_obj(*rgpio_dev);
	if (!rgpio_dev)
		return -ENOMEM;

	rgpio_dev->ref_args = *args;
	/*
	 * We keep the fwnode_handle reference, but ref_args.fwnode is put at
	 * the end of __fwnode_reset_control_get(), so get it one more time.
	 * Hold reference as long as rgpio_dev memory is valid.
	 */
	fwnode_handle_get(rgpio_dev->ref_args.fwnode);

	rgpio_dev->swnode = fwnode_create_software_node(properties, NULL);
	if (IS_ERR(rgpio_dev->swnode)) {
		ret = PTR_ERR(rgpio_dev->swnode);
		goto err_put_fwnode;
	}

	ret = reset_create_gpio_aux_device(rgpio_dev, parent);
	if (ret)
		goto err_del_swnode;

	reset_gpio_add_devlink(fwnode, rgpio_dev);
	list_add(&rgpio_dev->list, &reset_gpio_lookup_list);

	return 0;

err_del_swnode:
	fwnode_remove_software_node(rgpio_dev->swnode);
err_put_fwnode:
	fwnode_handle_put(rgpio_dev->ref_args.fwnode);
	kfree(rgpio_dev);

	return ret;
}

static struct reset_controller_dev *
__reset_find_rcdev(const struct fwnode_reference_args *args, bool gpio_fallback)
{
	struct fwnode_reference_args *rc_args;
	struct reset_controller_dev *rcdev;

	lockdep_assert_held(&reset_list_mutex);

	list_for_each_entry(rcdev, &reset_controller_list, list) {
		if (gpio_fallback && rcdev->dev &&
		    device_is_compatible(rcdev->dev, "reset-gpio")) {
			rc_args = dev_get_platdata(rcdev->dev);

			if (fwnode_reference_args_equal(args, rc_args))
				return rcdev;
		} else {
			if (args->fwnode == rcdev->fwnode)
				return rcdev;
		}
	}

	return NULL;
}

struct reset_control *
__fwnode_reset_control_get(struct fwnode_handle *fwnode, const char *id, int index,
			   enum reset_control_flags flags)
{
	bool optional = flags & RESET_CONTROL_FLAGS_BIT_OPTIONAL;
	bool gpio_fallback = false;
	struct reset_control *rstc = ERR_PTR(-EINVAL);
	struct reset_controller_dev *rcdev;
	struct fwnode_reference_args args;
	struct of_phandle_args of_args;
	int rstc_id = -EINVAL;
	int ret;

	if (!fwnode)
		return ERR_PTR(-EINVAL);

	if (id) {
		index = fwnode_property_match_string(fwnode, "reset-names", id);
		if (index == -EILSEQ)
			return ERR_PTR(index);
		if (index < 0)
			return optional ? NULL : ERR_PTR(-ENOENT);
	}

	ret = fwnode_property_get_reference_args(fwnode, "resets", "#reset-cells",
						 0, index, &args);
	if (ret == -EINVAL)
		return ERR_PTR(ret);
	if (ret) {
		if (!IS_ENABLED(CONFIG_RESET_GPIO))
			return optional ? NULL : ERR_PTR(ret);

		/*
		 * There can be only one reset-gpio for regular devices, so
		 * don't bother with the "reset-gpios" phandle index.
		 */
		ret = fwnode_property_get_reference_args(fwnode, "reset-gpios",
							 "#gpio-cells", 0, 0, &args);
		if (ret)
			return optional ? NULL : ERR_PTR(ret);

		gpio_fallback = true;

		ret = __reset_add_reset_gpio_device(fwnode, &args);
		if (ret) {
			fwnode_handle_put(args.fwnode);
			return ERR_PTR(ret);
		}
	}

	guard(mutex)(&reset_list_mutex);

	rcdev = __reset_find_rcdev(&args, gpio_fallback);
	if (!rcdev) {
		rstc = ERR_PTR(-EPROBE_DEFER);
		goto out_put;
	}

	if (WARN_ON(args.nargs != rcdev->fwnode_reset_n_cells)) {
		rstc = ERR_PTR(-EINVAL);
		goto out_put;
	}

	if (rcdev->of_xlate && is_of_node(fwnode)) {
		ret = of_parse_phandle_with_args(to_of_node(fwnode),
					 gpio_fallback ? "reset-gpios" : "resets",
					 gpio_fallback ? "#gpio-cells" : "#reset-cells",
					 gpio_fallback ? 0 : index,
					 &of_args);
		if (ret) {
			rstc = ERR_PTR(ret);
			goto out_put;
		}

		rstc_id = rcdev->of_xlate(rcdev, &of_args);
		of_node_put(of_args.np);
	} else if (rcdev->fwnode_xlate) {
		rstc_id = rcdev->fwnode_xlate(rcdev, &args);
	}
	if (rstc_id < 0) {
		rstc = ERR_PTR(rstc_id);
		goto out_put;
	}

	flags &= ~RESET_CONTROL_FLAGS_BIT_OPTIONAL;

	scoped_guard(mutex, &rcdev->lock)
		rstc = __reset_control_get_internal(rcdev, rstc_id, flags);

out_put:
	fwnode_handle_put(args.fwnode);

	return rstc;
}
EXPORT_SYMBOL_GPL(__fwnode_reset_control_get);

struct reset_control *__reset_control_get(struct device *dev, const char *id,
					  int index, enum reset_control_flags flags)
{
	bool shared = flags & RESET_CONTROL_FLAGS_BIT_SHARED;
	bool acquired = flags & RESET_CONTROL_FLAGS_BIT_ACQUIRED;
	bool optional = flags & RESET_CONTROL_FLAGS_BIT_OPTIONAL;
	struct fwnode_handle *fwnode = dev_fwnode(dev);

	if (WARN_ON(shared && acquired))
		return ERR_PTR(-EINVAL);

	if (fwnode)
		return __fwnode_reset_control_get(fwnode, id, index, flags);

	return optional ? NULL : ERR_PTR(-ENOENT);
}
EXPORT_SYMBOL_GPL(__reset_control_get);

int __reset_control_bulk_get(struct device *dev, int num_rstcs,
			     struct reset_control_bulk_data *rstcs,
			     enum reset_control_flags flags)
{
	int ret, i;

	for (i = 0; i < num_rstcs; i++) {
		rstcs[i].rstc = __reset_control_get(dev, rstcs[i].id, 0, flags);
		if (IS_ERR(rstcs[i].rstc)) {
			ret = PTR_ERR(rstcs[i].rstc);
			goto err;
		}
	}

	return 0;

err:
	while (i--)
		reset_control_put_internal(rstcs[i].rstc);

	return ret;
}
EXPORT_SYMBOL_GPL(__reset_control_bulk_get);

static void reset_control_array_put(struct reset_control_array *resets)
{
	int i;

	for (i = 0; i < resets->num_rstcs; i++)
		reset_control_put_internal(resets->rstc[i]);
	kfree(resets);
}

/**
 * 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;
	}

	reset_control_put_internal(rstc);
}
EXPORT_SYMBOL_GPL(reset_control_put);

/**
 * reset_control_bulk_put - free the reset controllers
 * @num_rstcs: number of entries in rstcs array
 * @rstcs: array of struct reset_control_bulk_data with reset controls set
 */
void reset_control_bulk_put(int num_rstcs, struct reset_control_bulk_data *rstcs)
{
	while (num_rstcs--)
		reset_control_put_internal(rstcs[num_rstcs].rstc);
}
EXPORT_SYMBOL_GPL(reset_control_bulk_put);

static void devm_reset_control_release(struct device *dev, void *res)
{
	reset_control_put(*(struct reset_control **)res);
}

static void devm_reset_control_release_deasserted(struct device *dev, void *res)
{
	struct reset_control *rstc = *(struct reset_control **)res;

	reset_control_assert(rstc);
	reset_control_put(rstc);
}

struct reset_control *
__devm_reset_control_get(struct device *dev, const char *id, int index,
			 enum reset_control_flags flags)
{
	struct reset_control **ptr, *rstc;
	bool deasserted = flags & RESET_CONTROL_FLAGS_BIT_DEASSERTED;

	ptr = devres_alloc(deasserted ? devm_reset_control_release_deasserted :
			   devm_reset_control_release, sizeof(*ptr),
			   GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	flags &= ~RESET_CONTROL_FLAGS_BIT_DEASSERTED;

	rstc = __reset_control_get(dev, id, index, flags);
	if (IS_ERR_OR_NULL(rstc)) {
		devres_free(ptr);
		return rstc;
	}

	if (deasserted) {
		int ret;

		ret = reset_control_deassert(rstc);
		if (ret) {
			reset_control_put(rstc);
			devres_free(ptr);
			return ERR_PTR(ret);
		}
	}

	*ptr = rstc;
	devres_add(dev, ptr);

	return rstc;
}
EXPORT_SYMBOL_GPL(__devm_reset_control_get);

struct reset_control_bulk_devres {
	int num_rstcs;
	struct reset_control_bulk_data *rstcs;
};

static void devm_reset_control_bulk_release(struct device *dev, void *res)
{
	struct reset_control_bulk_devres *devres = res;

	reset_control_bulk_put(devres->num_rstcs, devres->rstcs);
}

static void devm_reset_control_bulk_release_deasserted(struct device *dev, void *res)
{
	struct reset_control_bulk_devres *devres = res;

	reset_control_bulk_assert(devres->num_rstcs, devres->rstcs);
	reset_control_bulk_put(devres->num_rstcs, devres->rstcs);
}

int __devm_reset_control_bulk_get(struct device *dev, int num_rstcs,
				  struct reset_control_bulk_data *rstcs,
				  enum reset_control_flags flags)
{
	struct reset_control_bulk_devres *ptr;
	bool deasserted = flags & RESET_CONTROL_FLAGS_BIT_DEASSERTED;
	int ret;

	ptr = devres_alloc(deasserted ? devm_reset_control_bulk_release_deasserted :
			   devm_reset_control_bulk_release, sizeof(*ptr),
			   GFP_KERNEL);
	if (!ptr)
		return -ENOMEM;

	flags &= ~RESET_CONTROL_FLAGS_BIT_DEASSERTED;

	ret = __reset_control_bulk_get(dev, num_rstcs, rstcs, flags);
	if (ret < 0) {
		devres_free(ptr);
		return ret;
	}

	if (deasserted) {
		ret = reset_control_bulk_deassert(num_rstcs, rstcs);
		if (ret) {
			reset_control_bulk_put(num_rstcs, rstcs);
			devres_free(ptr);
			return ret;
		}
	}

	ptr->num_rstcs = num_rstcs;
	ptr->rstcs = rstcs;
	devres_add(dev, ptr);

	return 0;
}
EXPORT_SYMBOL_GPL(__devm_reset_control_bulk_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. _RST firmware method will be called for devices with ACPI.
 */
int __device_reset(struct device *dev, bool optional)
{
	enum reset_control_flags flags;
	struct reset_control *rstc;
	int ret;

#ifdef CONFIG_ACPI
	acpi_handle handle = ACPI_HANDLE(dev);

	if (handle) {
		if (!acpi_has_method(handle, "_RST"))
			return optional ? 0 : -ENOENT;
		if (ACPI_FAILURE(acpi_evaluate_object(handle, "_RST", NULL,
						      NULL)))
			return -EIO;
	}
#endif

	flags = optional ? RESET_CONTROL_OPTIONAL_EXCLUSIVE : RESET_CONTROL_EXCLUSIVE;
	rstc = __reset_control_get(dev, NULL, 0, flags);
	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.
 */

/**
 * fwnode_reset_control_get_count - Count number of resets available with a device
 *
 * @fwnode: firmware node that contains 'resets'.
 *
 * Returns positive reset count on success, or error number on failure and
 * on count being zero.
 */
static int fwnode_reset_control_get_count(struct fwnode_handle *fwnode)
{
	struct fwnode_reference_args args;
	int count = 0, ret;

	if (!fwnode)
		return -EINVAL;

	for (;;) {
		ret = fwnode_property_get_reference_args(fwnode, "resets", "#reset-cells",
							 0, count, &args);
		if (ret) {
			if (ret == -ENOENT)
				break;

			return ret;
		}

		fwnode_handle_put(args.fwnode);
		count++;
	}

	if (count == 0)
		count = -ENOENT;

	return count;
}

/**
 * fwnode_reset_control_array_get - Get a list of reset controls using
 *                                  a firmware node.
 *
 * @fwnode: firmware node for the device that requests the reset controls array
 * @flags: whether reset controls are shared, optional, acquired
 *
 * Returns pointer to allocated reset_control on success or error on failure
 */
struct reset_control *
fwnode_reset_control_array_get(struct fwnode_handle *fwnode,
			       enum reset_control_flags flags)
{
	bool optional = flags & RESET_CONTROL_FLAGS_BIT_OPTIONAL;
	struct reset_control_array *resets;
	struct reset_control *rstc;
	int num, i;

	num = fwnode_reset_control_get_count(fwnode);
	if (num < 0)
		return optional ? NULL : ERR_PTR(num);

	resets = kzalloc_flex(*resets, rstc, num);
	if (!resets)
		return ERR_PTR(-ENOMEM);
	resets->num_rstcs = num;

	for (i = 0; i < num; i++) {
		rstc = __fwnode_reset_control_get(fwnode, NULL, i, flags);
		if (IS_ERR(rstc))
			goto err_rst;
		resets->rstc[i] = rstc;
	}
	resets->base.array = true;

	return &resets->base;

err_rst:
	while (--i >= 0)
		reset_control_put_internal(resets->rstc[i]);

	kfree(resets);

	return rstc;
}
EXPORT_SYMBOL_GPL(fwnode_reset_control_array_get);

/**
 * devm_reset_control_array_get - Resource managed reset control array get
 *
 * @dev: device that requests the list of reset controls
 * @flags: whether reset controls are shared, optional, acquired
 *
 * 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 on success or error on failure
 */
struct reset_control *
devm_reset_control_array_get(struct device *dev, enum reset_control_flags flags)
{
	struct reset_control **ptr, *rstc;

	ptr = devres_alloc(devm_reset_control_release, sizeof(*ptr),
			   GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	rstc = fwnode_reset_control_array_get(dev_fwnode(dev), flags);
	if (IS_ERR_OR_NULL(rstc)) {
		devres_free(ptr);
		return rstc;
	}

	*ptr = rstc;
	devres_add(dev, ptr);

	return rstc;
}
EXPORT_SYMBOL_GPL(devm_reset_control_array_get);

/**
 * reset_control_get_count - Count number of resets available with a device
 *
 * @dev: device for which to return the number of resets
 *
 * Returns positive reset count on success, or error number on failure and
 * on count being zero.
 */
int reset_control_get_count(struct device *dev)
{
	struct fwnode_handle *fwnode = dev_fwnode(dev);

	if (fwnode)
		return fwnode_reset_control_get_count(fwnode);

	return -ENOENT;
}
EXPORT_SYMBOL_GPL(reset_control_get_count);