// 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);