/*
 * 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);

/**
 * 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);

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;
                }
        }
        of_node_put(args.np);

        if (!rcdev) {
                mutex_unlock(&reset_list_mutex);
                return ERR_PTR(-EPROBE_DEFER);
        }

        if (WARN_ON(args.args_count != rcdev->of_reset_n_cells)) {
                mutex_unlock(&reset_list_mutex);
                return ERR_PTR(-EINVAL);
        }

        rstc_id = rcdev->of_xlate(rcdev, &args);
        if (rstc_id < 0) {
                mutex_unlock(&reset_list_mutex);
                return ERR_PTR(rstc_id);
        }

        /* reset_list_mutex also protects the rcdev's reset_control list */
        rstc = __reset_control_get_internal(rcdev, rstc_id, shared);

        mutex_unlock(&reset_list_mutex);

        return rstc;
}
EXPORT_SYMBOL_GPL(__of_reset_control_get);

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 optional ? NULL : ERR_PTR(-EINVAL);
}
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
 *
 * Convenience wrapper for reset_control_get() and reset_control_reset().
 * This is useful for the common case of devices with single, dedicated reset
 * lines.
 */
int device_reset(struct device *dev)
{
        struct reset_control *rstc;
        int ret;

        rstc = reset_control_get(dev, NULL);
        if (IS_ERR(rstc))
                return PTR_ERR(rstc);

        ret = reset_control_reset(rstc);

        reset_control_put(rstc);

        return ret;
}
EXPORT_SYMBOL_GPL(device_reset);

/**
 * 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(sizeof(*resets) + sizeof(resets->rstc[0]) * 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);