/*
 * 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/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
 */
struct reset_control {
        struct reset_controller_dev *rcdev;
        struct list_head list;
        unsigned int id;
        unsigned int refcnt;
        int shared;
        atomic_t deassert_count;
};

/**
 * of_reset_simple_xlate - translate reset_spec to the reset line number
 * @rcdev: a pointer to the reset controller device
 * @reset_spec: reset line specifier as found in the device tree
 * @flags: a flags pointer to fill in (optional)
 *
 * This simple translation function should be used for reset controllers
 * with 1:1 mapping, where reset lines can be indexed by number without gaps.
 */
static int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
                          const struct of_phandle_args *reset_spec)
{
        if (reset_spec->args[0] >= rcdev->nr_resets)
                return -EINVAL;

        return reset_spec->args[0];
}

/**
 * reset_controller_register - register a reset controller device
 * @rcdev: a pointer to the initialized reset controller device
 */
int reset_controller_register(struct reset_controller_dev *rcdev)
{
        if (!rcdev->of_xlate) {
                rcdev->of_reset_n_cells = 1;
                rcdev->of_xlate = of_reset_simple_xlate;
        }

        INIT_LIST_HEAD(&rcdev->reset_control_head);

        mutex_lock(&reset_list_mutex);
        list_add(&rcdev->list, &reset_controller_list);
        mutex_unlock(&reset_list_mutex);

        return 0;
}
EXPORT_SYMBOL_GPL(reset_controller_register);

/**
 * reset_controller_unregister - unregister a reset controller device
 * @rcdev: a pointer to the reset controller device
 */
void reset_controller_unregister(struct reset_controller_dev *rcdev)
{
        mutex_lock(&reset_list_mutex);
        list_del(&rcdev->list);
        mutex_unlock(&reset_list_mutex);
}
EXPORT_SYMBOL_GPL(reset_controller_unregister);

static void devm_reset_controller_release(struct device *dev, void *res)
{
        reset_controller_unregister(*(struct reset_controller_dev **)res);
}

/**
 * devm_reset_controller_register - resource managed reset_controller_register()
 * @dev: device that is registering this reset controller
 * @rcdev: a pointer to the initialized reset controller device
 *
 * Managed reset_controller_register(). For reset controllers registered by
 * this function, reset_controller_unregister() is automatically called on
 * driver detach. See reset_controller_register() for more information.
 */
int devm_reset_controller_register(struct device *dev,
                                   struct reset_controller_dev *rcdev)
{
        struct reset_controller_dev **rcdevp;
        int ret;

        rcdevp = devres_alloc(devm_reset_controller_release, sizeof(*rcdevp),
                              GFP_KERNEL);
        if (!rcdevp)
                return -ENOMEM;

        ret = reset_controller_register(rcdev);
        if (!ret) {
                *rcdevp = rcdev;
                devres_add(dev, rcdevp);
        } else {
                devres_free(rcdevp);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(devm_reset_controller_register);

/**
 * reset_control_reset - reset the controlled device
 * @rstc: reset controller
 *
 * Calling this on a shared reset controller is an error.
 */
int reset_control_reset(struct reset_control *rstc)
{
        if (WARN_ON(rstc->shared))
                return -EINVAL;

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

        return -ENOTSUPP;
}
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.
 */
int reset_control_assert(struct reset_control *rstc)
{
        if (!rstc->rcdev->ops->assert)
                return -ENOTSUPP;

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

                if (atomic_dec_return(&rstc->deassert_count) != 0)
                        return 0;
        }

        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.
 */
int reset_control_deassert(struct reset_control *rstc)
{
        if (!rstc->rcdev->ops->deassert)
                return -ENOTSUPP;

        if (rstc->shared) {
                if (atomic_inc_return(&rstc->deassert_count) != 1)
                        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.
 * @rstc: reset controller
 */
int reset_control_status(struct reset_control *rstc)
{
        if (rstc->rcdev->ops->status)
                return rstc->rcdev->ops->status(rstc->rcdev, rstc->id);

        return -ENOTSUPP;
}
EXPORT_SYMBOL_GPL(reset_control_status);

static struct reset_control *__reset_control_get(
                                struct reset_controller_dev *rcdev,
                                unsigned int index, int 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);

                        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;
        rstc->refcnt = 1;
        rstc->shared = shared;

        return rstc;
}

static void __reset_control_put(struct reset_control *rstc)
{
        lockdep_assert_held(&reset_list_mutex);

        if (--rstc->refcnt)
                return;

        module_put(rstc->rcdev->owner);

        list_del(&rstc->list);
        kfree(rstc);
}

struct reset_control *__of_reset_control_get(struct device_node *node,
                                     const char *id, int index, int shared)
{
        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 < 0)
                        return ERR_PTR(-ENOENT);
        }

        ret = of_parse_phandle_with_args(node, "resets", "#reset-cells",
                                         index, &args);
        if (ret)
                return 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(rcdev, rstc_id, shared);

        mutex_unlock(&reset_list_mutex);

        return rstc;
}
EXPORT_SYMBOL_GPL(__of_reset_control_get);

/**
 * reset_control_put - free the reset controller
 * @rstc: reset controller
 */

void reset_control_put(struct reset_control *rstc)
{
        if (IS_ERR(rstc))
                return;

        mutex_lock(&reset_list_mutex);
        __reset_control_put(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, int shared)
{
        struct reset_control **ptr, *rstc;

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

        rstc = __of_reset_control_get(dev ? dev->of_node : NULL,
                                      id, index, shared);
        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);