/*
 * Fence mechanism for dma-buf and to allow for asynchronous dma access
 *
 * Copyright (C) 2012 Canonical Ltd
 * Copyright (C) 2012 Texas Instruments
 *
 * Authors:
 * Rob Clark <robdclark@gmail.com>
 * Maarten Lankhorst <maarten.lankhorst@canonical.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 */

#include <linux/slab.h>
#include <linux/export.h>
#include <linux/atomic.h>
#include <linux/fence.h>

#define CREATE_TRACE_POINTS
#include <trace/events/fence.h>

EXPORT_TRACEPOINT_SYMBOL(fence_annotate_wait_on);
EXPORT_TRACEPOINT_SYMBOL(fence_emit);

/*
 * fence context counter: each execution context should have its own
 * fence context, this allows checking if fences belong to the same
 * context or not. One device can have multiple separate contexts,
 * and they're used if some engine can run independently of another.
 */
static atomic64_t fence_context_counter = ATOMIC64_INIT(0);

/**
 * fence_context_alloc - allocate an array of fence contexts
 * @num:        [in]    amount of contexts to allocate
 *
 * This function will return the first index of the number of fences allocated.
 * The fence context is used for setting fence->context to a unique number.
 */
u64 fence_context_alloc(unsigned num)
{
        BUG_ON(!num);
        return atomic64_add_return(num, &fence_context_counter) - num;
}
EXPORT_SYMBOL(fence_context_alloc);

/**
 * fence_signal_locked - signal completion of a fence
 * @fence: the fence to signal
 *
 * Signal completion for software callbacks on a fence, this will unblock
 * fence_wait() calls and run all the callbacks added with
 * fence_add_callback(). Can be called multiple times, but since a fence
 * can only go from unsignaled to signaled state, it will only be effective
 * the first time.
 *
 * Unlike fence_signal, this function must be called with fence->lock held.
 */
int fence_signal_locked(struct fence *fence)
{
        struct fence_cb *cur, *tmp;
        int ret = 0;

        if (WARN_ON(!fence))
                return -EINVAL;

        if (!ktime_to_ns(fence->timestamp)) {
                fence->timestamp = ktime_get();
                smp_mb__before_atomic();
        }

        if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
                ret = -EINVAL;

                /*
                 * we might have raced with the unlocked fence_signal,
                 * still run through all callbacks
                 */
        } else
                trace_fence_signaled(fence);

        list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
                list_del_init(&cur->node);
                cur->func(fence, cur);
        }
        return ret;
}
EXPORT_SYMBOL(fence_signal_locked);

/**
 * fence_signal - signal completion of a fence
 * @fence: the fence to signal
 *
 * Signal completion for software callbacks on a fence, this will unblock
 * fence_wait() calls and run all the callbacks added with
 * fence_add_callback(). Can be called multiple times, but since a fence
 * can only go from unsignaled to signaled state, it will only be effective
 * the first time.
 */
int fence_signal(struct fence *fence)
{
        unsigned long flags;

        if (!fence)
                return -EINVAL;

        if (!ktime_to_ns(fence->timestamp)) {
                fence->timestamp = ktime_get();
                smp_mb__before_atomic();
        }

        if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                return -EINVAL;

        trace_fence_signaled(fence);

        if (test_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
                struct fence_cb *cur, *tmp;

                spin_lock_irqsave(fence->lock, flags);
                list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
                        list_del_init(&cur->node);
                        cur->func(fence, cur);
                }
                spin_unlock_irqrestore(fence->lock, flags);
        }
        return 0;
}
EXPORT_SYMBOL(fence_signal);

/**
 * fence_wait_timeout - sleep until the fence gets signaled
 * or until timeout elapses
 * @fence:      [in]    the fence to wait on
 * @intr:       [in]    if true, do an interruptible wait
 * @timeout:    [in]    timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
 *
 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
 * remaining timeout in jiffies on success. Other error values may be
 * returned on custom implementations.
 *
 * Performs a synchronous wait on this fence. It is assumed the caller
 * directly or indirectly (buf-mgr between reservation and committing)
 * holds a reference to the fence, otherwise the fence might be
 * freed before return, resulting in undefined behavior.
 */
signed long
fence_wait_timeout(struct fence *fence, bool intr, signed long timeout)
{
        signed long ret;

        if (WARN_ON(timeout < 0))
                return -EINVAL;

        if (timeout == 0)
                return fence_is_signaled(fence);

        trace_fence_wait_start(fence);
        ret = fence->ops->wait(fence, intr, timeout);
        trace_fence_wait_end(fence);
        return ret;
}
EXPORT_SYMBOL(fence_wait_timeout);

void fence_release(struct kref *kref)
{
        struct fence *fence =
                        container_of(kref, struct fence, refcount);

        trace_fence_destroy(fence);

        BUG_ON(!list_empty(&fence->cb_list));

        if (fence->ops->release)
                fence->ops->release(fence);
        else
                fence_free(fence);
}
EXPORT_SYMBOL(fence_release);

void fence_free(struct fence *fence)
{
        kfree_rcu(fence, rcu);
}
EXPORT_SYMBOL(fence_free);

/**
 * fence_enable_sw_signaling - enable signaling on fence
 * @fence:      [in]    the fence to enable
 *
 * this will request for sw signaling to be enabled, to make the fence
 * complete as soon as possible
 */
void fence_enable_sw_signaling(struct fence *fence)
{
        unsigned long flags;

        if (!test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags) &&
            !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
                trace_fence_enable_signal(fence);

                spin_lock_irqsave(fence->lock, flags);

                if (!fence->ops->enable_signaling(fence))
                        fence_signal_locked(fence);

                spin_unlock_irqrestore(fence->lock, flags);
        }
}
EXPORT_SYMBOL(fence_enable_sw_signaling);

/**
 * fence_add_callback - add a callback to be called when the fence
 * is signaled
 * @fence:      [in]    the fence to wait on
 * @cb:         [in]    the callback to register
 * @func:       [in]    the function to call
 *
 * cb will be initialized by fence_add_callback, no initialization
 * by the caller is required. Any number of callbacks can be registered
 * to a fence, but a callback can only be registered to one fence at a time.
 *
 * Note that the callback can be called from an atomic context.  If
 * fence is already signaled, this function will return -ENOENT (and
 * *not* call the callback)
 *
 * Add a software callback to the fence. Same restrictions apply to
 * refcount as it does to fence_wait, however the caller doesn't need to
 * keep a refcount to fence afterwards: when software access is enabled,
 * the creator of the fence is required to keep the fence alive until
 * after it signals with fence_signal. The callback itself can be called
 * from irq context.
 *
 */
int fence_add_callback(struct fence *fence, struct fence_cb *cb,
                       fence_func_t func)
{
        unsigned long flags;
        int ret = 0;
        bool was_set;

        if (WARN_ON(!fence || !func))
                return -EINVAL;

        if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
                INIT_LIST_HEAD(&cb->node);
                return -ENOENT;
        }

        spin_lock_irqsave(fence->lock, flags);

        was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);

        if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                ret = -ENOENT;
        else if (!was_set) {
                trace_fence_enable_signal(fence);

                if (!fence->ops->enable_signaling(fence)) {
                        fence_signal_locked(fence);
                        ret = -ENOENT;
                }
        }

        if (!ret) {
                cb->func = func;
                list_add_tail(&cb->node, &fence->cb_list);
        } else
                INIT_LIST_HEAD(&cb->node);
        spin_unlock_irqrestore(fence->lock, flags);

        return ret;
}
EXPORT_SYMBOL(fence_add_callback);

/**
 * fence_remove_callback - remove a callback from the signaling list
 * @fence:      [in]    the fence to wait on
 * @cb:         [in]    the callback to remove
 *
 * Remove a previously queued callback from the fence. This function returns
 * true if the callback is successfully removed, or false if the fence has
 * already been signaled.
 *
 * *WARNING*:
 * Cancelling a callback should only be done if you really know what you're
 * doing, since deadlocks and race conditions could occur all too easily. For
 * this reason, it should only ever be done on hardware lockup recovery,
 * with a reference held to the fence.
 */
bool
fence_remove_callback(struct fence *fence, struct fence_cb *cb)
{
        unsigned long flags;
        bool ret;

        spin_lock_irqsave(fence->lock, flags);

        ret = !list_empty(&cb->node);
        if (ret)
                list_del_init(&cb->node);

        spin_unlock_irqrestore(fence->lock, flags);

        return ret;
}
EXPORT_SYMBOL(fence_remove_callback);

struct default_wait_cb {
        struct fence_cb base;
        struct task_struct *task;
};

static void
fence_default_wait_cb(struct fence *fence, struct fence_cb *cb)
{
        struct default_wait_cb *wait =
                container_of(cb, struct default_wait_cb, base);

        wake_up_state(wait->task, TASK_NORMAL);
}

/**
 * fence_default_wait - default sleep until the fence gets signaled
 * or until timeout elapses
 * @fence:      [in]    the fence to wait on
 * @intr:       [in]    if true, do an interruptible wait
 * @timeout:    [in]    timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
 *
 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
 * remaining timeout in jiffies on success.
 */
signed long
fence_default_wait(struct fence *fence, bool intr, signed long timeout)
{
        struct default_wait_cb cb;
        unsigned long flags;
        signed long ret = timeout;
        bool was_set;

        if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                return timeout;

        spin_lock_irqsave(fence->lock, flags);

        if (intr && signal_pending(current)) {
                ret = -ERESTARTSYS;
                goto out;
        }

        was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);

        if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                goto out;

        if (!was_set) {
                trace_fence_enable_signal(fence);

                if (!fence->ops->enable_signaling(fence)) {
                        fence_signal_locked(fence);
                        goto out;
                }
        }

        cb.base.func = fence_default_wait_cb;
        cb.task = current;
        list_add(&cb.base.node, &fence->cb_list);

        while (!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
                if (intr)
                        __set_current_state(TASK_INTERRUPTIBLE);
                else
                        __set_current_state(TASK_UNINTERRUPTIBLE);
                spin_unlock_irqrestore(fence->lock, flags);

                ret = schedule_timeout(ret);

                spin_lock_irqsave(fence->lock, flags);
                if (ret > 0 && intr && signal_pending(current))
                        ret = -ERESTARTSYS;
        }

        if (!list_empty(&cb.base.node))
                list_del(&cb.base.node);
        __set_current_state(TASK_RUNNING);

out:
        spin_unlock_irqrestore(fence->lock, flags);
        return ret;
}
EXPORT_SYMBOL(fence_default_wait);

static bool
fence_test_signaled_any(struct fence **fences, uint32_t count)
{
        int i;

        for (i = 0; i < count; ++i) {
                struct fence *fence = fences[i];
                if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
                        return true;
        }
        return false;
}

/**
 * fence_wait_any_timeout - sleep until any fence gets signaled
 * or until timeout elapses
 * @fences:     [in]    array of fences to wait on
 * @count:      [in]    number of fences to wait on
 * @intr:       [in]    if true, do an interruptible wait
 * @timeout:    [in]    timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
 *
 * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
 * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
 * on success.
 *
 * Synchronous waits for the first fence in the array to be signaled. The
 * caller needs to hold a reference to all fences in the array, otherwise a
 * fence might be freed before return, resulting in undefined behavior.
 */
signed long
fence_wait_any_timeout(struct fence **fences, uint32_t count,
                       bool intr, signed long timeout)
{
        struct default_wait_cb *cb;
        signed long ret = timeout;
        unsigned i;

        if (WARN_ON(!fences || !count || timeout < 0))
                return -EINVAL;

        if (timeout == 0) {
                for (i = 0; i < count; ++i)
                        if (fence_is_signaled(fences[i]))
                                return 1;

                return 0;
        }

        cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
        if (cb == NULL) {
                ret = -ENOMEM;
                goto err_free_cb;
        }

        for (i = 0; i < count; ++i) {
                struct fence *fence = fences[i];

                if (fence->ops->wait != fence_default_wait) {
                        ret = -EINVAL;
                        goto fence_rm_cb;
                }

                cb[i].task = current;
                if (fence_add_callback(fence, &cb[i].base,
                                       fence_default_wait_cb)) {
                        /* This fence is already signaled */
                        goto fence_rm_cb;
                }
        }

        while (ret > 0) {
                if (intr)
                        set_current_state(TASK_INTERRUPTIBLE);
                else
                        set_current_state(TASK_UNINTERRUPTIBLE);

                if (fence_test_signaled_any(fences, count))
                        break;

                ret = schedule_timeout(ret);

                if (ret > 0 && intr && signal_pending(current))
                        ret = -ERESTARTSYS;
        }

        __set_current_state(TASK_RUNNING);

fence_rm_cb:
        while (i-- > 0)
                fence_remove_callback(fences[i], &cb[i].base);

err_free_cb:
        kfree(cb);

        return ret;
}
EXPORT_SYMBOL(fence_wait_any_timeout);

/**
 * fence_init - Initialize a custom fence.
 * @fence:      [in]    the fence to initialize
 * @ops:        [in]    the fence_ops for operations on this fence
 * @lock:       [in]    the irqsafe spinlock to use for locking this fence
 * @context:    [in]    the execution context this fence is run on
 * @seqno:      [in]    a linear increasing sequence number for this context
 *
 * Initializes an allocated fence, the caller doesn't have to keep its
 * refcount after committing with this fence, but it will need to hold a
 * refcount again if fence_ops.enable_signaling gets called. This can
 * be used for other implementing other types of fence.
 *
 * context and seqno are used for easy comparison between fences, allowing
 * to check which fence is later by simply using fence_later.
 */
void
fence_init(struct fence *fence, const struct fence_ops *ops,
             spinlock_t *lock, u64 context, unsigned seqno)
{
        BUG_ON(!lock);
        BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
               !ops->get_driver_name || !ops->get_timeline_name);

        kref_init(&fence->refcount);
        fence->ops = ops;
        INIT_LIST_HEAD(&fence->cb_list);
        fence->lock = lock;
        fence->context = context;
        fence->seqno = seqno;
        fence->flags = 0UL;

        trace_fence_init(fence);
}
EXPORT_SYMBOL(fence_init);