// SPDX-License-Identifier: GPL-2.0-only
/*
 * dma-fence-array: aggregate fences to be waited together
 *
 * Copyright (C) 2016 Collabora Ltd
 * Copyright (C) 2016 Advanced Micro Devices, Inc.
 * Authors:
 *      Gustavo Padovan <gustavo@padovan.org>
 *      Christian König <christian.koenig@amd.com>
 */

#include <linux/export.h>
#include <linux/slab.h>
#include <linux/dma-fence-array.h>

#define PENDING_ERROR 1

static const char *dma_fence_array_get_driver_name(struct dma_fence *fence)
{
        return "dma_fence_array";
}

static const char *dma_fence_array_get_timeline_name(struct dma_fence *fence)
{
        return "unbound";
}

static void dma_fence_array_set_pending_error(struct dma_fence_array *array,
                                              int error)
{
        /*
         * Propagate the first error reported by any of our fences, but only
         * before we ourselves are signaled.
         */
        if (error)
                cmpxchg(&array->base.error, PENDING_ERROR, error);
}

static void dma_fence_array_clear_pending_error(struct dma_fence_array *array)
{
        /* Clear the error flag if not actually set. */
        cmpxchg(&array->base.error, PENDING_ERROR, 0);
}

static void irq_dma_fence_array_work(struct irq_work *wrk)
{
        struct dma_fence_array *array = container_of(wrk, typeof(*array), work);

        dma_fence_array_clear_pending_error(array);

        dma_fence_signal(&array->base);
        dma_fence_put(&array->base);
}

static void dma_fence_array_cb_func(struct dma_fence *f,
                                    struct dma_fence_cb *cb)
{
        struct dma_fence_array_cb *array_cb =
                container_of(cb, struct dma_fence_array_cb, cb);
        struct dma_fence_array *array = array_cb->array;

        dma_fence_array_set_pending_error(array, f->error);

        if (atomic_dec_and_test(&array->num_pending))
                irq_work_queue(&array->work);
        else
                dma_fence_put(&array->base);
}

static bool dma_fence_array_enable_signaling(struct dma_fence *fence)
{
        struct dma_fence_array *array = to_dma_fence_array(fence);
        struct dma_fence_array_cb *cb = array->callbacks;
        unsigned i;

        for (i = 0; i < array->num_fences; ++i) {
                cb[i].array = array;
                /*
                 * As we may report that the fence is signaled before all
                 * callbacks are complete, we need to take an additional
                 * reference count on the array so that we do not free it too
                 * early. The core fence handling will only hold the reference
                 * until we signal the array as complete (but that is now
                 * insufficient).
                 */
                dma_fence_get(&array->base);
                if (dma_fence_add_callback(array->fences[i], &cb[i].cb,
                                           dma_fence_array_cb_func)) {
                        int error = array->fences[i]->error;

                        dma_fence_array_set_pending_error(array, error);
                        dma_fence_put(&array->base);
                        if (atomic_dec_and_test(&array->num_pending)) {
                                dma_fence_array_clear_pending_error(array);
                                return false;
                        }
                }
        }

        return true;
}

static bool dma_fence_array_signaled(struct dma_fence *fence)
{
        struct dma_fence_array *array = to_dma_fence_array(fence);
        int num_pending;
        unsigned int i;

        /*
         * We need to read num_pending before checking the enable_signal bit
         * to avoid racing with the enable_signaling() implementation, which
         * might decrement the counter, and cause a partial check.
         * atomic_read_acquire() pairs with atomic_dec_and_test() in
         * dma_fence_array_enable_signaling()
         *
         * The !--num_pending check is here to account for the any_signaled case
         * if we race with enable_signaling(), that means the !num_pending check
         * in the is_signalling_enabled branch might be outdated (num_pending
         * might have been decremented), but that's fine. The user will get the
         * right value when testing again later.
         */
        num_pending = atomic_read_acquire(&array->num_pending);
        if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &array->base.flags)) {
                if (num_pending <= 0)
                        goto signal;
                return false;
        }

        for (i = 0; i < array->num_fences; ++i) {
                if (dma_fence_is_signaled(array->fences[i]) && !--num_pending)
                        goto signal;
        }
        return false;

signal:
        dma_fence_array_clear_pending_error(array);
        return true;
}

static void dma_fence_array_release(struct dma_fence *fence)
{
        struct dma_fence_array *array = to_dma_fence_array(fence);
        unsigned i;

        for (i = 0; i < array->num_fences; ++i)
                dma_fence_put(array->fences[i]);

        kfree(array->fences);
        dma_fence_free(fence);
}

static void dma_fence_array_set_deadline(struct dma_fence *fence,
                                         ktime_t deadline)
{
        struct dma_fence_array *array = to_dma_fence_array(fence);
        unsigned i;

        for (i = 0; i < array->num_fences; ++i)
                dma_fence_set_deadline(array->fences[i], deadline);
}

const struct dma_fence_ops dma_fence_array_ops = {
        .get_driver_name = dma_fence_array_get_driver_name,
        .get_timeline_name = dma_fence_array_get_timeline_name,
        .enable_signaling = dma_fence_array_enable_signaling,
        .signaled = dma_fence_array_signaled,
        .release = dma_fence_array_release,
        .set_deadline = dma_fence_array_set_deadline,
};
EXPORT_SYMBOL(dma_fence_array_ops);

/**
 * dma_fence_array_alloc - Allocate a custom fence array
 * @num_fences:         [in]    number of fences to add in the array
 *
 * Return dma fence array on success, NULL on failure
 */
struct dma_fence_array *dma_fence_array_alloc(int num_fences)
{
        struct dma_fence_array *array;

        return kzalloc_flex(*array, callbacks, num_fences);
}
EXPORT_SYMBOL(dma_fence_array_alloc);

/**
 * dma_fence_array_init - Init a custom fence array
 * @array:              [in]    dma fence array to arm
 * @num_fences:         [in]    number of fences to add in the array
 * @fences:             [in]    array containing the fences
 * @context:            [in]    fence context to use
 * @seqno:              [in]    sequence number to use
 * @signal_on_any:      [in]    signal on any fence in the array
 *
 * Implementation of @dma_fence_array_create without allocation. Useful to init
 * a preallocated dma fence array in the path of reclaim or dma fence signaling.
 */
void dma_fence_array_init(struct dma_fence_array *array,
                          int num_fences, struct dma_fence **fences,
                          u64 context, unsigned seqno,
                          bool signal_on_any)
{
        WARN_ON(!num_fences || !fences);

        array->num_fences = num_fences;

        spin_lock_init(&array->lock);
        dma_fence_init(&array->base, &dma_fence_array_ops, &array->lock,
                       context, seqno);
        init_irq_work(&array->work, irq_dma_fence_array_work);

        atomic_set(&array->num_pending, signal_on_any ? 1 : num_fences);
        array->fences = fences;

        array->base.error = PENDING_ERROR;

        /*
         * dma_fence_array objects should never contain any other fence
         * containers or otherwise we run into recursion and potential kernel
         * stack overflow on operations on the dma_fence_array.
         *
         * The correct way of handling this is to flatten out the array by the
         * caller instead.
         *
         * Enforce this here by checking that we don't create a dma_fence_array
         * with any container inside.
         */
        while (num_fences--)
                WARN_ON(dma_fence_is_container(fences[num_fences]));
}
EXPORT_SYMBOL(dma_fence_array_init);

/**
 * dma_fence_array_create - Create a custom fence array
 * @num_fences:         [in]    number of fences to add in the array
 * @fences:             [in]    array containing the fences
 * @context:            [in]    fence context to use
 * @seqno:              [in]    sequence number to use
 * @signal_on_any:      [in]    signal on any fence in the array
 *
 * Allocate a dma_fence_array object and initialize the base fence with
 * dma_fence_init().
 * In case of error it returns NULL.
 *
 * The caller should allocate the fences array with num_fences size
 * and fill it with the fences it wants to add to the object. Ownership of this
 * array is taken and dma_fence_put() is used on each fence on release.
 *
 * If @signal_on_any is true the fence array signals if any fence in the array
 * signals, otherwise it signals when all fences in the array signal.
 */
struct dma_fence_array *dma_fence_array_create(int num_fences,
                                               struct dma_fence **fences,
                                               u64 context, unsigned seqno,
                                               bool signal_on_any)
{
        struct dma_fence_array *array;

        array = dma_fence_array_alloc(num_fences);
        if (!array)
                return NULL;

        dma_fence_array_init(array, num_fences, fences,
                             context, seqno, signal_on_any);

        return array;
}
EXPORT_SYMBOL(dma_fence_array_create);

/**
 * dma_fence_match_context - Check if all fences are from the given context
 * @fence:              [in]    fence or fence array
 * @context:            [in]    fence context to check all fences against
 *
 * Checks the provided fence or, for a fence array, all fences in the array
 * against the given context. Returns false if any fence is from a different
 * context.
 */
bool dma_fence_match_context(struct dma_fence *fence, u64 context)
{
        struct dma_fence_array *array = to_dma_fence_array(fence);
        unsigned i;

        if (!dma_fence_is_array(fence))
                return fence->context == context;

        for (i = 0; i < array->num_fences; i++) {
                if (array->fences[i]->context != context)
                        return false;
        }

        return true;
}
EXPORT_SYMBOL(dma_fence_match_context);

struct dma_fence *dma_fence_array_first(struct dma_fence *head)
{
        struct dma_fence_array *array;

        if (!head)
                return NULL;

        array = to_dma_fence_array(head);
        if (!array)
                return head;

        if (!array->num_fences)
                return NULL;

        return array->fences[0];
}
EXPORT_SYMBOL(dma_fence_array_first);

struct dma_fence *dma_fence_array_next(struct dma_fence *head,
                                       unsigned int index)
{
        struct dma_fence_array *array = to_dma_fence_array(head);

        if (!array || index >= array->num_fences)
                return NULL;

        return array->fences[index];
}
EXPORT_SYMBOL(dma_fence_array_next);