/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
/*
 * Copyright (c) 2016 Mellanox Technologies Ltd. All rights reserved.
 * Copyright (c) 2015 System Fabric Works, Inc. All rights reserved.
 */

#ifndef RXE_QUEUE_H
#define RXE_QUEUE_H

/* Implements a simple circular buffer that is shared between user
 * and the driver and can be resized. The requested element size is
 * rounded up to a power of 2 and the number of elements in the buffer
 * is also rounded up to a power of 2. Since the queue is empty when
 * the producer and consumer indices match the maximum capacity of the
 * queue is one less than the number of element slots.
 *
 * Notes:
 *   - The driver indices are always masked off to q->index_mask
 *     before storing so do not need to be checked on reads.
 *   - The user whether user space or kernel is generally
 *     not trusted so its parameters are masked to make sure
 *     they do not access the queue out of bounds on reads.
 *   - The driver indices for queues must not be written
 *     by user so a local copy is used and a shared copy is
 *     stored when the local copy is changed.
 *   - By passing the type in the parameter list separate from q
 *     the compiler can eliminate the switch statement when the
 *     actual queue type is known when the function is called at
 *     compile time.
 *   - These queues are lock free. The user and driver must protect
 *     changes to their end of the queues with locks if more than one
 *     CPU can be accessing it at the same time.
 */

/**
 * enum queue_type - type of queue
 * @QUEUE_TYPE_TO_CLIENT:       Queue is written by rxe driver and
 *                              read by client which may be a user space
 *                              application or a kernel ulp.
 *                              Used by rxe internals only.
 * @QUEUE_TYPE_FROM_CLIENT:     Queue is written by client and
 *                              read by rxe driver.
 *                              Used by rxe internals only.
 * @QUEUE_TYPE_FROM_ULP:        Queue is written by kernel ulp and
 *                              read by rxe driver.
 *                              Used by kernel verbs APIs only on
 *                              behalf of ulps.
 * @QUEUE_TYPE_TO_ULP:          Queue is written by rxe driver and
 *                              read by kernel ulp.
 *                              Used by kernel verbs APIs only on
 *                              behalf of ulps.
 */
enum queue_type {
        QUEUE_TYPE_TO_CLIENT,
        QUEUE_TYPE_FROM_CLIENT,
        QUEUE_TYPE_FROM_ULP,
        QUEUE_TYPE_TO_ULP,
};

struct rxe_queue_buf;

struct rxe_queue {
        struct rxe_dev          *rxe;
        struct rxe_queue_buf    *buf;
        struct rxe_mmap_info    *ip;
        size_t                  buf_size;
        size_t                  elem_size;
        unsigned int            log2_elem_size;
        u32                     index_mask;
        enum queue_type         type;
        /* private copy of index for shared queues between
         * driver and clients. Driver reads and writes
         * this copy and then replicates to rxe_queue_buf
         * for read access by clients.
         */
        u32                     index;
};

int do_mmap_info(struct rxe_dev *rxe, struct mminfo __user *outbuf,
                 struct ib_udata *udata, struct rxe_queue_buf *buf,
                 size_t buf_size, struct rxe_mmap_info **ip_p);

void rxe_queue_reset(struct rxe_queue *q);

struct rxe_queue *rxe_queue_init(struct rxe_dev *rxe, int *num_elem,
                        unsigned int elem_size, enum queue_type type);

int rxe_queue_resize(struct rxe_queue *q, unsigned int *num_elem_p,
                     unsigned int elem_size, struct ib_udata *udata,
                     struct mminfo __user *outbuf,
                     spinlock_t *producer_lock, spinlock_t *consumer_lock);

void rxe_queue_cleanup(struct rxe_queue *queue);

static inline u32 queue_next_index(struct rxe_queue *q, int index)
{
        return (index + 1) & q->index_mask;
}

static inline u32 queue_get_producer(const struct rxe_queue *q,
                                     enum queue_type type)
{
        u32 prod;

        switch (type) {
        case QUEUE_TYPE_FROM_CLIENT:
                /* used by rxe, client owns the index */
                prod = smp_load_acquire(&q->buf->producer_index);
                break;
        case QUEUE_TYPE_TO_CLIENT:
                /* used by rxe which owns the index */
                prod = q->index;
                break;
        case QUEUE_TYPE_FROM_ULP:
                /* used by ulp which owns the index */
                prod = q->buf->producer_index;
                break;
        case QUEUE_TYPE_TO_ULP:
                /* used by ulp, rxe owns the index */
                prod = smp_load_acquire(&q->buf->producer_index);
                break;
        }

        return prod;
}

static inline u32 queue_get_consumer(const struct rxe_queue *q,
                                     enum queue_type type)
{
        u32 cons;

        switch (type) {
        case QUEUE_TYPE_FROM_CLIENT:
                /* used by rxe which owns the index */
                cons = q->index;
                break;
        case QUEUE_TYPE_TO_CLIENT:
                /* used by rxe, client owns the index */
                cons = smp_load_acquire(&q->buf->consumer_index);
                break;
        case QUEUE_TYPE_FROM_ULP:
                /* used by ulp, rxe owns the index */
                cons = smp_load_acquire(&q->buf->consumer_index);
                break;
        case QUEUE_TYPE_TO_ULP:
                /* used by ulp which owns the index */
                cons = q->buf->consumer_index;
                break;
        }

        return cons;
}

static inline int queue_empty(struct rxe_queue *q, enum queue_type type)
{
        u32 prod = queue_get_producer(q, type);
        u32 cons = queue_get_consumer(q, type);

        return ((prod - cons) & q->index_mask) == 0;
}

static inline int queue_full(struct rxe_queue *q, enum queue_type type)
{
        u32 prod = queue_get_producer(q, type);
        u32 cons = queue_get_consumer(q, type);

        return ((prod + 1 - cons) & q->index_mask) == 0;
}

static inline u32 queue_count(const struct rxe_queue *q,
                                        enum queue_type type)
{
        u32 prod = queue_get_producer(q, type);
        u32 cons = queue_get_consumer(q, type);

        return (prod - cons) & q->index_mask;
}

static inline void queue_advance_producer(struct rxe_queue *q,
                                          enum queue_type type)
{
        u32 prod;

        switch (type) {
        case QUEUE_TYPE_FROM_CLIENT:
                /* used by rxe, client owns the index */
                if (WARN_ON(1))
                        pr_warn("%s: attempt to advance client index\n",
                                __func__);
                break;
        case QUEUE_TYPE_TO_CLIENT:
                /* used by rxe which owns the index */
                prod = q->index;
                prod = (prod + 1) & q->index_mask;
                q->index = prod;
                /* release so client can read it safely */
                smp_store_release(&q->buf->producer_index, prod);
                break;
        case QUEUE_TYPE_FROM_ULP:
                /* used by ulp which owns the index */
                prod = q->buf->producer_index;
                prod = (prod + 1) & q->index_mask;
                /* release so rxe can read it safely */
                smp_store_release(&q->buf->producer_index, prod);
                break;
        case QUEUE_TYPE_TO_ULP:
                /* used by ulp, rxe owns the index */
                if (WARN_ON(1))
                        pr_warn("%s: attempt to advance driver index\n",
                                __func__);
                break;
        }
}

static inline void queue_advance_consumer(struct rxe_queue *q,
                                          enum queue_type type)
{
        u32 cons;

        switch (type) {
        case QUEUE_TYPE_FROM_CLIENT:
                /* used by rxe which owns the index */
                cons = (q->index + 1) & q->index_mask;
                q->index = cons;
                /* release so client can read it safely */
                smp_store_release(&q->buf->consumer_index, cons);
                break;
        case QUEUE_TYPE_TO_CLIENT:
                /* used by rxe, client owns the index */
                if (WARN_ON(1))
                        pr_warn("%s: attempt to advance client index\n",
                                __func__);
                break;
        case QUEUE_TYPE_FROM_ULP:
                /* used by ulp, rxe owns the index */
                if (WARN_ON(1))
                        pr_warn("%s: attempt to advance driver index\n",
                                __func__);
                break;
        case QUEUE_TYPE_TO_ULP:
                /* used by ulp which owns the index */
                cons = q->buf->consumer_index;
                cons = (cons + 1) & q->index_mask;
                /* release so rxe can read it safely */
                smp_store_release(&q->buf->consumer_index, cons);
                break;
        }
}

static inline void *queue_producer_addr(struct rxe_queue *q,
                                        enum queue_type type)
{
        u32 prod = queue_get_producer(q, type);

        return q->buf->data + (prod << q->log2_elem_size);
}

static inline void *queue_consumer_addr(struct rxe_queue *q,
                                        enum queue_type type)
{
        u32 cons = queue_get_consumer(q, type);

        return q->buf->data + (cons << q->log2_elem_size);
}

static inline void *queue_addr_from_index(struct rxe_queue *q, u32 index)
{
        return q->buf->data + ((index & q->index_mask)
                                << q->log2_elem_size);
}

static inline u32 queue_index_from_addr(const struct rxe_queue *q,
                                const void *addr)
{
        return (((u8 *)addr - q->buf->data) >> q->log2_elem_size)
                                & q->index_mask;
}

static inline void *queue_head(struct rxe_queue *q, enum queue_type type)
{
        return queue_empty(q, type) ? NULL : queue_consumer_addr(q, type);
}

#endif /* RXE_QUEUE_H */