/*
 * Copyright (c) 2015-2016 Quantenna Communications, Inc.
 * All rights reserved.
 *
 * 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.
 *
 * 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/types.h>
#include <linux/io.h>

#include "shm_ipc.h"

#undef pr_fmt
#define pr_fmt(fmt)     "qtnfmac shm_ipc: %s: " fmt, __func__

static bool qtnf_shm_ipc_has_new_data(struct qtnf_shm_ipc *ipc)
{
        const u32 flags = readl(&ipc->shm_region->headroom.hdr.flags);

        return (flags & QTNF_SHM_IPC_NEW_DATA);
}

static void qtnf_shm_handle_new_data(struct qtnf_shm_ipc *ipc)
{
        size_t size;
        bool rx_buff_ok = true;
        struct qtnf_shm_ipc_region_header __iomem *shm_reg_hdr;

        shm_reg_hdr = &ipc->shm_region->headroom.hdr;

        size = readw(&shm_reg_hdr->data_len);

        if (unlikely(size == 0 || size > QTN_IPC_MAX_DATA_SZ)) {
                pr_err("wrong rx packet size: %zu\n", size);
                rx_buff_ok = false;
        } else {
                memcpy_fromio(ipc->rx_data, ipc->shm_region->data, size);
        }

        writel(QTNF_SHM_IPC_ACK, &shm_reg_hdr->flags);
        readl(&shm_reg_hdr->flags); /* flush PCIe write */

        ipc->interrupt.fn(ipc->interrupt.arg);

        if (likely(rx_buff_ok)) {
                ipc->rx_packet_count++;
                ipc->rx_callback.fn(ipc->rx_callback.arg, ipc->rx_data, size);
        }
}

static void qtnf_shm_ipc_irq_work(struct work_struct *work)
{
        struct qtnf_shm_ipc *ipc = container_of(work, struct qtnf_shm_ipc,
                                                irq_work);

        while (qtnf_shm_ipc_has_new_data(ipc))
                qtnf_shm_handle_new_data(ipc);
}

static void qtnf_shm_ipc_irq_inbound_handler(struct qtnf_shm_ipc *ipc)
{
        u32 flags;

        flags = readl(&ipc->shm_region->headroom.hdr.flags);

        if (flags & QTNF_SHM_IPC_NEW_DATA)
                queue_work(ipc->workqueue, &ipc->irq_work);
}

static void qtnf_shm_ipc_irq_outbound_handler(struct qtnf_shm_ipc *ipc)
{
        u32 flags;

        if (!READ_ONCE(ipc->waiting_for_ack))
                return;

        flags = readl(&ipc->shm_region->headroom.hdr.flags);

        if (flags & QTNF_SHM_IPC_ACK) {
                WRITE_ONCE(ipc->waiting_for_ack, 0);
                complete(&ipc->tx_completion);
        }
}

int qtnf_shm_ipc_init(struct qtnf_shm_ipc *ipc,
                      enum qtnf_shm_ipc_direction direction,
                      struct qtnf_shm_ipc_region __iomem *shm_region,
                      struct workqueue_struct *workqueue,
                      const struct qtnf_shm_ipc_int *interrupt,
                      const struct qtnf_shm_ipc_rx_callback *rx_callback)
{
        BUILD_BUG_ON(offsetof(struct qtnf_shm_ipc_region, data) !=
                     QTN_IPC_REG_HDR_SZ);
        BUILD_BUG_ON(sizeof(struct qtnf_shm_ipc_region) > QTN_IPC_REG_SZ);

        ipc->shm_region = shm_region;
        ipc->direction = direction;
        ipc->interrupt = *interrupt;
        ipc->rx_callback = *rx_callback;
        ipc->tx_packet_count = 0;
        ipc->rx_packet_count = 0;
        ipc->workqueue = workqueue;
        ipc->waiting_for_ack = 0;
        ipc->tx_timeout_count = 0;

        switch (direction) {
        case QTNF_SHM_IPC_OUTBOUND:
                ipc->irq_handler = qtnf_shm_ipc_irq_outbound_handler;
                break;
        case QTNF_SHM_IPC_INBOUND:
                ipc->irq_handler = qtnf_shm_ipc_irq_inbound_handler;
                break;
        default:
                return -EINVAL;
        }

        INIT_WORK(&ipc->irq_work, qtnf_shm_ipc_irq_work);
        init_completion(&ipc->tx_completion);

        return 0;
}

void qtnf_shm_ipc_free(struct qtnf_shm_ipc *ipc)
{
        complete_all(&ipc->tx_completion);
}

int qtnf_shm_ipc_send(struct qtnf_shm_ipc *ipc, const u8 *buf, size_t size)
{
        int ret = 0;
        struct qtnf_shm_ipc_region_header __iomem *shm_reg_hdr;

        shm_reg_hdr = &ipc->shm_region->headroom.hdr;

        if (unlikely(size > QTN_IPC_MAX_DATA_SZ))
                return -E2BIG;

        ipc->tx_packet_count++;

        writew(size, &shm_reg_hdr->data_len);
        memcpy_toio(ipc->shm_region->data, buf, size);

        /* sync previous writes before proceeding */
        dma_wmb();

        WRITE_ONCE(ipc->waiting_for_ack, 1);

        /* sync previous memory write before announcing new data ready */
        wmb();

        writel(QTNF_SHM_IPC_NEW_DATA, &shm_reg_hdr->flags);
        readl(&shm_reg_hdr->flags); /* flush PCIe write */

        ipc->interrupt.fn(ipc->interrupt.arg);

        if (!wait_for_completion_timeout(&ipc->tx_completion,
                                         QTN_SHM_IPC_ACK_TIMEOUT)) {
                ret = -ETIMEDOUT;
                ipc->tx_timeout_count++;
                pr_err("TX ACK timeout\n");
        }

        /* now we're not waiting for ACK even in case of timeout */
        WRITE_ONCE(ipc->waiting_for_ack, 0);

        return ret;
}