// SPDX-License-Identifier: GPL-2.0+
/*
 * Mellanox BlueField SoC TmFifo driver
 *
 * Copyright (C) 2019 Mellanox Technologies
 */

#include <linux/acpi.h>
#include <linux/bitfield.h>
#include <linux/circ_buf.h>
#include <linux/efi.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/types.h>

#include <linux/virtio_config.h>
#include <linux/virtio_console.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_net.h>
#include <linux/virtio_ring.h>

#include "mlxbf-tmfifo-regs.h"

/* Vring size. */
#define MLXBF_TMFIFO_VRING_SIZE                 SZ_1K

/* Console Tx buffer size. */
#define MLXBF_TMFIFO_CON_TX_BUF_SIZE            SZ_32K

/* Console Tx buffer reserved space. */
#define MLXBF_TMFIFO_CON_TX_BUF_RSV_SIZE        8

/* House-keeping timer interval. */
#define MLXBF_TMFIFO_TIMER_INTERVAL             (HZ / 10)

/* Virtual devices sharing the TM FIFO. */
#define MLXBF_TMFIFO_VDEV_MAX           (VIRTIO_ID_CONSOLE + 1)

/*
 * Reserve 1/16 of TmFifo space, so console messages are not starved by
 * the networking traffic.
 */
#define MLXBF_TMFIFO_RESERVE_RATIO              16

/* Message with data needs at least two words (for header & data). */
#define MLXBF_TMFIFO_DATA_MIN_WORDS             2

struct mlxbf_tmfifo;

/**
 * mlxbf_tmfifo_vring - Structure of the TmFifo virtual ring
 * @va: virtual address of the ring
 * @dma: dma address of the ring
 * @vq: pointer to the virtio virtqueue
 * @desc: current descriptor of the pending packet
 * @desc_head: head descriptor of the pending packet
 * @cur_len: processed length of the current descriptor
 * @rem_len: remaining length of the pending packet
 * @pkt_len: total length of the pending packet
 * @next_avail: next avail descriptor id
 * @num: vring size (number of descriptors)
 * @align: vring alignment size
 * @index: vring index
 * @vdev_id: vring virtio id (VIRTIO_ID_xxx)
 * @fifo: pointer to the tmfifo structure
 */
struct mlxbf_tmfifo_vring {
        void *va;
        dma_addr_t dma;
        struct virtqueue *vq;
        struct vring_desc *desc;
        struct vring_desc *desc_head;
        int cur_len;
        int rem_len;
        u32 pkt_len;
        u16 next_avail;
        int num;
        int align;
        int index;
        int vdev_id;
        struct mlxbf_tmfifo *fifo;
};

/* Interrupt types. */
enum {
        MLXBF_TM_RX_LWM_IRQ,
        MLXBF_TM_RX_HWM_IRQ,
        MLXBF_TM_TX_LWM_IRQ,
        MLXBF_TM_TX_HWM_IRQ,
        MLXBF_TM_MAX_IRQ
};

/* Ring types (Rx & Tx). */
enum {
        MLXBF_TMFIFO_VRING_RX,
        MLXBF_TMFIFO_VRING_TX,
        MLXBF_TMFIFO_VRING_MAX
};

/**
 * mlxbf_tmfifo_vdev - Structure of the TmFifo virtual device
 * @vdev: virtio device, in which the vdev.id.device field has the
 *        VIRTIO_ID_xxx id to distinguish the virtual device.
 * @status: status of the device
 * @features: supported features of the device
 * @vrings: array of tmfifo vrings of this device
 * @config.cons: virtual console config -
 *               select if vdev.id.device is VIRTIO_ID_CONSOLE
 * @config.net: virtual network config -
 *              select if vdev.id.device is VIRTIO_ID_NET
 * @tx_buf: tx buffer used to buffer data before writing into the FIFO
 */
struct mlxbf_tmfifo_vdev {
        struct virtio_device vdev;
        u8 status;
        u64 features;
        struct mlxbf_tmfifo_vring vrings[MLXBF_TMFIFO_VRING_MAX];
        union {
                struct virtio_console_config cons;
                struct virtio_net_config net;
        } config;
        struct circ_buf tx_buf;
};

/**
 * mlxbf_tmfifo_irq_info - Structure of the interrupt information
 * @fifo: pointer to the tmfifo structure
 * @irq: interrupt number
 * @index: index into the interrupt array
 */
struct mlxbf_tmfifo_irq_info {
        struct mlxbf_tmfifo *fifo;
        int irq;
        int index;
};

/**
 * mlxbf_tmfifo - Structure of the TmFifo
 * @vdev: array of the virtual devices running over the TmFifo
 * @lock: lock to protect the TmFifo access
 * @rx_base: mapped register base address for the Rx FIFO
 * @tx_base: mapped register base address for the Tx FIFO
 * @rx_fifo_size: number of entries of the Rx FIFO
 * @tx_fifo_size: number of entries of the Tx FIFO
 * @pend_events: pending bits for deferred events
 * @irq_info: interrupt information
 * @work: work struct for deferred process
 * @timer: background timer
 * @vring: Tx/Rx ring
 * @spin_lock: Tx/Rx spin lock
 * @is_ready: ready flag
 */
struct mlxbf_tmfifo {
        struct mlxbf_tmfifo_vdev *vdev[MLXBF_TMFIFO_VDEV_MAX];
        struct mutex lock;              /* TmFifo lock */
        void __iomem *rx_base;
        void __iomem *tx_base;
        int rx_fifo_size;
        int tx_fifo_size;
        unsigned long pend_events;
        struct mlxbf_tmfifo_irq_info irq_info[MLXBF_TM_MAX_IRQ];
        struct work_struct work;
        struct timer_list timer;
        struct mlxbf_tmfifo_vring *vring[2];
        spinlock_t spin_lock[2];        /* spin lock */
        bool is_ready;
};

/**
 * mlxbf_tmfifo_msg_hdr - Structure of the TmFifo message header
 * @type: message type
 * @len: payload length in network byte order. Messages sent into the FIFO
 *       will be read by the other side as data stream in the same byte order.
 *       The length needs to be encoded into network order so both sides
 *       could understand it.
 */
struct mlxbf_tmfifo_msg_hdr {
        u8 type;
        __be16 len;
        u8 unused[5];
} __packed __aligned(sizeof(u64));

/*
 * Default MAC.
 * This MAC address will be read from EFI persistent variable if configured.
 * It can also be reconfigured with standard Linux tools.
 */
static u8 mlxbf_tmfifo_net_default_mac[ETH_ALEN] = {
        0x00, 0x1A, 0xCA, 0xFF, 0xFF, 0x01
};

/* EFI variable name of the MAC address. */
static efi_char16_t mlxbf_tmfifo_efi_name[] = L"RshimMacAddr";

/* Maximum L2 header length. */
#define MLXBF_TMFIFO_NET_L2_OVERHEAD    36

/* Supported virtio-net features. */
#define MLXBF_TMFIFO_NET_FEATURES \
        (BIT_ULL(VIRTIO_NET_F_MTU) | BIT_ULL(VIRTIO_NET_F_STATUS) | \
         BIT_ULL(VIRTIO_NET_F_MAC))

#define mlxbf_vdev_to_tmfifo(d) container_of(d, struct mlxbf_tmfifo_vdev, vdev)

/* Free vrings of the FIFO device. */
static void mlxbf_tmfifo_free_vrings(struct mlxbf_tmfifo *fifo,
                                     struct mlxbf_tmfifo_vdev *tm_vdev)
{
        struct mlxbf_tmfifo_vring *vring;
        int i, size;

        for (i = 0; i < ARRAY_SIZE(tm_vdev->vrings); i++) {
                vring = &tm_vdev->vrings[i];
                if (vring->va) {
                        size = vring_size(vring->num, vring->align);
                        dma_free_coherent(tm_vdev->vdev.dev.parent, size,
                                          vring->va, vring->dma);
                        vring->va = NULL;
                        if (vring->vq) {
                                vring_del_virtqueue(vring->vq);
                                vring->vq = NULL;
                        }
                }
        }
}

/* Allocate vrings for the FIFO. */
static int mlxbf_tmfifo_alloc_vrings(struct mlxbf_tmfifo *fifo,
                                     struct mlxbf_tmfifo_vdev *tm_vdev)
{
        struct mlxbf_tmfifo_vring *vring;
        struct device *dev;
        dma_addr_t dma;
        int i, size;
        void *va;

        for (i = 0; i < ARRAY_SIZE(tm_vdev->vrings); i++) {
                vring = &tm_vdev->vrings[i];
                vring->fifo = fifo;
                vring->num = MLXBF_TMFIFO_VRING_SIZE;
                vring->align = SMP_CACHE_BYTES;
                vring->index = i;
                vring->vdev_id = tm_vdev->vdev.id.device;
                dev = &tm_vdev->vdev.dev;

                size = vring_size(vring->num, vring->align);
                va = dma_alloc_coherent(dev->parent, size, &dma, GFP_KERNEL);
                if (!va) {
                        mlxbf_tmfifo_free_vrings(fifo, tm_vdev);
                        dev_err(dev->parent, "dma_alloc_coherent failed\n");
                        return -ENOMEM;
                }

                vring->va = va;
                vring->dma = dma;
        }

        return 0;
}

/* Disable interrupts of the FIFO device. */
static void mlxbf_tmfifo_disable_irqs(struct mlxbf_tmfifo *fifo)
{
        int i, irq;

        for (i = 0; i < MLXBF_TM_MAX_IRQ; i++) {
                irq = fifo->irq_info[i].irq;
                fifo->irq_info[i].irq = 0;
                disable_irq(irq);
        }
}

/* Interrupt handler. */
static irqreturn_t mlxbf_tmfifo_irq_handler(int irq, void *arg)
{
        struct mlxbf_tmfifo_irq_info *irq_info = arg;

        if (!test_and_set_bit(irq_info->index, &irq_info->fifo->pend_events))
                schedule_work(&irq_info->fifo->work);

        return IRQ_HANDLED;
}

/* Get the next packet descriptor from the vring. */
static struct vring_desc *
mlxbf_tmfifo_get_next_desc(struct mlxbf_tmfifo_vring *vring)
{
        const struct vring *vr = virtqueue_get_vring(vring->vq);
        struct virtio_device *vdev = vring->vq->vdev;
        unsigned int idx, head;

        if (vring->next_avail == virtio16_to_cpu(vdev, vr->avail->idx))
                return NULL;

        /* Make sure 'avail->idx' is visible already. */
        virtio_rmb(false);

        idx = vring->next_avail % vr->num;
        head = virtio16_to_cpu(vdev, vr->avail->ring[idx]);
        if (WARN_ON(head >= vr->num))
                return NULL;

        vring->next_avail++;

        return &vr->desc[head];
}

/* Release virtio descriptor. */
static void mlxbf_tmfifo_release_desc(struct mlxbf_tmfifo_vring *vring,
                                      struct vring_desc *desc, u32 len)
{
        const struct vring *vr = virtqueue_get_vring(vring->vq);
        struct virtio_device *vdev = vring->vq->vdev;
        u16 idx, vr_idx;

        vr_idx = virtio16_to_cpu(vdev, vr->used->idx);
        idx = vr_idx % vr->num;
        vr->used->ring[idx].id = cpu_to_virtio32(vdev, desc - vr->desc);
        vr->used->ring[idx].len = cpu_to_virtio32(vdev, len);

        /*
         * Virtio could poll and check the 'idx' to decide whether the desc is
         * done or not. Add a memory barrier here to make sure the update above
         * completes before updating the idx.
         */
        virtio_mb(false);
        vr->used->idx = cpu_to_virtio16(vdev, vr_idx + 1);
}

/* Get the total length of the descriptor chain. */
static u32 mlxbf_tmfifo_get_pkt_len(struct mlxbf_tmfifo_vring *vring,
                                    struct vring_desc *desc)
{
        const struct vring *vr = virtqueue_get_vring(vring->vq);
        struct virtio_device *vdev = vring->vq->vdev;
        u32 len = 0, idx;

        while (desc) {
                len += virtio32_to_cpu(vdev, desc->len);
                if (!(virtio16_to_cpu(vdev, desc->flags) & VRING_DESC_F_NEXT))
                        break;
                idx = virtio16_to_cpu(vdev, desc->next);
                desc = &vr->desc[idx];
        }

        return len;
}

static void mlxbf_tmfifo_release_pending_pkt(struct mlxbf_tmfifo_vring *vring)
{
        struct vring_desc *desc_head;
        u32 len = 0;

        if (vring->desc_head) {
                desc_head = vring->desc_head;
                len = vring->pkt_len;
        } else {
                desc_head = mlxbf_tmfifo_get_next_desc(vring);
                len = mlxbf_tmfifo_get_pkt_len(vring, desc_head);
        }

        if (desc_head)
                mlxbf_tmfifo_release_desc(vring, desc_head, len);

        vring->pkt_len = 0;
        vring->desc = NULL;
        vring->desc_head = NULL;
}

static void mlxbf_tmfifo_init_net_desc(struct mlxbf_tmfifo_vring *vring,
                                       struct vring_desc *desc, bool is_rx)
{
        struct virtio_device *vdev = vring->vq->vdev;
        struct virtio_net_hdr *net_hdr;

        net_hdr = phys_to_virt(virtio64_to_cpu(vdev, desc->addr));
        memset(net_hdr, 0, sizeof(*net_hdr));
}

/* Get and initialize the next packet. */
static struct vring_desc *
mlxbf_tmfifo_get_next_pkt(struct mlxbf_tmfifo_vring *vring, bool is_rx)
{
        struct vring_desc *desc;

        desc = mlxbf_tmfifo_get_next_desc(vring);
        if (desc && is_rx && vring->vdev_id == VIRTIO_ID_NET)
                mlxbf_tmfifo_init_net_desc(vring, desc, is_rx);

        vring->desc_head = desc;
        vring->desc = desc;

        return desc;
}

/* House-keeping timer. */
static void mlxbf_tmfifo_timer(struct timer_list *t)
{
        struct mlxbf_tmfifo *fifo = container_of(t, struct mlxbf_tmfifo, timer);
        int rx, tx;

        rx = !test_and_set_bit(MLXBF_TM_RX_HWM_IRQ, &fifo->pend_events);
        tx = !test_and_set_bit(MLXBF_TM_TX_LWM_IRQ, &fifo->pend_events);

        if (rx || tx)
                schedule_work(&fifo->work);

        mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);
}

/* Copy one console packet into the output buffer. */
static void mlxbf_tmfifo_console_output_one(struct mlxbf_tmfifo_vdev *cons,
                                            struct mlxbf_tmfifo_vring *vring,
                                            struct vring_desc *desc)
{
        const struct vring *vr = virtqueue_get_vring(vring->vq);
        struct virtio_device *vdev = &cons->vdev;
        u32 len, idx, seg;
        void *addr;

        while (desc) {
                addr = phys_to_virt(virtio64_to_cpu(vdev, desc->addr));
                len = virtio32_to_cpu(vdev, desc->len);

                seg = CIRC_SPACE_TO_END(cons->tx_buf.head, cons->tx_buf.tail,
                                        MLXBF_TMFIFO_CON_TX_BUF_SIZE);
                if (len <= seg) {
                        memcpy(cons->tx_buf.buf + cons->tx_buf.head, addr, len);
                } else {
                        memcpy(cons->tx_buf.buf + cons->tx_buf.head, addr, seg);
                        addr += seg;
                        memcpy(cons->tx_buf.buf, addr, len - seg);
                }
                cons->tx_buf.head = (cons->tx_buf.head + len) %
                        MLXBF_TMFIFO_CON_TX_BUF_SIZE;

                if (!(virtio16_to_cpu(vdev, desc->flags) & VRING_DESC_F_NEXT))
                        break;
                idx = virtio16_to_cpu(vdev, desc->next);
                desc = &vr->desc[idx];
        }
}

/* Copy console data into the output buffer. */
static void mlxbf_tmfifo_console_output(struct mlxbf_tmfifo_vdev *cons,
                                        struct mlxbf_tmfifo_vring *vring)
{
        struct vring_desc *desc;
        u32 len, avail;

        desc = mlxbf_tmfifo_get_next_desc(vring);
        while (desc) {
                /* Release the packet if not enough space. */
                len = mlxbf_tmfifo_get_pkt_len(vring, desc);
                avail = CIRC_SPACE(cons->tx_buf.head, cons->tx_buf.tail,
                                   MLXBF_TMFIFO_CON_TX_BUF_SIZE);
                if (len + MLXBF_TMFIFO_CON_TX_BUF_RSV_SIZE > avail) {
                        mlxbf_tmfifo_release_desc(vring, desc, len);
                        break;
                }

                mlxbf_tmfifo_console_output_one(cons, vring, desc);
                mlxbf_tmfifo_release_desc(vring, desc, len);
                desc = mlxbf_tmfifo_get_next_desc(vring);
        }
}

/* Get the number of available words in Rx FIFO for receiving. */
static int mlxbf_tmfifo_get_rx_avail(struct mlxbf_tmfifo *fifo)
{
        u64 sts;

        sts = readq(fifo->rx_base + MLXBF_TMFIFO_RX_STS);
        return FIELD_GET(MLXBF_TMFIFO_RX_STS__COUNT_MASK, sts);
}

/* Get the number of available words in the TmFifo for sending. */
static int mlxbf_tmfifo_get_tx_avail(struct mlxbf_tmfifo *fifo, int vdev_id)
{
        int tx_reserve;
        u32 count;
        u64 sts;

        /* Reserve some room in FIFO for console messages. */
        if (vdev_id == VIRTIO_ID_NET)
                tx_reserve = fifo->tx_fifo_size / MLXBF_TMFIFO_RESERVE_RATIO;
        else
                tx_reserve = 1;

        sts = readq(fifo->tx_base + MLXBF_TMFIFO_TX_STS);
        count = FIELD_GET(MLXBF_TMFIFO_TX_STS__COUNT_MASK, sts);
        return fifo->tx_fifo_size - tx_reserve - count;
}

/* Console Tx (move data from the output buffer into the TmFifo). */
static void mlxbf_tmfifo_console_tx(struct mlxbf_tmfifo *fifo, int avail)
{
        struct mlxbf_tmfifo_msg_hdr hdr;
        struct mlxbf_tmfifo_vdev *cons;
        unsigned long flags;
        int size, seg;
        void *addr;
        u64 data;

        /* Return if not enough space available. */
        if (avail < MLXBF_TMFIFO_DATA_MIN_WORDS)
                return;

        cons = fifo->vdev[VIRTIO_ID_CONSOLE];
        if (!cons || !cons->tx_buf.buf)
                return;

        /* Return if no data to send. */
        size = CIRC_CNT(cons->tx_buf.head, cons->tx_buf.tail,
                        MLXBF_TMFIFO_CON_TX_BUF_SIZE);
        if (size == 0)
                return;

        /* Adjust the size to available space. */
        if (size + sizeof(hdr) > avail * sizeof(u64))
                size = avail * sizeof(u64) - sizeof(hdr);

        /* Write header. */
        hdr.type = VIRTIO_ID_CONSOLE;
        hdr.len = htons(size);
        writeq(*(u64 *)&hdr, fifo->tx_base + MLXBF_TMFIFO_TX_DATA);

        /* Use spin-lock to protect the 'cons->tx_buf'. */
        spin_lock_irqsave(&fifo->spin_lock[0], flags);

        while (size > 0) {
                addr = cons->tx_buf.buf + cons->tx_buf.tail;

                seg = CIRC_CNT_TO_END(cons->tx_buf.head, cons->tx_buf.tail,
                                      MLXBF_TMFIFO_CON_TX_BUF_SIZE);
                if (seg >= sizeof(u64)) {
                        memcpy(&data, addr, sizeof(u64));
                } else {
                        memcpy(&data, addr, seg);
                        memcpy((u8 *)&data + seg, cons->tx_buf.buf,
                               sizeof(u64) - seg);
                }
                writeq(data, fifo->tx_base + MLXBF_TMFIFO_TX_DATA);

                if (size >= sizeof(u64)) {
                        cons->tx_buf.tail = (cons->tx_buf.tail + sizeof(u64)) %
                                MLXBF_TMFIFO_CON_TX_BUF_SIZE;
                        size -= sizeof(u64);
                } else {
                        cons->tx_buf.tail = (cons->tx_buf.tail + size) %
                                MLXBF_TMFIFO_CON_TX_BUF_SIZE;
                        size = 0;
                }
        }

        spin_unlock_irqrestore(&fifo->spin_lock[0], flags);
}

/* Rx/Tx one word in the descriptor buffer. */
static void mlxbf_tmfifo_rxtx_word(struct mlxbf_tmfifo_vring *vring,
                                   struct vring_desc *desc,
                                   bool is_rx, int len)
{
        struct virtio_device *vdev = vring->vq->vdev;
        struct mlxbf_tmfifo *fifo = vring->fifo;
        void *addr;
        u64 data;

        /* Get the buffer address of this desc. */
        addr = phys_to_virt(virtio64_to_cpu(vdev, desc->addr));

        /* Read a word from FIFO for Rx. */
        if (is_rx)
                data = readq(fifo->rx_base + MLXBF_TMFIFO_RX_DATA);

        if (vring->cur_len + sizeof(u64) <= len) {
                /* The whole word. */
                if (is_rx)
                        memcpy(addr + vring->cur_len, &data, sizeof(u64));
                else
                        memcpy(&data, addr + vring->cur_len, sizeof(u64));
                vring->cur_len += sizeof(u64);
        } else {
                /* Leftover bytes. */
                if (is_rx)
                        memcpy(addr + vring->cur_len, &data,
                               len - vring->cur_len);
                else
                        memcpy(&data, addr + vring->cur_len,
                               len - vring->cur_len);
                vring->cur_len = len;
        }

        /* Write the word into FIFO for Tx. */
        if (!is_rx)
                writeq(data, fifo->tx_base + MLXBF_TMFIFO_TX_DATA);
}

/*
 * Rx/Tx packet header.
 *
 * In Rx case, the packet might be found to belong to a different vring since
 * the TmFifo is shared by different services. In such case, the 'vring_change'
 * flag is set.
 */
static void mlxbf_tmfifo_rxtx_header(struct mlxbf_tmfifo_vring *vring,
                                     struct vring_desc *desc,
                                     bool is_rx, bool *vring_change)
{
        struct mlxbf_tmfifo *fifo = vring->fifo;
        struct virtio_net_config *config;
        struct mlxbf_tmfifo_msg_hdr hdr;
        int vdev_id, hdr_len;

        /* Read/Write packet header. */
        if (is_rx) {
                /* Drain one word from the FIFO. */
                *(u64 *)&hdr = readq(fifo->rx_base + MLXBF_TMFIFO_RX_DATA);

                /* Skip the length 0 packets (keepalive). */
                if (hdr.len == 0)
                        return;

                /* Check packet type. */
                if (hdr.type == VIRTIO_ID_NET) {
                        vdev_id = VIRTIO_ID_NET;
                        hdr_len = sizeof(struct virtio_net_hdr);
                        config = &fifo->vdev[vdev_id]->config.net;
                        /* A legacy-only interface for now. */
                        if (ntohs(hdr.len) >
                            __virtio16_to_cpu(virtio_legacy_is_little_endian(),
                                              config->mtu) +
                            MLXBF_TMFIFO_NET_L2_OVERHEAD)
                                return;
                } else {
                        vdev_id = VIRTIO_ID_CONSOLE;
                        hdr_len = 0;
                }

                /*
                 * Check whether the new packet still belongs to this vring.
                 * If not, update the pkt_len of the new vring.
                 */
                if (vdev_id != vring->vdev_id) {
                        struct mlxbf_tmfifo_vdev *tm_dev2 = fifo->vdev[vdev_id];

                        if (!tm_dev2)
                                return;
                        vring->desc = desc;
                        vring = &tm_dev2->vrings[MLXBF_TMFIFO_VRING_RX];
                        *vring_change = true;
                }
                vring->pkt_len = ntohs(hdr.len) + hdr_len;
        } else {
                /* Network virtio has an extra header. */
                hdr_len = (vring->vdev_id == VIRTIO_ID_NET) ?
                           sizeof(struct virtio_net_hdr) : 0;
                vring->pkt_len = mlxbf_tmfifo_get_pkt_len(vring, desc);
                hdr.type = (vring->vdev_id == VIRTIO_ID_NET) ?
                            VIRTIO_ID_NET : VIRTIO_ID_CONSOLE;
                hdr.len = htons(vring->pkt_len - hdr_len);
                writeq(*(u64 *)&hdr, fifo->tx_base + MLXBF_TMFIFO_TX_DATA);
        }

        vring->cur_len = hdr_len;
        vring->rem_len = vring->pkt_len;
        fifo->vring[is_rx] = vring;
}

/*
 * Rx/Tx one descriptor.
 *
 * Return true to indicate more data available.
 */
static bool mlxbf_tmfifo_rxtx_one_desc(struct mlxbf_tmfifo_vring *vring,
                                       bool is_rx, int *avail)
{
        const struct vring *vr = virtqueue_get_vring(vring->vq);
        struct mlxbf_tmfifo *fifo = vring->fifo;
        struct virtio_device *vdev;
        bool vring_change = false;
        struct vring_desc *desc;
        unsigned long flags;
        u32 len, idx;

        vdev = &fifo->vdev[vring->vdev_id]->vdev;

        /* Get the descriptor of the next packet. */
        if (!vring->desc) {
                desc = mlxbf_tmfifo_get_next_pkt(vring, is_rx);
                if (!desc)
                        return false;
        } else {
                desc = vring->desc;
        }

        /* Beginning of a packet. Start to Rx/Tx packet header. */
        if (vring->pkt_len == 0) {
                mlxbf_tmfifo_rxtx_header(vring, desc, is_rx, &vring_change);
                (*avail)--;

                /* Return if new packet is for another ring. */
                if (vring_change)
                        return false;
                goto mlxbf_tmfifo_desc_done;
        }

        /* Get the length of this desc. */
        len = virtio32_to_cpu(vdev, desc->len);
        if (len > vring->rem_len)
                len = vring->rem_len;

        /* Rx/Tx one word (8 bytes) if not done. */
        if (vring->cur_len < len) {
                mlxbf_tmfifo_rxtx_word(vring, desc, is_rx, len);
                (*avail)--;
        }

        /* Check again whether it's done. */
        if (vring->cur_len == len) {
                vring->cur_len = 0;
                vring->rem_len -= len;

                /* Get the next desc on the chain. */
                if (vring->rem_len > 0 &&
                    (virtio16_to_cpu(vdev, desc->flags) & VRING_DESC_F_NEXT)) {
                        idx = virtio16_to_cpu(vdev, desc->next);
                        desc = &vr->desc[idx];
                        goto mlxbf_tmfifo_desc_done;
                }

                /* Done and release the pending packet. */
                mlxbf_tmfifo_release_pending_pkt(vring);
                desc = NULL;
                fifo->vring[is_rx] = NULL;

                /*
                 * Make sure the load/store are in order before
                 * returning back to virtio.
                 */
                virtio_mb(false);

                /* Notify upper layer that packet is done. */
                spin_lock_irqsave(&fifo->spin_lock[is_rx], flags);
                vring_interrupt(0, vring->vq);
                spin_unlock_irqrestore(&fifo->spin_lock[is_rx], flags);
        }

mlxbf_tmfifo_desc_done:
        /* Save the current desc. */
        vring->desc = desc;

        return true;
}

/* Rx & Tx processing of a queue. */
static void mlxbf_tmfifo_rxtx(struct mlxbf_tmfifo_vring *vring, bool is_rx)
{
        int avail = 0, devid = vring->vdev_id;
        struct mlxbf_tmfifo *fifo;
        bool more;

        fifo = vring->fifo;

        /* Return if vdev is not ready. */
        if (!fifo->vdev[devid])
                return;

        /* Return if another vring is running. */
        if (fifo->vring[is_rx] && fifo->vring[is_rx] != vring)
                return;

        /* Only handle console and network for now. */
        if (WARN_ON(devid != VIRTIO_ID_NET && devid != VIRTIO_ID_CONSOLE))
                return;

        do {
                /* Get available FIFO space. */
                if (avail == 0) {
                        if (is_rx)
                                avail = mlxbf_tmfifo_get_rx_avail(fifo);
                        else
                                avail = mlxbf_tmfifo_get_tx_avail(fifo, devid);
                        if (avail <= 0)
                                break;
                }

                /* Console output always comes from the Tx buffer. */
                if (!is_rx && devid == VIRTIO_ID_CONSOLE) {
                        mlxbf_tmfifo_console_tx(fifo, avail);
                        break;
                }

                /* Handle one descriptor. */
                more = mlxbf_tmfifo_rxtx_one_desc(vring, is_rx, &avail);
        } while (more);
}

/* Handle Rx or Tx queues. */
static void mlxbf_tmfifo_work_rxtx(struct mlxbf_tmfifo *fifo, int queue_id,
                                   int irq_id, bool is_rx)
{
        struct mlxbf_tmfifo_vdev *tm_vdev;
        struct mlxbf_tmfifo_vring *vring;
        int i;

        if (!test_and_clear_bit(irq_id, &fifo->pend_events) ||
            !fifo->irq_info[irq_id].irq)
                return;

        for (i = 0; i < MLXBF_TMFIFO_VDEV_MAX; i++) {
                tm_vdev = fifo->vdev[i];
                if (tm_vdev) {
                        vring = &tm_vdev->vrings[queue_id];
                        if (vring->vq)
                                mlxbf_tmfifo_rxtx(vring, is_rx);
                }
        }
}

/* Work handler for Rx and Tx case. */
static void mlxbf_tmfifo_work_handler(struct work_struct *work)
{
        struct mlxbf_tmfifo *fifo;

        fifo = container_of(work, struct mlxbf_tmfifo, work);
        if (!fifo->is_ready)
                return;

        mutex_lock(&fifo->lock);

        /* Tx (Send data to the TmFifo). */
        mlxbf_tmfifo_work_rxtx(fifo, MLXBF_TMFIFO_VRING_TX,
                               MLXBF_TM_TX_LWM_IRQ, false);

        /* Rx (Receive data from the TmFifo). */
        mlxbf_tmfifo_work_rxtx(fifo, MLXBF_TMFIFO_VRING_RX,
                               MLXBF_TM_RX_HWM_IRQ, true);

        mutex_unlock(&fifo->lock);
}

/* The notify function is called when new buffers are posted. */
static bool mlxbf_tmfifo_virtio_notify(struct virtqueue *vq)
{
        struct mlxbf_tmfifo_vring *vring = vq->priv;
        struct mlxbf_tmfifo_vdev *tm_vdev;
        struct mlxbf_tmfifo *fifo;
        unsigned long flags;

        fifo = vring->fifo;

        /*
         * Virtio maintains vrings in pairs, even number ring for Rx
         * and odd number ring for Tx.
         */
        if (vring->index & BIT(0)) {
                /*
                 * Console could make blocking call with interrupts disabled.
                 * In such case, the vring needs to be served right away. For
                 * other cases, just set the TX LWM bit to start Tx in the
                 * worker handler.
                 */
                if (vring->vdev_id == VIRTIO_ID_CONSOLE) {
                        spin_lock_irqsave(&fifo->spin_lock[0], flags);
                        tm_vdev = fifo->vdev[VIRTIO_ID_CONSOLE];
                        mlxbf_tmfifo_console_output(tm_vdev, vring);
                        spin_unlock_irqrestore(&fifo->spin_lock[0], flags);
                } else if (test_and_set_bit(MLXBF_TM_TX_LWM_IRQ,
                                            &fifo->pend_events)) {
                        return true;
                }
        } else {
                if (test_and_set_bit(MLXBF_TM_RX_HWM_IRQ, &fifo->pend_events))
                        return true;
        }

        schedule_work(&fifo->work);

        return true;
}

/* Get the array of feature bits for this device. */
static u64 mlxbf_tmfifo_virtio_get_features(struct virtio_device *vdev)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        return tm_vdev->features;
}

/* Confirm device features to use. */
static int mlxbf_tmfifo_virtio_finalize_features(struct virtio_device *vdev)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        tm_vdev->features = vdev->features;

        return 0;
}

/* Free virtqueues found by find_vqs(). */
static void mlxbf_tmfifo_virtio_del_vqs(struct virtio_device *vdev)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);
        struct mlxbf_tmfifo_vring *vring;
        struct virtqueue *vq;
        int i;

        for (i = 0; i < ARRAY_SIZE(tm_vdev->vrings); i++) {
                vring = &tm_vdev->vrings[i];

                /* Release the pending packet. */
                if (vring->desc)
                        mlxbf_tmfifo_release_pending_pkt(vring);
                vq = vring->vq;
                if (vq) {
                        vring->vq = NULL;
                        vring_del_virtqueue(vq);
                }
        }
}

/* Create and initialize the virtual queues. */
static int mlxbf_tmfifo_virtio_find_vqs(struct virtio_device *vdev,
                                        unsigned int nvqs,
                                        struct virtqueue *vqs[],
                                        vq_callback_t *callbacks[],
                                        const char * const names[],
                                        const bool *ctx,
                                        struct irq_affinity *desc)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);
        struct mlxbf_tmfifo_vring *vring;
        struct virtqueue *vq;
        int i, ret, size;

        if (nvqs > ARRAY_SIZE(tm_vdev->vrings))
                return -EINVAL;

        for (i = 0; i < nvqs; ++i) {
                if (!names[i]) {
                        ret = -EINVAL;
                        goto error;
                }
                vring = &tm_vdev->vrings[i];

                /* zero vring */
                size = vring_size(vring->num, vring->align);
                memset(vring->va, 0, size);
                vq = vring_new_virtqueue(i, vring->num, vring->align, vdev,
                                         false, false, vring->va,
                                         mlxbf_tmfifo_virtio_notify,
                                         callbacks[i], names[i]);
                if (!vq) {
                        dev_err(&vdev->dev, "vring_new_virtqueue failed\n");
                        ret = -ENOMEM;
                        goto error;
                }

                vqs[i] = vq;
                vring->vq = vq;
                vq->priv = vring;
        }

        return 0;

error:
        mlxbf_tmfifo_virtio_del_vqs(vdev);
        return ret;
}

/* Read the status byte. */
static u8 mlxbf_tmfifo_virtio_get_status(struct virtio_device *vdev)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        return tm_vdev->status;
}

/* Write the status byte. */
static void mlxbf_tmfifo_virtio_set_status(struct virtio_device *vdev,
                                           u8 status)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        tm_vdev->status = status;
}

/* Reset the device. Not much here for now. */
static void mlxbf_tmfifo_virtio_reset(struct virtio_device *vdev)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        tm_vdev->status = 0;
}

/* Read the value of a configuration field. */
static void mlxbf_tmfifo_virtio_get(struct virtio_device *vdev,

                                    unsigned int offset,
                                    void *buf,
                                    unsigned int len)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        if ((u64)offset + len > sizeof(tm_vdev->config))
                return;

        memcpy(buf, (u8 *)&tm_vdev->config + offset, len);
}

/* Write the value of a configuration field. */
static void mlxbf_tmfifo_virtio_set(struct virtio_device *vdev,
                                    unsigned int offset,
                                    const void *buf,
                                    unsigned int len)
{
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        if ((u64)offset + len > sizeof(tm_vdev->config))
                return;

        memcpy((u8 *)&tm_vdev->config + offset, buf, len);
}

static void tmfifo_virtio_dev_release(struct device *device)
{
        struct virtio_device *vdev =
                        container_of(device, struct virtio_device, dev);
        struct mlxbf_tmfifo_vdev *tm_vdev = mlxbf_vdev_to_tmfifo(vdev);

        kfree(tm_vdev);
}

/* Virtio config operations. */
static const struct virtio_config_ops mlxbf_tmfifo_virtio_config_ops = {
        .get_features = mlxbf_tmfifo_virtio_get_features,
        .finalize_features = mlxbf_tmfifo_virtio_finalize_features,
        .find_vqs = mlxbf_tmfifo_virtio_find_vqs,
        .del_vqs = mlxbf_tmfifo_virtio_del_vqs,
        .reset = mlxbf_tmfifo_virtio_reset,
        .set_status = mlxbf_tmfifo_virtio_set_status,
        .get_status = mlxbf_tmfifo_virtio_get_status,
        .get = mlxbf_tmfifo_virtio_get,
        .set = mlxbf_tmfifo_virtio_set,
};

/* Create vdev for the FIFO. */
static int mlxbf_tmfifo_create_vdev(struct device *dev,
                                    struct mlxbf_tmfifo *fifo,
                                    int vdev_id, u64 features,
                                    void *config, u32 size)
{
        struct mlxbf_tmfifo_vdev *tm_vdev, *reg_dev = NULL;
        int ret;

        mutex_lock(&fifo->lock);

        tm_vdev = fifo->vdev[vdev_id];
        if (tm_vdev) {
                dev_err(dev, "vdev %d already exists\n", vdev_id);
                ret = -EEXIST;
                goto fail;
        }

        tm_vdev = kzalloc(sizeof(*tm_vdev), GFP_KERNEL);
        if (!tm_vdev) {
                ret = -ENOMEM;
                goto fail;
        }

        tm_vdev->vdev.id.device = vdev_id;
        tm_vdev->vdev.config = &mlxbf_tmfifo_virtio_config_ops;
        tm_vdev->vdev.dev.parent = dev;
        tm_vdev->vdev.dev.release = tmfifo_virtio_dev_release;
        tm_vdev->features = features;
        if (config)
                memcpy(&tm_vdev->config, config, size);

        if (mlxbf_tmfifo_alloc_vrings(fifo, tm_vdev)) {
                dev_err(dev, "unable to allocate vring\n");
                ret = -ENOMEM;
                goto vdev_fail;
        }

        /* Allocate an output buffer for the console device. */
        if (vdev_id == VIRTIO_ID_CONSOLE)
                tm_vdev->tx_buf.buf = devm_kmalloc(dev,
                                                   MLXBF_TMFIFO_CON_TX_BUF_SIZE,
                                                   GFP_KERNEL);
        fifo->vdev[vdev_id] = tm_vdev;

        /* Register the virtio device. */
        ret = register_virtio_device(&tm_vdev->vdev);
        reg_dev = tm_vdev;
        if (ret) {
                dev_err(dev, "register_virtio_device failed\n");
                goto vdev_fail;
        }

        mutex_unlock(&fifo->lock);
        return 0;

vdev_fail:
        mlxbf_tmfifo_free_vrings(fifo, tm_vdev);
        fifo->vdev[vdev_id] = NULL;
        if (reg_dev)
                put_device(&tm_vdev->vdev.dev);
        else
                kfree(tm_vdev);
fail:
        mutex_unlock(&fifo->lock);
        return ret;
}

/* Delete vdev for the FIFO. */
static int mlxbf_tmfifo_delete_vdev(struct mlxbf_tmfifo *fifo, int vdev_id)
{
        struct mlxbf_tmfifo_vdev *tm_vdev;

        mutex_lock(&fifo->lock);

        /* Unregister vdev. */
        tm_vdev = fifo->vdev[vdev_id];
        if (tm_vdev) {
                unregister_virtio_device(&tm_vdev->vdev);
                mlxbf_tmfifo_free_vrings(fifo, tm_vdev);
                fifo->vdev[vdev_id] = NULL;
        }

        mutex_unlock(&fifo->lock);

        return 0;
}

/* Read the configured network MAC address from efi variable. */
static void mlxbf_tmfifo_get_cfg_mac(u8 *mac)
{
        efi_guid_t guid = EFI_GLOBAL_VARIABLE_GUID;
        unsigned long size = ETH_ALEN;
        u8 buf[ETH_ALEN];
        efi_status_t rc;

        rc = efi.get_variable(mlxbf_tmfifo_efi_name, &guid, NULL, &size, buf);
        if (rc == EFI_SUCCESS && size == ETH_ALEN)
                ether_addr_copy(mac, buf);
        else
                ether_addr_copy(mac, mlxbf_tmfifo_net_default_mac);
}

/* Set TmFifo thresolds which is used to trigger interrupts. */
static void mlxbf_tmfifo_set_threshold(struct mlxbf_tmfifo *fifo)
{
        u64 ctl;

        /* Get Tx FIFO size and set the low/high watermark. */
        ctl = readq(fifo->tx_base + MLXBF_TMFIFO_TX_CTL);
        fifo->tx_fifo_size =
                FIELD_GET(MLXBF_TMFIFO_TX_CTL__MAX_ENTRIES_MASK, ctl);
        ctl = (ctl & ~MLXBF_TMFIFO_TX_CTL__LWM_MASK) |
                FIELD_PREP(MLXBF_TMFIFO_TX_CTL__LWM_MASK,
                           fifo->tx_fifo_size / 2);
        ctl = (ctl & ~MLXBF_TMFIFO_TX_CTL__HWM_MASK) |
                FIELD_PREP(MLXBF_TMFIFO_TX_CTL__HWM_MASK,
                           fifo->tx_fifo_size - 1);
        writeq(ctl, fifo->tx_base + MLXBF_TMFIFO_TX_CTL);

        /* Get Rx FIFO size and set the low/high watermark. */
        ctl = readq(fifo->rx_base + MLXBF_TMFIFO_RX_CTL);
        fifo->rx_fifo_size =
                FIELD_GET(MLXBF_TMFIFO_RX_CTL__MAX_ENTRIES_MASK, ctl);
        ctl = (ctl & ~MLXBF_TMFIFO_RX_CTL__LWM_MASK) |
                FIELD_PREP(MLXBF_TMFIFO_RX_CTL__LWM_MASK, 0);
        ctl = (ctl & ~MLXBF_TMFIFO_RX_CTL__HWM_MASK) |
                FIELD_PREP(MLXBF_TMFIFO_RX_CTL__HWM_MASK, 1);
        writeq(ctl, fifo->rx_base + MLXBF_TMFIFO_RX_CTL);
}

static void mlxbf_tmfifo_cleanup(struct mlxbf_tmfifo *fifo)
{
        int i;

        fifo->is_ready = false;
        del_timer_sync(&fifo->timer);
        mlxbf_tmfifo_disable_irqs(fifo);
        cancel_work_sync(&fifo->work);
        for (i = 0; i < MLXBF_TMFIFO_VDEV_MAX; i++)
                mlxbf_tmfifo_delete_vdev(fifo, i);
}

/* Probe the TMFIFO. */
static int mlxbf_tmfifo_probe(struct platform_device *pdev)
{
        struct virtio_net_config net_config;
        struct device *dev = &pdev->dev;
        struct mlxbf_tmfifo *fifo;
        int i, rc;

        fifo = devm_kzalloc(dev, sizeof(*fifo), GFP_KERNEL);
        if (!fifo)
                return -ENOMEM;

        spin_lock_init(&fifo->spin_lock[0]);
        spin_lock_init(&fifo->spin_lock[1]);
        INIT_WORK(&fifo->work, mlxbf_tmfifo_work_handler);
        mutex_init(&fifo->lock);

        /* Get the resource of the Rx FIFO. */
        fifo->rx_base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(fifo->rx_base))
                return PTR_ERR(fifo->rx_base);

        /* Get the resource of the Tx FIFO. */
        fifo->tx_base = devm_platform_ioremap_resource(pdev, 1);
        if (IS_ERR(fifo->tx_base))
                return PTR_ERR(fifo->tx_base);

        platform_set_drvdata(pdev, fifo);

        timer_setup(&fifo->timer, mlxbf_tmfifo_timer, 0);

        for (i = 0; i < MLXBF_TM_MAX_IRQ; i++) {
                fifo->irq_info[i].index = i;
                fifo->irq_info[i].fifo = fifo;
                fifo->irq_info[i].irq = platform_get_irq(pdev, i);
                rc = devm_request_irq(dev, fifo->irq_info[i].irq,
                                      mlxbf_tmfifo_irq_handler, 0,
                                      "tmfifo", &fifo->irq_info[i]);
                if (rc) {
                        dev_err(dev, "devm_request_irq failed\n");
                        fifo->irq_info[i].irq = 0;
                        return rc;
                }
        }

        mlxbf_tmfifo_set_threshold(fifo);

        /* Create the console vdev. */
        rc = mlxbf_tmfifo_create_vdev(dev, fifo, VIRTIO_ID_CONSOLE, 0, NULL, 0);
        if (rc)
                goto fail;

        /* Create the network vdev. */
        memset(&net_config, 0, sizeof(net_config));

        /* A legacy-only interface for now. */
        net_config.mtu = __cpu_to_virtio16(virtio_legacy_is_little_endian(),
                                           ETH_DATA_LEN);
        net_config.status = __cpu_to_virtio16(virtio_legacy_is_little_endian(),
                                              VIRTIO_NET_S_LINK_UP);
        mlxbf_tmfifo_get_cfg_mac(net_config.mac);
        rc = mlxbf_tmfifo_create_vdev(dev, fifo, VIRTIO_ID_NET,
                                      MLXBF_TMFIFO_NET_FEATURES, &net_config,
                                      sizeof(net_config));
        if (rc)
                goto fail;

        mod_timer(&fifo->timer, jiffies + MLXBF_TMFIFO_TIMER_INTERVAL);

        fifo->is_ready = true;
        return 0;

fail:
        mlxbf_tmfifo_cleanup(fifo);
        return rc;
}

/* Device remove function. */
static int mlxbf_tmfifo_remove(struct platform_device *pdev)
{
        struct mlxbf_tmfifo *fifo = platform_get_drvdata(pdev);

        mlxbf_tmfifo_cleanup(fifo);

        return 0;
}

static const struct acpi_device_id mlxbf_tmfifo_acpi_match[] = {
        { "MLNXBF01", 0 },
        {}
};
MODULE_DEVICE_TABLE(acpi, mlxbf_tmfifo_acpi_match);

static struct platform_driver mlxbf_tmfifo_driver = {
        .probe = mlxbf_tmfifo_probe,
        .remove = mlxbf_tmfifo_remove,
        .driver = {
                .name = "bf-tmfifo",
                .acpi_match_table = mlxbf_tmfifo_acpi_match,
        },
};

module_platform_driver(mlxbf_tmfifo_driver);

MODULE_DESCRIPTION("Mellanox BlueField SoC TmFifo Driver");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Mellanox Technologies");