// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 *  Bluetooth HCI Three-wire UART driver
 *
 *  Copyright (C) 2012  Intel Corporation
 */

#include <linux/acpi.h>
#include <linux/bitrev.h>
#include <linux/crc-ccitt.h>
#include <linux/errno.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/of.h>
#include <linux/pm_runtime.h>
#include <linux/serdev.h>
#include <linux/skbuff.h>

#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>

#include "btrtl.h"
#include "hci_uart.h"

#define SUSPEND_TIMEOUT_MS      6000

#define HCI_3WIRE_ACK_PKT       0
#define HCI_3WIRE_LINK_PKT      15

/* Sliding window size */
#define H5_TX_WIN_MAX           4

#define H5_ACK_TIMEOUT  msecs_to_jiffies(250)
#define H5_SYNC_TIMEOUT msecs_to_jiffies(100)

/*
 * Maximum Three-wire packet:
 *     4 byte header + max value for 12-bit length + 2 bytes for CRC
 */
#define H5_MAX_LEN (4 + 0xfff + 2)

/* Convenience macros for reading Three-wire header values */
#define H5_HDR_SEQ(hdr)         ((hdr)[0] & 0x07)
#define H5_HDR_ACK(hdr)         (((hdr)[0] >> 3) & 0x07)
#define H5_HDR_CRC(hdr)         (((hdr)[0] >> 6) & 0x01)
#define H5_HDR_RELIABLE(hdr)    (((hdr)[0] >> 7) & 0x01)
#define H5_HDR_PKT_TYPE(hdr)    ((hdr)[1] & 0x0f)
#define H5_HDR_LEN(hdr)         ((((hdr)[1] >> 4) & 0x0f) + ((hdr)[2] << 4))

#define SLIP_DELIMITER  0xc0
#define SLIP_ESC        0xdb
#define SLIP_ESC_DELIM  0xdc
#define SLIP_ESC_ESC    0xdd

/* H5 state flags */
enum {
        H5_RX_ESC,              /* SLIP escape mode */
        H5_TX_ACK_REQ,          /* Pending ack to send */
        H5_WAKEUP_DISABLE,      /* Device cannot wake host */
        H5_HW_FLOW_CONTROL,     /* Use HW flow control */
        H5_CRC,                 /* Use CRC */
};

struct h5 {
        /* Must be the first member, hci_serdev.c expects this. */
        struct hci_uart         serdev_hu;

        struct sk_buff_head     unack;          /* Unack'ed packets queue */
        struct sk_buff_head     rel;            /* Reliable packets queue */
        struct sk_buff_head     unrel;          /* Unreliable packets queue */

        unsigned long           flags;

        struct sk_buff          *rx_skb;        /* Receive buffer */
        size_t                  rx_pending;     /* Expecting more bytes */
        u8                      rx_ack;         /* Last ack number received */

        int                     (*rx_func)(struct hci_uart *hu, u8 c);

        struct timer_list       timer;          /* Retransmission timer */
        struct hci_uart         *hu;            /* Parent HCI UART */

        u8                      tx_seq;         /* Next seq number to send */
        u8                      tx_ack;         /* Next ack number to send */
        u8                      tx_win;         /* Sliding window size */

        enum {
                H5_UNINITIALIZED,
                H5_INITIALIZED,
                H5_ACTIVE,
        } state;

        enum {
                H5_AWAKE,
                H5_SLEEPING,
                H5_WAKING_UP,
        } sleep;

        const struct h5_vnd *vnd;
        const char *id;

        struct gpio_desc *enable_gpio;
        struct gpio_desc *device_wake_gpio;
};

enum h5_driver_info {
        H5_INFO_WAKEUP_DISABLE = BIT(0),
};

struct h5_vnd {
        int (*setup)(struct h5 *h5);
        void (*open)(struct h5 *h5);
        void (*close)(struct h5 *h5);
        int (*suspend)(struct h5 *h5);
        int (*resume)(struct h5 *h5);
        const struct acpi_gpio_mapping *acpi_gpio_map;
        int sizeof_priv;
};

struct h5_device_data {
        uint32_t driver_info;
        struct h5_vnd *vnd;
};

static void h5_reset_rx(struct h5 *h5);

static void h5_link_control(struct hci_uart *hu, const void *data, size_t len)
{
        struct h5 *h5 = hu->priv;
        struct sk_buff *nskb;

        nskb = alloc_skb(3, GFP_ATOMIC);
        if (!nskb)
                return;

        hci_skb_pkt_type(nskb) = HCI_3WIRE_LINK_PKT;

        skb_put_data(nskb, data, len);

        skb_queue_tail(&h5->unrel, nskb);
}

static u8 h5_cfg_field(struct h5 *h5)
{
        /* Sliding window size (first 3 bits) and CRC request (fifth bit). */
        return (h5->tx_win & 0x07) | 0x10;
}

static void h5_timed_event(struct timer_list *t)
{
        const unsigned char sync_req[] = { 0x01, 0x7e };
        unsigned char conf_req[3] = { 0x03, 0xfc };
        struct h5 *h5 = timer_container_of(h5, t, timer);
        struct hci_uart *hu = h5->hu;
        struct sk_buff *skb;
        unsigned long flags;

        BT_DBG("%s", hu->hdev->name);

        if (h5->state == H5_UNINITIALIZED)
                h5_link_control(hu, sync_req, sizeof(sync_req));

        if (h5->state == H5_INITIALIZED) {
                conf_req[2] = h5_cfg_field(h5);
                h5_link_control(hu, conf_req, sizeof(conf_req));
        }

        if (h5->state != H5_ACTIVE) {
                mod_timer(&h5->timer, jiffies + H5_SYNC_TIMEOUT);
                goto wakeup;
        }

        if (h5->sleep != H5_AWAKE) {
                h5->sleep = H5_SLEEPING;
                goto wakeup;
        }

        BT_DBG("hu %p retransmitting %u pkts", hu, h5->unack.qlen);

        spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);

        while ((skb = __skb_dequeue_tail(&h5->unack)) != NULL) {
                h5->tx_seq = (h5->tx_seq - 1) & 0x07;
                skb_queue_head(&h5->rel, skb);
        }

        spin_unlock_irqrestore(&h5->unack.lock, flags);

wakeup:
        hci_uart_tx_wakeup(hu);
}

static void h5_peer_reset(struct hci_uart *hu)
{
        struct h5 *h5 = hu->priv;

        bt_dev_err(hu->hdev, "Peer device has reset");

        h5->state = H5_UNINITIALIZED;

        timer_delete(&h5->timer);

        skb_queue_purge(&h5->rel);
        skb_queue_purge(&h5->unrel);
        skb_queue_purge(&h5->unack);

        h5->tx_seq = 0;
        h5->tx_ack = 0;

        /* Send reset request to upper stack */
        hci_reset_dev(hu->hdev);
}

static int h5_open(struct hci_uart *hu)
{
        struct h5 *h5;

        BT_DBG("hu %p", hu);

        if (hu->serdev) {
                h5 = serdev_device_get_drvdata(hu->serdev);
        } else {
                h5 = kzalloc_obj(*h5);
                if (!h5)
                        return -ENOMEM;
        }

        hu->priv = h5;
        h5->hu = hu;

        skb_queue_head_init(&h5->unack);
        skb_queue_head_init(&h5->rel);
        skb_queue_head_init(&h5->unrel);

        h5_reset_rx(h5);

        timer_setup(&h5->timer, h5_timed_event, 0);

        h5->tx_win = H5_TX_WIN_MAX;

        if (h5->vnd && h5->vnd->open)
                h5->vnd->open(h5);

        set_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags);

        /*
         * Wait one jiffy because the UART layer won't set HCI_UART_PROTO_READY,
         * which allows us to send link packets, until this function returns.
         */
        mod_timer(&h5->timer, jiffies + 1);

        return 0;
}

static int h5_close(struct hci_uart *hu)
{
        struct h5 *h5 = hu->priv;

        timer_delete_sync(&h5->timer);

        skb_queue_purge(&h5->unack);
        skb_queue_purge(&h5->rel);
        skb_queue_purge(&h5->unrel);

        kfree_skb(h5->rx_skb);
        h5->rx_skb = NULL;

        if (h5->vnd && h5->vnd->close)
                h5->vnd->close(h5);

        if (!hu->serdev)
                kfree(h5);

        return 0;
}

static int h5_setup(struct hci_uart *hu)
{
        struct h5 *h5 = hu->priv;

        if (h5->vnd && h5->vnd->setup)
                return h5->vnd->setup(h5);

        return 0;
}

static void h5_pkt_cull(struct h5 *h5)
{
        struct sk_buff *skb, *tmp;
        unsigned long flags;
        int i, to_remove;
        u8 seq;

        spin_lock_irqsave(&h5->unack.lock, flags);

        to_remove = skb_queue_len(&h5->unack);
        if (to_remove == 0)
                goto unlock;

        seq = h5->tx_seq;

        while (to_remove > 0) {
                if (h5->rx_ack == seq)
                        break;

                to_remove--;
                seq = (seq - 1) & 0x07;
        }

        if (seq != h5->rx_ack)
                BT_ERR("Controller acked invalid packet");

        i = 0;
        skb_queue_walk_safe(&h5->unack, skb, tmp) {
                if (i++ >= to_remove)
                        break;

                __skb_unlink(skb, &h5->unack);
                dev_kfree_skb_irq(skb);
        }

        if (skb_queue_empty(&h5->unack))
                timer_delete(&h5->timer);

unlock:
        spin_unlock_irqrestore(&h5->unack.lock, flags);
}

static void h5_handle_internal_rx(struct hci_uart *hu)
{
        struct h5 *h5 = hu->priv;
        const unsigned char sync_req[] = { 0x01, 0x7e };
        const unsigned char sync_rsp[] = { 0x02, 0x7d };
        unsigned char conf_req[3] = { 0x03, 0xfc };
        const unsigned char conf_rsp[] = { 0x04, 0x7b };
        const unsigned char wakeup_req[] = { 0x05, 0xfa };
        const unsigned char woken_req[] = { 0x06, 0xf9 };
        const unsigned char sleep_req[] = { 0x07, 0x78 };
        const unsigned char *hdr = h5->rx_skb->data;
        const unsigned char *data = &h5->rx_skb->data[4];

        BT_DBG("%s", hu->hdev->name);

        if (H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT)
                return;

        if (H5_HDR_LEN(hdr) < 2)
                return;

        conf_req[2] = h5_cfg_field(h5);

        if (memcmp(data, sync_req, 2) == 0) {
                if (h5->state == H5_ACTIVE)
                        h5_peer_reset(hu);
                h5_link_control(hu, sync_rsp, 2);
        } else if (memcmp(data, sync_rsp, 2) == 0) {
                if (h5->state == H5_ACTIVE)
                        h5_peer_reset(hu);
                h5->state = H5_INITIALIZED;
                h5_link_control(hu, conf_req, 3);
        } else if (memcmp(data, conf_req, 2) == 0) {
                h5_link_control(hu, conf_rsp, 2);
                h5_link_control(hu, conf_req, 3);
        } else if (memcmp(data, conf_rsp, 2) == 0) {
                if (H5_HDR_LEN(hdr) > 2) {
                        h5->tx_win = (data[2] & 0x07);
                        assign_bit(H5_CRC, &h5->flags, data[2] & 0x10);
                }
                BT_DBG("Three-wire init complete. tx_win %u", h5->tx_win);
                h5->state = H5_ACTIVE;
                hci_uart_init_ready(hu);
                return;
        } else if (memcmp(data, sleep_req, 2) == 0) {
                BT_DBG("Peer went to sleep");
                h5->sleep = H5_SLEEPING;
                return;
        } else if (memcmp(data, woken_req, 2) == 0) {
                BT_DBG("Peer woke up");
                h5->sleep = H5_AWAKE;
        } else if (memcmp(data, wakeup_req, 2) == 0) {
                BT_DBG("Peer requested wakeup");
                h5_link_control(hu, woken_req, 2);
                h5->sleep = H5_AWAKE;
        } else {
                BT_DBG("Link Control: 0x%02hhx 0x%02hhx", data[0], data[1]);
                return;
        }

        hci_uart_tx_wakeup(hu);
}

static void h5_complete_rx_pkt(struct hci_uart *hu)
{
        struct h5 *h5 = hu->priv;
        const unsigned char *hdr = h5->rx_skb->data;

        if (H5_HDR_RELIABLE(hdr)) {
                h5->tx_ack = (h5->tx_ack + 1) % 8;
                set_bit(H5_TX_ACK_REQ, &h5->flags);
                hci_uart_tx_wakeup(hu);
        }

        h5->rx_ack = H5_HDR_ACK(hdr);

        h5_pkt_cull(h5);

        switch (H5_HDR_PKT_TYPE(hdr)) {
        case HCI_EVENT_PKT:
        case HCI_ACLDATA_PKT:
        case HCI_SCODATA_PKT:
        case HCI_ISODATA_PKT:
                hci_skb_pkt_type(h5->rx_skb) = H5_HDR_PKT_TYPE(hdr);

                /* Remove Three-wire header */
                skb_pull(h5->rx_skb, 4);

                hci_recv_frame(hu->hdev, h5->rx_skb);
                h5->rx_skb = NULL;

                break;

        default:
                h5_handle_internal_rx(hu);
                break;
        }

        h5_reset_rx(h5);
}

static int h5_rx_crc(struct hci_uart *hu, unsigned char c)
{
        struct h5 *h5 = hu->priv;
        const unsigned char *hdr = h5->rx_skb->data;
        u16 crc;
        __be16 crc_be;

        crc = crc_ccitt(0xffff, hdr, 4 + H5_HDR_LEN(hdr));
        crc = bitrev16(crc);

        crc_be = cpu_to_be16(crc);

        if (memcmp(&crc_be, hdr + 4 + H5_HDR_LEN(hdr), 2) != 0) {
                bt_dev_err(hu->hdev, "Received packet with invalid CRC");
                h5_reset_rx(h5);
        } else {
                /* Remove CRC bytes */
                skb_trim(h5->rx_skb, 4 + H5_HDR_LEN(hdr));
                h5_complete_rx_pkt(hu);
        }

        return 0;
}

static int h5_rx_payload(struct hci_uart *hu, unsigned char c)
{
        struct h5 *h5 = hu->priv;
        const unsigned char *hdr = h5->rx_skb->data;

        if (H5_HDR_CRC(hdr)) {
                h5->rx_func = h5_rx_crc;
                h5->rx_pending = 2;
        } else {
                h5_complete_rx_pkt(hu);
        }

        return 0;
}

static int h5_rx_3wire_hdr(struct hci_uart *hu, unsigned char c)
{
        struct h5 *h5 = hu->priv;
        const unsigned char *hdr = h5->rx_skb->data;

        BT_DBG("%s rx: seq %u ack %u crc %u rel %u type %u len %u",
               hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
               H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
               H5_HDR_LEN(hdr));

        if (((hdr[0] + hdr[1] + hdr[2] + hdr[3]) & 0xff) != 0xff) {
                bt_dev_err(hu->hdev, "Invalid header checksum");
                h5_reset_rx(h5);
                return 0;
        }

        if (H5_HDR_RELIABLE(hdr) && H5_HDR_SEQ(hdr) != h5->tx_ack) {
                bt_dev_err(hu->hdev, "Out-of-order packet arrived (%u != %u)",
                           H5_HDR_SEQ(hdr), h5->tx_ack);
                set_bit(H5_TX_ACK_REQ, &h5->flags);
                hci_uart_tx_wakeup(hu);
                h5_reset_rx(h5);
                return 0;
        }

        if (h5->state != H5_ACTIVE &&
            H5_HDR_PKT_TYPE(hdr) != HCI_3WIRE_LINK_PKT) {
                bt_dev_err(hu->hdev, "Non-link packet received in non-active state");
                h5_reset_rx(h5);
                return 0;
        }

        h5->rx_func = h5_rx_payload;
        h5->rx_pending = H5_HDR_LEN(hdr);

        return 0;
}

static int h5_rx_pkt_start(struct hci_uart *hu, unsigned char c)
{
        struct h5 *h5 = hu->priv;

        if (c == SLIP_DELIMITER)
                return 1;

        h5->rx_func = h5_rx_3wire_hdr;
        h5->rx_pending = 4;

        h5->rx_skb = bt_skb_alloc(H5_MAX_LEN, GFP_ATOMIC);
        if (!h5->rx_skb) {
                bt_dev_err(hu->hdev, "Can't allocate mem for new packet");
                h5_reset_rx(h5);
                return -ENOMEM;
        }

        h5->rx_skb->dev = (void *)hu->hdev;

        return 0;
}

static int h5_rx_delimiter(struct hci_uart *hu, unsigned char c)
{
        struct h5 *h5 = hu->priv;

        if (c == SLIP_DELIMITER)
                h5->rx_func = h5_rx_pkt_start;

        return 1;
}

static void h5_unslip_one_byte(struct h5 *h5, unsigned char c)
{
        const u8 delim = SLIP_DELIMITER, esc = SLIP_ESC;
        const u8 *byte = &c;

        if (!test_bit(H5_RX_ESC, &h5->flags) && c == SLIP_ESC) {
                set_bit(H5_RX_ESC, &h5->flags);
                return;
        }

        if (test_and_clear_bit(H5_RX_ESC, &h5->flags)) {
                switch (c) {
                case SLIP_ESC_DELIM:
                        byte = &delim;
                        break;
                case SLIP_ESC_ESC:
                        byte = &esc;
                        break;
                default:
                        BT_ERR("Invalid esc byte 0x%02hhx", c);
                        h5_reset_rx(h5);
                        return;
                }
        }

        skb_put_data(h5->rx_skb, byte, 1);
        h5->rx_pending--;

        BT_DBG("unslipped 0x%02hhx, rx_pending %zu", *byte, h5->rx_pending);
}

static void h5_reset_rx(struct h5 *h5)
{
        if (h5->rx_skb) {
                kfree_skb(h5->rx_skb);
                h5->rx_skb = NULL;
        }

        h5->rx_func = h5_rx_delimiter;
        h5->rx_pending = 0;
        clear_bit(H5_RX_ESC, &h5->flags);
        clear_bit(H5_CRC, &h5->flags);
}

static int h5_recv(struct hci_uart *hu, const void *data, int count)
{
        struct h5 *h5 = hu->priv;
        const unsigned char *ptr = data;

        BT_DBG("%s pending %zu count %d", hu->hdev->name, h5->rx_pending,
               count);

        while (count > 0) {
                int processed;

                if (h5->rx_pending > 0) {
                        if (*ptr == SLIP_DELIMITER) {
                                bt_dev_err(hu->hdev, "Too short H5 packet");
                                h5_reset_rx(h5);
                                continue;
                        }

                        h5_unslip_one_byte(h5, *ptr);

                        ptr++; count--;
                        continue;
                }

                processed = h5->rx_func(hu, *ptr);
                if (processed < 0)
                        return processed;

                ptr += processed;
                count -= processed;
        }

        if (hu->serdev) {
                pm_runtime_get(&hu->serdev->dev);
                pm_runtime_put_autosuspend(&hu->serdev->dev);
        }

        return 0;
}

static int h5_enqueue(struct hci_uart *hu, struct sk_buff *skb)
{
        struct h5 *h5 = hu->priv;

        if (skb->len > 0xfff) {
                bt_dev_err(hu->hdev, "Packet too long (%u bytes)", skb->len);
                kfree_skb(skb);
                return 0;
        }

        if (h5->state != H5_ACTIVE) {
                bt_dev_err(hu->hdev, "Ignoring HCI data in non-active state");
                kfree_skb(skb);
                return 0;
        }

        switch (hci_skb_pkt_type(skb)) {
        case HCI_ACLDATA_PKT:
        case HCI_COMMAND_PKT:
                skb_queue_tail(&h5->rel, skb);
                break;

        case HCI_SCODATA_PKT:
        case HCI_ISODATA_PKT:
                skb_queue_tail(&h5->unrel, skb);
                break;

        default:
                bt_dev_err(hu->hdev, "Unknown packet type %u", hci_skb_pkt_type(skb));
                kfree_skb(skb);
                break;
        }

        if (hu->serdev) {
                pm_runtime_get_sync(&hu->serdev->dev);
                pm_runtime_put_autosuspend(&hu->serdev->dev);
        }

        return 0;
}

static void h5_slip_delim(struct sk_buff *skb)
{
        const char delim = SLIP_DELIMITER;

        skb_put_data(skb, &delim, 1);
}

static void h5_slip_one_byte(struct sk_buff *skb, u8 c)
{
        const char esc_delim[2] = { SLIP_ESC, SLIP_ESC_DELIM };
        const char esc_esc[2] = { SLIP_ESC, SLIP_ESC_ESC };

        switch (c) {
        case SLIP_DELIMITER:
                skb_put_data(skb, &esc_delim, 2);
                break;
        case SLIP_ESC:
                skb_put_data(skb, &esc_esc, 2);
                break;
        default:
                skb_put_data(skb, &c, 1);
        }
}

static bool valid_packet_type(u8 type)
{
        switch (type) {
        case HCI_ACLDATA_PKT:
        case HCI_COMMAND_PKT:
        case HCI_SCODATA_PKT:
        case HCI_ISODATA_PKT:
        case HCI_3WIRE_LINK_PKT:
        case HCI_3WIRE_ACK_PKT:
                return true;
        default:
                return false;
        }
}

static struct sk_buff *h5_prepare_pkt(struct hci_uart *hu, u8 pkt_type,
                                      const u8 *data, size_t len)
{
        struct h5 *h5 = hu->priv;
        struct sk_buff *nskb;
        u8 hdr[4];
        u16 crc;
        int i;

        if (!valid_packet_type(pkt_type)) {
                bt_dev_err(hu->hdev, "Unknown packet type %u", pkt_type);
                return NULL;
        }

        /*
         * Max len of packet: (original len + 4 (H5 hdr) + 2 (crc)) * 2
         * (because bytes 0xc0 and 0xdb are escaped, worst case is when
         * the packet is all made of 0xc0 and 0xdb) + 2 (0xc0
         * delimiters at start and end).
         */
        nskb = alloc_skb((len + 6) * 2 + 2, GFP_ATOMIC);
        if (!nskb)
                return NULL;

        hci_skb_pkt_type(nskb) = pkt_type;

        h5_slip_delim(nskb);

        hdr[0] = h5->tx_ack << 3;
        clear_bit(H5_TX_ACK_REQ, &h5->flags);

        /* Reliable packet? */
        if (pkt_type == HCI_ACLDATA_PKT || pkt_type == HCI_COMMAND_PKT) {
                hdr[0] |= 1 << 7;
                hdr[0] |= (test_bit(H5_CRC, &h5->flags) && 1) << 6;
                hdr[0] |= h5->tx_seq;
                h5->tx_seq = (h5->tx_seq + 1) % 8;
        }

        hdr[1] = pkt_type | ((len & 0x0f) << 4);
        hdr[2] = len >> 4;
        hdr[3] = ~((hdr[0] + hdr[1] + hdr[2]) & 0xff);

        BT_DBG("%s tx: seq %u ack %u crc %u rel %u type %u len %u",
               hu->hdev->name, H5_HDR_SEQ(hdr), H5_HDR_ACK(hdr),
               H5_HDR_CRC(hdr), H5_HDR_RELIABLE(hdr), H5_HDR_PKT_TYPE(hdr),
               H5_HDR_LEN(hdr));

        for (i = 0; i < 4; i++)
                h5_slip_one_byte(nskb, hdr[i]);

        for (i = 0; i < len; i++)
                h5_slip_one_byte(nskb, data[i]);

        if (H5_HDR_CRC(hdr)) {
                crc = crc_ccitt(0xffff, hdr, 4);
                crc = crc_ccitt(crc, data, len);
                crc = bitrev16(crc);

                h5_slip_one_byte(nskb, (crc >> 8) & 0xff);
                h5_slip_one_byte(nskb, crc & 0xff);
        }

        h5_slip_delim(nskb);

        return nskb;
}

static struct sk_buff *h5_dequeue(struct hci_uart *hu)
{
        struct h5 *h5 = hu->priv;
        unsigned long flags;
        struct sk_buff *skb, *nskb;

        if (h5->sleep != H5_AWAKE) {
                const unsigned char wakeup_req[] = { 0x05, 0xfa };

                if (h5->sleep == H5_WAKING_UP)
                        return NULL;

                h5->sleep = H5_WAKING_UP;
                BT_DBG("Sending wakeup request");

                mod_timer(&h5->timer, jiffies + HZ / 100);
                return h5_prepare_pkt(hu, HCI_3WIRE_LINK_PKT, wakeup_req, 2);
        }

        skb = skb_dequeue(&h5->unrel);
        if (skb) {
                nskb = h5_prepare_pkt(hu, hci_skb_pkt_type(skb),
                                      skb->data, skb->len);
                if (nskb) {
                        kfree_skb(skb);
                        return nskb;
                }

                skb_queue_head(&h5->unrel, skb);
                bt_dev_err(hu->hdev, "Could not dequeue pkt because alloc_skb failed");
        }

        spin_lock_irqsave_nested(&h5->unack.lock, flags, SINGLE_DEPTH_NESTING);

        if (h5->unack.qlen >= h5->tx_win)
                goto unlock;

        skb = skb_dequeue(&h5->rel);
        if (skb) {
                nskb = h5_prepare_pkt(hu, hci_skb_pkt_type(skb),
                                      skb->data, skb->len);
                if (nskb) {
                        __skb_queue_tail(&h5->unack, skb);
                        mod_timer(&h5->timer, jiffies + H5_ACK_TIMEOUT);
                        spin_unlock_irqrestore(&h5->unack.lock, flags);
                        return nskb;
                }

                skb_queue_head(&h5->rel, skb);
                bt_dev_err(hu->hdev, "Could not dequeue pkt because alloc_skb failed");
        }

unlock:
        spin_unlock_irqrestore(&h5->unack.lock, flags);

        if (test_bit(H5_TX_ACK_REQ, &h5->flags))
                return h5_prepare_pkt(hu, HCI_3WIRE_ACK_PKT, NULL, 0);

        return NULL;
}

static int h5_flush(struct hci_uart *hu)
{
        BT_DBG("hu %p", hu);
        return 0;
}

static const struct hci_uart_proto h5p = {
        .id             = HCI_UART_3WIRE,
        .name           = "Three-wire (H5)",
        .open           = h5_open,
        .close          = h5_close,
        .setup          = h5_setup,
        .recv           = h5_recv,
        .enqueue        = h5_enqueue,
        .dequeue        = h5_dequeue,
        .flush          = h5_flush,
};

static int h5_serdev_probe(struct serdev_device *serdev)
{
        struct device *dev = &serdev->dev;
        struct h5 *h5;
        const struct h5_device_data *data;

        h5 = devm_kzalloc(dev, sizeof(*h5), GFP_KERNEL);
        if (!h5)
                return -ENOMEM;

        h5->hu = &h5->serdev_hu;
        h5->serdev_hu.serdev = serdev;
        serdev_device_set_drvdata(serdev, h5);

        if (has_acpi_companion(dev)) {
                const struct acpi_device_id *match;

                match = acpi_match_device(dev->driver->acpi_match_table, dev);
                if (!match)
                        return -ENODEV;

                data = (const struct h5_device_data *)match->driver_data;
                h5->vnd = data->vnd;
                h5->id  = (char *)match->id;

                if (h5->vnd->acpi_gpio_map)
                        devm_acpi_dev_add_driver_gpios(dev,
                                                       h5->vnd->acpi_gpio_map);
        } else {
                data = of_device_get_match_data(dev);
                if (!data)
                        return -ENODEV;

                h5->vnd = data->vnd;
        }

        if (data->driver_info & H5_INFO_WAKEUP_DISABLE)
                set_bit(H5_WAKEUP_DISABLE, &h5->flags);

        h5->enable_gpio = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_LOW);
        if (IS_ERR(h5->enable_gpio))
                return PTR_ERR(h5->enable_gpio);

        h5->device_wake_gpio = devm_gpiod_get_optional(dev, "device-wake",
                                                       GPIOD_OUT_LOW);
        if (IS_ERR(h5->device_wake_gpio))
                return PTR_ERR(h5->device_wake_gpio);

        return hci_uart_register_device_priv(&h5->serdev_hu, &h5p,
                                             h5->vnd->sizeof_priv);
}

static void h5_serdev_remove(struct serdev_device *serdev)
{
        struct h5 *h5 = serdev_device_get_drvdata(serdev);

        hci_uart_unregister_device(&h5->serdev_hu);
}

static int __maybe_unused h5_serdev_suspend(struct device *dev)
{
        struct h5 *h5 = dev_get_drvdata(dev);
        int ret = 0;

        if (h5->vnd && h5->vnd->suspend)
                ret = h5->vnd->suspend(h5);

        return ret;
}

static int __maybe_unused h5_serdev_resume(struct device *dev)
{
        struct h5 *h5 = dev_get_drvdata(dev);
        int ret = 0;

        if (h5->vnd && h5->vnd->resume)
                ret = h5->vnd->resume(h5);

        return ret;
}

#ifdef CONFIG_BT_HCIUART_RTL
static int h5_btrtl_setup(struct h5 *h5)
{
        struct btrtl_device_info *btrtl_dev;
        struct sk_buff *skb;
        __le32 baudrate_data;
        u32 device_baudrate;
        unsigned int controller_baudrate;
        bool flow_control;
        int err;

        btrtl_dev = btrtl_initialize(h5->hu->hdev, h5->id);
        if (IS_ERR(btrtl_dev))
                return PTR_ERR(btrtl_dev);

        err = btrtl_get_uart_settings(h5->hu->hdev, btrtl_dev,
                                      &controller_baudrate, &device_baudrate,
                                      &flow_control);
        if (err)
                goto out_free;

        baudrate_data = cpu_to_le32(device_baudrate);
        skb = __hci_cmd_sync(h5->hu->hdev, 0xfc17, sizeof(baudrate_data),
                             &baudrate_data, HCI_INIT_TIMEOUT);
        if (IS_ERR(skb)) {
                rtl_dev_err(h5->hu->hdev, "set baud rate command failed\n");
                err = PTR_ERR(skb);
                goto out_free;
        } else {
                kfree_skb(skb);
        }
        /* Give the device some time to set up the new baudrate. */
        usleep_range(10000, 20000);

        serdev_device_set_baudrate(h5->hu->serdev, controller_baudrate);
        serdev_device_set_flow_control(h5->hu->serdev, flow_control);

        if (flow_control)
                set_bit(H5_HW_FLOW_CONTROL, &h5->flags);

        err = btrtl_download_firmware(h5->hu->hdev, btrtl_dev);
        /* Give the device some time before the hci-core sends it a reset */
        usleep_range(10000, 20000);
        if (err)
                goto out_free;

        btrtl_set_quirks(h5->hu->hdev, btrtl_dev);

out_free:
        btrtl_free(btrtl_dev);

        return err;
}

static void h5_btrtl_open(struct h5 *h5)
{
        /*
         * Since h5_btrtl_resume() does a device_reprobe() the suspend handling
         * done by the hci_suspend_notifier is not necessary; it actually causes
         * delays and a bunch of errors to get logged, so disable it.
         */
        if (test_bit(H5_WAKEUP_DISABLE, &h5->flags))
                set_bit(HCI_UART_NO_SUSPEND_NOTIFIER, &h5->hu->flags);

        /* Devices always start with these fixed parameters */
        serdev_device_set_flow_control(h5->hu->serdev, false);
        serdev_device_set_parity(h5->hu->serdev, SERDEV_PARITY_EVEN);
        serdev_device_set_baudrate(h5->hu->serdev, 115200);

        if (!test_bit(H5_WAKEUP_DISABLE, &h5->flags)) {
                pm_runtime_set_active(&h5->hu->serdev->dev);
                pm_runtime_use_autosuspend(&h5->hu->serdev->dev);
                pm_runtime_set_autosuspend_delay(&h5->hu->serdev->dev,
                                                 SUSPEND_TIMEOUT_MS);
                pm_runtime_enable(&h5->hu->serdev->dev);
        }

        /* The controller needs reset to startup */
        gpiod_set_value_cansleep(h5->enable_gpio, 0);
        gpiod_set_value_cansleep(h5->device_wake_gpio, 0);
        msleep(100);

        /* The controller needs up to 500ms to wakeup */
        gpiod_set_value_cansleep(h5->enable_gpio, 1);
        gpiod_set_value_cansleep(h5->device_wake_gpio, 1);
        msleep(500);
}

static void h5_btrtl_close(struct h5 *h5)
{
        if (!test_bit(H5_WAKEUP_DISABLE, &h5->flags))
                pm_runtime_disable(&h5->hu->serdev->dev);

        gpiod_set_value_cansleep(h5->device_wake_gpio, 0);
        gpiod_set_value_cansleep(h5->enable_gpio, 0);
}

/* Suspend/resume support. On many devices the RTL BT device loses power during
 * suspend/resume, causing it to lose its firmware and all state. So we simply
 * turn it off on suspend and reprobe on resume. This mirrors how RTL devices
 * are handled in the USB driver, where the BTUSB_WAKEUP_DISABLE is used which
 * also causes a reprobe on resume.
 */
static int h5_btrtl_suspend(struct h5 *h5)
{
        serdev_device_set_flow_control(h5->hu->serdev, false);
        gpiod_set_value_cansleep(h5->device_wake_gpio, 0);

        if (test_bit(H5_WAKEUP_DISABLE, &h5->flags))
                gpiod_set_value_cansleep(h5->enable_gpio, 0);

        return 0;
}

struct h5_btrtl_reprobe {
        struct device *dev;
        struct work_struct work;
};

static void h5_btrtl_reprobe_worker(struct work_struct *work)
{
        struct h5_btrtl_reprobe *reprobe =
                container_of(work, struct h5_btrtl_reprobe, work);
        int ret;

        ret = device_reprobe(reprobe->dev);
        if (ret && ret != -EPROBE_DEFER)
                dev_err(reprobe->dev, "Reprobe error %d\n", ret);

        put_device(reprobe->dev);
        kfree(reprobe);
        module_put(THIS_MODULE);
}

static int h5_btrtl_resume(struct h5 *h5)
{
        if (test_bit(H5_WAKEUP_DISABLE, &h5->flags)) {
                struct h5_btrtl_reprobe *reprobe;

                reprobe = kzalloc_obj(*reprobe);
                if (!reprobe)
                        return -ENOMEM;

                __module_get(THIS_MODULE);

                INIT_WORK(&reprobe->work, h5_btrtl_reprobe_worker);
                reprobe->dev = get_device(&h5->hu->serdev->dev);
                queue_work(system_long_wq, &reprobe->work);
        } else {
                gpiod_set_value_cansleep(h5->device_wake_gpio, 1);

                if (test_bit(H5_HW_FLOW_CONTROL, &h5->flags))
                        serdev_device_set_flow_control(h5->hu->serdev, true);
        }

        return 0;
}

static const struct acpi_gpio_params btrtl_device_wake_gpios = { 0, 0, false };
static const struct acpi_gpio_params btrtl_enable_gpios = { 1, 0, false };
static const struct acpi_gpio_params btrtl_host_wake_gpios = { 2, 0, false };
static const struct acpi_gpio_mapping acpi_btrtl_gpios[] = {
        { "device-wake-gpios", &btrtl_device_wake_gpios, 1 },
        { "enable-gpios", &btrtl_enable_gpios, 1 },
        { "host-wake-gpios", &btrtl_host_wake_gpios, 1 },
        {},
};

static struct h5_vnd rtl_vnd = {
        .setup          = h5_btrtl_setup,
        .open           = h5_btrtl_open,
        .close          = h5_btrtl_close,
        .suspend        = h5_btrtl_suspend,
        .resume         = h5_btrtl_resume,
        .acpi_gpio_map  = acpi_btrtl_gpios,
        .sizeof_priv    = sizeof(struct btrealtek_data),
};

static const struct h5_device_data h5_data_rtl8822cs = {
        .vnd = &rtl_vnd,
};

static const struct h5_device_data h5_data_rtl8723bs = {
        .driver_info = H5_INFO_WAKEUP_DISABLE,
        .vnd = &rtl_vnd,
};
#endif

#ifdef CONFIG_ACPI
static const struct acpi_device_id h5_acpi_match[] = {
#ifdef CONFIG_BT_HCIUART_RTL
        { "OBDA0623", (kernel_ulong_t)&h5_data_rtl8723bs },
        { "OBDA8723", (kernel_ulong_t)&h5_data_rtl8723bs },
#endif
        { },
};
MODULE_DEVICE_TABLE(acpi, h5_acpi_match);
#endif

static const struct dev_pm_ops h5_serdev_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(h5_serdev_suspend, h5_serdev_resume)
        SET_RUNTIME_PM_OPS(h5_serdev_suspend, h5_serdev_resume, NULL)
};

static const struct of_device_id rtl_bluetooth_of_match[] = {
#ifdef CONFIG_BT_HCIUART_RTL
        { .compatible = "realtek,rtl8822cs-bt",
          .data = (const void *)&h5_data_rtl8822cs },
        { .compatible = "realtek,rtl8723bs-bt",
          .data = (const void *)&h5_data_rtl8723bs },
        { .compatible = "realtek,rtl8723cs-bt",
          .data = (const void *)&h5_data_rtl8723bs },
        { .compatible = "realtek,rtl8723ds-bt",
          .data = (const void *)&h5_data_rtl8723bs },
#endif
        { },
};
MODULE_DEVICE_TABLE(of, rtl_bluetooth_of_match);

static struct serdev_device_driver h5_serdev_driver = {
        .probe = h5_serdev_probe,
        .remove = h5_serdev_remove,
        .driver = {
                .name = "hci_uart_h5",
                .acpi_match_table = ACPI_PTR(h5_acpi_match),
                .pm = &h5_serdev_pm_ops,
                .of_match_table = rtl_bluetooth_of_match,
        },
};

int __init h5_init(void)
{
        serdev_device_driver_register(&h5_serdev_driver);
        return hci_uart_register_proto(&h5p);
}

int __exit h5_deinit(void)
{
        serdev_device_driver_unregister(&h5_serdev_driver);
        return hci_uart_unregister_proto(&h5p);
}