// SPDX-License-Identifier: GPL-2.0+
/*
 *          mxser.c  -- MOXA Smartio/Industio family multiport serial driver.
 *
 *      Copyright (C) 1999-2006  Moxa Technologies (support@moxa.com).
 *      Copyright (C) 2006-2008  Jiri Slaby <jirislaby@gmail.com>
 *
 *      This code is loosely based on the 1.8 moxa driver which is based on
 *      Linux serial driver, written by Linus Torvalds, Theodore T'so and
 *      others.
 *
 *      Fed through a cleanup, indent and remove of non 2.6 code by Alan Cox
 *      <alan@lxorguk.ukuu.org.uk>. The original 1.8 code is available on
 *      www.moxa.com.
 *      - Fixed x86_64 cleanness
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial.h>
#include <linux/serial_reg.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>

#include <asm/io.h>
#include <asm/irq.h>
#include <linux/uaccess.h>

/*
 *      Semi-public control interfaces
 */

/*
 *      MOXA ioctls
 */

#define MOXA                    0x400
#define MOXA_SET_OP_MODE        (MOXA + 66)
#define MOXA_GET_OP_MODE        (MOXA + 67)

#define RS232_MODE              0
#define RS485_2WIRE_MODE        1
#define RS422_MODE              2
#define RS485_4WIRE_MODE        3
#define OP_MODE_MASK            3

/* --------------------------------------------------- */

/*
 * Follow just what Moxa Must chip defines.
 *
 * When LCR register (offset 0x03) is written the following value, the Must chip
 * will enter enhanced mode. And a write to EFR (offset 0x02) bit 6,7 will
 * change bank.
 */
#define MOXA_MUST_ENTER_ENHANCED        0xBF

/* when enhanced mode is enabled, access to general bank register */
#define MOXA_MUST_GDL_REGISTER          0x07
#define MOXA_MUST_GDL_MASK              0x7F
#define MOXA_MUST_GDL_HAS_BAD_DATA      0x80

#define MOXA_MUST_LSR_RERR              0x80    /* error in receive FIFO */
/* enhanced register bank select and enhanced mode setting register */
/* This works only when LCR register equals to 0xBF */
#define MOXA_MUST_EFR_REGISTER          0x02
#define MOXA_MUST_EFR_EFRB_ENABLE       0x10 /* enhanced mode enable */
/* enhanced register bank set 0, 1, 2 */
#define MOXA_MUST_EFR_BANK0             0x00
#define MOXA_MUST_EFR_BANK1             0x40
#define MOXA_MUST_EFR_BANK2             0x80
#define MOXA_MUST_EFR_BANK3             0xC0
#define MOXA_MUST_EFR_BANK_MASK         0xC0

/* set XON1 value register, when LCR=0xBF and change to bank0 */
#define MOXA_MUST_XON1_REGISTER         0x04

/* set XON2 value register, when LCR=0xBF and change to bank0 */
#define MOXA_MUST_XON2_REGISTER         0x05

/* set XOFF1 value register, when LCR=0xBF and change to bank0 */
#define MOXA_MUST_XOFF1_REGISTER        0x06

/* set XOFF2 value register, when LCR=0xBF and change to bank0 */
#define MOXA_MUST_XOFF2_REGISTER        0x07

#define MOXA_MUST_RBRTL_REGISTER        0x04
#define MOXA_MUST_RBRTH_REGISTER        0x05
#define MOXA_MUST_RBRTI_REGISTER        0x06
#define MOXA_MUST_THRTL_REGISTER        0x07
#define MOXA_MUST_ENUM_REGISTER         0x04
#define MOXA_MUST_HWID_REGISTER         0x05
#define MOXA_MUST_ECR_REGISTER          0x06
#define MOXA_MUST_CSR_REGISTER          0x07

#define MOXA_MUST_FCR_GDA_MODE_ENABLE   0x20 /* good data mode enable */
#define MOXA_MUST_FCR_GDA_ONLY_ENABLE   0x10 /* only good data put into RxFIFO */

#define MOXA_MUST_IER_ECTSI             0x80 /* enable CTS interrupt */
#define MOXA_MUST_IER_ERTSI             0x40 /* enable RTS interrupt */
#define MOXA_MUST_IER_XINT              0x20 /* enable Xon/Xoff interrupt */
#define MOXA_MUST_IER_EGDAI             0x10 /* enable GDA interrupt */

#define MOXA_MUST_RECV_ISR              (UART_IER_RDI | MOXA_MUST_IER_EGDAI)

/* GDA interrupt pending */
#define MOXA_MUST_IIR_GDA               0x1C
#define MOXA_MUST_IIR_RDA               0x04
#define MOXA_MUST_IIR_RTO               0x0C
#define MOXA_MUST_IIR_LSR               0x06

/* received Xon/Xoff or specical interrupt pending */
#define MOXA_MUST_IIR_XSC               0x10

/* RTS/CTS change state interrupt pending */
#define MOXA_MUST_IIR_RTSCTS            0x20
#define MOXA_MUST_IIR_MASK              0x3E

#define MOXA_MUST_MCR_XON_FLAG          0x40
#define MOXA_MUST_MCR_XON_ANY           0x80
#define MOXA_MUST_MCR_TX_XON            0x08

#define MOXA_MUST_EFR_SF_MASK           0x0F /* software flow control on chip mask value */
#define MOXA_MUST_EFR_SF_TX1            0x08 /* send Xon1/Xoff1 */
#define MOXA_MUST_EFR_SF_TX2            0x04 /* send Xon2/Xoff2 */
#define MOXA_MUST_EFR_SF_TX12           0x0C /* send Xon1,Xon2/Xoff1,Xoff2 */
#define MOXA_MUST_EFR_SF_TX_NO          0x00 /* don't send Xon/Xoff */
#define MOXA_MUST_EFR_SF_TX_MASK        0x0C /* Tx software flow control mask */
#define MOXA_MUST_EFR_SF_RX_NO          0x00 /* don't receive Xon/Xoff */
#define MOXA_MUST_EFR_SF_RX1            0x02 /* receive Xon1/Xoff1 */
#define MOXA_MUST_EFR_SF_RX2            0x01 /* receive Xon2/Xoff2 */
#define MOXA_MUST_EFR_SF_RX12           0x03 /* receive Xon1,Xon2/Xoff1,Xoff2 */
#define MOXA_MUST_EFR_SF_RX_MASK        0x03 /* Rx software flow control mask */

#define MXSERMAJOR       174

#define MXSER_BOARDS            4       /* Max. boards */
#define MXSER_PORTS_PER_BOARD   8       /* Max. ports per board */
#define MXSER_PORTS             (MXSER_BOARDS * MXSER_PORTS_PER_BOARD)
#define MXSER_ISR_PASS_LIMIT    100

#define WAKEUP_CHARS            256

#define MXSER_BAUD_BASE         921600
#define MXSER_CUSTOM_DIVISOR    (MXSER_BAUD_BASE * 16)

#define PCI_DEVICE_ID_MOXA_RC7000       0x0001
#define PCI_DEVICE_ID_MOXA_CP102        0x1020
#define PCI_DEVICE_ID_MOXA_CP102UL      0x1021
#define PCI_DEVICE_ID_MOXA_CP102U       0x1022
#define PCI_DEVICE_ID_MOXA_CP102UF      0x1023
#define PCI_DEVICE_ID_MOXA_C104         0x1040
#define PCI_DEVICE_ID_MOXA_CP104U       0x1041
#define PCI_DEVICE_ID_MOXA_CP104JU      0x1042
#define PCI_DEVICE_ID_MOXA_CP104EL      0x1043
#define PCI_DEVICE_ID_MOXA_POS104UL     0x1044
#define PCI_DEVICE_ID_MOXA_CB108        0x1080
#define PCI_DEVICE_ID_MOXA_CP112UL      0x1120
#define PCI_DEVICE_ID_MOXA_CT114        0x1140
#define PCI_DEVICE_ID_MOXA_CP114        0x1141
#define PCI_DEVICE_ID_MOXA_CB114        0x1142
#define PCI_DEVICE_ID_MOXA_CP114UL      0x1143
#define PCI_DEVICE_ID_MOXA_CP118U       0x1180
#define PCI_DEVICE_ID_MOXA_CP118EL      0x1181
#define PCI_DEVICE_ID_MOXA_CP132        0x1320
#define PCI_DEVICE_ID_MOXA_CP132U       0x1321
#define PCI_DEVICE_ID_MOXA_CP134U       0x1340
#define PCI_DEVICE_ID_MOXA_CB134I       0x1341
#define PCI_DEVICE_ID_MOXA_CP138U       0x1380
#define PCI_DEVICE_ID_MOXA_C168         0x1680
#define PCI_DEVICE_ID_MOXA_CP168U       0x1681
#define PCI_DEVICE_ID_MOXA_CP168EL      0x1682

#define MXSER_NPORTS(ddata)             ((ddata) & 0xffU)
#define MXSER_HIGHBAUD                  0x0100

enum mxser_must_hwid {
        MOXA_OTHER_UART         = 0x00,
        MOXA_MUST_MU150_HWID    = 0x01,
        MOXA_MUST_MU860_HWID    = 0x02,
};

static const struct {
        u8 type;
        u8 fifo_size;
        u8 rx_high_water;
        u8 rx_low_water;
        speed_t max_baud;
} Gpci_uart_info[] = {
        { MOXA_OTHER_UART,       16, 14,  1, 921600 },
        { MOXA_MUST_MU150_HWID,  64, 48, 16, 230400 },
        { MOXA_MUST_MU860_HWID, 128, 96, 32, 921600 }
};
#define UART_INFO_NUM   ARRAY_SIZE(Gpci_uart_info)

static const struct pci_device_id mxser_pcibrds[] = {
        { PCI_DEVICE_DATA(MOXA, C168,           8) },
        { PCI_DEVICE_DATA(MOXA, C104,           4) },
        { PCI_DEVICE_DATA(MOXA, CP132,          2) },
        { PCI_DEVICE_DATA(MOXA, CP114,          4) },
        { PCI_DEVICE_DATA(MOXA, CT114,          4) },
        { PCI_DEVICE_DATA(MOXA, CP102,          2 | MXSER_HIGHBAUD) },
        { PCI_DEVICE_DATA(MOXA, CP104U,         4) },
        { PCI_DEVICE_DATA(MOXA, CP168U,         8) },
        { PCI_DEVICE_DATA(MOXA, CP132U,         2) },
        { PCI_DEVICE_DATA(MOXA, CP134U,         4) },
        { PCI_DEVICE_DATA(MOXA, CP104JU,        4) },
        { PCI_DEVICE_DATA(MOXA, RC7000,         8) }, /* RC7000 */
        { PCI_DEVICE_DATA(MOXA, CP118U,         8) },
        { PCI_DEVICE_DATA(MOXA, CP102UL,        2) },
        { PCI_DEVICE_DATA(MOXA, CP102U,         2) },
        { PCI_DEVICE_DATA(MOXA, CP118EL,        8) },
        { PCI_DEVICE_DATA(MOXA, CP168EL,        8) },
        { PCI_DEVICE_DATA(MOXA, CP104EL,        4) },
        { PCI_DEVICE_DATA(MOXA, CB108,          8) },
        { PCI_DEVICE_DATA(MOXA, CB114,          4) },
        { PCI_DEVICE_DATA(MOXA, CB134I,         4) },
        { PCI_DEVICE_DATA(MOXA, CP138U,         8) },
        { PCI_DEVICE_DATA(MOXA, POS104UL,       4) },
        { PCI_DEVICE_DATA(MOXA, CP114UL,        4) },
        { PCI_DEVICE_DATA(MOXA, CP102UF,        2) },
        { PCI_DEVICE_DATA(MOXA, CP112UL,        2) },
        { }
};
MODULE_DEVICE_TABLE(pci, mxser_pcibrds);

static int ttymajor = MXSERMAJOR;

/* Variables for insmod */

MODULE_AUTHOR("Casper Yang");
MODULE_DESCRIPTION("MOXA Smartio/Industio Family Multiport Board Device Driver");
module_param(ttymajor, int, 0);
MODULE_LICENSE("GPL");

struct mxser_board;

struct mxser_port {
        struct tty_port port;
        struct mxser_board *board;

        unsigned long ioaddr;
        unsigned long opmode_ioaddr;

        u8 rx_high_water;
        u8 rx_low_water;
        int type;               /* UART type */

        u8 x_char;              /* xon/xoff character */
        u8 IER;                 /* Interrupt Enable Register */
        u8 MCR;                 /* Modem control register */
        u8 FCR;                 /* FIFO control register */

        struct async_icount icount; /* kernel counters for 4 input interrupts */
        unsigned int timeout;

        u8 read_status_mask;
        u8 ignore_status_mask;
        u8 xmit_fifo_size;

        spinlock_t slock;
};

struct mxser_board {
        unsigned int idx;
        unsigned short nports;
        int irq;
        unsigned long vector;

        enum mxser_must_hwid must_hwid;
        speed_t max_baud;

        struct mxser_port ports[] /* __counted_by(nports) */;
};

static DECLARE_BITMAP(mxser_boards, MXSER_BOARDS);
static struct tty_driver *mxvar_sdriver;

static u8 __mxser_must_set_EFR(unsigned long baseio, u8 clear, u8 set,
                bool restore_LCR)
{
        u8 oldlcr, efr;

        oldlcr = inb(baseio + UART_LCR);
        outb(MOXA_MUST_ENTER_ENHANCED, baseio + UART_LCR);

        efr = inb(baseio + MOXA_MUST_EFR_REGISTER);
        efr &= ~clear;
        efr |= set;

        outb(efr, baseio + MOXA_MUST_EFR_REGISTER);

        if (restore_LCR)
                outb(oldlcr, baseio + UART_LCR);

        return oldlcr;
}

static u8 mxser_must_select_bank(unsigned long baseio, u8 bank)
{
        return __mxser_must_set_EFR(baseio, MOXA_MUST_EFR_BANK_MASK, bank,
                        false);
}

static void mxser_set_must_xon1_value(unsigned long baseio, u8 value)
{
        u8 oldlcr = mxser_must_select_bank(baseio, MOXA_MUST_EFR_BANK0);
        outb(value, baseio + MOXA_MUST_XON1_REGISTER);
        outb(oldlcr, baseio + UART_LCR);
}

static void mxser_set_must_xoff1_value(unsigned long baseio, u8 value)
{
        u8 oldlcr = mxser_must_select_bank(baseio, MOXA_MUST_EFR_BANK0);
        outb(value, baseio + MOXA_MUST_XOFF1_REGISTER);
        outb(oldlcr, baseio + UART_LCR);
}

static void mxser_set_must_fifo_value(struct mxser_port *info)
{
        u8 oldlcr = mxser_must_select_bank(info->ioaddr, MOXA_MUST_EFR_BANK1);
        outb(info->rx_high_water, info->ioaddr + MOXA_MUST_RBRTH_REGISTER);
        outb(info->rx_high_water, info->ioaddr + MOXA_MUST_RBRTI_REGISTER);
        outb(info->rx_low_water, info->ioaddr + MOXA_MUST_RBRTL_REGISTER);
        outb(oldlcr, info->ioaddr + UART_LCR);
}

static void mxser_set_must_enum_value(unsigned long baseio, u8 value)
{
        u8 oldlcr = mxser_must_select_bank(baseio, MOXA_MUST_EFR_BANK2);
        outb(value, baseio + MOXA_MUST_ENUM_REGISTER);
        outb(oldlcr, baseio + UART_LCR);
}

static u8 mxser_get_must_hardware_id(unsigned long baseio)
{
        u8 oldlcr = mxser_must_select_bank(baseio, MOXA_MUST_EFR_BANK2);
        u8 id = inb(baseio + MOXA_MUST_HWID_REGISTER);
        outb(oldlcr, baseio + UART_LCR);

        return id;
}

static void mxser_must_set_EFR(unsigned long baseio, u8 clear, u8 set)
{
        __mxser_must_set_EFR(baseio, clear, set, true);
}

static void mxser_must_set_enhance_mode(unsigned long baseio, bool enable)
{
        mxser_must_set_EFR(baseio,
                        enable ? 0 : MOXA_MUST_EFR_EFRB_ENABLE,
                        enable ? MOXA_MUST_EFR_EFRB_ENABLE : 0);
}

static void mxser_must_no_sw_flow_control(unsigned long baseio)
{
        mxser_must_set_EFR(baseio, MOXA_MUST_EFR_SF_MASK, 0);
}

static void mxser_must_set_tx_sw_flow_control(unsigned long baseio, bool enable)
{
        mxser_must_set_EFR(baseio, MOXA_MUST_EFR_SF_TX_MASK,
                        enable ? MOXA_MUST_EFR_SF_TX1 : 0);
}

static void mxser_must_set_rx_sw_flow_control(unsigned long baseio, bool enable)
{
        mxser_must_set_EFR(baseio, MOXA_MUST_EFR_SF_RX_MASK,
                        enable ? MOXA_MUST_EFR_SF_RX1 : 0);
}

static enum mxser_must_hwid mxser_must_get_hwid(unsigned long io)
{
        u8 oldmcr, hwid;
        int i;

        outb(0, io + UART_LCR);
        mxser_must_set_enhance_mode(io, false);
        oldmcr = inb(io + UART_MCR);
        outb(0, io + UART_MCR);
        mxser_set_must_xon1_value(io, 0x11);
        if (inb(io + UART_MCR) != 0) {
                outb(oldmcr, io + UART_MCR);
                return MOXA_OTHER_UART;
        }

        hwid = mxser_get_must_hardware_id(io);
        for (i = 1; i < UART_INFO_NUM; i++) /* 0 = OTHER_UART */
                if (hwid == Gpci_uart_info[i].type)
                        return hwid;

        return MOXA_OTHER_UART;
}

static bool mxser_16550A_or_MUST(struct mxser_port *info)
{
        return info->type == PORT_16550A || info->board->must_hwid;
}

static void mxser_process_txrx_fifo(struct mxser_port *info)
{
        unsigned int i;

        if (info->type == PORT_16450 || info->type == PORT_8250) {
                info->rx_high_water = 1;
                info->rx_low_water = 1;
                info->xmit_fifo_size = 1;
                return;
        }

        for (i = 0; i < UART_INFO_NUM; i++)
                if (info->board->must_hwid == Gpci_uart_info[i].type) {
                        info->rx_low_water = Gpci_uart_info[i].rx_low_water;
                        info->rx_high_water = Gpci_uart_info[i].rx_high_water;
                        info->xmit_fifo_size = Gpci_uart_info[i].fifo_size;
                        break;
                }
}

static void __mxser_start_tx(struct mxser_port *info)
{
        outb(info->IER & ~UART_IER_THRI, info->ioaddr + UART_IER);
        info->IER |= UART_IER_THRI;
        outb(info->IER, info->ioaddr + UART_IER);
}

static void mxser_start_tx(struct mxser_port *info)
{
        guard(spinlock_irqsave)(&info->slock);
        __mxser_start_tx(info);
}

static void __mxser_stop_tx(struct mxser_port *info)
{
        info->IER &= ~UART_IER_THRI;
        outb(info->IER, info->ioaddr + UART_IER);
}

static bool mxser_carrier_raised(struct tty_port *port)
{
        struct mxser_port *mp = container_of(port, struct mxser_port, port);

        return inb(mp->ioaddr + UART_MSR) & UART_MSR_DCD;
}

static void mxser_dtr_rts(struct tty_port *port, bool active)
{
        struct mxser_port *mp = container_of(port, struct mxser_port, port);
        u8 mcr;

        guard(spinlock_irqsave)(&mp->slock);
        mcr = inb(mp->ioaddr + UART_MCR);
        if (active)
                mcr |= UART_MCR_DTR | UART_MCR_RTS;
        else
                mcr &= ~(UART_MCR_DTR | UART_MCR_RTS);
        outb(mcr, mp->ioaddr + UART_MCR);
}

static int mxser_set_baud(struct tty_struct *tty, speed_t newspd)
{
        struct mxser_port *info = tty->driver_data;
        unsigned int quot = 0, baud;
        unsigned char cval;
        u64 timeout;

        if (newspd > info->board->max_baud)
                return -1;

        if (newspd == 134) {
                quot = 2 * MXSER_BAUD_BASE / 269;
                tty_encode_baud_rate(tty, 134, 134);
        } else if (newspd) {
                quot = MXSER_BAUD_BASE / newspd;
                if (quot == 0)
                        quot = 1;
                baud = MXSER_BAUD_BASE / quot;
                tty_encode_baud_rate(tty, baud, baud);
        } else {
                quot = 0;
        }

        /*
         * worst case (128 * 1000 * 10 * 18432) needs 35 bits, so divide in the
         * u64 domain
         */
        timeout = (u64)info->xmit_fifo_size * HZ * 10 * quot;
        do_div(timeout, MXSER_BAUD_BASE);
        info->timeout = timeout + HZ / 50; /* Add .02 seconds of slop */

        if (quot) {
                info->MCR |= UART_MCR_DTR;
                outb(info->MCR, info->ioaddr + UART_MCR);
        } else {
                info->MCR &= ~UART_MCR_DTR;
                outb(info->MCR, info->ioaddr + UART_MCR);
                return 0;
        }

        cval = inb(info->ioaddr + UART_LCR);

        outb(cval | UART_LCR_DLAB, info->ioaddr + UART_LCR);    /* set DLAB */

        outb(quot & 0xff, info->ioaddr + UART_DLL);     /* LS of divisor */
        outb(quot >> 8, info->ioaddr + UART_DLM);       /* MS of divisor */
        outb(cval, info->ioaddr + UART_LCR);    /* reset DLAB */

        if (C_BAUD(tty) == BOTHER) {
                quot = MXSER_BAUD_BASE % newspd;
                quot *= 8;
                if (quot % newspd > newspd / 2) {
                        quot /= newspd;
                        quot++;
                } else
                        quot /= newspd;

                mxser_set_must_enum_value(info->ioaddr, quot);
        } else {
                mxser_set_must_enum_value(info->ioaddr, 0);
        }

        return 0;
}

static void mxser_handle_cts(struct tty_struct *tty, struct mxser_port *info,
                u8 msr)
{
        bool cts = msr & UART_MSR_CTS;

        if (tty->hw_stopped) {
                if (cts) {
                        tty->hw_stopped = false;

                        if (!mxser_16550A_or_MUST(info))
                                __mxser_start_tx(info);
                        tty_wakeup(tty);
                }
                return;
        } else if (cts)
                return;

        tty->hw_stopped = true;
        if (!mxser_16550A_or_MUST(info))
                __mxser_stop_tx(info);
}

/*
 * This routine is called to set the UART divisor registers to match
 * the specified baud rate for a serial port.
 */
static void mxser_change_speed(struct tty_struct *tty,
                               const struct ktermios *old_termios)
{
        struct mxser_port *info = tty->driver_data;
        unsigned cflag, cval;

        cflag = tty->termios.c_cflag;

        if (mxser_set_baud(tty, tty_get_baud_rate(tty))) {
                /* Use previous rate on a failure */
                if (old_termios) {
                        speed_t baud = tty_termios_baud_rate(old_termios);
                        tty_encode_baud_rate(tty, baud, baud);
                }
        }

        /* byte size and parity */
        cval = UART_LCR_WLEN(tty_get_char_size(tty->termios.c_cflag));

        if (cflag & CSTOPB)
                cval |= UART_LCR_STOP;
        if (cflag & PARENB)
                cval |= UART_LCR_PARITY;
        if (!(cflag & PARODD))
                cval |= UART_LCR_EPAR;
        if (cflag & CMSPAR)
                cval |= UART_LCR_SPAR;

        info->FCR = 0;
        if (info->board->must_hwid) {
                info->FCR |= UART_FCR_ENABLE_FIFO |
                        MOXA_MUST_FCR_GDA_MODE_ENABLE;
                mxser_set_must_fifo_value(info);
        } else if (info->type != PORT_8250 && info->type != PORT_16450) {
                info->FCR |= UART_FCR_ENABLE_FIFO;
                switch (info->rx_high_water) {
                case 1:
                        info->FCR |= UART_FCR_TRIGGER_1;
                        break;
                case 4:
                        info->FCR |= UART_FCR_TRIGGER_4;
                        break;
                case 8:
                        info->FCR |= UART_FCR_TRIGGER_8;
                        break;
                default:
                        info->FCR |= UART_FCR_TRIGGER_14;
                        break;
                }
        }

        /* CTS flow control flag and modem status interrupts */
        info->IER &= ~UART_IER_MSI;
        info->MCR &= ~UART_MCR_AFE;
        tty_port_set_cts_flow(&info->port, cflag & CRTSCTS);
        if (cflag & CRTSCTS) {
                info->IER |= UART_IER_MSI;
                if (mxser_16550A_or_MUST(info)) {
                        info->MCR |= UART_MCR_AFE;
                } else {
                        mxser_handle_cts(tty, info,
                                        inb(info->ioaddr + UART_MSR));
                }
        }
        outb(info->MCR, info->ioaddr + UART_MCR);
        tty_port_set_check_carrier(&info->port, ~cflag & CLOCAL);
        if (~cflag & CLOCAL)
                info->IER |= UART_IER_MSI;
        outb(info->IER, info->ioaddr + UART_IER);

        /*
         * Set up parity check flag
         */
        info->read_status_mask = UART_LSR_OE | UART_LSR_THRE | UART_LSR_DR;
        if (I_INPCK(tty))
                info->read_status_mask |= UART_LSR_FE | UART_LSR_PE;
        if (I_BRKINT(tty) || I_PARMRK(tty))
                info->read_status_mask |= UART_LSR_BI;

        info->ignore_status_mask = 0;

        if (I_IGNBRK(tty)) {
                info->ignore_status_mask |= UART_LSR_BI;
                info->read_status_mask |= UART_LSR_BI;
                /*
                 * If we're ignore parity and break indicators, ignore
                 * overruns too.  (For real raw support).
                 */
                if (I_IGNPAR(tty)) {
                        info->ignore_status_mask |=
                                                UART_LSR_OE |
                                                UART_LSR_PE |
                                                UART_LSR_FE;
                        info->read_status_mask |=
                                                UART_LSR_OE |
                                                UART_LSR_PE |
                                                UART_LSR_FE;
                }
        }
        if (info->board->must_hwid) {
                mxser_set_must_xon1_value(info->ioaddr, START_CHAR(tty));
                mxser_set_must_xoff1_value(info->ioaddr, STOP_CHAR(tty));
                mxser_must_set_rx_sw_flow_control(info->ioaddr, I_IXON(tty));
                mxser_must_set_tx_sw_flow_control(info->ioaddr, I_IXOFF(tty));
        }


        outb(info->FCR, info->ioaddr + UART_FCR);
        outb(cval, info->ioaddr + UART_LCR);
}

static u8 mxser_check_modem_status(struct tty_struct *tty,
                                struct mxser_port *port)
{
        u8 msr = inb(port->ioaddr + UART_MSR);

        if (!(msr & UART_MSR_ANY_DELTA))
                return msr;

        /* update input line counters */
        if (msr & UART_MSR_TERI)
                port->icount.rng++;
        if (msr & UART_MSR_DDSR)
                port->icount.dsr++;
        if (msr & UART_MSR_DDCD)
                port->icount.dcd++;
        if (msr & UART_MSR_DCTS)
                port->icount.cts++;
        wake_up_interruptible(&port->port.delta_msr_wait);

        if (tty_port_check_carrier(&port->port) && (msr & UART_MSR_DDCD)) {
                if (msr & UART_MSR_DCD)
                        wake_up_interruptible(&port->port.open_wait);
        }

        if (tty_port_cts_enabled(&port->port))
                mxser_handle_cts(tty, port, msr);

        return msr;
}

static void mxser_disable_and_clear_FIFO(struct mxser_port *info)
{
        u8 fcr = UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT;

        if (info->board->must_hwid)
                fcr |= MOXA_MUST_FCR_GDA_MODE_ENABLE;

        outb(fcr, info->ioaddr + UART_FCR);
}

static int mxser_activate(struct tty_port *port, struct tty_struct *tty)
{
        struct mxser_port *info = container_of(port, struct mxser_port, port);
        unsigned long flags;
        int ret;

        ret = tty_port_alloc_xmit_buf(port);
        if (ret < 0)
                return ret;

        spin_lock_irqsave(&info->slock, flags);

        if (!info->type) {
                set_bit(TTY_IO_ERROR, &tty->flags);
                spin_unlock_irqrestore(&info->slock, flags);
                ret = 0;
                goto err_free_xmit;
        }

        /*
         * Clear the FIFO buffers and disable them
         * (they will be reenabled in mxser_change_speed())
         */
        mxser_disable_and_clear_FIFO(info);

        /*
         * At this point there's no way the LSR could still be 0xFF;
         * if it is, then bail out, because there's likely no UART
         * here.
         */
        if (inb(info->ioaddr + UART_LSR) == 0xff) {
                spin_unlock_irqrestore(&info->slock, flags);
                if (capable(CAP_SYS_ADMIN)) {
                        set_bit(TTY_IO_ERROR, &tty->flags);
                        return 0;
                }

                ret = -ENODEV;
                goto err_free_xmit;
        }

        /*
         * Clear the interrupt registers.
         */
        (void) inb(info->ioaddr + UART_LSR);
        (void) inb(info->ioaddr + UART_RX);
        (void) inb(info->ioaddr + UART_IIR);
        (void) inb(info->ioaddr + UART_MSR);

        /*
         * Now, initialize the UART
         */
        outb(UART_LCR_WLEN8, info->ioaddr + UART_LCR);  /* reset DLAB */
        info->MCR = UART_MCR_DTR | UART_MCR_RTS;
        outb(info->MCR, info->ioaddr + UART_MCR);

        /*
         * Finally, enable interrupts
         */
        info->IER = UART_IER_MSI | UART_IER_RLSI | UART_IER_RDI;

        if (info->board->must_hwid)
                info->IER |= MOXA_MUST_IER_EGDAI;
        outb(info->IER, info->ioaddr + UART_IER);       /* enable interrupts */

        /*
         * And clear the interrupt registers again for luck.
         */
        (void) inb(info->ioaddr + UART_LSR);
        (void) inb(info->ioaddr + UART_RX);
        (void) inb(info->ioaddr + UART_IIR);
        (void) inb(info->ioaddr + UART_MSR);

        clear_bit(TTY_IO_ERROR, &tty->flags);
        kfifo_reset(&port->xmit_fifo);

        /*
         * and set the speed of the serial port
         */
        mxser_change_speed(tty, NULL);
        spin_unlock_irqrestore(&info->slock, flags);

        return 0;
err_free_xmit:
        tty_port_free_xmit_buf(port);
        return ret;
}

/*
 * To stop accepting input, we disable the receive line status interrupts, and
 * tell the interrupt driver to stop checking the data ready bit in the line
 * status register.
 */
static void mxser_stop_rx(struct mxser_port *info)
{
        info->IER &= ~UART_IER_RLSI;
        if (info->board->must_hwid)
                info->IER &= ~MOXA_MUST_RECV_ISR;

        outb(info->IER, info->ioaddr + UART_IER);
}

/*
 * This routine will shutdown a serial port
 */
static void mxser_shutdown_port(struct tty_port *port)
{
        struct mxser_port *info = container_of(port, struct mxser_port, port);

        scoped_guard(spinlock_irqsave, &info->slock) {
                mxser_stop_rx(info);

                /*
                 * clear delta_msr_wait queue to avoid mem leaks: we may free the irq
                 * here so the queue might never be waken up
                 */
                wake_up_interruptible(&info->port.delta_msr_wait);

                info->IER = 0;
                outb(0x00, info->ioaddr + UART_IER);

                /* clear Rx/Tx FIFO's */
                mxser_disable_and_clear_FIFO(info);

                /* read data port to reset things */
                (void)inb(info->ioaddr + UART_RX);

                if (info->board->must_hwid)
                        mxser_must_no_sw_flow_control(info->ioaddr);
        }

        /* make sure ISR is not running while we free the buffer */
        synchronize_irq(info->board->irq);

        tty_port_free_xmit_buf(port);
}

/*
 * This routine is called whenever a serial port is opened.  It
 * enables interrupts for a serial port, linking in its async structure into
 * the IRQ chain.   It also performs the serial-specific
 * initialization for the tty structure.
 */
static int mxser_open(struct tty_struct *tty, struct file *filp)
{
        struct tty_port *tport = tty->port;
        struct mxser_port *port = container_of(tport, struct mxser_port, port);

        tty->driver_data = port;

        return tty_port_open(tport, tty, filp);
}

static void mxser_flush_buffer(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        scoped_guard(spinlock_irqsave, &info->slock) {
                kfifo_reset(&info->port.xmit_fifo);

                outb(info->FCR | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
                     info->ioaddr + UART_FCR);
        }

        tty_wakeup(tty);
}

static void mxser_close(struct tty_struct *tty, struct file *filp)
{
        tty_port_close(tty->port, tty, filp);
}

static ssize_t mxser_write(struct tty_struct *tty, const u8 *buf, size_t count)
{
        struct mxser_port *info = tty->driver_data;
        size_t written;
        bool is_empty;

        scoped_guard(spinlock_irqsave, &info->slock) {
                written = kfifo_in(&info->port.xmit_fifo, buf, count);
                is_empty = kfifo_is_empty(&info->port.xmit_fifo);
        }

        if (!is_empty && !tty->flow.stopped)
                if (!tty->hw_stopped || mxser_16550A_or_MUST(info))
                        mxser_start_tx(info);

        return written;
}

static int mxser_put_char(struct tty_struct *tty, u8 ch)
{
        struct mxser_port *info = tty->driver_data;

        guard(spinlock_irqsave)(&info->slock);
        return kfifo_put(&info->port.xmit_fifo, ch);
}


static void mxser_flush_chars(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        if (kfifo_is_empty(&info->port.xmit_fifo) || tty->flow.stopped ||
                        (tty->hw_stopped && !mxser_16550A_or_MUST(info)))
                return;

        mxser_start_tx(info);
}

static unsigned int mxser_write_room(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        return kfifo_avail(&info->port.xmit_fifo);
}

static unsigned int mxser_chars_in_buffer(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        return kfifo_len(&info->port.xmit_fifo);
}

/*
 * ------------------------------------------------------------
 * friends of mxser_ioctl()
 * ------------------------------------------------------------
 */
static int mxser_get_serial_info(struct tty_struct *tty,
                struct serial_struct *ss)
{
        struct mxser_port *info = tty->driver_data;
        struct tty_port *port = &info->port;
        unsigned int closing_wait, close_delay;

        guard(mutex)(&port->mutex);

        close_delay = jiffies_to_msecs(info->port.close_delay) / 10;
        closing_wait = info->port.closing_wait;
        if (closing_wait != ASYNC_CLOSING_WAIT_NONE)
                closing_wait = jiffies_to_msecs(closing_wait) / 10;

        ss->type = info->type;
        ss->line = tty->index;
        ss->port = info->ioaddr;
        ss->irq = info->board->irq;
        ss->flags = info->port.flags;
        ss->baud_base = MXSER_BAUD_BASE;
        ss->close_delay = close_delay;
        ss->closing_wait = closing_wait;
        ss->custom_divisor = MXSER_CUSTOM_DIVISOR;

        return 0;
}

static int mxser_set_serial_info(struct tty_struct *tty,
                struct serial_struct *ss)
{
        struct mxser_port *info = tty->driver_data;
        struct tty_port *port = &info->port;
        speed_t baud;
        unsigned int old_speed, close_delay, closing_wait;

        if (tty_io_error(tty))
                return -EIO;

        guard(mutex)(&port->mutex);

        if (ss->irq != info->board->irq || ss->port != info->ioaddr)
                return -EINVAL;

        old_speed = port->flags & ASYNC_SPD_MASK;

        close_delay = msecs_to_jiffies(ss->close_delay * 10);
        closing_wait = ss->closing_wait;
        if (closing_wait != ASYNC_CLOSING_WAIT_NONE)
                closing_wait = msecs_to_jiffies(closing_wait * 10);

        if (!capable(CAP_SYS_ADMIN)) {
                if ((ss->baud_base != MXSER_BAUD_BASE) ||
                                (close_delay != port->close_delay) ||
                                (closing_wait != port->closing_wait) ||
                                ((ss->flags & ~ASYNC_USR_MASK) != (port->flags & ~ASYNC_USR_MASK)))
                        return -EPERM;

                port->flags = (port->flags & ~ASYNC_USR_MASK) |
                                (ss->flags & ASYNC_USR_MASK);
        } else {
                /*
                 * OK, past this point, all the error checking has been done.
                 * At this point, we start making changes.....
                 */
                port->flags = ((port->flags & ~ASYNC_FLAGS) |
                                (ss->flags & ASYNC_FLAGS));
                port->close_delay = close_delay;
                port->closing_wait = closing_wait;
                if ((port->flags & ASYNC_SPD_MASK) == ASYNC_SPD_CUST &&
                                (ss->baud_base != MXSER_BAUD_BASE ||
                                ss->custom_divisor !=
                                MXSER_CUSTOM_DIVISOR)) {
                        if (ss->custom_divisor == 0)
                                return -EINVAL;

                        baud = ss->baud_base / ss->custom_divisor;
                        tty_encode_baud_rate(tty, baud, baud);
                }

                info->type = ss->type;

                mxser_process_txrx_fifo(info);
        }

        if (tty_port_initialized(port)) {
                if (old_speed != (port->flags & ASYNC_SPD_MASK)) {
                        guard(spinlock_irqsave)(&info->slock);
                        mxser_change_speed(tty, NULL);
                }

                return 0;
        }

        int retval = mxser_activate(port, tty);
        if (retval == 0)
                tty_port_set_initialized(port, true);

        return retval;
}

/*
 * mxser_get_lsr_info - get line status register info
 *
 * Purpose: Let user call ioctl() to get info when the UART physically
 *          is emptied.  On bus types like RS485, the transmitter must
 *          release the bus after transmitting. This must be done when
 *          the transmit shift register is empty, not be done when the
 *          transmit holding register is empty.  This functionality
 *          allows an RS485 driver to be written in user space.
 */
static int mxser_get_lsr_info(struct mxser_port *info,
                unsigned int __user *value)
{
        unsigned int result;
        u8 status;

        scoped_guard(spinlock_irqsave, &info->slock)
                status = inb(info->ioaddr + UART_LSR);
        result = ((status & UART_LSR_TEMT) ? TIOCSER_TEMT : 0);
        return put_user(result, value);
}

static int mxser_tiocmget(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;
        unsigned char control;
        u8 msr;

        if (tty_io_error(tty))
                return -EIO;

        scoped_guard(spinlock_irqsave, &info->slock) {
                control = info->MCR;
                msr = mxser_check_modem_status(tty, info);
        }

        return ((control & UART_MCR_RTS) ? TIOCM_RTS : 0) |
                    ((control & UART_MCR_DTR) ? TIOCM_DTR : 0) |
                    ((msr & UART_MSR_DCD) ? TIOCM_CAR : 0) |
                    ((msr & UART_MSR_RI) ? TIOCM_RNG : 0) |
                    ((msr & UART_MSR_DSR) ? TIOCM_DSR : 0) |
                    ((msr & UART_MSR_CTS) ? TIOCM_CTS : 0);
}

static int mxser_tiocmset(struct tty_struct *tty,
                unsigned int set, unsigned int clear)
{
        struct mxser_port *info = tty->driver_data;

        if (tty_io_error(tty))
                return -EIO;

        guard(spinlock_irqsave)(&info->slock);

        if (set & TIOCM_RTS)
                info->MCR |= UART_MCR_RTS;
        if (set & TIOCM_DTR)
                info->MCR |= UART_MCR_DTR;

        if (clear & TIOCM_RTS)
                info->MCR &= ~UART_MCR_RTS;
        if (clear & TIOCM_DTR)
                info->MCR &= ~UART_MCR_DTR;

        outb(info->MCR, info->ioaddr + UART_MCR);

        return 0;
}

static int mxser_cflags_changed(struct mxser_port *info, unsigned long arg,
                struct async_icount *cprev)
{
        struct async_icount cnow;
        int ret;

        /* atomic copy */
        scoped_guard(spinlock_irqsave, &info->slock)
                cnow = info->icount;

        ret =   ((arg & TIOCM_RNG) && (cnow.rng != cprev->rng)) ||
                ((arg & TIOCM_DSR) && (cnow.dsr != cprev->dsr)) ||
                ((arg & TIOCM_CD)  && (cnow.dcd != cprev->dcd)) ||
                ((arg & TIOCM_CTS) && (cnow.cts != cprev->cts));

        *cprev = cnow;

        return ret;
}

/* We should likely switch to TIOCGRS485/TIOCSRS485. */
static int mxser_ioctl_op_mode(struct mxser_port *port, int index, bool set,
                int __user *u_opmode)
{
        int opmode, p = index % 4;
        int shiftbit = p * 2;
        u8 val;

        if (port->board->must_hwid != MOXA_MUST_MU860_HWID)
                return -EFAULT;

        if (set) {
                if (get_user(opmode, u_opmode))
                        return -EFAULT;

                if (opmode & ~OP_MODE_MASK)
                        return -EINVAL;

                guard(spinlock_irq)(&port->slock);
                val = inb(port->opmode_ioaddr);
                val &= ~(OP_MODE_MASK << shiftbit);
                val |= (opmode << shiftbit);
                outb(val, port->opmode_ioaddr);

                return 0;
        }

        scoped_guard(spinlock_irq, &port->slock)
                opmode = inb(port->opmode_ioaddr) >> shiftbit;

        return put_user(opmode & OP_MODE_MASK, u_opmode);
}

static int mxser_ioctl(struct tty_struct *tty,
                unsigned int cmd, unsigned long arg)
{
        struct mxser_port *info = tty->driver_data;
        struct async_icount cnow;
        void __user *argp = (void __user *)arg;

        if (cmd == MOXA_SET_OP_MODE || cmd == MOXA_GET_OP_MODE)
                return mxser_ioctl_op_mode(info, tty->index,
                                cmd == MOXA_SET_OP_MODE, argp);

        if (cmd != TIOCMIWAIT && tty_io_error(tty))
                return -EIO;

        switch (cmd) {
        case TIOCSERGETLSR:     /* Get line status register */
                return  mxser_get_lsr_info(info, argp);
                /*
                 * Wait for any of the 4 modem inputs (DCD,RI,DSR,CTS) to change
                 * - mask passed in arg for lines of interest
                 *   (use |'ed TIOCM_RNG/DSR/CD/CTS for masking)
                 * Caller should use TIOCGICOUNT to see which one it was
                 */
        case TIOCMIWAIT:
                /* note the counters on entry */
                scoped_guard(spinlock_irqsave, &info->slock)
                        cnow = info->icount;

                return wait_event_interruptible(info->port.delta_msr_wait,
                                mxser_cflags_changed(info, arg, &cnow));
        default:
                return -ENOIOCTLCMD;
        }
        return 0;
}

        /*
         * Get counter of input serial line interrupts (DCD,RI,DSR,CTS)
         * Return: write counters to the user passed counter struct
         * NB: both 1->0 and 0->1 transitions are counted except for
         *     RI where only 0->1 is counted.
         */

static int mxser_get_icount(struct tty_struct *tty,
                struct serial_icounter_struct *icount)

{
        struct mxser_port *info = tty->driver_data;
        struct async_icount cnow;

        scoped_guard(spinlock_irqsave, &info->slock)
                cnow = info->icount;

        icount->frame = cnow.frame;
        icount->brk = cnow.brk;
        icount->overrun = cnow.overrun;
        icount->buf_overrun = cnow.buf_overrun;
        icount->parity = cnow.parity;
        icount->rx = cnow.rx;
        icount->tx = cnow.tx;
        icount->cts = cnow.cts;
        icount->dsr = cnow.dsr;
        icount->rng = cnow.rng;
        icount->dcd = cnow.dcd;
        return 0;
}

/*
 * This routine is called by the upper-layer tty layer to signal that
 * incoming characters should be throttled.
 */
static void mxser_throttle(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        if (I_IXOFF(tty)) {
                if (info->board->must_hwid) {
                        info->IER &= ~MOXA_MUST_RECV_ISR;
                        outb(info->IER, info->ioaddr + UART_IER);
                } else {
                        info->x_char = STOP_CHAR(tty);
                        outb(0, info->ioaddr + UART_IER);
                        info->IER |= UART_IER_THRI;
                        outb(info->IER, info->ioaddr + UART_IER);
                }
        }

        if (C_CRTSCTS(tty)) {
                info->MCR &= ~UART_MCR_RTS;
                outb(info->MCR, info->ioaddr + UART_MCR);
        }
}

static void mxser_unthrottle(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        /* startrx */
        if (I_IXOFF(tty)) {
                if (info->x_char)
                        info->x_char = 0;
                else {
                        if (info->board->must_hwid) {
                                info->IER |= MOXA_MUST_RECV_ISR;
                                outb(info->IER, info->ioaddr + UART_IER);
                        } else {
                                info->x_char = START_CHAR(tty);
                                outb(0, info->ioaddr + UART_IER);
                                info->IER |= UART_IER_THRI;
                                outb(info->IER, info->ioaddr + UART_IER);
                        }
                }
        }

        if (C_CRTSCTS(tty)) {
                info->MCR |= UART_MCR_RTS;
                outb(info->MCR, info->ioaddr + UART_MCR);
        }
}

/*
 * mxser_stop() and mxser_start()
 *
 * This routines are called before setting or resetting tty->flow.stopped.
 * They enable or disable transmitter interrupts, as necessary.
 */
static void mxser_stop(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        guard(spinlock_irqsave)(&info->slock);
        if (info->IER & UART_IER_THRI)
                __mxser_stop_tx(info);
}

static void mxser_start(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        guard(spinlock_irqsave)(&info->slock);
        if (!kfifo_is_empty(&info->port.xmit_fifo))
                __mxser_start_tx(info);
}

static void mxser_set_termios(struct tty_struct *tty,
                              const struct ktermios *old_termios)
{
        struct mxser_port *info = tty->driver_data;

        scoped_guard(spinlock_irqsave, &info->slock)
                mxser_change_speed(tty, old_termios);

        if ((old_termios->c_cflag & CRTSCTS) && !C_CRTSCTS(tty)) {
                tty->hw_stopped = false;
                mxser_start(tty);
        }

        /* Handle sw stopped */
        if ((old_termios->c_iflag & IXON) && !I_IXON(tty)) {
                tty->flow.stopped = 0;

                if (info->board->must_hwid) {
                        guard(spinlock_irqsave)(&info->slock);
                        mxser_must_set_rx_sw_flow_control(info->ioaddr, false);
                }

                mxser_start(tty);
        }
}

static bool mxser_tx_empty(struct mxser_port *info)
{
        guard(spinlock_irqsave)(&info->slock);
        return !(inb(info->ioaddr + UART_LSR) & UART_LSR_TEMT);
}

/*
 * mxser_wait_until_sent() --- wait until the transmitter is empty
 */
static void mxser_wait_until_sent(struct tty_struct *tty, int timeout)
{
        struct mxser_port *info = tty->driver_data;
        unsigned long expire, char_time;

        if (info->type == PORT_UNKNOWN)
                return;

        if (info->xmit_fifo_size == 0)
                return;         /* Just in case.... */

        /*
         * Set the check interval to be 1/5 of the estimated time to
         * send a single character, and make it at least 1.  The check
         * interval should also be less than the timeout.
         *
         * Note: we have to use pretty tight timings here to satisfy
         * the NIST-PCTS.
         */
        char_time = (info->timeout - HZ / 50) / info->xmit_fifo_size;
        char_time = char_time / 5;
        if (char_time == 0)
                char_time = 1;
        if (timeout && timeout < char_time)
                char_time = timeout;

        char_time = jiffies_to_msecs(char_time);

        /*
         * If the transmitter hasn't cleared in twice the approximate
         * amount of time to send the entire FIFO, it probably won't
         * ever clear.  This assumes the UART isn't doing flow
         * control, which is currently the case.  Hence, if it ever
         * takes longer than info->timeout, this is probably due to a
         * UART bug of some kind.  So, we clamp the timeout parameter at
         * 2*info->timeout.
         */
        if (!timeout || timeout > 2 * info->timeout)
                timeout = 2 * info->timeout;

        expire = jiffies + timeout;

        while (mxser_tx_empty(info)) {
                msleep_interruptible(char_time);
                if (signal_pending(current))
                        break;
                if (time_after(jiffies, expire))
                        break;
        }
}

/*
 * This routine is called by tty_hangup() when a hangup is signaled.
 */
static void mxser_hangup(struct tty_struct *tty)
{
        struct mxser_port *info = tty->driver_data;

        mxser_flush_buffer(tty);
        tty_port_hangup(&info->port);
}

/*
 * mxser_rs_break() --- routine which turns the break handling on or off
 */
static int mxser_rs_break(struct tty_struct *tty, int break_state)
{
        struct mxser_port *info = tty->driver_data;
        u8 lcr;

        guard(spinlock_irqsave)(&info->slock);
        lcr = inb(info->ioaddr + UART_LCR);
        if (break_state == -1)
                lcr |= UART_LCR_SBC;
        else
                lcr &= ~UART_LCR_SBC;
        outb(lcr, info->ioaddr + UART_LCR);

        return 0;
}

static bool mxser_receive_chars_new(struct mxser_port *port, u8 status)
{
        enum mxser_must_hwid hwid = port->board->must_hwid;
        u8 gdl;

        if (hwid == MOXA_OTHER_UART)
                return false;
        if (status & (UART_LSR_BRK_ERROR_BITS | MOXA_MUST_LSR_RERR))
                return false;

        gdl = inb(port->ioaddr + MOXA_MUST_GDL_REGISTER);
        if (hwid == MOXA_MUST_MU150_HWID)
                gdl &= MOXA_MUST_GDL_MASK;

        while (gdl--) {
                u8 ch = inb(port->ioaddr + UART_RX);
                if (!tty_insert_flip_char(&port->port, ch, 0))
                        port->icount.buf_overrun++;
        }

        return true;
}

static u8 mxser_receive_chars_old(struct tty_struct *tty,
                                struct mxser_port *port, u8 status)
{
        enum mxser_must_hwid hwid = port->board->must_hwid;
        int ignored = 0;
        int max = 256;
        u8 ch;

        do {
                if (max-- < 0)
                        break;

                ch = inb(port->ioaddr + UART_RX);
                if (hwid && (status & UART_LSR_OE))
                        outb(port->FCR | UART_FCR_CLEAR_RCVR,
                                        port->ioaddr + UART_FCR);
                status &= port->read_status_mask;
                if (status & port->ignore_status_mask) {
                        if (++ignored > 100)
                                break;
                } else {
                        u8 flag = 0;
                        if (status & UART_LSR_BRK_ERROR_BITS) {
                                if (status & UART_LSR_BI) {
                                        flag = TTY_BREAK;
                                        port->icount.brk++;

                                        if (port->port.flags & ASYNC_SAK)
                                                do_SAK(tty);
                                } else if (status & UART_LSR_PE) {
                                        flag = TTY_PARITY;
                                        port->icount.parity++;
                                } else if (status & UART_LSR_FE) {
                                        flag = TTY_FRAME;
                                        port->icount.frame++;
                                } else if (status & UART_LSR_OE) {
                                        flag = TTY_OVERRUN;
                                        port->icount.overrun++;
                                }
                        }
                        if (!tty_insert_flip_char(&port->port, ch, flag)) {
                                port->icount.buf_overrun++;
                                break;
                        }
                }

                if (hwid)
                        break;

                status = inb(port->ioaddr + UART_LSR);
        } while (status & UART_LSR_DR);

        return status;
}

static u8 mxser_receive_chars(struct tty_struct *tty,
                struct mxser_port *port, u8 status)
{
        if (!mxser_receive_chars_new(port, status))
                status = mxser_receive_chars_old(tty, port, status);

        tty_flip_buffer_push(&port->port);

        return status;
}

static void mxser_transmit_chars(struct tty_struct *tty, struct mxser_port *port)
{
        int count;

        if (port->x_char) {
                outb(port->x_char, port->ioaddr + UART_TX);
                port->x_char = 0;
                port->icount.tx++;
                return;
        }

        if (kfifo_is_empty(&port->port.xmit_fifo) || tty->flow.stopped ||
                        (tty->hw_stopped && !mxser_16550A_or_MUST(port))) {
                __mxser_stop_tx(port);
                return;
        }

        count = port->xmit_fifo_size;
        do {
                u8 c;

                if (!kfifo_get(&port->port.xmit_fifo, &c))
                        break;

                outb(c, port->ioaddr + UART_TX);
                port->icount.tx++;
        } while (--count > 0);

        if (kfifo_len(&port->port.xmit_fifo) < WAKEUP_CHARS)
                tty_wakeup(tty);

        if (kfifo_is_empty(&port->port.xmit_fifo))
                __mxser_stop_tx(port);
}

static bool mxser_port_isr(struct mxser_port *port)
{
        u8 iir, status;

        iir = inb(port->ioaddr + UART_IIR);
        if (iir & UART_IIR_NO_INT)
                return true;

        iir &= MOXA_MUST_IIR_MASK;

        scoped_guard(tty_port_tty, &port->port) {
                struct tty_struct *tty = scoped_tty();

                status = inb(port->ioaddr + UART_LSR);

                if (port->board->must_hwid) {
                        if (iir == MOXA_MUST_IIR_GDA ||
                            iir == MOXA_MUST_IIR_RDA ||
                            iir == MOXA_MUST_IIR_RTO ||
                            iir == MOXA_MUST_IIR_LSR)
                                status = mxser_receive_chars(tty, port, status);
                } else {
                        status &= port->read_status_mask;
                        if (status & UART_LSR_DR)
                                status = mxser_receive_chars(tty, port, status);
                }

                mxser_check_modem_status(tty, port);

                if (port->board->must_hwid) {
                        if (iir == 0x02 && (status & UART_LSR_THRE))
                                mxser_transmit_chars(tty, port);
                } else {
                        if (status & UART_LSR_THRE)
                                mxser_transmit_chars(tty, port);
                }

                return false;
        }

        status = inb(port->ioaddr + UART_LSR);
        outb(port->FCR | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
                        port->ioaddr + UART_FCR);
        inb(port->ioaddr + UART_MSR);

        return true;
}

/*
 * This is the serial driver's generic interrupt routine
 */
static irqreturn_t mxser_interrupt(int irq, void *dev_id)
{
        struct mxser_board *brd = dev_id;
        struct mxser_port *port;
        unsigned int int_cnt, pass_counter = 0;
        unsigned int i, max = brd->nports;
        int handled = IRQ_NONE;
        u8 irqbits, bits, mask = BIT(max) - 1;

        while (pass_counter++ < MXSER_ISR_PASS_LIMIT) {
                irqbits = inb(brd->vector) & mask;
                if (irqbits == mask)
                        break;

                handled = IRQ_HANDLED;
                for (i = 0, bits = 1; i < max; i++, irqbits |= bits, bits <<= 1) {
                        if (irqbits == mask)
                                break;
                        if (bits & irqbits)
                                continue;
                        port = &brd->ports[i];

                        int_cnt = 0;
                        guard(spinlock)(&port->slock);
                        do {
                                if (mxser_port_isr(port))
                                        break;
                        } while (int_cnt++ < MXSER_ISR_PASS_LIMIT);
                }
        }

        return handled;
}

static const struct tty_operations mxser_ops = {
        .open = mxser_open,
        .close = mxser_close,
        .write = mxser_write,
        .put_char = mxser_put_char,
        .flush_chars = mxser_flush_chars,
        .write_room = mxser_write_room,
        .chars_in_buffer = mxser_chars_in_buffer,
        .flush_buffer = mxser_flush_buffer,
        .ioctl = mxser_ioctl,
        .throttle = mxser_throttle,
        .unthrottle = mxser_unthrottle,
        .set_termios = mxser_set_termios,
        .stop = mxser_stop,
        .start = mxser_start,
        .hangup = mxser_hangup,
        .break_ctl = mxser_rs_break,
        .wait_until_sent = mxser_wait_until_sent,
        .tiocmget = mxser_tiocmget,
        .tiocmset = mxser_tiocmset,
        .set_serial = mxser_set_serial_info,
        .get_serial = mxser_get_serial_info,
        .get_icount = mxser_get_icount,
};

static const struct tty_port_operations mxser_port_ops = {
        .carrier_raised = mxser_carrier_raised,
        .dtr_rts = mxser_dtr_rts,
        .activate = mxser_activate,
        .shutdown = mxser_shutdown_port,
};

/*
 * The MOXA Smartio/Industio serial driver boot-time initialization code!
 */

static void mxser_initbrd(struct mxser_board *brd, bool high_baud)
{
        struct mxser_port *info;
        unsigned int i;
        bool is_mu860;

        brd->must_hwid = mxser_must_get_hwid(brd->ports[0].ioaddr);
        is_mu860 = brd->must_hwid == MOXA_MUST_MU860_HWID;

        for (i = 0; i < UART_INFO_NUM; i++) {
                if (Gpci_uart_info[i].type == brd->must_hwid) {
                        brd->max_baud = Gpci_uart_info[i].max_baud;

                        /* exception....CP-102 */
                        if (high_baud)
                                brd->max_baud = 921600;
                        break;
                }
        }

        if (is_mu860) {
                /* set to RS232 mode by default */
                outb(0, brd->vector + 4);
                outb(0, brd->vector + 0x0c);
        }

        for (i = 0; i < brd->nports; i++) {
                info = &brd->ports[i];
                if (is_mu860) {
                        if (i < 4)
                                info->opmode_ioaddr = brd->vector + 4;
                        else
                                info->opmode_ioaddr = brd->vector + 0x0c;
                }
                tty_port_init(&info->port);
                info->port.ops = &mxser_port_ops;
                info->board = brd;

                /* Enhance mode enabled here */
                if (brd->must_hwid != MOXA_OTHER_UART)
                        mxser_must_set_enhance_mode(info->ioaddr, true);

                info->type = PORT_16550A;

                mxser_process_txrx_fifo(info);

                spin_lock_init(&info->slock);

                /* before set INT ISR, disable all int */
                outb(inb(info->ioaddr + UART_IER) & 0xf0,
                        info->ioaddr + UART_IER);
        }
}

static int mxser_probe(struct pci_dev *pdev,
                const struct pci_device_id *ent)
{
        struct mxser_board *brd;
        unsigned int i, base;
        unsigned long ioaddress;
        unsigned short nports = MXSER_NPORTS(ent->driver_data);
        struct device *tty_dev;
        int retval = -EINVAL;

        i = find_first_zero_bit(mxser_boards, MXSER_BOARDS);
        if (i >= MXSER_BOARDS) {
                dev_err(&pdev->dev, "too many boards found (maximum %d), board "
                                "not configured\n", MXSER_BOARDS);
                goto err;
        }

        brd = devm_kzalloc(&pdev->dev, struct_size(brd, ports, nports),
                        GFP_KERNEL);
        if (!brd)
                goto err;

        brd->idx = i;
        __set_bit(brd->idx, mxser_boards);
        base = i * MXSER_PORTS_PER_BOARD;

        retval = pcim_enable_device(pdev);
        if (retval) {
                dev_err(&pdev->dev, "PCI enable failed\n");
                goto err_zero;
        }

        /* io address */
        ioaddress = pci_resource_start(pdev, 2);
        retval = pcim_request_region(pdev, 2, "mxser(IO)");
        if (retval)
                goto err_zero;

        brd->nports = nports;
        for (i = 0; i < nports; i++)
                brd->ports[i].ioaddr = ioaddress + 8 * i;

        /* vector */
        ioaddress = pci_resource_start(pdev, 3);
        retval = pcim_request_region(pdev, 3, "mxser(vector)");
        if (retval)
                goto err_zero;
        brd->vector = ioaddress;

        /* irq */
        brd->irq = pdev->irq;

        mxser_initbrd(brd, ent->driver_data & MXSER_HIGHBAUD);

        retval = devm_request_irq(&pdev->dev, brd->irq, mxser_interrupt,
                        IRQF_SHARED, "mxser", brd);
        if (retval) {
                dev_err(&pdev->dev, "request irq failed");
                goto err_relbrd;
        }

        for (i = 0; i < nports; i++) {
                tty_dev = tty_port_register_device(&brd->ports[i].port,
                                mxvar_sdriver, base + i, &pdev->dev);
                if (IS_ERR(tty_dev)) {
                        retval = PTR_ERR(tty_dev);
                        for (; i > 0; i--)
                                tty_unregister_device(mxvar_sdriver,
                                        base + i - 1);
                        goto err_relbrd;
                }
        }

        pci_set_drvdata(pdev, brd);

        return 0;
err_relbrd:
        for (i = 0; i < nports; i++)
                tty_port_destroy(&brd->ports[i].port);
err_zero:
        __clear_bit(brd->idx, mxser_boards);
err:
        return retval;
}

static void mxser_remove(struct pci_dev *pdev)
{
        struct mxser_board *brd = pci_get_drvdata(pdev);
        unsigned int i, base = brd->idx * MXSER_PORTS_PER_BOARD;

        for (i = 0; i < brd->nports; i++) {
                tty_unregister_device(mxvar_sdriver, base + i);
                tty_port_destroy(&brd->ports[i].port);
        }

        __clear_bit(brd->idx, mxser_boards);
}

static struct pci_driver mxser_driver = {
        .name = "mxser",
        .id_table = mxser_pcibrds,
        .probe = mxser_probe,
        .remove = mxser_remove
};

static int __init mxser_module_init(void)
{
        int retval;

        mxvar_sdriver = tty_alloc_driver(MXSER_PORTS, TTY_DRIVER_REAL_RAW |
                        TTY_DRIVER_DYNAMIC_DEV);
        if (IS_ERR(mxvar_sdriver))
                return PTR_ERR(mxvar_sdriver);

        /* Initialize the tty_driver structure */
        mxvar_sdriver->name = "ttyMI";
        mxvar_sdriver->major = ttymajor;
        mxvar_sdriver->minor_start = 0;
        mxvar_sdriver->type = TTY_DRIVER_TYPE_SERIAL;
        mxvar_sdriver->subtype = SERIAL_TYPE_NORMAL;
        mxvar_sdriver->init_termios = tty_std_termios;
        mxvar_sdriver->init_termios.c_cflag = B9600|CS8|CREAD|HUPCL|CLOCAL;
        tty_set_operations(mxvar_sdriver, &mxser_ops);

        retval = tty_register_driver(mxvar_sdriver);
        if (retval) {
                printk(KERN_ERR "Couldn't install MOXA Smartio/Industio family "
                                "tty driver !\n");
                goto err_put;
        }

        retval = pci_register_driver(&mxser_driver);
        if (retval) {
                printk(KERN_ERR "mxser: can't register pci driver\n");
                goto err_unr;
        }

        return 0;
err_unr:
        tty_unregister_driver(mxvar_sdriver);
err_put:
        tty_driver_kref_put(mxvar_sdriver);
        return retval;
}

static void __exit mxser_module_exit(void)
{
        pci_unregister_driver(&mxser_driver);
        tty_unregister_driver(mxvar_sdriver);
        tty_driver_kref_put(mxvar_sdriver);
}

module_init(mxser_module_init);
module_exit(mxser_module_exit);