// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright 2003 Digi International (www.digi.com)
 *      Scott H Kilau <Scott_Kilau at digi dot com>
 *
 *      NOTE TO LINUX KERNEL HACKERS:  DO NOT REFORMAT THIS CODE!
 *
 *      This is shared code between Digi's CVS archive and the
 *      Linux Kernel sources.
 *      Changing the source just for reformatting needlessly breaks
 *      our CVS diff history.
 *
 *      Send any bug fixes/changes to:  Eng.Linux at digi dot com.
 *      Thank you.
 *
 */

#include <linux/delay.h>        /* For udelay */
#include <linux/io.h>           /* For read[bwl]/write[bwl] */
#include <linux/serial.h>       /* For struct async_serial */
#include <linux/serial_reg.h>   /* For the various UART offsets */
#include <linux/pci.h>
#include <linux/tty.h>

#include "jsm.h"        /* Driver main header file */

static struct {
        unsigned int rate;
        unsigned int cflag;
} baud_rates[] = {
        { 921600, B921600 },
        { 460800, B460800 },
        { 230400, B230400 },
        { 115200, B115200 },
        {  57600, B57600  },
        {  38400, B38400  },
        {  19200, B19200  },
        {   9600, B9600   },
        {   4800, B4800   },
        {   2400, B2400   },
        {   1200, B1200   },
        {    600, B600    },
        {    300, B300    },
        {    200, B200    },
        {    150, B150    },
        {    134, B134    },
        {    110, B110    },
        {     75, B75     },
        {     50, B50     },
};

static void cls_set_cts_flow_control(struct jsm_channel *ch)
{
        u8 lcrb = readb(&ch->ch_cls_uart->lcr);
        u8 ier = readb(&ch->ch_cls_uart->ier);
        u8 isr_fcr = 0;

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn on CTS flow control, turn off IXON flow control */
        isr_fcr |= (UART_EXAR654_EFR_ECB | UART_EXAR654_EFR_CTSDSR);
        isr_fcr &= ~(UART_EXAR654_EFR_IXON);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /*
         * Enable interrupts for CTS flow, turn off interrupts for
         * received XOFF chars
         */
        ier |= (UART_EXAR654_IER_CTSDSR);
        ier &= ~(UART_EXAR654_IER_XOFF);
        writeb(ier, &ch->ch_cls_uart->ier);

        /* Set the usual FIFO values */
        writeb((UART_FCR_ENABLE_FIFO), &ch->ch_cls_uart->isr_fcr);

        writeb((UART_FCR_ENABLE_FIFO | UART_16654_FCR_RXTRIGGER_56 |
                UART_16654_FCR_TXTRIGGER_16 | UART_FCR_CLEAR_RCVR),
                &ch->ch_cls_uart->isr_fcr);

        ch->ch_t_tlevel = 16;
}

static void cls_set_ixon_flow_control(struct jsm_channel *ch)
{
        u8 lcrb = readb(&ch->ch_cls_uart->lcr);
        u8 ier = readb(&ch->ch_cls_uart->ier);
        u8 isr_fcr = 0;

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn on IXON flow control, turn off CTS flow control */
        isr_fcr |= (UART_EXAR654_EFR_ECB | UART_EXAR654_EFR_IXON);
        isr_fcr &= ~(UART_EXAR654_EFR_CTSDSR);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Now set our current start/stop chars while in enhanced mode */
        writeb(ch->ch_startc, &ch->ch_cls_uart->mcr);
        writeb(0, &ch->ch_cls_uart->lsr);
        writeb(ch->ch_stopc, &ch->ch_cls_uart->msr);
        writeb(0, &ch->ch_cls_uart->spr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /*
         * Disable interrupts for CTS flow, turn on interrupts for
         * received XOFF chars
         */
        ier &= ~(UART_EXAR654_IER_CTSDSR);
        ier |= (UART_EXAR654_IER_XOFF);
        writeb(ier, &ch->ch_cls_uart->ier);

        /* Set the usual FIFO values */
        writeb((UART_FCR_ENABLE_FIFO), &ch->ch_cls_uart->isr_fcr);

        writeb((UART_FCR_ENABLE_FIFO | UART_16654_FCR_RXTRIGGER_16 |
                UART_16654_FCR_TXTRIGGER_16 | UART_FCR_CLEAR_RCVR),
                &ch->ch_cls_uart->isr_fcr);
}

static void cls_set_no_output_flow_control(struct jsm_channel *ch)
{
        u8 lcrb = readb(&ch->ch_cls_uart->lcr);
        u8 ier = readb(&ch->ch_cls_uart->ier);
        u8 isr_fcr = 0;

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn off IXON flow control, turn off CTS flow control */
        isr_fcr |= (UART_EXAR654_EFR_ECB);
        isr_fcr &= ~(UART_EXAR654_EFR_CTSDSR | UART_EXAR654_EFR_IXON);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /*
         * Disable interrupts for CTS flow, turn off interrupts for
         * received XOFF chars
         */
        ier &= ~(UART_EXAR654_IER_CTSDSR);
        ier &= ~(UART_EXAR654_IER_XOFF);
        writeb(ier, &ch->ch_cls_uart->ier);

        /* Set the usual FIFO values */
        writeb((UART_FCR_ENABLE_FIFO), &ch->ch_cls_uart->isr_fcr);

        writeb((UART_FCR_ENABLE_FIFO | UART_16654_FCR_RXTRIGGER_16 |
                UART_16654_FCR_TXTRIGGER_16 | UART_FCR_CLEAR_RCVR),
                &ch->ch_cls_uart->isr_fcr);

        ch->ch_r_watermark = 0;
        ch->ch_t_tlevel = 16;
        ch->ch_r_tlevel = 16;
}

static void cls_set_rts_flow_control(struct jsm_channel *ch)
{
        u8 lcrb = readb(&ch->ch_cls_uart->lcr);
        u8 ier = readb(&ch->ch_cls_uart->ier);
        u8 isr_fcr = 0;

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn on RTS flow control, turn off IXOFF flow control */
        isr_fcr |= (UART_EXAR654_EFR_ECB | UART_EXAR654_EFR_RTSDTR);
        isr_fcr &= ~(UART_EXAR654_EFR_IXOFF);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /* Enable interrupts for RTS flow */
        ier |= (UART_EXAR654_IER_RTSDTR);
        writeb(ier, &ch->ch_cls_uart->ier);

        /* Set the usual FIFO values */
        writeb((UART_FCR_ENABLE_FIFO), &ch->ch_cls_uart->isr_fcr);

        writeb((UART_FCR_ENABLE_FIFO | UART_16654_FCR_RXTRIGGER_56 |
                UART_16654_FCR_TXTRIGGER_16 | UART_FCR_CLEAR_RCVR),
                &ch->ch_cls_uart->isr_fcr);

        ch->ch_r_watermark = 4;
        ch->ch_r_tlevel = 8;
}

static void cls_set_ixoff_flow_control(struct jsm_channel *ch)
{
        u8 lcrb = readb(&ch->ch_cls_uart->lcr);
        u8 ier = readb(&ch->ch_cls_uart->ier);
        u8 isr_fcr = 0;

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn on IXOFF flow control, turn off RTS flow control */
        isr_fcr |= (UART_EXAR654_EFR_ECB | UART_EXAR654_EFR_IXOFF);
        isr_fcr &= ~(UART_EXAR654_EFR_RTSDTR);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Now set our current start/stop chars while in enhanced mode */
        writeb(ch->ch_startc, &ch->ch_cls_uart->mcr);
        writeb(0, &ch->ch_cls_uart->lsr);
        writeb(ch->ch_stopc, &ch->ch_cls_uart->msr);
        writeb(0, &ch->ch_cls_uart->spr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /* Disable interrupts for RTS flow */
        ier &= ~(UART_EXAR654_IER_RTSDTR);
        writeb(ier, &ch->ch_cls_uart->ier);

        /* Set the usual FIFO values */
        writeb((UART_FCR_ENABLE_FIFO), &ch->ch_cls_uart->isr_fcr);

        writeb((UART_FCR_ENABLE_FIFO | UART_16654_FCR_RXTRIGGER_16 |
                UART_16654_FCR_TXTRIGGER_16 | UART_FCR_CLEAR_RCVR),
                &ch->ch_cls_uart->isr_fcr);
}

static void cls_set_no_input_flow_control(struct jsm_channel *ch)
{
        u8 lcrb = readb(&ch->ch_cls_uart->lcr);
        u8 ier = readb(&ch->ch_cls_uart->ier);
        u8 isr_fcr = 0;

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn off IXOFF flow control, turn off RTS flow control */
        isr_fcr |= (UART_EXAR654_EFR_ECB);
        isr_fcr &= ~(UART_EXAR654_EFR_RTSDTR | UART_EXAR654_EFR_IXOFF);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /* Disable interrupts for RTS flow */
        ier &= ~(UART_EXAR654_IER_RTSDTR);
        writeb(ier, &ch->ch_cls_uart->ier);

        /* Set the usual FIFO values */
        writeb((UART_FCR_ENABLE_FIFO), &ch->ch_cls_uart->isr_fcr);

        writeb((UART_FCR_ENABLE_FIFO | UART_16654_FCR_RXTRIGGER_16 |
                UART_16654_FCR_TXTRIGGER_16 | UART_FCR_CLEAR_RCVR),
                &ch->ch_cls_uart->isr_fcr);

        ch->ch_t_tlevel = 16;
        ch->ch_r_tlevel = 16;
}

/*
 * cls_clear_break.
 * Determines whether its time to shut off break condition.
 *
 * No locks are assumed to be held when calling this function.
 * channel lock is held and released in this function.
 */
static void cls_clear_break(struct jsm_channel *ch)
{
        unsigned long lock_flags;

        spin_lock_irqsave(&ch->ch_lock, lock_flags);

        /* Turn break off, and unset some variables */
        if (ch->ch_flags & CH_BREAK_SENDING) {
                u8 temp = readb(&ch->ch_cls_uart->lcr);

                writeb((temp & ~UART_LCR_SBC), &ch->ch_cls_uart->lcr);

                ch->ch_flags &= ~(CH_BREAK_SENDING);
                jsm_dbg(IOCTL, &ch->ch_bd->pci_dev,
                        "clear break Finishing UART_LCR_SBC! finished: %lx\n",
                        jiffies);
        }
        spin_unlock_irqrestore(&ch->ch_lock, lock_flags);
}

static void cls_disable_receiver(struct jsm_channel *ch)
{
        u8 tmp = readb(&ch->ch_cls_uart->ier);

        tmp &= ~(UART_IER_RDI);
        writeb(tmp, &ch->ch_cls_uart->ier);
}

static void cls_enable_receiver(struct jsm_channel *ch)
{
        u8 tmp = readb(&ch->ch_cls_uart->ier);

        tmp |= (UART_IER_RDI);
        writeb(tmp, &ch->ch_cls_uart->ier);
}

/* Make the UART raise any of the output signals we want up */
static void cls_assert_modem_signals(struct jsm_channel *ch)
{
        if (!ch)
                return;

        writeb(ch->ch_mostat, &ch->ch_cls_uart->mcr);
}

static void cls_copy_data_from_uart_to_queue(struct jsm_channel *ch)
{
        int qleft = 0;
        u8 linestatus = 0;
        u8 error_mask = 0;
        u16 head;
        u16 tail;
        unsigned long flags;

        if (!ch)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /* cache head and tail of queue */
        head = ch->ch_r_head & RQUEUEMASK;
        tail = ch->ch_r_tail & RQUEUEMASK;

        /* Get our cached LSR */
        linestatus = ch->ch_cached_lsr;
        ch->ch_cached_lsr = 0;

        /* Store how much space we have left in the queue */
        qleft = tail - head - 1;
        if (qleft < 0)
                qleft += RQUEUEMASK + 1;

        /*
         * Create a mask to determine whether we should
         * insert the character (if any) into our queue.
         */
        if (ch->ch_c_iflag & IGNBRK)
                error_mask |= UART_LSR_BI;

        while (1) {
                /*
                 * Grab the linestatus register, we need to
                 * check to see if there is any data to read
                 */
                linestatus = readb(&ch->ch_cls_uart->lsr);

                /* Break out if there is no data to fetch */
                if (!(linestatus & UART_LSR_DR))
                        break;

                /*
                 * Discard character if we are ignoring the error mask
                 * which in this case is the break signal.
                 */
                if (linestatus & error_mask)  {
                        linestatus = 0;
                        readb(&ch->ch_cls_uart->txrx);
                        continue;
                }

                /*
                 * If our queue is full, we have no choice but to drop some
                 * data. The assumption is that HWFLOW or SWFLOW should have
                 * stopped things way way before we got to this point.
                 *
                 * I decided that I wanted to ditch the oldest data first,
                 * I hope thats okay with everyone? Yes? Good.
                 */
                while (qleft < 1) {
                        tail = (tail + 1) & RQUEUEMASK;
                        ch->ch_r_tail = tail;
                        ch->ch_err_overrun++;
                        qleft++;
                }

                ch->ch_equeue[head] = linestatus & (UART_LSR_BI | UART_LSR_PE
                                                                 | UART_LSR_FE);
                ch->ch_rqueue[head] = readb(&ch->ch_cls_uart->txrx);

                qleft--;

                if (ch->ch_equeue[head] & UART_LSR_PE)
                        ch->ch_err_parity++;
                if (ch->ch_equeue[head] & UART_LSR_BI)
                        ch->ch_err_break++;
                if (ch->ch_equeue[head] & UART_LSR_FE)
                        ch->ch_err_frame++;

                /* Add to, and flip head if needed */
                head = (head + 1) & RQUEUEMASK;
                ch->ch_rxcount++;
        }

        /*
         * Write new final heads to channel structure.
         */
        ch->ch_r_head = head & RQUEUEMASK;
        ch->ch_e_head = head & EQUEUEMASK;

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}

static void cls_copy_data_from_queue_to_uart(struct jsm_channel *ch)
{
        u16 tail;
        int n;
        int qlen;
        u32 len_written = 0;
        struct circ_buf *circ;

        if (!ch)
                return;

        circ = &ch->uart_port.state->xmit;

        /* No data to write to the UART */
        if (uart_circ_empty(circ))
                return;

        /* If port is "stopped", don't send any data to the UART */
        if ((ch->ch_flags & CH_STOP) || (ch->ch_flags & CH_BREAK_SENDING))
                return;

        /* We have to do it this way, because of the EXAR TXFIFO count bug. */
        if (!(ch->ch_flags & (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM)))
                return;

        n = 32;

        /* cache tail of queue */
        tail = circ->tail & (UART_XMIT_SIZE - 1);
        qlen = uart_circ_chars_pending(circ);

        /* Find minimum of the FIFO space, versus queue length */
        n = min(n, qlen);

        while (n > 0) {
                writeb(circ->buf[tail], &ch->ch_cls_uart->txrx);
                tail = (tail + 1) & (UART_XMIT_SIZE - 1);
                n--;
                ch->ch_txcount++;
                len_written++;
        }

        /* Update the final tail */
        circ->tail = tail & (UART_XMIT_SIZE - 1);

        if (len_written > ch->ch_t_tlevel)
                ch->ch_flags &= ~(CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);

        if (uart_circ_empty(circ))
                uart_write_wakeup(&ch->uart_port);
}

static void cls_parse_modem(struct jsm_channel *ch, u8 signals)
{
        u8 msignals = signals;

        jsm_dbg(MSIGS, &ch->ch_bd->pci_dev,
                "neo_parse_modem: port: %d msignals: %x\n",
                ch->ch_portnum, msignals);

        /*
         * Scrub off lower bits.
         * They signify delta's, which I don't care about
         * Keep DDCD and DDSR though
         */
        msignals &= 0xf8;

        if (msignals & UART_MSR_DDCD)
                uart_handle_dcd_change(&ch->uart_port, msignals & UART_MSR_DCD);
        if (msignals & UART_MSR_DDSR)
                uart_handle_dcd_change(&ch->uart_port, msignals & UART_MSR_CTS);

        if (msignals & UART_MSR_DCD)
                ch->ch_mistat |= UART_MSR_DCD;
        else
                ch->ch_mistat &= ~UART_MSR_DCD;

        if (msignals & UART_MSR_DSR)
                ch->ch_mistat |= UART_MSR_DSR;
        else
                ch->ch_mistat &= ~UART_MSR_DSR;

        if (msignals & UART_MSR_RI)
                ch->ch_mistat |= UART_MSR_RI;
        else
                ch->ch_mistat &= ~UART_MSR_RI;

        if (msignals & UART_MSR_CTS)
                ch->ch_mistat |= UART_MSR_CTS;
        else
                ch->ch_mistat &= ~UART_MSR_CTS;

        jsm_dbg(MSIGS, &ch->ch_bd->pci_dev,
                "Port: %d DTR: %d RTS: %d CTS: %d DSR: %d " "RI: %d CD: %d\n",
                ch->ch_portnum,
                !!((ch->ch_mistat | ch->ch_mostat) & UART_MCR_DTR),
                !!((ch->ch_mistat | ch->ch_mostat) & UART_MCR_RTS),
                !!((ch->ch_mistat | ch->ch_mostat) & UART_MSR_CTS),
                !!((ch->ch_mistat | ch->ch_mostat) & UART_MSR_DSR),
                !!((ch->ch_mistat | ch->ch_mostat) & UART_MSR_RI),
                !!((ch->ch_mistat | ch->ch_mostat) & UART_MSR_DCD));
}

/* Parse the ISR register for the specific port */
static inline void cls_parse_isr(struct jsm_board *brd, uint port)
{
        struct jsm_channel *ch;
        u8 isr = 0;
        unsigned long flags;

        /*
         * No need to verify board pointer, it was already
         * verified in the interrupt routine.
         */

        if (port >= brd->nasync)
                return;

        ch = brd->channels[port];
        if (!ch)
                return;

        /* Here we try to figure out what caused the interrupt to happen */
        while (1) {
                isr = readb(&ch->ch_cls_uart->isr_fcr);

                /* Bail if no pending interrupt on port */
                if (isr & UART_IIR_NO_INT)
                        break;

                /* Receive Interrupt pending */
                if (isr & (UART_IIR_RDI | UART_IIR_RDI_TIMEOUT)) {
                        /* Read data from uart -> queue */
                        cls_copy_data_from_uart_to_queue(ch);
                        jsm_check_queue_flow_control(ch);
                }

                /* Transmit Hold register empty pending */
                if (isr & UART_IIR_THRI) {
                        /* Transfer data (if any) from Write Queue -> UART. */
                        spin_lock_irqsave(&ch->ch_lock, flags);
                        ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        cls_copy_data_from_queue_to_uart(ch);
                }

                /*
                 * CTS/RTS change of state:
                 * Don't need to do anything, the cls_parse_modem
                 * below will grab the updated modem signals.
                 */

                /* Parse any modem signal changes */
                cls_parse_modem(ch, readb(&ch->ch_cls_uart->msr));
        }
}

/* Channel lock MUST be held before calling this function! */
static void cls_flush_uart_write(struct jsm_channel *ch)
{
        u8 tmp = 0;
        u8 i = 0;

        if (!ch)
                return;

        writeb((UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_XMIT),
                                                &ch->ch_cls_uart->isr_fcr);

        for (i = 0; i < 10; i++) {
                /* Check to see if the UART feels it completely flushed FIFO */
                tmp = readb(&ch->ch_cls_uart->isr_fcr);
                if (tmp & UART_FCR_CLEAR_XMIT) {
                        jsm_dbg(IOCTL, &ch->ch_bd->pci_dev,
                                "Still flushing TX UART... i: %d\n", i);
                        udelay(10);
                } else
                        break;
        }

        ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
}

/* Channel lock MUST be held before calling this function! */
static void cls_flush_uart_read(struct jsm_channel *ch)
{
        if (!ch)
                return;

        /*
         * For complete POSIX compatibility, we should be purging the
         * read FIFO in the UART here.
         *
         * However, clearing the read FIFO (UART_FCR_CLEAR_RCVR) also
         * incorrectly flushes write data as well as just basically trashing the
         * FIFO.
         *
         * Presumably, this is a bug in this UART.
         */

        udelay(10);
}

static void cls_send_start_character(struct jsm_channel *ch)
{
        if (!ch)
                return;

        if (ch->ch_startc != __DISABLED_CHAR) {
                ch->ch_xon_sends++;
                writeb(ch->ch_startc, &ch->ch_cls_uart->txrx);
        }
}

static void cls_send_stop_character(struct jsm_channel *ch)
{
        if (!ch)
                return;

        if (ch->ch_stopc != __DISABLED_CHAR) {
                ch->ch_xoff_sends++;
                writeb(ch->ch_stopc, &ch->ch_cls_uart->txrx);
        }
}

/*
 * cls_param()
 * Send any/all changes to the line to the UART.
 */
static void cls_param(struct jsm_channel *ch)
{
        u8 lcr = 0;
        u8 uart_lcr = 0;
        u8 ier = 0;
        u32 baud = 9600;
        int quot = 0;
        struct jsm_board *bd;
        int i;
        unsigned int cflag;

        bd = ch->ch_bd;
        if (!bd)
                return;

        /*
         * If baud rate is zero, flush queues, and set mval to drop DTR.
         */
        if ((ch->ch_c_cflag & (CBAUD)) == 0) {
                ch->ch_r_head = 0;
                ch->ch_r_tail = 0;
                ch->ch_e_head = 0;
                ch->ch_e_tail = 0;

                cls_flush_uart_write(ch);
                cls_flush_uart_read(ch);

                /* The baudrate is B0 so all modem lines are to be dropped. */
                ch->ch_flags |= (CH_BAUD0);
                ch->ch_mostat &= ~(UART_MCR_RTS | UART_MCR_DTR);
                cls_assert_modem_signals(ch);
                return;
        }

        cflag = C_BAUD(ch->uart_port.state->port.tty);
        baud = 9600;
        for (i = 0; i < ARRAY_SIZE(baud_rates); i++) {
                if (baud_rates[i].cflag == cflag) {
                        baud = baud_rates[i].rate;
                        break;
                }
        }

        if (ch->ch_flags & CH_BAUD0)
                ch->ch_flags &= ~(CH_BAUD0);

        if (ch->ch_c_cflag & PARENB)
                lcr |= UART_LCR_PARITY;

        if (!(ch->ch_c_cflag & PARODD))
                lcr |= UART_LCR_EPAR;

        /*
         * Not all platforms support mark/space parity,
         * so this will hide behind an ifdef.
         */
#ifdef CMSPAR
        if (ch->ch_c_cflag & CMSPAR)
                lcr |= UART_LCR_SPAR;
#endif

        if (ch->ch_c_cflag & CSTOPB)
                lcr |= UART_LCR_STOP;

        switch (ch->ch_c_cflag & CSIZE) {
        case CS5:
                lcr |= UART_LCR_WLEN5;
                break;
        case CS6:
                lcr |= UART_LCR_WLEN6;
                break;
        case CS7:
                lcr |= UART_LCR_WLEN7;
                break;
        case CS8:
        default:
                lcr |= UART_LCR_WLEN8;
                break;
        }

        ier = readb(&ch->ch_cls_uart->ier);
        uart_lcr = readb(&ch->ch_cls_uart->lcr);

        quot = ch->ch_bd->bd_dividend / baud;

        if (quot != 0) {
                writeb(UART_LCR_DLAB, &ch->ch_cls_uart->lcr);
                writeb((quot & 0xff), &ch->ch_cls_uart->txrx);
                writeb((quot >> 8), &ch->ch_cls_uart->ier);
                writeb(lcr, &ch->ch_cls_uart->lcr);
        }

        if (uart_lcr != lcr)
                writeb(lcr, &ch->ch_cls_uart->lcr);

        if (ch->ch_c_cflag & CREAD)
                ier |= (UART_IER_RDI | UART_IER_RLSI);

        ier |= (UART_IER_THRI | UART_IER_MSI);

        writeb(ier, &ch->ch_cls_uart->ier);

        if (ch->ch_c_cflag & CRTSCTS)
                cls_set_cts_flow_control(ch);
        else if (ch->ch_c_iflag & IXON) {
                /*
                 * If start/stop is set to disable,
                 * then we should disable flow control.
                 */
                if ((ch->ch_startc == __DISABLED_CHAR) ||
                        (ch->ch_stopc == __DISABLED_CHAR))
                        cls_set_no_output_flow_control(ch);
                else
                        cls_set_ixon_flow_control(ch);
        } else
                cls_set_no_output_flow_control(ch);

        if (ch->ch_c_cflag & CRTSCTS)
                cls_set_rts_flow_control(ch);
        else if (ch->ch_c_iflag & IXOFF) {
                /*
                 * If start/stop is set to disable,
                 * then we should disable flow control.
                 */
                if ((ch->ch_startc == __DISABLED_CHAR) ||
                        (ch->ch_stopc == __DISABLED_CHAR))
                        cls_set_no_input_flow_control(ch);
                else
                        cls_set_ixoff_flow_control(ch);
        } else
                cls_set_no_input_flow_control(ch);

        cls_assert_modem_signals(ch);

        /* get current status of the modem signals now */
        cls_parse_modem(ch, readb(&ch->ch_cls_uart->msr));
}

/*
 * cls_intr()
 *
 * Classic specific interrupt handler.
 */
static irqreturn_t cls_intr(int irq, void *voidbrd)
{
        struct jsm_board *brd = voidbrd;
        unsigned long lock_flags;
        unsigned char uart_poll;
        uint i = 0;

        /* Lock out the slow poller from running on this board. */
        spin_lock_irqsave(&brd->bd_intr_lock, lock_flags);

        /*
         * Check the board's global interrupt offset to see if we
         * acctually do have an interrupt pending on us.
         */
        uart_poll = readb(brd->re_map_membase + UART_CLASSIC_POLL_ADDR_OFFSET);

        jsm_dbg(INTR, &brd->pci_dev, "%s:%d uart_poll: %x\n",
                __FILE__, __LINE__, uart_poll);

        if (!uart_poll) {
                jsm_dbg(INTR, &brd->pci_dev,
                        "Kernel interrupted to me, but no pending interrupts...\n");
                spin_unlock_irqrestore(&brd->bd_intr_lock, lock_flags);
                return IRQ_NONE;
        }

        /* At this point, we have at least SOMETHING to service, dig further. */

        /* Parse each port to find out what caused the interrupt */
        for (i = 0; i < brd->nasync; i++)
                cls_parse_isr(brd, i);

        spin_unlock_irqrestore(&brd->bd_intr_lock, lock_flags);

        return IRQ_HANDLED;
}

/* Inits UART */
static void cls_uart_init(struct jsm_channel *ch)
{
        unsigned char lcrb = readb(&ch->ch_cls_uart->lcr);
        unsigned char isr_fcr = 0;

        writeb(0, &ch->ch_cls_uart->ier);

        /*
         * The Enhanced Register Set may only be accessed when
         * the Line Control Register is set to 0xBFh.
         */
        writeb(UART_EXAR654_ENHANCED_REGISTER_SET, &ch->ch_cls_uart->lcr);

        isr_fcr = readb(&ch->ch_cls_uart->isr_fcr);

        /* Turn on Enhanced/Extended controls */
        isr_fcr |= (UART_EXAR654_EFR_ECB);

        writeb(isr_fcr, &ch->ch_cls_uart->isr_fcr);

        /* Write old LCR value back out, which turns enhanced access off */
        writeb(lcrb, &ch->ch_cls_uart->lcr);

        /* Clear out UART and FIFO */
        readb(&ch->ch_cls_uart->txrx);

        writeb((UART_FCR_ENABLE_FIFO|UART_FCR_CLEAR_RCVR|UART_FCR_CLEAR_XMIT),
                                                 &ch->ch_cls_uart->isr_fcr);
        udelay(10);

        ch->ch_flags |= (CH_FIFO_ENABLED | CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);

        readb(&ch->ch_cls_uart->lsr);
        readb(&ch->ch_cls_uart->msr);
}

/*
 * Turns off UART.
 */
static void cls_uart_off(struct jsm_channel *ch)
{
        /* Stop all interrupts from accurring. */
        writeb(0, &ch->ch_cls_uart->ier);
}

/*
 * cls_get_uarts_bytes_left.
 * Returns 0 is nothing left in the FIFO, returns 1 otherwise.
 *
 * The channel lock MUST be held by the calling function.
 */
static u32 cls_get_uart_bytes_left(struct jsm_channel *ch)
{
        u8 left = 0;
        u8 lsr = readb(&ch->ch_cls_uart->lsr);

        /* Determine whether the Transmitter is empty or not */
        if (!(lsr & UART_LSR_TEMT))
                left = 1;
        else {
                ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                left = 0;
        }

        return left;
}

/*
 * cls_send_break.
 * Starts sending a break thru the UART.
 *
 * The channel lock MUST be held by the calling function.
 */
static void cls_send_break(struct jsm_channel *ch)
{
        /* Tell the UART to start sending the break */
        if (!(ch->ch_flags & CH_BREAK_SENDING)) {
                u8 temp = readb(&ch->ch_cls_uart->lcr);

                writeb((temp | UART_LCR_SBC), &ch->ch_cls_uart->lcr);
                ch->ch_flags |= (CH_BREAK_SENDING);
        }
}

/*
 * cls_send_immediate_char.
 * Sends a specific character as soon as possible to the UART,
 * jumping over any bytes that might be in the write queue.
 *
 * The channel lock MUST be held by the calling function.
 */
static void cls_send_immediate_char(struct jsm_channel *ch, unsigned char c)
{
        writeb(c, &ch->ch_cls_uart->txrx);
}

struct board_ops jsm_cls_ops = {
        .intr =                         cls_intr,
        .uart_init =                    cls_uart_init,
        .uart_off =                     cls_uart_off,
        .param =                        cls_param,
        .assert_modem_signals =         cls_assert_modem_signals,
        .flush_uart_write =             cls_flush_uart_write,
        .flush_uart_read =              cls_flush_uart_read,
        .disable_receiver =             cls_disable_receiver,
        .enable_receiver =              cls_enable_receiver,
        .send_break =                   cls_send_break,
        .clear_break =                  cls_clear_break,
        .send_start_character =         cls_send_start_character,
        .send_stop_character =          cls_send_stop_character,
        .copy_data_from_queue_to_uart = cls_copy_data_from_queue_to_uart,
        .get_uart_bytes_left =          cls_get_uart_bytes_left,
        .send_immediate_char =          cls_send_immediate_char
};