Merge tag 'sh-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

[cascardo/linux.git] / drivers / staging / dgnc / dgnc_neo.c

/*
 * Copyright 2003 Digi International (www.digi.com)
 *      Scott H Kilau <Scott_Kilau at digi dot com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 *
 *      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/kernel.h>
#include <linux/sched.h>        /* For jiffies, task states */
#include <linux/interrupt.h>    /* For tasklet and interrupt structs/defines */
#include <linux/delay.h>        /* For udelay */
#include <asm/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 "dgnc_driver.h"        /* Driver main header file */
#include "dgnc_neo.h"           /* Our header file */
#include "dgnc_tty.h"
#include "dgnc_trace.h"

static inline void neo_parse_lsr(struct dgnc_board *brd, uint port);
static inline void neo_parse_isr(struct dgnc_board *brd, uint port);
static void neo_copy_data_from_uart_to_queue(struct channel_t *ch);
static inline void neo_clear_break(struct channel_t *ch, int force);
static inline void neo_set_cts_flow_control(struct channel_t *ch);
static inline void neo_set_rts_flow_control(struct channel_t *ch);
static inline void neo_set_ixon_flow_control(struct channel_t *ch);
static inline void neo_set_ixoff_flow_control(struct channel_t *ch);
static inline void neo_set_no_output_flow_control(struct channel_t *ch);
static inline void neo_set_no_input_flow_control(struct channel_t *ch);
static inline void neo_set_new_start_stop_chars(struct channel_t *ch);
static void neo_parse_modem(struct channel_t *ch, uchar signals);
static void neo_tasklet(unsigned long data);
static void neo_vpd(struct dgnc_board *brd);
static void neo_uart_init(struct channel_t *ch);
static void neo_uart_off(struct channel_t *ch);
static int neo_drain(struct tty_struct *tty, uint seconds);
static void neo_param(struct tty_struct *tty);
static void neo_assert_modem_signals(struct channel_t *ch);
static void neo_flush_uart_write(struct channel_t *ch);
static void neo_flush_uart_read(struct channel_t *ch);
static void neo_disable_receiver(struct channel_t *ch);
static void neo_enable_receiver(struct channel_t *ch);
static void neo_send_break(struct channel_t *ch, int msecs);
static void neo_send_start_character(struct channel_t *ch);
static void neo_send_stop_character(struct channel_t *ch);
static void neo_copy_data_from_queue_to_uart(struct channel_t *ch);
static uint neo_get_uart_bytes_left(struct channel_t *ch);
static void neo_send_immediate_char(struct channel_t *ch, unsigned char c);
static irqreturn_t neo_intr(int irq, void *voidbrd);


struct board_ops dgnc_neo_ops = {
        .tasklet =                      neo_tasklet,
        .intr =                         neo_intr,
        .uart_init =                    neo_uart_init,
        .uart_off =                     neo_uart_off,
        .drain =                        neo_drain,
        .param =                        neo_param,
        .vpd =                          neo_vpd,
        .assert_modem_signals =         neo_assert_modem_signals,
        .flush_uart_write =             neo_flush_uart_write,
        .flush_uart_read =              neo_flush_uart_read,
        .disable_receiver =             neo_disable_receiver,
        .enable_receiver =              neo_enable_receiver,
        .send_break =                   neo_send_break,
        .send_start_character =         neo_send_start_character,
        .send_stop_character =          neo_send_stop_character,
        .copy_data_from_queue_to_uart = neo_copy_data_from_queue_to_uart,
        .get_uart_bytes_left =          neo_get_uart_bytes_left,
        .send_immediate_char =          neo_send_immediate_char
};

static uint dgnc_offset_table[8] = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };


/*
 * This function allows calls to ensure that all outstanding
 * PCI writes have been completed, by doing a PCI read against
 * a non-destructive, read-only location on the Neo card.
 *
 * In this case, we are reading the DVID (Read-only Device Identification)
 * value of the Neo card.
 */
static inline void neo_pci_posting_flush(struct dgnc_board *bd)
{
        readb(bd->re_map_membase + 0x8D);
}

static inline void neo_set_cts_flow_control(struct channel_t *ch)
{
        uchar ier = readb(&ch->ch_neo_uart->ier);
        uchar efr = readb(&ch->ch_neo_uart->efr);


        DPR_PARAM(("Setting CTSFLOW\n"));

        /* Turn on auto CTS flow control */
#if 1
        ier |= (UART_17158_IER_CTSDSR);
#else
        ier &= ~(UART_17158_IER_CTSDSR);
#endif

        efr |= (UART_17158_EFR_ECB | UART_17158_EFR_CTSDSR);

        /* Turn off auto Xon flow control */
        efr &= ~(UART_17158_EFR_IXON);

        /* Why? Becuz Exar's spec says we have to zero it out before setting it */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Turn on UART enhanced bits */
        writeb(efr, &ch->ch_neo_uart->efr);

        /* Turn on table D, with 8 char hi/low watermarks */
        writeb((UART_17158_FCTR_TRGD | UART_17158_FCTR_RTS_4DELAY), &ch->ch_neo_uart->fctr);

        /* Feed the UART our trigger levels */
        writeb(8, &ch->ch_neo_uart->tfifo);
        ch->ch_t_tlevel = 8;

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

        neo_pci_posting_flush(ch->ch_bd);
}


static inline void neo_set_rts_flow_control(struct channel_t *ch)
{
        uchar ier = readb(&ch->ch_neo_uart->ier);
        uchar efr = readb(&ch->ch_neo_uart->efr);

        DPR_PARAM(("Setting RTSFLOW\n"));

        /* Turn on auto RTS flow control */
#if 1
        ier |= (UART_17158_IER_RTSDTR);
#else
        ier &= ~(UART_17158_IER_RTSDTR);
#endif
        efr |= (UART_17158_EFR_ECB | UART_17158_EFR_RTSDTR);

        /* Turn off auto Xoff flow control */
        ier &= ~(UART_17158_IER_XOFF);
        efr &= ~(UART_17158_EFR_IXOFF);

        /* Why? Becuz Exar's spec says we have to zero it out before setting it */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Turn on UART enhanced bits */
        writeb(efr, &ch->ch_neo_uart->efr);

        writeb((UART_17158_FCTR_TRGD | UART_17158_FCTR_RTS_4DELAY), &ch->ch_neo_uart->fctr);
        ch->ch_r_watermark = 4;

        writeb(32, &ch->ch_neo_uart->rfifo);
        ch->ch_r_tlevel = 32;

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

        /*
         * From the Neo UART spec sheet:
         * The auto RTS/DTR function must be started by asserting
         * RTS/DTR# output pin (MCR bit-0 or 1 to logic 1 after
         * it is enabled.
         */
        ch->ch_mostat |= (UART_MCR_RTS);

        neo_pci_posting_flush(ch->ch_bd);
}


static inline void neo_set_ixon_flow_control(struct channel_t *ch)
{
        uchar ier = readb(&ch->ch_neo_uart->ier);
        uchar efr = readb(&ch->ch_neo_uart->efr);

        DPR_PARAM(("Setting IXON FLOW\n"));

        /* Turn off auto CTS flow control */
        ier &= ~(UART_17158_IER_CTSDSR);
        efr &= ~(UART_17158_EFR_CTSDSR);

        /* Turn on auto Xon flow control */
        efr |= (UART_17158_EFR_ECB | UART_17158_EFR_IXON);

        /* Why? Becuz Exar's spec says we have to zero it out before setting it */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Turn on UART enhanced bits */
        writeb(efr, &ch->ch_neo_uart->efr);

        writeb((UART_17158_FCTR_TRGD | UART_17158_FCTR_RTS_8DELAY), &ch->ch_neo_uart->fctr);
        ch->ch_r_watermark = 4;

        writeb(32, &ch->ch_neo_uart->rfifo);
        ch->ch_r_tlevel = 32;

        /* Tell UART what start/stop chars it should be looking for */
        writeb(ch->ch_startc, &ch->ch_neo_uart->xonchar1);
        writeb(0, &ch->ch_neo_uart->xonchar2);

        writeb(ch->ch_stopc, &ch->ch_neo_uart->xoffchar1);
        writeb(0, &ch->ch_neo_uart->xoffchar2);

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

        neo_pci_posting_flush(ch->ch_bd);
}


static inline void neo_set_ixoff_flow_control(struct channel_t *ch)
{
        uchar ier = readb(&ch->ch_neo_uart->ier);
        uchar efr = readb(&ch->ch_neo_uart->efr);

        DPR_PARAM(("Setting IXOFF FLOW\n"));

        /* Turn off auto RTS flow control */
        ier &= ~(UART_17158_IER_RTSDTR);
        efr &= ~(UART_17158_EFR_RTSDTR);

        /* Turn on auto Xoff flow control */
        ier |= (UART_17158_IER_XOFF);
        efr |= (UART_17158_EFR_ECB | UART_17158_EFR_IXOFF);

        /* Why? Becuz Exar's spec says we have to zero it out before setting it */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Turn on UART enhanced bits */
        writeb(efr, &ch->ch_neo_uart->efr);

        /* Turn on table D, with 8 char hi/low watermarks */
        writeb((UART_17158_FCTR_TRGD | UART_17158_FCTR_RTS_8DELAY), &ch->ch_neo_uart->fctr);

        writeb(8, &ch->ch_neo_uart->tfifo);
        ch->ch_t_tlevel = 8;

        /* Tell UART what start/stop chars it should be looking for */
        writeb(ch->ch_startc, &ch->ch_neo_uart->xonchar1);
        writeb(0, &ch->ch_neo_uart->xonchar2);

        writeb(ch->ch_stopc, &ch->ch_neo_uart->xoffchar1);
        writeb(0, &ch->ch_neo_uart->xoffchar2);

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

        neo_pci_posting_flush(ch->ch_bd);
}


static inline void neo_set_no_input_flow_control(struct channel_t *ch)
{
        uchar ier = readb(&ch->ch_neo_uart->ier);
        uchar efr = readb(&ch->ch_neo_uart->efr);

        DPR_PARAM(("Unsetting Input FLOW\n"));

        /* Turn off auto RTS flow control */
        ier &= ~(UART_17158_IER_RTSDTR);
        efr &= ~(UART_17158_EFR_RTSDTR);

        /* Turn off auto Xoff flow control */
        ier &= ~(UART_17158_IER_XOFF);
        if (ch->ch_c_iflag & IXON)
                efr &= ~(UART_17158_EFR_IXOFF);
        else
                efr &= ~(UART_17158_EFR_ECB | UART_17158_EFR_IXOFF);


        /* Why? Becuz Exar's spec says we have to zero it out before setting it */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Turn on UART enhanced bits */
        writeb(efr, &ch->ch_neo_uart->efr);

        /* Turn on table D, with 8 char hi/low watermarks */
        writeb((UART_17158_FCTR_TRGD | UART_17158_FCTR_RTS_8DELAY), &ch->ch_neo_uart->fctr);

        ch->ch_r_watermark = 0;

        writeb(16, &ch->ch_neo_uart->tfifo);
        ch->ch_t_tlevel = 16;

        writeb(16, &ch->ch_neo_uart->rfifo);
        ch->ch_r_tlevel = 16;

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

        neo_pci_posting_flush(ch->ch_bd);
}


static inline void neo_set_no_output_flow_control(struct channel_t *ch)
{
        uchar ier = readb(&ch->ch_neo_uart->ier);
        uchar efr = readb(&ch->ch_neo_uart->efr);

        DPR_PARAM(("Unsetting Output FLOW\n"));

        /* Turn off auto CTS flow control */
        ier &= ~(UART_17158_IER_CTSDSR);
        efr &= ~(UART_17158_EFR_CTSDSR);

        /* Turn off auto Xon flow control */
        if (ch->ch_c_iflag & IXOFF)
                efr &= ~(UART_17158_EFR_IXON);
        else
                efr &= ~(UART_17158_EFR_ECB | UART_17158_EFR_IXON);

        /* Why? Becuz Exar's spec says we have to zero it out before setting it */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Turn on UART enhanced bits */
        writeb(efr, &ch->ch_neo_uart->efr);

        /* Turn on table D, with 8 char hi/low watermarks */
        writeb((UART_17158_FCTR_TRGD | UART_17158_FCTR_RTS_8DELAY), &ch->ch_neo_uart->fctr);

        ch->ch_r_watermark = 0;

        writeb(16, &ch->ch_neo_uart->tfifo);
        ch->ch_t_tlevel = 16;

        writeb(16, &ch->ch_neo_uart->rfifo);
        ch->ch_r_tlevel = 16;

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

        neo_pci_posting_flush(ch->ch_bd);
}


/* change UARTs start/stop chars */
static inline void neo_set_new_start_stop_chars(struct channel_t *ch)
{

        /* if hardware flow control is set, then skip this whole thing */
        if (ch->ch_digi.digi_flags & (CTSPACE | RTSPACE) || ch->ch_c_cflag & CRTSCTS)
                return;

        DPR_PARAM(("In new start stop chars\n"));

        /* Tell UART what start/stop chars it should be looking for */
        writeb(ch->ch_startc, &ch->ch_neo_uart->xonchar1);
        writeb(0, &ch->ch_neo_uart->xonchar2);

        writeb(ch->ch_stopc, &ch->ch_neo_uart->xoffchar1);
        writeb(0, &ch->ch_neo_uart->xoffchar2);

        neo_pci_posting_flush(ch->ch_bd);
}


/*
 * No locks are assumed to be held when calling this function.
 */
static inline void neo_clear_break(struct channel_t *ch, int force)
{
        ulong lock_flags;

        DGNC_LOCK(ch->ch_lock, lock_flags);

        /* Bail if we aren't currently sending a break. */
        if (!ch->ch_stop_sending_break) {
                DGNC_UNLOCK(ch->ch_lock, lock_flags);
                return;
        }

        /* Turn break off, and unset some variables */
        if (ch->ch_flags & CH_BREAK_SENDING) {
                if ((jiffies >= ch->ch_stop_sending_break) || force) {
                        uchar temp = readb(&ch->ch_neo_uart->lcr);
                        writeb((temp & ~UART_LCR_SBC), &ch->ch_neo_uart->lcr);
                        neo_pci_posting_flush(ch->ch_bd);
                        ch->ch_flags &= ~(CH_BREAK_SENDING);
                        ch->ch_stop_sending_break = 0;
                        DPR_IOCTL(("Finishing UART_LCR_SBC! finished: %lx\n", jiffies));
                }
        }
        DGNC_UNLOCK(ch->ch_lock, lock_flags);
}


/*
 * Parse the ISR register.
 */
static inline void neo_parse_isr(struct dgnc_board *brd, uint port)
{
        struct channel_t *ch;
        uchar isr;
        uchar cause;
        ulong lock_flags;

        if (!brd || brd->magic != DGNC_BOARD_MAGIC)
                return;

        if (port > brd->maxports)
                return;

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

        /* Here we try to figure out what caused the interrupt to happen */
        while (1) {

                isr = readb(&ch->ch_neo_uart->isr_fcr);

                /* Bail if no pending interrupt */
                if (isr & UART_IIR_NO_INT)  {
                        break;
                }

                /*
                 * Yank off the upper 2 bits, which just show that the FIFO's are enabled.
                 */
                isr &= ~(UART_17158_IIR_FIFO_ENABLED);

                DPR_INTR(("%s:%d isr: %x\n", __FILE__, __LINE__, isr));

                if (isr & (UART_17158_IIR_RDI_TIMEOUT | UART_IIR_RDI)) {
                        /* Read data from uart -> queue */
                        brd->intr_rx++;
                        ch->ch_intr_rx++;
                        neo_copy_data_from_uart_to_queue(ch);

                        /* Call our tty layer to enforce queue flow control if needed. */
                        DGNC_LOCK(ch->ch_lock, lock_flags);
                        dgnc_check_queue_flow_control(ch);
                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                }

                if (isr & UART_IIR_THRI) {
                        brd->intr_tx++;
                        ch->ch_intr_tx++;
                        /* Transfer data (if any) from Write Queue -> UART. */
                        DGNC_LOCK(ch->ch_lock, lock_flags);
                        ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                        neo_copy_data_from_queue_to_uart(ch);
                }

                if (isr & UART_17158_IIR_XONXOFF) {
                        cause = readb(&ch->ch_neo_uart->xoffchar1);

                        DPR_INTR(("Port %d. Got ISR_XONXOFF: cause:%x\n", port, cause));

                        /*
                         * Since the UART detected either an XON or
                         * XOFF match, we need to figure out which
                         * one it was, so we can suspend or resume data flow.
                         */
                        if (cause == UART_17158_XON_DETECT) {
                                /* Is output stopped right now, if so, resume it */
                                if (brd->channels[port]->ch_flags & CH_STOP) {
                                        DGNC_LOCK(ch->ch_lock, lock_flags);
                                        ch->ch_flags &= ~(CH_STOP);
                                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                                }
                                DPR_INTR(("Port %d. XON detected in incoming data\n", port));
                        }
                        else if (cause == UART_17158_XOFF_DETECT) {
                                if (!(brd->channels[port]->ch_flags & CH_STOP)) {
                                        DGNC_LOCK(ch->ch_lock, lock_flags);
                                        ch->ch_flags |= CH_STOP;
                                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                                        DPR_INTR(("Setting CH_STOP\n"));
                                }
                                DPR_INTR(("Port: %d. XOFF detected in incoming data\n", port));
                        }
                }

                if (isr & UART_17158_IIR_HWFLOW_STATE_CHANGE) {
                        /*
                         * If we get here, this means the hardware is doing auto flow control.
                         * Check to see whether RTS/DTR or CTS/DSR caused this interrupt.
                         */
                        brd->intr_modem++;
                        ch->ch_intr_modem++;
                        cause = readb(&ch->ch_neo_uart->mcr);
                        /* Which pin is doing auto flow? RTS or DTR? */
                        if ((cause & 0x4) == 0) {
                                if (cause & UART_MCR_RTS) {
                                        DGNC_LOCK(ch->ch_lock, lock_flags);
                                        ch->ch_mostat |= UART_MCR_RTS;
                                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                                }
                                else {
                                        DGNC_LOCK(ch->ch_lock, lock_flags);
                                        ch->ch_mostat &= ~(UART_MCR_RTS);
                                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                                }
                        } else {
                                if (cause & UART_MCR_DTR) {
                                        DGNC_LOCK(ch->ch_lock, lock_flags);
                                        ch->ch_mostat |= UART_MCR_DTR;
                                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                                }
                                else {
                                        DGNC_LOCK(ch->ch_lock, lock_flags);
                                        ch->ch_mostat &= ~(UART_MCR_DTR);
                                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                                }
                        }
                }

                /* Parse any modem signal changes */
                DPR_INTR(("MOD_STAT: sending to parse_modem_sigs\n"));
                neo_parse_modem(ch, readb(&ch->ch_neo_uart->msr));
        }
}


static inline void neo_parse_lsr(struct dgnc_board *brd, uint port)
{
        struct channel_t *ch;
        int linestatus;
        ulong lock_flags;

        if (!brd)
                return;

        if (brd->magic != DGNC_BOARD_MAGIC)
                return;

        if (port > brd->maxports)
                return;

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

        linestatus = readb(&ch->ch_neo_uart->lsr);

        DPR_INTR(("%s:%d port: %d linestatus: %x\n", __FILE__, __LINE__, port, linestatus));

        ch->ch_cached_lsr |= linestatus;

        if (ch->ch_cached_lsr & UART_LSR_DR) {
                brd->intr_rx++;
                ch->ch_intr_rx++;
                /* Read data from uart -> queue */
                neo_copy_data_from_uart_to_queue(ch);
                DGNC_LOCK(ch->ch_lock, lock_flags);
                dgnc_check_queue_flow_control(ch);
                DGNC_UNLOCK(ch->ch_lock, lock_flags);
        }

        /*
         * This is a special flag. It indicates that at least 1
         * RX error (parity, framing, or break) has happened.
         * Mark this in our struct, which will tell me that I have
         *to do the special RX+LSR read for this FIFO load.
         */
        if (linestatus & UART_17158_RX_FIFO_DATA_ERROR) {
                DPR_INTR(("%s:%d Port: %d Got an RX error, need to parse LSR\n",
                        __FILE__, __LINE__, port));
        }

        /*
         * The next 3 tests should *NOT* happen, as the above test
         * should encapsulate all 3... At least, thats what Exar says.
         */

        if (linestatus & UART_LSR_PE) {
                ch->ch_err_parity++;
                DPR_INTR(("%s:%d Port: %d. PAR ERR!\n", __FILE__, __LINE__, port));
        }

        if (linestatus & UART_LSR_FE) {
                ch->ch_err_frame++;
                DPR_INTR(("%s:%d Port: %d. FRM ERR!\n", __FILE__, __LINE__, port));
        }

        if (linestatus & UART_LSR_BI) {
                ch->ch_err_break++;
                DPR_INTR(("%s:%d Port: %d. BRK INTR!\n", __FILE__, __LINE__, port));
        }

        if (linestatus & UART_LSR_OE) {
                /*
                 * Rx Oruns. Exar says that an orun will NOT corrupt
                 * the FIFO. It will just replace the holding register
                 * with this new data byte. So basically just ignore this.
                 * Probably we should eventually have an orun stat in our driver...
                 */
                ch->ch_err_overrun++;
                DPR_INTR(("%s:%d Port: %d. Rx Overrun!\n", __FILE__, __LINE__, port));
        }

        if (linestatus & UART_LSR_THRE) {
                brd->intr_tx++;
                ch->ch_intr_tx++;
                DGNC_LOCK(ch->ch_lock, lock_flags);
                ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                DGNC_UNLOCK(ch->ch_lock, lock_flags);

                /* Transfer data (if any) from Write Queue -> UART. */
                neo_copy_data_from_queue_to_uart(ch);
        }
        else if (linestatus & UART_17158_TX_AND_FIFO_CLR) {
                brd->intr_tx++;
                ch->ch_intr_tx++;
                DGNC_LOCK(ch->ch_lock, lock_flags);
                ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                DGNC_UNLOCK(ch->ch_lock, lock_flags);

                /* Transfer data (if any) from Write Queue -> UART. */
                neo_copy_data_from_queue_to_uart(ch);
        }
}


/*
 * neo_param()
 * Send any/all changes to the line to the UART.
 */
static void neo_param(struct tty_struct *tty)
{
        uchar lcr = 0;
        uchar uart_lcr = 0;
        uchar ier = 0;
        uchar uart_ier = 0;
        uint baud = 9600;
        int quot = 0;
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t   *un;

        if (!tty || tty->magic != TTY_MAGIC) {
                return;
        }

        un = (struct un_t *) tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC) {
                return;
        }

        ch = un->un_ch;
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC) {
                return;
        }

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC) {
                return;
        }

        DPR_PARAM(("param start: tdev: %x cflags: %x oflags: %x iflags: %x\n",
                ch->ch_tun.un_dev, ch->ch_c_cflag, ch->ch_c_oflag, ch->ch_c_iflag));

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

                neo_flush_uart_write(ch);
                neo_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);
                neo_assert_modem_signals(ch);
                ch->ch_old_baud = 0;
                return;

        } else if (ch->ch_custom_speed) {

                baud = ch->ch_custom_speed;
                /* Handle transition from B0 */
                if (ch->ch_flags & CH_BAUD0) {
                        ch->ch_flags &= ~(CH_BAUD0);

                        /*
                         * Bring back up RTS and DTR...
                         * Also handle RTS or DTR toggle if set.
                         */
                        if (!(ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE))
                                ch->ch_mostat |= (UART_MCR_RTS);
                        if (!(ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE))
                                ch->ch_mostat |= (UART_MCR_DTR);
                }
        } else {
                int iindex = 0;
                int jindex = 0;

                ulong bauds[4][16] = {
                        { /* slowbaud */
                                0,      50,     75,     110,
                                134,    150,    200,    300,
                                600,    1200,   1800,   2400,
                                4800,   9600,   19200,  38400 },
                        { /* slowbaud & CBAUDEX */
                                0,      57600,  115200, 230400,
                                460800, 150,    200,    921600,
                                600,    1200,   1800,   2400,
                                4800,   9600,   19200,  38400 },
                        { /* fastbaud */
                                0,      57600,   76800, 115200,
                                131657, 153600, 230400, 460800,
                                921600, 1200,   1800,   2400,
                                4800,   9600,   19200,  38400 },
                        { /* fastbaud & CBAUDEX */
                                0,      57600,  115200, 230400,
                                460800, 150,    200,    921600,
                                600,    1200,   1800,   2400,
                                4800,   9600,   19200,  38400 }
                };

                /* Only use the TXPrint baud rate if the terminal unit is NOT open */
                if (!(ch->ch_tun.un_flags & UN_ISOPEN) && (un->un_type == DGNC_PRINT))
                        baud = C_BAUD(ch->ch_pun.un_tty) & 0xff;
                else
                        baud = C_BAUD(ch->ch_tun.un_tty) & 0xff;

                if (ch->ch_c_cflag & CBAUDEX)
                        iindex = 1;

                if (ch->ch_digi.digi_flags & DIGI_FAST)
                        iindex += 2;

                jindex = baud;

                if ((iindex >= 0) && (iindex < 4) && (jindex >= 0) && (jindex < 16)) {
                        baud = bauds[iindex][jindex];
                } else {
                        DPR_IOCTL(("baud indices were out of range (%d)(%d)",
                                iindex, jindex));
                        baud = 0;
                }

                if (baud == 0)
                        baud = 9600;

                /* Handle transition from B0 */
                if (ch->ch_flags & CH_BAUD0) {
                        ch->ch_flags &= ~(CH_BAUD0);

                        /*
                         * Bring back up RTS and DTR...
                         * Also handle RTS or DTR toggle if set.
                         */
                        if (!(ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE))
                                ch->ch_mostat |= (UART_MCR_RTS);
                        if (!(ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE))
                                ch->ch_mostat |= (UART_MCR_DTR);
                }
        }

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

        if (baud == 0)
                baud = 9600;

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

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

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

        if (ch->ch_c_cflag & CREAD) {
                ier |= (UART_IER_RDI | UART_IER_RLSI);
        }
        else {
                ier &= ~(UART_IER_RDI | UART_IER_RLSI);
        }

        /*
         * Have the UART interrupt on modem signal changes ONLY when
         * we are in hardware flow control mode, or CLOCAL/FORCEDCD is not set.
         */
        if ((ch->ch_digi.digi_flags & CTSPACE) || (ch->ch_digi.digi_flags & RTSPACE) ||
                (ch->ch_c_cflag & CRTSCTS) || !(ch->ch_digi.digi_flags & DIGI_FORCEDCD) ||
                !(ch->ch_c_cflag & CLOCAL))
        {
                ier |= UART_IER_MSI;
        }
        else {
                ier &= ~UART_IER_MSI;
        }

        ier |= UART_IER_THRI;

        if (ier != uart_ier)
                writeb(ier, &ch->ch_neo_uart->ier);

        /* Set new start/stop chars */
        neo_set_new_start_stop_chars(ch);

        if (ch->ch_digi.digi_flags & CTSPACE || ch->ch_c_cflag & CRTSCTS) {
                neo_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 == _POSIX_VDISABLE) || (ch->ch_stopc == _POSIX_VDISABLE))
                        neo_set_no_output_flow_control(ch);
                else
                        neo_set_ixon_flow_control(ch);
        }
        else {
                neo_set_no_output_flow_control(ch);
        }

        if (ch->ch_digi.digi_flags & RTSPACE || ch->ch_c_cflag & CRTSCTS) {
                neo_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 == _POSIX_VDISABLE) || (ch->ch_stopc == _POSIX_VDISABLE))
                        neo_set_no_input_flow_control(ch);
                else
                        neo_set_ixoff_flow_control(ch);
        }
        else {
                neo_set_no_input_flow_control(ch);
        }

        /*
         * Adjust the RX FIFO Trigger level if baud is less than 9600.
         * Not exactly elegant, but this is needed because of the Exar chip's
         * delay on firing off the RX FIFO interrupt on slower baud rates.
         */
        if (baud < 9600) {
                writeb(1, &ch->ch_neo_uart->rfifo);
                ch->ch_r_tlevel = 1;
        }

        neo_assert_modem_signals(ch);

        /* Get current status of the modem signals now */
        neo_parse_modem(ch, readb(&ch->ch_neo_uart->msr));
}


/*
 * Our board poller function.
 */
static void neo_tasklet(unsigned long data)
{
        struct dgnc_board *bd = (struct dgnc_board *) data;
        struct channel_t *ch;
        ulong  lock_flags;
        int i;
        int state = 0;
        int ports = 0;

        if (!bd || bd->magic != DGNC_BOARD_MAGIC) {
                APR(("poll_tasklet() - NULL or bad bd.\n"));
                return;
        }

        /* Cache a couple board values */
        DGNC_LOCK(bd->bd_lock, lock_flags);
        state = bd->state;
        ports = bd->nasync;
        DGNC_UNLOCK(bd->bd_lock, lock_flags);

        /*
         * Do NOT allow the interrupt routine to read the intr registers
         * Until we release this lock.
         */
        DGNC_LOCK(bd->bd_intr_lock, lock_flags);

        /*
         * If board is ready, parse deeper to see if there is anything to do.
         */
        if ((state == BOARD_READY) && (ports > 0)) {
                /* Loop on each port */
                for (i = 0; i < ports; i++) {
                        ch = bd->channels[i];

                        /* Just being careful... */
                        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                                continue;

                        /*
                         * NOTE: Remember you CANNOT hold any channel
                         * locks when calling the input routine.
                         *
                         * During input processing, its possible we
                         * will call the Linux ld, which might in turn,
                         * do a callback right back into us, resulting
                         * in us trying to grab the channel lock twice!
                         */
                        dgnc_input(ch);

                        /*
                         * Channel lock is grabbed and then released
                         * inside both of these routines, but neither
                         * call anything else that could call back into us.
                         */
                        neo_copy_data_from_queue_to_uart(ch);
                        dgnc_wakeup_writes(ch);

                        /*
                         * Call carrier carrier function, in case something
                         * has changed.
                         */
                        dgnc_carrier(ch);

                        /*
                         * Check to see if we need to turn off a sending break.
                         * The timing check is done inside clear_break()
                         */
                        if (ch->ch_stop_sending_break)
                                neo_clear_break(ch, 0);
                }
        }

        /* Allow interrupt routine to access the interrupt register again */
        DGNC_UNLOCK(bd->bd_intr_lock, lock_flags);

}


/*
 * dgnc_neo_intr()
 *
 * Neo specific interrupt handler.
 */
static irqreturn_t neo_intr(int irq, void *voidbrd)
{
        struct dgnc_board *brd = (struct dgnc_board *) voidbrd;
        struct channel_t *ch;
        int port = 0;
        int type = 0;
        int current_port;
        u32 tmp;
        u32 uart_poll;
        unsigned long lock_flags;
        unsigned long lock_flags2;

        if (!brd) {
                APR(("Received interrupt (%d) with null board associated\n", irq));
                return IRQ_NONE;
        }

        /*
         * Check to make sure its for us.
         */
        if (brd->magic != DGNC_BOARD_MAGIC) {
                APR(("Received interrupt (%d) with a board pointer that wasn't ours!\n", irq));
                return IRQ_NONE;
        }

        brd->intr_count++;

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

        /*
         * Read in "extended" IRQ information from the 32bit Neo register.
         * Bits 0-7: What port triggered the interrupt.
         * Bits 8-31: Each 3bits indicate what type of interrupt occurred.
         */
        uart_poll = readl(brd->re_map_membase + UART_17158_POLL_ADDR_OFFSET);

        DPR_INTR(("%s:%d uart_poll: %x\n", __FILE__, __LINE__, uart_poll));

        /*
         * If 0, no interrupts pending.
         * This can happen if the IRQ is shared among a couple Neo/Classic boards.
         */
        if (!uart_poll) {
                DPR_INTR(("Kernel interrupted to me, but no pending interrupts...\n"));
                DGNC_UNLOCK(brd->bd_intr_lock, lock_flags);
                return IRQ_NONE;
        }

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

        current_port = 0;

        /* Loop on each port */
        while ((uart_poll & 0xff) != 0) {

                tmp = uart_poll;

                /* Check current port to see if it has interrupt pending */
                if ((tmp & dgnc_offset_table[current_port]) != 0) {
                        port = current_port;
                        type = tmp >> (8 + (port * 3));
                        type &= 0x7;
                } else {
                        current_port++;
                        continue;
                }

                DPR_INTR(("%s:%d port: %x type: %x\n", __FILE__, __LINE__, port, type));

                /* Remove this port + type from uart_poll */
                uart_poll &= ~(dgnc_offset_table[port]);

                if (!type) {
                        /* If no type, just ignore it, and move onto next port */
                        DPR_INTR(("Interrupt with no type! port: %d\n", port));
                        continue;
                }

                /* Switch on type of interrupt we have */
                switch (type) {

                case UART_17158_RXRDY_TIMEOUT:
                        /*
                         * RXRDY Time-out is cleared by reading data in the
                         * RX FIFO until it falls below the trigger level.
                         */

                        /* Verify the port is in range. */
                        if (port > brd->nasync)
                                continue;

                        ch = brd->channels[port];
                        neo_copy_data_from_uart_to_queue(ch);

                        /* Call our tty layer to enforce queue flow control if needed. */
                        DGNC_LOCK(ch->ch_lock, lock_flags2);
                        dgnc_check_queue_flow_control(ch);
                        DGNC_UNLOCK(ch->ch_lock, lock_flags2);

                        continue;

                case UART_17158_RX_LINE_STATUS:
                        /*
                         * RXRDY and RX LINE Status (logic OR of LSR[4:1])
                         */
                        neo_parse_lsr(brd, port);
                        continue;

                case UART_17158_TXRDY:
                        /*
                         * TXRDY interrupt clears after reading ISR register for the UART channel.
                         */

                        /*
                         * Yes, this is odd...
                         * Why would I check EVERY possibility of type of
                         * interrupt, when we know its TXRDY???
                         * Becuz for some reason, even tho we got triggered for TXRDY,
                         * it seems to be occasionally wrong. Instead of TX, which
                         * it should be, I was getting things like RXDY too. Weird.
                         */
                        neo_parse_isr(brd, port);
                        continue;

                case UART_17158_MSR:
                        /*
                         * MSR or flow control was seen.
                         */
                        neo_parse_isr(brd, port);
                        continue;

                default:
                        /*
                         * The UART triggered us with a bogus interrupt type.
                         * It appears the Exar chip, when REALLY bogged down, will throw
                         * these once and awhile.
                         * Its harmless, just ignore it and move on.
                         */
                        DPR_INTR(("%s:%d Unknown Interrupt type: %x\n", __FILE__, __LINE__, type));
                        continue;
                }
        }

        /*
         * Schedule tasklet to more in-depth servicing at a better time.
         */
        tasklet_schedule(&brd->helper_tasklet);

        DGNC_UNLOCK(brd->bd_intr_lock, lock_flags);

        DPR_INTR(("dgnc_intr finish.\n"));
        return IRQ_HANDLED;
}


/*
 * Neo specific way of turning off the receiver.
 * Used as a way to enforce queue flow control when in
 * hardware flow control mode.
 */
static void neo_disable_receiver(struct channel_t *ch)
{
        uchar tmp = readb(&ch->ch_neo_uart->ier);
        tmp &= ~(UART_IER_RDI);
        writeb(tmp, &ch->ch_neo_uart->ier);
        neo_pci_posting_flush(ch->ch_bd);
}


/*
 * Neo specific way of turning on the receiver.
 * Used as a way to un-enforce queue flow control when in
 * hardware flow control mode.
 */
static void neo_enable_receiver(struct channel_t *ch)
{
        uchar tmp = readb(&ch->ch_neo_uart->ier);
        tmp |= (UART_IER_RDI);
        writeb(tmp, &ch->ch_neo_uart->ier);
        neo_pci_posting_flush(ch->ch_bd);
}


static void neo_copy_data_from_uart_to_queue(struct channel_t *ch)
{
        int qleft = 0;
        uchar linestatus = 0;
        uchar error_mask = 0;
        int n = 0;
        int total = 0;
        ushort head;
        ushort tail;
        ulong lock_flags;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        DGNC_LOCK(ch->ch_lock, 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;

        /*
         * If the UART is not in FIFO mode, force the FIFO copy to
         * NOT be run, by setting total to 0.
         *
         * On the other hand, if the UART IS in FIFO mode, then ask
         * the UART to give us an approximation of data it has RX'ed.
         */
        if (!(ch->ch_flags & CH_FIFO_ENABLED))
                total = 0;
        else {
                total = readb(&ch->ch_neo_uart->rfifo);

                /*
                 * EXAR chip bug - RX FIFO COUNT - Fudge factor.
                 *
                 * This resolves a problem/bug with the Exar chip that sometimes
                 * returns a bogus value in the rfifo register.
                 * The count can be any where from 0-3 bytes "off".
                 * Bizarre, but true.
                 */
                if ((ch->ch_bd->dvid & 0xf0) >= UART_XR17E158_DVID) {
                        total -= 1;
                }
                else {
                        total -= 3;
                }
        }


        /*
         * Finally, bound the copy to make sure we don't overflow
         * our own queue...
         * The byte by byte copy loop below this loop this will
         * deal with the queue overflow possibility.
         */
        total = min(total, qleft);

        while (total > 0) {

                /*
                 * Grab the linestatus register, we need to check
                 * to see if there are any errors in the FIFO.
                 */
                linestatus = readb(&ch->ch_neo_uart->lsr);

                /*
                 * Break out if there is a FIFO error somewhere.
                 * This will allow us to go byte by byte down below,
                 * finding the exact location of the error.
                 */
                if (linestatus & UART_17158_RX_FIFO_DATA_ERROR)
                        break;

                /* Make sure we don't go over the end of our queue */
                n = min(((uint) total), (RQUEUESIZE - (uint) head));

                /*
                 * Cut down n even further if needed, this is to fix
                 * a problem with memcpy_fromio() with the Neo on the
                 * IBM pSeries platform.
                 * 15 bytes max appears to be the magic number.
                 */
                n = min((uint) n, (uint) 12);

                /*
                 * Since we are grabbing the linestatus register, which
                 * will reset some bits after our read, we need to ensure
                 * we don't miss our TX FIFO emptys.
                 */
                if (linestatus & (UART_LSR_THRE | UART_17158_TX_AND_FIFO_CLR)) {
                        ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                }

                linestatus = 0;

                /* Copy data from uart to the queue */
                memcpy_fromio(ch->ch_rqueue + head, &ch->ch_neo_uart->txrxburst, n);
                dgnc_sniff_nowait_nolock(ch, "UART READ", ch->ch_rqueue + head, n);

                /*
                 * Since RX_FIFO_DATA_ERROR was 0, we are guarenteed
                 * that all the data currently in the FIFO is free of
                 * breaks and parity/frame/orun errors.
                 */
                memset(ch->ch_equeue + head, 0, n);

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

        /*
         * 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;

        /*
         * Now cleanup any leftover bytes still in the UART.
         * Also deal with any possible queue overflow here as well.
         */
        while (1) {

                /*
                 * Its possible we have a linestatus from the loop above
                 * this, so we "OR" on any extra bits.
                 */
                linestatus |= readb(&ch->ch_neo_uart->lsr);

                /*
                 * If the chip tells us there is no more data pending to
                 * be read, we can then leave.
                 * But before we do, cache the linestatus, just in case.
                 */
                if (!(linestatus & UART_LSR_DR)) {
                        ch->ch_cached_lsr = linestatus;
                        break;
                }

                /* No need to store this bit */
                linestatus &= ~UART_LSR_DR;

                /*
                 * Since we are grabbing the linestatus register, which
                 * will reset some bits after our read, we need to ensure
                 * we don't miss our TX FIFO emptys.
                 */
                if (linestatus & (UART_LSR_THRE | UART_17158_TX_AND_FIFO_CLR)) {
                        linestatus &= ~(UART_LSR_THRE | UART_17158_TX_AND_FIFO_CLR);
                        ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
                }

                /*
                 * Discard character if we are ignoring the error mask.
                 */
                if (linestatus & error_mask)  {
                        uchar discard;
                        linestatus = 0;
                        memcpy_fromio(&discard, &ch->ch_neo_uart->txrxburst, 1);
                        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) {
                        DPR_READ(("Queue full, dropping DATA:%x LSR:%x\n",
                                ch->ch_rqueue[tail], ch->ch_equeue[tail]));

                        ch->ch_r_tail = tail = (tail + 1) & RQUEUEMASK;
                        ch->ch_err_overrun++;
                        qleft++;
                }

                memcpy_fromio(ch->ch_rqueue + head, &ch->ch_neo_uart->txrxburst, 1);
                ch->ch_equeue[head] = (uchar) linestatus;
                dgnc_sniff_nowait_nolock(ch, "UART READ", ch->ch_rqueue + head, 1);

                DPR_READ(("DATA/LSR pair: %x %x\n", ch->ch_rqueue[head], ch->ch_equeue[head]));

                /* Ditch any remaining linestatus value. */
                linestatus = 0;

                /* Add to and flip head if needed */
                head = (head + 1) & RQUEUEMASK;

                qleft--;
                ch->ch_rxcount++;
        }

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

        DGNC_UNLOCK(ch->ch_lock, lock_flags);
}


/*
 * This function basically goes to sleep for secs, or until
 * it gets signalled that the port has fully drained.
 */
static int neo_drain(struct tty_struct *tty, uint seconds)
{
        ulong lock_flags;
        struct channel_t *ch;
        struct un_t *un;
        int rc = 0;

        if (!tty || tty->magic != TTY_MAGIC) {
                return -ENXIO;
        }

        un = (struct un_t *) tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC) {
                return -ENXIO;
        }

        ch = un->un_ch;
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC) {
                return -ENXIO;
        }

        DPR_IOCTL(("%d Drain wait started.\n", __LINE__));

        DGNC_LOCK(ch->ch_lock, lock_flags);
        un->un_flags |= UN_EMPTY;
        DGNC_UNLOCK(ch->ch_lock, lock_flags);

        /*
         * Go to sleep waiting for the tty layer to wake me back up when
         * the empty flag goes away.
         *
         * NOTE: TODO: Do something with time passed in.
         */
        rc = wait_event_interruptible(un->un_flags_wait, ((un->un_flags & UN_EMPTY) == 0));

        /* If ret is non-zero, user ctrl-c'ed us */
        if (rc) {
                DPR_IOCTL(("%d Drain - User ctrl c'ed\n", __LINE__));
        }
        else {
                DPR_IOCTL(("%d Drain wait finished.\n", __LINE__));
        }

        return rc;
}


/*
 * Flush the WRITE FIFO on the Neo.
 *
 * NOTE: Channel lock MUST be held before calling this function!
 */
static void neo_flush_uart_write(struct channel_t *ch)
{
        uchar tmp = 0;
        int i = 0;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC) {
                return;
        }

        writeb((UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_XMIT), &ch->ch_neo_uart->isr_fcr);
        neo_pci_posting_flush(ch->ch_bd);

        for (i = 0; i < 10; i++) {

                /* Check to see if the UART feels it completely flushed the FIFO. */
                tmp = readb(&ch->ch_neo_uart->isr_fcr);
                if (tmp & 4) {
                        DPR_IOCTL(("Still flushing TX UART... i: %d\n", i));
                        udelay(10);
                }
                else
                        break;
        }

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


/*
 * Flush the READ FIFO on the Neo.
 *
 * NOTE: Channel lock MUST be held before calling this function!
 */
static void neo_flush_uart_read(struct channel_t *ch)
{
        uchar tmp = 0;
        int i = 0;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC) {
                return;
        }

        writeb((UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR), &ch->ch_neo_uart->isr_fcr);
        neo_pci_posting_flush(ch->ch_bd);

        for (i = 0; i < 10; i++) {

                /* Check to see if the UART feels it completely flushed the FIFO. */
                tmp = readb(&ch->ch_neo_uart->isr_fcr);
                if (tmp & 2) {
                        DPR_IOCTL(("Still flushing RX UART... i: %d\n", i));
                        udelay(10);
                }
                else
                        break;
        }
}


static void neo_copy_data_from_queue_to_uart(struct channel_t *ch)
{
        ushort head;
        ushort tail;
        int n;
        int s;
        int qlen;
        uint len_written = 0;
        ulong lock_flags;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        DGNC_LOCK(ch->ch_lock, lock_flags);

        /* No data to write to the UART */
        if (ch->ch_w_tail == ch->ch_w_head) {
                DGNC_UNLOCK(ch->ch_lock, lock_flags);
                return;
        }

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

        /*
         * If FIFOs are disabled. Send data directly to txrx register
         */
        if (!(ch->ch_flags & CH_FIFO_ENABLED)) {
                uchar lsrbits = readb(&ch->ch_neo_uart->lsr);

                /* Cache the LSR bits for later parsing */
                ch->ch_cached_lsr |= lsrbits;
                if (ch->ch_cached_lsr & UART_LSR_THRE) {
                        ch->ch_cached_lsr &= ~(UART_LSR_THRE);

                        /*
                         * If RTS Toggle mode is on, turn on RTS now if not already set,
                         * and make sure we get an event when the data transfer has completed.
                         */
                        if (ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE) {
                                if (!(ch->ch_mostat & UART_MCR_RTS)) {
                                        ch->ch_mostat |= (UART_MCR_RTS);
                                        neo_assert_modem_signals(ch);
                                }
                                ch->ch_tun.un_flags |= (UN_EMPTY);
                        }
                        /*
                         * If DTR Toggle mode is on, turn on DTR now if not already set,
                         * and make sure we get an event when the data transfer has completed.
                         */
                        if (ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE) {
                                if (!(ch->ch_mostat & UART_MCR_DTR)) {
                                        ch->ch_mostat |= (UART_MCR_DTR);
                                        neo_assert_modem_signals(ch);
                                }
                                ch->ch_tun.un_flags |= (UN_EMPTY);
                        }

                        writeb(ch->ch_wqueue[ch->ch_w_tail], &ch->ch_neo_uart->txrx);
                        DPR_WRITE(("Tx data: %x\n", ch->ch_wqueue[ch->ch_w_head]));
                        ch->ch_w_tail++;
                        ch->ch_w_tail &= WQUEUEMASK;
                        ch->ch_txcount++;
                }
                DGNC_UNLOCK(ch->ch_lock, lock_flags);
                return;
        }

        /*
         * We have to do it this way, because of the EXAR TXFIFO count bug.
         */
        if ((ch->ch_bd->dvid & 0xf0) < UART_XR17E158_DVID) {
                if (!(ch->ch_flags & (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM))) {
                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                        return;
                }

                len_written = 0;

                n = readb(&ch->ch_neo_uart->tfifo);

                if ((unsigned int) n > ch->ch_t_tlevel) {
                        DGNC_UNLOCK(ch->ch_lock, lock_flags);
                        return;
                }

                n = UART_17158_TX_FIFOSIZE - ch->ch_t_tlevel;
        }
        else {
                n = UART_17158_TX_FIFOSIZE - readb(&ch->ch_neo_uart->tfifo);
        }

        /* cache head and tail of queue */
        head = ch->ch_w_head & WQUEUEMASK;
        tail = ch->ch_w_tail & WQUEUEMASK;
        qlen = (head - tail) & WQUEUEMASK;

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

        while (n > 0) {

                s = ((head >= tail) ? head : WQUEUESIZE) - tail;
                s = min(s, n);

                if (s <= 0)
                        break;

                /*
                 * If RTS Toggle mode is on, turn on RTS now if not already set,
                 * and make sure we get an event when the data transfer has completed.
                 */
                if (ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE) {
                        if (!(ch->ch_mostat & UART_MCR_RTS)) {
                                ch->ch_mostat |= (UART_MCR_RTS);
                                neo_assert_modem_signals(ch);
                        }
                        ch->ch_tun.un_flags |= (UN_EMPTY);
                }

                /*
                 * If DTR Toggle mode is on, turn on DTR now if not already set,
                 * and make sure we get an event when the data transfer has completed.
                 */
                if (ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE) {
                        if (!(ch->ch_mostat & UART_MCR_DTR)) {
                                ch->ch_mostat |= (UART_MCR_DTR);
                                neo_assert_modem_signals(ch);
                        }
                        ch->ch_tun.un_flags |= (UN_EMPTY);
                }

                memcpy_toio(&ch->ch_neo_uart->txrxburst, ch->ch_wqueue + tail, s);
                dgnc_sniff_nowait_nolock(ch, "UART WRITE", ch->ch_wqueue + tail, s);

                /* Add and flip queue if needed */
                tail = (tail + s) & WQUEUEMASK;
                n -= s;
                ch->ch_txcount += s;
                len_written += s;
        }

        /* Update the final tail */
        ch->ch_w_tail = tail & WQUEUEMASK;

        if (len_written > 0) {
                neo_pci_posting_flush(ch->ch_bd);
                ch->ch_flags &= ~(CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
        }

        DGNC_UNLOCK(ch->ch_lock, lock_flags);
}


static void neo_parse_modem(struct channel_t *ch, uchar signals)
{
        volatile uchar msignals = signals;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        DPR_MSIGS(("neo_parse_modem: port: %d msignals: %x\n", ch->ch_portnum, msignals));

        /*
         * Do altpin switching. Altpin switches DCD and DSR.
         * This prolly breaks DSRPACE, so we should be more clever here.
         */
        if (ch->ch_digi.digi_flags & DIGI_ALTPIN) {
                uchar mswap = msignals;

                if (mswap & UART_MSR_DDCD) {
                        msignals &= ~UART_MSR_DDCD;
                        msignals |= UART_MSR_DDSR;
                }
                if (mswap & UART_MSR_DDSR) {
                        msignals &= ~UART_MSR_DDSR;
                        msignals |= UART_MSR_DDCD;
                }
                if (mswap & UART_MSR_DCD) {
                        msignals &= ~UART_MSR_DCD;
                        msignals |= UART_MSR_DSR;
                }
                if (mswap & UART_MSR_DSR) {
                        msignals &= ~UART_MSR_DSR;
                        msignals |= UART_MSR_DCD;
                }
        }

        /* Scrub off lower bits. They signify delta's, which I don't care about */
        msignals &= 0xf0;

        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;

        DPR_MSIGS(("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)));
}


/* Make the UART raise any of the output signals we want up */
static void neo_assert_modem_signals(struct channel_t *ch)
{
        uchar out;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        out = ch->ch_mostat;

        if (ch->ch_flags & CH_LOOPBACK)
                out |= UART_MCR_LOOP;

        writeb(out, &ch->ch_neo_uart->mcr);
        neo_pci_posting_flush(ch->ch_bd);

        /* Give time for the UART to actually raise/drop the signals */
        udelay(10);
}


static void neo_send_start_character(struct channel_t *ch)
{
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        if (ch->ch_startc != _POSIX_VDISABLE) {
                ch->ch_xon_sends++;
                writeb(ch->ch_startc, &ch->ch_neo_uart->txrx);
                neo_pci_posting_flush(ch->ch_bd);
                udelay(10);
        }
}


static void neo_send_stop_character(struct channel_t *ch)
{
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        if (ch->ch_stopc != _POSIX_VDISABLE) {
                ch->ch_xoff_sends++;
                writeb(ch->ch_stopc, &ch->ch_neo_uart->txrx);
                neo_pci_posting_flush(ch->ch_bd);
                udelay(10);
        }
}


/*
 * neo_uart_init
 */
static void neo_uart_init(struct channel_t *ch)
{

        writeb(0, &ch->ch_neo_uart->ier);
        writeb(0, &ch->ch_neo_uart->efr);
        writeb(UART_EFR_ECB, &ch->ch_neo_uart->efr);


        /* Clear out UART and FIFO */
        readb(&ch->ch_neo_uart->txrx);
        writeb((UART_FCR_ENABLE_FIFO|UART_FCR_CLEAR_RCVR|UART_FCR_CLEAR_XMIT), &ch->ch_neo_uart->isr_fcr);
        readb(&ch->ch_neo_uart->lsr);
        readb(&ch->ch_neo_uart->msr);

        ch->ch_flags |= CH_FIFO_ENABLED;

        /* Assert any signals we want up */
        writeb(ch->ch_mostat, &ch->ch_neo_uart->mcr);
        neo_pci_posting_flush(ch->ch_bd);
}


/*
 * Make the UART completely turn off.
 */
static void neo_uart_off(struct channel_t *ch)
{
        /* Turn off UART enhanced bits */
        writeb(0, &ch->ch_neo_uart->efr);

        /* Stop all interrupts from occurring. */
        writeb(0, &ch->ch_neo_uart->ier);
        neo_pci_posting_flush(ch->ch_bd);
}


static uint neo_get_uart_bytes_left(struct channel_t *ch)
{
        uchar left = 0;
        uchar lsr = readb(&ch->ch_neo_uart->lsr);

        /* We must cache the LSR as some of the bits get reset once read... */
        ch->ch_cached_lsr |= lsr;

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

        return left;
}


/* Channel lock MUST be held by the calling function! */
static void neo_send_break(struct channel_t *ch, int msecs)
{
        /*
         * If we receive a time of 0, this means turn off the break.
         */
        if (msecs == 0) {
                if (ch->ch_flags & CH_BREAK_SENDING) {
                        uchar temp = readb(&ch->ch_neo_uart->lcr);
                        writeb((temp & ~UART_LCR_SBC), &ch->ch_neo_uart->lcr);
                        neo_pci_posting_flush(ch->ch_bd);
                        ch->ch_flags &= ~(CH_BREAK_SENDING);
                        ch->ch_stop_sending_break = 0;
                        DPR_IOCTL(("Finishing UART_LCR_SBC! finished: %lx\n", jiffies));
                }
                return;
        }

        /*
         * Set the time we should stop sending the break.
         * If we are already sending a break, toss away the existing
         * time to stop, and use this new value instead.
         */
        ch->ch_stop_sending_break = jiffies + dgnc_jiffies_from_ms(msecs);

        /* Tell the UART to start sending the break */
        if (!(ch->ch_flags & CH_BREAK_SENDING)) {
                uchar temp = readb(&ch->ch_neo_uart->lcr);
                writeb((temp | UART_LCR_SBC), &ch->ch_neo_uart->lcr);
                neo_pci_posting_flush(ch->ch_bd);
                ch->ch_flags |= (CH_BREAK_SENDING);
                DPR_IOCTL(("Port %d. Starting UART_LCR_SBC! start: %lx should end: %lx\n",
                        ch->ch_portnum, jiffies, ch->ch_stop_sending_break));
        }
}


/*
 * neo_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 neo_send_immediate_char(struct channel_t *ch, unsigned char c)
{
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        writeb(c, &ch->ch_neo_uart->txrx);
        neo_pci_posting_flush(ch->ch_bd);
}


static unsigned int neo_read_eeprom(unsigned char __iomem *base, unsigned int address)
{
        unsigned int enable;
        unsigned int bits;
        unsigned int databit;
        unsigned int val;

        /* enable chip select */
        writeb(NEO_EECS, base + NEO_EEREG);
        /* READ */
        enable = (address | 0x180);

        for (bits = 9; bits--; ) {
                databit = (enable & (1 << bits)) ? NEO_EEDI : 0;
                /* Set read address */
                writeb(databit | NEO_EECS, base + NEO_EEREG);
                writeb(databit | NEO_EECS | NEO_EECK, base + NEO_EEREG);
        }

        val = 0;

        for (bits = 17; bits--; ) {
                /* clock to EEPROM */
                writeb(NEO_EECS, base + NEO_EEREG);
                writeb(NEO_EECS | NEO_EECK, base + NEO_EEREG);
                val <<= 1;
                /* read EEPROM */
                if (readb(base + NEO_EEREG) & NEO_EEDO)
                        val |= 1;
        }

        /* clock falling edge */
        writeb(NEO_EECS, base + NEO_EEREG);

        /* drop chip select */
        writeb(0x00, base + NEO_EEREG);

        return val;
}


static void neo_vpd(struct dgnc_board *brd)
{
        unsigned int i = 0;
        unsigned int a;

        if (!brd || brd->magic != DGNC_BOARD_MAGIC)
                return;

        if (!brd->re_map_membase)
                return;

        /* Store the VPD into our buffer */
        for (i = 0; i < NEO_VPD_IMAGESIZE; i++) {
                a = neo_read_eeprom(brd->re_map_membase, i);
                brd->vpd[i*2] = a & 0xff;
                brd->vpd[(i*2)+1] = (a >> 8) & 0xff;
        }

        if  (((brd->vpd[0x08] != 0x82)     /* long resource name tag */
                &&  (brd->vpd[0x10] != 0x82))   /* long resource name tag (PCI-66 files)*/
                ||  (brd->vpd[0x7F] != 0x78))   /* small resource end tag */
        {
                memset(brd->vpd, '\0', NEO_VPD_IMAGESIZE);
        }
        else {
                /* Search for the serial number */
                for (i = 0; i < NEO_VPD_IMAGEBYTES - 3; i++) {
                        if (brd->vpd[i] == 'S' && brd->vpd[i + 1] == 'N') {
                                strncpy(brd->serial_num, &(brd->vpd[i + 3]), 9);
                        }
                }
        }
}