/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2005 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * This file contains a module version of the ioc3 serial driver. This
 * includes all the support functions needed (support functions, etc.)
 * and the serial driver itself.
 */
#include <linux/errno.h>
#include <linux/tty.h>
#include <linux/serial.h>
#include <linux/circ_buf.h>
#include <linux/serial_reg.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/serial_core.h>
#include <linux/ioc3.h>

/*
 * Interesting things about the ioc3
 */

#define LOGICAL_PORTS           2       /* rs232(0) and rs422(1) */
#define PORTS_PER_CARD          2
#define LOGICAL_PORTS_PER_CARD (PORTS_PER_CARD * LOGICAL_PORTS)
#define MAX_CARDS               8
#define MAX_LOGICAL_PORTS       (LOGICAL_PORTS_PER_CARD * MAX_CARDS)

/* determine given the sio_ir what port it applies to */
#define GET_PORT_FROM_SIO_IR(_x)        (_x & SIO_IR_SA) ? 0 : 1


/*
 * we have 2 logical ports (rs232, rs422) for each physical port
 * evens are rs232, odds are rs422
 */
#define GET_PHYSICAL_PORT(_x)   ((_x) >> 1)
#define GET_LOGICAL_PORT(_x)    ((_x) & 1)
#define IS_PHYSICAL_PORT(_x)    !((_x) & 1)
#define IS_RS232(_x)            !((_x) & 1)

static unsigned int Num_of_ioc3_cards;
static unsigned int Submodule_slot;

/* defining this will get you LOTS of great debug info */
//#define DEBUG_INTERRUPTS
#define DPRINT_CONFIG(_x...)    ;
//#define DPRINT_CONFIG(_x...)  printk _x
#define NOT_PROGRESS()  ;
//#define NOT_PROGRESS()        printk("%s : fails %d\n", __func__, __LINE__)

/* number of characters we want to transmit to the lower level at a time */
#define MAX_CHARS               256
#define FIFO_SIZE               (MAX_CHARS-1)   /* it's a uchar */

/* Device name we're using */
#define DEVICE_NAME             "ttySIOC"
#define DEVICE_MAJOR            204
#define DEVICE_MINOR            116

/* flags for next_char_state */
#define NCS_BREAK               0x1
#define NCS_PARITY              0x2
#define NCS_FRAMING             0x4
#define NCS_OVERRUN             0x8

/* cause we need SOME parameters ... */
#define MIN_BAUD_SUPPORTED      1200
#define MAX_BAUD_SUPPORTED      115200

/* protocol types supported */
#define PROTO_RS232             0
#define PROTO_RS422             1

/* Notification types */
#define N_DATA_READY            0x01
#define N_OUTPUT_LOWAT          0x02
#define N_BREAK                 0x04
#define N_PARITY_ERROR          0x08
#define N_FRAMING_ERROR         0x10
#define N_OVERRUN_ERROR         0x20
#define N_DDCD                  0x40
#define N_DCTS                  0x80

#define N_ALL_INPUT             (N_DATA_READY | N_BREAK                    \
                                        | N_PARITY_ERROR | N_FRAMING_ERROR \
                                        | N_OVERRUN_ERROR | N_DDCD | N_DCTS)

#define N_ALL_OUTPUT            N_OUTPUT_LOWAT

#define N_ALL_ERRORS            (N_PARITY_ERROR | N_FRAMING_ERROR \
                                                | N_OVERRUN_ERROR)

#define N_ALL                   (N_DATA_READY | N_OUTPUT_LOWAT | N_BREAK    \
                                        | N_PARITY_ERROR | N_FRAMING_ERROR  \
                                        | N_OVERRUN_ERROR | N_DDCD | N_DCTS)

#define SER_CLK_SPEED(prediv)   ((22000000 << 1) / prediv)
#define SER_DIVISOR(x, clk)     (((clk) + (x) * 8) / ((x) * 16))
#define DIVISOR_TO_BAUD(div, clk) ((clk) / 16 / (div))

/* Some masks */
#define LCR_MASK_BITS_CHAR      (UART_LCR_WLEN5 | UART_LCR_WLEN6 \
                                        | UART_LCR_WLEN7 | UART_LCR_WLEN8)
#define LCR_MASK_STOP_BITS      (UART_LCR_STOP)

#define PENDING(_a, _p)         (readl(&(_p)->vma->sio_ir) & (_a)->ic_enable)

#define RING_BUF_SIZE           4096
#define BUF_SIZE_BIT            SBBR_L_SIZE
#define PROD_CONS_MASK          PROD_CONS_PTR_4K

#define TOTAL_RING_BUF_SIZE     (RING_BUF_SIZE * 4)

/* driver specific - one per card */
struct ioc3_card {
        struct {
                /* uart ports are allocated here */
                struct uart_port icp_uart_port[LOGICAL_PORTS];
                /* the ioc3_port used for this port */
                struct ioc3_port *icp_port;
        } ic_port[PORTS_PER_CARD];
        /* currently enabled interrupts */
        uint32_t ic_enable;
};

/* Local port info for each IOC3 serial port */
struct ioc3_port {
        /* handy reference material */
        struct uart_port *ip_port;
        struct ioc3_card *ip_card;
        struct ioc3_driver_data *ip_idd;
        struct ioc3_submodule *ip_is;

        /* pci mem addresses for this port */
        struct ioc3_serialregs __iomem *ip_serial_regs;
        struct ioc3_uartregs __iomem *ip_uart_regs;

        /* Ring buffer page for this port */
        dma_addr_t ip_dma_ringbuf;
        /* vaddr of ring buffer */
        struct ring_buffer *ip_cpu_ringbuf;

        /* Rings for this port */
        struct ring *ip_inring;
        struct ring *ip_outring;

        /* Hook to port specific values */
        struct port_hooks *ip_hooks;

        spinlock_t ip_lock;

        /* Various rx/tx parameters */
        int ip_baud;
        int ip_tx_lowat;
        int ip_rx_timeout;

        /* Copy of notification bits */
        int ip_notify;

        /* Shadow copies of various registers so we don't need to PIO
         * read them constantly
         */
        uint32_t ip_sscr;
        uint32_t ip_tx_prod;
        uint32_t ip_rx_cons;
        unsigned char ip_flags;
};

/* tx low water mark.  We need to notify the driver whenever tx is getting
 * close to empty so it can refill the tx buffer and keep things going.
 * Let's assume that if we interrupt 1 ms before the tx goes idle, we'll
 * have no trouble getting in more chars in time (I certainly hope so).
 */
#define TX_LOWAT_LATENCY      1000
#define TX_LOWAT_HZ          (1000000 / TX_LOWAT_LATENCY)
#define TX_LOWAT_CHARS(baud) (baud / 10 / TX_LOWAT_HZ)

/* Flags per port */
#define INPUT_HIGH              0x01
        /* used to signify that we have turned off the rx_high
         * temporarily - we need to drain the fifo and don't
         * want to get blasted with interrupts.
         */
#define DCD_ON                  0x02
        /* DCD state is on */
#define LOWAT_WRITTEN           0x04
#define READ_ABORTED            0x08
        /* the read was aborted - used to avaoid infinate looping
         * in the interrupt handler
         */
#define INPUT_ENABLE            0x10

/* Since each port has different register offsets and bitmasks
 * for everything, we'll store those that we need in tables so we
 * don't have to be constantly checking the port we are dealing with.
 */
struct port_hooks {
        uint32_t intr_delta_dcd;
        uint32_t intr_delta_cts;
        uint32_t intr_tx_mt;
        uint32_t intr_rx_timer;
        uint32_t intr_rx_high;
        uint32_t intr_tx_explicit;
        uint32_t intr_clear;
        uint32_t intr_all;
        char rs422_select_pin;
};

static struct port_hooks hooks_array[PORTS_PER_CARD] = {
        /* values for port A */
        {
        .intr_delta_dcd = SIO_IR_SA_DELTA_DCD,
        .intr_delta_cts = SIO_IR_SA_DELTA_CTS,
        .intr_tx_mt = SIO_IR_SA_TX_MT,
        .intr_rx_timer = SIO_IR_SA_RX_TIMER,
        .intr_rx_high = SIO_IR_SA_RX_HIGH,
        .intr_tx_explicit = SIO_IR_SA_TX_EXPLICIT,
        .intr_clear = (SIO_IR_SA_TX_MT | SIO_IR_SA_RX_FULL
                                | SIO_IR_SA_RX_HIGH
                                | SIO_IR_SA_RX_TIMER
                                | SIO_IR_SA_DELTA_DCD
                                | SIO_IR_SA_DELTA_CTS
                                | SIO_IR_SA_INT
                                | SIO_IR_SA_TX_EXPLICIT
                                | SIO_IR_SA_MEMERR),
        .intr_all =  SIO_IR_SA,
        .rs422_select_pin = GPPR_UARTA_MODESEL_PIN,
         },

        /* values for port B */
        {
        .intr_delta_dcd = SIO_IR_SB_DELTA_DCD,
        .intr_delta_cts = SIO_IR_SB_DELTA_CTS,
        .intr_tx_mt = SIO_IR_SB_TX_MT,
        .intr_rx_timer = SIO_IR_SB_RX_TIMER,
        .intr_rx_high = SIO_IR_SB_RX_HIGH,
        .intr_tx_explicit = SIO_IR_SB_TX_EXPLICIT,
        .intr_clear = (SIO_IR_SB_TX_MT | SIO_IR_SB_RX_FULL
                                | SIO_IR_SB_RX_HIGH
                                | SIO_IR_SB_RX_TIMER
                                | SIO_IR_SB_DELTA_DCD
                                | SIO_IR_SB_DELTA_CTS
                                | SIO_IR_SB_INT
                                | SIO_IR_SB_TX_EXPLICIT
                                | SIO_IR_SB_MEMERR),
        .intr_all = SIO_IR_SB,
        .rs422_select_pin = GPPR_UARTB_MODESEL_PIN,
         }
};

struct ring_entry {
        union {
                struct {
                        uint32_t alldata;
                        uint32_t allsc;
                } all;
                struct {
                        char data[4];   /* data bytes */
                        char sc[4];     /* status/control */
                } s;
        } u;
};

/* Test the valid bits in any of the 4 sc chars using "allsc" member */
#define RING_ANY_VALID \
        ((uint32_t)(RXSB_MODEM_VALID | RXSB_DATA_VALID) * 0x01010101)

#define ring_sc         u.s.sc
#define ring_data       u.s.data
#define ring_allsc      u.all.allsc

/* Number of entries per ring buffer. */
#define ENTRIES_PER_RING (RING_BUF_SIZE / (int) sizeof(struct ring_entry))

/* An individual ring */
struct ring {
        struct ring_entry entries[ENTRIES_PER_RING];
};

/* The whole enchilada */
struct ring_buffer {
        struct ring TX_A;
        struct ring RX_A;
        struct ring TX_B;
        struct ring RX_B;
};

/* Get a ring from a port struct */
#define RING(_p, _wh)   &(((struct ring_buffer *)((_p)->ip_cpu_ringbuf))->_wh)

/* for Infinite loop detection  */
#define MAXITER         10000000


/**
 * set_baud - Baud rate setting code
 * @port: port to set
 * @baud: baud rate to use
 */
static int set_baud(struct ioc3_port *port, int baud)
{
        int divisor;
        int actual_baud;
        int diff;
        int lcr, prediv;
        struct ioc3_uartregs __iomem *uart;

        for (prediv = 6; prediv < 64; prediv++) {
                divisor = SER_DIVISOR(baud, SER_CLK_SPEED(prediv));
                if (!divisor)
                        continue;       /* invalid divisor */
                actual_baud = DIVISOR_TO_BAUD(divisor, SER_CLK_SPEED(prediv));

                diff = actual_baud - baud;
                if (diff < 0)
                        diff = -diff;

                /* if we're within 1% we've found a match */
                if (diff * 100 <= actual_baud)
                        break;
        }

        /* if the above loop completed, we didn't match
         * the baud rate.  give up.
         */
        if (prediv == 64) {
                NOT_PROGRESS();
                return 1;
        }

        uart = port->ip_uart_regs;
        lcr = readb(&uart->iu_lcr);

        writeb(lcr | UART_LCR_DLAB, &uart->iu_lcr);
        writeb((unsigned char)divisor, &uart->iu_dll);
        writeb((unsigned char)(divisor >> 8), &uart->iu_dlm);
        writeb((unsigned char)prediv, &uart->iu_scr);
        writeb((unsigned char)lcr, &uart->iu_lcr);

        return 0;
}

/**
 * get_ioc3_port - given a uart port, return the control structure
 * @the_port: uart port to find
 */
static struct ioc3_port *get_ioc3_port(struct uart_port *the_port)
{
        struct ioc3_driver_data *idd = dev_get_drvdata(the_port->dev);
        struct ioc3_card *card_ptr = idd->data[Submodule_slot];
        int ii, jj;

        if (!card_ptr) {
                NOT_PROGRESS();
                return NULL;
        }
        for (ii = 0; ii < PORTS_PER_CARD; ii++) {
                for (jj = 0; jj < LOGICAL_PORTS; jj++) {
                        if (the_port == &card_ptr->ic_port[ii].icp_uart_port[jj])
                                return card_ptr->ic_port[ii].icp_port;
                }
        }
        NOT_PROGRESS();
        return NULL;
}

/**
 * port_init - Initialize the sio and ioc3 hardware for a given port
 *                      called per port from attach...
 * @port: port to initialize
 */
static int inline port_init(struct ioc3_port *port)
{
        uint32_t sio_cr;
        struct port_hooks *hooks = port->ip_hooks;
        struct ioc3_uartregs __iomem *uart;
        int reset_loop_counter = 0xfffff;
        struct ioc3_driver_data *idd = port->ip_idd;

        /* Idle the IOC3 serial interface */
        writel(SSCR_RESET, &port->ip_serial_regs->sscr);

        /* Wait until any pending bus activity for this port has ceased */
        do {
                sio_cr = readl(&idd->vma->sio_cr);
                if (reset_loop_counter-- <= 0) {
                        printk(KERN_WARNING
                               "IOC3 unable to come out of reset"
                                " scr 0x%x\n", sio_cr);
                        return -1;
                }
        } while (!(sio_cr & SIO_CR_ARB_DIAG_IDLE) &&
               (((sio_cr &= SIO_CR_ARB_DIAG) == SIO_CR_ARB_DIAG_TXA)
                || sio_cr == SIO_CR_ARB_DIAG_TXB
                || sio_cr == SIO_CR_ARB_DIAG_RXA
                || sio_cr == SIO_CR_ARB_DIAG_RXB));

        /* Finish reset sequence */
        writel(0, &port->ip_serial_regs->sscr);

        /* Once RESET is done, reload cached tx_prod and rx_cons values
         * and set rings to empty by making prod == cons
         */
        port->ip_tx_prod = readl(&port->ip_serial_regs->stcir) & PROD_CONS_MASK;
        writel(port->ip_tx_prod, &port->ip_serial_regs->stpir);
        port->ip_rx_cons = readl(&port->ip_serial_regs->srpir) & PROD_CONS_MASK;
        writel(port->ip_rx_cons | SRCIR_ARM, &port->ip_serial_regs->srcir);

        /* Disable interrupts for this 16550 */
        uart = port->ip_uart_regs;
        writeb(0, &uart->iu_lcr);
        writeb(0, &uart->iu_ier);

        /* Set the default baud */
        set_baud(port, port->ip_baud);

        /* Set line control to 8 bits no parity */
        writeb(UART_LCR_WLEN8 | 0, &uart->iu_lcr);
        /* UART_LCR_STOP == 1 stop */

        /* Enable the FIFOs */
        writeb(UART_FCR_ENABLE_FIFO, &uart->iu_fcr);
        /* then reset 16550 FIFOs */
        writeb(UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
               &uart->iu_fcr);

        /* Clear modem control register */
        writeb(0, &uart->iu_mcr);

        /* Clear deltas in modem status register */
        writel(0, &port->ip_serial_regs->shadow);

        /* Only do this once per port pair */
        if (port->ip_hooks == &hooks_array[0]) {
                unsigned long ring_pci_addr;
                uint32_t __iomem *sbbr_l, *sbbr_h;

                sbbr_l = &idd->vma->sbbr_l;
                sbbr_h = &idd->vma->sbbr_h;
                ring_pci_addr = (unsigned long __iomem)port->ip_dma_ringbuf;
                DPRINT_CONFIG(("%s: ring_pci_addr 0x%p\n",
                               __func__, (void *)ring_pci_addr));

                writel((unsigned int)((uint64_t) ring_pci_addr >> 32), sbbr_h);
                writel((unsigned int)ring_pci_addr | BUF_SIZE_BIT, sbbr_l);
        }

        /* Set the receive timeout value to 10 msec */
        writel(SRTR_HZ / 100, &port->ip_serial_regs->srtr);

        /* Set rx threshold, enable DMA */
        /* Set high water mark at 3/4 of full ring */
        port->ip_sscr = (ENTRIES_PER_RING * 3 / 4);

        /* uart experiences pauses at high baud rate reducing actual
         * throughput by 10% or so unless we enable high speed polling
         * XXX when this hardware bug is resolved we should revert to
         * normal polling speed
         */
        port->ip_sscr |= SSCR_HIGH_SPD;

        writel(port->ip_sscr, &port->ip_serial_regs->sscr);

        /* Disable and clear all serial related interrupt bits */
        port->ip_card->ic_enable &= ~hooks->intr_clear;
        ioc3_disable(port->ip_is, idd, hooks->intr_clear);
        ioc3_ack(port->ip_is, idd, hooks->intr_clear);
        return 0;
}

/**
 * enable_intrs - enable interrupts
 * @port: port to enable
 * @mask: mask to use
 */
static void enable_intrs(struct ioc3_port *port, uint32_t mask)
{
        if ((port->ip_card->ic_enable & mask) != mask) {
                port->ip_card->ic_enable |= mask;
                ioc3_enable(port->ip_is, port->ip_idd, mask);
        }
}

/**
 * local_open - local open a port
 * @port: port to open
 */
static inline int local_open(struct ioc3_port *port)
{
        int spiniter = 0;

        port->ip_flags = INPUT_ENABLE;

        /* Pause the DMA interface if necessary */
        if (port->ip_sscr & SSCR_DMA_EN) {
                writel(port->ip_sscr | SSCR_DMA_PAUSE,
                       &port->ip_serial_regs->sscr);
                while ((readl(&port->ip_serial_regs->sscr)
                        & SSCR_PAUSE_STATE) == 0) {
                        spiniter++;
                        if (spiniter > MAXITER) {
                                NOT_PROGRESS();
                                return -1;
                        }
                }
        }

        /* Reset the input fifo.  If the uart received chars while the port
         * was closed and DMA is not enabled, the uart may have a bunch of
         * chars hanging around in its rx fifo which will not be discarded
         * by rclr in the upper layer. We must get rid of them here.
         */
        writeb(UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR,
               &port->ip_uart_regs->iu_fcr);

        writeb(UART_LCR_WLEN8, &port->ip_uart_regs->iu_lcr);
        /* UART_LCR_STOP == 1 stop */

        /* Re-enable DMA, set default threshold to intr whenever there is
         * data available.
         */
        port->ip_sscr &= ~SSCR_RX_THRESHOLD;
        port->ip_sscr |= 1;     /* default threshold */

        /* Plug in the new sscr.  This implicitly clears the DMA_PAUSE
         * flag if it was set above
         */
        writel(port->ip_sscr, &port->ip_serial_regs->sscr);
        port->ip_tx_lowat = 1;
        return 0;
}

/**
 * set_rx_timeout - Set rx timeout and threshold values.
 * @port: port to use
 * @timeout: timeout value in ticks
 */
static inline int set_rx_timeout(struct ioc3_port *port, int timeout)
{
        int threshold;

        port->ip_rx_timeout = timeout;

        /* Timeout is in ticks.  Let's figure out how many chars we
         * can receive at the current baud rate in that interval
         * and set the rx threshold to that amount.  There are 4 chars
         * per ring entry, so we'll divide the number of chars that will
         * arrive in timeout by 4.
         * So .... timeout * baud / 10 / HZ / 4, with HZ = 100.
         */
        threshold = timeout * port->ip_baud / 4000;
        if (threshold == 0)
                threshold = 1;  /* otherwise we'll intr all the time! */

        if ((unsigned)threshold > (unsigned)SSCR_RX_THRESHOLD)
                return 1;

        port->ip_sscr &= ~SSCR_RX_THRESHOLD;
        port->ip_sscr |= threshold;
        writel(port->ip_sscr, &port->ip_serial_regs->sscr);

        /* Now set the rx timeout to the given value
         * again timeout * SRTR_HZ / HZ
         */
        timeout = timeout * SRTR_HZ / 100;
        if (timeout > SRTR_CNT)
                timeout = SRTR_CNT;
        writel(timeout, &port->ip_serial_regs->srtr);
        return 0;
}

/**
 * config_port - config the hardware
 * @port: port to config
 * @baud: baud rate for the port
 * @byte_size: data size
 * @stop_bits: number of stop bits
 * @parenb: parity enable ?
 * @parodd: odd parity ?
 */
static inline int
config_port(struct ioc3_port *port,
            int baud, int byte_size, int stop_bits, int parenb, int parodd)
{
        char lcr, sizebits;
        int spiniter = 0;

        DPRINT_CONFIG(("%s: line %d baud %d byte_size %d stop %d parenb %d "
                        "parodd %d\n",
                       __func__, ((struct uart_port *)port->ip_port)->line,
                        baud, byte_size, stop_bits, parenb, parodd));

        if (set_baud(port, baud))
                return 1;

        switch (byte_size) {
        case 5:
                sizebits = UART_LCR_WLEN5;
                break;
        case 6:
                sizebits = UART_LCR_WLEN6;
                break;
        case 7:
                sizebits = UART_LCR_WLEN7;
                break;
        case 8:
                sizebits = UART_LCR_WLEN8;
                break;
        default:
                return 1;
        }

        /* Pause the DMA interface if necessary */
        if (port->ip_sscr & SSCR_DMA_EN) {
                writel(port->ip_sscr | SSCR_DMA_PAUSE,
                       &port->ip_serial_regs->sscr);
                while ((readl(&port->ip_serial_regs->sscr)
                        & SSCR_PAUSE_STATE) == 0) {
                        spiniter++;
                        if (spiniter > MAXITER)
                                return -1;
                }
        }

        /* Clear relevant fields in lcr */
        lcr = readb(&port->ip_uart_regs->iu_lcr);
        lcr &= ~(LCR_MASK_BITS_CHAR | UART_LCR_EPAR |
                 UART_LCR_PARITY | LCR_MASK_STOP_BITS);

        /* Set byte size in lcr */
        lcr |= sizebits;

        /* Set parity */
        if (parenb) {
                lcr |= UART_LCR_PARITY;
                if (!parodd)
                        lcr |= UART_LCR_EPAR;
        }

        /* Set stop bits */
        if (stop_bits)
                lcr |= UART_LCR_STOP /* 2 stop bits */ ;

        writeb(lcr, &port->ip_uart_regs->iu_lcr);

        /* Re-enable the DMA interface if necessary */
        if (port->ip_sscr & SSCR_DMA_EN) {
                writel(port->ip_sscr, &port->ip_serial_regs->sscr);
        }
        port->ip_baud = baud;

        /* When we get within this number of ring entries of filling the
         * entire ring on tx, place an EXPLICIT intr to generate a lowat
         * notification when output has drained.
         */
        port->ip_tx_lowat = (TX_LOWAT_CHARS(baud) + 3) / 4;
        if (port->ip_tx_lowat == 0)
                port->ip_tx_lowat = 1;

        set_rx_timeout(port, 2);
        return 0;
}

/**
 * do_write - Write bytes to the port.  Returns the number of bytes
 *                      actually written. Called from transmit_chars
 * @port: port to use
 * @buf: the stuff to write
 * @len: how many bytes in 'buf'
 */
static inline int do_write(struct ioc3_port *port, char *buf, int len)
{
        int prod_ptr, cons_ptr, total = 0;
        struct ring *outring;
        struct ring_entry *entry;
        struct port_hooks *hooks = port->ip_hooks;

        BUG_ON(!(len >= 0));

        prod_ptr = port->ip_tx_prod;
        cons_ptr = readl(&port->ip_serial_regs->stcir) & PROD_CONS_MASK;
        outring = port->ip_outring;

        /* Maintain a 1-entry red-zone.  The ring buffer is full when
         * (cons - prod) % ring_size is 1.  Rather than do this subtraction
         * in the body of the loop, I'll do it now.
         */
        cons_ptr = (cons_ptr - (int)sizeof(struct ring_entry)) & PROD_CONS_MASK;

        /* Stuff the bytes into the output */
        while ((prod_ptr != cons_ptr) && (len > 0)) {
                int xx;

                /* Get 4 bytes (one ring entry) at a time */
                entry = (struct ring_entry *)((caddr_t) outring + prod_ptr);

                /* Invalidate all entries */
                entry->ring_allsc = 0;

                /* Copy in some bytes */
                for (xx = 0; (xx < 4) && (len > 0); xx++) {
                        entry->ring_data[xx] = *buf++;
                        entry->ring_sc[xx] = TXCB_VALID;
                        len--;
                        total++;
                }

                /* If we are within some small threshold of filling up the
                 * entire ring buffer, we must place an EXPLICIT intr here
                 * to generate a lowat interrupt in case we subsequently
                 * really do fill up the ring and the caller goes to sleep.
                 * No need to place more than one though.
                 */
                if (!(port->ip_flags & LOWAT_WRITTEN) &&
                    ((cons_ptr - prod_ptr) & PROD_CONS_MASK)
                    <= port->ip_tx_lowat * (int)sizeof(struct ring_entry)) {
                        port->ip_flags |= LOWAT_WRITTEN;
                        entry->ring_sc[0] |= TXCB_INT_WHEN_DONE;
                }

                /* Go on to next entry */
                prod_ptr += sizeof(struct ring_entry);
                prod_ptr &= PROD_CONS_MASK;
        }

        /* If we sent something, start DMA if necessary */
        if (total > 0 && !(port->ip_sscr & SSCR_DMA_EN)) {
                port->ip_sscr |= SSCR_DMA_EN;
                writel(port->ip_sscr, &port->ip_serial_regs->sscr);
        }

        /* Store the new producer pointer.  If tx is disabled, we stuff the
         * data into the ring buffer, but we don't actually start tx.
         */
        if (!uart_tx_stopped(port->ip_port)) {
                writel(prod_ptr, &port->ip_serial_regs->stpir);

                /* If we are now transmitting, enable tx_mt interrupt so we
                 * can disable DMA if necessary when the tx finishes.
                 */
                if (total > 0)
                        enable_intrs(port, hooks->intr_tx_mt);
        }
        port->ip_tx_prod = prod_ptr;

        return total;
}

/**
 * disable_intrs - disable interrupts
 * @port: port to enable
 * @mask: mask to use
 */
static inline void disable_intrs(struct ioc3_port *port, uint32_t mask)
{
        if (port->ip_card->ic_enable & mask) {
                ioc3_disable(port->ip_is, port->ip_idd, mask);
                port->ip_card->ic_enable &= ~mask;
        }
}

/**
 * set_notification - Modify event notification
 * @port: port to use
 * @mask: events mask
 * @set_on: set ?
 */
static int set_notification(struct ioc3_port *port, int mask, int set_on)
{
        struct port_hooks *hooks = port->ip_hooks;
        uint32_t intrbits, sscrbits;

        BUG_ON(!mask);

        intrbits = sscrbits = 0;

        if (mask & N_DATA_READY)
                intrbits |= (hooks->intr_rx_timer | hooks->intr_rx_high);
        if (mask & N_OUTPUT_LOWAT)
                intrbits |= hooks->intr_tx_explicit;
        if (mask & N_DDCD) {
                intrbits |= hooks->intr_delta_dcd;
                sscrbits |= SSCR_RX_RING_DCD;
        }
        if (mask & N_DCTS)
                intrbits |= hooks->intr_delta_cts;

        if (set_on) {
                enable_intrs(port, intrbits);
                port->ip_notify |= mask;
                port->ip_sscr |= sscrbits;
        } else {
                disable_intrs(port, intrbits);
                port->ip_notify &= ~mask;
                port->ip_sscr &= ~sscrbits;
        }

        /* We require DMA if either DATA_READY or DDCD notification is
         * currently requested. If neither of these is requested and
         * there is currently no tx in progress, DMA may be disabled.
         */
        if (port->ip_notify & (N_DATA_READY | N_DDCD))
                port->ip_sscr |= SSCR_DMA_EN;
        else if (!(port->ip_card->ic_enable & hooks->intr_tx_mt))
                port->ip_sscr &= ~SSCR_DMA_EN;

        writel(port->ip_sscr, &port->ip_serial_regs->sscr);
        return 0;
}

/**
 * set_mcr - set the master control reg
 * @the_port: port to use
 * @mask1: mcr mask
 * @mask2: shadow mask
 */
static inline int set_mcr(struct uart_port *the_port,
                          int mask1, int mask2)
{
        struct ioc3_port *port = get_ioc3_port(the_port);
        uint32_t shadow;
        int spiniter = 0;
        char mcr;

        if (!port)
                return -1;

        /* Pause the DMA interface if necessary */
        if (port->ip_sscr & SSCR_DMA_EN) {
                writel(port->ip_sscr | SSCR_DMA_PAUSE,
                       &port->ip_serial_regs->sscr);
                while ((readl(&port->ip_serial_regs->sscr)
                        & SSCR_PAUSE_STATE) == 0) {
                        spiniter++;
                        if (spiniter > MAXITER)
                                return -1;
                }
        }
        shadow = readl(&port->ip_serial_regs->shadow);
        mcr = (shadow & 0xff000000) >> 24;

        /* Set new value */
        mcr |= mask1;
        shadow |= mask2;
        writeb(mcr, &port->ip_uart_regs->iu_mcr);
        writel(shadow, &port->ip_serial_regs->shadow);

        /* Re-enable the DMA interface if necessary */
        if (port->ip_sscr & SSCR_DMA_EN) {
                writel(port->ip_sscr, &port->ip_serial_regs->sscr);
        }
        return 0;
}

/**
 * ioc3_set_proto - set the protocol for the port
 * @port: port to use
 * @proto: protocol to use
 */
static int ioc3_set_proto(struct ioc3_port *port, int proto)
{
        struct port_hooks *hooks = port->ip_hooks;

        switch (proto) {
        default:
        case PROTO_RS232:
                /* Clear the appropriate GIO pin */
                DPRINT_CONFIG(("%s: rs232\n", __func__));
                writel(0, (&port->ip_idd->vma->gppr[0]
                                        + hooks->rs422_select_pin));
                break;

        case PROTO_RS422:
                /* Set the appropriate GIO pin */
                DPRINT_CONFIG(("%s: rs422\n", __func__));
                writel(1, (&port->ip_idd->vma->gppr[0]
                                        + hooks->rs422_select_pin));
                break;
        }
        return 0;
}

/**
 * transmit_chars - upper level write, called with the_port->lock
 * @the_port: port to write
 */
static void transmit_chars(struct uart_port *the_port)
{
        int xmit_count, tail, head;
        int result;
        char *start;
        struct tty_struct *tty;
        struct ioc3_port *port = get_ioc3_port(the_port);
        struct uart_info *info;

        if (!the_port)
                return;
        if (!port)
                return;

        info = the_port->info;
        tty = info->port.tty;

        if (uart_circ_empty(&info->xmit) || uart_tx_stopped(the_port)) {
                /* Nothing to do or hw stopped */
                set_notification(port, N_ALL_OUTPUT, 0);
                return;
        }

        head = info->xmit.head;
        tail = info->xmit.tail;
        start = (char *)&info->xmit.buf[tail];

        /* write out all the data or until the end of the buffer */
        xmit_count = (head < tail) ? (UART_XMIT_SIZE - tail) : (head - tail);
        if (xmit_count > 0) {
                result = do_write(port, start, xmit_count);
                if (result > 0) {
                        /* booking */
                        xmit_count -= result;
                        the_port->icount.tx += result;
                        /* advance the pointers */
                        tail += result;
                        tail &= UART_XMIT_SIZE - 1;
                        info->xmit.tail = tail;
                        start = (char *)&info->xmit.buf[tail];
                }
        }
        if (uart_circ_chars_pending(&info->xmit) < WAKEUP_CHARS)
                uart_write_wakeup(the_port);

        if (uart_circ_empty(&info->xmit)) {
                set_notification(port, N_OUTPUT_LOWAT, 0);
        } else {
                set_notification(port, N_OUTPUT_LOWAT, 1);
        }
}

/**
 * ioc3_change_speed - change the speed of the port
 * @the_port: port to change
 * @new_termios: new termios settings
 * @old_termios: old termios settings
 */
static void
ioc3_change_speed(struct uart_port *the_port,
                  struct ktermios *new_termios, struct ktermios *old_termios)
{
        struct ioc3_port *port = get_ioc3_port(the_port);
        unsigned int cflag;
        int baud;
        int new_parity = 0, new_parity_enable = 0, new_stop = 0, new_data = 8;
        struct uart_info *info = the_port->info;

        cflag = new_termios->c_cflag;

        switch (cflag & CSIZE) {
        case CS5:
                new_data = 5;
                break;
        case CS6:
                new_data = 6;
                break;
        case CS7:
                new_data = 7;
                break;
        case CS8:
                new_data = 8;
                break;
        default:
                /* cuz we always need a default ... */
                new_data = 5;
                break;
        }
        if (cflag & CSTOPB) {
                new_stop = 1;
        }
        if (cflag & PARENB) {
                new_parity_enable = 1;
                if (cflag & PARODD)
                        new_parity = 1;
        }
        baud = uart_get_baud_rate(the_port, new_termios, old_termios,
                                  MIN_BAUD_SUPPORTED, MAX_BAUD_SUPPORTED);
        DPRINT_CONFIG(("%s: returned baud %d for line %d\n", __func__, baud,
                                the_port->line));

        if (!the_port->fifosize)
                the_port->fifosize = FIFO_SIZE;
        uart_update_timeout(the_port, cflag, baud);

        the_port->ignore_status_mask = N_ALL_INPUT;

        info->port.tty->low_latency = 1;

        if (I_IGNPAR(info->port.tty))
                the_port->ignore_status_mask &= ~(N_PARITY_ERROR
                                                  | N_FRAMING_ERROR);
        if (I_IGNBRK(info->port.tty)) {
                the_port->ignore_status_mask &= ~N_BREAK;
                if (I_IGNPAR(info->port.tty))
                        the_port->ignore_status_mask &= ~N_OVERRUN_ERROR;
        }
        if (!(cflag & CREAD)) {
                /* ignore everything */
                the_port->ignore_status_mask &= ~N_DATA_READY;
        }

        if (cflag & CRTSCTS) {
                /* enable hardware flow control */
                port->ip_sscr |= SSCR_HFC_EN;
        }
        else {
                /* disable hardware flow control */
                port->ip_sscr &= ~SSCR_HFC_EN;
        }
        writel(port->ip_sscr, &port->ip_serial_regs->sscr);

        /* Set the configuration and proper notification call */
        DPRINT_CONFIG(("%s : port 0x%p line %d cflag 0%o "
                       "config_port(baud %d data %d stop %d penable %d "
                        " parity %d), notification 0x%x\n",
                       __func__, (void *)port, the_port->line, cflag, baud,
                       new_data, new_stop, new_parity_enable, new_parity,
                       the_port->ignore_status_mask));

        if ((config_port(port, baud,    /* baud */
                         new_data,      /* byte size */
                         new_stop,      /* stop bits */
                         new_parity_enable,     /* set parity */
                         new_parity)) >= 0) {   /* parity 1==odd */
                set_notification(port, the_port->ignore_status_mask, 1);
        }
}

/**
 * ic3_startup_local - Start up the serial port - returns >= 0 if no errors
 * @the_port: Port to operate on
 */
static inline int ic3_startup_local(struct uart_port *the_port)
{
        struct ioc3_port *port;

        if (!the_port) {
                NOT_PROGRESS();
                return -1;
        }

        port = get_ioc3_port(the_port);
        if (!port) {
                NOT_PROGRESS();
                return -1;
        }

        local_open(port);

        /* set the protocol */
        ioc3_set_proto(port, IS_RS232(the_port->line) ? PROTO_RS232 :
                                                        PROTO_RS422);
        return 0;
}

/*
 * ioc3_cb_output_lowat - called when the output low water mark is hit
 * @port: port to output
 */
static void ioc3_cb_output_lowat(struct ioc3_port *port)
{
        unsigned long pflags;

        /* the_port->lock is set on the call here */
        if (port->ip_port) {
                spin_lock_irqsave(&port->ip_port->lock, pflags);
                transmit_chars(port->ip_port);
                spin_unlock_irqrestore(&port->ip_port->lock, pflags);
        }
}

/*
 * ioc3_cb_post_ncs - called for some basic errors
 * @port: port to use
 * @ncs: event
 */
static void ioc3_cb_post_ncs(struct uart_port *the_port, int ncs)
{
        struct uart_icount *icount;

        icount = &the_port->icount;

        if (ncs & NCS_BREAK)
                icount->brk++;
        if (ncs & NCS_FRAMING)
                icount->frame++;
        if (ncs & NCS_OVERRUN)
                icount->overrun++;
        if (ncs & NCS_PARITY)
                icount->parity++;
}

/**
 * do_read - Read in bytes from the port.  Return the number of bytes
 *                      actually read.
 * @the_port: port to use
 * @buf: place to put the stuff we read
 * @len: how big 'buf' is
 */

static inline int do_read(struct uart_port *the_port, char *buf, int len)
{
        int prod_ptr, cons_ptr, total;
        struct ioc3_port *port = get_ioc3_port(the_port);
        struct ring *inring;
        struct ring_entry *entry;
        struct port_hooks *hooks = port->ip_hooks;
        int byte_num;
        char *sc;
        int loop_counter;

        BUG_ON(!(len >= 0));
        BUG_ON(!port);

        /* There is a nasty timing issue in the IOC3. When the rx_timer
         * expires or the rx_high condition arises, we take an interrupt.
         * At some point while servicing the interrupt, we read bytes from
         * the ring buffer and re-arm the rx_timer.  However the rx_timer is
         * not started until the first byte is received *after* it is armed,
         * and any bytes pending in the rx construction buffers are not drained
         * to memory until either there are 4 bytes available or the rx_timer
         * expires.  This leads to a potential situation where data is left
         * in the construction buffers forever - 1 to 3 bytes were received
         * after the interrupt was generated but before the rx_timer was
         * re-armed. At that point as long as no subsequent bytes are received
         * the timer will never be started and the bytes will remain in the
         * construction buffer forever.  The solution is to execute a DRAIN
         * command after rearming the timer.  This way any bytes received before
         * the DRAIN will be drained to memory, and any bytes received after
         * the DRAIN will start the TIMER and be drained when it expires.
         * Luckily, this only needs to be done when the DMA buffer is empty
         * since there is no requirement that this function return all
         * available data as long as it returns some.
         */
        /* Re-arm the timer */

        writel(port->ip_rx_cons | SRCIR_ARM, &port->ip_serial_regs->srcir);

        prod_ptr = readl(&port->ip_serial_regs->srpir) & PROD_CONS_MASK;
        cons_ptr = port->ip_rx_cons;

        if (prod_ptr == cons_ptr) {
                int reset_dma = 0;

                /* Input buffer appears empty, do a flush. */

                /* DMA must be enabled for this to work. */
                if (!(port->ip_sscr & SSCR_DMA_EN)) {
                        port->ip_sscr |= SSCR_DMA_EN;
                        reset_dma = 1;
                }

                /* Potential race condition: we must reload the srpir after
                 * issuing the drain command, otherwise we could think the rx
                 * buffer is empty, then take a very long interrupt, and when
                 * we come back it's full and we wait forever for the drain to
                 * complete.
                 */
                writel(port->ip_sscr | SSCR_RX_DRAIN,
                       &port->ip_serial_regs->sscr);
                prod_ptr = readl(&port->ip_serial_regs->srpir) & PROD_CONS_MASK;

                /* We must not wait for the DRAIN to complete unless there are
                 * at least 8 bytes (2 ring entries) available to receive the
                 * data otherwise the DRAIN will never complete and we'll
                 * deadlock here.
                 * In fact, to make things easier, I'll just ignore the flush if
                 * there is any data at all now available.
                 */
                if (prod_ptr == cons_ptr) {
                        loop_counter = 0;
                        while (readl(&port->ip_serial_regs->sscr) &
                               SSCR_RX_DRAIN) {
                                loop_counter++;
                                if (loop_counter > MAXITER)
                                        return -1;
                        }

                        /* SIGH. We have to reload the prod_ptr *again* since
                         * the drain may have caused it to change
                         */
                        prod_ptr = readl(&port->ip_serial_regs->srpir)
                            & PROD_CONS_MASK;
                }
                if (reset_dma) {
                        port->ip_sscr &= ~SSCR_DMA_EN;
                        writel(port->ip_sscr, &port->ip_serial_regs->sscr);
                }
        }
        inring = port->ip_inring;
        port->ip_flags &= ~READ_ABORTED;

        total = 0;
        loop_counter = 0xfffff; /* to avoid hangs */

        /* Grab bytes from the hardware */
        while ((prod_ptr != cons_ptr) && (len > 0)) {
                entry = (struct ring_entry *)((caddr_t) inring + cons_ptr);

                if (loop_counter-- <= 0) {
                        printk(KERN_WARNING "IOC3 serial: "
                               "possible hang condition/"
                               "port stuck on read (line %d).\n",
                                the_port->line);
                        break;
                }

                /* According to the producer pointer, this ring entry
                 * must contain some data.  But if the PIO happened faster
                 * than the DMA, the data may not be available yet, so let's
                 * wait until it arrives.
                 */
                if ((entry->ring_allsc & RING_ANY_VALID) == 0) {
                        /* Indicate the read is aborted so we don't disable
                         * the interrupt thinking that the consumer is
                         * congested.
                         */
                        port->ip_flags |= READ_ABORTED;
                        len = 0;
                        break;
                }

                /* Load the bytes/status out of the ring entry */
                for (byte_num = 0; byte_num < 4 && len > 0; byte_num++) {
                        sc = &(entry->ring_sc[byte_num]);

                        /* Check for change in modem state or overrun */
                        if ((*sc & RXSB_MODEM_VALID)
                            && (port->ip_notify & N_DDCD)) {
                                /* Notify upper layer if DCD dropped */
                                if ((port->ip_flags & DCD_ON)
                                    && !(*sc & RXSB_DCD)) {
                                        /* If we have already copied some data,
                                         * return it.  We'll pick up the carrier
                                         * drop on the next pass.  That way we
                                         * don't throw away the data that has
                                         * already been copied back to
                                         * the caller's buffer.
                                         */
                                        if (total > 0) {
                                                len = 0;
                                                break;
                                        }
                                        port->ip_flags &= ~DCD_ON;

                                        /* Turn off this notification so the
                                         * carrier drop protocol won't see it
                                         * again when it does a read.
                                         */
                                        *sc &= ~RXSB_MODEM_VALID;

                                        /* To keep things consistent, we need
                                         * to update the consumer pointer so
                                         * the next reader won't come in and
                                         * try to read the same ring entries
                                         * again. This must be done here before
                                         * the dcd change.
                                         */

                                        if ((entry->ring_allsc & RING_ANY_VALID)
                                            == 0) {
                                                cons_ptr += (int)sizeof
                                                    (struct ring_entry);
                                                cons_ptr &= PROD_CONS_MASK;
                                        }
                                        writel(cons_ptr,
                                               &port->ip_serial_regs->srcir);
                                        port->ip_rx_cons = cons_ptr;

                                        /* Notify upper layer of carrier drop */
                                        if ((port->ip_notify & N_DDCD)
                                            && port->ip_port) {
                                                uart_handle_dcd_change
                                                        (port->ip_port, 0);
                                                wake_up_interruptible
                                                    (&the_port->info->
                                                     delta_msr_wait);
                                        }

                                        /* If we had any data to return, we
                                         * would have returned it above.
                                         */
                                        return 0;
                                }
                        }
                        if (*sc & RXSB_MODEM_VALID) {
                                /* Notify that an input overrun occurred */
                                if ((*sc & RXSB_OVERRUN)
                                    && (port->ip_notify & N_OVERRUN_ERROR)) {
                                        ioc3_cb_post_ncs(the_port, NCS_OVERRUN);
                                }
                                /* Don't look at this byte again */
                                *sc &= ~RXSB_MODEM_VALID;
                        }

                        /* Check for valid data or RX errors */
                        if ((*sc & RXSB_DATA_VALID) &&
                            ((*sc & (RXSB_PAR_ERR
                                     | RXSB_FRAME_ERR | RXSB_BREAK))
                             && (port->ip_notify & (N_PARITY_ERROR
                                                    | N_FRAMING_ERROR
                                                    | N_BREAK)))) {
                                /* There is an error condition on the next byte.
                                 * If we have already transferred some bytes,
                                 * we'll stop here. Otherwise if this is the
                                 * first byte to be read, we'll just transfer
                                 * it alone after notifying the
                                 * upper layer of its status.
                                 */
                                if (total > 0) {
                                        len = 0;
                                        break;
                                } else {
                                        if ((*sc & RXSB_PAR_ERR) &&
                                            (port->
                                             ip_notify & N_PARITY_ERROR)) {
                                                ioc3_cb_post_ncs(the_port,
                                                                 NCS_PARITY);
                                        }
                                        if ((*sc & RXSB_FRAME_ERR) &&
                                            (port->
                                             ip_notify & N_FRAMING_ERROR)) {
                                                ioc3_cb_post_ncs(the_port,
                                                                 NCS_FRAMING);
                                        }
                                        if ((*sc & RXSB_BREAK)
                                            && (port->ip_notify & N_BREAK)) {
                                                ioc3_cb_post_ncs
                                                    (the_port, NCS_BREAK);
                                        }
                                        len = 1;
                                }
                        }
                        if (*sc & RXSB_DATA_VALID) {
                                *sc &= ~RXSB_DATA_VALID;
                                *buf = entry->ring_data[byte_num];
                                buf++;
                                len--;
                                total++;
                        }
                }

                /* If we used up this entry entirely, go on to the next one,
                 * otherwise we must have run out of buffer space, so
                 * leave the consumer pointer here for the next read in case
                 * there are still unread bytes in this entry.
                 */
                if ((entry->ring_allsc & RING_ANY_VALID) == 0) {
                        cons_ptr += (int)sizeof(struct ring_entry);
                        cons_ptr &= PROD_CONS_MASK;
                }
        }

        /* Update consumer pointer and re-arm rx timer interrupt */
        writel(cons_ptr, &port->ip_serial_regs->srcir);
        port->ip_rx_cons = cons_ptr;

        /* If we have now dipped below the rx high water mark and we have
         * rx_high interrupt turned off, we can now turn it back on again.
         */
        if ((port->ip_flags & INPUT_HIGH) && (((prod_ptr - cons_ptr)
                                               & PROD_CONS_MASK) <
                                              ((port->
                                                ip_sscr &
                                                SSCR_RX_THRESHOLD)
                                               << PROD_CONS_PTR_OFF))) {
                port->ip_flags &= ~INPUT_HIGH;
                enable_intrs(port, hooks->intr_rx_high);
        }
        return total;
}

/**
 * receive_chars - upper level read.
 * @the_port: port to read from
 */
static int receive_chars(struct uart_port *the_port)
{
        struct tty_struct *tty;
        unsigned char ch[MAX_CHARS];
        int read_count = 0, read_room, flip = 0;
        struct uart_info *info = the_port->info;
        struct ioc3_port *port = get_ioc3_port(the_port);
        unsigned long pflags;

        /* Make sure all the pointers are "good" ones */
        if (!info)
                return 0;
        if (!info->port.tty)
                return 0;

        if (!(port->ip_flags & INPUT_ENABLE))
                return 0;

        spin_lock_irqsave(&the_port->lock, pflags);
        tty = info->port.tty;

        read_count = do_read(the_port, ch, MAX_CHARS);
        if (read_count > 0) {
                flip = 1;
                read_room = tty_buffer_request_room(tty, read_count);
                tty_insert_flip_string(tty, ch, read_room);
                the_port->icount.rx += read_count;
        }
        spin_unlock_irqrestore(&the_port->lock, pflags);

        if (flip)
                tty_flip_buffer_push(tty);

        return read_count;
}

/**
 * ioc3uart_intr_one - lowest level (per port) interrupt handler.
 * @is : submodule
 * @idd: driver data
 * @pending: interrupts to handle
 */

static int inline
ioc3uart_intr_one(struct ioc3_submodule *is,
                        struct ioc3_driver_data *idd,
                        unsigned int pending)
{
        int port_num = GET_PORT_FROM_SIO_IR(pending);
        struct port_hooks *hooks;
        unsigned int rx_high_rd_aborted = 0;
        unsigned long flags;
        struct uart_port *the_port;
        struct ioc3_port *port;
        int loop_counter;
        struct ioc3_card *card_ptr;
        unsigned int sio_ir;

        card_ptr = idd->data[is->id];
        port = card_ptr->ic_port[port_num].icp_port;
        hooks = port->ip_hooks;

        /* Possible race condition here: The tx_mt interrupt bit may be
         * cleared without the intervention of the interrupt handler,
         * e.g. by a write.  If the top level interrupt handler reads a
         * tx_mt, then some other processor does a write, starting up
         * output, then we come in here, see the tx_mt and stop DMA, the
         * output started by the other processor will hang.  Thus we can
         * only rely on tx_mt being legitimate if it is read while the
         * port lock is held.  Therefore this bit must be ignored in the
         * passed in interrupt mask which was read by the top level
         * interrupt handler since the port lock was not held at the time
         * it was read.  We can only rely on this bit being accurate if it
         * is read while the port lock is held.  So we'll clear it for now,
         * and reload it later once we have the port lock.
         */

        sio_ir = pending & ~(hooks->intr_tx_mt);
        spin_lock_irqsave(&port->ip_lock, flags);

        loop_counter = MAXITER; /* to avoid hangs */

        do {
                uint32_t shadow;

                if (loop_counter-- <= 0) {
                        printk(KERN_WARNING "IOC3 serial: "
                               "possible hang condition/"
                               "port stuck on interrupt (line %d).\n",
                                ((struct uart_port *)port->ip_port)->line);
                        break;
                }
                /* Handle a DCD change */
                if (sio_ir & hooks->intr_delta_dcd) {
                        ioc3_ack(is, idd, hooks->intr_delta_dcd);
                        shadow = readl(&port->ip_serial_regs->shadow);

                        if ((port->ip_notify & N_DDCD)
                            && (shadow & SHADOW_DCD)
                            && (port->ip_port)) {
                                the_port = port->ip_port;
                                uart_handle_dcd_change(the_port,
                                                shadow & SHADOW_DCD);
                                wake_up_interruptible
                                    (&the_port->info->delta_msr_wait);
                        } else if ((port->ip_notify & N_DDCD)
                                   && !(shadow & SHADOW_DCD)) {
                                /* Flag delta DCD/no DCD */
                                uart_handle_dcd_change(port->ip_port,
                                                shadow & SHADOW_DCD);
                                port->ip_flags |= DCD_ON;
                        }
                }

                /* Handle a CTS change */
                if (sio_ir & hooks->intr_delta_cts) {
                        ioc3_ack(is, idd, hooks->intr_delta_cts);
                        shadow = readl(&port->ip_serial_regs->shadow);

                        if ((port->ip_notify & N_DCTS) && (port->ip_port)) {
                                the_port = port->ip_port;
                                uart_handle_cts_change(the_port, shadow
                                                & SHADOW_CTS);
                                wake_up_interruptible
                                    (&the_port->info->delta_msr_wait);
                        }
                }

                /* rx timeout interrupt.  Must be some data available.  Put this
                 * before the check for rx_high since servicing this condition
                 * may cause that condition to clear.
                 */
                if (sio_ir & hooks->intr_rx_timer) {
                        ioc3_ack(is, idd, hooks->intr_rx_timer);
                        if ((port->ip_notify & N_DATA_READY)
                                                && (port->ip_port)) {
                                receive_chars(port->ip_port);
                        }
                }

                /* rx high interrupt. Must be after rx_timer.  */
                else if (sio_ir & hooks->intr_rx_high) {
                        /* Data available, notify upper layer */
                        if ((port->ip_notify & N_DATA_READY) && port->ip_port) {
                                receive_chars(port->ip_port);
                        }

                        /* We can't ACK this interrupt.  If receive_chars didn't
                         * cause the condition to clear, we'll have to disable
                         * the interrupt until the data is drained.
                         * If the read was aborted, don't disable the interrupt
                         * as this may cause us to hang indefinitely.  An
                         * aborted read generally means that this interrupt
                         * hasn't been delivered to the cpu yet anyway, even
                         * though we see it as asserted when we read the sio_ir.
                         */
                        if ((sio_ir = PENDING(card_ptr, idd))
                                        & hooks->intr_rx_high) {
                                if (port->ip_flags & READ_ABORTED) {
                                        rx_high_rd_aborted++;
                                }
                                else {
                                        card_ptr->ic_enable &= ~hooks->intr_rx_high;
                                        port->ip_flags |= INPUT_HIGH;
                                }
                        }
                }

                /* We got a low water interrupt: notify upper layer to
                 * send more data.  Must come before tx_mt since servicing
                 * this condition may cause that condition to clear.
                 */
                if (sio_ir & hooks->intr_tx_explicit) {
                        port->ip_flags &= ~LOWAT_WRITTEN;
                        ioc3_ack(is, idd, hooks->intr_tx_explicit);
                        if (port->ip_notify & N_OUTPUT_LOWAT)
                                ioc3_cb_output_lowat(port);
                }

                /* Handle tx_mt.  Must come after tx_explicit.  */
                else if (sio_ir & hooks->intr_tx_mt) {
                        /* If we are expecting a lowat notification
                         * and we get to this point it probably means that for
                         * some reason the tx_explicit didn't work as expected
                         * (that can legitimately happen if the output buffer is
                         * filled up in just the right way).
                         * So send the notification now.
                         */
                        if (port->ip_notify & N_OUTPUT_LOWAT) {
                                ioc3_cb_output_lowat(port);

                                /* We need to reload the sio_ir since the lowat
                                 * call may have caused another write to occur,
                                 * clearing the tx_mt condition.
                                 */
                                sio_ir = PENDING(card_ptr, idd);
                        }

                        /* If the tx_mt condition still persists even after the
                         * lowat call, we've got some work to do.
                         */
                        if (sio_ir & hooks->intr_tx_mt) {
                                /* If we are not currently expecting DMA input,
                                 * and the transmitter has just gone idle,
                                 * there is no longer any reason for DMA, so
                                 * disable it.
                                 */
                                if (!(port->ip_notify
                                      & (N_DATA_READY | N_DDCD))) {
                                        BUG_ON(!(port->ip_sscr
                                                 & SSCR_DMA_EN));
                                        port->ip_sscr &= ~SSCR_DMA_EN;
                                        writel(port->ip_sscr,
                                               &port->ip_serial_regs->sscr);
                                }
                                /* Prevent infinite tx_mt interrupt */
                                card_ptr->ic_enable &= ~hooks->intr_tx_mt;
                        }
                }
                sio_ir = PENDING(card_ptr, idd);

                /* if the read was aborted and only hooks->intr_rx_high,
                 * clear hooks->intr_rx_high, so we do not loop forever.
                 */

                if (rx_high_rd_aborted && (sio_ir == hooks->intr_rx_high)) {
                        sio_ir &= ~hooks->intr_rx_high;
                }
        } while (sio_ir & hooks->intr_all);

        spin_unlock_irqrestore(&port->ip_lock, flags);
        ioc3_enable(is, idd, card_ptr->ic_enable);
        return 0;
}

/**
 * ioc3uart_intr - field all serial interrupts
 * @is : submodule
 * @idd: driver data
 * @pending: interrupts to handle
 *
 */

static int ioc3uart_intr(struct ioc3_submodule *is,
                        struct ioc3_driver_data *idd,
                        unsigned int pending)
{
        int ret = 0;

        /*
         * The upper level interrupt handler sends interrupts for both ports
         * here. So we need to call for each port with its interrupts.
         */

        if (pending & SIO_IR_SA)
                ret |= ioc3uart_intr_one(is, idd, pending & SIO_IR_SA);
        if (pending & SIO_IR_SB)
                ret |= ioc3uart_intr_one(is, idd, pending & SIO_IR_SB);

        return ret;
}

/**
 * ic3_type
 * @port: Port to operate with (we ignore since we only have one port)
 *
 */
static const char *ic3_type(struct uart_port *the_port)
{
        if (IS_RS232(the_port->line))
                return "SGI IOC3 Serial [rs232]";
        else
                return "SGI IOC3 Serial [rs422]";
}

/**
 * ic3_tx_empty - Is the transmitter empty?
 * @port: Port to operate on
 *
 */
static unsigned int ic3_tx_empty(struct uart_port *the_port)
{
        unsigned int ret = 0;
        struct ioc3_port *port = get_ioc3_port(the_port);

        if (readl(&port->ip_serial_regs->shadow) & SHADOW_TEMT)
                ret = TIOCSER_TEMT;
        return ret;
}

/**
 * ic3_stop_tx - stop the transmitter
 * @port: Port to operate on
 *
 */
static void ic3_stop_tx(struct uart_port *the_port)
{
        struct ioc3_port *port = get_ioc3_port(the_port);

        if (port)
                set_notification(port, N_OUTPUT_LOWAT, 0);
}

/**
 * ic3_stop_rx - stop the receiver
 * @port: Port to operate on
 *
 */
static void ic3_stop_rx(struct uart_port *the_port)
{
        struct ioc3_port *port = get_ioc3_port(the_port);

        if (port)
                port->ip_flags &= ~INPUT_ENABLE;
}

/**
 * null_void_function
 * @port: Port to operate on
 *
 */
static void null_void_function(struct uart_port *the_port)
{
}

/**
 * ic3_shutdown - shut down the port - free irq and disable
 * @port: port to shut down
 *
 */
static void ic3_shutdown(struct uart_port *the_port)
{
        unsigned long port_flags;
        struct ioc3_port *port;
        struct uart_info *info;

        port = get_ioc3_port(the_port);
        if (!port)
                return;

        info = the_port->info;
        wake_up_interruptible(&info->delta_msr_wait);

        spin_lock_irqsave(&the_port->lock, port_flags);
        set_notification(port, N_ALL, 0);
        spin_unlock_irqrestore(&the_port->lock, port_flags);
}

/**
 * ic3_set_mctrl - set control lines (dtr, rts, etc)
 * @port: Port to operate on
 * @mctrl: Lines to set/unset
 *
 */
static void ic3_set_mctrl(struct uart_port *the_port, unsigned int mctrl)
{
        unsigned char mcr = 0;

        if (mctrl & TIOCM_RTS)
                mcr |= UART_MCR_RTS;
        if (mctrl & TIOCM_DTR)
                mcr |= UART_MCR_DTR;
        if (mctrl & TIOCM_OUT1)
                mcr |= UART_MCR_OUT1;
        if (mctrl & TIOCM_OUT2)
                mcr |= UART_MCR_OUT2;
        if (mctrl & TIOCM_LOOP)
                mcr |= UART_MCR_LOOP;

        set_mcr(the_port, mcr, SHADOW_DTR);
}

/**
 * ic3_get_mctrl - get control line info
 * @port: port to operate on
 *
 */
static unsigned int ic3_get_mctrl(struct uart_port *the_port)
{
        struct ioc3_port *port = get_ioc3_port(the_port);
        uint32_t shadow;
        unsigned int ret = 0;

        if (!port)
                return 0;

        shadow = readl(&port->ip_serial_regs->shadow);
        if (shadow & SHADOW_DCD)
                ret |= TIOCM_CD;
        if (shadow & SHADOW_DR)
                ret |= TIOCM_DSR;
        if (shadow & SHADOW_CTS)
                ret |= TIOCM_CTS;
        return ret;
}

/**
 * ic3_start_tx - Start transmitter. Called with the_port->lock
 * @port: Port to operate on
 *
 */
static void ic3_start_tx(struct uart_port *the_port)
{
        struct ioc3_port *port = get_ioc3_port(the_port);

        if (port) {
                set_notification(port, N_OUTPUT_LOWAT, 1);
                enable_intrs(port, port->ip_hooks->intr_tx_mt);
        }
}

/**
 * ic3_break_ctl - handle breaks
 * @port: Port to operate on
 * @break_state: Break state
 *
 */
static void ic3_break_ctl(struct uart_port *the_port, int break_state)
{
}

/**
 * ic3_startup - Start up the serial port - always return 0 (We're always on)
 * @port: Port to operate on
 *
 */
static int ic3_startup(struct uart_port *the_port)
{
        int retval;
        struct ioc3_port *port;
        struct ioc3_card *card_ptr;
        unsigned long port_flags;

        if (!the_port) {
                NOT_PROGRESS();
                return -ENODEV;
        }
        port = get_ioc3_port(the_port);
        if (!port) {
                NOT_PROGRESS();
                return -ENODEV;
        }
        card_ptr = port->ip_card;
        port->ip_port = the_port;

        if (!card_ptr) {
                NOT_PROGRESS();
                return -ENODEV;
        }

        /* Start up the serial port */
        spin_lock_irqsave(&the_port->lock, port_flags);
        retval = ic3_startup_local(the_port);
        spin_unlock_irqrestore(&the_port->lock, port_flags);
        return retval;
}

/**
 * ic3_set_termios - set termios stuff
 * @port: port to operate on
 * @termios: New settings
 * @termios: Old
 *
 */
static void
ic3_set_termios(struct uart_port *the_port,
                struct ktermios *termios, struct ktermios *old_termios)
{
        unsigned long port_flags;

        spin_lock_irqsave(&the_port->lock, port_flags);
        ioc3_change_speed(the_port, termios, old_termios);
        spin_unlock_irqrestore(&the_port->lock, port_flags);
}

/**
 * ic3_request_port - allocate resources for port - no op....
 * @port: port to operate on
 *
 */
static int ic3_request_port(struct uart_port *port)
{
        return 0;
}

/* Associate the uart functions above - given to serial core */
static struct uart_ops ioc3_ops = {
        .tx_empty = ic3_tx_empty,
        .set_mctrl = ic3_set_mctrl,
        .get_mctrl = ic3_get_mctrl,
        .stop_tx = ic3_stop_tx,
        .start_tx = ic3_start_tx,
        .stop_rx = ic3_stop_rx,
        .enable_ms = null_void_function,
        .break_ctl = ic3_break_ctl,
        .startup = ic3_startup,
        .shutdown = ic3_shutdown,
        .set_termios = ic3_set_termios,
        .type = ic3_type,
        .release_port = null_void_function,
        .request_port = ic3_request_port,
};

/*
 * Boot-time initialization code
 */

static struct uart_driver ioc3_uart = {
        .owner = THIS_MODULE,
        .driver_name = "ioc3_serial",
        .dev_name = DEVICE_NAME,
        .major = DEVICE_MAJOR,
        .minor = DEVICE_MINOR,
        .nr = MAX_LOGICAL_PORTS
};

/**
 * ioc3_serial_core_attach - register with serial core
 *              This is done during pci probing
 * @is: submodule struct for this
 * @idd: handle for this card
 */
static inline int ioc3_serial_core_attach( struct ioc3_submodule *is,
                                struct ioc3_driver_data *idd)
{
        struct ioc3_port *port;
        struct uart_port *the_port;
        struct ioc3_card *card_ptr = idd->data[is->id];
        int ii, phys_port;
        struct pci_dev *pdev = idd->pdev;

        DPRINT_CONFIG(("%s: attach pdev 0x%p - card_ptr 0x%p\n",
                       __func__, pdev, (void *)card_ptr));

        if (!card_ptr)
                return -ENODEV;

        /* once around for each logical port on this card */
        for (ii = 0; ii < LOGICAL_PORTS_PER_CARD; ii++) {
                phys_port = GET_PHYSICAL_PORT(ii);
                the_port = &card_ptr->ic_port[phys_port].
                                icp_uart_port[GET_LOGICAL_PORT(ii)];
                port = card_ptr->ic_port[phys_port].icp_port;
                port->ip_port = the_port;

                DPRINT_CONFIG(("%s: attach the_port 0x%p / port 0x%p [%d/%d]\n",
                        __func__, (void *)the_port, (void *)port,
                                phys_port, ii));

                /* membase, iobase and mapbase just need to be non-0 */
                the_port->membase = (unsigned char __iomem *)1;
                the_port->iobase = (pdev->bus->number << 16) |  ii;
                the_port->line = (Num_of_ioc3_cards << 2) | ii;
                the_port->mapbase = 1;
                the_port->type = PORT_16550A;
                the_port->fifosize = FIFO_SIZE;
                the_port->ops = &ioc3_ops;
                the_port->irq = idd->irq_io;
                the_port->dev = &pdev->dev;

                if (uart_add_one_port(&ioc3_uart, the_port) < 0) {
                        printk(KERN_WARNING
                          "%s: unable to add port %d bus %d\n",
                               __func__, the_port->line, pdev->bus->number);
                } else {
                        DPRINT_CONFIG(("IOC3 serial port %d irq %d bus %d\n",
                          the_port->line, the_port->irq, pdev->bus->number));
                }

                /* all ports are rs232 for now */
                if (IS_PHYSICAL_PORT(ii))
                        ioc3_set_proto(port, PROTO_RS232);
        }
        return 0;
}

/**
 * ioc3uart_remove - register detach function
 * @is: submodule struct for this submodule
 * @idd: ioc3 driver data for this submodule
 */

static int ioc3uart_remove(struct ioc3_submodule *is,
                        struct ioc3_driver_data *idd)
{
        struct ioc3_card *card_ptr = idd->data[is->id];
        struct uart_port *the_port;
        struct ioc3_port *port;
        int ii;

        if (card_ptr) {
                for (ii = 0; ii < LOGICAL_PORTS_PER_CARD; ii++) {
                        the_port = &card_ptr->ic_port[GET_PHYSICAL_PORT(ii)].
                                        icp_uart_port[GET_LOGICAL_PORT(ii)];
                        if (the_port)
                                uart_remove_one_port(&ioc3_uart, the_port);
                        port = card_ptr->ic_port[GET_PHYSICAL_PORT(ii)].icp_port;
                        if (port && IS_PHYSICAL_PORT(ii)
                                        && (GET_PHYSICAL_PORT(ii) == 0)) {
                                pci_free_consistent(port->ip_idd->pdev,
                                        TOTAL_RING_BUF_SIZE,
                                        (void *)port->ip_cpu_ringbuf,
                                        port->ip_dma_ringbuf);
                                kfree(port);
                                card_ptr->ic_port[GET_PHYSICAL_PORT(ii)].
                                                        icp_port = NULL;
                        }
                }
                kfree(card_ptr);
                idd->data[is->id] = NULL;
        }