/*
 *      Support for the asynchronous serial interface (DUART) included
 *      in the BCM1250 and derived System-On-a-Chip (SOC) devices.
 *
 *      Copyright (c) 2007  Maciej W. Rozycki
 *
 *      Derived from drivers/char/sb1250_duart.c for which the following
 *      copyright applies:
 *
 *      Copyright (c) 2000, 2001, 2002, 2003, 2004  Broadcom Corporation
 *
 *      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 of the License, or (at your option) any later version.
 *
 *      References:
 *
 *      "BCM1250/BCM1125/BCM1125H User Manual", Broadcom Corporation
 */

#if defined(CONFIG_SERIAL_SB1250_DUART_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/compiler.h>
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/major.h>
#include <linux/serial.h>
#include <linux/serial_core.h>
#include <linux/spinlock.h>
#include <linux/sysrq.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/types.h>

#include <linux/atomic.h>
#include <asm/io.h>
#include <asm/war.h>

#include <asm/sibyte/sb1250.h>
#include <asm/sibyte/sb1250_uart.h>
#include <asm/sibyte/swarm.h>


#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
#include <asm/sibyte/bcm1480_regs.h>
#include <asm/sibyte/bcm1480_int.h>

#define SBD_CHANREGS(line)      A_BCM1480_DUART_CHANREG((line), 0)
#define SBD_CTRLREGS(line)      A_BCM1480_DUART_CTRLREG((line), 0)
#define SBD_INT(line)           (K_BCM1480_INT_UART_0 + (line))

#define DUART_CHANREG_SPACING   BCM1480_DUART_CHANREG_SPACING

#define R_DUART_IMRREG(line)    R_BCM1480_DUART_IMRREG(line)
#define R_DUART_INCHREG(line)   R_BCM1480_DUART_INCHREG(line)
#define R_DUART_ISRREG(line)    R_BCM1480_DUART_ISRREG(line)

#elif defined(CONFIG_SIBYTE_SB1250) || defined(CONFIG_SIBYTE_BCM112X)
#include <asm/sibyte/sb1250_regs.h>
#include <asm/sibyte/sb1250_int.h>

#define SBD_CHANREGS(line)      A_DUART_CHANREG((line), 0)
#define SBD_CTRLREGS(line)      A_DUART_CTRLREG(0)
#define SBD_INT(line)           (K_INT_UART_0 + (line))

#else
#error invalid SB1250 UART configuration

#endif


MODULE_AUTHOR("Maciej W. Rozycki <macro@linux-mips.org>");
MODULE_DESCRIPTION("BCM1xxx on-chip DUART serial driver");
MODULE_LICENSE("GPL");


#define DUART_MAX_CHIP 2
#define DUART_MAX_SIDE 2

/*
 * Per-port state.
 */
struct sbd_port {
        struct sbd_duart        *duart;
        struct uart_port        port;
        unsigned char __iomem   *memctrl;
        int                     tx_stopped;
        int                     initialised;
};

/*
 * Per-DUART state for the shared register space.
 */
struct sbd_duart {
        struct sbd_port         sport[2];
        unsigned long           mapctrl;
        atomic_t                map_guard;
};

#define to_sport(uport) container_of(uport, struct sbd_port, port)

static struct sbd_duart sbd_duarts[DUART_MAX_CHIP];


/*
 * Reading and writing SB1250 DUART registers.
 *
 * There are three register spaces: two per-channel ones and
 * a shared one.  We have to define accessors appropriately.
 * All registers are 64-bit and all but the Baud Rate Clock
 * registers only define 8 least significant bits.  There is
 * also a workaround to take into account.  Raw accessors use
 * the full register width, but cooked ones truncate it
 * intentionally so that the rest of the driver does not care.
 */
static u64 __read_sbdchn(struct sbd_port *sport, int reg)
{
        void __iomem *csr = sport->port.membase + reg;

        return __raw_readq(csr);
}

static u64 __read_sbdshr(struct sbd_port *sport, int reg)
{
        void __iomem *csr = sport->memctrl + reg;

        return __raw_readq(csr);
}

static void __write_sbdchn(struct sbd_port *sport, int reg, u64 value)
{
        void __iomem *csr = sport->port.membase + reg;

        __raw_writeq(value, csr);
}

static void __write_sbdshr(struct sbd_port *sport, int reg, u64 value)
{
        void __iomem *csr = sport->memctrl + reg;

        __raw_writeq(value, csr);
}

/*
 * In bug 1956, we get glitches that can mess up uart registers.  This
 * "read-mode-reg after any register access" is an accepted workaround.
 */
static void __war_sbd1956(struct sbd_port *sport)
{
        __read_sbdchn(sport, R_DUART_MODE_REG_1);
        __read_sbdchn(sport, R_DUART_MODE_REG_2);
}

static unsigned char read_sbdchn(struct sbd_port *sport, int reg)
{
        unsigned char retval;

        retval = __read_sbdchn(sport, reg);
        if (SIBYTE_1956_WAR)
                __war_sbd1956(sport);
        return retval;
}

static unsigned char read_sbdshr(struct sbd_port *sport, int reg)
{
        unsigned char retval;

        retval = __read_sbdshr(sport, reg);
        if (SIBYTE_1956_WAR)
                __war_sbd1956(sport);
        return retval;
}

static void write_sbdchn(struct sbd_port *sport, int reg, unsigned int value)
{
        __write_sbdchn(sport, reg, value);
        if (SIBYTE_1956_WAR)
                __war_sbd1956(sport);
}

static void write_sbdshr(struct sbd_port *sport, int reg, unsigned int value)
{
        __write_sbdshr(sport, reg, value);
        if (SIBYTE_1956_WAR)
                __war_sbd1956(sport);
}


static int sbd_receive_ready(struct sbd_port *sport)
{
        return read_sbdchn(sport, R_DUART_STATUS) & M_DUART_RX_RDY;
}

static int sbd_receive_drain(struct sbd_port *sport)
{
        int loops = 10000;

        while (sbd_receive_ready(sport) && --loops)
                read_sbdchn(sport, R_DUART_RX_HOLD);
        return loops;
}

static int __maybe_unused sbd_transmit_ready(struct sbd_port *sport)
{
        return read_sbdchn(sport, R_DUART_STATUS) & M_DUART_TX_RDY;
}

static int __maybe_unused sbd_transmit_drain(struct sbd_port *sport)
{
        int loops = 10000;

        while (!sbd_transmit_ready(sport) && --loops)
                udelay(2);
        return loops;
}

static int sbd_transmit_empty(struct sbd_port *sport)
{
        return read_sbdchn(sport, R_DUART_STATUS) & M_DUART_TX_EMT;
}

static int sbd_line_drain(struct sbd_port *sport)
{
        int loops = 10000;

        while (!sbd_transmit_empty(sport) && --loops)
                udelay(2);
        return loops;
}


static unsigned int sbd_tx_empty(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);

        return sbd_transmit_empty(sport) ? TIOCSER_TEMT : 0;
}

static unsigned int sbd_get_mctrl(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);
        unsigned int mctrl, status;

        status = read_sbdshr(sport, R_DUART_IN_PORT);
        status >>= (uport->line) % 2;
        mctrl = (!(status & M_DUART_IN_PIN0_VAL) ? TIOCM_CTS : 0) |
                (!(status & M_DUART_IN_PIN4_VAL) ? TIOCM_CAR : 0) |
                (!(status & M_DUART_RIN0_PIN) ? TIOCM_RNG : 0) |
                (!(status & M_DUART_IN_PIN2_VAL) ? TIOCM_DSR : 0);
        return mctrl;
}

static void sbd_set_mctrl(struct uart_port *uport, unsigned int mctrl)
{
        struct sbd_port *sport = to_sport(uport);
        unsigned int clr = 0, set = 0, mode2;

        if (mctrl & TIOCM_DTR)
                set |= M_DUART_SET_OPR2;
        else
                clr |= M_DUART_CLR_OPR2;
        if (mctrl & TIOCM_RTS)
                set |= M_DUART_SET_OPR0;
        else
                clr |= M_DUART_CLR_OPR0;
        clr <<= (uport->line) % 2;
        set <<= (uport->line) % 2;

        mode2 = read_sbdchn(sport, R_DUART_MODE_REG_2);
        mode2 &= ~M_DUART_CHAN_MODE;
        if (mctrl & TIOCM_LOOP)
                mode2 |= V_DUART_CHAN_MODE_LCL_LOOP;
        else
                mode2 |= V_DUART_CHAN_MODE_NORMAL;

        write_sbdshr(sport, R_DUART_CLEAR_OPR, clr);
        write_sbdshr(sport, R_DUART_SET_OPR, set);
        write_sbdchn(sport, R_DUART_MODE_REG_2, mode2);
}

static void sbd_stop_tx(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);

        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS);
        sport->tx_stopped = 1;
};

static void sbd_start_tx(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);
        unsigned int mask;

        /* Enable tx interrupts.  */
        mask = read_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2));
        mask |= M_DUART_IMR_TX;
        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), mask);

        /* Go!, go!, go!...  */
        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_EN);
        sport->tx_stopped = 0;
};

static void sbd_stop_rx(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);

        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), 0);
};

static void sbd_enable_ms(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);

        write_sbdchn(sport, R_DUART_AUXCTL_X,
                     M_DUART_CIN_CHNG_ENA | M_DUART_CTS_CHNG_ENA);
}

static void sbd_break_ctl(struct uart_port *uport, int break_state)
{
        struct sbd_port *sport = to_sport(uport);

        if (break_state == -1)
                write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_START_BREAK);
        else
                write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_STOP_BREAK);
}


static void sbd_receive_chars(struct sbd_port *sport)
{
        struct uart_port *uport = &sport->port;
        struct uart_icount *icount;
        unsigned int status, ch, flag;
        int count;

        for (count = 16; count; count--) {
                status = read_sbdchn(sport, R_DUART_STATUS);
                if (!(status & M_DUART_RX_RDY))
                        break;

                ch = read_sbdchn(sport, R_DUART_RX_HOLD);

                flag = TTY_NORMAL;

                icount = &uport->icount;
                icount->rx++;

                if (unlikely(status &
                             (M_DUART_RCVD_BRK | M_DUART_FRM_ERR |
                              M_DUART_PARITY_ERR | M_DUART_OVRUN_ERR))) {
                        if (status & M_DUART_RCVD_BRK) {
                                icount->brk++;
                                if (uart_handle_break(uport))
                                        continue;
                        } else if (status & M_DUART_FRM_ERR)
                                icount->frame++;
                        else if (status & M_DUART_PARITY_ERR)
                                icount->parity++;
                        if (status & M_DUART_OVRUN_ERR)
                                icount->overrun++;

                        status &= uport->read_status_mask;
                        if (status & M_DUART_RCVD_BRK)
                                flag = TTY_BREAK;
                        else if (status & M_DUART_FRM_ERR)
                                flag = TTY_FRAME;
                        else if (status & M_DUART_PARITY_ERR)
                                flag = TTY_PARITY;
                }

                if (uart_handle_sysrq_char(uport, ch))
                        continue;

                uart_insert_char(uport, status, M_DUART_OVRUN_ERR, ch, flag);
        }

        tty_flip_buffer_push(uport->state->port.tty);
}

static void sbd_transmit_chars(struct sbd_port *sport)
{
        struct uart_port *uport = &sport->port;
        struct circ_buf *xmit = &sport->port.state->xmit;
        unsigned int mask;
        int stop_tx;

        /* XON/XOFF chars.  */
        if (sport->port.x_char) {
                write_sbdchn(sport, R_DUART_TX_HOLD, sport->port.x_char);
                sport->port.icount.tx++;
                sport->port.x_char = 0;
                return;
        }

        /* If nothing to do or stopped or hardware stopped.  */
        stop_tx = (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port));

        /* Send char.  */
        if (!stop_tx) {
                write_sbdchn(sport, R_DUART_TX_HOLD, xmit->buf[xmit->tail]);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                sport->port.icount.tx++;

                if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                        uart_write_wakeup(&sport->port);
        }

        /* Are we are done?  */
        if (stop_tx || uart_circ_empty(xmit)) {
                /* Disable tx interrupts.  */
                mask = read_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2));
                mask &= ~M_DUART_IMR_TX;
                write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), mask);
        }
}

static void sbd_status_handle(struct sbd_port *sport)
{
        struct uart_port *uport = &sport->port;
        unsigned int delta;

        delta = read_sbdshr(sport, R_DUART_INCHREG((uport->line) % 2));
        delta >>= (uport->line) % 2;

        if (delta & (M_DUART_IN_PIN0_VAL << S_DUART_IN_PIN_CHNG))
                uart_handle_cts_change(uport, !(delta & M_DUART_IN_PIN0_VAL));

        if (delta & (M_DUART_IN_PIN2_VAL << S_DUART_IN_PIN_CHNG))
                uport->icount.dsr++;

        if (delta & ((M_DUART_IN_PIN2_VAL | M_DUART_IN_PIN0_VAL) <<
                     S_DUART_IN_PIN_CHNG))
                wake_up_interruptible(&uport->state->port.delta_msr_wait);
}

static irqreturn_t sbd_interrupt(int irq, void *dev_id)
{
        struct sbd_port *sport = dev_id;
        struct uart_port *uport = &sport->port;
        irqreturn_t status = IRQ_NONE;
        unsigned int intstat;
        int count;

        for (count = 16; count; count--) {
                intstat = read_sbdshr(sport,
                                      R_DUART_ISRREG((uport->line) % 2));
                intstat &= read_sbdshr(sport,
                                       R_DUART_IMRREG((uport->line) % 2));
                intstat &= M_DUART_ISR_ALL;
                if (!intstat)
                        break;

                if (intstat & M_DUART_ISR_RX)
                        sbd_receive_chars(sport);
                if (intstat & M_DUART_ISR_IN)
                        sbd_status_handle(sport);
                if (intstat & M_DUART_ISR_TX)
                        sbd_transmit_chars(sport);

                status = IRQ_HANDLED;
        }

        return status;
}


static int sbd_startup(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);
        unsigned int mode1;
        int ret;

        ret = request_irq(sport->port.irq, sbd_interrupt,
                          IRQF_SHARED, "sb1250-duart", sport);
        if (ret)
                return ret;

        /* Clear the receive FIFO.  */
        sbd_receive_drain(sport);

        /* Clear the interrupt registers.  */
        write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_BREAK_INT);
        read_sbdshr(sport, R_DUART_INCHREG((uport->line) % 2));

        /* Set rx/tx interrupt to FIFO available.  */
        mode1 = read_sbdchn(sport, R_DUART_MODE_REG_1);
        mode1 &= ~(M_DUART_RX_IRQ_SEL_RXFULL | M_DUART_TX_IRQ_SEL_TXEMPT);
        write_sbdchn(sport, R_DUART_MODE_REG_1, mode1);

        /* Disable tx, enable rx.  */
        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS | M_DUART_RX_EN);
        sport->tx_stopped = 1;

        /* Enable interrupts.  */
        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2),
                     M_DUART_IMR_IN | M_DUART_IMR_RX);

        return 0;
}

static void sbd_shutdown(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);

        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS | M_DUART_RX_DIS);
        sport->tx_stopped = 1;
        free_irq(sport->port.irq, sport);
}


static void sbd_init_port(struct sbd_port *sport)
{
        struct uart_port *uport = &sport->port;

        if (sport->initialised)
                return;

        /* There is no DUART reset feature, so just set some sane defaults.  */
        write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_TX);
        write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_RX);
        write_sbdchn(sport, R_DUART_MODE_REG_1, V_DUART_BITS_PER_CHAR_8);
        write_sbdchn(sport, R_DUART_MODE_REG_2, 0);
        write_sbdchn(sport, R_DUART_FULL_CTL,
                     V_DUART_INT_TIME(0) | V_DUART_SIG_FULL(15));
        write_sbdchn(sport, R_DUART_OPCR_X, 0);
        write_sbdchn(sport, R_DUART_AUXCTL_X, 0);
        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), 0);

        sport->initialised = 1;
}

static void sbd_set_termios(struct uart_port *uport, struct ktermios *termios,
                            struct ktermios *old_termios)
{
        struct sbd_port *sport = to_sport(uport);
        unsigned int mode1 = 0, mode2 = 0, aux = 0;
        unsigned int mode1mask = 0, mode2mask = 0, auxmask = 0;
        unsigned int oldmode1, oldmode2, oldaux;
        unsigned int baud, brg;
        unsigned int command;

        mode1mask |= ~(M_DUART_PARITY_MODE | M_DUART_PARITY_TYPE_ODD |
                       M_DUART_BITS_PER_CHAR);
        mode2mask |= ~M_DUART_STOP_BIT_LEN_2;
        auxmask |= ~M_DUART_CTS_CHNG_ENA;

        /* Byte size.  */
        switch (termios->c_cflag & CSIZE) {
        case CS5:
        case CS6:
                /* Unsupported, leave unchanged.  */
                mode1mask |= M_DUART_PARITY_MODE;
                break;
        case CS7:
                mode1 |= V_DUART_BITS_PER_CHAR_7;
                break;
        case CS8:
        default:
                mode1 |= V_DUART_BITS_PER_CHAR_8;
                break;
        }

        /* Parity and stop bits.  */
        if (termios->c_cflag & CSTOPB)
                mode2 |= M_DUART_STOP_BIT_LEN_2;
        else
                mode2 |= M_DUART_STOP_BIT_LEN_1;
        if (termios->c_cflag & PARENB)
                mode1 |= V_DUART_PARITY_MODE_ADD;
        else
                mode1 |= V_DUART_PARITY_MODE_NONE;
        if (termios->c_cflag & PARODD)
                mode1 |= M_DUART_PARITY_TYPE_ODD;
        else
                mode1 |= M_DUART_PARITY_TYPE_EVEN;

        baud = uart_get_baud_rate(uport, termios, old_termios, 1200, 5000000);
        brg = V_DUART_BAUD_RATE(baud);
        /* The actual lower bound is 1221bps, so compensate.  */
        if (brg > M_DUART_CLK_COUNTER)
                brg = M_DUART_CLK_COUNTER;

        uart_update_timeout(uport, termios->c_cflag, baud);

        uport->read_status_mask = M_DUART_OVRUN_ERR;
        if (termios->c_iflag & INPCK)
                uport->read_status_mask |= M_DUART_FRM_ERR |
                                           M_DUART_PARITY_ERR;
        if (termios->c_iflag & (BRKINT | PARMRK))
                uport->read_status_mask |= M_DUART_RCVD_BRK;

        uport->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                uport->ignore_status_mask |= M_DUART_FRM_ERR |
                                             M_DUART_PARITY_ERR;
        if (termios->c_iflag & IGNBRK) {
                uport->ignore_status_mask |= M_DUART_RCVD_BRK;
                if (termios->c_iflag & IGNPAR)
                        uport->ignore_status_mask |= M_DUART_OVRUN_ERR;
        }

        if (termios->c_cflag & CREAD)
                command = M_DUART_RX_EN;
        else
                command = M_DUART_RX_DIS;

        if (termios->c_cflag & CRTSCTS)
                aux |= M_DUART_CTS_CHNG_ENA;
        else
                aux &= ~M_DUART_CTS_CHNG_ENA;

        spin_lock(&uport->lock);

        if (sport->tx_stopped)
                command |= M_DUART_TX_DIS;
        else
                command |= M_DUART_TX_EN;

        oldmode1 = read_sbdchn(sport, R_DUART_MODE_REG_1) & mode1mask;
        oldmode2 = read_sbdchn(sport, R_DUART_MODE_REG_2) & mode2mask;
        oldaux = read_sbdchn(sport, R_DUART_AUXCTL_X) & auxmask;

        if (!sport->tx_stopped)
                sbd_line_drain(sport);
        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS | M_DUART_RX_DIS);

        write_sbdchn(sport, R_DUART_MODE_REG_1, mode1 | oldmode1);
        write_sbdchn(sport, R_DUART_MODE_REG_2, mode2 | oldmode2);
        write_sbdchn(sport, R_DUART_CLK_SEL, brg);
        write_sbdchn(sport, R_DUART_AUXCTL_X, aux | oldaux);

        write_sbdchn(sport, R_DUART_CMD, command);

        spin_unlock(&uport->lock);
}


static const char *sbd_type(struct uart_port *uport)
{
        return "SB1250 DUART";
}

static void sbd_release_port(struct uart_port *uport)
{
        struct sbd_port *sport = to_sport(uport);
        struct sbd_duart *duart = sport->duart;
        int map_guard;

        iounmap(sport->memctrl);
        sport->memctrl = NULL;
        iounmap(uport->membase);
        uport->membase = NULL;

        map_guard = atomic_add_return(-1, &duart->map_guard);
        if (!map_guard)
                release_mem_region(duart->mapctrl, DUART_CHANREG_SPACING);
        release_mem_region(uport->mapbase, DUART_CHANREG_SPACING);
}

static int sbd_map_port(struct uart_port *uport)
{
        const char *err = KERN_ERR "sbd: Cannot map MMIO\n";
        struct sbd_port *sport = to_sport(uport);
        struct sbd_duart *duart = sport->duart;

        if (!uport->membase)
                uport->membase = ioremap_nocache(uport->mapbase,
                                                 DUART_CHANREG_SPACING);
        if (!uport->membase) {
                printk(err);
                return -ENOMEM;
        }

        if (!sport->memctrl)
                sport->memctrl = ioremap_nocache(duart->mapctrl,
                                                 DUART_CHANREG_SPACING);
        if (!sport->memctrl) {
                printk(err);
                iounmap(uport->membase);
                uport->membase = NULL;
                return -ENOMEM;
        }

        return 0;
}

static int sbd_request_port(struct uart_port *uport)
{
        const char *err = KERN_ERR "sbd: Unable to reserve MMIO resource\n";
        struct sbd_duart *duart = to_sport(uport)->duart;
        int map_guard;
        int ret = 0;

        if (!request_mem_region(uport->mapbase, DUART_CHANREG_SPACING,
                                "sb1250-duart")) {
                printk(err);
                return -EBUSY;
        }
        map_guard = atomic_add_return(1, &duart->map_guard);
        if (map_guard == 1) {
                if (!request_mem_region(duart->mapctrl, DUART_CHANREG_SPACING,
                                        "sb1250-duart")) {
                        atomic_add(-1, &duart->map_guard);
                        printk(err);
                        ret = -EBUSY;
                }
        }
        if (!ret) {
                ret = sbd_map_port(uport);
                if (ret) {
                        map_guard = atomic_add_return(-1, &duart->map_guard);
                        if (!map_guard)
                                release_mem_region(duart->mapctrl,
                                                   DUART_CHANREG_SPACING);
                }
        }
        if (ret) {
                release_mem_region(uport->mapbase, DUART_CHANREG_SPACING);
                return ret;
        }
        return 0;
}

static void sbd_config_port(struct uart_port *uport, int flags)
{
        struct sbd_port *sport = to_sport(uport);

        if (flags & UART_CONFIG_TYPE) {
                if (sbd_request_port(uport))
                        return;

                uport->type = PORT_SB1250_DUART;

                sbd_init_port(sport);
        }
}

static int sbd_verify_port(struct uart_port *uport, struct serial_struct *ser)
{
        int ret = 0;

        if (ser->type != PORT_UNKNOWN && ser->type != PORT_SB1250_DUART)
                ret = -EINVAL;
        if (ser->irq != uport->irq)
                ret = -EINVAL;
        if (ser->baud_base != uport->uartclk / 16)
                ret = -EINVAL;
        return ret;
}


static const struct uart_ops sbd_ops = {
        .tx_empty       = sbd_tx_empty,
        .set_mctrl      = sbd_set_mctrl,
        .get_mctrl      = sbd_get_mctrl,
        .stop_tx        = sbd_stop_tx,
        .start_tx       = sbd_start_tx,
        .stop_rx        = sbd_stop_rx,
        .enable_ms      = sbd_enable_ms,
        .break_ctl      = sbd_break_ctl,
        .startup        = sbd_startup,
        .shutdown       = sbd_shutdown,
        .set_termios    = sbd_set_termios,
        .type           = sbd_type,
        .release_port   = sbd_release_port,
        .request_port   = sbd_request_port,
        .config_port    = sbd_config_port,
        .verify_port    = sbd_verify_port,
};

/* Initialize SB1250 DUART port structures.  */
static void __init sbd_probe_duarts(void)
{
        static int probed;
        int chip, side;
        int max_lines, line;

        if (probed)
                return;

        /* Set the number of available units based on the SOC type.  */
        switch (soc_type) {
        case K_SYS_SOC_TYPE_BCM1x55:
        case K_SYS_SOC_TYPE_BCM1x80:
                max_lines = 4;
                break;
        default:
                /* Assume at least two serial ports at the normal address.  */
                max_lines = 2;
                break;
        }

        probed = 1;

        for (chip = 0, line = 0; chip < DUART_MAX_CHIP && line < max_lines;
             chip++) {
                sbd_duarts[chip].mapctrl = SBD_CTRLREGS(line);

                for (side = 0; side < DUART_MAX_SIDE && line < max_lines;
                     side++, line++) {
                        struct sbd_port *sport = &sbd_duarts[chip].sport[side];
                        struct uart_port *uport = &sport->port;

                        sport->duart    = &sbd_duarts[chip];

                        uport->irq      = SBD_INT(line);
                        uport->uartclk  = 100000000 / 20 * 16;
                        uport->fifosize = 16;
                        uport->iotype   = UPIO_MEM;
                        uport->flags    = UPF_BOOT_AUTOCONF;
                        uport->ops      = &sbd_ops;
                        uport->line     = line;
                        uport->mapbase  = SBD_CHANREGS(line);
                }
        }
}


#ifdef CONFIG_SERIAL_SB1250_DUART_CONSOLE
/*
 * Serial console stuff.  Very basic, polling driver for doing serial
 * console output.  The console_lock is held by the caller, so we
 * shouldn't be interrupted for more console activity.
 */
static void sbd_console_putchar(struct uart_port *uport, int ch)
{
        struct sbd_port *sport = to_sport(uport);

        sbd_transmit_drain(sport);
        write_sbdchn(sport, R_DUART_TX_HOLD, ch);
}

static void sbd_console_write(struct console *co, const char *s,
                              unsigned int count)
{
        int chip = co->index / DUART_MAX_SIDE;
        int side = co->index % DUART_MAX_SIDE;
        struct sbd_port *sport = &sbd_duarts[chip].sport[side];
        struct uart_port *uport = &sport->port;
        unsigned long flags;
        unsigned int mask;

        /* Disable transmit interrupts and enable the transmitter. */
        spin_lock_irqsave(&uport->lock, flags);
        mask = read_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2));
        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2),
                     mask & ~M_DUART_IMR_TX);
        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_EN);
        spin_unlock_irqrestore(&uport->lock, flags);

        uart_console_write(&sport->port, s, count, sbd_console_putchar);

        /* Restore transmit interrupts and the transmitter enable. */
        spin_lock_irqsave(&uport->lock, flags);
        sbd_line_drain(sport);
        if (sport->tx_stopped)
                write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS);
        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), mask);
        spin_unlock_irqrestore(&uport->lock, flags);
}

static int __init sbd_console_setup(struct console *co, char *options)
{
        int chip = co->index / DUART_MAX_SIDE;
        int side = co->index % DUART_MAX_SIDE;
        struct sbd_port *sport = &sbd_duarts[chip].sport[side];
        struct uart_port *uport = &sport->port;
        int baud = 115200;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';
        int ret;

        if (!sport->duart)
                return -ENXIO;

        ret = sbd_map_port(uport);
        if (ret)
                return ret;

        sbd_init_port(sport);

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);
        return uart_set_options(uport, co, baud, parity, bits, flow);
}

static struct uart_driver sbd_reg;
static struct console sbd_console = {
        .name   = "duart",
        .write  = sbd_console_write,
        .device = uart_console_device,
        .setup  = sbd_console_setup,
        .flags  = CON_PRINTBUFFER,
        .index  = -1,
        .data   = &sbd_reg
};

static int __init sbd_serial_console_init(void)
{
        sbd_probe_duarts();
        register_console(&sbd_console);

        return 0;
}

console_initcall(sbd_serial_console_init);

#define SERIAL_SB1250_DUART_CONSOLE     &sbd_console
#else
#define SERIAL_SB1250_DUART_CONSOLE     NULL
#endif /* CONFIG_SERIAL_SB1250_DUART_CONSOLE */


static struct uart_driver sbd_reg = {
        .owner          = THIS_MODULE,
        .driver_name    = "sb1250_duart",
        .dev_name       = "duart",
        .major          = TTY_MAJOR,
        .minor          = SB1250_DUART_MINOR_BASE,
        .nr             = DUART_MAX_CHIP * DUART_MAX_SIDE,
        .cons           = SERIAL_SB1250_DUART_CONSOLE,
};

/* Set up the driver and register it.  */
static int __init sbd_init(void)
{
        int i, ret;

        sbd_probe_duarts();

        ret = uart_register_driver(&sbd_reg);
        if (ret)
                return ret;

        for (i = 0; i < DUART_MAX_CHIP * DUART_MAX_SIDE; i++) {
                struct sbd_duart *duart = &sbd_duarts[i / DUART_MAX_SIDE];
                struct sbd_port *sport = &duart->sport[i % DUART_MAX_SIDE];
                struct uart_port *uport = &sport->port;

                if (sport->duart)
                        uart_add_one_port(&sbd_reg, uport);
        }

        return 0;
}

/* Unload the driver.  Unregister stuff, get ready to go away.  */
static void __exit sbd_exit(void)
{
        int i;

        for (i = DUART_MAX_CHIP * DUART_MAX_SIDE - 1; i >= 0; i--) {
                struct sbd_duart *duart = &sbd_duarts[i / DUART_MAX_SIDE];
                struct sbd_port *sport = &duart->sport[i % DUART_MAX_SIDE];
                struct uart_port *uport = &sport->port;

                if (sport->duart)
                        uart_remove_one_port(&sbd_reg, uport);
        }

        uart_unregister_driver(&sbd_reg);
}

module_init(sbd_init);
module_exit(sbd_exit);