/* MN10300 On-chip serial port UART driver
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

static const char serial_name[] = "MN10300 Serial driver";
static const char serial_version[] = "mn10300_serial-1.0";
static const char serial_revdate[] = "2007-11-06";

#if defined(CONFIG_MN10300_TTYSM_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/module.h>
#include <linux/serial.h>
#include <linux/circ_buf.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/ioport.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/bitops.h>
#include <asm/serial-regs.h>
#include <unit/timex.h>
#include "mn10300-serial.h"

static inline __attribute__((format(printf, 1, 2)))
void no_printk(const char *fmt, ...)
{
}

#define kenter(FMT, ...) \
        printk(KERN_DEBUG "-->%s(" FMT ")\n", __func__, ##__VA_ARGS__)
#define _enter(FMT, ...) \
        no_printk(KERN_DEBUG "-->%s(" FMT ")\n", __func__, ##__VA_ARGS__)
#define kdebug(FMT, ...) \
        printk(KERN_DEBUG "--- " FMT "\n", ##__VA_ARGS__)
#define _debug(FMT, ...) \
        no_printk(KERN_DEBUG "--- " FMT "\n", ##__VA_ARGS__)
#define kproto(FMT, ...) \
        printk(KERN_DEBUG "### MNSERIAL " FMT " ###\n", ##__VA_ARGS__)
#define _proto(FMT, ...) \
        no_printk(KERN_DEBUG "### MNSERIAL " FMT " ###\n", ##__VA_ARGS__)

#define NR_UARTS 3

#ifdef CONFIG_MN10300_TTYSM_CONSOLE
static void mn10300_serial_console_write(struct console *co,
                                           const char *s, unsigned count);
static int __init mn10300_serial_console_setup(struct console *co,
                                                 char *options);

static struct uart_driver mn10300_serial_driver;
static struct console mn10300_serial_console = {
        .name           = "ttySM",
        .write          = mn10300_serial_console_write,
        .device         = uart_console_device,
        .setup          = mn10300_serial_console_setup,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &mn10300_serial_driver,
};
#endif

static struct uart_driver mn10300_serial_driver = {
        .owner          = NULL,
        .driver_name    = "mn10300-serial",
        .dev_name       = "ttySM",
        .major          = TTY_MAJOR,
        .minor          = 128,
        .nr             = NR_UARTS,
#ifdef CONFIG_MN10300_TTYSM_CONSOLE
        .cons           = &mn10300_serial_console,
#endif
};

static unsigned int mn10300_serial_tx_empty(struct uart_port *);
static void mn10300_serial_set_mctrl(struct uart_port *, unsigned int mctrl);
static unsigned int mn10300_serial_get_mctrl(struct uart_port *);
static void mn10300_serial_stop_tx(struct uart_port *);
static void mn10300_serial_start_tx(struct uart_port *);
static void mn10300_serial_send_xchar(struct uart_port *, char ch);
static void mn10300_serial_stop_rx(struct uart_port *);
static void mn10300_serial_enable_ms(struct uart_port *);
static void mn10300_serial_break_ctl(struct uart_port *, int ctl);
static int mn10300_serial_startup(struct uart_port *);
static void mn10300_serial_shutdown(struct uart_port *);
static void mn10300_serial_set_termios(struct uart_port *,
                                         struct ktermios *new,
                                         struct ktermios *old);
static const char *mn10300_serial_type(struct uart_port *);
static void mn10300_serial_release_port(struct uart_port *);
static int mn10300_serial_request_port(struct uart_port *);
static void mn10300_serial_config_port(struct uart_port *, int);
static int mn10300_serial_verify_port(struct uart_port *,
                                        struct serial_struct *);

static const struct uart_ops mn10300_serial_ops = {
        .tx_empty       = mn10300_serial_tx_empty,
        .set_mctrl      = mn10300_serial_set_mctrl,
        .get_mctrl      = mn10300_serial_get_mctrl,
        .stop_tx        = mn10300_serial_stop_tx,
        .start_tx       = mn10300_serial_start_tx,
        .send_xchar     = mn10300_serial_send_xchar,
        .stop_rx        = mn10300_serial_stop_rx,
        .enable_ms      = mn10300_serial_enable_ms,
        .break_ctl      = mn10300_serial_break_ctl,
        .startup        = mn10300_serial_startup,
        .shutdown       = mn10300_serial_shutdown,
        .set_termios    = mn10300_serial_set_termios,
        .type           = mn10300_serial_type,
        .release_port   = mn10300_serial_release_port,
        .request_port   = mn10300_serial_request_port,
        .config_port    = mn10300_serial_config_port,
        .verify_port    = mn10300_serial_verify_port,
};

static irqreturn_t mn10300_serial_interrupt(int irq, void *dev_id);

/*
 * the first on-chip serial port: ttySM0 (aka SIF0)
 */
#ifdef CONFIG_MN10300_TTYSM0
struct mn10300_serial_port mn10300_serial_port_sif0 = {
        .uart.ops       = &mn10300_serial_ops,
        .uart.membase   = (void __iomem *) &SC0CTR,
        .uart.mapbase   = (unsigned long) &SC0CTR,
        .uart.iotype    = UPIO_MEM,
        .uart.irq       = 0,
        .uart.uartclk   = 0, /* MN10300_IOCLK, */
        .uart.fifosize  = 1,
        .uart.flags     = UPF_BOOT_AUTOCONF,
        .uart.line      = 0,
        .uart.type      = PORT_MN10300,
        .uart.lock      =
        __SPIN_LOCK_UNLOCKED(mn10300_serial_port_sif0.uart.lock),
        .name           = "ttySM0",
        ._iobase        = &SC0CTR,
        ._control       = &SC0CTR,
        ._status        = (volatile u8 *) &SC0STR,
        ._intr          = &SC0ICR,
        ._rxb           = &SC0RXB,
        ._txb           = &SC0TXB,
        .rx_name        = "ttySM0/Rx",
        .tx_name        = "ttySM0/Tx",
#ifdef CONFIG_MN10300_TTYSM0_TIMER8
        .tm_name        = "ttySM0/Timer8",
        ._tmxmd         = &TM8MD,
        ._tmxbr         = &TM8BR,
        ._tmicr         = &TM8ICR,
        .tm_irq         = TM8IRQ,
        .div_timer      = MNSCx_DIV_TIMER_16BIT,
#else /* CONFIG_MN10300_TTYSM0_TIMER2 */
        .tm_name        = "ttySM0/Timer2",
        ._tmxmd         = &TM2MD,
        ._tmxbr         = (volatile u16 *) &TM2BR,
        ._tmicr         = &TM2ICR,
        .tm_irq         = TM2IRQ,
        .div_timer      = MNSCx_DIV_TIMER_8BIT,
#endif
        .rx_irq         = SC0RXIRQ,
        .tx_irq         = SC0TXIRQ,
        .rx_icr         = &GxICR(SC0RXIRQ),
        .tx_icr         = &GxICR(SC0TXIRQ),
        .clock_src      = MNSCx_CLOCK_SRC_IOCLK,
        .options        = 0,
#ifdef CONFIG_GDBSTUB_ON_TTYSM0
        .gdbstub        = 1,
#endif
};
#endif /* CONFIG_MN10300_TTYSM0 */

/*
 * the second on-chip serial port: ttySM1 (aka SIF1)
 */
#ifdef CONFIG_MN10300_TTYSM1
struct mn10300_serial_port mn10300_serial_port_sif1 = {
        .uart.ops       = &mn10300_serial_ops,
        .uart.membase   = (void __iomem *) &SC1CTR,
        .uart.mapbase   = (unsigned long) &SC1CTR,
        .uart.iotype    = UPIO_MEM,
        .uart.irq       = 0,
        .uart.uartclk   = 0, /* MN10300_IOCLK, */
        .uart.fifosize  = 1,
        .uart.flags     = UPF_BOOT_AUTOCONF,
        .uart.line      = 1,
        .uart.type      = PORT_MN10300,
        .uart.lock      =
        __SPIN_LOCK_UNLOCKED(mn10300_serial_port_sif1.uart.lock),
        .name           = "ttySM1",
        ._iobase        = &SC1CTR,
        ._control       = &SC1CTR,
        ._status        = (volatile u8 *) &SC1STR,
        ._intr          = &SC1ICR,
        ._rxb           = &SC1RXB,
        ._txb           = &SC1TXB,
        .rx_name        = "ttySM1/Rx",
        .tx_name        = "ttySM1/Tx",
#ifdef CONFIG_MN10300_TTYSM1_TIMER9
        .tm_name        = "ttySM1/Timer9",
        ._tmxmd         = &TM9MD,
        ._tmxbr         = &TM9BR,
        ._tmicr         = &TM9ICR,
        .tm_irq         = TM9IRQ,
        .div_timer      = MNSCx_DIV_TIMER_16BIT,
#else /* CONFIG_MN10300_TTYSM1_TIMER3 */
        .tm_name        = "ttySM1/Timer3",
        ._tmxmd         = &TM3MD,
        ._tmxbr         = (volatile u16 *) &TM3BR,
        ._tmicr         = &TM3ICR,
        .tm_irq         = TM3IRQ,
        .div_timer      = MNSCx_DIV_TIMER_8BIT,
#endif
        .rx_irq         = SC1RXIRQ,
        .tx_irq         = SC1TXIRQ,
        .rx_icr         = &GxICR(SC1RXIRQ),
        .tx_icr         = &GxICR(SC1TXIRQ),
        .clock_src      = MNSCx_CLOCK_SRC_IOCLK,
        .options        = 0,
#ifdef CONFIG_GDBSTUB_ON_TTYSM1
        .gdbstub        = 1,
#endif
};
#endif /* CONFIG_MN10300_TTYSM1 */

/*
 * the third on-chip serial port: ttySM2 (aka SIF2)
 */
#ifdef CONFIG_MN10300_TTYSM2
struct mn10300_serial_port mn10300_serial_port_sif2 = {
        .uart.ops       = &mn10300_serial_ops,
        .uart.membase   = (void __iomem *) &SC2CTR,
        .uart.mapbase   = (unsigned long) &SC2CTR,
        .uart.iotype    = UPIO_MEM,
        .uart.irq       = 0,
        .uart.uartclk   = 0, /* MN10300_IOCLK, */
        .uart.fifosize  = 1,
        .uart.flags     = UPF_BOOT_AUTOCONF,
        .uart.line      = 2,
#ifdef CONFIG_MN10300_TTYSM2_CTS
        .uart.type      = PORT_MN10300_CTS,
#else
        .uart.type      = PORT_MN10300,
#endif
        .uart.lock      =
        __SPIN_LOCK_UNLOCKED(mn10300_serial_port_sif2.uart.lock),
        .name           = "ttySM2",
        .rx_name        = "ttySM2/Rx",
        .tx_name        = "ttySM2/Tx",
        .tm_name        = "ttySM2/Timer10",
        ._iobase        = &SC2CTR,
        ._control       = &SC2CTR,
        ._status        = &SC2STR,
        ._intr          = &SC2ICR,
        ._rxb           = &SC2RXB,
        ._txb           = &SC2TXB,
        ._tmxmd         = &TM10MD,
        ._tmxbr         = &TM10BR,
        ._tmicr         = &TM10ICR,
        .tm_irq         = TM10IRQ,
        .div_timer      = MNSCx_DIV_TIMER_16BIT,
        .rx_irq         = SC2RXIRQ,
        .tx_irq         = SC2TXIRQ,
        .rx_icr         = &GxICR(SC2RXIRQ),
        .tx_icr         = &GxICR(SC2TXIRQ),
        .clock_src      = MNSCx_CLOCK_SRC_IOCLK,
#ifdef CONFIG_MN10300_TTYSM2_CTS
        .options        = MNSCx_OPT_CTS,
#else
        .options        = 0,
#endif
#ifdef CONFIG_GDBSTUB_ON_TTYSM2
        .gdbstub        = 1,
#endif
};
#endif /* CONFIG_MN10300_TTYSM2 */


/*
 * list of available serial ports
 */
struct mn10300_serial_port *mn10300_serial_ports[NR_UARTS + 1] = {
#ifdef CONFIG_MN10300_TTYSM0
        [0]     = &mn10300_serial_port_sif0,
#endif
#ifdef CONFIG_MN10300_TTYSM1
        [1]     = &mn10300_serial_port_sif1,
#endif
#ifdef CONFIG_MN10300_TTYSM2
        [2]     = &mn10300_serial_port_sif2,
#endif
        [NR_UARTS] = NULL,
};


/*
 * we abuse the serial ports' baud timers' interrupt lines to get the ability
 * to deliver interrupts to userspace as we use the ports' interrupt lines to
 * do virtual DMA on account of the ports having no hardware FIFOs
 *
 * we can generate an interrupt manually in the assembly stubs by writing to
 * the enable and detect bits in the interrupt control register, so all we need
 * to do here is disable the interrupt line
 *
 * note that we can't just leave the line enabled as the baud rate timer *also*
 * generates interrupts
 */
static void mn10300_serial_mask_ack(unsigned int irq)
{
        u16 tmp;
        GxICR(irq) = GxICR_LEVEL_6;
        tmp = GxICR(irq); /* flush write buffer */
}

static void mn10300_serial_nop(unsigned int irq)
{
}

static struct irq_chip mn10300_serial_pic = {
        .name           = "mnserial",
        .ack            = mn10300_serial_mask_ack,
        .mask           = mn10300_serial_mask_ack,
        .mask_ack       = mn10300_serial_mask_ack,
        .unmask         = mn10300_serial_nop,
        .end            = mn10300_serial_nop,
};


/*
 * serial virtual DMA interrupt jump table
 */
struct mn10300_serial_int mn10300_serial_int_tbl[NR_IRQS];

static void mn10300_serial_dis_tx_intr(struct mn10300_serial_port *port)
{
        u16 x;
        *port->tx_icr = GxICR_LEVEL_1 | GxICR_DETECT;
        x = *port->tx_icr;
}

static void mn10300_serial_en_tx_intr(struct mn10300_serial_port *port)
{
        u16 x;
        *port->tx_icr = GxICR_LEVEL_1 | GxICR_ENABLE;
        x = *port->tx_icr;
}

static void mn10300_serial_dis_rx_intr(struct mn10300_serial_port *port)
{
        u16 x;
        *port->rx_icr = GxICR_LEVEL_1 | GxICR_DETECT;
        x = *port->rx_icr;
}

/*
 * multi-bit equivalent of test_and_clear_bit()
 */
static int mask_test_and_clear(volatile u8 *ptr, u8 mask)
{
        u32 epsw;
        asm volatile("  bclr    %1,(%2)         \n"
                     "  mov     epsw,%0         \n"
                     : "=d"(epsw) : "d"(mask), "a"(ptr)
                     : "cc", "memory");
        return !(epsw & EPSW_FLAG_Z);
}

/*
 * receive chars from the ring buffer for this serial port
 * - must do break detection here (not done in the UART)
 */
static void mn10300_serial_receive_interrupt(struct mn10300_serial_port *port)
{
        struct uart_icount *icount = &port->uart.icount;
        struct tty_struct *tty = port->uart.state->port.tty;
        unsigned ix;
        int count;
        u8 st, ch, push, status, overrun;

        _enter("%s", port->name);

        push = 0;

        count = CIRC_CNT(port->rx_inp, port->rx_outp, MNSC_BUFFER_SIZE);
        count = tty_buffer_request_room(tty, count);
        if (count == 0) {
                if (!tty->low_latency)
                        tty_flip_buffer_push(tty);
                return;
        }

try_again:
        /* pull chars out of the hat */
        ix = port->rx_outp;
        if (ix == port->rx_inp) {
                if (push && !tty->low_latency)
                        tty_flip_buffer_push(tty);
                return;
        }

        ch = port->rx_buffer[ix++];
        st = port->rx_buffer[ix++];
        smp_rmb();
        port->rx_outp = ix & (MNSC_BUFFER_SIZE - 1);
        port->uart.icount.rx++;

        st &= SC01STR_FEF | SC01STR_PEF | SC01STR_OEF;
        status = 0;
        overrun = 0;

        /* the UART doesn't detect BREAK, so we have to do that ourselves
         * - it starts as a framing error on a NUL character
         * - then we count another two NUL characters before issuing TTY_BREAK
         * - then we end on a normal char or one that has all the bottom bits
         *   zero and the top bits set
         */
        switch (port->rx_brk) {
        case 0:
                /* not breaking at the moment */
                break;

        case 1:
                if (st & SC01STR_FEF && ch == 0) {
                        port->rx_brk = 2;
                        goto try_again;
                }
                goto not_break;

        case 2:
                if (st & SC01STR_FEF && ch == 0) {
                        port->rx_brk = 3;
                        _proto("Rx Break Detected");
                        icount->brk++;
                        if (uart_handle_break(&port->uart))
                                goto ignore_char;
                        status |= 1 << TTY_BREAK;
                        goto insert;
                }
                goto not_break;

        default:
                if (st & (SC01STR_FEF | SC01STR_PEF | SC01STR_OEF))
                        goto try_again; /* still breaking */

                port->rx_brk = 0; /* end of the break */

                switch (ch) {
                case 0xFF:
                case 0xFE:
                case 0xFC:
                case 0xF8:
                case 0xF0:
                case 0xE0:
                case 0xC0:
                case 0x80:
                case 0x00:
                        /* discard char at probable break end */
                        goto try_again;
                }
                break;
        }

process_errors:
        /* handle framing error */
        if (st & SC01STR_FEF) {
                if (ch == 0) {
                        /* framing error with NUL char is probably a BREAK */
                        port->rx_brk = 1;
                        goto try_again;
                }

                _proto("Rx Framing Error");
                icount->frame++;
                status |= 1 << TTY_FRAME;
        }

        /* handle parity error */
        if (st & SC01STR_PEF) {
                _proto("Rx Parity Error");
                icount->parity++;
                status = TTY_PARITY;
        }

        /* handle normal char */
        if (status == 0) {
                if (uart_handle_sysrq_char(&port->uart, ch))
                        goto ignore_char;
                status = (1 << TTY_NORMAL);
        }

        /* handle overrun error */
        if (st & SC01STR_OEF) {
                if (port->rx_brk)
                        goto try_again;

                _proto("Rx Overrun Error");
                icount->overrun++;
                overrun = 1;
        }

insert:
        status &= port->uart.read_status_mask;

        if (!overrun && !(status & port->uart.ignore_status_mask)) {
                int flag;

                if (status & (1 << TTY_BREAK))
                        flag = TTY_BREAK;
                else if (status & (1 << TTY_PARITY))
                        flag = TTY_PARITY;
                else if (status & (1 << TTY_FRAME))
                        flag = TTY_FRAME;
                else
                        flag = TTY_NORMAL;

                tty_insert_flip_char(tty, ch, flag);
        }

        /* overrun is special, since it's reported immediately, and doesn't
         * affect the current character
         */
        if (overrun)
                tty_insert_flip_char(tty, 0, TTY_OVERRUN);

        count--;
        if (count <= 0) {
                if (!tty->low_latency)
                        tty_flip_buffer_push(tty);
                return;
        }

ignore_char:
        push = 1;
        goto try_again;

not_break:
        port->rx_brk = 0;
        goto process_errors;
}

/*
 * handle an interrupt from the serial transmission "virtual DMA" driver
 * - note: the interrupt routine will disable its own interrupts when the Tx
 *   buffer is empty
 */
static void mn10300_serial_transmit_interrupt(struct mn10300_serial_port *port)
{
        _enter("%s", port->name);

        if (!port->uart.state || !port->uart.state->port.tty) {
                mn10300_serial_dis_tx_intr(port);
                return;
        }

        if (uart_tx_stopped(&port->uart) ||
            uart_circ_empty(&port->uart.state->xmit))
                mn10300_serial_dis_tx_intr(port);

        if (uart_circ_chars_pending(&port->uart.state->xmit) < WAKEUP_CHARS)
                uart_write_wakeup(&port->uart);
}

/*
 * deal with a change in the status of the CTS line
 */
static void mn10300_serial_cts_changed(struct mn10300_serial_port *port, u8 st)
{
        u16 ctr;

        port->tx_cts = st;
        port->uart.icount.cts++;

        /* flip the CTS state selector flag to interrupt when it changes
         * back */
        ctr = *port->_control;
        ctr ^= SC2CTR_TWS;
        *port->_control = ctr;

        uart_handle_cts_change(&port->uart, st & SC2STR_CTS);
        wake_up_interruptible(&port->uart.state->port.delta_msr_wait);
}

/*
 * handle a virtual interrupt generated by the lower level "virtual DMA"
 * routines (irq is the baud timer interrupt)
 */
static irqreturn_t mn10300_serial_interrupt(int irq, void *dev_id)
{
        struct mn10300_serial_port *port = dev_id;
        u8 st;

        spin_lock(&port->uart.lock);

        if (port->intr_flags) {
                _debug("INT %s: %x", port->name, port->intr_flags);

                if (mask_test_and_clear(&port->intr_flags, MNSCx_RX_AVAIL))
                        mn10300_serial_receive_interrupt(port);

                if (mask_test_and_clear(&port->intr_flags,
                                        MNSCx_TX_SPACE | MNSCx_TX_EMPTY))
                        mn10300_serial_transmit_interrupt(port);
        }

        /* the only modem control line amongst the whole lot is CTS on
         * serial port 2 */
        if (port->type == PORT_MN10300_CTS) {
                st = *port->_status;
                if ((port->tx_cts ^ st) & SC2STR_CTS)
                        mn10300_serial_cts_changed(port, st);
        }

        spin_unlock(&port->uart.lock);

        return IRQ_HANDLED;
}

/*
 * return indication of whether the hardware transmit buffer is empty
 */
static unsigned int mn10300_serial_tx_empty(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        return (*port->_status & (SC01STR_TXF | SC01STR_TBF)) ?
                0 : TIOCSER_TEMT;
}

/*
 * set the modem control lines (we don't have any)
 */
static void mn10300_serial_set_mctrl(struct uart_port *_port,
                                     unsigned int mctrl)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s,%x", port->name, mctrl);
}

/*
 * get the modem control line statuses
 */
static unsigned int mn10300_serial_get_mctrl(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        if (port->type == PORT_MN10300_CTS && !(*port->_status & SC2STR_CTS))
                return TIOCM_CAR | TIOCM_DSR;

        return TIOCM_CAR | TIOCM_CTS | TIOCM_DSR;
}

/*
 * stop transmitting characters
 */
static void mn10300_serial_stop_tx(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        /* disable the virtual DMA */
        mn10300_serial_dis_tx_intr(port);
}

/*
 * start transmitting characters
 * - jump-start transmission if it has stalled
 *   - enable the serial Tx interrupt (used by the virtual DMA controller)
 *   - force an interrupt to happen if necessary
 */
static void mn10300_serial_start_tx(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        u16 x;

        _enter("%s{%lu}",
               port->name,
               CIRC_CNT(&port->uart.state->xmit.head,
                        &port->uart.state->xmit.tail,
                        UART_XMIT_SIZE));

        /* kick the virtual DMA controller */
        x = *port->tx_icr;
        x |= GxICR_ENABLE;

        if (*port->_status & SC01STR_TBF)
                x &= ~(GxICR_REQUEST | GxICR_DETECT);
        else
                x |= GxICR_REQUEST | GxICR_DETECT;

        _debug("CTR=%04hx ICR=%02hx STR=%04x TMD=%02hx TBR=%04hx ICR=%04hx",
               *port->_control, *port->_intr, *port->_status,
               *port->_tmxmd, *port->_tmxbr, *port->tx_icr);

        *port->tx_icr = x;
        x = *port->tx_icr;
}

/*
 * transmit a high-priority XON/XOFF character
 */
static void mn10300_serial_send_xchar(struct uart_port *_port, char ch)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s,%02x", port->name, ch);

        if (likely(port->gdbstub)) {
                port->tx_xchar = ch;
                if (ch)
                        mn10300_serial_en_tx_intr(port);
        }
}

/*
 * stop receiving characters
 * - called whilst the port is being closed
 */
static void mn10300_serial_stop_rx(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        u16 ctr;

        _enter("%s", port->name);

        ctr = *port->_control;
        ctr &= ~SC01CTR_RXE;
        *port->_control = ctr;

        mn10300_serial_dis_rx_intr(port);
}

/*
 * enable modem status interrupts
 */
static void mn10300_serial_enable_ms(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        u16 ctr, cts;

        _enter("%s", port->name);

        if (port->type == PORT_MN10300_CTS) {
                /* want to interrupt when CTS goes low if CTS is now high and
                 * vice versa
                 */
                port->tx_cts = *port->_status;

                cts = (port->tx_cts & SC2STR_CTS) ?
                        SC2CTR_TWE : SC2CTR_TWE | SC2CTR_TWS;

                ctr = *port->_control;
                ctr &= ~SC2CTR_TWS;
                ctr |= cts;
                *port->_control = ctr;

                mn10300_serial_en_tx_intr(port);
        }
}

/*
 * transmit or cease transmitting a break signal
 */
static void mn10300_serial_break_ctl(struct uart_port *_port, int ctl)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s,%d", port->name, ctl);

        if (ctl) {
                /* tell the virtual DMA handler to assert BREAK */
                port->tx_break = 1;
                mn10300_serial_en_tx_intr(port);
        } else {
                port->tx_break = 0;
                *port->_control &= ~SC01CTR_BKE;
                mn10300_serial_en_tx_intr(port);
        }
}

/*
 * grab the interrupts and enable the port for reception
 */
static int mn10300_serial_startup(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);
        struct mn10300_serial_int *pint;

        _enter("%s{%d}", port->name, port->gdbstub);

        if (unlikely(port->gdbstub))
                return -EBUSY;

        /* allocate an Rx buffer for the virtual DMA handler */
        port->rx_buffer = kmalloc(MNSC_BUFFER_SIZE, GFP_KERNEL);
        if (!port->rx_buffer)
                return -ENOMEM;

        port->rx_inp = port->rx_outp = 0;

        /* finally, enable the device */
        *port->_intr = SC01ICR_TI;
        *port->_control |= SC01CTR_TXE | SC01CTR_RXE;

        pint = &mn10300_serial_int_tbl[port->rx_irq];
        pint->port = port;
        pint->vdma = mn10300_serial_vdma_rx_handler;
        pint = &mn10300_serial_int_tbl[port->tx_irq];
        pint->port = port;
        pint->vdma = mn10300_serial_vdma_tx_handler;

        set_intr_level(port->rx_irq, GxICR_LEVEL_1);
        set_intr_level(port->tx_irq, GxICR_LEVEL_1);
        set_irq_chip(port->tm_irq, &mn10300_serial_pic);

        if (request_irq(port->rx_irq, mn10300_serial_interrupt,
                        IRQF_DISABLED, port->rx_name, port) < 0)
                goto error;

        if (request_irq(port->tx_irq, mn10300_serial_interrupt,
                        IRQF_DISABLED, port->tx_name, port) < 0)
                goto error2;

        if (request_irq(port->tm_irq, mn10300_serial_interrupt,
                        IRQF_DISABLED, port->tm_name, port) < 0)
                goto error3;
        mn10300_serial_mask_ack(port->tm_irq);

        return 0;

error3:
        free_irq(port->tx_irq, port);
error2:
        free_irq(port->rx_irq, port);
error:
        kfree(port->rx_buffer);
        port->rx_buffer = NULL;
        return -EBUSY;
}

/*
 * shutdown the port and release interrupts
 */
static void mn10300_serial_shutdown(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        /* disable the serial port and its baud rate timer */
        port->tx_break = 0;
        *port->_control &= ~(SC01CTR_TXE | SC01CTR_RXE | SC01CTR_BKE);
        *port->_tmxmd = 0;

        if (port->rx_buffer) {
                void *buf = port->rx_buffer;
                port->rx_buffer = NULL;
                kfree(buf);
        }

        /* disable all intrs */
        free_irq(port->tm_irq, port);
        free_irq(port->rx_irq, port);
        free_irq(port->tx_irq, port);

        *port->rx_icr = GxICR_LEVEL_1;
        *port->tx_icr = GxICR_LEVEL_1;
}

/*
 * this routine is called to set the UART divisor registers to match the
 * specified baud rate for a serial port.
 */
static void mn10300_serial_change_speed(struct mn10300_serial_port *port,
                                          struct ktermios *new,
                                          struct ktermios *old)
{
        unsigned long flags;
        unsigned long ioclk = port->ioclk;
        unsigned cflag;
        int baud, bits, xdiv, tmp;
        u16 tmxbr, scxctr;
        u8 tmxmd, battempt;
        u8 div_timer = port->div_timer;

        _enter("%s{%lu}", port->name, ioclk);

        /* byte size and parity */
        cflag = new->c_cflag;
        switch (cflag & CSIZE) {
        case CS7: scxctr = SC01CTR_CLN_7BIT; bits = 9;  break;
        case CS8: scxctr = SC01CTR_CLN_8BIT; bits = 10; break;
        default:  scxctr = SC01CTR_CLN_8BIT; bits = 10; break;
        }

        if (cflag & CSTOPB) {
                scxctr |= SC01CTR_STB_2BIT;
                bits++;
        }

        if (cflag & PARENB) {
                bits++;
                if (cflag & PARODD)
                        scxctr |= SC01CTR_PB_ODD;
#ifdef CMSPAR
                else if (cflag & CMSPAR)
                        scxctr |= SC01CTR_PB_FIXED0;
#endif
                else
                        scxctr |= SC01CTR_PB_EVEN;
        }

        /* Determine divisor based on baud rate */
        battempt = 0;

        if (div_timer == MNSCx_DIV_TIMER_16BIT)
                scxctr |= SC0CTR_CK_TM8UFLOW_8; /* ( == SC1CTR_CK_TM9UFLOW_8
                                                 *   == SC2CTR_CK_TM10UFLOW) */
        else if (div_timer == MNSCx_DIV_TIMER_8BIT)
                scxctr |= SC0CTR_CK_TM2UFLOW_8;

try_alternative:
        baud = uart_get_baud_rate(&port->uart, new, old, 0,
                                  port->ioclk / 8);

        _debug("ALT %d [baud %d]", battempt, baud);

        if (!baud)
                baud = 9600;    /* B0 transition handled in rs_set_termios */
        xdiv = 1;
        if (baud == 134) {
                baud = 269;     /* 134 is really 134.5 */
                xdiv = 2;
        }

        if (baud == 38400 &&
            (port->uart.flags & UPF_SPD_MASK) == UPF_SPD_CUST
            ) {
                _debug("CUSTOM %u", port->uart.custom_divisor);

                if (div_timer == MNSCx_DIV_TIMER_16BIT) {
                        if (port->uart.custom_divisor <= 65535) {
                                tmxmd = TM8MD_SRC_IOCLK;
                                tmxbr = port->uart.custom_divisor;
                                port->uart.uartclk = ioclk;
                                goto timer_okay;
                        }
                        if (port->uart.custom_divisor / 8 <= 65535) {
                                tmxmd = TM8MD_SRC_IOCLK_8;
                                tmxbr = port->uart.custom_divisor / 8;
                                port->uart.custom_divisor = tmxbr * 8;
                                port->uart.uartclk = ioclk / 8;
                                goto timer_okay;
                        }
                        if (port->uart.custom_divisor / 32 <= 65535) {
                                tmxmd = TM8MD_SRC_IOCLK_32;
                                tmxbr = port->uart.custom_divisor / 32;
                                port->uart.custom_divisor = tmxbr * 32;
                                port->uart.uartclk = ioclk / 32;
                                goto timer_okay;
                        }

                } else if (div_timer == MNSCx_DIV_TIMER_8BIT) {
                        if (port->uart.custom_divisor <= 255) {
                                tmxmd = TM2MD_SRC_IOCLK;
                                tmxbr = port->uart.custom_divisor;
                                port->uart.uartclk = ioclk;
                                goto timer_okay;
                        }
                        if (port->uart.custom_divisor / 8 <= 255) {
                                tmxmd = TM2MD_SRC_IOCLK_8;
                                tmxbr = port->uart.custom_divisor / 8;
                                port->uart.custom_divisor = tmxbr * 8;
                                port->uart.uartclk = ioclk / 8;
                                goto timer_okay;
                        }
                        if (port->uart.custom_divisor / 32 <= 255) {
                                tmxmd = TM2MD_SRC_IOCLK_32;
                                tmxbr = port->uart.custom_divisor / 32;
                                port->uart.custom_divisor = tmxbr * 32;
                                port->uart.uartclk = ioclk / 32;
                                goto timer_okay;
                        }
                }
        }

        switch (div_timer) {
        case MNSCx_DIV_TIMER_16BIT:
                port->uart.uartclk = ioclk;
                tmxmd = TM8MD_SRC_IOCLK;
                tmxbr = tmp = (ioclk / (baud * xdiv) + 4) / 8 - 1;
                if (tmp > 0 && tmp <= 65535)
                        goto timer_okay;

                port->uart.uartclk = ioclk / 8;
                tmxmd = TM8MD_SRC_IOCLK_8;
                tmxbr = tmp = (ioclk / (baud * 8 * xdiv) + 4) / 8 - 1;
                if (tmp > 0 && tmp <= 65535)
                        goto timer_okay;

                port->uart.uartclk = ioclk / 32;
                tmxmd = TM8MD_SRC_IOCLK_32;
                tmxbr = tmp = (ioclk / (baud * 32 * xdiv) + 4) / 8 - 1;
                if (tmp > 0 && tmp <= 65535)
                        goto timer_okay;
                break;

        case MNSCx_DIV_TIMER_8BIT:
                port->uart.uartclk = ioclk;
                tmxmd = TM2MD_SRC_IOCLK;
                tmxbr = tmp = (ioclk / (baud * xdiv) + 4) / 8 - 1;
                if (tmp > 0 && tmp <= 255)
                        goto timer_okay;

                port->uart.uartclk = ioclk / 8;
                tmxmd = TM2MD_SRC_IOCLK_8;
                tmxbr = tmp = (ioclk / (baud * 8 * xdiv) + 4) / 8 - 1;
                if (tmp > 0 && tmp <= 255)
                        goto timer_okay;

                port->uart.uartclk = ioclk / 32;
                tmxmd = TM2MD_SRC_IOCLK_32;
                tmxbr = tmp = (ioclk / (baud * 32 * xdiv) + 4) / 8 - 1;
                if (tmp > 0 && tmp <= 255)
                        goto timer_okay;
                break;

        default:
                BUG();
                return;
        }

        /* refuse to change to a baud rate we can't support */
        _debug("CAN'T SUPPORT");

        switch (battempt) {
        case 0:
                if (old) {
                        new->c_cflag &= ~CBAUD;
                        new->c_cflag |= (old->c_cflag & CBAUD);
                        battempt = 1;
                        goto try_alternative;
                }

        case 1:
                /* as a last resort, if the quotient is zero, default to 9600
                 * bps */
                new->c_cflag &= ~CBAUD;
                new->c_cflag |= B9600;
                battempt = 2;
                goto try_alternative;

        default:
                /* hmmm... can't seem to support 9600 either
                 * - we could try iterating through the speeds we know about to
                 *   find the lowest
                 */
                new->c_cflag &= ~CBAUD;
                new->c_cflag |= B0;

                if (div_timer == MNSCx_DIV_TIMER_16BIT)
                        tmxmd = TM8MD_SRC_IOCLK_32;
                else if (div_timer == MNSCx_DIV_TIMER_8BIT)
                        tmxmd = TM2MD_SRC_IOCLK_32;
                tmxbr = 1;

                port->uart.uartclk = ioclk / 32;
                break;
        }
timer_okay:

        _debug("UARTCLK: %u / %hu", port->uart.uartclk, tmxbr);

        /* make the changes */
        spin_lock_irqsave(&port->uart.lock, flags);

        uart_update_timeout(&port->uart, new->c_cflag, baud);

        /* set the timer to produce the required baud rate */
        switch (div_timer) {
        case MNSCx_DIV_TIMER_16BIT:
                *port->_tmxmd = 0;
                *port->_tmxbr = tmxbr;
                *port->_tmxmd = TM8MD_INIT_COUNTER;
                *port->_tmxmd = tmxmd | TM8MD_COUNT_ENABLE;
                break;

        case MNSCx_DIV_TIMER_8BIT:
                *port->_tmxmd = 0;
                *(volatile u8 *) port->_tmxbr = (u8) tmxbr;
                *port->_tmxmd = TM2MD_INIT_COUNTER;
                *port->_tmxmd = tmxmd | TM2MD_COUNT_ENABLE;
                break;
        }

        /* CTS flow control flag and modem status interrupts */
        scxctr &= ~(SC2CTR_TWE | SC2CTR_TWS);

        if (port->type == PORT_MN10300_CTS && cflag & CRTSCTS) {
                /* want to interrupt when CTS goes low if CTS is now
                 * high and vice versa
                 */
                port->tx_cts = *port->_status;

                if (port->tx_cts & SC2STR_CTS)
                        scxctr |= SC2CTR_TWE;
                else
                        scxctr |= SC2CTR_TWE | SC2CTR_TWS;
        }

        /* set up parity check flag */
        port->uart.read_status_mask = (1 << TTY_NORMAL) | (1 << TTY_OVERRUN);
        if (new->c_iflag & INPCK)
                port->uart.read_status_mask |=
                        (1 << TTY_PARITY) | (1 << TTY_FRAME);
        if (new->c_iflag & (BRKINT | PARMRK))
                port->uart.read_status_mask |= (1 << TTY_BREAK);

        /* characters to ignore */
        port->uart.ignore_status_mask = 0;
        if (new->c_iflag & IGNPAR)
                port->uart.ignore_status_mask |=
                        (1 << TTY_PARITY) | (1 << TTY_FRAME);
        if (new->c_iflag & IGNBRK) {
                port->uart.ignore_status_mask |= (1 << TTY_BREAK);
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns to (for real raw support).
                 */
                if (new->c_iflag & IGNPAR)
                        port->uart.ignore_status_mask |= (1 << TTY_OVERRUN);
        }

        /* Ignore all characters if CREAD is not set */
        if ((new->c_cflag & CREAD) == 0)
                port->uart.ignore_status_mask |= (1 << TTY_NORMAL);

        scxctr |= *port->_control & (SC01CTR_TXE | SC01CTR_RXE | SC01CTR_BKE);
        *port->_control = scxctr;

        spin_unlock_irqrestore(&port->uart.lock, flags);
}

/*
 * set the terminal I/O parameters
 */
static void mn10300_serial_set_termios(struct uart_port *_port,
                                         struct ktermios *new,
                                         struct ktermios *old)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s,%p,%p", port->name, new, old);

        mn10300_serial_change_speed(port, new, old);

        /* handle turning off CRTSCTS */
        if (!(new->c_cflag & CRTSCTS)) {
                u16 ctr = *port->_control;
                ctr &= ~SC2CTR_TWE;
                *port->_control = ctr;
        }
}

/*
 * return description of port type
 */
static const char *mn10300_serial_type(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        if (port->uart.type == PORT_MN10300_CTS)
                return "MN10300 SIF_CTS";

        return "MN10300 SIF";
}

/*
 * release I/O and memory regions in use by port
 */
static void mn10300_serial_release_port(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        release_mem_region((unsigned long) port->_iobase, 16);
}

/*
 * request I/O and memory regions for port
 */
static int mn10300_serial_request_port(struct uart_port *_port)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        request_mem_region((unsigned long) port->_iobase, 16, port->name);
        return 0;
}

/*
 * configure the type and reserve the ports
 */
static void mn10300_serial_config_port(struct uart_port *_port, int type)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);

        _enter("%s", port->name);

        port->uart.type = PORT_MN10300;

        if (port->options & MNSCx_OPT_CTS)
                port->uart.type = PORT_MN10300_CTS;

        mn10300_serial_request_port(_port);
}

/*
 * verify serial parameters are suitable for this port type
 */
static int mn10300_serial_verify_port(struct uart_port *_port,
                                        struct serial_struct *ss)
{
        struct mn10300_serial_port *port =
                container_of(_port, struct mn10300_serial_port, uart);
        void *mapbase = (void *) (unsigned long) port->uart.mapbase;

        _enter("%s", port->name);

        /* these things may not be changed */
        if (ss->irq             != port->uart.irq       ||
            ss->port            != port->uart.iobase    ||
            ss->io_type         != port->uart.iotype    ||
            ss->iomem_base      != mapbase ||
            ss->iomem_reg_shift != port->uart.regshift  ||
            ss->hub6            != port->uart.hub6      ||
            ss->xmit_fifo_size  != port->uart.fifosize)
                return -EINVAL;

        /* type may be changed on a port that supports CTS */
        if (ss->type != port->uart.type) {
                if (!(port->options & MNSCx_OPT_CTS))
                        return -EINVAL;

                if (ss->type != PORT_MN10300 &&
                    ss->type != PORT_MN10300_CTS)
                        return -EINVAL;
        }

        return 0;
}

/*
 * initialise the MN10300 on-chip UARTs
 */
static int __init mn10300_serial_init(void)
{
        struct mn10300_serial_port *port;
        int ret, i;

        printk(KERN_INFO "%s version %s (%s)\n",
               serial_name, serial_version, serial_revdate);

#ifdef CONFIG_MN10300_TTYSM2
        SC2TIM = 8; /* make the baud base of timer 2 IOCLK/8 */
#endif

        set_intr_stub(EXCEP_IRQ_LEVEL1, mn10300_serial_vdma_interrupt);

        ret = uart_register_driver(&mn10300_serial_driver);
        if (!ret) {
                for (i = 0 ; i < NR_PORTS ; i++) {
                        port = mn10300_serial_ports[i];
                        if (!port || port->gdbstub)
                                continue;

                        switch (port->clock_src) {
                        case MNSCx_CLOCK_SRC_IOCLK:
                                port->ioclk = MN10300_IOCLK;
                                break;

#ifdef MN10300_IOBCLK
                        case MNSCx_CLOCK_SRC_IOBCLK:
                                port->ioclk = MN10300_IOBCLK;
                                break;
#endif
                        default:
                                BUG();
                        }

                        ret = uart_add_one_port(&mn10300_serial_driver,
                                                &port->uart);

                        if (ret < 0) {
                                _debug("ERROR %d", -ret);
                                break;
                        }
                }

                if (ret)
                        uart_unregister_driver(&mn10300_serial_driver);
        }

        return ret;
}

__initcall(mn10300_serial_init);


#ifdef CONFIG_MN10300_TTYSM_CONSOLE

/*
 * print a string to the serial port without disturbing the real user of the
 * port too much
 * - the console must be locked by the caller
 */
static void mn10300_serial_console_write(struct console *co,
                                           const char *s, unsigned count)
{
        struct mn10300_serial_port *port;
        unsigned i;
        u16 scxctr, txicr, tmp;
        u8 tmxmd;

        port = mn10300_serial_ports[co->index];

        /* firstly hijack the serial port from the "virtual DMA" controller */
        txicr = *port->tx_icr;
        *port->tx_icr = GxICR_LEVEL_1;
        tmp = *port->tx_icr;

        /* the transmitter may be disabled */
        scxctr = *port->_control;
        if (!(scxctr & SC01CTR_TXE)) {
                /* restart the UART clock */
                tmxmd = *port->_tmxmd;

                switch (port->div_timer) {
                case MNSCx_DIV_TIMER_16BIT:
                        *port->_tmxmd = 0;
                        *port->_tmxmd = TM8MD_INIT_COUNTER;
                        *port->_tmxmd = tmxmd | TM8MD_COUNT_ENABLE;
                        break;

                case MNSCx_DIV_TIMER_8BIT:
                        *port->_tmxmd = 0;
                        *port->_tmxmd = TM2MD_INIT_COUNTER;
                        *port->_tmxmd = tmxmd | TM2MD_COUNT_ENABLE;
                        break;
                }

                /* enable the transmitter */
                *port->_control = (scxctr & ~SC01CTR_BKE) | SC01CTR_TXE;

        } else if (scxctr & SC01CTR_BKE) {
                /* stop transmitting BREAK */
                *port->_control = (scxctr & ~SC01CTR_BKE);
        }

        /* send the chars into the serial port (with LF -> LFCR conversion) */
        for (i = 0; i < count; i++) {
                char ch = *s++;

                while (*port->_status & SC01STR_TBF)
                        continue;
                *(u8 *) port->_txb = ch;

                if (ch == 0x0a) {
                        while (*port->_status & SC01STR_TBF)
                                continue;
                        *(u8 *) port->_txb = 0xd;
                }
        }

        /* can't let the transmitter be turned off if it's actually
         * transmitting */
        while (*port->_status & (SC01STR_TXF | SC01STR_TBF))
                continue;

        /* disable the transmitter if we re-enabled it */
        if (!(scxctr & SC01CTR_TXE))
                *port->_control = scxctr;

        *port->tx_icr = txicr;
        tmp = *port->tx_icr;
}

/*
 * set up a serial port as a console
 * - construct a cflag setting for the first rs_open()
 * - initialize the serial port
 * - return non-zero if we didn't find a serial port.
 */
static int __init mn10300_serial_console_setup(struct console *co,
                                                 char *options)
{
        struct mn10300_serial_port *port;
        int i, parity = 'n', baud = 9600, bits = 8, flow = 0;

        for (i = 0 ; i < NR_PORTS ; i++) {
                port = mn10300_serial_ports[i];
                if (port && !port->gdbstub && port->uart.line == co->index)
                        goto found_device;
        }

        return -ENODEV;

found_device:
        switch (port->clock_src) {
        case MNSCx_CLOCK_SRC_IOCLK:
                port->ioclk = MN10300_IOCLK;
                break;

#ifdef MN10300_IOBCLK
        case MNSCx_CLOCK_SRC_IOBCLK:
                port->ioclk = MN10300_IOBCLK;
                break;
#endif
        default:
                BUG();
        }

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);

        return uart_set_options(&port->uart, co, baud, parity, bits, flow);
}

/*
 * register console
 */
static int __init mn10300_serial_console_init(void)
{
        register_console(&mn10300_serial_console);
        return 0;
}

console_initcall(mn10300_serial_console_init);
#endif