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mn10300-serial.c

/* 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 <asm/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));
      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.info->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 (uart_tx_stopped(&port->uart) ||
          uart_circ_empty(&port->uart.info->xmit))
            mn10300_serial_dis_tx_intr(port);

      if (uart_circ_chars_pending(&port->uart.info->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.info->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.info->xmit.head,
                  &port->uart.info->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

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